Siemens SIPROTEC 7SD610 Manual page 184

Functions
2.13 Circuit Breaker Failure Protection
In principle, the starting condition logic for the delay time(s) is designed similar to that for the common phase
initiation, however, individually for each of the three phases (as shown in Figure 2-72). Thus, current and initi-
ation conditions are processed for each CB pole. Also during a 1-pole automatic reclosure, the current inter-
ruption is reliably monitored for the tripped CB pole only.
Initiation of an individual phase, e.g. „Start L1", is only valid if the starting signal (= tripping signal of the feeder
protection) appears for this phase and if the current criterion is met for at least this phase. If it is not met, the
circuit breaker auxiliary contact can be interrogated according to Figure 2-67 – if parameterised (Chk BRK
CONTACT = YES).
The auxiliary contact criterion is also processed for each individual circuit breaker pole. If, however, the circuit
breaker auxiliary contacts are not available for each individual circuit breaker pole, then a 1-pole trip command
is assumed to be executed only if the series connection of the normally open (NO) auxiliary contacts is inter-
rupted. This information is provided to the circuit breaker failure protection by the central function control of the
device (refer to Section 2.16.1).
The 3-phase starting signal „Start L123" is generated if there are start signals for more than one phase. The
input "BF Start w/o I" (e.g. from Buchholz protection) operates only in 3-phase mode. The function is the same
as with common phase initiation.
The additional release-signal „>BF release" (if assigned to a binary input) affects all external initiation con-
ditions. Initiation can be blocked via the binary input „>BLOCK BkrFail" (e.g. during test of the feeder pro-
tection relay).
184
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011