Parameter:
Delay 2
•
Default setting:
120 ms
Settings Example
50BF DTL1/50BF DTL2
The time delays run concurrently within the relay. The time delay applied to the CB fail protection must be in
excess of the longest CB operate time + relay reset time + a safety margin.
First Stage (Retrip)
Trip relay operate time
10 ms
Reset time
20 ms
CB tripping time
50 ms
Safety margin
40 ms
Overall first stage CBF time delay
120 ms
Second Stage (Back Trip)
First CBF time delay
120 ms
Trip relay operate time
10 ms
CB tripping time
50 ms
Reset time of measuring element
20 ms
Margin
60 ms
Overall second stage CBF time delay
260 ms
The safety margin is extended by 1 cycle for the second CBF stage as this will usually involve a back-trip of a
busbar tripping scheme.
[dw_7SR5_function50BFSettingExample1, 1, en_US]
Figure 6-2
Single Stage Circuit-Breaker Fail Timing
[dw_7SR5_function50BFSettingExample2, 1, en_US]
Figure 6-3
2 Stage Circuit-Breaker Fail Timing
Supervision Functions
6.1 50BF Circuit-Breaker Failure Protection – 3 Pole
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Reyrolle 7SR5, Transformer Protection Device, Device Manual
C53000-G7040-C015-1, Edition 11.2019