Thermal characteristics of transformers

[jd68]

I wanted to determine the thermal characteristics of distribution transformer (IEC 354-1991, page 33).
Temperature rise test was made on 50 kVA transformer, and the following thermal characteristics were obtained:
- oil time constant;
- top-oil temperature rise;
- average winding temperature rise;
- winding gradient;
- winding time constant.

How can I determine following thermal characteristics:
- x: oil exponent;
- y: winding exponent, and
- H: hot-spot factor.

Best regards,

 

[prc]

The factors x,y and H are already given in IEC 354 page33 ie .8,1.6and 1.1 for distribution transformers.So you need not derive it out.Using these factors and test results you can calculate the relevant parameters resulting during operation