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ANSI11000240 V1 EN-US
Figure 60: Example of breaker-and-a-half station
All breakers are normally closed. The requirement for the busbar protection scheme is
that the scheme must have two independent differential zones, one for each busbar. In
case of an internal fault on one of the two buses, all circuit breakers associated with the
faulty busbar have to be tripped, but the supply to any load will not be interrupted. The
breaker failure protection tripping logic also needs careful design.
This type of busbar arrangement can be very easily protected. The most common
setups for this type of station are described in the following table.
Table 19: Typical solutions for breaker-and-a-half stations when CBF for middle breaker is not
required
Version of REB670 IED Number of diameters in
the station
Number of REB670 IEDs
required for the scheme
3PH; 2-zones, 4-bays BBP (A20) 2/4 1/2
3PH; 2-zones, 8-bays BBP (A31) 4/8 1/2
1Ph; 2-zones, 12-bays BBP (B20) 6/12 3/6
1Ph; 2-zones, 12-bays BBP (B21) 6/12 3/6
1Ph; 2-zones, 24-bays BBP (B31) 12/24 3/6
Please note that Table 19 is given for the preconfigured versions of REB670 which do
not contain any VT inputs.
Section 6 1MRK 505 370-UUS A
Differential protection
144 Busbar protection REB670 2.2 ANSI
Application manual
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