Indoor Transformer Installations

By Nirmal -
Indoor
1. Only dry type transformer shall be installed inside residential./ commercial buildings.

While using oil filled transformers certain steps are there to be followed:

a. it must be installed OUTDOOR only.
b.Easy access of fire station vehichles.
c.the transformer room/building must be 1.5 mtr away from the residence/commercial building
d. the substation must be weather proof, walls must have minimum thickness of 230mm of thick RCC, Fire resistant wall must be there.
e. outside corporation area minimum distance between transformer and substation must be 6m.

2. dry type transformer must be installed above ground floor.
3.ABSF/VCB ust be provided at primary side.
4. Minimum cable size at primary must be 150sq.mm XLPE (aluminium) or 70 sq.mm XLPE (Aluminium) if backup fuse is provided.
5.Oil filled TRFR must be segregated from HT and MV switchgear.
6.oil drainage facility/soak pits must be provided for oil filled transformers if oil quantity is above 2000 litres.
7. 1.25m al round clearance must be provided for indoor transformers.
8. transformer must be installed at the periphery of the building for easy access.
9. doors and windows of TRFR room must be non inflammable materials.
10. minimum 50cm headroom clearance must be provided for transformer.
11. 130mm phase to phase clearance and 80mm phase to earth clearance must be provided for bus bar.
12. 1 meter clearance must be there in front of HT panel

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