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4. Panel design and equipment
Internal interlocking of panel with switch-
disconnector
To prevent hazardous situations and incorrect
operation, there is a series of interlocks to
protect both personnel and equipment:
• The switch-disconnector can only be
switched on if the earthing switch is off. The
earthing switch can only be switched on if
the switch-disconnector is off. The switch-
disconnector and earthing switch are
mutually mechanically interlocked.
• The door of the lower HV cable part of the
panel can only be opened if the earthing
switch is on. During the closing of the
earthing switch the insulating plate is
automatically inserted in the isolating
distance of switch-disconnector, which
increases safety. This plate is automatically
removed again during the opening of the
earthing switch.
• The earthing switch can only be operated if
the cable compartment door is closed.
• If the control voltage is not connected, the
switch-disconnector can be open and closed
only manually. The manual operation of
switch-disconnector and earthing switch can
be prevented if the slides of the operating
openings are locked up.
• In panels with digital control techniques the
protection against incorrect operation is
basically carried out by the panel software.
But the earthing switch is operated locally by
the operating lever 1 (Figure 20). The
mechanical interlocking between the switch-
disconnector and earthing switch is still in
operation.
• Details of other possible interlocks, e.g. in
connection with a locking magnet on the
switch-disconnector, can be obtained from
the relevant order documents.
WARNING
The door of the upper HV part of the panel can
only be opened if the off-circuit condition of the
switch-disconnector is verified. This means that
the off-circuit condition must be
unconditionally verified both on the upper and
lower contacts of the switch-disconnector.
Figure 19: Switch-disconnector compartment - open
position. Insulating plate in the isolating distance of
switch-disconnector.
Figure 20: Preparation for the operation of earthing
switch in panel with the switch-disconnector
1 Position indicator of switch-disconnector
2 Switch-disconnector
3 Movable insulation plate
4 Insulation partition wall
Operating lever prepared for the OFF operation
1 Operating lever
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