2 Functions
188
7SD610 Manual
C53000-G1176-C145-4
Discrepancy is permitted only for a short time interval during a single-pole automatic
reclose cycle.
The scheme functionality is shown in Figure 2-76. 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 („ ≥ one pole closed“)
and at the same time not all three poles are closed („ ≥ one pole open“).
Additionally, the current criteria (from Figure 2-63) are processed. Pole discrepancy
can only be detected when current is not flowing through all three poles, 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 is detected, this is indicated by a fault detection signal. This signal
identifies the pole which was open before the trip command of the pole discrepancy
supervision occurred.
Figure 2-76 Function diagram of pole discrepancy supervision
2.13.2 Setting Notes
General The circuit breaker failure protection and its ancillary functions (end fault protection,
pole discrepancy supervision) can only operate if they were set during configuration
of the scope of functions (address 139 BREAKER FAILURE, setting Enabled or
enabled w/ 3I0>).
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.
If the breaker failure is configured with zero sequence current threshold (address 139
= enabled w/ 3I0>), the pickup threshold for the zero sequence current 3I0> BF
(address 3912) can be set independently of I> BF.
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.
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