Voltage Detector for Underground Cable 2

[LDG0926]

Hi

Is there anyone can help me fine a tool/equipment that can detect the Ring Main Unit underground cables? Other RMU's has capacitive test point and this will be determine by using the voltmeter. But other RMU's dont have and the termination is not elbowed rather lug type connection.

I am going to open the kiosk switchgear and earthed the cables. This determing the cable is dead because it is earthed. What I will do next is to unearthed the cable becasue I am going to test it. In order for me to test the cable is to unearthed the cable again.But I want to have a double check that the volatge (11KV,22,33KV) is not present on the cable "test before you touch" anybody?

Thanks.

 

[Marmite]

LDG0926, can you provide details on the maufacturer and type/voltage of the ring main units you want to test between, please?
Regards
Marmite

 

[TestBeforeTouch]

If you have not tested the cable for absence of voltage you need to consider it energized. When you are making the test for the absence of voltage you need to wear the same PPE as if it is energized, because it may be energized. Grounding switches can fail, the wrong circuit could be locked out, you could have a potentially fatal induced voltage as mentioned by David Beach. Before you attach a megger or hipot tester to the cable, test the cable for the absence of voltage. It does not matter if the ground switch was closed or is closed. Test every conductor before you touch it.

 

[davidbeach]

I don't actually work with the circuits personally, so I'd never touch any of it, even with the grounds still on, but that doesn't change the nature of induced voltages.

The way I've read the original post and explanations, it sounds to me as though it is being stated that it is possible and permissible to ground (earth) something, remove those grounds, and then touch the conductor. Once the grounds are removed it has to be treated as energized as it is no longer grounded, how could it be treated otherwise? If you need to test a conductor installed around energized circuits, the conductor would be switched off, grounded, proper test equipment connected, and then the grounds lifted. Such test equipment will be grounded and will contain MOVs or spark gaps to protect the test equipment from overvoltages beyond the insulation rating of the test equipment. At the conclusion of the test the grounds would be reapplied before the test equipment would be disconnected.

 

[petamm]

I agree with davidbeach and testbeforetouch last posts:Once the grounds are removed it has to be treated as energized as it is no longer grounded! Testing the cables you apply sometimes higher voltage then Uo.It means from the point you connect your test equipement and remove the ground you MUST treat it as energized. ALWAYS use the protective gloves according to the voltage level you work on - during connecting the test probes,of course, not writting a testprotocol after finishing the test

 

[isquaredr]

I agree with davidbeach that good "testing practice" is to ground - connect equipment - remove ground - do the test, not all test equipment have a ground reference to discharge induced voltages which may build ie cable identifiers, phasing boxes etc
In the uk if a rmu was to be worked on all remote infeeds wood be isolated and a ground applied, before the rmu was released for work it would be proved dead by testing the lv local transformer terminals with all rmu switches in the "on" position.
If a cable was to be worked on from an rmu it again would be isolated and grounded, it would be identified to the point of work either by injected signal or visual trace (transfered ring) and then proved dead by spiking.
With all that in mind the work location on a particular cable could be some 10-miles away from the ground and its route runs beneath transmission lines for 5-miles.

I have seen earths applied to live circuits, fortunately all our switchgear is rated for the fault level and no serious incident has occurred apart from loss of supply, this may or may not have been prevented by some kind of voltage indication, who knows when humans are involved.

Excellent training, up to date system diagrams and procedures are essential whilst working on an electrical system.