Siemens siprotec 7SD5 User Manual

2 Functions
368
7SD5 Manual
C53000-G1176-C169-1
ancy is permitted only for a short time interval during a single-pole automatic reclose
cycle.
The scheme functionality is shown in Figure 2-158. The signals which are processed
here are the same as those used for the breaker failure protection. The pole discrep-
ancy condition is established when at least one pole is closed („ ≥any pole closed“)
and at the same time not all three poles are closed („ ≥any pole open“).
Additionally, the current criteria (from Figure 2-145) are processed. Pole discrepancy
can only be detected when current is not flowing through all three poles (<3), i.e.
through only one or two poles. When current is flowing through all three poles, all three
poles must be closed even if the breaker auxiliary contacts indicate a different status.
If pole discrepancy of the breaker poles is detected, this is indicated in each phase by
a „fault detection signal“. This signal identifies the pole which was open before the trip
command of the pole discrepancy supervision occurred.
Figure 2-158 Function diagram of pole discrepancy supervision
2.20.2 Setting Notes
General The breaker failure protection and its ancillary functions (end fault protection, pole dis-
crepancy supervision) can only operate if they were configured as Enabled during
configuration of the scope of functions (adress 139 BREAKER FAILURE).
Breaker Failure
Protection
The breaker failure protection is switched ON or OFF at address 3901 FCT
BreakerFail.
The current threshold I> BF (address 3902) should be selected such that the protec-
tion will operate with the smallest expected short-circuit current. A setting of 10 %
below the minimum fault current for which breaker failure protection must operate is
recommended. On the other hand, the value should not be set lower than necessary.
Normally, the breaker failure protection evaluates the current flow criterion as well as
the position of the breaker auxiliary contact(s). If the auxiliary contact(s) status is not
available in the device, this criterion cannot be processed. In this case, set address
3909 Chk BRK CONTACT to NO.
Two-stage Breaker
Failure Protection
With two-stage operation, the trip command is repeated after a time delay T1 to the
local feeder breaker, normally to a different set of trip coils of this breaker. A choice
can be made whether this trip repetition shall be single-pole or three-pole if the initial
feeder protection trip was single-pole (provided single-pole trip is possible). This
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Siemens siprotec 7SD5 Specifications

General

Brand	Siemens
Model	siprotec 7SD5
Category	Relays
Language	English