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Characterization of Streamers in Liquid Nitrogen Under AC Voltages Using UHF Techniques

Characterization of Streamers in Liquid Nitrogen Under AC Voltages Using UHF Techniques
Characterization of Streamers in Liquid Nitrogen Under AC Voltages Using UHF Techniques
Pre-breakdown phenomena in liquid nitrogen (LN2), often referred as streamers, are the precursor of total breakdown due to the more conductive nature of density-change channels compared to the liquid. The paper characterizes streamer behavior in LN2 under AC voltages using ultra high frequency (UHF) and radio frequency current transformer (RFCT) measurements. The aim is to further understand the role of LN2 as insulation as well as the application of non-conventional partial discharge (PD) detection techniques in condition monitoring of future HTS devices. An experiment has been developed to measure PD events in LN2 using narrowband and wideband methods simultaneously. PD detection following IEC 60270 standards allows measurement of the amount of charge transferred at the terminals while the use of a UHF senor with a bandwidth up to 3 GHz can provide better resolution in the time domain. Results from the UHF sensor show that PD in LN2 appears in the form of multiple pulses which are suggested to be due to the expansion and collapse of the gaseous channels. The pulse burst phenomenon was not observed by the narrowband detection. Instead, a slowly damped signal was measured, which may result from the integration of multiple individual events. The experiment also allows correlation of PD measurements with images of pre-breakdown streamers using shadow photography. The characteristics of streamers in LN2 are discussed based on the observation of the density-change channels together with the corresponding discharge signature.
Dielectric liquids, high temperature superconducting, partial discharges, UHF detection.
1109-1118
Truong, L H
a52e7edc-a28b-4a9c-ac7b-9251d45bb769
Lewin, P L
78b4fc49-1cb3-4db9-ba90-3ae70c0f639e
Judd, M D
87cb96de-3216-4824-9092-1465c90a5a13
Truong, L H
a52e7edc-a28b-4a9c-ac7b-9251d45bb769
Lewin, P L
78b4fc49-1cb3-4db9-ba90-3ae70c0f639e
Judd, M D
87cb96de-3216-4824-9092-1465c90a5a13

Truong, L H, Lewin, P L and Judd, M D (2014) Characterization of Streamers in Liquid Nitrogen Under AC Voltages Using UHF Techniques. IEEE Transactions on Dielectrics & Electrical Insulation, 21 (3), 1109-1118. (doi:10.1109/TDEI.2014.6832255).

Record type: Article

Abstract

Pre-breakdown phenomena in liquid nitrogen (LN2), often referred as streamers, are the precursor of total breakdown due to the more conductive nature of density-change channels compared to the liquid. The paper characterizes streamer behavior in LN2 under AC voltages using ultra high frequency (UHF) and radio frequency current transformer (RFCT) measurements. The aim is to further understand the role of LN2 as insulation as well as the application of non-conventional partial discharge (PD) detection techniques in condition monitoring of future HTS devices. An experiment has been developed to measure PD events in LN2 using narrowband and wideband methods simultaneously. PD detection following IEC 60270 standards allows measurement of the amount of charge transferred at the terminals while the use of a UHF senor with a bandwidth up to 3 GHz can provide better resolution in the time domain. Results from the UHF sensor show that PD in LN2 appears in the form of multiple pulses which are suggested to be due to the expansion and collapse of the gaseous channels. The pulse burst phenomenon was not observed by the narrowband detection. Instead, a slowly damped signal was measured, which may result from the integration of multiple individual events. The experiment also allows correlation of PD measurements with images of pre-breakdown streamers using shadow photography. The characteristics of streamers in LN2 are discussed based on the observation of the density-change channels together with the corresponding discharge signature.

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Accepted/In Press date: 14 January 2014
e-pub ahead of print date: 16 June 2014
Published date: June 2014
Keywords: Dielectric liquids, high temperature superconducting, partial discharges, UHF detection.
Organisations: EEE

Identifiers

Local EPrints ID: 366604
URI: http://eprints.soton.ac.uk/id/eprint/366604
PURE UUID: 630fd4e4-57c3-4f7b-bcfb-2b1f3a14f019

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Date deposited: 03 Jul 2014 11:25
Last modified: 25 Oct 2019 16:30

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Contributors

Author: L H Truong
Author: P L Lewin
Author: M D Judd

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