It has been already indicated that the erstwhile Bombay ElectricSupply & Tramways Company started supplying electricity to the cityin 1905. Until 1926, the Company had been generating its own electricityfor distribution to its consumers. Later, the Tata Electric Companies startedsupplying electricity to the BEST.The Tata Electric Companies (The Andhra Valley Power Supply Co. TheTata Power Supply Co., The Tata Hydroelectric Power Supply Co.) generatedelectricity from their reservoirs at Bhira, Bhivpuri and Khopoli in theWestern Ghats. A major portion of it was transmitted through 110,000 Voltsoverhead lines to their Receiving Stations at Dharavi and Parel. In theseReceiving Stations the voltage used to be transformed to 22,000 and 6,600volts for ease of distribution. The Tata Electric Companies provided, throughtheir 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 pointsknown 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 22,000Volts and transformed through Tatas transformers to 5,500 Volts at Kussaraand to 6,600 Volts at Kingsway and Mahim. From these receiving points thecable network carried power to 247 Substations situated in different areasof the city. With the help of transformers at these substations, the voltagewas 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 voltagedistribution network and service cables to individual buildings. The majorportion 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 convertit into D.C., Rotary Converters were operated at Pathakwadi, Telwadi, Apolloand Palton Road Substations and Mercury Arc Rectifiers were used at PhirozshahMehta Road substation.
PROGRESS SINCE MUNICIPALISATION
Soon after the Corporation took over the Company, India got its freedom.This meant a reconsideration of the major objectives of the Undertakingand a reorientation of its outlook in the context of the changing politicalsituation. The Second World War had also given a new impetus to the utilisationof electricity.
The Undertaking not only continued many of the healthy traditions setby the Company but also improved its methods of working. The Undertakingis now well known in India for its service of providing electricity withminimum interruptions and at proper voltage, at the minimum cost. It isalso known for the quick restoration of supply in the event of any faultsdeveloping in the distribution system.
In the fifty years since municipalisation, the maximum demand on thesystem has risen from 53,000 kilowatts to 6,33,000 kilowatts; the numberof substations from 247 to about 1733; the length of underground cablesfrom 1,263 kilometres to 6,966 kilometres; the number of consumers from1,08,000 to 7,98,152; the number of street lamps from 2,215 to 33,534.
Refrigerators, air-conditioners, geysers, television sets and otherelectrical appliances are now being extensively used in homes. The useof air-conditioning and better standards of lighting in the office is alsobecoming increasingly popular. In the factories and entertainment centresthe use of electricity is on the increase. Skyscrapers have come into beingand so have hutments. All this expansion has necessitated the use of modernand sophisticated equipment. The responsibilities of the electric supplybranch of the Undertaking have become correspondingly greater and morecomplex.
ELECTRIC SUPPLY SYSTEM
In the days of the BEST Company some parts of the network were suppliedat 5,500 Volts and in some other areas the distribution voltage was 6,600Volts. This non-uniformity led to considerable loss of flexibility. Moreimportant, it was realised that at the higher voltage of 6,600 voltage,20 per cent more electricity could be conveyed and this without major replacementof equipment. So, after elaborate planning, in 1954, the 5,500 Volts systemwas changed over to 6,600 Volts. This major change was carried out withno interruptions in the supply to consumers.
In 1949 the Undertaking established its first 22000 volts receivingstation at Grant Road. This was followed by 22,000 volts receiving stationat Apollo. In 1955, two more receiving stations at Kingsway and Kussarawere changed over 22,000 volts and all 6600 volts metering points wereeliminated. As on today BEST has 35 receiving stations including two 110KV receiving stations. The demands on the system were growing and furtherchanges were necessary. Under an Agreement with Tatas in 1956, theyestablished a third Receiving Station at Carnac Bunder. This new stationand the existing 2 stations at Parel and Dharavi, now became the Undertakingsonly points of supply. The supply was now taken at these 3 points and meteredat 22,000 Volts. The Undertaking laid 22 KV cables from these points toit own receiving stations, the voltage was stepped down from 22,000 voltsto 6,600 volts through the Undertakings own transformers for feeding intoits 6,600 Volts system. The elimination of the old 6,600 Volts ReceivingStations was spread over a period of years. It was changed over to 22,000Volts as and when new Receiving Stations were built by the B.E.S.T. Thusin 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 responsibilityof the Supply Branch. There are considerable variations in the voltagereceived from Tatas at the different Receiving Stations. To compensatefor these fluctuations, the Undertaking installed, on its 22 KV transformers,equipment known as "On load tap changers". This device absorbs the fluctuationsand enables supply of a steady voltage to consumers.
D.C. TO A.C. CONVERSION
It has already been mentioned that Direct Current electricity was suppliedto the Girgaum, Kalbadevi and Fort areas in South Bombay. An appreciableportion of the electricity distributed in 1947 was accounted for by this.An alternating Current supply had many advantages over supply at DirectCurrent. It is more convenient and cheaper to transmit electricity at AlternativeCurrent through smaller cables at a higher voltage than through largercables 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 : appliancessuch 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 towardsthe cost of changing their appliances. The total compensation paid underthe scheme was Rs.50 lakhs. But the expenditure was well worthwhile, asit enabled elimination of costly and wasteful equipment used for conversionfrom 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.
STREET LIGHTING
The Municipal Corporation had a contract with the Bombay Gas Companyfor gas lamps for street lighting. This contract was to expire in 1962.Until then, there were about 7500 electric lamps and 7000 gas lamps onthe roads of Mumbai. The Municipal Corporation then decided to change overcompletely to electric street lamps and simultaneously to improve the levelof illumination. A crash programme was taken in hand by the B.E.S.T. in1966. When all the gas street lamps had been converted into electric lampsin July 1968, the number of electric street lamps had increased from 7500to 19000. On 1st July 1968, Bombay wished a sentimental farewell to gaslamps when the Mayor switched on the "Queens 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 inIndia and one of the best-lit in the world. It is one of the spots a visitorto Mumbai does not like to miss. Now with the introduction of sodium vapourlamps, it is called as Golden Necklace.
CONTROL OF STREET LIGHTING
Initially, the Undertaking used to control each lamp separately by aswitch, by a man going on his rounds every evening and morning to switchthem on and off. This system had several disadvantages, especially in timesof emergency. To provide central control points, it would be necessaryto lay hundreds of kilometre of cables at enormous cost and dig up Mumbaisroads to lay them. Other methods had therefore to be devised. One methodwas to install time-switches which automatically control the street lights,depending on the time of sunrise and sunset, but the use of this deviceis also limited. Another method tried is that which uses photo-electricswitches. These contain devices which are sensitive to light. When thenatural light on the road falls to a particular level, this device actuatesa switch which puts on the street lamp. When the natural light improvesto a particular level, the device switches off the lamp.
RIPPLE CONTROL EQUIPMENT
A ripple control scheme for controlling street lamps from one or twocentral points in the city was then considered. The ripple control equipmentis installed at predetermined places in the electric supply network. Theequipment sends out high frequency signals over the existing undergroundcables. These signals are picked up by a special device installed on eachlamp or a group of lamps. Thus by pressing a button at central controlpoints one can either switch off or switch on all the street lights inthe city. But this scheme was costly and involved import of much of theequipment.; hence it was decided not to consider the scheme.
At present there are over 33,000 street lighting poles and most of themare on automatic control. The automatic control of street lighting poleshas got two versions. out of 93 Street Lighting Poles used for remote controlfor street light poles, 53 are provided with masters/slaves arrangementfor efficient controlling Remaining SLPs are provided with time switchwhich will switch on/off street lights at the specified timing.
In future, we are exploring the concept of pagers system for quick andefficient operation of street light poles throughout Mumbai.
Sodium-vapour lamps made an appearance in the commercial areas of Mumbaiin 1980. To save on fuel and, as an alternative, considering the risingcost of oil, mercury-vapour lamps were chosen for street-lighting. Fluorescentmercury vapour lights went up in large numbers in 1982. In 1990 came "EnergyEfficient" lamps and "Energy Fluorescent" lamps followed them in 1993.
And the Electricity department does not work the magic only on the roadsof Mumbai; Electricity is provided by the department for various publicfunctions 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 yearsthe arrangements have kept improving.
And now the devotees of Lord Ganesh venturing some distance into thesea are helped by strong shafts of light.
REMOTE CONTROL OF RECEIVING STATIONS
Prior to the success in implementing effective remote control of streetlights, the Undertaking had started controlling Receiving stations fromtwo control points. There are now 35 receiving stations in the Undertakingwhere 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 theseReceiving Stations is therefore vital, if the consumer is to receive reliablesupply 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 1966to employ the Remote Control Scheme. It was possible to immediately implementthis decision, because the control cables required for this purpose hadalready been laid. The manufacture of the equipment was entrusted to theIndian Telephone Industries at Bangalore. The two main control points arelocated at the Esplanade Receiving Station and the Kingsway Receiving Stationfrom where all the Receiving Stations are monitored and controlled. Theremote Control equipment was installed in 1970 at the Vidyut Buildingnear the Esplanade Receiving Station and at Kingsway in 1972.
SCADA FOR RECEIVING STATION CONTROL
The system provided by the Indian Telephone Industries was designedon electro-mechanical relay principle. Due to this it had limitations forthe speed of operation. There was no data acquisition also. These factorsforced the Undertaking to keep the system to a minimum level.
In 1980 BEST replaced the Supervisory Remote Control system with microprocessor based Supervisory Control and Data Acquisition System (SCADA).Additional to SRC System SCADA functions are data acquisition, analysisand report generation.
The communication between the master control and receiving station isthrough underground communication cables.
To further improve the reliability and quick restoration of supply BESTis going in for microware wireless communication in the years to come.A very-high frequency radio link which was established in 1963 for quickcommunications is now getting outdated. This is being replaced by microwavesystem and cellular phones.
With the installation of this equipment, the restoration of supply whena 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 indicatorsat the central points. With the help of the links the operator at the controlpoints can direct the field staff to quickly reach the places where thefaults have occured and restore supply with the minimum delay.
POWER POOL SCHEME
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 distributionsystem well ahead of the demand, it has ultimately to depend on the supplyfrom Tatas. In the early fifties for three consecutive years the monsoonhad failed. The low water levels in Tatas reservoirs, which are a sourceof power supply to Mumbai, had created a severe power shortage in the area.It became necessary to make alternative arrangements. Many industrialinstallations 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 ownrequirements. The power thus released was utilised to serve the other consumers.This scheme came to be know as the Power Pool Scheme. The Undertaking hadtaken a lead and played an important role in implementing this Scheme notonly in Mumbai city but also in the entire State. Later the installationof more efficient generators in the Railways generating station at Cholaand a new generating station installed at Trombay by Tatas, considerablyimproved the position, and in 1961 the Power Pool Scheme was discontinued.
SOME SIGNIFICANT FEATURES
In the old days when plenty of space was available, nobody had perhapsever heard the words Underground Substation and Package Type Substation.Due to the tremendous increase in the demand for electricity in all partsof the city, the need for Substations has been increasing. The procurementof sites for Substations, especially in the congested areas in the city,presents many serious problems. In the rural areas it is customary to havepole-mounted substations. Owing to the tall buildings around, the erectionof such substations is dangerous in the city. Moreover, nobody would likethe idea of building such pole-mounted Substations in a city like Mumbai,from the aesthetic point of view. In 1964, on an experimental basis, 5vault-type transformers were imported. Our experience of them, since theirinstallation 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. Problemstoo have been growing fast; Slums, without the basic facilities, have beencoming up alongside roads. In many cases, the slums have crossed the footpathto the bus-shelter. On the one hand, there is the lovingly nursed dreamof a clean and beautiful Mumbai and on the other the depressing realityof a slum. On one side there is the slogan of a green Mumbai and on theother the sad sight of a footpath swallowed up by an ugly slum. When willthis stop? The question has to wait for an answer. A voice is sometimesraised against this by the white-collared gentry. Efforts are made nowand then to pull down or push back the ramshackle huts. But soon enoughthey re-appear on the same spots. As time passes, the huts come to be regularisedand the Electric Supply branch had to install a separate meter for everyhut. Now the paths snaking through the huts have their lighting like thehuts themselves. The sensible Mumbaites have accomodated these huts too.
During last some years more and more of Sky scrapers have been goingup - and up! The sea has literally been pushed back in several places tomake room for some of them. The Cuffe Parade, Nariman Point and the BackbayReclamation areas are now virtually cement jungles. To provide electricityto 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 andAudio Sets, mainly to entertain and the washing machine and air-conditioningto make life easier. And a variety of machines, small and big, are cominginto 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-scrapersparticularly for computers and air-conditioners. The demand for commercialuse of electricity, too, has been growing fast.
The height of buildings creates several problems in reaching electricityto them. Therefore, the need for a high pressure electricity set-up. Onesuch set-up required for a Sky scraper is adequate for 400 residentialand office buildings.
At present, the Undertaking buys its electricity from the Tata ElectricCompany. 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 andthe consumers demand can be met better. For this purpose the Undertakingis launching its own generation programme in the near future.
The BEST was the first organization in India to supply electricity throughunderground 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 stationof the capacity of 110 KV. In this country such a sub-station is normallyoutside a building and also far from a residential zone. This one is withina building. And, except for the lower floors, this building is used forprivate establishment. Most people working every day on the upper floorsare probably not aware that below them is a power-station of the capacityof 110 KV. In 1993 the Undertaking also set up a receiving station of 110KV at Khetwadi. This one also is inside a building.
SOME NOTABLE FEATURES
Switch-gears : It has already been stated that the Undertakinghas been in the forefront in using the latest technology in the systemof electric supply. At present the Undertaking uses switch-gears of varioustypes and using various technologies. For example, airblast, minimum oilcircuit breakers, SF-6 circuit-breakers, Vacuum circuit-breakers and gas-insulatedcircuit-breakers. These circuit-breakers, being of the latest type, donot need supervision.
As these switch-gears occupy less space, it is possible to set themup where otherwise enough space is not available. Thus, the use of thesegears has been quite profitable to the Undertaking.
Cables and their Testing : The BEST has the largest undergroundcable distribution system. As a matter of fact, compared to the overheadsystem, the method of carrying electricity through underground cable isfar more costly. But considering the congested housing and the crowdedroads of Mumbai the overhead system would be unthinkable. So, althoughthe underground system is costly, from the viewpoint of reliability andsafety, it is advantageous.
Later, the Undertaking started using upto-date technology in the cableand 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-powertransmission, XLPE cable was brought into use in 1982.
The short-circuit test was employed on the underground cables. The BESTwas the leading organization in testing low-pressure cables. Till 1980,high-voltage cables were tested by the "Bridge Method". During 1980 forthe 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-voltagecables. This van was bought although it costs a great deal. Its main advantageis that by removing the faults in an electrical set-up in the minimum time,it enables the undertaking to provide good, dependable and prompt serviceto the consumers. The undertaking is using four of such "Testing Vans"at present.
Communication and Monitoring Systems : BEST is the first electricsupply organization to start VHF communication and that it did in 1960.For the messages to be delivered promptly, the wireless message systemwas started in 1963. It has now become a simple operation to restore theelectric supply by detecting the defects by going to the spot quickly ina mobile van.
For the efficient operations during the year 1967, the area was bifurcatedinto North and South. In 1991, the department concerned with the operationsand maintenance activities was again bifurcated into four zones namelyNorth, Central North, South and Central South. If there was any fault inthe machinery, in order to spot it and to take prompt action to correctit, a "supervisory remote control" of the most modern kind was set up.
Meters and Relays : Over the years, changes have been takingplace in the electric meters used. The old type of meters did not proveas efficient as they might have. Therefore, in 1994, the electricity sectionbrought into use "electronic meters" and solid state relays. As recentlyas 1995, with the help of modern technology and computers, the Undertakingproposes to launch the "remote metering system".
Computerisation in the Electricity Supply Departments :The computeris now used in a big way in the BEST Undertaking. Of, course, computerizationhas assumed importance in all areas of activity. Even then, it must bestated, the BEST was the first organisation in the country to issue electricitybills 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 fixedperiod the bills are delivered to the consumers at their houses, unerringly.In 1988 began the use of the Personal Computer in the department. As aresult 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 consumers name, address, meter number, system number, the use to whichthe electricity is put - whether domestic, commercial or industrial- thepressure, the capacity of the cable etc. You dont have to go looking forthe statistics or record.
The most important stage in the development of computerization of theElectricity Supply Department is the "digitizing" with the topographicalmap of the entire cable network.
Once the digitizing with the topographical map of the cable networkis 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 thesupply system from the beginning. Studies are continuously undertaken tosee how the new advances in the science of electro-technology can be utilisedand adapted to meet the constantly increasing needs of the electricityconsumer in Mumbai.
