Monitoring Method for Pollution Class of Roof Insulators in EMUs Using Lissajous Figure and Morphologic Characters

Accurately grasping the surface pollution class (PC) of roof insulators is of great importance for the safe operation of electric multiple units (EMUs). In this paper, we propose a new method for monitoring the PC of roof insulators in EMUs. In this approach, the input voltage and the leakage current of the insulator are combined into a graph, i.e., a Lissajous figure with more characteristic information. The variation of the Lissajous figure under different factors is then studied. Digital image processing technique was used for morphological analysis of the Lissajous figure. The results show that the eccentricity of the insulator's Lissajous ellipse can be used as an effective monitoring index of the PC of roof insulators.