Megger Transformers

[gray.one]

I just read a post on here where someone said the megger transformers annually. I don't know much about routine maintenance, but meggering is a destructive test. Won't this shorten the life of the transformer?

What is gained by Meggering? I thought transformers were tested by sampling the oil.


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[JFletcher]

Welcome to the forum. There are a few different tests for checking insulation; some are destructive, some arent:

https://en.wikipedia.org/wiki/Hipot

 

[MD84]

There are factory insulation resistance tests and maintenance testing standards. The latter are not as destructive.

What type of Transformers are you referring to? There are many types of Transformers. In general, I would say the current trend of maintenance is moving toward predictive testing such as oil testing or infrared scans. Even annual oil samples are being phased out in many cases. Instead total combustible gas measurement of the gas headspace is taken.

Of course this greatly depends on the type of transformer and the characteristics of the system in which it is being used. The more difficult it is to source a new transformer and the more critical the load, the more testing would be warranted.

 

[zog]

Depends on the type of transformer, duty, criticality, and environment. If you are talking about oil filled I would at the very least draw a DGA sample annually.

 

[Sahib]

What is gained by Meggering?

An opportunity to fail a transformer during test rather than in service.

 

[zog]

Also trend analysis as a predictive maintenance tool

 

[GoldDigger]

Also note that hi-pot testing is often a destructive testing, capable of causing a complete breakdown of deteriorating or marginal insulation, while megger testing is normally done at a voltage below the rated insulation voltage and will report suspect leakage current at that voltage.
Megger testing will not cause failure of good insulation unless done at too high a voltage.

 

[wbdvt]

If it is an oil filled power transformer, Doble testing is probably one of the best tools for determining transformer health.