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Shaleshwar Rana
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Join Date: Nov 2006
Location: Kullu (H.P) India
Posts: 9

Power Transformer

07/20/2010 1:08 AM

Hi all, we are running a small hydro power project of 4.5 MW Capacity with two units each of 2.25 MW cpacity. We have installed a single power transformer of 6.5 MVA,6.6/33 KV for both units. The plant is operational for last two years. Recently we conducted tests on transformer oil and the results were not satisfactory. The carbon dioxide content was 8100 ppm and BDV of oil is 46 KV. According to our observations the temprature of transformer is going high and it might be damaging the paper insulation. I would like to know the reasons behind this and solution for this. Regards.
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Anonymous Poster
#1

Re: Power Transformer

07/20/2010 2:45 AM

Just like in movie Swadesh you built it,great. I also want to do it but may be later. Love you guys.
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PWSlack
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#2

Re: Power Transformer

07/20/2010 3:30 AM

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

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kumarpradeep
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Join Date: Mar 2017
Posts: 41
#12
In reply to #2

Re: Power Transformer

10/05/2018 8:11 AM

Imagine your life without electricity! Now, imagine your life with a high surge of electricity! Both these conditions are catastrophic. This clearly shows that we all need electricity, but one that is maintained at a safe level to be used by us. So, how is the high power of electricity produced in the power grid brought down to a safer level to be used by us in our homes and offices? It is done with the help of power transformers in India. Transformers are those magical equipment that transfer electricity from one circuit to another through electromagnetic induction.

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electricalexpert65
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Join Date: Oct 2009
Posts: 2061
Good Answers: 169
#3

Re: Power Transformer

07/20/2010 8:06 AM

Why don't you carry out a thorough inspection & testing of the transformer before the problem aggrevates to something serious?
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PeterT
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Join Date: May 2010
Location: Liverpool, NY
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#4

Re: Power Transformer

07/20/2010 3:24 PM

A 6.5MVA transformer should be enough for 4.5MW of generation, unless something is really wild about your power factor (not usually the case). You need to determine what is causing your transformer to overheat. However, based on the information you gave, there is not enough information there to evaluate if the transformer is deteriorating. What are measured temperatures of the transformer oil, if you have a gauge on the unit? What other tests were done on it?

8100ppm of CO2 is not necessarily excessive - was there any significant concentration of carbon monoxide (CO), more than about 600ppm? 46kV dielectric strength for mineral oil is pretty good. Were any other oil tests done?

Does the oil level gauge on the transformer work? What level does it show? If the oil level is too low, the oil won't circulate in the radiators naturally, because it cannot flow in the top tubes - I have seen transformers that have half their radiators not effectively in use because the transformer was on a foundation that was not level, and with low oil there was insufficient flow.

One easy way to help cool your transformer is to add fans if they are not there already.

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jvrj
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#5
In reply to #4

Re: Power Transformer

07/21/2010 2:03 AM

I have to agree, your stated "specs" dont ring alarm bells, however, i take you dont have moisture in the oil (not stated) but it seems you have no oil flow internally, (oil level) or even airflow.

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amarnath.sn
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Join Date: Mar 2009
Posts: 51
Good Answers: 4
#6

Re: Power Transformer

07/21/2010 3:19 AM

As peter Said you have to do a very corrective study on the temperatures of the transformer, whether its heated due to the:

1. Transformer loading.

2. External climatic conditions (with all cooling considered as per the installed location)

3. what type of cooling is provided in the transformer, is it forced type or natural cooling.

The Winding temperature and Oil temperature guages in the transformer are working?, as if they are been set as per the design requirements and ambient we can easily find the reason for heating.

the Silica breather in the transformer is of which colour blue or pink?.

Normally we can take the temperature of the transformers in different timings and make a report comparing with the test done before during commissioning to see the abnormalities. any recent IR test done on the transformer?
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Humayun A Chaudhry
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Join Date: Jun 2010
Posts: 34
#7

Re: Power Transformer

07/21/2010 3:35 AM

What is the cooling method of your transformer ONAN or forced cooling and what type of installation location, outdoor, in an open transformer vault or indoor.

The answer to your question lies in the points if you scrutinize carefuly.

The oil for the hydropower projects transformers are to be comparitively checked more frequently for the moisture contents.
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Anonymous Poster
#8

Re: Power Transformer

07/21/2010 5:59 AM

Kindly get in touch with me. I would like to discuss more in detail along with possibility of business development in small hydropower projects

Engr. Mueed Mahmood

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BB Raina
Commentator

Join Date: Jun 2010
Posts: 75
#9

Re: Power Transformer

07/21/2010 6:39 AM

The observations made by you are not alarming. A BDV of 46 KV is pretty good. You said the temperature is going high. How much is it? There are various grades of insulating materials classified on the basis of temperature withstand capability and thermal stability. Please refer to IS 1271. May be your transformer has insulating material which is of high thermal classification. Obviously, it would look to be overheating when actually it may not be the case. Please check with your transformer manufacturer on this. Also don't forget to check and calibrate the thermometer mounted on the transformer.

BB Raina
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HiTekRedNek
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Location: 44.56024"N 15.307971E
Posts: 8277
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#10

Re: Power Transformer

07/21/2010 7:32 AM

What type of insulating oil are you using?Did you get oil samples from the bottom and top of the transformer?If mineral oil, the bottom will show the highest moisture content.If it is the "old" (banned in the USA PCB based oil) the water will be at the top sample.As for the overheating, the other posters have given good advice.Make sure the oil level is proper, the transformer is mechanically level, and pressurize the tranformer to about 5PSIG with compressed air.All transformers should have an air pressure guage large enough to be read from the ground mounted on the pressure port.This make it easy to check air pressure and detect leaks.This will insure moisture infiltration does not get into the oil tanks. It will also provide a visual indication of leaks in the system.

Good Luck.

HTRN

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ashoktoshniwal
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Join Date: Aug 2006
Posts: 183
Good Answers: 2
#11

Re: Power Transformer

07/22/2010 7:46 AM

Dear Shaleshwar Rana

You wrote, "temp. of transformer is going high". Could you also inform, the absolute temp. of oil, ambient temp., voltage impressed on primary. of transformer & load on transformer? This will give better insight.

Thanks and regards

Ashok Toshniwal, Bangalore, India.
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Users who posted comments:

amarnath.sn (1); Anonymous Poster (2); ashoktoshniwal (1); BB Raina (1); electricalexpert65 (1); HiTekRedNek (1); Humayun A Chaudhry (1); jvrj (1); kumarpradeep (1); PeterT (1); PWSlack (1)

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