WO2020191825A1 - 基于相位关系的配电网单相断线故障辨识方法 - Google Patents

基于相位关系的配电网单相断线故障辨识方法 Download PDF

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WO2020191825A1
WO2020191825A1 PCT/CN2019/082821 CN2019082821W WO2020191825A1 WO 2020191825 A1 WO2020191825 A1 WO 2020191825A1 CN 2019082821 W CN2019082821 W CN 2019082821W WO 2020191825 A1 WO2020191825 A1 WO 2020191825A1
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phase
fault
distribution network
voltage
disconnection
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PCT/CN2019/082821
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刘亚东
李科君
罗林根
钱勇
盛戈皞
江秀臣
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上海交通大学
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks

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  • the invention relates to a method for identifying a line fault in a distribution network, in particular to a method for identifying a single-phase disconnection fault in a distribution network based on a phase relationship.
  • the distribution network is directly connected to users and is an important part of the power system. Its operating status is directly related to the power quality and personal safety of users.
  • the single-phase disconnection fault occurs in the distribution network, the three-phase voltage on the downstream load side of the fault appears obvious imbalance, which causes the three-phase power equipment such as the motor to run out of phase, and finally burns due to heat, causing serious economic losses;
  • a phase disconnection fault occurs, it is often accompanied by a ground fault.
  • This disconnection and ground fault is different from the common single-phase ground fault in the distribution network. It is very likely to cause safety accidents such as electric shocks for humans and animals, fires in mountains and forests, and has a high risk. Sex, posing a huge threat to the safety of people’s lives and property.
  • WAMS is provided by the global positioning system to provide accurate time scales to obtain high-sampling rate, high-precision current, voltage and frequency signals. It has the characteristics of phasor acquisition, synchronous acquisition and real-time data processing. It can be widely used for monitoring and control of the entire network. Various fields such as protection control, fault diagnosis and pollution source location.
  • WAMS adopts synchronous phase angle measurement technology and arranges the phasor measurement unit PMU at the key monitoring points of the power grid to realize the synchronous collection of the phasors of the whole network.
  • the PMU synchronizes the time through GPS technology, and sends the information with the time stamp to the monitoring master station, and the dispatcher monitors the operation status of the power grid in real time based on the synchronization information.
  • WAMS systems are widely used in a number of advanced operation analyses such as power system state estimation, power grid transient and steady-state control, relay protection and automation control, fault diagnosis and fault location. Foreign research on WAMS began around 1990. The United States, Spain and other countries have successively conducted research on the simultaneous measurement and field application of WAMS systems; my country’s research on WAMS systems began in 2000, and research and development focused on phasors. Design and use of test equipment.
  • a distributed measuring device can be used to detect and analyze the voltage on the downstream load side of the fault, and use this as a basis to identify single-phase disconnection faults to solve the current single-phase disconnection fault identification in the distribution network Difficult question.
  • the purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a single-phase disconnection fault identification method for distribution network based on the three-phase voltage phase relationship, by using a wide area measurement system to synchronously measure the three-phase voltage on the downstream load side of the fault, The phase relationship of the three-phase voltage on the load side is calculated and analyzed to solve the problem of difficult identification of single-phase disconnection faults in the current distribution network.
  • a single-phase disconnection fault identification method for distribution network based on distributed measurement includes the following steps
  • Step S1 Use the wide-area measurement system to monitor the distribution network online. When a fault is detected, use the voltage and current data collected by the wide-area measurement system to locate the fault according to the D-type traveling wave positioning method , And use the symmetrical component method to obtain positive sequence, negative sequence, zero sequence voltage and current data;
  • Step S2 According to the boundary conditions of the single-phase ground fault and the single-phase disconnection fault, it is preliminarily judged whether the fault is a single-phase ground fault or a single-phase disconnection fault. If it is a single-phase ground fault or a single-phase disconnection fault, go to step S3; if it is not a single-phase ground fault or a single-phase disconnection fault, determine that the fault is not a single-phase disconnection fault, and end the fault identification;
  • Step S3 Synchronously collect the A, B, and C three-phase voltage data of the measuring device in the downstream wide-area measurement system of the fault point at the time of the fault t, and store it;
  • Step S4 Define phase C as the fault phase, pass the stored A, B, and C three-phase voltage data through Fourier transform to obtain A, B, C three-phase voltage vectors U AL , U BL , U CL ; then calculate U
  • the angle value ⁇ between CL and (U AL + U BL ) is as follows:
  • Step S5 Perform fault identification based on the included angle value ⁇ : when
  • the present invention analyzes and calculates the equivalent circuit models of the power supply side and the load side under different grounding conditions and different grounding transition resistance values, and the obtained fault identification method has better identification accuracy and comparison.
  • the wide range of application provides a feasible and effective new solution for the identification of single-phase disconnection faults in distribution networks.
  • Figure 1 is the equivalent circuit diagram of the Y-Y transformer
  • Figure 2 is the equivalent circuit diagram of a ⁇ -Y transformer
  • Figure 3 is the load side voltage vector diagram of a single-phase ground fault
  • YY type transformers have two wiring methods, YY type and ⁇ -Y type.
  • YY type transformers the equivalent circuit is shown in Figure 1.
  • U IA , U IB , U IC are the three-phase input voltage of the three-phase line A, B, C to the transformer;
  • C A , C B , C C are the distributed capacitance to the ground of the three-phase line;
  • Z A , Z B and Z C are the three-phase windings of the transformer respectively;
  • R 0 is the grounding transition resistance.
  • the impedance converted according to the formula 1/jwC is much larger than the three-phase impedance of the transformer Z A , Z B , Z C and the grounding transition resistance R 0 , so In this case, when calculating the equivalent circuit of the transformer, the current flowing into the ground through C A and C B can be ignored and regarded as an open circuit; and the parallel impedance value of R 0 and C C can be regarded as R 0 .
  • equations (1) and (2) can be unified into the following form as the expression of U CL :
  • PSCAD/EMTDC software to establish the simulation model of the single circuit distribution network line, the rated voltage of the line is 10kV, and its topology is shown in Figure 5.
  • Two sets of faults are set at different positions in the distribution network line in Figure 5.
  • Each set of faults includes single-phase disconnection faults and single-phase grounding faults.
  • the set fault location is located at line 5-6 in Figure 5, and the voltage on the primary side of the transformer downstream of the fault is measured after the fault occurs.
  • the ground transition resistance R 0 is changed for simulation measurement (for the convenience of drawing comparison, it is assumed that the ground transition resistance R 1 and R 2 of the power supply side and the load side of the single-phase disconnection fault are equal, and R 0 ), the obtained angle ⁇ varies with R 0 as shown in Figure 6.

Abstract

一种利用广域测量系统对对故障下游负载侧的三相电压进行同步测量，并对负载侧三相电压的相位关系进行计算分析，得出了一种基于三相电压向量夹角关系的单相断线故障辨识方法。相对于传统辨识方法，该方法对不同接地情况、不同接地过渡电阻阻值下的电源侧、负载侧等效电路模型进行了分析计算，得出的故障辨识方法具有较好的辨识准确度与较广泛的适用范围，为解决配电网单相断线故障辨识难题提出了一种可行有效的新方案。

Description

基于相位关系的配电网单相断线故障辨识方法 技术领域
本发明涉及配电网线路故障辨识方法，具体是一种基于相位关系的配电网单相断线故障辨识方法。
背景技术
配电网与用户直接相连，是电力系统的重要组成部分，其运行状态与用户的用电质量和人身安全直接相关。配电网单相断线故障发生后，故障下游负载侧三相电压出现明显的不平衡现象，导致电动机等三相动力设备缺相运行，最终因发热而烧毁，造成严重的经济损失；同时单相断线故障发生时往往还伴随着接地故障，这种断线接地故障与配电网中常见的单相接地故障不同，极有可能导致人畜触电、山林失火等安全事故，具有很高的危险性，对人民的生命财产安全造成巨大威胁。
目前，虽然已经有许多学者专注于在配电网中利用单相断线故障的电压、电流特征进行故障辨识，如山东大学学者在研究中对三种不同接地情况下的单相断线故障的三相序电压、序电流进行了较为详细的分析，提出采用正、负序电流及其变化量作为单相断线故障辨识的判据，但是对接地过渡电阻的阻值范围考虑不足，实际辨识效果不理想。
在我国以小电流接地方式为主的配电网中，由于单相断线故障与单相接地故障在电源侧的电气特征十分相似，以传统的集中式测量装置难以进行故障辨识，配电网在单相断线故障发生后可能继续保持运 行数小时，严重威胁配网的安全可靠运行。虽然单相断线故障与单相接地故障具有难以分辨的电源侧电气特征，但是这两种故障在负载侧却有着不同的电压特性。根据这一特点，为获取故障负载侧的故障信息，基于广域监测系统(WAMS，Wide Area Measurement System)对配电网进行分布式测量，并在此基础上进行故障辨识。
WAMS由全球定位系统提供精准时标，获取高采样率、高精度的电流、电压以及频率信号，具有相量获取、同步采集以及数据实时处理的特性，可广泛用于全网运行监测控制，区域保护控制，故障诊断以及污染源定位等各个领域。
WAMS采用同步相角测量技术，将相量量测单元PMU布置在电网的关键监测点，实现对全网相量的同步采集。PMU通过GPS技术同步对时，将带有时标的信息发送至监控主站，调度人员根据同步信息实时监控电网的运行状态。WAMS系统被广泛应用于电力系统状态估计、电网暂态与稳态控制、继电保护与自动化控制、故障诊断与故障定位等多项高级运行分析之中。国外对于WAMS的研究开始于1990年前后，美国、西班牙等国家先后针对WAMS系统的同步量测、现场应用等方面进行了研究；我国对于WAMS系统的研究开始于2000年，研发重点关注相量量测装置的设计及使用。
在WAMS的基础上，可以通过分布式测量装置对故障下游负载侧电压进行检测分析，并以此为依据对单相断线故障进行故障辨识，以解决目前配电网中单相断线故障辨识难的问题。
发明内容
本发明目的在于克服上述现有技术的不足，提供基于三相电压相位关系的配电网单相断线故障辨识方法，通过利用广域测量系统对故 障下游负载侧的三相电压进行同步测量，并对负载侧三相电压的相位关系进行计算分析，以解决目前配电网中单相断线故障辨识难的问题。
本发明的技术解决方案如下：
一种基于分布式测量的配电网单相断线故障辨识方法，该方法包括以下步骤
步骤S1：利用广域测量系统对配电网在线监测，当监测到故障发生，则通过所述广域测量系统采集到的电压和电流数据，按照D型行波定位方法对故障进行区段定位，并利用对称分量法得出正序、负序、零序电压、电流数据；
步骤S2：按照单相接地故障与单相断线故障的边界条件初步判别故障是否为单相接地故障或单相断线故障。如果是单相接地故障或单相断线故障，则进入步骤S3；如果不是单相接地故障或单相断线故障，则判定故障不是单相断线故障，结束故障辨识；
步骤S3：同步采集故障t时刻的故障点下游广域测量系统中测量装置的A、B、C三相电压数据，并存储；
步骤S4：定义C相为故障相，将存储的A、B、C三相电压数据通通过傅里叶变换得到A、B、C三相电压向量U AL、U BL、U CL；则计算U CL与(U AL+U BL)的夹角值θ,公式如下：
Figure PCTCN2019082821-appb-000001
步骤S5：基于夹角值θ进行故障辨识：当|θ|≥90°时，判定为单相接地故障；当|θ|<90°时，则判定为单相断线故障。
相对于传统辨识方法，本发明对不同接地情况、不同接地过渡电 阻阻值下的电源侧、负载侧等效电路模型进行了分析计算，得出的故障辨识方法具有较好的辨识准确度与较广泛的适用范围，为解决配电网单相断线故障辨识难题提出了一种可行有效的新方案。
附图说明
图1是Y-Y型变压器等效电路图
图2是Δ-Y型变压器等效电路图
图3是单相接地故障负载侧电压向量图
图4单相断线故障负载侧电压向量图
图5配电网仿真拓扑结构图
图6仿真故障的θ-R0关系图
具体实施方式
下面结合附图，给出本发明的较佳实施例，并予以详细描述，但不应以此限制本发明的保护范围。
常用的配电变压器有Y-Y型与Δ-Y型两种接线方式，对于Y-Y型变压器，其等效电路如图1所示。其中U IA、U IB、U IC分别为A、B、C三相线路对变压器的三相输入电压；C A、C B、C C分别为三相线路的对地分布电容；Z A、Z B、Z C分别为变压器的三相绕组；R 0为接地过渡电阻。
由于配网线路对地分布电容C A、C B、C C很小，根据公式1/jwC 换算得到阻抗远远大于变压器三相阻抗Z A、Z B、Z C与接地过渡电阻R 0，因此在这种情况下对变压器等效电路进行计算时可以忽略经过C A、C B流入大地的电流，将其视为断路；并且R 0与C C并联阻抗值可以视为R 0。同时假设变压器三相绕组对称，即三相绕组阻值Z A＝Z B＝Z C＝Z 1。
对于断线故障，以图2电路进行计算，得到Y-Y型变压器C相一次侧电压值U CL：
Figure PCTCN2019082821-appb-000002
接着对Δ-Y型变压器(其等效电路如图2所示)进行相似的分析计算。图中U IA、U IB、U IC分别为A、B、C三相线路对变压器的三相输入电压；C A、C B、C C分别为三相线路的对地分布电容；Z AB、Z BC、ZA C分别为变压器的三相绕组；R 0为接地过渡电阻。同理忽略配网线路对地分布电容的影响，并且三相绕组阻值Z AB＝Z BC＝Z CA＝Z 2。
得到Δ-Y型变压器C相一次侧电压值U CL：
Figure PCTCN2019082821-appb-000003
通过将式(1)与式(2)中与绕组阻抗相关的项记为等效阻抗Z k，可以将式(1)与式(2)统一为以下形式，作为U CL的表达式：
Figure PCTCN2019082821-appb-000004
对于单相接地故障，由于线路无断线，故障上下游电压相等，故可以按照通常公式计算：
Figure PCTCN2019082821-appb-000005
由此可以得出如图3所示的负载侧的电压向量图。
而对于单相断线故障，C相的输入电压U IC变为0。基于式(3)，对单相断线故障的负载侧进行分析，可以得出如图4所示的关系图。
通过对比图3与图4可知，对于单相接地故障，故障后C相测量到的电压U CL与U AL+U BL之和的夹角的绝对值|θ k|大于90度；而对于单相断线故障，|θ k|小于90度，并且这一关系已经考虑到所有可能的系统参数与故障发生条件。所以，利用负载侧电压三相相位之间的关系对单相断线故障进行辨识是一种可行有效的思路。
通过对故障电压特征的对比分析，可以得出利用故障后负载侧变压器电压进行单相断线故障与单相接地故障的故障辨识的一个基本思路：假设C相为故障相，同时测量负载侧变压器的三相电压向量U AL、U BL、U CL，计算向量(U AL+U BL)与U CL的夹角θ，当|θ|>90°时，判定为单相接地故障；而当|θ|<90°时，则判定为单相断线故障。
使用PSCAD/EMTDC软件建立单回线配电网线路的仿真模型，线路额定电压为10kV，其拓扑图如图5所示。在图5配网线路中不同位置设置两组故障，每组故障中包含单相断线故障与单相接地故障。所设置的故障位置位于图5中的线路5-6处，并对故障发生后故障下游的变压器一次侧电压进行测量。
在线路5-6故障中，通过改变接地过渡电阻R 0进行仿真测量(为 了方便绘图对比，假设单相断线故障电源侧与负载侧的接地过渡电阻R 1与R 2相等，并以R 0表示)，得到的夹角θ随R 0变化曲线图如图6所示。
在图6中，可以看出故障夹角θ随R 0变化的共同特点：单相断线故障的夹角θ 1从90度开始随R 0上升；而单相接地故障的夹角θ 2与R 0从90度开始随R 0下降。通过仿真得出的两种故障夹角θ随R 0的变化趋势与通过理论计算得出的结果基本一致。从图中可以看出，在接地电阻较大(即R 0>30Ω)时，单相断线故障夹角θ 1始终小于90度；而单相断线故障夹角θ 1始终大于90度。故此时以夹角θ为依据可以准确地对两种故障进行故障辨识。

Claims (1)

  1. 一种基于分布式测量的配电网单相断线故障辨识方法，其特征在于，该方法包括以下步骤：
    步骤S1：利用广域测量系统对配电网在线监测，当监测到故障发生，则通过所述广域测量系统采集到的电压和电流数据，按照D型行波定位方法对故障进行区段定位，并利用对称分量法得出正序、负序、零序电压、电流数据；
    步骤S2：按照单相接地故障与单相断线故障的边界条件初步判别故障是否为单相接地故障或单相断线故障。如果是单相接地故障或单相断线故障，则进入步骤S3；如果不是单相接地故障或单相断线故障，则判定故障不是单相断线故障，结束故障辨识；
    步骤S3：同步采集故障t时刻的故障点下游广域测量系统中测量装置的A、B、C三相电压数据，并存储；
    步骤S4：定义C相为故障相，将存储的A、B、C三相电压数据通通过傅里叶变换得到A、B、C三相电压向量U AL、U BL、U CL；则计算U CL与(U AL+U BL)的夹角值θ,公式如下：
    Figure PCTCN2019082821-appb-100001
    步骤S5：基于夹角值θ进行故障辨识：当|θ|≥90°时，判定为单相接地故障；当|θ|<90°时，则判定为单相断线故障。
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