EXTERNAL - WORKS



ELECTRIFICATION WORKS – EXTERNAL

16E.1. GENERAL

16E.1.1 Scope

I) These general specifications indicate the requirements and precautions to be taken during the execution of Electrical Installation works involving power cables and/or overhead lines, to ensure efficient, safe, economical and practical use of materials and equipments including prevention of risks and fire hazards.

II) These general specifications are subject to revision from time to time.

III) This section covers the general requirements applicable to works contracts for such external electrical Installation works.

16E.1.2 Related documents - Each work has its own particular requirements.  Therefore, in addition to the general specifications, governing Bureau of Indian Standards, Indian Electricity Rules, Standard Contract Conditions etc. there would be necessity of additional conditions/specifications for a particular work.  In case of any discrepancy such additional conditions / specifications will override these general specifications.

16E.1.3 Terminology - The definition of terms shall be in accordance with relevant Indian Standards are indicated in Section 0.2.1.

16E.1.4. Submission of tenders (where works are taken up on contract basis)

16E.1.4.1. The tender shall be submitted complete with the following -

i) Complete tender documents as purchased from PWD / concerned authorities duly filled in and signed.  The price part of the tender shall be indicated only on the tender schedule of work.

ii) Earnest Money Deposit in one of the specified forms.

iii) Any other supplementary details required for the evaluation of the tenders such as drawings, technical literature / catalogues, data etc.

iv). Deviations, if any, from tender specifications and/or tender conditions, with reasons thereof.  It is open to the department whether or not to accept them.

16E.1.4.2. Where two part tendering system is proposed to be adopted in any particular work, the procedure for submission and opening of tenders shall be indicated in tender documents for that work.

16E.1.5. Rates

16E.1.5.1. The work shall be treated as on works contract basis and the rates tendered shall be for complete items of work (except the materials, if any, stipulated for supply by the department) inclusive of all taxes  (including works contract tax, if any), duties, and levies etc. and all charges for items contingent to the to the work, such as, packing, forwarding, insurance, freight and delivery at site for the materials to be supplied by the contractor, watch and ward of all materials (including those, if any supplied by the department) for the work at site etc.

16E.1.5.2. Prices quoted shall be firm.  Price adjustments shall however be governed by the conditions of contract.  All relevant documents shall be produced by the contractor to the engineer whenever called upon y him to do so, for working out such adjustments in rates.

16E.1.6 Taxes and duties

Being an indivisible works contract, Sales Tax, Excise Duty etc. are not payable separately.

The works contract tax shall be deducted from the bills of the contractor as applicable, at the time of payments.

Octroi shall not be paid separately for the materials supplied by the contractor, but Octroi exemption certificate can be furnished by the department, on demand.  However, the department is not liable to reimburse the octroi duty in case such exemption certificates are not honored by the concerned authorities.

16E.1.7. Mobilisation advance - No mobilisation advance shall be paid for the work, unless otherwise stipulated in tender papers for any individual works.

16E.1.8. Completeness of tender - All sundry fittings, assemblies, accessories, hardware items, foundation bolts, termination lugs for electrical connections as required, and all other sundry items

which are useful and necessary for proper assembly and efficient working of the various components of the work shall be deemed to have been included in the tender, whether such items are specifically mentioned in the tender documents or not.

16E.1.9. Works to be arranged by the department - Unless and otherwise specified in the tender documents, the following works shall be arranged by the department

1. Covered storage space for accommodation of all the equipments, components and materials involved in the work, till they are installed and commissioned.

2. Power supply as per 16E-1.12.

3. Masonry ducts within and outside the buildings for the cables.

16E.1.10. Works to be done by the contractor - Unless and otherwise mentioned in the tender documents, the following works shall be done by the contractor, and therefore their cost shall be deemed to be included in their tendered cost

1. Foundation, brackets and components wherever required, including foundations bolts.

2. Suspenders and brackets for suspending / supporting cables, as required.

3.  Suspenders for cable trays for laying the cables, where required.

4. Excavation and refilling of trenches in soil wherever the pipes cables/are to be laid directly in ground, including necessary base treatment and supports for pipes as specified

5. Sealing of all openings provided by the department for pipes and cables, from fire safety point of view, after laying of the same.

6. Painting of all exposed metal surfaces of equipments and components with appropriate colour.

7. Making good all damages caused to the structure during installation and restoring the same to their original finish.

8. Testing and commissioning of the completed installation.

16E.1.11. Storage and custody of materials - suitable and lockable storage accommodation shall be provided by the department free of cost to the contractor.  However, the watch and ward of the stores and their safe custody shall be his responsibility till the final taking over of the installation by the department. 

16E.1.12. Electric power supply - The power supply to the required extent for the erection, testing and commissioning of the installation shall be made available free of charge to the contractor within 25M of the site of actual consumption at one or more places as required.  Further power distribution to the various locations shall be done by the contractor at his own cost.

The contractor shall not misuse the power supply for any purpose other than, which it is intended for.  The power supply shall be forthwith disconnected in case of such default and the contractor shall then have to arrange for the required power supply at his cost.

Machinery for erection - All tools and tackles required for unloading of equipments and erection at site shall be the responsibility of the contractor.

16E.1.14. Payment terms

Unless otherwise specified in the additional conditions of the contact, the payment shall be made as per the relevant clauses of the tender documents.

Security deposit shall be deducted from each running bill and the final bill to the extent of 10% of the gross amount payable subject to the maximum limit specified.  The earnest money deposit shall be adjusted against this security deposit.  The security deposit shall be released on the expiry of guarantee / maintenance period stipulated in the contract.  However, the contractor can furnish a bank guarantee in the specified format from a schedule bank for the full value of the security deposit, in which event no recovery shall be made towards security deposit from his bills. The bank guarantee shall be kept valid till the expiry of the above guarantee / maintenance period.

16E.1.15. Co-ordination with other agencies - The contractor shall co-ordinate with all other agencies involved in the site of work so that the works of other agencies are not hampered due to delay in his work, security or other reasons.

16E.1.16. Care of buildings - Care shall be taken by the contractor to avoid damage to the building during execution of his part of the work.  He shall be responsible for repairing all damages and restoring the same to their original finish at his cost.  He shall also remove at his cost all unwanted and waste materials arising out of his work from the site.

As far as possible, cutting of roads, lawns etc. should be avoided.  Where it becomes inescapable to cut them, these shall be repaired immediately.

16E.1.17. Structural alterations to buildings - No structural member in the building shall be damaged / altered, without prior approval from the competent authority through the engineer.

Structural provisions like openings, pipes, if any, provided by the department for the work, shall be used. Where these require modifications, such contingent works shall be carried out by the contractor, at his cost.

All cut out openings in floors provided by the department shall be closed, after installing the cables, in accordance with the item therefore in the schedule of work.

All cuttings made by the contractor in connection with the works shall be filled by him at his cost to the original finish.

16E.1.18. Addition to an installation - An addition, temporary or permanent, shall not be made to the authorised load of an existing installation until it has been definitely ascertained that the current carrying capacity and the condition of the existing accessories, conductors, switches etc. affected, including those of the supply authorities are adequate for the increased load.

16E.1.19. Work in occupied buildings - When work is executed in occupied buildings, there should be minimum inconvenience to the occupants.  The work shall be programmed in consultation with the engineer and the occupying department. If so required, the work may have to be done even before and after office hours.

The contractor shall be responsible to abide by the regulations or restrictions set in regard to entry into and movement within the premises of the site of work.

The contractor shall not tamper with any of the existing installations, including their switching operations or connections there to, without specific approval from the engineer.

16E.1.20. Drawings - The work shall be carried out in accordance with the drawing(s) if any, enclosed with the tender and also in accordance with modification (s) if any thereto from time to time approved by the engineer, and also instructions from him in the course of execution of the works.

All schematics, layout diagrams etc. shall be deemed to be ‘Drawings’ within the meaning of the terms as used in the conditions of contract.

All circuits, poles, feeder pillars etc. shall be indicated and numbered in the layout diagrams(s).

16E.1.21. Conformity to IE act, IE rules, and standards - All Electrical works shall be carried out in accordance with the provisions of Indian Electricity Act, 1910 and Indian Electricity Rules, 1956 amended up to date (Date of call of tender unless specified otherwise).

The works shall also conform to relevant Indian Standard Codes of Practice (COP) for the type of work involved.

Materials to be used in work shall be ISI marked, whenever such ISI marked materials are available.

In all electrical installation works, relevant Safety codes of practices shall be followed.  Guidelines on safety procedure as outlined in Annexure 16E-A.1 to the general specifications for electrical works – (Internal), shall be followed. Annexure 16E-A.2 gives the list of standards to be referred to.

16E.1.22. General requirements of components

16E.1.22.1. Quality of materials - All materials and equipments supplied by the contractor shall be new.  They shall be of such design, size and materials as to satisfactorily function under the rated conditions of operation and to withstand the environmental conditions at site.

16E.1.22.2. Inspection of materials and equipments - Materials and equipments to be used in the work shall be inspected by the departmental officers.  Such inspection will of following categories

1. Inspection of materials / equipments to be witnessed at the manufacturer’s premises in accordance with relevant BIS / Agreement Inspection Procedure.

2.  To receive materials at site with Manufacturer’s Test Certificate (s).

3.  To inspect materials at the Authorised Dealer’s Godowns to ensure delivery of genuine materials at site.

4.  To receive materials after physical inspection at site.

The departmental officers will take adequate care to ensure that only tested and genuine materials of proper quality are used in work.

Similarly, for fabricated equipments, the contractor will first submit dimensional detailed drawings for approval before fabrication is taken up in the factory.  Suitable stage inspection at factory also will be made to ensure proper use of materials, workmanship and quality control.

The tender specifications will stipulate the Inspection requirements or their waival for various materials/equipments including norms of inspection in specific cases.

16E.1.22.3. Ratings of components - All current carrying components in an installation shall be of appropriate ratings of voltage, current, and frequency, as required at the respective sections of the electrical installations in which they are used, without their respective ratings being exceeded.

16E.1.23. Workmanship - Good workmanship is an essential requirement to be complied with.  The entire work of manufacture / fabrication, assembly and installation shall conform to sound engineering practice.

The work shall be carried out under the direct supervision of a first class licensed foreman or of a person holding a certificate of competency issued by the State Government for the type of work involved, employed by the contractor, who shall rectify then and there the defects pointed out by the engineer during the progress of work.

16E.1.23.3. Fabrication of panels in a CPRI approved workshop - Unless otherwise specified, switch boards/LT panels etc. will be fabricated by a fabricating workshop having CPRI Certificate for short circuit withstand capability for manufacture / fabrication for the rating of Switch Boards specified.  The workshop also should have reasonable quality control, and testing facilities, besides having a proper 7-tank process for proper treatment and painting of metal parts.

16E.1.24. Testing - All tests prescribed in these general specifications, to be done before, during and after installation, shall be carried out, and the test results shall be submitted to the engineer in prescribed proforma, forming part of the Completion Certificate.

16E.1.25. Commissioning on completion - After the work is completed, it shall be ensured that the installation is tested and commissioned.

16E.1.26. Completion plan and completion certificate - For all works costing more than

Rupees one lakh, completion certificate including the proforma for test results shall be submitted to the engineer after completion of work.

Completion plan drawn to a suitable scale in tracing cloth with ink indicating the following along with three blue print copies of the same shall also be submitted.

a) General layout of the site showing therein routes of cables and overhead lines.

b) Schedule of lengths, types and sizes of cables and overhead conductors.

c) Positions of all cable joints type wise, supports, stays, struts, lightning arresters, feeder pillars, and pipes or closed ducts.

d) Positions of cable route markers and joint markers with respect to permanent land marks available at site.

e) Type of street light fittings.

f) Name of work, job number, accepted tender reference, actual date of completion, names of Division/Sub-Division, and name of the firm who executed the work with their signature(s).

16E.1.26.3 In the case of works costing less than Rs.100000 the completion plan shall be prepared by the departmental and signed by the contractor before final payment is made.

16E.1.27. Guarantee - The installation will be handed over to the department after necessary testing and commissioning.  The installation will be guaranteed against any defective design/workmanship.  Similarly, the materials supplied by the contractor will be guaranteed against any manufacturing defect, inferior quality.  The guarantee period will be for a period of 12 months from the date of handing over to the department if so specified in the agreement.  Installation/equipments or components thereof shall be rectified repaired at the discretion of the engineer.

16E.1.28. Maintenance - The periodicity of important maintenance activities are indicated in the Annexure 16E-A.5 for guidance.

16E.2. specifications of Cable Work

16E.2.1 Scope - This section covers the requirements for the selection, installation and jointing of power cables for low, medium and high voltage applications up to and including 33KV.  For details not covered in these Specifications, IS: 1255-1983 shall be referred to.  All references shall be to BIS Specifications and codes with amendments issued up to date i.e. till the date of call of tender.

16E.2.2. Types of cables

The cables for applications for low and medium voltage (up to and including 1.1KV) supply shall be one of the following: -

(i) PVC insulated and PVC sheathed, conforming to IS: 1554 (Part-1)-1988.

(ii) Cross linked polyethylene insulated, PVC sheathed (XLPE), conforming to IS: 7098(part-1)-1988

The cable for applications for high voltage (above 1.1KV but up to and including 11KV supply) supply shall be one of the following:-

i) PVC insulated and PVC sheathed, conforming to IS: 1554 (Part-2)-1988.

ii) Paper insulated, lead sheathed (PILCA) conforming to IS: 692-1973.

iii) Cross linked polyethylene (XLPE) insulated, PVC sheathed conforming to IS: 7098 (Part-2)-1985.

The cables for applications above 11KV but up to and including 33KV supply shall be one of the following:

i) Paper insulated lead sheathed (PILCA) conforming to IS: 692-1973.

ii) Cross linked polyethylene insulated (XLPE), conforming to IS: 7098 (Part-2)-1985.

The cables shall be with solid or stranded aluminium conductors, as specified, copper conductors may be used, only in special applications, where use of aluminium conductors is not technically acceptable.

Where paper insulated cables are used in predominantly vertical situations, these shall be of non-draining type.

16E.2.3. Armouring and serving

All multicore cables liable for mechanical damage and all HV cables (irrespective of the situation of installation) shall be armored.  Where armoring is unavoidable in single core cables, either the armour should be made of nonmagnetic material, or it should be ensured that the armouring is not shorted at terminations, thus preventing the flow of circulating currents therein.

Short runs of cables laid in pipes, closed masonry trenches and similar protected or secured enclosures need not be armoured.

PVC and XLPE cables, when armored, shall have galvanised steel wires (flat or round) for armouring.

Paper insulated cables shall have for armouring, a double layer of steel tape for normal applications.  Steel wire armouring is preferred where the cables are liable to tensile stresses in applications such as vertical runs, suspended on brackets or laid in soil that is likely to subside.

Serving over armouring in paper insulated cables shall consist of a complete layer or layers of suitable compounded Hessian materials.

16E.2.4. Selection of cable sizes

The cables sizes shall be selected by considering the voltage drop in the case of MV (distribution) cables and current carrying capacity in the case of HV (feeder) cables.  Due consideration should be given for the prospective short circuit current and the period of its flow, especially in the case of HV cables.

While deciding upon the cable sizes, derating factors for the type of cable and depth of laying, grouping, ambient temperature, ground temperature, and soil resistivity shall be taken into account.

Guidance for the selection of cables shall be derived from relevant Bureau of Indian Standards such as IS: 3961: (Part-1)-1967 for paper insulated lead sheathed cables, IS: 3961(part-2)-1967 for PVC insulated and PVC sheathed heavy duty cables, IS: 5819-1970 for recommended short circuit ratings of high voltage PVC cables, IS: 1255-1983 on code of practice for installation, and maintenance of power cables up to and including 33 KV rating etc. (See Table No.1(A) to I(E) for M.V and H.V. selection)

16E.2.5 Storage and handling

16E.2.5.1. Storage

i) The cable drums shall be stored on a well drained, hard surface, so that the drums do not sink in the ground causing rot and damage to the cable drums.  Paved surface is preferred, particularly for long term storage.

ii) The drums shall always be stored on their flanges, and not on their flat sides.

iii) Both ends of the cables especially of PILCA cables should be properly sealed to prevent ingress / absorption of moisture by the insulation during storage.

iv) Protection from rain and sun is preferable for long term storage for all types of cables.  There should also be ventilation between cable drums.

v) During storage, periodical rolling of drums once in, say, 3 months through 90 degrees shall be done, in the case of paper insulated cables.  Rolling shall be done in the direction of the arrow marked on the drum.

vi)  Damaged battens of drums etc. should be replaced, as may be necessary.

16E.2.5.2. Handling

i) When the cable drums have to be moved over short distances, they should be rolled in the direction of the arrow marked on the drum.

ii) For manual transportation over long distances, the drum should be mounted on cable drum wheels, strong enough to carry the weight of the drum, and pulled by means of ropes.  Alternatively, they may be mounted or on a trailer or on a suitable mechanical transport.

iii) For loading into and unloading from vehicles, a crane or a suitable lifting tackle should be used.  Small sized cable drums can also be rolled down carefully on a suitable ramp or rails, for unloading, provided no damage is likely to be caused to the cable or to the drum.

16E.2.6 Installation

2.6.1 General

i) Cables with kinks, straightened kinks or any other apparent defects like defective armouring etc. shall not be installed.

ii) Cables shall not be bent sharp to a small radius either while handling or in installation.  The minimum safe bending radius for PVC/XLPE (MV) cables shall be 12 times the overall diameter of the cable.  The minimum safe bending radius for PILCA/XLPE (HV) cables shall be as given in Table-II.  At joints and terminations, the bending radius of individual cores of a multicore cable of any type shall not be less then 15 times its overall diameter.

iii) The ends of lead sheathed cables shall be sealed with solder immediately after cutting the cables.  In case of PVC cables, suitable sealing compound / tape shall be used for this purpose, if likely exposed to rain in transit storage.  Suitable heat shrinkable caps may also be used for the purpose.

16E.2.6.2 Route - Before the cable laying work is undertaken, the route of the cable shall be decided by the engineer considering the following.

i) While the shortest practicable route should be preferred, the cable route shall generally follow fixed developments such as roads, footpaths etc. with proper offsets so that future maintenance, identification etc. are rendered easy.  Cross-country run merely to shorten the route length shall not be adopted.

ii) Cable route shall be planned away from drains and near the property, especially in the case of LV/MV cables, subject to any special local requirements that may have to be necessarily complied with.

iii) As far as possible, the alignment of the cable route shall be decided after taking into consideration the present and likely future requirements of other services including cables enroute, possibility of widening of roads / lanes etc.

iv) Corrosive soils, ground surrounding sewage effluent etc. shall be avoided for the routes.

v) Route of cables of different voltages

Whenever cables are laid along well-demarcated or established roads, the LV/MV cables shall be laid farther from the kerb line than HV cables.

Cables of different voltages, and also power and control cables shall be kept in different trenches with adequate separation. Where available space is restricted such that this requirement cannot be met, LV/MV cables shall be laid above HV cables.

Where cables cross one another, the cable of higher voltage shall be laid at a lower level than the cable of lower voltages.

16E.2.6.3 Proximity to communication cables - Power and communication cables shall as afar as possible cross each other at right angles.  The horizontal and vertical clearances between them shall not be less than 60cm. 

16E.2.6.4 Railway crossing - Cables under railway tracks, shall be laid in spun reinforced concrete, or cast iron or steel pipes at such depths as may be specified by the railway authorities, but not less than 1m, measured from the bottom of the sleepers to the top of the pipe.  Inside railway station limits, pipes shall be laid up to the point of the railway boundary or to a point to be decided by the railway authorities.  Outside the railway station limits, pipes shall be laid up to a minimum distance of 3m from the center of the nearest track on either side.

16E.2.6.5 Way leave - Way leave for the cable route shall be obtained as necessary, from the appropriate authorities, such as Municipal authorities, Department of telecommunication, Gas works, Railways, Civil Aviation authorities, Owners of properties etc.  In case of private property, section 12/51 of the Indian Electricity Act shall be complied with.

16E.2.6.6 Methods of laying - The cables shall be laid direct in ground, pipe, closed or open ducts, cable trays or on surface of wall etc.  The method(s) of laying required shall be specified in the tender schedule of work.

16E.2.6.7 Laying direct in ground

16E.2.6.7.1 General - This method shall be adopted where the cable route is through open ground, along roads/lanes, etc., and where no frequent excavations are likely to be encountered and where re-excavation is easily possible without affecting other services.

16E.2.6.7.2 Trenching

(i) Width of trench - The width of the trench shall first be determined on the following basis (Refer Fig. 1).

  1. The minimum width of the trench for laying a single cable shall be 35cm.
  2. Where more than one cable, is to be laid in the same trench in horizontal formation, the width of the trench shall be increased such that the inter-axial spacing between the cables, except where otherwise specified, shall be at least 20cm.
  3. There shall be a clearance of at least 15cm between axis of the end cables and the sides of the trench.

(ii) Depth of trench - The depth of the trench shall be determined on the following basis. Where the cables are laid in a single tier formation, the total depth of trench shall not be less than 75cm for cables up to 1.1.KV and 1.2m for cables above 1.1.KV.

  1. When more than one tier of cables is unavoidable and vertical formation of laying is adopted, the depth of the trench in (ii) a above shall be increased by 30 cm for each additional tier to be formed.
  2. Where no sand cushioning and protective covering are provided for the cables as per 2.6.7.3(I) (b), 2.6.7.3 (vii) (c) and 2.6.7.3 (ix) (d) below, the depth of the trench as per (ii) (a) and (b) above shall be increased by 25cm.

(iii) Excavation of trenches

  1. The trenches shall be excavated in reasonably straight line. Wherever, there is a change in the direction, a suitable curvature shall be adopted complying with the requirements of clauses 2.6.1(ii).
  2. Where gradients and changes in depth are unavoidable, these shall be gradual.
  3. The bottom of the trench shall be level and free from stones, brickbats etc.
  4. The excavation should be done by suitable means manual or mechanical.  The excavated soil shall be stacked firmly by the side of the trench such that it may not fall back into the trench.
  5. Adequate precautions should be taken not to damage any existing cable(s), pipes or any other such installations in the route during excavation.  Wherever bricks, tiles or protective covers or bare cables are encountered, further excavation shall not be carried out without the approval of the engineer.
  6. Existing property if any exposed during trenching shall be temporarily supported adequately as directed by the engineer.  The trenching in such cases shall be done in short lengths, necessary pipes laid for passing cables therein and the trench refilled in accordance with clause 2.6.7.4.
  7. If there is any danger of trench collapsing or endangering adjacent structures, the sides should be well shored up with sheeting as the excavation proceeds.  Where necessary, these may even be left in place when back filling the trench.
  8. Excavation through lawns shall be done in consultation with the department concerned.

16E.2.6.7.3. Laying of cable in trench

(i) Sand cushioning

  1. The trench shall then be provided with a layer of clean, dry sand cushion of not less then 8cm in depth, before laying the cables therein.
  2. However, sand cushioning as per (a) above need not be provided for MV cables, where there is no possibility of any mechanical damage to the cables due to heavy or shock loading on the soil above such structure shall be clearly specified in the tender documents.
  3. Sand cushioning as per (a) above shall however be invariably provided in the case of HV cables.

(ii) Testing before laying - At the time of issue of cables for laying, the cables shall be tested for continuity and insulation resistance (See also clause 2.8.1).

(iii) The cable drum shall be properly mounted on jacks, or on a cable wheel at a suitable location, making sure that the spindle, jack etc. are strong enough to carry the weight of the drum without failure, and that the spindle is horizontal in the bearings so as to prevent the drum creeping to one side while rotating.

iv) The cable shall be pulled over on rollers in the trench steadily and uniformly without jerks and strain.  The entire cable length shall as far as possible be laid off in one stretch.  PVC/XLPE cables less then 120sqmm size may be removed by “Flaking” i.e. by making one long loop in the reverse direction.

Note - For short runs and sizes up to 50sq mm of MV cables, any other suitable method of direct handling and laying can be adopted without strain or excess bending of the cables.

v) After the cable has been so uncoiled, if shall be lifted slightly over the rollers beginning from one end by helpers standing about 10m apart and drawn straight.  The cable shall then be lifted off the rollers and laid in a reasonably straight line.

vi) Testing before covering - The cables shall be tested for continuity of cores and insulation resistance (Refer clause 2.8.1) and the cable length shall be measured, before closing the trench.  The cable end shall be sealed / covered as per clause 2.6.1. (iii)

vii) Sand covering - Cables laid in trenches in a single tier formation shall have a covering of dry sand of not less then 17cm above the base cushion of sand before the protective cover is laid.

In the case of vertical multi-tier formation, after the first cable has been laid, a sand cushion of 30cm shall be provided over the base cushion before the second tier is laid.  If additional tiers are formed, each of the subsequent tiers also shall have a sand cushion of 30cm as stated above. Cables in the top most tier shall have a final sand covering not less than 17cm before the protective cover is laid.

Sand covering as per (a) and (b) above need not be provided for MV cables where a decision is taken by the engineer in charge as per sub clause (I) (b) above, but the inter tier spacing should be maintained as in (b) above with soft soil instead of sand between tiers and for covering.

Sand cushioning as per (a) and (b) above shall however be invariably provided in the case of HV cables.

viii) Extra loop cable

a) At the time of original installation, approximately 3m of surplus cable shall be left on each terminal end of the cable and on each side of the underground joints.  The surplus cable shall be left in the form of a loop.  Where there are long runs of cables such loose cable may be left at suitable intervals as specified by the engineer.

b) Where it may not be practically possible to provide separation between cables when forming loops of a number of cables as in the case of cables emanating from a substation, measurement shall be made only to the extent of actual volume of excavation, sand filling etc. and paid for accordingly.

ix) Mechanical protection over the covering

  1. Mechanical protection to cables shall be laid over the covering in accordance with (b) and (c) below to provide warning to future excavators of the presence of the cable and also to protect the cable against accidental mechanical damage by pickaxe blows etc.
  2. Unless otherwise specified, the cables shall be protected by second class brick of nominal size 22cmx11.4cmx7cm or locally available size, placed on top of the sand (or, soil as the case may be).  The bricks shall be placed breadth-wise for the full length of the cable.  Where more than one cable is to be laid in the same trench, this protective covering shall cover all the cables and project at least 5cm over the sides of the end cables.
  3. Where bricks are not easily available, or are comparatively costly, there is no objection to use locally available materiel such as tiles or slates or stone/cement concrete slabs.  Where such an alternative is acceptable, the same shall be clearly specified in the tender specifications.
  4. Protective covering as per (b) and (c) above need not be provided only for MV cables, in exceptional cases where there is normally no possibility of subsequent excavation.  Such cases shall be particularly specified in the Tender specifications.
  5. The protective covering as per (b) and (c) above shall however invariably be provided in the case of HV cables.

16E.2.6.7.4. Back filling

i) The trenches shall be then back-filled with excavated earth, free from stones or other sharp edged debris and shall be rammed and watered, if necessary in successive layers not exceeding 30cm depth.

ii) Unless otherwise specified, a crown of earth not less than 50mm and not exceeding 100mm in the center and tapering towards the sides of the trench shall be left to allow for subsidence.  The crown of the earth however, should not exceed 10cms so as not to be a hazard to vehicular traffic.

iii) The temporary reinstatement of roadways should be inspected at regular intervals, particularly during wet weather and settlements should be made good by further filling as may be required.

iv)  After the subsidence has ceased, trenches cut through roadways or other paved areas shall be restored to the same density and materials as the surrounding area and re-paved in accordance with the relevant building specifications to the satisfaction of the engineer. v) Where road berms or lawns have been cut out of necessity, (r kerb stones displaced, the same shall be repaired and made good,

except for turfing / asphalting, to the satisfaction of the engineer and all the surplus earth or rock shall be removed to places as specified.

16E.2.6.7.5. Laying of single core cables

i) Three single core cables forming one three phase, circuit shall normally be laid in close trefoil formation and shall be bound together at intervals of approximately 1m.

ii) The relative position of the three cables shall be changed at each joint at the time of original installation, complete transposition being effected in every three consecutive cable lengths.

2.6.7.6 Route markers

i) Location - Route markers shall be provided along the runs of cables at locations approved by the engineer and generally at intervals not exceeding 100m.  Markers shall also be provided to identify change in the direction of the cable route and at locations of underground joints.

(a) Plate type marker - Route markers shall be made out of 100mm x 5mm GI/Aluminium plate welded / bolted on 35mm x 35 mm x 6mm angle iron, 60cm long.  Such plate markers shall be mounted parallel to and at about 0.5m away from the edge of the trench.

b) CC Marker - Alternatively, cement concrete 1:2:4 (1cement:2 coarse sand: 4 graded stone aggregate of 20mm in size) as shown in Fig. 2 shall be laid flat and centered over the cable.  The concrete markers, unless otherwise instructed by the engineer, shall project over the surrounding surface so as to make the cable route easily identifiable.

c) Inscription - The words ‘PWD-MV / HV CABLE’ as the case may be, shall be inscribed on the marker.

16E.2.6.8 Laying in pipes / closed ducts - In locations such as road crossing, entry in to buildings, paved areas etc., cables shall be laid in pipes or closed ducts.  Metallic pipe shall be used as protection pipe for cables fixed on poles of overhead lines.

Stone ware pipes, GI CI or spun reinforced concrete pipes shall be used for cables in generally however only GI pipe shall be used as protection pipe on poles.

The size of the pipe shall not be less than 10cm in diameter for a single cable and not less than 15cm for more than one cable.

Where steel pipes are employed for protection of single core cable feeding AC load, the pipe should be large enough to contain both cables in the case of single phase system and all cables in the case of poly phase system.

Pipes for MV and HV cables shall be independent ones.

In the case of new construction, pipes as required (including for anticipated future requirements) shall be laid along with the civil works and jointed according to the PWD building specifications.

Pipes shall be continuous and clear of debris or concrete before cables are drawn.  Sharp edges if any, at ends shall be smoothened to prevent damage to cable sheathing.

These pipes shall be laid directly in ground without any special bed except for SW pipe which shall be laid over 10cm thick cement concrete 1:5:10: (1cement:5 coarse sand:10graded stone  aggregate of 40mm nominal size) bed.  No sand cushioning or tiles need be used in such situations.

16E.2.6.8.4 Road crossings - The top surface of pipes shall be at a minimum depth or 1m from the pavement level when laid under roads pavements etc.

The pipes shall be laid preferably askew to reduce the angle of bend as the cable enters and leaves the crossing.  This is particularly important for HV cables.

When pipes are laid cutting on existing road, care shall be taken so that the soil filled up after laying the pipes is rammed well in layers with watering as required to ensure proper compaction.  A crown of earth not exceeding 10cm should be left at the top.

The temporary reinstatements of roadways should be inspected at regular intervals, particularly after a rain, and any settlement should be made good by further filling as may be required.

After the subsidence has ceased, the top of the filled up trenches in roadways or other paved areas shall be restored to the same density and material as the surrounding area in accordance with the relevant Karnataka Building Specifications to the satisfaction of the engineer.

16E.2.6.8.5. Manholes shall be provided to facilitate feeding / drawing in of cables with sufficient working space for the purpose.  They shall be covered by suitable manhole covers.  Sizes and other details shall be indicated in the Schedule of work.

16E.2.6.8.6 Cable entry into the building - Pipes for cable entries to the building shall slope downwards from the building.  The pipes at the building end shall be suitably sealed to avoid entry of water, after the cables are laid.

16E.2.6.8.7 Cable grip / draw-wires, winches etc. may be employed for drawing cables through pipes / closed ducts.

16E.2.6.8.8 Measurement for drawing / laying cables in pipes / closed duct shall be on the basis of the actual length of the pipe / duct for each run of the cable, irrespective of the length of cable drawn through.

16E.2.6.9. Laying in open ducts

16E.2.6.9.1. Open ducts with suitable removable covers (RCC slabs or chequered plate) are generally provided in substations, switch room, plant room, workshops etc, for taking the cables.  The cable ducts should be of suitable dimensions for the number of cables involved.

16E.2.6.9.2. (i) Laying of cables with different voltage ratings in the same duct shall be avoided.  Where it is inescapable to take HV & MV cables same trench, they shall be laid with a barrier between them or alternatively, one of the two (HV/MV) cables may be taken through pipe(s).

(ii) Splices or joints of any type shall not be permitted inside the ducts.

16E.2.6.9.3.The cables shall be laid directly in the duct such that unnecessary crossing of cables is avoided.

Where specified, cables may be fixed with clamps on the walls of the duct or taken in hooks / brackets /troughs in ducts.

16E.2.6.9.4 Where specified, ducts may be filled with dry sand after the cables are laid and covered as above, or finished with cement plaster, specially in high voltage applications.

16E.2.6.10.   Laying on surface

This method may be adopted in places like switch rooms, workshops, tunnels, rising (distribution) mains in buildings etc.  This may also be necessitated in the works of additions and / or alterations to the existing installation, where other methods of laying may not be feasible.

Cables may be laid in surface by any of the following methods as specified.

  1. Directly clamped by saddles or clamps,
  2. Supported on cradles,
  3. Laid on troughs / trays, duly clamped.

(i) The saddles and clamps used for fixing the cables on surface shall comply with the requirements given in Table-III.

(ii) Saddles shall be secured with screws to suitable approved plugs.  Clamps shall be secured with nuts on to the bolts, grouted in the supporting structure in an approved manner.

(iii) In the case of single core cables, the clamps shall be of non-magnetic material. A suitable non-corrosive packing shall be used for clamping unarmoured cables to prevent damage to the cable sheath.

(iv)  Cables shall be fixed neatly without undue sag or kinks.

The arrangements of laying the cables in cradles are permitted only in the case of cable of 1.1KV grade of size exceeding 120sqmm.  In such cases, the cable may be suspended on MS flat cradles of size 50mm x 5mm which in turn shall be fixed on the wall by bolts grouted into the wall in an approved manner at spacing of not less than 60 cm.

 All MS components used in fixing the cables shall be either galvanised or given a coat of red oxide primer and finished with 2 coats of approved paint.

16E.2.6.11. Laying on cable tray - This method may be adopted in places like indoor substations, air-conditioning plant room, generator rooms etc., or where long horizontal runs of cables are required within the building and where it is not convenient to carry the cable in open ducts.  This method is preferred where heavy sized cables or a number of cables are required to be laid.  The cable trays may be either of perforated sheet type or of ladder type.

16E.2.6.11.2 Perforated type cable tray

(i) The cable tray shall be fabricated out of slotted perforated MS sheets as channel sections, single or double bended.  The channel sections shall be supplied in convenient lengths and assembled at site to the desired lengths.  These may be galvanised or painted as specified.  Alternatively, where specified, the cable tray may be fabricated by two angle irons of 50mmx50mmx6mm as two longitudinal members, with cross bracing between them by 50mmx5mm flats welded / bolted to the angles at 1 m spacing. 2mm thick MS perforated sheet shall be suitably welded /bolted to the base as well as on the two sides.

ii) The jointing between the sections shall be made with coupler plats of the same material and thickness as the channel section.  Two coupler plates, each of minimum 200mm length, shall be bolted on each of the two sides of the channel section with 8mm dia round headed bolts, nuts and washers.  In order to maintain proper earth continuity bond, the paint on the contact surfaces between the coupler plates and cable tray shall be scraped and removed before the installation.

(iii) The maximum permissible uniformly distributed load for various sizes of cables trays and for different supported span are given in Table IV. The sizes shall be specified considering the same.

(iv) The width of the cable tray shall be chosen so as to accommodate all the cables in one tier, plus 30 to 50% additional width for future expansion.  This additional width shall be minimum 100mm.  The overall width of one cable tray shall be limited to 800mm.

(v) Factory fabricated bends, reducers, tee/cross junctions, etc. shall be provided as per good engineering practice. The radius of bends, junctions etc. shall not be less than the minimum permissible radius of bending of the largest size of cable to be carried by the cable tray.

(vi) The cable tray shall be suspended from the ceiling slab with the help of 10mm dia MS rounds or 25mmx5mm flats at specified spacing (based on Table III).  Flat type suspenders may be used for channels up to 450mm width bolted to cable trays.  Round suspenders shall be threaded and bolted to the cable trays or to independent support angles 50mmx50mmx5mm at the bottom end as specified.  These shall be grouted to the ceiling slab at the other end through an effective means, as approved by the engineer, to take the weight of the cable tray with the cables.

(viii) The entire tray (except in the case of galvanised type) and the suspenders shall be painted with two coats of red oxide primer paint after removing the dirt and rust, and finished with two coats of spray paint of approved make synthetic enamel paint.

(ix) The cable tray shall be bonded to the earth terminal of the switch bonds at both ends.

(x) The cable trays shall be measured on unit length basis, along with the centerline of the cable tray, including bends, reducers, tees, cross joints, etc, and paid for accordingly.

16E.2.6.11.3 Ladder type cable tray

(i) The ladder type of cable tray shall be fabricated of double bended channel section longitudinal members with single bended channel section rungs of cross members welded to the base of the longitudinal members at a center to center spacing of 250cm.

(ii) Alternatively, where specified, ladder type cable trays may be fabricated out of 50mmx50mmx6mm (minimum) angle iron for longitudinal members, and 30mmx6mm flat for rungs.

(iii) Typical details of fabrication and dimensions of both the types of trays are shown in figure 4 A, B, C and D.

(iv) The maximum permissible loading, jointing of channel sections, width of the cable tray, provision of elbows, bends, reducers, horizontal tee/cross junctions etc. suspension of cable tray from the ceiling slab, painting and measurement of the cable tray shall be as per sub-clauses (ii) to (x) below clause 2.6.11.2, except that the overall width of one cable tray may be limited to 800mm.

16E.2.6.11.4 Cables laid on cable trays shall be clamped on to the tray at suitable intervals as per Table – III.

16E.2.6.12 Cable identification tags - Whenever more than one cable is laid / run side by side, marker tags as approved, inscribed with cable identification details shall be permanently attached to all the cables in the manholes / pull pits / joint pits / entry points in buildings / open ducts etc.  These shall also be attached to cables laid direct in ground at specified intervals, before the trenches are backfilled.

16E. 2.7 Jointing

16E.2.7.1 Location

(i) Before laying a cable, proper locations for the proposed cable joints, if any shall be decided, so that when the cable is actually laid, the joints are made in the most suitable places.  As far as possible, water logged locations, carriage ways, pavements, proximity to telephone cables, gas or water mains, inaccessible places, ducts, pipes, racks etc. shall be avoided for locating the cable joints.

(ii) Joints shall be staggered by 2m to 3m when joints are to be done for two or more cables laid together in the same trench.

16E.2.7.2 Joints pits

(i) Joint pits shall be of sufficient dimensions as to allow easy and comfortable working. The sides of the pit shall be well protected from loose earth falling into it.  It shall also be covered by a tarpaulin to prevent dust and other foreign matter being blown on the exposed joints and jointing materials.

(ii) Sufficient ventilation shall be provided during jointing operation in order to disperse fumes given out by fluxing.

16E.2.7.3 Safety precaution

(i) A caution board indicating “CAUTION – CABLE JOINTING WORK IN PROGRESS” shall be displayed to warn the public and traffic where necessary.

(ii) Before jointing is commenced, all safety precautions like isolation, discharging, earthing, display of caution board on the controlling etc. shall be taken to ensure that the cable would not be inadvertently charged from live supply.  Metallic armour and external metallic bonding shall be connected to earth.  Where “permit to work” system is in vogue, safety procedures prescribed shall be complied with.

16E.2.7.4. Jointing materials

(i) Jointing materials and accessories like conductor ferrules, solder, flux, insulating and protective tapes, filling compound, jointing boxes, heat shrinking joint kit etc. of right quality and correct sizes, conforming to relevant Bureau of Indian Standards, wherever they exist, shall be used.

(ii) The design of the joint box and the composition of the filling compound shall be such as to provide an effective sealing against entry of moisture in addition to affording proper electrical characteristic to joints.

iii) Where special type of splicing connector kits or epoxy resin spliced joints or heat shrinkable jointing kits are specified, materials approved for such application shall be used. Storing as well as jointing instructions of the manufacturer of such materials shall be strictly followed.

16E.2.7.5 Jointer - Jointing work shall be carried out be a licensed / experienced (where there is no licensing system for jointers) cable jointer.

16E.2.7.6 Cable work with joints

(i) About 3m long surplus cable shall be left on each side of joints as laid down clause 16E.2.6.7.3 (viii).

(ii) Insulation resistance’s of cables to be jointed shall be tested as per clause 16E.2.8.1.  Unless the insulation resistance values are satisfactory, jointing shall not be done.

(iii) Cores of the cables must be properly identified before jointing.

(iv) Where a cable is to be jointed with the existing cable, the sequence should be so arranged as to avoid crossing of cores while jointing.

(v) Whenever the aluminium conductor is exposed to outside atmosphere, a highly tenacious oxide film is formed which makes the soldering of aluminium conductor difficult.  This oxide film should be removed by using appropriate type of flux.

(vi) The clamps for the armour shall be clean and tight.

16E.2.7.7 Joint types - The type of joint shall be suitable for the type of cable as per Table V and shall be specified in the Tender Schedule of Work.

16E.2.7.8 Jointing procedure - While it would be necessary to follow strictly the instructions for jointing furnished by the manufacturers of cables and joint kits, a brief on the jointing procedures is given for general guidance in Appendix F.

16E.2.8 Testing

16E.2.8.1 Testing before laying - All cables, before laying, shall be tested with a 500V Megger for cables of 1.1KV grade, or with a 2500/5000V Megger for cables of higher voltage.  The cable cores shall be tested for continuity, absence of cross phasing, insulation resistance from conductors to earth / armour and between conductors.

16E.2.8.2. Testing before backfilling - All cables shall be subjected to the above mentioned tests, before covers and back filling and also before taking up any jointing operation.

16E.2.8.3. Testing after laying.

(i) After laying and jointing, the cable shall be subjected to a 15 minutes pressure test.  The test pressure shall be as given in Table VI.  DC pressure testing may normally be preferred to AC pressure testing.

(ii) In the absence of facilities for pressure testing as above, it is sufficient to test for one minute with 1,000V megger for cables of 1.1KV grade and with 2,500 / 5,000 V megger for cables of higher voltages.

The distance up to which different sizes of U.G  aluminium conductor cables can be used for different current ratings for 8 volts when laid in ground (PVC insulated, PVC sheathed, 3 core or 4 core) cable grading is 1.1 KV) (Maximum conductor temperature – 70 degree c)

Table A (Clause 16E.2.4.3)

Current

Distance in Meters for the following cable sizes in Sq. mm.

Amp.

6

10

16

25

35

50

70

95

120

150

185

240

300

5

165

260

415

725

895

1300

1925

2360

3065

3555

4300

5770

6460

10

80

130

205

360

50

650

960

1180

1530

1775

2150

2885

3230

15

55

85

140

240

300

430

640

785

1020

1185

1430

1920

2155

20

40

65

100

180

225

325

480

590

765

890

1075

1440

1615

25

30

50

80

145

180

260

385

470

610

710

860

1150

1290

30

25

40

70

120

150

215

320

390

570

590

715

960

1075

40

20

30

50

90

110

160

240

295

380

445

535

720

805

50

-

25

40

70

90

130

190

235

305

355

430

575

645

60

-

-

35

60

75

110

160

195

255

295

355

480

535

70

-

-

30

50

65

90

135

165

215

255

305

410

460

80

-

-

-

45

55

80

120

145

190

220

265

360

405

90

-

-

-

40

50

70

105

130

170

195

235

320

360

100

-

-

-

35

45

65

95

115

150

175

215

290

320

110

-

-

-

-

40

60

85

105

140

160

195

260

290

120

-

-

-

-

35

55

80

95

125

145

180

240

270

130

-

-

-

-

-

50

75

90

115

135

165

220

250

140

-

-

-

-

-

45

70

80

110

125

150

205

230

150

-

-

-

-

-

-

65

75

100

115

140

190

215

160

-

-

-

-

-

-

60

70

95

110

130

180

200

170

-

-

-

-

-

-

55

70

90

105

125

170

190

180

-

-

-

-

-

-

50

65

85

100

120

160

180

190

-

-

-

-

-

-

-

60

80

90

110

150

170

200

-

-

-

-

-

-

-

60

75

90

105

145

160

225

-

-

-

-

-

-

-

-

65

80

95

125

145

250

-

-

-

-

-

-

-

-

-

70

85

115

130

275

-

-

-

-

-

-

-

-

-

-

80

105

115

300

-

-

-

-

-

-

-

-

-

-

70

95

105

                           
                           
                           

Note 1: - PVC insulated electrical cable for voltage grade up to 1.1KV is based on 8 volts drop

This table is based on current and resistance as given in M/s. Incab’s Cable and Table (April 1964.Table No. 17 and 33).

The distances are given in meters and after rounding.

The conditions of installation of cable is ground temperature of 15 degree C.

Note 2 - For Temperature correction please see as detailed below - When the voltage drop and length is constant then to find the size of cable for following temperature multiply the respective current ratings of the chart to obtain the calculated load current by the following factors and then see the size according to that ratings which was multiplied by the temperature factor.

Ground Temp. 20o C 25o C 30o C 35o C
Rating Factors 0.95 0.90  0.85 0.80

Table B (Clause 16E.2.4.3)

Short circuit ratings In KA for 11 KV (Screened) paper insulated aluminium conductor cables to IS: 692-1973

Nominal Area Sq.mm.

0.1 Sec.

0.2 Sec.

0.5 Sec.

1.0 Sec.

2.0 Sec.

5.0 Sec.

1.5

0.376

0.260

0.164

0.116

0.084

0.065

2.5

0.604

0.427

0.270

0.191

0.135

0.085

4

0.936

0.663

0.419

0.286

0.209

0.132

6

1.46

1.04

0.656

0.463

0.328

0.207

10

2.54

1.78

1.02

0.795

0.512

0.356

16

3.70

2.62

1.66

1.17

0.830

0.524

25

6.37

4.53

2.87

2.40

1.44

0.91

35

8.04

5.68

3.60

2.54

1.80

1.14

50

11.3

7.96

5.04

3.56

2.54

1.59

70

17.5

12.3

7.81

5.52

3.90

2.47

95

22.5

15.9

10.1

7.12

5.00

3.18

120

28.8

21.8

12.9

9.10

6.44

4.07

150

38.1

24.0

15.1

10.7

7.56

4.80

185

42.4

30.0

18.9

13.4

9.47

6.00

225

52.8

37.4

23.6

16.7

11.8

7.46

140

61.0

43.2

27.3

19.3

13.6

8.63

300

70.0

49.5

31.3

22.1

15.6

9.88

400

101.0

71.1

45.0

31.8

22.5

14.4

500

118.0

83.5

52.8

37.3

26.4

16.7

625

150.0

106.0

67.0

47.4

33.5

21.2

800

187.0

132.0

83.6

59.1

41.8

26.4

1000

239.0

169.0

107.0

75.5

53.4

33.8

Above short circuit ratings are based on the following assumptions.

  1. Conductor temperature prior to short circuit – 70 Degree C.
  2. Conductor temperature at the termination of short circuit. - 160 Degree C.

Table I (C)

(Clause 16E.2.4.3)

Short circuit ratings in KA for 11kv (belted), 22 KV & 33 KV paper insulated aluminium conductor to IS:  692-1973

Nominal Area Sq.mm.

0.1 Sec.

0.2 Sec.

0.5 Sec.

1.0 Sec.

2.0 Sec.

5.0 Sec.

16

3.80

2.69

1.70

1.20

0.853

0.538

25

6.54

4.65

2.95

2.10

1.48

0.935

35

8.26

5.84

3.70

2.61

1.85

1.170

50

11.60

8.18

5.18

3.66

2.61

1.630

70

18.00

12.60

8.02

5.67

4.01

2.500

95

23.10

16.30

10.40

7.31

5.14

3.270

120

29.60

22.40

13.30

9.35

6.62

4.180

150

39.10

24.70

15.50

11.00

7.77

4.930

185

43.60

30.80

19.40

13.80

9.73

6.160

225

54.20

38.40

24.20

17.20

12.10

7.660

240

62.70

44.40

28.00

19.80

14.00

8.870

300

71.90

50.90

32.20

22.70

16.00

10.100

400

104.00

73.00

46.20

32.70

23.10

14.800

500

121.00

85.80

54.20

38.30

27.10

17.200

625

154.00

109.00

68.80

48.70

34.40

21.800

800

192.00

136.00

85.90

60.70

42.90

27.100

1000

246.00

174.00

110.00

77.60

54.90

34.700

Above short circuit ratings are based on the following assumptions:

  1. Conductor temperature prior to short circuit - 65 Degree C.
  1. Conductor temperature at the termination of short circuit -160 Degree C.

Table D (Clause 16E.2.4.3)

Permissible maximum short circuit current ratings for XLPE cables

Conductor area

Short circuit ratings for one second duration

Sq. mm.

Copper conductors

Aluminium conductors

A

B

16

2570

1730

25

3970

2670

35

5500

3690

50

7800

5220

70

10850

7400

95

14600

9740

120

18400

12200

150

23000

15200

185

28200

18700

240

36400

24200

300

45300

30100

400

60200

39900

500

74800

49800

630

92700

62000

800

---

78800

1000

---

97800

Initial conductor temperature.- 90 Degree C.

Final conductor temperature.- 250 Degree C.

Note - For large currents the force between the conductors must be considered especially when single core cables are used.

Table II

(Clause 16E.2.6.1 (ii))

Minimum bending radius – paper insulated cables and XLPE cables.

System Voltage

Minimum Bending Radius

Single Core

Multi core

 

Unarmoured

Armoured

11 KV

20 D

15 D

12 D

22 KV

25 D

20 D

15 D

33 KV

30 D

25 D

20 D

“D” is the overall diameter of the cable.

Table III

Clause 16E.2.6.10.3(I) & 16E.2.6.11.4)

Clamping of cables on surface

Types of cables

Size

Clamping by

Fixing Intervals

KV

Up to and including 25 sq. mm.

Saddles 1mm thick

45 cm

KV & HV

35 sq. mm. To 120sq. mm.

Clamps 3mm thick 25mm wide

60 cm

KV & HV

150 sq. mm and above

Clamps 3mm thick 40 mm wide

60 cm

Note - The fixing intervals specified apply to straight runs.  In the case of bends, additional clamping shall be provided at 30cm from the center of the bend on both sides.

Table IV

Clause 16E. 2.6.11.2(iv))

Schedule of permissible loads for cable trays

The figures given below represent the maximum permissible uniformly distributed load in kgs, per running meter for different unsupported free spans.

Channel Section Size

Unsupported Free Span

Width (mm)

Depth (mm)

Thickness (mm)

800 mm

1200 mm

1800 mm

2500 mm

100

50

1.6

1430

355

156

87

150

50

1.6

1458

362

159

88

225

50

1.6

1498

371

160

89.4

300

50

1.6

1540

380

162

91.3

375

50

2.0

1955

483

210

116.7

450

50

2.0

1958

483

210

110.7

600

50

2.0

1964

481

208

110.4

300

62.5

2.0

2680

664

290

161.3

375

62.5

2.0

2685

664

290

158.9

450

62.5

2.0

2689

664

289

161.3

600

62.5

2.0

2698

664

289

157.1

750

62.5

2.0

2707

666

287

155.7

900

62.5

2.0

2716

667

287

153.7

600

75.0

2.0

3491

861

377

206.5

750

75.0

2.0

3513

868

377

205.02

900

75.0

2.0

3535

874

378

205.02

Note: - i) The maximum permissible load at mid-span may be obtained from the formula.

P = (1/2) x U x S

Where P = Maximum permissible point load in kgs. at mid-span.

U = Maximum permissible uniformly distributed load in kg. per running meter, &

S = The particular free span in meter.

ii) In case of a span not listed above the corresponding maximum permissible uniformly distributed load may be found from the formula      

U = 4(U at 2 m. span) /S2

iii) Free spans exceeding 16 ft. are not recommended.

Table V

Type of cable joints (Clause 16E.2.7.7)

PVC Cables

1.1 KV

XLPE cables

1.1 KV

PVC cables

11KV

XLPE cables

11KV & above

Pilca cables

11KV & above

1

2

3

4

5

Yes

No

Yes

No

No

No

No

No

No

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Table VI

Test pressure in KV (Clause 16E.2.8.3)

Working volts in KV

AC 15 Minutes test

DC 15 Minutes test

 

Between conductors

Conductor to earth

Between conductors

Conductor to earth

Upto

 

 

 

 

1.1

2.0

2.0

3.0

3.0

3.3

6.0

3.5

9.0

5.0

6.6

12.0

7.0

18.0

10.5

11

20.0

11.5

30.0

17.5

22

40.0

23.0

60.0

35.0

33

-

-

-

60.0

16E.3. SPECIFICATIONS FOR OVERHEAD LINE WORK

16E.3.1 Scope - This section covers the requirements for installation, testing and commissioning of overhead lines for power supply up to and including 33 KV, service connection, including the materials used therein.

16E.3.2 Materials and construction

16E.3.2.1 Supports

16E.3.2.1.1 Types of supports

i) Supports for overhead lines shall be any of the following types, as specified in tender documents. (In particular cases, any other type of supports may also be specified)

  1. Steel tubular poles,
  2. Steel rail poles,
  3. Cement concrete (RCC/PCC) poles, and
  4. Fabricated poles.

ii) Supports shall be of adequate strength and conform to Rule 76 of the Indian Electricity Rules.  The sizes of pole sections shall be selected in accordance with relevant BIS specifications to suit the requirements of loading.

iii) Length of supports shall be specified in tender papers, so as to satisfy the relevant functional requirements like the ground clearance of lines when installed, street lighting etc.

16E.3.2.1.2 Steel tubular poles

i) These shall conform to IS: 2713(Parts 1 to 3)-1980. These shall be of seamless/swaged and welded type in three stepped sections as specified.

ii) The pole shall be complete with cap and base plate.

iii) Unless otherwise specified, one sixth of the length of the pole plus 30cm from its base shall be coated with black bituminous paint, both internally and externally.  The remaining portion of the pole shall be painted with one coat offered oxide primer on its external surface.

16E.3.2.1.3 Steel rail poles -  These shall conform to the standard specifications of the Indian Railways.

16E.3.1.1.4 Cement concrete (RCC/PCC) poles

i) Reinforced cement concrete (RCC) and pre-stressed cement concrete (PCC) poles shall conform to IS: 785-1964 and IS: 1678-1978 respectively.  These shall carry an earth bond in accordance with Rule 90 of the Indian Electricity Rules.

ii) The dimensions shall be as per designed conforming to local requirements.

iii) Concrete poles shall be treated with suitable chemicals like silicate for the portion to be buried in ground where the subsoil water level is high and / or acidic as in coastal areas.

iv) The selection of the pole shall be done in accordance with IS: 7321-1974.

16E.3.2.1.5 Fabricated poles - These shall be made from Galvanised Iron (GI) pipes or mild steel (MS) pipes (seamless or ERW), or fabricated from structural steel.  Details of such supports shall be specified in tender papers.

16E.3.2.2 Line materials

16E.3.2.2.1 Cross arms

i) (a) The cross arms for overhead lines shall be made either of MS angle iron of size not less than 50mmx50mmx6mm thick (4.5kg/m) for LV/MV lines and 65mmx65mmx6mm thick (5.8kg/m) for 11 KV lines, or of MS channel iron of size not less than 75mmx40mmx4.8mm thick(7.14kg/m), (for LV/MV/11KV lines0 as specified.  The channel iron cross arms may be straight type for LV/MV, and straight or V-cross arms for 11KV, as specified.

(b) The cross arms for overhead lines for 22KV/33KV shall be fabricated either from 75mmx40mm (7.14lg/m), or from 100mm x 50mm(9.56 kg/m) channel iron, as specified fabricated as V-cross arms.

ii) (a) The length of cross arms shall be suitable for accommodating the required number of insulators on them with the spacing of conductors in accordance with clause 16E.3.3.3.1.

(b) Where guard wire cradle is specified to be fixed directly to the cross arms (without additional brackets), the length of cross arms supporting the cradle shall be such that the clearances specified in clause 16E.3.3.3.7 is satisfied.

(c) The cross arms shall have holes for fixing on to the poles and for taking insulator pins, wire guards etc., as required.  A minimum distance of 5cm for LV/MV lines and 10cm for HV lines shall be left from the center of the extreme insulator pin hole to the end of the cross arm.

(d) Table VII indicates the cross arm lengths based on the above requirements.

iii) Unless otherwise specified, a triangular configuration shall be adopted for HV overhead lines.  Where specified, the cross arm supporting the lower two conductors over pin insulators shall be provided with 50mmx50mmx6mm thick (4.5kg/m), angle iron bracket duly welded to it so that the cross arms are double clamped to the poles for rigidity.  However, such double clamping arrangement shall necessarily be provided in cases of HV overhead lines, where in-line configuration is adopted, whether or not so specified in tender paper.

iv) The cross arms shall be complete with pole clamps made of MS flat of size not less than 50mmx6mm with necessary bolts, nuts and washers.

16E.3.2.2.2 D-Iron clamps

i) Where vertical configuration is specified in tender documents for MV overhead lines, the conductors shall be supported on shackle insulators which shall be fixed to the poles by means of D-shaped clamps made of MS flat of size not less than 50mmx6mm and galvanised.

Note - Vertical configuration shall not be adopted for HV lines.

ii) The dimensions of D-iron clamp shall be such as to hold a 75mm high and 90mm (nominal) diameter shackle insulator.

iii) The D-iron clamp shall be complete with pole clamp, made of 40mmx6mm flat iron and necessary GI bolts, nuts and washers and holes for fixing insulator pins.

16E.3.2.2.3 GI straps

i) Where D-iron clamps are not specified for shackle insulators, a pair of strap plates of hot dip galvanised iron of size 40mmx3mm thick and length 23 cm shall be used.

ii) The fittings shall conform to IS: 7935 – 1975.

16E.3.2.2.4 Pole top bracket - The pole top bracket for supporting a single pin type insulator shall be made of flat iron 50mm x 8mm as shown in figure – 6C.

16E.3.2.2.5 Cradle guard bracket - Where brackets are used for supporting cradle guards on cross arms, these shall be made of 50mm 6mm flat iron, shaped such that clearance with the line conductors as specified in 3.3.3.7 is achieved.  These shall be welded to the cross arms or fixed to them with double bolts nuts and washers, thus preventing its movement sideways.

16E.3.2.2.6 the nuts bolts and washers used for fixing of hardware accessories shall be cadmium passivated or galvanised.

16E.3.2.3 Stay sets

16E.3.2.3.1 Locations and number

i) Stays shall be provided on to the poles at locations where a pull from the conductors on one direction is likely to be experienced such as terminal poles or at the deviation point(s) of the line from straight run etc.  These shall be specified in the drawings.

ii) The stays shall be provided on the side of the pole opposite to the likely direction of pull from the line i.e., opposite to where the shackle/disc insulators are provided.  In the case of deviations from straight runs, the stays shall be provided opposite to the side of deviation and preferably on the bisection of the angle of deviation.

iii) The number of stay sets to be provided shall be decided depending on the likely pull to be experienced on the pole, dictated by the length of span, number and size of conductors etc.

16E.3.2.3.2 Construction

i) A stay set shall consist of stay rod, anchor plate, bow tightened or turnbuckle, thimbles, stay wire, strain insulator and stay clamp.

ii) All components of the stay set assembly shall be of MS and galvanised.

iii) The stay rod shall be not less than 1.80m long and 19mm dia.  The stay rod shall be with stay clamp in case turnbuckle is used instead of bow tightened.

iv) The anchor plate shall be not less than 45cmx45cmx7.5mm thick.

v) The stay wire shall be either 7/4mm dia or 7/3.15mm dia GI as specified and generally conform to grade 2 of IS: 2141-1979.

vi) The strain insulator shall conform to IS: 5300-1969.

The recommended types of strain insulators for use on stay wires of overhead lines of different voltage levels are as follows.

Line voltage

Designation of insulation

240V/415V

“A”

11KV/33KV

“C”

(2 Insulators to be used / line for 33KV)

16E.3.2.4 Struts

Struts are provided wherever stays cannot be provided due to any obstruction, or where the stays themselves can cause an obstruction.  A strut is normally provided opposite to the direction in which a stay would have been provided.

Normally, one strut would be adequate for each pole.  However, where the angle of deviation is large, two struts may be required for each pole at the point of deviation.

A strut shall generally consist of a pole of the same section, which it supports, or slightly lighter as specified in the contract.

16E.3.2.5 Insulators & insulator fittings

16E.3.2.5.1 Insulators – general

i) Porcelain insulators shall conform to IS: 1445-1977 for lines below 1000V and to IS: 731-1971 for lines with voltage greater than 1000V.

ii) The insulators shall be vitreous throughout and non-absorbent.  The exposed surface shall be glazed.

iii) These shall have adequate mechanical strength, high degree of resistance to electrical puncture and to climate and atmospheric attack.

16E.3.2.5.2. Types of insulators

i) The insulator shall be any of following types, as specified.

  1. Pin/Shackle insulators for LV/MV overhead lines.
  2. Pin/Disc type insulators for HV overhead lines.

ii) Shackle insulators shall be used when the configuration of conductors (in MV lines) is vertical.  Shackle/disc insulators shall also be erected on cross arms of supports in case of long spans, deviation from straight line by more than 30 degrees, terminal positions, junction poles etc.

16E.3.2.5.3 Size of insulators

i) The minimum size of shackle insulator for LV/MV overhead lines shall be 90mm dia x 75mm high.

ii) The minimum size of pin insulator for LV/MV overhead lines shall be 65mm dia x 100mm high.

iii) The pin insulator shall be suitable for 12mm cordeau threaded GI pin, nuts and washers.

16E.3.2.5.4 Insulator fittings

i) The insulator fittings shall comply with IS: 2486 (Part-1)-1971 and IS: 2486 (Part 2)-1989 for 1KV and 33KV insulators, and with IS: 7935-975 for LV/MV insulators.

ii) Pin insulator fittings

a) The pins suitable for the pin insulators for the LV and MV overhead lines shall have a stalk length 135 mm shank length of 125mm and minimum failing load of 2KN.

b) The pins suitable for 11KV pin insulator shall have stalk length of 165mm and shank length of 150mm and minimum failing load of 5 KN.

c) The pins suitable for the 33 KV pin insulators shall be large steel head type L 300 N as per IS 2486 Part II having stalk length of 300mm and shank length of 150mm and minimum failing load of 100KN.

d) The pins for pin insulators shall conform to the requirements in Table VII.

e)The pins shall be of single piece MS without joints, obtained by the process of forging.

f)The pins, nuts and washers, shall be galvanized.

g)The threads of nuts and tapped holes shall be cut before galvanizing and shall be well oiled or greased.

iii) Disc insulator fittings

a) The insulator fittings for disc insulators shall be either of ball and socket type or clevis and tongue type depending upon the type of disc insulators specified in the tender documents.

b) The strain clamps for string insulators shall be suitable for ACSR conductors 7/3.55mm (50sq.mm aluminium area), 7/4 .09 mm (80sqmm aluminium area) and 6/4.72mm and 7/1.52mm (100 sq.mm aluminium area), as required.  The ultimate strength of the clamps shall not be less than 41Kn.

16E.3.2.6. Conductors

16E.3.2.6.1 Types of conductors - The conductors shall be any of the following types as specified.

a) All aluminium stranded conductors conforming to IS: 398 (Part-I)-1976.

b) Aluminium conductors’ galvanised steel reinforced, conforming to IS: 398 (Part-2)-1976.

c) Aluminium alloy stranded conductor, conforming to IS: 398 (Part-4)-1979.

Note - Broad details of some conductors are given in Table VIII.

16E.3.2.6.2. Choice of conductors

i) The physical and electrical properties of different conductors shall be in accordance with relevant Indian Standards.

ii) All conductors shall have a breaking strength of not less than 350kg.  However, for LV lines with spans less than 15m, conductors with breaking strength of not less than 140kg may be used.

iii) The size of conductors for a line shall be selected considering the power to be transmitted, length of line, line voltage, permissible voltage regulation etc.

The size(s) shall be specified in contract.

iv) No conductor of cross section smaller than the following shall be used for distribution lines.

Voltage of line

All aluminium

Stranded

ACSR

Aluminium Alloy stranded

LV/MV

7/2.21mm

6/1/2.11mm

7/2.09mm

(20sq.mm Al area)

11KV/33KV

-----

6/1/2.11mm

7/2.56mm

(30sq.mm Al area)

16E.3.2.7. Binding material - Binding of conductors with the insulators shall be done with 2.6mm (12 SWG) soft aluminium conductors.

16E.3.2.8. Guard wire

i) Guard wire shall be of GI 4mm dia (8SWG), AAC (7/3.10mm) or ACSR (7/2.59mm).  Cross lacings may be of GI wire (minimum 3.15mm dia) or scrap lengths of AAC or ACSR conductors used in the line.  It shall have a minimum breaking strength of 635kg, in accordance with Rule 88 of the Indian Electricity Rules.

ii) It shall also be of sufficient current carrying capacity to ensure rendering the line dead without the risk of fusing the guard wire or wires, till the contact of the line weir has been removed.

iii) Protective guarding of overhead lines shall comply with the requirements of Rule 88 of the Indian Electricity Rules.

16E.3.2.9 Earth wire - The size of the continuous earth wire shall not be less than 4mm (8SWG) GI.

16E.3.2.10. Lightning arresters

These shall conform to IS: 3070 (Part-1)-1985.

3.2.10.1. Types of lightning arresters

i) Horn gap type arrester. - This type of arrester shall be used for LV/MV lines as specified.

ii) Surge diverter- Single pole units enclosed in GI case for outdoor mounting shall be used for system not exceeding 650V.

iii) Non-linear Resister type lightning arrester

a) This type of arrester shall be used in an effectively earthed system with a nominal line voltage of 11KV/22KV/33/KV.

b) The rated voltage of the lightning arresters suitable for 33KV lines shall be 30KV (RMS) with nominal discharge current rating of 10KA (Station class) in lines.

c) The rated voltage of lightning arresters suitable for 11KV lines shall be 9KV (RMS) with a nominal discharge current rating of 5KA.

d) The system shall be effectively earthed (coefficient of earth not exceeding 80 percent as per IS: 4004-1985) with the neutrals of all the transformers directly earthed.

16E.3.2.10.2. the lightning arrester system shall conform to Rule92 of the Indian Electricity Rules.

16E.3.2.11 Paint

i) Only paints of approved make and shade conforming to relevant Bureau of Indian Standards shall be used.  These shall be in original containers of the manufacturers.

ii) Primer coats shall be with red oxide paint.

16E.3.3 Line layout

16E.3.3.1 Route

16E.3.3.1.1 General - The route of overhead lines shall be adopted considering the following: -

i) The route of LV/MV overhead lines shall generally follow the layout of roads except in particular stretches specified.  However, HV lines can be routed through cross-country also, especially in remote locations.

ii) As far as possible, the present and future requirements of other agencies and utility services affected shall be considered, both for the line and for stays/struts.

iii) Overhead lines shall not be erected in the vicinity of Aerodromes until the Aerodrome authorities have approved in writing the route of the proposed lines in accordance with Rule 84 of the Indian Electricity Rules.

iv) The route shall be so chosen as to avoid use of struts and continuous curve in the overhead line as far as possible.

16E.3.3.1.2 LV / MV lines - The following shall be considered for locating the poles of LV/MV overhead lines: -

i) Poles shall be located alongside roads, on the road berm, a little away from the road edge and drain.

ii) There shall be a pole located at each road junction..

iii) Junction of main road and a service lane shall be preferred for location of pole so that the street light will benefit the service lane as well.

iv) Front of entrance to building shall be avoided for locating poles.  However, in the case of residential colonies, the street lighting poles shall be located such that the entrances to the blocks are lit up, as far as possible.

16E.3.3.1.3. The route of overhead lines and pole locations shall be indicated in tender drawings, Modifications, if any, required to suit site conditions can be done only with the prior approval of the engineer.

16E.3.3.1.4. Way leave - Way leave for the proposed route of overhead line shall be arranged by the department from the appropriate authorities, such as State Public Works, Drainage, Public Health and Water works / Municipal Authorities, Telephone and Telegraph, Gas works, Railways, Director General of Civil Aviation, other undertakings, owners of properties etc. as may be required.

16E.3.3.1.5 Cutting of trees etc. - Where the route of overhead lines involves a need to cut branches of trees or clearing of other construction that may come in the way of the overhead lines, this may only be done with the prior approval of the engineer and with the permission of the owners concerned.

16E.3.3.2 Spacing of poles - Spans of overhead lines shall be decided considering the following: -

i) Clearances as laid down in clause 3.3.3 shall be satisfied, for the pole length and conductor sizes selected.

ii) Requirements of Rule 85 of the Indian Electricity Rules shall be complied with.

iii) Where street lightning is provided with overheard line system, the span shall be such that lighting is adequate, but the span may not exceed 45 m.

16E.3.3.3. Clearances - The spacing of conductors depends on their disposition and is determined by the line voltage, sag, span, swing amplitude and type of structure.  It shall comply with the requirements given in table IX.

The minimum clearance of the lowest conductor above ground level across a street, along a street and elsewhere for different voltage systems shall be in accordance with Rule 77 of the Indian Electricity Rules.

The minimum clearance of overhead lines and service lines for different voltage systems from buildings shall be in accordance with Rules 79 and 80 of the Indian Electricity Rules.

When conductors of different voltage are erected on the same support, Rule 81 of the Indian Electricity Rules shall be complied with.  The clearance between LV/MV and 11KV lines shall be not less than 1m.

A clearance of not less than the height of the tallest support may be maintained between parallel overhead lines on different supports.

When two overhead lines cross, the crossing shall be made at right angles as far as possible.  The vertical clearance between LV/MV lines and 11KV lines shall not be less than 1.25m.  The clearance between LV/MV lines and 22KV/33KV lines shall not be less than 2m.

The minimum clearance between guard wire and LV/MV line shall be 10cm and between guard wire and 11KV/33KV line shall be 30cm.

Rules 86 and 87 of the Indian Electricity Rules shall be followed for clearance between power and telecommunication lines and shall not be less than 1.5m for lines up to 11KV, and 2m for lines above 11KV and up to 33KV.

Crossing of Railway lines shall be done as per specifications for crossings and in consultation with the Railway authorities.

16E.3.4 Excavation for foundation

16E.3.4.1. General

The locations of supports, stays and struts shall be pegged accurately before the excavation work is taken up.

Care shall be taken to see that the minimum amount of soil is disturbed so as to take advantage of the bearing capacity of the virgin ground, (and that the pits are not oversized) after taking into consideration the size of the foundation.

Pits shall not be left unfilled for unduly long periods so as to avoid accidents.  While being kept open, protective measures such as suitable caution signs, caution lights, barricading etc. as necessary should be provided near the pit(s) to warn the pedestrians / vehicular traffic, till such time the pit is back filled and surface leveled.

The pit for support/stay/strut shall be filled up or concreted only in the presence of the engineer in charge of the work.

16E.3.4.2 Excavation for supports

The depth of pit shall be such that normally 1/6th of the length of the pole is buried in the ground.  The size of the pit shall be suitable for the foundation of the supports as per clause 3.5.1.

The pits should be excavated in the direction of the lines.

16E.3.4.3 Excavation for stays

The position of pit shall normally be such that the stay makes an angle of 30 to 60 degrees with the support. (Higher angle is preferred).

The depth of pit shall be such that normally a length of 45cm of stay rod shall project above the ground level.  The size of the pit shall be suitable for the foundation of stay as per clause 16E.3.5.2.2.

16E.3.4.4 Excavation for struts

The pit for struts shall be located at a distance of not less than 1.8m from the pole.

The depth of pit shall be such that at least 1.2m of the strut is buried in the ground and the size of the pit shall be suitable for the foundation of the struts.

16E.3.5 Erection

16E.3.5.1 Erection of supports - The supports shall be correctly aligned before concreting or the back filling of the pit, as the case may be.

All supports including RCC and PCC poles shall be erected over a cement concrete 1:3:6 (1 cement: 3 coarse sand: 6 graded stone aggregate of 40mm nominal size) bed of 15cm thick, either cast in situ or precast and laid in the excavated pit, irrespective of the provision of a base plate.  The area of this cement concrete bed shall be 0.35 sqm for steel tubular/rail and other steel poles and 0.5sqm for RCC/PCC poles.

The supports shall be erected in the following manner depending on the type of support. 

a) Steel tubular / steel rail / other steel poles shall be fixed in cement concrete 1:3:6 (1cement: 3 coarse sand: 6 graded stone aggregate of 40mm nominal size) foundation with not less than 20cm thick layer of the cement concrete all round the support, the foundation being continued up to 15cm above ground level and tapered suitably into a collar.

b) RCC/PCC poles shall be erected with a filling of, brick or stone ballast, with excavated earth as binder, well consolidated.  The ramming shall be done in layers of 20cm water, as necessary shall be used during this operation.   The sectional area of the consolidated ballast foundation shall not be less than 0.5sqm including the area occupied by the support itself and shall be maintained upto the ground level.

RCC/PCC poles, except where specified otherwise, do not require any setting in concrete.  No cement concrete collar is also necessary for such types of poles.

After concreting, the excavated earth shall be back filled and well consolidated in layers of 20cm.

Watering of concreted foundation above ground level and curing for at least two weeks shall be done by using moist gunny bags etc., before loading the pole.

16E.3.5.2 Erections of stay sets and struts - The stay rod will be set in position in the excavated pit, the rod being straight or bent as laid down in clause 16E.3.5.2.as the case may be.  The correct positioning and setting of stay set is essential.

i) The straight stay rod with the anchor plate shall be embedded in cement concrete 1:3:6 (1 cement: 3 coarse sand: 6 graded stone aggregate of 40mm nominal size) not less than 0.28cum in content in such a way that the top of the concrete block is well below the ground level to prevent uprooting of the stay rod.

ii) Alternatively, the bent stay rod shall be embedded vertically in cement concrete 1:3:6  (1cement: 3 coarse sand: 6 graded stone aggregate of 40mm nominal size) foundation 42cm x 42cm in section, the anchor plate lying over 15cm thick cement concrete.  The bend in the stay rod shall be such that the stay wire and the bent portion of stay rod are in correct alignment.  Care must be taken to avoid sharp bend or damage to galvanization.

After the concrete has set, back filling shall be done with excavated earth and ramming in layer of 20cm using water as required.

The top surface of concrete around the stay rod shall be cured by means of moist gunny bags etc.  for at least 2 weeks before loading the stays.

The stay clamp shall be located just below the lowest cross arm on the pole so that it is as close to the center of gravity of the pull of the overhead conductors as possible.  In the case of poles with vertical formation LV/MV line, special bracket.

One end of the stay wire shall be fixed to the bow tightened or the stay grip of the stay rod and the other end to the clamp fixed to the pole by means of well spliced joints using GI thimbles.  A string insulator shall be provided approximately at the middle of the stay wire.  Turn buckle, when used, shall be installed at the top of the stay wire.

The stay wire shall be connected and bonded properly to the continuous earth wire.

Where double sets are specified due to large pulling force, these shall as far as possible be set parallel to each other or shall be so placed that one does not reduce the strength of the other by suitable spacing between the two pits.

The stay rod, where so specified in tender documents, shall be protected with GI pipe, which shall not be less than 5cm dia and 1.5m long, placed so as to be 0.6m. below ground.  The length of the stay rod shall accordingly be increased.

The stay rod cannot be erected in accordance with the above clauses due to the existence of a road or an obstruction etc., bow stay, fly stay or strut, whichever is suitable to the location shall be used, as may be directed by the engineer.

Bow stay

i) Bow stay shall consist of a brace made of 50mm x 50mm x 6mm thick angle iron with a 5cm pulley on the outer end or a hole, to allow for free motion of stay wire, in addition to other accessories required for stay set mentioned in clause 16E.3.2.3.

ii) The stay wire shall be clamped to the pole on the top and the other end to a stay rod, passing over the pulley or through the hole in the brace.  The brace shall be clamped at about 2/3rd height of the pole from the ground level.  This can be increased if so required, but in no case should be brace be closer to the lowest cross arm/D-Iron clamp by less than 1m.  The stay rod shall be embedded in cement concrete foundation in the usual manner, as near as possible to the pole at about 1m from the pole.

iii) Where the site condition does not permit allowing a space of 1m as above, the bottom end of the stay wire may be clamped to the pole near ground.

Fly stay

i) The fly stay shall consist of a fly pole, stay wire running over the obstruction and the usual stay arrangement for the fly pole.

ii) The stay wire crossing the obstruction shall be clamped at one end to the top of the fly pole with a turnbuckle.  The fly stay shall be taken at such a height as may be directed by the engineer.  When a fly stay is taken across a road, it shall conform to traffic regulations.

Erection of struts - The strut shall be buried in the ground as mentioned in clause 16E.3.4.4 and erected in the same manner as the pole.  It shall rest on the pole squarely and shall be firmly secured by GI clamp.

16E.3.5.3 Erection of line materials

16E.3.5.3.1 Cross arms

i) Cross arms shall be clamped to the support properly, taking into consideration the orientation of the lines.

ii) Double clamping shall be provided where required, as laid down in clause 16E.3.2.2.1 (iii).

16E.3.5.3.2 D-Iron clamps

i) D-Iron clamps shall be fixed to the support either by a through bolt and nut arrangement, or by a suitable GI pole – clamp, bolt and nut.

ii) These shall be installed vertically on the supports complying with the required vertical clearance between conductors.

16E.3.5.4 Erection of insulators - Pin insulators and shackle / disc insulators shall be erected on cross arms.  Where D-Iron clamps or GI straps are specified, shackle insulators shall be erected in them.

Where so directed by the engineer in charge, pin insulators may be provided above in addition to disc / shackle insulators over the cross arm, so that the line conductors are properly routed with adequate clearances.

Care shall be taken that insulators are not damaged during handling and erection.  Damaged insulators shall not be used for any reason.

3.5.5 Stringing of conductors

3.5.5.1 Handling

i) The general precautions during storage and handling shall be taken in accordance with the clause 16E.2.5 of these general specifications.

ii) Particular attention is necessary when handling aluminium (AAC/ACSR) conductors because of their relative softness.

iii) While paying off, the conductors shall be taken from the top of the drum and the drum shall be rotated in the direction of the arrow marked on it.

iv) Care shall be taken during paying off to avoid damage due to contact with steel works, fence etc. by giving soft wood protection, using wooden rollers etc.

When the work is being carried out adjacent to and / or for connecting to an existing system in operation, adequate safety precautions for isolation discharging, earthing etc. shall be taken on the existing line to ensure that the lines do not inadvertently get charged from live supply.  Where “Permit to work: system is in vogue, the prescribed safety procedure shall be complied with.

Appropriate tools only shall be used for the stringing work.  All the strands of the conductor must be gripped securely when pulling the conductor. 

During the stringing operation, standard sag tables or charts shall be followed.

Care shall be taken to see that there are no kinks in the conductors.

Angle or section points shall be selected while pulling the conductors.  While stringing, conductors of sufficient length shall be kept at shackle terminations for making jumpers.

After stringing the conductor, it shall be clamped permanently with shackle or strain clamps.

Joints if any in conductors shall be staggered.  Mid span joints in conductors shall however be generally avoided.

16E.3.5.6. Binding of conductors - The binding of conductors to insulators shall be sufficiently firm and tight to ensure that no intermittent contacts develop.

The ends of the binding wire shall be twisted in a closely spaced spiral around the conductor to ensure good electrical contact and to strengthen the conductor.

16E.3.5.7 Jumpers - Jumpers shall be neat and as far as possible symmetrical to the run of conductors.  These shall be so made as to prevent occurrence of fault due to wind or birds.

Where necessary, the jumpers shall be with insulated conductors or taken on intermediate pin insulators as specified.  For HV lines, the jumpers should be so arranged that there is a minimum clearance of 30 cm under maximum deflection condition due to wind between the live jumper and other metallic parts.  Erection of intermediate pin insulators may be necessary for fixing these jumpers (see also clause 16E.3.5.4).

Parallel groove (PG) clamps may be preferred to binding of conductors at jumper locations or service taps.

Umbers used shall normally be of the same material as the line conductor and they shall be of adequate current carrying capacity.  If the material of the jumper wire is different from that of the line conductor, suitable bimetallic clamps are to be used, it should be ensured that the aluminium conductor is situated above the copper conductor so that no copper contaminated water comes in contact with aluminium.

16E.3.5.8 Earth wire

A continuous GI earth wires of size not less than 4mm (8SWG) shall be run all along the LV/MV distribution lines and service lines. This shall be securely flattened to the cross arms by means of cast iron reels or by suitable clamps as directed by the engineer.

Where a continuous carpet guard wire is provided, the same shall serve the purpose of continuous earth wire run mentioned above.

16E.3.5.9. Erection  of guard A guard shall be provided at all road crossings of overhead lines, crossings with other lines and between HV and LV/MV lines carried on the same support.

A cage guard shall be provided for LV/MV overhead lines of vertical configuration.  Cradle guard shall be used for overhead lines of horizontal configuration. Where no guard of any of these types is provided, a ring guard supported from the pole shall be arranged (refer Figure 10).

In case of cradle / cage guards, at least 9 laces shall be provided for each span.

The guard wires shall be bonded to the earth wire. Reel insulator shall be used to bind the cage guard to the neutral.

The guard wire shall always run not less than 30cm beyond the outer barest conductor of the configuration in the case of 11KV/33KV lines, and 10cm in the case of LV/MV lines.

16E.3.5.10. Earthing - Earthing installation shall conform to various clauses under section 16 electrical works (Internal), 1994.

All metal supports and RCC/PCC supports of overhead line, and metallic fittings attached there-to shall be permanently and efficiently earthed, and for this purpose a continuous earth wire shall be run as per clause 3.5.8.  In the case of RCC/PCC poles, all insulator pins, cross arms, stays, street light brackets and other metallic fittings shall be bonded to the continuous earth wire.

The continuous earth wire shall be connected to earth.  There shall be not less than 3 connections with the earth per kilometer, spaced at equidistance as far as possible.  Where a continuous earth wire cannot be provided, every pole should be earthed and all the metal parts are to be bonded, with the concurrence of the engineer.

Junctions, end terminal locations, and all special structures may be selected for connecting to earth.

he lead from the earth electrode shall be suitably protected by a 15mm dia GI pipe up to a height of 3m from the ground level and shall be bonded to the continuous earth wire.

The protection pipe and the earth lead shall be suitably clamped to the support.

16E.3.5.11 Safety and protective devices

16E.3.5.11.1 Danger board - All supports carrying HV Lines shall be fitted with danger plate conforming to IS: 2551-1982 at a height of 3m from ground and it shall indicate the voltage of the line.

16E.3.5.11.2. Anti-climbing devices - Necessary arrangements for preventing unauthorized persons from ascending any of the supports carrying HV lines without the aid of a ladder or special appliances shall be made.  Unless otherwise specified, barbed wire conforming to IS: 278-978 having 4 point barbs, spaced 75cm ± 12cm apart and weighing 108/125gm/m, shall be wrapped helically with a pitch of 75mm around the limb of the support and tied firmly commencing from a height of 3.5m and up to a height of 5m or 6m as directed by the engineer.

16E.3.5.11.3 Lightning arresters

i) Horn Gap type lightning arrester

a) Horn gap type lightning arrester for LV/MV lines and surge diverter suitable for MV lines shall be employed with each phase at terminals and any other places where specified, depending upon the local climatic conditions.  These shall be mounted on cross arms.

b) A short and definite air gap not exceeding 2cm must be maintained between the horns.

ii) No-linear resistor type lightning arrester

a) Non-linear resistor type lightning arrester suitable for HV lines shall be installed, one unit per phase, at the terminals, transformer stations etc. as specified.

b) These devices shall be connected ahead of fuses, if any, provided.

iii) Earthing for lightning arresters

a) An independent earth electrode shall be provided for lightning arresters.

b) The earth lead from the earth electrode to the lightning arresters shall be continuous, and where specified, it shall be insulated throughout above the earth surface by an walkathon pipe.

16E.3.5.12 Double / triple / four pole structure - Where a HT overhead line deviates by more than 10 degrees, a double pole, triple pole or four pole structure may be erected at the point of deviation depending upon the angle of deviation.  Normally, a double pole structure should suffice for an angle of deviation up to about 30 degrees, a triple pole structure up to an angle of deviation up to 60 degrees, and a four pole structure beyond that angle of deviation.

The structure shall comprise of the same type of poles as used for the other overhead lines unless otherwise specified.

A set of double channel iron cross-arms of the same length duly clamped by through bolts and nuts shall be provided for each double pole structure.  Similar set of double channel iron cross-arm shall be likewise clamped to each side of the triple and four pole structures.  The two channel iron lengths of the double channel iron cross arm shall be stepped to each other by 50mm x 6mm flat iron strips to prevent bulging of the cross arms during stringing of the lines.  These flat iron strips shall be bolted to the two channel iron lengths adjacent to each strain / disc insulator fittings supported by the cross arm.

A set of double channel iron cross-arms of the same length duly clamped to the poles by through bolts and nuts shall be provided for each double pole structure.  Similar set of double channel iron cross-arms shall be likewise clamped to each side of the triple and four pole structures.  The two channel iron lengths of the double channel iron cross-arm shall be strapped to each other by 50mm x 6 mm flat iron strips to prevent bulging of the cross arms during stringing of the lines.  These flat iron strips shall be bolted to the two channel iron lengths adjacent to each strain / discs insulator fitting supported by the cross arm.

16E.3.5.12.5 Cross bracing’s

i) A set of cross bracings fabricated out of 50mm x 50mm x 6mm angle iron for 11KV lines, and out of 65mm x 65mm x 6mm for 33KV lines shall be provided for each double pole structure.

ii) Three such sets of cross bracings shall be provided for each triple pole structure.

iii) Four sets of such cross bracings shall be provided for each four pole structure.

iv) The horizontal members of the bracings shall be fixed to the poles by means of clamps fabricated out of 50mm x 6mm flat iron.  The inclined members of the cross bracings shall be fixed to the horizontal members by suitable bolts and nuts, after pressing together by forging the two sides of the angle iron at either end of the inclined members.

v) The cross bracings shall be so fixed as to from rectangle of minimum size 1.4m width x 2.5m height in case of 11KV lines, and of 2.4m width x 2.8m height in case of 33KV lines.

vi) The cross bracings shall be fixed more or less in the middle of the structure.

16E.3.6 Service connection line

16E.3.6.1. No service connection shall be taken off an overhead line except at a point of support.

16E. 3.6.2. The service line shall be either through an overhead services or underground cable, as specified.  In case of overhead service, the same may be provided with either (a) bare conductors, or (b) insulated conductors.

16E.3.6.3 Service line with bare conductors

16E.3.6.3.1. any of the following methods shall be adopted as specified: -

i) First Method

a) The bare conductors shall be strung with shackle insulators fixed to cross arms at both ends.  The feeding end cross arm shall be fixed to the support and the one at receiving end shall be mounted on a GI pipe of minimum 5cm dia. 
b) The bare conductors shall be kept at a height of at least 2.5m from the top of the structure in accordance with Rule 79 of the Indian Electricity Rules.

c) The GI pipe shall be provided with double bends at the top.  The pipe shall be secured by at least 2 clamps made of 50mm x 6mm MS flats fixed firmly to the wall in the vertical position.  It shall in addition be provided with a GI stay wire of 7/3.15mm size anchored to the building with an eye bolt.

c) Service connection shall be given from the overhead service line, with weather proof / PVC insulated cable through this GI pipe.  Well fitting PVC bushes shall be provided at both ends of this GI pipe.

ii) Second method

a) The bare conductors shall be strung with shackle insulators as above except at the receiving end, where the insulators shall be fixed to a bracket in a suitable form made of angle iron of size not less than 50mm x50mm x6mm.  The ends of the bracket shall be cut and split and embedded in the wall with cement mortar.

b) The bare conductor shall be kept at least 1.2m away from the edge of the structure in accordance with Rule 79 of the Indian Electricity Rules.

c) The service connection shall be given with weather proof/PVC insulated cable through GI pipe of minimum 4cm dia fixed to the wall.  The GI pipe shall be bent downwards near the service entry.  Well fitting PVC bushes shall be provided at both end of the GI pipe.

16E.3.6.3.2.The service line with bare conductors shall be guarded wherever required in accordance with the Indian Electricity Rules.

16E.3.6.4 Service line with insulated conductors

i) Service connection may be given by weatherproof cable/PVC insulated PVC sheathed cable on GI bearer wire.

ii) The cable shall be supported by the bearer wire by means of suitable link clips spaced 30cm apart, or by porcelain cleats 50cm apart.

iii) The GI bearer wire shall be of minimum 3.2mm (10 SWG) size.  One end of the GI bearer wire shall be attached to a clamp, which is fastened to the nearest pole carrying the distribution lines from where the service connection is intended to be given.  The other end of GI wire shall be fastened to a 5cm dia GI pipe for a span up to 4.5m which shall be fixed to the wall with guy etc.

iv) The GI pipe shall be fixed to an angle iron of size 40mm x 40mm x 6mm thick with suitable guy for high supports and for a span exceeding 4.5m.

v) Alternatively, when the height of the structure permits minimum ground clearance the other end of this GI bearer wire may be fixed to a hook, eye-bolt or bracket embedded with cement mortar in the wall.  The weatherproof/PVC insulated and PVC sheathed cable shall pass through GI pipe of minimum dia 5cm, which is bent downwards.  Well fitting PVC bushes shall be provided at both end of the GI pipe.

16E.3.6.5 Service line by underground cable

i) Service cables shall be PVC insulated PVC sheathed armored UG cables to the specified size(s).

ii) The service cable from an overhead distribution line shall be fixed to the support with 2 nos. of clamp of MS flat of size 50mm x 6mm.  This shall be protected up to a height of 3m from ground level by a GI pipe of adequate size, clamped to the support with 2 nos. of MS flat of size 50mm x 6mm. The service cable shall be laid in accordance with specifications.

iii) The service cable shall be terminated to an outdoor cable termination box fixed to the support.  The connection with the over head line shall be given either by the cores of the service cable directly or through separate insulated leads as specified.

16E.3.6.6 Service fuses - Unless otherwise specified, an ICDB (with rewire able fuses) may be provided on the pole for the purpose.

16E.3.7 Painting

16E.3.7.1 Treatment of all supports and line materials before or at the time of erection shall be done in accordance with the relevant sub clauses of clause 16E.3.2.11.  The cross arms and the pole clamps shall be treated with one coat of red oxide primer before erection and finished with two coats of approved paint after erection along with other hardware.

3.7.2 After erection, the external surface of metal supports above ground level and all pole fittings shall be given finishing coats of painting.

16E.3.7.3 The following procedure for painting/repainting works shall be adopted.

i) In the case of line accessories, all rust and scale shall be removed scraping, or by brushing with steel wire brush.  All dust and dirt shall be carefully and thoroughly wiped away.  Painting shall not be done when the surface is wet or covered with dirt / dust.

ii) The primer coat shall be applied with red oxide paint.  In the case of new supplies, this shall be done before supplying to the site.

iii) Application of finishing coat at site shall be done with brushes and the paint shall be spread as evenly and as smooth as possible. The surface shall be given two or more coats as specified.

16E.3.8. Numbering of supports

3.8.1 All supports shall be numbered after painting, as directed by the engineer.

3.8.2 Separate number plates may be used, if so specified.

16E.3.9. Testing of overhead line

16E.3.9.1.Before connecting the services to transformer, equipments etc. a pressure test of appropriate standard shall be carried out on the line as directed by the engineer in charge.

16E.3.9.2. Before charging the MV lines, the same shall be tested with a 500V megger for insulation resistance.  Similar testing shall be done for 11KV lines with a 2500V megger and for 33KV lines with a 5000V megger.

16E.3.9.3 Where pressure test is not done on a MV line, it shall be tested with 2500 V/5000V megger for insulation before charging.

16E.3.9.4. All earth sets associated with the work shall be tested.

16E.3.9.5. All test results including earth test results shall be recorded and submitted to the engineer.

16E.3.10 Commissioning

The distribution lines shall be charged only if the pressure/megger test and earth test results are satisfactory.

The lines shall be commissioned in the presence of the engineer.

16E.3.11.Measurement of overhead conductors and earth wire.

The weight of overhead conductors and earth wire shall be determined by measuring the distance from center of one pole to the center of another pole and computing the weight of the earth wire or conductor by using a standard table.  3% extra shall be allowed collectively for wastage, sag, jointing, binding, jumpers etc.

Table VII

Cross arm lengths (Clause 16E.3.3.2.1 (ii) (d)

Line voltage

No. of horizontal conductors

Length of cross arm

LV/MV

2

55 cm

LV/MV

4

115 cm

LV/MV

4 + Guard

175 cm

11 KV

3

230 cm

Note: If cradle guard is proposed below the 11 KV line, additional Z clamps should be provided from the ends of cross arm, with horizontal conductors of 30 cm from the outer conductors.

Table VIII

Overhead conductor details (Clause 16E.3.3.6.1 (Note))

Conductor

Standing and wire diameter

Conductor area

App. Equiv. Copper area

Calculated resistance at 20deg. c when corrected to standard weight

App. Current carrying capacity

App. weight

App. ultimate strength

1

2

3

4

5

6

7

8

 

No. of Dia. Mm  Strands

Sq. mm.

Sq. mm

OHM/KM

40 DEG

C

45 DEC

C

45 DEG. C

KG/KM AMB.TEM

All aluminium (stranded) conductor (A.A.C)

 

7

2.21

26.85

16

1.07100

--

--

73

485

 

7

2.79

42.80

25

0.67210

178

165

117

737

 

7

3.10

52.85

30.00

0.54440

204

189

144

832

 

7

3.40

63.55

40.00

0.45260

229

212

174

1051

 

7

3.66

73.65

45.00

0.39360

252

234

201

1203

 

7

3.78

78.55

48.00

0.36620

264

245

215

1273

 

7

3.91

84.05

50.00

0.34220

275

255

230

1356

 

7

4.17

95.60

60.00

0.30090

298

276

261

1523

 

7

4.39

106.00

65.00

0.27150

318

295

290

1623

Aluminium conductor steel reinforced (A.C.S.R)

6/1

2.11

24.48

13.00

1.37400

115

107

85

771

6/1

2.36

30.62

16.00

1.09800

133

123

106

952

6/1

2.59

36.88

20.00

0.91160

150

139

128

1136

6/1

3.00

49.48

25.00

0.67950

181

681

171

1503

6/1

3.35

61.70

30.00

0.54490

208

193

214

1860

6/1

3.66

73.65

40.00

0.45650

234

217

255

2200

6/1

3.99

87.53

45.00

0.38410

261

242

303

2613

6/1

4.09

91.97

48.00

0.34340

270

259

318

2746

Lower and higher sized conductors, which are not in normal use in CPWD have not been considered and cable charts and I.S 398 (Parts 1 & 2 ) 1976.

Table IX

Minimum clearance between conductors on the same supports (Clause 16E.3.4.3.1)

a) L.V. Lines

i) Vertical configuration of conductors

Minimum clearance between earth and live conductors……………..  30 cm.

Minimum clearance between live conductors………………………… 20 cm.

ii) Horizontal configuration of conductors

Minimum clearance between live wires on either side of a suppor…………45 cm.

Minimum clearance between live wires on the same side of  support……..30 cm.

Minimum distance between the centre of insulator pin hole and end of cross arm..5 cm.

b) H.V. Lines

Triangular configuration

i) 11 KV lines - The conductors shall be erected in such a way that they form an equilateral triangular pattern of side of 1 meter minimum. I

ii) 33 KV lines - The conductors shall be erected in such a way that they form an equilateral triangular pattern of side of 1.5 meter minimum.

16. E. 4.  Other external electrical works

16E.4.1 Scope - This chapter covers the requirements of External Electrical Installation works, other than cable work and overhead line work.  Works relating to street lighting compound, lighting and general lighting of open areas, and feeder pillars are covered.  Functional flood lighting involving close design parameters, high mast lighting etc. are not covered here.

16E.4.2 SPECIFICATIONS FOR External Lighting Works

16E.4.2.1 Materials

16E.4.2.1.1 Supports

i) The supports of overhead LV/MV distribution lines should, as far as possible, be used for street lighting for the corresponding streets.

ii) Where underground cables are used for LV/MV distribution, the street lighting poles may be of RCC/PCC, or steel tubular type, as specified.

iii) Street lighting poles shall be of appropriate length, after taking into account the bracket design to meet the lighting design.  The stresses likely to be experienced due to wind, and weight of the bracket and luminaires shall be the guiding factor for the selecting the pole section as per relevant BIS.

16E.4.2.1.2 Brackets - Brackets for taking the luminaries with fluorescent tubes shall be of GI pipe of size matching the fixing requirement of the luminaires.  Brackets for luminaries with other types of discharge lamps shall be of GI or MS, with or without an extension pipe piece welded to the same, as may be required to fix the luminaires thereto.

16E.4.2.1.3 Looping box

i) A looping box shall be provided with every pole having underground cable connection.

ii) The looping box shall be fabricated out of 1.6mm (16SWG) thick MS sheet, with hinged front cover having fixing/locking arrangement.  The hinge should preferably be at the top to enable self closing of the cover.

iii) The looping box shall be of minimum size 250mm x 200mm x 100mm where 2 core cables alone are involved, minimum 250mm x300mmx100mm where 4 core cables are involved, or any other specified size to suit the individual site requirements.

iv) The box shall be complete with brass compression gland(s) of appropriate size(s) if specified, earth stud, two MS clamps of 25mmx3mm section for fixing to the pole the required number of terminal blocks with brass connector strips and fuse carrier with base/MCB, as specified.

v) The box shall be treated with anti-corrosive paint before erection.

vi) Depending upon local uses, the control box of CI or some other materials, which will be specifically provided in the tender.

16E.4.2.2 Selection of compound / Street lighting luminaires -  Such luminaires are available in one of the following forms:

1. Incandescent

2. Halogen

3. Compact Fluorescent

4. Fluorescent

5. HP MV

6 HP SV

7 LP SV

8 Metal Halide

Use of incandescent lamp should be avoided as far as possible due to very low lumen output and life.  For other type table X gives the average lumen output, efficacy, colour rendering and life.  Careful selection should be made for most suitable and economical application.

16E.4.2.3 Installation

i) The poles shall be erected as per relevant standards.

ii) Where the work involves provision of looping boxes for cables in street lighting works, these should be installed at 60cm from ground level or above high flood level whichever is more.  The cables shall be routed from ground through GI pipes of suitable size to the looping box.  These pipes shall be suitably bent outwards and embedded when the foundation work is done, thus avoiding any cutting later.

iii) Looping boxes for compound lighting poles may be installed within the concrete pedestal for the poles (before casting of the pedestal) at such a height that rainwater may not enter these boxes.  Necessary cable entry pipe(s) shall be fixed to the box properly bent outwards, when fixing the box to the pole.  Necessary chamfering should be done on the pedestal to enable lifting the front cover of looping box and having proper access inside for maintenance.

iv) Brackets for luminaries shall be fixed to the poles firmly so as not to be disturbed by wind or by manual pressures during maintenance.  Clamps, locking studs or any other reliable means shall be adopted for this purpose.  The luminaries shall be fixed to the brackets firmly such that they are not disturbed by wind, vibration due to traffic etc.  Arrangement, if any recommended by the manufacturer, should be followed.

v) Wiring of poles from looping box to the fittings should be done with specified size of copper conductor PVC insulated cables.

vi)  Where compression type glands are used with the boxes, the cables shall be terminated on to them.  Where the cable entry pipes are terminated directly on to the boxes, without the provision of cable gland(s), suitable metallic clamp shall be provided with each cable end for earthing the cable armour through the earth terminal in the boxes.

vi) The poles shall be painted in approved colour with 2 coats of approved paint suitable for outdoor applications.  The interior of the looping boxes shall be painted with synthetic enamel paint.  All poles shall be numbered with figure height of 30 mm.

16E.4.2.4. Earthing

i) Earthing of poles shall be carried out as per clause 3.5.10.  The earth terminal in the looping box shall be connected to this by bare GI wire.

ii) Though earth continuity shall be ensured through cable armour, 4mm dia (8SWG) GI wire shall be run additionally along the cable route and looped at the poles by stud and washers arrangement.

iii) The luminaires body shall be connected to the earth stud in the looping box by bare conductor of 4 sq. mm Aluminium.

16E.4.3 SPECIFICATIONS FOR FEEDER PILLAR

16E.4.3.1 General

i) Feeder pillar shall be of floor mounting, freestanding type, suitable for outdoor installation in dust, vermin and weatherproof construction.

ii) This shall be suitable for continuous operation on 415V (nominal) 3 phase 4 wire 50Hz supply.  The number type and capacities of protection gear forming part of the feeder pillar assembly shall be as specified.

iii) The fabrication work should be taken up, only after the detailed and dimensioned drawing is prepared by the contractor and approved by the engineer.

16E.4.3.2 Enclosure

i) The enclosure shall be fabricated out of at least 2mm thick MS sheet, with suitable stiffeners.

ii) Hinged double doors of the same material shall be provided on the front and rear sides, with necessary handles and inbuilt locks with double, keys.  Neoprene gaskets shall be provided for the doors.

Note: In the case of feeder pillars, whose width may not exceed 60cm, single leafed doors may be permitted both on the front and the rear sides.

iii) Suitable MS top cover of 2mm thick with suitable slants/over hang shall be provided for protection against rain/weather etc.

iv) Detachable gland plate(s) shall be provided at the bottom, with compression type cable glands to the sizes as specified.  Adequate space should be provided below the same for safe bending and termination cables.

v) The enclosure shall be provided with ventilation louver, covered with wire mess, lifting hooks, supporting legs, and double earth terminals with double washers.

vi) The internal design shall be such as to permit suitable arrangement of incoming and outgoing switchgears, bus bars, incoming and outgoing cables.  Due provision should be kept for routing of cables, their support and termination.  Ample working space should be left for maintenance.

vii) The metallic parts of the enclosure shall be subjected to seven tank process to include cleaning, deducting, rinsing, phosphatising etc.

viii) All holes necessary for fixing the components shall be drilled before primer painting.  Two coats of red lead anti corrosive primer shall be given on all sides internal as well external, before taking up stove enameled / powder painting process.

16E.4.3.3 Internals

i) Bus bars and bus bar supports shall conform to relevant sub-clauses under 16E.7.1.2 and 16E.7.1.3 of section 16 of Karnataka Buildings Specifications.

ii) Adequate clearance should be maintained between phases and between phase and earth as per clause 16E.7.1.3.3 of Section 16 of Karnataka Buildings Specification (Electrification work-Internal) Bus bars shall be insulated with necessary sleeves/tapes of PVC or heat shrinkable insulating material.

iii) An independent earth bus shall be provided, to which all earth connections (Incoming as well as outgoing, including body earth) will be terminated.  This shall be complete with the required number of holes, bolts, nuts, double washers etc.

iv) The protective gear may be re-wire able / HRC fuses in fuse carries and bases, MCB or MCCB, as specified.  These may be bus bar mounted or supported independent of bus bars.  In both cases, the supports, including intermediate supports, shall be substantial in construction capable of withstanding the loads under fault conditions.

v) There shall be a suitable incoming switch mounted insider at a convenient location.

vi) Provision shall be available for lighting the interior, when the doors are opened.

vii) Generally the internal arrangement and design of feeder pillar shall be one of the following categories: -

a) Metal clad incoming switch shall feed an enclosed bus bars chamber, Metal clad outgoing switches shall be connected to the bus bars chamber.

b) Metal clad incoming switch shall feed an enclosed bus bars chamber. Fuse fittings will be mounted on bus bars.  The outgoing cables will be connected to the fuse fittings.

c) The above incoming switch, bus bars, outgoing switches incoming and out going cables shall be accommodated in a cubicle panel, with switch bays, bus bars bays and cable alleys.  The cable entry can be from back or front side.

Note - The design, depending upon the actual requirements will provide for a suitable schedule of work for the feeder pillar.  If required suitable rupturing capacity in KA and weather protection as per IP 54 will be specified, which may require suitable testing and test certificates?

viii) The front operable / lockable door shall act as a cover for the switch boards as above.

ix) Illustrative sketches of different type of feeder pillars are enclosed (See Figure 21).

16E.4.3.4 Installation

i) The feeder pillar shall be installed on a suitable pedestal of masonry or RCC.  The pedestal shall be built to appropriate dimensions, with provisions for cable entry through the pedestal, and cable bending from below into the feeder pillar. The minimum height of the pedestal above ground level shall be 45cm.  This may be increased, where so specified, considering the local conditions (like high flood level) in individual cases.

ii) The installation shall be done at locations approved by the engineer.  The locations shall be at about 1m to 2m from any road bream, clear of any service pipes, ducts, cable routes etc.  and convenient in taking the distribution cables.

iii) Finishing coats (2 coats) of painting shall be given in approved colour, using approved makes and type of paint in original containers.

iv) MV Danger board shall be provided on each door.  Flexible earth connection with the body should be provided for each door.

v) Each feeder pillar shall be earthed with 2 GI pipe electrodes.

vi) All cable connections shall be made using appropriate accessories like crimped lugs, flat and spring washers, bolts and nuts etc. as suitable for the type of termination.  In no case, any mechanical pull from cable connections shall be experienced at the terminations.

vii) Circuit details should be indicated by painting on the back of one of the doors.

viii) After all cable terminations no openings or unplugged holes shall be allowed, which may allow ingress of insect etc.

ix) All incoming and outgoing switchgears shall be properly marked indicating the load connected, cable sizes and out going connection etc.

16E.4.3.5 Testing - The feeder pillar shall be tested using a 500V DC megger before commissioning.

Table X

Selection of luminaries (Clause 16E.4.2.2)

Lamp Type

Range

Luminous Flux  (Lumens)

Efficacy Lm/W

Life hours

Colour rendering

GLS (Incandescent)

25W-1000W

230-18000

9-18

1000

Excellent

Halogen

300W-1000W

5100-22000

17-22

2000

Excellent

CFL

9W-25W

450-1200

59-78

8000

Good

 

5W-11W

250-900

50-82

8000

Good

Fluorescent

18W-65W

970-4000

49-77

5000

Good to moderate

ML

160W

2900

18

5000

Moderate

HP MV

80W-1000W

3500-58000

44-58

5000

Moderate

HP SV

70W-400W

5800-47500

83-119

12000-15000

Fair

LP SV

18W – 35W

1800-4500

100-129

10000

Poor

Metal Halide

 

 

 

 

 

i) a) HPI-T

250W

17000W

70-90

10000

Good

   b) HPI-T

400W

31500W

70-90

10000

Good

   c) HPI-T

1000W

81000W

70-90

10000

Good

   d) HPI-T

2000W

189000W

70-90

10000

Good

ii) a) HPI-BU

250W

17500W

70

10000

Good

    b) HPI-BU

400W

27600W

70

10000

Good

iii) a)MHNTD

70w

5500w

75-80

6000

Excellent

    b) MHNTD

150W

11250W

75-80

6000

Excellent

Annexure 16E-A.1

JOINTING OF POWER CABLE (Clause 16E.2.7.8)

 1 General: - The reliability of a power cable network depends, among other factors, on the quality of joints made (End/Tee/Straight through) in the network.  The conductivity and insulation under normal and short circuit conditions should be the same in the joint as in the conductor proper and the breaking load of joint shall be at least 60 percent of that of the conductor.  This is achieved by using materials, accessories and tools of approved standards and to a large extent this also depends upon the skill in adhering to standard procedures approved for such work.  All materials and accessories shall conform to relevant Indian Standards wherever they exist.  For special type of splicing connector kits or epoxy resin spliced joints, makes approved for such applications shall be used.

 2. Jointing procedure: -

 2.1 The joint operation consists briefly of removal of the serving and/or sheathing, armour where provided and core insulation of the cable(s), jointing and conductor and completing the joint either with compound in case of paper insulated /PVC cable or with cold resin epoxy for PVC cables.  Jointing in more than one cable laid in the same trench should be staggered as shown in Figure 12.

 2.2 Jointing of conductor: - Aluminium is now the conductor material in general use.  The jointing of aluminium conductors is an important step and the methods generally adopted, irrespective of the type of insulation of the cable are

a) Soft soldering

b) Welding

c) Mechanical compression.

Brief particulars on the above methods of jointing of conductors are given in paragraphs 2.2.2., 2.2.3, and 2.2.4 respectively.  For complete details reference may be made to IS: 1255-1983.

2.2.2. Soft soldering method.

2.2.2.1 In order to ensure that the wires are firmly embedded in solder, the strands at the joint end of the cable are fanned out, after removing the insulation about 10mm more than the length required for the conductor jointing.  Individual strands shall be cleaned thoroughly by a scraper to remove any impregnation compound or oil.  The conductor shall be preheated by basting with solder in the interstices of the strands and then applying the aluminium solder flux with a stiff brush, particular care being taken to ensure that the flux and solder reach the underside of the conductor.  The flux removes the oxide film and assists the spreading of molten solder.  The conductor shall be basted with solder several times and the process repeated till a shining surface is obtained.  Basting, which consists of pouring of liquid (solder in this case) with a small ladle, is done usually from the insulated end to the cut end of the conductor to push away any traces of flux left in the interstices of the conductor.  The fanned out strands are closed back together in a circular shape and excess solder wiped out.  The ferrule which is generally weak back type and is of copper shall also be tinned with aluminium solder and flux and fitted on to the conductor firmly but not completely.  The ferrule is then basted with solder to allow the solder to fill in between the conductor and ferrule properly.  Excess solder is wiped out.  As the oxide film, which is a bad conductor of electricity forms rapidly over any surface of pure aluminium exposed to atmosphere, the whole process should be carried out skillfully and quickly.

In case of termination with a cable lug, a similar procedure is adopted.  However, in the case of large sockets (say for 50 sq. mm and above) a hole is drilled at the closed end of the lug before tinning the same.  After the conductor is inserted in the lug, the space between the lug and the conductor insulation is filled with fiber glass/asbestos, held in position by a flame resistant tape, to save the insulation from being damaged by the molten solder.  Molten solder is poured through the drilled hole.  Gentle tapping of the solder point would facilitate the setting of the solder inside the lug.  The pouring is continued till the solder flows freely. Excess solder is wiped and the assembly is allowed to cool without disturbance.   Particular care is required when jointing PVC cables, to ensure that the PVC insulation / sheath are not damaged due to excessive heat.

The most important precaution in this method is the maintenance of temperature of solder within limits in accordance with the recommendations of the manufactures.  The liquids temperature for solder is about 220 degrees C and its solid temperature, 150 degrees C. Care should be taken that the pouring temperature does not exceed 300 degrees C.  as the flux tends to char at temperature exceeding this limit.  This is normally achieved by maintaining the pot temperature at 360 degrees C.

As the temperature of solder plays an important role in the jointing of conductors, any crude method of checking the adequacy of heating the solder should not be resorted to.  A thermometer should invariably by used for the measurement of temperature of solder.

2.2.2.2 Friction soldering method is also followed for soldering conductors.  Special solder sticks with embedded cadmium crystals are used in this method.  No flux is used.  After heating the strands and the solder sticks, the strands are wiped with solder stick when the cadmium scratches out the oxide film and the solder adheres to the strands.

2.2.3 Welding method - The strands of the conductor end are first welded solids.  For this, the strands are cleaned with petrol or kerosene after the insulation is stripped and the strands have been fanned out.  The strands are smeared with aluminium flux and then brought back to position.  With the conductor end kept vertical a pair of cooling tongs, an asbestos flame shield disc, a two part sheet steel tube, or a carbon tube (mould) are placed along the conductor in the above order from the insulation end.  The tube should project about 5 to 10 mm above the conductor end.  The conductor is heated and welded by puddling with an iron wire and adding aluminium metal.  The welded conductor strands and the solid aluminium at the end should be about 10 to 20 mm depending on the cross sectional area of the conductor.  The two conductor ends to be jointed after being welded solid are placed in a mould whose interior is coated with mould paint.  A thin coat of flux is applied to the ends and the conductors are welded by heating an aluminium wire, coated with a thin layer of flux.  Care is taken to ensure that only part of the solid ends is melted in this operation.  The flame shield and cooling tongs are also used as above one set for each cable.

After welding, the mould is allowed to cool and then removed.  The joint is then filed smooth.  Instead of an open mould, some times a closed mould is used, where initial welding of individual conductor end is not necessary after cleaning of the strands and smearing them with flux.  The weld should be puddled with continued heating to ensure that it fills the mould fully without any cavity etc

In the case of end terminations, the solid welded conductor end is welded to the cable lug, as above, using the flame shield, cooling tongs etc.

2.2.4 Mechanical compression method - A special sleeve is pressed on to the conductor ends to be jointed with some gap between the ends ( or the conductor ends and the inner edge of lug as the case may be) to allow for elongation by a hydraulic / mechanical compressor with a special die holder or compression tool.  The compression is done in stages from the center to the sleeve end with an overlap of 1/3 of the die width.  The recommendations of manufactures of the tool in this regard should be followed.

2.3. Jointing of paper insulated cable

2.3.1. Section 11 of IS: 1255-1983 describes the jointing method of paper insulated cables.  The brief particulars extracted therefrom are given below for general guidance.

2.3.2. It should be ensured that all jointing materials and tools are clean and free from any trace of moisture.

2.3.3. The cables to be jointed are lined up side by side with adequate overlap and suitably supported.  The serving, armour and bedding are cut and removed, after making and binding with wire binders the points up to which they are to be removed.

2.3.4. The lead sheaths are cleaned and the points thereon of wipe are marked with plumbers black and the clean portion of sheath with a coat of tallow. The joint center is marked on the sheaths of both the cables.  The cables are cut squarely allowing at least 6 mm overlap of the cable ends.

2.3.5 With one of the cables wrapped in cloth/paper the lead sleeve is slid over it and rested with its compound filling hole facing down and covered with another piece of cloth.  Lead plumbing rings are passed on, one for each cable and bolted down at the correct distance.

2.3.6 The limits up to which the lead sheaths need to be removed are marked by a peripheral cut to about half the sheath thickness.  The sheath is cut through, starting from the cable end and peeled out.  A binding of insulation tape (belt tape) is applied to about 3mm width over the insulation, near the cut ends of sheath.

2.3.7 Belt insulation where provided, paper/jute fillers etc. are cut and removed upto the belt tape applied above.  Commencing at the crotch, a layer of protective non-adhesive tape is applied individually to the remainder of the cores.

2.3.8. The cores to be jointed are placed in position and the joint center is marked.  The protective tape and paper insulation are removed up to the desired length (i.e. half the ferrule length + 10 mm), shaped conductors are made round.

2.3.9 Before jointing the paper insulation layers, one next to the sheath and the other next to conductor are tested for the presence of moisture.  For this, single strips of paper from these layers are immersed in hot insulating compound or paraffin wax.  Presence of moisture is indicated by formation of bubbles in compound and cracking sound in case of paraffin wax.  These test strips of paper insulation should be handled carefully to avoid contamination by perspiration (refer IS: 1255-1983)

2.3.10 The cores are jointed as explained in 2.2 above.

2.3.11 The protective tape is removed sufficiently at either end of the ferrule, a temporary binder applied on the paper insulation which is then trimmed with a knife into the form of a sharpened pencil.

2.3.12 Insulation tape is applied tight, first to build up the spaces between the ferrule and the binder and then end to end over the ferrule and core insulation to the required thickness. Care is taken that while taping there is an overlap of about half the width of tape.  The binders protective tape etc. are removed when taping.

2.3.13 The core spreaders are inserted between cores at about 12 mm from the ends of belt insulation and bonded to the cores with insulation tapes.

2.3.14 The lead sleeve that had been slipped earlier is warmed to remove traces of moisture inside.  It is then passed over the joints and gently pressed down to the plumbing rings / sheath itself as the case may be.

2.3.15 The sheath is cleaned and plumbers black applied to limit the flow of plumbing metal to the area to be plumbed.  When dry, the rest of sheathing is coated with tallow, warming the cable and sleeve, the plumb (wipe) is built up from the metal pot and finally finished with a blow lamp and fallowed pad of mole skin cloth.

2.3.16. Lead strips are wrapped over the armour till it equals the diameter of the armour grip or joint box.  The bottom of the box is placed in position and securely fixed with armour clamps.  The bottom of the box and sleeve are filled with hot compound (pouring temperature not exceeding 150 degrees C.) and the sleeve toped up after cooling and sealed by plumbing.  The bottom of the box is then topped with compound until it spills over the vee groove when the top of the box is bolted in position.  The remainder of the box is then filled up with compound and plugged when the compound is still hot.  The procedure is described in detail in IS: 1255-1983.  Care should be taken to use compound of standard makes in cable joints, as the joint is likely to fail with a poor quality compound.

2.3.17 Typical straight through joint and indoor type termination for paper insulated cables are shown in figures 14 and 15 respectively.  Typical out door cable termination arrangement is shown in figure 16.

2.4 Jointing of PVC cables

2.4.1 Jointing using cable compound -The procedure outlined above shall mutatis mutandis be applicable for outdoor jointing of PVC cables also, but the operations concerning lead sleeve etc. are not applicable as the sheathing is also of PVC.  Since too hot compound could damage the PVC insulation, adequate care is to be exercised to maintain the temperature of compound within recommended limits.

2.4.2 Epoxy jointing - Cold pouring casting resin system for PVC cables jointing has been developed for application up to 11KV grade cables.  The compound consists of a resin base and a poly amino hardener.  The two component liquids are mixed at site in accordance with the recommendation of manufacturers.  In this system of jointing, the insulation etc., are removed and conductors jointed as explained in clause 2.2.  The jointed cores in case of LV/MV cables should be kept apart to avoid any flash over between them.  Spaces are provided between them.  Spacers are provided between cores for HV cables.  No insulation is applied over the jointed cores. A cover ring is placed tight over the two cut ends of armour and soldered to the armour wires.  The two rings are then jointed b a copper wire and the cut ends of armouring are bent over the rings.

Sandpaper is applied to the inner sheath surface and cleaned using methyl chloride.  The joint is enclosed by plastic mould, which is in two parts whose ends are duly cut to match the size of cables.  PVC tape is wrapped at the two places where the mould will touch the cables.  The two places where the mould will touch the cables.  The two halves are pasted together and kept clamped to avoid any air gap.  The mould ends are enclosed with putty, which is supplied in the joint kit. 

Expiry date of resin is checked and hardener added to resin.  The mixture is churned thoroughly for about 15 to 20 minutes till the colour of the mixed compound is grey.  The mix is poured slowly into the mould taking care to avoid formation of air bubbles till the mould is filled and it comes out at the risers.

Allow the joint to set for minimum three hours till it becomes a solid mass before changing the cable.  The mould may be removed, if desired. 

Normally all the components required for joints are supplied as a kit for various sizes of cables.

2.4.3 Termination using compression glands - PVC cables upto1.1 KV grade shall preferably be terminated in the indoor electrical switch gear using compression glands.

The nipple of the gland is first screwed to the switchgear to which the cable is to be terminated and locked with check nut from inside the housing.  Compression ring, washer, rubber ring and again another washer are slipped in succession over the cable.  The cable sheath is removed to desired length and the armour strands splayed out.  The armour wire is then cut to the overall diameter of the second washer. Sharp edges are removed and armour cleaned.  A third washer is now slipped on to trap the trimmed strands and armour between the second and the third washer.  The cable end is pushed through the gland nipple (body).  The compression ring is then tightened when the rubber ring will expand and hold the cable tightly by the sheath. The cores are terminated in the usual manner.

2.4.4. Jointing using heat shrinkable insulating material for MV cable  - Heat shrinkable tubes of different diameters are available, for cable jointing applications.  Tube of the appropriate size and of good quality (going by the successful test certificates from Independent bodies) should only be used.  After preparing the cable end for jointing, the tube is inserted over the cable end and held back.  The lugging/straight through conductor jointing operation is done.  The surface is thoroughly cleaned.  The tube is moved over the joint and heated from one end towards the other by a blow lamp, so that no air bubble gets entrapped.  The tube shrinks on to the insulation and lug (cases tare reported of moisture travel through the space close to the lugs and hence the covering the same is desirable.)  The joint can be energised, immediately after the surface has cooled down.

2.5 Use of heat shrinkable joints on high voltage joints - This type of joint can be adopted indoor/outdoor, for HV upto and including 33KV (at present).  The size of cable, as well as voltage of system should be indicated while ordering.  In the case of HV cables, the electrostatic stresses tend to concentrate near the screen, which is earthed, at the location where the cable is cut (for any type of joint).  This stress has to be relieved, in order to avoid failure of insulation at that location.  Semi-conducting tapes can be used for the purpose, but if the workmanship is not satisfactory, there can be entrapped air pockets where partial discharge can occur.  Heat shrinkable tube with semi-conducting properties can be provided there and shrunk.  A further insulating tube is heat shrunk over the same.  In HV joints, particular precautions are taken to (I) stress relief at cut ends, (ii) prevention of moisture entry at lug position and (iii) build up of the required insulation with the outer covering having anti-tracking property.  Heat shrinkable joint can be used for PVC, PILC and XLPE cables, for end terminations as well as for straight through/tee joints.  The procedure, though apparently simple, needs to be carefully and skillfully followed to avoid failures later.  Assistance may be taken from Manufacturer’s representative.

2.6 Jointing of XLPE (cross linked polythene insulated) cables

2.6.1 XLPE cable is highly resistant to moisture, hence jointing and terminations of XLPE cable is similar than PILC cables.  Up to 3.3 KV grade, cable can be terminated straightaway with compression glands similar to other PVC cables.

2.6.2 Jointing of conductors - Since the maximum permissible short circuit temperature is 250 degrees C in XLPE cables, soldered type joints become unsuitable as solder melts at much lower temperature.  Welded or crimped/compression type conductor joints are therefore adopted for XLPE cables.

2.6.3 Insulation build up - The conductor joint is insulated lapping or EPR self amalgamated (SA) tape to required thickness.  S.A tape is universally accepted as most reliable jointing materials because of its resistance to water and ozone, capacity to operate at higher temperature, high dielectric strength and void amalgamating properties.

For cables above 3.3 KV grade semi-conducting S.A. tape is to be applied on the conductor before starting insulator build up to equalise distribution of electrical stress on conductor surface.

The insulated jointed cores are further lapped with semi conducting SA tape to serve as core screening. 

For cable rated at 3.3 KV and below use of semi-conducting SA tape is not necessary.

2.6.4 Straight through joints - The jointed assembly (with insulated cores is encapsulated in special cast resin compound.

2.6.5 Stress relieved termination -  The termination of cables above 3.3 KV is provided with stress cone to relieve electrical stresses formed on the insulator at the point of termination of cable screen.  SA tape is lapped over the insulation to the required thickness to build up the stress cone.

2.6.6 Indoor type termination - Indoor type termination for cables above 3.3 KW is provided with stress cone but it does not require any compound for encapsulation.  However, it must be protected by lapping of adhesive PVC for protection against external abuses.

2.6.7 Outdoor termination - Outdoor type termination for cable above 3.3KV is provided with stress core but this termination is encapsulated in special cast compound to protect the joint from atmosphere abuses.

Note: - The above procedure is only indicative of the general requirements.  However, the procedure detailed by the manufacturer as suitable for the type of cables and for the type of joints shall be strictly followed.

Annexure 16E-A.2

IMPORTANT INDIAN STANDARDS

(Clause 16E-1.21.2 & 16E-1.21.3)

Poles  

1

Reinforced concrete poles for overhead power and telecommunication lines

785 – 1964

2

Pre-stressed concrete poles for overhead power, traction and telecommunication line

1678 – 1978

3

Pre-stressed concrete street lighting poles

2193 – 1986

4

Pre-cast reinforced concrete street lighting poles

1332 – 1986

5

Methods of test for concrete poles for overhead power and telecommunication lines

2905 – 1989

6

Tubular poles for overhead power and telecommunication lines

2713 – 1980 

(Part 1 to 3)

Conductors

1

Aluminium conductors for overhead transmission purposes:-

 

i)

Aluminium stranded conductors

398(Part–1)-1976

ii)

Aluminium conductors galvanised steel reinforced

398(Part-2)-1976

iii)

Aluminium alloy stranded conductors

398(Part-4)-1979

2

Aluminium steel core wire for aluminium conductors (ACSR)

3835-1966

3

Conductors and earth wire accessories for overhead power lines: Armour rods, binding wires and tapes for conductors

2121(Part-1)-1981

4

Conductors and earth wire accessories for overhead power lines: Mid span joints and repair sleeves for conductors

2121(Part-2)-1981

Cables :

1

PVC insulated (Heavy duty) electric cables: -

 

i)

For working voltage upto and including 1100V

1554(Part-1)-1988

ii)

For working voltage from 3.3 KV upto and including 11KV

1554(Part-2)-1988

2

Paper insulated lead sheathed cables for electricity supply

692-1973

3

Cross linked polyethylene insulated PVC sheathed (XLPE) cables: -

 

i)

For working voltage upto and including 1100Volts

7098(Part-1)-1988

ii)

For working Voltage from 3.3KV upto and including 33KV

7098(Part-2)-1985

4

Recommended current ratings for cables:

 

i)

Paper insulated and lead sheathed cables

3961(Part-1)-1967

ii)

PVC insulated and PVC sheathed heavy duty cables

3961(Part-2)-1967

5

Recommended short-circuit  ratings of high voltage PVC cables

5819-1980

Insulators :

1

Porcelain insulators for overhead power lines with a nominal voltage upto and including 1000V

1445-1977

2

Porcelain insulators for overhead power lines with a nominal voltage greater than 1000V

731-1971

3

Porcelain guy strain insulator

2300-1969

4

Characteristics of string insulator units

3188-1980

5

Insulator fittings for overhead power lines with a nominal voltage upto and including 1000V

7935-1975

6

Insulator Fittings for overhead power lines with a nominal voltage greater than 1000V

 

i)

General requirements and tests

2486(Part-1)-1971

ii)

Dimensional requirements

2486(Part-2)-1974

iii)

Locking devices

2486(Part-3)-1974

Codes of Practice :

1

Design, installation and maintenance of overhead power lines

 

i)

Upto and including 11KV

5613-(Part-1) sections 1 and 2) – 1985

ii)

Above 11KV and upto and including 220KV

5613(Part-2 Sections 1 & 2) – 1985

2

Selection, handling and erection of concrete poles for overhead power and telecommunication lines

7321-1974

3

Installation and maintenance of power cables upto and including 33 KV rating

1255-1983

4

Lighting of public thorough-fares for main and secondary roads(Group A and B)

1944-(Parts-1   and 2) – 1970

Safety Standard :

1

Guide for safety procedures and practices in electrical works:

 

i)

General

5216(Part-1)-1982

ii)

Life saving techniques

5216(Part-2)-1982

2

Excavation work

3764-1966

3

Rubber gloves for electrical purposes

4770-1981

General :

1

Dimensions for hot rolled steel beam, column channel and angle sections

808-1989

2

Galvanised stay strand

2141-1979

3

Galvanised steel barbed wire for fencing

278-1978

4

Cast iron manhole covers and frames:

1726(Part-II)-1974

5

Luminaries for road and street lighting

10322(Part-5/Sec 3)-1987

6

Voltage bands for electrical installations including preferred voltage and frequency

12360-1988

Electro – Technical Vocabulary

1

Overhead transmission and distribution of electrical energy

1885(Part-30)1971

2

Cables, conductors and accessories for electricity supply

1885(Part-32)1971

3

Insulators

1885(Part-54)1980

Lightning Arrester

1

Application guide for non-linear resistor type surge arresters for A.C. system

4004-1985

2

Lightning arresters for A.C. systems: Non-linear resistor type lightning arresters

3070(Part-1)  1985

 

* * * *