Cable Training - Part 1

8/10/2019 Cable Training - Part 1

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Electrical Markets Division

CABLES - PART 1

Review of Power Cable Theory

CABLES - PART 2

Cable Preparation & Failure Causes

RLG, August, 2004


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CABLES - PART 1

Gene Olson & Bob Goodman - 2000


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CABLE CONFIGURATIONS

Single Conductor

Three Conductor


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SHIELDED POWER CABLE

COMPONENTS

1. Conductor

2. Strand Shield

3. Insulation

6. Jacket

4. & 5. Insulation Shield

(4) Semi-conducting Layer

(5) Metallic Shield


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COMMON

1/C INDUSTRIAL CABLES

Tape Shielded

Wire Shielded

UniShield

PILC

UniShield is a registered trademark of BICC Cables


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COMMON

1/C UTILITY CABLES

Concentric Neutral (CN)

Jacketed Concentric Neutral (JCN)

Longitudinally Corrugated (LC)


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COMMON

3/C INDUSTRIAL CABLES

Interlocked Armor

orC-L-X

PILC


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CONDUCTORIntended for Carrying the Current

COPPER

ALUMINUM

Widely used for industrial applications

Many years of reliable service

Highly conductive

Widely used for utility applications

Lighter weight than copper Surface forms insulating oxide

Coefficient of expansion greater than copper


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CONDUCTORS

Flexible Compressed( 97% of Concentric )

ConcentricStranded

SolidCompact Round(90% of Concentric)


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CONDUCTORS

CompactSector

Segmental Annular


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STRAND SHIELD(or conductor shield)

NO SHIELDPartial Discharges (Corona)

SHIELDEDStrand Shield (Semi-Con)

SEMI-CONDUCTING LAYER

Acts as aFaraday Cageto shield the insulation

fromair surrounding the conductor strands


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CORONA TREES(XLPE Cable Insulation)


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INSULATION

Intended to contain the Voltage

Insulation

Insul. Operating Emergency

Type Temperature Temperature

PILC 80oC 95oC

XLPE 90oC 130oC

EPR 90oC 130oC

EPR* 105oC 140oC

*Note: MV105 Cable

INSULATION

Intended to contain the Voltage


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INSULATION

Emergency Temperature

EMERGENCY OPERATION

. . . applicable for 1500 hours cumulative

during the life of the cable . . .


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SYSTEM OPERATING VOLTAGE

15 kV Rated Example

14.4 kV 14.4 kV

14.4 kV Phase-to-phase

8.3 kV

Phase-to-ground

8.3 kV 8.3 kV

A B C


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STANDARD VOLTAGE RATINGS

(Phase-to-Phase)

2.5 kV 92.0 kV

5.0 kV 115.0 kV

Medium 8.7 kV 138.0 kV

Voltage 15.0 kV 161.0 kV

25.0 kV 196.0 kV

34.5 kV 230.0 kV

46.0 kV 287.5 kV

69.0 kV 345.0 kV

Note: Medium Voltage Range = 2001 V - 34.5 kV


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TYPICAL SYSTEMS

WYE (or STAR)

(Formerly Grounded

System)

100 %

Insulation Level

A

BC

DELTA

(Formerly UngroundedSystem)

133%Insulation Level

A

B

C


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Selection ofcable insulation levelshall be made on the

basis of the applicablephase-to-phase Voltage and

general system category.

INSULATION LEVELS

The system protection willclear ground faults:

100% Level - within 1 minute

133% Level - not to exceed 1 hour 173% Level - time is indefinite


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INSULATION

Non-shielded Cable

Corona

Electric

Flux Lines

Grounded

Conduit

High Stress

Concentration


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INSULATION

Shielded Cable

Even Field

Distribution

Semi-Conductor

&

Metallic Shield


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INSULATION

Field Plot

EQUIPOTENTIAL LINES

20%

40%

60%

80%

100%


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INSULATION

Electric Field Distribution

90O

Flux

Line

Equipotential

Line

ELECTRIC FLUX LINES

EQUIPOTENTIAL LINES


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INSULATION SHIELD

Semi-Con

Semi-con

It is intended to:

Shield the Insulation from

the air that is between the

insulation and metallic shield


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INSULATION SHIELD

Metallic Shield

THE SHIELD MUST BE GROUNDED !

1. To confine thedielectric fieldwithin the cable

2. To obtain symmetricalradial distribution of

Voltage stress within the dielectric3. To limitradio interference

4. To reduce the hazard ofshock

5. To provide return forshort circuit current

in the event of a cable failure

6. Forconcentric neutral cables, to provide a

neutral return path

Metallic ShieldFUNCTIONS


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BEDDING TAPE or FILLERS

Intended to addmechanical strength to the cable

Filler (cut-off & discard)

Bedding Tape (cut-off & discard)


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JACKET

(Sheath)

Jacket

Intended to provide physical

protection and keep moisture

out of the cable

Common Types

Rubber (e.g. Neoprene)

Thermoplastic (e.g. PVC)

Lead


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SPLICING & TERMINATING

What Cable I nformation Do I Need?

? Voltage Class (and insulation level)? _______________

Conductor Size (and Copper or Aluminum)? _________

Cable Type (type of shield, armor, 3/C, etc.)?_________ Location (indoor, outdoor, manhole, pole, etc.)? ______

Other? (e.g. conductor: stranded, compact, solid, etc.)?__

Documents

Cable Training - Part 1