Power Transformer Testing (Help!!!!)
Power Transformer Testing (Help!!!!)
(OP)
Hello:
We need to test a group of transformer ranging in size from 3750kVA to 20mVA. We are in a budgetery crunch at the present time (what else is new...?); of all the tests: doble, insulation and winding resistance, turns-ratio, etc, which ones do I need to do at an absolute bare minimum.
Thank you,
Gene Hidalgo, PE
We need to test a group of transformer ranging in size from 3750kVA to 20mVA. We are in a budgetery crunch at the present time (what else is new...?); of all the tests: doble, insulation and winding resistance, turns-ratio, etc, which ones do I need to do at an absolute bare minimum.
Thank you,
Gene Hidalgo, PE






RE: Power Transformer Testing (Help!!!!)
Please remember that a shorted turn will be found very quickly (read ka boom).
Don't forget to test the oil DGA recommended with oil acidity.
RE: Power Transformer Testing (Help!!!!)
Are you buyer, seller, testing firm or inspection agency? It may seem trivial at this point, but a prime aspect of the process is likely spelled out in the contractual/procurement documents.
RE: Power Transformer Testing (Help!!!!)
Gene Hidalgo, PE
RE: Power Transformer Testing (Help!!!!)
RE: Power Transformer Testing (Help!!!!)
Dean
RE: Power Transformer Testing (Help!!!!)
The listed sizes are not exactly cookie-cutter/“toss out” transformer sizes. Consider the potential cost of “production” loss.
Start with §7.2 of NETA Maintenance Testing Specifications, 2001.
RE: Power Transformer Testing (Help!!!!)
RE: Power Transformer Testing (Help!!!!)
First: Sample the oil and perform "screening test" and "Gas Analisys" Cost about $110.00 each. No Shut down required. (This should be done ahead of time if you plan on shutting down so that any problems detected can be addressed.)
Second: Power factor and excitation current. Depending on the difficulty in isolation the time for this can vary. On average this testing will take two technicians about 8 hours. Estimated cost about $1500.00
Third: Megger, Turns Ratio and Winding Resistance testing are usually done together since they require relativly little time each. If done in conjunction with the power factor testing then this would usually take an additional 8 manhours assuming the connections have already been removed. Estimated cost = about $750.00
Some savings could be gained if you have site electrician to do the connections and cleaning of the bushings. If you were doing several transformers in a day that would also reduce the final cost.
One last note. Make sure that you are fully aware of what you want and how you want it done. For example, some contractors may give you a price based on not disconnecting the transformers even though this is not the recommended method. A clear scope of work is vital!
RE: Power Transformer Testing (Help!!!!)
2003
Acceptance Testing Specifications
for
Electrical Power Distribution
Equipment and Systems
7. INSPECTION AND TEST PROCEDURES
7.2.1.2 Transformers, Dry Type, Air-Cooled, Large
and
7. INSPECTION AND TEST PROCEDURES
7.2.2 Transformers, Liquid-Filled
© Copyright 2003
by
InterNational Electrical Testing Association
PO Box 687, 106 Stone Street
Morrison, CO 80465
Voice: 303.697.8441 Facsimile: 303.697.8431
E-mail: neta@netaworld.org • Web: www.netaworld.org