Harmonic behavior during arcing faults on power distribution feeders

The waveforms of normal and arcing fault currents on power distribution feeders are investigated and compared in terms of the percentage amplitude with respect to the amplitude of the normal fundamental. The purpose of the study is to find better parameters to indicate arcing faults. The effect of capacitor banks on distribution feeder harmonics is discussed briefly.     

Lightning-caused distribution circuit breaker operations

As a part of EPRI Research Project 2542-1, Characteristics of Lightning Surges on Distribution Lines, a coincident lightning events detector (CLED) was developed, tested, and installed in a test area on the Florida Power Company distribution system in St. Petersburg, Florida. The CLED provided the data to determine the number of lightning-caused circuit breaker operations for the first time. During the 3-year recording period, a total of 546 faults causing circuit breaker operations occurred on the seven circuits in the test area. Of these faults, 415 (or 76%) were temporary faults. A lightning strike was coincident with 42% of the temporary faults. Improper operation of line fuses was traced to the absence of lightning arresters at line fuse locations     

Field tests of a circuit breaker synchronous control

A circuit breaker synchronous control interface which controls the point-on-wave at which shunt reactor circuit breakers open or close has been developed and tested on Hydro-Quebec's 735-kV power system. It takes into account the influence of outdoor temperature on the breaker closing and opening times. It is also equipped with a reignition and a high-inrush-current detection system. Opening tests at different preset arcing times were conducted and the arcing time range where there are no re-ignitions in air-blast breakers was established. The tests showed that the interface is a valuable device for the elimination of re-ignitions associated with the interruption of small inductive currents. Closing tests have shown that the interface is also useful for the limitation of high inrush currents by selecting an appropriate point-on-wave for circuit breaker closing     

畸变电压下单相电路谐波和无功电流综合检测方法

在现有单相电路基波电流分离法基础上,分析了锁相环相位检测误差和畸变电压对谐波和无功电流检测的影响,得出由锁相环及畸变电压引起的相位检测误差不影响谐波电流的检测,但对谐波和无功电流的综合检测以及直流侧电压调整有影响的结论.提出了一种谐波和无功电流综合检测新方法,采用无锁相环、提取功率角的方式,实现了畸变电压下单相电路谐波和无功电流的综合检测.仿真结果验证了该检测方法应用于有源电力滤波器中的有效性.     

Transient response of a ferroresonant circuit

The transient response of a partical ferroresonant circuit with quintic nonlinearity has been obtained. A suitable closed loop block digram for this circuit is used to allow an iterative approximation technique to be used for the determination of the transient response due to the sudden application of a sinusoidal voltage. The effect of the variation of the amplitude and the angle of the applied voltage and of the various circuit parameters on the voltage across and the current through the nonlinear inductor of the circuit has been investigated.     

基于RTDS分布式光伏接入配电网的谐波分析

为了更好地研究光伏发电中电力电子装置对配电网谐波的影响,建立了基于实时数字仿真仪(RTDS)的配电网模型。针对几种典型接入方式的情况下,仿真计算三相逆变器对配电网谐波的影响。分析了光伏接入配电网上不同节点,光伏发电不同的出力量均对配电网谐波造成不同程度的影响。实验表明,光伏并网与大电网间的公共连接点之间的阻抗对谐波影响很大。     

无人值守配电线路保护系统的研究

介绍了一种10kV配电线路电流保护原理，保护采用80196单片机及VFC技术，能实现速断，定时限、反时限过流保护及自动重合闸功能，并配有LCD显示及远动接口，适于无人值守变电站的需要。     

基于Wigner-Ville分布的电力电子电路故障诊断技术

提出了一种基于Wigner-Ville分布的电力电子电路故障诊断方法,首先建立各种类型故障信号的Wigner-Ville模时频矩阵,然后计算故障信号Wigner-Ville模时频矩阵与标准模时频矩阵的相似度,以相似度最大为判别依据实现故障的诊断。三相桥式可控整流电路晶闸管故障诊断仿真结果表明该方法能准确对电力电子电路故障进行类型的识别和故障元的定位,对噪声具有鲁棒性,且算法简单,在解决电力电子电路故障问题上有着很好的工程实用价值。     

短路故障下接地网电位分布的讨论

对一个实际的变电站地网在短路故障下的电位分布进行了讨论。通过对短路故障下地网中的电位分布和地表面的电位分布在各种情况下的分析计算得到了一些可应用于工程实际中的结论 ,有限元法作为一种有力的工程分析方法可应用于短路故障下地网电位分布的研究     

变配电站交流操作二次电路设计有关问题探讨

变配电站交流操作具有二次电路简单与投资少等特点,中小型变配电站采用较多,常规继电保护交流操作二次电路简单可靠。微机继电保护用于变配电站交流操作时,在操作电源与事故跳闸回路设计上出现了一些新的问题。文中提出了一个微机保护交流操作事故跳闸回路设计方案,并对交流操作常规继电保护与微机继电保护的应用进行了分析,提出了在采用交流操作微机继电保护二次电路设计中应注意的几个问题。     

Long term accelerated aging tests on distribution cables under wetconditions

Two accelerated aging test procedures are proposed for use on solid dielectric extruded distribution cables under wet conditions. One test method is a fixed time duration test in which the degree of cable specimen aging is assessed in terms of breakdown tests, while the other test method is a time to breakdown test in which the cable specimens are voltage stressed until failure ensues     

Harmonic propagation on an electric distribution system: fieldmeasurements compared with computer simulation

Increasing use of power electronic loads on distribution feeders together with greater use of power factor correction capacitors on the distribution system can result in poor operating conditions in the form of high harmonic levels propagating through a distribution system. HARMFLO (Harmonic Power Flow Study Program) was developed by EPRI (Electric Power Research Institute) for use in the analysis of harmonics on a power system. However, for a typical analysis of a distribution system, data for some of the parameters required by HARMFLO are not available. Furthermore, exact load information is usually not available. Harmonic levels determined from field tests on a distribution system are compared to results of HARMFLO simulations to determine if this analysis tool can provide useful results despite the lack of exact information for load modeling and other system parameters     

东莞配电网谐波测量及其统计分析

对东莞市配电网的谐波问题进行了全面的普查,对东莞市8个镇,131个企业,247个配变,采用了便携式电能质量分析仪和在线长期监测相结合的方式,进行了实地监测.对监测数据进行统计分析后,得出了东莞配电网的谐波污染现状.结果表明,东莞配电网的谐波污染严重,超过33%的监测点的谐波电流含量超过10%,急需进行谐波治理.     

新型厂矿企业配电网谐波抑制和无功补偿方案

针对电解企业配电网因电解整流装置产生的高次谐波电流含量大、功率因数低的现状,提出一种新型的谐波治理、功率因数校正综合补偿方案。在该方案中,补偿系统由无源滤波器和有源滤波器混合构成。由整流装置产生的主要特征谐波电流由无源滤波器滤除。无源滤波器在抑制谐波的同时还可以补偿无功功率,以提高功率因数。有源部分采用注入式电路,用来抑制无源支路跟电网等效电感产生的谐振现象以及改善无源滤波器的滤波性能。对该混合补偿系统的稳态补偿性能、抑制谐波谐振性能进行了详细分析,并对补偿方案进行了数字仿真。理论分析和仿真结果证明了该综合补偿系统的有效性和可行性。     

The application of current limiting to distribution circuit protection

Many electric utility systems are reaching the point where available short-circuit currents, during severe faults, exceed the interrupting capability of available circuit interrupters of conventional types such as circuit breakers, distribution-circuit reclosers, and expulsion fuses. The needs are being met by the use of current-limiting fuses to protect individual distribution transformers or, sometimes, groups of distribution transformers, but there are difficult problems of coordination. The current-limiting fuses are not inherently capable of covering the full range of short-circuit currents, so that they must be used in addition to, or in combination with, interrupters of other types. This paper studies these problems in depth and makes recommendations for even wider use of current-limiting fuses to achieve more effective protection of the entire distribution system, including protection of distribution feeders at the substation. This approach also provides effective preventive measures to inhibit disruptive transformer failures which have become a severe problem with increasing short-circuit-current capability.     

A rapid activating device for synthetic tests of high-voltage AC circuit breakers

Characteristics of a rapid activating device intended for connecting a current source to a tested circuit breaker during synthetic tests of the making capacity are presented. Test results obtained by electric measurements and by means of rapid photo diagnostic devices are considered. The activating device based on an original self-activating rapid discharge gap fully complies with the requirements of IEC standards.     

支柱绝缘子对交流滤波器断路器电场分布的影响研究

交流滤波器断路器是特高压直流输电系统交流滤波器场的重要组成部分,是系统无功功率变化时保证交流滤波器可靠频繁投切的重要电气设备.近年来,±800kV换流站内屡次出现交流滤波器断路器在投切过程中发生击穿及爆裂的现象,严重威胁着直流输电系统的安全稳定运行.为分析其原因,本文基于PSCAD/EMTDC搭建某±800kV直流输电...     

Comparison of waveshape quality of artificial lines used forshort-line fault breaking tests on HV circuit breakers

The authors present a comparison of the waveshape quality of six different artificial-line circuits used to produce the high rate-of-rise of recovery voltage specified by ANSI and IEC standards. For a purely capacitive and inductive pi-section circuit, it is shown that even eight pi sections do not meet the requirements. With the addition of a resistance in the first branch, this circuit design produces adequate solutions but requires a large number of components. The analysis reveals that the KEMA circuit easily meets the requirements for the rated peak factor of 1.6 but for the 1.8 peak factor a compensation would be required for the initial part of the wave. The simplest circuit comprising only three (RLC) components meets the specifications with a high voltage-peak overstress factor of 1.3     

孤岛微电网中制氢负荷谐波功率分配策略

制氢与微电网相结合是实现新能源高效消纳的重要途经之一。实际微电网的负荷优先级和电压质量要求存在差异,而制氢负荷接入会引入谐波功率,通过互联变换器(ILC)与高优先级直流子网相连,会出现直流母线多倍频脉动,其本质是谐波功率分配问题。目前已有功率分配策略大多致力于均分,忽略了高优先级子网的电压质量需求。为此,建立优先驱动的ILC功率协调控制模型,优化目标是使子网的总直流电压/交流频率偏差最小;建立制氢负荷模型,推导得到谐波视在功率的简化公式;基于谐波功率、子网优先级系数和谐波阻抗重塑理论,提出谐波功率在ILC和交流子网之间的自适应控制策略。通过硬件在环实验验证了所提策略的有效性。     

消防设备配电回路主设备的选择

根据有关设计规范,结合目前产品情况,讨论了由传统分立元器件组成的消防设备的配电回路主要设备选择应注意的问题。