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Sub Station Guideline (As per NBC)
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| Substation Location |
Location of substation in the basement should be avoided, as far as possible. |
| If there is only one basement in a building, the substation/switch room shall not be provided in the basement and the floor level of the substation shall not be lowest point of the basement. |
| Substation shall not be located immediately above or below plumbing water tanks or sewage treatment plant (STP) water tanks at the same location |
| Substation Door/Shutter |
All door openings from substation, electrical rooms, etc, should open outwards |
| Vertical shutters (like rolling shutters) may also be acceptable provided they are combined with a single leaf door opening outwards for exit in case of emergency |
| For large substation room/electrical room having multiple equipment, two or more doors shall be provided which shall be remotely located from each other |
| No services or ventilation shafts shall open into substation or switch room unless specific to substation or switch room |
| Transformer Location |
In case of HV panel and transformers located at different floors or at a distance more than 20 m, HV isolator shall be provided at transformer end |
| In case transformer and main MV/LV panel room are located at different floors or are at a distance more than 20 m, MV/LV isolator shall be provided at transformer end |
| In case of two transformers (dry type or transformers with oil quantity less than 2 000 liter) located next to each other without intermittent wall, the distance between the two shall be minimum 1 500 mm for 11 kV, minimum 2 000 mm for 22 kV and minimum 2 500 mm for 33 kV. Beyond 33 kV, two transformers shall be separated by baffle wall of 4 h fire rating. |
| If dry type transformer is used, it may be located adjacent to medium voltage switchgear in the form of unit type substation. In such a case, no separate room or fire barrier for the transformer is required either between transformers or between transformer and the switchgear, thereby decreasing the room space requirement; however, minimum distances as specified. |
| Oil Filled Equipment (Transformer / C.B) |
Substations with oil-filled equipment/apparatus transformers and high voltage panels shall be either located in open or in a utility building |
| They shall not be located in any floor other than the ground floor or the first basement of a utility building not be located below first basement slab of utility building. |
| They shall have direct access from outside the building for operation and maintenance of the equipment. |
| It shall be separated from the adjoining buildings including the main building by at least 6 m clear distance to allow passage of fire tender between the substation/utility building and adjoining building/main building. |
| Substation equipment having more than 2 000 liter of oil whether located indoors in the utility building or outdoors shall have baffle walls of 4 h fire rating between apparatus. |
| Provision of suitable oil soak-pit, and where use of more than 9 000 liter of oil in any one oil tank, receptacle or chamber is involved, provision shall be made for the draining away or removal of any oil which may leak or escape from the tank, receptacle or chamber containing the same |
| Power Supply Voltage |
supply is at 240 V single phase up to 5 kVA, 415/240 V 3-phase from 5 kVA to 100 kVA, 11 kV (or 22 kV) for loads up to 5 MVA and 33 kV or 66 kV for consumers of connected load or contract demand more than 5 MVA. |
| In case of connected load of 100 kVA and above, the relative advantage of high voltage three-phase supply should be considered. |
| In case of single point high voltage metering, energy meters shall be installed in building premise,such a place which is readily accessible to the owner/operator of the building and the Authority. The supplier or owner of the installation shall provide at the point of commencement of supply a suitable isolating device fixed in a conspicuous position at not more than 1.7 m above the ground so as to completely isolate the supply to the building in case of emergency |
| Trench Drain |
In case of cable trench in substation/HV switch room/MV switch room, the same shall be adequately drained to ensure no water is stagnated at any time with live cables.
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| Fence for Substation |
Enclose any part of the substation which is open to the air, with a fence (earthed efficiently at both ends) or wall not less than 1800 mm (preferably not less than 2400 mm) in height
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| HV Distribution in Building |
The power supply HV cables voltage shall not be more than 12 kV and a separate dedicated and fire compartmented shaft should be provided for carrying such high voltage cables to upper floors in a building. These shall not be mixed with any other shaft and suitable fire detection and suppression measures shall be provided throughout the length of the cable on each floor.
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| Switch Room / MV switch room |
Switch room / MV switch room shall be arrived at considering 1200 mm clearance requirement from top of the equipment to the below of the soffit of the beam .In case cable entry/exit is from above the equipment (transformer, HV switchgear, MV switchgear), height of substation room/HV switch room/MV switch room shall also take into account requirement of space for turning radius of cable above the equipment height.
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