Transformer Shortcircuit
Transformer Shortcircuit
(OP)
Can we put the power transformer into service after short circuit testing per IEC 60076-5 (i.e.after the transformer sucessfully passing all the tests after the short circuit tests) in to our 132kV Grid. There are some objection from operation Dept. of our company. Please share your experience.
Thanks you
Thanks you






RE: Transformer Shortcircuit
RE: Transformer Shortcircuit
Rafiq Bulsara
http://www.srengineersct.com
RE: Transformer Shortcircuit
RE: Transformer Shortcircuit
If this is a new transformer, an acceptance testing should be done. You will have to do a lot more testing, and perhaps that includes a "soak test" as mentioned in the early post.
RE: Transformer Shortcircuit
RE: Transformer Shortcircuit
RE: Transformer Shortcircuit
In the above test. windings will be stretched to the maximum limit and hence the apprehension of the suitability for regular use.Many years back, it was a special design or development test on the prototype.But today many utilities are considering this as a type test to be done on the first unit.40 years back,when transformers were ordered, utility wanted an impulse test certificate from tests done on a similar transformer ie he did not want impulse test to be done on his transformer. Today, thanks to the progress in fault detection techniques,impulse test is a routine test, at least for EHV units.
The test you mentioned is not short circuit testing,but " impedance voltage and load loss measurement" as per ANSI or "Measurement of short circuit impedance and load loss " as per IEC.This is a routine test and will always be done in factories.
RE: Transformer Shortcircuit
Mrrbulsara
The objection is obvious. As per IEC after the shortcircuit tests,all routine tests and impulse tests (if agreed) shall be conducted. However the point is these tests alone may not prove the integrity of transformer. Naturally Operation will have their objection.
jgrist
There are more technical papers on the present performance of transformers during short circuit. Some of the technical papers mention as many as 30% transformers failed during short circuit.Margin in the present transformer design is very less.Hence our company want to carry out short circuit test and not just rely on calculations only.
Just by passing the test or routine testing the transformer after short circuit as suggested by IEC, we can not conclude the transformer is 100% healthy.That is why I would like to have member experience in this.How many of you used the transformer successfully after short circuit test in network
burnt2X
Please check IEC 60076-5.
Prc
IEC advises 2% change in reactance value acceptable criteria for transformer 2.5MVA to 100MVA and for above 100MVA it is 1 to 2%. For values above this, detail examination required after dismantling. Is your transformer manufacturer guarantee the performance or you accepted without guarantee. We would like to know the risk in accepting the transformer.
RE: Transformer Shortcircuit
As regards,using short circuit tested trfs in service I confirmed that in India there are hundreds of transformers in service which were SC tested. Manufacturers give performance gurantee for such units.Risk is not for utility but for the manufacturer.My personal experiene is from 1984 when a 12.5 MVA traction feed transformer was Sc tested and then it was in service for many years.
RE: Transformer Shortcircuit
Suppose I would like to purchase 60MVA 132/13.8kV YNyn0d1 transformer. I would like to accept the transformer without short circuit and on the basis of calculation only. Calculation can :
a. comparison with transformer (reference transformer) which passed short circuit test or
b. Manufacturer design rules.
We would like to select calculation based on transformer per (a) i.e transformer passed short circuit test.As per IEC for transformer with absorbed power (rated power/per unit short circuit impedance) 30% to 130% relating to reference transformer (which per IEC this is known as similar transformer) can be accepted with calculated forces not exceeding 120% times of reference transformer.
This seems to be large margin.My question is can we just go per IEC or suppose I require 100MVA power transformer using some thump rule I insists the manufacturer should have conducted short circuit test for 40 to 120 MVA and then per calculation I can accept 100 MVA power transformer.
As I already mentioned we prefer manufacturer who conducted short circuit tests near the rating I require then accept the new transformer and not just calculation only.
Please share you experience. Sorry for reference to IEC as in our part of the world (Middle East) IEC is normal standard reference. Presume ANSI requirements aresimilar
Thanks
RE: Transformer Shortcircuit
NO it is not obvious yet what the objection is. Your OP implies you concluded the short circuit test as well as other tests and yet operations will not allow putting it back in service.
While your last post suggests that you want to accept the transformer without the short circuit test (and perhaps other tests) and operations has objection to test.
Which is correct? To me sounds like your operations are in the right. No test prove all the integrity of a transformer, but they do provide a reasonable assurance. But you do need to do some testing. When there are standards recommending them, it is only wise to follow them.
Rafiq Bulsara
http://www.srengineersct.com
RE: Transformer Shortcircuit
Muthu
www.edison.co.in
RE: Transformer Shortcircuit
Ask the operations department this:
If you had a power transformer in service and there was a fault on the secondary bus, would you scrap the transformer if there were no indication that it was damaged by the fault?
If not, why scrap a new transformer that was subject to a similar fault?
RE: Transformer Shortcircuit
RE: Transformer Shortcircuit