Setting Notes - Siemens siprotec SJ62 User Manual

2.13.2 Setting Notes

General
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
The protection function for intermittent ground faults can only take effect and is only
accessible if the current to be evaluated (133, INTERM.EF or with Ignd) was con-
figured in address with 3I0 with Ignd,sens.. If not required, this function is set
to Disabled.
The function can be turned ON or OFF under address 3301 INTERM.EF.
The pickup threshold (r.m.s. value) is set in address 3302 Iie>. A rather sensitive
setting is possible to respond also to short ground faults since the pickup time shortens
as the current in excess of the setting increases. The setting range depends on the
selection of the current to be evaluated at address 133 INTERM.EF.
The pickup time can be prolonged at address 3303 T-det.ext.. This pickup stabi-
lization is especially important for the coordination with existing analog or electrome-
chanical overcurrent relays. The time T-det.ext. can also be disabled (T-
det.ext. = 0).
The stabilized pickup starts the counter T-sum det.. This counter is stopped but not
reset when the picked up function drops out. Based on the last counter content the
counter resumes counting when the stabilized function picks up next. This sum of in-
dividual pickup times, which are to initiate tripping, is set at address 3304 T-sum
det.. It represents one of the four selectivity criteria (pickup value Iie>, detection ex-
tension time T-det.ext., counter T-sum det. and reset time T-reset) for coor-
dinating the relays on adjacent feeders and is comparable to the time grading of the
time overcurrent protection. The relay in the radial network which is closest to the in-
termittent fault and picks up, will have the shortest summation time T-sum det..
The reset time, after which the summation is reset in healthy operation and the pro-
tection resumes normal status, is configured to T-reset at address 3305.
Figure 2-80 Example of selectivity criteria of the intermittent ground fault protection
Address 3306 Nos.det. specifies the number of pickups after which a ground fault
is considered intermittent.
2.13 Intermittent Ground Fault Protection
226