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Earthing Switch In the High Voltage Panel

06/19/2013 5:24 AM

I have seen a earthing switch in the 11kV RMU(Ring main unit) near to the VCB(vacuum circuit breaker).

Can any body tell me the purpose of that earthing switch?

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#1

Re: Earthing switch in the High voltage panel

06/19/2013 5:29 AM

Yes. The equipment manufacturers can, and the best way of asking them is to use the telephone.

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#2

Re: Earthing Switch In The High Voltage Panel

06/19/2013 8:43 AM

Its function will also be detailed in the switching procedures at the facility. If these cannot be found and read, talk to the Senior Authorised Person at the facility about its use.

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#3

Re: Earthing Switch In The High Voltage Panel

06/19/2013 9:10 AM

It's there for personnel safety to be closed during equipment maintenance, because you can't see the state of the vacuum breaker contacts. It's one of many "Darwin Award Circuits" found on potentially lethal equipment.

If you have to ask, you're not "Trained Personnel".

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Guru

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#4

Re: Earthing Switch In The High Voltage Panel

06/19/2013 9:12 AM

Let's see. It's a switch. Now, what do switches do? Not sure here, I'll have to Google it.

About 1,760,000 results (0.21 seconds)

It says that switches, "are mainly used to protect personnel when working on equipment.".

Novel though, that ,"to protect personnel when working on equipment" could catch on as a concept.

Really that helpless? !!!!!!!

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#5

Re: Earthing Switch In the High Voltage Panel

06/19/2013 3:24 PM

Safety.

Jack - Safety, safety, die for safety.

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#6

Re: Earthing Switch In the High Voltage Panel

06/19/2013 9:59 PM

The earthing switches are for the various cables. No work can be carried out on a MV cable unless it's earthed at both ends.

They have another function. By earthing all the cables connected to the RMU it becomes safe to work on after proving dead.

The bottom line, they are you're first line of defence when it comes to safety.

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#7

Re: Earthing Switch In the High Voltage Panel

06/19/2013 11:38 PM

Earthing switch should be interlocked with main breaker or isolator.

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#8
In reply to #7

Re: Earthing Switch In the High Voltage Panel

06/20/2013 3:51 AM

Indeed. It wouldn't do to close the earthing switch while the supply breaker were still closed, would it?

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#10
In reply to #8

Re: Earthing Switch In the High Voltage Panel

06/20/2013 9:19 AM

All to easy to do on a ring main. Forget to open the feeder end of the cable first and you're in trouble.

Most earth switches are fault making and have anti reaction mechanisms to stop you trying to switch it back off under fault.

I'm just looking at altering an 11KV ring to take part of it off a private network for connection to the public network. The switching procedures are quite complex to keep it safe.

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Guru

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#9

Re: Earthing Switch In the High Voltage Panel

06/20/2013 8:11 AM

If you are asking this question here you should NOT BE NEAR OR WORKING WITH THIS EQUIPMENT!

I shall assume you were a by stander, the first port of call is the OPERATORS MANUAL: It has a brief and drawings of the switch. Usually a comprehensive book. Worth reading!

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#11

Re: Earthing Switch In the High Voltage Panel

06/22/2013 11:49 PM

As others have mentioned, earth switches are for safety, but I don't think anyone has explained the underlying reasons why they are used. So I'll give it a shot for the benefit of the OP:

A cable has shunt capacitances between phases and to earth and these can be significant, especially for long cables and at MV/HV. These capacitances are charged when the cable is energised. When the cable is de-energised at both ends, there is the possibility of trapped charges in the cable due to these capacitances. The capacitances will discharge to earth through leakage paths in the insulation, but this can be a slow(ish) process.

If someone were to work on the cable and trapped charges were still present, then they could receive an electric shock. Therefore, an earth switch is used to short the cable and discharge all the capacitances to earth before anyone is allowed to work on it.

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Power-User

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#12
In reply to #11

Re: Earthing Switch In the High Voltage Panel

06/24/2013 3:28 AM

Thank you so much Mr.Juleselec I got nice explanation from you.

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#13

Re: Earthing Switch In the High Voltage Panel

06/22/2016 6:37 AM

Earthing switch connected the live parts and earth. Switch is normally open. It is used to earth the live parts during maintenance and used during testing process. Earthing switch should be linked with main breaker or isolator.

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#14

Re: Earthing Switch In the High Voltage Panel

09/06/2016 3:49 AM

Dear All,

As far as my little knowledge, the earth switches are nothing but a switch arrangement which will earth the dead ends of the bus to ground while doing maintenance / repair at the cables connected to that breaker. This is to prevent any inadvertence charging of the lines when people are working on the cables. as regard to the capacitance, the thumb rule of any maintenance engineer attending any portion of the cable is (1) to discharge the stray / accumulated capacitive charge by touching the conductor with earthed rod (2) Earth the load side terminals of the breaker before working on the cables

Note.Such discharge is also done when we do the HIPOT testing on cables.

Thanks

Ramesh.A

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highvoltpower (1); IQ (1); jack of all trades (1); juleselec (1); lyn (1); Muthuvel (1); pnaban (1); PWSlack (3); RAMConsult (1); Rramesh (1); TonyS (2)

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