Download  Print this page

Setting Guidelines (insulated Systems); Figure 66: Phasor Diagrams For Insulated System With C Phase Fault - GE MiCOM P40 Agile Technical Manual

Feeder management ied.
Hide thumbs
   
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668

Advertisement

P14x
E00628

Figure 66: Phasor diagrams for insulated system with C phase fault

The current imbalance detected by a core balanced current transformer on the healthy feeders is the vector
addition of Ia1 and Ib1. This gives a residual current which lags the polariing voltage (–3Vo) by 90°. As the healthy
phase voltages have risen by a factor of Ö3, the charging currents on these phases are also Ö3 times larger than
their steady state values. Therefore, the magnitude of the residual current IR1, is equal to 3 times the steady state
per phase charging current.
The phasor diagram indicates that the residual currents on the healthy and faulted feeders (IR1 and IR3
respectively) are in anti-phase. A directional element (if available) could therefore be used to provide discriminative
earth fault protection.
If the polarising is shifted through +90°, the residual current seen by the relay on the faulted feeder will lie within
the operate region of the directional characteristic and the current on the healthy feeders will fall within the
restrain region.
The required characteristic angle setting for the SEF element when applied to insulated systems, is +90°. This is for
the case when the protection is connected such that its direction of current flow for operation is from the source
busbar towards the feeder. If the forward direction for operation were set such that it is from the feeder into the
busbar, then a –90° RCA would be required.
Note:
Discrimination can be provided without the need for directional control. This can only be achieved, however, if it is possible to
set the IED in excess of the charging current of the protected feeder and below the charging current for the rest of the system.
11.6.2

SETTING GUIDELINES (INSULATED SYSTEMS)

The residual current on the faulted feeder is equal to the sum of the charging currents flowing from the rest of the
system. Further, the addition of the two healthy phase charging currents on each feeder gives a total charging
current which has a magnitude of three times the per phase value. Therefore, the total imbalance current is equal
to three times the per phase charging current of the rest of the system. A typical setting may therefore be in the
order of 30% of this value, i.e. equal to the per phase charging current of the remaining system. Practically though,
the required setting may well be determined on site, where suitable settings can be adopted based on practically
obtained results.
When using a core-balanced transformer, care must be taken in the positioning of the CT with respect to the
earthing of the cable sheath:
P14xEd1-TM-EN-1
IR1
Ia1
Vcpf
Vres
(= 3Vo)
An RCA setting of ±90º shifts the
"centre of the characteristic" to here
Chapter 6 - Current Protection Functions
Vaf
Restrain
Vapf
Ib1
Operate
Vbpf
IR3 = (IH1 + IH2)
Vbf
137

Advertisement

Table of Contents

   Also See for GE MiCOM P40 Agile

   Related Manuals for GE MiCOM P40 Agile

Comments to this Manuals

Symbols: 0
Latest comments: