1,721,067 research outputs found
Partial Discharge Development and Detection in Dielectric Liquids
No full textPD measurements in dielectric liquids have been normally performed in the past only using conventional narrow bandwidth detectors. The more recent use of ultra-wide bandwidth instruments has permitted to support once again the thesis that the PDs in oils are the consequence of the streamer (vapor phase) formation and its development. In the paper simultaneous PD measurements in insulating liquids using both narrow and ultra-wide bandwidth detectors are presented. Whilst PD detection with narrow bandwidth instruments gives only integrated signals, the use of ultra-wide bandwidth techniques permits to have much more precise information on PD phenomena, which appear to be in the form of pulses (bursts) of ascending magnitude as the bubble within the liquid expands in volume. As reported in the paper, the use of the ultra-wide bandwidth instruments permits also to distinguish the PD pulses occurring in regular voids of oil-paper insulations and PD pulses formed directly in the liquids as consequence of the streamer development. Also in the paper the meaning of the PDIV in oils is discussed, showing its dependence with the definition used, the unpredictable level of the background noise as well as the randomness of the PD initiation process
Partial discharge measurements in dielectric liquids
No full textPD measurements in dielectric liquids have been normally performed in the past only using conventional narrow bandwidth detectors. The more recent use of ultra-wide bandwidth instruments has permitted to support once again the thesis that the PDs in oils are the consequence of the streamer (vapor phase) formation and its development. In the paper simultaneous PD measurements in insulating liquids using both narrow and ultra-wide bandwidth detectors are presented. Whilst PD detection with narrow bandwidth instruments gives only integrated signals, the use of ultra-wide bandwidth techniques permits to have much more precise information on PD phenomena, which appear to be in the form of pulses (bursts) of ascending magnitude as the bubble within the liquid expands in volume. As reported in the paper, the use of the ultra-wide bandwidth instruments permits also to distinguish the PD pulses occurring in regular voids of oil-paper insulations and PD pulses formed directly in the liquids as consequence of the streamer development. Also in the paper the meaning of the PDIV in oils is discussed, showing its dependence with the definition used, the unpredictable level of the background noise as well as the randomness of the PD initiation process
Linee Guida per l’uso delle migliori tecniche di¬sponibili (BAT) per la decontaminazione dei PCB e degli apparati contenenti PCB
No full text
On partial discharge measurement in dielectric liquids
No full textPartial 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
- …
