The Greater Dhaka Power Project

transcript

The Greater Dhaka power projectSince 1973, the power system of the Greater Dhaka area ofBangladesh has undergone major expansion. The demand forelectricity in Dhaka is increasing rapidly and British engineersare working on a project to update the system to enable it tocope with present and future demand.

by Ronald Roff

The People's Republic of Bangladesh is situatedin the north-east corner of the Indiansubcontinent, and encompasses the largestdelta in the world covering an area of65 000 km2. This is just under 45% of the totalarea of Bangladesh which is roughly equal insize to England and Wales. The country iseffectively divided into two by theBrahmaputra-Jamuna river which is an average2 km wide and in the rainy season sometimes6 km or more. However, the river and itstributaries form a highway for the majority ofimports, as the most effective means ofreaching their final destination is by river. Mostof the electricity in the eastern zone isgenerated by natural gas and hydroelectricplant whereas all generation in the westernzone uses oil. The completion of the 230 kVeast-west interconnector (see References 1 and2) is now helping to alleviate the high cost ofoil-fired generation and the power flow isvirtually all east to west. A secondinterconnector is under consideration forcompletion by 1993.

The climate and terrain create unique andchallenging tasks for the power engineer toovercome. Much of the Bengal basin is lowlying and Dhaka, the capital, is less than 4 mabove sea level. The need for compacted sitefill and foundations designed to cater forhydrostatic uplift are therefore the norm ratherthan the exception.

Need for power system developmentEwbank and Partners (now part of the

Ewbank Preece Consulting Group) first becameinvolved in Bangladesh during 1973 when thecompany was asked to carry out a detailedstudy for development and rehabilitation of thesystem. In 1973, Greater Dhaka was suppliedat 132 kV from two bulk supply points,Siddhirganj and Ullon, and the system wasliable to many interruptions. Siddhirganj hadonly two 25/30 MVA 132/33 kV transformers,the original 30/50 MVA 132/33 kV transformerat Ullon) wasjseverely damaged during the civilwar, and was replaced by a single 25/31 MVAtransformer. The maximum demand at that

POWER ENGINEERING JOURNAL JANUARY 1987

time was about 90 MVA, roughly equal to thecurrent maximum demand of Worthing orEastbourne. Thus a single transformer outagemeant that one-third of the consumers had tobe shed. The general shortage of capacity inthe 33 kV system was also reflected in the11 kV and 400 V distribution network.

No detailed layout or schematic plans of thedistribution network were available—mostwere destroyed during the 1971 civil war. Theshortage of material meant that connectorswere virtually non-existent and twistedconnections were quite common. It was notunusual for LV conductors to glow red hotbefore finally sagging to touch each other andcausing a short circuit.

Congestion of service connections at thepole top led to severe maintenance difficultiesand power service failure owing to theinevitable chafing of insulation that occurs,particularly in the monsoon (see Fig. 1).

1 Typical serviceconnection before theprogramme began

2 11 kV pole-mounteddistribution substation

3 132 kV switchyard onthe outskirts of GreaterDhaka

Phase 1The urgent need for completion of a study

and development plan was readily apparentand agreement was finally reached betweenthe Government of Bangladesh (GOB), theBangladesh Power Development Board (BPDB),and the UK Overseas DevelopmentAdministration (ODA) for the latter to provide agrant of £27 million to cover the foreignexchange element of the scheme and inaddition to pay for the cost of a consultant toplan and manage the project. The first supplyonly contracts for Phase 1 were placed byJanuary 1977.

Dhaka city, as encompassed by a 132 kVring, covers an area of approximately 900 km2

with a population in excess of 4 000 000.Greater Dhaka covers an area of 2800 km2

(approximately twice the area of GreaterLondon) with a population approaching20 000 000. Power transmission was increasedduring Phase 1 by two new 132/33 kV and fivenew 33/11 kV substations with 70 km of33 kV transmission line and cables. Twoexisting 132/33 kV substations and 1533/11 kV substations were enlarged and

extended, and local distribution improved bythe addition of 440 km of new 11 kV and low-voltage lines and cables plus some 500 newdistribution substations.

Phase 1ASubsequent to Phase 1 development,

agreement was reached with the ODA toprovide a further grant of £7.5 million underPhase 1A to rehabilitate a 33/11 kV substationand to improve local distribution by a further400 km of 11 kV and LV lines and cables and300 distribution substations. This work wascompleted at the end of June 1985 and atypical example of the new distributionsubstations is shown in Fig. 2.

The master planThis, however, was not the end of the story

but rather the beginning. The recent 'Powersystem master plan'3 has shown that, in anation in which more than 90% of the peoplehave no electrical connection whatsoever, thedemand is virtually insatiable. Between 1980and 1983 the annual growth rate was 13-14%,and in 1984 the growth increased to 15%.There is every sign that peak demand couldhave risen by a similar amount to 880 MW hadit not been for extensive load shedding.

Phase 2Thus, in 1982, Ewbank Preece commenced

work on a new load study and developmentplan to meet expected demands up to 1987-1988 (Phase 2) of the project.

Under Phase 2, which is being jointlyfinanced by the Asian Development Bank andthe UK Overseas Development Administration,4

power transmission will be further increased byone new 132/33 kV substation and nine new33/11 kV substations. 31 km of new132/33 kV lines and cables will be installedplus the stringing of the second circuit of theDhaka 132 kV ring on a 70 km route lengthand 92 km of new 33 kV lines and cables. Fiveexisting 132/33 kV substations and 1233/11 kV substations will be enlarged andextended (see Tables 1 and 2). Localdistribution will be improved by approximately805 km of 11 kV and LV lines and cables andby additional transformers aggregating 128MVA.

The overall power development for GreaterDhaka has been planned to meet the expectedgrowth in load from 105 MW in 1974 toapproximately 480 MW in 1987 with industrialdemand accounting for 70% of theconsumption. The complexity of the project isperhaps better appreciated when you considerthat the demand for Greater Dhaka constitutesapproximately 30% of the demand of thecountry as a whole.

Tender documents for Phase 2 were issuedduring 1984, and initial contracts divided intoten separate packages and a further five arebeing implemented. Five of these are turnkeytype and ten supply only. The total value ofimported material is in the region of £43million with a local expenditure of 600 millionTaka (£13.3 million). Completion for Phase 2 is

planned for late 1987, a programme of a littleunder three years.

Distribution control centreTo reduce outages in an area with an

average of 80 thunderstorms per year, a newdistribution control centre with a hand dressedmimic panel is being provided under Phase 2with facilities for future conversion to an activetelecontrol system. To facilitate efficientoperation and maintenance of the transmissionand distribution networks, a radiocommunications system will give full speechcoverage of the Greater Dhaka area byUHF/VHF radio, pilot telephone cables andmodification of the existing 132 kV power linecarrier system.

132 kV transmission linesDouble circuit design was selected for the

Dhaka 132 kV ring and to keep costs down inPhase 1 the ring was erected with only onecircuit strung. The second circuit is now beingcompleted in Phase 2. Because of the verydifficult ground conditions prevailing in GreaterDhaka where the soil is largely alluvial andsubject to flooding for up to six months in theyear, only half the year can be used forfoundation construction. Stringing can, ofcourse, be carried out during the rainy season,but with difficulty.

Foundations were a particular problem and anumber of alternative solutions wereconsidered. Piling was ruled out due to theproblems of access with heavy pilingequipment and subsequent costs.Conventional reinforced concrete foundationsbecame the first choice wherever practicable asthey are labour intensive and materials areusually available locally. Owing to the poor soilconditions, most pad foundations are designedfor a 15° frustrum angle.

33 kV linesAfter careful consideration a lattice design

was selected for all 33 kV lines, being judgedas giving the best degree of reliability. Woodenpoles were eliminated fairly early on asexperience indicated that their life expectancywould be relatively short in the alternately wetand dry soil conditions. Steel poles are nowbeing utilised in Phase 2.

SubstationsIn Phase 1 the main design criteria were to

provide:

• switchgear of proven reliability• easy maintenance• ground level above highest known flood

level• minimum cost allowing reasonable flexibility

of switching.

The demand for land is high and the situationis exacerbated by the growth inindustrialisation, the continuing trend of peoplemoving into the city area and the large amountof flooded land during the rainy season. It wasclearly imperative that substation sites shouldbe above the worst known flood level.

Table 1:132/33 kV substations (3 x 35/50 50/83 50/75 MVAtransformers)

existing

GhorasalTongiUllonSiddhirganj

Phase 1 work

nonenoneextensionextensionMir purPostogola (Hasnabad)

Phase 2 work

noneextensionextensionextensionextensionextensionDhanmondi

As an example, the Postogola (Hasnabad)site situated on the river bank covers some33 000 m2 and to meet the above criteria thesite had to be raised by 5 m involving a totalinfill of 162 000 m3. Construction problemswere overcome by building a clay bund andthen filling the area with river silt by use of adredger.

Drains were constructed from the bund toallow water drainage and test holes were dugto check that the silt was compacting. Thesubstation was surfaced using bricks and aweak cement. This task had to be carried outexpeditiously as soon as the silt dried toprevent erosion by wind and rain.

Temporary, but nevertheless extremely wellbuilt, jetties had to be constructed at suitablelocations to enable transformers to bedelivered by barge at the height of the floodseason.

In Phase 1, the Bangladesh Power Board,based on past experience, opted for SOVswitchgear at 132 kV, 3500 MVA and 33 kVbulk oil switchgear rated at 1000 MVA. Detailsof substations constructed in Phase 1 andPhase 2 are shown in Tables 1 and 2. UnderPhase 2, 132 kV SF6 puffer type open terminaloutdoor switchgear 25 kA 3s 3150 A is beingprovided. 33 kV switchgear indoor is bulk oilmetal-clad 1200/2000 A 25 kA and outdoorbulk oil open terminal 1200/2000 A 25 kA. 11kV switchgear is vacuum metal-clad 630/2000A 20 kA. A typical 132 kV substation is shownin Fig. 3 and 33 kV indoor gear in Fig. 4. Theexpected 132/33 kV network at the end of

P U 9 D

4 Typical 33 kV indoorswitchgear

0 . GPOWER ENGINEERING JOURNAL JANUARY 1987 11

Kabipur

Aricha33kV

Joydevpur3 3 k v-rTT2x10 § | L

Isurdi

w 2x52x5 Nayarhat

Man! kganj

8 =132 kV

132kV"5EI3x50 Mirpur

33k\£

I33kV -

Ashuganj

2x14 © 2 x 1 4Old Kafru lMirpur

33kV_J_J_ BaridharaGulshan § 2 x 1 4

Jigatola D h a n m o n d l ( = ) $ 2 x 7 52x14 33 kV.

Satmasjid2x13.3C

- M - 33 kV-02x14

Tejgaon Magbazar

2x10Khilgaon

Hasnabad 6& 2x28

2x28KawranBazar

Ramna 33 kV

• j — 33kV 11 I J J K V — T - -@2x14 @2x14 2x14@

Kamalapur Basabo Oayaganj

33kV ' . '

©2x14Postogola

33kV 33kV'2x14 Lalbagh Fort 6

D2x14Narayanganj

33kV-2x14 Fa tu l la ^

Mirkadim ©2x14 Srinagar

- C D - "2x83 2x25

Siddhirganj

O2x14Madanganj

Baidyar bazar

5 132kVand33kVsystems at the end ofPhase 2

Phase 2 is shown in Fig. 5.In Phase 2 the first major transformer feeder

substation is being provided in the centre ofDhaka with two 50/75 MVA transformers andin Phase 3 this design trend is likely to beaugmented in view of the major cost savingprovided in land usage.

DistributionDistribution planning was clearly a key factor

in meeting consumer demand in Phase 1 and aplanning section was accordingly set upconsisting of four expatriate distributionplanning engineers together with their PowerBoard counterparts.

The almost total absence of records meantthat their principal task was to document theexisting system. This planning nucleus hasbeen built up over the years and today a seniorplanning engineer is a crucial part of theconsultants' site team.

A major store has been provided at Tongisubstation and prior to the construction ofdistribution lines in Phase 2 the store is holdingup to £10 million of material.

Distribution planning is fast becomingcomputerised and with the total stock held atTongi on computer it is possible to feed therequirements of a distribution area into thecomputer and immediately receive a completelist of all poles, fittings, insulators andconductor sizes required etc.

As can be imagined, rehabilitation andextension of the 11 kV system and theassociated 400 V lines is a major task and oldDhaka provided its own particular problemsbecause of very narrow streets. Burying thecables underground was not always practicablein some areas owing to the disruption thatwould be caused by digging up the road andlack of information on services already buried.Nearly all 400 V lines are now provided withinsulated conductor which reduces the risk tolife and has also been very instrumental inreducing illegal tappings.

Management studyAs a means of protecting initial and future

investments, a management study of theDhaka Electricity Supply Authority was carriedout during 1982-1983 and recommendationshave been made for improvement of themanagement organisation, operationalactivities, finance and accounting functions,manpower development, supporting servicesand a reduction of system losses. Therecommendations made are beingimplemented.

Consultants' organisationA key factor in the success of any major

project is the availability of high-calibre sitestaff. Current staff in Dhaka consist of a projectmanager, a senior civil engineer with three localassistants or clerks of works, two HVsubstation engineers, one overhead lineengineer, two distribution engineers, one seniorplanning engineer with a team of Power Boardstaff and a stores manager. Power Boardengineers are seconded to the team for liaison,

Table 2: 33/11 kV substations (3 x 10/14 20/28 MVA transformers)

existing

KaliganjOld MirpurNayarhetTongi ITongi IIOrdnance factoryMachine-tool factoryJoydevpurGulshanShere BanglaKamalapurPostogolaKanchanGhorasalDemraSavarAdaHaripurSatmasjidFatullaTejgaonDhanmondiNarsingdiMirkadimMadanganjKhilgaon

Phase 1 work

extensionextensionnonenoneextensionnonenonenoneextensionnonenoneextensionnonenoneextensionnoneextensionextensionextensionextensionextensionnoneextensionextensionextensionextensionManikganjMagbazarBasaboLalbagh FortTongi III

Phase 2 work

extensionextensionextensionnonenonenonenoneextensionnonenonenonenoneextensionnew substationextensionnoneextensionextensionnonenonenoneextensionnonenonenonenonenoneextensionnoneextensionextensionKafrulBaridharaUttaraKazlaNarayanganjJigatolaKawranbazarRamna

training and assistance with the work invarying numbers, all working under thedirection of the Power Board project director.There is therefore a close liaison between ourown staff and the Power Board staff at alllevels.

Phase 3Work is already in hand on the development

plan, design study and documentation forPhase 3 of the Greater Dhaka power projectwhich will forecast power and energy demandsfrom 1987 to 1995, by which date thedemand is forecast to reach 1150 MW. Phase3 is expected to be greater in scope thanPhases 1 and 2 together and will need to makeprovision for the increasing industrialisationboth east and west of the river. The increasingdemand for jute manufactured products,textiles, the clothing industry, ceramics andporcelain, cable manufacture, agriculturaldevelopment etc. is bringing ever-increasingdemands for power. Specific objectives includeoptimised design for supply security as well asaesthetics in the central city areas. The project

Joydevpur

Isurdi—_Tangai

Kabirpu

Manikganj

Ghorasal ^/ - ^ ^ t e = — Ashugiinj

Dhanmondi BasaboBangsal

Ashuganj

existing 230 kVnew 230 kVexisting 132 kV

SC overhead

newi§2kV J lines

existing 132 kV substationnew 132 kV substationnew 230 kV substation

6 230kVand132kVoverhead line routes

is expected to include a degree of automaticcentral control to key switching points withautomatic data recording, to minimiseunplanned outage periods and enhanceefficient system operation.

The same voltages will be maintained underPhase 3, but to carry power from the centralgenerating locations at Ghorasal andSiddhirganj into the 132 kV ring around DhakaCity, new lines and transformation points at230 kV will be needed from 1990-1991. Newtransmission lines at 230 kV and 132 kV willtotal 175 km, of which 35 km will beunderground in the city. The lines will providepower to 13 new transformation points. Linestotalling 2200 km at 33 kV, 11 kV and 400 V,of which approximately 400 km will beunderground in the city, will provide power tomore than 2000 transformation pointssupplying an estimated 200 000 newconsumers, in addition to growth amongexisting consumers. At 1986 prices theestimated total cost is £250 million divided into13 separate contract packages, and it is likelythat the overall project will be split into twophases A and B. The expected 230/132 kVnetwork at the end of Phase 3 is shown inFig. 6.

Preliminary financial evaluations indicate anIRR in line with GOB requirements at thepresent tariff levels, assuming that these areperiodically adjusted to accommodate

inflationary trends.Recent generation deficits have enforced

restrictions on consumers at peak demandperiods. These restrictions will be removedduring 1986 and 1987 as new generatingplant comes into service. It is important toplace orders for the electrical equipment inPhase 3 by the end of 1987, otherwise thetransmission and distribution systems will lackcapacity to carry the unrestricted demand from1988-1989 onwards.

Lessons to be learnedThroughout Ewbank Preece's period of

involvement and responsibility for this majorpower project, there has been a significantimprovement in conditions within Bangladesh.Training has been a crucial factor throughoutthe project phases and Power Board staff haveworked closely alongside our expatriate siteteam. UK training was arranged for selectedstaff within the Northern Ireland ElectricityBoard and, by arrangement with BritishElectricity International, UK linesmen have beenseconded to our own staff in Dhaka to buildup a nucleus of experienced people bothwithin the Power Board and with local erectioncontractors appointed to install the mass ofmaterial provided by internationalmanufacturers. Training programmes have alsobeen arranged with turnkey contractorsproviding HV switchgear and undergroundcable.

The futureThe future for the power sector in

Bangladesh is a highly optimistic one. Duringthe period 1985-2000 estimated expenditureon transmission line extensions is estimated at£250 million, news which alone should be ofgreat benefit to the people of Bangladesh.

AcknowledgmentAcknowledgment is gratefully made to the

Bangladesh Power Development Board, theOverseas Development Administration, theAsian Development Bank, T. J. Wiltshire,Divisional Director, and colleagues at EwbankPreece Ltd. for assistance rendered in preparingthis article.

References1 CHANDLER, J. A., HINCH, L W, HUGHES, D. A,

McDOWELL, D. M., ROWE, R W. and WOOD,A. B.: 'Jamuna River 230 kV crossing,Bangladesh—Pt. 1: Design; IEE Proc. C, 1984,131, pp. 303-318.

2 CHANDLER, J. A, HINCH, L. W, FAIR, R. I.,HUGHES, D. A, PERAINO, J. and ROWE, P. W:'Jamuna River 230 kV crossing, Bangladesh—Pt.2: Construction; ibid, 1984,131, pp. 319-332.

3 The power system master plan'. AcresInternational.

4 ODA appraisal mission documentation.5 JONES, D. A: The role of the consultant in

developing countries', IEE Proc. A, 1981,128, pp.18-25.

Ronald Roff is Assistant Director of Ewbank Preece,Prudential House, North Street, Brighton, East SussexBN1 1RW, UK. He is an IEE Fellow

14 POWER ENGINEERING JOURNAL JANUARY 1987

The Greater Dhaka Power Project

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