111
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7. Operation of the switchgear
Power cable test
The power cable test can be carried out by AC
voltage, DC voltage or AC voltage applicable for
very low frequency (VLF) testing at 0,1Hz. For
maximum cable test voltage see table on the next
page.
General
Voltage applied during cable testing can damage
voltage transformers, surge arresters if fitted. It
is therefore necessary to disconnect them from
the circuit before performing cable test.The
below described procedure shall be used to carry
outcable test on the power cables without
disconnecting the cables from the switchgear.
Caution:
All the operations below must be carried out by
qualified and skilled personnel with in-depth
knowledge of the panel and apparatus.
Procedure described below must be followed to
accesscable test points:
• Switch OFF the circuit breaker
• Rack out the circuit breaker from service to
test position
• Open CB door
• Withdraw the circuit breaker from the panel
• De-energise the cable
• Switch ON the earthing switch
• Test the off-circuit condition
• Disconnect voltage transformers, surge
arresters if fitted
• Insert modified shutters lifting truck (after
demounting of bottom actuating elements) -
Figure 184 inside the CB compartement
• Push this modified shutters lifting truck to
service position by insulating operating
handle. The lower (cable connection) shutter
shall open. Cable test points (contact pins)
shall be accessible.
• Connect the cable test equipment to the test
points (contact pins in the CB compartement
– 2 (Figure 182) and to the main earth busbar.
• Swith OFF earthing switch
• Carry out the cable test as required
Note:
Pictures show the shutters lifting truck for panel
12 kV 650 mm. Shutters lifting truck for other
configurations may be slightly different but
functionality is preserved.
Caution:
The test circuit is designed for a maximum
applied voltage of table below
To restore normal operating conditions:
• De-energise cable connection. Switch-ON the
earthing switch
• Test the off-circuit condition
• Disconnect the cable test equipment.
• Connect voltage transformers, surge
arresters if fitted
• Switch-OFF earthing switch
• Insert the circuit breaker into CB
compartment
• Close CB door
• If needed rack-in the circuit breaker from test
to service position
• If needed switch-ON cir cuit breaker
Caution:
After testing, the test connections may retain a
lethal electrical charge after the test equipment
is switched OFF. Discharge the test points using
a safety ground (e.g. earthing switch to earthed
ON position) and ensure that the test
connections are dead before disconnecting the
cable test equipment. In all cases, ensure that
the test points are really dead.
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