IS : 3961 ( Part 1 ) : 1967

( Reaffirmed 1996
( Reaffirmed 2001) )

Indian Standard
RECOMMENDED CURRENT RATINGS
FOR CABLES
PART 1 PAPER-INSULATED LEAD-SHEATHED CABLES

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Tenth Reprint SEPTEMBER 1997
( Incorporating Amendment No. I )

UDC 621.315.221.5.02 : 621.315.614.6

I%IJREAU OF INDIAN STANDARDS

MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002
 IS : 3961 (.Part I ) - 1967

Indian Standard
RECOMMENDED CURRIZNT RATINGS
FOR CABLES
PART I PAPER-INSULATED LEAD-SHEATHED CABLES

Conductors and Cablea Sectional Committee, ETDC 32

Chairman Representing 1

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SHRIK. MATTHAN Federation of Electricity Undertakings of India Ltd,
Bombay
Members
SHRI K. 'I'.
CHAIJRAL (~ltcwnte to
Shri K. Matthan )
SHRI S. D. BANA Gujarat Electricity Board, Baroda
SHRIJ. H. PATEL ( ll/tCmtC)
SIIRI L. C. BANSAL Electrical Manufacturing Co Ltd, Calcutta
SHRI R.K. SENCUPTA (Afternote)
SHRI P. K. B~~ARIJC~~A Insurance Association of India, Bcmbay
SHRI A. C. MODY ( Alfernate)
SJZRI M.R. BEIAT Bombay Suburban Electric Supply Ltd, Bombay
SHRI N. N. CI~AKRABORTI 13ectrical Inspector to the Government of West
Bengal, Calcutta
SHRI M. L. DONC.RE Bombay Electric Supply & Transport Undertaking,
Bombay
SHRI S. D. CHOTRANEY ( All~rnate)
CDR N. G. FADNAVIS Naval Headquarters
LT CDR N.N. MIJKERJIX (&t~rnnt~)
SHRI N. P. GHOSH Inspectorate of Mints (Ministry of Labour &
Rehabilitation ), Dhanbad
SEIRl IT. I<.&<XTTAClIAI:Jl-I?
( /f!tPWZte)
SHRI K. C. GROVER Central Public Works Department
SHRI S. I).Inorr~p ( Affernate)
SHRI 11.T. Grrnsnrr~x~ Directorate General of Supplies & Disposals ( Inspec-
tion Wing ) ( Ministry of Supply, Technical
Devclopmrnt & Materials Planning )
SIIRI ,?.1~.I<APUR ( ,,/tfVUtP)
SIIRI HA~NAMSINCF~ Controller Gcnraral of Inspection & Planning
( Ministry of Defcnce )
&RX S. R. MANX ( Ahmnte )
SHRI A. K. KAIIALI Indian Cable Co Ltd, Calcutta
&RI N. v. IcAMAN (~km~e)
SITRI S. K. KANJILAL Railway Board ( Ministry of Railways )
SIIRI N. PA~~MANA~I~AN ( _&lernale )
SHRI1>.M. IdAM Directorate General of Posts & Telcgtaphs ( Depart-
ment of Communications ) ( Ministry of Trans-
port & Communications )
DIVISIONAL ENGINEER TELE-
GRAPIIS (C) ( Alternnfr )

BUREAU OF INDIAN STANDARDS

M..A,NAKBHAVAN, 9 BAHADUR SHAH ZAFAR MARC3
NEW DELHI 110002
B : 3961( Part I ) - 1967

4 Continuedfrom page 1)
Members Representing
Wo GDR D. J. LADLER Directorate of Technical Development & Production
(Air ) ( Ministry of Defence )
SQN LDR H. S. BHATIA ( Altematc )
SHRI M. R. LODH Devidayal Cable Industries Ltd, Bombay
SHRI KAMAL A~QARWAL ( Alternate )
Stiar A. K. MITRA Calcutta Electric Supply Corporation Ltd, Calcutta
SHRI P. S. SRINIVA~A MODALUR Radio and Electricals Manufacturing Co Ltd,
Bangalore
SHRI V. R. CHANDER( Alternate )
SHRI S. N. MUXERJI National Test House, Calcutta
SHRI B. K. MUKHHRJ~E( Alternate 1

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SHRI P. MUKUNDAN -Hindustan Cables Ltd, Rupnarainpur
SHRI R. SEN ( Al&ma& )
SHRI H. V. NARAYANARAO Central Water & Power Commission ( Power Wing )
SHRI S. S. MURTHY 4 Alternate )
SHEI V. G. G. NAYAR Oriental Power Cables Ltd, Kota
SHRI K. S. .TOSHI (Alternate )
SHRI S. PEER M&~AM&D . Aluminium Industries Ltd, Kundara
SHRI S. N. .NAYAR ( Alternate )
SHRI B. H. RAI National Insulated Cable Co of India Ltd, Calcutta
SHRI J. S. BHAN ( Alternate )
SHRI A. K. RAYAN Asian Cables Corporation Ltd, Bombay
SHRI P. K. SANYARANARAYANAN
( Aleak )
SERI M. J. RAO Tata,Hydro-Electric Supply Co Ltd, Bombay
SHRI M. V. GONDHALEKAR ( Altmate )
SHRI i;. P. SAKENA Fort Gloster Industries Ltd, Calcutta
SHRI L. K. SANOHI ( Altemate )
Sm K. SRINIVASARAO Directorate General of Technical Development
I Heavv Electricals Directorate 1
fknr A. SUBRAXANIAM Madras S&e Electricity Board, Madras
SHRI A. T. SRE~HTA ( Altemab )
SHRI I.. R. SUBRAUANYAY Henley Cables ( India ) Ltd, Bombay
SHRI K. V. RAMA RAO ( Al&mate )
SHRI G. H. SWATEX Cable Corporation of India Ltd, Bombay
DR P. S. SHAH ( Alternate)
&RI Y. $5.VBNKATEBWARAN, Director General, BIS ( Ex-ojicio Member )
Director ( Elec tech ) ( Scnctary
)

Panel for Current Ratings of the Different Types of Cables,

ETDC 32/P5

SHIU N. V. RAMAN Indian Cable Co Ltd, Calcutta

&RI M. DEY ( Altunate )
SHRI R. RAMANUJ~ The Aluminium Industries Ltd, Kundara
SHRI S. KRISHNAMOORTHY ( Altemote )
S,mx H. V. NARAYANARAO Central Water 82 Power Commission
SH~I S. S. MURTHY ( Alternate )
S~pPSK~~A~uP~~~~~~~~N Asian Cables Corporation Ltd, Bombay
. . Cable Corporation of India Ltd, Bombay

2
 fS:3961(Partf)-1967

CONTENTS
PAGE
0. FOREWORD ... ... ... ... ,.. 7
1. SCOPE ... ... ... ... ... 8
2. BASICASSUMPTIONS ... ... ... ... 8
3. METHODS OF INSTALLATION ... ... ... 9
4. QIZESOF THE DUCTS ... ... ... ... 10
5. RATINGFACTORS ... ... ... ... 11

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6. EFFECTOF GROUPINGOF CABLESINAIR ... ... 11
TABLE 1 CURRENT RATINGS(ac AND.&) FOR PAPER-INSULATED
ARMOURED SERVED TWIN BELTED LEAD-C•VERFD
1.1kV CABLES ... ... ... ... 12
TABLE 2 CURRENT RATINGS(ac AND dc) FOR PAPER-INSULATED
UNARMOURED SERVED TWIN BELTED LEAD-COVERED
1.1kV CABLES ... ... ... ... 13
TABLE 3 CURRENT RATINGS (ac) FOR PAPER-INSULATED
ARMOURED SERVED THREE-, FOUR- AND FIVE-CORE
BELTED LEAD-COVERED1-lkV CABLES ... ... 14
TABLE 4 CURRENT RATINGS (ac) FOR PAPER-INSULATED
~!KX~RXC~YRED
SERVED THREE-,FOUR- AND FIVE-C•
RO
BELTED LEAD-COVERED1’1 kV CABLES ,.. ,.. '4
TABLE 5 CL!RRENTRATINGS ( ac AND dc) FOR .Two PAPLK-
INSULATED SERVED SINGLE-CORE LEAD-COVERED
I.1kV CABLES ... ... ... ... 15
TABLE 6 CURRENT RATI~VGS(ac) FOR THREE PAPER-INSULATED
UNARMOURED SERVED SINGLE-CORE LEAD-COVERED
l-1kV CABLES ... ... ... ... 16
TABLE 7 CURRENT RATINGS (ac) FOR PAPER-INSULATED
ARMOURED SERVED THREE-CORE BELTED LEAD-
CO-JERED3.3AND 6.6kV CABLES ... ... 16
TABLET CURRENT RATINGS (ac) FOR PAPER-INSULATED
UN~RMOURED SERVED THREE-CORE BELTED LEAD-
COVERED 3'3,AND6.6kV CABLES ... ... 17
TABLET CURRENT RATINGS (ac) FOR THREE PAPER-INSULATED
UNARMOURED SERVED SINGLE-CORE LEAD-COVERED
3.3AND 6.6kV CABLES ... ... ... 17

3
IS t 3961( Part f ) - 1967

PAGE
TABLE 10 CURRENT RATINGS ( ac ) FOR PAPER-INSULATED
ARMOURED SERVED THREE-CORE BELTED LEAD-
COVERED11 kV CABLES . .. ... ... 18

TABLE 11 CURRENT RATINGS ( ac ) FOR PAPER-INSULATED

UNARMOURED SERVED THREE-CORE BELTED LEAD-
COVERED11 kV CABLES ... ... ... 18

TABLE 12 CURRENT RATINGS ( ac ) FOR PAPER-INSULATED

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ARM~URED SERVED THREE-CORE SCREENED LEAD-
COVEREDOR THREE-CORESL 11 kV CABLES ... 19

TABLE 13 CURRENT RATINGS ( ac ) FOR PAPER-INSULATED

UNARMO~RED SERVED THREE-CORE SCREENEDLEAD-
COVERED11 kV CABLES .. . . .. ... 19

TABLE 14 CURRENTRATINGS( ac ) FOR THREE PAPER-INSULATED

UNARMOURED SERVED SINGLE-CORE LEAD-COVERED
11 kV CABLES ... ... ... ... 20

TABLE 15 CURRENT. RATINGS ( ac ) FOR PAPER-INSULATED

ARMOURED SERVED THREE-CORE SCREENED LEAD-
COVEREDOR THREE-CORESL 22 kV CABLES ... 20

TABLE 16 CURRENT RATINGS ( ac ) FOR PAPER-INSULATED

UNARMOURED SERVED THREE-CORF: SCREENEDLEAD-
COVERED22 kV CABLES ... ... ... 21

TABLE 17 CURRENTRATINGS ( ac ) FOR THREE PAPER-INSULATED

UNARMOURED SERVED SINGLE-CORE LEAD~COVERED
22 kV CABLES ... ... ... ... 21

TABLE 18 CURRENT RATINGS ( ac ) FOR PAPER-INSULATED

ARMOURED SERVED THREE-CORE SCREENED LEAD-
COVEREDOR ‘~‘HREE-CORESL 33 kV CABLES ... 22

TABLE 19 CURRENT RATINGS ( ac ) FOR PAPER-INSULATED

UNARMOUREDSERVED THREE-CORE SCREENEDLEAD-
COVETED,33 kV CABLES . .. ... ... 22

TABLE 20 CURRENTRATINGS( ac ) FOR THREE PAPER-INSULATED

UNARMOURED SERVED SINGLE-CORE LEAD-COVERED
33 kV CABLES ... ... ... ... 23

TABLE 21 RATING FACTORSI;OR DEPTH OF LAYING ( POR CABLES

LAID DIRECTIN THE GROUND ) ... ... 23

TABLE 22 RATING FACTORSFORVARIATIONIN GROUND TEMPERA-

TURE( EORCABLES LAID DIRECT IN THE GROUND ) . .. 24

4
 !S : 3961 ( Part I ) .- 1967

PAGE

TABLE 23 RATING FACTORSFOR VARIATIONIN THERMALRESISTI-

VITY OF SOIL ( TWIN AND MULTI-CORE CABLESLAID
DIRECTIN THE GROUND) ... . .. . .. 24

TABLE 24 RATII;JGFACTORSFOR VARIATIONIN THERMALRESISTI-

VITY OF SOIL, Two AND I’HREE SINGLE-CORECABLES
LAID DIRECTIN THE GROUND . . . ... ... 25

T&IX 25 GROUP RATING FACTORSFOR TWIN AND MUL.TI-CORE

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CABLES IN HORIZONTAL FORMATIONLAID DIRECT IN
THE GROUND ... ... ... ... 26

TABLE 26 GROUP RATING FACTORSFOR TWIN AND MULTI-CORE

CABLES IN TIER FORMATION, LAID DIRECT IN THE
GROUND ( FOR 1.1 TO 33 kV CABLES) ... ... 26

TABLE 27 GROUP RATING FACTORSFOR CIRCUITSOF Two SINGLE-

CORE CABLESSIDE BY SIDEAND TOUCHING,HORIZONTAL
FORMATION,LAID DIRECT IN THE GROUND ... 27

TABLE 28 GROUP RATING FACTORS FOR CIRCUITS OF TZIREE

SINGLE-CORE CABLES IN TREFOIL AND TOUCHING
HORIZONTALFORMATION,LAID DIRECTIN THE GROUND 27

TABLE 29 RATING FACTORS FOR DEPTH OF LAYING (TWIN AND

MULTI-CORE CABLESIN SINGLE-WAY DUCTS) ... 28

TABLE 30 RATINGFACTORSFORVARIATIONIN GROUND TEMPERA-

TURE ( FORARMOUREDCABLESIN DUCTS) ... 28

TABLE 31 RATING FACTORSFOR VARIATIONIN GROUNPTEMPERA-

TURE ( FORUNA~MOUREDCABLESIN DUCTS) ... 29

TABLE 32 RATING FACTORSFOR VARIATIONIN THERMALRESISTI-

VITY OF SOIL ( TWIN AND MULTI-CORE CABLES IN
SINGLE-WAY DUCTS) ,.. . .. ... 29

TABLE 33 RATING FACTORYFOR VARIATIONIN THERMAL RESISTI-

VITY OF SOIL ( Two AND THREE SINGLE-CORECABLES
IN DUCTS) ... ... ... .. . 30

TABLE 34 RATING FACTORS FOR MULTI-WAY DUCTS ( FOR USE

WHEN A MULTI-WAY DUCT DOES NOT CONTAINTHE
FULL NUMBEROF LOADEDARMOUREDCABLES) ... 31

FIG. 1 RATING FACTORSFOR WIRE-ARMOUREDCABLES IN MULTI-

WAY DUCTS ... ... ... .., 31

5
IS:3961( Part I ) - 1967

?AGE
TABLE 35 GROUP RATING FACTORSFOR TWIN AND MULTI-CORE
CABLESIN SINGLE-WAY STONEWAREDUCTS AND IRON
PIPESIN TIER FORMATiON ... ... ... 32

TABLE 36 GROUP RATING FACTORSFOR SINGLE-CORE CABLES IN

TREFOILSTONEWAREDUCTSIN TIER FORMATION .. . 33

TABLE 37 GROUP RATING FACTORS FOR TWIN AND MULTI-CORE

CABLESIN SINGLE-WAY DUCTS AND PIPES,IN HORIZON-
TAL FORMATION .., ... ... ... 34

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TABLE 38 GROUP RATING FACTORSFOR SINGLE-CORECABLES IN
TREFOILDUCTS, HORIZONTALFORMATION ... 34

TABLE 39 RATING FACTORS FOR THREE UNARMOURED SINGLE-

CORE CABLES( ac ) IN FLAT FORMATIONIN AIR ... 35

TABLE 40 RATING FACTORS FOR VARIATION IN AMBIENT AIR

TLZMPERATURE . . . ... ... ... 35

6
 IS:3961(PartI)-1967

Indian Standard
RECOMMENDED CURRENT RATINGS
FOR CABLES
PART I PAPER-INSULATED LEAD-SHEATHED CABLES

0. FOREWORD

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0.1 This Indian Standard ( Part I ) was adopted by the Indian Standards
Institution on 26 June 1967, after the draft finalized by the Conducton
and Cables Sectional Committee had beeri approved by the Electrotechnical
Division Council.
0.2 This standard has been drawn up to provide to the users general
guidance for loading of cables. The over-loading of cables will reduce the
life expectancy of the cable and at the same time under-loading it will
mean unecbnomic utilization of its capacity: Depending upon the
loading cycle met with in practice, the installation engineer may decide
the economic loading of cables.
0.3 The current ratings given in the standard have been drawn up on
certain assumptions pertaining to soil conditions prevalent in this country,
permissible temperature-rise of insulating materials, conductor, etc. It is,
however, to be expected that these conditions may be somewhat different
in different places in a vast country like ours. In such cases the installa-
tion engineer’ is expected to keep in mind the loading conditions, the soil
and atmospheric conditions in the area, etc, before deciding on the choice
of the proper size of cable.
0.4 For cables laid direct and in underground ducts, ratings have been
provided corresbonding to the value for the thermal resistivity of the soil
as 1~0°C cm/W as agreed to by IEC for tropical climates. This covers
the value commonly encoufitered in India, but ratings corresponding to
other values can be determined from rating factors given in Tables 33 and
34. It is, however, emphasized that actual measurements of soil thermal
resistivity at the proposed depth of laying should be made along the route
prior to laying the cables where practicable and the cable ratings .based
upon the values so determined..
0.5 The permissible current ratings have been specified for three commonly
adopted conditions of installation, namely, laid direct in ground, laid in
ducts, and for cables in air.

7
IS t 3961 ( Part I ) - 1967

0.6 This is one of the series of Indian Standards on recommended current

ratings for various types of cables. Others in the series are:
IS : 3961 ( Part II’)-1967 Recommended current ratings for cables:
Part II PVC insulated and PVC sheathed heavy duty cables
IS : 3961 ( Part III )-I968 Recommended current ratings for cables:
Part III Rubber insulated cables
IS : 3961 ( Part IV )-I968 Recommended current ratings for cables:
Part IV Polythene insulated cables
IS : 3961 ( Part V )-I 968 Recommended current ratings for cables:

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Part V PVC insulated light dutv cables and wires

0.7 In preparing this standard, assistance has been derived from the
following:
ERA Report No. F/T 183 Current ratings for paper insulated cables
to BS 480 : 1954 and Varnished-cambric insulated cables to
BS 608 : 1955. British Electrical and Allied Industries Researct
;Association, U.K.
IEE Wiring regulations. Instnute of Electrical Engineers, U.K.

0.8 For the purpose of deciding whether a particular requirement of this,

standard is complied with, the final value, observed or calculated, express-
ing the result of a test or analysis, shall be rounded off in accordance with
IS : 2-1960*. The number of significant places retained in the rounded off
value should be the same as that of the specified value in this standard.

1. SCOPE
1.1 This standard ( Part I ) co\ :rs recommended current ratings for paper-
insulated lead-sheathed cables covered by IS : 692-1973t, either laid direct
in ground, in ducts or in air.

2. BASIC ASSUMPTIONS
2.1 The current ratings given in Tables 1 to 20 in the standard are based
on the following assumptions:
a) Maxrmum Conductor Temjurature - The maximum conductor tem-
peratures assumed for various voltage classes and types of cables

*Rule for rounding off numerical values ( rrvisrd).

tSp&fication for paper insulated lead-sheathed cables for electricity supply ( SmOd
WiSilW).

8
 ISt3961 ( Part I ) - 1967

are given in the folJowing table:

Maximum
V0ltlJgt Type Conductor
Temperature
OC
i) 1.1 kV cables Single-core 80
Twin and multi-core ( belted) 80
ii) 3.3 and 6.6 kV Single-core 80
cables { Three-core ( belted ) 80
r Single-core ‘70

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iii) 11 kV cables Three-core ( belted ) 65
I Three-core ( screened ) 70
Single-core
iv) 22 kV cables Three-core ( screened) and s6;
-I three-core SL
r Single-core 65
v) 33 kV cables Three-core ( screened ) and 65
t three-core SL
NOTE-Unarmoured cables laid direct in ducts are subjected to
additional regulations that maximum permissible temperature-rise above
ambient shall not exceed the following:
1.1, 3.3 and 6.6 kV cables 45%
11, 22 and 33 kV cables 35oc

b) Thermal Resistivity of Soil 150°C cm/W

cl Ground Temperature 30°C
4 Ambient Air Temperature 40%

e>top De$th of Laying - to the highest point of cables laid direct or to

surface of ducts, is taken to be as follows:
1.1 kV cables J50 mm
3.3, 6.6 and 11 kV cables 900 mm
22 and 32 kV ca’jles 1 050mm
NOTE- In the case of twin and multi-core cables ( except SL cables ) with
conductors of sizes 25 mm* and above, tire current ratings given are for sector shaped
conductors. For round conductors, tire current ratings would be somewhat lower.

3. METHODS OF INSTALLATION
3.1 The current ratings given in this standard are for methods of installa-
tion as given in the following table:
Type of Cable Tyke of Installation Method of Installation
Single-core a) Laid direct in the i)Three in trefoil groups
ground touching, or
ii) Two in horizontal formation
touching

9
ISr3961(PartI)-1967

Tyjc of Cab16 Tyje of Installation Method of installation

Single-core b) In ducts i) Three in trefoil ducts, or

( contd)
ii) Two in horizontal formation

c) In aQ i) Two single-core cables

installed one above the
other fixed to a vertical wall
as follows, the distance bet-
ween the wall and the
surface of the cable being

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25 mm in each case:

1) Cables of sizes up to and

including 185 mm2 are
installed at a distance
between centres of twice
the overall diameter of
the cable
2) Cables of sizes 225 mm2
and above are installed at
a distance between centres
of 90 mm

NOTE - The ratings for two

cables may be applied with
safety in cases where such
cables are installed in horizon-
tal formation, on brackets fixed
to a wall, either spaced as
indicated above or touching
throughout.

ii) Three single-core cables in

*refoil groups touching

Twin and multi- Installed singly

core

4. SIZES OF THE DUCTS

4.1 The current ratings specified in the tables apply to cables laid in ducts
of inner diameter, 100, 125 and 150 mm and are based on the use of
arthenware ducts with a thermal .resistivity of 120°C cm/W. They,
however, apply with sufficient accuracy to fibre ducts and cast iron pipes.
The latter will not be used for individual single-core cables on ac systems,

10
 ES: 3961( Part I ) - 1967

5. RATING FACTORS
5.1 The current ratings given in the respective tables apply to continuous
loading of cables under the specific conditions of installation mentioned
$2.1,3.1 and 4.1. For the various rating factors which may have to be
used under different conditions, reference shall be made to tables as shown
below:
Ref to Table No.
a) Cables Laid Direct in the Ground

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i) For depth of laying 21
ii) For variation in ground tcm- 22
perature
iii) For variation in thermal 23 and 24
resistivity of soil
iv) For group rating factors 25, 26, 27 and 28

b) Cables Installed in Ducts

i) For depth of laying 29
ii) For variation in ground tem- 30 and 31
perature
iii) For variation in thermal 32 and 33
resistivity of soil
iv) For cables in multi-way ducts 34 and Fig. 1
v) For group rating factors 35, 36, 37 and 38

C) Cables Itvtallcd in Air

i) For three unarmoured single- 39
core cables in flat formation
in air
ii) For variation in ambient air 40 -
temperature

6. EFFECT OF GROUPING OF CABLES IN AIR

6.1 For cables of sizes up to 70 mm2, no reduction in rating need be
applied provided that the circuits are run with a clearance of at least
7.5 cm; and provided that if the number of circuits exceeds three, they are
installed in a horizontal plane. For cables of sizes above 7.0 mm2 no
reduction in rating need be applied provided that the circuits are run
with a clearance of at least 15 cm; and provided that if.the number of
circuits exceeds four, they are installed in a horizontal plane.
 TABLE 1 CURRENT RATINGS (ac AND dc ) FOR PAPER-INSULATE& ARMOURED
SERVED TWIN BELTED LEAD-COVERED i-1 kV CABLES

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Gi
( Chre 2.1 )

NOMINAL DIRECTIN THE GROUND IN SINGLE-WAYDUCTS IN AIR 2

AREA OP ‘~~---_---_-_-_-,~ c-c----- -_-- y-_---A- ?,
COlVDUCrOR Direct Alternating Direct Alternating Direct Alternating’
Current Current Current Current Current Current q
__:-A--_ _--_.A- -- ---- ----- ---h---B t---b ’
“Copper Alumi- * Copper Alumi-‘ ‘Copper Alumi-w kopper Alumi- Copper
__ Alumi- Copper __ Alumi- g
nium nium -_ nium _ mum nium nium h
q

(1) ‘(2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)

mms A A A A A A A A A A A A

;5 6 57 45 57 45 41 51 41

:,” 1:;
61 77
lb0 ;;
it3
89 2:
68
89
::
69
7°F
93 2
93
50
125
155
190
2
120
150
::z
190
98
120
150
120
140
165
90
110
130
120
140
165
90
110
130
120
150 115
145
150
190
1;;
145
70 E 270
230 180 205 160 205 160 ;E! 185 235 185
222 210 190 220 280 220
1:; 310 240 310 ;z E E 210 3E 255 320 255
150 355 275 345 :A 315 245 310 240 375 220 370 290
185 315 395 310 $65 275 420 335
225 ztz 315
280 % 310 :z iii 475 375
470 355
370 :.E 345
355 % 325 405 320 510 400 495 390
;ii 530 415 400 475 370 445 355 590 460 570 440
620 480 Ei 455 570 520 415 710 560 670 530
z 510 640 iit 570 465 820 650 740 600
625 E t: 630
700 590 740 590 630 520 980 770 850 710

NOTE- For basic assumptions and method of installation, ZII 2 and 3.

 TABLE 2 CURRENT RATINGS ( ac AND dc ) FOR PAPER-INSULATED UNARMOURED
SERVED TWIN BELTED LEAD-COVERED 1-l kV CABLES

( Clause 2.1 )

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NOMINAL DIRECTINTHE GROUND IN SINGLE-WAY Ducm IN AIR
AREA OF , _---L--y -_-_---A__----~
r
C-_-_--h ------__
CONDUCTOR. Direct Direct Alternating Direct Alternating’
Current Current Current Current Current
_--L_-, _A- _-- rc--A--y _--h-_, ----~--~ c__-_+
‘copper Alumi-. ‘Copper Alumi-‘ ‘copper Alumi: ‘Copper Alumi: ‘Copper Alumi- Copper Alwmi~
nium nium nium nium nium

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)

mm* A A A A A A A A A A A A

59 46 59 46 49 38 49 38 52 41 52 41
62 55 69
1;:
130 1E
1::
130
f;
105
5:
110
;: 8”;
110
:A
1::
f;
150
120 z3 1%
:2”

160 125 160 125 130 lo”; 130 115 150 1;:
195 150 195 150 160 125 160 125 185 145 185 145
235 185 235 185 195 150 195 150 230 180 230 180
95 275 220 275 220 230 185 230 185 275 220 270 220
120 313 245 310 245 265 205 260 205 320 250 320 250 z. .
150 360 280 355 280 300 235 300 235 370 290 420
370 290
335 g
185 410 320 405 320 340 270 340 270 430 340 Q1
225 460 450 355 385 300 380 385
240 475 E 465 370 400 310 395 % 510
490 E 395
380 ,’
3Q0 543 420 530 420 450 350 445 350 590 2: 580 455
630 490 600 480 540 415 510 410 710 560 690 550 ?
400
500 710 530 670 540 600 470 570 465 820 650 780 640 :!
625 820 640 770 640 700 660 550 980 770 900 760 ,”
I
NOTE - For basic assumptions and method of installation, see 2 and 3. r
I$:
- 4
IS : 3961(Part I ) - 1967

TABLE 3 CURRENT RA INGS ac) FOR PAPAR-INSULATED

ARMOURED SERVED TIi&-, F&R- AND FIVECORE BELTED
LEAD-COVERED 1-l kV CABLES
(Clause 2.1 )
NOMINAL DIRECT IN GROUND IN SINGLE-WAY Ducm INAIR
A REA OF r---rr--, r-_h_--r____h-___,~

CONDUCTOR copper Aluminium Copper Alutninium Aluminium

(1) ‘“A ‘2 (5) , (7)
mm1 A A ‘A
42
3:
65
57
74
105
130 l”do 1;:

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

155 125 140

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY

190 150 170
-95 220 175 200
120 255 195 230
150 290 225 260
185 335 295
225 370 2’z
240 385 300 Pii
300 425 385
485 3zi 435
% 530 420 470
625 570 475 510 430 610
NOTE - For basic assumptions and method of installation, sea 2 az?3.

TABLE 4 CURRENT RATINGS ac) FOR PAPER-INSULATED

UNARMOURED SERVED THR d E, FOUR- AND FIVE-CORE
BELTED LEAD-COVERED 1.1 kV CABLES
( Claw 2.1 )
NOMINAL DIRECTIN GROUND IN SINGLE-WAY Ducrs IN AIR
AREA OE F----h----\ p-h ----_-_-_
CONDUCTOR Copper Aluminium Copper Aluminium’ ’ Copper Aluminium
(1) ‘2 ‘“d ‘2 (“A. (;J (2
mms
6 48 38 41 32 43 34
z: 59
:6” :: :: E f!E
25 110 1;: 81
!30 1z 110 z 125
:z 160 125 135 105 160 1E
70 200 155 165 130 155
230 185 195 185
1;; 265 205 225 175
155 E 220
150 300 245 255 200 320 255
i85 345 270 290 225 370 295
225 385 250 420 335
240 400 % 330
320 350
300 440 350 365 290
260 E 395
400 500 400 430 345 600 480
500 395 670 550
625 2: zz; 530
485 440 780 650
Nom -For basic assumptions and method of installation, see 2 and 3.

14
 TABLE 5 CURBENT RATINGS ( ac AND de ) FOR TWO PAPER-XNSULATED
SERVED SINGLE-CORE LEAD-COVERED I.1 kV GABLES

( CIaurc2.1 )

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
NOMINAL DIRECT IN THE GROUND IN Ducx IN AIR
AREA OF WITH SERVINGS TOUCHING r------ -_---_ y-w_- L--w-
CONDUC- y---- *------T Direct Current Direct Current Alternating Direct Current Alternating
TOR Direct Current Alternating Armoured Unarmoured __ Current Axmoured or tiurrent
Armoured or L;urrent r--_--_ r-_-h_? Unarmoured Unarmourcd Unarmoured
Unarmoured Unarmourcd Copper Alumi- Copper Alumi- T-T+---iC---A---%
c-*-+---T nium nium Copper Alumi- Copper Alumi- Copper Alumi-
Copper Alumi- Copper Alumi- nium nium nium
nium nium

(1) 12) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15)
mm2 A A A A A A A A A A A A A A
t:
61 58 45 58 45 59 47 59 47
1: :6” 2; f: 2: tf 59 63 63
110 110 1:: 83 1:: 5: 1;: 1:: 1::
:5 ‘140 IC 1;: 140 110 130 105 130 1;: 1c 1:
35 165 130 :: 130 165 130 155 125 155 125 :g 135 :E 135
205 155 205 155 200 155 190 150 190 150 215 170 215 170
;8 250 190 250 190 245 190 230 180 230 180 270 210
95 290 230 290 230 290 230 270 219 270 210 ::: % 325 250
120 330 265 330 265 330 255 310 240 305 240 380 300 380
150 380 300 380 300 380 290 360 280 350 275 440 350 440 :z
185 430 340 425 335 330 410 315 395 310 510 400 510
225 380 470 370 % 370 455 350 430 340 580 455 570 :8
240 % 395 490 385 490 385 470 365 445 350 600 475 590 470
300 570 450 550 440 440 530 415 390

%
670
760
520
!%
510
570
%
730
510
580
630
710
485 %
zz:
fE
950
%
750
Ei
920
zz
750
625 880 % 780 650 840 660 820 ;z zz 560 1 120 880 I 060 880
NOTZ - For basic assumptions and method of installation, set 2 and 3.
IS : 3961( Part I ) - 1967

TABLE 6 - CURRENT RATINGS ( ac ) FOR THREE PAPER-

INSULATED UNARMOURED SERVED SINGLE-CORE LEAD
COVERED 1’1 kV CABLES
( Clausr 2.1 )
NOMINAL TREFOILGROUPS LAID IN TRE FOIL DUCTS IN TREFOILGROUPSIN
AREA OF DIRECTIN IHE GROUND r----*----~ AIR WITH SERVINGS
CONDUCTOR WITH SERVINGS TOUCHING Copper Aluminium TOUCHING
c-- ----_--- r-_---_-Y
Copper Aluminium Copper Aluminium
(1) S) ‘2 2). (2 ‘2 “A
mm2

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
6 42 54 42

;: ;: 56
70 ;:
90 3:
71 ; 57
77
25 1% 90 120 l?l 125 98
3; 140
170 130
110 165
140 135 160
195 150
120

70 205 160 200 160 240 190

1% 240
270 210
190 240
265 205
185 290
335 225
260
150 305 240 300 235 385 300
185 345 275 330 260 445 350
225 380 305 365 285 500 395
240 395 315 380 295 520 410
300 445 355 420 330 600 475
400 510 405 470 380 720 570
500 560 450 510 415 800 G50
625 610 500 550 465 910 760
NOTE -For basic assumptions and method of installation, see 2 and 3.

TABLE 7 CURRENT RATINGS (ac) FOR PAPER-INS;yTED

ARMOURED SERVED THREE-CORE BELTED LEAD-
COVERED 3-3 AND 6-6 kV CABLES
( Cluusc 2.1 )
NOMINAI DIRECTIN THE GROUND IN SINGLE-WAYDUCTS IN AIR
AREA OF C--_h___-~ p_"_--_--~ ~-_-_*_-__~
CONDUCTOR Copper Aluminium Copper Aluminium Copper Aluminium
(1) 2) ‘“d 2) ‘“d 2) ‘71’
-mm*

:“5 110
83 65
85 74
95 7”: 1;: 84
64
35 130 105 ::: 1:: 130 105
50 160 125 165 130
70 190 150 175 135 205 155
1;; 230
255 200
180 205
225 160
180 240
275 220
190

150 290 225 260 200 320 255

185 330 260 295 230 370 295
225 365 290 330 260 420 335
240 380 300 340 270 440 350
300 420 330 380 300 500 395
400 475 380 430 345 590 4c;5
NOTE - For basic assumptions and method of installation, scc 2 and 3.

16
 IS I 3961( Part I ) - 1967

TABLE 8 CURRENT RATINGS ( oc ) FOR PAPER-INSULATED

UNARMOURED SERVED, THREE-CORE BELTED LEAD
COVERED 3.3 AND 6.6 kV CABLES
(Clause 2.1 )
NOMINAL DIRECTINTHEGROUND IN SINGLE-WAY Ducts IN AIR
AREA OF r---‘rr_- - c-__-h-----5 I----~
C~N~IJCT~R Copper Aluminium Copper Alurninium Capper Hluminium
(1) (2) (3) (4) (5) (6) (7)
mm* A A A A A A

2 ;i

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
:s 110
85 Sf 1:: 64
84
35 130 105 115 87 130. 105
50 160 125 105 165 130
70 195 150 z 130 205 155
95 235 180 195 150 240 190
120 265 205 220 170 285 220
150 300 235 25.5 191 330 260
185 340 265 285 225 380 295
225 375 3& 320 250 430 335
330 260 450 350
z 440
390 310
345 370 295 510
400 500 405 435 350 610 z:
NOTE- For basic assumptions and method of installation, see 2 and 3.

TABLE 9 CURRENT RATINGS ( .C ) FOR THREE PAPER-

INSULATED UNARMOURED SERVED SINGLE-CORE W
COVERED 3.0 AND 6% &V CABLES
( ClafI.%2.1 )
Nourr;ar. Tr:r POILGkOuPs Lhm IN TREFOIL Ducts IN TREXL GROUPSI’V
ARbA 01 %RLT INTHEGROUND ,- ---A,------ AIR WITH SERVINGS
~.:OXOIJCT:~FWITI SERVINGS TOL’CHINC Copper Aluminium ToucHrNG
_-___-_h____ ---- h-__.-_ __
Aluminium Alum:.l&
(3) (4) (5) (7)
A A A A A
69 91 69 98 77
87 120 130 1FS
105 140 1;; 165 125
130 165 130 200 155
155 200 160 245 195
185 230 185 295 235
205 265 340 270
23.5 300 % 390 310
270 330 260 455 360
300 365 285 520 4.05
910 375 295 540 420
345 415 330 610 485
395 465 380 730 590
445 510 420 820 660
500 550 465 930 760
NOTE - For basic assumptions and method of installation, SET2 and 3.

17
ltS:3%1(PartI)-1967

TABLE 10 CURRENT RATINGS ( ac ) FOR PAPER-lNSULATED

ARMOURED SERVED THREE-CORE BELTED LEAD-
COVERED 11kV CABLFS
IClause 2.1 )
Now.u Dnmcr IN THE GROUND IN &NC&E-WAY DWX3 IN AIR
ARE.4 OF *--- - r- -L-_ _-‘--
CoNDucToa tipper Aluminium Copper Aluminium WPer Aluminium

(1) (2) - (3) (4) (5) (6) (7)

mm’ A A A A A A

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
16 70 58 64 49 65 50
15 82 68
35 1;; I: ;: 11’5 80
50 135 105 1% 130 100
130 145 1:; 160 125
;z 165
195 155 170 135 195 155
120
::
215
250
170
190
220
190
225
255
155
175
200
215
250
290
:2
230
225 3g 240 280 220 330 260
250 290 -225 345 275
% 315
355 280 320 250 395 310

Nom - For Basic assumptions and method of installation, see 2 and 3.

,
TABLE 11 CURRENT RATINGS ( ac ) FOR PAPER-INSULATED
UNARMOURED SERVED TRREE-CORE BELTED LEAD-
COVERED llkVCABLES
(Clausr
2.1 )

NODAL Dnuxr IN TIE GROUND IN !kNGLE-WAY Ducrs IN AIR

hEA OF r-----y ------l y----q
CONDucrOa C&v= Aluminium Copper Aluminium Copper Aluminium

(1) (2) (3) (4) (5) (6) (71

mm’ A A A A A A
g 110
zz 55
:: 64
83 2:
77 105
:: 65
50

% 135
165 105 150
1;: 1:: 130
160 125
1;

1% 215
195 170
:z! 190
170 135
150 215
195 155
175
150 25C, 215 170 250 200
185 285 :g 250 195 295 230
225 250 285 225 330 265
240 260 295 235 z 275
300 375 300 335 265 315

Nom - For basic assumptions and method of installation, sue 2 and 3.

-.
18
 IS:3961 (PartI)-1967

TABLE 12 CURRENT RATINGS ( rc) FOR PAPER-INSULATED

ARM~~fE$RiED THREE-CORE SCREENED LEAD-
THREE-CORR SL 11 kV CABLES
( clmrtc 2.1)
NOMINAL hkECS!NTHE Gnoum IN SINGLE-WAY Ducrs IN &R
AURA OF r--------h--- c--_-A _-.-, *--_,
CkmDlJcToR CoPper Aluminium Qppcr Aluminium Copper Aluminium
(1) (2) (3) (4) (5) :6) (7)

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
mm’ A A A A A A

;: 210
175 165
140 I85
160
145
125 215
185 E
120 235 185 205 160 250 200
150 265 205 235
185 300 235 265 E 32 fE
225 335 265 295 230 380 500
240 345 275 305 ;E 395 310
300 380 300 340 440 345
NATE- For basic assumptions and method of installation, SM2 and 3.

TABLE 13 CURRENT RATINGS PC ) FOR PAPER-INSULATED

UNARMOURED SERVED TH I$ E-CORE SCREENED LEAD-
COVERED 11 kV CABLES
(Clause 2.1 )
NONSNU Dmqzr IN THE GROUND IN SINGLE-WAY Ducrs IN Ara
AREA OF 0----- c‘-----*L--_-~ r-------y
CoNDUCToR Copper Aluminium Copper Aluminium Copper Aluminium
(1) (6) (7)
mm’ A A A A A A
16 79 60 65
_- !il
25 105 73 ss
125 92 18i 77
:: 59
77
150 115 120 94 150
120 I”r”5
185 140
E 165
140 150
175 115
135 215 175
240 185 195 155 250
270 210 225 175 290 $2
345
310 275
245 285
255 ;g % 265
300
355 285 400 315
395 310 z:z 265 455 355
NOTE-For basic assumptions and method of installation, see 2 and 3.

19
 IS : 3961(Part I ) - 1967

TABLE 14 CURRENT RATINGS (PC ) FOR THREE PAPER.

INSULATED UNARMOURED SERVED SINGLE-CORE LEAD-
COVERED II kV CABLES
(Cfause 2.1 )
NOMINAL TREFOIL GROUPS LAID INTREPOILDUCTS IN TREFOIL GROUTSIN
AREA OP DIRECT IN THE GROUND ---A-- AIR WITH SERVINGS
CONDXXXOR WITH SERViNCS Copper Ahninium TOUCHING
TOUCHING 7__~-_-7
Copper Alurhinium
F Lpper Aluminium~
(l) (2) (3) (4) (5) (6) (7)

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
Inma A A A A A A
63 1:: 62 l? 66
2 78
.-
125 !z 135 1::
120
145
180
ii”5 150
175
11.5
140
170
215
130
165
210
246
E
185 210
235 f fZ % 230
200
270 210 260 205 340 265
300 240 290 230
330 260 320 250 % 300
340
340 270 330 260 450 355
380 305 360 285 510 400
445 355 410 335 610 490
490 395 445 365 700 570
540 445 485 410 800 670
NOTE - For basic assumptions and method of installation, sue 2 and 3.

TABLE 15 CURRENT RATINGS (PC ) FOR PAPER-INSULATED

ARMOURED SERVED THRI$ECOIlE SCREENED LEAD.
COVERED OR THREE-CORE SL 22 kV CABLES
( c1uuse2.1 )
NOMINAL DIRECTINTHEGROUND INSINGLE-WAY DUCTS IN. AIR
AREA OF -w-h--
.I _--h___y ----
CONDUCTOR Copper Aluzz Copper Aluminium Copper Aluminium
(11 (2) (3) (4) (5) (6) (7)
mm* A A A A A- A

1:; ;: 1:: ;: 1:: ;:

140 105 120 97 140 105
165 130 150 120 170 130
195 155 180 140 200 160
215 170 200 155 235 180
250 190 225 175 265 210
i85 280 220 255 205 310 245
225 310 240 280 225 345 275
320 250 290 230 360 285
z 355 275 325 255 400 320
NOTE - For basic assumptions and method of installation, SW 2 and 3.

20
 IS : 3961 ( Part I ) - 1967

TABLE 16 CURRENT RATINGS ( ac ) FOR PAPER-INSULATED

UNARMOURED SERVED THREE-CURE SCREENED LEAD-
COVERED 22 kV CABLES
( Clause 2.1 )
NOMINAL DIRECTINTHEGROUND IN SINGLE-WAYDUCTS IN AIR
AREAOF r---*_--_ 7 ~-___h---_ 7 c- ___h_____~
C~~NDUCX~R Copper Aluminium Copper Aluminium Copper Aluminium
(1) (2) (3) (4) (5) (6) (7)
mms A A A A A A

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
25 lY20 ;“7 81 62 92 ;;
z: 135 105 *:“o 76 135
110 105

:: 165
195 150
130 170
150 135
1% 200
170 130
155
120 225 175 195 150 235 180
150 255 200 220 170 270 215
185 285 225 250 200 310 245
225 320 250 280 220 350 280
240 330 260 290 230 365 290
300 370 285 325 255 410 325
NOTE - For basic assumptions and method of installation, see 2 and 3.

TABLE 17 CURRENT RATINGS ( IC ) FOR THREE PAPER-

INSULATED UNARMOURED SERVED SINGLE-CORE LEAD-
COVERED 22 kV CABLES

( Clause 2.1 )
NOMINAL DIRECTIN TIIE GROUND INTRBFOILDUCTS IN AIR
&WA OF (--___h___-7 C--__h-_-_ ..-)~-_-_-L.-___~
(:ONDUCTOR <Copper Aluminium Copper Aluminium Copper Aluminium
(1) (2) (3) (4) (5) (6) (7)
mma A A A A A A
:“5 75 59
74 105
79 62
82 105
78 61

z; 1;:
140 1:: 120
145 115
95 130
155 125
:z

70 170 130 170 135 195 150

95 200 155 205 160 230 180
120 225 175 230 180 265 205

:fz
5 255
285 200
225 255
285 200
225 305
350 240
275
225 320 255 315 245 395 310
240 330 265 325 255 410 325
300 370 29.5 360 285 465 370
400 420 335 400 325 560 445
500 455 370 43.5 360 620 500
625 510 420 470 4-05 710 590
Now -- For basic assumptions and method of installation, It% 2 and 3.

21
IS:3961 (PartI)-

TABLE 18 CURRENT RATINGS ( ac ) FOR PAPER-INSUtiTED

ARMOURED SERVED THREE-CORE SCREENED LEAD-
COVERED OR THREE-CORE SL 33 tV CABLES

( c/uusc
2.1 )
NOMINAL DIRECT IN THE GROUND IN SINOLE-WAY DUCTS IN AIR
AREA OF r-----h_--- T--L_ ---i-
CONDUCTOR Copper Aluminium Copper Aluminium Copper Aluminium

(1) (2) (3) (4) (5) (6) (7)

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
mm* A A A A A A

70 165 130 150 120 170 135

95 195 155 180 140 205 160
120 215 170 200 155 235 180
150 245 190 225 175 265 210
185 275 220 255 200 305 240
225 300 240 285 220 345 275
240 310 245 295 230 360 285
300 345 270 325 255 400 320
NOTE -For basic assumptions and method of installation, IM 2 and 3.

TABLE 19 CURRENT RATINGS (ac ) FOR PAPER-INSULATED

UNARMOURED SERVED THREE-CORE SCREENED LEAD-
COVERED 33 kV CABLES
( chuc 2.1)

NOMINAL DIRECTIN THE GROUND IN SINGLE-WAY DUCTS IN Am

AREA OF r---k--- --rr---- r--- *p-m,
CONDUCTOR Copper Aluminium Copper Aluminium tipper Aluminium

(1) (2) (3) (4) (5) (6) (7)

mm’ A A A A A A

70 165 130 145 115 170 135

95 195 155 175 135 205 160
120 215 170 195 150 235 180
150 250 190 220 170 270 215
185 280 220 245 195 310 245
225 310 245 275 215 350 275
240 320 255 285 225 365 285
300 360 285 320 250 410 325
NOTE - For basic assumptions and method of installation, see 2 and 3.
-.
22
 IS:3961 (PartI)-

TABLE 20 CURRENT RATINGS ( EC) FOR THREE PAPER-

INSULATED UNARMOURED SERVED SINGLE-CORE LEAD-
COVERED 33 kV CABLES

NOMINAL TREFOILGROUPSLAID IN TREFOIL Ducts IN TREFOIL GROUPSIN

AREA OF DIRECTINTHEGROUND r--h_---y AIR WITH SERVINGS
~~NOUOTOR wmz SERVINGS Copper Aluminium TOUCHING
TOUCHING r___-* --y
r----_h___~ Copper Aluminium
Copper Aluminium

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
,(l) (2) (3) (4) (5) (6) (7)
mm’ A A A A A A
70 165 130 175 135 195 150
95 195 155 205 160 230 180
120 220 175 230 180 265 205
150 250 195 255 200 305 240
185 280 225 285 225 350 275
225 310 240 315 245 395 310
240 320 255 325 255 410 325
300 360 290 355 280 465 370
400 415 730 400 325 560 445
500 455 365 435 360 620 500
625 500 415 475 400 710 590

NOTE - For basic assumptions and method of installation, SM 2 and 3.

TABLE 21 RATING FACTORS OR DEPTH OF LAYING

(FOR CABLES LAID DIREC % IN THE GROUND)
[Clause 5.1 (aj (i) ]

DEPTH OF CABLW FOR VOLTADES

LAYING r---- -_h --------7
Up to and Including 1.1 kV 3’3 kV, 6.6 kV 22 kV and
r-----_---h,----~ and 11 kV 33 kV
up to Above 25 mm* Above All Sizes All Sizes
cm 25 mm* up to 300 mm3 300 mm’

(1) (2) (3) (4) (5) (6)

75 1*oo 1*oo 1.00 -
90 0.99 0.98 0.97 1.00 -
105 0.98 3.97 0.96 0.99 1.oo
120 0.97 O&j6 0.95 0.98 0.99
150 0.96 0.94 0.92 0.96 0.97
180 or 0.95 0.93 0.91 0.95 0.96
more

23
 IS : 3961 ( Part I ) - 1967

TABLE 22 RATING FACTORS FOR VARIATION iN GROUND

TEMPERATURE ( FOR CABLES LAID DIRECT IN THE
GROUND )

[ Claust 5.1 la) (ii) ]

hlnwduhr GROUND~'EMPBRATIJRE ‘C
co.uuricron r- L
\
‘1’EalreH;vrrrKk 15 20 25 30 35 40 45
OC

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
110 1.1.i 1.10 I.05 I.0 0.95 0.89 @a4
70 1.17 I.12 l-06 1.0 0.94 O-87 0.79
65 1.L’o 1.13 I .07 1.o 0.93 0.85 0.76

TABLE 23 RATING FAClTORS FOR VARIATIGN IN THERMAL

RESISTIVITY OF SOIL (TWIN AND MULTI-CORE CABLES LAID
DIRECT IN THE GROUND )

[ Clause 5.1 (a) (iii) ]

NOMINAL RATING FACTORS FOR VALUE OF THERMALRESISTIVITYOF SOIL IN ‘C cm/W

hEA 01' ~-_~~~~~-~_~~~~_ h--___-----___-_-~
CONDUCTOR 100 120 150 200 250 300
mm2

6 l.Ilj I.05 1.0 0.92 0.86 0.81

10 1.10 1.OG 1.0 0.92 0.85 O-80
I6 I:12 l-06 1.0 0.91 0.64 0.79
25 1.14 198 I.0 0.91 0.84 0.78
35 1.1.5 I .08 1.0 0.91 0.84 0.77
50 1.15 I.011 1.0 0.91 0.84 0.77
70 1.15 1.o:: 1.0 0.90 0.83 0.76
95 1.15 1.08 1.a 0.90 0.83 O-76
120 1.17 1f)9 I.0 0.90 0.62 0.76
150 1.17 1.09 I.0 0.90 0.82 0.76
1% 1.18 1.09 1.0 0.89 0’81 o-75
225 1.18 1.03 1.0 0.89 0.81 o-76
240 1.18 1.09 1.0 0.89 0.81 @75
300 1.18 1.09 1.0 0.89 0.81 i.75
400 1.19 l-10 1.0 0.89 0.81 0’75
500 1.21 1.10 1.0 0.89 0.81 0.75
625 1.22 1.10 1-o 0.89 0.81 0.74

24
 TABLE 24 RATING FACTORS FOR VARIATION IN THERMAL RESISTIVITY OF SOIL,
TWO AND THREE SINGLE-CORE CABLES LAID DIRECT IN THE GROUND

[ Clause 5.1 (3) (iii) ]

NOMINAL Two CABLES TOUCHDIG, FOR VALUES OF THERMAL ‘I HREE CSSLEE IX TREFOIL TOUCHING, FOR VALUES OF
AREA OF RESISTIVIT~ OF S&L IN “C cm/M’ THERMAL RESIITIVITY OF SOIL IN “C cm/W
CoNDUCToR _--_-_-_-___h _--___- ---_ _-____-___I-__-__--_-__
100 200 150 200 250 300 1 100 200 150 200 250 300 n

nun’

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
6 1.15 1.08 1.oo 0.91 0.84 0.78 1.18 1.09 I.00 0.90 0.82 0.76
10 I.15 1.08 1.00 0.90 0.83 0’77 1.18 1.09 I.00 0.89 0.81 II.75
16 1.17 I.09 1.00 0.90 0.83 0.77 1.19 1.09 1.00 0.89 0.81 0.74

25 1.18 1.09 I.00 0.90 0.32 0.76 1.19 I.09 1.00 0.88 0.80 0.74
35 1.18 1.09’ 1.00 0.90 0.82 0.75 1.20 I.09 1.oo 0.88 0.80 0.74
50 1’18 1.09 l-00 0.90 0.82 0.75 1.20 1.09 1.00 0.88 0.80 0.74

70 1.19 1.09 1.00 0.89 0.81 0.74 1.21 1.10 1.00 0.&8 0.80 0.74
95 1.19 1.09 1.00 0.89 0.81 -0’74 1.22 1.10 1.00 0.88 0.80 o-74
120 1’21 I.10 I.00 0.89 0.80 0.74 1.22 1.10 1.00 0.88 079 0.74

150 1.21 1.10 1.00 0.89 0.80 0974 , .‘2 1.10 1.00 0.88 0.79 0.73 g
185 1.21 1.10 1.00 0.89 0.80 0.74 1.22 I.10 1.00 0.88 0.79 0.73 z
225 1.21 1.10 1.00 0’89 0.80 0.74 1.22 1.10 1 .oo 0.89 0.79 0.73 B
246 1’21 1’10 1.00 0.69 o,i?o 0.74 1.22 l.iO 1.oo O.&Z 0.79 0.73 ;
300 1.21 1.10 1.00 0.89 0.80 0.74 1.2’ 1.10 1.00 0.88 0.79
0.72 !z
400 1.21 1.10 1.11 0.71 cc
1.oo 0.88 O-80 0.74 1. 2 1.00 0.8G 0,59 Y
500 1*21 1’10 1.00 0.88 0.80 0.74 1.2.t 1.11 1.00 0.88 0.79 o-72 y
625 1.22 1.10 1.00 0.88 0.80 0’74 1.24 1.11 I.00 0.88 0.79 0.72
IS:3961 (Part I)-1967
TABLE 25 GROUP RATING FACTORS FOR TWIN AND MULTI-CORE
CABLES IN HORIZONTAL FORMATION LAID DIRECT IN THE GROUND
[ Claws 5.1 (a) (iv) ]

NUMBER SPACING FOR CABLES

()F CABLEs ~____--------~*_-------_-_-_-_-__-~
.IN GROUP 1.1 to 22 kV 33 kV
f----- *_-_-_-_~~-_---_-~_--___~
Touch- 15 30 45 60 Touch- 15 30 45 60
ing ing

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
2 0.79 0.Z 0% zfo 0% 0.80 cz3 0% 0% 0?9?

: 0.69
0.62 0.69
0.75 0.79
0.74 0.83
0.79 0.86
0.82 0.63
0.69 0.72 0.76
o.72 0.80
0.76 0.83
0.79

6” 0.54
0.58 0.61
0.65 0.69
0.72 0.76
0.75 0.78
0.80 0.55
0.58 0.59
8’:::
. 0.68
0.65 0.72
0.70 0.76
0.74
;: 0.52
0.50 0.57
0.59 0.66
0.68 0.72
0.73 0.77
0.76 0.50
0.52 0.54
0.56 062
0.63 0.67
0.68 0.72
0.73

1: 0.46
0.47 0.55
0.54 o”:z 0.70
0.7 1 0.74
0.75 0.46
0.48 0.52
0.51 0.60
0.59 0.65
0.66 0.71
0.70
0.45 0.53 0.63 0.69 0.74 0.45 0.50 0.58 0.65 0.70
0.44 0.52 0.62 0.68 0.73 0.44 0.49 0.57 0.64 0.69

TABLE 26 GROUP RATING FACTORS FOR TWIN AND MULTI-

CORE CABLES IN TDZR FORMATION, LAID DIRECT IN
THE GROUND (FOR l-1 to 33 kV CABLES )
[Clause 5.1 (a) (iv) 1

vw,vv
NUMBER
yJ rfvvv
!5PAcING
000
000
000
vvv
vvv
SPACING
OF CABLES r--- --- --_*_-_. v-w_ --_-__
IN GRCVJP Touching 15 cm 30 cm 45 cm 60 cm
r--h- -y--~--y---h_-_- --A--T r_--Lc_-T
Up to 33 kV Upto 33 kV Up to 33 kV Up to 33 kV Up to 33 kV
22 kV cables 22 kV cables 22 kV cables 22 kV cables 22 kV cables
cables cables cables cables cables
0.81 - 0.84 - 0.88 - 0.90 - 0.91 -
0.69 0.73 0.79 0.82 0.85
0.60 0% 0.67 024 0.73 0;s 0.76 0;2 0.78 O-74
0.55 0.61 0.67 - 0.71 0,73
0.51 0:2 0.57 0:;5 0.63 0.60 0.67 O-69 0.69 0;5
0.48 - 0.54 - 0.59 - 0.63 - 0.64 -
0.45 0.51 - 0.57 0.59 0.61
0.44 oY3 0.48 0.46 0.54 o;o 0.56 0.53 0.58 Oy6
0.42 - 046 - 0.51 - 0.54 - 0.56 -
0.41 - 0.45 0.50 0.53 0.55
0.40 0.48 0.45 0% 0.49 o-ts 0.52 078 0.54 071
 IS : 3961( Part I ) - 1967
TABLE 27 GROUP RATING FACTORS FOR CIRCUITS OF TWO SINCLE-
CORE CABLES SIDE BY SIDE AND TOUCHING, HORIZONTAL
FORMATION, LAID DIRECT IN THE GROUND
[Clause 5.1 (a) (iv) ]

f-
00-+
L SPACING,--
NUMBER OF SPAGINO
CIRCUITs (OF r--_----_-_-_--L__ .-_- ‘---7
Ty;zRy;) Touching, 15 cm 30 cm 45 cm 60 cm

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
3’ 0.79
0.69 o-78
0.86 0.84
0.91 0.93 0.95.
o-88 0.91
: o-59
0.64 O-70
0’73 0.81
0.79 0.86 0.88
0.84 o-87
0.56 @67 cl.79 0.83. 0.87
7” 0.53 0.66 0.76 0.82 0.86
a 0.51 0’65 0.75 0.82 o.86
1: o-49 0.64 0.74 0.81 0.85
o-48 O-63 0’74 0.81 0.85
11 0.46 0.62 0.73 0.80 0.85
12 o-45 0.62 0.73 0.80 0.85

TABLE 28 GROUP RATING FACTORS FOR CIRCUITS OF THREE SINGLE-

CORE CABLES IN TREFOIL AND TOUCHING, HORIZONTAL
FORMATION, LAID DIRECT IN THE GROUND
[ Chfe 5.1 la) (iv) ]

c-_-SPACING- -4
NUMBEROF SPACING FORCABLES
CIRCUITs r---- ___-__*_-_-_--_~--~__-~
(OFTHREE 1-l to 22 kV 33 kV
CABLES) r---___-A_---_7r_ ---- h-----_,~
IN GROUP Touch- 15 30 45 60 Touch- 15 30 45 60
ing ing
2 0.78 El 0% 0% of,“, 0.80 @2 0% 0% OF97
3 0.68 0’71 0.77 0.81 0.83 0.68 0.71 0.76 0.79 0.82
4 0.61 0.65 0.72 0.76 0.79 0.62 0.65 0.71 0.75 0.79

5 0.56
0.53 O-58
0.61 0.66
0.68 0’71
0.73 0.76
0.77 0.54
@57 0.57
0.60 0.64
0.67 0.69
0.72 0.74
0.75
7 0.50 0.55 . 0.64 0.69 0.74 0.51 0’55 0.62 0.67 0.72

; 0.48
0.46 0’54
0.52 0.62
0.61 0’67
067 0.72 0.47
0.49 0’51
0.53 0.60
0.59 0.65
0.66 0.70
0.71
:: 0.44
0.45 0.51
0’50 ’ 0.59
0’60 0.66
0.67 0.71
0.72 044
0.46 0.49
0.50 0.57
0.58 0.63
0.64 0.68
0.69

12 0.43 0.49 0.59 0.66 0.71 0.43 0’48 0.56 0.63 0.68
IS : 3961( Part I ) - 1967

TABLE 29 RATYNG FACTORS FOR DEPTH OF LAYING

( TWIN AND MULTI-CORE CABLES IN SINGLE-WAY DUCTS )

[ Classe 5.1 (b) (i) ]

DEPTH OF LAYING 1.1 kV CABLES 3.3, 6.6 AND 11 kV 22 AND 33 kV

CABLES CABLES

cm

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
75 1.00 - -
90 O-99 1.00 -
105 0.98 O-99 1.00
120 0.97 0.98 0.99
150 0.96 0.97 O-98
180 0.95 0.96 0.97
270 0.92 O-93 0.94
360 0.91 0.92 o-92
450 0.90 O-91 O-91
540 or more O-89 0.90 O-90

TABLE 30 RATING FACTORS FOR VARIATION IN GROUND

TEMPERATURE ( FOR ARMOURED CABLES IN DUCTS )

[ Clause 5.1 (b) (ii) ]

MAXIMUM GROUND TEMPERATURE o C

CONDUCTOR (--_---_,--_---2b--_
-----------7
TEMPERA- 15 20 25 30 35 40 45
TURE

“C

80 1.14 1.10 1.05 1.0 0.95 O-89 0.84

70 1.17 1.12 1.06 1.0 0.94 0.87 0.79
c5 l-20 1.13 1.07 1-O 0.93 0.85 0.76

28
 IS: 3961 (Part I)- 1967

TABLE 31 RATING FACTORS FOR VARIATION IN GROUND

TEMPERATURE (FOR UNARMOURED CABLES IN DUCTS )

[ Clause 5.1 (b) (ii) ]

MAXIMUM GROUND TEMPERATURE‘C

CONDUCTOR ~_-_--_-______-*--_-_____---_~~
TSMPERA- 15 20 25 30 35 40 45
TURE

80 1.00 1.oo 1.00 1.00 1.00 0.94 0.88

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
70 1*oo l*OO 1.00 1.00 1.oo 0’93 0.85
65 1.00 1.00 1.00 1*oo 0.93 0.85 0.76

TABLE 32 RATING FACTORS FOR VARIATION IN THERMAL

RESISTIVITY OF SOIL (TWIN AND MULTI-CORE CABLES IN
SINGLE-WAY DUCTS )

[Clause 5.1 (b) (iii) ]

NOMINAL RATING FACTORSFOR VALUES OF THERMAL RESISTIVI-IYOF SOIL IN “C cm/W

AREA OP r--_----_-_-.~ h- ____ _ ____ -_---_
CONDUCTOR 100 120 150 200 250 300

mm’

6 1.05 1.03 1.00 0.96 0.91 688

10 1.05 1.03 1.00 0.95 0.90 0.87
16 1*06 1.03 1.oo 0.95 0.90 O-86
25 1.07 1.04 1.00 0.95 0.90 O-85
35 1.98 l-04 1.00 0.94 0.89 0.84
50 1.08 1.04 1.00 0.94 689 0.84
70 1.08 1.04 1.00 0.94 0.88 0.83
95 1.08 1.04 1.oo 0.94 0.87 0.83
120 l-09 I .05 1.00 0.94 0.87 0.82
150 1.09 1.05 1.00 0.93 0.8G 0.82
185 1.10 1*05 1*oo 0.93 0.86 O-81
225 1.10 1.05 l-00 0.99 0.86 O-81
240 1.10 1.05 l-00 0.92 0.86 OS1
300 1.10 1.05 1.00 @92 0.86 0.81
400 1.11 1.OG 1*oo o-92 0.86 0.81
500 1.12 1.06 1.00 0.92 O-86 0.81
625 1.12 1.06 l-00 0.92 0.85 0.80

29
 TABLE 33 RATING FACTORS FOR VARUTION IN THERMAL BESISTIVITY OF SOIL
( TWO AND THF SINGLECORE CABLES IN DUCTS)

[ Clauses0.4 and 5.1 (b) (iii) ]

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
NOMINAL Two CABLES IN TWO-WAY Duct, FOR VALUES OF THREE CABLES IN TRRPOIL Dum, FOR VALUES OF
AREA OF THERMALRESISTIVITYOF SOIL IN “C cm/W THERMAL RR~IS~MTY OF SOIL IN “C cm/W
--- h----------~ ~____-_-h___-_ ------ *
CuNDUcToR e-
100 120 150 200 250 300. 100 120 150 200 250
e
mm* 5;
6 1.07 1.04 1.00 0.96 0.91 0.86 1.10 1.05 I*00 0.94 0.87 0.83 5

10 1.07 1.04 1.00 0.95 0.90 @85 1.10 1.05 1.00 0.93 0.86 0.82
16 1.08 1.04 1.00 @94 0.89 0.84 1.10 1.05 1.00 0.92 0.86 0.81

25 1‘08 1.04 1.00 0.94 0% 0’83 1.10 1.05 l+O 092 0.85 0.80
35 1.09 1.05 1.00 0.94 0.87 0.83 1.11 1.06 1.00 0.92 0.85 0.80

50 1.09 1.05 I.00 0.94 0.87 0.83 I.12 I *06 1.00 0.92 0.85 0.80
70 I.09 1.05 1.00 0.94 0.87 0.83 1.12 1.06 1.00 891 0.85 0.79

95 1.10 1.05 1.oo 0.93 0.86 0.82 1.13 1.06 1.00 0.91 0.84 0.79
120 I.10 1.05 1.00 0.92 0.85 0.81 1.13 1.06 1.00 0.91 0.84 0.78
150 I.10 1.05 l%IO 0.92 0.85 0.81 l-14 1.07 1.00 0’91 0.84 @78
185 1.10 1.05 1.00 0.92 0.85 0.80 1.15 1.08 1.00 0.91 0.84 0.77

225 1.10 1.05 1*oo 0.92 0.85 0.80 1.15 1.08 1.00 0.91 0.84 0.77
240 1.11 1.06 I.00 0.92 k85 0.80 1.15 1.08 l-00 0.91 0.83 0+7i

300 I.12 1.06 1.00 0.92 0.85 0.80 1.15 1.08 1.00 @90 0.83 0.76
400 I.12 1.06 1.00 0.91 0.85 0.79 l-16 1.08 1.00 0.90 0.83 0.76
500 1.12 1.06 1’00 0.91 0.85 0.79 l-16 1.08 1.00 0.90 O-82 0.76
625 I.13 1.06 1.00 0.91 0.84 0.79 l-17 1.09 I.00 0.96 0.82 0.76
 IS : 3961 ( Part I ) - 1967

TABLE 34 RATING FACTORS FOR MULTI-WAY DUCTS ( FOR USE WHEN

A MULTI-WAY DUCT DOES NOT CONTAIN THE FULL NUMBER
OF LOADED ARMOURED CABLES.)
[ Clauses 0.4 and 5.1 (b) (iv) ]

NUMBEROFLOADEDCABLESIN
r--- -- ---h--- _-__ - -----~
3-Way Duct 6-Way Duct g-Way Duct
---A--_ c--A---~ r-_--A--~
1 2 4 5 7 a

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
1.15 1.07 I.10 l-04 1.10 1.05

SIZE QF CONDUCTOR IN SO mm

Fro. 1 RATINO FACTORSFOR WIRE-ARMOURIED CABLES IN MULTI-WAY

DUCTS ( To BB APPLIED TO RATINQ OF CORRESPONDING CABLE
IN A SINGLE-WAY Ducr TO OBTAIN RATING FOR
CABLE IN MULTI-WAY DUCT)

81
SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED
IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
 TABLE 36 GROUP RATING FACTORS FOR SINGLE-CORE CABLES IN TREFOIL
STONEWARE DUCTS IN TIER FORMATION

[ Clausr 5.1 (b) (vj ]

QQ 0
00
0
00 Q
00
0

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
w
w
I--- SPACING4
Q Q 00
0 0
00 Q
00
a

Q Q 0
00
0
00

SPACING UP TO 33 kV UP TO 33 kV UP TO 33 kV UP TO
OF DUCTS 22 kV 22 kV 22 kV 22 kV
cm

Approximac 0.76 o-71 O-70 065 0.64 0.59 @61 0.55 ,”

I
touching
45 0.78 0.76 0.73 0.70 0.67 0.63 0.64 0.60 t;
o?
iS I 3961 ( Part i ) - 1967

TABLE 37 GROUP RATING FACTORS FOR TWIN AND MULTI-

CORE CABLES IN SINGLE-WAY DUCTS AND PIPES, IN
HORIZONTAL FORMATION
[Clause 5.1 (b) (v) ]
NUMBER OF SPACINGS p0R CABLES
Ducrs IN r---- ~~~--~~~~~~~--~___~~-~
GROUP 1.1 kV to 22 kV 33 kV
I --h --7 ------ h-_____-T
Touch- 30 cm 45 cm 60 cm Touch- 30 cm 45 cm 60 cm
kg ing
2 0.88 0.90 0.92 0.94 0.86 0.89 0.90 0.92

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
3 0.82 0.84 0.87 0.89 0.77 0.80 0.83 0.85
4 0.77 0.80 0.84 0.87 9.72 0.76 0.80 0.82
5 0.74 0.78 0.82 0.85 0.68 0.72 .0.77 0.80
6 0.71 0.76 0.81 084 0.65 0.70 0.75 @78
7 0.69 0.74 0.79 0.83 0.62 0.68 0.73 0.77
8 0.67 0.73 0.78 0.82 o*i;o 0.66 0.72 0.76
9 0.66 0.72 0.77 0.82 0.59 0.65 0.70 0.75
10 0.65 0.71 0.77 0.81 0.57 0.64 0.70 0.74
11 0.64 0.70 076 0.81 0.56 0.63 0.69 0.74
12 0.63 0.69 0.76 0.81 0.55 0.62 0.68 0.73

TABLE 38 GROUP RATING FACTORS FOR SINGLE-CORE

CABLES IN TREFOIL DUCTS, HORIZONTAL FORMATION
[ Clause 5.1 (b) (v)]

NUMBER OF SPACINGS FOR CABLES

Ducn IN r--- ----A ------------ 7
GROUP 1.1 kV to 22 kV 33 kV
r---- h-p--- ~ ~~_~~_h_~~~__
Touching 45 cm 60 cm Touching 45 cm 60 cm
2 0.87 0.90 0.91 0.83 0.86 0.88
3 0.79 0.83 0.86 0.72 0.78 0.80
4 0.74 0’79 0.82 0.67 0.73 0.77
5 0.71 0.76 0.80 0.62 0.69 0.73
6 0.69 0.74 078 0.60 0.67 0.71
7 0.67 0.72 0.77 0.57 0.65 0.70
8 0.65 0.71 0.76 0’55 0.64 0.68
9 0.64 0’70 0.75 0.54 0.63 0.67
10 0.63 0.70 0.75 0.53 0.62 0.67
11 0.62 0’69 0.75 0.51 0.61 0.66
12 0.62 0.68 0.75 0.50 0.60 @65

34
 IS : 3961 ( Part I ) - 1967

TABLE 39 RATING FACTORS FOR THREE* UNARMOURED

SINGLE-CORE CABLES ( ae ) IN FLAT FORMATION IN AIR
(TO BE APPLIED TO THE CORRESPONDING RATING
FOR TREFOIL GROUPS IN AIR )
[ Clnwe 5.1 (c) (i) ]
NOMINAL 1-l kV TO 11 kV INCLUSIVE 22 AND 33 kV
AREAOF (-_____h______~ _-___-h-----7
CONDUCTOR Transposed Untransposed Transposed Untransoosed

SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
mms
Up to and
Including

185 1.08 1.07 1.08 I.07

225 1.11 1.10 1:05 1.04
240 l-11 1.10 1.05 1.04
300 1.10 1.08 1.05 1.03
400 l-08 1.04 1.04 l-00
625 1.06 1.00 1.03 0.97
*Applicable also to four cables carrying three phaSes and neutral.
.-_

TABLE 40 RATING FACTORS FOR VARIATION IN AMBIENT

AIR TEMPERATURE

[ Claurc 5.1 (c) (ii) ]

M‘AXIMUM AIRTEMPERATURE%
CONDUCTOR r---- --- 3
TEMPERATURE 25 30 35 40 45

“C
80 1.19 l-12 l-06 1 so0 8-92
70 1.25 1.16 1.09 1.00 0.90
65 1.30 l-21 l-10 1 *oo 0.88

35
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SUPPLIED BY BOOK SUPPLY BUREAU TO ACME TELE POWER LIMITED

IMT, MANESAR FOR INTERNAL USE AT THIS LOCATION ONLY
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