Description
2.3 Protection system
3WA1 air circuit breaker
Equipment Manual, 02/2023, 92310000002-06
63
Current transformer configurations
Depending on the network topology of the power distribution system, several current
transformers are required for the detection of ground-fault currents on the infeed side. In
practice, current transformers of class TPS (former designation class X) according to
IEC 60044-6 are used in a transformer combination. If only one current transformer is
used in the neutral point of the transformer, the ground-fault currents of the outgoing
feeders are also acquired via this transformer.
Ground fault interruption
The ground fault on the outgoing side can be interrupted with the circuit breaker.
When a ground fault is detected on the infeed side, the ETU600 LSIG Hi-Z electronic trip
unit issues a signal to open the medium-voltage circuit breaker on terminals X7-11 und
X7-12 of the circuit breaker. In this case, the ETC600 external trip controller can be
integrated in the intertripping circuit of the medium-voltage circuit breaker and can also
open the low-voltage 3WA circuit breaker by means of the second tripping solenoid F6.
The tripping solenoid F6 operates independently of the ETU600 electronic trip unit and
prevents reclosing after the circuit breaker has been opened. The circuit breaker can
only be closed after resetting the reclosing lockout locally, marked EXT TRIP in the figure
below. The 3WA is the only circuit breaker capable of this functionality.
ETU TRIP, reclosing lockout not active
EXT TRIP, reclosing lockout active
ETC600 external trip controller
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