Problems with Dry Type Transformers on cold loading in backup power situations

[emmjea001]

Hi Everyone,

I was wondering about experience using dry type TX where they are used as step up units as part of the generator backup scheme - here you will have the plant load immediately present on the TX's once the generators have started, and they take the full plant load from cold.

I recall reading that cold loading to rated capacity can lead to tracking / cracks in the resin, and early TX failure

Anyone had any experience or got a view on this one?

Thanks

 

[waross]

One issue is that Percent Impedance Voltage and from that Available Fault Current is detremined with transformers at operating temperature. The actual fault current will be slightly higher when the transformer is cold.

Bill
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"Why not the best?"
Jimmy Carter

 

[prc]

In good quality cast resin transformers, sudden 100 % loading will not, or should not cause any cracking of resin etc. In factory, temperature rise test is done by applying 100 % current suddenly and later followed by dielectric tests.