A
Absorption current, 57–58, 155
Accelerated water-treeing test (AWTT), 380
Acceptance tests, 341. See also Field assessment of power cable systems
Admittance, 72
AEIC. See Association of Edison Illuminating Companies (AEIC)
Aging effects
cellulose, 122
dielectric fluid, 122
paper–fluid combination, 122–123
Air gaps, 388
Air insulated conductors
corona, 15
voltage, conductor and ground, 14–15
Alternating current
corrosion, 407
spark test, 232
voltage withstand test, 232
water tank test, 232
Alternative test methods, 346
Aluminum Association (AA), 205
American National Standards Institute (ANSI), 206
American Society for Testing and Materials (ASTM), 41, 46–47, 88, 110, 150, 159, 172, 206–207, 213, 292, 305–306
American wire gauge (AWG), 25, 207
AWG/kcmil system, 27
definitions, 26
Ampacities of Cables in Open Top Trays, 283
bonding jumper capability, 318
calculations, 273–279, 282–283
center ground, 315
conductor losses
AC conductor resistance, 276
DC conductor resistance, 275–276
hysteresis and eddy current effects, 277
proximity effect, 277
dielectric loss, 277
heat, 315
heat transfer model, 273
simplified thermal circuit, 274
load and loss factor, 274
metallic shield losses
approach, 279
magnitude of voltage, 277, 278
spacing effect, 278
shield conductivity
electrical resistivity of metals, 317
single-conductor cables, 316
shield losses
conductor, 316
current flows, 316
single-conductor transmission cables, 316
under short circuit conditions methods, 284
tables
manufacturers, 283
and voltage drop calculations, 284
Annealing, 47, 86, 159, 208, 219, 379, 421
Anodic corrosion
point, 406
street railway systems, 405
Antioxidants, 102–103, 109, 126–127, 153, 229
Armor corrosion
EPRI Project EL-4042, 419
single-conductor cables, 419
URD cables, 419
Association of Edison Illuminating Companies (AEIC), 176, 178, 204, 209–210, 246, 374, 380, 396–397
documents, 206
ASTM. See American Society for Testing and Materials (ASTM)
AWG. See American wire gauge (AWG)
B
Banbury process, 109
Basic impulse level (BIL), 386
Birmingham wire gage (BWG), 27
Blocked strand, 208
Bow tie growing from contaminant, 375
Breakdown and failure
intrinsic strength, 160
strength considerations, 160–162
Breakdown strength, 14–15, 17, 19, 132, 157, 160–163, 190
Brown and Sharpe gage (B&S), 27
Bunch stranding, 42
Bush tree growing from shield, 375
Butyl rubber, 7–9, 77, 107, 111
C
Cable installation
pipe cable section lengths, 246
pipe-type cable, 246
research results
EPRI research, 247
underground extruded power cable pulling guide, 246
Cable pulls, 235
advances, 236
coefficient of friction, 238
electric power research institute, 236
group of, 236
maximum allowable tension on conductors, 237
pipe-type, 236
pulling multiple cables in duct
cradled configuration, 240
triangular configuration, 240–241
weight correction factor, 241, 242
pulling tension calculations, 237–238
sidewall bearing pressure, 238
pulling forces, 239
Cables
AEIC data, 400
data analysis
cumulative miles, 400
expression, 399
failure rates, 399
failures
locating, 330
statistics, 400
insulation
dielectric loss in, 59
resistance, 56
jacket materials, 214
low-voltage cable ratings, 55–56
in magnetic metallic conduit, 50
manufacturers, 400
performance
AEIC cable failure data, 396–399
EEI, 396
electrical failures of, 396, 397
PILC cable failures, 396
response, 155
spacing, 302
street light, 178
surface resistivity, 57
as transformer
single-point grounding, 314
volume insulation resistance, 56–57
Cable with extruded insulations
cooling, thermoplastic materials, 222–223
curing
ethylene propylene rubber, 221
Monosil, 222
polyethylene, 221
Sioplas, 222
Canadian Standards Association (CSA), 206
Capacitance, 333, 349–351, 353, 355, 358, 362–363, 391, 422
of cables, 71
Capacitive reactance, 61
Capacitive–resistive (CR), 19
Carbon–hydrogen polymeric structure, 81
Cathodic corrosion
elimination of, 406
hydrogen ions, 406
potential of, 406
Cellulose, 122
Chain branching phenomenon, 83
for alternating current operation, 61–62
Chemical corrosion, 407
Chlorinated polyethylene (CPE), 127, 179
Chlorosulfonated polyethylene (CSPE, Hypalon), 117, 127, 181
Circular mils (cmil), 27, 36, 43, 48, 207, 213, 276, 317
Class B and C stranding, 41, 207–208
3/C Low volt cable with sector-shaped conductors, 199
Coefficient of friction, 238
Cold shrink splices, 268
Combination thumper and TDR equipment, 331–332
Compacted granular backfills, 302–303
Compact stranding, 42
Compressed stranding, 41–42, 207
Concentric-lay-stranded conductor resistance, 28–35
Concentric neutral cables
coated wires, 172
complicating factor, 172
ICEA standards, 172
Concentric neutral corrosion
cable failures, 408
causes of, 408
electric power systems, 408
electromotive series (see Electromotive series)
mechanisms
combinations, 410
decaying vegetation, 410
differential aeration, 409
dissimilar metal, 410
galvanic influence, 410
oxygen content, 409
stray DC current, 409
unjacketed cable, 409
research efforts, 408
soil composition
physical and chemical characteristics, 408
Concrete as backfill, 306
for cable, 307
Florida test installation, 307–308
test results, 308
Condition assessment tests, 342. See also Field assessment of power cable systems
Conduction, 154
Conductor losses
AC conductor resistance
electromotive force, 276
DC conductor resistance
aluminum conductor, 276
conductor material, 275
hysteresis and eddy current effects, 277
proximity effect, 277
Conductors, 20
American wire gauge (AWG), 26–27
insulation
with single layer of, 189
with insulation and insulation shield, 17–18
manufacturing
annealing, 219
diameter, 218
stranding, 219
temper, 219
wire drawing, 218
properties
standards and specifications
blocked strand, 208
compressed strand, 207
identification, 208
resistance, 207
Conductor shielding, 171
materials, 170
purpose of, 169
semiconducting extruded layers, 170
super smooth, super clean, 170
water-impervious material, 170
Conduit
installation in, 428
and manhole systems
percent fill, 243
Cone, stress, 253–254, 256–257
Consensus organizations, 206–207
Continuous vulcanizing (CV) tubes, 9
Controlled molecular weight distribution technology, 89–90
Corona, 15
Corrective thermal backfills
quality control, 305
use of, 301
Corrosion, 19–20, 401, 404–405
AC conditions
electrochemical potentials, 418
threshold of, 418
weight loss tests, 418
alternating current, 407
armor wires, 417
cathodic, 406
chemical, 407
under direct current (DC) conditions performing weight loss studies, 417
galvanic, 406
local cell, 407
location sites, 411
mechanism
for copper, 405
electrochemical action, 404
nature of, 404
oxidation, 405
release of, 405
resistivity measurements of neutral wires, 411
service-inflicted conditions, 417
types of metals, 417
Cradled configuration, 240
Critical soil moisture, 292
Cross-linked polyethylene (XLPE), 8, 144, 150, 153, 155, 157, 161–163, 167, 386, 396
AC breakdown, 161
cross-linking, 90
jacket, 181
temperature influence, 100–102
Cross-linking process, 91
chain length of polyethylene effects, 91
coiled chains, 92
“sol” fraction, 92
Currents in armor system
alternating current, 414
effective values, 416
multi-grounded system, 416
single-conductor cables, 414
three-conductor cables, 416–417
D
Deformation resistant thermoplastic (DRTP) shield, 178
Dielectric
absorption, 58
loss, 151
Dielectric spectroscopy, 364–365
Differential decay method, 334
Dimethyl benzyl alcohol, 95
Direct current
advantages and disadvantages, testing, 347–348
high voltage testing, 347
spark test, 232
water tank test, 232
Direct voltage testing, 344–345
high and low voltage direct current tests, 346–347
Dispersion
contaminants, 153
function of frequency, 151–152
polymer chains, regions, 151
TR-XLPE, 153
Dissipation factor (DF), 64, 124, 144–145, 151–153, 167
testing
advantages and disadvantages, 355
measurement and equipment, 355
method, 354
with very low frequency sinusoidal wave form, 355–356
Double needle test specimen, 379
“Dry cure” cables, 10
Dual style crosshead, 226
Duty-cycle test, 386
E
Early Edison cable, 4
Earth gradient, 332
Earth interface temperature, 309
Earth resistivity, 293
Edison Electric Institute (EEI), 395
Electrical breakdown, 414
Electrical insulation (dielectric), 21
materials
polyethylene copolymers, 80–83, 87–88
Electrical tests
for low voltage cables, 332
for medium voltage cables, 332
Electrical treeing, 368
growing from contaminant on conductor shield, 376
possibilities, 374
Electric fields, 21
capacitive coupling, 173
tapes supplemented, 173
Electric lighting, 3
Electric Power Research Institute (EPRI), 390, 395
Final Report EL-2847, 236
research, 8
Electromagnetic fields, 173, 200–201
concentration tends, 403
electrochemical equivalents
theoretical amount, 403
hydrogen ion concentration
equivalent weight, 403
significance of, 404
tendency for metals, 402
Elements of testing, 342
Energy distribution for lighting, 3–5
EPR. See Ethylene propylene rubber (EPR)
EPRI. See Electric Power Research Institute (EPRI)
Ethylene copolymer insulations (EPR), 110
AC breakdown stress retention of, 112
Banbury process, 109
Buss kneader, 109
composed of, 106
as elastomers, 107
long-life EPR formulations, 113
Ethylene propylene rubber (EPR), 8, 106, 144, 153–155, 162, 167, 182, 386, 396
insulation, 106
jacket, 182
Ethylene silane copolymer cross-linking, 99
Ethylene vinyl acetate (EVA), 113
External thermal environment, 292
Extruded cable rejuvenation
in-service procedure for
diagnostic procedures, 134–135
rejuvenation chemistry
oligomerization process, 133
Extruded cables, 170
Extruded dielectric power cables, 7–8
Extruded insulation shields
resistivity, 212
thickness, 212
Extruded thermoplastic shields, 9
Extruder, 220
and crosshead, 221
Extrusion line
assembly, 227
extrusion heads, 226
single extruder line, 223
true triple extrusion, 225–226
F
Failures analysis, 268
Failures locating
cables, 330
capacitance measurements, 333
capacitor discharge (thumper) set, 331
earth gradient, 332
instruments infrequently used in North America, 333–334
radar or time domain reflectometry, 331
Faulted circuit indicators, 334
automatic reset with, 336
designed with reset button, 335
magnetic fault indicators, 334
manual reset fault indicator, 335
for overhead application, 338
remote target, 337
separable connector, 337
Fault location, 327–328, 330–334
Field assessment of power cable systems
acceptance tests, 341
alternative test methods, 346
condition assessment tests, 342
direct voltage testing, 344–345
installation tests, 341
on-line and off-line testing, 344
withstand tests, 342
Field experience
installation, 247
older conduits, 247
paper-insulated lead covered, 248
steel armor wires, 418
weight loss of, 418
Field molded splices, 267
Fill, conduit, 243
Flat configuration multiconductor cables, 195–197
Florida test installation, 307–308
Fluidized thermal backfills (FTB), 305–306
Friction, coefficient, 238
G
Galvanic corrosion
corrosive force, 406
dissimilar metals, 406
Geometric spacing, 63
Global evaluation and pinpointing defects, 343
Grounding, 313
H
HDPE. See High-density polyethylene (HDPE)
Heat transfer, 273–274, 288–292, 296
High-density polyethylene (HDPE), 178–179
High molecular weight polyethylene (HMWPE), 8–9, 81
High potential testing, 124
High stress, 156
“High temperature” XLPE, 10
High thermal resistivity soil, 290
High voltage direct current tests. See also Direct voltage testing
direct current withstand test, 347
leakage current—time tests, 347
step-voltage/leakage current tip-up tests, 347
Hilborn loop, 333
Hypalon, 127
I
ICEA. See Insulated Cable Engineers Association (ICEA)
IEC. See International Electrotechnical Commission (IEC)
IEEE Standard Power Cable Ampacity Tables, 283
Impregnating
control, 230
fluid, conditioning, 230
Impulse current differential method, 334
Impulse strength, 66
Inception voltage and extinction voltage
cable wall, 165
gas pressure, 165
geometry of void, 165
void size, 166
Inductance, 69
in coaxial cables, 70
in multiconductor cables, 69–70
mutual, 63
Installation, cable
properties, 136
resistance, 57
Installation tests, 341. See also Field assessment of power cable systems
Insulated Cable Engineers Association (ICEA), 204
divisions in, 204
standards, 205
Insulation
AC dielectric strength, 66
dielectric strength, 66
electrical requirements, 211
impulse strength, 66
layer requirements, 19
resistance test, 232
test voltages, insulation thickness, 210–211
voltage stress in cables, 65–66
Insulation materials
operating stress
cable response, 155
conduction, 154
dielectric losses, 151
interfacial polarization, 153–154
mineral filled systems, 153–154
specific inductance capacitance, 149–151
Insulation response, high stress in
breakdown and failure, 160–163
for medium voltage cables
concentric neutral cables, 172
stress relief layer, 171
Interlocked armor, 183
cables of, 182
galvanized steel, 182
low voltage cable, 200
mechanical protection, 182
International Electrotechnical Commission (IEC), 206–207
AWG/kcmil sizes, 36
IEC 60228, 36
J
Jacket layer insulation
low smoke zero halogen jacket, 194
polyvinyl chloride jacket, 193–194
sunlight and flame resistance, 193
THHN and THWN, 193
Jackets, 19–20, 116–118, 175, 192–194, 410
Jam ratio, 242
Jointing theory
connecting conductors, 264
connector, 263
insulation for joints, 263–265
metallic shield, 263
penciling, 263
shield materials, 265
taped splice, 262
K
kcmil, 27
L
Lay length, 199
Lead length, 393
Lightning protection of distribution cable systems
arresters connections, 393
natural lightning strokes, 390
surge arrestor operation, 388–389
traveling waves, 391
velocity of propagation, 392
wave shape and rate of rise, 387
Linear low density polyethylene (LLDPE), 177–179
Line-to-line voltage, 386
Load factor, 274
Local cell corrosion
differential aeration, 407
electrolytic cells, 407
rate of, 407
specific form, 407
Losses, shield, 316
Loss factor, 274
Low smoke zero halogen (LSZH) jackets, 180
Low thermal resistivity soil, 290
Low-voltage armored cables, 200
Low-voltage cables, 44, 56, 60
conductor considerations, 188
jacket layer insulation, 192–194
metallic coverings, 188
multiconductor cables, 195–201
nonmetallic coverings, 188
plexed single conductor wires and cables, 194–195
shielding
electric fields, 173
magnetic fields, 173
single layer insulation, 189–192
Low-voltage polymeric
secondary cables, 130
M
Magnetic fault indicators, 334
Magnetic fields
shielding factor, 173
Maintenance tests, 341–342. See also Field assessment of power cable systems
Manual reset fault indicator, 335
Material considerations in conductors
ampacity, 25
direct current resistance, 25
short circuits, 25
voltage regulation, 25
weight, 25
Medium density polyethylenes (MDPEs), 88–89
Medium voltage cables
insulation shielding
concentric neutral cables, 172
stress relief layer, 171
Medium voltage insulating materials, 135–137
Medium voltage shielded cables, 20
Metallic armor, 413
Metallic sheath, 414
Metallic shield
materials, 171
single-conductor cable, 172
Metallic shielding
concentric neutral cables, 213–214
options for, 213
Metal oxide arresters (MOV), 389
distribution systems, 389
load break elbow arresters, 389
URD system, 390
Metal oxide varistor (MOV) arrester, 386
Methylene blue dying technique, 382–383
harmonization, 36
Mineral filled systems and interfacial polarization, 153
conventional polarization, 154
EPR compound, 154
Multiconductor cables
low voltage armored, 200
shielded low voltage cables, 200–201
Multiple-point grounding
advantages, 318
current flow, 318
disadvantages, 318
N
National Electrical Code (NEC), 188, 190–191, 193, 195–197, 200, 207, 243
National Electrical Manufacturers Association (NEMA), 205
National Electric Light Association (NELA), 395
Native soil thermal resistivity, 293–295
Natural lightning strokes
EPRI, 390
inductance of, 391
rate of rise, 390
standard, 391
NEC. See National Electrical Code (NEC)
compounds, 181
thermosetting characteristics of, 181
New British standard (NBS). See Standard wire gauge (SWG)
Nonshielded power cable, 20
Nylon, 180
O
Off-line power frequency testing
characteristics, 350
test apparatus requirements, 349–350
On-line and off-line testing, 344
On-line power frequency testing
advantages, 348
measurements, 348
Open circuit sheath, 278
Organic soils, 293
test
advantages and disadvantages, 363
apparatus, 363
criteria, 362
general description of test method, 362
procedures, 364
Oxidative degradation, 102
P
cooling cycle, control
cylinder, 231
drying and impregnating, 228–230
insulation, 227
Paper-insulated lead-covered cables (PILC), 76, 257, 395
Paper insulation, 5–6, 119–120, 155–156, 227
Partial discharge, 163, 165, 167, 343
phenomena parameters
inception and extinction voltage, 165–166
residue voltage, 166
time lag, 166
measurement, 352
Peak failure rates, 385
100 percent level, 55
133 percent level, 55
173 percent level, 55
Permittivity, 60
and specific inductance capacitance, 149–151
Peroxide-induced cross-linking, 93–97
Phase-to-phase voltage, 16
Phenyldimethyl siloxane (PMDMS), 132–133
polymerization, 133
PILC. See Paper-insulated lead-covered cables (PILC)
Plasticizer, 117
Plexed single conductor wires and cables, 195
triplexed and quadruplexed cables., 194
Polarization, 146–147, 148, 153–154
Maxwell–Wagner polarization, 149
nonpolar regions, 147
orientation, principles, 146
polar functionality, 147
process, 149
carbon black, 177
controlled molecular weight distribution technology, 89–90
densities, 177
HDPE, 178
LLDPE, 177
structures of, 84
types of, 87
“Polyhydric” alcohol, 122
Polymerization process, 83
Polymers
antioxidant(s), incorporating, 149
charge migration on, 147
electrical properties, 143
physicochemical properties, 143–144
under voltage stress, 148
Polyolefin-based polymers, 78
Polypropylene, 179
Polyvinyl chloride/nitrile-butadiene, 182
Polyvinyl chloride (PVC), 127, 144, 150, 176–177, 191–192
compounds, 176
jacket, 176
limitations of, 176
moisture resistance, 177
Poor thermal soils, 301
Power Cable Ampacities, 272
Present-day medium voltage insulations, 79
Primary voltage cables, 8
Pulling calculations
tension out of horizontal bend values for various exponents, 244–245
Pulse decay, 333
PVC. See Polyvinyl chloride (PVC)
R
Radar/time domain reflectometry, 331
Radiation-induced cross-linking, 97–98
Random coiled configuration, 84
capacitive reactance, 72
inductive reactance, 71
total reactance, 72
“Ready-to-extrude” compounds, 220
Rejuvenation, 131
Resistance, 25, 48–49, 50–51, 67–68, 275
Resistivity, 24, 69, 145–146, 293–295
Rising voltage, 16
electric field lines, 17
tracking, 17
Rogowski electrodes, 159
Round configuration multiconductor cables, 197–200
Route thermal survey elements
analysis, 310
corrective thermal backfill and thermal stability, 310–311
laboratory testing, 310
quality assurance, 311
review and planning, 309
RTV silicone, 129
Rural Utilities Service (RUS), 206
S
Seasonal temperature changes at operating depth, 295
Sector conductors, 43
dimensions of, 44
and aluminum conductors, 45
Selection of joints and terminations
environmental conditions, 268
Self-inductance, 69
Semiconducting jackets
ANSI/ICEA S-94-649, 178
moisture transmission, 178
thermo-mechanical bending test, 178
Type I and Type II, 178
URD cable, 178
value of, 179
Semiconducting materials, 178–179
Separator, 190
Service entrance cables, 197
Sheath bonding and grounding
cable systems, 314
multiple-point grounding, 318
Sheaths
AEIC and ICEA standards, 175–176
conductor, 18–19, 169–171, 208–209
Shielded low voltage cables, 200–201
Shielding layer requirements, 19
Shield materials
Short circuit current, 284
SIC. See Specific inductive capacitance (SIC)
Sidewall bearing pressure (SWBP), 236, 238–239
Silane-induced cross-linking, 98–100
Silicone oil, observation in, 383
Single-conductor, 413
Single layer insulation
crystalline insulations, 189
shrink back, 189
tape separator, 189
thermoplastic polyvinyl chloride wire, 191–192
Single pass
with one dual extruder, 225
with three extruders, 224
Single-point and cross-bonding
advantages, 319
auxiliary cable bonding, 325
continuous cross-bonding, 324–325
cross-bonded circuits, 324
disadvantages, 319
induced sheath voltage, 319–320
right angle arrangement, 321
multigrounded cable run, 323
open-circuit sheath, 319
single-point bonding methods, 319–320
standing voltage, 319
“Sioplas,” 99
Soil
components, 289
texture, 289
thermal stability, 295
heat rate, 296
moisture, 297
type and density, 297
water influence on, 291
Soil thermal resistivity, 272–273, 288–292
Solid conductor
single-core and multicore cables, 37
Specific inductive capacitance (SIC), 59, 60, 149–151
Splice box, 5
Splicing/jointing
design and installation
insulation for joints, 264–265
jackets for joints, 265
shield materials, 265
theory
cable ends, 262
conducting layer and splice and metallic shield, 263
penciling and insulation, 263
tape splice, 262
Standard Penetration Tests (SPT), 309–310
Standard wire gauge (SWG), 27
Stranded conductors
single-core and multicore cables, 38–39
bunch stranding, 42
compact stranding, 42
unilay conductors, 46
Stress relief, 171
extruded insulation shield, 171
ICEA, 171
nonmetallic layer, 171
polymer layer, 171
Surge arrestor, operation
air gaps, 388
valve, 389
Surge protection
coefficient of grounding, 387
discharge, 387
highest power voltage, 386
insulation resistance discharge voltage, 387
protective margin, 386
sparkover, 387
voltage rating, 386
T
TDR. See Time domain reflectometry (TDR)
copper, 47
Tensile strength, 124
Termination
lugs
sealing, 258
paper-insulated cable terminations, 257
separable connectors, 258
conductor PILC cable termination, 257, 260
connector, 260
gas-filled termination, 257, 259
grounding eye, 261
stress cone design
capacitive graded termination, 256
departure angle, 257
voltage gradient design
capacitive and resistive graded materials, 257
Termination theory
electrical stress, 253
field plots
conductor, 252
electric flux lines, 252
with simple stress relief, 253
creepage/leakage distance, 254–255
equipotential plot, shield removed, 254
stress cone, 254
splice and joint, 251
voltage gradient terminations
cold shrink, 255
Testing
factory, 232
field, 341
Test methods, 160
configurations, 158
curved Rogowski electrodes, 158–159
Thermal circuits of cables
continuous load
external thermal circuit, 282
external thermal circuit and cable in duct, 281
primary cable with metallic shield and jacket, 280
shielded cable with several heat sources, 280
single layer of insulation, 279–280
internal thermal circuit for shielded cable with jacket, 279
Thermoplastic
insulation, 7
Thermoplastic elastomer (TPE), 180
Thermoplastic jackets
chlorinated polyethylene, 179
LSZH/LSHF jackets, 180
nylon, 180
polypropylene, 179
semiconducting jackets, 178–179
thermoplastic elastomer, 180
Thermosetting
Thermosetting jacket materials, 180
chlorosulfonated polyethylene, 181
cross-linked polyethylene, 181
ethylene–propylene rubber, 182
neoprene, 181
polyvinyl chloride/nitrile-butadiene, 182
Three conductor round cable, 198
Time considerations, 343
Time domain reflectometry (TDR), 393
Total cable reactance, 64
Tracking, 17
Traveling waves
attenuation, 391
electric system, 391
surge impedance, 391
worst-case scenarios, 392
combination of water and electrical trees, 377–379
electrical, 368
tree-like deterioration in paper insulation, 368
water, 368
Tree-resistant cross-linked polyethylene (TR-XLPE), 10, 77
commercial, 105
fundamental approaches, 104
as insulation materials, 105
modification, 105
Tree-retardant cross-linked polyethylene (TR-XLPE), 104–105, 144, 153, 167
Triple style crosshead, 226
Triple tandem single pass extrusion, 223–224
Triplexed and quadruplexed cables, 194–195
True triple extrusion, 225–226
Two-pass extrusion process, 9, 223–224
Type W Flat 4 Conductor Mining Cable, 196
U
Underground cable systems, 12
Underground residential distribution (URD), 7, 18, 20, 178–179, 190–191, 329, 390, 395, 419
Underground system, fault locating, 327
cable locating, 330
capacitance measurements, 333
capacitor discharge (thumper) set, 331–332
conduit and manhole systems, 328–329
faulted circuit indicators, 334–338
instruments infrequently used in North America, 333–334
radar/time domain reflectometry, 331
residential distribution, 329–330
Underground Systems Reference Book, 236
Underwriters Laboratories (UL), 207
Unilay conductors and strand, 46
URD. See Underground residential distribution (URD)
V
Valve arresters
blocks, 389
high voltage of, 389
nonlinear resistance, 389
Vapor transmission, 117
Varley loop, 333
Velocity of propagation, 331–332
distribution systems, 392
doubled wave, 392
protection of, 392
radar, 392
slightly slower, 392
traveling wave, 392
Vented fan trees, 372
Very low frequency (about 0.1 Hz) testing, 356
with cosine-pulse waveform, 358–359
with sinusoidal waveform, 359–360
with VLF sinusoidal waveform, 360–362
Voids
air, dielectric strength, 163
degradation process, 164
“0” voltage line, 14
Voltage regulation, 25
Voltage stress, 65–66, 156–157, 253
Volume resistivity (VR), 56–57, 68–69, 144, 145–146
insulation resistance, 145
surface resistivity, 145
“Vul-cup,” 96
W
Wall thickness, insulation, 156–157
Water blocking technology, 118–119, 208
Water treeing, 368
accelerated testing, 374
deterrents to, 373
electrical trees and, 371
examples of, 371
influenced by, 369
methods to minimize, 372
from pie plate indent, 381
test specimen, “pie plate,” 380
Water trees, 10, 103, 124, 131, 157–158, 368
Wave shape and rate of rise
combination of, 388
lightning artificial, 387
natural lightning, 387
slope of, 388
surge arresters, 388
Wavy line, 81
Weight correction factor, 241
Wire drawing, 219
Withstand tests, 342. See also Field assessment of power cable systems
Withstand voltage, 347
X
XLPE. See Cross-linked polyethylene (XLPE)