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Title: Deformation of contact surfaces in a vacuum interrupter after high-current interruptions

Abstract

In a high-current interruption, the contact surface in a vacuum interrupter might be severely damaged by constricted vacuum arcs causing a molten area on it. As a result, a protrusion will be initiated by a transient recovery voltage after current zero, enhancing the local electric field and making breakdowns occur easier. The objective of this paper is to simulate the deformation process on the molten area under a high electric field by adopting the finite element method. A time-dependent Electrohydrodynamic model was established, and the liquid-gas interface was tracked by the level-set method. From the results, the liquid metal can be deformed to a Taylor cone if the applied electric field is above a critical value. This value is correlated to the initial geometry of the liquid metal, which increases as the size of the liquid metal decreases. Moreover, the buildup time of a Taylor cone obeys the power law t = k × E{sup −3}, where E is the initial electric field and k is a coefficient related to the material property, indicating a temporal self-similar characteristic. In addition, the influence of temperature has little impact on the deformation but has great impact on electron emission. Finally, the possiblemore » reason to initiate a delayed breakdown is associated with the deformation. The breakdown does not occur immediately when the voltage is just applied upon the gap but is postponed to several milliseconds later when the tip is formed on the liquid metal.« less

Authors:
; ; ; ; ; ;  [1]
  1. State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an 710049 (China)
Publication Date:
OSTI Identifier:
22597687
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 120; Journal Issue: 5; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BREAKDOWN; BUILDUP; DAMAGE; DEFORMATION; ELECTRIC FIELDS; ELECTRIC POTENTIAL; ELECTRON EMISSION; ELECTRONS; FINITE ELEMENT METHOD; INTERFACES; LIQUID METALS; SURFACES; TIME DEPENDENCE

Citation Formats

Wang, Haoran, Wang, Zhenxing, E-mail: zxwang@xjtu.edu.cn, Zhou, Zhipeng, Jiang, Yanjun, Wang, Jianhua, Geng, Yingsan, and Liu, Zhiyuan. Deformation of contact surfaces in a vacuum interrupter after high-current interruptions. United States: N. p., 2016. Web. doi:10.1063/1.4960447.
Wang, Haoran, Wang, Zhenxing, E-mail: zxwang@xjtu.edu.cn, Zhou, Zhipeng, Jiang, Yanjun, Wang, Jianhua, Geng, Yingsan, & Liu, Zhiyuan. Deformation of contact surfaces in a vacuum interrupter after high-current interruptions. United States. doi:10.1063/1.4960447.
Wang, Haoran, Wang, Zhenxing, E-mail: zxwang@xjtu.edu.cn, Zhou, Zhipeng, Jiang, Yanjun, Wang, Jianhua, Geng, Yingsan, and Liu, Zhiyuan. 2016. "Deformation of contact surfaces in a vacuum interrupter after high-current interruptions". United States. doi:10.1063/1.4960447.
@article{osti_22597687,
title = {Deformation of contact surfaces in a vacuum interrupter after high-current interruptions},
author = {Wang, Haoran and Wang, Zhenxing, E-mail: zxwang@xjtu.edu.cn and Zhou, Zhipeng and Jiang, Yanjun and Wang, Jianhua and Geng, Yingsan and Liu, Zhiyuan},
abstractNote = {In a high-current interruption, the contact surface in a vacuum interrupter might be severely damaged by constricted vacuum arcs causing a molten area on it. As a result, a protrusion will be initiated by a transient recovery voltage after current zero, enhancing the local electric field and making breakdowns occur easier. The objective of this paper is to simulate the deformation process on the molten area under a high electric field by adopting the finite element method. A time-dependent Electrohydrodynamic model was established, and the liquid-gas interface was tracked by the level-set method. From the results, the liquid metal can be deformed to a Taylor cone if the applied electric field is above a critical value. This value is correlated to the initial geometry of the liquid metal, which increases as the size of the liquid metal decreases. Moreover, the buildup time of a Taylor cone obeys the power law t = k × E{sup −3}, where E is the initial electric field and k is a coefficient related to the material property, indicating a temporal self-similar characteristic. In addition, the influence of temperature has little impact on the deformation but has great impact on electron emission. Finally, the possible reason to initiate a delayed breakdown is associated with the deformation. The breakdown does not occur immediately when the voltage is just applied upon the gap but is postponed to several milliseconds later when the tip is formed on the liquid metal.},
doi = {10.1063/1.4960447},
journal = {Journal of Applied Physics},
number = 5,
volume = 120,
place = {United States},
year = 2016,
month = 8
}
  • High-current interruption experiments were carried out on low-surge contact material Ag-WC set in axial magnetic field electrodes. The most influential factors on high-current interruption are the contact material, the axial magnetic field, and the initial opening speed. Though the interruption ability of conventional contact material was limited up to 20 kA, the ability of the improved material rose up to 40 kA in the test using the laboratory model vacuum circuit breaker.
  • The authors carried out shunt capacitor switching tests on the 24 kV model vacuum interrupters with contact material CuW and contact material CuCr. The restriking probability of the contact material CuW is lower than that of contact material CuCr. The contact material CuW is also an excellent candidate for the shunt capacitor switching except for its high current interruption ability. The restriking probability of 24 kV--25 kA vacuum interrupter with contact material CuW is calculated as 10{sup {minus}5}, which is practically zero.
  • Studies of nonsustained disruptive discharges (NSDD), isolated cases of which can occur in vacuum interrupters, are presented. They indicate lateral discharges between the cathode and shield, which can initiate a brief discharge between the contacts. To facilitate the study of such discharges, they were triggered by a surface discharge induced by a spark gap, built into the side of the cathode, and observed with a high-speed film camera and an image-converter camera. The tests showed a cathode spot after igniting. The electrons emitted here first charge the shield negatively and are directed toward the anode. The discharge burns at amore » high voltage, with currents ranging from 10 to 100 A. After a period of up to 400{mu}s, the current demand increases abruptly; an arc discharge occurs between the contacts and discharges the capacitances near the switch. The contact gap undergoes a rapid dielectric recovery, and the restored voltage is maintained.« less
  • This paper reports the investigation of vacuum arcs of up to 20-kA peak current. The surface temperature of the anode area melted during the anode spot mode was determined by pyrometry and the evaluation of thermionic currents. The measurements confirm the computations of heating and cooling of the anode, taking into account heat conduction, melting/solidification, and evaporation.