Current rating medium voltage cables with impregnated paper insulation – triple core

acc. to HD 621 S1, part 4C

This section applies to triple-core cables with impregnated paper insulation.

General conditions

Temperatures °C (conductor) NKBY/NAKBY NHKBY/NAHKBY & NEKEBY/NAEKEBY
6/10 kV 6/10 kV 12/20 kV 18/30 kV
highest permissible operating temperature +65 +70 +65 +60
highest short circuit temperature (max. 5 s) +170 *) +170 *) +170 *) +150

*) 160°C for soldered conductor connections.

metal sheath and concentric conductors are grounded on both ends.
Operating frequency 50 Hz.
The tabulated loading capacities ​​are based on various conditions such as
– operating mode,
– laying conditions,
– environmental conditions.
In the event of deviating operating conditions, the loading capacities ​​are to be multiplied by suitable conversion factors, which are based on the same calculation principles and operating conditions as the given values.

Current carrying capacity of medium voltage cables 6/10 kV

Laying in earth (20°C)
Recommended values according to HD 621 S1, part 4C, table 11
U0 / U
 6 / 10 kV
Design short code *) NKBY
 NHKBY
 NEKEBY
 NAKBY
 NAHKBY
 NAEKEBY
Arrangement
Cross-section
mm²		 copper conductor
rated current in A		 aluminium conductor
rated current in A
25 122 136 136 95 106 106
35 150 163 164 117 126 127
50 179 192 194 139 149 150
70 222 236 238 173 183 185
95 269 282 285 209 219 221
120 308 321 324 240 250 253
150 347 361 364 270 281 284
185 392 407 412 307 318 322
240 454 471 477 357 370 374
300 511 528 538 403 417 424
400 577 597 609 461 477 485
500 – – 685 – – 554

*) The current carrying capacity is identical for designs with other protective sheaths.

Laying in air (30°C)
Recommended values according to HD 621 S1, part 4C, table 12
U0 / U
 6 / 10 kV
Design short code *) NKBY
 NHKBY
 NEKEBY
 NAKBY
 NAHKBY
 NAEKEBY
Arrangement
Cross-section
mm²		 copper conductor
rated current in A		 aluminium conductor
rated current in A
25 100 114 116 78 88 90
35 123 139 141 96 107 109
50 148 166 169 115 129 131
70 187 208 211 145 162 164
95 228 253 257 177 196 199
120 263 291 296 205 227 231
150 301 332 337 234 258 262
185 345 380 385 270 297 301
240 408 449 453 320 352 355
300 467 511 519 368 403 408
400 536 591 596 428 472 475
500 – – 684 – – 552

*) The current carrying capacity is identical for designs with other protective sheaths.

Current carrying capacity of medium voltage cables 12/20 kV

Laying in earth (20°C)
Recommended values according to HD 621 S1, part 4C, table 11
U0 / U
 12 / 20 kV
Design short code *) NHKBY
 NEKEBY
 NAHKBY
 NAEKEBY
Arrangement
Cross-section
mm²		 copper conductor
rated current in A		 aluminium conductor
rated current in A
25 127 129 99 100
35 153 155 119 121
50 182 185 141 144
70 230 229 179 178
95 276 274 214 213
120 314 314 245 244
150 354 354 276 275
185 399 402 312 314
240 459 468 361 367
300 515 530 407 417
400 580 600 465 478
500 – 674 – 545

*) The current carrying capacity is identical for designs with other protective sheaths.

Laying in air (30°C)
Recommended values according to HD 621 S1, part 4C, table 12
U0 / U
 12 / 20 kV
Design short code *) NHKBY
 NEKEBY
 NAHKBY
 NAEKEBY
Arrangement
Cross-section
mm²		 copper conductor
rated current in A		 aluminium conductor
rated current in A
25 108 111 84 86
35 131 134 102 104
50 157 161 122 125
70 198 200 154 156
95 240 243 186 189
120 275 279 214 218
150 312 317 243 247
185 356 363 279 284
240 415 426 326 334
300 472 488 372 384
400 543 560 433 445
500 – 641 – 516

*) The current carrying capacity is identical for designs with other protective sheaths.

Current carrying capacity of medium voltage cables 18/30 kV

Laying in earth (20°C)
Recommended values according to HD 621 S1, part 4C, table 11
U0 / U
 18 / 30 kV
Design short code *) NHKBY
 NEKEBY
 NAHKBY
 NAEKEBY
Arrangement
Cross-section
mm²		 copper conductor
rated current in A		 aluminium conductor
rated current in A
25 – – – –
35 143 146 111 113
50 170 174 132 135
70 217 215 169 167
95 259 259 202 201
120 295 297 230 231
150 329 334 257 260
185 372 379 292 297
240 432 442 340 347
300 486 501 384 394
400 551 569 441 454
500 – 644 – 520

*) The current carrying capacity is identical for designs with other protective sheaths.

Laying in air (30°C)
Recommended values according to HD 621 S1, part 4C, table 12
U0 / U
 18 / 30 kV
Design short code *) NHKBY
 NEKEBY
 NAHKBY
 NAEKEBY
Arrangement
Cross-section
mm²		 copper conductor
rated current in A		 aluminium conductor
rated current in A
25 – – – –
35 122 126 95 98
50 146 150 113 117
70 186 187 145 145
95 224 227 174 176
120 256 261 200 203
150 289 295 225 230
185 328 338 257 264
240 383 397 301 311
300 434 453 343 356
400 497 519 398 414
500 – 594 – 478

*) The current carrying capacity is identical for designs with other protective sheaths.

Permissible short-circuit temperatures and rated short-time current densities

Recommended values according to HD 621 S1, part 4C, table 14
Cables with
 admissible short-circuit temperature
°C		 rated short-circuit current densities in A/mm²
for a rated short-circuit duration of 1s
conductor temperature at the beginning of short-circuit in °C
70 65 60 50 40 30 20
copper conductor
6/10 kV
& 12/20 kV		 170 120 124 127 134 141 147 154
18/30 kV 150 – – 117 124 131 138 145
aluminium conductor
6/10 kV
& 12/20 kV		 170 80 82 84 89 93 97 102
18/30 kV 150 – – 77 82 87 91 96


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