Breaker Failure Protection (50Bf); Description Of Breaker Failure Protection - Siemens SIPROTEC 7SJ62 Instruction Manual

Functions
6.13

Breaker Failure Protection (50BF)

6.13.1 Description of Breaker Failure Protection

General
Initiation
Criteria
6-124
The breaker failure protection function monitors the reaction of a circuit breaker to a
trip signal. If after a programmable time delay, the circuit breaker has not opened, a
breaker failure trip signal issued, and all adjacent circuit breakers that represent sourc-
es to the fault can be tripped (see Figure 6-53). To determine if the circuit breaker has
properly opened in response to a trip signal, one of the following methods is used to
ascertain the status of the circuit breaker:
• The current flow through the circuit breaker.
• The position of a circuit breaker auxiliary contact.
Protective
Schutzfunktion
Function Trip
Figure 6-53 Functional Principle of the Breaker Failure Protection Function
The breaker failure protection function can be initiated by two different sources:
• Internal protective function of the 7SJ62,
• External trip signals via binary inputs.
For each of the two sources, a unique pickup message is generated, a unique time
delay is initiated, and a unique tripping signal is generated. The setting values for
breaker failure pickup and delay apply to both sources.
The criteria used to determine if the circuit breaker has operated is selectable and
should depend on the protective function that initiated the breaker failure function. If
voltage protection initiated breaker failure protection, fault current may or may not be
flowing through the circuit breaker, therefore, current flow through the circuit breaker
is not a reliable indication as to whether the circuit breaker operated properly. In this
case, the position of the breaker auxiliary contact should be used to determine if the
circuit breaker properly operated. For protective functions that operate in response to
currents (e.g. directional and non-directional overcurrent protection, etc.), both the
current flow through the circuit breaker and the position of the circuit breaker auxiliary
contact can be used to determine if the circuit breaker properly operated. However,
operation of a circuit breaker auxiliary contact does not always mean that the circuit
52
52
52
Breaker Failure Protection
Schalterversagerschutz
I>I
MIN
52
BF Ttrip 0
&
Trip
7A
7SJ62 Manual
C53000-G1140-C121-1