Electric Supply

It has been already indicated that the erstwhile Bombay Electric Supply & Tramways Company started supplying electricity to the city in 1905. Until 1926, the Company had been generating its own electricity for distribution to its consumers. Later, the Tata Electric Companies started supplying electricity to the BEST.The Tata Electric Companies (The Andhra Valley Power Supply Co. The Tata Power Supply Co., The Tata Hydroelectric Power Supply Co.) generated electricity from their reservoirs at Bhira, Bhivpuri and Khopoli in the Western Ghats. A major portion of it was transmitted through 110,000 Volts overhead lines to their Receiving Stations at Dharavi and Parel. In these Receiving Stations the voltage used to be transformed to 22,000 and 6,600 volts for ease of distribution. The Tata Electric Companies provided, through their cables, electricity at requisite voltage to the industries and mills, the Railways, the Bombay Suburban Electric Supply Company and the BEST.

In 1947, when the Company was taken over by the Municipal Corporation, the Undertaking was buying electricity from Tatas at nine receiving points known as : Kussara, Mahim, Kingsway, Jamnadas, Suparibag, Lalbaug, Esplanade, Palton and Backbay. At all these points, except Kussara, Kingsway and Mahim, the supply was received at 6,600 Volts. The supply was received at 22,000 Volts and transformed through Tatas’ transformers to 5,500 Volts at Kussara and to 6,600 Volts at Kingsway and Mahim. From these receiving points the cable network carried power to 247 Substations situated in different areas of the city. With the help of transformers at these substations, the voltage was further transformed to 400/230 Volts, suitable for use in the factory, shop and home. It was made available to the consumers through a low voltage distribution network and service cables to individual buildings. The major portion of electricity distributed was at Alternating Current (A.C.). But, in some areas of South Bombay, particularly Fort, Kalbadevi and Girgaum, Direct Current (D.C.) was supplied at a voltage of 460/230 Volts. To convert it into D.C., Rotary Converters were operated at Pathakwadi, Telwadi, Apollo and Palton Road Substations and Mercury Arc Rectifiers were used at Phirozshah Mehta Road substation.


Soon after the Corporation took over the Company, India got its freedom. This meant a reconsideration of the major objectives of the Undertaking and a reorientation of its outlook in the context of the changing political situation. The Second World War had also given a new impetus to the utilisation of electricity.

The Undertaking not only continued many of the healthy traditions set by the Company but also improved its methods of working. The Undertaking is now well known in India for its service of providing electricity with minimum interruptions and at proper voltage, at the minimum cost. It is also known for the quick restoration of supply in the event of any faults developing in the distribution system.

In the fifty years since municipalisation, the maximum demand on the system has risen from 53,000 kilowatts to 6,33,000 kilowatts; the number of substations from 247 to about 1733; the length of underground cables from 1,263 kilometres to 6,966 kilometres; the number of consumers from 1,08,000 to 7,98,152; the number of street lamps from 2,215 to 33,534.

Refrigerators, air-conditioners, geysers, television sets and other electrical appliances are now being extensively used in homes. The use of air-conditioning and better standards of lighting in the office is also becoming increasingly popular. In the factories and entertainment centres the use of electricity is on the increase. Skyscrapers have come into being and so have hutments. All this expansion has necessitated the use of modern and sophisticated equipment. The responsibilities of the electric supply branch of the Undertaking have become correspondingly greater and more complex.


In the days of the BEST Company some parts of the network were supplied at 5,500 Volts and in some other areas the distribution voltage was 6,600 Volts. This non-uniformity led to considerable loss of flexibility. More important, it was realised that at the higher voltage of 6,600 voltage, 20 per cent more electricity could be conveyed and this without major replacement of equipment. So, after elaborate planning, in 1954, the 5,500 Volts system was changed over to 6,600 Volts. This major change was carried out with no interruptions in the supply to consumers.

In 1949 the Undertaking established its first 22000 volts receiving station at Grant Road. This was followed by 22,000 volts receiving station at Apollo. In 1955, two more receiving stations at Kingsway and Kussara were changed over 22,000 volts and all 6600 volts metering points were eliminated. As on today BEST has 35 receiving stations including two 110 KV receiving stations. The demands on the system were growing and further changes were necessary. Under an Agreement with Tatas in  1956, they established a third Receiving Station at Carnac Bunder. This new station and the existing 2 stations at Parel and Dharavi, now became the Undertaking’s only points of supply. The supply was now taken at these 3 points and metered at 22,000 Volts. The Undertaking laid 22 KV cables from these points to it own receiving stations, the voltage was stepped down from 22,000 volts to 6,600 volts through the Undertaking’s own transformers for feeding into its 6,600 Volts system. The elimination of the old 6,600 Volts Receiving Stations was spread over a period of years. It was changed over to 22,000 Volts as and when new Receiving Stations were built by the B.E.S.T. Thus in 1956, the Worli Receiving Station was established at Fergusson Road. This was followed by many Receiving Stations at various places.

To supply electricity at a steady voltage is an important responsibility of the Supply Branch. There are considerable variations in the voltage received from Tatas at the different Receiving Stations. To compensate for these fluctuations, the Undertaking installed, on its 22 KV transformers, equipment known as “On load tap changers”. This device absorbs the fluctuations and enables supply of a steady voltage to consumers.


It has already been mentioned that Direct Current electricity was supplied to the Girgaum, Kalbadevi and Fort areas in South Bombay. An appreciable portion of the electricity distributed in 1947 was accounted for by this. An alternating Current supply had many advantages over supply at Direct Current. It is more convenient and cheaper to transmit electricity at Alternative Current through smaller cables at a higher voltage than through larger cables at a lower voltage.

In 1952, there were 25,000 consumers using D.C. A change-over to A.C. meant changing their D.C. appliances where rotation was involved : appliances such as motors, fans, lifts, refrigerators. This presented a major problem. It required a considerable amount of special effort to persuade the D.C. consumers. As an inducement, they were offered partial compensation towards the cost of changing their appliances. The total compensation paid under the scheme was Rs.50 lakhs. But the expenditure was well worthwhile, as it enabled elimination of costly and wasteful equipment used for conversion from A.C. to D.C. As a result of persistent efforts, all the 25,000 consumers, except a hard core of 17, had changed over to A.C., by March 1972.


The Municipal Corporation had a contract with the Bombay Gas Company for gas lamps for street lighting. This contract was to expire in 1962. Until then, there were about 7500 electric lamps and 7000 gas lamps on the roads of Mumbai. The Municipal Corporation then decided to change over completely to electric street lamps and simultaneously to improve the level of illumination. A crash programme was taken in hand by the B.E.S.T. in 1966. When all the gas street lamps had been converted into electric lamps in July 1968, the number of electric street lamps had increased from 7500 to 19000. On 1st July 1968, Bombay wished a sentimental farewell to gas lamps when the Mayor switched on the “Queen’s New Necklace” on Marine Drive. This was a string of the lastest type of high power, coloured-corrected, mercury vapour lamps. Marine Drive is reputed to be the best-lit road in India and one of the best-lit in the world. It is one of the spots a visitor to Mumbai does not like to miss. Now with the introduction of sodium vapour lamps, it is called as ‘Golden Necklace’.


Initially, the Undertaking used to control each lamp separately by a switch, by a man going on his rounds every evening and morning to switch them on and off. This system had several disadvantages, especially in times of emergency. To provide central control points, it would be necessary to lay hundreds of kilometre of cables at enormous cost and dig up Mumbai’s roads to lay them. Other methods had therefore to be devised. One method was to install time-switches which automatically control the street lights, depending on the time of sunrise and sunset, but the use of this device is also limited. Another method tried is that which uses photo-electric switches. These contain devices which are sensitive to light. When the natural light on the road falls to a particular level, this device actuates a switch which puts on the street lamp. When the natural light improves to a particular level, the device switches off the lamp.


A ripple control scheme for controlling street lamps from one or two central points in the city was then considered. The ripple control equipment is installed at predetermined places in the electric supply network. The equipment sends out high frequency signals over the existing underground cables. These signals are picked up by a special device installed on each lamp or a group of lamps. Thus by pressing a button at central control points one can either switch off or switch on all the street lights in the city. But this scheme was costly and involved import of much of the equipment.; hence it was decided not to consider the scheme.

At present there are over 33,000 street lighting poles and most of them are on automatic control. The automatic control of street lighting poles has got two versions. out of 93 Street Lighting Poles used for remote control for street light poles, 53 are provided with masters/slaves arrangement for efficient controlling Remaining SLP’s are provided with time switch which will switch on/off street lights at the specified timing.

In future, we are exploring the concept of pagers system for quick and efficient operation of street light poles throughout Mumbai.

Sodium-vapour lamps made an appearance in the commercial areas of Mumbai in 1980. To save on fuel and, as an alternative, considering the rising cost of oil, mercury-vapour lamps were chosen for street-lighting. Fluorescent mercury vapour lights went up in large numbers in 1982. In 1990 came “Energy Efficient” lamps and “Energy Fluorescent” lamps followed them in 1993.

And the Electricity department does not work the magic only on the roads of Mumbai; Electricity is provided by the department for various public functions and religious celebrations. As many as twenty-five years ago, the department had made special arrangements for lighting at Girgaum Chowpatty, on the occasion of the immersion of the Ganesh idols. During the years the arrangements have kept improving.

And now the devotees of Lord Ganesh venturing some distance into the sea are helped by strong shafts of light.


Prior to the success in implementing effective remote control of street lights, the Undertaking had started controlling Receiving stations from two control points. There are now 35 receiving stations in the Undertaking where the voltage is stepped down from 110KV to 11 KV, 33 KV to 11 KV, 22 KV to 11KV and 22 KV to 6.6 KV.

On an average, each receiving station supplies power to 50 substations, feeding 21,000 consumers. The efficient operation of the equipment in these Receiving Stations is therefore vital, if the consumer is to receive reliable supply at a steady voltage.

With the help of this equipment we can control the circuit breakers, tap change control gear and the voltage. The Undertaking decided in 1966 to employ the Remote Control Scheme. It was possible to immediately implement this decision, because the control cables required for this purpose had already been laid. The manufacture of the equipment was entrusted to the Indian Telephone Industries at Bangalore. The two main control points are located at the Esplanade Receiving Station and the Kingsway Receiving Station from where all the Receiving Stations are monitored and controlled. The remote Control equipment was installed in 1970 at the ‘Vidyut’ Building near the Esplanade Receiving Station and at Kingsway in 1972.


The system provided by the Indian Telephone Industries was designed on electro-mechanical relay principle. Due to this it had limitations for the speed of operation. There was no data acquisition also. These factors forced the Undertaking to keep the system to a minimum level.

In 1980 BEST replaced the Supervisory Remote Control system with micro processor based Supervisory Control and Data Acquisition System (SCADA). Additional to SRC System SCADA functions are data acquisition, analysis and report generation.

The communication between the master control and receiving station is through underground communication cables.

To further improve the reliability and quick restoration of supply BEST is going in for microware wireless communication in the years to come. A very-high frequency radio link which was established in 1963 for quick communications is now getting outdated. This is being replaced by microwave system and cellular phones.

With the installation of this equipment, the restoration of supply when a fault develops in a system has become much more efficient and quicker. When a fault occurs in the system, a message is registered on the indicators at the central points. With the help of the links the operator at the control points can direct the field staff to quickly reach the places where the faults have occured and restore supply with the minimum delay.


Shortages are caused when the supply does not keep pace with the demand. But in spite of whatever the Undertaking might do to expand its distribution system well ahead of the demand, it has ultimately to depend on the supply from Tatas. In the early fifties for three consecutive years the monsoon had failed. The low water levels in Tata’s reservoirs, which are a source of power supply to Mumbai, had created a severe power shortage in the area. It became necessary to make alternative  arrangements. Many industrial installations in the city had generators of their own to serve as a stand-by. These private owners were asked to operate their generators for their own requirements. The power thus released was utilised to serve the other consumers. This scheme came to be know as the Power Pool Scheme. The Undertaking had taken a lead and played an important role in implementing this Scheme not only in Mumbai city but also in the entire State. Later the installation of more efficient generators in the Railways’ generating station at Chola and a new generating station installed at Trombay by Tatas, considerably improved the position, and in 1961 the Power Pool Scheme was discontinued.


In the old days when plenty of space was available, nobody had perhaps ever heard the words ‘Underground Substation’ and ‘Package Type Substation’. Due to the tremendous increase in the demand for electricity in all parts of the city, the need for Substations has been increasing. The procurement of sites for Substations, especially in the congested areas in the city, presents many serious problems. In the rural areas it is customary to have pole-mounted substations. Owing to the tall buildings around, the erection of such substations is dangerous in the city. Moreover, nobody would like the idea of building such pole-mounted Substations in a city like Mumbai, from the aesthetic point of view. In 1964, on an experimental basis, 5 vault-type transformers were imported. Our experience of them, since their installation in 1967 was not encouraging.

The population of Mumbai has been growing at a fast pace. Every day, hordes of people come to the city and the city accomodates them. Problems too have been growing fast; Slums, without the basic facilities, have been coming up alongside roads. In many cases, the slums have crossed the footpath to the bus-shelter. On the one hand, there is the lovingly nursed dream of a clean and beautiful Mumbai and on the other the depressing reality of a slum. On one side there is the slogan of a green Mumbai and on the other the sad sight of a footpath swallowed up by an ugly slum. When will this stop? The question has to wait for an answer. A voice is sometimes raised against this by the white-collared gentry. Efforts are made now and then to pull down or push back the ramshackle huts. But soon enough they re-appear on the same spots. As time passes, the huts come to be regularised and the Electric Supply branch had to install a separate meter for every hut. Now the paths snaking through the huts have their lighting like the huts themselves. The sensible Mumbaites have accomodated these huts too.

During last some years more and more of Sky scrapers have been going up – and up! The sea has literally been pushed back in several places to make room for some of them. The Cuffe Parade, Nariman Point and the Backbay Reclamation areas are now virtually cement jungles. To provide electricity to these sky scrapers and this ever-widening expanse, is not a simple job. There are the new buildings and the new technology : T.V. Sets, Video and Audio Sets, mainly to entertain and the washing machine and air-conditioning to make life easier. And a variety of machines, small and big, are coming into use on a larger and larger scale. And the computer age is upon us. Naturally, the demand for electricity has rocketed; the demand from sky-scrapers particularly for computers and air-conditioners. The demand for commercial use of electricity, too, has been growing fast.

The height of buildings creates several problems in reaching electricity to them. Therefore, the need for a high pressure electricity set-up. One such set-up required for a Sky scraper is adequate for 400 residential and office buildings.

At present, the Undertaking buys its electricity from the Tata Electric Company. But if it produces its own electricity it will be more convenient, and will also effect a large saving. Its production cost will be less and the consumers demand can be met better. For this purpose the Undertaking is launching its own generation programme in the near future.

The BEST was the first organization in India to supply electricity through underground cables – and that too using the latest technology. Since 1989, the voltage of its receiving stations has been increased from 22KV to 33KV. Not only that, it built at Nariman Point that very year a receiving station of the capacity of 110 KV. In this country such a sub-station is normally outside a building and also far from a residential zone. This one is within a building. And, except for the lower floors, this building is used for private establishment. Most people working every day on the upper floors are probably not aware that below them is a power-station of the capacity of 110 KV. In 1993 the Undertaking also set up a receiving station of 110 KV at Khetwadi. This one also is inside a building.


Switch-gears : It has already been stated that the Undertaking has been in the forefront in using the latest technology in the system of electric supply. At present the Undertaking uses switch-gears of various types and using various technologies. For example, airblast, minimum oil circuit breakers, SF-6 circuit-breakers, Vacuum circuit-breakers and gas-insulated circuit-breakers. These circuit-breakers, being of the latest type, do not need supervision.

As these switch-gears occupy less space, it is possible to set them up where otherwise enough space is not available. Thus, the use of these gears has been quite profitable to the Undertaking.

Cables and their Testing : The BEST has the largest underground cable distribution system. As a matter of fact, compared to the ‘overhead’ system, the method of carrying electricity through underground cable is far more costly. But considering the congested housing and the crowded roads of Mumbai the ‘overhead’ system would be unthinkable. So, although the underground system is costly, from the viewpoint of reliability and safety, it is advantageous.

Later, the Undertaking started using upto-date technology in the cable and jointing system. There was a shortage of the copper used in the cables. The government brought control on the use of copper. Finally, as an alternative, aluminium cables were brought into use. Then came “PVC”. For high-power transmission, XLPE cable was brought into use in 1982.

The short-circuit test was employed on the underground cables. The BEST was the leading organization in testing low-pressure cables. Till 1980, high-voltage cables were tested by the “Bridge Method”. During 1980 for the testing of high-voltage cables BIECCO surge generators were purchased. And in 1990, the Undertaking got a “testing van”. equipped with full apparatus. This van is able to detect the faults in both high-voltage and low-voltage cables. This van was bought although it costs a great deal. Its main advantage is that by removing the faults in an electrical set-up in the minimum time, it enables the undertaking to provide good, dependable and prompt service to the consumers. The undertaking is using four of such “Testing Vans” at present.

Communication and Monitoring Systems : BEST is the first electric supply organization to start VHF communication and that it did in 1960. For the messages to be delivered promptly, the wireless message system was started in 1963. It has now become a simple operation to restore the electric supply by detecting the defects by going to the spot quickly in a mobile van.

For the efficient operations during the year 1967, the area was bifurcated into North and South. In 1991, the department concerned with the operations and maintenance activities was again bifurcated into four zones namely North, Central North, South and Central South. If there was any fault in the machinery, in order to spot it and to take prompt action to correct it, a “supervisory remote control” of the most modern kind was set up.

Meters and Relays : Over the years, changes have been taking place in the electric meters used. The old type of meters did not prove as efficient as they might have. Therefore, in 1994, the electricity section brought into use “electronic meters” and ‘solid state relays’. As recently as 1995, with the help of modern technology and computers, the Undertaking proposes to launch the “remote metering system”.

Computerisation in the Electricity Supply Departments : The computer is now used in a big way in the BEST Undertaking. Of, course, computerization has assumed importance in all areas of activity. Even then, it must be stated, the BEST was the first organisation in the country to issue electricity bills to consumers through the computer and also use it on a large scale. The computerised billing has been going on since 1974 and within a fixed period the bills are delivered to the consumers at their houses, unerringly. In 1988 began the use of the Personal Computer in the department. As a result the work of the Department has been going on even more efficiently. It is easier than ever now to provide prompt service to the consumers. Consumers complaints are settled without delay giving them full satisfaction.

The computer gets you the details you want in a few moments. For example, the consumer’s name, address, meter number, system number, the use to which the electricity is put – whether domestic, commercial or industrial- the pressure, the capacity of the cable etc. You don’t have to go looking for the statistics or record.

The most important stage in the development of computerization of the Electricity Supply Department is the “digitizing” with the topographical map of the entire cable network.

Once the ‘digitizing’ with the topographical map of the cable network is accomplished, there will be complete change from A to Z, one might say, in the methods of operation of the Department.

Research, development and planning have been an integral part of the supply system from the beginning. Studies are continuously undertaken to see how the new advances in the science of electro-technology can be utilised and adapted to meet the constantly increasing needs of the electricity consumer in Mumbai.

One Response to “Electric Supply”

  1. Voice Changers Says:


    It was quite useful reading, found some interesting details about this topic. Thanks.

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