Single-phase earth fault current distribution between optical fiber composite overhead ground wire and ordinary ground wire in transmission system

It is important for the safety of transmission system to accurately calculate single-phase earth fault current distribution.Features of double sided elimination method were illustrated.Quantitative calculation of single-phase earth fault current distribution and case verification were accomplished by using the loop method.Influences of some factors,such as single-phase earth fault location and ground resistance of poles,on short-circuit current distribution were discussed.Results show that:1) results of the loop method conform to those of double sided elimination method;2) the fault location hardly influences macro-distribution of short-circuit current.However,current near fault location is evidently influenced;and 3) the short-circuit current distribution is not so sensitive to the ground resistance of poles.

Fault Line Selection Method Considering Grounding Fault Angle for Distribution Network

In the distribution network system with its neutral point grounding via arc suppression coil, when single-phase grounding fault occurred near zero-crossing point of the phase voltage, the inaccuracy of the line selection always existed in existing methods. According to the characteristics that transient current was different between the fault feeder and other faultless feeders, wavelet transformation was performed on data of the transient current within a power frequency cycle after the fault occurred. Based on different fault angles, wavelet energy in corresponding frequency band was chosen to compare. The result was that wavelet energy in fault feeder was the largest of all, and it was larger than sum of those in other faultless feeders, when the bus broke down, the disparity between each wavelet energy was not significant. Fault line could be selected out by the criterion above. The results of MATLAB/simulink simulation experiment indicated that this method had anti-interference capacity and was feasible.

近场地震动竖向与水平分量统计特性对比

为研究近场地震动竖向与水平分量特性,本文对PEER数据库中1202组近场强震的地震动进行统计分析,研究了竖向水平加速度峰值比PGAv/PGAh、反应谱之比Sav(T)/Sah(T)、竖向水平峰值到达时间的特性。讨论了PGAv/PGAh与断层距、场地条件、震源机制的关系,并采用对数正态分布拟合不同场地条件、不同震源机制的PGAv/PGAh分布;对比了不同断层距、不同场地条件Sav(T)/Sah(T)的变化规律;研究了近场强震水平竖向分量峰值加速度的大小和到达时间上的相关性,并对结构分析过程中竖向地震动的选择提出建议。结果表明:断层距、场地条件、震源机制都会影响近场地震动的竖向分量,断层距小、走滑断层、场地条件差都易产生较大的竖向地震动;断层距小、场地条件差时,地震动竖向分量高频成分越强,断层距大、场地条件好,竖向地震动低频成分越强;竖向分量峰值加速度的大小与到达时间和两正交水平分量峰值加速度的大小与到达时间的几何平均数有明显的线性关系。

超、特高压交流线路反时限零序过流后备保护的整定建议

针对国家电网“六统一”线路保护装置,提出了超、特高压交流线路反时限零序过流保护的整定原则。反时限零序过流保护在保证灵敏性方面并无困难,整定原则的核心问题是解决选择性和速动性的矛盾。根据该保护的原理和逻辑提出了转折电流的概念以及接地距离保护与反时限零序过流保护的配合原则;充分考虑配合时间定值和最小时间定值对保护动作特性的影响,综合超、特高压电网实际短路电流水平和接地距离保护的过渡电阻耐受能力,将反时限零序过流保护低电流区的选择性与接地距离保护高电流区的选择性进行结合,提升了对接地故障全域电流范围的选择性切除能力;提出了方向元件投退原则。通过对某省级电网进行算例分析,验证了整定原则的有效性,该整定原则已经在实际电网中进行了应用。

一起110 kV GIS开关合闸瞬间交直流窜电故障分析

交直流窜电是变电站直流系统中较为严重的接地故障,极有可能造成保护误动或拒动,严重影响供电可靠性。针对某实际运行的110 kV变电站交直流窜电故障,首先结合保护动作、故障录波情况给出了事故原因分析与故障排查过程;然后进一步结合二次原理图与现场接线情况提出了整改方案,并验证了整改后回路的安全性;最后给出了此类故障的预防措施与建议,可为防范交直流窜电引起保护误动、拒动提供参考。

Fault protection method of single-phase break for distribution network considering the influence of neutral grounding modes

With the rapid development of modern distribution network and the access of distributed generation,the network structure is becoming increasingly complex.Frequent single-phase break faults have seriously affected equipment and personal safety and stable operation of the power system.However,with the development and application of the composite neutral grounding modes,the protection of single-phase break fault is facing new challenges.This paper proposes a protection method of single-phase break fault for distribution network considering the influence of neutral grounding modes.The characteristics of neutral voltage and sequence current are analyzed under normal operation and single-phase break fault with different grounding modes.Following this,the protection criterion based on neutral voltage and sequence current variation is constructed.The protection method of singlephase break fault for distribution network is proposed,which is applicable for various neutral grounding modes.Theoretical analysis and simulation results show that the protection method is less affected by system asymmetry,fault location and load distribution.The method has higher sensitivity,reliability and adaptability.

Multiple Random Forests Based Intelligent Location of Single-phase Grounding Fault in Power Lines of DFIG-based Wind Farm

To address the problems of wind power abandonment and the stoppage of electricity transmission caused by a short circuit in a power line of a doubly-fed induction generator(DFIG) based wind farm, this paper proposes an intelligent location method for a single-phase grounding fault based on a multiple random forests(multi-RF) algorithm. First, the simulation model is built, and the fundamental amplitudes of the zerosequence currents are extracted by a fast Fourier transform(FFT) to construct the feature set. Then, the random forest classification algorithm is applied to establish the fault section locator. The model is resampled on the basis of the bootstrap method to generate multiple sample subsets, which are used to establish multiple classification and regression tree(CART) classifiers. The CART classifiers use the mean decrease in the node impurity as the feature importance,which is used to mine the relationship between features and fault sections. Subsequently, a fault section is identified by voting on the test results for each classifier. Finally, a multi-RF regression fault locator is built to output the predicted fault distance. Experimental results with PSCAD/EMTDC software show that the proposed method can overcome the shortcomings of a single RF and has the advantage of locating a short hybrid overhead/cable line with multiple branches. Compared with support vector machines(SVMs)and previously reported methods, the proposed method can meet the location accuracy and efficiency requirements of a DFIG-based wind farm better.

Protection of Zero-Sequence Power Variation in Mountain Wind Farm Collector Lines Based on Multi-Mode Grounding

The arc-suppression coil(ASC)in parallel low resistance(LR)multi-mode grounding is adopted in the mountain wind farm to cope with the phenomenon that is misoperation or refusal of zero-sequence protection in LR grounding wind farm.If the fault disappears before LR is put into the system,it is judged as an instantaneous fault;while the fault does not disappear after LR is put into the system,it is judged as a permanent fault;the single-phase grounding fault(SLG)protection criterion based on zerosequence power variation is proposed to identify the instantaneous-permanent fault.Firstly,the distribution characteristic of zero-sequence voltage(ZSV)and zero-sequence current(ZSC)are analyzed after SLGfault occurs in multi-mode grounding.Then,according to the characteristics that zero-sequence power variation of non-fault collector line is small,while the zero-sequence power variation of fault collector line can reflect the active power component of fault resistance,the protection criterion based on zero-sequence power variation is constructed.The theoretical analysis and simulation results show that the protection criterion can distinguish the property of fault only by using the single terminal information,which has high reliability.

GE控制系统(AC)接地保护原理与故障点快速诊断

为了快速判断和处理GE控制系统(AC)接地故障,分析了交流电动轮卡车接地保护电路的主要部件的作用及接地保护电路的工作原理,通过wPTU软件来对卡车实时运行数据进行数据分析,可以快速地判别接地故障的大概范围。结果表明:通过此处理方法可以大大地提高维修工作效率,避免了因盲目维修而造成的不必要损失。

Elman-Adaboost集成人工神经网络高压交流输电线路单相接地初始电压行波模量幅值比单端故障测距

针对现有单端行波故障测距方法对高阻接地故障不灵敏、反射波波头识别不准等问题,提出了一种Elman-Adaboost集成人工神经网络高压交流输电线路单相接地初始电压行波模量幅值比单端故障测距的方法。首先,基于行波衰减原理,通过推导高压交流输电线路故障距离与线路首端初始暂态电压行波线模分量与零模分量幅值比之间的计算公式,发现两者存在与过渡电阻无关的非线性关系;其次,利用Elman-Adaboost集成人工神经网络拟合初始暂态电压行波线模分量与零模分量小波能量比和故障距离之间的关系,构建集成人工神经网络故障定位模型,通过该模型可直接得到高压交流输电线路故障位置。实验结果表明,方法精度不受过渡电阻影响,测距精度较高。

一起750kV交流滤波器断路器合闸电阻故障案例分析

2022年2月16日,某换流站无功控制逻辑自动投入7624小组交流滤波器过程中,第二大组交流滤波器母线差动保护及7624交流滤波器差动速断保护A/B套动作,经现场检查故障原因为断路器内部合闸电阻击穿并最终发展为接地故障。首先,详细说明了合闸电阻原理及投入期间正常波形,结合故障录波,对此次故障原因进行分析定位。然后,根据故障断路器解体情况,对本次故障发展过程进行深入分析,进一步对分析结果进行验证。最后,针对带合闸电阻的交流滤波器断路器投切控制进行了PSCAD仿真,分析了详细投切过程,阐明了过程中电流等电气量变化特点,提出了根本处理措施及跟踪分析方法,为带合闸电阻的交流滤波器断路器故障机理研究及运行维护提供参考和借鉴。

Faulty Feeder Identification and Fault Area Localization in Resonant Grounding System Based on Wavelet Packet and Bayesian Classifier

Accurate fault area localization is a challenging problem in resonant grounding systems(RGSs).Accordingly,this paper proposes a novel two-stage localization method for single-phase earth faults in RGSs.Firstly,a faulty feeder identification algorithm based on a Bayesian classifier is proposed.Three characteristic parameters of the RGS(the energy ratio,impedance factor,and energy spectrum entropy)are calculated based on the zero-sequence current(ZSC)of each feeder using wavelet packet transformations.Then,the values of three parameters are sent to a pre-trained Bayesian classifier to recognize the exact fault mode.With this result,the faulty feeder can be finally identified.To find the exact fault area on the faulty feeder,a localization method based on the similarity comparison of dominant frequency-band waveforms is proposed in an RGS equipped with feeder terminal units(FTUs).The FTUs can provide the information on the ZSC at their locations.Through wavelet-packet transformation,ZSC dominant frequency-band waveforms can be obtained at all FTU points.Similarities of the waveforms of characteristics at all FTU points are calculated and compared.The neighboring FTU points with the maximum diversity are the faulty sections finally determined.The proposed method exhibits higher accuracy in both faulty feeder identification and fault area localization compared to the previous methods.Finally,the effectiveness of the proposed method is validated by comparing simulation and experimental results.

水轮发电机转子一点接地故障分析与处理

综合多起水轮发电机转子一点接地故障排查经验,提出了总体上按励磁测量保护回路、励磁直流回路、励磁交流回路对转子一点接地故障的回路检查方法,规范了故障排查流程,提高了排查效率。同时针对水轮发电机空载态报转子一点接地故障且故障点50%,从发生原理进行深入剖析、系统总结,采取相应措施为后续有效处理类似故障保障。

交流电源系统绝缘故障模拟与智能选线技术研究

针对站用交流电源的绝缘接地故障精确辨识较难的问题,研究了基于电弧真型嵌入的交流绝缘接地故障模拟方法,建立了交流电源单相接地故障仿真模型,提出了基于小波分解相时频特征的交流绝缘故障智慧感知辨识方法。在此基础上研制出智慧型交流电源剩余电流监测系统,通过在河北省南部电网某智慧变电站示范应用,验证了系统绝缘故障感知与选线辨识方法的有效性,为智慧变电站交流电源绝缘接地故障监测提供了有效的解决方案。

柔性直流配电网接地方式对故障特性的影响分析

采用理论分析和仿真验证相结合的方法研究了柔性直流配电系统接地方式对其故障特性的影响。首先,介绍了柔性直流配电网的系统架构,确定了直流侧电容的接地方式;其次,分析了直流不平衡电压恢复的理论依据;接着讨论了联接变压器的接地方式对换流器交流侧不同位置单相故障的影响;随后分析了联接变压器接地方式对直流侧单极接地故障的影响,并讨论了不同过渡电阻情况下的故障特性。与电压源型直流输电技术(voltage-sourced converter high-voltage direct current,VSC-HVDC)分析故障特性方法不同,为提高配网供电可靠性,在分析直流侧单极接地故障时,考虑了绝缘栅双极型晶体管(insulated gate bipolar transistor,IGBT)不闭锁的情况。最后讨论了在实际应用中实现IGBT运行在不闭锁状态下的方法。分析结果表明,接地方式对系统的故障过程和故障恢复过程有显著影响。分析方法和结论为柔性直流配网的接地方式选取、保护方案配置提供了参考。

配电网单相接地故障定位技术实验研究

配电网中单相接地故障发生概率最大,传统的故障定位方法不能有效解决配电网多分支、长线路、高电阻等故障定位难题。研究发现,直流定位法不受分支数量、过渡电阻和线路长度的影响,能够较好地解决配电网定位难题。通过仿真和现场实验证实了直流定位法的可行性;在直流法的基础上,为简化定位操作,提出60Hz交流定位法,该方法可以地面检测,大大缩短定位时间。实验证明,直流法和交流法结合的综合定位法是配电网故障定位的可行方法。

中低压直流配电系统的主动保护研究

分布式发电和储能的大量接入、直流负荷的快速增长、电力电子技术的迅速发展,使得直流配电越来越受关注。直流配电系统将会成为未来配电技术的一个重要组成部分。但直流配电保护是直流配电系统快速发展的一个关键问题,亟需深入研究。针对中低压直流配电网中常见的短路、接地、环网、交直流混接、绝缘下降等典型故障类型,该文分析了这些故障的特点和发展过程,并提出了一种基于电力电子技术的主动保护方案,即将直流保护与电力电子变换器有效集成,基于变换器的拓扑结构和运行机理,保护动作逻辑与器件控制逻辑协调配合,实现快速保护和故障自然隔离。该文阐述了直流主动保护的应用场景,分析了主动保护各功能的实现原理和方法,论述了直流配电系统的短路主动保护和接地主动保护,以及直流环网、交直流混接故障的出现机理和基于主动保护的解决方法。最后通过试验进行验证,结果表明,主动保护能够有效可以实现故障的快速切断和准确隔离,从而保障系统的稳定。

互联系统电磁暂态交互作用研究,Ⅲ:交流侧对直流侧的影响

我国电力系统正在形成交直流互联的巨大网络,交直流系统操作及故障、直流换流阀的动作、负荷变化产生的ns、μs、ms级的电磁暂态将在直流系统和交流系统中交互作用,交直流互联系统的电磁暂态交互作用可对交流系统和直流系统构成危害,特别是导致直流系统的换相失败及闭锁等严重事故。鉴于此,在已有的能比较准确反映交直流互联系统关键元件电磁暂态特征的宽频特性模型基础上,在PSCAD/EMTDC平台上建立计算模型,揭示交流系统对直流侧的电磁暂态传递机理及影响规律。结果表明,交流电网对直流系统的电磁暂态影响较严重,换流站330 kV交流母线的出线发生三相短路故障时,直流极线对地、换流阀两端的过电压达到了1000 kV,超过了绝缘保护水平的设计值。该研究为分析交、直流互联系统电磁暂态交互作用打下了基础。

互联系统电磁暂态交互作用研究,Ⅳ:直流侧对交流侧的影响

我国电力系统正在形成交直流互联的巨大网络,交直流系统操作及故障、直流换流阀的动作、负荷变化产生的ns、μs、ms级的电磁暂态将在直流系统和交流系统中交互作用,交直流互联系统的电磁暂态交互作用可对交流系统和直流系统构成危害,特别是导致直流系统的换相失败及闭锁等严重事故。鉴于此,在已有的能比较准确反映交直流互联系统的关键元件电磁暂态特征的宽频特性模型的基础上,在PSCAD/EMTDC平台上建立计算模型,基于交流侧冬小、冬大、夏小、夏大4种运行方式,分别对应直流系统的3种运行方式(双极大地回路、单极大地回路、单极金属回线),进行各种故障时的电磁暂态计算,为防止交直流互联系统的电磁暂态交互影响提供电磁兼容设计及测试参数。结果表明,直流系统对交流系统的电磁暂态影响较小,发生各类故障时在交流侧750、330kV线路及母线产生的过电压幅值均在规程中规定的允许范围内。该研究为分析交、直流互联系统的电磁暂态交互作用打下了基础。