Detection and localization of partial discharge in high voltage power cable joints

Laboratory performance test of the high voltage power cable joints at lower voltages is not crucial, nor has the continuous monitoring of partial discharge (PD) been considered necessary. However for HV power cable joints at higher voltages, such as 420 kV, the reliable PD detection during performance test as well as the on-line continuous PD monitoring have been considered desirable to an increasing extent. Accordingly, a system was developed to facilitate such tasks. The system is based on decoupling of PD by means of inductive sensors, signal treatment and investigation according to a technique called INTECH, Inductive Measurement Technique. The laboratory system sensitivity is about 5 pC when the cable is not loaded with any power current and about 30 pC when the cable load is about 2000 A. The first prototype system was tested in the field on a 420 kV cable joint. This paper describes the system and presents some of the field test results.