Calculating Settings For Lv-Side Breaker Failure Protection Ccrbrf (50Bf) - ABB REC650 Applications Manual

Section 3
REC650 setting examples
3.1.9
58
Protection
operate time
The fault Retrip delay t1
occurs
Trip and Start
BFP
EN05000479 V1 EN
Figure 13: Overexcitation protection characteristics
Calculating settings for LV-side breaker failure protection,
CCRBRF (50BF)
The breaker failure protection can use either the position indication of the circuit breaker
or measure the current going through the CT in order to detect correct breaker functioning.
For transformer protections it is most suitable to use current measurement as a circuit
breaker failure check.
1. Set GlobalBaseSel to 2
The (LV) winding data should be related to Global base 2.
2. Set FunctionMode to Current
3. Set BuTripMode to 1 out of 3
The current measurement function uses the three-phase currents from the line CT
and either, a measured residual current or a calculated 3I0. Based on this analogue
data one of the following rules can be chosen in order to determine a breaker failure:
Normal t
cbopen
t after re-trip
cbopen
Minimum back-up trip delay t2
Critical fault clearance time for stability
1MRK 511 286-UUS A
t
BFPreset
Margin
Application manual
Time
en05000479.vsd