A new method for the interneedle-distance optimization of a multineedle-to-plane barrier discharge reactor is presented. As we know, there is gas breakdown when, in some regions between electrodes, the electric field is higher than the breakdown field; hence, the regionmay play a dominant role for the discharge, and the enhancement of its volume ratio in the reactor will allow an increase in discharge energy density. This can be achieved by structure optimization. With the finite-element method, the 3-D profiles of an electrostatic field in the reactor are acquired for a series of interneedle distances, thereby the one-to-one relationship between the volume ratio and interneedle distance is obtained. This allows the optimal interneedle distance for power input ef-ficiency to be identified, as related to the maximal volume ratio. The optimal distance is between 7.2 and 8.4 mm in our simulation range, decreasing with the increase of operating voltages from 16 to 26 kV. The simulation results are experimentally validated by discharge energy measurement as well as the performance of SO2 removal from indoor air. This structure optimization method leads to a simple way to obtain the optimal interneedle distance for energy input efficiency and hence benefits commercial use.

命哲 荣;Dingxin Liu;Dong Wang;Biao Su;小华 王;翊 吴

IEEE Transactions on Plasma Science

2010-4

Sulfur hexafluoride (SF₆) gas has a quite high global warming potential and hence it is required that applying any substitute for SF ₆ gas. Much interest in the use of a mixture of helium and SF ₆ as arc quenching medium was investigated indicating a higher recovery performance of arc interruption than that of pure SF₆. It is known that the electrical breakdown in a circuit breaker after arc interruption occurs in a hot gas environment, with a complicated species composition because of the occurrence of dissociation and other reactions. The likelihood of breakdown relies on the electron interactions with all these species. The critical reduced electric field strength (the field at which breakdown can occur, relative to the number density) of hot SF₆/He mixtures related to the dielectric recovery phase of a high voltage circuit breaker is calculated in the temperature range from 300 K to 3500 K. The critically reduced electric field strength of these mixtures was obtained by balancing electron generation and loss mechanisms. These were evaluated using the electron energy distribution function derived from the Boltzmann transport equation under the two-term approximation. Good agreement was found between calculations for pure hot SF₆ and pure hot He and experimental results and previous calculations. The addition of He to SF₆ was found to decrease the critical reduced electric field strength in the whole temperature range due to a lack of electron impact attachment process for helium regardless its high ionization potential. This indicates that not the behaviour of dielectric strength but possibly the higher energy dissipation capability caused mainly by light mass and high specific heat as well as thermal conductivity of atomic helium contributes most to a higher dielectric recovery performance of arc interruption for SF₆/He mixtures.

Weizong Wang;Xin Tu;Danhua Mei;命哲 荣

Physics of Plasmas

2013-11

This paper focuses on the research of a new high-speed DC switch repulsion mechanism with experimental and simulation methods. Multi-physical equations reflecting the transient electromagnetic field, electric circuit, mechanical motion and material deformation are coupled in the calculation. For the reason of accuracy, skin effect and the proximity effect caused by the current in the coil are also taken into account. According to the simulation results, which indicate several key parameters severely affecting the mechanism speed, a high-speed DC switch repulsion mechanism is developed. By the test of mechanism motion, its average speed can be up to 8.4m/s and its mechanism response time is 250 μs, which verifies the simulation results. Furthermore, during high speed motion the stress on the metal plate and moving contact is also discussed. It is noticed that the influence of the material deformation on the mechanical motion is very important.

翊 吴;Hailong He;Zhengyong Hu;Fei Yang;命哲 荣;Yang Li

IEICE Transactions on Electronics

2011-9

The IEC codes method is the most widely used method in fault diagnosis of oil-immersed device, but it has shortcoming, especially when there is more than one type of fault existing in a device, and the IEC code results cannot be matched with the true fault type. So, the IEC code method needs the aid of more sophisticated analysis methods such as the fuzzy diagnosis method. In order to improve the diagnosis accuracy, a fault diagnosis based on the combination of genetic algorithm (GA) and fuzzy logic to identify the faults of oil-immersed electrical devices is proposed. This method fuzzy the boundary of characteristics gas ratios and IEC codes, obtain the optimum fuzzy membership functions using GA, and obtain fault diagnosis results using fuzzy inference. Compared with the improved IEC methods, the method introduced improved the diagnosis accuracy to a certain extent.

命哲 荣;小华 王;Ding Xin Liu;翊 吴;Fei Yang

Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering

2006-12

This paper focuses on the numerical investigation of low-voltage arc plasma behaviour with the contact opening process included. A flexible experimental setup with a rotating contact is designed to support this study. Based on the magnetohydrodynamic arc model, the elongation and the commutation behaviour of the arc plasma during the contact rotation progress are simulated. Under the given conditions of the external magnetic field and the contact rotating velocity, the arc motion is described in detail by the temperature distribution. The stagnation together with the following rapid jump of two arc roots is observed by both calculation and experiment. The rapid rise in the arc voltage is mainly caused by the increasing difference between the two arc roots displacement in the moving direction, and the jump instant of the arc root on the moving contact is according to the moment of the maximal voltage value.

翊 吴;命哲 荣;Zhiqiang Sun;小华 王;Fei Yang;兴文 李

Journal Physics D: Applied Physics

2007-2-7

The switching performances of several improved silver tin-oxide materials with some kinds of additives, including WO₃,Bi₂O₃,In₂O₃, were conducted in accelerated testing machine. Based on the experimental results and the observations of the contacts surface microstructure, the effects of additives on the silver tin-oxide contacts erosion behavior are mainly studied. It is indicated that the effects of additives on the wettability between liquid silver metal and the contact surface, the distribution and the thermal stability of additives are critical in the decision of erosion characteristics and the morphology feature of contact surface. The erosion behaviors of silver-tin oxide materials with different additives are compared, the doping effect on surface morphology is presented.

命哲 荣;Qiping Wang

Electrical Contacts, Proceedings of the Annual Holm Conference on Electrical Contacts

1993

This paper mainly focuses on the influence of three kinds of media: air, air-10%PA (Nylon) and air-10% POM (polyoxymethylene) on low-voltage circuit breaker arcs. A three-dimensional (3-D) model of arc motion under the effect of external magnetic field is built based on magnetohydrodynamics (MHD) equations. By adopting the commercial computational fluid dynamics (CFD) package based on the control-volume method, the above MHD equations are solved. For the media of air-10%PA and air-10%POM, the distributions of stationary temperature and electrical potential and the transient motion processes are compared with those of air arc. The research shows that both air-10%PA and air -10% POM can cool the arc plasma and the former is more effective. Both of them can increase the stationary voltage as well. Moreover, the presence of the two mixtures can accelerate the arc motion toward the quenching area and ensures the arc quenched in time.

Qian Yang;命哲 荣;Anthony B. Murphy;翊 吴

Plasma Science and Technology

2006-11-1

This paper focuses on the numerical investigation of the arc plasma behaviour with eddy currents mainly in electrodes and splitter plate generated by arc motion in arc splitting process. The elongation and splitting process are simulated through a three-dimensional (3D) magneto-hydro-dynamic (MHD) model. Without external magnetic field, the arc motion is described in detail by the temperature distribution. The arc roots generating process on the ferromagnetic splitter plate is observed through the calculation results. Besides column voltage, sheath voltage is also included in arc voltage, which is expressed by a simple nonlinear resistor model. The effect of ferromagnetic material's nonlinear permeability is involved in the calculation.

F. Yang;命哲 荣;Z. Sun;翊 吴;W. Wang

2008

The liquid metal current limiter (LMCL) is a possible alternative to limit the short current of power system due to its special merits. This paper is devoted to the investigation of the arc behavior in liquid metal GaInSn for current limiting application. Firstly, the arc evolution including arc initiation, arc expansion and arc extinguish is observed through an experimental device. The resistance of arc and the self healing property of liquid metal are described. Subsequently, the arc erosion on electrodes is presented with its causes analyzed. Finally, the arc characteristics with the influence of rise rate of prospective current and channel diameter are discussed in details.

Yiying Liu;命哲 荣;翊 吴;Chenxi Pan;Hong Liu;Shijie Yu

IEICE Transactions on Electronics

2009

During DC hybrid breaking, the transfer arc temperature decays quickly due to fast current commutation from the mechanical switch to the parallel connected branch, which may lead to deviation from thermal equilibrium. In this study, numerical investigation on a two-temperature calculation for SF₆ transfer arc has been performed in order to study the arc's behavior under the effect of thermal non-equilibrium. The free decay and post-arc phase have been studied. This model allows us to calculate electron and heavy-species temperatures, gas velocity, and electron number density. In addition, various energy exchange mechanisms including radiation, ohmic heating, and elastic collision energy are discussed. It has been predicted that the departure from thermal equilibrium appears near the arc edge and electrodes due to insufficient collision energy exchange between electrons and heavy species. Particularly the formation of a circular velocity vortex makes the gas temperature in the vortex zone exceed the arc core temperature at zero current, which does not favor the residual plasma withstanding the recovery voltage at post arc. After carrying out a simulated hybrid breaking experiment, the dynamic motion process of the transfer arc and post-arc current were determined experimentally and compared to theoretical results obtained from a two-temperature model. This comparison validated the model and showed that the presence of a vortex high-temperature zone is more prone to cause the breakdown.

Yifei Wu;命哲 荣;翊 吴;Hantian Zhang

Journal Physics D: Applied Physics

2018-5-4