On-Load Tap Changing Transformer’s Impedances

Abstract

It was noted the relevance of determining the impedances on all branches of on-load tap-changing transformers, because, in accordance with State Standard, only short-circuit voltages on the main and extreme branches are measured and indicated in the technical documentation. While these data are necessary to calculate the modes of power system’s electrical networks, including short circuit currents, melting currents, to diagnose deformation and displacement of the transformer windings, as well as to select settings and check the sensitivity of relay protection. The article considers and compares on a concrete example well-known and offered by the authors methods of calculation: with the use of fractional-rational function; linear interpolation of short-circuit voltages with recalculation on short-circuit impedances; interpolation by exponential function of short-circuit impedances; correction of the solution of "generating" challenge, approximated by linear and exponential functions. The conclusion is made that it is necessary to compare methods on other types of transformers.