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

acc. to HD 621 S1, part 3C

This section applies to single-core cables with impregnated paper insulation – also for pre-stranded cables.

General conditions

Temperatures °C (conductor) 6/10 kV 12/20 kV 18/30 kV
highest permissible operating temperature +70 +65 +60
highest short circuit temperature (max. 5 s) +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 3C, table 6
U0 / U
 6 / 10 kV
NKY
 NKLEY
 NAKY
 NAKLEY
Arrangement
Cross-section
mm²		 Rated current
in A		 Rated current
in A
25 140 160 139 158 108 124 108 124
35 167 191 166 188 129 148 129 147
50 197 226 196 220 153 175 153 173
70 241 275 240 264 188 214 187 209
95 289 328 286 310 224 256 223 247
120 329 371 324 345 256 291 254 278
150 369 414 361 377 287 325 283 306
185 417 465 405 414 325 366 320 340
240 483 534 465 461 378 423 369 383
300 544 595 515 495 427 474 413 418
400 617 668 574 535 489 537 467 461
500 695 741 631 569 558 606 524 500
630 – – – – – – – –
800 – – – – – – – –
1000 – – – – – – – –
Laying in air (30°C)
Recommended values ​​according to HD 621 S1, part 3C, table 7
U0 / U
 6 / 10 kV
NKY
 NKLEY
 NAKY
 NAKLEY
Arrangement
Cross-section
mm²		 Rated current
in A		 Rated current
in A
25 124 145 124 144 96 112 96 112
35 151 176 150 175 117 137 117 136
50 181 213 181 210 141 165 141 164
70 228 267 226 261 177 208 176 205
95 279 327 276 315 216 254 215 248
120 322 378 318 360 251 295 249 286
150 368 431 361 402 286 336 283 322
185 423 494 413 452 330 387 325 366
240 501 584 484 517 392 459 384 425
300 577 666 549 566 453 527 438 473
400 668 767 626 626 529 614 507 534
500 770 874 705 679 619 711 583 592
630 – – – – – – – –
800 – – – – – – – –
1000 – – – – – – – –

Current carrying capacity of medium voltage cables (12/20 kV)

Laying in earth (20°C)
Recommended values ​​according to HD 621 S1, part 3C, table 8
U0 / U
 12 / 20 kV
NKY
 NKLEY
 NAKY
 NAKLEY
Arrangement
Cross-section
mm²		 Rated current
in A		 Rated current
in A
25 137 150 137 148 106 117 106 116
35 164 182 163 178 127 141 127 139
50 194 216 193 211 150 168 150 166
70 237 266 234 254 184 207 183 202
95 284 317 280 298 220 247 219 238
120 323 359 317 332 251 281 248 268
150 362 400 353 362 282 314 277 294
185 409 450 396 398 319 355 313 327
240 474 516 452 443 371 409 361 369
300 534 575 501 476 419 458 403 403
400 605 644 557 516 480 520 455 445
500 682 714 610 550 548 585 508 484
630 – – – – – – – –
800 – – – – – – – –
1000 – – – – – – – –
Laying in air (30°C)
Recommended values ​​according to HD 621 S1, part 3C, table 9
U0 / U
 12 / 20 kV
NKY
 NKLEY
 NAKY
 NAKLEY
Arrangement
Cross-section
mm²		 Rated current
in A		 Rated current
in A
25 118 134 118 133 92 104 92 104
35 143 163 143 161 111 126 111 125
50 172 196 171 193 133 152 133 151
70 215 245 213 238 167 191 166 188
95 262 299 260 287 204 233 202 227
120 303 346 299 327 236 270 234 261
150 345 393 338 365 268 307 265 293
185 396 450 385 409 309 353 304 332
240 468 529 450 467 366 417 357 384
300 537 604 509 513 421 479 407 429
400 621 692 579 568 492 556 470 484
500 715 787 649 617 573 642 537 537
630 – – – – – – – –
800 – – – – – – – –
1000 – – – – – – – –

Current carrying capacity of medium voltage cables (18/30 kV)

Laying in earth (20°C)
Recommended values ​​according to HD 621 S1, part 3C, table 10
U0 / U
 18 / 30 kV
NKY
 NKLEY
 NAKY
 NAKLEY
Arrangement
Cross-section
mm²		 Rated current
in A		 Rated current
in A
25 – – – – – – – –
35 156 168 155 165 121 130 120 129
50 185 200 184 195 144 155 143 153
70 229 247 227 238 178 192 177 188
95 276 297 272 281 215 232 212 224
120 316 339 309 317 246 266 243 254
150 354 382 345 351 276 299 271 283
185 400 431 385 384 313 340 305 317
240 463 499 440 427 363 395 351 357
300 522 555 486 461 410 444 392 391
400 591 619 539 499 470 502 442 432
500 666 684 590 535 536 564 494 471
630 – – – – – – – –
800 – – – – – – – –
1000 – – – – – – – –
Laying in air (30°C)
Recommended values ​​according to HD 621 S1, part 3C, table 11
U0 / U
 18 / 30 kV
NKY
 NKLEY
 NAKY
 NAKLEY
Arrangement
Cross-section
mm²		 Rated current
in A		 Rated current
in A
25 – – – – – – – –
35 134 149 133 147 104 116 104 115
50 160 179 160 176 124 139 124 138
70 200 224 198 217 155 174 155 171
95 244 273 241 261 189 213 188 207
120 281 315 276 297 219 246 216 237
150 319 357 312 332 248 279 245 266
185 366 408 355 371 286 321 280 301
240 432 480 414 423 338 379 329 348
300 495 546 467 266 388 433 375 390
400 572 623 529 515 453 501 431 439
500 658 706 594 563 527 577 492 490
630 – – – – – – – –
800 – – – – – – – –
1000 – – – – – – – –

Current carrying capacity of medium voltage cables

Permissible short-circuit temperatures and rated short-time current densities
Recommended values ​​according to HD 621 S1, part 3C, table 13

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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