An investigation on the influence of tap changer on Frequency Response Analysis

Tap changer in power transformer has a high failure rate thus its condition requires extra attention. In this paper, the possibility of using Frequency Response Analysis to monitor tap changer status was explored. Initial study showed that the settings in tap changer can influence the frequency response of HV and LV windings. In addition, the low frequency region of the inductive inter-winding response was used to calculate the winding turns ratio. By simulating a faulty tap changer, the frequency response was able to show clear variations especially on the short circuit test. With the findings, a flow chart was proposed, which can be served as a guideline to determine the condition of tap changer based on the changes in the response. The chart also considered other types of fault.