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.

基于低压侧负序量特征的小电流系统单相接地故障检测方法

随着台区智能终端量测技术的逐步成熟,实现低压侧全息感知的同时,具备对上级中压配网的多点监测能力。提出基于低压侧负序量特征的小电流系统单相接地故障检测方法。分析了中压侧发生单相接地故障后低压侧负序量的变化规律;利用负序电流大小区分故障线路和非故障线路;提出通过负序电压与正序电压的比值系数,多点协同计算对比判断故障点区段位置,且考虑了低压侧不平衡负荷,以及故障点位于线路一端的特殊情况。通过MATLAB软件和动模实验对中低压联合配电系统的仿真计算,验证了所提方法具有良好的鲁棒性和准确性。通过智能配变终端监测上级中压配网负序量信息,实现小电流接地系统故障检测,具有实际应用和推广价值。

基于线路容流暂态信号能量流向特征的小电流单相接地故障区段定位算法

针对配电网小电流系统单相接地故障定位难的问题,提出一种基于线路容流暂态信号能量流向特征的小电流单相接地故障定位算法。该算法能够在故障发生时准确识别故障线路并定位故障区间,同时对故障前后波形的离散采样数据进行软件滤波,得到线路的容流暂态信号分量,利用其能量流向特征对单相接地故障进行识别和区段定位。实验结果表明,所提算法能够准确区分出故障与非故障线路区段,具有自举性,可方便应用于就地型馈线自动化开关节点,具有较好的实用性。

综合零序电流信号分量的单相接地故障选线方法

文章提出了一种优化变分模态分解(VMD)参数与综合零序电流信号分量的选线方法,旨在解决目前矿井经消弧线圈接地供电系统发生单相接地故障时,存在的故障信号特征提取困难、噪声信号影响严重等问题。该方法利用鲸鱼优化VMD参数对零序电流信号进行分解,并根据非工频分量能量、工频分量极性和波形相关性的多重判据进行故障线路判别。利用RTDS/RSCAD搭建矿井供电系统模型,仿真测试了不同的故障情况,包括不同故障线路的故障接地电阻、故障初始相位角、故障点位置。结果显示,无论故障条件如何,该方法都有更加准确和可靠的选线结果。

基于复频率信号注入的直流接地极线路故障测距方法

在直流输电系统接地极线路配备阻抗监视系统的背景下,可利用高频测量阻抗特性实现故障距离的精确计算。然而,分析发现直流系统接地极线路在不同故障条件下可能产生相同的高频测量阻抗,这意味着测量阻抗与故障距离间不是一一映射关系,由单一测量阻抗难以得到准确的故障距离。文中分析了高频测量阻抗的重合特性随注入信号变化的特征,提出了基于复频率信号注入的故障测距方法,并给出了复频率的选定策略。该方法改进了基于高频测量阻抗幅相特性的接地极线路故障测距方法,实现了故障位置的准确计算。最后,通过仿真算例充分验证了所提测距方法的可行性和精确性。

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.

基于信号包络与希尔伯特边际谱的高阻接地故障检测方法

配电网高阻接地故障(HIF)信号具有失真性和随机性,故障特征微弱,难以被有效检测。为此,本文提出一种基于信号包络(SE)和希尔伯特边际谱(HMS)的HIF诊断方法。该方法对长时间尺度的零序电压提取SE和HMS,分别代表HIF的失真性和随机性特征。将这些特征转化为图像,利用ResNet18实现对HIF的检测。该方法的有效性已在10kV真型试验中得到验证,试验结果表明,该方法的HIF检测精度明显优于对比方法,尤其是在谐振接地系统中。

电力电缆接地故障特征及识别方法研究

针对当前电力系统中电缆故障频发对供电可靠性和经济效益造成的严重影响,文章通过深入分析电缆接地故障的电气特性,结合高精度的信号处理技术,提出了基于电缆零序电流和电压波形分析的故障识别方法,能够有效区分电缆的持续性接地故障和间歇性接地故障,提高电力系统的故障检测效率和准确性,为电力电缆故障的快速诊断提供了理论依据和技术支持。

铁路信号电缆接地故障的定位方法分析

阐述电缆接地故障原因,探讨铁路信号电缆接地故障点定位方法,包括电桥法、冲击电流法、脉冲反射法、故障定位系统。如果接地故障比较严重,应该根据实际情况,合理选用检测方法。

电力系统接地极线路故障类型识别技术研究

针对电力系统接地极线路故障类型识别中存在的响应速度慢、识别精度低等问题,提出一种基于信号处理、模式识别以及数据融合的故障类型识别方法。首先利用小波变换和经验模态分解(Empirical Mode Decomposition,EMD)提取故障电流、电压信号的时频域特征量,其次分别构建支持向量机(Support Vector Machine,SVM)和概率神经网络(Probabilistic Neural Network,PNN)故障识别模型,最后采用证据理论融合两种模型的诊断结果,得到最终的故障类型判断。实验结果表明,该方法能够有效识别单相金属性接地、单相高阻接地以及两相短路等典型故障类型,识别精度高、可靠性强,为保障电力系统的安全运行提供有力支撑。

悬浮电压在大型水电厂监控系统开关量中的应用及研究

经过隔离变压器输出的直流电压,没有与大地相连,对地测量到的浮动的电压就是悬浮电压。大型水电厂监控系统开关量电源一般采用直流24 V的悬浮电压,由于悬浮电压不接地,当开关量直流回路发生一点接地故障时并不马上产生后果,当出现第二点接地时,就可能发生短路造成继电保护、自动装置、开关等误动,严重时甚至导致事故停机。针对悬浮电压在水电厂监控系统开关量中的应用,研究并总结了一套快速排查开关量接地故障的技术。

基于改进小波包分析的三相供电电源线路接地故障诊断方法

三相供电电源线路的接地故障信号复杂且易受干扰,这一特性在进行故障诊断时会降低诊断的灵敏度。因此,提出基于改进小波包分析的三相供电电源线路接地故障诊断方法。通过部署高精度传感器、模数转换、无线传输以及归一化处理措施,提升接地信号的质量。利用优化频带划分、融合快速傅里叶变换及隔点采样技术,提取接地故障信号特征。建立故障诊断模型,并辅以欧氏距离相似度匹配,实现接地故障的智能自动诊断。实验结果表明,设计方法能够提升诊断的灵敏度,确保在复杂的电力环境中实现故障的快速、准确识别。

基于行波信号的10 kV配电线路单相接地故障诊断方法

为解决配电线路单相接地故障诊断准确率低的问题,引入行波信号开展了基于行波信号的10 k V配电线路单相接地故障诊断方法的研究。首先利用行波信号提取配电线路故障特征,然后设置配电线路两端行波记录点,通过测距定位确定故障位置实现配电线路单相接地故障诊断。结果表明,应用该方法后,配电线路单相接地故障诊断识别准确率达到98.5%以上,可行性较高。

基于并联电阻扰动信号的配电网故障定位方法分析

基于并联电阻扰动信号的配电网故障定位方法利用对外加扰动信号的追踪来实现定位,已在配电网故障定位中较为广泛应用。但该方法在实际应用中会出现施加扰动信号后故障特征变化规律不确定的问题,使得故障定位装置误判,导致故障定位失败。为此,文中建立了小电流接地系统等值电路,深入研究了扰动信号通过不同非故障相注入后单相接地故障电流的变化规律,分析了负荷电流以及接地过渡电阻的影响,对基于并联电阻扰动信号的配电网故障定位方法的有效性进行理论论证。提出了对中性点不接地系统或经欠补偿消弧线圈接地系统扰动信号应通过故障相的滞后相注入,对中性点经过补偿消弧线圈接地系统扰动信号应通过故障相的超前相注入的优化方法。仿真结果证明了所提优化方法的有效性。

小电流接地系统单相接地故障选线测距和定位的新技术

按照小电流接地系统单相接地故障的特点，本文提出了通过检测注入信号的路径和特征来实现故障选线、测距和定位的“S注入法”选线、测距和定位新原理，导出了有关的公式和算法，研制出了相应的装置，并已在较大范围内推广应用。“S注入法”的主要特点有：（1）通过接地时暂时处于空闲状态的接地相PT注入信号，毋需增加任何一次设备，不会对运行设备产生任何不良影响；（2）注入信号具有不同于系统中任何一种固有信号的特征，对它的检测不受系统运行情况影响；（3）注入的信号电流仅在接地线路接地相中流通，不会流系统的其它部位。

注入方波信号的经消弧线圈接地系统故障选线方法

提出一种注入方波信号的经消弧线圈接地系统故障选线方法。通过从故障相电压互感器向系统注入一特定频率的方波信号,探测各支路零序电流,并分析其基波与3次谐波电流幅值之间的关系来确定故障线路。详细分析了注入方波信号的单相接地故障选线原理并提出了选线判据。模拟实验结果证明该方法能准确、稳定、快速地实现故障选线,检测精度高且能有效地排除系统对地电容的影响。