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Imran Nawazish
01-01-2014 12:31 AM

Isolator Interlocking Conditions!?

In case if we have to open/close the isolator of 110 kV Bus Section then what are the Interlocking conditions? Is it necessary that one of the two buses must be isolated and at 0 V before open/close operation.
Please share any link or refer a book where I can find the interlocking conditions for the main substation equipment.
Many thanks.
01-01-2014 03:14 AM
Top #2
Moses Wakatama
01-01-2014 03:14 AM
It would be easier after looking at the circuit configuration .i.e a single line diagram.generalising switching as a one solution fits all is a dangerous practice.
01-01-2014 05:31 AM
Top #3
Alan Maltz
01-01-2014 05:31 AM

"...Is it necessary that one of the two buses must be isolated and at 0 V before open/close operation..." This is easy to determine, just put yourself in the position of someone who is working on the isolated bus when a live bus is closed on to it. A properly interlocked bus cannot ever be allowed to be energized.

01-01-2014 07:49 AM
Top #4
Kamal Khan
01-01-2014 07:49 AM
it will be better to comment if you share circuit configuration
01-01-2014 10:30 AM
Top #5
Aijaz Hussain
01-01-2014 10:30 AM
But remember one basic rule, 110 kV isolator must not be opened until your 110 kV CB is still feeding or connecting two loaded bus sections...and should be closed before CB closing.
01-01-2014 12:46 PM
Top #6
Imran Nawazish
01-01-2014 12:46 PM
Thank you for the replies,
Mr. Aijaz I'll be very thankful to you if you can share the document for this basic rule as I am dealing with an interlocking scheme where in Service Position (not test position); CB Closed command is executable even when both the isolators are open on both sides of the CB (Bus Section and Bus Coupler CB) and the reply I'm getting from the designer is "There shall be no constraints for the closing operation of 110kV Circuit Breaker"
01-01-2014 03:12 PM
Top #7
Ing. Ole Knudsen
01-01-2014 03:12 PM
The essential interlock should be that the isolators must not be operated if the CB is closed.
The isolators are not designed to withstand any arcing caused by any load currents.
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