Study on limit angle in terahertz time-domain spectral reflectance measurement

Cross-linked polyethylene cable has the advantages of safety, convenience, and simple maintenance, and has gradually become the main power transmission cable. However, the internal moisture content of the XLPE insulation sheath of buried cable will lead to the decline of power cable insulation performance. The accurate detection and location of water content distribution in power cables is very important for the safe operation of the power system. This paper presents a method of measuring the cable interior using reflection terahertz time-of-flight tomography. However, the tolerance of the terahertz optical path is very important for the usability of the test device. Through the test results of the angle tolerance of the terahertz optical path system in the insulating sheath, the angle incident tolerance of the system is finally obtained, and the location and area of the leakage defect of the insulating sheath are accurately measured within the range of the angle tolerance, the potential application of terahertz time-domain spectroscopy in cable detection is verified in this paper