aluminum cables for power distribution aech_chapter_10

7/28/2019 Aluminum Cables for Power Distribution AECH_Chapter_10

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Section III Covered and Insulated Aluminum Wire and Cable

Chapter 10

Product Classification and Technical DataThis chapter deals with cable types available for powerdistribution, including related user applications. Insulatedconductors for instrumentation, communications, andprotection are not described. Considerable informationregarding applications, engineering design, and insulationis in previous chapters. Installation practices and connector selection are covered in Chapter II. For ease ofreference some Chapter 7 descriptions of cable types arerepeated in part.Manufacturers' cata'logs should be consulted for detailed specifications, and particularly as to sizes availablein each category. To save space, not all available sizesare included in the description of each classification.Omissions, however, do not imply lack of use or demand.Similarly, only a few of the available insulations arelisted as a part of the description of each type of cable.Other varieties of insulation including those mentionedin Chapter 8 may be available upon inquiry.The product classifications in this chapter follow theplan of previous chapters by proceeding from the lowvoltage cables to those of high-voltage. First to be

considered are the service cables.The usual table of ampacity ratings is omitted in thedescriptions of each style of conductor. Instead, referenceis made to a specified vertical column of Tables 10.. 1,10-7, and 10-9, in which typical ampacity ratings arelisted for the applicable conductor size, insulation, andtemperature.Ampacity listings for installations to 35 kV are foundin NEC Article 310, Tables 310-16 to 310-31, and exceptfor utility installations, the NEC is the governing document. See Appendix 9A of this Handbook for discussionof ampacity ratings as listed by lCEA.In addition, a modified type of stranding, 19 wire

combination "Unilay," is now available as described inASTM B 786 in its uninsulated form. Details of thevarious sizes of this conductor are listed in Table 4-26.Service and Secondary CablesClass 10-1Messenger-Supported, Service-Drop and Secondary Cable(Duplex, Triplex and Quadruplexj (Figure 101)

This cable ordinarily is installed by the power supplier

(utility) for both secondary runs and service drops. Thecable construction consists of a bare neutral-messengersupport member, which serves as a neutral, cabled withone, two or three insulated conductors. Service-dropand secondary cable are commonly manufactured tocomply with the appropriate ICEA Specification S-66-524for crosslinked polyethylene (XLPE) insulated conductorsrated at 900 C maximum; and S-61402 for polyethylene(PE) insulated conductors rated at 75 0 C maximum. Cablesof this type are suitable for applications where phase-tophase voltage does not exceed 600 volts.The following are typical sizes and insulation thicknesse1for phase conductors:

Conductor size ThicknessAWG orkcmil mils millimeters8 through 2 45 1.141 through 4/0 60 1.52250 through 500 80 2.03Available sizes - Generally all constructions are available in sizes No. 6 through 410, with large sizes through500 kcmil available upon special inquiry.Neutral-Messengers-Constructions are available withfull Or reduced sizes AAC, ACSR. ACSRlAW and Aluminum Alloy (6201) neutral-messengers.Based on the referenced guide below Table 10-1,ampacities at a fixed condition of 40'C ambient, no windor sun, are tabulated in Table 10-1.

InsulatedPhase ----,Conductor

Ba",NeutralMessenger

Fig. 10-1. Neutral-supported duplex secondary cable withsolid Or stranded po wer conductor and bare, strandedneutral.10 ..1


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covered and insulated aluminum wire and cableType insulation Table 101and construction Col. R efe renee

PolyethyleneDuplex, Triplex 3Quadruplex 4

CrosslinkedPolyethylene

Duplex, Triplex 1Quadruplex 2

Class 102 Preassembled Parallel Secondary Cable (Fig. 102) This cable serves a similar purpose as Class 101, except it is used more for secondary runs than for servicedrops. The introductory comments for Class 101 alsoapply to it. The two or three insulated power conductorsare laid parallel and are secured to a bare neutralmessenger by means of flat aluminumalloy binder ribbonapplied helically about the assembly. The usually availableinsulations are cross inked polyethylene (XLPE) rated

90'C, high density polyethylene (HDPE) and conventionalpolyethylene (PE) rated 75'C of the same thicknessesas listed for Class IO\. The neutral messenger used withcables of Class 102 is the same as those specified forClass 101 cables, either full size or reduced size.Ampacities are the same as those for duplex triplexClass 101, according to the kind of insulation.Class 103 Reverse Twist Secondary Cable (RTS) (Fig. 103)

This cable is similar to Class 101 and the introductorycomments also apply. RTS cable is generally used assecondary distribution cable and occasionally used forservice drops. Cable construction consists of two orthree insulated phase conductors cabled about a straightneutral messenger with direction of lay reversed at regularspecified intervals throughout the length of the cable.The conductors are bound to the messenger with analuminum flat strap binder. This cable is particularlyuseful in secondary distributions and where Ttaps arerequired since "slack" can be obtained by untwistingthe cable conductors. Ampacities for these constructionsare listed in Table IO\.Flat BareBinder NeutralWire Messenger

Fig. 10-2. Preassembled parallel secondary cable.

InsulatedFlat PhaseBinder

Bare Neutral Messenger

Fil!.. 103. Preassembled reverse lay twist cable.Class 104 Type SE-Style U Service Entrance Cable (Fig. 10-4)

Cable construction includes two or three insulatedconductors with a bare concentric neutral considered asa conductor. Three-conductor SE-Style "U" (SEU) cableis the more widely used construction. It is employed asservice entrance from the attachment point of the servicedrop cable down through the meter socket and then tothe service panel. Three-conductor cables consist of twoinsulated conductors paralleled, about which is applieda bare concentric conductor. The assembly is compacted,protected and strengthened by a reinforcement tape,and an extruded polyvinyl chloride (PVC) jacket appliedoverall. SEU cable is manufactured to comply with theUL standard for service entrance cables (UL 854).Application is governed by local building codes whichgenerally reference the NEe. Phase conductors in serviceentrance cable are usually NEC types XHHW and RHW.SE cables are recognized in Article 338 'of the NEC foruse as feeder and branch circuit conductors with certainlimitations. Typical applications include range and dryercircuits.Class 10-5 Type SE-Style SER Service Entrance Cable (Fig. 10-5)

SER cables meet all of the requirements of Class 10-4above for SEU cables. Style SER cables differ from SEUin that the neutral conductor is insulated and cabled withthe phase conductors. This difference produces a roundconfiguration for three-and four-conductor cables. Available constructions are: three-conductor cable (two insulated phase conductors cabled with an insulated neutralconductor); and four-conductor cable (the same as threeconductor, plus a cabled bare equipment-groundingconductor).

SER cables are suitable for voltages not exceeding10-2


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TABLE 10-1 Typical Ampacities for Various Sizes and Types of Stranded Conductors in Cables of the Class Descriptions Mentioned in the Text* (600 Volts or Less)

NOiE: It is suggeued that this table not be used diractly. but only to supply information as a supplement to the Clan Descriptions which should be consulted first. Except for Classes 10-4. -5, and -8, the listed ampacitie$ afe based on 400C ambient for cable in air or 1n conduits in air, and 200 C ambient for cables in buried du ct or direct earth burial, assuming 100% load factor and RHO-gO earth thermal resistivity. The listed ampacitiei for Clauss 104, -6, and -8 are based an 300e ambient.

InsulatfllConductorsAWGkemU

121086421I/O2/03/04/025035050075010001250150017502000

' .....1(}.1, 10-2. 10-3and"l ~ 0 4 l : "10-6 10.5T%mp I...... 90-. , .1-4-75 - . . I 75 19 0 75C

i( x.t : e . ~ t . l ! H p a :. lit Q. .. l'I l2 in6'"0CoLNo, I (117095130

185215250295

(2)

90125175200235275

6 .. O ..(31 (4)

60BO 75110 105

150 140175 165205 195240 230

15)

405065#100#110#125'150fl175#200

Air16)

64B51161501742012322693123474315447078539821103

12161321

I (7)

55739712814917219923026S29737046660673084094410391128

.

Class 1().6 III 1..-- Cla$$107 _ .... 110-8 1..- Class 10-9.u 15Triplexodin Air(8)

61699112314416119322.26229236445B59B716

~ ..

(9)

445978106123143165192224251312392512612

90 15 90 75 I 90 75 I 90 15160190 75 I 90 75 I 90 15Triplex T,ipl.x I 3.l/e ~ zlC or 31Cin Buried 3/e in in Concentricin Conduit Duct Air Conduit NM Neutral110) 1111 112)11'31 I 114)iI15) ( 1 . 1 1 1 ~ ( 1 . (m l_. ~ 152543 37 50 45 3058 50 66 60 65 53 68 5076 65 86 78 S5 70 76 65 150 135102 87 I I . 103 115 92 102 87 190 175122 104 131 119 135 108 122 104 220 200139 119 150 136 155 125 139 119 250 225159 137 172 156 lBO 144 159 137 280 255189 162 196 178 205 166 189 162 315 290217 186 226 205 240 192 217 186 365 330249 213 250 227 265 214 249 213 400 360303 259 304 276 330 265 303 259 480 435

381 326 372 338 410 330 3Bl 326 580 530488 417 4B8 425 530 424 4SB 417578 493 546 494 625 500 578 493

. - L ~ " _--'_ .

In Pl. . .i.DuctRibbOn not triplex~ 1 I 1 = ~ . I H

130175 16 .200 19021525 24550285 275325 315350 345415 3BO

110 90125 110145 12514570195 165225 190250 215

"ICI...0-1(.90 151 75Tripl$x100% IF

(,IC and ron.Neutral) abfe(25) 11261 (,7)

105 96 50135 123 6517. 160 90201 182 100229 206 115260 235 135296 266 15038 170370 303331448 39S543 481617 550

-The listed ampacities generally are from ICEA tables, and may differ from ratings in NEe 310 tables as qualified by footnotes, and after adjustment for difference of ambient temperatures. If dif1erenr.:es occur, use adjusted NEC values when NEe conditions must be met. Some ratings are in even figures, and others are roundad to nearest 6ampere values, This lack of uniformity Is e:xp!alnod by noting that ampacity ratings of suecea:sive batches may show a variation'of 2%. hence the rounding to nearest I) amperes is allowable. Some listings from industrY sources are based on 62% tACS elumlnum conductivity, bu t most tabulated values are bas.ed on 61% conductivity. The effact on ampacity is only 8/10 of 1% in favor of the 62% aluminum, hence the difference is ignored in the tables. Adjustment of ampaeity values for cables closely adjacent in rigid cable supports, trou ghs. or where there is no maintained spacing. should be rriade according to factors in Appendix 9A,# Ampacities are from the NEe for throe-wire, slngte-phase residential services.-o. w


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covered and insulated aluminum wire and cable

Un nsulatedInsulated, - - - - - , - P h a . eConductors

Fig. 10-4. Type SE-style U three-conductor service-entrance cable.

Sa",Insulated GroundingPha.e Conductor

.Jacket----,

Insulated'-------- NeutralConductor

Fig. 10-5. Typical type SE-styte SER cable.

600 volts. SER cable is primarily used in residential wiringto subfeed distribution panels in multi-unit dwellings.The four-conductor cable provides an insulated neutralrequired by the NEC for feeders and branch circuits,as well as an equipment-grounding conductor. Cable issized per NEC requirements. Where cables are used asbranch circuit conductors, cable ratings are based on thetype of conductor insulation within the cable - forexample, XHHW for 900C dry locations at the applicableampacity caned for in NEC tables.Class 10-6600-11)(J() Volt Power and Lighting Cable (not especiallydesigned jo r direct burial) (Fig. 10-6)

Cables of the 600-volt and lOOO-volt class are similarexcept for a slight difference of insulation thickness.NEC describes the 6OO-'\'0It class completely for codeapplications, and its Art. 710 refers to requirements for"over 600 volts." Under NEC conditions, the (I)(J()-voltcables mostly are applied for certain circuits related to

industrial processes, motor loads, large fluorescentlighting installations, and sometimes where ungroundedneutrals are used. Some manufacturers include theII)(J()-volt cables in a group specified for 6Ol-21)(J() volts.Cables of the 6OO-voh class sometimes are referred toas building wires because of the extensive use of singleconductors for interior circuits. The Aluminum BuildingWire Installation Manual and Design Guide of TheAluminum Association lists sizes of the 600-volt class

and NEC designations of insulation for various iemperatures and environments, hence they are not repeatedin this handbook. This classification includes insulatedsingle or multiplexed cables for installation in air, duct,cable tray, metallic or non-metallic conduit, or suspendedfrom messenger. It does not include multi-conductorcables (an assembly of several conductors under one jacketor sheath) nor cables designed especially for undergrounddirect burial, though some cables of this class may besuitable for direct burial.Table 10-2 shows the usual range of sizes and kinds

10-4


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c

of insulation generally used for the 600-volt class on thebasis of 100 percent insulation level, with groundedneutral. The insulation thickness for 1000 volts is slightlymOre than for 600 volts. I f the thickness is shown as adouble number, the right-hand value applies to the jacketonly.The EPM-EPDM insulation, listed in Table 10-2,

represents the formulation used for 1000 volts or less of theEPR ozone-resistant insulation listed in Table 8-2.

A

B

Jacket InsufionL____ .---l.-(-'1_Flat BareBinder

oPhase

Conductors

Fig. 10-6. Typical 600-voll insulated power and lightcables.A-No outer covering required.B--Comparative!y thick jacket, neoprene, etc.C--Comparatively thin jacket, nylon, etc.D-Assembled aerial cable; phase conductors, eithercabled or layed up with reverse lay twist to facilitateside taps.

product classification and technical dataAmpacity ratings' for these conductors in air at 40'Cambient (not buried or in underground duct) are listed inthe following deSignated columns of Table 10 . 1:

90'C 7S'CSingle conductor. in airEach conductor of a triple;x:ed

assembly in airEach conductor of a triplexedassemhly in steel conduit in air

Col. 6

Cel. 8Col. 10

Co!. 7

Co!. 9Col. 11

Ampacity rating of each conductor of a triplexed as ..sembly in buried duct at 20C ambient is listed in columnsof Table 10-1 as below: 9O'C 7S'CEach conductor in iripEexed assemblyin nonmetallic duct. buried, Cot 12 Col. 13of two phase conductors andneutralClass 10-7Three-Conductor Cable (600-1000 Volts) (Fig. 10-7J

Although a triplexed cable has three cunductors, itwas included in Class 10-6 because essentially it iscomprised of three closely spaced single conductor cablesand is not designated as a multi .conductor cable.A multi-conductor cable, on the other hand, as usuallydefined, has two or more phase conductors, usuallycabled, and the entire assembly is enclosed in a Close-fittingtubular jacket or sheath which may contain fillers toround out its circular shape. It may also have an insulatingjacket under the sheath.Sector stranded conductors are sometimes used inthree-conductor cable as a means of reducing diameter.

The Type SER service-entrance 6OO ..volt cable qualifiesas a three-conductor cable, but because of its specialapplication it is listed as Class 10-5. The Types NM andNMC also are three-conductor cables, but because ofavailability only in small sizes for branch circuits they areseparately considered as Class 10-8. It is characteristicof three-conductor cables that the outer jacket must fitclosely, hence pre-assembled cables in a comparativelylarge duct are not included. Many portable powercables are three .conductor cables, with flexible neopreneor plastic jackets.

Armored aluminum multi-conductor power cables,Fig. 10..7, available as Type MC (metal clad) with NECconductors No. 12 AWG and larger, have an outerprotective covering of corrugated or interlocked design.A modification in branch-circuit and feeder sizes, TypeAC (armor clad), has an internal bonding strip ofaluminum in intimate contact with the armor for its entirelength. Another style of Type Me aluminum corrugatedcable has the tube formed around the assembly ofinsulated conductors, with the longitudinal seam closed

.. Ampacity ratings for this class are from leRA Pub. P ~ 4 6 - 4 6 2(1962) as described in Chapter 9.

10.. 5


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...o0-TABLE 10-2

Typical Insulation Thicknesses of Power andLighting Secondary Cables (600 volts)

I_

Cro.. LinkedPolyethylene

Thickness of Insulation in Mils (1/1000 in.)-------- , ----------PolyvinylChloride

1onductorSizeAWG-kcmilCia. . B

900C Dry750C WetXHHW

900C Dry750C WetUSE-RHWRHH++750CWetTHW

NylonJacketTHHN++gooC DryTHWN750C Wet

SBRRubber750 C WetNeopreneJacketRHWUSE

ButylOOOC Dry750 C WetNeoprene

JacketRHH-RHWUSE++Stranded Mils mm Mils mm Mils mm Mils mm Mils12-10 30 0.76 45 1.14 45 1.14 45-15**8-2 45 1.14 60 1.52 60 1.52 ,. 60-301-4/0 55 1.40 80 2.03 80 2.031 507 1.27 .18180-45213-600 65 1.65 95 2.41 95 2.411 608 1.52.20 195.65501-1000 80 2.03 110 2.791110 2.79 70-9 1.78-.23 110651001-2000 95 2.41 125 3.18 125 3.18

mm Mils- - - - - - - + ~1.14.38 45-15'"1.52.76 60-302.031.14 80452.161.65 95-652.791.65 11065

mm1.14.381.52-.762.03-1.142. 161.652.791.65

EPMEPDMEthylenePropyleneRubber900C Dry750C WetSyn-Rubber

JacketRHH-RHW-USE++Mils mm3015 0.76.38

# #55-45 1.401.146565 1.65-1.6580-65 2.031.65

*100% insulation may also be used with ungrounded neutrals provided the fault-clearing devices clear the fault in less than one minute and completely de-energize the faulted section. If this condition cannot be met, it may -be necessary to use insulation for 133 perce nt level (see manufacturer). Ilf thickness is shown as a double number, righthand number indicates thickness of jacketl. "For No. 12, values are 154 mils (.38.10 mml; for No. 10, value. are 20-4 mils {.51. tOmml; for No.8 and No.6, values are 305 mils (.76.13 mml; for No.4 and No.2, value. are 406 mils (1.02.15 mm). A 3Q.mil jacket is required for aerial instal1ation. ++NEC limits wetlocation rating to 750 C, bu t ICEA and industry ratings allow 900 C wet or dry for cables having these insulation thicknesses. #For sizes No.8 and No.7, values are 45-15 mils (1.14.38 mml; for size. No. 62. value, are 45-30 m i l ~ (1.14.76 mml.
http:///reader/full/1.14%E7%AE%B38http:///reader/full/1.52-.76http:///reader/full/2.03-1.14http:///reader/full/2.79%E7%B1%AE65http:///reader/full/1.02%E7%AE%B15http:///reader/full/1.14%E7%AE%B38http:///reader/full/1.14%E7%AE%B76http:///reader/full/1.14%E7%AE%B38http:///reader/full/1.52-.76http:///reader/full/2.03-1.14http:///reader/full/2.79%E7%B1%AE65http:///reader/full/1.02%E7%AE%B15http:///reader/full/1.14%E7%AE%B38http:///reader/full/1.14%E7%AE%B76


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CodingTapeInsulation

Conductor

Armor Tape(Interlocking)or CorrugatedGroundingConductors

Fillers

Fig. 10-7. Typical three-conductor impervious-corrugatedor interlocked, corrugated armored cable.by welding, and Ihe corrugations roll-formed to provideflexibility.

Still another MC type is aluminum sheathed cable.formerly Type ALS. This cable has a smooth tubularaluminum sheath surrounding three or more NEC conductors of branch-circuit size with ampacity ratings from2()..amp to 90amp. The insulation of individual conductors used in this cable type may be any listed forClass 106 cables. These cables are particularly usefulin control circuit wiring. where provision for growth isnot necessary. Its use eliminates cost of conduit installation and wire pulling.

In any of these MC types. a fourth insulated conductorcan be included for three-phase. Y connected applications.

The equivalent of a separate bare or covered groundingconductor may be included as one or more conductorsin the interstices of the cable arrangement. The groundingconductors for Type MC cables are tabulated in Section7.9 of ICEA Standard 566524 and Section 7.10 of5-19-81. The protective sheath or armor is not designedfor use as a neutral conductor and for interlocked metalstrip design is not recognized as a grounding conductor.The exterior surface of metal clad cables must beadditionally protected by a suitable jacketing materialwhen exposed to destructive corrosive conditions. Colored

PVC jackets are commonly used for this purpose.There are moderate NEC limitations as to where TypeMC and similar cables may be installed. Generally, theyare placed in trays or on other rigid suppons in powerstations. industrial plants and commercial installations,though some types are suitable for embedded or underground use.

product classification and technical dataFor calculating voltage drop in 6OO-volt three-conductor

armored cable. the factors of Table 9-6 may be applied,using those for aluminum conduit for cables with aluminum armor, and those for steel conduit for cableswith steel. armor. The armor is thinner Ihan the wall ofstandard conduit. but since it is closer to the conductors.its inductive effect is about the same.

The ampacity of the three-conductor unarmored oraluminum-armored cables in air at 75C with 40C ambient is per Col. 15 of Table 10-1 and at 90C per Col. 14.For three single-conductor cables in steel conduit, theampacity is as shown in Col. 17 for 75C and Col. 16 for90C. The range of available sizes of cables with weldedtube corrugated armor differs from that of cable with interlocked armor. For further information consult manufacturers' lists.Three-conductor non-metallic-iacketed cable

This cable is similar to Type MC armored or sheathedcable exrept that the protective covering is a round plasticjacket instead of a metallic sheath or armor. This designis used where it is desired to maintain a fixed configuration of the conductors along with moderate protectionagainst crushing and abrasion. such as when pullingthrough a duct or after installation on supports, particularly in wet locations. The insulation of the individualconductors may be any listed for Class 10-6 cables, thoughthe conductors usuallY do not require additional jackeling.In wet locations. the insulation should be selected forwet conditions. The outer jacket is usually of neopreneor polyvinyl chloride. If the cable is in air at 4QoCambient, the ampacity rating of Col. 15 for 75 0C andCol. 14 for 900C of Table 10-1 may be used. I f installedin underground duct at 200C ambient. Col. 13 for 750Cand Col. 12 for 900C may be used.

These plastic-jacketed three-conductor cables may beinstalled in the same manner as single power cables (Class10-6).

Class 10-'8Types NM and NMC Nonmetallic Sheathed Cable(Fig. 108)This two, three- or four-conductor cable is used extensively for interior wiring of branch circuits throughthe 75-amp ratings. It is listed by UL for sizes No. 12through No. 2 for aluminum. The insulated conductorsin the usual sizes of No. 12 and No. 10 are arranged inparallel for twoconductor cables; three and fourconductor cables are cabled into a round configuration.Assemblies are enclosed in a moisture and abrasionresistant extruded PVC jacket. The three-insulatedconductor round style is suitable for 3-wire circuits withone insulated conductor serving as neutral.

NM and NMC cable is satisfactory for use in circuitsnO! exceeding 600 volts and where conductor temperatures107


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Type NM (2Cdr. with Ground, Oval Section)(Can be obtatned without gfOuodlng conductor;

Type NM (3 Conductor, Round Section) (Also available with bare grounding conducfor)

Fig. 10-8. Type NM branch-wiring cables.

do not exceed 600C. Cable construclions are availablewilh or without a bare grounding conductor.Conductors of No. to size or smaller are solid, andannealed for flexibility, because an advantage of this type

of cable is that it readily may be bent into place. TheType I'M cable is approved for installation in bothexposed and concealed work in normally dry locations,but not for exposure to corrosive conditions, nor mayit be run in masonry, concrete, or plaster.Type NMC cable resembles type NM but has an

integral jacket which is fungus- and corrosion-resistanInstallation in moist or corrosive locations is approveand under certain conditions it may be used where TypNM is prohibited. Neither type is approved for serviceentrance use, nor for locations as limited in NECSection 336-3. Ampacities, based on 300C ambient,in Col. 18, Table 10-1. ar

Class 10-9Secondary-Distribution Single- or Three-ConductorCables for Underground Residential Distribution(URD) 600 Volts (Fig. 10-9)Although these cables are usually designated as foURD, they are of course suitable for any other direcburial use within their ratings. NEC cables designatedType UF (underground feeder) are included to 4/0Certain other conductors in Class 10-6 are also suitablfor direct burial, such as USE or the combinatioType USE-RHW -RHH available in several insulationsSome sizes are available in both solid and concentricstranded aluminum conductors; the solid type is a

intermediate temper.Bare aluminum neutrals are usually not permittefor URD cables because of the possibility of corrosioin wet earth. A popular cable is a triplexed assemblof which one conductor is an insulated neutral, Fig. 1O-9C

A less frequently used form has a copper-wire neutraspiraled closely around one or two paralleled insulatedconductors. (Fig. 1O-9A & 9B) Copper is used for thearth contact because of its resistance to corrosiounder buried conditions. Still another form is the ribbo

3

(A) (8)Two-Conductor Three-ConductorConcentric Neutral Type Concentric Neutral TypePlain or Corugaled Pla.tic Duct

(e )TriplexType

(D) IE)Ribbon TrlplexedType Plasllc Conduit TypoNote: A concentric-neutral cable may be used instead of the triplexed as shown for installation in plastic conduit (E

Fig. 10-9: Typical600-volt cables lor direct burial.108


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product classificatIon and technical dataTABLE 10-3

Typical Insulation Thicknesses of Secondary Cables (600V) fo r Direct Burial or Underground in Duct Thickness of Insulation in Mils (1/1000 in_). Millimeters(1 ) (2)

Cross Linked(3)Polyethylene (4) (5) (6)Polyvinyl Chloride or Low-Density Polyethylene

ConductorSize

WG-kcmil

ConcentricNeutral, orTriplexed90CMils mm

ParallelRibbonType'90CMils mm

ConcentricNeutral, orTriplexed75CMils mm

ParallelRibbonType'75CMils mm

PlasticConduitType75CMils mm

4-21-4/0225-500608095

1.522.032.41758595

1.912.162.41608095

1.522.032.4195125-

2.413.18-608095

1.522.032.41Sizes are concentric stranded -conductors; for solid-conductor sizes (except for Column 5) refer to manufacturer. Special inquiryalso is required for availability of sizes for Column 2 for sizes above 300 kernil.*The thicknesses shown include 30 mils for jacket.

cable in which two parallel insulated phase conductorshave an insulated neutral between them, Fig. 10-9D.The insulation is extruded over the three conductorssimultaneous1y so there is a thin conne.cting web betweenthe conductors, or the web may be only a part of a jacket.The web is easily torn away during i n s t a l l a t i o ~ .

Available constructions include cable in a duct. Thisconstruction consists of tw o or more conductors pre-assembled at the factory in a plastic duct (Figure 10-9E).Use of this product provides for conductor replacementafter installation. Duct sizes ar e compatible with existingaccessories and, through supplier inquiry, may be sizedto allow for some degree of enlargement on the systemas installed.

The insulated conductors in any of the above-describedcable assemblies can be any of the conductors of Class10-6 listed by NEC as suitable for direct burial.Table 10-3 shows the usual range of sizes and kinds ofinsulation generally used for the 6oo-volt cables of thetypes described and Table 10-1, Cols. 19 to 26 summarizes ampacities that conform to ICEA requirements,

and to local codes requiring that underground secondaryservice cables leading directly to the home be UL-listed.Care should be taken by the purchaser to assure thatthe product offered is UL-Iabeled for these applicationswhere required.The threeCconductor URD cables for 600 volts in thearrangements shown in Fig. 10-9 are for three-wiresingle-phase circuits. If the cables are for three-phase(3 or 4 conductors), the ampacities shown in Table 10-1should be reduced. Consult suppliers.

Cols. 19 and 20 of Table 10-1 list ampacities of 600volt buried cables of the concentric-neutral type (havingspiraled bare copper neutrals) at 200 C ambient for insulation suitable for 900 C and 75 0 C, respectively. The

ampacities of triplexed buried cables are listed in Cols. 25and 26. The ribbon type has ampacities according to industry sOurces and tests as listed in Col. 21 for 900 C andfor 75 0 C as in Col. 22.

In all cases of direct burial Or duct installation anearth thermal resistance of RHO-90 is assumed with a loadfactor of 100 percent; that is, the cables will withstandthese ampacity ratings for continu.ous operation.

The ampacity ratings of the cables pre-assembled inplastic ducts for the 900 C ratings are in Col. 23 andfor the 75 0 C ratings in Col. 24.Class 10-10 Portable Aluminum Cables (600 Volts or less) (Fig. 10-10)

Portable aluminum cables, either single or multipleconductoc, are constructed to yield a high degree offlexibility. Flexible cables usually employ an intermediatetempered aluminum conductor which is insulated witha synthetic rubber or thermoplastic material. Theseconductors are phase-identified for circuit applications.Tw o or three conductor cables, with or without equipmentgrounding conductors, are cabled together with thenecessary fillers to construct a round cable and employan overall jacket of thermoplastic or synthetic rubber.Flat constructions are also available with conductorsarranged parallel to one another and with a commonoverall jacket. Portable aluminum cables possess a lighterweight than other constructions, which facilitates theiruse. Single-conductor portable cables are available forspecial applications where flexibility is a requirementdue to installation handling or vibration is a consideration.

Single-conductor portable cables usually are availablefrom No. 8 to 1000 kcmi!, and multiple conductorportable cables from No. 12 to 4/ 0 AWG. Ampacityratings are usually approximately as follows for 75 0 C

109


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A S C D

{AI T w o ~ c o n d u c t o r (S) Twosonductor (C) T w o ~ c o n d u c t o r (D) T h r e e ~ c ( J O d u c t o rWith Flat With Stranded With StrandedEquipment- E q u i p m e n t ~ EquipmentGround Ground GroundConductor Conductor Conductor

Fig. 10-10. Typical cross-sections oj portable cables, com Note: The web-tape cushion prevents longitudinal sepprising aluminum conductors, insulation, web-tape cushion, aration of insulation and jacket durin.g bending oj thand overall jacketing. cable.

operating temperatures and 400C ambient temperatures:Single-conductor cables Col. 3 in Table 101Two-conductor parallel or

round type Col. 4 in Table 101Three-condllctor, round Col. 27 in Table 101

Often a long portable cable is partly held on a gathering reel. The above ampacity values are reduced for suchcases by multiplying by the foUowing correction factors:One layer on roll 0.85Two layers on roll 0.65Three layers on roll 0.45Four layers on roll 0.35

Class JOll (Fig. 10-11)Aluminum Con.trol Cables (for 600 Volts or less)Because of the wide variety of multiconductor cablesused for control and signal circuits and the generallysmall size of the individual conductors, no detaileddescriptive listing of them is attempted for this book.The individual conductors (either stranded or solid) are

insulated with compounds that best meet conditions,and the whole, assembly is contained within a round thickoverall jacket of neoprene or thermoplastic material.Where the application environment is severe, constructionsare available with reinforced overall jackets or armoring.These control cables have wide application in utilities,industrial, municipal, and railroad installations for controland signal purposes. The automatic control of machinetool operations is a recent application for which controlcables of oil-resistant type are used. Manufacturers' listsshould .be consulted,

1010

Fig. W-ll. Typical aluminum multiconductor control andsignal cable, available with 2 to 18 conductors, A WG 9 to14, suitable jo r installation in ducts, direct burial, or jo raerial suspension jrom messenger.

Cables For Primary Distribution VoltagesThe types and voltage range of primary distributioncables with aluminum conductors were briefly describedin Chapter 7. Those with rubber or thermoplastic insulations mostly are for 5, 15-, 25-, and 35kV all withgrounded neutral. The 3-kV and 8-kV ratings sometimesare listed, but are less used because the trend is toward thenext higher voltage in anticipation of load growth, eventhough the actual increase from the lower circuit levelsmay be long delayed.


11/22

Customarily, primary-distribution insulated cables arevoltage-rated on the basis on the phase-to-phase voltageof a three-phase circuit of which they are a part. or wouldbe a part if the three-phase circuit were complete. Thus.an insulated conductor of a single-phase branch circuitincluding a phase wire and a ground wire that is connected to the wye ground of a 25-kV three-phase wyegrounded circuit is still rated 25 kV although the actualrms kV of the single-phase circuit is only 251\13 or 14.4kV. This notation applies principally to the single insulated primary conductor of the two-conductor cable thatsupplies the single-phase transformer that feeds the secondary three-wire circuits.

Cable descriptions in this book and in the literature distinguish between the insulation thicknesses required forhigh-voltage cables in circuits with grounded neutral andthose with ungrounded neutral, the latter requiring thickerinsulation. It is recognized. however, that there are otherconditions than lack of neutral ground that may make athicker insulation desirable. To meet this condition theconcept of grounded and ungrounded neutral is in theprocess of being eliminated as a sole criterion. Instead theinsulation thicknesses are assigned based on insulationlevel (AEIC #5 and 1987 NEC, Table 310-13).The selection of the cable insulation level to be used ina particular installation shall be made on the basis of theapplicable phase-to-phase voltage and the general systemcategory as outlined below:100 Percent Level-Cables in this category may be applied where the system is provided with relay protection such that ground faults will be cleared as rapidlyas possible, but in any case within one minute. Whilethese cables are applicable to the great majority ofcable installations which are on grounded systems, theymay be used also on other systems for which the application of cables is acceptable provided the above clearingrequirements are met in completely de-energizing thefaulted section.'133 Percent Level-This insulation level corresponds tothat formerly designated for ungrounded systems.Cables it! this category may be applied in situationswhere the clearing time requirements of the 100 percentlevei category cannot be met, and yet there is adequateassurance that the faulted section will be de-energizedin a time not exceeding one hour. Also they may be usedwhen additional insulation strength over the 100 percentlevel category is desirable.173 Percent Level--Cables in this category should beapplied on systems where the time required to deenergize a grounded section is indefinite. Their use isrecommended also for resonant grotindedsystems. Consult the manufacturer far insulation thicknesses.

Where additional insulation thickness is desired, it shall bethe same as for the 133 percent insulation level

product classification and technical dataThe AElC reference to the preceding statement regarding insulation levels also includes the following:In common with other electrical equipment, the use ofcables is not recommended on systems where the ratioof zero to positive sequence reactance of the system atthe point of cable application lies between -I and -40,since excessively high voltages may be encountered inthe case of ground faults.Consideration of this requirement is in the province ofthe system electrical engineer.

Tabular Voltages for Determining .Insulation ThicknessFor three-phase systems with grounded or ungroundedneutral the thickness values are those given in the respective columns of Table 10-4. For three-phase delta systemswhere one leg may be grounded for periods of over onehour, consult the 173 percent insulation level referencedabove. For single- and two-phase grounded systems,multiply the voltage to ground by 1.73 and select thicknessfor that voltage in the grounded neutral column. For adirect-current system up to and including 2000 voltsconsider it the same as a single-phase alternating-currentsystem of the same rms voltage.

Jacket ThicknessThe insulation of unshielded cables may be of suchquality that it will withstand all environmental conditionslikely to be encountered, such as moisture, oil, sunlight,and abrasion in handling. I f so, no jacket has to be added.Several of the modem insulations meet this requirement,but often a slight increase in insulation thickness isused to provide for expected surface wear and to equalother advantages obtained by a jacket.Shielded cables, on tbe other hand, unless protected byarmor, require a jacket, not necessarily for improvingsurface quality, but as protection for the insulation shield

ing. The jacket material selected is the most suitable tomeet conditions. and usually it is a different compoundthan that of the insulation.The minimum thickness that qualifies a coating as ajacket on cables 2 kV and ..above is 30 mils, but the thickness also depends on diameter of the cable and voltage.Jacket thicknesses have subsfantially become standardizedas shown in Tables 10-5 and 10-6. The relative suitabilityof jackets of various materials can be determined fromTable 8-4. Jacket thicknesses generally conform to thoselisted in Table 10-5, based on diameter, and in Table 10-6for single conductor cables, based on AWG-kcmil size.The individual conductors of a multi-conductor cable thathas a jacket surrounding all conductors may have thinnerjackets than those specified in Table 10-6, and conform tocolumn 3 of Table 10-5. Column 4 lists thickness of theoverall jacketIt is necessary to distinguish between an overall jacket

1011


12/22

covered and insulated aluminum wire and coble

InsulalionSirand

Jacket MetallicWireShietd

Fig. /0-12. Typical unshielded aluminum insulated pri Fig. 10-13. Typical 5 kV to 35 kV shielded insulatedmary cable 5 k V with jacket. primary cable.Note: The metallic shielding may be tape as shown, orhelically applied closely spaced small wires.

'ICEA S-61-402 Table 4.

SeparatorTape

and a band of belt insulation, as found in some kindsof cable, such as for series-lighting circuits.Primary Unshielded Cables3 kV and 5 kV

The 5 kV rating is the most used of this type, Fig.10-12. If the insulation does not have a satisfactorysurface for withstanding eilvironmental conditions ajackel is added.The usual cable construction without jacket comprisesa Class-B stranded conductor (or it may be solid round

in small sizes). a resistive conductor-shield and insulationof the thickness listed in Table 10-4. The' insulationmust be ozone and corona discharge-resistant, suitablefor wet or dry locations, flame retardant, and suitablefor sunlight exposure, although the latter two qualitiesmay be obtained by jacketing, if nOt a characteristicof the insulation. The jacket, if used, must also becorona discharge resistant.Primary Cables with InsulationShielding (to 35 k V)

The conditions that require shielding at 5 kV arestated in ICEA' and pertain principally to single conductors at 133 percent insulation level or where cablesare installed underground directly buried, in ducts or inwet locations. The shields are also required if theinsulation or jacket is not one that protects againstOzOne or its effects. Insulation thicknesses are listed inTable 10-4. Generally, except for the shielding, the same

construction applies as for nonshielded cables. Figt0-13 is typical.

Triplexed preas sembled cable, or three-conductor cableeither jacketed or in metallic armor of constructions previously described is often used in the 5-kV-and-abovratings, Figs. 10-14 to -16. For ampacities see Table 10-7Primary Interlocked-Armor Cables (Fig. /0-16)

The description of interlocked corrugated armor usedon cables for 600 volts (page 10-5) applies to cables fothe primary voltages except for strand and insulatioshielding requirements. Howe,,'er. the impenrious seamlescorrugated armor is not as yet available in as manvoltage ratings or sizes as the interlocked armor. Threeconductor armored cables are the most used. Singleconductor cables are available for special applications witnon-magnetic aluminum armor.

The cables are available both with and without an extruded outer covering under the armor. Either aluminumor steel armor is available. Voltage drop at circuit powefactors less than 100 percent is increased if steel armois used, but is negligibly affected by aluminum armorThe ampacity rating of a three-conductor cable witaluminum corrugated armor is substantially the same anmay be somewhat more than that of the insulatethree-conductor cable in air; the increase in area becausof the corrugations and the closeness of the conductorto the armor both serve to increase the rate of heatransfer. For ampacities, see Table 10-7.

10-12


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produ,ct classification and technical dataTABLE 10-4 Insulation Thickness Inot including jackets) for HighVoltage Conductors in ThreePhase Systems with 100%

and 133% Insulation Levels, (or Grounded Neutral and Ungrounded Neutral, respectively). Thickness in Mils (=1/1000 in.) Note: The values in this table are obtained from ICEA or industry designations of thickness for the insulations named. However,because of variations of dates at which the values were issued, and because of lack of uniformity of the s i z e ~ s t e p s , slightvariations occur. Also some cable manufacturers issue specifications that in some respects show more favorable values. Theinsulations are those used for ozone-resistant conditions. In the 5OOO-volt class certain other insulations listed in Table 8-2and may be used bu t not necessarily at the listed thickness. I ButylPR Silicone (SAl,. XLPE or PE(1)Voltage . (21 Un Grounded Grounded Unn Grounded orand Size Grounded Neutral Grounded Neutral Grounded UngroundedroundedAWG Neutral Neutral Neutral Neutraleutraland kcmit mils mm mils mm mils mm ! mils mm mils mmils mm mils mm

:UNSHIELDED2OO15000V(31"90 "9 0 2,29 3,94 **15510 2,79 110 2.79 2.29 "155 3.94 155 3.94

22550084/0

*So *90 4,32 4,32525-1000

120 3.05 3.05 2.29 2.29 "170 4.32 17020 " ' 7 0*90 "9 0 **170 **17030 3.30 130 3.30 2.29 2.29 4.32 4.32 170 4.32

SHIELDED2oo1-5000v8-410 3,940 2.29 90 2.29 90 2.29 90 2.29 155 155 3.94 225500 4,325251000

90 2.29 90 2.29 90 90 2.29 170 4,32 170.292,290 90 2.29 90 2.29 2.29 170 4.32

5OO18000V 90 4.32 ! 170, I4.83 . 250,9215 140 3.56 11 5 140 3.56 190 4.83

525-1000 : 115 6500 2.92 2.92 4,83 25040 3.56 115 2.92 140 3.56 190 4.83

8001150ooV I21000 175 4.45 175 4.45 295 7.49 11000 21 5 5.46 215 10.6720.46 ! !1500125000V11000 8.7660 6.60 ! 345 260 6.60 345 8.76 45511.5625OO1-28000V11000 7.11 280 7,1180 7.11 420 7.11 42 0 705001 12 .28001350ooV

110-1000 345 8.761 420 7.11 345 8.76 42 0 7.11

2Conductor Concentrid41Helical Bare Grounded Neutral

5kV XLPE HPE#4350 90 9015 kV

#4350 175 17525kV

#2-350 26 0 26035 kV1/0-350 345 345NOTE: The difference of thickness between unshielded andshielded 5 kV cables using XLPE or PE insulations reflectsth e fact that the unshielded cable has a potential distributionno t as even as that of. the shielded cable.See page 10-15 for additional notes.

*Required by specification to have an outer jacket; maximum 3.phase voltage for 133% insulation level 3000V

JACKET THICKNESSAWG or kcmil Mils mm8 6 30 0,764-210 45 1.143/0-1000 65 1.65

**Required by specification to have an outer jacket

JACKET THICKNESSAWG or kcmil Mils mm8-1 45 1,141/0-4/0 65 1.65225-750 65 1.651000 95 2.41

1013
http:///reader/full/45511.56http:///reader/full/45511.56


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covered and insulated aluminum wire and cableTABLE 1()'5 Jacket Thicknesses for Single- and Multiple-Conductor Power cables According to Diameter Under Jacket

For all uses; Conduit, Tray. Trough, Underground Duct, Aerial, andOirect Burialt but does no t include Communication'or Portable CablesJacket Thickness

Sing1c-conductor Cable Multiple-cQtlductor Cables"i l l (21 (31 (41

Calculated Diameter of Cable Undef Jacket Noll$hielded Shielded" IndividualConduct.... t Overallinche$ mm mils mm mils mm mils mm mils mm0.250 or I. . . 6.35 or less 15 0.38 45 1.14 15 0.38 45 1.140.2510.425 6.38-10.80 30 0.76 45 1.14 25 0.64 45 1.140.426-0.700 10.8217.78 45 1.14 60 1.52 30 0.76 60 1.520.7011.500 17.7138.10 65 1.65 60 2.03 60 1.27 60 2.031.5012.500 38.13-63.50 95 2.41 110 2.79 60 2.03 110 2.792.501 and larger 63.53 ond lorger 125 3.18 140 3.56 140 3.56

+ Under common jacket.t These thicknesses apply to jackets only and do not apply to colored coatings used for the purpose of circuit identification onthe individual conductors of multiple-conduClor cables. +Single-conductor cables in sizes 9 AWG and smaller shall not be used for direct earth burial.

_. In calculating the diameter under the jacket of single-conductor shielded conductors that are part of a multi-conductor cable,add 45 mils to the insulation thickness to allow for thickness of the inSUlation shield. Also add the thlckness of the separatorand strand tapes. Eqs. 9-3, 9-4, and 9-5 provide a means for calculation of diameter, provided Di is the inside diameter of thejacket instead of the outer sheath.Two-conductor cables for direct burial having helical bare copper wire ground conductors have an outer protective covering ofconducting material that also serves as an insulation shield. The layer is not less than 30 mils thick.NOTE-For flat twin cable, use the calculated major core diameter under the jacket to determine the jacket thickness fromColumn 4. Source: ICEA 5-61-402

TABLE 1()'6 Jacket Thicknesses fo r Single-Conductor Power Cables, According to AWGkcmil Sizes

For all uses; Condui t. Trays. Troughs . Underground Duct. Aerial and Direct Surial. not including Communication or PortableCables.It is assumed that the jacket material is compatible with the insulation for the designated kV ratings. These thicknesses also applyto single-conductor cables if they are triplexed, but they do not necessarily apply to the cables that are a part of a three-conductorcable. for which the thickness may be according to column (3) of Table l()..S

VoltsPercentInsulationLevel 30 (0.761

Thickness of Jacket, Mils (= 111 000 In.), (mm)45 (1.14) 60 (152) 65 (1.65) 80 (2.03) 110 (2.79)

UNSHIELDED2001 . 5000 100 & 133% #8 #6 #4 210 310 1000SHIELDED200150018001

. 5000. 8000 15000

100 & 133%100%133%100%133%

#8 #6 2/0#6 - I/O#6 2

3/0 10002/0 1000#1 750#2 750#1 800

10001000750 100015001 25000 100%133% #1#1 500350 600 1000400 100025001 28000 100% #1 500 800 . 100028001 35000.Source. ICEA S-61-402

100% I I/O . 350 400 100010-14


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80 ..Messenger

produd c:lassification and technical dataTABLE 10-4 NOTES(1) The characteristics for the kinds of insulation shown are listed in Tables 8-2, 8-3, and 84 . for which also see rated temperatures.(2) If insulation is rated acoording to "percent insulation level," use column "grounded neutral" for 100% level. and column for"ungrounded neutral" fo r 133% level.(3) Solid die lear lc insulated conductors operated above 2000 volts generally f"equlre shielding under the NEe. Conditions under whichshielding is not required in the 2000-8(100 volts range are detailed in NEe Section 3 1 0 ~ 6 .(41 The cables listed in the main body of the table are generally available in the sizes shown as single conductors or cabled fo r aerialmessenger support, or in tray or d u c t ~ and with some insulations are suitable for direct burial. The two-conductor concentricneutral cables are mostly used for direct burial, but they also may be used in duct or be aerial-supported. The insulation thickness

tO t coaxial cables (in which the neutral is tubular) are Similar,

Fig. 10-14. Typical pre-assembled triplexed 5-k V to 25kV shielded primary cable bound to composite aluminumsteel (ACSR or A CSR lAW) or aluminum-alloy messengerwith aluminum tape. A fourth insulated neutral maybe n ~ l u d e d ifrequired.The construction of each conductor is similar to that depicted in Fig. 10-13. Also available with one, or two phaseconductors.For certain sizes reverse-lay may be obtained (see Fig.10-3). Also fo r parallel lay (not Iriplexed) field-spinningequipment is available' so that the assembly with lashingwire may be performed at the site.Similar pre-assembled triplexed (or parallel) cables areavailable without insulation shielding to 5 k V.

Primary Cables for UndergroundResidential Distribution-URDDirectly buried URD/UD style cables are increasinglybeing used as "main-line" threephase distributionfeeders.However. by far the most used primary cables forURD are those thaI supply single phase primary voltageto the singlephase 1ransformers supplying 120240 Vthree-wire circuits to the residences or other use.poimsin the area. These singlephase primary cables are of

ShlaldFig. 1015. Typical three-conductor 5-kV to 35-kVshielded primary cable in jacket,The construction of each conductor is similar to tfuJt depicted in Fig. }0}3. Triangular fillers in the intersticesaid in forming a cylindrical exterior that still will withstandbending from reel. Bare grounding conductors may beused in the interstices if required.

the two-conductor type. One conductor is an insulatedphase wire. The other is either a copper-wire concentricneutral conductor of equal conductivity to that of thealuminum insulated conductor, Fig. 10-17, or a concentric.flat strap neutral, Fig. 10-18, particularly adapted to conditions where substantially full metallic coverage isdesired. These copper neutrals are directly in contact withthe ground when buried.The phase conductors of these cables have semiconducting strand shielding and semi'conducting compound undernea1h the concentric wires or "raps to serveas an insulation shield.The insulation thickness around the phase conductoris generally the same as listed in Table 10-4. For ampacities see Tables 1O9A and 109B.

1015


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covered and insulated aluminum wire and cableHigh Voltage Primary Cables

Aluminum cables are commonly available through115 kV levels, Advances in materials and manufacturingexpertise have resulted in available cables in this andhigher voltage levels, While previous cable constructionsemployed paper insulation, with some gas-filled designs.today's market offers some cables of this type with soliddielectric insulations. Polyethylene and crosslinked poly.ethylene and similar materials are being employed incable designs. Information concerning availability anddesign should be directed to individual cable manufacturers.

As typical of such construction, a IISkV, 500kcmilaluminum cable for direct burial, with strand andinsulation shielding has 0.740 in. XLPE insulation thickness (0.525-in. for 69 kV), with a 0.140in. thick PVCjacket, and 2.90in, overall diameter (2.37 in. for 69-kV).Ampacity of High VoltageAluminum Cables

The ampacity values listed in Table 10-7A, -B, and -Cfor the designated cable types and installation conditionsmostly are those listed in ICEP. Pub. 46-426 Vol. II foraluminum, as explained in Chapter 9, applying to rubberor thermoplastic-insulated cables. The insulation is assumed to have a power factor of 0.035, dielectric constantof 4.5, and thicknesses for the various voltages that werelisted in ICEA Standards in 1962 when the ampacityvalues were published. Cables directly buried or in under-

Insulation ConductorShieldc ~ ; " ~ ~ ~ ~ o r l ' n S l u . a i ~ ~ ; n dTape Shield(OPliOr 11 FillersArmor(Inlerlocklng)

Tape

Fig. 1().16. Three-conductor shielded cable 5 kV to 15k V with interlocked or impervious corrugated steel oraluminum armor.

Bare CoatedCopper Neutral StrandInsulation Shield

Fig. ]()"17. Typical 5 to 35 kV two-conductor concentricwire neutral primary cable for direct burial, duct or aerialapplication.Bare Coated Strand

Copper Neutral Insulation Shield

Conductor

Fig. ]()'18. Typical 1535 kV two-conductor concentricflnt-strap neutral primary cable for direct burial or duct.

ground ducts are assumed to be in circuits of 100% loadfactor and RHO-90 earth resistivity. For 75% load factor,direct burial, increase ampacity by 6%, or for duct 3%;and for 50% ],f, by 14% and 6% respectively. Table 107 is based on 40'C ambient for cables in air, and 20'Cambient if underground, Adjustment factors for otherambients are in Table 10-8.

Separate tables 10-9A and JO-9B list the arnpacities ofconcentric-neutral primary cables for direct burial in duct,at 200C ambient, and also for installation of the cablesin air, or in duct in air, at 400C ambient, as necessaryfor leads into ai r from an underground installation.Table JO9A also includes ampacities for 35 kV cablewhen buried directly or in duct.

Inasmuch as ICEA and industry standards now allowsome reduction of thickness of certain kinds of insulationsas compared with the values that prevailed in 1962, andalso because most insulations have a luwer p.f. than 0.035,

1016


17/22

1

product classification and technical dataTABLE 10-7A Typical Ampacities of 5 kV Cables with Aluminum Conductors of Various Types and for Various Installation Conditions

5 kV in Air 4o"C 5 kV in Duct 20"'C 5 kV Directly Buried 20"'CAmbienl Onshieldedt

Conductor Grounded or Neutral RHO-go 10 0 LF RHO-SO ' 00 IFSize Ie in Ai , ~ ~ ' o f ;u : T h ~ ~ n d . ! Interlocked : j N.u".' 1No.".1AWG : lof3C : Armorkernil!

1 of 3C lC : Triplexed Three Condo I lCTriplexed

: , lC of 3 lo f3C leof 3(1)' (Z) (3)' (4)" (5) ' (6) m' (8) ' 19)] 19o"C !7SoC W C 175"C 190 ' C 7 5 ' C loo'c : 'SoC 9O'C 7S'C 90C 75C 'W C !90'C .S;'C i : 75" loo'C 55 64 : 44 51 39 46 - -: 56 62 45: 42 46 n 84 65 726 73 85 59 69 53 , 61 54 63 73 1 60 55 61 9B ____ 108' 94 924 ........ 97 11 3 78 : 9 'ii) 81 71 : 8: 96 78 72 80 127 14U : lU 8 119.....2 129 12: 9 10 8 95 125 ; 1 10 3 94 163, 180 13914" 144 12 . 113 131 14 3 119, 131 10 9 120 18 4 20, 158110 ~ , 167 14 5 131 150, 163 13 6 15e 1:151 13 8 : -. . 231 18 0210 , < '.3 ", 16 8 15 3 174 187 205,_ 15 6 , 17: 143 156 ,26' .3i n 26' 192 22 4 16 6 19 4 27 2- i ~ - ~ : ~ ; : l ~ - - 5 0 ~ 16 4 -- 18 0 : j 1 E ~2 9 9 ;: ; ~ f i10=i~

- 1 ~2000

2681 3' 22 4 262 19 : .224 , .7 206 30 731 ""2 214 '5 0 I 21. 256 1 269 29 6 22 20 22 8 33 53101 43 : 36 4 : 26 5 30 9 I 21 32 0 321 360. 276 304 25: 278 403 44 4 349

466 54 4 45 8 33 0 38 5 I 335 39 8 401 4 4 2 1 3 3 8 . _ ~ 308 . 34 0 49 0 54 0 42 4606 70 """ , 42, 4" 5 43 ' .....51. .0 5 556 425 386, 426 605 667 525: 57973{J 8531 71 6 i 499 58 4 .515 605 59 I 65 ' I 49. 546 44 7 : 49 5 i 70 6 , 778 5" " b7 2840 : ' 781 ,9"" 1103 73 90 . g;:10391 1216 I 79 8801 930 "128 1321 85" 9401 99 0 1094

j notes l"t'Iay be found under Table: 10-7C Source: ICEA P-46-425TABLE 10-7B Typical Ampacities of 15 kV Cables with Aluminum Conductors of Various Types and for Various Installation Conditions

SizeAWGkcmil

1/11010

2'>035 0

=ii15001750

2000

II

15 leV in Ai r 40C Ambient15 kV in Duct 20C : 15 leV Directly Buried 20CAmbrent-Shielded ' AmbjentShidded

Shiekted R H ~ 9 0 10 LF RHO90 100 LFGrounded Neutral Grounded Neutta' Grounded NeutralIlnwrlocked !, Armor

TripMxed TareeCond. iThne Condo Triplexed ThreeCond, Triplexed1e in Air l eo f3 1 of 3C 1 of 3C Ie 1C of3 1 of 3C lC 1C of 3t1)" (2 ) (31 (4)44 (51 161 i1I 18) 191

7SoC go'c 75C 9(lC 75C: 90C i 75C 90aC 75C ,90 C : 7SoC ; ~ C 75C: 90C: 7SoC! SOoC "/Soc oooei

130 152 115 135 10 9 12 8 95 119 12 6 13 9 ' 11 0 1121 10 6 11 7 149 154 133 ; 147125 ' 144 159 12 5 :3 8 12 0 133 .70 187 152 : 167

17 0 2Q 2 " 3 17 8 14 3 I , 12 1 15 8 164 181 14 2 ,157 : 13 7 101 ''''' 21 3 'I. '"'99 , 232 175 20 5 16 4 19 2 14 6 183 181 ;rob , ., 1 I. 1" " 1 12 2 "" :'


18/22

covered and insulated aluminum wire and cablethe ampacity listings of Table 10-7 are conservative forsome applications, and cable manufacturers may offermoderately larger ampacities. However, as previouslystated. the 0.035 p.f. value is an ICEA estimate of whatthe p.f. may become after many years of exposure and use.

The ampacity ratings of the types shown in Table 10-7for 35 kV and 46 kV are practically the same as those of25 k V for installations in air, and only up to about 2 percent less for direct burial, hence values for 35 kV and46 kV are omitted from Table 10-7. Also inasmUCh as

high-voltage cables are not used in rigid conduit to textent formerly (cables in interlocked armor have largesuperseded them), ampacities for high-voltage conduit istallations are not listed. Ampacities to 35 kV conduinstallations are listed in NEC Article 310 Tables, alonwith ampacities for cables in :fiee air, direct burial anun


19/22

produd c1(>ssification and technical data

TABLE 10-8 Adjustment Factors for Ampacity Values in Table 10-7 for Variations of Ambient Temperature The following factors may be used to adjust ampacities for various ambient temperatures:

If me ampacity is known for: Conductor Temperature 900(; 750 C 9()OC 750 C

Ambient Temperatur. 400C 400 C 200 C 200C

New AmbientTemperature Multiplication Factor (MF) MUltiply by the indicated acc 1.34 1.46 1.13 1.17 factor to obtain the new IOOC 1.26 1.36 1.07 1.09 ampacity for the new 200C l.1e 1.25 1.00 1.00 ambient temperature: 300c 1.09 1.13 0.93 0.89 400C 1.00 1.00500C 0.89 0.e5

For example: A cable may have .. known ampacity of 100 amps when operating at a 9()OC conductor temperature in a 400cambient. The same cable operated at 900c conductor temperature in a 3QoC has an ampacity of 109 amps; while in a 500(;ambient. 89 amps.-Table factors are derived from the following equation:

MF=

12 = I,(MF)where: II ampacity from tables at ambient TAl

12 = ampacity at desired ambient TA2 TC conductor temperature in degrees C TA1 = ambient from tables in degrees C TA2 = desired ambient in degrees C

TC-TA,

1019


20/22

covered and insulated aluminum wire and coble

TABLE 10-9A Ampacities of TwoConductor ConcentricNeutral +Underground Distribution Cable fo r Direct Burial and for Installation in Buried Duct (see Figs. 1017 and 1018)

Ambient Temperature 20C Load Factor 100 Percent"The 7S'C ratings apply to cable with Hi-Mol Polyethylene Insulation.

The 90'C ratings apply to cables with Cross-Linked Polyethylene Insulation. The left-hand entries of any pair are ampacities when directly buried.

The right-hand entries are ampacities when in duct.Conductor

15 kV90'C 75'C 9O'C

132-88 116-83 128-91174-115 152-108 168-119199-132 175-124 193-137226-150 198-141 218-155256-172 225-161 248-177

. 2 S k ~ J 35 kVize 5 kVIAWG or kcmil4211102/03/04/0250300

75'C i_ 90O5'C 75 OCT 90 0 C ..-120-80 I 1 4 ~ ~ 1 0 5 . - ~165-115158-104 I181-120 . 165-120205-136 I 190-135232-156264177304205336-229379-260

215-155291-195 258182 284-201 245170335-226 294209 324-230 280-200370-252 327-233 360-257 310220418287 366264 403291 350-250.. i

190-135210-150 190-135 210-1I240-170 215155 2401275-195 245170 275-1315225 280-200 315-2350250395-280

Ampacity v.lues for 5 kV and 15 kV cables are from ICEA tables; those 25 kV and 35 kV are from other industry sources.*Multiplying Correction Factors for Load Factors of 75 and 50 percent

75 percent Load Factor 50 percent Load Factor

15 kV 1.08 1.04 1.16 1.0725kV 1.08 1.04 1.16 1.07

Cable Rating Cable Cable in Cable Cable inkV Buried Duct Buried Duct5kV L 1.09 1.04 1.16--.. . I~ - i lL

+Refer to The Aluminum Association's Aluminum Underground Distribution Reference Book fo r additional typical inform

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product classification and technical data

TABLE 10-9B Ampacities of Two-Conductor Concentric-Neutral Underground Distribution Cable when Installed in Air or in Duct in Air (usually as leads from an underground buried or duct installation) (see Figs. 10-17 and 10-18)

Ambient Temperature 40 CThe 75'C ratings apply to cable with Hi-Mol PolyethyleneInsu lation.The 90C ratings apply to cable with Cross LinkedPolyethylene Insulation.The left-hand entries of any pair are ampacities for cable onlyin air. The righthand entries are ampacities when cable is in duct, in air.

Cond. 5kV 15kVAWG/kcmil 75C 90C 75'C gooC

4 75-65 9076 8168 95792 103-86 120100 107-88 1251031 119-99 139116 124102 145119110 137-112 160131 142116 166-1352/0 159128 186149 163-132 1901543/0 181-146 211170 187151 : 2181764/0 212-169 247-197 217-172 i 253201250 238-188 278219 244-1931285.225300 273214 319250 278218 324254

Ampa.lty values are from ICEA tables.

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aluminum cables for power distribution aech_chapter_10

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