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GRID 

 The Tata Power Companies (TPC) and the Maharashtra State Electricity Board

(MSEB) have their generating stations located in different parts of Maharashtra

State and form an interconnected transmission system grid in the Mumbai-Pune

region. Electric Power from this system is transmitted at 220/110kV through

overhead conductors and underground cables amongst others to TPC’s sub-stations

at Carnac, Parel, Dharavi,Backbay & Mahalaxmi. From here power is made available

to BEST at 110/33/22kV.

 The BEST Undertaking on behalf of BrihanMumbai Municipal Corporation (who are

the licensees for the distribution of electric power within the City Limits of Mumbai)

receives power in bulk from the TPCs. At 110 / 33 / 22kV, 3 Phase, 50Hertz.

BEST SYSTEM 

110 / 33 / 22 kV Distribution System: 

 The 110 / 33 / 22 kV substations are completely indoor

equipped with power transformers, switch-gears, controlpanels, reactors, capacitors, batteries and other auxiliary

equipment.

Bulk power at 110 / 33 / 22 kV is transmitted from

 Tata’s five sub-stations through underground cables to

BEST’s receiving sub-stations situated at different localities in Mumbai where the

BEST Undertaking has installed 110 / 11 kV, 110 / 33 kV, 33 / 11-6.6 kV or 22 / 11-

6.6 kV or 33/11 kV power transformers. The Power transformers have been provided

with On load Tap Changing (OLTC) gear for regulating the voltage for giving

stabilised supply to the consumers.

11/6.6 kV distribution system: 

Each distribution substation comprises one or more

incoming and outgoing feeders and one or more

transformers of 1600/1000/630 kVA. The outgoing feeders

and primary of the transformers are controlled and

protected by 11 KV oil circuit breakers in conjunction with

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their associated trip coils and current transformers. The distribution substations are

normally equipped with 11 kV switch-gear, distribution transformers and Low

Voltage Distribution boards or pillars. 56 kVAr capacitor banks are connected on the

L. V. side of transformers for power factor improvement.

 The distribution substations in the city are of the following three types :

 

Indoor Type – Where the switchgear and the

transformers are located inside a building.

 

Outdoor Type – Where the switchgear and the

transformers are located in open land and directly

subjected to outside atmosphere.

 

Indoor/Outdoor Type – Where the switchgear is

located inside a building and the transformers are

located in an outdoor plot open to sky.

 

11 / 6.6 kV Cable Network:

Underground 11kV cables radiate from the BEST receiving sub-stations to supply

power to a large number of distribution substations and to certain consumer’s

substations. These feeders form a radial network under which each feeder supplies

on an average four to five substations in series.

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