Development of a thermal self-diagnostics system for a digital current and voltage instrument transformer

Abstract

Abstract Ivanovo State Power Engineering University (ISPEU) staff have developed and put into operation innovative designs of digital current and voltage instrument transformers (DCVT) based on resistor dividers performing technical and commercial electric power accounting, and also participating in work of relay protection and automation systems. Thermal self-diagnostics systems working in real time for instrument transformers do not exist in electric power engineering, while thermal examination is often conducted according to maintenance schedules, which negatively impacts the reliability of electrical equipment functioning. Development and building of new systems of self diagnostics for instrument transformer thermal state, revealing temperatures at several points, including values for the most heated up part, in real time, is therefore a vital task, especially for controlling operation of “smart” grids. Based on the results of physical and mathematical simulation of the process of heat exchange between a transformer and its environment at different values of ambient temperature, insolation and grid voltage, methods have been developed to determine the impact of the above factors on the thermal mode of DCVT operation. Algorithm has also been developed for thermal self-diagnostics and thermal protection against overheating of instrument transformers. System of thermal self diagnostics has been developed for 6-220 kV.