Simulation And Analysis Of Impedance Characteristics Of Mv Cable Joint With Different Moisture Degree

The cable joint is one of the most vulnerable areas in cable. Based on the theoretical knowledge of time domain reflectometry, this paper establishes a three-dimensional simplified single-core model of the 10kV cold-shrinkable intermediate joint in the CST (Computer Simulation Technology) Studio Suite, and carries out a detailed analysis on joint intruded by water. This paper briefly describes the reflection principle of traveling waves propagating on transmission lines, analyzes changes of reflection waveform and impedance characteristics under different moisture degree at composite interface of joint, and studies the corresponding relationship between moisture degree and impedance characteristics. The results show that the impedance of moisture part will decrease with increase of moisture degree, and amplitude of reflected waveform decreases, and in the severe case, pulses in the opposite direction will appear. At last, two types of basis, vertical comparison and horizontal comparison, are put forward to judge water inflow and moisture degree in cable joint.