Visualization of arcing process in an auto-expansion circuitbreaker

The arcing process in an auto-expansion circuit breaker, a new generation of high voltage circuit breakers, has been simulated and visualized by implementing an arc model into a general purpose computation fluid dynamics (CFD) package, PHOENICS. The model takes account of radiation transport, arc radiation induced inner wall ablation, turbulence enhanced momentum and energy transport and the moving parts of the breaker. Details of the temperature, pressure, velocity and electric fields within the breaker can be visualized thus helping the optimization of the geometry and operation characteristics of a breaker     

高压直流断路器测控装置的设计与试验分析

直流输(配)电是目前电网发展的趋势,而高压直流断路器的研发是影响其发展的关键技术之一。测量与控制装置的研究是高压直流断路器的研发要点。采用高压电力电子器件,DSP+FPGA相结合的控制方式,对其测控装置进行研究分析,提出了区间阈值的控制方法及相应的控制时序,从高压直流输电、能源多样化的发展需求入手,将机械开关和固态开光相结合,设计了一套混合式高压直流断路器样机。通过对样机进行合分闸试验及故障分闸试验,证明了所研制的高压直流断路器样机具有分闸动作快,限弧能力强,动作一致性好等优点。     

Time-Resolved Laser Doppler Measurements in the Underexpanded Jet of a Model Gas-Blast Circuit Breaker under Arcing Conditions

A differential laser Doppler system has been used in conjunction with a self-triggered oscillographic raster display system for measuring particle concentrations and flow velocities in a model gas-blast circuit breaker. The flow velocities have been correlated with particle size to enable extrapolation to be made to determine the true plasma flow velocity. The results have been deconvoluted to take account of lateral movements of the arc column. The measurements have been taken with air as the host arcing medium and a flow through a 25-mm-diameter orifice sustained by an upstream pressure of about 7 bar (downstream pressure 1 bar). The arc was sustained by sinusoidal cuffents of peak values 3 and 8 kA and a frequency of 85 Hz. These two currents corresponded to conditions when the model circuit breaker successfully and unsuccessfully interrupted the arc-sustaining current, respectively. The results show that in the case of the 8-kA arc, the flow pattern is severely distorted from that under nonarcing conditions, suggesting that this is a contributory reason for the poorer perfonnance of the model circuit breaker at this higher current level.     

A new concept for a current switch based on a high-temperature superconductor

A new concept for a device for protecting an alternating-current network is offered. It is based on a combination of a superconducting limiter of a short-circuit current and a circuit breaker. A high-temperature superconductor in the form of a pile of plane rings is used as the active element of the limiter. The test results of a model of such a limiter are obtained in the steady-state short-circuit regime. The characteristics of composite silverless materials used for design of the breaker are given.     

Arc Motion in Vacuum Circuit Breakers

Arc motion due to self-magnetic fields is investigated theoretically and experimentally. Using an array of four Hall probes 90° apart around a vacuum breaker, we unambiguously determine arc rotation. It is primarily the radio component of magnetic induction that causes this motion. For a particular vacuum breaker design we find that arc rotation is a sensitive function of gap spacing and arc current. (Abstract provided by Editor.)     

Investigations of Nozzle Materials in SF6 Circuit Breakers

With a puffer and a self-blast type SF6 circuit breaker (CB), various nozzle materials have been investigated. In addition, a small-scaled model SF6 breaker has been attached to a time-of-flight mass spectrometer (TOFMS) in order to study the exhausted gas contaminated with ablated material. The experimental results clearly show an influence of the nozzle material on the interrupting capability of the SF6 CB. The observed nozzle ablation is mainly determined by the geometry of the arcing device. The erosion of the nozzle and the chemical composition of arced SF6 gas depend slightly on the quality of the PTFE nozzles only.     

Influence of a Pulsed Axial Magnetic Field on a High-Current Arc of a Vacuum Circuit Breaker

Russian Physics Journal - The effect of a relatively short external axial magnetic field on the characteristics of a vacuum arc discharge in a vacuum circuit breaker is studied. A pulsed magnetic...     

EAST���򳡵�Դʧ������ϵͳ����Ƽ�ģ��ʵ��

给出了EAST极向场磁体电源失超保护系统的设计方案,描述了两种失超保护开关——直流快速开关和爆炸开关采用的两级换流结构的设计和工作原理,分析了这种结构在换流过程中的规律,该结构有效地解决了开关开断直流大电流的难点。通过模拟实验证明了该失超保护系统满足设计要求。     

Mass spectrometry of arcs in SF6 circuit breakers

Today, SF₆ is used to a great extent as insulating and arc-quenching medium in high-voltage gas-blast circuit breakers. The arcing in SF₆ during current interruption forms decomposition products. These can influence the arc-quenching properties of the circuit breaker. Furthermore, they can cause corrosion of the circuit breaker housing. In this comprehensive study we present results obtained for the first time from a direct mass spectrometric investigation of the exhaust gases of a high pressure SF₆ arc in a model circuit breaker. Our mass spectrometric system consists of a time-of-flight mass spectrometer (TOFMS) equipped with a molecular beam sampling systems. This device allows us to measure mass spectra of high pressure sources with a time resolution of up to 10,000 spectra per second. We have determined the formation rate of the most abundant decomposition products in a SF₆ arc at 1 bar. These products are SF₄, CF₄, WF₆, SOF₂, SO₂, CS₂ S₂F₂ and HF. The fast detection time inherent to our system permits also the determination of the formation of SF₄, which is 0.45–0.50 Vol. %/(kJ/1SF₆). In addition, we have studied the influence of water and oxygen impurities which are responsible for the production of highly corrosive HF. Finally, we have considered the influence of the thermal degradation of teflon (P.T.F.E.), which is used as nozzle and insulating material in circuit breakers. On this occasion we have demonstrated that CF₄, which exhibits dielectric properties similar to SF₆, is the main decomposition product formed from teflon. However, we have found that besides CF₄ also excess carbon is formed, which is deposited on insulators of the model circuit breaker.Our time-resolved mass spectra reveal that the CF₄ production from teflon is delayed by a few milliseconds with respect to the SF₆ dissociation in the arc. This delay can influence the interrupting process of the circuit breaker by changing the plasma composition during the arcing period. Although our experiments have been performed on a model circuit breaker we claim that the results presented in this study can be applied to real circuit breakers, since the arc current density and the energy dissipated per liter SF₆ are of the same order of magnitude in both devices.     

基于人工过零的失超保护100 kA真空断路器试验北大核心CSCD

在超导磁体电源系统中,失超保护系统具有重要的地位,能够将磁体能量迅速转移并消耗。聚变堆主机关键系统综合研究设施项目对失超保护系统提出了100 kA直流分断的技术要求,其中采用真空断路器作为转移支路开关。针对CRAFT失超保护系统,设计了串联结构的100 kA直流真空断路器并完成了样机制造。通过现场试验,在人工过零电路的配合下,所设计和制造的真空断路器完成了100 kA直流分断测试。     

Prediction of Circuit-Breaker Performance Based on a Refined Cybernetic Model

An improved empirical model for circuit-breaker arcs is presented. The model makes it possible to predict the breaker thermal short-circuit interruption performance within the entire range of practical interest, using only a small number of measurements from synthetic tests of a production SF6 breaker. The procedure is based on the cybernetic model developed by Hochrainer et al. The key improvement is that the response time characteristic is expressed as a function of the dynamic conductance and not of the externally imposed current. The numerical method consists of an iterative process for fitting the characteristic functions to the measured data by means of truncated Chebyshev series, and does not require manual intervention. This procedure has a significant advantage over most previous treatments in that it does not require any smoothing of the measured data, and has proved to be insensitive against noise.     

Mathematical modeling of SF6 puffer circuit breakers.II. Current zero region

For pt.I see ibid., vol.24, p.490 (1996). A mathematical model of arc behavior in an SF₆ puffer gas-blast circuit breaker in the high current phase was reported in a previous paper. This model is extended to the current zero region by solving the full partial differential are conservation equations taking account of both turbulent and radiation effects. The critical RRRV for the breaker can therefore be calculated based on the whole arcing history. The predicted values are compared with the experimental results of Noeske et al. (1983), and good agreement is found providing that the free parameter in the turbulence model is set appropriately. Results for temperature, electric field, and velocity are also presented and analyzed     

Current Chopping Introduced by Arc Collapse

The intensive cooling by a moving gas can cause violent elongations and curls of the circuit breaker arc, especially when small currents are interrupted. During the elongation the arc voltage increases rapidly. This introduces a breakdown across a smaller distance by short circuiting a part of the arc. Such a breakdown is called here arc colapse. The abrupt decrease in resistance and arc voltage may give rise to an oscillating discharge of the circuit breaker parallel capacitance into the arc path. This oscillation can force the main current to zero and thus cause current chopping. In this paper this kind of current chopping is studied and compared with chopping by instability oscillation. It is theoretically explained why these independent origins for chopping produce the same chopping levels.     

Cellular Automata Models of Traffic Behavior in Presence of SpeedBreaking Structures

In this article, we study traffic flow in the presence ofspeed breaking structures. The speed breakers are typically used toreduce the local speed of vehicles near certain institutions such asschools and hospitals. Through a cellular automata model we study the impact of such structures on global traffic characteristics. The simulation results indicate that the presence of speed breakers could reduce the global flow under moderate global densities. However, under low and high global density traffic regime the presence of speed breakers does not have an impact on the global flow. Further the speed limit enforced by the speed breaker createsa phase distinction. For a given global density and slowdown probability, as the speed limit enforced by the speed breaker increases, the traffic moves from the reduced flow phase to maximum flow phase. This underlines the importance of proper design of these structures to avoid undesired flow restrictions.     

断路器控制信号电路仿真装置的设计与演示

根据二次回路实验装置的现状、存在的缺陷及发展趋势,研制了一套高压断路器控制及事故信号电路的仿真实验装置用于电气专业教学和实习.经过在相关实验课中应用,取得了较好的教学效果.     

Observation of weakly ionized dusty plasma in exhaust gas in acompact-size SF6 gas circuit breaker

Measurement of exhausted gas was carried out in an exhaust chamber of a practical compact-size gas circuit breaker. The result show that the gas is weakly ionized, ablated metallic materials exist as metal clusters of sizes from 10 to 100 μm, and their major constituent is iron     

Study of the dynamics of the roots of a low-voltage break-arc

In this paper, a preceding study is resumed (see Velleaud et al., ibid., vol.19, no.3, p.510-4 (1991)). A few modifications have been brought to the mathematical model used to process the induction signals measured. Thus, the dynamics of the anodic and cathodic roots of a 2500 A break-arc at 200 V can be obtained with a set up almost similar to a low-voltage circuit breaker     

Perturbed Arcs in Turbulent Axial Gas Flow IV. Thermal Reignition Experiments

By means of the short-circuiting of electric arcs burning in turbulent axial gas coolant flow and their reaction on a (recovering) voltage ramp the reignition in circuit breakers is modelled. Strong stochasticity of thermal reignition is demonstrated even under relatively weak conditions. Channels or nozzles showing flow detachment are further deteriorated by that. Corresponding low-current test experiments are recommended for in-scale circuit breaker development tests.