52 / 2018-08-20 15:47:12

Finite Element Simulation Analysis of Infrared Thermal Wave Detection on Composite Insulators

composite insulators,internal defects,nondestructive testing,infrared thermal wave detection,finite element simulation

Composite insulators are now being used in wide range of power grid since these insulators are less influenced by adverse environmental factors in addition to their high pollution flashover voltage. However, there are still some concerns for composite insulators due to their hidden faults during their in-service, such as hole defects which may result in their breakage. Therefore, in order to decrease these hidden defaults of composite insulators, a Nondestructive Testing (NDT) method based on infrared thermal wave technology was raised. Using different types of thermal excitation source to heat the detected composite insulator actively, different structure of the inner composite insulator will change thermal wave’s conduction. The surface information of the composite insulator about temperature field can be collected constantly by infrared detector. It can be deduced that there is a certain relationship between inner structure and surface information about temperature field. Therefore, if we had an extensive knowledge of the process of heat wave conduction, the detection system can be effectively configured where we can attain the information of the subsurface structure of the composite insulator through the record of the surface information. In this paper, the process of composite insulators about internal heat conduction are analyzed by finite element simulation. The cylinder, which consists of the inner core and outer layer, is used to simulate the non-umbrella skirt mandrel of the composite insulator. Besides, the outer layer is made of silicon rubber and the inner core is made of epoxy resin, and a range of air gaps are set with different sizes and depths to simulate different hole defects. After it is built, the model is simulated by applying different heat incentives, and the records of surface’s temperature field can be obtained. In the purpose of the further analysis on types of hidden defects, we should extract the detailed statistics of temperature field respectively from surface areas corresponding to defects and non-defect areas. Based on the extracted statistics, we can plot the temperature-time curves which show the law of temperature change with time . Making a comparison between these curves of different defect types, extracting features of the curve such as maximum temperature difference to analyze, we can distinguish the type of different defects based on the characteristics of these curves. Thus, it brought us quantitative relationship between defect’s size and depth with surface temperature field by correlating records of surface information with different defects, which lays a foundation for carrying the defect information completely and interpreting it deeply. Finally, under the condition that the distance between the defect and the outer surface remains unchanged, we changed the size of the cylinder’s inner core and repeated the experiment, for the sake of comprehensive simulation about defects of different insulators. The relationship between the size of the inner core and the heat wave conduction can be obtained by comparing the results of several experiments. Above all, the practical results indicate that it is feasible to employ the infrared thermal wave method on the nondestructive detection of the hidden defaults of the composite insulators.