Light rail transit DC traction power system surge overvoltageprotection

At present, there are no industry standards or recommended guidelines for the application of DC surge arresters. It appears that such devices are applied based upon a rule of thumb without the benefit of analyzing characteristics, wave shape, and energy content of the expected overvoltage surges against the capabilities of the surge arrester. AC surge arresters are rerated for DC application. A difficulty arises due to a lack of clear published application literature on DC surge arresters, as well as lack of measured data on DC power system transient surges. This leads to the application of surge protective devices, which may be inappropriate. This paper describes the application of DC surge arresters to a typical light rail transit traction power system, and it makes a recommendation for the need of a standard on DC surge arresters test requirements and application guidelines     

采用架空线的MMC-HVDC单极接地过电压分析

采用架空线传输方式的远距离柔性直流输电线路,极易发生输电线路单极接地故障,必须采用多种方式保护设备应对暂态过电压。文中研究了采用半桥子模块的柔性直流输电系统在直流侧接地故障下的暂态过电压特性,并分析了系统结构、设备参数和故障特征等对过电压的影响,同时分析了换流器闭锁、避雷器和直流断路器对抑制直流侧故障过电压的效果。研究表明系统设备参数对过电压峰值影响最大,当保护措施启动时,系统保护装置会成为主要的过电压影响因素。最后,提出了应对直流侧故障过电压的避雷器优化配置方案。     

Impact of shunt capacitor banks on substation surge environment andsurge arrester applications

The introduction of high voltage shunt capacitor banks on a power system can result in a number of overvoltage problems that tend to be associated with capacitor switching. The paper describes how proper application of surge arresters near a shunt capacitor bank requires careful analysis of the power system, the switching devices and their arrangements, the insulation level of nearby equipment, the type of grounding and the arrester energy dissipation duty     

Surge protection of high voltage shunt capacitor banks on AC powersystems survey results and application considerations

A survey of power utilities has been carried out to obtain data on high-voltage shunt capacitor bank surge protection practices which presently exist. The questionnaire sought answers to questions relating to voltage rating, size of bank, number of banks, installation practices, switching arrangements, and the application of surge arresters for overvoltage protection. A summary of the results of the survey is presented along with some general comments and conclusions on the findings. The high rate of return on the survey indicates the widespread interest of utilities in surge arrester protection of high voltage shunt capacitor banks. It does not appear to be common practice among electric utilities to apply surge arresters to shunt capacitor banks for overvoltage protection. Where surge arresters are applied, they are often used to protect other equipment, such as transformers and circuit breakers, against overvoltages during capacitor switching     

Coordination of surge arresters with medium-voltagecurrent-limiting fuses

Current-limiting fuses (CLFs) are commonly used for unit substation primary protection. Simultaneously, surge arresters are also provided on the primary side of the transformers, more so for the dry-type transformers. The arc voltages generated by CLFs will store energy in the inductive elements of a distribution system. This stored energy divides between the CLF and surge arrester, and the surge arrester may operate. This paper outlines a procedure to calculate the energy diverted to the surge arresters and shows that, in some cases, surge arresters may fail on operation of the CLFs. Guidelines are developed for selection and application of the surge arresters at 13.8-, 4.16-, and 2.4-kV voltage levels     

Simulation of Lightning Overvoltage Distribution on Stator Windings of Wind Turbine GeneratorsEI北大核心CSCD

This paper analyzes lightning surge on the stator windings of wind turbine generators. The path of lightning in the wind turbines was analyzed. An equivalent circuit model for megawatt direct-driven wi...     

配电线路避雷器雷电感应过电压防护研究

应用ATP-EMTP对配网架空线路雷电感应过电压下,线路避雷器的保护效果进行了仿真计算研究。仿真计算结果表明,安装线路避雷器可以对配网架空线路雷电感应过电压进行防护,其保护效果与避雷器的配置方式及线路杆塔接地电阻有关,降低杆塔接地电阻可以减小线路避雷器的安装密度。     

Impact of surge arrester number and placement on reliability and lightning overvoltage level in high voltage substations

Surge arresters are the most critical equipment for protecting high voltage substations. They play an important role in substations for limiting switching and lightning surges and diverting these surges to ground. On the other hand, surge arrester number and placement for high voltage substations can be determined based on some evaluations in the designing process of substations. Surge arresters can be placed on the both ends of substations, transformers, circuit breakers, reactors, capacitors and also high long bus-bars and etc. Therefore, failure of arresters during overvoltage can put substations in risk condition. Moreover, surge arresters may be inclined to be short circuit during normal operation condition due to ageing process and/or improper quality. This paper attempts to assess reliability of three common substation configurations namely: (1) one breaker and a half; (2) double-bus double-breaker; and (3) ring bus-bar in different placement of surge arresters. At first, maximum voltages on equipment are calculated in different lightning stroke locations through simulation in EMTP-RV. Studies without surge arrester and the presence of surge arrester in different locations are analyzed and compared. Then surge arrester’s placement impacts on the substations reliability indices are calculated in normal operating condition and overvoltage condition by minimal cut set method and simulation results. Analytical studies reveal that surge arrester can increase substations reliability. But for low annual number of lightning stroke, substation reliability may decrease. Also increasing surge arrester number more than substation need reduces reliability.     

An imitation model of a power-supply system of oxygen-converter manufacturing to analyze switching overvoltage

This paper considers switching overvoltage that occurs in the power-supply system of oxygen-converter manufacturing when a circuit vacuum breaker is triggered. The particular features of such systems are analyzed, and a typical power supply scheme is considered. It is noted that overvoltage manifesting a highfrequency behavior can be produced as a result of the peculiarities of arc interruption in vacuum (current chopping, voltage escalation, and arc reignition). Such overvoltage negatively affects electric motors with insulation that have the lowest margin of dielectric strength. Conventional means of overvoltage protection—such as conventional spark-gapped arresters, metal-oxide surge arresters, and spark gaps—are inefficient at high-frequency overvoltage because of a sharp increase in their voltage-second characteristics at low pulse duration. This paper suggests using RC circuits as protection from such overvoltage. Their application is accompanied by quite exact simulations since an incorrect choice of their parameters can worsen the commutation process. The main particular features of construction of a simulation model to study switching overvoltage and to analyze protection functioning are considered. A depiction of the simulation model and results of simulations are also presented. The validity of the suggested model is determined.     

天生桥—广州直流工程控制保护系统改造后的过电压分析

基于改造后的天生桥—广州±500 kV高压直流输电工程,计算分析了在换流变Y/Y线圈阀侧单相接地、交流相间操作冲击、逆变侧失交流电源和逆变侧闭锁而旁通对未解锁4种典型故障工况下的系统过电压,确保在改造后的控制保护系统下,系统各点过电压及避雷器能耗限制在合理范围内,各电气设备能安全运行。分析结果表明:换流变Y/Y线圈阀侧单相接地故障将在中性母线上产生较高过电压,中性母线避雷器能耗较大;交流相间操作冲击会在阀两端产生较大过电压,阀避雷器动作;逆变侧失交流电源会在逆变站交流母线产生较高过电压,交流母线避雷器动作。逆变侧闭锁而旁通对未解锁会在逆变侧直流极线产生很高的过电压,直流极线避雷器能耗较大。上述4种故障工况下,各避雷器能耗均未超过设计通流容量,避雷器能安全稳定运行。     

Temporary overvoltage capability of surge arresters for 1000 kV power systems

Insulation level (LIWV 2250 kV) of 1000 kV gas insulated switchgear will be adopted by installing high performance 1000 kV surge arresters. But when temporary overvoltage (TOV) is generated in power systems at line faults and load rejection including Ferranti effects, high performance surge arresters flow discharge current according to the value of TOV. Therefore, it is important to check TOV discharge capability of surge arresters. This paper describes the screening of zinc oxide elements using thermography (thermal uniformity factor) obtained by an infrared radiation camera, with discharge capability of surge arresters for 1000 kV power system.     

Evaluation of line surge arrester failure rate for multipulse lightning stresses

This paper develops a method to analyze energy stresses on transmission line surge arresters. The approach computes the failure rate of arresters due to energy stresses, convolving the density probabilities of first and subsequent pulses. Multipulse stroke effects are considered in a 138 kV line case study, typical of single circuit lines, located in regions with high densities of ground flashes, in SE Brazil. The proposed method provides an improved insight into energy stress evaluation for selection of line surge arresters.     

Criteria for phase-to-phase clearances of HV substations

To facilitate uprating of HV substations, a reexamination is made of line-to-line insulation design criteria. The basis for existing practices and the principles of line-to-line lightning surge overvoltage stresses are reviewed. Results of a digital study for a realistic substation are presented. The conclusions show that the line-to-line stresses, as limited by surge arresters, are substantially higher than line-to-ground stresses. This represents increased requirements as compared to existing standards. However, due to the low protective levels of modern arresters, substantial reduction of line-to-line clearances is still feasible     

考虑微观特性的ZnO压敏电阻计算模拟模型

电力设备的绝缘水平建立在避雷器的过电压保护水平基础之上。ZnO压敏电阻具有优良的非线性电压-电流特性和浪涌能量吸收能力,被广泛用作电力系统避雷器的核心元件。ZnO压敏电阻的电气特性由其复杂的微结构和晶界特性决定。该文以Voronoi网络模型为基础,建立ZnO压敏电阻的微观结构模型。采用考虑晶间旁路效应的晶界分区模型,建立求解氧化锌压敏电阻宏观电气性能的大规模非线性电阻网络方程。针对难以采用常规牛顿迭代方法求解的问题,提出基于分段线性化和差分重构的快速求解优化算法,计算结果误差指标在10-3数量级以下。采用模型计算得到了尖晶石含量、晶粒尺寸不均匀度以及气孔率等微观结构参数对ZnO压敏电阻宏观电气性能的影响规律。     

Analytical Method for Coordination of Surge Arresters with Current-Limiting Fuses

Many industrial power systems have lightning exposure, requiring surge (lightning) arresters; dry-type transformers, requiring low protective levels; and high available fault currents, making the use of current-limiting fuses desirable. On occasion, current-limiting fuse arc voltages have resulted in destruction of low characteristic arresters. A traditional guideline has been to select arrester types and ratings that will not spark over on current limiting fuse maximum arc voltage?an approach that may not be entirely viable for industrial systems. A step-by-step analytical approach to the selection of surge arresters for use with current-limiting fuses is presented. The method presumes arrester sparkover and is based on determination of system energy, fuse arc voltage and arrester back voltage characteristics, and arrester energy capability.     

冲击发电机系统的过电压防护研究

为了设计冲击发电机系统的金属氧化物避雷器MOA保护系统,计算了开断时间极快,产生过电压较断路器操作过电压高的限流熔断器过电压;采用有限元方法分析限流熔断器熔体的熔化、汽化过程,得到熔体的热电耦合模型,该模型可求出熔断器开断过程的电阻-时间特性;在EMTP/ATP中建立熔断器开断试验系统模型,并分析接入不同类型MOA时,发电机端、熔断器端的过电压幅值;建立MOA的有限元模型,研究MOA的热特性和使用寿命。在冲击发电机系统中进行的不同型号限流熔断器开断试验验证了计算结果,该MOA保护方案能有效的保护发电机。     

配电网架空线路感应雷过电压产生机理与防护

对配电网架空线路感应雷过电压产生机理进行了详细的探讨,提出静电感应分量是配电网线路感应雷过电压的主要构成部分。通过对架空线路雷击静电感应过电压模型的求解,给出了感应雷过电压的计算方法。在配电网输电系统中采用以下措施——架设避雷线;安装避雷器;减小工频电弧建弧率;提高线路耐雷水平,可以有效地防护配电网架空线路感应雷过电压,保证系统安全、经济运行。     

Development of polymeric surge ZnO arresters for 500-kV compact transmission line

The 500-kV polymeric ZnO surge arresters for compact transmission line against lightning overvoltage were developed and have been put into operation, which consists of arrester unit and series gap. The design of the arrester unit, including structure design, selection of ZnO varistor, parameter determination, polymeric housing design, and mechanical structure design was discussed. The design of the series gap and the determination of the series gap length were presented. The calculated results state the line surge arrester can highly improve the lightning withstand level of the compact transmission line, and the line surge arrester can withstand the effects of lightning.     

取消750 kV断路器合闸电阻的可行性研究

取消750 kV线路断路器合闸电阻可节省费用,提高断路器运行可靠性。笔者以即将建设的兰州东-银川东750 kV输电线路工程为背景,结合国外对取消合闸电阻的研究,利用电磁暂态计算程序(ATP/EMTP)计算装设1组避雷器和断路器合闸电阻时,线路三相合空线、单相自动重合闸统计操作过电压水平。计算表明,在首末端装设1组避雷器时,三相合空线、单相自动重合闸统计操作过电压最大值分别为2.38 p.u.和2.57 p.u.,在线路线路长度较短时,两端装设避雷器的方法可以将上述两种统计操作过电压抑制到1.80 p.u.以下,可见在线路较短时取消合闸电阻成为可能。     

Methods for analyzing the performance of gapless metal oxide surgearresters

The development and use of practical methods for analyzing the performance of gapless metal oxide surge arresters under various surge and power frequency overvoltage conditions is described. Using these methods, the thermal requirements of ANSI and IEC standards are examined in detail. The results, showing large differences between the two standards, indicate the need for further harmonization of standards. Recommendations are made to bring ANSI and IEC standards to a closer agreement