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mhidayat
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Join Date: Jul 2010
Posts: 3

Heated Bolt at Transformer Conservator Tank Flanges

07/20/2010 4:37 AM

I need some explaination how can the transformer flanges bolts got heated up to 245 degree C. Some oil leaking observed around the flanges and the insulation oil start vaporizing. We are using Shell diala B as the insulation oil.

If you guys have any experience before, please share some info. BTW my Tx is rated at 900MVA
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mhidayat
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Posts: 3
#1

Re: Heated bolt at transformer conservator tank flanges

07/20/2010 4:50 AM

Picture of the heated bolt. we did the thermograph scan and found out one of the bolt temperature gone up to 245 C. at the moment the tx is still energized
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PWSlack
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#2

Re: Heated bolt at transformer conservator tank flanges

07/20/2010 5:51 AM

What does the transformer manufacturer have to say on the subject?

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kvsridhar
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#3

Re: Heated Bolt at Transformer Conservator Tank Flanges

07/20/2010 7:16 AM

Just a wild guess... any chance of stray fields causing some eddy currents?

In which case the manufacturer would have made them non-magnetic stainless steel or something. In any case, the manufacturer of an almost 1 GVA tfr wouldn't have missed a silly point like this

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PeterT
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#4
In reply to #3

Re: Heated Bolt at Transformer Conservator Tank Flanges

07/20/2010 3:30 PM

I would agree with kvsridhar - It's possible that at the factory, someone ran short of stainless steel bolts, and substituted standard, plated steel bolts. In the vicinity of the large electromagnetic fields of the transformer, these bolts can heat up.

Check the bolts with a magnet - quick clue to their composition (but de-energize first!).

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manindra
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Join Date: Jun 2010
Location: Kolkata, West Bengal, India
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Good Answers: 1
#5

Re: Heated Bolt at Transformer Conservator Tank Flanges

07/21/2010 8:23 AM

It is guessed that at time of manufacturing/assembly of the Transformer in workshop or maintenance activities at site someone by mistake fixed up MS bolt inplace of nonmagnetic stainless steel bolt. As a result when the Transformer is energised condition, due linkage of stray magnetic flux, due eddycurrent effect the subject bolt is heated up.

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bethini.hanumanthu
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Join Date: Feb 2010
Posts: 40
#6

Re: Heated Bolt at Transformer Conservator Tank Flanges

07/22/2010 3:49 AM

Hai,

I agreee with Kvsridar and also chance of ..........

In power TX shunt is connceted to tank walls and earthed to tank body for reducing leakage / eaddy currents. If earth point open, Heating occurs at same place.

I faced similar this type of problem in our Rectifier TX.

Pls contact to Manfacture for further

I hope this help some extent.
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mhidayat
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Join Date: Jul 2010
Posts: 3
#7
In reply to #6

Re: Heated Bolt at Transformer Conservator Tank Flanges

07/22/2010 4:16 AM

Hi all,

Thanks to all for the info. i will check on the nut material once we sut down the unit. ill check the earth integrity as well

we did DGA analysis and no abnormalities found.Anyway the OEM Areva recommend to do internal inspection of the tx. we still considering the proposed work by OEM.

below is the IR scan report.
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bethini.hanumanthu
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Join Date: Feb 2010
Posts: 40
#8
In reply to #7

Re: Heated Bolt at Transformer Conservator Tank Flanges

07/22/2010 7:43 AM

Hai Midiyat,

After examination of TX by Areva, Pls post exact reason and ther recomendations.

This helps learning to all

Reg,

Hanu
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Users who posted comments:

bethini.hanumanthu (2); kvsridhar (1); manindra (1); mhidayat (2); PeterT (1); PWSlack (1)

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