Location of partial discharge at joint section of XLPE cable using acoustic emission technique

In this study, an acoustic emission (AE) technique was used for diagnosing a joint section of cross-linked polyethylene (XLPE) cable. The correlation between AE signal and partial discharge (PD) current was first investigated. The joint section of XLPE cable was 22 kV T branch joint with a diameter of 91.6 mm. Three AE sensors were located at the cable surface, 140 mm and 130 mm from the head of cable joint. The sensors use magnet holders for detecting PDs. For each distance from the head of cable joint, the AE sensors were placed at cable surface with the angle deviations of 120 degrees. At the tip of the head of cable joint, an artificial void was made with a diameter of 1.5 mm. The AE signal detected by the AE sensors was amplified by a preamplifier and a main amplifier. A high voltage electrode was inserted into the joint section of XLPE cable, and then high voltage was applied to generate PDs. PD current was detected by a Rogowski coil. The AE signal from the main amplifier was sent to a digital oscilloscope and recorded in a personal computer for further analyses, such as the fast Fourier transform (FFT). The correlation between AE signal and PD current was clarified. The increase of AE signal has the same linear tendency with increasing PD current. Furthermore, estimated PD locations were found around the head part of joint section of XLPE cable.