An adaptive PMU based fault detection/location technique fortransmission lines. I. Theory and algorithms

An adaptive fault detection/location technique based on a phasor measurement unit (PMU) for an EHV/UHV transmission line is presented. A fault detection/location index in terms of Clarke components of the synchronized voltage and current phasors is derived. The line parameter estimation algorithm is also developed to solve the uncertainty of parameters caused by aging of transmission lines. This paper also proposes a new discrete Fourier transform (DFT) based algorithm (termed the smart discrete Fourier transform, SDFT) to eliminate system noise and measurement errors such that extremely accurate fundamental frequency components can be extracted for calculation of fault detection/location index. The EMTP was used to simulate a high voltage transmission line with faults at various locations. To simulate errors involved in measurements, Gaussian-type noise has been added to the raw output data generated by EMTP. Results have shown that the new DFT based method can extract exact phasors in the presence of frequency deviation and harmonics. The parameter estimation algorithm can also trace exact parameters very well. The accuracy of both new DFT based method and parameter estimation algorithm can achieve even up to 99.999% and 99.99% respectively, and is presented in Part II. The accuracy of fault location estimation by the proposed technique can achieve even up to 99.9% in the performance evaluation, which is also presented in Part II     

一种基于PMU的线路自适应故障测距算法

提出一种新的基于相量测量单元(PMU)的输电线路故障测距的自适应算法.该算法利用PMU装置获得高压线路两端的电压和电流相量,在线计算线路参数,解决了线路实际参数与电力局所提供参数的不同、线路参数在运行过程中的不确定性等问题.采用前置带通滤波器与全波傅氏算法相结合的滤波算法,提取相当精确的突变量基频分量,用于输电线路故障测距.大量的EMTP仿真计算结果和实际系统参数验证结果表明,该测距算法不受系统的运行方式、故障点过渡电阻、故障类型、故障距离等因素的影响,具有很高的测距精度.     

一种基于PMU的线路自适应故障测距算法

提出一种新的基于相量测量单元(PMU)的输电线路故障测距的自适应算法。该算法利用PMU装置获得高压线路两端的电压和电流相量,在线计算线路参数,解决了线路实际参数与电力局所提供参数的不同、线路参数在运行过程中的不确定性等问题。采用前置带通滤波器与全波傅氏算法相结合的滤波算法,提取相当精确的突变量基频分量,用于输电线路故障测距。大量的EMTP仿真计算结果和实际系统参数验证结果表明,该测距算法不受系统的运行方式、故障点过渡电阻、故障类型、故障距离等因素的影响,具有很高的测距精度。     

A new PMU-based fault detection/location technique for transmission lines with consideration of arcing fault discrimination-part II: performance evaluation

The theory and algorithms of the proposed technique have been presented in Part I of this two-paper set. In Part II of this two-paper set, the proposed technique is evaluated by considerable simulation cases simulated by the Matlab/Power system Blockset simulator. For the proposed fault detector, the trip time achieved can be up to 3.25 ms and the average value of trip times is about 8 ms for both permanent and arcing faults on transmission lines. For the proposed fault locator, the accuracy can be up to 99.99% and the error does not exceed 0.45%. Moreover, the proposed arcing fault discriminator can discriminate between arcing and permanent faults within four cycles after fault inception. It has proven to be an effective tool to block reclosing on the permanent faults in the computer simulations. The simulation results also demonstrate that the presented extended discrete Fourier transform algorithm eliminates effectively the error caused by exponentially decaying dc offset on fundamental and harmonic phasor computations. Finally, a test case using the real-life measured data proves the feasibility of the proposed technique.     

Wide area measurements based faultdetection and location method fortransmission lines

Electric power grids are critical infrastructure for delivering energy from generation stations to load centers. To maximize utilization of assets, it is desirable to increase the power transferred over transmission systems. Reliable protection of transmission systems is essential for safeguarding the integrity and reliability of the power grid. Distance protection is the most widely used scheme for protecting transmission lines. Most existing protection systems use local measurements to make a decision while pilot protection is used in some circumstances. Distance protection may fail under stressed operating conditions, which could lead to cascading faults. This paper proposes a system integrity protection scheme by utilizing wide area measurements. The scheme partitions the system into subnetworks or protection zones and employs current measurements to derive a fault identification vector indicating the faulted zone. Then the fault location is pinpointed based on wide area measurements and network data. The proposed method is able to deal with multiple, simultaneous faults, and is applicable to both transposed and untransposed lines. Evaluation studies based on simulation studies are presented.     

基于有限PMU配置的配电网故障定位

提出一种仅需要有限的相量测量单元(PMU)便能实现单故障和多重故障定位的配电网故障定位方法.首先通过叠加原理和等效变换推导故障网络节点电压方程,基于此建立压缩感知模型.然后利用l1正则化最小二乘法求解近似故障电流并进行归一化处理,确定疑似故障区间.通过电压残差公式和故障测距公式依次计算可能故障数目下对应的电压残差和故障...     

A new adaptive PMU based protection scheme fortransposed/untransposed parallel transmission lines

This paper proposes a brand-new adaptive phasor measurement unit (PMU) based protection scheme for both transposed and untransposed parallel transmission lines. The development of the scheme is based on the distributed line model and the synchronized phasor measurements at both ends of lines. By means of eigenvalue/eigenvector theory to decouple the mutual coupling effects between parallel lines, the fault detection and location indices are derived. The two proposed indices are used in coordination such that the internal and external fault events can be distinguished completely. By on-line estimation of the line parameters under the actual power system conditions, the proposed scheme will respond more accurately to power system faults. Extensive simulation results using EMTP have verified that the accuracy of the fault location achieved is up to 99.9%. The proposed protection system responds well and fast with regard to dependability and security. All the results show that the performance of the proposed detection/location indices is independent of fault types, locations, resistance, source impedance, fault inception angles, and load flows     

一种基于参数检测的双端故障测距算法

提出了一种基于参数检测的双端故障测距算法,仅需双端系统的电气量,通过三相解耦推导出故障测距的解析表达式.该算法能计算出双端系统的非同步角和随着环境影响变化的线路参数,克服了传统故障测距的弊端,不存在伪根问题、算法简单实用、计算量小,无需搜索和迭代,鲁棒性强.该算法也不受故障类型、过渡电阻等因素的影响.高压输电线路采用分布式参数模型,通过ATP-EMTP对该算法进行了仿真验证.     

A new wavelet based fault detection,classification and location in transmission lines

This paper deals with the application of wavelet transforms for the detection, classification and location of faults on transmission lines. A Global Positioning System clock is used to synchronize sampling of voltage and current signals at both the ends of the transmission line. The detail coefficients of current signals of both the ends are utilized to calculate fault indices. These fault indices are compared with threshold values to detect and classify the faults. Artificial Neural Networks are employed to locate the fault, which make use of approximate decompositions of the voltages and currents of local end. The proposed algorithm is tested successfully for different locations and types of faults.     

A new PMU-based fault detection/location technique for transmission lines with consideration of arcing fault discrimination-part I: theory and algorithms

A new fault detection/location technique with consideration of arcing fault discrimination based on phasor measurement units for extremely high voltage/ultra-high voltage transmission lines is presented in this two-paper set. Part I of this two-paper set is mainly aimed at theory and algorithm derivation. The proposed fault detection technique for both arcing and permanent faults is achieved by a combination of a fault detection index |M| and a fault location index |D|, which are obtained by processing synchronized fundamental phasors. One is to detect the occurrence of a fault and the other is to distinguish between in-zone and out-of-zone faults. Furthermore, for discriminating between arcing and permanent faults, the proposed technique estimates the amplitude of arc voltage by least error squares method through the measured synchronized harmonic phasors caused by the nonlinear arc behavior. Then, the discrimination will be achieved by comparing the estimated amplitude of arc voltage to a given threshold value. In addition, in order to eliminate the error caused by exponentially decaying dc offset on the computations of fundamental and harmonic phasors, an extended discrete Fourier transform algorithm is also presented.     

A new fault location technique for two- and three-terminal lines

A method for the computation of fault location in two- and three-terminal high voltage lines is presented. It is based on digital computation of the three-phase current and voltage 60/50 Hz phasors at the line terminals. The method is independent of fault type and insensitive to source impedance variation or fault resistance. Furthermore, it considers the synchronization errors in sampling the current and voltage waveforms at the different line terminals. The method can be used online following the operation of digital relays or offline using data transferred to a central processor from digital transient recording apparatus. The authors start with a two-terminal line to explain the principles and then present the technique for a three-terminal line. The technique was first tested using data obtained from a steady-state fault analysis program to evaluate the convergence, observability, and uniqueness of the solution. The technique was then tested using EMPT-generated transient data. The test results show the high accuracy of the technique     

A performance oriented impedance based fault location algorithm for series compensated transmission lines

This paper proposes a performance oriented fault location algorithm for series compensated transmission lines. The algorithm estimates the fault location based on the calculated fault voltage and current using two end measurements and line parameters. Fault location computations are carried out considering faults existed before or after the compensator location on the line. The calculated MOV impedance is the key factor in determining whether or not the fault is located in front of the compensator. A 380 kV transmission line with a series capacitor and an MOV has been tested for various fault types, fault locations and fault resistances. The results show that the algorithm accurately estimates the fault location for all cases.     

配电网下基于PMU量测的混合故障测距法

精确的故障定位是节省巡线人力和物力的关键,对于提高供电可靠性,减小持续停电造成的损失具有重要意义。针对目前输电网故障测距技术比较成熟,而配电网精确故障测距尚待深入研究的实际情况,提出了配电网故障测距策略,其包括两个步骤:首先基于故障指示器(FI)实现故障区段或故障分支定位,然后利用所提的混合故障测距法,实现带分支辐射型配电网的精确故障测距。最后通过MATLAB仿真验证了所提故障测距策略的有效性,实验结果表现出了较高的故障测距精度。     

A new technique,based on voltages,for fault location on three-terminal transmission lines

A new method for fault location on three-terminal transmission lines is described in this paper. Through this method, the faulty line branch is determined and the fault point located in a reliable and simple manner. For this, to reduce mathematical errors, a complete line model including the various characteristics of the network is used and a simple calculation method is applied, based on a new concept referred to as the ‘branch factor’. The method only uses the main components (50/60 Hz) of fault and prefault voltage values measured at the three terminals of the transmission line. Moreover, this method is independent of the fault and prefault current, type of fault and fault resistance, as well as the synchronization of recording devices located at the three terminals of the transmission line, and the prefault conditions. This paper also reviews the sensitivity of this method to errors in input data.     

基于行波原理的优化组合故障测距技术

对现代D型双端和A型单端输电线路行波故障测距原理的准确性和可靠性进行了综合评价。在此基础上,提出了基于这两种行波原理的优化组合测距思想,并成功用于实际故障暂态行波分析。与单独的D型或A型行波测距方案相比,本方案的最大优点是能够利用A型行波原理对D型行波原理给出的测距结果进行验证和校正,从而同时提高了测距可靠性和准确性。实际应用表明,优化组合行波测距方案是可行的,并且测距精度得到明显提高。     

基于行波原理的优化组合故障测距技术

对现代D型双端和A型单端输电线路行波故障测距原理的准确性和可靠性进行了综合评价.在此基础上,提出了基于这两种行波原理的优化组合测距思想,并成功用于实际故障暂态行波分析.与单独的D型或A型行波测距方案相比,本方案的最大优点是能够利用A型行波原理对D型行波原理给出的测距结果进行验证和校正,从而同时提高了测距可靠性和准确性.实际应用表明,优化组合行波测距方案是可行的,并且测距精度得到明显提高.     

An adaptive high and low impedance fault detection method

An integrated high impedance fault (HIF) and low impedance fault (LIF) detection method is proposed in his paper. For a HIF detection, the proposed technique is based on a number of characteristics of the HIF current. These characteristics are: fault current magnitude; magnitude of the 3rd harmonic current; magnitude of the 5th harmonic current; the angle of the third harmonic current; the angle difference between the third harmonics current and the fundamental voltage; and the negative sequence current of HIF. These characteristics are identified by modeling the distribution feeders in EMTP. Apart from these characteristics, the above ambient (average) negative sequence current is also considered. An adjustable block out region around the average load current is provided. The average load current is calculated at every 18000 cycles (5 minutes) interval. This adaptive feature will not only make the proposed scheme more sensitive to low fault current, but it will also prevent the relay from tripping during the normal load current. In this paper, the logic circuit required for implementing the proposed HIF detection method is also included. With minimal modifications, the logic developed for the HIF detection can be applied to low impedance fault detection. A complete logic circuit which detects both the HIF and LIF is proposed. Using this combined logic, the need of installing separate devices for HIF and LIF detection can be eliminated     

基于FastICA的输电线路行波故障测距方法

为了解决输电线路故障信号存在抵偿效应导致测距精度不足的问题,建立线性瞬时混合的线路模型。采用快速独立成分分析法(FastICA)对采集的多通道线路故障原始数据(观测信号)进行相关分析,将表征故障特征的各分量逐一提取。以能量比函数对故障分量进行求解,设定能量比阈值以定位故障时刻,实现基于行波原理的线路精确测距。大干扰条件下故障特征受噪声信号干扰,会对测距精度产生影响。对此,FastICA算法能将噪声信号从故障原始数据中分离,避免噪声对测距过程产生的影响,进一步提高测距精度。仿真实验证明:所提出的方法能有效避免噪声干扰的影响,能适应大干扰条件下的故障测距,具有较好的抗干扰性。     

An accurate fault location algorithm for parallel transmission lines using one-terminal data

An accurate fault location algorithm for parallel transmission lines, using fundamental frequency components of post-fault voltage and current measured at one terminal, is described in this paper. Parallel transmission lines can be decoupled into the common component net and differential component net. In differential component net, the current distributing coefficient is a function of fault distance, and the differential component current at the fault point can be expressed in terms of the current at the local terminal. Therefore, for asymmetrical faults, the phase fault current can also be expressed as a function of local terminal current and fault distance. With the fault boundary conditions for a given fault type, the fault location equations can then be derived. Based on distributed parameter line model, the proposed algorithm achieves superior locating accuracy, with mutual coupling between circuits, source impedance and fault resistance having very little influence on the locating accuracy. The performance of new algorithm is verified by computer simulation results for transposed and non-transposed lines.     

基于RL模型的双回线单端时域法故障定位

提出了一种基于双回线单端电气量的RL模型时域法故障定位方法.该方法是建立在集中参数模型基础上,利用单端电压电流通过微分方程计算故障相的沿线电压,根据故障边界条件,用环流电流来计算故障电流,再根据故障支路的电压电流关系进行故障定位.由于该定位方法在时域中进行,所需数据窗短,计算量小.利用分布参数模型的故障数据对该方法进行仿真验证,结果表明具有实用价值,并给出了提高定位精度的措施.