2.20 Circuit Breaker Failure Protection
363
7SD5 Manual
C53000-G1176-C169-1
Figure 2-149 Breaker failure protection with phase segregated initiation — example for initia-
tion by an external protection device with release by a fault detection signal
Figure 2-150 Breaker failure protection with phase segregated initiation — example for initia-
tion by an external protection device with release by a separate set of trip con-
tacts
Initiation of a single-phase, e.g. „Start L1 only“ is valid when the starting input (= trip
command of any feeder protection) appears for only this phase and current flow is de-
tected in at least this phase. If current flow is not detected, the auxiliary contact posi-
tion can be interrogated according to Figure 2-146, dependent on the setting (Chk
BRK CONTACT = YES).
The auxiliary contact criterion is also processed for each individual breaker pole. If,
however, the breaker auxiliary contacts are not available for each individual breaker
pole, then a single-pole trip command is assumed to be executed only once the series
connection of the normally open (NO) auxiliary contacts is interrupted. This informa-
tion is provided to the breaker failure protection by the central function control of the
device (refer to Section 2.23.1).
The three-phase starting signal „Start L123“ is generated if trip signals appear in more
than one pole (regardless from which protection function). Phase segregated initiation
is then blocked. The input "BF Start w/o I" (e.g. from Buchholz protection) operates in
three-phase mode as well. The function is the same as with common phase initiation.
The additional release-signal „>BF release“ (if assigned to a binary input) affects
all initiation conditions. Initiation can be blocked via the binary input „>BLOCK
BkrFail“ (e.g. during test of the feeder protection relay).
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