Technical Aspects - Bakun

8/12/2019 Technical Aspects - Bakun

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Technical Aspects

Many studies have been undertaken on the technical aspects of the Bakun HEP,particularly those relating to the safety of the dam and structures as well as thefeasibility of transmitting electricity through long submarine cables Although both thedam and the submarine cables are larger and longer than those associated withpro!ects e"isting today, the Bakun HEP does not represent a #$uantum leap# Thetechnical studies completed to%date and the final design, which will be carried outduring pro!ect implementation, will ensure that the Bakun HEP will be safe andefficient

Evolution Of The Bakun HEP Dam DesignMaster Plan Studies, 1981

The Bakun HEP site, proposed on the Balui &iver, 'arawak, as shown in Map (, was

first identified and studied as part of the )*+) Master Plan for the Power 'ystem-evelopment of 'arawak, the third of a series of studies following those carried outin )*./0.1 and )*2202* This comprehensive study identified more than )34potential pro!ects, of which the largest was Bakun 5urther, a multistage screening oftechnical, economic and other relevant merits of the identified power pro!ects wasperformed leading to the selection of the Bakun pro!ect as the best hydroelectricpro!ect in terms of its hydrological efficiency

5ollowing the initial pro!ect screening, the 6overnment directed that furtherinvestigations be based on a ma"imum power demand scenario involving High7oltage -irect 8urrent 9H7-8: bulk transmission to Peninsula Malaysia The Bakun

HEP, along with ten other pro!ects, was subse$uently selected for more detailedinvestigations reaching a pre%feasibility level

6eological and topographical assessments led to the conclusion that the Bakun sitewould allow a dam of about /44 metres high, for which only a rockfill or arch damwould be suitable Pending further geological investigations, the study concludedthat a /4.%metre%high concrete arch dam would be cheaper than the rockfill damalternative for the narrow, 7%shaped valley at the Bakun dam site

Bakun Hdroele!tri! Pro"e!t #easi$ilit %e&ort, 198'

The overall feasibility study initiated by 'E'8o and carried out by a consortium of6erman consultants, commenced in ;ctober )*+) Three types of dams wereconsidered anew to determine the optimal height of the dam, vi< a rockfill dam, aconcrete gravity dam, and a concrete arch dam The concrete arch dam wasselected for the detailed feasibility design studies based on 9): feasibility%levellayouts and cost estimates prepared for each dam type alternative, and 9/: thelength of time to complete each alternative


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BAKUN HYDROELECTRIC PROJECT SITE

The significant features, resulting from the detailed feasibility studies of the generallayout and ma!or components of the pro!ect, are highlighted below=

a /4>%metre high concrete arch dam with a crest length of about ),)44 metres

and a total concrete volume of 1* million cubic metres 9mcm: 5our bottomoutlets with a combined outflow capacity of .,244 cubic metres per second9cumecs: were incorporated in the middle section of the arch dam, controlledby four radial gates?

an underground powerhouse with eight 144%M@ 5rancis units, giving a total

generating capacity of /,>44 M@ The main transformers and the switchgearwere housed in a separate cavern situated downstream of the powerhousecavern?

an inlet bay in front of the intake structure consisting of eight steel%linedpressure shafts and an outlet bay downstream comprising eight tailracetunnels?

a concrete chute spillway with si" radial gates situated at the left abutment

The spillway would have capacity of )2,4>4 cumecs? and a river diversion scheme comprising upstream and downstream cofferdams

and two concrete%lined diversion tunnels located at the left abutment The twotunnels have a combined discharge capacity of 3,)23 cumecs

Panel Evaluation in Mid(198)s

A panel of e"perts, comprising -r ohn ewberry, (vor Pinkerton, et al, issued fourreports between )*+3 and )*+. regarding the design of the hydropower componentof the Bakun pro!ect and the preparation of bid documents for the construction ofthese works The Panel assisted in the design evolution during this period

-uring the design development under the Panel#s review, additional geological

e"ploration showed the site to be less favourable for an arch dam than earliere"plorations had indicated The Panel preferred an earth core rockfill dam 9E8&-:,


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provided suitable core material within economic haulage distance of the dam sitecould be found ;therwise, the Panel suggested the adoption of a concrete facerockfill dam 985&-:

(n view of the geological conditions, the revised layout incorporated both the power

facilities 9including a surface powerhouse: and the spillway on the left bank

-iversion capacity was raised to allow for a )%in%344%year flood The design at thispoint incorporated three )/%metre%diameter concrete lined diversion tunnels with themain cofferdam 9which forms part of the upstream rockfill


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The selection on the type of dam to be constructed at the Bakun site was sub!ectedto e"tensive study in the proposal because the dam type is of paramount importanceto the cost of the pro!ect and the completion schedule Another consideration wasthat although a 85&- at Bakun may still be the highest of its type in the world, in theperiod since )*+2, many such dams approaching the height of the Bakun dam have

been completed The study focused on a comparison between a slightly modifiedE8&- and a 85&-, finally supporting the choice of a 85&- 5urther modificationswere made to the rest of the pro!ect design presented in the earlier bid documentsmainly to reduce construction costs and0or the construction period

Te!hni!al Evaluation Of Ekran Berhad.s Pro&osal

The 6overnment, with the assistance of Har


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BAKUN HYDRO CO$PONENT LAYOUT

8&;'' 'E8T(; ;5 THE BADC -AM

P#%er Ina&e An' S(i!!%ay8oncerns about large e"cavation $uantities, slope stability and support

re$uirements were raised in connection with these components of thepro!ect Modifications were suggested to reduce the $uantities andheight of the cuts including shifting both the power intake and thespillway toward the left abutment of the dam, with less space betweenthem

Di"ersi#n Tunne!s Lengh An' P#ra!s

By modifying the alignment, the length of each diversion tunnel couldbe reduced by about /44 metres


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P#%erh#use Ty(e An' L#)ai#n

5urther improvement by optimising the layout is possible, including 9):choosing a powerhouse orientation more parallel with the river,

resulting in less e"cavation in the steep%sided valley? and 9/: using si"units of >44 M@ each rather than eight units of 144 M@, resulting in areduction of the length of the powerhouse and also e"cavation

Pens#)& Si*e

;ptimisation of the penstock si


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dams led to the poor reputation of 85&-s This dramatically slowed the useof high as well as low 85&-s in the following period

Transii#n Peri#' +-0. / -2.1

8onstruction of 85&-s resumed in the )*34s However, once again thehigher dams with dumped rockfill e"perienced leakage problems and costswere e"cessive A ma!or breakthrough occurred when dumped rockfill wasreplaced with compacted rockfill This transition began in )*33, and since)*.2, no dams of the dumped rockfill type have been constructed Thecompacted rockfill achieved the higher modulus of compressibility that wasdesired to enable the concrete face to perform better To obtain the highermodulus, the smooth drum vibratory roller 9used earlier in highwayconstruction: was employed, and soon became a standard piece ofe$uipment in 85&- construction (n addition to reviving the construction of

85&-s, compacted rockfill enabled small rocks of low compressive strengthto be utilised

$#'ern Peri#' +-2. / Presen1

The use of compacted rockfill enabled dams to be designed with limiteddeformation and as a result many 85&-s were constructed throughout theworld in increasing numbers and for increasing heights -uring this period, ama!or new development in their design was the use of a slipformed, nearlymonolithic face slab, with no hori4%metre%high Piedras -am in 'pain, completed in )*245ollowing the successful use of this monolithic face slab in three Australian-ams 9Pindari in )*24, Dangaroo 8reek in )*24, and 8ethana in )*2):, allsubse$uent dams worldwide were designed with it

5ollowing the construction of the ))4%metre%high 8ethana -am, thedevelopment of 85&-s progressed rapidly throughout the world Thecompleted modern 85&-s, that broke previously set height precedents, in the)*24s, )*+4s and )**4s were Alto Anchicaya in 8olombia, 5o< de Areia inBra


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Tiansheng$iao 8hina )**2 )+4

5o< de Areia Bra )>4

8hu )13

Doman Albania )*+. )11

ew E"che$uer C'A )*.. )14

6olillas 8olombia )*2+ )14

Dhao Faem Thailand )*+> )14

'hiroro igeria )*+> )14

8irata (ndonesia )*+2 )/3

&eece Australia )*+. )//

everi 7ene


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dam without incurring e"cessive additional costs or introducing constructionschedule delays

The main function of a dam is to retain the reservoir This is accomplished byincorporating a watertight element in the embankment (n the case of a 85&-,

watertightness depends on the upstream concrete face and the foundation Thesetwo elements interface in the plinth or perimeter slab A brief description of thesedetails is as follows=

the concrete face is not monolithic but composed of vertical strips or slabs

The !oints between these vertical strips are carefully designed toaccommodate movement between slabs and preserve the continuity of theface?

the concrete face%plinth !oint, also called the perimetric !oint, receives carefulattention during design, and later during construction, to control leakage The!oint detail includes a


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&ockfill dams, with an impervious upstream face, have been constructed for over)44 years Their inherent stability has been established by their long service recordwithout failures

The Kha# Lae3 C#n)ree Fa)e R#)&4i!! Da3, Thai!an'

8ompaction of the rockfill in layers of specified thickness, proper selection ofmaterials, careful treatment of the foundation and appropriate embankment slopescan only improve their stability At Bakun, detailed stability analysis of the dam hasbeen performed -uring the final design phase and construction of the dam,additional analyses will be performed to verify and confirm the stability

Seismi! Sta$ilit Of Bakun *#%D

The dam is located in an area of low to very low natural seismic activity This is

confirmed by the fact that only twelve tremors have been felt in the area in the last)44 years The pro!ect area is located in a stable block far from the seismically activeplate boundaries The seismic ha


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A modern well%compacted 85&-, such as Bakun, undergoing an earth$uake woulde"perience smaller settlements that would not endanger the stability of the dam

'everal high 85&-s have been constructed in areas of moderate to high seismicity

;f the above, only 5o< do Areia, Bra3 moderate

Alto Anchicaya,

8olombia

)>4 moderate

6olillas, 8olombia )14 moderate

8irata, (ndonesia )/3 highN#e5 u6' 7 un'er 'esign8 u6) 7 un'er )#nsru)i#n

%eservoir ndu!ed Seismi!it

(t is generally accepted that changes in water pressure within the rock masssupporting the reservoir are the primary causes of observed reservoir inducedseismicity 9&(': (t is also accepted, based on the available data on &(', that

reservoir induced earth$uakes re$uire the e"istence of an active fault along whichthe tectonic stresses can be relieved The water pressure reduces the strength ofpre%e"isting fractures bringing their strength closer to the stress field e"isting withinthe rock mass, facilitating the release of tectonic stresses through an earth$uakeE"isting data also indicated that the &(' events are smaller than the ma"imumnaturally occurring earth$uake 8onditions favouring &(' are not present at theBakun site e"cept for the si


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the rock mass, formed by greywacke and shale0mudstone se$uences,presents low permeability? and

the groundwater elevations are high at the pro!ect site and within the

pro!ected reservoir

/n!illar *om&onents

The pro!ect works are designed taking into consideration state%of%the%practiceprocedures for each of the pro!ect elements 'afety concerns during operation andconstruction are the primary influence on the selection of the technical solutionsadopted This design process will continue during the construction phase, when thedetailed design will be prepared To assure that the construction takes placeaccording to the design philosophy, detailed $uality control procedures will beestablished These $uality control procedures will encompass all constructionactivities including environmental protection, river diversion, e"cavation, fillplacement, concrete construction, road construction, e$uipment fabrication,

e$uipment erection, initial filling of the reservoir and e$uipment start%up Theprocedures will include inspection and audit of construction procedures andactivities, including surveillance before work, in some cases, during work, after work,and testing To aid the process, instrumentation will be installed within the dam, itsfoundation and at other ma!or structures -ata provided by the instrumentation willbe evaluated during construction, first filling and initial operation, and during thecontinued operation of the pro!ect 'pecific technical and safety aspects for the mostimportant of the civil structures are discussed in the following paragraphs

The Segre'# C#n)ree Fa)e R#)&4i!! Da3, Bra*i!

Ri"er Di"ersi#n 9#r&sThe river diversion works provide protection to the construction site, thecontractor#s e$uipment and personnel, the pro!ect#s civil works andmechanical and electrical e$uipment during construction The diversionwill consist of upstream and downstream cofferdams, three riverdiversion tunnels and other ancillary structures The river diversionworks are designed to provide protection from floods of up to 344%yearrecurrence interval

Three )/%metre internal diameter diversion tunnels, appro"imately)>44 metres long, will be used to evacuate the flood waters during


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construction The tunnels will be stabilised using rock bolts anddrainholes as well as through a process of consolidation grouting andconcrete lining The concrete lining will also contribute to the safety ofthe tunnels, protecting the rock e"cavation against erosion due to thehigh flow velocities ;ne of the tunnels will be converted to a bottom

outlet after construction of the pro!ect The intake structures aredesigned to convey the flood waters in the tunnels with minimumlosses The outlet structures are designed to protect the tunnels fromretrogressing erosion

Kenyir HEP:s s(i!!%ay

S(i!!%ayThe spillway is composed of a gated ogee, an open concrete chute, aflip bucket and a plunge pool The ogee, with crest elevation of /4*metres, is divided into four )3 metre wide bays separated by .3 metre%wide piers The spillway will be founded on competent rock in a largee"cavation The slopes of this e"cavation will be designed for long%termstability The stabilisation measures will include regularly spaced rockbenches, a surface drainage system, drainholes and rock anchors

The spillway is the safety valve of the reservoir dam system @heninflows to the reservoir are larger than the outflows re$uired forgeneration, and the reservoir is full, these inflows need to bedischarged through the spillway by opening the gates The amount of

opening depends on the volume of inflow, and is determined followingan operation rule designed to ma"imise the flows available forgeneration but always considering the general safety of the dam Thedimensions of the spillway are selected based on the ProbableMa"imum 5lood 9PM5: The probability of occurrence of the PM5 inany single year approaches


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control the erosive forces of the discharged waters (ts sides will beprotected with a concrete slab anchored in the rock9aer C#n'u)#rsThe water conductors include the power intakes and the pressureshafts and tunnels The eight power intakes are !oined together and

located in an e"cavation ne"t to the spillway, in the left abutment of thedam The eight pressure shafts and tunnels convey the water from theintake to the turbines in the powerhouse

Power (ntake The power intake structures are designed to safelywithstand the forces applied to them by the reservoir and inflowThe e"ternal dimensions of the structures are selected to bestable under static and earth$uake conditions The internaldimensions of the intake structure are chosen based on there$uirements for the hydraulic passages and the dimensions ofthe mechanical e$uipment housed in them

Power 'hafts And Tunnels The power shafts and tunnels are

designed to convey the water from the reservoir to the turbineswithout large head losses The geotechnical parameters of therock mass surrounding the tunnels, the relative position of eachtunnel, the groundwater regime in the tunnel area, both presentand future, after the pro!ect is in operation were consideredduring the design process and will be continuously monitoredduring the construction phase to obtain a safe and economicalpower corridor Additional tests within the rock mass will beundertaken to provide appropriate parameters for detaileddesign

P#%erh#useThe powerhouse will be of the surface type, located on the left bank ofthe river, near the toe of the dam but separate from it The powerhousewill provide enough space to install and later operate all the e$uipmentnecessary to generate energy using an installed capacity of /,>44 M@The powerhouse will be e$uipped with cranes of sufficient capacity tohandle the erection and later the maintenance of the e$uipment (ngeneral, although providing the spacing re$uirements for the electro%mechanical e$uipment, and a safe and comfortable workingenvironment, the powerhouse will be a very compact building to

decrease construction costs

The substructure of the powerhouse will be founded on sound rockThe dimensions of the substructure besides being controlled by thespace re$uirements of the e$uipment, will be selected to providesufficient weight for static and seismic stability, and to resist thestresses imposed by gravitational, hydraulic and mechanical forces,and the vibration of the e$uipment The slopes of the e"cavation will bedesigned for long%term stability 5or this purpose, the e"cavation wallswill incorporate regularly spaced rock benches and a surface drainagesystem, and drainholes and rock anchors will be placed where re$uired

for stability The substructure will also provide safety against floodingdue to a rising tailwater level


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The P#%erh#use a he J#r P#%er Sai#n, Pera&

Energ /nd Poer 6eneration

(n order to assess the energy generation of the Bakun reservoir and power plant, asimulation 0 optimisation type mathematical model was used The model applies thestorage%continuity e$uation, driven by a series of reservoir inflows, taking intoaccount net evaporation from the lake, seepage looses and the reservoir storagedefined between the permissible ma"imum and minimum operating levels (n itsoptimisation option, the applied algorithm ma"imises the continuous power output ofthe reservoir The optimisation procedure is based on a well%tested dichotomoussearch techni$ue which uses continuos power as its ob!ective value

The basic operating rule for each monthly interval was assumed as follows=

water release will be made so as to !ust meet the target continuous power? should the continuous power release cause the reservoir to fall below the

minimum operating level, the water release is reduced such that this minimumoperating level is !ust reached at the end of the month? and

should the continuous power release cause the reservoir to rise above the

ma"imum operating level, the water release is increased to !ust reach thema"imum operating level at the end of the month? e"tra releases are turbinedas much as possible and the amount in e"cess of the total turbine capacity isspilled

The reservoir operation and power generation studies were carried out for thereconstituted monthly%based hydrological period )*>* % )**1 At the ma"imumoperating level of //+ metres above sea level 9m asl:, the Bakun reservoir has asurface area of .*3 s$uare kilometres and a storage capacity of >1+ billion cubicmetres At the minimum operating level of )*3 m asl, the storage capacity is />.billion cubic metres The active storage volume of )*/ billion cubic metres ise$uivalent to about )2+ days of mean reservoir inflow The revised long%term meanstream flow at the Bakun -ischarge Measurement 'tation was determined to be),1)> cumics

The capacity and energy generation data for the Bakun hydroelectric power plant aresummarised


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The average monthly power and energy output, as well as the monthly energyproduction during a wet year and dry year

8apacity and Energy 6eneration of theBakun HEP

Ma"imum 6enerating 8apacity 9at //+metres asl:

/,>44 M@

Average 6enerating 8apacity /,13* M@

Minimum 6enerating 8apacity 9at )*3metres asl:

),+/4 M@

5irm 8apacity 9delivered: ),.31 M@

Average Annual Energy 6eneration).,2+36@h

5irm Annual Energy 6eneration )3,3.46@h

Average Plant 5actor +44J

5irm0Average Energy &atio */3J

$AP OF THE BAKUN HEP RESER;OIR AREA


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CONTINUOUS PO9ER AND $A,0.. $9 INSTALLED CAPACITY

/verage Monthl Poer and Energ Out&ut 4nstalled *a&a!it 7,-))M05

Month6enerating

*a&a!it 4M05Plant

#a!tor/verage

Produ!tion 460h5

Energ Produ!tion460h5

0et ear Dr ear

anuary /,1.> +> ),>+> ),21> ),1/)

5ebruary /,1.2 +> ),11/ ),.)1 ),)*1

March /,1.. +) ),>)+ ),.>) ),1/)

April /,1.. +3 ),>>+ ),2/. ),/2*May 1,12) +3 ),>*+ ),2+. ),1/)

une /,12. +) ),1+4 ),3/+ ),/2*

uly /,1.* 23 ),1/+ ),1/1 ),1)*

August /,13. 2. ),11* ),1/1 ),1/)

'eptember /,1>/ 2* ),1/2 ),/+4 ),/2*

;ctober /,113 2* ),1+) ),1/1 ),1/)

ovember /,11* +/ ),1+1 ),./* ),/2*

-ecember /,131 +> ),>.2 ),233 ),1//ear 7,'29 8) 1,:82 18,1 12,222


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Te!hni!al /nd Safet /s&e!ts Of H;D* Su$marine *a$leEvolution Of *a$le Design Sin!e The 198)s

5or high power H7-8 submarine cables, the principal area of development has

been in developing conductor insulating material to operate at higher voltages Thisin turn enables higher power levels to be achieved &esearch is continuing into thebehaviour of cable insulation under changing temperature 0 pressure 0 stressconditions, and both testing and operating e"periences are being accumulated Theoperation of the Bakun cable will enable the pro!ect to take advantage of the latestdevelopments in this area The control fle"ibility possible with modern H7-8converter stations can therefore be used to increase the operating voltage on theH7-8 submarine cables when the conditions in the cables permit this

Modern converter control technology utilises computer techni$ues 8onse$uently,data can be continuously fed into the control system representing the conditions inthe cables in such a way that the H7-8 converters will control the H7-8 system toavoid undesirable electrical conditions arising in the submarine cables At leastthree, and possibly four, H7-8 schemes have control features specifically to coveraspects of cable loading

Although the Bakun pro!ect will have the longest and highest rated H7-8 submarinecables, this may be overtaken early ne"t century by even longer installations An(celand to 'cotland 9CD: submarine cable link is under serious study, which involvesa route length of over *44 kilometres An (celand%orway alternative, which has alsobeen suggested, would involve a route length of over ),/44 kilometres, that is about

twice the Bakun cable route length The power capacity being considered for the(celand pro!ect would re$uire cables of similar rating 9if not higher: to the Bakuncables

;riginally, submarine cables were laid from conventional ships, in which the cablewas coiled in one or more holds, and paid out either over the bow or via the stern, asthe ship moved along the cable route The orwegians developed poweredturntables on a large barge for a pro!ect in )*2., which enabled easier laying of largecables with satellite navigational positioning systems and a device to follow thetouch%down point of the cable on the sea floor 'uch very accurate and highlycontrolled cable laying has become the current practice Turntable capacity is now

ade$uate for over )14 kilometres of the Bakun cable, or over /44 kilometres of aslightly smaller cable

8ables have been laid in a very wide range of conditions and depths The Mersina'traits cables were laid through an area of rocky outcrops and tidal currents up to si"knots The 8ook 'trait ew Kealand cables were laid at depths up to /.4 metres,through a


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design operating temperature for the paper insulation in the cable is usually 34o8,such a high sea floor temperature means that there is a smaller temperature rangeavailable for cable load current heating The smaller temperature range does helpthe insulation design and conse$uently the combined diameter of the central copperconductor and the paper insulation for the Bakun cables will be no greater than for

the /34 kilometres Baltic cable which was laid between 6ermany and 'weden in)**>

%elia$ilit /nd Safet Of Su$marine *a$les

(nternational e"perience shows that H7-8 submarine cables are inherently reliable,and that breakdown 9or failure: is primarily the result of e"ternal causes By far thegreatest cause of failure is related to shipping activities, either from anchors orfishing 0 trawling e$uipment Probably, the ne"t highest cause of failure is related torepair !oints which are sometimes made under difficult conditions and in hasteModern and specially%built repair ships and newer !oint making techni$ues are

overcoming repair !oint problems

The early English 8hannel cables of the )*34s achieved about 34 per centavailability because of fre$uent anchor damage 'ome of the earlier 'candinaviancables also suffered high numbers of cable failures caused by shipping

The introduction of double wire armoured cables provided protection against impactdamage from light to medium trawling e$uipment, but were unable to completelyprotect against impact damage from very large heavy anchors, or the very heavytrawling e$uipment

Burial of cables in areas e"posed to large anchors and trawls commenced in theearly )*+4s The newer English 8hannel cables laid in )*+. for the England%5rance/,444 M@ link were buried over their full length in trenches 9)3 metres deep: cutinto the hard sea floor, and deliberately backfilled This has been entirely successfulas no damage has been reported

8able repair is performed by locating the damage area, cutting the cable close to thedamaged location, lifting each end of the cut cable and inserting a new piece toreplace the damaged portion by !oining it to the cut ends, then dropping the cableback to the sea bed This procedure leaves loops of cable each time it is done and is

one reason why multiple cables are laid with a relatively large spacing &epair timesare dependent on=

time to mobilise repair personnel and e$uipment to the fault location?

time to locate the fault 9usually achieved before mobilisation is complete:?

weather conditions at the fault locations? and difficulty of recovering cable from its buried 9or partially buried: state on the

sea floor, that is depth of water and depth of burial

Cnder good conditions, where mobilisation of repair vessels and personnel isimmediate and where the faulted cable can be easily and $uickly lifted from the sea

floor, a short length of cable may be spliced in and the cable returned to service inthe order of )4 days This is the typical situation in orway where repair vessels and


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personnel are immediately on hand However, the owners of the 5ennoskan cablebetween 'weden and 5inland e"pect the repair 0 return%to%service time for their cableto be about /3 days 5or Bakun cables, their protection and fre$uency of repair arethe sub!ect of ongoing investigations &epair of the cable for Bakun will be relativelyeasy because of the shallow water, and the relatively mild weather ;n the other

hand, the length of the cable may increase the time to find the fault location Positivemeasures to protect the integrity of the cable include the provision for ade$uateburial, the proposal to maintain a ship on site to repair and store spare cables onsite, and the provision of false cables to prevent anchors hitting the real cable

Sstem Sta$ilit

Modern networks of electrical power generation, distribution and consumption are inbalance, that is, at any given moment, the power being generated is beingconsumed in its entirety Because consumers are constantly connecting anddisconnecting electrical e$uipment, the operator of a power system must be

constantly ad!usting the generation to suit the re$uired load demand

Apart from adding and subtracting consumption 9load:, there are from time to time,e$uipment failures which disturb the balance and the ability of the interconnectednetwork to maintain a stable balance known as the stability of the system Adisturbance 9such as the failure of a particular power line: causes the remaining linesto be overloaded and blackouts to occur, and thus leads to a temporary problem ofinstability However, the resulting effect on the systems may only be a slight changein the fre$uency of the supply or voltage 9normally />4 volt, 34 cycle in Malaysia:This could only be of mild concern 9such as causing an electrical clock to lose time:,but in a modern economy there are many connected facilities that are susceptible tofre$uency and voltage variation or industries which suffer badly from power failuresThe ob!ective of system planners and controllers is, therefore, to achieve a stablesystem which will not fail under the conditions of normally e"pected disturbances

8onnecting the power system of 'arawak and Peninsula Malaysia 9indirectly: by thecable will be a ma!or change in the configuration of the Malaysian system and theeffects of this linkage are being carefully studied as part of the Bakun HEP

The following scenarios are being studies as part of the system stability evaluations=

damage to one of the cables causing a sudden loss in the power beingsupplied by Bakun?

the effect of e$uipment failure in Peninsula Malaysia on the generators at

Bakun and on the supply of power to 'arawak? and the control re$uirements of the link to enable the system to be ade$uately

protected

The result of these studies will be incorporated into the power system

3ong Distan!e Su$marine *a$les 0orldide


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'ince the )*+4s, at least ten H7-8 long distance cable links have been installedwith cables similar si


22/24

Manufa!turer Poer4M05

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Se!tion /rea4S44

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Pirelli

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8ables

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23/24

N#e5$ass i3(regnae' +s#!i'1 insu!ai#n si3i!ar # he )a?!e 'esigne' 4#r he Ba&un HEP

Shie!' 9iresThe ma!or evolution in the selection of shield wires has been thedevelopment of fibre optics 'hield wires are used to protect the

overhead current carrying conductors from direct lightning strikes Thedevelopment of overhead shield wires with fibre optics providessignificant benefits as the shield wire is used for the dual purpose oflighting protection and communications

%elia$ilit Sta$ilit /nd Safet Of Transmission *a$les

(n general, the words reliability and stability are terms associated with a system ora network However, in terms of a conductor in a transmission system, they areassociated with the physical preservation of the conductor within the system (ngeneral, damage to conductors can occur at the attachment points where theconductors are held in place with clamps, at the locations close to the tower where

proper distance from the the tower must be maintained to satisfy the minimum gapclearances for a particular voltage level, and at any point where current carryingconductors are not properly protected by shield wires 5lashes from conductor toground have the potential of damaging the strands of conductors and will re$uirerepair

The reliability and stability of the line are improved by designing the line with a highdegree of probability for the insulation and gap clearances to withstand theanticipated over voltages resulting from the system operations (n addition, linereliability and stability are enhanced by protecting the conductors and the line fromthe effects of lightning

The parameters that affect the lightning performance of the line include the kerauniclevel of the area, tower geometry, insulation at each tower 9gap clearances andnumber of insulators:, and grounding at each tower location

The -8 lines for the Bakun HEP have been designed for a keraunic level of )+4days 0 year which is indicative activity that takes place in the vicinity of the line routeThe lines will be designed to limit the tripout rate of the -8 overhead lines to lessthan 4/3 outages per pole per )44 kilometres of line per year

'afety of transmission cables are associated with ground clearances 5or the BakunHEP, provisions will be made in the design of the line to incorporate increases in thetemperature of the conductor produced as a result of circulating currents and thedesign will consider the worst ambient conditions for the caseAppendi" ((showshows the technical characteristics of the Bakun HEP
http://www.mtc.com.my/publication/library/bakun/app2.htmhttp://www.mtc.com.my/publication/library/bakun/app2.htm


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Trans3issi#n #%ers an' !ines in Peninsu!a $a!aysia

*on!lusionThe design of the Bakun HEP has evolved since the initial studies carried out in theearly )*+4s, taking into account developments worldwide in design and constructiontechnology of high dams and high voltage direct current submarine cables Thedesign of the hydro dam has incorporated features that will ensure the highestdegree of safety and economics The pro!ect will also capitalise on the vastimprovements in technology in cable design and manufacture that has occurred overthe last )4 years These factors will together produce an e"cellent hydroelectricpro!ect to serve both the peninsula and 'arawak

Technical Aspects - Bakun

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