Siemens SIPROTEC 7SJ61 - Breaker Failure Protection 50 BF; Description

Functions
2.12 Breaker Failure Protection 50BF
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008
185
2.12 Breaker Failure Protection 50BF
The breaker failure protection function monitors proper switchoff of the relevant circuit breaker.
2.12.1 Description
General
If after a programmable time delay, the circuit breaker has not opened, breaker failure protection issues a trip
signal via a superordinate circuit breaker (see example in the figure below).
Figure 2-62 Function principle of the breaker failure protection
Initiation
The breaker failure protection function can be initiated by two different sources:
• Trip signals of internal protective functions of the 7SJ61,
• external trip signals via binary inputs („>50BF ext SRC“).
For each of the two sources, a unique pickup message is generated, a unique time delay is initiated, and a
unique trip signal is generated. The setting values of current threshold and delay time apply to both sources.
Criteria
There are two criteria for breaker failure detection:
• Check whether the current flow has effectively disappeared after a tripping command was issued,
• Evaluate the circuit breaker's auxiliary contacts.