cable training - part 1
TRANSCRIPT
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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.)?__