Supervisory Functions
143
7SS52 V4 Manual
C53000-G1176-C182-1
5.5.1.7 Cyclic Test
Central unit The ”cyclic test” as part of the self-diagnosis checks cyclically all measuring systems
and connected bay units from the digitized measured values up to the trip relays. As
this test is treated like a real fault and uses the same transmission links for measured
values and TRIP commands, it yields utmost security and reliability.
This test does not influence the protection functions.
The test is performed only if there is no pickup of the protection.
On detecting a failure, the identical test routine is repeated twice. After this a reset is
performed.
The following alarms are generated:
• Group alarms: “Flt autotest M” (FNo. 10429/CU)
• Single alarm: “Flt aut $00“ (FNo. 176.1190/CU)
Bay unit
In the bay units, the trip command circuits are monitored additionally.
The following alarms are generated:
• Group alarms: “Flt autotest M” (FNo. 10429/CU)
• Single alarms: “Flt aut $00“ (FNo. 176.1190/CU)
5.5.1.8 Supervision of External Current Transformer Circuits
Interruptions or short circuits in the secondary circuits of the main current transform-
ers, as well as errors in the connections or in the configuration of the busbar protec-
tion, are systematically detected and reported by the system. It evaluates for this pur-
pose the differential currents which are formed in the protection processor modules
ZPS-BSZ1 to ZPS-BSZ3.
Differential current
supervision
The differential current of each measuring system is individually monitored. Under no-
fault conditions, the differential current of each measuring system is approximately ze-
ro. If no feeders are assigned to a measuring system, the differential current and the
stabilizing current are set to zero. The differential current supervision picks up if the
mean value of the differential current exceeds a certain threshold within an interval set
with the parameter T-Idiff SUPERV (6307/CU). This threshold can be set individ-
ually for the check zone with the parameter Id> SUPERV CZ (6309/CU), and for the
selective protection with the parameter Id> SUPERV BZ (6308/CU).
If the differential current falls below the threshold before the set time, the time delay is
restarted if it occurs again.
The differential current supervision can be activated and deactivated with the param-
eter DIFF SUPERV (6306/CU).
The blocking is reset by operator input ”Reset Id-Block” or via binary input ”>Re-
set Id-Block” (BI FNo. 6/CU) in the central unit.
In case of a pickup of the differential current supervision, the reaction can be set indi-
vidually for the check zone (with the parameter DIF SUP mode CZ (6311/CU)) and
for the selective protection (with the parameter DIF SUP mode BZ (6310/CU). The
following alarms are generated:
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