Cable Connectors Location in High Voltage Cables Based on the Time Domain Reflectometry

摘要

This paper describes a method for location of the connectors in high voltage cables using the time domain reflectometry (TDR). Firstly, the wave impedances along the connectors of 10kV/20kV cables are calculated according to their structures. The results show that the degree of impedance discontinuity at the connector decreases as the cable's current capacity and the voltage level increases. A three-stage connector model is established in EMTP-ATP. Secondly, the attenuation law of the pulse with the cable length and the number of connectors is simulated. Because the pulse will be deformed due to the attenuation of high-frequency components during transmission, a method for the determination of the starting point of the reflected wave is proposed. A 5.5km cable with intermediate connectors every 500m is calculated. The location error is less than 0.5%. The pulse deformation makes the rise time of the pulse longer, leading to lower amplitude of the reflected wave at the short connector than that at a long one. Therefore, longer cable connectors make positioning more accurate. It's recommended that the input square wave pulse has the amplitude above 1kV, the pulse width longer than 150ns, and the rising time shorter than 1ns. Such a pulse meets the connectors positioning requirements of all 10kV/20kV cables. The experiments are carried out using a 204m cable with 3 connectors. The results are in good agreement with the simulation. The positioning error is within 0.5%.