Dynamic Resistance Measurements and Result Interpretation for Various On-Load Tap Changers

Dynamic Resistance Measurement (DRM) is introduced in the last decade and provides more information about the condition of the OLTC than static measurements. However, there is little information available on how to interpret the results from the DRM for different types of tap changers and different faults. In this paper, different faults are introduced in a typical tap changer and it is then subjected to DRM tests. The test results are presented and interpreted. DRM measurements are performed on resistor-type and vacuum-type OLTCs and their DRM behavior is simulated in Simulink to compare with the measured results for further studies. Results demonstrate the possibility to determine and locate the likely cause of a problem in an OLTC, thus improving fault identification and further optimizing maintenance and reliability of a transformer.