Electrical substations shall normally be required in case of office buildings with a total plinth(covered) areas of 5000 sqr. m; even buildings with smaller plinth (covered) areas but with large loading may require a substation, the load limit being set by regulations in the Electricity Act or by the relevant electrical utilities.
To arrive at the of the substation required, a load factor of 70% shall be applied to the estimated load of the building, unless future expansion requirements dictate that a higher figure be considered.
Location
In a multi-storied building, the substation shall preferably be installed on the lowest floor level, but direct access from the street for installation or removal of the equipment shall be provided. The floor level of the substation or switch room shall be above the highest flood level of the locality. Suitable arrangements should exist to prevent the entrance of the storm or flood water into the substation area.
It is preferable to locate the electrical substation adjacent to the the air-conditioning plant room(if any) in such a way that the distance from the controlling switchboard of the air-conditioning plant rooms and corresponding switches in the electrical substation are kept minimum.
In case of a building complex, or a group of buildings belonging to the same organization, the substation should preferably be located in a separate building and should be adjacent to the generator room, if any. Location of substation in the basement floor should be avoided. In case the electric substation has to be located within the main building itself for unavoidable reasons, it should be located on ground floor with easy access from outside.
For transformers having large oil content ( more than 2,000 litres), soak pits are to be provided.
The minimum area required for substation and transformer room for different capacity are given in Table-1.
Table-1 : Area Required for Transformer Room and Substation for Different Capacities
The minimum height of the substation room shall be 3.6 m.
To arrive at the of the substation required, a load factor of 70% shall be applied to the estimated load of the building, unless future expansion requirements dictate that a higher figure be considered.
Location
In a multi-storied building, the substation shall preferably be installed on the lowest floor level, but direct access from the street for installation or removal of the equipment shall be provided. The floor level of the substation or switch room shall be above the highest flood level of the locality. Suitable arrangements should exist to prevent the entrance of the storm or flood water into the substation area.
It is preferable to locate the electrical substation adjacent to the the air-conditioning plant room(if any) in such a way that the distance from the controlling switchboard of the air-conditioning plant rooms and corresponding switches in the electrical substation are kept minimum.
In case of a building complex, or a group of buildings belonging to the same organization, the substation should preferably be located in a separate building and should be adjacent to the generator room, if any. Location of substation in the basement floor should be avoided. In case the electric substation has to be located within the main building itself for unavoidable reasons, it should be located on ground floor with easy access from outside.
For transformers having large oil content ( more than 2,000 litres), soak pits are to be provided.
The minimum area required for substation and transformer room for different capacity are given in Table-1.
Table-1 : Area Required for Transformer Room and Substation for Different Capacities
Capacity of
Transformer
(Kva)
|
Transformer Room Area( m2)
|
Total Substation Area (with HT,
LT Panels &;Transformer Room but without Generators) (m2)
|
1 x 150
|
12
|
42
|
1 x 250
|
13
|
45
|
2 x 250
|
26
|
90
|
1 x 400
|
13
|
45
|
2 x 400
|
26
|
90
|
3 X 400
|
39
|
135
|
2 X 630
|
26
|
90
|
3 X 630
|
39
|
135
|
2 x 1000
|
26
|
90
|
3 X 1000
|
39
|
135
|
The minimum height of the substation room shall be 3.6 m.
Layout
In allocating the areas within a substation, it is to be noted that the flow of electric power is from supply company network to HT room, then to transformer and finally to the low voltage switchgear room. The layout of the rooms shall be in accordance with the flow.
The area given in Table-1 hold good if they are provided with windows and independent access doors in accordance with local regulations.
All the rooms shall be provided with partitions up to the ceiling and shall have proper ventilation. Special care should be taken to ventilate the transformer rooms and where necessary louvers at lower level and exhaust fans at higher level shall be provided at suitable locations in such a way that cross ventilation is maintained.
Arrangement shall be made to prevent storm water entering the transformer and switch rooms through the soak pits, if the floor level of the substation is low.
Provision for Standby Supply
In buildings where interruption of electrical power supply would result in panic, hazard to life and property or major production loss, provision should be made for standby power supply.
The capacity of standby generating set shall be chosen on the basis of essential light load, essential air-conditioning load, essential equipment load and essential services load, such as one lift out of a bank of lifts, one or all water pumps, etc. Table-2 shows minimum generator room area requirements for different sizes of generators.
The generating set should be housed in the substation building to enable transfer of electrical load quickly as well as to avoid transfer of vibration and noise to the main building. The generator house should have proper ventilation and fire fighting equipment installed.
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