ABB REB500 - Page 49

1MRK 505 350-UEN Section 5
Additional protection options
Technical Manual 41
Distributed busbar protection REB500
The BFP L0 system is an integrated part in the conventional BFP function that can
be activated and configured separately.
The neutral measuring system of BFP for I
0
covers the ground potential as a fourth
phase and evaluates breaker failure conditions accordingly. To allow for individual
fault handling, separate configuration for the I
0
threshold and timer stage t
1
is
possible.
When activated, the function is completely integrated into the existing BFP
function. With the exceptions mentioned above, both timer t
2
and the intertripping
system are used by the BFP phase and L0 system.
The following diagram shows a simplified representation of the extension of the
conventional BFP system with the L0 system.
Figure 10 Simplified block diagram of the BFP L0 system
When enabled, the L0 system of BFP can be started by dedicated logical starting
signals.
Logical starting signals of the BFP phase system can be connected to the BFP L0
system by enabling the parameter “Connect phase start signals” (see Section 5.2.2).
To avoid bypassing of the conventional BFP, timer t
1
of the BFP L0
system will only be initiated by start signals for the phase system if
each of the independent phase currents is below the setting for the
phase system.
I
L1
I
L2
I
L3
I
L1
> setting
I
L2
> setting
I
L3
> setting
I
L0
I
L0
> setting
Σ
0t
Active for L0
≥1
≥1
&
≥1
&
Connect phase start signals
23340_BFP TRIP L0
&
Start L1 signals
Start L2 signals
Start L3 signals
Start L1L2L3 signals
≥1
13795_Start BFP L0_1
13796_Start BFP L0_2
13797_BP_Start BFP L0
Trip/Intertrip, OCDT, PDF, ext. Trip
BFP t1 trip signals
BFP t2 initiation
Referenced Internal Signals
Referenced Parameters
Legend:
3I0 calculated
Timer t1-L0