Analysis on internal defects of electrical equipments in substation analysis on internal defects of electrical equipments in substation using heating simulation for infrared diagnose using heating simulation for infrared diagnose

The infrared detection has been widely used in electrical industry with the safety, high sensitivity, high efficiency and calculability. Referring to technical regulations such as Application rules of infrared diagnosis for live electrical equipment(DL/T 664-2008), only infrared image feature and temperature difference can be indicated for the heating equipment caused by voltage. The quantitative analysis of internal defects parameters such as capacitance and dielectric loss with infrared images hasn´t been developed. In order to guide the precise infrared detective and diagnose for the electical equipments in substation, this paper built the equivalent physical and theoretical heating models for several types of the equipments such as arresters and current transformers to research the identification principles of the internal defects with infrared thermography. According to the heating principles of electrical equipments, the equivalent physical models were fabricated to simulate the internal defects with the same heat-transferring path and surface. By setting the calculated heating power, degradation of the key parameters such as dielectric loss, capacitance, resistive current of arresters was simulated and estimated with infrared detection of the surface. 3-D models of the electric equipments were built for precise calculation of the internal heat-transferring process and external surface temperature distribution. The calculation was based on the design sketches of the equipments in the finite-element method. Models was configured with special heat source, the characteristics parameters of the materials and other unknown parameters probed with iterative algorithm. The results were proved by the infrared detection of the real equipments and the equivalent physical models. It´s concluded that temperature rise and difference of the surface can be used to judge the internal defects of the electrical equipments in substation. A variety of heating simulation models - or electrical equipments can be built with the method in this paper. It´s expected that the more detailed detection and diagnosis principle with infrared thermography will be set down.