Research on Undetected Overheat Fault of the GIS Bus Bar Contacts Based on Infrared Thermal Imaging

Abstract

The overheating problem of GIS contacts would lead to a major accident. Recently, it was found that the infrared thermal imager cannot detect the overheating fault timely in many cases. In order to solve the above issues, a temperature rise test platform of the 252 kV GIS bus bar was built, and the bus bar temperature field distribution under normal operation and fault conditions was obtained. Then a three-dimensional simulation model was established based on the experimental platform. With the use of the finite element method, the temperature distribution of the GIS bus bar were compared with the experimental data. Results show that the temperature rise at normal contact condition is very small. The temperature distribution of the three-phase conductor is basically the same. The temperature of the SF6 gas is tiny difference in the upper area of the GIS cavity while the SF6 gas temperature is significantly different in the area below the GIS cavity. The air temperature outside the shell gradually decreases from the top to the bottom along the vertical direction, with the highest temperature at the top and the lowest at the bottom. However, the contact temperature would rise greatly rapidly at poor contacts while the shell temperature changes very small. Therefore, the method of measuring the shell temperature by infrared thermal imager can only be applied to the relatively slow temperature rise process in the GIS, in which the slow change of the contact temperature can be reflected on the shell. On the contrary, this method cannot be applied to the fault with fast temperature rise, as the contact temperature changes cannot be reflected on the shell timely. The above research work could provide theoretical basis and data support for revealing the temperature distribution inside GIS and determining the most sensitive position of temperature monitoring.