ABB
18
Uniswitc h Operation a nd
Mainte na nc e Manua l
UNI S14GB 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.
