ABB
18
Uniswitch Operation and
Maintenance Manual
UNIS14GB 05-02
3.5.3 Interlockings of the withdrawable type switchgear
3.5.3.1 Cubicle internal interlocking
Interlocks There is a series of interlocks to protect both personnel and equipment:
The withdrawable part can only be moved from the test/disconnected
position (and back) when the circuit-breaker and earthing switch are in
the open position.
Figure 3.9
View inside the circuit-breaker compartment
The withdrawable part can only be moved from the test/disconnected
position when the control wiring plug (44.4) (Figure 3.5) has been
connected to socket (50.1) (mechanical interlock).
The circuit-breaker can only be switched on when the withdrawable part
is in the test or service position. In the intermediate position, the circuit-
breaker is mechanically interlocked. When the circuit-breakers have an
electrical release, the interlock is also electrical.
In cubicles with digital control technology, prevention of malfunction of
the circuit-breaker can also be achieved by means of the cubicle
software.
In the service or test positions, the circuit-breaker can only be switched
off manually when no control voltage is applied and it cannot be closed
(electromechanical interlock).
Connecting and disconnecting the control wiring plug (44.4) (Figure 3.5)
is only possible in the test/disconnected position of the withdrawable
part due to the door interlock.
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