ABB
15
Uniswitch Operation and
Maintenance Manual
UNIS14GB 05-02
3.5 Interlockings
3.5.1 Interlocking principle
Purpose The purpose of the interlocking devices is to prevent incorrect operation
of the switch-disconnector and earthing switch and thereby to ensure
personnel safety. The interlocking is in operation even if the doors to the
cable and control compartments are open.
Interlockings Interlocking includes:
• Normal interlocking which is fitted as standard in every cubicle.
• Additional interlocking devices which are optional and to be chosen
by the customer.
3.5.2 Interlockings of the fixed type switchgear
3.5.2.1 Interlocking unit
General Permitted control operations of the Uniswitch switchgear and the three-
position SFG switch-disconnector are defined by the position of the
selector of the interlocking mechanism.
Positions The interlocking selector has four positions:
Position 1: Operation
SFG switch-disconnector can only be operated close-open. The cable
compartment door cannot be opened.
Position 2: Padlock
SFG switch-disconnector cannot be operated and the cable
compartment door cannot be opened.
Position 3: Test and earthing
SFG switch-disconnector can only be operated open-earthed. The cable
compartment door cannot be opened.
Earthing switches The interlocking applies also to the earthing switches EF and EM, which
are used for earthing the bottom of the fuses and current transformers.
These switches are mechanically connected to the operating device of
SFG switch-disconnector and they are operating simultaneously with the
SFG when it is operated between open and earthed position.
Position 4: Door open
The SFG switch-disconnector is in the earthed position and cannot be
operated. The cable compartment door can only be opened if the
switch-disconnector is in the earthed position and the interlocking device
is in the ‘Door open’ position.
Refer to 3.5.2.2 Normal interlocking.
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