Siemens SIPROTEC 7SJ62 Manual page 245

Logic Diagram
The following figure shows the logic diagram for the intermittent ground fault protection function.
Figure 2-93 Logic diagram of the intermittent ground fault protection – principle
Fault Logging
A fault event and thus fault logging is initiated when the non-stabilized IiE element picks up for the first time. A
message „IIE Fault det" is produced. The message „IIE Fault det" is issued and entered in the
fault log (and reported to the system interface) so often until the number of pickups „IIE Fault det" has
reached the value set for parameter Nos.det.. When this happens, the message „Intermitt.EF" is issued
and „IIE Fault det" is blocked for the fault log and the system interface. This method accounts for the fact
that the IiE element may also pick up for a normal short-circuit. In this case the pickup does not launch the
alarm „Intermitt.EF".
Intermittent ground faults may cause other overcurrent elements to pick up (e.g. 50-1, 50N-1, 50Ns-1), which
may result in a burst of messages. In order to avoid an overflow of the fault log, its messages are no longer
entered in the fault log after detection of intermittent ground faults (indication „Intermitt.EF"), unless they
cause a trip command. If an intermittent ground fault has been detected, the following pickup messages of the
time overcurrent protection will still be reported without restraint (see Table 2-16):
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
2.13 Intermittent Ground Fault Protection
Functions
245