Annexure IX

Area requirements for sub-stations of buildings-


  1. For additional 1000 of covered area, a load of 90 KVA will come up with 150 KVA TR. capacity at 60% loading capacity.
  2. For the  addition of one transformer as per the covered area, a space of 16 additional sq.m is to be provided.
  3. In case of any deviation in space size, the same shall be considered with the approval of the Electricity Board.
  4. The floor of the substation shall have cable trenches of 0.6 m depth, the layout for which will be given at the time of actual construction.

For this purpose, a dummy floor up to 0.6 m depth shall be provided to facilitate cutting/digging of floor for the installation of equipment and making subsequent changes in trenches. This floor shall be capable to withstand a minimum load of 10 tones of each transformer which will be mounted on four wheels.

The break-up spaces required for different installations in a substation are given as below:

  1. Supply company’s Switchgear room and/or space for meters.
  2. Transformer Rooms: The number and size of transformer rooms shall be ascertained from the total power requirements of the company. To determine the size of transformer and clearance around a transformer, this practice shall be referred to- ‘I.S.1887-1967 code of practice for installation and maintenance of Transformer’. A 500 KVA transformer shall be provided with a minimum space of 4 m x 4 m. If a transformer is to be installed, outdoor space shall be provided and the adequate provision for a safety enclosure is to be made. Transformers can be installed inside or outside provided that the movement of fire tender is unobstructed. For transformers having a lot of oil content (more than 2000 lt.) soak pits are to be provided in accordance with rule 64 of Indian Electricity Rules, 1956. Only dry type transformers shall be permitted if installed in the 1st basement.
  3. High Voltage Switch Rooms – In case of substations having one transformer, the owner is required to provide only one high voltage switch. In the case of single point supply for two transformers, the number of switches required is 3 and for ‘n’ transformers the number of switches is n+1. The floor area required in case of a single switch will be roughly 4 m x 1m and for every additional switch the length should be increased by 1mt.
  4. Low Voltage Switch Rooms – The floor area requirement in respect of low voltage switchgear room cannot be determined by any formula.
  5. Room for Stand-by-Generator – A room space not less than 6 m x 9 m shall be provided for housing a standby Generator set of 50 KW.

1.1.1 A: Location of electric sub-station in basement of multistoried buildings-

The electric sub-station should be provided in the approved/sanctioned covered area of the buildings not below the first basement level. It should be on the periphery of the building with a clear independent round the clock approach having a proper ramp with slope.

1.1.2 Other Requirements for Substations

  1. The substation will preferably be located on the ground level failing which it can be in the basement floor in no case at higher level.
  2. The substation can be split at various levels as per space availability.
  3. The minimum width of the sub-station space shall not be less than 6 m.
  4. The areas given above in respect of the different categories of rooms hold good if they are provided with windows and independent access doors.
  5. All the rooms should be provided with partitions up to the ceilings. They shall have proper ventilation. Special care should be taken to ventilate the transformer rooms and where necessary, louvers at lower levels and exhaust fans at higher levels shall be provided at suitable locations.
  6. In order to prevent storm water entering the transformer and switch rooms through the soak pits, the floor level of the substation shall be at least 15 cm above the highest flood water level that may be anticipated in the locality.
  7. DG & panels to roof : Allowed on roof and setback provided movement of fire tender is unobstructed.

1.2 Cable Trenches Shafts Etc.

1.2.1 A suitable number of vertical shafts, rising mains, distribution boxes, etc. shall also be provided as per the requirements at suitable location. Cable trenches with suitable handy covers for the entry of the cables up to the substation onwards up to the street adjoining other buildings shall also be provided as per the requirements. These vertical shafts, rising mains, distribution boxes, cable trenches, etc. shall be so constructed as to be accessible only to authorized personnel.

The rising mains and other installations in the vertical shafts, tap off boxes distribution boxes etc. required at each floor shall be provided, installed and maintained by the owner at their own cost. Adequate enclosed space shall also be provided at each floor for installation of equipments for distribution on respective floors such as distribution boxes, cut-out, and meter boxes and main switches.

1.2.2 Location of Switch Room: In large installations other than where a substation is provided, a separate switch room shall be provided. This shall be located as closely as possible to the electrical load center and suitable ducts shall be laid with a minimum number of bends form the point of entry of the supply to the position of the main switchgear. The switch room shall also be placed in such a position that rising ducts may readily be provided there from to the upper floors of the building in one straight vertical run.

In larger buildings, more than one rising duct and horizontal ducts may also be required for running cables from the switch room to the foot of each rising main. Such cable ducts shall be reserved for the electrical services only, which may, however, include medium and low voltage installations, such as call bell systems. Telephone installation should be suitably segregated.

1.2.3 Location and Requirement of Distribution Panels: The electrical gear distribution panels and other apparatus, which are required on such floor, shall conveniently be mounted adjacent to the rising mains, and adequate space should be provided at each floor for this purpose.

1.2.4 Location and Requirement of the PBX/PABX Room: Information regarding provision and location of PBX/PABX room, telephone outlets and riser shall be ascertained from the relevant Authority / concerned local body. Adequate space should be provided for installation of the Sub-Distribution Board.

1.3. General

The maintenance of the built up space for electric sub-station, distribution equipment, Vertical shafts and enclosure at each floor shall be done by the owner. The standby arrangement for electricity supply up to and including the substation equipment and distribution pillars at the substation shall be provided compulsorily.