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Chapter 6) 7SR17 Commissioning and Maintenance Guide
3.7
CB Fail (50BF)
Voltage Inputs:
Current Inputs:
Disable:
Map Pickup LED:
With reference to the Circuit Breaker Fail Protection logic diagram (see chapter 1 'Description of Operation')
The circuit breaker fail protection time delays are initiated when:
Phase current > 50BF Setting,
or,
Earth current > 50BF-I4 Setting:
And
A binary output mapped as Trip Contact in the OUTPUT CONFIG>BINARY OUTPUT CONFIG menu,
or
A binary input mapped as 50BF Ext Trip in the INPUT CONFIG>INPUT MATRIX menu.
or
A binary input mapped as 50BF Mech Trip in the INPUT CONFIG>INPUT MATRIX menu.
Apply a trip condition by injection of current to cause operation of a suitable protection element. Allow current to
continue after the trip at a level of 110% of the 50BF Setting current level on any phase. Measure the time for
operation of 50BF-1 Delay and 50BF-2 Delay.
Repeat the sequence with the 50BF CB Faulty input energised and ensure the 50BF-1 and 50BF-2 outputs
operate without delay, by-passing the timer delay settings.
Repeat the sequence with current at 90% of the 50BF Setting current level after the element trip and check for no
CB Fail operation.
Repeat the sequence by injecting the current to I4 and using the 50BF-I4 Setting.
Page 56 of 62
n/a
I
, I
, I
, I
A
B
C
G
37, 46, 46Ph Rev, 14, 48/66, 49, 50, 50N, 51, 51N
50BF-n - Self Reset
©2014 Siemens Protection Devices Limited
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