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Topic Title: Proving Dead on 11kV Switchgear
Topic Summary: Is there a commercially available switchgear design for proving dead?
Created On: 20 March 2014 03:37 PM
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 20 March 2014 03:37 PM
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Can anyone help with a query I have come across whilst trying to choose a replacement for existing GEC VMX circuit breakers please?

Is there a standard product or design option on 11kV extensible indoor switchgear for proving dead prior to switching to earth? It seems that all new designs are going away from the withdrawable truck style such as VMX or Hawkgas where you can pull out the circuit breaker and prove dead at the spouts. I have looked at Genie Evo, Hawker Eclipse etc but I am not aware that you can positively confirm that the voltage is not present.
Obviously you cannot rely on a neon potential indicator as per the Evo for dead confirmation prior to earthing.
Many thanks
 20 March 2014 04:20 PM
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Well, using VIPS neon, you test live at the start of your switching and test not live prior to earthing.

That is sufficient.

Note that many networks no longer require a prove dead prior to earthing (some safety rules now say insertion of test prods and indicators into live spouts is forbidden). Is approaching (and encroaching) the safety distance of a live HV conductor really a good idea (and it is to be considered and treated live until proven dead) if you can avoid doing so?

The ONLY way you can close a breaker or switch to earth a live circuit is if you make several switching errors prior to that.

If somebody is incompetent enough to make several switching errors, I would not want them in the truck housing fiddling with live breaker spouts!

Edited: 20 March 2014 at 06:31 PM by Zuiko
 21 March 2014 12:32 AM
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If you have proper switching procedures and a "rated earth switch" that can cope with the fault current during the time it takes the protection to operate, then there is no issue. In my opinion, the specification for the new switchgear should allow it to earth a live HV circuit.


 21 March 2014 08:59 AM
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Thanks for the useful comments, I will take them on board.

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