Busbar Protection
105
7SS52 V4 Manual
C53000-G1176-C182-1
The protected zone ends at the current transformer. All electrical elements including
the isolators Q1 and Q2 are part of the line.
Configuration note:
The dotted part must not be displayed with Digsi!
5.1.3.6 Transfer Busbars
During transfer operation, the line isolator in the feeder which is located on the bypass
busbar is replaced by the line isolator of the bus coupler. Monitoring of the isolator
states in the feeder and coupling bays ensures that this happens only after the bus or
feeder isolator had been opened.
Up to the final bypass operation, intermediate switching positions occur. The alloca-
tion of the respective feeder to the bus zone during this time depends on the current
transformer location (bus side or line side).
With external transformers, the transfer busbar can be protected selectively. In the
case of a fault, the tripping of the transfer breaker (coupler) and a transfer trip com-
mand for the tripping of the circuit breaker takes place at the opposite end of the line.
Figure 4-31, page 82 shows a plant configuration with transfer bus. Figure 5-13, page
106 summarizes the busbar allocation of the feeders.
Normally the check zone measurement does not require any isolator status informa-
tion. The coupler's current, however, has to be included in the check zone measure-
ment, if a feeder with internal CT is connected to the transfer bus.
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