is 7098 part 2

© BIS 2008

B U R E A U O F I N D I A N S T A N D A R D SMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

IS : 7098 (Part 2) - 1985(Reaffirmed 2005)

Edition 2.2(2007-11)

Price Group 5

Indian StandardSPECIFICATION FOR

CROSSLINKED POLYETHYLENE INSULATEDPVC SHEATHED CABLES

PART 2 FOR WORKING VOLTAGES FROM3.3 kV UP TO AND INCLUDING 33 kV

( First Revision )(Incorporating Amendment Nos. 1 & 2)

UDC 621.315.221.8 [678.742.2]

IS : 7098 (Part 2) - 1985

© BIS 2008

BUREAU OF INDIAN STANDARDS

This publication is protected under the Indian Copyright Act (XIV of 1957) andreproduction in whole or in part by any means except with written permission of thepublisher shall be deemed to be an infringement of copyright under the said Act.




( First Revision )Power Cables Sectional Committee, ETDC 59

Chairman

SHRI M. L. DONGREM-3, Satyam,

88, Sion Circle, Bombay

Members RepresentingSHRI J. P. AGAL Bharat Heavy Electricals Ltd, Hyderabad

SHRI B. P. RAI ( Alternate )SHRI M. R. BHAT Tata Consulting Engineers, Bombay

SHRI D. K. BASU ( Alternate )CHIEF ENGINEER

(ELECTRICAL) ICentral Public Works Department, New Delhi

SURVEYOR OF WORKS (ELECT) V ( Alternate )DR K. DAS GUPTA Calcutta Electric Supply Corporation (India) Ltd,

CalcuttaSHRI P. NEOGI ( Alternate )

DIRECTOR Central Power Research Institute, BangaloreSHRI M. C. RATRA ( Alternate )

DIRECTOR OF MINES SAFETY(ELECT) (HQ)

Directorate General of Mines Safety, Dhanbad

DIRECTOR OF MINES SAFETY(ELECT) ( Alternate )

SHRI RAVI K. DUTT Cable and Conductor Manufacturers’ Association ofIndia, New Delhi

SHRI S. R. SARAN ( Alternate )SHRI P. GHOSH Indian Cable Co Ltd, Jamshedpur

SHRI K. V. R. RAO ( Alternate )SHRI M. M. HONAVAR Cable Corporation of India Ltd, Bombay

SHRI S. R. PADMANBHAN ( Alternate )( Continued on page 2 )

IS : 7098 (Part 2) - 1985

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( Continued from page 1 )

Members RepresentingSHRI D. K. JAIN Directorate of Technical Development & Production

(Air), New DelhiSHRI V. K. SHARMA ( Alternate )

SHRI K. S. JOSHI Bombay Suburban Electric Supply Ltd, BombaySHRI R. K. SEHGAL ( Alternate )

SHRI S. L. KAKKAR Universal Cables Ltd, SatnaSHRI R. C. AGRAWAL ( Alternate )

SHRI RAJ K. MITAL Delhi Electric Supply Undertaking, New DelhiSHRI V. K. SAKHUJA ( Alternate )

SHRI R. V. NARAYANAN Directorate General of Supplies & Disposals(Inspection Wing), New Delhi

SHRI D. R. CHANDRA ( Alternate )SHRI H. M. PAI The Federation of Electricity Undertakings of India,

BombaySHRIMATI C. BALIGA ( Alternate )

SHRI S. N. PARWAL The Premier Cable Co Ltd, EranakulamSHRI A. K. RAMAN Asian Cables Corporation Ltd, BombaySHRI S. M. SAKHALKAR Bombay Electric Supply & Transport Undertaking,

BombaySHRI S. V. UPASANI ( Alternate )

SHRI L. K. SANGHI Fort Gloster Industries Ltd, HowrahSHRI A. S. BHATTACHARJEE ( Alternate )

LT-COL S. R. SEN Controllerate of Inspection Electronics, BangaloreSHRI S. K. MALHOTRA ( Alternate )

DR M. S. SUKHUJA Punjab Research Institute, RajpuraSHRI U. S. VERMA National Test House, Calcutta

SHRI R. RAMAKRISHAN ( Alternate )SHRI K. G. WARRIER Oriental Power Cables Ltd, Kota

SHRI B. K. MUNDHRA ( Alternate )SHRI S. P. SACHDEV,

Director (Elec tech)Director General, ISI ( Ex-officio Member )

Secretary

SHRI K. M. BHATIA

Joint Director (Elec tech), ISI

Panel for Elastomeric and Thermoplastic Cables, ETDC 59/P4

ConvenerSHRI L. K. SANGHI Fort Gloster Industries Ltd, Howrah

MembersSHRI A. S. BHATTACHARJEE ( Alternate to

Shri L. K. Sanghi )ADDITIONAL GENERAL MANAGER

(TECH)Delhi Electric Supply Undertaking, New Delhi

( Continued on page 22 )

IS : 7098 (Part 2) - 1985

3




( First Revision )0. F O R E W O R D

0.1 This Indian Standard (Part 2) (First Revision) was adopted by theIndian Standards Institution on 30 September 1985, after the draftfinalized by the Power Cables Sectional Committee had been approvedby the Electrotechnical Division Council.

0.2 Experience has shown that it is possible to use crosslinkedpolyethylene (XLPE) insulated cables for the class of voltages coveredby this standard, in place of armoured paper-insulated lead-sheathedcables.

0.3 This standard was originally published in 1973 when theexperience in the country about manufacture of these types of cableswas limited. Since then, a considerable progress has been made and anumber of manufacturers have come up. This standard has beenrevised to take into account the experience gained during manufactureof these cables in the country. The opportunity has also been utilized toalign the format of this specification with other specifications fordifferent types of cables.

0.4 Particular attention is drawn to the limitations of the short-circuitratings of the types of cable covered by this standard owing to theabsence of the metallic sheath and the possible loss of electricalcontact between the strands of the armour as a result of corrosion orthe presence of compound between them or both. A separate standardabout recommended short-circuit ratings of these types of cables isunder preparation.

0.5 Attention is also drawn to the fact that the current ratings of thetypes of cable covered by this standard are different from those of thepaper-insulated metal-sheathed cables. This standard does not includeany data on the current ratings, but information on this aspect will be

IS : 7098 (Part 2) - 1985

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covered in a separate Indian Standard later. In the meanwhile, usersare advised to consult the manufacturers for information on thisaspect.

0.6 The correct type of cables should be selected for the system keepingin view whether the system is earthed or unearthed.

NOTE — It should be realized that in an electric system where an earth-fault is notautomatically and promptly eliminated, the extra stresses on the insulation of thecables during the earth fault reduce the life of the cable to a certain extent.Therefore, if the system is expected to be operated quite often with a prolongedearth-fault, it is advisable to select the cables suitable for unearthed system.

0.7 In the preparation of this standard, assistance has been derivedfrom IEC Publication 502 (1983) ‘Extruded solid dielectric insulatedpower cables for rated voltages from 1 kV to 30 kV’, issued by theInternational Electrotechnical Commission.

0.8 This edition 2.2 incorporates Amendment No. 1 (November 1988)and Amendment No. 2 (November 2007). Side bar indicatesmodification of the text as the result of incorporation of theamendments.

0.9 For the purpose of deciding whether a particular requirement ofthis standard is complied with, the final value, observed or calculated,expressing the result of a test, shall be rounded off in accordance withIS : 2-1960*. The number of significant places retained in the roundedoff value should be the same as that of the specified value in thisstandard.

SECTION 1 GENERAL

1. SCOPE

1.1 This standard (Part 2) covers the requirements of followingcategories of crosslinked polyethylene insulated and PVC sheathedpower cables for single phase or three phase (earthed or unearthed)systems for electricity supply purposes:

*Rules for rounding off numerical values ( revised ).

a) Types of Cables1) Single-core unscreened, unarmoured (but non-magnetic

metallic tape covered);2) Single-core screened, unarmoured;3) Single-core armoured (non-magnetic) screened or

unscreened; and4) Three-core armoured, screened or unscreened.

IS : 7098 (Part 2) - 1985

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NOTE 1 — Cables of 6.35/11 kV grade (earthed system) are suitable for use on6.6/6.6 kV (unearthed system) also.

NOTE 2 — The cables conforming to this standard may be operated continuously at apower frequency voltage 10 percent higher than rated voltage.

NOTE 3 — Under Rule 54 of the Indian Electricity Rules 1956, in case of high voltage,the permissible variation of declared voltage at the point of commencement of supplyis percent.

1.2 These cables are suitable for use where combination of ambienttemperature and temperature-rise due to load results in conductortemperature not exceeding 90ºC under normal operation and 250ºCunder short-circuit conditions.

1.3 Armoured cables up to 11 kV grade specified in this standard aresuitable for use in mines also. However, for such cables, additionalrequirements have been included, wherever necessary (3.1.1, 16.5and 20.2).

2. TERMINOLOGY

2.0 For the purpose of this standard, the following definitions inaddition to those given in IS : 1885 (Part 32)-1971*, shall apply.

2.1 Routine Tests — Tests made by the manufacturer on all finishedcable lengths to demonstrate the integrity of the cable.

2.2 Type Tests — Tests required to be made before supply on a generalcommercial basis a type of cable in order to demonstrate satisfactoryperformance characteristics to meet the intended application.

NOTE — These tests are of such a nature that after they have been made they neednot be repeated unless changes are made in the cable materials or design whichmight change the performance characteristics.

2.3 Acceptance Tests — Tests carried out on samples taken from alot for the purpose of acceptance of the lot.

2.4 Optional Tests — Special tests to be carried out, when required,by agreement between the purchaser and the supplier.

b) Voltage Grade ( Uo/U )1) Earthed System — 1.9/3.3 kV, 3.8/6.6 kV, 6.35/11 kV,

12.7/22 kV and 19/33 kV.2) Unearthed System — 3.3/3.3 kV and 11/11 kV.

*Electrotechnical vocabulary : Part 32 Cables, conductors and accessories forelectricity supply.

+6– 9

IS : 7098 (Part 2) - 1985

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2.5 Earthed System — An electric system which fulfils any of thefollowing conditions:

2.6 Unearthed System — An electric system which does not fulfil therequirement of the earthed system ( see 2.5 ).

SECTION 2 MATERIALS

3. CONDUCTOR

3.1 The conductors shall be composed of plain copper or aluminiumwires complying with IS : 8130-1984*.

3.1.1 Mining cables to be used in gassy mines shall be of copperconductor only.

4. INSULATION

4.1 The insulation shall be of crosslinked polyethylene conforming tothe requirements given in Table 1.

5. SCREENING

5.1 The screening shall consist of one or more of the following, asspecified:

NOTE — The semi-conducting tape and semi-conducting compound shall be suitable forthe operating temperature of the cable and compatible with the insulating material.

a) Neutral-point or the mid-point connection is earthed in such amanner that, even under fault conditions, the maximum voltagethat can occur between any conductor and the earth does notexceed 80 percent of the nominal system voltage;

b) The neutral-point or the mid-point connection is not earthed buta protective device is installed which automatically cuts out anypart of the system which accidentlly becomes earthed; or

c) In case of ac systems only, the neutral-point is earthed throughan arc suppression coil with arrangement for isolation within 1 hof occurrence of the fault for the non-radial field cables andwithin 8 h for radial cables, provided that the total of suchperiods in a year does not exceed 125 h.

*Specification for conductors for insulated electric cables and flexible cords ( firstrevision ).

a) Non-metallic semi-conducting tape,b) Non-metallic semi-conducting compound, andc) Non-magnetic metallic tape wire, strip or sheath.

IS : 7098 (Part 2) - 1985

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5.1.1 Non-Magnetic Metallic Tape for Single-Core Unscreened andUnarmoured Cables — Requirements for this tape shall be as agreedto between the purchaser and the manufacturer.

6. FILLERS AND INNER SHEATH

6.1 The fillers and inner sheath shall be of the following:

a) Vulcanized or unvulcanized rubber; or

b) Thermoplastic materials.

6.2 Vulcanized or unvulcanized rubber or thermoplastic material usedfor inner sheath shall not be harder than XLPE and PVC used forinsulation and outer sheath respectively. Fillers and inner sheathmaterials shall be chosen to be compatible with the temperatureratings of the cable and shall have no deleterious effect on any othercomponent of the cable.

7. ARMOURING

7.1 Armouring shall be of the following:

7.2 The galvanized round steel wires/formed steel wires (strips) usedfor armouring shall conform to IS : 3975-1999*. The requirements ofnon-magnetic material shall be as agreed to between the purchaserand the supplier.

8. OUTER SHEATH

8.1 The outer sheath shall be of polyvinyl chloride (PVC) compoundconforming to the requirements of Type ST2 of IS : 5831-1984†.

SECTION 3 CONSTRUCTION

9. CONDUCTOR

9.1 The conductor shall be of stranded construction, size 25 mm2 andabove, complying with Class 2 of IS : 8130-1984‡.

a) Galvanized round steel wire, orb) Galvanized steel formed wire (strip), orc) Any metallic non-magnetic wire/strip.

*Specification for low carbon galvanized steel wires, formed wires and tapes forarmouring of cables ( third revision ).

†Specification for PVC insulation and sheath of electric cables ( first revision ).‡Specification for conductors for insulated electric cables and flexible cords ( first

revision ).

IS : 7098 (Part 2) - 1985

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9.2 In case of 3.3 kV cables, a protective barrier may be applied betweenthe conductor and insulation at the discretion of the manufacturer.Such barrier, when used, shall be compatible with insulating materialand suitable for the operating temperature of the cable.

10. CONDUCTOR SCREENING

10.1 All cables rated above 3.3/3.3 kV shall be provided with conductorscreening. Conductor screening shall be provided over the conductor byapplying non-metallic semi-conducting tape or by extrusion of semi-conducting compound or a combination of the two.

11. INSULATION

11.1 The conductor (with protective barrier or screen, where applied),shall be provided with crosslinked polyethylene insulation applied byextrusion.

11.2 Thickness of Insulation — The average thickness of insulationshall be not less than the nominal value ( ti ) specified in Table 2.

11.3 Tolerance on Thickness of Insulation — The smallest ofmeasured values of thickness of insulation shall not fall below thenominal value ( ti ) specified in Table 2 by more than 0.1 mm + 0.1 ti.

11.4 Application of Insulation — The insulation shall be so appliedthat it fits closely on the conductor (or conductor screening or barrier ifany) and it shall be possible to remove it without damaging theconductor.

12. INSULATION SCREENING

12.1 All cables rated above 3.3/3.3 kV shall be provided with insulationscreening.

12.2 The insulation screening shall consist of two parts; namely,metallic and non-metallic.

12.3 Non-metallic part shall be applied directly over the insulation ofeach core and shall consist of either a semi-conducting tape orextruded semi-conducting compound or a combination of the two oreither material with a semi-conducting coating.

12.4 Metallic part shall consist of either tape, or braid, or concentricserving of wires or a sheath; shall be non-magnetic and shall beapplied over the non-metallic part. For single core armoured cables,the armouring may constitute the metallic part of the screening.

IS : 7098 (Part 2) - 1985

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13. CORE IDENTIFICATION

13.1 Core identification for three core cables shall be as follows:

13.1.1 For identification by different colouring of XLPE insulation, orby using coloured strips, red, yellow and blue colours respectively shallbe used to identify phase conductors.

14. LAYING UP OF CORES

14.1 In three core cables, the cores (with or without barrier orscreening, as the case may be) shall be laid together with a suitableright hand lay. Where necessary, the interstices shall be filled withnon-hygroscopic material.

15. INNER SHEATH (COMMON COVERING)

15.1 The laid up cores shall be provided with inner sheath appliedeither by extrusion or by wrapping. It shall be ensured that the shapeis as circular as possible.

15.2 The inner sheath shall be so applied that it fits closely on the laidup cores and it shall be possible to remove it without damage to theinsulation.

15.2.1 In case of single core cables where there are both metallicscreening and armouring, there shall be extruded inner sheathbetween them.

15.3 Thickness of Inner Sheath — The thickness of inner sheath(common covering) shall be as given in Table 3. Single core cablesexcept those specified in 15.2.1 shall have no inner sheath.

15.3.1 When one or more layers of binder tapes are applied over thelaid up cores, the thickness of such tapes shall not be construed as apart of the inner sheath.

Voltage GradekV

Method of Identification

1.9/3.3 and 3.3/3.3a) Different colouring of XLPE insulation, orb) Coloured strips applied on the cores, orc) By numerals (1, 2, 3) either by applying

numbered strips or by printing on thecores.

3.8/6.6, 6.35/11, a) Coloured strips applied on the cores, or11/11, 12.7/22 and

19/33b) By numerals (1, 2, 3) either by applying

numbered strips or by printing on thecores.

IS : 7098 (Part 2) - 1985

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16. ARMOURING16.1 Armouring shall be applied over the insulation or protective barrieror non-metallic part of insulation screening, if any, in case of single corecables or inner sheath in case of screened and armoured single corecables, and over the inner sheath in case of three core cables.16.1.1 The armour wires/strips shall be applied as closely as practicable.16.1.2 The direction of lay of the armour shall be left hand. For doublewires/strips armoured cables, this requirement shall apply to the innerlayer of wires/strips. The outer layer shall, except in special cases, beapplied in the reverse direction to the inner layer, and there shall be aseparator of suitable non-hygroscopic material; such as plastic tape,bituminized cotton tape, bituminized hessian tape, rubber tape, proofedtape between the inner and outer layers of armour wires strips.16.1.3 A binder tape may be applied on the armour.16.2 Type of Armour — Where the calculated diameter belowarmouring does not exceed 13 mm, the armour shall consist ofgalvanized round steel wires. The armour of cables having calculateddiameter below armouring greater than 13 mm shall consist of eithergalvanized round steel wires or galvanized steel strips.16.2.1 In the case of single-core cables, the armouring shall be of non-magnetic material.16.3 Dimensions — The dimensions of galvanized steel wires orstrips shall be as specified in Table 4. The tolerance on nominaldimensions shall be as per IS : 3975-1999. However, for formed steelwires compliance shall be ensured only for dimensions ‘A’ & ‘C’.16.4 Joints — The joints in armour wires of strips shall be made bybrazing or welding and the surface irregularities shall be removed. Ajoint in any wire/strip shall be at least 300 mm from the nearest jointin any other armour wire/strip in the completed cable.16.5 Resistance — In case of cables for use in mines, the resistance ofarmour shall not exceed that of conductor as specified inIS : 8130-1984 by more than 33 percent. To satisfy this, substitution ofgalvanized wires/strips in the armour by required number of tinnedcopper wires/strips is permissible.16.6 The round steel wires/formed steel wires taken from the cableshall meet the following requirements:

a) The tensile strength of round steel wire/formed steel wire shall benot less than 250 N/mm2 and not more 580 N/mm2.

b) The elongation at break of round steel wire/formed steel wireshall be not less than 6 percent.

IS : 7098 (Part 2) - 1985

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c) Round steel wire shall meet the requirements of torsion test. Thegauge length between vices and the minimum number of turnswithout break shall be as per Table 6 of IS : 3975-1999*.

17. OUTER SHEATH

17.1 The outer sheath shall be applied by extrusion. It shall be applied:

a) over the non-magnetic metallic tape covering the insulation orover the non-magnetic metallic part of insulation screening incase of unarmoured single core cables, and

b) over the armouring in case of armoured cables.

17.2 Colour of outer sheath shall be black or any other colour as agreedto between the purchaser and the supplier.

17.3 Thickness of Outer Sheath

17.3.1 Unarmoured Cables — The thickness of outer sheath of un-armoured cables determined by taking the average of a number ofmeasurements shall be not less than the nominal value specified in col3 of Table 5 and the smallest of the measured values shall be not less thanthe minimum value specified in col 4 of Table 5.

17.3.2 Armoured Cables — The thickness of outer sheath shall be notless than the minimum value specified in col 5 of Table 5.

d) The zinc coating shall not show any cracks and shall not flake offon rubbing by the bare finger when the formed steel wire issubjected to winding test.

e) The uniformity of zinc coating of round steel wire/formed steelwire shall comply with the requirements of IS : 3975-1999*subject to the following.— The minimum number of dips shall be reduced by one

half-minute dip— in case of formed wires, dip test is applicable only for the face.

f) The mass of zinc coating of round steel wire shall be not lessthan 95 percent of the mass specified in Table 2 ofIS : 4826-1979.The mass of zinc coating of formed steel wire shall be not lessthan 95 percent of the mass specified in IS : 3975-1999*.

g) The resistivity of the round steel wire/formed steel wire shallmeet the requirements of IS : 3975-1999*.

*Specification for low carbon galvanized steel wires, formed wires and tapes forarmouring of cables ( third revision ).

IS : 7098 (Part 2) - 1985

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SECTION 4 TESTS

18. CLASSIFICATION OF TESTS* †

18.1 Type Tests — The following shall constitute type tests:

*Methods of test for cables.†Specification for conductors for insulated electric cables and flexible cords ( first

revision ).

Test For Requirements, Ref

For Test Method, Ref Part No. of

IS : 10810*a) Test on conductor

i) Annealing test (forcopper)

IS : 8130-1984† 1

ii) Tensile test (for alu-minium)

IS : 8130-1984† 2

iii) Wrapping test (foraluminium)

IS : 8130-1984† 3

iv) Resistance test IS : 8130-1984† 5b) Tests for round steel

wire/formed steel wire(strip) armour:1) Dimensions 16.3 of

IS : 692Part 36 ofIS : 10810

2) Physical tests onround/formed wire:

i) Tensile strength 16.6(a) ofIS : 7098 (Part 2)

Part 37 ofIS : 10810

ii) Elongation atbreak

16.6(b) ofIS : 7098 (Part 2)


iii) Torsion test forround wires

16.6(c) ofIS : 7098 (Part 2)


iv) Winding test forformed wires

16.6(d) ofIS : 7098 (Part 2)


v) Uniformity of zinccoating

16.6(e) of IS : 7098 (Part 2)


vi) Mass of zinccoating

16.6(f) ofIS : 7098 (Part 2)


vii) Resistivity 16.6(g) ofIS : 7098 (Part 2)


c) Test for thickness ofinsulation and sheath

Clauses 11, 15and 17, Table 2,Table 3 andTable 5

6

IS : 7098 (Part 2) - 1985

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Test For Requirements, Ref

For Test Method, Ref Part No. of

IS : 10810*

d) Physical tests for insula-tion

i) Tensile strength andelongation at break

Table 1 7

ii) Ageing in air oven Table 1 11iii) Hot test Table 1 30iv) Shrinkage test Table 1 12v) Water absorption

(gravimetric)Table 1 33

e) Physical test for outersheath

i) Tensile strength andelongation at break

IS : 5831-1984† 7

ii) Ageing in air oven IS : 5831-1984† 11iii) Shrinkage test IS : 5831-1984† 12iv) Hot deformation IS : 5831-1984† 15v) Loss of mass in air

ovenIS : 5831-1984† 10

vi) Heat shock do 14vii) Thermal stability do Appendix B of

IS : 5831-1984†

g) Partial discharge test 19.2 46h) Bending test 19.3 50j) Dielectric power factor test 19.4 48

i) As a function of voltageii) As a function of

temperaturek) Insulation resistance

(volume resistivity) testTable 1 43

m) Heating cycle test 19.5 49n) Impulse withstand test 19.6 47p) High voltage test 19.7 45q) Flammability test 19.8 53

*Methods of test for cables.†Specification for PVC insulation and sheath of electric cables ( first revision ).

IS : 7098 (Part 2) - 1985

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18.1.1 Tests (g), (h), (j), (m), (n) are applicable only to screened cables,out of which test (j) is applicable to cables with rated voltage6.35/11 kV and above only.

18.1.2 With the exception and provision of 18.1.1, the following testson screened cables shall be performed successively on the same testsample of completed cable, not less than 10 m in length between thetest accessories:

18.1.2.1 If a sample fails in test (g), one more sample shall be taken forthis test, preceded by tests (b) and (e).

18.2 Acceptance Tests — The following shall constitute acceptancetests:

NOTE — Partial discharge test shall be carried out on full drum length.

18.2.1 A recommended sampling plan for acceptance tests is given inAppendix A.

a) Partial discharge test,b) Bending test followed by partial discharge test,c) Dielectric power factor as a function of voltage,d) Dielectric power factor as a function of temperature,e) Heating cycle test followed by dielectric power factor as a

function of voltage and partial discharge tests,f) Impulse withstand test, andg) High voltage test.

a) Annealing test (for copper),b) Tensile test (for aluminium),c) Wrapping test (for aluminium)d) Conductor resistance test,e) Test for thickness of insulation and sheath,f) Hot set test for insulation,g) Tensile strength and elongation at break test for insulation and

outer sheath,h) Partial discharge test (for screened cables only),j) High voltage test, andj) Insulation resistance (volume resistivity) test.

IS : 7098 (Part 2) - 1985

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18.3 Routine Tests — The following shall constitute routine tests:

NOTE — Partial discharge test shall be carried out on full drum length.

18.4 Optional Test — Cold impact test for outer sheath (IS : 5831-1984*) shall constitute the optional test.

19. DETAILS OF TESTS

19.1 General — Unless otherwise stated in this standard, the testsshall be carried out in accordance with appropriate part of IS : 10810†,taking into account additional information given in this standard.

19.2 Partial Discharge Test — The partial discharge magnitude attest voltage equal to 1.5 Uo shall not exceed 20pC.

19.3 Bending Test — The diameter of the test cylinder shall be20D ± 5 percent where D is the overall diameter of the completedcable. After completing the bending operations, the test sample shallbe subjected to partial discharge measurement and shall comply withthe requirements given in 19.2.

19.4 Dielectric Power Factor Test

19.4.1 Tan δ as a Function of Voltage — The measured value of tan δat Uo shall not exceed 0.004 and the increment of tan δ between 0.5 Uoand 2 Uo shall not be more than 0.002.

19.4.2 Tan δ as a Function of Temperature — The measured value oftan δ shall not exceed 0.004 at ambient temperature and 0.008 at90°C.

19.5 Heating Cycle Test — The sample, which has been subjected toprevious tests, shall be laid out on the floor of the test room andsubjected to heat cycles. After third cycle, the sample shall besubjected to dielectric power factor as a function of voltage (19.4.1) andpartial discharge test (19.2).

a) Conductor resistance test,b) Partial discharge test (for screened cables only),c) High voltage test, andd) Resistance test for armour (for mining cables) in accordance with

IS : 10810 (Part 42) and 16.5.

*Specification for PVC insulation and sheath of electric cables ( first revision ).†Methods of test for cables.

IS : 7098 (Part 2) - 1985

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19.6 Impulse Withstand Test — Impulse voltage level shall be asgiven below:

19.7 High Voltage Test19.7.1 Type/Acceptance Test — The cable shall withstand withoutbreakdown an ac voltage equal to 3Uo but not less than the valuespecified in 19.7.2 when applied to the sample between conductor andscreen/metallic tape/armour (and between conductors in case of un-screened cable). The voltage shall be gradually increased to thespecified value and maintained for a period of 4 hours.

If while testing, interruption occurs during the 4 hour period thetest shall be prolonged to the same extent. If the interruption periodexceeds 30 minutes, the test shall be repeated.19.7.2 Routine Test — The cables shall withstand without any failure,the test voltages given below, when applied for a period of five minutesfor each test connection.

19.8 Flammability Test — Period of burning after removal of theflame shall not exceed 60 seconds and the unaffected (uncharred)portion from the lower edge of the top clamp shall be at least 50 mm.

SECTION 5 IDENTIFICATION, PACKING AND MARKING

20. IDENTIFICATION20.1 Manufacturer’s Identification — The manufacturer shall beidentified throughout the length of cable by manufacturer’s name ortrade-mark and the voltage grade and year of manufacture indented,printed or embossed or by means of a tape bearing this information. Theindentation, printing or embossing shall be done only on the outer sheath.

Rated voltage, kV 3.8/6.6 6.35/11 11/11 12.7/22 19/33Impulse voltage, kV 60 75 95 125 170No breakdown of the insulation shall occur during the test.

VOLTAGE GRADE TEST VOLTAGE

Between Conductorsand Screen/Armour

Between Conductors

kV kV (rms) kV (rms)1.9/3.33.3/3.3

10 10

3.8/6.6 12 —6.35/11 17 —11/11 28 —12.7/22 32 —19/33 48 —

IS : 7098 (Part 2) - 1985

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For manufacturer’s name, if none of these methods is employed or ifthe purchaser so desires, colour identification threads in accordancewith a scheme to be approved by the Indian Standards Institutionshall be employed.

20.2 Cable Identification — In case of cables intended for use inmines, the word ‘MINING’ shall be indented, printed or embossed onthe outer sheath throughout the length of the cable.

20.3 Cable Code — The following code shall be used for designatingthe cable:

NOTE — No code letter for conductor is required when the conductor material iscopper.

21. PACKING AND MARKING

21.1 The cable shall be wound on a drum ( see IS : 10418-1982* ) andpacked. The ends of the cable shall be sealed by means of non-hygroscopic sealing material.

21.2 The cable shall carry the following information either stencilledon the drum or contained in a label attached to it:

Sl No. Constituent Code Letteri) Aluminium conductor A

ii) XLPE insulation 2Xiii) Steel round wire armour Wiv) Non-magnetic round wire armour Wav) Steel strip armour F

vi) Non-magnetic strip armour Favii) Double steel round wire armour WW

viii) Double steel strip armour FFix) PVC outer sheath Y

*Specification for drums for electric cables.

a) Reference to this Indian Standard, for example, ref ISS 7098(Part 2);

b) Manufacturer’s name or trade-mark;c) Type of cable and voltage grade;d) Number of cores;e) Nominal cross-sectional area of conductor;f) Cable code;g) Length of cable on the drum;h) Number of lengths on the drum (if more than one);

IS : 7098 (Part 2) - 1985

18

21.2.1 The cable (drum or label) may also be marked with the ISICertification Mark.

NOTE — The use of the ISI Certification Mark is governed by the provisions of theIndian Standards Institution (Certification Marks) Act and the Rules andRegulations made thereunder. The ISI Mark on products covered by an IndianStandard conveys the assurance that they have been produced to comply with therequirements of that standard under a well-defined system of inspection, testing andquality control which is devised and supervised by ISI and operated by the producer.ISI marked products are also continuously checked by ISI for conformity to thatstandard as a further safeguard. Details of conditions under which a licence for theuse of the ISI Certification Mark may be granted to manufacturers or processors,may be obtained from the Indian Standards Institution.

SECTION 6 TABLES

j) Direction of rotation of drum (by means of an arrow);k) Gross mass;m) Country of manufacture; andn) Year of manufacture.

TABLE 1 PROPERTIES OF XLPE INSULATION( Clause 4.1 )

SLNO.

PROPERTY REQUIREMENT

(1) (2) (3)i) Tensile strength 12.5 N/mm2, Min

ii) Elongation at break 200 percent, Miniii) Ageing in air oven:

a) Treatment TemperatureDuration

135 ± 3°C7 days

b) Tensile strength variation ± 25 percent, Maxc) Elongation variation ± 25 percent, Max

iv) Hot set:

a) TreatmentTemperatureTime under loadMechanical stress

200 ± 3°C15 minutes20 N/cm2

b) Elongation under load 175 percent, Maxc) Permanent elongation (set) after

cooling15 percent, Max

v) Shrinkage


130 ± 3°C1 hour

b) Shrinkage 4 percent, Maxvi) Water absorption (gravimetric):


85 ± 2°C14 days

b) Water absorbed 1 mg/cm2, Maxvii) Volume resistivity:

a) at 27°C 1 × 1014 ohm-cm, Minb) at 90°C 1 × 1012 ohm-cm, Min

IS : 7098 (Part 2) - 1985

19

TABLE 2 NOMINAL THICKNESS OF INSULATION( Clauses 11.2 and 11.3 )

NOMINAL NOMINAL THICKNESS OF INSULATION ( ti )AREA OF

CONDUCTOR 1.9/3.3 and3.3/3.3 kV

3.8/6.6 kV 6.35/11 kV 11/11 kV 12.7/22 kV 19/33 kV

Singlecorearmou-redcable

Single coreunarmou-red andthree corecables

(1) (2) (3) (4) (5) (6) (7) (8)mm2 mm mm mm mm mm mm mm2535507095

2.52.52.52.52.5

2.22.22.22.22.2

2.82.82.82.82.8

3.63.63.63.63.6

5.55.55.55.55.5

—6.06.06.06.0

——8.88.88.8

120150185240300

2.52.52.52.52.5

2.22.22.22.22.2

2.82.82.82.83.0

3.63.63.63.63.6

5.55.55.55.55.5

6.06.06.06.06.0

8.88.88.88.88.8

400500630800

1 000

2.62.83.03.33.5

2.22.42.62.83.0

3.33.53.53.53.6

3.63.63.63.63.6

5.55.55.55.55.5

6.06.06.06.06.0

8.88.88.88.88.8

TABLE 3 THICKNESS OF INNER SHEATH( Clause 15.3 )

All dimensions in millimetres.

CALCULATED DIAMETER OVER LAID UP CORES/OVER SCREEN FOR SINGLE CORE CABLES

IN ACCORDANCE WITH 15.3 [REFIS : 10462 (PART 1)-1983*]

THICKNESS OF INNERSHEATH ( MIn )

Over Up to and Including

(1) (2) (3)—25354555

25354555—

0.30.40.50.60.7

*Fictitious calculation method for determination of dimensions of protectivecoverings of cables: Part 1 Elastomeric and thermoplastic insulated cables.

IS : 7098 (Part 2) - 1985

20

TABLE 4 DIMENSIONS OF ARMOUR — ROUND WIRES AND STRIPS( Clause 16.3 )

All dimensions in millimetres.CALCULATED DIAMETERUNDER ARMOUR [REFIS : 10462 (PART 1)-

1983*]

NOMINAL THICKNESS OF STEEL STRIP

NOMINAL DIAMETEROF ROUND WIRE

Over Up to andIncluding

(1) (2) (3) (4)a) For all diameter in

excess of 13 or

0.8 —

b) —1325405570

1325405570—

—0.80.81.41.41.4

1.401.602.002.503.154.00

NOTE — (a) and (b) indicate two methods of practice in the application of armouring.

*Fictitious calculation method for determination of dimensions of protectivecoverings of cables: Part 1 Elastomeric and thermoplastic insulated cables.

TABLE 5 THICKNESS OF OUTER SHEATH( Clauses 17.3.1 and 17.3.2 )

All dimensions in millimetres.

CALCULATED DIAMETER UNDERTHE OUTER SHEATH [REF

IS : 10462 (PART 1)-1983*]

THICKNESS OF OUTER SHEATH FOR UNARMOURED

CABLES

MINIMUM THICKNESS OF OUTER SHEATH FOR

ARMOURED CABLES

Over Up to andIncluding

Nominal( ts )

Minimum

(1) (2) (3) (4) (5)—1525354045505560657075

1525354045505560657075—

1.82.02.22.42.62.83.03.23.43.63.84.0

1.241.401.561.721.882.042.202.362.522.682.843.00

1.241.401.561.721.882.042.202.362.522.682.843.00

*Fictitious calculation method for determination of dimensions of protectivecoverings of cables : Part 1 Elastomeric and thermoplastic insulated cables.

IS : 7098 (Part 2) - 1985

21

A P P E N D I X A( Clause 18.2.1 )

SAMPLING OF CABLES

A-1. LOT

A-1.1 In any consignment the cables of the same size manufacturedunder essentially similar conditions of production shall be groupedtogether to constitute a lot.

A-2. SCALE OF SAMPLING

A-2.1 Samples shall be taken and tested from each lot for ascertainingthe conformity of the lot to the requirements of the specification.

A-2.2 The number of samples to be selected shall be as given below:

A-2.2.1 These samples shall be taken at random. In order to ensurethe radomness of selection, procedure given in IS : 4905-1968* may befollowed.

A-3. NUMBER OF TESTS AND CRITERION FOR CONFORMITY

A-3.1 From each of the drums selected, suitable lengths of testsamples shall be taken. These test samples shall be subjected to eachof the acceptance tests ( see 20.2 ). A test sample is called defective if itfails in any one of the acceptance tests. If the number of defectives isless than or equal to the corresponding permissible number givenin A-2.2, the lot shall be declared as conforming to the requirements ofacceptance tests; otherwise not.

No. of Drumsin the Lot

No. of Drums to beTaken as Sample

Permissible No.of Defectives

Up to 25 3 026 to 50 5 051 to 100 8 0

101 to 300 13 1301 and above 20 1

*Methods for random sampling.

IS : 7098 (Part 2) - 1985

22

( Continued from page 2 )

Members RepresentingSHRI B. ROY CHOWDHURY Calcutta Electric Supply Corporation (India) Ltd,

CalcuttaSHRI P. NEOGI ( Alternate )

SHRI M. M. HONAVAR Cable Corporation of India Ltd, BombaySHRI S. R. PADMANABHAN ( Alternate )

SHRI S. L. KAKKAR Universal Cables Ltd, SatnaSHRI R. C. AGRAWAL ( Alternate )

SHRI J. V. MEHTA The Ahmedabad Electricity Company Ltd,Ahmadabad

SHRI S. MITRA The National Insulated Cable Co of India Ltd,Calcutta

DR V. TIKKU ( Alternate )SHRI B. K. MUNDHRA Oriental Power Cables Ltd, Kota

SHRI A. K. JAIN ( Alternate )DR S. K. RAY Indian Cable Co Ltd, Calcutta

SHRI K. V. R. RAO ( Alternate )SHRI S. R. SARAN Industrial Cables (India) Ltd, Rajpura

Bureau of Indian StandardsBIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promoteharmonious development of the activities of standardization, marking and quality certification ofgoods and attending to connected matters in the country.

CopyrightBIS has the copyright of all its publications. No part of these publications may be reproduced in anyform without the prior permission in writing of BIS. This does not preclude the free use, in the courseof implementing the standard, of necessary details, such as symbols and sizes, type or gradedesignations. Enquiries relating to copyright be addressed to the Director (Publications), BIS.

Review of Indian StandardsAmendments are issued to standards as the need arises on the basis of comments. Standards are alsoreviewed periodically; a standard along with amendments is reaffirmed when such review indicatesthat no changes are needed; if the review indicates that changes are needed, it is taken up forrevision. Users of Indian Standards should ascertain that they are in possession of the latestamendments or edition by referring to the latest issue of ‘BIS Catalogue’ and ‘Standards : MonthlyAdditions’.This Indian Standard has been developed by Technical Committee : ETDC 59 and amended by ET 9

Amendments Issued Since Publication

Amend No. Date of IssueAmd. No. 1 November 1988Amd. No. 2 November 2007

BUREAU OF INDIAN STANDARDSHeadquarters:

Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002.Telephones: 323 01 31, 323 33 75, 323 94 02

Telegrams: Manaksanstha(Common to all offices)

Regional Offices: Telephone

Central : Manak Bhavan, 9 Bahadur Shah Zafar MargNEW DELHI 110002

323 76 17323 38 41

Eastern : 1/14 C. I. T. Scheme VII M, V. I. P. Road, KankurgachiKOLKATA 700054

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is 7098 part 2

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