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finasks
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Join Date: Sep 2011
Location: Riyadh
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Voltage transformer back energization

02/28/2012 2:04 PM

Is there is any technical issues if i back energize a Voltage transformer?

I have a gas insulated VT with rated primary voltage 115KV and sec voltage 115V.What is the significance of doing Vt back energization test?

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North of 60
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#1

Re: Voltage transformer back energization

02/28/2012 4:25 PM

What type of transformer has a 115KV primary and a 115 volt secondary? Watch you dont manage to kill yourself or anyone else.

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PeterT
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#4
In reply to #1

Re: Voltage transformer back energization

02/29/2012 3:40 PM

An instrument transformer (either VT or CCVT) used for transmission level relaying & metering could be of that ratio. They're usually connected phase-to-ground. They are not high capacity (maybe 500 to several thousand VA), but they do have that high a ratio. You can get them even higher, such as 345kV or 500kV primary.

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North of 60
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#5
In reply to #4

Re: Voltage transformer back energization

03/01/2012 5:38 PM

Agreed... but, someone who would work with this class of equipment on a regular basis would not likely be asking for advice in this forum.

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finasks
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#7
In reply to #1

Re: Voltage transformer back energization

03/05/2012 7:56 AM

Hi

Just search about the components in a HV substation.....

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67model
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#2

Re: Voltage transformer back energization

02/28/2012 6:57 PM

So long as you realise the HV voltage is lethal, and you do not exceed LV winding rated current or voltage [use a VARIAC 115V source, LV ammeter and LV voltmeter and step slowly up from zero volts], I do not see any issues for the transfo.

But you must be very sure the LV and HV winding are grounded and YOU are not the shortest, most inviting, path to ground from the HV terminal.

Personally, I would like to be behind a tall grounded metal mesh fence, standing on metal sheet, all bonded to the transfo LV winding ground, turning the variac from the far end of a wooden broom handle. Heavy duty voltage dependent resistors across the LV winding would be a good precaution.

These things are best done with all the right gear and precautions, according to an approved written procedure from the manufacturer, whose warranty probably depends on following that.

This would at least show the HV winding will take rated voltage. It should be possible to compare the LV magnetizing current with the specified HV magnetising current X transfo ratio.
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finasks
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#6
In reply to #2

Re: Voltage transformer back energization

03/05/2012 7:54 AM

Thanks for your reply...

Above said VT is installed in gas insulated substation (GIS).This VT has 2 secondary cores (115V & 155/1.73V).Our plan is to inject voltage in one secondary core and measure Im and voltage induced in other secondary core.Nothing is going to measure in primary.Thanks for the precautions mentioned in your reply.I already contact the manufacturer for their comments.

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67model
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#8
In reply to #6

Re: Voltage transformer back energization

03/06/2012 5:27 AM

Thank you for clarifying the installation.

If you had mentioned two facts, at the expense of a minute on the keyboard by you....

  1. The V.T. is installed in switchgear.
  2. It has two secondaries.

-- the concerns of CR4 folk about safety would have been allayed and the possibilities for test more evident.

I hope you have learnt the importance of including all the relevant facts in a question.

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finasks
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#9
In reply to #8

Re: Voltage transformer back energization

03/06/2012 12:40 PM

Yes Boss,,,,,,,,, will be specific next time,,,,,, thank you.....

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TonyS
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#3

Re: Voltage transformer back energization

02/28/2012 9:59 PM

I've got to ask, why are you wanting to do these tests? Have you got the equipment to measure the OP voltage if you do the tests?

Pure folly to my mind.

Blow yourself up if you want, please don't endanger anyone else!

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