Transient Fault Locating Method Based on Line Voltage and Zero-mode Current in Non-solidly Earthed Network

为解决配电网小电流接地故障时故障点定位困难的问题，提出一种基于线电压和零模电流暂态分量的故障定位新方法。该方法借助馈线自动化（feeder automation，FA）系统实现，不需要额外增加设备。馈线终端检测线电压和零模电流信号，利用暂态线电压的希尔伯特变换与暂态零模电流的乘积计算故障方向参数，FA主站根据故障点前后方向参数极性相反的特征确定故障点所在的线路区段。介绍基于线电压的小电流接地故障检测和接地故障相确定的算法。数字仿真与试验结果表明该方法是正确可行的。

Fault-tolerance wide voltage conversion gain DC/DC converter for more electric aircraft

In this paper,a fault-tolerance wide voltage conversion gain DC/DC converter for More Electric Aircraft(MEA)is proposed.The proposed converter consists of a basic Cuk converter module and n expandable units.By adjusting the operation state of the expandable units,the voltage conversion gain of the proposed converter could be regulated,which makes it available for wide voltage conversion applications.Especially,since mutual redundancy can be realized between the basic Cuk converter module and the expandable units,the converter can continuously work when an unpredictable fault occurs to the fault-tolerant parts of the proposed converter,which reflects the fault tolerance of the converter and significantly improves the reliability of the system.Moreover,the advantages of small input current ripple,automatic current sharing and low voltage stress are also integrated in this converter.The working principle and features of the proposed converter are mainly introduced,and an experimental prototype with 800 W output power has been manufactured to verify the practicability and availability of the proposed converter.

A Review of Series Voltage Source Converter with Fault Current Limiting Function

The series voltage source converter(SVSC)is widely used in the power electronic equipment,such as series active power filter,dynamic voltage restorer,unified power flow controller and so on.However,while the SVSC is more vulnerable to the impact of fault current,its applications are increasing,bringing huge challenges to the safe operation of the grid.In recent years,the topology and control strategy of the series voltage source converter with fault current limiting(SVSC-FCL)are a research hotspot.In this paper,it suggests classifying SVSC-FCL based SVSC into two groups:the control scheme optimization group and the existing topology improvement group.The research challenges and perspectives of the SVSC-FCL are introduced in detail.This paper aims to illustrate current research progress on SVSC-FCL and enrich the available pool of the multi-functional power electronic equipment.

New “Intellectual Networks” (Smart Grid) for Detecting Electrical Equipment Faults, Defects and Weaknesses

The most important elements of “intellectual networks” (Smart Grid) are the systems of monitoring the parameters of electrical equipment. Information-measuring systems (IMS), which described in this paper, were proposed to use together with rapid digital protection against short-circuit regimes in transformer windings. This paper presents an application’s experience of LVI-testing, some results of the use of Frequency Response Analysis (FRA) to check the condition of transformer windings and infra-red control results of electrical equipment. The LVI method and short-circuit inductive reactance measurements are sensitive for detecting such faults as radial, axial winding deformations, a twisting of low-voltage or regulating winding, a losing of winding’s pressing and others.

考虑风电机组故障电压穿越特性的连锁故障关键线路辨识

新能源的接入提高了电网连锁故障发生的概率,给故障传播中关键线路的辨识增加了难度。为此,建立了考虑风电机组故障电压穿越特性和线路可靠性的连锁故障仿真模型,从线路失负荷严重程度、失负荷不均匀性和结构脆弱性3个角度建立了线路综合风险指标评价集。基于状态故障网络计及线路失负荷程度和线路失负荷不均匀性,分别定义了失负荷风险指标和不均匀风险指标;基于电气介数提出了考虑分布式新能源接入的脆弱结构指标;同时,考虑电网的网络结构和状态转移特性,采用模糊熵权法定义综合风险指标,以衡量线路开断的综合影响。通过IEEE 39节点和IEEE 118节点系统算例验证所提方法用于关键线路辨识的有效性,且针对关键线路的缓解措施能显著降低大停电风险。

非侵入式低压用电故障监测措施及装置选择

文章介绍了非侵入式低压用电故障监测,并分析了常见的几种低压用电故障类型,如接触电阻过大、线路过载、短路问题和漏电故障。提出了针对这些故障监测的措施,包括故障信号提取方法、小波分析算法、信号奇异性检测及监测系统的整体架构。针对不同的监测需求推荐了相应的装置选择,为非侵入式低压用电故障监测提供了实用的技术参考。

基于多维特征与随机森林的低压用电安全隐患预警方法

故障电弧作为低压用电常见安全隐患,因存在隐蔽性和随机性,导致难以在故障前夕有效感知,现有保护方法通常于故障发生后采取措施,容易造成电气火灾发生。针对这些问题,提出基于多维特征与随机森林的低压用电安全隐患预警方法。首先,搭建真型实验平台复现多种负载故障电弧真实场景,采集实验数据进行去噪、归一化和样本化等预处理;接着分析故障前、后波形变化情况,进而实行特征有效性分析,提取多维与故障相关程度较高的特征值,提高特征普适性。然后,搭建随机森林模型并进行超参数优化,以最小化节点信息熵为目标完成模型训练,提升模型整体性能和学习效率。最后,通过实验验证表明,所提方法在多种不同负载运行工况下预测准确率可高达99.4%以上,且预测准确率高于4种主流分类预测模型。

基于改进遗传算法的高压电气设备故障信号低复杂度快速提取模型

提取速度过慢,提取位置不准确会直接影响电气设备的正常运行,为了解决这个问题,基于改进遗传算法提出高压电气设备故障信号低复杂度快速提取模型。建立了目标函数,构建了适用于高压电气生产设备故障信号提取的信息网络模型,对高压电气生产设备运行中的数据信息进行采集整理,根据数据类型和关键特征进行分类提取,代入运算程序进行故障检测运算模型,代入电气设备运行数据;引入改进后的遗传算法,选择适当的改进过程,实现对高压电器生产设备故障信号的低复杂度、准确、快速的提取。实验结果表明,该模型能够精准地判断故障类型,提取速度提高了20%~30%,复杂度较低,工作效果更好,应用性能更强。

基于机器视觉的变电站高压电气设备绝缘自动监测方法

变电站高压电气设备绝缘故障检测的过程中,因图像背景干扰,出现图像空洞问题,导致绝缘故障的识别结果不准确.对此,研究基于机器视觉的绝缘故障自动监测方法.通过采用机器视觉中的多轴平行摄影技术对高压电气设备运行异常图像进行采集,结合中值滤波和双边滤波两种方法对采集到的异常图像进行预处理,采用四帧差分算法对预处理后的异常现象图像进行绝缘故障前景目标的识别,解决了图像出现空洞的问题,通过Canny边缘检测算法提取绝缘故障前景目标的完整边缘轮廓信息,得到边缘轮廓准确清晰的绝缘故障图像,并采用三点定位法计算绝缘故障发生的具体位置,获取绝缘故障图像和位置监测结果.实验表明:该方法的定位精度最高可达98.63%,单帧处理时间仅为21 ms,误检次数为0,检测准确率可达98.34%,能够准确完整地识别出绝缘故障发生的区域,并解决图像空洞问题,具有优越的检测性能.

低碳背景下低压电动机电缆选型思路

目前低压电动机配电使用的4芯电缆比3芯电缆多出的1芯PE线在实际工程中往往并未发挥作用。GB 50217—2018《电力工程电缆设计标准》的实施首次提出了TN-S系统低压电动机配电宜选用3芯电缆的表述。通过解析新规范内容,结合实例对目前主流的低压电动机配电电缆的选型方案进行了对比分析,指出在合规和满足适用需求的情况下合理选用电缆,可实现节能和环保。

Design and Testing of Three Earthing Systems for Micro-Grid Protection during the Islanding Mode

This paper presents and tests three earthing systems (TT, TN and IT) for Micro-Grid (MG) protection against various fault types when the MG transferred to the islanding mode. The main contribution of this work is including the models of all micro sources which interfaced to the MG by power electronic inverters. Inverters in turns are provided with current limiters and this also included with the inverter models to exactly simulate the real situation in the MG during fault times. Results proved that the most suitable earthing system for MG protection during the islanding mode is the TN earthing system. That system leads to a suitable amount of fault current sufficient to activate over current pro-tection relays. With using TN earthing system, touch voltages at the faulted bus and all other consumer’s buses are less than the safety limited values during islanding mode. For the two others earthing systems (TT and IT), fault currents are small and nearly equal to the over load currents which make over current protection relay can not differentiate between fault currents and overload currents. All models of micro sources, earthing systems, inverters and control schemes are built using Matlab?/Simulink? environment.

Comparison the Performances of Three Earthing Systems for Micro-Grid Protection during the Grid Connected Mode

This paper presents, tests and compares three earthing systems (TT, TN and IT) for Micro-Grid (MG) protection against various fault types during the connected mode. The main contribution of this work is including the models of all the micro sources which interfaced to the MG by power electronic inverters. Inverters in turns are provided with current limiters and this also included in the inverter models to exactly simulate the real situation in the MG during fault times. Results proved that the most suitable earthing system for MG protection during the connecting mode is the TN earthing system. That system leads to a suitable amount of fault current sufficient to activate over current protection relays. With using TN system, Touch voltages at the faulted bus and all other consumer’s buses are less than the safety limited value if current limiter is included with the transformer of the main grid which connects MG. For the two others earthing systems (TT and IT), fault current is small and nearly equal to the over load current which make over current protection relay can not differentiate between fault current and overload current. All models of micro sources, earthing systems, inverters, main grid and control schemes are built using Matlab?/Simulink? environment.

Analysis of the Impact of Different PEV Battery Chargers during Faults

With a high penetration of Plug-In Electric Vehicles (PEVs) in the electric grid, utilities will have to face the challenges related to them. Considerable research is being done to study and mitigate the impact of PEVs on the electric grid and devise methodologies to utilize them for energy storage and distributed generation. In this paper, the impact of PEVs in a smart car park, placed in an unbalanced distribution system, during a Single Line to Ground fault with auto-recloser operation is studied. Level-2, bidirectional battery chargers with Current Controlled and Voltage Controlled Voltage Source Converters are modeled for the battery charging systems of the PEVs. A smart car park, with 16 vehicles connected to each of the three phases is simulated at one of the buses in the IEEE 13 Bus Test Feeder. The impacts observed during the fault are analyzed and a method to mitigate them is suggested.

论高压触电案件责任主体界定标准

高压触电致人损害案件的赔偿主体如何界定一直都是理论界与实务界的难题。以立法学角度观之,是因为不同部门及位阶的法律规范之间存在大量冲突。而择法教义学角度分析,是司法者机械解释“经营者”等不确定概念,未能回归高度危险理论来探究“经营者”的本质内涵所致。实际上,高压电能一样具有观念上的产权,当高压触电事故发生时,应当由高压电能产权人以及高压电能载体产权人共同承担无过错侵权责任。无论是高压电能的生产主体、还是销售主体抑或是使用主体,三者皆可“实际控制”高压电能运行,具体由何者承担,应当根据具体的电能交易形式进行责任判定。

高压触电侵权案件中受害人的过错

在高压触电侵权案件中,在无过错归责原则下,高压电设施经营者承担了较重的责任。依据《民法典》第1240条,高压触电侵权案件受害人对损害发生具有过错的,高压电设施经营者可以免责、减责。目前,在高压电设施经营者的免责事由中,受害人故意包括直接故意和间接故意,但实务界处理高压触电侵权案件时存在对受害人故意内容的认定不统一、受害人是否构成故意的判定标准不统一、对受害人故意和过失的界限认定不统一等问题。今后,应不断完善高压触电侵权案件办案思路,判定受害人是否构成故意时,不能仅以受害人存在违法行为为由认定其主观存在故意;在判断受害人的过错状态时,除非有特别事由,否则仅应在受害人过失范围内依据其违反注意义务的等级判断其过失程度;对于受害人有预谋的自伤自杀、不顾明显警示和他人反复劝阻的行为,应当认定为故意。

基于低压量测的小电流系统单相接地故障检测方法

小电流系统单相接地故障带来严重的公共安全隐患。配电物联网的发展建设为配电网的智能监测、自动化和保护控制带来了新的机遇和技术手段。该文提出一种基于配变低压侧的智能配变终端采集数据,识别中压配网单相接地故障线路,并将故障定位至大致范围的新方法。故障引发低压侧的暂态线模电压突变量在系统中不同点位的分布具有一定规律;在故障线路上,其瞬时值在故障点处最高并沿故障线路两侧递减,在电源母线处最小;而非故障线路低压侧的瞬时值要远小于故障线路,且沿线路递减,由此可以判断故障线路;最后通过比较故障线路下各台区低压侧的暂态线模电压突变量的最大值,确定故障点所处区段范围。仿真及真型试验结果验证了所提方法的有效性。通过广泛部署的智能配变终端多点协同监测中压配网状态信息,实现小电流接地系统故障检测,无需额外投资具有良好工程推广价值。

基于负序电压变化量的灵活接地配电网永久性单相接地故障定位

针对灵活接地配电网,提出一种基于负序电压变化量的灵活接地配电网永久性单相接地故障定位方法。首先基于并联小电阻投入前后的负序电压变化量确定故障区域,其次根据零序电流修正投影比例系数判断故障分支从而确定故障区段,然后利用负序电压变化量测量值与计算值之间的偏差计算故障概率,对比故障区段内各个虚拟节点的故障概率进行精确定位,同时提出一种适用于该区段定位方法的测量点优化布置方案。最后利用PSCAD搭建仿真模型,仿真数据分析验证了所提永久性单相接地故障定位方法的有效性及可靠性。

基于暂态电压比初始值和时域迭代的直流配电网单端测距方法

针对直流配电网线路单端故障测距精度不高的问题,提出了一种基于暂态电压比的单端故障测距方法。该方法通过分析故障发生后限流电抗器两端故障电气量的特征和数学表达式,构建了时域内基于限流电抗器两端暂态电压比的故障测距方案,并利用迭代的方法削弱过渡电阻对故障测距精度的影响。该方法利用单端电气量,耐过渡电阻能力强,对通信无严格要求,无需安装同步装置,提高了直流配电网线路单端故障测距的精度。在PSCAD/EMTDC平台搭建多端直流配电网模型,对所提测距方法进行仿真分析,结果证明所提方法可以实现基于单端电气量的精确故障测距。

直流分压器故障诊断分析

直流分压器是一种重要的设备,分析了电力系统中直流分压器的结构和原理,对直流分压器的测量和控制进行研究。开展常见故障诊断和测试,对直流分压器的故障进行诊断和分析,消除安全隐患,分析和故障诊断过程对于工程具有一定的参考和应用价值。

无交流电容的构网型换流器电压电流比例控制及故障限流

通过引入电压电流比例关系,构建了适用于高压构网型换流器的无电容矢量电压控制,可与传统内环电流控制组成构网型换流器级联控制架构,保留正序电流限幅和负序电流抑制能力,防止换流器在电网故障时发生过流闭锁和损坏。与传统外环电压控制不同,该电压电流比例控制不依赖于交流侧并联容性滤波器的电气关系构建,适用于无交流电容的高压构网型换流器的外环电压控制。通过选取特定的交流电压频率指令值,构网型换流器可实现恒电压运行或虚拟同步机运行。时域仿真结果表明,所提高压构网型换流器控制在电网故障时可自动实现换流器的负序电流抑制和故障穿越功能,避免换流器过流闭锁及损坏,并在故障清除后恢复正常运行。