Siemens SIPROTEC 7SJ61, Руководство пользователя, Страница: 158 / 454

Functions
2.10 Intermittent Ground Fault Protection
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008
158
Figure 2-54 Logic diagram of the intermittent ground fault protection – principle
Fault Logging
A fault event and thus fault logging is initiated when the non-stabilized
Ii
E 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
Ii
E 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 stages to pick up (e.g. 50-1 , 50N-1 , 50Ns-1 ) and
produce a burst of messages. To avoid overflow of the fault log such messages are not entered anymore in the
fault log after detection of an intermittent ground fault (message
„Intermitt.EF“
) unless they cause a trip-
ping 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 2-8):