the signals of these functions after detection of an intermittent ground fault (signal
Intermittent
gnd.flt.
).
The special mechanism is applied for the following listed functions and other functions are not influenced:
•
Overcurrent protection, phases
•
Overcurrent protection, ground
•
Directional overcurrent protection, phases
•
Directional overcurrent protection, ground
•
Overcurrent protection, 1-phase
•
Negative-sequence protection with definite-time characteristic curve
•
Directional negative-sequence protection with definite-time delay
•
Directional overcurrent-protection stage with cos phi or sin phi measurement
•
Directional overcurrent-protection stage with 3I0-phi (V,I) measurement
•
Sensitive ground-current protection with 3I0
If a function picks up, normally its output signals are sent directly to the information targets, for example, the
pickup signal is written to the fault log. To avoid overflow of logs due to intermittent ground faults, a special
log buffer mechanism is used. If one of the preceding functions or stages picks up after an intermittent ground
fault has been detected (signal
Intermittent gnd.flt.
has been issued), its output signals are processed
as shown in the following 2 tables.
Table 6-10 Processing of the Signal Status Changes
Processing of Signal Status Changes Description
Special buffering mechanism The status changes of signals are written to a special
buffer. This buffer can store a maximum of 2 status
changes (the most recent ones) for each signal.
With the pickup signal as example, if one of the
preceding protection functions or stages picks up
during an active
Intermittent gnd.flt.
signal,
the pickup signal is not written in the fault log
anymore unless one of the preceding functions oper-
ates. After the operation, the buffered signals are
written to the information target with the original
time stamp. This measure ensures that a pickup
signal, although delayed, is always signaled in associ-
ation with each operate command.
Discard The signal status changes are discarded.
Pass through The signal is forwarded to the information target
without restriction.
Special buffering does not apply for specific informa-
tion targets as protection measure, for example,
reverse interlocking, need these signals for proper
operation.
Table 6-11 Information Target with Different Processing of Signal Status Changes
Information Target Processing of Signal Status Changes
Processing of Signal Status
Changes
Operational log
Fault log
Ground-fault log
User-defined log
Special buffering mechanism
Protection and Automation Functions
6.13 Non-Directional Intermittent Ground-Fault Protection
SIPROTEC 5, Overcurrent Protection, Manual 547
C53000-G5040-C017-8, Edition 07.2017
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