Varnish on Insulators

[buzzp]

I have a new 3MVA, 480VAC Dry Type transformer, VPI. The manufacturer claims they then dip the transformer, along with the copper bus and insulators after the VPI process. Obviously, this coats the insulators with varnish. Has anyone seen this before? As far as I know, this is not anti-tracking varnish. My instinct is to have them clean off the insulators prior to approving the new equipment. Any thoughts?

 

[cuky2000]

Below is a description of the ABB's VPI process with a picture showing a submersion tank. I do not see the need for applying varnish to the bushings.


>>>>>>>>>>>>>>>>>>>

VPI PROCESS SPECIFICATION:
* Apply one (1) cycle polyester protective shield of varnish to the coils and a protective shield to the bus, core and support structure.
* The varnish shall be cured on the core and coil assembly following an established temperature vs. time baking cycle in a hot air circulating oven.
* The VPI process shall effectively impregnate the entire core and coil assembly which results in a unit which is virtually impermeable to moisture, dust, dirt, salt air, and other industrial contaminants.

 

[JG2828]

The manufacturer claims they then dip the transformer, along with the copper bus and insulators after the VPI process. Obviously, this coats the insulators with varnish.

Maybe by 'insulators', they mean the red insulating material between the 3 phases (in cucky2000's photo), and not the porcelain or resin insulator bushings.

 

[buzzp]

There is copper buss in the power center, which is attached to the transformer via cable. There is bushings/insulators between the buss work. These bushings, along with the copper buss, is supposedly dipped in varnish, after the transformer VPI process. I find it hard to believe they would dip the copper buss and porcelain insulators/bushings after it was assembled...makes no sense. It may have been 'sprayed' but likely not dipped. In any case, I have not seen bushings with varnish on them in the field and is what my concern is. Thanks

 

[electricpete]

I wouldn’t be happy about that. If nothing else, it wouldn't be as easy/effective to inspect/clean the vpi'd insulators as it would be on a smooth insulator (on the rare opportunities when you do have an opportunity to inspect/clean... that's usually a step when investigating abnormal electrical test results).

One wonders whether it will have an effect on factory electrical testing results.


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(2B)+(2B)' ?

 

[buzzp]

Thanks for the feedback. I raised my concerns and it was accepted anyway. Nevermind any real factory tests...power it up and if it hums, all is good.

 

[unclebob]

Hmm, I always tought that the windings were dipped one at a time. And then installed on the iron core thereafter.

 

[buzzp]

unclebob,
I am sure that is how it is normally done. I have a hard time believing it was all dipped, with buswork and bushings, afterwards.

 

[cuky2000]

https://hub.acutran.com/blog/dry-type_transformer