Siemens siprotec SJ62 User Manual page 224

Logic Diagram
Figure 2-79 Logic diagram of the intermittent ground fault protection – principle
Fault Logging
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
The following figure shows the logic diagram for the intermittent ground fault protection
function.
A fault event and thus fault logging is initiated when the non-stabilized IN 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 IN 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 time overcurrent elements to pick up (e.g.
50-1, 50N-1, 50Ns-1) and produce a burst of messages. To avoid overflow of the fault
log, messages are not entered anymore in the fault log after detection of an intermit-
tent ground fault (message „Intermitt.EF") unless they cause a tripping com-
mand. If an intermittent ground fault has been detected, the following pickup messag-
es of the time overcurrent protection will still be reported without restraint (see Table
2-13):
2.13 Intermittent Ground Fault Protection
222