Two-Zone Busbar Arrangements; General; Single Busbar Arrangements - ABB REB670 Applications Manual

Section 6
Differential protection
6.1.4
6.1.4.1
6.1.4.2
136
Trip circuit supervision is mostly required to supervise the trip circuit from the
individual bay IED panel to the circuit breaker. It can be arranged also for the tripping
circuits from the busbar protection.
However, it can be stated that the circuit from a busbar protection trip relay located in
the busbar protection panel is not so essential to supervise as busbar faults are very rare
compared to faults in bays, especially on overhead power lines. Also it is normally a
small risk for faults in the tripping circuit and if there is a fault which affects only one
bay and all other bays are thus correctly tripped meaning that the fault current
disappears or is limited to a low value.

Two-zone busbar arrangements

General

Busbar differential protection application principles for typical busbar arrangements,
up to two differential zones, are shown and described in the following sections.

Single busbar arrangements

The simplest form of busbar protection is a one-zone protection for single busbar
configuration, as shown in Figure 54. When different CT ratios exist in the bays
compensation is done by setting the CT ratio individually for each bay.
The only requirement for busbar protection is that the protection scheme must have one
differential zone. For any internal fault all circuit breakers must be tripped, which will
cause loss of supply to all loads connected to the station.
ZA
152 152
152
ANSI06000087 V1 EN-US
Figure 54: Example of single busbar section with six feeder bays
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.
152
xx06000087_ansi.vsd
1MRK 505 370-UUS A
M12121-4 v3
Busbar protection REB670 2.2 ANSI
Application manual
M6640-3 v2
M6641-3 v5