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TABLE 2

IDdaIDSOS-WPRectangularDusbar: CurrentRatings

,,- ~ ,,;::..,, ' ""-'-" ->--- --- ,--~._-'

Notes: 1. Ratings are for 50° C rise over 35' C ambient temperature in still but unconfined air.2. For. multiple-bar arrangements, the space between bars is equal to the bar thickness.3. A.C. ratings are based on spacings at which proximity-effcct is negligible.4. Ratings may be increased by approximately 20% if the busbar is painted with a non-metallic matt finish paint.5. To obtain the current rating for Indal CI5-M busbar, multiply the approl?riate figure above by 1.03.

i

--':--'

. . G1 BAR 2 BARS 3 BARS 4 DARS

Size mm IndalD.C.! 50cIs I

D.C. 50cIsI D.C. I

50 cIsI D.C. \

50cIs(in.) Ref. No. A.C. A.e. A.C. A.C.

AMPERES

25.4x6.35-r--. F204(I xi> 355 355 710 70S 980' 970 1120 1100

38.1x6.3S--... F13(Itx1) 520 520 1030 1020 1380 1350 1585 1535

50.8 x6.3s......,-- F15 670 670 13i5 1290 1765 2050(2x i) , 1705 1940 I63.5 x6.35.... " . '

(21xH - F74 820 810 1550 1510 2100 2000 2430 2260

76.2x6.35--- F33(3X t) 970 960 I 1805 1740--- 2440 2310 2860 2620

'.101.6x6.35. - :.-=-(4'X1) 36 1260 - i235 . 2260 2140,) 3060 2800 3640 9200127.0x6.35... .......

(5xt) -- F249 ' 1545 1505 2700 2510 3660 3240 4410 3700152.4x6.35, -- F271 1840 1780 3130 2860 4290 3680(6xl) 5250 4240

,

Sizemm Indal 50Cf.sI D.C-

50 Cf.s 50 s 50cIs

(in.) Ref. No', D.C. A; C. A.C. D.C. A.. D.C. A.C.

SO.8x9.53 'F16 840 830 1560 1500 2090 1970 2460 2260

(2x i)-.

76.2x9.53 F182 1210 1180 , 2180 2050 2940 2660 3510 3030

(3x i) ( F 96 1495 2710 2480 3660101.6 x9.S3 1550

3150 4400 3560

(4x i>127:0x9.53 F113 1940 1860 3290 2930 4450 .3660 5400 4200

(5xt)152.4x9.53 F272 2260 2120 3770 3340 5140 4080 6300 4680

(6xi) F273 2750 4800 4150 5740203.2x9.53 2940 6500 4900 8060

(8 Xi)

76.2x 12.1- F 34 1405 1355 2450 2240 3290 2830 4000 3240

(3xH' 1740101.6xI2.7 F 66 183Q 3100 2729 4170 3360 5100 . 3900

(4XI) ,

.'

127.0xI2.7 FI44 2230 2080 3720 3120 5040 1900 6170 4550

(5 x i)

152.4xI2.7 F 67 2620 2420 4300 3500 5850 4400 7200 5100

(6 x I) 5450 4450 ' 7420 6150203.2 x12. 7 F 54 3380 3060 5300 9110

(8 x i) 4080 3640 6500 5000 8860 6000 10900 68502S4.0x12.7 F 69(IOxi) '.

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TABLE 5

Correction Factors(To be applied when necessary to the rating values given In Tables 1 to 4)

'"

* These factors apply only to non-m9.gnetict.nclosur.::sin whic~ negligibleheat is induced by the current in the' busbar. .

** To be applied to the ratings for Indal DSOSWPin Tables 2, 3 and 4.The factors are approximate.

*** Electrical-purity aluminium, material ElEM, IS: 5082-1969 (WroughtAluminium and Aluminium Alloys for Electrical Purposes-Bars and

'" Sections).

-'C'C' - -:~--~ --,-,.. uC ',co ~Z~.-,.:',~,:::~='~''''l

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\(heating in the plates. The plates must. be sufficiently" thickto prevent distortion and ensure even contact pressure. Thepreparation of the mating surfaces is exactly as detailed earlier.

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An advantage of clamp plates is that they can be used onprefabricated bars when the e~act dimensions of the site are notavailable, or when detailed installation drawings have not beenprepared. They also eliminate the precision drilling of joints inmultiple bars.

Alwl1in~um-to-CopperConnections :Exactly the same procedures as are detailed above (including

the method of cleaning) should be used iQ.making aluminium~to~copper connections. Preferably, the copper should be cleanedwith a separate wire brush or emery cloth that will not after-

. wards be used on' ~luminium-to-aluminilim joints. Since inaluminium-to~copper joip.ts two dissimilar metals are in electricaJcontact, it is necessary to ensure that moisture is excluded: ifno moisture is present, there is no possibility or electrolytic action;The grease used as a jqint compound, will protect an indoor in-staUatfon in clean surroundings. In particularly aggressive condi:'

. tions:f~rther protection can be obtained by binding with an inhibi-ted tape. This method of protecting aluminium-to-copper jointshas been proved by many years of experience of bi-metallic jointsin overhead distribution lines. '

Other methods of protecting a joint against the ingress ofmoisture include painting or coating with plastic compounds.

,In aUbi-metallicjoints that are subject to rain or considerable,condensation it is advisable to have the aluminium bar abovethe copper one to avoid the risk of water contaminated withcopper salts running on.1o the aluminium bar.

In considering bi-metallic joints it should be borne in mindthat any busbar carrying current will be above ambient tempe-rature and js therefore more likelyto be dry than are the surround-ings. If it is dry there will be no electrolytic re~ction.

. 64

TemperatureRise Derating Factor, -

1. Bar temperature rise 40°Coverambient 35°C 0.88

2. Bar temperature rise 30°Coverambient 35°C 0.75

..'

Cross-Sectional '<.'Area of Busbar

Enclosure + Total Cross- Derating,- SectionalArea Factor*

of Enclosure----1. Outdoors <1% 0.95

5% 0.9010% 0.85

2. Indoors where the enclosure itself is <1% 0.85-...in a well-ventilated room ' 5% 0.75,

10% 0.65"

3. Indoors where the enclosure itself <1% 0.65is poorly ventilated and the room 5'

g.,temperature is high 10Yo .,

IS: 733-1967 (Wrought Aluminium andAluminium Alloys for 'General Engi- Indah-\lIoy Ratingneering Purposes-Bars, Rods and Factor**Sections) Symbol - ,-

- *** CISM 1.03EIC-M 2SM 1.02HEI5-WP B26SWP 0.83HE9-WP 50SWP 0.94HE30-WP B51SWP 0.92NES-M 54SM 0.77NE6-M A56SM 0.72HE-20WP 65SWP 0.88

ALTITUDE

Where busbar intended for use at high altitudes is tested near sealevel, the limits of. temperature rise should be reduced by 1% for each300m in excess of 1000m above sea-level at which the busbar is to beinstailed.

- - ----- ---

TABLE 6

Derating Factors for Proximity-Effect: Three-Phase Channel InstallationTwo Channels Per Phase In Box Form

.. Width is taken as,,the horizontal measurement W, in Table 3.

TABLE 7

Clearances for Open and Enclosed Indoor Air-Insulated Busbar and, Connections(Electrically Non-Exposed)

Clearances for Open Outdoor Busbar and Busbar Connections Not 'Exceeding15 kV Rated Voltage for Electrically Exposed or Non-ExposedInstallations

~

. The clearances quoted in Tables 8 to 12 should be regarded as theminimum values which should be used in any circumstance.

Busbar for use in systems with special requirements or 'conditionsrequires special consideration and reference phould always be madeto -the details included in B.~. 159: 1957 (Busbars and Busbar Con-nections), from which Tables 8-12 have been taken. .

-,Phase Spacing.. Derating Factor

3 channel width 0.824 channel width 0.895 channel width 0.956 channel width 0.99

Rated Minimum MinimumVoltage C!e.aranceto Clearance in

kV Earth in Air Air Betweenmm Phases mm

Not exceeding6.6 140

I

17811 178 22915 216 267

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Determination of Short-Circuit Heating

It is assumed that when a through short circuit flows in ,abusbar all the heat produced is devoted to raising the tempera-ture of the conductor and none escapes by convection or radia-tion in the very short time of the fault. By equating the heat pro-duced and the heat stored it foIlows tha.1 for aluminium alloybusbar (TNDAL D50SWP) :

l.e = 2.17 x 1()4 A

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or = 2.17 x 1()4 A / [Og~

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And for 100% lACS copper bu~bar :

lie == 3.41 X 104 A //og1ofl +0.00395 (Op-20)]. if"" T 'V II +0.00395(01- 20)

or = 3.41 x 104 ~, jloglo

[

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Where 0p = final conductor temperature after the fault (° C)81 == initial conductor temperature before the

fault COC)

A = cross sectional area of conductor (sq. em.)T = duration of fault (sec.)

In the above equations the specific heat of Indal D50SWPhas been taken as 0.21 and that of copper as 0.092.

From these equations it foIlowsthat for busbar of equal area,aluminiumalloy will carry 64%the short-circuit cunent of copperfor the same temperature rise. For bars of the same continuouscurrent-carrying capacity the aluminium aIloy will carry 90-95%the short-circuit current, and fo rbars of equal resistance the'aluminium aIloy bar will carry 120~~ the current that a copper

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