CONSTRUCTION STANDARDS



  CONSTRUCTION STANDARDS:

I.

ERECTION OF 33/11 KV SUBSTATION

1

The switchyard must be 300 mm (one foot) high over the highest level of the adjacent area.

2

Substation steel structure

 

152 x 152 mm H type beams/9.1 m PSCC poles

 

All members shall be with Galvanized M.S. Channel of size 100 x 50 mm. All parts to be hot dip galavanized after fabrication.

 
  1. 33 KV bay width shall be : 4.5mm
 
  1. 11 Kv bay width shall be :' 3.5mm
 
  1. Minimum height over head line take off 6.4 mts (19 feet)
 
  1. 33 KV LA's : Stn type (for common bus)
 
  1. 33 Kv and 11 KV bus conducted shall be of 200 sq mm AAA conductor (panther)

3

i)  3 Nos single phase PT's to be erected on 33 KV bus on the structures.

 

ii) 1 No. 3-Ph PT to be erected on the structures in 11 KV bus

      4

33 KV HG fuse set to be erected on independent structure. Arcing homes shall be 25 x 6 mm Tinned coated copper flat. Bimetallic connectors to be provided for giving to conductor at both ends. Horn gap shall be 15 inches.

5

Galvanized step Bolts to be provided for the foundation supports of VCB.

6

Station DTR with AB switch and H.G fuse set to be erected on structure

7

Bolts  Nuts shall be hot dip galvanized

8

33 KV 800 A AB switch double break shall be errected

9

11 Kv side : 11 KV 400 A AB swicth double break shall be errected 9bus Side)

10

11 KV 400 AAB switches for feeders shall be errected.

11

11 Kv line type LA's to be orected 3 nos each feeder

12

Earthing :

 
  1. Every structure shall be double earthed with 50 x 6 mm GI flat.
 
  1. PTR neutral shall be double earthed. One to separate earth pit and other to earth grid with flexible jumps at neutral of PTR.
 
  1. AB switch handile shall be earthed through No. 8 GI wire closely in the spring shape.
 
  1. The metalic fencing shall be connected to the earth grid.
 
  1. The perimeter of the earth grid will extend for 1 m more out side metalic fencing.
 
  1. The metalic fencing should be connected to the earth grid at each corner and at points not exceeding 50 metres.
 
  1. Body. OLTC and tank of PTR shall be earthed.
 
  1. Minimum 14 nos earth pits shall be provided.

   13

Earth Electrode: 100mm dia (inner dia) 10mm thick and 2.7m long Ci pipe with flange at the top

 

Earth grid connections between electrodes with 75 x 8mm M.S flat. All joints shall be of but jointing.

 

Connections between earth grid and equipment (Top connections) with 50 x 6 mm Gi flat.

 

Back filling with Bentonite soil of 300mm dia metre around the earth electrode (Coke and shall not be used as they are corrosive)

 

All junctions and raisers in the grid shall be painted with bituman paint and then covered with Hessain tape avoid rusting.

14

The combined earth grid resistance shall be less than 1 Ohm.

II.

ERECTION OF POLES

 

S.No

Support

Size of Concrete

 

1

    8.0 / 9.01 mts PSCC pole or RS joist / Rail pole

0.6 x 0.6x 1.5 mts

 

2

    9.5 mts PSCC/RS joistpole/Railpole

0.6 x 0.6 x 1.8 mts

 

3

    11.0 mts spun pole

0.75 x 0.75 x 2.0 mts

 

4

    Stay set

0.45 x 0.45 x 1.265 mts

Note : Coping shall be provided for RS joist/ Rail pole Planting depth of pole shall be 1/6th of  the total length.

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