On partial discharge measurement in dielectric liquids

Abstract

Partial discharge detection in dielectric liquids requires particular PD measurement techniques and instruments. Simultaneous partial discharge (PD) measurements that are employed on insulating liquids, using dual narrow/wide band detectors, are described. Narrow band PD detectors, which are of the integrating type are suitable for the measurement of the total charge transfer in pC of the overall discharge event. Wide band measurement techniques permit the acquisition of the discrete PD pulses in dielectric liquids, that comprise the overall PD pulse burst signal. These PD pulse bursts are comprised of discrete high frequency pulses of usually ascending magnitude charge transfers. The time position of these pulses within the pulse burst is determined by the times at which the Paschen's minima occur across the expanding cavity due to the small size of the microcavities. In order for them to undergo discharge requires enormously high internal pressures (ca 10 MPa) to ensure a sufficient number of charge carriers. The life duration of these cavities is of the order of several's, with the cavity collapsing, when its size reaches dynamic instability

Partial discharge based diagnostics for impurities in insulating fluid

“…Pompili et al [23] showed that negative streamers comprise of several high frequency pulses with ascending magnitude as the bubble within the fluid expands in volume. However, these pulses become integrated to a single PD event by the integration time of the PD detector (~10 s [24]).…”

The possibility of using a needle plane electrode for partial discharge inception voltage measurement

“…It gives high local electric field stress to simulate a local PD site. Examples of applying the needle -plane electrode systems for the measurement of PDIV and PD have been reported in [10][11][12][13]. Because the electric field stress on the tested liquid greatly depends on the electrode configuration so the PDIV value of the same liquid is different when it is tested with various types or configuration of the electrode arrangement.…”

Application of Non-destructive Testing for Measurement of Partial Discharges in Oil Insulation Systems

“…The most important are occurrence of a current pulse, emission of electromagnetic waves of ultra-high frequency (UHF), generation of optical radiation and high-energy radiation (X-/gamma rays), chemical transformations in the isolation, an elastic shock deformation and the associated acoustic wave generation. Based on these phenomena, diagnostic methods have been developed for detection, measurement and localization of PD, which may occur in insulating systems of power devices [1][2][3][4][5][6][7][8]. Currently, the assessment of electrical discharges shall apply the following non-destructive methods: electric [9][10][11][12][13], gas chromatography and acoustic emission (AE) [14][15][16][17][18][19][20] as well as the optical method [21][22][23].…”