A non-contact directional sensor for partial discharge measurements

Noise suppression has been one of the most difficult tasks in partial discharge (PD) measurements on in-service HV equipment. PD measurements could be seriously affected by disturbances of various origins. There are basically three types of noise: random (white noise), continuous oscillating or pulse-shaped. Although random and continuous oscillating noise could be removed according to its statistic characteristics and frequencies, the pulse-shape noise may be mistaken for discharges occurring within the test sample, leading to confusing results. The new non-contact directional sensor presented in this paper uses an innovative technique to detect the direction of PD pulses travelling along a conductor (busbar, bushing, lead etc), which help to discriminate pulse-shaped noise entering the equipment terminal. The noise can therefore be identified and suppressed. There is no direct electrical connection to the HV conductors which makes it more flexible and reliable to measure PDs on transformers, generators, switchgear and cables in service.