Siemens SIPROTEC 7SJ62 Manual page 244

Functions
2.13 Intermittent Ground Fault Protection
The (much longer) resetting time T-reset (message „IEF Tres run.") is launched simultaneously with
T-sum det. when a ground fault occurs. Unlike T-sum det., each new ground fault resets this time to its
initial value and it expires anew. If T-reset expires and no new ground fault is recorded during that time, all
memories are reset and the protection resumes normal position. T-reset thus determines the time during
which the next ground fault must occur to be processed yet as intermittent ground fault in connection with the
previous fault. A ground fault that occurs later will be considered a new fault event.
The message „IIE Fault det" will be entered in the fault log and reported to the system interface only until
the message „Intermitt.EF" is issued. This prevents a burst of messages. If the message is allocated to
an LED or a relay, this limitation does not apply. This is accomplished by doubling the message (message
numbers 6924, 6926).
Interaction with the Automatic Reclosure Function
Automatic reclosure is not an effective measure against intermittent ground faults as the function only trips after
repeated detection of a fault or after expiration of the summation monitoring time T-sum det. and besides
this, its basic design is to prevent thermal overload. For these reasons, the intermittent ground fault protection
is not implemented as starting feature of the automatic reclosing function.
Interaction with Breaker Failure Protection
A pickup that is present when the time delay TRIP-Timer has expired is interpreted by the breaker failure pro-
tection as a criterion for a tripping failure. Since permanent pickup is not ensured after a tripping command by
the intermittent ground fault protection, cooperation with the breaker failure protection is not sensible. There-
fore, this function is not activated by the intermittent ground fault protection.
244
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008