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Ultra high voltage direct current(UHVDC) electrode sites choosing become more and more difficult due to the limited land resource,and it results in an urgent requirement of common electrode technology.The optimized designing method of two kinds of electrodes commonly used by multi converter stations is studied in this paper.The performance criteria and the rational jointing style between electrode lines and electrodes are analysed and determined at first,based on which,the mathematical model of the two kinds of electrodes is established,and an inequality equation set is formed to satisfy the relative standards of environmental impact on ground electrodes.Consequently the optimized designing method is presented through simplification of the model.After all,a specific example is given based on the parameters of Southwest Hydroelectric Project in China,in which two electrode sites had been pre-chosen.The results show that,tens of plans of the two kinds of electrodes together with their electrode performances can be provided based on the presented method.The errors of current distribution ratio in all the examined plans are maintained about 1%,the maximum error of earthing resistance is 7% and the maximum error of step voltage is 4%,which prove the engineering practicality of the method. 相似文献
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Gas spark switch is one of the key parts in pulsed power technology.Electrode erosion has great influence on the switch performance and lifetime.In this paper,a field distortion gas switch is selected for the experiment and a great deal of discharging experiments have been conducted in different test conditions.The forming process of etch pit as well as its influencing factors is discussed briefly and surface roughness coefficient(SRC) of the electrode is put forward to evaluate the state of electrode erosion.Experimental results show that current peak plays an important role in electrode erosion when waveforms of discharge current are the same,and electric charge and oscillation frequency of discharge current also have great effect on the electrode erosion when waveforms of discharge current are different.With the increase of discharge times,SRC decreases slowly at first and then decreases quickly after three thousand of discharge times. 相似文献
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This paper calculates and researches on lightning accident of ±500 kV Xing-An DC transmission line in Guangdong based on ATP-EMTP and the simulation calculation model of the HVDC has been constructed. The results show that: when a lightning current strikes to the positive polar conductor of double circuit transmission line and the flashover of insulator strings occurs, as the over-voltage wave propagating along the lines due to the coupling effect between the conductors, the grounding electrode lines would produce the coupling voltage wave, which makes the flashover of the insulator strings occur at the different place along the grounding electrode lines, the unbalanced current of the grounding polar line is produced due to the insulator strings flashover and the unbalanced current exists for a long time, when the unbalanced current is up to the locking condition, the negative polar conductor is locked and the double-pole block fault occurs. In the paper, some effective measures are given to prevent this accident. 相似文献
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The aim of this paper is to calculate accurately the grounding performance of an unbounded grounding system under high-magnitude fault current.In this work,a finite element model is presented to compute the characteristic parameters of the grounding system in frequency domain.The ionization phenomenon in the soil surrounding the grounding electrode is taken into account by setting the resistivity of every soil element while the resistivity of each element is varying with the electric field intensity;not a priori hypothesis on the geometrical shape of the ionized region around the electrodes has to be enforced.Open boundaries of the grounding system are represented by introducing a spatial transformation formulation,which translates the semi-infinite space into the finite space without shortening the domain as in the traditional approach.The suggested modeling is validated by comparison of the calculated results,which are laid out for grounding rod and grounding grid,with experimental and simulation results found in literature. 相似文献
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Pawel Rozga 《高电压技术》2013,(8):1805-1812
Looking at the problem of electrical discharge development in mineral oil, it is easy to see that most studies in this area focused on the setups of bare high voltage electrodes having a point-plane electrode arrangement. The setups with insulated electrodes are the mar- gin of these studies but it seems to be important to find the dependences between the paper insulation on high voltage electrode and parameters of the discharges initiated in the vicinity of this electrode. Hence, in this paper the results of researches intended to reveal the role of insulation wrapping on a HV electrode in the mechanism of electrical discharges in transformer oil under lightning impulse of both polar- ities are presented. This role is determined by analysis of the parameters characterizing the discharges (onset voltage, propagation velocity, time to initiation, rise-time of light impulses) and also by observation of their spatio-temporal development and oscillograms of the light emitted by their channels. The research was performed for two model electrode configurations: an electrode with paper insulation and a bare electrode which had the same outer dimensions as the insulated one. The most essential conclusion from performed experiment is related to times to initiation. These times, equal in the case of insulated electrodes and model bare electrode, indicate that the source of "weak points" of the paper-oil insulation system is the oil, not the surface of insulation wrapping or the metal. 相似文献
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More and more applications of ZnO arrester in electrical system experienced more problems.One thing,that is still under some investigation,is the effect of multiple lightning strike to the performance of ZnO arrester.As we know,the design of ZnO arrester for transmission system and for distribution system differs in the point of view of the number of ZnO blocks.Transmission system,due to its higher nominal voltage than distribution system,has more numbers of ZnO blocks inside an arrester tube.In term of the current rating of an arrester,it is found that there is some different value of the current rating.The current rating of an arrester installed closer to electrical substation is higher than that of some further away from the substation.To the respond of a lightning impulse strike,the arrester will let a high value of impulse current flowing.It tends to heat the ZnO material of the arrester.If the number of impulse strike is quite high then it may give the effect to the change of the arrester performance.This condition will endanger the equipment that is protected by the arrester from lightning strikes.During this research,the scope of work is limited to making an impulse current generator toward to one having 8/20 μs wave-shape.This kind of impulse current wave-shape is the one that is used for studying the performance of ZnO block.The effect of the inductance and capacitance of the impulse current generator were also studied.A 10 fused cut out was blown by an impulse having 10321 A of 17.8/37.8 μs.A ZnO arrester block brokendown/allowed large value of current :10982 A flowing under the voltage of 10.5 kV 相似文献
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The total electric field(TEF) at ground level induced by high-voltage direct current(HVDC) overhead transmission lines is one of the important indexes for evaluating the lines’ electromagnetic environment.Based on analyzing the existing TEF sensors and the measurement principle of ion-current density,the influence from ions on TEF measurements is quantitively studied.The results show that the ions generated by the corona from a HVDC transmission line in operation cause errors in the measurement of TEF.This error is determined through analyzing the component of total measuring current on the filed mill’s sensing electrode: if no appropriate approach taken,the maximum measurement error reaches up to 4.3%.Furthermore,a method that can eliminate such error,and hence improve the accuracy of TEF sensors is designed. 相似文献
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变压器直流偏磁及其与接地电阻关系的研究 总被引:3,自引:2,他引:1
Recently years,UHVDC transmission system is paid more attention to in the field of China’s power system.It takes key part in the China electrical power development stratagem.But,many problems are caused by UHVDC system,such as DC bias,corrosion of metal underground and so on.DC bias is harm to the transformers nearby UHVDC grounding polar.In this paper,the influences of DC grounding current on transformer are introduced and some suggestions of DC bias solution were provided.And,the relationship between UHVDC Grounding Current and grounding Resistance of Substation was analyzed.Firstly,two-part network circuit was used to equivalent the grounding circuit.Then,an analysis of rules was done between DC bias current and grounding resistance.Finally,the conclusion is given that DC bias current rises fast as DC grounding resistance or AC grounding resistance rises.It drops when resistance of AC transmission line or interaction resistance between DC grounding system and AC grounding system rises.Decreasing AC grounding resistance and DC grounding resistance is important to restrain DC bias current.Increasing resistance of AC transmission line such as adding resistance into transformer neutral-point grounding is a useful way to limit DC bias current. 相似文献
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With the increasing penetration of distributed generations(DGs)into power grids,the fault ride-through ability of DG is attracting more and more attention.Recent grid codes require a DG to maintain its connection with the grid during grid faults and to play an active role in the recovery of grid voltage.This paper chooses the doublyfed induction generator(DFIG)as the typical wind turbine for study.Firstly,a dynamic reactive power control strategy is proposed to improve the fault ride-through characteristic of a DFIG.The contributions of a DFIG to the fault current under the dynamic reactive power control and the Crowbar control are analyzed and compared based on the mathematical expressions and control behaviors.The impacts of a DFIG under two control strategies on distribution protections are discussed.Studies show that although a DFIG under the dynamic reactive power control provides more fault current component than one under the Crowbar control,its impacts on distribution protections are acceptable.Finally,a 10kV distribution network with a DFIG is simulated in PowerFactory DIgSILENT.The simulation results prove the correctness of above theoretical analysis. 相似文献
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G.Maslowski V.A.Rakov S.Wyderka J.Bajorek B.A.DeCarlo J.Jerauld G.H.Schnetzer J.Schoene M.A.Uman K.J.Rambo D.M.Jordan W.Krata 《高电压技术》2008,34(12):2575-2582
We present a comparison of data obtained during testing of lightning protective system of a residential structure in rocket-triggered lightning experiment at the International Center for Lightning Research and Testing(ICLRT)at Camp Blanding,Florida,and current surge generator experiment at Rzeszow University of Technology in Poland.Three different configurations of LPS were tested in Poland with the dc grounding resistances of the entire system 4.09 Ω(LPS 1a),1.65 Ω(LPS 1b),and 2.88 Ω(LPS 2).For LPS 1a with three ground rods the value of the peak current entering the electrical circuit neutral was about 56% of the injected current peak,and for LPS 1b with two additional ground rods and two 5 m long buried horizontal conductors it was about 16%.For LPS 2 with five ground rods interconnected by a buried loop conductor this ratio was 21%.The current waveshapes in the ground rods differed from the injected current waveshapes and the current waveshapes in other parts of the test system,especially,for poorer-grounding LPS 1a.The surge-generator results are consistent with those of triggered-lightning experiments at Camp Blanding,Florida(DeCarlo et al.,2008 [2]). 相似文献
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高压直流输电系统处于单极大地回线运行方式时,有很大的直流电流通过直流接地极流入大地,这将造成接地极本身及附近输电杆塔接地网的腐蚀。在理论分析接地极和杆塔接地网电磁场的基础上,应用有限元分析软件COMSOL Multiphysics,以德宝直流输电工程千阳接地极为例,建立了多层大地土壤结构下的直流接地极和杆塔接地网数值模型,添加相关边界条件,进行网格划分处理,计算分析了接地极地表电位分布规律,并对杆塔接地网附近电位及泄漏电流密度进行了研究,结果发现:接地极地表电位沿径向距离逐渐降低;杆塔接地网本体上的电位最高,接地网的射线末端泄漏电流密度最大,射线首端的泄漏电流密度最小,接地网矩形与射线的连接处电流密度有突变。该研究对掌握直流接地极及杆塔接地网周围电场分布情况和腐蚀规律,具有重要的意义。 相似文献
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直流接地极线路不同于直流输电线路,其在正常运行下,电压电流的值均很小,且极址点是通过阻值很小的过渡电阻接地,因此接地极线路精确定位是故障测距的难点。理论分析和仿真表明,当接地极线路发生接地故障,且接地点电阻大于或等于极址电阻时,流入故障点的电流很小,利用沿线电压分布推导得到的故障点电压不再是电压在线路上分布的最小值,而极址点电压是沿线电压分布的最小值。因此根据故障点电压相等来构造测距函数的测距原理存在不足之处。利用极址点电压相等构造测距函数,提出一种基于故障录波数据的耐受高阻接地的直流接地极线路故障测距新方法。大量仿真表明,该算法可以实现接地极线路的精确定位,对采样率要求不高,便于工程实际运用。 相似文献
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Ramamoorty M. Narayanan M.M.B. Parameswaran S. Mukhedkar D. 《Power Delivery, IEEE Transactions on》1989,4(4):2053-2059
An analytical method to determine the transient performance of grounding grids is presented. In the proposed method, the leakage current to ground of each element of the grounding grid is represented more realistically than by considering the grid as an equivalent circular plate. Vertical ground rods of the grid are also considered. The maximum voltage to which a station grounding grid is raised due to incident impulse current can be determined. This is an important criterion in evaluating the transient performance of substation grounding grids which are generally designed from the point of view of power frequency fault currents. It has been found from both analytical and field studies that, in cases where impulse current injection is at the corner of the grid, the voltage induced and hence the impulse impedance are the highest. If the impulse current is incident at any other location within the grid, the grid exhibits a lower value of impulse impedance. Comparison of analytical results and field results shows good correlation for maximum induced voltages and impulse impedances 相似文献
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椭圆环布置的垂直型直流接地极占地面积小,地形适应能力强,具有推广应用价值,但椭圆环布置带来的溢流不均匀特性值得深入研究。分析并对比接地极外形尺寸对溢流特性的影响,外形参数包括椭圆率、极环周长、电极长度、电极间距、电极数量。研究表明,椭圆率越大、电极长度越长、电极间距越小、电极数量越少,则电极之间的不均匀程度也越高;且影响程度最大的是椭圆率,其次是电极长度和电极间距,再次是电极数量。采用椭圆环布置垂直接地极时,需要考虑电极之间和单个电极本身的两类溢流不均匀特性的叠加,以控制任一点上的最大溢流密度偏差系数。 相似文献
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由于在实际接地网中测量接地网电流是不可能的,因此,提出了一种实验室接地模拟的方法来分析实际接地网的电流分布,即在实验水池中,用电量隔离传感器测量接地网的电流分布,测出不同接地网——单根垂直接地体、十字形接地网、水平接地网、复合接地网的电流分布,所得的实验结果为研究接地网中的电位分布及接地网的设计提供较准确的科学数据。 相似文献