Section 5: Supervision Functions; Circuit Breaker Failure (50Bf); Figure 5.1-1 Logic Diagram: Circuit Breaker Fail Protection (50Bf) - Siemens 7SR224 Technical Manual

Section 5: Supervision Functions

5.1

Circuit Breaker Failure (50BF)

The circuit breaker fail function has two time delayed outputs that can be used for combinations of re-tripping or
back-tripping. CB Fail outputs are given after elapse of the 50BF-1 Delay or 50BF-2 Delay settings.
The circuit breaker fail protection time delays are initiated either from:
An output Trip Contact of the relay (MENU: OUTPUT CONFIG\BINARY OUTPUT CONFIG\Trip
Contacts), or
A binary input configured 50BF Ext Trip (MENU: INPUT CONFIG\BINARY INPUT MATRIX\50BF Ext
Trip).
A binary or virtual input assigned to 50BF Mech Trip (MENU: INPUT CONFIG\INPUT MATRIX\ 50BF
Mech Trip).
CB Fail outputs will be issued providing any of the 3 phase currents are above the 50BF Setting or the current in
the fourth CT is above 50BF-I4 for longer than the 50BF-n Delay setting, or for a mechanical protection trip the
circuit breaker is still closed when the 50BF-n Delay setting has expired – indicating that the fault has not been
cleared.
Both 50BF-1 and 50BF-2 can be mapped to any output contact or LED.
If the 50BF CB Faulty input (MENU: INPUT CONFIG\INPUT MATRIX\50BF CB Faulty) is energised when a CB
trip is given the time delays 50BF-n Delay will be by-passed and the output given immediately.
Operation of the CB Fail elements can be inhibited from:
Inhibit 50BF

Figure 5.1-1 Logic Diagram: Circuit Breaker Fail Protection (50BF)

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A binary or virtual input.
7SR224 Argus Description of Operation
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