Diagnosis of the Condition High-Voltage Support Insulators by Leakage Currents

Abstract

The assessment of the discharge strength of the insulation is of the utmost importance for the prevention of overlap and the establishment of the deadline for the implementation of preventive measures. Preventive measures used in electric networks to prevent insulator overlap have low efficiency, and existing diagnostic and control tools are not always able to correctly assess the insulating capacity of insulators during operation. The main reasons for overlapping and damage to the insulation are its contamination with various chemical substances, which is also accompanied by moisture. Overlapping of the surface of the insulators leads to single-phase short circuits to the ground or to interphase short circuits. The greatest danger is caused by short-circuits accompanied by an intermittent electric arc, which can cause large overvoltages in the electrical network, and their value reaches 3...3.2Uf. Such conditions, in turn, are very favorable for covering the surfaces of insulators. The non-destructive control method of assessing the insulating capacity of insulators based on the measured values of leakage currents is the most suitable not only for insulators of complete switchgears of 10 kV, but also for external insulation of open switchgears of 35 kV, as it allows continuous automatic control of the degree of contamination of the insulator. The purpose of the research is to establish the functional dependence between the leakage current of the contaminated insulator and its discharge voltage. As a result of theoretical studies of the working conditions of insulation during operation, the characteristics of the surface layer of insulators contaminated in natural conditions were determined, these characteristics were analyzed depending on the location of the substation and the time elapsed since the last cleaning. According to the methods of regression and correlation analysis, based on experimental data, an empirical regression line was constructed, which made it possible to determine the insulator leakage current, which is dangerous from the point of view of overlapping.