Specifications

7SR242 Duobias Applications Guide
Stage 1 CBF Timer (Retrip) = 120ms
Failed CB Retrip
Operation
40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 360340
System
Fault
Relay
Operation
and CBF
Timer
Started
Main
Trip
Relay
Operation
CB's
Fails to
Trip
No Reset of
CBF elements
CBF Retrip
Operation
CBF Retrip
Trip Relay
CB Operate Time
Stage 2 CBF Timer (Backtrip) = 250ms
No Reset of
CBF elements
CBF Back trip
Operation
Backtrip
Trip Relay
Operation
Operation of all
BB CB's
Reset of
CBF elements
ms fro
m
occur
i
Figure 5-3 - Two Stage Circuit Breaker Fail Timing
Example of Required Settings (e.g. HV CB)
FUNCTION CONFIG>
Gn CB Fail Enabled
SUPERVISION > CB FAIL > 50BF-1
Gn 50BF-1 Element Enabled
Gn 50BF-1 Setting 0.2 x In
Gn 50BF-1-1 Delay 120ms
Gn 50BF-1-2 Delay 250ms
INPUT CONFIG>INPUT MATRIX>
50BF-1 Ext Trip BIn
OUTPUT CONFIG>OUTPUT MATRIX>
50BF-1-1 BOn, Ln
50BF-1-2 BOn, Ln
OUTPUT CONFIG>BINARY OUTPUT CONFIG>
CB1 Trip Contacts BOn
The above based on:
First Stage Backtrip (or Re-trip) Typical Times
Trip Relay operate time 10ms
CB Tripping time 50ms
DUOBIAS-M Reset Time 30ms
Safety Margin 30ms
Overall First Stage CBF Time Delay 120ms
Second Stage (Back Trip)
First CBF Time Delay 120ms
Trip Relay operate time 10ms
DUOBIAS-M Reset Time 30ms
CB Tripping time 50ms
Margin 50ms
Overall Second Stage CBF Time Delay 260ms
©2010 Siemens Protection Devices Limited Chapter 7 Page 45 of 56