Supervisory Functions - Siemens SIPROTEC 7SS523 V3.2 Manual

5.5

Supervisory Functions

5.5.1 Functional Description
5.5.1.1 Zone-Selective Blocking
The 7SS52 V4 protection system incorporates comprehensive self-monitoring func-
tions which cover both the hardware and the software. This guarantees a high availa-
bility and security against overfunctioning and underfunctioning as well as low demand
on maintenance.
The entire protection system is cyclically monitored from the measuring inputs through
the data communication between central unit and bay units up to the trip relay coils.
Time monitoring functions (watchdogs) continuously check the program sequences of
each processor module. Failure of a processor or malfunctions in the program se-
quence cause an automatic reset of the processor system.
Additional plausibility checks and program runtime checks ensure that program
processing errors are reliably detected. Such errors also lead to a processor reset and
a system restart.
After three unsuccessful restarts, the complete protection system automatically re-
moves itself from service. In case of a malfunction in the central unit, the readiness
relays 1 and 2 on the input/output module (EAZ) drop off and, being equipped with NC
contacts, generate a live status annunciation "Dev.operative" (FNo. 00051/CU).
Each bay unit has moreover its own NC contacts which generate a live status annun-
ciation "Dev.operative" (FNo. 51/BU).
In these cases the red "ERROR" LED shines on the front panel of the central unit or
of the affected bay unit.
In most cases it will be desirable, in the case of external or internal faults and malfunc-
tions of the 7SS52 protection system, to block only those measuring systems (protec-
tion zones) that are affected so that the healthy portion of the system can continue to
operate. The setting of the parameter BLOCKING MODE (6305/CU) specifies whether
the blocking acts selectively for a zone and perhaps a phase, or for the entire protec-
tion system.
Caution!
In the presence of a fault in a feeder which is in operation or a measuring error, the
feeder current is not available for the check zone measuring system either. In such
cases the release signal for tripping by the check zone measuring system is
artificially generated so that in case of a busbar fault the necessary tripping
conditions are fulfilled. The check zone is released with a delay adjustable via the
parameter T-Idiff SUPERV. (6307/CU) and is documented with the alarm
CZ release FNo. 10477/CU
" " (
As selective blocking does not offer the additional security provided by the check
zone, the cause of the fault should be eliminated as promptly as possible.
).
7SS52 V4 Manual
C53000-G1176-C182-1
Supervisory Functions
139