Transformer Winding Resistance

[SecondGen]

Hi everyone, I hope you all doing okay. I wonder something and you are the best crew i can ask
When we test winding resistance test for transformer we saw discrepancy in results when compare with the Factory Test results. Is there any way to calculate the result and see the true values? I research it but i couldnt find a good way.
Thank already...

As other have stated, I'd make sure you are using the exact same connections and test current as the factory test results. Also be mindful of additional bus you may be including, the readings you have wouldn't' raise alarm to me if I didn't see the factory results and my readings were within tolerance between each phase.

[rmr660]

Hi
I want to try and calculate the values based off the voltage, current and power if its possible.

So your winding resistance test set, what ever brand you use, should inject the winding(s) with a voltage and current. You usually can change the current you inject into the transformer. The results you got were the "true values" at the time. As windings heats up and if there are faults or contamination in the oil the resistance will go up; this is what changes your results from the factory. if you wanted to calculate the resistance you would just use ohms law. But that doesn't mean you will get a "true value" because no conductor is a perfect conductor and there is always capacitance and reactance.

I hope that helps

[SecondGen]

So your winding resistance test set, what ever brand you use, should inject the winding(s) with a voltage and current. You usually can change the current you inject into the transformer. The results you got were the "true values" at the time. As windings heats up and if there are faults or contamination in the oil the resistance will go up; this is what changes your results from the factory. if you wanted to calculate the resistance you would just use ohms law. But that doesn't mean you will get a "true value" because no conductor is a perfect conductor and there is always capacitance and reactance.

I hope that helps

Good point, I totally forgot to mention temperature is important as well. If you had just de-energized the transformer the winding temp will most likely be elevated and this should be corrected same as the factory results for true comparison.