Relation of Winding Resistance Measurement and Dissolved Gas Analysis for Power Transformers

Winding Resistance Measurement and Dissolved Gas Analysis are two common methods in diagnostics of oil filled power transformers. Since winding resistance measurements are simple to perform and are not aggressive for the transformer, this test is commonly used off-line to check the state of transformers. WRM is executed as a factory test, during installation, scheduled maintenance routine, troubleshooting or unscheduled maintenance. Unlike WRM, oil sampling and Dissolved Gas Analysis can be done even when the transformer is in operation. DGA can be useful in detection of the faults that lead to some key gas formation and usually some of those faults can also be detected by WRM. In this paper, DGA and WRM results for several case studies are presented and their contribution for faults detection is investigated. The results show the agreement between DGA and WRM and also show how WRM can be used to fairly localize the problem.