Influence Estimation of the On-Load Tap-Changing Transformeron the Currents in Schemes of Ice Melting on Overhead Transmission Lines

Abstract

The influence of regulated under load transformer's (on-load tap-changing transformer) ratio and imped-ance on the short circuits’ currents and currents in the schemes of ice melting with AC and DC current is ana-lyzed. Accounting for changes in the transformer ratio is not difficult as it is provided in the technical data for all branches (tap positions). The transformer resistances used in the calculations, which are reduced to the un-regulated side of the transformer, are proportional to the short-circuit (SC) voltages. SC voltages are known, according to GOST, only for three tap positions - main (middle) and two extreme (top and bottom) positions, and for other tap positions are determined approximately according to different methods. It is shown on the typical example, that the error of the melting current calculation is significantly less than the error of the ap-proximated transformer's resistance calculation by the method of linear interpolation of resistances, the error of which for different types of on-load tap-changing transformers does not exceed 3 %.