Dynamic analysis and testing of on-load tap changer (OLTC) by the dynamic resistance measurement (DRM)

Power transformers represent the most expensive chain links connecting generation to utilization. One very important component of a power transformer is the on load tap changer (OLTC). There are two common technologies of OLTC in the market. The so called inductive ones, which are typically used in North America on the low voltage side, and the resistive OLTCs, which are typically used in the rest of the world on the high voltage side. This paper focuses on the resistive OLTCs. As opposed to other more static components in a transformer, the OLTC consists of a lot of moving parts. Therefore, a typical maintenance cycle, mostly depending on the total number of switching operations, is given by the manufacturer. The switching time of the OLTC is typically below 100 ms. This is very fast and…