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.

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.

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.

基于深度学习的一二次融合装备全场景故障研究

提出了基于深度学习的一二次融合装备全场景故障分析方法。针对低压配电网故障场景的类型和方式进行了说明,分析了影响配电网故障仿真的影响因素。针对低压配电网单相接地故障模型进行了说明,建立了小电阻接地系统模型、消弧线圈接地系统模型,分析二者在模拟故障时的影响因素。基于深度学习技术提出了卷积神经网络的故障场景诊断方式,结合一二次设备融合装置的功能特点进行了流程分析。针对仿真分析验证了所提出故障场景模拟在数据准确率以及训练数据结果方面的有效性。

发电厂电气二次设备接地故障的处理对策分析

阐述发电厂电气二次设备的接地故障类型,探讨接地故障预防处理对策,包括互感器二次侧接地故障、直流系统接地故障、电磁干扰的预防处理对策。

基于小波分析和卷积神经网络的互感器二次多点接地故障智能检测

为了准确检测互感器二次多点接地故障,提出基于小波分析和卷积神经网络的互感器二次多点接地故障智能检测方法。采用基于小波阈值滤波的互感器信号去噪方法,去除互感器信号噪声;通过基于小波分析的互感器信号特征提取方法,提取去噪后互感器信号的有效特征向量;使用流行学习方法,实现互感器有效信号特征非线性降维;把降维后信号特征作为基于卷积神经网络的二次多点接地故障智能检测方法的输入样本,使用检测合格的卷积神经网络,作为互感器二次多点接地信号特征分类器,实现互感器二次多点接地故障智能检测。实验结果显示,此方法检测结果与实际互感器运行情况相符,检测结果准确。

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.

Fault Feeder Identification in Non-effectively Grounded Distribution Network with Secondary Earth Fault

Secondary earth faults occur frequently in power distribution networks under harsh weather conditions.Owing to its characteristics,a secondary earth fault is typically hidden within the transient of the first fault.Therefore,most researchers tend to focus on a feeder with single fault while disregarding secondary faults.This paper presents a fault feeder identification method that considers secondary earth faults in a non-effectively grounded distribution network.First,the wavelet singular entropy method is used to detect a secondary fault event.This method can identify the moment at which a secondary fault occurs.The zero-sequence current data can be categorized into two fault stages.The first and second fault stages correspond to the first and secondary faults,respectively.Subsequently,a similarity matrix containing the time-frequency transient information of the zero-sequence current at the two fault stages is defined to identify the fault feeders.Finally,to confirm the effectiveness and reliability of the proposed method,we conduct simulation experiments and an adaptability analysis based on an electromagnetic transient program.

分布式等电位接地网与变电站主接地网连接方式

变电站中二次设备集中区域如主控室、保护小室内均安装有等电位接地网,等电位接地网与主接地网的连接对二次设备安全有重要意义,目前相关规范的要求在关键点上往往论述的比较含混。因此从等电位接地网的作用入手,通过数值计算,分析了在工频和雷击故障下,分布式的等电位接地网与主接地网连接方式对二次电缆电压、电流的影响,并综合考虑了二次等电位接地网的主要功能,提出了等电位接地网与主接地网的连接方式和限流措施。研究表明:每个等电位接地网采用单点与主接地网连接的方式,相比每个等电位接地网多点与主接地网连接的方式,能够有效降低二次电缆上承受的电压;增设排流线可以显著降低二次电缆承载的电压,降低电缆屏蔽层内流过的电流;采用全站等电位接地网与主接地网仅一点接地的做法虽然可以使二次接地网等电位,但会导致等电位接地网远端与主接地网之间产生较大电位差,造成设备绝缘击穿、接触电位差过大等问题。

不受电压互感器二次回路两点接地影响的零序方向元件

电压互感器二次回路出现两点接地情况(简称"两点接地")下再发生单相故障,若引起零序方向元件误判,零序电压和故障相电压之间相位差较小,而正常情况下故障零序电压与故障相电压之间的相位差一般较大,文中据此提出了电压互感器二次回路两点接地的实时识别方法。根据两点接地再故障时附加电压分量对各相电压影响的特点,提出用健全相相间电压替代零序电压的零序方向算法。将两点接地的实时识别和零序方向新算法结合形成一种不受两点接地影响的零序方向元件,可有效防止纵联零序保护不正确动作。现场事故录波数据的分析验证了该方法的有效性。

500kV上承Ⅲ线带串补工程人工单相瞬时接地故障试验分析

利用自主研发的人工接地试验装置,国网冀北电科院(华北电科院)在上承III线带串补工程系统调试过程进行了上承III线B相人工瞬时接地故障试验。介绍了人工接地试验装置的工作原理、人工接地试验方法和试验结果,并对人工接地试验时线路及串补装置的保护动作行为以及潜供电流等进行了分析。在人工接地试验过程中串补装置动作正确动作并重投成功,两侧线路断路器故障相正确动作并单相重合成功。

同沉积断层研究综述

同沉积断层是沉积盆地最基本的地质构造形式,控制着盆地的空间展布、几何形态、沉积韵律以及油气储层的分布。结合国内外研究进展,本文从特征和分类、次生构造、研究方法、成因和演化理论等方面对同沉积断层的研究现状进行了总结和论述,认为同沉积断层的精细探测、定量评价和高精度模拟是今后研究的重点。基于一些构造地裂缝的发育特征和同沉积断层特点,提出了同沉积地裂缝的概念,并以西安地裂缝为例,阐述了同沉积地裂缝的特征,指出从同沉积作用出发研究地裂缝的发育模式、形成机制、破裂扩展效应以及影响带宽度是今后构造地裂缝研究的方向。

基于配电网一二次融合成套设备的接地故障处理方案研究

针对单相接地故障检测和快速隔离的难题,提出了基于配电网一二次融合技术的接地故障处理方案。方案通过一二次融合成套设备及小波包暂态零序选线技术,利用来电合闸、无压分闸、合于故障加速跳闸、故障路径优先等策略,有效解决了多分支、多供电方式下单终端选线选段的难题。同时结合现场应用案例,证明了所提方案可以快速实现接地故障区段的定位和隔离,具有普遍的适用性。

一起接线错误引起定子接地保护动作的事故分析

介绍了发电机定子接地保护动作的故障概况,分析了保护动作的故障原因,提出了事故的处理方法。

电流回路2点接地致主变差动保护误动作事故分析

电流二次回路2点接地可以引起保护装置不正确动作,对1例二次回路2点接地引起220 kV主变差动保护误动事故进行详细分析,指出引起事故的根本原因和主要因素,并提出相关的整改和防范措施。

基于二次注入的配电网接地故障有源电压消弧方法

针对中性点非有效接地配电网中存在的单相接地故障消弧问题,提出了一种基于二次注入的配电网接地故障有源电压消弧方法。该方法通过向配电网中性点注入工频电流来达到单相接地故障消弧目的,确保电网安全稳定运行。注入电流的参考值由二次注入特定电流的方法得到,将注入电流偏差信号通过比例谐振控制器,驱动逆变器开关管产生逆变电流,经滤波电路后注入电网中性点,抑制故障点电压和电流到零。仿真及10kV接地故障实验表明,该方法响应速度快、灵敏度高,能补偿配电网接地故障电流的无功电流分量、有功电流分量及谐波分量,实现瞬时接地故障快速可靠灭弧。

配电网单相接地快速处置装置运行情况研究

为确保配电网单相接地保护装置的正确动作水平,需开展人工单相接地系统试验,对消弧线圈以及小电流选线装置的动作性能进行系统测试。以西安地区开展的真实环境下人工单相接地系统试验为基础,总结了消弧线圈运行中存在的各类故障及小电流选线装置自身故障、二次接线错误等问题。结合发现问题,进一步给出配电网单相接地故障快速处置改造施工和运行的相关建议,为提高单相接地处置装置正确动作水平奠定了基础。

参数识别法在10kV小电流接地系统继发性单相接地故障检测中的应用研究

继发性单相接地故障易导致10k V小电流接地系统配电线路故障区段定位失败,文章简要阐述了继发性单相接地故障的产生机理及特征,提出一种基于参数识别法的小电流接地系统继发性单相接地故障检测方法。通过对馈出线各自动化节点的零序电压、零序电流进行电容参数计算,并绘制电容参数正负特性—时间曲线,从而判断是否有继发性故障发生。仿真结果和现场实例说明,所提方法能有效避免继发性单相接地故障检测错误,可为现有配电网单相接地故障处理提供理论和实践参考。