Statistical characteristics of transient enclosure voltage in ultra-high-voltage gas-insulated switchgear

Transient enclosure voltage(TEV),which is a phenomenon induced by the inner dielectric breakdown of SF_6 during disconnector operations in a gas-insulated switchgear(GIS),may cause issues relating to shock hazard and electromagnetic interference to secondary equipment.This is a critical factor regarding the electromagnetic compatibility of ultra-high-voltage(UHV)substations.In this paper,the statistical characteristics of TEV at UHV level are collected from field experiments,and are analyzed and compared to those from a repeated strike process.The TEV waveforms during disconnector operations are recorded by a self-developed measurement system first.Then,statistical characteristics,such as the pulse number,duration of pulses,frequency components,magnitude and single pulse duration,are extracted.The transmission line theory is introduced to analyze the TEV and is validated by the experimental results.Finally,the relationship between the TEV and the repeated strike process is analyzed.This proves that the pulse voltage of the TEV is proportional to the corresponding breakdown voltage.The results contribute to the definition of the standard testing waveform of the TEV,and can aid the protection of electronic devices in substations by minimizing the threat of this phenomenon.

Repeated Strike Process During Disconnector Operation in Ultra-High Voltage Gas-Insulated Switchgear

Very fast transient over-voltage(VFTO),induced by disconnector operations in gasinsulated switchgears,has become the limiting dielectric stress at ultra-high voltage levels.Much work has been done to investigate single-strike waveforms of VFTO.However,little study has been carried out investigating the repeated strike process,which would influence VFTO significantly.In this paper,we carried out 450 effective experiments in an ultra-high voltage test circuit,and conducted calculations through the Monte Carlo simulation method,to investigate the repeated strike process.Firstly,the mechanism of the repeated strike process is proposed,based on the experimental results.Afterwards,statistical breakdown characteristics of disconnectors are obtained and analyzed.Finally,simulations of the repeated strike process are conducted,which indicate that the dielectric strength recovery speed and polarity effect factor have a joint effect on VFTO.This study enhances the understanding of the nature of VFTO,and may help to optimize the disconnector designed to minimize VFTO.

Test Study on Corona Onset Voltage of UHV Transmission Lines Based on UV Detection

Corona discharge is being detected by UV imaging detection technology at home and abroad in recent years.This technology is used in the corona tests of conductor bundles in this paper.In order to further research the corona characteristic,optimize geometry parameters and diameter of sub-conductor,and increase corona onset voltage of transmission lines,corona tests of three model conductors which are placed inside the outdoor corona cage are conducted.Corona cage could be used to simulate the corona activities on transmission lines under a low voltage and different conditions in an effective and economical way.Photon which was created by UV light as a result of corona discharge on conductors is detected by the UV detection apparatus.The photon number within unit interval,namely photon counting rate is adopted as the parameter of quantifying the intensity of corona discharge.According to the apparent change of photon number,corona onset voltage can be judged.All tests are conducted under almost same atmosphere condition.Using the method,corona onset voltage is acquired.The results indicate that the tests have a good repeatability,in other words,repeating same test twice same result can be aquired.The corona onset voltage can be acquired exactly from the curve of applied voltage vs.photon counting rate.Therefore UV detection apparatus can not only used to find discharge point exactly,but also applied on corona discharge research and live detection for power equipments.The method using in this paper is proved that is a new available method.

Measurement and Simulation of Induced Voltage and Current on 110 KV Crossing Transmission Lines under UHV AC Transmission Lines

The induced electricity of 110 kV transmission lines which cross the UHV AC transmission lines may threaten personal safety of the maintenance staff. In this paper, field measurement of the induced voltage and induced current on a 110 kV crossing line inside Jinhua in Zhejiang province is performed. The electrostatic induced voltage on the measured line is 12.24 kV. The power frequency electromagnetic field simulation model is established, and the calculation results are consistent with the measured. Influence factors analysis shows that the electrostatic induced voltage on the 110 kV line is 12.78 kV, the electromagnetic induced voltage is 12.3 V, the induced current through ground wire is less than 1A when the UHV lines operate at full load. The induced voltage and current decrease while the crossing distance increases. Parallel lines induction is much higher than crossing lines. The electromagnetic induced voltage after ground knife-switch shut down would exceed the human safety voltage 36 V while the crossing angle is less than 30?, so the temporary ground wire must be hanged to ensure safety of the maintenance staff.

A High Capacity and Working Voltage Potassium-Based Dual Ion Batteries

Potassium-based dual ion batteries(KDIBs)have attracted significant attention owing to high working voltage,high safety,low processing cost,and environmental friendliness.Nevertheless,one great challenge for practical KDIBs is to develop suitable anode materials with high specific capacity.Herein,we report an architecture of hierarchically porous antimony nanoparticles/carbon nanofibers(HPSb CNFs)as flexible,free-standing anode for high-performance KDIBs.The HPSb CNFs with hierarchically porous structure,and high-content nitrogen doping,not only offer sufficient free space to tolerate the repetitive volume expansion of Sb nanoparticles during long-term cycling,but also greatly facilitate the transport of electrons and ions within electrode,ensuring high material utilization ratio.Thus,the KDIBs,constituted by HPSb CNFs-700(calcined at 700°C)anode and graphite cathode,exhibited a high reversible capacity of 440 m Ah g^(-1)with high discharge medium voltage of 4.5 V at a specific current of 200 m A g^(-1)(the highest capacity for all KDIBs normalized by the mass of the anode),and excellent cyclic life.Outstanding electrochemical reversibility of the KDIBs was further demonstrated by ex situ XRD,ex situ Raman spectrum,and HRTEM.These results suggest the as-designed HPSb CNFs-700 with highcapacity and long-term cycling stability is a promising anode material for high-performance KDIBs.

Influencing Factors of the Power Fluctuation on the Ultra High Voltage Transmission Line Caused by Faults at the Remote Ends of the Interconnected Grid

After the North China grid and the Central China grid get into connection with the UHVAC demonstration, a new phenomenon is discovered according to some simulations. That is, the faults at the remote end of the UHV interconnected grid will result in significant power fluctuation and voltage drop on the UHV transmission line and even system splitting. But the faults near the UHV line only have marginal effects. Further, the simulation results also indicate that the short-circuit current of the buses near the UHV line is larger than that of the buses far away from the UHV line. This phenomenon is divergent from the traditional view. In this paper, the detail will be introduced, and the factors influencing the system stability after faults are presented and analyzed. The results indicate that transmission power of the UHV line and of the lines between the remote end and the major grid influence the fluctuation on UHV line. The load model and the grid structure of the remote end also have effect on it. Finally, corresponding control scheme is presented to improve the operation conditions of the UHV interconnected grid and ensure its security and stability.

Fault simulation in ultrahigh voltage substation

Ultrahigh voltage(UHV)and extra-high voltage(EHV)have been widely used in power system,so the requirement for technology of operation management,as well as the accident analysis and disposal are more pressing.Based on the theory of Newton-Laphson power flow method,this simulation system imitates the primary device and secondary circuit,together with the normal,the abnormal and accidents in operation.Through simulation in various situations,it validates that this design is capable of simulating the complicated faults in UHV and EHV accurately and in real time.In addition,it can analyse and dispose them efficiently.

不同风场中特高压换流站阀厅屋盖风压特性试验研究

特高压(ultra high voltage,UHV)换流站阀厅的金属屋面系统在风荷载作用下易发生屋面表层风揭事故。为深入探讨该类建筑屋面的风压极值特性,基于风洞试验分别探讨了大气边界层(atmospheric-boundary-layer,ABL)风、壁面射流、均匀湍流三种风场作用下的屋面风压特性,比较了平均风剖面、风速、风向、湍流强度等因素对屋面风压的影响。结果表明:阀厅屋盖迎风前缘负风压最大,且控制风向角在45°左右;壁面射流风场下平均风压系数与脉动风压系数均超过大气边界层风场的结果;风速对阀厅屋盖的负风压系数均值和极值影响较小,而湍流度对风压系数的极值影响较大;大气边界风场时,JGJ/T 481—2019《屋盖结构风荷载标准》的最不利风压系数建议值偏于安全;而在壁面射流风场下,阀厅屋盖全风向最不利风压系数在所有区域都大于JGJ/T 481—2019的建议值,设计中应加以重视。

UHV串联式TV高压隔离部分的有限元分析及优化

用于超高压和特高压的电压互感器可采用多台电压互感器在一次侧和二次侧串联实现,一次绕组的串联结构与传统的串级结构相似,二次侧的串联结构需要使用高压隔离电压互感器,目前这种互感器还没有设计的经验。为此以1 000 kV串联式标准电压互感器为例,用有限元分析软件ANSYS对高压隔离互感器的三维电场分布进行了数值模拟计算和性能优化。结果表明,基于有限元法的数值模拟是分析和设计串联式电压互感器的有效手段,经优化设计后的高压隔离互感器能够同时满足绝缘和精度方面的要求,优化结果为更高电压等级的串联式电压互感器的设计和制造提供了可靠的、科学的数据。

1200 kV雷电冲击电压标准测量系统

目前,冲击电压测量系统溯源所需的国家计量标准系统额定电压只有700 kV,无法满足3500 kV及以上的特高压电器的溯源需求。对研制的1200 kV电阻分压器进行结构分析,并对建立的1200 kV冲击电压测量系统进行性能测试及改进,在700 kV电压范围内与已有的700 kV冲击电压国家标准测量系统进行比对校准,在700 kV至1200 kV电压范围进行线性度实验。对1200 kV标准冲击电压测量系统进行了不确定度评定,评定结果表明研制的1200 kV雷电冲击电压标准测量系统的试验电压、波前时间、半峰值时间的测量误差均在国际标准IEC 60060及国家标准GB/T 16927允许范围内,将我国的冲击电压国家标准测量系统额定电压等级提高至1200 kV。

UHVDC换流变压器油纸绝缘缺陷直流局部放电发展过程

特高压换流变压器绝缘承受的直流电压高,绝缘缺陷劣化发展迅速,且单凭局部放电(PD)量值和放电次数无法对绝缘缺陷的发展阶段进行分析诊断。为此,研究了特高压换流变压器内部油纸绝缘缺陷直流局部放电特征及其发展过程,构建了油纸针-板等7种局部放电模型。采用阶梯式升压法研究在长期外加电压作用下,绝缘纸板从起始放电到被击穿的整个缺陷发展过程中脉冲电流信号的实时特征及其统计特性,通过拍照的方式给出各模型各发展阶段纸板表面电腐蚀状态,并给出各相应发展阶段电场的空间分布。结果表明:直流局部放电发展过程复杂,初期以大放电脉冲为主,放电频率低,等待恢复时间随机性强;中期和末期以小脉冲放电为主,等待恢复时间均匀分布;临界击穿时等待恢复时间分布集中。结合多种放电模型直流局部放电试验,可断定不同缺陷结构从起始直流局部放电到击穿的过程中,其局部放电的总体发展趋势表现一致。

UHV对接入区域高压配电网安全稳定的影响

采用EPRI-E'等值方法建立包含特高压和大中型城市高压配电网的多电压等级电网仿真模型,从特高压线路故障后退出、配电网内部线路和主要电源点N-1故障的时域仿真分析,研究了特高压投运后高压配电网稳定受到的影响,并定义最短路径确定受影响程度较大的区域.仿真结果表明,特高压线路发生故障后双线跳开,最短路径为5左右的220kV站点出线潮流变化较大,部分将过载或重载,可能诱发系统的连锁故障;配电网内部的故障如果是在特高压系统故障后发生,系统存在崩溃的风险.最后,针对特高压投运后系统的运行特征,提出了相应稳定控制的措施,确保电网安全稳定运行.

基于合成场强仪的输电工程地面合成电场研究

高压直流(DC)输电线路交叉跨越是我国特高压(UHV)技术发展中出现的问题。由于两回DC线路相互影响,交叉跨越区域内合成电场呈复杂的三维分布,UHV DC输电工程地面合成电场计算较为困难。选取典型±800 kV UHV DC输电工程进行地面合成电场的实测研究。参照GB 39220—2020,采用HDEM-01合成场强仪进行野外现场实测。测量参数为有效期内的场磨传感器上积聚的电荷量。测量结果与运行初期实测数据的对比结果表明:±800 kV换流站周边运行初期合成电场强度略低于后期,且整体水平较低;沿线电磁环境敏感目标运行初期、后期的实测数据中,74%的数值小于5 kV/m。通过此次研究,明确了UHV DC输电工程合成电场不同时期的特性。该研究有助于推进UHV DC输电工程的快速建成,并提高其运行安全性,从而推动电力工程建设的发展。

±1100 kV特高压输电塔线体系风振响应分析

为研究角度风下长横担输电塔线体系动力响应,采用有限元时程方法分析准东—华东±1100 kV特高压输电线路单塔及塔线体系风振响应。首先,利用线性滤波法计算得到三维脉动风速场,并结合准定常理论得到单塔及输电塔线体系脉动风荷载。其次,建立单塔及输电塔线体系有限元模型,利用模态分析方法计算结构的动力特性,研究导地线及长横担结构对输电塔动力特性的影响。最后,利用有限元时程方法对单塔及塔线体系进行动力分析,研究了风向角、长横担结构及塔线耦合效应等因素对结构动力响应的影响。结果表明:长横担结构会导致扭转频率降低,扭转振型出现顺序前移;塔线耦合效应降低了塔架结构自振频率,提高了结构阻尼比;根据位移均值计算结果,最不利风向角为15°和75°;根据扭转角均方根计算结果,最不利风向角为0°;单塔顺风向响应主要受背景分量和1阶振型的影响,塔线体系还受到导地线低阶共振分量的影响,扭转角主要受扭转1阶振型影响。

基于±800 kV特高压直流输电线路的中美规范风荷载对比研究

针对±800 kV特高压直流输电线路设计的中美标准,从结构重要性系数、分项系数、重现期等方面对风荷载进行全面探讨分析,并深入研究基本风速、地形地貌和高度影响因素、风载体型系数以及动力特性的取值方法。结合典型±800 kV特高压直流输变电工程,将中美规范的风荷载进行对比分析,得出美国规范的线条风荷载和塔身风荷载标准值均高于中国规范,但线条风荷载设计值小于中国规范30%左右,塔身风荷载总设计值(各风压段之和)与中国规范基本相等。结合典型杆塔计算分析,发现美国规范的风荷载整体设计水平低于中国规范约23%。

基于无微波金刚石NV色心测磁技术的电流测量应用

为了在特高压(UHV)环境下使用氮-空位(NV)色心量子测量技术,研究了金刚石主轴与磁场夹角对相应曲线及电流测量精度的影响。构建金刚石氮-空位七能级超精细结构模型,根据仿真结果得到不同磁场方向下最高灵敏度范围和最佳测量范围,从而确定探头的最佳放置角度。基于无微波金刚石氮-空位技术搭建了直流大电流测量实验平台,测试了100~5000A范围内荧光电压对电流的响应曲线。实验结果表明,该平台对5000A直流电流测量误差在0.25%以内。作为无源器件,无微波金刚石氮-空位色心测磁传感器全光纤信号传输具备良好耐压性能,同时可在室温下工作,并具有结构紧凑、灵敏度高、抗电磁干扰能力强等优势,适用于特高压环境下的直流电流测量,为传统电力行业检测提供了新的检测方法。

基于序电流相位差的EHV/UHV输电线路高阻抗故障选相研究

为了实现超高压和特高压输电线路的故障快速诊断,将序电流相位差技术应用到输电线路高阻抗故障选相中。开展了三相网络单相接地故障和相间接地故障分析,通过零序和负序电流分量相位差对故障相区间进行了划分,建立了序电流相位差、相阻抗、相间阻抗、3段距离继电器保护范围与故障类型、故障相别的关系;提出了一种以序电流相位差为判断依据的超高压和特高压输电线路高阻抗故障选相新方法;在500 kV,400 km的输电线路上对该故障选相方案的精确性及可靠性进行了评价,并进行了RTDS仿真测试。研究结果表明:该故障选相方案能够实现精确可靠的识别,并有足够的边际应对意外因素或计算误差,即使在电网振荡时,也可以实现可靠的系统故障相识别。

UHV输电线路中绝缘子串电位分布的仿真计算

利用三维电磁场分析软件Ansoft对铁塔、导线、绝缘子按实际尺寸建立三维模型。综合考虑了芯棒、伞群、球头球窝、导线、连接金具、铁塔、均压环等因素对1000kV特高压输电线路中的绝缘子表面电场分布进行了计算。分析了导线、连接金具、均压环、铁塔、三相中其余两相对Ⅰ型绝缘子串和V型绝缘子串电场分布的影响。计算结果可以为绝缘子的正确使用和优化设计提供参考。分析可知,使用均压环可使绝缘子上的电位分布有较大地改善。