How many times does the Lightning Impulse test and AC withstand test can be done?

[SamHans05]

Hello Everyone,

Just to ask regarding the testing of our 230kV transformer. The vendor is telling us that the the AC withstand test and Lightning impulse test can be done in one time only. My question is, does it written somewhere in IEC or any standard that this test shall be one time test only? I know that this test will stress the windings of my equipment where it also affect the life span on my transformer.

Pls. help me to investigate whether there is a strong reason or if have a written standard?

Thanks.

 

[prc]

No.Repetition of dielectric tests are permissible. See IEC 60076-1 (2000) Power Transformers_general Clause 9.0
9 Repeated dielectric tests
For transformers which have already been in service and have been refurbished or serviced,
dielectric tests according to 7.2, 7.3 and 7.4 shall be repeated at test levels of 80 % of the
original values, unless otherwise agreed upon, and provided that the internal insulation has not
been modified. Long-duration AC induced tests (ACLD) according to 12.4 shall always be
repeated at 100 % test level.
NOTE The partial discharge criteria should be discussed between the purchaser and supplier depending on theextent of the repair.
Repetition of tests required to prove that new transformers, having been factory tested to 7.2,
7.3 and 7.4, continue to meet the requirements of this standard is always performed at 100 %
of test level.

 

[SamHans05]

Hi PRC,

I Checked in IEC 60076-1 (2000), there is no written standards saying that
no repetition for dielectric test... I check also this item in IEC 60076-3..

Anyway thanks for your kind reply.

Regards,