Experimental Research On Insulation Material Defect Detection Based On Terahertz Imaging Technology

Insulation material is one of the basic materials of electrical insulation devices.The insulation performance of insulation material can directly affect the safety of power equipment and the whole power supply system.Due to the influence of electrical,thermal,mechanical and other factors in the process o f preparation and use of insulating materials,internal or surface defects will inevitably occur,resulting in the gradual degradation of their electrical performance and insulation failure in serious cases.Therefore,in order to reduce the safety risks c aused by mechanical defects of insulating materials,it is particularly important to detect the defects of insulating materials.At present,due to the influence of the characteristics of the technology itself,the widely used defect detection methods in power industry have some limitations in the defect detection of materials.Compared with the traditional detection methods,terahertz imaging technology is a new visual detection method,which not only has high security and anti-interference ability,but also can form a good complementary advantage with the existing nondestructive detection methods.This paper mainly studies the application of terahertz imaging technology in the nondestructive testing of insulating materials.Firstly,the terahertz response characteristics of silicone rubber and epoxy resin are studied on the basis of experiments.Secondly,according to the characteristics of lamination,inclusion and other defects of silicone rubber and epoxy resin,the corresponding artificial defect samples are made,and the terahertz nondestructive testing is carried out,and the analysis and discussion of the detection results of various defects of two kinds of insulation materials are completed.The main research work includes:(1)The terahertz spectra of three groups of insulating silicone rubber and epoxy resin with different thickness were measured by transmission terahertz time-domain spectrum system.The response characteristics of the two insulating materials in terahertz band were discussed from the wave characteristics of time domain spectrum,frequency spectrum,absorption spectrum and refraction spectrum.(2)Terahertz time-domain spectroscopy(THz-TDS)was used to measure and analyze the transmission of three kinds of defects in insulating sil icone rubber materials,including scratch,delamination and inclusion.The time-domain spectra,frequency-domain spectra,refraction spectra and absorption spectra of three kinds of defects in the frequency range of 0.2～1.5 THz were obtained.Compared with the THz absorption spectra of the samples without defects,the causes of THz absorption peaks of different defects were discussed and analyzed in detail.(3)Based on the transmission THz-TDS system,the terahertz spectra of delamination,inclusion and crack defects in epoxy resin composites were measured.The time domain spectra,frequency domain spectra,refraction spectra and characteristic absorption spectra of three kinds of defects in the frequency range of0.2～1.5THz were obtained.Based on the anal ysis of the experimental data and defect structure of epoxy resin,the source of the measured spectral difference is discussed.