Earthing Switch - Type Em; General - ABB Uniswitch Operation And Maintenance Manual

4.4.5 Earthing switch - type EM

4.4.5.1 General

Operating principle
Figure 4.22
Auxiliary switches and
mechanism for earthing
switch type EM.
ABB
Uniswitc h Operation and
Maintenanc e Manual
The earthing switch - type EM - has a snap closing mechanism, which is
independent of the rotation of the drive shaft.
An earthing switch allocated to a circuit-breaker is only enabled for
switching when withdrawable part is in the test/disconnected position or
removed from the switchgear cubicle.
Only turn earthing switches on when the door is
closed.
Indication of position 2 (Figure 4.24)
The position of earthing switch can be indicated electrically by means of
auxiliary switch (50.2). The auxiliary switch has been fixed on the same
mounting plate as the earthing switch and is connected mechanically by
a lever (61.8) to the main shaft (61.1) of earthing switch.
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UNI S14GB 05-02