The Calculation Method of Ice Melting Schemes’ Relay Protection Settings and Clarification of the Ice Depositions Control Method on Steel Lightning Protection Wires

Abstract

The method of current values calculation of overcurrent and undercurrent relay protections included in the complex of relay protection of ice melting schemes by alternating current on steel lightning protection wires of overhead transmission lines is analysed. A comparison with the generally accepted method, called the element-by-element method, is made. The element-by-element method is based on using the parameters of all the elements included in the ice melting scheme to calculate the maximum and minimum melting currents, from which the corresponding protections must be adjusted. These parameters have a significant variation, especially the active and internal reactive resistances of steel lightning protection wires at alternating current, what increases the calculation error. The proposed method, called the recalculation method, is based on the use of the trial melting mode parameters, carried out annually in the autumn season on lightning protection wires, with a duration up to 2 minutes. In difference to the usual practice, the trial melting has to be carried out 2 times with different currents. According to the parameters of the mode the settings of relay protection are recalculated using the given methods. The methodological and additional errors of the new method are estimated, that shows proposed method advantage. The parameters of the trial melting mode can be used to specify the methodology for remote control of ice formation (the length of the ice formation zone).