Electrical Equipment layout Design GuidelinesSubstation shall be located in a safe area close to the load Centre. In exceptional cases, e.g., in view of restricted space on offshore platforms, electrical substations may be located in a hazardous area classified as Zone 2, subject to approval by the Principal. The following requirements shall then apply:- Interior of the building shall be pressurized in accordance with IEC 60079-13;- An overpressure of at least 50 Pa (0.5 mbar) shall be maintained by a duplicate fan system with a suitable dry element dust filtering system to ensure a supply of clean air, each fan system being capable of supplying the required pressure;- The fan systems shall be suitable for a Zone 1 area and shall be supplied from two independent sources of electricity;- Both fans shall normally be in operation and shall have individual alarms to indicate Failure in a manned control Centre Proper access shall be provided for Maintenance and Operation of Indoor and Outdoor Equipment.Substation floor shall be raised above grade level with a cable cellar. The cable cellar floor shall be at least 300mm above the approach road level and shall be cemented. It shall have a minimum clear height of 2.5m and shall house all the cable trays and its supports.Transformer floor shall be at least 150mm above the approach road level.In addition to the entry to substation for operating personnel, a separate entry of minimum 3m x 3m with rolling shutter shall be provided for bringing in all equipment for installation. The main entry for operating personnel for pressurized substations shall be provided with double door system with an airlock lobby. It shall also have an emergency door opening outwards.Substation building shall be without any columns within the switchgear room to ensure optimum space utilization, unless otherwise specified.If electrical equipment is installed on the roof of the substation, e.g., air-conditioning compressor / condensers, a cage ladder shall be provided leading from an entrance platform to the roof.Battery banks shall be located in a separate adequately ventilated room in the substation with necessary exhaust system (minimum 2 exhaust fans) and water connection with sink. Floor of the battery room and walls up to 1.5m height shall have acid / alkaline resistant protective epoxy paint. Light fittings in this room shall be chemical resistant type. However, separate battery room is not required in case of VRLA batteries.UPS and other power electronic equipment e.g. VSD shall be located in air-conditioned room unless otherwise specified.Substation shall have fire extinguishers, first aid boxes and other safety equipment as per statutory requirements. Insulating mats of required rating shall be provided in front of switchboards.Equipment like transformers, neutral grounding resistors, reactor and HV capacitor Banks shall be located in bays adjacent to the substation building. All bays shall have well drained floor, surfaced with gravel or other suitable material.Substation wall adjacent to the transformer bays and walls separating transformers shall be 355mm thick in case of brick construction and 230mm thick in case of RCC construction.Transformer bay shall have R.C.C. foundation with steel rails for transformer. The height of the foundation shall be at least 500 mm above the finished grade level. Transformer entry/exit shall be through gates. In order to prevent oil, whether from a small leakage or outflow from transformer tank, from reaching and polluting the water bearing stratum, transformers shall have following provisions, depending on the oil capacity of the transformerOil capacity upto 2000 litres: Shall be provided with a layer of 100mm deep stones of about 40mm granulation, all around the transformer, for a width of 20% of the transformer height or a minimum width of about 800mm.Oil capacity exceeding 2000 litres: Shall be provided with oil containing pits. The pit shall extend all around the transformer for a width of 20% of the transformer height or a minimum width of about 800mm. In case oil capacity exceeds 900 litres, in any chamber, provision shall be made for draining away of any oil, which may escape or leak from the tanks to a waste oil tank.Substation building shall be sized to maintain adequate clearances between equipment for ease of maintenance. The following minimum clearances shall be maintained.Sr. No.LocationClearance

1Front clearance of Medium voltage Switchgear2500 mm

2Front clearance of all other switchboards2000 mm

3Rear Clearance for panels having front only access = 750mm

4Rear Clearance for panels having rear access 1500mm for MV & 1000mm for LV

5Side clearance between 2 switchgear1000mm after considering space for future panels

6All around clearance for Transformer1000 mm

7All around clearance for NGR1000 mm on 2 sides and 200mm on other 2 sides

8All around clearance for Capacitor bank and Series Reactor1000 mm

9Front clearance for wall mounted equipment1000 mm

10Front clearance for operator station / Annunciation panel / Control panel2000 mm

11Head Room Clearance below bus duct or any other overhead equipment 2000 mm

12Battery Rack to wall clearance for Single row Single/Double tier & Double row Single tier100 mm

13Battery Rack to wall clearance for Double row Double tier 750 mm

14Battery rack to rack Clearance 750 mm

Vertical Clearance above the top of the highest equipment shall be minimum 1500mm measured form bottom of Roof Slab (except transformer bay where same shall be 1000mm) and minimum 500mm measured from the bottom of the lowest roof beam. However, for the areas with false ceiling, minimum clearance of 750mm shall be provided between false ceiling and top of any equipment. Space for Future extension of Switchboards shall be provided (one panel extension on each side minimum)DG sets shall preferably be located in a separate building in a safe area to reduce the noise level in substation. In case, it is located in the substation, DG set foundation shall be structurally delinked from the slab / floor of the rest of the substation. Exhaust of the Diesel engine shall be kept away from the process area. Diesel day tank shall be kept outside the DG room. Suitable ventilation shall be provided to avoid heat accumulation in the room.All cable entry holes in the substation floor or walls shall be suitably sealed. Where such cable entry holes are required to be gas tight and/or fire resistant, multi-cable transits blocks shall be installed, or silicone foam, weak-mix concrete (in floors only) or a chemical compound with subliming heat resistant and fire retardant properties may be used.Instrumentation and control system interface panels should be located in the same switch room as the associated switchboard.A smoke detection system comprising of point detectors or beam detector(s) should be installed in substations. A common alarm shall be routed from each substation direct to the plant's central fire and gas alarm system, i.e., independently of the substation alarm annunciator.SF6 Gas Insulated Switchgear (GIS) shall be installed in a separate room. This room shall have a gas detection and alarm system which shall provide for an alarm display at the outside near the entrance doors, and a remote alarm in a manned control room. An exhaust system shall be installed which shall automatically be switched on in the event of a gas release. The exhaust shall be at floor level, and shall be directed to the outside of the building at a location where the gas will be quickly diluted with air.Warning plates shall be provided at the outside of the building, instructing people not to enter without personal protection when the alarm display is on.All auxiliary equipment related to the GIS, e.g., protection and control systems, shall be installed in a separate room