Siemens siprotec 7SA6 - Page 420

Functions
6-238 7SA6 Manual
C53000-G1176-C133-1
Circuit Breaker
Pole Discrepancy
Supervision
The pole discrepancy supervision has the task to detect discrepancies in the position
of the three circuit breaker poles. Under steady-state conditions, either all three poles
of the breaker must be closed, or all three poles must be open. Discrepancy is
permitted only for a short time interval during a single-pole automatic reclose cycle.
The scheme functionality is shown in Figure 6-126. The signals which are processed
here are the same as those used for the breaker failure protection. The pole
discrepancy condition is established when at least one pole is closed (“CB any pole
closed”) and at the same time not all poles are closed (“CB any pole open”).
Additionally, the current criteria (from Figure 6-113) 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 is detected, this is annunciated by a fault detection signal. This
signal identifies the pole which was open before the trip command of the pole
discrepancy supervision occurred.
Figure 6-126 Function block diagram of pole discrepancy supervision
6.16.2 Applying the Function Parameter Settings
General The breaker failure protection and its ancillary functions (end fault protection, pole
discrepancy supervision) can only operate if they were configured as HQDEOHG during
setting of the scope of functions (see Section 5.1, address ).
Breaker Failure
Protection
The complete breaker failure protection including its ancillary functions is switched
Off
or
On under address  )&7%UHDNHU)DLO.
The current threshold ,!%) (address ) should be selected such that the
protection will operate with the smallest expected short-circuit current. To ensure this,
the value should be 10 % less than the minimum anticipated fault current. On the other
hand, the value should not be set lower than necessary.
3932
T-PoleDiscrep.
BF CBdiscr TRIP
<3
L2>
L3>
L1>
T
&
&
(from Fig 6-113)
&
&
BF CBdiscr L1
BF CBdiscr L3
FNo 1500
FNo 1499
FNo 1498
FNo 1497
0
BF CBdiscr L2
CB any pole closed
CB any pole open