ABB
27
Uniswitch Operation and
Maintenance Manual
UNIS14GB 05-02
4.3.1.5 Operations in fixed mounted circuit-breaker cubicles
General To achieve an isolating distance in accordance with specified
requirements a 3-position switch-disconnector with an earthing switch is
mounted between the busbar and circuit-breaker. An EM earthing switch
is connected to the other side of the circuit-breaker (current
transformers and HV-cables).
The switch-disconnector and EM earthing switch are mechanically
connected to the operating device and they are operated simultaneously
between open and earthed position.
Because the switch-disconnector is capable of breaking currents under
normal circuit conditions there is not any need for mechanical interlocks
between the circuit-breaker and switch-disconnector.
Operating sequences:
Earthing the cubicle
Figure 4.5
Operating and signalling
parts of fixed type HD4
circuit-breaker
1) Open the circuit-breaker either electrically or mechanically by push
button (43.1).
2) Open the SFG switch-disconnector (see 4.3.1.2).
3) Close the earthing switches on both sides of the circuit-breaker (see
4.3.1.3).
Operating sequences:
Connecting the cubicle
in the network
1) Open the earthing switches (see 4.3.1.4).
2) Close the switch-disconnector (see 4.3.1.1).
3) Close the circuit-breaker by push button (43.2).
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