Siemens 7SR105 Rho - Circuit Breaker Failure (50 BF); Figure 4-6 Logic Diagram: Circuit Breaker Fail Protection (50 BF)

7SR105 Rho Description of Operation
©2018 Siemens Protection Devices Chapter 1 Page 42 of 57
4.6 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 MATRIX\Trip
Contacts), or
A binary input configured 50BF Ext Trip (MENU: INPUT CONFIG\BINARY INPUT MATRIX\50BF Ext
Trip).
CB Fail outputs will be issued providing any of the 3 phase currents are above the 50BF Setting for longer than
the 50BF-n Delay setting – indicating that the fault has not been cleared.
Both 50BF-1 and 50BF-2 can be mapped to any output contact or LED.
Operation of the CB Fail elements can be inhibited from:
Inhibit 50BF A binary or virtual input.
Trip Contact
50BF-n-1
50BF-n-2
≥
1
I
A
>
Enabled
&
I
C
I
B
&
≥
1
&
I
G
>
≥
1
&
&
Inhibit 50BF
50BF Element
50BF Ext Trip
50BF Mech Trip
CB Closed
50BF Setting
50BF CB Faulty
50BF-I4 Setting
50BF-1 Delay
50BF-2 Delay
&
&
≥
1
≥
1
50BCL CB Fail
Figure 4-6 Logic Diagram: Circuit Breaker Fail Protection (50BF)