Modeling of the Partial Discharge Process in a Liquid Dielectric: Effect of Applied Voltage, Gap Distance, and Electrode Type

Abstract

Abstract:The partial discharge (PD) process in liquid dielectrics is influenced by several factors. Although the PD current contains the information representing the discharge process during the PD event, it is difficult to determine the detailed dynamics of what is happening in the bulk of the liquid. In this paper, a microscopic model describing the dynamics of the charge carriers is implemented. The model consists of drift-diffusion equations of electrons, positive and negative ions coupled with Poisson's equation. The stochastic feature of PD events is included in the equation. First the model is validated through comparison between the calculated PD current and experimental data. Then experiments are conducted to study the effects of the amplitude of the applied voltage, gap distance and electrode type on the PD process. The PD currents under each condition are recorded. Simulations based on the model have been conducted to analyze the dynamics of the PD events under each condition, and thus explain the mechanism of how these factors influence the PD events. The space charge generated in the PD process is revealed as the main reason affecting the microscopic process of the PD events.

Effect of electrodes material on transient currents in dielectric liquid

“…It is established that the presence of space charges in the liquid leads to the initiation of the pre-breakdown processes, namely bubbles, streamers. Several experimental and theoretical works are published in this area [2][3][4][5][6][7], and it is often considered that the electrical charges are ionic and of intrinsic origin. It is assumed that they are created into the dielectric either through the electrodissociation phenomenon of neutral species and/or by molecular ionisation of the organic liquid itself.…”

“…It is assumed that they are created into the dielectric either through the electrodissociation phenomenon of neutral species and/or by molecular ionisation of the organic liquid itself. Both ways need high electric fields and, for ensuring its intensification, researchers are more interested to use a specific geometry of electrodes, where one of them is of tip shape [4,[8][9][10]. In a realistic situation of in-service power transformer, the insulating liquid is often in contact with metallic materials (windings and the transformer walls), and earlier works [11][12][13] evoke the influence of the cathode interface on the processes of charge creation in dielectric liquids, where extrinsic charges are suspected to be injected from the metal into the liquid with which it is in contact.…”

Interaction of Helium Rydberg State Molecules with Dense Helium

“…It is, however, still difficult to predict the behavior of these liquids in high electric fields, in particular, breakdown characteristics, without having to recourse to numerous and expensive experimental investigations . The electric breakdown of liquids consists of a complex sequence of correlated events − and the investigation of such processes requires the application of high electric fields, which can be achieved, for example, by corona discharge in the liquid. The corona discharge method is technically simple and can be used to interrogate mechanistic aspects of liquid breakdown.…”

An Intelligent Sensor for the Ultra-High-Frequency Partial Discharge Online Monitoring of Power Transformers

“…Partial discharge (PD) online monitoring is an effective way to identify potential faults and inspect insulation defects in power transformers [1][2][3][4][5][6][7][8]. PD is generally a transient phenomenon accompanied by physical and chemical phenomena, such as electrical pulse, electromagnetic wave, ultrasonic signal, mechanical vibration, and light and gas components, which can be detected by corresponding sensors [9][10][11][12][13][14][15][16]. Among those methods, the ultra-high-frequency (UHF) PD detection method becomes an international, advanced research hotspot because of its advantages such as high sensitivity, strong anti-interference ability, high reliability, and ability to recognize and locate discharge sources [17][18][19][20][21][22].…”