2.2 Protection Data Interfaces and Protection Data Topology
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7SD5 Manual
C53000-G1176-C169-1
within less than 2 seconds. If GPS synchronization (with satellite receiver) is used,
asymmetric transmission times are recognized and corrected immediately.
The maximum permissible unbalance of the delay times can be set. If the delay time
in the transmit and receive path is different, a differential current is calculated by the
devices because of this difference. This has a direct influence on the sensitivity of the
differential protection system. The automatic self-restraint of the protection adapts the
restraint quantities to these differences so that a spurious operation of the differential
protection due to these influences is prevented. Thus, higher difference values reduce
the sensitivity of the protection, which may be noticeable in case of very low-current
faults. With GPS synchronization, transmission time differences do not affect the sen-
sitivity of the differential protection as long as GPS synchronization is intact. When the
GPS synchronization detects that the permissible time difference is exceeded during
operation, the message „PI 1 PD unsym.“ (No. 3250 for interface 1) will be issued.
When a transmission time jump exceeds the maximum permissible transmission delay
time, this is annunciated. If transmission time jumps occur frequently the regular op-
eration of the differential protection is no longer ensured. Protection communication
via this communication link can be blocked via a setting parameter (e.g. 4515 PI1
BLOCK UNSYM). If a chain topology was configured, failure of one transmission link
blocks the differential protection. If a ring topology is configured, the system switches
to chain topology. A corresponding alarm is output („PI1 unsym.“, No. 3256 for in-
terface 1). This blocking of the link can only be reset via a binary input („>SYNC PI1
RESET“, No. 3252 for interface 1).
Changeover of
Operating Mode
During protection test, plant inspection, but also during operational switch-off of a
feeder, it is possible to change the operating mode of a device in order to perform such
work without effect on running operation.
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