Research on Scanning Frequency and Broadband Impedance Spectroscopy Technology for Cable Defect Diagnosis

Based on the statistical data of fine cable management of State Grid Corporation of China, the main causes of XLPE cable faults were analyzed in the statistical data of power cable faults, including mechanical damage, non-standard installation, insulation aging, manufacturing quality, and overvoltage damage. As a key demonstration area for the construction of a new power system, Xinjiang's social development demand for electricity and the scale of power transmission are constantly increasing. However, the existing problems are also obvious. For example, in the Xinjiang power grid, XLPE cable failures are mainly caused by mechanical damage (72.1%), improper installation (10.6%), insulation aging (8.4%), manufacturing defects (3.4%), and overvoltage damage (5.5%). The annual growth rate of power cable laying in Xinjiang is expected to exceed 35%, but special environmental conditions such as extreme low temperatures and large temperature differences between day and night accelerate cable insulation aging and defect exposure, leading to faults and safety accidents. According to data from Urumqi Power Supply Company in the past 5 years, cable accessory faults account for as high as 97%, with 110kV single core cable buffer layer faults being the most common. In order to solve the operation and maintenance problems of power cable systems in the special large temperature difference environment of Xinjiang region, this paper analyzes the broadband input impedance spectrum and its transmission characteristics at the beginning of the cable, studies the influence mechanism and degree of local defects on the cable impedance spectrum, and develops a new impedance spectrum data analysis method. It effectively separates the characteristic parameters that characterize the cable operating state parameters from the cable impedance spectrum, realizes the localization and state evaluation of cable local defects, and solves the problems of mechanical damage, non-standard installation, insulation aging, and manufacturing defects. The research results achieve timely detection and fault localization of cable operating defects.