Breaker Failure Protection 50Bf; Description - Siemens SIPROTEC 7SJ62 Manual

Multi-functional protective relay with local control

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2.16 Breaker Failure Protection 50BF

Breaker Failure Protection 50BF

The breaker failure protection function monitors proper switchoff of the relevant circuit breaker.

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 2-101

The breaker failure protection function can be initiated by two different sources:

• Trip signals of internal protective functions of the 7SJ62/64,

• 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.

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.

Function principle of the breaker failure protection

SIPROTEC, 7SJ62/64, Manual

C53000-G1140-C207-2, Release date 01.2008