H.V. Ring Main

[Pete999]

I have been looking through all of my paperwork, something to do now I'm retired, and an interesting question came to mind regarding H.V. Ring Mains.

I appreciate not every one would have worked on one but for those who have here is the question, When I was involved we always operated an open Ring, now for example if you needed to isolate a run of cable, say you needed to splice into the H,V, cable to, maybe add another DSS somewhere, the procedure I adopted was to close the ring, at where ever it was left open and proceed to isolate the cable that needed work done on it, we would isolate and earth down the cable, now for the life of me I cant recall if it needed earthing at both points of isolation, can't see the point of doing this really, but perhaps someone who is currently involved could throw some light on the subject, as I say it is just something that got stuck in my head, and I couldn't answer it, sad I know but hey hoe, grateful if someone could help me relax and put my mind at ease.

Not every ones cup of tea I know.

 

[DPG]

I have never worked on HV networks, but I seem to remember reading that a cable can still have charge if it is not earthed at both ends and maybe even at intervals if it is a long run. Again, this is a vague memory from reading something, but I thought I would put it forward for discussion! Daz

 

[Pete999]

I have never worked on HV networks, but I seem to remember reading that a cable can still have charge if it is not earthed at both ends and maybe even at intervals if it is a long run. Again, this is a vague memory from reading something, but I thought I would put it forward for discussion! Daz

Thanks Daz the more I think about it what you said does ring some bells for me, lets see what anyone else come up with, but I think your statement is true.

 

[Bobster]

Yes, earthed at both ends of the cable being worked on.

Not only earthed but locked off in that position.

 

[Pete999]

Yes, earthed at both ends of the cable being worked on.

Not only earthed but locked off in that position.

Yep I know Rob locked off, safety signs fitted, switching program, mimic diagram updated and Permit to work issued all coming back now.

 

[ian.settle1]

Spiking the HV cable as well

 

[Pete999]

Spiking the HV cable as well

Good one, blimey I could get another APs job with all this info, not

 

[Lucien Nunes]

Earthing in any position of a continuous cable will completely discharge it, however if it is broken for the work to take place then one side would not be earthed, hence the need to earth both ends and also to prevent current being driven along it to the point at which it is earthed if the other end were to be energised.

 

[Bobster]

Spiking the HV cable as well

Not always necessary.

 

[Pete999]

Not always necessary.

Go on then Rob explain why not

 

[Bobster]

Go on then Rob explain why not

No need if you can physically trace the cable from end to end.

 

[Pete999]

No need if you can physically trace the cable from end to end.

Right, but highly unlikely you would be able to trace from end to end on a long run in the middle of a field, don;t think I would risk it, any way if you are going to cut into the cable to add a new DSS, spiking makes it even safer, you know you have the right cable, but theoretically you are correct, but practically I wouldn't chance it.

 

[Bobster]

Right, but highly unlikely you would be able to trace from end to end on a long run in the middle of a field, don;t think I would risk it, any way if you are going to cut into the cable to add a new DSS, spiking makes it even safer, you know you have the right cable, but theoretically you are correct, but practically I wouldn't chance it.

Not underground no, we had a few substations linked together with ladder, so you could walk the length never loosing site of it.

Yes 90% of the time you will spike the cable, just wanted to point out it's not always mandatory.

 

[Pete999]

Not underground no, we had a few substations linked together with ladder, so you could walk the length never loosing site of it.

Yes 90% of the time you will spike the cable, just wanted to point out it's not always mandatory.

Thanks Mate, yes easy in your case, anyway my question has been answered regarding earthing at both ends, so I can sleep easy tonight.

 

[wemejimmy]

Hi Guys, interested in the topic, Im not an AP, but have been involved with our power downs over the years, as the assistant to the AP, I'm confused with some of the terminology, can someone explain to get it right in my head. I hear them talking about the open ring, this confuses me , a ring as in ring main is closed ? then closing the ring its already closed ? Can you open one part and earth down while working on the other part of the system, Three HV transformers to be maintained, one at a time?