大气条件下纳秒脉冲放电及其声特性分析(英文)

There was no well-resolved mechanism of audible noise caused by corona discharge on UHV transmission lines. Hence we measured the sound pressure of pulsed discharges between needle-plane electrodes under different discharge conditions in air, for revealing the intrinsic relationship between discharge and its audible noise(AN). The relationship between discharge parameters and audio characte- ristics was drawn from the analysis of the electric and sound signals obtained in experiments. Experiment results showed that nanosecond pulsed discharges produce the sound pressure with a microsecond pulse lagging behind the discharge pulse in their waveforms. The peak value of the sound pulse decreases and its high frequency component gradually attenuates, when the measuring distance from discharges increases. The sound pulses correlate with the discharge current and voltage significantly, especially the current. The audible noise produced by repetitive pulsed discharge increases with the strength, duration, and pulse repetition rate of discharge.     

特高压直流输电线路雷击上行先导竞机制(英文)

Research on the lightning shielding failure characteristics of UHVDC transmission lines is important for adequate transmission line protection and safe operation of a power grid.Focusing the competition characteristics of upward leaders in the lightning attachment process,this work provides technical reference for efficient evaluations of lightning shielding failures and reliable lightning protection designs of UHVDC transmission lines.The charge simulation method is employed to calculate electric field distributions.Based on the calculation and some data obtained by recent long-gap discharge and lightning observations,the effect of several upward leaders starting from UHVDC transmission lines on lightning attachment processes is studied by numerical simulation.The results show that the upward leader inception is delayed,the propagation velocity is smaller,and the propagation direction of the upward leader is changed with interaction among all upward leaders,which influences the selection of lightning striking point.Therefore,in order to improve the accuracy of calculating the lightning shielding failure rate of UHVDC transmission lines,the interaction characteristics of upward leaders should be taken into account.In addition,an analysis of the influence of operating voltage and the protection angle of UHVDC transmission lines based on competition mechanism of upward leaders is made.It is found that the existence of operating voltage mainly affects the ability of the conductor and the overhead ground wire at the same side to incept upward leaders,while the protection angle mainly affects the position of the "starting points" of upward leaders.The results indicate that positive polar conductors should be installed closer to hillsides and the negative protection angle of towers is suggested.     

Research on Electro-Magnetic Environment of UHV Transmission Lines

Employing even higher voltage level to promote power transmission economy is an important subject in the program of power transmission from west to east. The influence of electro-magnetic environment of transmission project being closely related with human health and construction cost has to be seriously considered before advancing transmission voltage. This paper analyzes and discusses overseas and domestic research achievements on radio interference, audible noise, power frequency electric field, power frequency magnetic fields, DC resultant field intensity and ion stream involved in power transmission at ultra-high-voltage (UHV) AC and±800 kV DC or even higher voltage levels. Suggestions on limiting electro-magnetic effects and their ceiling value as well as measures to improve electro-magnetic environment are put forward.     

Time–frequency multiresolution of fault-generated transient signals in transmission lines using a morphological filter

The ongoing transformation of electrical power systems highlights the weaknesses of the protection schemes of traditional devices because they are designed and configured according to traditional characteristics of the system. Therefore, this work proposes a new methodology to study the fault-generated high frequency transient signals in transmission lines through multiresolution analysis. The high frequency components are determined by a new digital filtering technique based on mathematical morphology theory and a spectral energy index. Consequently, wide spectra of signals in the time–frequency domain are obtained. The performance of this method is verified on an electrical power system modeled in ATP-Draw, where simulation and test signals are developed for different locations, fault resistances, inception angles, high frequency noises, sampling frequencies, types of faults, and shapes of the structuring element. The results show the characteristics of the fault such as the traveling wave frequency, location, and starting time.     

Study on Electromagnetic Environment of AC-DC Hybrid Transmission Lines

With the expansion of electricity demand,transmission corridors are becoming scarce.AC and DC circuits running parallel to each other and sharing the same right-of-way or even the same tower become a possible option.Due to the existence of the adjacent line,space electromagnetic field and corona of another line may be changed.Different characteristics of two line types make the electromagnetic field of transmission corridors become more complex.Hybrid line is viewed as a whole.The calculation contains surface gradient,ground level electric field,radio interference and audible noise.Interaction between the two line types is considered.The calculation results show that the interaction is mainly concentrated in the inner corridor.In the role of DC electric field,AC electric field is no longer symmetrical and ground level electric field is significantly enhanced.Under the negative DC voltage,the positive corona of the waveform is significantly strengthened,and it is inhibited under the positive DC voltage.It is better to erect the positive DC line near AC line.     

特高压直流输电用电晕笼的设计(英文)

For the purpose of testing and analysing the corona characteristics of UHVDC bundle conductors, UHVDC corona cage would be built in China. Corona cage is one of the indispensable equipments for conductor corona performance researches. Tests of conductor co- rona characteristics in corona cages can overcome the shortages of those with test lines.The dimensions of several corona cages constructed overseas were introduced in this paper. Based on foreign experiences and the requirement of State Grid Corporation of China, the UHVDC corona cage was designed as double-cage, double-layer, three-sections, and catenary shape with the size of 70 m×22 m×13 m. The corona loss measurement system, radio interference measuring system, and the audible noise measuring system are also detailed, including the measurement theory, connection with the cage, the parameters and the designing basis. The UHVDC corona cage has been put into service. It now undergoes a large amount of audible noise and radio frequency interference tests.     

基于随机理论的特高压输电线路雷电屏蔽模型

The operation data obtained abroad indicates that shielding failure in UHV transmission lines mostly accounts for the tripping-out accidents introduced by lightning striking the transmission line.Based on the discharge theories of long air gap and randomness theory,a leader progression model of lightning shielding failure is presented in this paper.The random characteristics of the downward and upward leader are simulated in this model.The ground slope angel is also considered in this model by using coordinate transformation.Moreover,the system voltage is also taken into consideration in this model.The simulation results show that the good agreement between this model and the field data.And the results suggest that return striking exist obviously in UHV transmission line.     

交直流复合电压下电晕放电实验研究(英文)

Converter transformers are one of the most important electrical apparatuses in the ultra high voltage(UHV) DC transmission systems.The valve side and the low voltage(LV) bushing are stressed by long-term AC and DC composite voltage leading to significant partial discharge(PD) and posing great danger to the insulation system.In this paper AC and DC composite voltage is applied on a metal needle-plate model to produce PD signal sequences,and then the pulse waveshape and frequency spectrum are analyzed and compared with PD signals under conventional AC or DC voltage.In the end,the phase-resolved distribution is analyzed to depict the new characteristics of PD under this composite voltage.     

现代架空线输电系统中的高压电缆段

Electrical power transmission is dominated by overhead line systems at present.This is mainly based on more than hundred years of experience of utilities in running overhead lines.Furthermore,overhead lines have proven their operational reliability and functional assurance.In the past,cables were used in distribution networks in urban areas for the most part with the exception of direct current submarine cables.New developments of high voltage XLPE cables make it possible to use this technology for EHV level applications in transmission networks.Within this paper,mixed network configurations,consisting of overhead lines and high voltage cables,are investigated.An exemplary EHV transmission line with a total length of about 100 km,which is quite typical for Central Europe,has been studied.Several different line combinations are discussed with varied rates between overhead line sections and cable sections length in practice.The length of the cable sections are ranging from several kilometers up to lengths of 100 km.In this paper the work focuses on the transient behavior of combined 400 kV overhead and cable lines during switching processes and lightning impacts.A number of calculations were carried out to get an overview of the transient stress in numerous network nodes along the transmission system.Numerical programs like ATP/EMTP have been used for these simulations.Peak values and wave shapes of the transient voltage stress have been evaluated,based on different systems and within possible combinations.In respect of the insulation coordination and transient stress at network nodes,the voltage-time trends are also analyzed.The combination of high voltage overhead and cable transmission systems,especially such with lengths of more than about 50 km,are making tightened and extended demands to the network design,to the operational management and of course to the network protection also.As an output of this investigations,the results might influence the strategy in running this new type of combined transmission systems.     

多回直流输电线路的离子流场计算

An upwind finite element(FE)based algorithm to calculate the ion flow field in the vicinity of multi-circuit DC transmission lines is described.The initial value estimation and boundary condition are optimized,so details of the transmission lines such as bundle conductors and ground wires can be taken into account in the simulation model.Comparison between measured and computed ground level total electrical field and ion current density shows satisfactory agreement.The ion flow field of a ±500 kV HVDC project with bipolar lines on the same tower is simulated.The total electrical field and ion current density on ground level are compared among different line arrangements.     

交、直流电场作用下交联聚乙烯中的空间电荷习性

Polyethylene is one of the widely studied polymeric insulation materials,which have been used extensively for cable insulation.One of the major issues related to polymeric materials is its easy formation of space charge,a high chance to cause electric field distortions.This phenomenon is more significant under high voltage direct current(HVDC)stresses.Space charge can also be observed under high voltage alternative current(HVAC)stresses but with much less intensity due to the limited charge injection period and the effect of charge recombination caused by the constantly variance of the external fields.When considering the situation of an AC voltage combined with a DC offset,a possible scenario in HVDC technology,there was little research on charge dynamics in the insulation in terms of both experimental and simulation work.In this paper,a numerical simulation based a bipolar charge injection/transport model is used to obtain characteristics of space charge in polyethylene under the combined AC and DC high voltage at room temperature.The bipolar charge injection/transport model,which is widely used in HVDC space charge simulation,is applied in the combined conditions.The overall applied voltage,consisted of root mean square(RMS)values of the AC voltage and DC voltage,is kept the same,while the DC component’s voltage ratio and AC component’s frequency are changed respectively,to illustrate their effects on the space charge dynamics within the insulation under combined electric fields.The simulated charge distributions present notable differences when DC offset is increasingly added in,while relatively small differences when AC component’s frequency altering,especially for the cases whose frequency exceeding 0.5 Hz.     

交、直流电场作用下交联聚乙烯中的空间电荷习性（英文）

Polyethylene is one of the widely studied polymeric insulation materials,which have been used extensively for cable insulation.One of the major issues related to polymeric materials is its easy formation of space charge,a high chance to cause electric field distortions.This phenomenon is more significant under high voltage direct current(HVDC)stresses.Space charge can also be observed under high voltage alternative current(HVAC)stresses but with much less intensity due to the limited charge injection period and the effect of charge recombination caused by the constantly variance of the external fields.When considering the situation of an AC voltage combined with a DC offset,a possible scenario in HVDC technology,there was little research on charge dynamics in the insulation in terms of both experimental and simulation work.In this paper,a numerical simulation based a bipolar charge injection/transport model is used to obtain characteristics of space charge in polyethylene under the combined AC and DC high voltage at room temperature.The bipolar charge injection/transport model,which is widely used in HVDC space charge simulation,is applied in the combined conditions.The overall applied voltage,consisted of root mean square(RMS)values of the AC voltage and DC voltage,is kept the same,while the DC component’s voltage ratio and AC component’s frequency are changed respectively,to illustrate their effects on the space charge dynamics within the insulation under combined electric fields.The simulated charge distributions present notable differences when DC offset is increasingly added in,while relatively small differences when AC component’s frequency altering,especially for the cases whose frequency exceeding 0.5 Hz.     

重复雷击和操作冲击时单相GIB的金属微粒运动形态

Transient over voltages due to lightning and switching surges cause steep build-up of voltage on transmission lines and other electrical apparatus,like circuit breakers,transformers,insulators etc.Therefore it is necessary for the GIS also to withstand such voltages without breakdown of Insulation.The system has to be tested under these conditions.Usually the GIS system operates on power frequency.Lightning Impulse Voltage of 1050 kV and Switching Impulse Voltage of 750 kV superimposed on Power frequency voltages of 75 kV,100 kV and 132 kV are applied to Single Phase Gas Insulated Busduct and the maximum movement of Aluminum,Copper and Silver particles is determined.The movement patterns are also determined with and without Monte Carlo Simulation for movement of particle in axial and radial directions.The results show that there is a sudden jump in the movement at the application of impulse on sine wave.This is because of high magnitude voltage of 1050 kV during 1.2/50 μs.Similar movement patterns of reduced maximum movement is observed for Switching Impulse superimposed on sine wave.The results are presented and analyzed.     

基于支持向量机的配电网过电压模式识别(英文)

The internal and external overvoltage in distribution networks is the main reason of accidents. Based on overvoltage data in distribution network recorded by overvoltage on-line monitoring system, this paper analyzes the characteristics of zero sequence voltage waveform. The maximum amplitude and RMS value of zero sequence voltage, the minimum RMS of low frequency component of three phase voltage in stable range and other five parameters are selected as characteristic parameters to identify internal and external overvoltage. According to the operation data and record, all overvoltage data recorded by on-line monitoring system were labeled as internal or external overvoltage and the discrimination function is constructed by support vector machine method. The test results of field acquired overvoltage data indicate that the identification parameters and method based on the zero sequence voltage and support vector machine (SVM) are correct and effective.     

针水电极电晕放电中的离子风风压分布(英文)

The negative DC corona discharge in air at atmospheric pressure was investigated in a needle-to-water system to obtain the pressure distribution of corona ionic wind.The deformation of water surface was measured and the distribution of wind pressure over the water surface was calculated.The effects of varying discharge parameters,such as applied voltage,gap spacing,tip radius of needle,and the shape of grounded electrode,on the wind pressure were studied.The measured wind pressure ranges from several Pa to several tens of Pa and up to 33 Pa over a small area;the pressure is comparatively large in the center and decreases quickly outwards.In the experiment system,a higher voltage on a 3 mm gap resulted in a stronger pressure of the ionic wind;around the onset voltage,using a needle with tip radius of 50μm obtained a larger wind pressure than using a needle with 100μm tip radius,but the latter one can produce larger pressure at higher voltages.Plus,the shape of the grounded electrode only influences the wind pressure a little.     

在共面介质阻挡放电中大气压等离子体射流的特性(英文)

Non-thermal plasma jet at atmospheric pressure has recently attracted lots of attention because of its applications in plasma bullet or plasma plume.Thus,we studied on generating plasma jet by coplanar dielectric barrier discharge in a device driven by sinusoidal voltage.The processes of plasma discharges in both positive and negative half cycles were recorded using a high-speed ICCD(intensified charge-coupled device)camera;based on the results we estimated the velocity of plasma propagation,and investigated the influence of gas flow on the plasma development.It is shown that the plasma bullets,which have velocity in the order of 103～104m/s,exist only outside the cathode.APPJ(atmospheric pressure plasma jet)is created by the electron beam from the cathode,and then sustained by a strong radial electric field near and outside the cathode.The gas flow influences the APPJ length in air but not the APPJ discharge,while the discharge is affected significantly by the applied voltage.     

外电场及预电离对大功率脉冲氙灯放电等离子体特性的影响(英文)

This work is devoted to experimentally study the characteristics of discharge plasma in high power xenon flashlamps.In the experiments,plasma channel profiles are captured by using a high speed CCD camera,and the radiation energy of the flashlamp is obtained by a pyroelectric energy meter.Voltage and current curves are recorded to shed light on the plasma characteristics.With these diagnostic methods,typical factors influencing the evolution process of plasma channel are studied,including the external electric field and the pre-ionization.The electric potential distribution in the flashlamp influence the plasma channel characteristics the most significantly.The plasma channel pattern for the cases with grounded wires is different from that with ungrounded metal wires.When the wire is ungrounded,it is the coupling voltage between the metal wire and the flashlamp that influences the development of plasma channel.In terms of radiation efficiency,it is proven that there is an optimal interval within 200～300μs between the pre-ionization pulse and the main pulse.     

特高压直流输电系统多换流站共用两个接地极的优化设计(英文)

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.     

带并联电抗器的交流特高压输电线路单相自适应重合闸故障识别方法(英文)

In order to avoid single-phase adaptive reclosure overlap in a permanent fault,accurate identification of the fault types on transmission line is necessary.We present a fault nature identification method for ultra-high voltage alternating current(UHVAC) transmission lines with shunt reactor.The voltage amplitude ratios of the neutral small reactance voltage to terminal voltage under transient fault and permanent fault are calculated.The significant differences of the ratio under the two faults have been analyzed.It is found that the ratio can be a criterion to distinguish the fault type,transient or permanent,accurately.Additionally,we also proposed a method that delays a beat frequency oscillation cycle to decide the fault types for the existence of beat frequency oscillation which will cause misidentification on transient faults.Abundant simulation results of ATP/EMTP show that the voltage amplitude ratio under transient fault is between 0.6 and 0.7,which is bigger than 2.5,the ratio under permanent fault.     

特高压直流与双回超高压交流同塔架设输电线路导线布置方式及换位方式分析(英文)

For AC and DC hybrid transmission lines,the arrangement and transposition modes of AC conductors not only affect the unbalance factor of AC lines,but also influence the bias current of DC converter transformers by AC and DC coupling.Excessive bias current will influence the normal operation of converter transformers,thus the optimal AC phase arrangement and transposition mode of hybrid lines was studied to minimize the coupling effect between AC and DC lines to fit the requirements on both aspects.Based on the parameters of the Ximeng-Shanghai project in China,a detailed simulation model of the DC converter station and the hybrid transmission line with double-circuit AC 500 kV transmission lines and DC ±800 kV transmission lines were presented in the software PSCAD-EMTDC,and the coupling effects of the hybrid transmission lines were elucidated.The fundamental frequency components of DC poles with different operation conditions,arrangements of conductors and operation modes were analyzed,and the effective arrangement and transposition limiting the fundamental frequency current component of the DC line were compared.Simulation results show that AC operating conditions can affect DC induced components while the DC system operation mode has no apparent effect.With compact arrangement and inconsistent transposition of AC lines,the fundamental frequency component on DC lines can be reduced effectively;the three-transposed mode within the hybrid line is the optimal layout scheme,considering both the requirements of DC bias current and AC unbalance degree.