Siemens SIPROTEC 7SA6 Manual page 444

Distance protection relay for all voltage levels

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prot. device

Figure 6-127 Breaker failure protection with phase segregated initiation — example for

initiation by an external protection device with release by a separate set of trip

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 6-123, 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 fail protection by the central function control of the de-

vice (refer to Section 6.22.2).

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) op-

erates in three-phase mode as well. The function is the same as with common phase

The additional release-signal " >BF release " (if assigned to a binary input) affects all

starting conditions. Initiation can be blocked via the binary input " >BLOCK BrkFail "

(e.g. during test of the feeder protection relay). Additionally, an internal blocking option

is provided.

>BF Start L1

>BF Start L2

>BF Start L3

C53000-G1176-C156-2