Tranformer Oil DGA & Furan

Did you telephone the transformer manufacturer, Agnes?

I did, but they don't have an equvation. Is there any general methods for that?

No! Do your homework↓
a guide to transformer oil analysis - transformer chemistry

Sreekumar while I always admire and encourage new thinking which brings in innovations, but as far Dissolved Gas Analysis is concerned it is a diagnostic tool than knowing operating temperature of oil under normal operation.

For example if hot spots are developing inside transformer DGA will diagnose same. For knowing normal operating temperature of transformer oil Temperature Gauge and Transmitter are better tools.

DGA; dissolved gas analysis measures dissolved gas and working temperature measures temperature. Farane test measures the amount of paper (ie insulation) in the oil. There is no equation for the relationship. Eventually the windings will lose enough paper to cause hot spots which will increase the dissolved gas and the oil temperature and the whole thing will blow up but there is no formula for this. (Why does everything have to have a formula?)

As beentheredonethat stated, DGA measures dissolved GAS. Furanic analysis measures paper dissolved in the oil, which is not a gas. The two are not related, as DGA gives you only some indications of insulation failure. Apart from hot-spots, DGA will also give warning of internal arcing (I've twice had cases where there was warning if internal arcing picked up by DGA, both times due to tap-changers that had their tap settings changed after years of being in the same position). Furanic analysis is an indirect measurement of paper insulation condition, but still worthwhile on older transformers. The other alternative is a direct sample of the paper, but for that the transformer has to be opened up, so it is a rather invasive procedure.

Gideon

You're quite right. That is why it is advisable to have on line tap changers on a separate oil system (tank and conservator).