锦屏—苏南±800kV特高压直流输电工程换流站过电压及绝缘配合(英文)

Regarding to the problems of equipments manufacturing and layout in Jinping-Sunan ±800 kV UHVDC transmission system,overvoltage protection and insulation coordination in converter stations were studied.Configuration of arresters was studied at first,and scheme of MH arresters and V arresters connected in series was used to protect the high voltage Yy transformer’s valve side of dual 12-pulse converters.Overvoltage caused by DC faults and the withstand level of equipment in converter stations were studied using electromagnetic transient simulation.Based on operation parameters and characteristics of AC and DC system,equivalent models of both systems were set,together with most of the equipment in converter stations which would influence simulation results.The AC arresters’ transient response to AC faults was also simulated.For the most severe case,the peak voltage on AC bus arresters is up to 752 kV,along with stresses about 12.0 MJ in energy and 12.4 kA in current.Simulation results of transient overvoltage in converter stations were used to verify insulation coordination by comparing with the design value.The maximum insulation level would be less than 1 600 kV,which is no more than that in former UHVDC projects.     

±800kV特高压直流输电系统换流站换流阀过电压机理和计算条件(英文)

The thyristor converter valve is the key equipment of commutation in ultra high voltage direct current(UHVDC) transmission systems.Owing to the limited voltage and current overload capacity,any transient overvoltage may cause permanent damage to the thyristor converter valve.In order to specify the converter valves’ overvoltage levels of the ±800 kV UHVDC transmission system,the mechanisms of its generation and development are discussed in detail,from which the calculation conditions for the highest stresses of the converter valves are given.Finally,the converter valve’s overvoltage of Xiluodu UHV converter station is simulated.The research results show that the overvoltages of the converter valves in the upper 3-pulse group of the high voltage(HV) and low voltage(LV) 12-pulse converter are generated jointly by the DC line voltage and the converter transformer’s voltage at its valve side.Calculation conditions for this overvoltage are: DC system in bipolar operation mode,converter station operating as rectifier,maximum DC system operating voltage,minimum DC current,minimum AC system voltage of the converter station.Furthermore,the other converter valves’ overvoltage is caused by the phase-to-phase switching surge generated at the converter station’s AC side,penetrating into the valve hall.Overall,the maximum overvoltages of Xiluodu converter station in the upper 3-pulse group of the HV and LV 12-pulse converter are 379.1 kV and 384.9 kV,for other converter valves the maximum overvoltage is 375.3 kV.     

±800KV特高压直流输电系统换流变阀侧绕组过电压与绝缘配合(英文)

The determination of insulation levels for valve windings of ± 800 kV UHVDC converter transformers is a key problem for designing and manufacturing of the converter transformers.Based on the Yunnan-Guangdong ±800 kV DC power transmission project,the arrester parameters for direct or indirect protection of the valve windings are selected.The EMTDC program is used to calculate several faults,which determine mainly the specified insulation levels of valve winding for temporary,switching and lightning impulses,and the overvoltage generating mechanisms according to these faults are analyzed.The polarity reversal overvoltage and the related reversal time at valve windings caused by the emergency switch off sequence of converters(ESOF) are calculated to confirm the necessity of DC voltage polarity reversal type tests of valve windings.The reasonability of the three insulation coordination methods,which determine converter transformers’ switching impulse insulation levels,is analyzed.Method 1 is concluded to be more reasonable,and it is used to determine the switching impulse withstand voltage(SIWV) from the switching overvoltage calculation results.The lightning impulse withstand voltage(LIWV) of valve windings can be determined by the ratio between LIWV and SIWV.The principle of the ratio selection is presented,and it is used to determine the LIWV.The operation experience of Yunnan-Guangdong ±800 kV DC project has proven that the presented insulation levels is appropriate.     

云南—广东特高压直流输电线路孤岛运行方式下过电压水平及其影响因素(英文)

Overvoltage is one of the key factors influencing whether Yunnan-Guangdong UHVDC Project can be operated in Islanded Mode or not.Based on the on-site test parameters of primary equipments and the actual control and protection system of the project,this paper performs calculations of the overvoltage level in islanded operation models.The influence of BLOCK process and load retard speed of Yunnan-Guangdong UHVDC on the overvoltage level in islanded mode is also studied.The results show that it is an important measure for suppressing the overvoltage level to switch off the converter transformer after ac filters have been switched off.The maximum per unit switching overvoltage is 1.71(reference value is 449 kV) under various fault conditions.The maximum transient overvoltage is 1.66(reference value is 318 kV),but its duration is short.The maximum transient recovery voltage across AC filter/capacitor bank circuit breakers is less than 1 300 kV.The arrester’s absorption energy in the case of a bipolar BLOCK can be greatly reduced with the protection logic modified with respect to decreasing current characteristic,which was compared with the protection logic of direct load retard.It is favorable for the reduction of both,overvoltage and arrester’s absorption energy,to lower the force retard speed in the case of bipolar ESOF command.     

串联扼流圈对配电变压器操作过电压暂态衰减过程的影响（英文）

Distribution transformers operating in modern system grids or in industrial networks are subjected to many switching transients,which may occur due to routine operations,network reconfigurations or as reaction on protection signals.Depending on the network configuration and parameters,such events may lead to external overvoltages and result in additional stresses on the insulation system.This paper presents the influence of a series choke on damping of switching transients in distribution transformers.The impact of the choke is assessed by both amplitude and rise time reduction.The suppression of the transient rise time is shown for a test configuration involving distribution transformers connected to low loss cable lines and a medium voltage breaker.Such phenomena are especially typical for industrial networks where switching operations are very frequent.Both simulation and experiment results are given.Simulation results as well as measurement results confirmed that switching events can lead to high dU/dt and in consequence,can have adverse impacts on insulation system.Voltage escalation during switching event is strongly related with system conditions.The results obtained for presented mitigation method are promising and indicate significant dU/dt reduction as well as number of ignitions and voltage peak value.The protection of distribution transformers with a series choke is a new approach dedicated to environments prone to the occurrence of transients with high steepness.Experimental results show that the application of serial choke with suitable parameters realizes the reduction of dU/dt at the machines terminal from 24 kV/μs to 5 kV/μs,as well as the reduction of voltage peak value from 10 kV to 5 kV.The number of ignitions is also reduced.     

电缆外护套环流分布在线监测系统的研制(英文)

The value of metal sheath’s circulating current of cross-linked power cables is very small in ideal condition, but the value is not so small that the circulating current can’t be ignored because of various factors in actual running condition. The circulating current method can judge whether the multipoint earthing fault happens by monitoring the variety of metal sheath’s circulating current value. This article introduces an on-line monitoring system which uses the circulating current method to monitor the multipoint earthing fault of the metal sheath. In the hardware layer, we use distributed current sensors and microcontroller’s acquisition units to complete the signal acquisition and signal conditioning of the circulating current value. After the distributed acquisition and conditioning, the signals, through the RS485 bus, will be sent to the Ethernet Serial Device Server network system and then connected to the console cabinet. The computer of the console cabinet could read the circulating current value on-line by the Real Com Mode of the Ethernet Serial Device Server. This distributed on-line monitoring system has a simple structure, excellent real-time performance and high reliability proved by the practical operation.     

锦屏—苏南±800kV特高压直流输电工程直流滤波器的暂态额定计算(英文)

DC filter components and devices in converter stations of a high voltage DC transmission project may withstand a certain amount of transient overvoltage due to the impact of transient impulses.In order to protect them,suitable arresters should be equipped properly in the filters to limit the transient overvoltage to an acceptable level.By utilizing the method of DC filter simulation and transient calculation model,the paper studies the transient overvoltage in the DC filters of the Jinping-Sunan ultra high voltage direct current(UHVDC) transmission project under the most severe transient operation conditions.Three arresters are installed inside each filter,which consequently decide the insulation levels of the filter component: mainly capacitors,reactors and resistors.The lightning impulse insulation levels for the high voltage reactors of the two filters are 648 kV and 788 kV respectively,while they are 464 kV and 627 kV for the low voltage reactors,and 648 kV and 788 kV for the resistors.The insulation level for the high voltage capacitors is no more than 815 kV.The calculation results provide basis for choice of the DC filter components.     

高压下非均匀电场中局放机理的建模

Partial discharges in air in non-uniform electric field occur in surroundings made of high curvature elements.The equivalent electrode system,needle-plane refers both to external components of high voltage insulating systems and to micro sharpness in the internal structure of those systems.The ionization zone,accumulation of space charge and formation of corresponding current pulses depend on electrode configuration,voltage level,pressure,temperature and humidity of air.The assessment of pressure influence on discharge mechanism in non-homogenous electric field has been performed on the basis of empirical density distributions of discharge charges at different voltage levels,electrode distance,curvature of high voltage electrode and taking into account solid dielectric barrier in serial configuration.The measurement results obtained at variable voltage level yield the influence of electric field strength in the needle electrode zone.While increasing voltage,a deviation from normal distribution may be observed that reveals other forms of discharge.     

Electricity Price Forecasting Based on AOSVR and Outlier Detection

Electricity price is of the first consideration for all the participants in electric power market and its characteristics are related to both market mechanism and variation in the behaviors of market participants. It is necessary to build a real-time price forecasting model with adaptive capability; and because there are outliers in the price data, they should be detected and filtrated in training the forecasting model by regression method. In view of these points, this paper presents an electricity price forecasting method based on accurate on-line support vector regression (AOSVR) and outlier detection. Numerical testing results show that the method is effective in forecasting the electricity prices in electric power market.     

高压过电压的未屏频采样技术研究

高压电网过电压在线监测数据采集方法利用新型的套管末屏电压传感器捕捉系统一次电压,可实时监测电网内部过电压和大气过电压,精确、完整记录过电压的变化过程,监测数据可为电力系统的事故分析及采取相应的防范措施提供科学依据,该监测系统运用了变频采样技术。     

110kV变电站过电压在线监测系统及其波形分析

过电压是造成电网绝缘损害的主要原因之一,也是选择电气设备绝缘强度的决定性因素,电力系统过电压在线监测对分析过电压事故原因和改善系统绝缘配合具有重要的现实意义。在研制成功110kV过电压传感器以及高速变频采集系统的基础上,重庆110kV先锋过电压在线监测系统可自动捕获10、35、110kV电网中出现的外部和内部过电压。另外还介绍了该系统的结构、用于过电压信号采集的低阻尼阻容分压器和套管式分压器、变频采集系统及系统软件等关键模块。根据现场采集到的典型过电压波形样本,结合值班室记录,分析了雷电、操作及暂时等过电压的波形特点和产生原因,监测结果可为输电线路防雷、变电站过电压防护、电力系统规划和设计提供科学依据。     

CVT暂态过电压响应研究

当电力系统中存在雷击或操作过程时,其高频暂态过电压会以静电感应和电磁耦合的方式从高压系统传递到低压系统,会对二次系统的测量装置、保护装置以及二次设备本身和运行造成严重的影响.本文通过对比电容式电压互感器（CVT）暂态过电压响应特性的试验研究和仿真分析,对高频过电压在CVT中的传递特性作了一定的探讨和分析,并对响应试验和仿真过程遇到的问题作出了归纳总结,为过电压在线监测等工作提供了参考.     

电网过电压监测装置的研究与应用

介绍了一种能实时,高精度地自动监测与记录电网过电压装置,并从硬件、软件两方面介绍了暂态过电压监测与记录系统的相关要求与设计,通过现场过电压数据波形与参数分析表明,该暂态过电压监测与记录系统能对电网过电压进行高精度实时的在线数据采集,并记录过电压发展的整个过程.     

基于比值法的铁磁谐振过电压分类研究

在变电站实测过电压波形基础上,根据铁磁谐振过电压发生机理及波形特征,将小波变换良好的时频局部化特性和傅里叶变换良好的频域分析能力有机结合,提取了能够有效反映铁磁谐振过电压的特征参量,并提出利用比值法识别铁磁谐振过电压的方法。结果表明该理论基础直观,大量现场实测数据验证了该方法在识别铁磁谐振过电压时的有效性和可靠性。     

贵阳区域电网过电压在线监测研究

通过建立宽频带过电压分压取样系统和暂态过电压在线监测装置,开发了区域电网过电压在线监测系统,并将其应用于贵阳东部电网的两个变电站,实现了对变电站及所连接线路的过电压实时监测。监测数据表明,该系统既能准确快速捕捉、记录从工频过程到雷电冲击过程的过电压数据,又能满足节省存储空间的要求。将实测结果与仿真结果比较,验证了该系统的有效性。     

考虑波形起始点的特高压变电站雷电入侵过电压分析

变电站雷电入侵过电压是特高压输变电工程的重要课题。为研究工频电压对变电站雷电侵入波过电压的影响,考虑雷电入侵时刻工频电压的波形起始点对雷电入侵过电压的影响,以某1 000 kV特高压GIS变电站为例,采用电磁暂态仿真程序ATP/EMTP建模研究了不同波形起始点对应的雷电侵入波过电压,并根据波形起始点的分布概率,研究了雷电侵入波过电压的分布规律,提出以90°波形起始点为依据进行雷电侵入波过电压计算和绝缘配合的建议。     

晶闸管装置过压和过流问题的研讨

文章首先叙述晶闸管装置出现过电压的情况和相应的保护措施。过电压包括装置的交流侧与直流侧过电压,以及晶闸管换流过电压。保护措施有交流侧接入过电压吸收电路与加设接地屏蔽绕组,直流侧接入非线性电阻元件,晶闸管并联吸收元件与均压保护。然后介绍了晶闸管装置过电流的情况和相应的保护措施。过电流可以由过电压、短路以及导通角增大引起的,保护措施就是晶闸管串联快速熔断器,且保护措施在实际应用中起到了良好的效果。     

基于容性设备泄漏电流的电网电压分频测量方法分析

为优化电网过电压在线监测的测量技术,提出了一种基于测量容性设备泄漏电流的电网过电压的测量方法。该方法是使用2个不同磁导率的线圈分别获取容性设备泄漏电流中频率为30～3 000 Hz以及3kHz～1MHz的电流成分,经过积分滤波处理后将2路信号求和还原为线路电压。分析了泄漏电流与电压的传递函数,研究了电压传感器的工作原理及其影响因素。最终采用分频的方式实现了工频、操作冲击和雷电冲击过电压的测量。采用的电压传感器结构简单,与高压系统没有电气连接,具有很好的安全特性。工频、操作冲击和雷电冲击过电压试验结果表明设计的传感器具有很好的准确度和线性度,可以用于高压电网的电压测量。     

基于电容分压的配电网过电压在线监测

设计了一种基于阻容分压器的配电网内外过电压在线监测装置.该装置采用低阻尼电容分压器作为过电压获取设备,并对其设计方法和响应特性的影响因素进行了分析;通过有限元法对其进行误差分析表明该分压器具有良好的精度,能满足内外过电压监测需要.此外,通过PCI总线和数据双缓冲技术,能在高频下采样较长的数据和实现较短的采样间隔时间.通过现场实测数据表明,该装置能满足内外过电压监测的需要.