ABB Uniswitch Operation And Maintenance Manual page 11

Pressure relief flaps
ABB
Uniswitc h Operation and
Maintenanc e Manual
When opening, the user should take measures to ensure
safety (ie. Busbar must be dead).
2) Gas filled compartment
The three position switch-disconnector is located between the main
busbar and cable compartments. Its epoxy resin shell forms an SF
filled space in which the electrical parts of the switches are situated.
This compartment is designated a "non-accessible
compartment". It must not be opened.
3) Cable compartment
About 75 % of the cubicle volume is reserved for the incoming/feeder
cable connections, fuses, earthing switches or instrument transformers.
The circuit-breaker (SF6 or vacuum) is located to the left of the cable
comparment.
If the cubicles are equipped with switch-disconnectors, there are
interlocks to ensure that live parts inside are dead and earthed before
opening. Such a compartment is then designated an "interlock-
controlled accessible compartment".
If the cubicles are not equipped with switch-disconnectors, the
comparments are provided with facilities for padlocking. Such a
compartment is then designated a "procedure-controlled accessible
compartment".
4) Control and Secondary Apparatus Compartment
The compartment includes space for switch-disconnector and earthing
switch operating mechanisms, and mechanical interlocks with position
indicators. Other components, such as auxiliary contacts, trip coils,
voltage indicators and relays, can be fitted in this compartment. It is also
usual to fit secondary wiring, terminal blocks and cable channels here.
The pressure relief flaps (10.3) (Figure 3.1) in the rear plate of the
cubicles open and divert the excess pressure and gases behind the
switchgear. This way, the risk of injury to the operator has been
minimized during a possible arc-fault condition.
Each cubicle rear plate has three arc-pressure relief devices:
•
The upper arc-pressure relief flap is for the busbar compartment.
•
The switch-disconnector has its own arc-pressure relief device.
•
The lower arc-pressure relief flap is for the circuit-breaker and cable
compartment.
! A separate exhaust duct at the rear of the switchgear is
also available.
-gas
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UNI S14GB 05-02