Functions
2.38 Breaker Failure Protection (ANSI 50BF)
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
263
2.38 Breaker Failure Protection (ANSI 50BF)
The breaker failure protection can be assigned to the current inputs of side 1 or side 2 during configuration of
the protective functions (see Section 2.4). The breaker failure protection monitors whether the associated
circuit breaker is opened correctly. In machine protection it concerns usually the mains breaker.
2.38.1 Functional Description
Mode of Operation
The following two criteria are available for circuit breaker failure protection:
• Checking whether the current in all three phases undershoots a set threshold following a trip command,
• Evaluation of the position of a circuit breaker auxiliary contact for protective functions where the current cri-
terion is perhaps not representative, e.g. frequency protection, voltage protection, rotor earth fault protec-
tion.
If the circuit breaker has not opened after a programmable time delay (breaker failure), a higher-level circuit
breaker can initiate disconnection (see the following example).
Figure 2-120 Function Principle of the Breaker Failure Protection Function
Initiation
The breaker failure protection function can be initiated by two different sources:
• Internal functions of the 7UM62, e.g. trip commands of protective functions or via CFC (internal logic func-
tions),
• external start commands e.g. via binary input.
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