ABERDARE POWER CABLES

This booklet has been revised several times to meet the demands of an ever-changing market, as well as specification changes as the result of improvingtechnology. It is not a treatise on electrical technology, but it is published to givesupplementary information to engineers, technicians and electricians involved incable selection and installation.

Aberdare hopes that users find it useful and invites any constructive (or corrective)criticism.

1.0 How to Select a Cable1.1 Load to be supplied ...1.2 Permissible Voltage Drop .1.3 Prospective Fault Current .

1.4 Environmental Conditions of Installation'1.4.1 Cables Laid Directinthe Ground .1.4.2 CableslnstaliedinAir .

1.4.3 Cables installed in Ducts1.4.4 Composite Cable Routes1.4.5 Intermittent Operation ....1.4.6 Solar Heating

2.0 Useful Electrical Formulae2.1 VoltDrop . . .

2.2 Charging Current ..2.3 Per Unit System2.4 Load Growth .2.5 Load Factor .2.6 Capacitor Voltage Rise2.7 LoadSharing'"2.8 Conductor Resistance2.9 Lead Resistance2.10 Wire Armour Resistance

11

...................... 1

47899

............... . ·····10

'''10. 11

1212

. 13

13..... 13

·13. 13

.................... 14

·14····15

15

3.0 Transport, Handling and Installation of Electric Cables3.1 Cables on Wooden Drums .

3.2 Cable Transportation3.3 CableStorage .

3.4 Mechanical Forces on Cables during Installation3.5 Pulling Cables through Pipes or Ducts . .3.6 Preparation for Cable Laying . .

3.7 Backfilling and Reinstatement .3.8 RepairstoPVCOversheaths .

1616

····17.. 18

18·..··19... 21

26..·26

Paper Insulated and Lead Covered 6.35/11 kV ~ables4.1 Notes on impregnating compound ..4.2 Moistur~ in Paper cables .....4.3 Derating factors for non-standard conditions4.4 Short circuit ratings for PILC cables ....4.5 Earth fault ratings .

27···27··.. 27

·29·····30

······..·31

Medium Voltage XLPE Insulated, PVC Bedded, SWA, PVCsheathed 6.35/11 kV Cables5.1 Notes on XLPE insulation 325.2 Derating factors for non-standard conditions 345.3 Short circuit ratings for XLPE insulated 6.35/11 kVcables 355.4 Earth fault current 36

6.0 Low Voltage PVC and XLPE insulated 600/1 OOOVPower Cables 376.1 Notes on PVCand XLPE insulation 376.2 Cable cross section 376.3 Derating factors for non-standard conditions 446.4 Short circuit ratings for PVCand XLPE insulated 600/1OOOV

cables 46

9.0 Innovative products 529.0 INTERDAC3 52

vYllon selocllng 0 coble for youl oppllcatlon, a nurnber of wmaUlesI1Hll1ll0 attention. Tlwse are{<I) Size and typo olload to be SUI)pllod{bi F'OiTnisSlble voltn\10 drop{(J F'rospectlV() fault current(;Ii CncUit proh1clionI~ii ErwlfOmnental CCH1(Jltions01Installahon

full loacl runnmg cOII(li!rf)l) IS 5')" fhom no hard arId last lule as to theallowable volt drop under starllnfj conditions, DepcmJlnq on the type of loadto 110star!(;d, there IS the possibility tMt tho torque rnay be comproflllseddumH;J ;;tarlinQ, If the motOi IS subjected to (lifflcult starling conditions Areasonal)le volt drop should be chosen In these cases,

Load to be suppliedIn Older 10solecllho appnlpnato cable, It ISnecessdry to know tho voltaqe andth(~ load current In amps ThiS Infonnatlon will bo available either directly Inamps or as kW Of kVA

(a) Multiplyinq the current by the Impedance of the length of cable Calculatethe percentage volt GlOp by reference 10the phase to earHl voltnge.

Hit: followinfj formulae apply.

kW x lOOO

(b) Mutllply the current by tho length of caUle. and then multiply Hw ((;sull bythe v011drop per amp metre figure as given In table 62 or 6:3 on paqe38 or page 39 on tl10 type of conductor

Previous example using method (a)

Starlinq current :1 )( runnl!lQ current

,161 Amps4113Amps

Impedanc(! of 50m of 501'lnf c;\bIG 6 ;~ipg 38

kVA 1000xV

U"e this value of current fo determine Ihe cable size by reference to there IQ vant lat)les givnn In Seclion 4 (Paper Insulated), Seclion 5 (XLPEnlsulatod medium voltaqo} Of Section 6 (PVC and XLPE insulaled low vollage)!or C:opper or AlurnirmJln conductors

A 2Jfll:Jhtly larger conduclor Sl/:O rnay 1)0 chosen 101safety aspects, and toprovido for Iho 111gherHian usual current which Inay b(l Hxponenced dunnfj~,jartin9 01Hlectric motors,

o 02359 ohms

483 x 002359

11,394 volts

SUPP'OtiO It IS required to supply a 3111 ovm n distance of 50rnkno'ivn tel IhIVe 'I loctor of 0,9l)8 caiculatod

400 volt. 1OOkW motor connecledc1imct in ground. The motor load IS

The full load lino cumml. L. canUsing method (b)Slartmq current \161 ;"Imps

41)3 Arnps

0.817 mViA/m (Tablo 6.2) PO 38

0.817 )( 10 x 483 x 50

19,73 'lolls

Volt drop per amp por fTh)lro

Voll dmp

Wo now reler 10 tatlle 62 on pq 38 and nole that Ihe sinai lest copporc(jfl(juctor. PVC Insulated cable. Ihal can supply a curront of 161 amps In Iheground. 15 a 50 rnm" rated area cable This caUle can carry 169 ampscontinuously If installed under standard conditions

1.2 Permissible Voil.age DropCalculate lilt} hlfJhest current drawn by the load, by rnutllplylnq the cUfmnt ascaiculaleclln i.l by an appropnate lactm If a 8lm/Dolta motor slarter is usedon a I'!!otor, thiS I,JelOr IS3, II the motor IS sturted dlwcl on line, Ihen \JSOa factor01 G. Whoro tho load IS reSl$lIve healrnq, IrqhHng or a hansfomlOr, 11is notnecessary to IrlCreas/;) Iho current as calculaled In 1 1, Calcuiate the volt dropwhfCIl Will be at the load tennrnals by reference 10 laUte 62 or 6,3on p q JS or pg The maJomum 'loll drop allowed by 8ANS1 0142~ 1 duonq

Note: II ollen happenstlwn that calcutated in 1

runs of electnc cable lhat a tarqer conductortequlred for volt drop reasons

EXAMPLE OF CABLE SELECTION FOR MEDIUM VOLTAGE (11 kV)We Wish 10 supply a 2MVA11 kV transfonner Irom on Eskom supply pOlnlwhich IS 3krn away We i,rF 10 use an undornround paper Hlsulated, copperconductor cable The denf!~1of burial 01 the cable IS 125m Ground thennalresistivity IS2Km;W The.youl1d temperature IS 25C and there are no olhercables In the IlOlich.

Short CirCUit level rnay be assurn\ld to be 250 MVA, and the oal1h fault level100 MVA, and J! may Ue assumed !flat a fault will be cleared in half a second

Om alinq factor for Depth of Bunal at1 ,25 m is 0,9G

Doratlnq factor for Soil Thermal Resistivity at 2 K.miW IS 0,84

Derating factor for Ground Tomperature of 2tl'C IS 1,00.

1050,8064

130 Amps

Table 4.2 on pg 28 shows that a 35 nun? Copper conductor cable would becapable of carrYlnq this load (130A), ThiS is confirmed by reference to thePaper Insulated Cable brochure (Page 13).

Tho cable size reqUIred is fhus 35 mrn" Copper conductor, 3 Core Generalpurpose belted cable. (Table 17 SANS 97)

Checking for volt drop

Volt drop IS seldom a problem at Medium Voltnge, even for 10I1[) nms of srnallconductor size as shown above.

Checkino for fault current

Pfospectivo symmetncal (Shol1 CirCUit) current

x K K is 115 A!mm? lor copper....... ~~~·.~/"····t····· conductors, pnpHr insulated<

Nearest standard size ISa 95 mrn) Copper conductorThis tHiS a current filling of 235 Amps under standard conditlr)lls.

Earth fault current lor half a second:Lead area for a 95 :3 Core PILe cable IS approximately 200 tnm:'

In many cases, the cab'·e conductor size is larger than rllctated by the full loadcurrent, and is chosen III order 10survive the prospective short Circuit curren!.

The use of large conductors can be aVOided by improving the speed ofprotection, (fuses for example) ami In the case of earth faul! current, by the useof sensitive earth fault protection.

1.3 Prospective Fault CurrentElectric cables are designed to operate below a certain maxirnumlemperature, thiS ben19 dependent on lhe conductor malerial and the type andthe thickness of the insulntlOn.

Cable selection for a particular Installation must therefore be made on thltbaSIS of not oxceedinothE,se temperature hITH!S.

Suppose the 400 volt dis:ribution board from which a cable IS fed has a faultlevel of 5 MVA ThIS translates to a faull current of 7,22 kA. and the cable rnustbe capable of passing t':i:; current without darnaoe untilltlO fault IScleared

The smallest ctlble tha! Gem safely handle thlS fault current for a 1 second fault,ISa 70 111m"copper conductor cable, or a 95 rnrn? aluminlwn conductor cabin.Suppose now that the fault clearance time (Including any mechanical delayson the tripping med1anisrn) is closer to 2 secon(js, then the srnatlest cablewould be a 95 rnmc cappo!! conductor(1 0,925'0v2= 7,725 kA for 2 seconds)or a 150 mm2 alurnlnlwn conductor (11,400../2 = 8,061 kA for 2 seconds),likeWise, a fault duration less than 1 second Will allow the use of smallerconductors than were calculated tor the 1second ratmg

/lnDtilef ExampleCon:; idOl the following diagram'Oi8grarnrnatically, the systern IS

l1kVx Board

bOO kVA2::0,05 p.JJ

lK\jHinG X~/- x

From Table 6.2 on pg38thejrnpedanceof 18Smmicable "" 0,144b 1J /kmThus tht.; impedance of1 00 In 0,01445 n

The fault level at the siJb,dist board i$ then found by dividing the base MVA bythe total pet unit impedance.

Sub0;" Board 5,J,!,?~...1OOQQQQ

;,/;3)(400

X Mwn LVOi" Board

PUSYSTEMP u !,owce impedance

xbaseMVAVI

Reference to pg 7, where 115A/rmn" for rvc / Copper cables, shows thata 70 mm" copper cable can wjthstand a short circuif current of 8.05 kA for 1second. This IS above the potential faulf level of the system Moreover, thedurallon of tho .fault or the tinm taken by the protective deVice to operate has tobe conSidered. The circuit supplying tho motor would very likely be protectedby a 200 amp fuse or a circllIt bleaker. Both these devices would operate wellwiU11n 1 second, the actual time being read fro In the curves showing shortcircuil cunent i tripping time relationships s\Jpplied by the protectiveeqUipment manufacturer Suppose the fault is cleared after 0,2 seconds, Weneed to determine what short CirCUit current the cable can withstand fOI thiStime.

Example 1 USII'It) a base of 100 MVAand the per W'lt method, the Impedance01 the systern (It the sub,dlst boald can be deterrnine<1:

Tt,Hlstorn10l: 100 x 00505

V'itmre K l1510rPVC Gopporcables 161TG)K 143101 XL PE / Copper cables (flOC ....250 'G)f\ Tn lor PVG !Alurmnum (solid or stranded) cables (1OC IBOG)K 92 lor XLPE! Alummum (solid or stranded) callies (90G 250G)K 1/5 for PIL C , Copper cables /60'e)1< !'lilor PILG! Aluminum (slranrled) cables (70C ~160'C)

and vvhcre A ISthe conductor cross sectional area Hl mrn and tthe duration otthe fault in seconds

Thib is well in (1XGCSSot ttH) syslorn potential fault Icvt11 and so It can beconcluded that a 70 111m"cable is suitable for thIS exarnplr\ Dunng Iho ponodof shorl circuits, the forces acling upon IndiVidual cores of a 3 phase systemaru ot1orrnOUSnlOse are forcos of repulSion and attraction, and hence causethe cores to move If Irvldequatoly wstrained In the case of 3 com arrnouredcdbl!)s~ Hw fact that the cores are laid up, and the restrainlf1g effect of thea'mour wires is such as to Hrmt tire corc rnovernenL Bursting strengths are,however, still nnportant In the case of PILe cables where the effect of theresultant voids loft In tho Insulation (even after small movement) may bedell! f1lontal to the Ion\) term life of tile cable so affected

Elwiro nmental Conditions of Installation

nw data usoej for detern11f11nq the. cunent ratings given tn. thiS publicationarE! t:m.sHcj ()n calculations accortJlntl to IEC 287 Ra1rnos for multlcorecables are for a 8111£Jlecable run. Where groups of cables run In acomn1on the appropnate doralinq factors are given in the tables onpaqes2:9 .34 and 44 depending on the Iype of cable bQing useel.

Slfflrl,lrlv when Ihe installation conditions diller from standard, the dera1rnglactu r~,In the aj)propriate sections must be used

A qualilalive assessment of the cmKlitions Imrnedli1tely surrounding the cable;;hould be made. Factors such as the need for a fire retardant sheath,ndclitl(mat mectlanlcal protection, ;;afeguards agclIflst chemical attack amjCDlfosion should be conSidered in this category, These :nfluences affectrntlln Iy trH1external linish otthe cable, the armounng and serving

Cables are sornelimes speclfred with a termte repellent sheath It is worH1rnontloninn thaI no sheath will repel insects since sheath matorral has to be;flqestmj by the termite to be talal Thus, the statement 'cable Wltt1 a ten1llWrepell<llit sheath' ISsomewhat erronoous.

In tl1e case of paper lead cables there are several alternatlvo sheath metalsnV31lHtlle. pure lead IS prone to fatigue when SUlljected to Vibration. Alloy E:;;!,ealt1can be supplied whieh Will resist dcteriorahon Ulrough fatigue.

rho foregoinq notos am by no means an exhaustive lreatrnent of the points toCO!l~'ldor WiIOn chOOSing a cable for a particufar application but are rather£1Uideli nos to Hie salient POll1tSwhich need consideration

1.4,1 Cables Laid Direct in the GroundThe ratings 91ven are based on a £lfOWld thermal resls1rvlty (g) of 1,2 Km!VY1he factor (£1)'vanes conSiderably Wllh dlffenng 9round conditions and hasa pronounced effect on a cable's current carrying capaclty,f heonlysweway to detennlne (q) IS to ITwasum It along the cable route. ThiS practice ISnormally reserved for $upertension cables. but there could bE! otherapplications whore soil thermal reSistiVity is critical

Clay: Clay is a dense, corr,iPact matenaL greasy 10the touch whenwet andwhich has a low Thermal ResistiVity even In the fully dned,out cemdlhonMost clays however, shrink'when dry in\) and can thus not tJe used as abeddin£1 for the cable. They can be used as backfill and sI10uld beconsolidated by rollln£1 rather than tampif1q.

Sand: Sand is a crumbly malerial with particle gmins easily (jlstrngUishedilnd 9ritty to the touch even when wet Partlde sizes lar90r than 2mrn areknown as gravel, Sea s,and or sand obtHined from a nver llE)d usuallyconsists of sphencal particles and has a very high Therrnal Resistivity whendry. Seme quarried salids, and marHllade sands as used for makingconcrete, have irregularly shaped particles of varyltlg size and can becompacted to a high denSity, These can be used as a bedding matenalespeCially when 510'\, Clay is added amJ Will have a satlsfactonly lowThennal ReSistivity in the dnedout stalo. Sand/gravel mIxes should be usedwith cate as sharp p£lJli(:lescandamage the callie serving.

Sand clay: Sand clay IS,as lIs name implies, a lruxtum of sand and clay. It ISan ideal material for use as bedding and backfill and IS best compacted byrollinq. 11rarely dries outto Idwer than G% mOisture content

Loam: Loam can vary in corour from roddlS11 brown to dark brown and maycontain quantities 01 or£1anlc matte! It crurnbles '11011,even when dry, andcan be well compacted to achievo satisfactory values of Itlennal ReSistivity.It IS very SUitable as a bedcl1nn rnatmial.

Chalk: CI1alk ISa soft whlto qr SJlCY porous matenal havln9 a lower TllennalReslSllvlty when wet, but drying out 10 very high values and is unsuitable fOIuse as bedding or backfill in any area where drying out is likely,

Ouklip: Ouklip is decomposed rocky material, varyin9 In particle size andhaving very low Thermal ReSIstiVity in the undisturbed state. It can be usedasa backfill material when ml,\cd with 10arn or clay but should not tJe usedas a cable boddln9,

Peal: Peat or humus IScomposed mainly of or9al11c matena! and ISblack ordark brown In colour, It should not t}e used as bedding or backfill as dried~out TtJorrnal ReSistivity v'dlLies of over 4 Kn1/W arc usually obtained Itshould be rernoved and al1.ematlve material used for both bedding thecables and tJ£Jckfiliing thetrof)ch.

Make-up soil: This is a general ternl for the soil In any area, Hle level ofwhich has been raised artificially uSing imported fill which rnay consist ofbfiCks, concrote, cinders, ash, slag. stonos, other refuse or any of thematena! considered above, II any doubt eXists as to sUitability, It IS bestH111l0vetJcompletely and a suitable material imported,

Mine sand: Mine san(1 is thennally very satisfactory, but IS fllnhly corrosive,lI1d ~jflOUld therefore not be used,

T"(PICAL VALUES OF THERMAL RESISTIVITY OF SUBSTANCESENCOUNTERED IN CABLE INSTALLATIONS

Material ThermalResistivity(9) K,m

Sandy Soil 1,20

a~ 1~0Chalky Soil 1,80

Concreto 0,90

Water lonned growKIGrovel

0.501.00

lhe tll(Hmal resistivity of a substance IS greatly influenced by the mOisturecontent at a given lime, The hioher the quantity of retained moisture thelower Will be 1t1Othermal resistivity, A 11eavily loaded cable Will dry out thesoH around the cable and cause an incremlH in (0), ThiS pmcoss IScumulative and damage could be done to the cable insulation through overheallntl

lrnpunlies such as slag, ash and tho like increase the value of (g). as doosIntenso vegetallon on the cable route, by drawing mOISture from the ground.

1.4.2 CableslnstalledlnAirMulticore cables should be Installed With a space 01 0,3 x overall diameterand Single core cables with a space of > 0.5 x overall di,lIneter !H)tweenthmnselves and the vertical wall or surface supporting thern as per IEC 287,Ifthey aie installt3d in direct contact with the wall then the current rating givenshQuld be reduced by 5~,;'as a rouqh nuide line prOVided there IS a sp,lce of150rnm or six tUrles the overall diarneter of the cable whichever is the greaterbetween adjacent cables or cable nroups in the case 01 sinnle core cables.If Ule installation faOs to comply wlIIl this requirement then Hw deratinglactors In the relevant sections should be applied.

Wlwro the ambient temperature along a route vanes. the highest valuesiiouid be taken to selHclthe cablo Size,

1.4.3 Cables Installed in DuctsTIH~ air within'a pipe or duct will incmase the thermal resistance of the heatdlssipallon path, Consequently the current rating or a cable nm In a duct!plpe) IS lower than that for an eqUivalent cable in t!1Ooround or in free air.rhe ratings oiver, can be applied to cables laid in conGfote, asbestos,

Pilch fibre, PVC, earUlerWiarQ or cast iron pipes which are tile ITlore commonmaterials encountered. tt should be noted that sinnle core cables forrmng apart of an a,c, system Silouid not be individually installed in cast lion pipesdue to the heavy losses Iflcu!red by eddy current Induction

Generally the size of the duct (pipe) chosen should depend upon the ease ofpulling In. maul, tho cab ie, It should be borne in mind that a targer Cablemay be reqUired In the future to cater for increased load qrowth. Commonpipe sizes used in South Afliea aretOOmrn and 150rmn internal dlarnetersWhen groups of cables aro run in pipes along the same route. they shouldbe derated according to !tl0 factors given in the relevant tables.

1.4,4 Composite Cable RoutesIt frequently happens that a (,':ablerun ISmade partly In air, partly direct in theground and partly in ducts, The lalter conditions lead to the lowest ralmOand It IS here that altenl!<Jn must be focused Very lillie heat travelslongitudinally along the cilbio, the main dissipation being vertically 1tlroughthe duCtw£11l and swrourHl:ng ground. Anyrating where the route is partoround, pmi duct must ther!;jlore be treated With care,

, J

Where the length of ductlng does not exceed 5 mlJtres per 100m of routelennth, the cable rating may be assurned to be that for dlfect bUl'lal In thenfOund

1.4.5 Intermittent OperationCertain types of loads have an intermittent characteristic where the load ISswitched on and off before the callie has time to cool completely.Dependlno upon the load cycle it may be possible to selcct a smaller cablefor lntennittent operalJon than would be the case if the load werecontinuously applied, When a current In excess of Itle normal ruted currentIS apphod, the heating of the cable wJ!I be a conespondinnly quickeropera1Jon than the coolinq

Equivalent RMS currentCurrent flowmg rlurmg ttJ penod (InCludingpenmJs of lero current),[)umUon of "Iii periodNun:fmf of periocts. (includes penods 01 zero

1

NL (t,,)

Example:SIJppOse a process cycle i!3as follows

1bOAmpsforl flunute

50 An1!"; for 2 nllnufoc;

100 Amps for 3 nHnules

o Arnps fur 4 mlrHJtos

n N

Ln

n N

nms a continuous current of 76 amps flOWlrH] over the 10 mlnule cycle tanewould produce Uw samu huatln£) unoct as the individual cyclic cunerils, aridtho Site of callie could be selected based on 76 amps,

1.4.6 Solar Heating

Wllerl cables are installed In direct sunllght an apprecIable healing due tosotor absorption lakes place ThIS rw,ults In a significant reduction Hl theel:1bl,$ current canYHlg capaCIty and for this reason it IS stronglyrecommended that cables be protecter1 trom direct sunliphL The maximumillf"iilSity of solar radiation rneasured in South Afnc,l vdries between 1000a!l(j 1250 Wim" dependlflq upon IOCdtion

VoltOropThe voltage drop In a Single ph;;.se cHeUlI is byVoltnqc drop 2 x I K(Rem; (h x

Admiltancev,;fI()(e

Line CUfnjfl[ an1f.)sCirCUlI n'!jdslal1C€J oilmsWhasoCircuit roUGlunCGoturls/phase

/)elvveen current amI voilage

(HB rnhos(onauclanCe (Sien/OIIS!;usceplanCG (Siemens)

Where t'L band c are the dlsf;ltlce In rnm between tl10 centres at the threephases conductors

C;eol1wtric mean diamefer mrnConductor radiUS rnrn:\elalrvc permltlivlty of dieloctne

Capacitance per phaseLirH~to line voltage

In the case of an underground cable with shaped conductors, C IS 1l1cmasedIlyS'};'

I~erunit impedance referred to a given base MVA

Base MVAFull load MVA

Lo (ft 190 ) MW

L I~nLji'ifLdlJaI..cons,lJrner$ ,_~.Silnuitaneous M.D. recorded during the manit)

3 phase capacitor kVAR3"iJhilso"ialJlijevelkVA

{ i {

Angie 01 load currentAngle ottransll1Issien line!An!]!e ottriJ/JSII1lSSlan iffle 2

1/ [p + ct (T TJ]d. c. rosrstance at temperatura I CInitial ,f c IHs/slance at temperature r. cTempGralure GO' efficient 01 resistancG otconductor material

(/ c. res/stancesklf! effect factorproxlmilyellect factor

CONDUCTORAREAmm~

Up to 1852403004005006308001000

+y+

Single Core

1,019f.0271,0481,0871,1361,2081,3151,516

3 Core

1,0271,0411,0681,11 !'l1,175

Wire Armour Resistance185,03

Resistance fIN

whom ()N

wire rHamelorNumber of wires

0,093

1065

AluminiumAnnealed

28,03

2,703

23)( 10"

0,24

659

It can be shown that alummium has 18"" of the current. carrylf'1g capacity ofan eqwvalonl size copper conduclor The current raling of a cable dependsupon U10thermal diSSipation of the conductor IH losses, Usin£jlhe suffixes'c' for copper and 'a' tor aluminium, equal conductor losses are satisfiedby,

(al Tho cable drurn IS manufactured from Garflfully selected locally grownwood with a low moisture contont (lypical no! more than 15%) (Fig,!) ifthey are required to be treated It shall be done In accordance wilhSANS 05 with a Ciass C preservative or wllh chromate copper arsenate,Saligna. which is a hardwood, does not reqwre lreatment.

(b) Mwklng on drum flanges shouk] be clear, stencilled or burned Into thewood and should lrlcl\Jde the following information:

(i) Monulacturer's name or trade mark.(ii) Haled voltage, area. number 01cores and speCification(iii) Length olthe ill melres,(iV) Year of manufacfure,(v) Gross mass in kilograms.(vi) The Instruction "NOT TO BE LAtD FLAT",(vii) Serial number or oUler identilication.(Viii) On each flange an arrow \Nlth 1Ile words "ROLL THIS WAY"(ix) SABS Mark (ifapplicatJle).

(C) Both ends at ll'1ecadh~s on ttle drurn should be sealed and the Inner ondflxod to the flange 01 the cable drum to prevent loose coiling. The outerend is fixed to tile f1a\lge as weH. for trlO same reason.

(e) In tile past. it was COmn10n practice to r()tate slored cable drums through180' to re'distribute the rosin Impregnation oillhrough the dielectriC. Thouse of MIND cables l'1asobviated lhis reason for rotating drums However.it is still recommentJed. Ulat wooden cable drums that are stmed in theopen. irrespective of the type of cable contained. should be penodicallyrotated to avoid the drurn limber rotting through flsing damp

(ol Preparation[i) Tho truck rnusl match the drum size,III Do not overload the Hucksiii) Gable ends inu~;tbe sealed, secured and protectedIV) Use specml cable trailers for depot to Sito tram;portalion If possible

;?)

(bj Loading(I) Check drums for correct cable and Size, senal number, mass and

possible dama£1e,(II) Select conoctlorklilt'cnme(ili) Seler;t r;onoctslingsand spindle nnd check slln£1condition(rvi If a crano ISto be used, ensure that a spreader IS incorporated to

prevent damaqe to drum tlnnges,(VI If tho drum is to be rolled, ol)servo cmf(lct rolling dlrectron by

referllng to arrows on flnnges,(vi) Ensure Ihat the drum bolts are light\Vii) Enswe that truck surface ISclear 01obstructions, nails ote.(viii) Do l1{)tdrop drums onto truck loading bed,

(e) Securing(I) Secure drums to the truck brld to prevent sliding and rollin!] uSing

ndequote steel chams arid chocks.(11) Always try tu pack cJnlrns flange· to-flange(;il) Do not lay drum:; flat[IV) Stop the vehicle dUllng transportation and cheCk that the lo;;:\(jIs

secure,

(dl Oflloading(I) Check lor to cabte drums.(Il)Solect Gormetspindle lor the drum Sizeand mass and onsulB

that sam(~am in qood order, €lI1surethot a spreader is used,[Iii) 00 not drop drums but lower !]ently onto linn and relatively level

surfaces(lvi Oft load drums rnsuch a way that they oro eosily accessible

(V) If USinga that It is 01adequate size rolativ9 to thotm;kat hand,

(Vi) Ensure that the fork·truck tyres lateral spaCing is conect(vii) Take care thM tho protruding tyros do not damage other eqUipment

ortlrurns '(Viii)There ore two methods of rollinq drums frorn loading beds II Granes

aro notovwlable

Figure 3Method 1:H()l$ excavatr~d H1dXlmurnsJope1 [0 '10 to njC01Vn

3,3 Cable storage(a) Indoors

(I) Stack Hango to,flango amJpreferably not one on top of the othel(Ii) Stack so that drums are easily accessible(Iii) Observe fire prever,tlon rules,(Iv) Cable eods musl t,e seal9d at alltllnes,(v) Despatch on "firSll'\ ·firsl our' basiS.(vi) nOlate Paper Insulated cable drums one complete revolulion per

annum,

(b) Outdoors(I) Drurns Should a hEmJsurface at a slight angle and the aloa

sl10uldhave a syslem,(iI) Drums should be on a "llIslln Illst our baSIS(Iii) Cabl9 ends should at all trrnes,(iv) Stock flange,to·flange but if this ISnot possible limit ver11eolstaCking

Flfdctreeto smaller drwnsonly,(V) Stack in suct1a way,that drums are easily accessible.(vi) Ohserve file protection rules,(Vii) Cable racks nre ideal for storage but lake care not to oV9r1oad(Viii)Cables musl be Identifiable at all trroes(IX) If drums af() 9xpectod to be stored for a long tllne they must be

spoclally treated or rnade of hard wood(x) Rotale Paper insuLllpd cabie drurns one complote mVolutlon per

~ Iannum,

3.4 Mechanical Forces on Cables during InstallationAny cable has a maxirnum pu,1lingforce which should not be exe99tJeddunngrnstallalion, The cable cons!wctlon irnposes the limitation on the pulling·inforce When a cable stockH1(JISused the maXlnU.JiI1force can be related tooverall cable dlometer In mm as follows:·

I

Sleel Wife Armoured CablesSleel lape Armoured or Unannoured CableControl ar\(l Connnunication Cat)les

094 d'x lO'kN(J39 {f'x10'kN0..26 (j' xl 0' kN

Attempts should be made to limit the pUlling force required to a rmnimum toavoid stretching the outer layers of the cable This is particularly relevantwhere control and communicalion cables are concerned since Instances areknown where the cores have fimslllJd 2·3 metres inSide HI€} sheath andinsufficient overlap at straight Joint positions has necessitated rEI·laying somelengths.

An increase in the pulling force is permissible when the cable is laid by meansof a pulling eye attached to the conductors. As a rule of thumb, the follOWingforce:> may be applierj to a conductor:·

CopperAIUf1llnium

4.9 x 10 kNlrnm'294 x 10 kN/mm

Then. for example the rnaxlmum force that should be applied Vii! a pulling eyeto a 70rnm? 3 core copper cable IS:

Genorally when cables are installed uSing wellorled rollers and jacks, thefollowing forces can be expected:,

straight routetS 20% of cai)le wmght2 90 t>ends 20 40% 01 cable Weight

Cables laid in ooen trenches should be lelt slightly "snaked" so that anylongitUdinal expansion or contraciron can be ,)ccomrnodated. Similarly whencabins are installed in cleats or onhangers a slight sag between fixing points ismCQrnmended.

3,5 Pull i ng cab Ius through Pipes or Ducts

Whun a cable is pulledthmugh a pipe, friction between the cable serving andtllO pipe material increases the longitudinal force requirements.HQpresentative values for the coefhclent of Inc!lon ( p ) between the morecommon cable servings and pipe rnaterials are given below:-

Table 1.1

Serving Material

PVCPVCPVCPVC

g

0,650.480,550,35

AsbestosMetal (steel)Pitch Fibre

PVC

BltuITlenlzedhessfanor Jute

AsbestosMetal (steel)Pitch Fibre

0,970,760,86

ThiS Information can readily be used to determine ltm maximum length ofcable thai can be pulled throUgh a given pipe Without exceeding the rnaximumpermissible pulling force Take for exarnple the 70 Inm" x 3 core cablepreviously quoted, if tillS IS 11 low voltage cable With a rvc sheath and it isdesired 10 know the rnuXlrllum length of PVC pipe it can be pullcrj throughthen'

for PVC to PVClJBulfaree

035J.1 x Reactive force~l x Cable weight~1 x

From the table the mass 0170 mm" x 3 Coro copper cable is 3,fi kg/m.Thus the maximum length bfcable that can be pulled through a rvc pIpe IS:

If ltleHI am any bends in HIe route then these will create additional loading andreduce the theoretical length of cable that can be installed.

In certiun II1stances when long runs in pipes or ducts Hre encountered it maybe benefiCial to ~lrease the' cable Wllt1 petroleum jelly or some other nonHggresslve compound to!aCilitate the pulling~In.

Considerable damage can t'c) done to cable serving at the rnouttl of a pipe andprecautions should be exarClsed at such pOints.. This point is achieVing moreimportance with the present day trend towards impermeable anti corrosivesheaths which have to wltilstand periodic pressure tests, Included mnong theprotective measures tM! can Ue adopted are the fitting of a rubber grommet tothe mouth of the pipe and inserting a reasonable thickness of rag.

,When unarrnoured cable,; are pulled into pipes it will be beneficial to ensurethat there is no loreign malter present which could cause damage to thesheath before pulling. Pushing a r1raw rod through the pipe will usually clearany obstruction,

PlanningWflen planrlinq a cable route tbere are several factors to Ue cOlJSldered.among tt1ell1ostlrnportanl 01these are:ill Ground Thermal reSistiVIty(TR)tests

Position bays!II i} PrOVISionto indlcnto on the 'as kmf drawmgs, the serial or drum

number of the cable InstalledIIVJ ri18 use of mnss or pre Impregnated nondralnln£J Paper Insulated

cables, XLPE and PVC (jlOlectncs has all but elirnitJatedthe need forspecial precautions when laying cables on steep slopes in shafts.

LV cablos are normally buried at 500 rmn. Soil thermal resls!lvlty(!t)e ablhly of the soil to conduct or diSSipate Ileat) is standard at1.2 KrnNV

(ii) !tIe actual 5011 tbenrla! resistivity alon\) the proposed route should bemeasured eithor rneans of an ERA needle probe or the SASSneodle probe, but are outSide the scope of this papor, suffice Itto say tMt different soil compositions along the route will havedifferent rates of hoat dissipation and could result in "hOIspols'

(III) 10 overcome thiS, boddH1\Jand backfill SOils may hav," to uo"irnpor1ed".

.(t)j Drum HandlingH Always use the best hOistingequipment available.(lI) 00 not drop drums of callie onto ltw qround as this not only

damages the drum but will damaqe tl1e cable as well (especiallyPaller Insulated cabie)

(ili) It I110s1important that a ITJillltnumof rolltl1fJof !tJe (jrums on theground be allowed and then onty II) the direction of ttle arrowsp arntedon the flan(jos.

\l\JJ "Alhen rolltnq a drum of cable. to chanqe dilOclion use ;> steelplates with grease I)otween thorn, and by standino one flan(je onthose plates the cable drum may then be swivelled in !tHJdomroddirectionPOSitionthe drum pnor to cable,pullin(J so that the cable ISpulledfrorn tho top of (hedrum.

IVI) Note that il dlurn of power cable can wCI(Jhup to 10 tons so rnakesure thaI adeqiJate cable (hum Jacks are that tho spindle isstronq 10 hold the drum and U1althe stand on firm(.1roundand IIley hold tlw spindle hQrizontal.

(vlir Site the drum at the most convenient place for cable·pulling,usually ilt the start of a reilSCJniltJlystraight section near thecommencement of the trench work

(VIII) Allow for drum braking.

(d) Positioning of Joint BaysEnsure tllat there is suffiCientworking space, consider passing traffiCandotl18r obstructions, If ii, IS not pOSSibleto positron the joint bays atstandard cable length ,);st,mces, remember tllat the cable can be orderedin specific lengtlls, Consicler drainage tor large bays ami try to constructthe bays prior to cabfo pulling to prevent any damage to the cable at alalor stage.

(e) Recording Cable Drum Serial Numbers on "As Laid" DrawingsIn tile unlikely event of a cable fartum in the future, quotin!iJ the cabledrum serial number Will the cable manufacturer in nls qualitycontrol, as this serial fllJruiJer IS rolated tQ the manufactunnq and UIWmaterial management in tile factory

(fl Preparing for Cable LayingnJe following "VITAL ACTIONS" rnust be observed pnor to a cable pull.

Cable rollers must Deplaced between 2 and 3 rn apart in Ihe trench(depending on Slle of cable) (See fig, 4a on page 23),

(iii) Check that skidgood alternalive

are secure and In pOSition,corner rollers are a4b on page 23)

(c} GroundThermal Resistivity(IJ ThiS often governs the rating ot a power cable buried directly, as

cloes !JW temperature of the soil. Losses for cables running ilt the!TlilXlilium lernpemtum at which UlOdielectric system can faithfullyoperate for a rnaximum life of say, 2b years, alO considerable,rnnging from 15 W!rn for normal distrrbulion cabfes. Cableconductor tornporature and tile soil surrounding the cable n1uStbeable to (jlsslfmte thIs heat cffeclivoly or !t)orrnal instability(nmilway)"vlilmsull For example an XLPE Insulated 1t kV cable Withconductors runnlrllJ af 90"C could end up with a surface temperaturoof aboul80C rosuiling In dryln\),out of the SOILDepth of bUlial playsan impl..Jftantfaclor here and has been set at 800 mm. Most MV Cablecurrent ratings are calculated with ground temperatures at 25(; atdepHls 01burial of 800 rmn

(Iv) Ensure thaI eacl) member of Ihe pullinq gan\) knows exactly wllat heis to do and that cornrnunication Sl\)nalsbetween members are clear.

(v) The trench floor must be clear of stones and other obstructions andtho cable bedding I.lmmctly (Hspersed

('IIi C,\!)!e CO'lersU!e avwlalJle atconvnnient pOint!'"

(VII) Any objects thai rnay fall Into the trench and damage the cable duringthe pull and pnor to backfilling have been removecL

(viii) lithe ambl('nt temperature IS below we or has IJeen so lor the pasl 24hours, the cable on the drum will have to be covered with a tarpaulin andhealed with sUitable Irunps or heaters for at least 24 hours under closeSlJprHVI$IOn, Ensure tha! suHicient ventilation exist:;, and pay the cable o!fthe drum slowly and carefully. The drum should be lagged with only illewof the bottom la9s removed dunng the heatin9 process.

(ix) Place the (hurn at a convenient pOint pnor to the pull on stron9 jacksand on sound footing (as mentioned (mrlier) WIth the arrow on the (JrumIlfJnues POINTING IN THE OPPOSITE DIRECTION to the rotation wl10nIhl1 callie ISbeing pulled

(x) Eleforc pulfin9, cut the inner end of the cable free,

(xi) Hernovo the dnHl1 battens carefully and from the tlOt!om.

Inspect the cablo onds for any Sign of loakage (especially Paper Insulatedcabins). If a leak IS suspected, it can be rlfovod by heating the cap untilJust 100 hot to touch and Insul£lting oil will exude out, U,fJcap Sl10uld then1)1" lomoved and the extont of the damagfJ assessed, by means of therhuloctnc test (See Seclion 4.2). Cables wifh extrUded dielectrics shouldtJe sealed and flOe from moisture.

(XIII) The ciJ.blo rnusl be payfJd off from the IrJp ot tho drum but take care not 10tiond It too sharply',

(XIV) Cable pulling stOCkings Should be examined and placed over the nose oftho cable with care (see fig. 4c & d on pg 23) ,. The pulling rope or wilemust be attached to the stocking III such a way that the cable cap will notbe damaged dunnq tile pull. The use ot sWivels is recommended toprevent tWisting of the stocking The use of stOCkings IS prefmable totYing a rope directly to Ih~,cable for pulling In.

(xvi) Bending radius of cabict> ,is recommended by the Inanufacturer shouldnot be exceederL They am

Paper Insulated Cables• Single Core• Multicore

Bending radiusup to and Including

11kV

22and

33

20)( d12 x (J

25 x d15 x d

PVC Insulated Cables 10QQ• Multi IJnd Single Core 16"50 sq rllm• Armoured Multi &70sq mm and

XLPE Insulated Cables• Single Core• Mufticore

17 x d15 x d

17 x d15)( d

(xvii) One Inan should rernall~ at the drum and "brake" the drum In order fOmaintain the correct fenS)(Jn on the cable during the pull.

If a Winch is being used toare encountered, £1tenSion at bend

Gable Plltl~)d to a pOSition as noarsfl(HCh block as possH.llo. Thon cabinand bond detached from blod( anOpOSltionOd around skid plales assl10wn

the cable and unaVOidable sharp bendsblock could be used to assist Ihe pulling

(XX) Heavy leadsnoathed Paper Insulated cables Inneed very large gangs of rnen if no winch isinsulated cables reqUire fewer men.

lengths maylighffir XLPE

(9) SealingofCabfeEndsOnce the cable pull is completed. Ihe nose· end of the cable IS carefullylifted olf the rollers and placed on tho bottom of the tmnch. leavingenounh slack to termrnalO the cable and observing the minimum bendingradius. Immedrately after cutting. the cable should be suitably sealed onboth ends of the cui 10prevent the in£lress of mOisture. Examine the nosecap and make good <lny damane that may have occurred during pulling

(llj Bond PullingThose techl1lques are npplied when t1e<lvy catlles are to be laid or thetrench undergoes many changes of dneclion or very long lengths ofcable have to be laid. or a combination olthese.

As In the previously mentioned methods of cable pullin9, the trenchWQUld have been prepared with cable rollers, corner rollers and skidplates Snatch bloCKS would have been anchored to the sides of thetrench at bends and a Winch placed at the far end of the section, At thenoar end a mobile bond carrier is placed conveniently adjacent to ttlOcable drum, onsunnq that its brakin9 systern IS H(Jequate and tMt It hasreWinding facilities. A steel rope, more than twice the tength of the cable10be pulled, is wound onto the bond camer drum and its end fed over therollers amI through the snatch blocks and then secured to the drum of !Ilf)winch

The cable end is manhandled onto the first rollers and hod to the stefllrope (See fig. 6) at !lltervals of about 2 fllotres, Sfart the Winch and as thenose 01 the cable amves at the snatch block untie it from me steml cable.take it around the corrH)r roller and retle on the Strai9h\.

Once the nose has reached tho wlnel) end, and allOWing the necessaryslaCK, the c'3ble can be untied. the steel rope rewound onto the bondcarner Further prepariltlon for backfilling may then be comrnenced

Figure 6BOND PULLING

Stlllli wirll bond

Cable drum Cable tied

Bondwire

"Mobilebondcarrier

Cableuntied

Snatchblock

Skidplate

Once Ule cables have been 1<1I(J.amI before commencu)g With backfilling carryout a vlsualmspection of the installation 10ensure that:

la) The cables are properly bedded(b) Correct spacing between cables If there ISmore than one In the tronclL(c) Cable entrances at ducts me suitably protected against tile pOSSibility of

vermin gaining entrance(d) Laying and pU'liing equipmentl'8s been removed(e) That there is no obvlow:i darnage to cable sheaths Up 10 90% of the

sorvlce failures exponnnced II) any cable system can be avoided IIappropnate action is taklO!l al tillS stage.

As menl!oned above PVC: sheaths damaged 'during pullinn' should berepaired taking every caro to do a workmanhke job.

(a) Superficial DamageGenerally the local area damaged should be removed, tho romaif1lngsheath chamfered for 25 mm at the edges. A EPR self,amalgamatingtape is Ihen applied after cleaning the affected area thoroughly with asuitable solvent (Le, Genklene). The PVC tape should be apprmdrnately30 mm Wide and is appliod under tension with a 50% overlap continuingup the chamfer until trle top is reached plus 4 layers extending 75 rnmbeyond the chamfer.

(b) Holes or Slits in the PVC SheathChamfer the edges 01.Ihl1 damaged area for a distance of 30 mm andabrade the area WIth Carborundum stnp for a further 20mnL

Clean the area with a ;sdlyent and apply a filling putty (B sealing tape)followed by a layer of EPR,self·amalgamating tape applied at high tensionextendmg 50 mm !lorn the patCh. followed by 3 layers of rvc tapeoxtend,ng 100 mm from the edges of the EPR tape.

(c) Removal of a completlll section of oversheathUpon removal of the darhaged ring, chamfer the remaining edges ,for adistance of 30 mm, clean With the solvent and apply 4 layers of EPR tapeat high tension to 50 mm ·beyond the chamfer Apply ryc self,adhesivetape at one tlwd overlap ·to a level corresponding to the original oversheath diameter, Five layers of PYC self,adheslve tape are then applied.each one extending 5 mrn further atong the cable.

The repair is then completed with a resin poultice reinforcementconsisting of 6 layers of ribbon gauge or bandage. impregnated andpainted with an approvo(j grade of freshly mixed epoxy resin Allow 12hours to cure

4.0 Paper Insulated And Lead·covered 6.35111kV CablesThe folil:)Wlflq chapter generally covers 6,35/11kV PllC cables For hlgl)ervoltapes or slnqle core applications please consul! ou! application engrneersfor speclalised technical or Installation Information, the cables described If)

UW5 sec11(mare manufachHed according to SANS 91 (For greater details seehroch ure covennq ttllSproduct).

4.1 Notes on impregnating compoundPresont day paper Insulated cabte are mass impregnated with non·rlmmingcompound (MIND). ThiSPoly-lso,Butylene compound remains in a solid stateat norma Ioperahng temperatures and mel!..sat approXimately 100'C

Compound migrat1on, as wa:, e~;penenced in earlier rosin-oil impregnate(jcablos installed vertically or on Inclines, has thus been eliminated by till,)use 01Ihls non, draining compound

4,2 Moisture in Paper cablesIf cable Is damaged and tho leadsll0ath or end cap ISpunctured, moisturealmost Iflvdnably Into the Insulation and, if not detectedImmediately and removed, milY cause trouble at a later dale, In overv suchcase, trlorefore, a mOislure test should be calfled out and the cable cui backunlil all traces of dampness are removed The following Simple, but reliablelest I~Hecommended;

Moisture Test: Heat about 11ltroof 011compound (or melted paraffin wax) In asaucepan 10 a temperature of 150'C (check by lt1ermometer), timn()VoIIldivldual paper lapes 1romtho cable under test and immerse thern in tllO 110tcompound II any mOisture IS present. it wll! boil out olft1a paper and formbubbles or froth. which will rise to the surface of 11113 liquid. If no moisture ISpresenl, the hot compound will be undisturbed.

When car rying out the above lost do not handle the portion of thl.~paper tapesto be imlTlorsed In tile compound, as mOisturefrom tho hands may give [ISO tofalse c(mcluSions, As moisture IS most likely to travel along the cable underthe Ifli)d Sheath or along the conductors, the papers next to the stlealh andconductors arethoso mosllikely to contain mOisture,

To nllnirnise the penetration of mOisture Into the cable from the atmosphQre orother sources, U)ecores should be moisture'I)locked at each end, by sweatingthem sol\d or Usingsolid centre ferrules,

Ambient air temperature (free air"'Shaded)

Ground Thermal ResistiVity___,~~_~,~,""",."~""«<=""~ __ .-.-,>w,""v-",,.,,,,._..""__ ~"m"'~

Depth of laying to top of cable or duct

~ ~ m C M n ~ N 7 ~",.,W<:t'flf0!,-;(")<:t

M ~ ~ ~ ~ ~ ; ~ ~ ~

r:: 2~ ~ 03 ~ ill ;s; ~t--.·""rcn"l""'(O f'-->t:tl""- \.0 M (") ~. N ¥'"

c;c)(~;>OOOaC)

~~M~~~~~f.i ~ ~ ~ ~ ~ ~ ~

C}) Ft-... t- to" M r-oc to '1'6 c:i 0

ig81rci~<o~i5~ ~ g f'-- '7 ~ ::

6 0 c:i c:i c:i 6 ci

Depth of laving

800100012S01!5002000

In slng.l. way ducts

1,00

0,990.970,960.94

1.000.980.960.950.92

1.071.000.920.340.75

1.031.000,950.830.82

Table 4.3.3 Grouping of PILC cables H' Horizontal Formation at standard soilconditions {mullicore cables)

Ingroup

2

3 0,69 0,75 0,80 0.84 0.86 0.80 0.84 0,87 0,89

4 0.63 0.70 0.77 0.80 0.84 0.75 0.81 0.84 0.87

c 0,57 0.66 0,73 0.18 0,81 0,71 0,77 0,82 0.35;..)

6 055 0.63 0.71 0,76 0,80 0,69 0,75 0,80 0.84

Ground Temperature. eC)Maximum

Conductor 25 30 35 40 45Temperature

(1o-C)1,00 0.95 0.90 0,85 0.80

Air Temperature eC)MaximumConductor 1

25 30 35 40 45Temperature

(70"C) ....•.....

,00 0,87 0.19

NOTE: PILe Cables may begrouped in air Without derallng providing thatthe cables are HlstalleO on cable ladders. and that for

{a) Horizontal formationThe clearance between IS not less Ulan 6 K the overall diameter 01tho larO(ISl cable {or 150 Imn) whH;hevor is least

{bl Verticallormation ,(i) The clearance from 11 SUPPOftlno walliS greater than 20 rnm, and(ii) The vertical clearanc(!, between cables i5 greater than 150 mm.

NOTE: If tho number of cablos 4. they are to t)C l!lstalled HI a henzontalplane.

Cross-sectional area ofconductor

mm3

Correction Factors

Solar Radiation1000 W!m3 1250 Wlm2

4.4 Short circuit ratings for PILC. cablesShert circuli ratings do not lend themselves to rigid treatmont due 10 unknownvanables, and wherever pOSSible conservative values should be applied.

With tho continued growth of power sysWm fault capacity, attention must begiven, when selectino a cable. to its short CirCUit capacity as well as to H,econtinuous current ratinO.

Other Iimllino effecls In aVQldlf19 damage during subsequent short CirCUitconditlons are as lollows>

(a) \Neakenlng of jOints duo to softening of solder at conductor temporaturesabove 160"C

(bl If cnrnped or welded ferrules and lugs are used {see At ,2 of annox ASJ\NS 97) tempQratures of 250'C can be tolerated,

(c) Bursting effects are only of concern with unarmoured screened cableslarger than 150 nun", Multicore wire armoured cables are only likely totlurat at currents in excess of 33 kA for cable sizes below 70mm!, Inoxccs s 0139 kA for cables below 150 mOl! and in excess of 22 kA forcables below 300 0101"-

Cable short cIrcuit ratings are baserj on thl) adiabatic performance of 1t1!)

conductors and may thus be regarded as "internal ratings" Which are notaffected by external faclors as in the case of current ratings, Therefore, noderatl ng factors are needed

whore IK

short CirCUIt TiJting In Ampscons/ant combmmg tempera/um /lllllts and conductormatorl8f propertiesarea of conductor(iufatlon of short Circuit III secollrJs

The valuos of K for copper and alunllnlum comluctors of 6,35/11 kV PllCcables are 115 & 76 amps/rnm2 respectively, For a conductor lernperaturerlsinU from 70"C 10 160C,

SOllie syslerns make provision lor reducing earth fault currents by theinclusion 01 a neutral earthing resistor (NERl at thn star point 01the distributiontransforlnor.

Where thiS IS not tile caSH, thn resultant high earth fault current under a faultcondi1ion will be carried by the lead sheath and by the galvaniSHd sleel wirearmOUL The bitumlsecl steel tape llrmour IS expected to rust in Ume andshould not be included in any calculation to carry fault current

The value of K for lead sheaths and galvanised steel wire armour is 24 & 44anlps,rnrn" respectivnly. The follOWing formula must be applied:

rhe area of the lead sheath and the armour wires of the cable must beol)t81ned.

5.0 MEDIUM VOLTAGE XLPE INSULATED, PVC BEDDED, SWA, PVCSHEATHED CABLESThe followin hapter generally covers 6,35/11 kV XLPE cables, For hlllhervollages or core applicatloi'rs please consult our application engineerslor speclalised technical or installation information, The cables described inthiS section are manufactured according to SANS 1339, {For greater detailsSHebrochure covenng ttllS product).

Quality AssuranceMV XLPE cable rnanufacturerj by Aberdare Cables IS required to undergo apartial discharge test at our StaMlord Road Port Elizabeth factory, The partialdischarge Ineasurement technlq0e involves scanning of every metre of everydrlJrn of cable uSing the only· such scanner Installed in the SouthernHemisphere, The technIque flUs been in use since the introduction of XLPE byAberdare Cables and has given superb performance over the past 20 years,

The advantage of the scanninq \(;lchnlque is that f1(m"cornplying XlPE corescan be re"lnsulatecl before they 2lre further proct)ssed {applicatIon of coppertape screen, laying up of 3 OOr1:18,application of PVC bedding. application ofSteel Wire Armour and extrusion (jl outer sheath), Although this is a expenSiveoperation, It IS dramatically cheaper than rectification of faulls at final test orafter installation on the customer premises, In factories where partialdischarge detection is carried but only as a final test, and assuming a non,complying partial discharge IS :detected. tI1e decision to scrap the cabie oralternatIvely to stnp ancl replace an XlPE core Will be very costly

The advantage to the customer of the above testing is that he is assuree! ofquality cable with an acceptable level of partial discharge,

Aberdare's unrivalled quality record in experiencing only one field failure 01XLPE cable during its twenty years of rnanufacture 01this product ISadequateproof olthe superiority of thiS testtng mothod

5.1 Notes on XLPE insulationFor XLPE insulated conductors. contmuous conductor temperatures of 90 Care permissible with overload ex:cursions up 10 130"C for a rnaximurn of 8hours continuous per event, with a max:imwn total of 125 hours per annum, Inthe case of short circuits the insulation can withstand conductor temperaturesof up to 250C for 1 second,

25"C

30"C

1,2KIWW

800mrn

Tab\e5,ZE!Bctricai a.nd Physical Propertied of -3COTe XLPE insulated P\/C be;;j,(jf:;(1 stee:w!t8 arrncurG',j, P\/C Sheat.hed6 ..J5,(i 1k\/ cabh}s to S,AJ.JS1338 Type A OndividuaBy screened}

CableSize

Current 1 second Diameter Approx., Current 1 second Diameter Approx.rating short overall Cable rating short overall Cable

circuit Mass circuit Mass(Ground) rating (Ground) rating

(1"111"11') (Al (kA) (Al (ilillm) (IIA) (1"111"11) (kglkml

25 140 09353 3.575 47.3 4655

35 170 0.,(3783 5.005 497 521550 200 0.5067 7 150 526 5895 155 0.8284 4.600 52.6 501570 240 03581 563 6995 190 0.5767 6.440 56 ..3 5635

95 290 0.2665 13,585 60,5 8'7(\ 225 0.4213 8.740 60.5 6340; tV

120 325 0.2187 160 64,2 9370 255 0.3375 11.040 64.2 7045150 360 0,-1847 21 450 68,8 11240 285 () 2795 13,800 688 8350

185 410 0.157-1 26455 72,8 12775 320 0,2285 17020 72.8 9245

240 470 0.1317 34.320 79.1 14955 370 0.1821 22080 79,1 10580

300 520 0,1160 42900 85.6 17865 4.20 0.1535 27.600 85,6 12070

ri ria en 0'1 ~ W f0 '2:is' Q

.;} (') s: VI VI0 ~ ~

~

:I ';::1 .~ ~ (.,III 0.'""i :IlIll C 0 0 0 0 F- 0 c 0' ';'" 'a ~

....• S- Oc ~ Cl..., ~ :; ()1 co (C (3CI) i3 ;src cj ~ UQ US· S-rr;i w ><3 0 0 0 0 0 ;) r

m 0; 0 :-... ro Q -0U mI\:l ro 0 ..;-;.. co ()1 tn :3

0 (Jl

~ ~ nro"",_~_,m._,.~. _______· ro :rr

~ e-m ~.;,:

:2 0 c 0 <..'":)'''~ ("2-

G) §: {C -.; '4 ....•.i ro '" Qw a r>J (Jl <0 '.J g0 Nc <0 n;::I 0iiS 0 ;)0.

f} :::l e:n §:.;} §0 c ? 0 0 C § a

3 v" ;;,'J ,.) ro ~ n 3w "C to $\,,) en 0 •..~ ::r <is(Jl s- » :RCI) 3'..• IC ~ 6I»..• at §i. ;)c :R..• -! 13CI)

III 0 0 0 0 9 N lIll 0 ~"0 J:. ~ :-... :-... 0, 0, to lJ'l 0 :Ii 0 ro0, 0 .9 .;. co 0 C) 0 cf lIll n aco '< & 5.- 0. iil:; c

0 ~ Q2- ;r <D

0 0 0 0 0 0 ..• '9.C: +> ro 0, m {£;, <c 0 :r-

w (Jl -w- ~ ....• w 0 {It,

+> .;.

0 (J1 0 (J1 f\:) 0 -"l <;.;;.., CI):E III'-" i

~'<

0~-

1Il

!tc ? 0 0 ~ ~ ~ s-m- 'I 0, <c 0 (:, r.len 1'0 0 0 C '0:; W IC..•

0C:I0.

s-Ins-ID

0 ? 0 0 ~ ..• ..• lii':..j co ro i:c 0 ..• !'0 ~.;:. 0 tn w' 0 tv co

'<0.c:n..•'I/>

ri VI

0 a ~.(0 lii 0;a VI (0

co :r ~ -.t;, 1"0 0 (J1 gj S. !.()1 (J1 0 S-o 0 0 0

iii IQ

C c:; 'S. 0 iii-OJ .;:. f0 0 0 ;::I c ng 0 0 0 0 IQ '9. 00 0 :;:7'3 -.9.- In3 Q- g

::l:::l VI§. Iii

:::('i 0.0 llol

/"""\ 9 0 0 a<.0 (D -'(0 0 X nf\:) w t,r, 0 r 0

v :::m -~()~ 0u :::Q In

...._ ...... _ ....._-_ .._~ '":; nIII 0cf w

00

0 0 0 0 lii :3i:o (.0 <c i:o 0 .~~+> (J1 (Jl C) 0

'<0.C!LIII

Maximum Air Temperatures (·C)Conductor

30 35 40 ! 45 50Temperature

(OO'C) Hl 0,95 0,89 0,84 0,78

Note: Carlies may be grouped H' tIIr without derating provided that the cablesHlstdlled on cable ladders, and that for

(a) Horizontal formationThe clearance I;etween cables IS not less than 6 x the overall diameter of thelarnest cable (or 1bO mrn) whichever ISleast

(I)) Vertical formationnHl cloaranco from a supporlinq wall is greater than 20 mm, andrho V(H'tica! clearance between cablr}!:; IS oreater than 150 111m,

Note: If the number of cables,> 4, thoy are to be Installed 1['1 a honzontalplane,

CrO$$w$eqt!onalarea ofc:onduetor

mm~

Correction Factor.Solar Radiation

Short circuit ratlflgs cio not lenel themselves readily to rigid treatrmmt due toUI1!il1mvn vanHbles Wherever pOSSible COIlServHl!ve values should beappli(;lj As the Growth of a power system inoeases so do the system fHultlevels, When selecting a cable attention must be given to It'S short circuitcapability, as w(}11as to the continuous current mllng:"

Other hrnillng effects in aVOldlnfJ darnage during short cirCUit conditions are asfollows:

fa) Weakening, of jOinls duo to softening of the solder at a conducttemperature of 160C anCI Hbove, although, most conductor JOiningnowadays ISdone by compresslol, fittings, particulHrly on XLPE Insulatedcables,

(b) Bucking of the conductors H'ljOmt boxes due to longitudinal expansion 01cables lard direct in ground

Cables short cirCUit rHtlngs are· based on the adiabatic porformance of theconductors. This assumes no hnalloss from the cHble during the period of thefault No (ieraling !Hctors are necessary with regard to soilternperature, depthof bun.al etc,

I Short circuit rallng in AmpsK conslanl coml)lf)lng lomperalure /inllts and conduclor

material propertiesA area ofConduClorI (iuralion of shor/' Circuit in seconcfs

The value of K for copper qneJ: alumlnlUln conductors of 6,35/11 kV XLPEcables is 143 & 92 amps/rnm;' respectively, for H conductor tempemture risHlqfrom 90"C to 250C

5,4 Earth Fault Current

Some systems proVide for t'Oejucing earltl fault currents by the inclusion of aneutml earthing resistor (NEil) at the star point 01 the distribution translonner.to typically 300 A,

'v'vhere tillS IS not the case, tile resistHnce of the copper tapes and steol wifeHrrnour should be included in the calculation

lyplcal1 second Earth rHult ratings for XLPE insulated 6,35/11 kVType A cables mHnulactured to SANS 1339 - 1991 are shown in table 5,3

19,7

20,825,0

~ .~ Qr.;- 15'=l :3 :::z ~ '"C 0'.., ~ ..,

C '0 a<: ~ '"0 (1).., 3 ..,g tr

0 cvC S; ~..,

.~£2. ~~ $ <is

~)

':3'

.

U ! Jll l> Q - 3::, :; .., III3 Jll

CT 0 !:tc 1e :l :3:l Q, ;So - c:..; .~3;" i l\) c::r ..• (Il-< (I)S- -.ot a;- s:::3 •lQ 3 .~- e. Jll

0 'tI S-(I)

0 ..• <II!! 0.

'tl s:::0 ..•... (I)('l .,=Jll ..•CT AIli AI

_.-~

C"l N0

"W r0 "" 'tl0 0 tr 0 <:::;

~0 0 0 (')

~(r N

~0

"W N q;;

0 0 v-, 03 3 D 0 03 .~ m

;! ':'" 9'lc- o{fj () -n Z 9- "Q "'. -n Z -l r-?' 0 c- o § Q 0 0 0;2 0- Vi 5' S' .=::5 x ro en

2- q :0. tt v 1>g r < 0 <:u X 0 (5 '" 0 ::I Z 00 m ,... U\ .;:' '9: "0 fJ)

~(J)

'" <: ...•;;; "0 2!.:5 m c iJ: (') Ql »~ ~

~ ~-

i5 iiG S- o C)5' ::£ ::l -J;:;. ro ~ ~ ~ fJ} m

<: t:i VI -5- 0c:: 6 c "0

2 '" tt (5 .~2, a :::; ~ <:x :; Q <5 :3 (')::; n o'1.0 ~ -e o' co :l c () »;:;; .~ (") :::l 3 g ~ ~ :::l Z-...., =r 6 S?ill ~

~u '5 0

~ ~ ~v

3 § xC ,.'"

,...~ 9... " 3 " x "0

Q 0 '" ;p m.t1 ::J 0"'''; f5 -0 a.iii (") Z0 s; ;;.;.: '20 § '" (Jl

'0 ~ 0 a.C£ a. p:; :3 S.~ c s- o

w 0 :D QS?, 0 § ~ m0 '" 15 0

N 0(J1 j " ~ en

Q 0 0:::s g e0 cc ill C :3 ..•u; .~ () i'5

0~ 0-0 5 ;::!' 0 0~ :x a ~ <:

~3 c 1:J

3 c ,.,0-0 Q :E

3 S?, '0 ~ '0 '0 m:r ::0

<.0 .g '4 (')a:'i 0 CI> qQ; »:::r 0 OJ- n.0 Ol0 2 3 rc .e>

'" min <il a .~;;; w

Table 6,2Electrical and Physical Properties of 3 and 4 core PVC Insulaled PVC bedded S'NA PVC sheathed 600/1000 V cables manufactured toSANS 1507·3

·15 24 14,4S 25,000 %.33 125 1.25 14.13 H95' 448 5012.5 32 26 26 8,87 15,363 9,61 10,56 -1,25 ,25 15,23 16.18 522 5974 42 34 35 5.52 9.561 11,40 12,57 1,25 125 17,02 1839 667 7626 53 43 45 3,69 6,391 12,58 13,90 1,25 1,25 18.40 1972 790 91010 70 58 62 2,19 3,793 4,384 14.59 16,14 1,25 1..25 20,41 21,96 996 116916 91 75 83 1,38 2,390 V59 16,55 19,18 1,25 USO 22,37 25.92 1295 176825 119 96 110 0,8749 1,515 1,749 19.46 2D4 1.60 1 2646 28,34 1838 219635 143 116 135 0.6335 1,007 1,267 20,89 23,97 1,60 .60 27,89 31,i7 2215 273250 169 138 163 0,4718 0,817 0.944 24,26 28,14 1,60 2,00 3t46 36,54 2871 389370 210 171 207 0,3325 0,576 0,665 27,07 31,29 2,00 2,00 35.47 40,09 3617 483795 251 205 251 0,2460 0,427 0492 31,i9 35,82 2,00 2.00 3999 44,62 4901 6115120 285 234 200 0,2012 0.348 0,402 33,38 38,10 2,00 2,00 42,18 47,40 5720 7269150 320 263 332 0,1698 0,294 0.339 36,68 42,05 2,00 250 45,98 52,65 6908 9250

I185 361 298 378 0.1445 0,250 0,289 40.82 46,75 2,50 2,50 5112 57,45 8600 11039240 416 344 445 0.1220 0.,211 0,244 46,43 53,06 2,50 250 57,13 64,16 10767 13726300 465 385 510 0,1000 0,189 0.218 51,i0 2.50 6220 70,13 12950 16544w ..........J

0;

~ E!ectriC3: andSANS 1507 .. 3

CableSize

lmpe- 3$dance Volt

drpp

hVpltdrop

3c ~ 4c 3c 4c(mm') (AI (A) (A) (Oikm) (mV/Ai (mm) (mm) (mm) (mm) (mm) (mm) (kg/k

26 90 73 80 ,4446 2.502 2.889 17 76 1 60 2476 27.6:5 1301 155it35 108 87 99 1 .0465 1,E113 2.093 1'3.33 21 .93 1,60 ,. 60 2633 291 3 1477 175750 129 104 119 0,,7749 1,342 1,549 21 .87 25.05 1,,60 1 60 29,07 32,25- 1782 215070 158 130 151 0.5388 0,933 1.078 24.76 29.27 1.60 1 60 31 96 37.67 2132 293095 192 157 186 03934 0.681 0787 28,68 33.73 2,00 2.00 37.08 42,53 2908 3647

120 219 179 216 03148 0545 0.629 3109 35.44 200 2,00 39.89 44.24 3328 4023150 245 201 250 0.2607 0452 0.521 3399 39.,39 2.00 2.50 4279 49.69 3837 5276185 278 229 287 0.21 33 0.369 (},427 3780 4451 200 2.50 47,10 5AJ31 4557 6231240 324 268 342 01 708 0.296 0.342 426O 50.,04 2,50 2.50 52.9 6"~ 14 59?7 7550

Table 6,4Electrical and PhySical Properties of 3 and 4 core XlPE Insulated PVCbedded SWA PVC sheathed 600i 1000 V cables manufactured toSANS 1501 . 4

Cable Rating Impe- 3$ 10 Npminal Diameters Approx. MassSize dance Volt Volt

Ground Duets Air drop drop 01 02

:ic ~ 4c 3c 3c(A) (A) (A) (n/llm) (mm) (mm) (mm) (mm)

27 22 """'> i~.~ ."1 2C,?2B .30,861 8.08 885 1 "it:. 13~70 1447 416 A."/~-LL _ .. "'....' ~..",)

2.5 35 30 29 9.45 16,368 18.900 9.'18 10,08 1,25 L25 1480 15 487 5214 46 39 37 5.88 10,184 11.761 10.06 1107 1.25 1 ."1"" 15,138 16.69 566 650L0

6 57 49 46 3.93 6.807 7.862 11,25 12AO 1.25 125 16,87 1802 683 77810 76 67 61 2.33 4.053 4.663 1325 14,64 1.25 1.25 19,07 20.46 890 103316 9° 92 80 1,46 2.546 2924 15.21 17,68 1.25 125 2103 24.42 1191 154425 147 119 138 0.9313 1.613 1.863 18.13 19.86 1.60 '1.60 25.13 26.86 1693 201835 175 142 168 0.6738 1,167 1.348 1956 22,32 1.60 1.60 2656 29,52 2025 251150 207 169 204 0.5009 0.868 1.002 22.49 25.76 1.60 L60 2969 32.96 2606 324270 253 207 256 0.3521 0,610 0.704 25.74 29,81 2.00 2,00 3294 38,21 3323 450395 302 248 312 0.2589 0.448 0,518 2876 33. 2,00 2,00 37 16 41.90 4442 5650120 344 282 362 0.2109 0.365 0.422 3139 35.87 2,00 2.00 40.19 44.67 5335 6731150 387 318 416 0,1775 0,307 0.355 34.69 40,12 2,50 2.50 4349 50,42 6403 8708185 435 359 478 0.1500 0260 0.300 39,05 44.77 2.50 250 49.35 55.07 8184 1034324\} 498 413 557 0.1247 0.216 0.249 44.22 50.58 2,50 250 54.52 Bl .68 10073 12932300 558 471 634 0.1099 0.190 0.219 48,45 55.56 2.50 2 ..50 58.35 67. 16 12076 !5575P-

o

Table 6.5:: E!ectrlcal and PhYSicai Proper'liM (,13 and 4 core XLPE !ns,,!a.t'Sd pve b'Sddoo S,VA PVC sheath8G 600il000 V (~;,ll)iesmanufactured to

SANS 1507 4

Cable!Size

(roro~) (AI (A)

25 115 9235 138 11150 164 13270 199 16195 238 194120 272 221150 306 249185 344 283240 392 325

lrope- .3$dance Volt

drop

1~Voltdrop 02

4c 3<: 4c(roro) (kgfkro kgfkm)

26.16 925 137727,44 1307 154930.26 1550 187234.98 1911 237139.39 2254 315842~OO 2929 358446,05 3457 427452,132 4132 56506150 5375 7024

3<:(rom)

4e(mm)

108 15408 2,669 3.082 15,53 19,16 1.25131 1 1159 1,933 2,232 18.00 20,44 160 -i.50160 0.8258 1,430 1.652 20,09 2306 1,l30 1,60200 0.5736 0,994 1,147 2343 27.38 1.60 1.60245 04178 0,724 0836 25.85 30 __99 160 2,00285 0.3337 0,573 0667 29,09 3320 2.00 2,00328 0,2756 0,477 0,551 3215 36.75 200 2,00378 0,2247 0.389 0.449 3602 42.52 2,00 2,50438 0.1785 0.309 0.357 4039 50.40 2.50 2.50

Table 6.6Single core PVC insulated cables with stranded copper conductors, unarmoured, with PVC sheaU. 600il 000 V to SANS 1507-3

L~ '-oI .•~f" , '. ,2 '.-~ - - ,'- ...

35 7.00 1296 469 0,6356 156 156 1,27 153 132 141 1

50 8.15 15,15 632 0,4745 186 19t 095 180 155 172 0,82

70 9,79 16.57 880 0,3356 232 246 0.67 221 190 223 0.58

95 11,54 1904 1160 0.2500 281 300 050 265 226 273 0,43

120 12,96 20.24 141.3 0.2054 324 349 0,41 301 256 318 0,36

150 14,39 22,07 1734 0.1734 370 404 0.35 338 287 369 0.30

185 16.10 24,80 2145 01499 424 463 0,30 381 323 424 026

240 18.71 27.81 2725 0,1268 498 549 0.25 442 372 504 0.22

300 21.45 30,75 3375 0,1131 566 635 0.23 499 419 584 0.20

400 24.30 34.10 4395 0,1028 651 742 0.21 565 472 679 0.18

500 2651 37,13 5299 0,0963 740 835 0,19 634 532 778 0.17

630 33.15 43,62 6965 0.0890 836 953 0.18 718 603 892 0.15

800 37.70 49,00 9118 0,0852 931 1086 017 792 689 1020 0,15

1000 42.25 5345 11050 0,0819 1041 1216 0.16•

856 741 1149 0,14

CableSixe

NominalDiameters

mmNominal

Mass

14>Cables A.C. or D.C.

34;Cables In Trefoil Formation.

NOTE: (1) D1 is the diameter over the conductor ..4 (2) D2 is the diameter over the PVC sheathN

Table 6.7t; Sw~glecore XlPE;nsu!ated catAes ,-,vittistranded copper c-nnductors, UnDnnGL~J8d..v·nth PVC sheath E>OCt" 1000 V to SANS 15Q7--4

-~-~"~~'-T'-'-~'"Nominal hmpedancei

Mass I ;kg/11m I

NominalDiameters

mm

1~Cables A.C. or D.C.

3,';Cables in Trefoil Formation.Cable

SizeVolt drop Current Rating "loftdropper amp per

per metre permV Ground Duct mV

1R9 174 1,866 151 137 137 1 616205 2-1-1 1,352 181 164 167 1 1 71245 257 1,007 213 192 203 0.872302 326 (} 71 260 235 257 0.615366 404 1}S26 312 281 318 0,456422 475 0.431 355 319 372 0.373480 542 0,36-3 397 356 426 0.31 5554 629 0309 449 494 0,268656 753 0.259 522 594766 881 0229 589 692902 1045 0207 668 807 01791040 1182 0.192 750 925 0.1671229 1417 0.178 848 1094 0.1541366 1603 0.1 71 942 1254 01481486 1790 0.166 1025 1400 0.144

0.93320,67600,50360.35520,26310,21540.18180,1545012950.1149

5,957008.159.7911.541296143916.1018.7121,4524,3026,5133.1537,7042.25

11,8112.8614.3816.22"17,97198221.4223.6326,6930,0533,3036,3342.7948,8454.21

328426567824107113041628199524613182411750326641853510676

25355070951201501852403004005006308001000

0.085600831

Dl IS the diameter over Hie conductorD2 is the diameter over the PVC sheath

rj rj 9'r:T r:T wii ii 00'> 0'> 0(.;> p aN .... '3 5'tv (p ()1 <.00 Vl I\) 0 0 00 0 0 u' 0 0 0 ~ 0 Ql"('() 0 0 0 0 ~ <'>

~ ~ 0';to- §"0;-

0 :::5" 0u; :::~~

Q iii':::c.Ql

0 0 0 0 0 ...<.0 <.0 to <.0 <.0 £. c.

<'>:r I\} w .,t.;,.. V1 ....;.;J 0

~ '< :::5 ~

El(Q

:1 0':::

(0 ~ III[f)0. (')

0< ;;;~III

()

"3 pS' a

§; IC 0"0 0 0 0 0 i" ':'1

?i <.0 <.0 <.0 <.0 <.0 0 ~Q w •• v"l O'l ..., 0 ~m0 Cl.~ It:U 11iF!!! III

-+::rII>

~ 3e!.t\) f'0 - .... - 3 :.01:.n <:> (;,"l rv 0

~ II>III- 0l:%<~

......

0::;II>g,

0 p 0 - - S'~j .0:> ~ 0 <:>m w w 0 co IC..•

0l::::Cl.

S-IIIS-IC

0 0 0 .... - i"Co Co (c <:> 0 ~~J 0:> O'l 0 ;;. Q.l

'<Q.c::nII>

ojr:T

O'l V1 ;;. W (i0'>(.;>

0 0 p (.;><.n C; ...,(Q w 0 0 '" 0

0 0;- C

0 0 0CD ::J iiJ

0 () ~~5c; ~ :..... ~ 2 Ql....; 0 ~ 0:: ..• r::T c..(Q

III 0"Sl ~"!

P <;; P 0 if~j •••••.j m enm OJ ;;. IQac0 0 0 0 :ICD CD CD CD Cl.rv w m '"

0 0 0CD :eo <.0 ~.0"> -.,j 0 ()

:~ p

~ vroa. ww 5'

I S- 2.::;!e. fft Q

:I ~ NII> IC () 0

" <r 0 2.I:'l) :l e-o ~ g

0 0 p 0 0 .I» S' ~ 0' 0CD en o:l to to Ul IQ ::; 30 -- Q.

'"CJ ....; <0 0 OJ :I l: 2t~ 51 ~ is

lh ?h 0 0 0 0 0

~A <.0 <.0 <.0 <.0 (0 2t0 0 w OJ

Maximum Ground Temperatures (OC)Conductor

Temperature("e) 25 30 3' 40 45 50;)

10 (PVC) 1.00 0,95 090 0,85 0,80 0,70

90 (XLPE) 1.00 096 0,92 0,88 0.82 0,76

Maximum ConductorTemperature (OC)

30 35 4C 45

1.00 0.94 0.87 0.79

1,00 0,95 0,89 0

Table 6.3.6 Derating factors for 9fouping of multicore cable Installedhorrzontally in air

Note: Cables may be grouped in alr without dem.llng, providod tlwt thecables are Installed on ladders. and Iii at for:,

HorlzontallormallonThe clearance IS greater tt1an 6 x the cable overall diameter (or 150rnrn.whichever is the leas!).

(b) Vertical formation(I) ThiJ clearance from a vertical walliS QIE,ater than 20 mrn, and(ii) The vertical clearance brcllweerr cables is greater than 150 rnm.

Cross-sectional area ofconductor'

mm2

6,4 Short circuit ratings lor PVC.and for XLPE insulated 600il000V cables toSANS 1507.

With PVC and with XLPE insulated cablos, care inust be taken to Irnllt theconductor temperature for. c<m\lnuous oper1:ltion and tor short Circuitconditions as indicated in Tab!!} 69

ShOit cirCUit ratings are fOlwrded as Intornal ratings. Tl10lr calculation isbased on an adiabatiC eqiJatlOn and is not atlected by external consideralionDue to unknown variables, short CirCUit ralinSlS do not lend themselves readilyto treatment, so W!10never possl!)le conservative values should be

ShOft circlill' raring in ampsA constant C')fflbintng temperaturo limits and properties ofconductor mfltenatsarea of conductorduratloll or short cirCUit in seconds

ThO followlnq chapter 9€merally covers Type 41 and 61 elastomenc tralilngcablm. For other elastorr1onc cables or different voltages please consult ourapplication engineers for SpeCii:llised technical or Installation Information. TheCil.bliJs described In this section are manufactured according to SANS 1520part;2 (for qrealor (Jolmls soe brochure CQV(lfI!)SJthis procJuct).

Features of Aberdare's trailing cablesAlxmlof€l"s nllrl!ng trailing cables are manufactured according to SANS 1 52 Clparl1 and 2 and bear the SANS mark up to 33 kV The sheath 13 reinforced l)ymeans of an open'lnesh braid In order to limit cut·spread The elastomersUSICj(j for the sheaths are carefully selected tn ensure that the product willwithsiand even the 111gllostlevels of ultraviolot radlallon found 1t1South Africa.

CONDUCTORS:INSULATION;SCREENS:

finned so11copperCo·extrusion 01 EPMICSM3 Power cores individuallyscreened with copper/lexlilebralt!. Pilot core unseraened

SHEATH: EXlra~HeavyDuty CRRATED VOLTAGE: 64Cl/l 100VSPECIFICATION: SANS 1520 Part 1

APPLICATIONS: Selfpropelle(J electrically dnven machmes, movable (llectncapparatus in hazardous dleas (Minerals Act, 1991 j, typically.• Type 41 . 4 111m"tOi small pumps. (JfilIs. fans etc.• Type 41. 10 and 16 mm" for shullle·cars

. . .. ., Il'-- 'G .::~::. ....

CONDUCTORS:INSULATION:SCREENS:

Tinned soft copperCooxtrusion of EPM/CSM3 Power cores individuallyscreened with copper/textilebraid 3 Pilot COfCSunscreened ..

SHEATH; EXlra·Heavy·Duty CRRATED VOLTAGE:64011 100VSPECIFICATION: SANS I 520 Part 1

APPLICATIONS: Snll,propellod electncally driven machmes. portable nlectncapparatus and movable eloctric apparatus In hazardousaroas (Minerals Act. 1991). typically.• Type61A 2511111\"for CHD's

10 f1l1n;'for Sileamr and reeling applications• 1ypo 61B 70 mmi for Continuous Miners and nonrenling

applications whore a lighter cable is required.

I

. 0

~ [OJ.: ~

DERATING FACTORS FOR AMBIENT TEMPERATURES(MINING CABLES)

DERATING FACTORS FOR NUMBER OF LAYERS ONA REELING DRUM

Cablesize

(mmt)

1(;

2S:lS5070

Cablesize

(mmt)

95

(kA)

2,0

;$ 1

4,3G,1

8,5

Bn$eci on an iniliat conductor temperaturo at 90"C and a finaltemperature of 200'C

GP HD EHD

8 11 15

250 250 250

5 7,5 10

strength(min.)

at(min.)

Ahllninllml conductom have acilleved wide acceptance all over the world forusn in overhead transnw,sion flt1ddistnlJulion lines Genorally a stnol core isused With the alUlnlnlWrl to Qive the conductor mectlarllcat strenqth, ThiSarrangenlfmt is termed AIWTlInium conductor steol fOlnforCtJd or ACSRConductors GOInpnsed entirely of alunwlIwn are known as All alunllrllurnconductors or MC nlese corlductors are extensively used for busbars Inoutdoor sUbstations whero are short All aluminium alloy conductorsorAAAC conSist of an alloy alurniniUlTIto give a tensile strength In excess ofthat of AAC, aUowlng longer spans These conductors me recollllllOnded forcoastal areas where severe CI)nOSIOnISa problem.

Hard drawn aluminium In HSltemper ISused HI both ACSR and MC Highstrain steel wire IS used In !\,CSf1 and this IS sometimes protected frOlllcorrosion by an applicat!(XI of grease. Such measures are parlicularlyadopted when the conductor ISlntended for use in amJlfJsslveenVIronmentsas encountemd in cmwtal regions

Aberdare Cables manufacture a WI(te range of Me, ACSR and MAC tocustomers' roquirernents ,national speClHcations, The Infonnalioncontflillod in table 82 relates ta the more popular sizes and standards undorthe follOWingcondilions

Table 8.1 Current Rating pararneters

blentTemperature 30C75C

0,44 rn/s

25C

and Hmsion charts are (welliable on request The follOWing Infonnationto be supplied'

\\J~]is(})

UJ1)C

N f,j

ro(ll

7:i~

•...ic Cl

~ c: 0 C~ 0 (::::i 0

i! <0 ,~ <V ll') (')

:;, C') "'t '" w "0 "-

/1/ e-O 0c :!"Ecr.) 0) (f')

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Intermediate voltage 3 phase •• wire 1900/3300 V underground supplycable(al Use or Intermediate Voltage allows Increased power transfer over long

distances with smaller conductor siZOs,eg for loads typically 25 kVA thisrepresents a conslderat)\e saving when cornpared to conventionalsysterns

(b) Under£lfOund cable with a specially adaptod tractor. Itw cable can bebUriedwith minimum lallow, and thus least cost.

(el Screened cable conslrucUon for ease 01fault loC<,1Ion,(d) BUriodcable results Ina 'clean" lanetscape" no poles or overtlOad lines to

tunder lann vehicles

Construction3 Circular stranded plair! soft copper conductors,XLPE Insulated, layed up With one circular strandedtinned soft copper earthing conductor, collectivelyscmened With an alumnllum' polyethyl,me laminate(APL) tape, polyethylene sheathed 1900/3300 Vunderground supply cable

Mechanical forces during in$ta'UatlonThe mHXlmurn pulling lorce'tilat should be applied to the conductor 01INTERDAC3 Cable durin~l instelli'ltlon is 200 kg,

M 0 10q ~

cO ~ <").- (~ N

o Cl"": N

'" ('J11) t'-_Phase Conductor Resistance~Earth Conductor Resistance'

DCat20CIn ground, Soil tempemtuTf) 25"0 Depth of lay SOD mm, Soli thermalresislivlty 1,2 Km/W,'Pperaling temperature gOG,

Phase Conductor CClnstruc!l()nonductor Construction

Insulation Thickness (n()rnjn<ll)Aluminum Screen HncknessSheath ThicknessCal)le DiameterApiproxirnate Cable MassMinimum Bending RadiUS

20,5

545205