Study on Terahertz Time-domain Spectroscopy Method of Detecting Inorganic Salt in Outdoor Insulation Contamination

Pollution flashover caused by outdoor insulation contamination of power transmission and transformation equipment seriously threatens the safe and stable operation of power system. It is of great significance to accurately identify the contamination components for the evaluation of insulation state of equipment. In this paper, the non-destructive detection method based on terahertz time-domain spectroscopy was used to identify the insulator contamination components. Several groups of mixed samples containing different proportions of NaCl and CaSO4 were prepared respectively to explore the difference of terahertz spectrum when the proportion and type of salt were changed. In order to simulate the natural contamination, kaolin was added into the samples to make salt-ash mixture. The terahertz time-domain spectrum and absorption spectrum of the samples were obtained and analyzed. It was found that the terahertz time-domain spectrum has an obvious rule when the salt proportion and type are changed in the contamination. This conclusion was also tested and proved by vector-subspace angle criterion. Through experimental demonstration and data analysis, it can be concluded that terahertz time-domain spectroscopy method can accurately identify the proportion and type of inorganic salt in the contamination.