Previous in Forum: shart fall   Next in Forum: selection of vector group
Close
Close
Close
4 comments
Rate Comments: Nested
Associate
Jordan - Member - New Member

Join Date: Aug 2007
Location: Saudi Arabia
Posts: 25

How to Test Power Transformers

01/23/2009 4:54 PM

hi everybody

could you please advise If I have number of new oil type transformers ( 440v-220, delta/star), how I can test these transformers befor energizing the power

( of course I'm asking about special tests using special tools not a quick test using ohmmeter .

can I use a megger for testing , and how much the resistance reading range which will be acceptable

thanks for all

Register to Reply
Pathfinder Tags: transformer testing
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Anonymous Poster
#1

Re: testing power transformer

01/23/2009 11:00 PM

A meggar "a dc generator self contained meter primarily usedfor checking insulation values to ground"

Between phases very low resistance use ohm scale between Prim and Secondary better be close to infinate on meg scale test at or near transformer rated voltage ,

Primary leads to ground meggar resistance at voltage rating of transformer

reading should be infinate

Secondary leads to ground meggar reading at voltage rating of transformer reading should be infinate to ground.

Since you have several transformers if rated the same winding resistance will be close for all within 5-7% variance no real problem.

There are of course other "Toys" that can be used if you have the budget $. but a meter and a meggar do do the trick..........................

Register to Reply
Guru

Join Date: Mar 2007
Posts: 2550
Good Answers: 103
#2

Re: testing power transformer

01/24/2009 1:06 AM
__________________
Fantastic ideas for a Fantastic World, I make the illogical logical.They put me in cars,they put me in yer tv.They put me in stereos and those little radios you stick in your ears.They even put me in watches, they have teeny gremlins for your watches
Register to Reply Off Topic (Score 5)
Guru
Safety - ESD - New Member India - Member - New Member Engineering Fields - Energy Engineering - New Member

Join Date: May 2007
Location: Pune , India
Posts: 875
Good Answers: 42
#3

Re: How to Test Power Transformers

01/25/2009 10:41 AM

Hi os

The transformer manufacturers normally carry out standard routine test prescribe by the specification before final dispatch to the site. If there are orders for many transformers , the purchaser can ask for conducting heat run test and the type test of transformer ( to be carried out in presence of the purchaser at manufacturers premises)

At site before commissioning Insulation test of the windings must be carried with the help of megger of requireed voltage level. The transformer oil must be tested before charging with the help of standard transformer oil testing machine. If required filtration of oil need to be carried out if the oil testing results are below the required value .

Register to Reply
Commentator

Join Date: Jan 2009
Posts: 62
Good Answers: 4
#4

Re: How to Test Power Transformers

01/30/2009 5:33 PM

In the electric utility where I work, we have 3 tests we always conduct on our transformers from 10 kVA to 500 kVA.

These are:

1. Insulation resistance test - HV-G, LV-G, HV-LV; minimum value: 2000 megOhms

2. Transformer turns ratio test - on all tap positions; minimum deviation from computed values: 5%

3. Oil Dielectric Breakdown Voltage test - to test the dielectric strength of the oil; minimum value: 30 kV (ASTM 877)

This tests worked for us. This may not work for others.

__________________
Patriotism is the last refuge of scoundrels
Register to Reply
Register to Reply 4 comments
Copy to Clipboard

Users who posted comments:

Anonymous Poster (1); myn1996 (1); sb (1); V.I.Abraham (1)

Previous in Forum: shart fall   Next in Forum: selection of vector group

Advertisement