Impedance-based Fault Location Methods Research Articles

A new fault location scheme based on local measurements for transmission lines connected to inverter-based resources

This paper aims to reveal conventional impedance-based fault location methods’ shortcomings in the presence of inverter-based resources (IBRs) through an analytical framework established for the analysis of the IBR sequence impedances. Thereafter, a single-ended method is put forward in order to accurately specify the fault location in the lines emanating from the IBRs. The proposed fault location formulation utilizes the negative and zero sequence currents as alternative polarizing currents, therefore it is independent of the pre-fault data, and it can be applied for all kinds of asymmetrical short circuit fault. Furthermore, the established formulation is further amended to make it applicable to long transmission lines. The suggested method also provides acceptable accuracy in various conditions, such as different fault resistances, different host grid codes, and dynamic behavior of the fault resistance. The performance of the proposed scheme is scrutinized using the PSCAD/EMTDC software with an extensive number of simulations. The obtained results reveal the effectiveness and efficacy of the proposed fault location method in the presence of IBRs.

Fault current constrained impedance-based method for high resistance ground fault location in distribution grid

Fault locating technology is crucial to the safe operation of a distribution grid. Impedance-based method is quite promising in fault locating due to its low cost and easy implementation. However, this method suffers from low precision when locating high resistance ground fault. This paper proposes a fault current constrained impedance-based fault location method. This method establishes location equations via the assumption that fault resistance consumes zero reactive power. First, this method adds the Thevenin equivalent to the downstream network after the fault. Second, the increment of fault current caused by distributed generations is quantified. These efforts provide an exact estimation of fault current, leading to a higher locating precision when encountering a high resistance ground fault. Simulations based on IEEE-34 node network show that the proposed method outperforms the traditional impedance-based method in precision significantly. Moreover, the proposed method does not need to distinguish fault type in advance, and is compatible to different fault scenarios.

An impedance-multi-method-based fault location methodology for transmission lines connected to inverter-based resources

This paper is motivated by the growing penetration of Inverter-Based Resources (IBRs) in power systems and their impacts on fault diagnosis systems. Also, a motivating factor is the scarcity of works in the literature that evaluate the effects and provide solutions to impedance-based fault location in lines interconnecting IBRs to the grid. In this context, the performance of ten traditional impedance-based (one- and two-terminal) fault location methods is evaluated, and a multi-method methodology that minimizes the obtained fault location errors is proposed. To conduct the analysis and propose the methodology, the PSCAD software is used to carry out massive fault simulations on two systems with different voltage levels and connection topologies of IBRs to the grid. The results demonstrate that the proposed methodology significantly minimizes the fault location percentage errors, being a very promising proposal, especially for conditions in which communication channels between the line terminals are unavailable.

Design and Implementation of Real-time Fault Location Experimental System for Teaching and Training University Students

The fault location problem is one of the most important issues in power system operation and control. To obtain an experimental system for teaching and training electrical engineering students, this paper performed a study to design and implement a real-time fault location laboratory-scale model from practical hardware components. The impedance-based fault location method is embedded in the system to determine the distance to fault in the transmission line. Furthermore, the monitoring and controlling program is designed by the Matlab App Designer – A new professional app to create the graphical user interface and use the integrated editor quickly. Several fault types including three-phase fault, phase-to-phase fault, phase-to-ground fault are created to evaluate the performance of the fault location experimental system. The real-time measurement results which are acquired and observed on the user guide interface of the program confirm the effectiveness of the experimental system; therefore, the system can be considered a powerful tool for electrical engineering students.

A zero-sequence impedance-based fault location method for MV distribution feeders with sparse measurements

A zero-sequence impedance-based fault location method for MV distribution feeders with sparse measurements

Performance Comparison of Impedance-Based Fault Location Methods for Transmission Line

Electric transmission lines play a very essential role in transmitting power energy from generation centers to consumption regions. They can be exposed to fault occurrences due to various reasons, such as lightning strikes, malfunction of components, and human errors. Since fault is unpredictable, a fast fault location method is required to minimize the impact of fault in power systems. This paper presents a research work for comparing the performance of the impedance-based fault location methods, in which the impedance parameter of the faulted line section is calculated as a measure of the distance to the fault. To evaluate the capability of the methods for correctly detecting and locating the fault locations, comprehensive simulation results are carried out. This computation is based on modeling and simulating a three-phase 220kV overhead transmission line in the Matlab/Simulink software. Short circuits which occur in various fault resistances and locations along the transmission line are emulated to investigate several case studies and the accuracy of fault location determination is calculated to compare the performance among these fault location methods.

Wide area fault location on transmission systems using synchronized/unsynchronized voltage/current measurements

Wide area impedance-based fault location methods use global positioning system (GPS) for pinpointing the fault position. GPS signal loss occurs repeatedly in power system because of slow communication link or lack of synchronized sampling infrastructure that makes synchronized measurements unavailable in some parts of the grid. To overcome the grid synchronization problem this paper presents a fault location method that integrates synchronized and unsynchronized current and voltage measurements in a system of equation form. In this system the magnitude of measurements is considered for all measurements and the phase angle is considered only for synchronized measurements. On the other hand, any type of measurements (current and voltage) which is done synchronized or unsynchronized can be integrated in the developed system. The integration of GPS synchronized and unsynchronized measurements prevents the GPS signal loss to affect the fault location problem, while many of the previous methods are not applicable under these conditions. Then the formed system is solved with the aim of finding the location of fault utilizing an iterative approach. The line distributed parameter model is used in this paper, which provides more accurate results nearer to real values. The proposed method is validated by WSCC 9-bus and IEEE 39-bus test systems which reveal accurate estimation even in conditions that the GPS signal is not accessible.

Fault Classification and Voltage Sag Parameter Computation Using Voltage Ellipses

Fault classification and voltage sag parameter computation using voltage ellipses in Clarke's domain are presented in this paper. The voltage sag parameters computed were the point-on-wave of initiation and recovery, residual voltage, and phase-angle jump. A change in the phase reference in Clarke's transformation was proposed to simplify the fault classification procedure. The point-on-wave of initiation and recovery were defined based on the reference circle in Clarke's domain, as described by the system during normal operation. The residual voltage and phase-angle jump were computed using the expressions of $\alpha$ and $\beta$ components in Clarke's domain and trigonometric theorems. The proposed fault classification and voltage sag characteristics computation were applied to real data provided by the Department of Energy and the Electric Power Research Institute. From the results obtained, it is concluded that the zero-sequence component must be taken in consideration to compute the residual voltage and the phase-angle jump correctly, and to use these results to improve the accuracy of impedance-based fault location methods. The proposed fault classification algorithm is capable of classifying events and computing the residual voltage and phase-angle jump. Additionally, the voltage sag duration of short events and multistage events was successfully computed. This work is an incremental contribution within the field of voltage sag analysis in the time domain using Clarke's transformation.

Universal model‐based fault location for improved system integrity

Transmission lines are a vital part of power systems and are prone to a variety of short-circuit faults. It is imperative to identify the fault location to restore the system as quickly as possible for maintaining the system integrity. Impedance-based fault location algorithms are most commonly used but they are prone to several sources of error such as fault resistance and mutual coupling between the lines and may not provide accurate results in the presence of complex network configurations such as three-terminal lines. Though information about mutual coupling or knowledge of complex network configuration is known, they cannot be directly used in impedance-based fault location algorithms. This study proposes a novel automated generic framework for model-based fault location approach which uses the power system model to overcome the shortcomings of impedance-based fault location methods. A combination of power system simulation software and a control and processing software provide the flexibility to be able to incorporate all the available information about the system to accurately estimate the fault location. Furthermore, this study provides key insights to implement the proposed framework in an effective and efficient manner by using reduced equivalent circuits.

Novel modified impedance-based methods for fault location in the presence of a fault current limiter

A fault current limiter (FCL) is promising novel electric equipment to effectively reduce excessive short circuit current in power networks. The presence of a FCL at the time of a fault occurrence makes it necessary to consider new settings for protective relays and fault locators. This paper examines the presence of a FCL in power networks and its effects on single-ended impedance-based fault location methods. It will be shown that FCL deployment in a transmission line makes the traditional fault location method inefficient. Two modified methods are presented to solve the problem. The modified methods locate the fault point using remote bus impedance in the presence of the FCL. The accuracy of the proposed methods is validated using the IEEE 14-bus system. The simulation results indicate that the proposed methods have considerable superiority over the conventional technique and perform well for different faults and FCL types.

Fault Location in Double Circuit Medium Power Distribution Networks Using an Impedance-Based Method

The distribution network is extended throughout cities, towns, and villages. Because of the increase in loads and the decrease in power passageways and public corridor reduction, double circuit lines are increasingly being used instead of single circuit lines. Fault location in double circuit power networks is very important because it decreases the repair time and consequently the power outage time. In this paper, a new improved method for fault location in double circuit medium power distribution lines is proposed. The suggested impedance-based fault location method takes into account the mutual effect of double circuit lines on each other. To the best of our knowledge, the proposed method is the first of its kind which supports double circuit distribution networks. In the proposed method, a new quadratic equation for locating fault in power distribution networks is obtained using recorded voltage and current at the beginning of feeder. In this method, the π line model is used for improving the accuracy of the suggested method. The proposed method is supported by mathematical proofs and derivation. To evaluate the accuracy of the proposed method, the proposed method is tested on a thirteen-node network in different conditions, such as instrument error, various fault resistances, and different fault inception angles in various distances and fault types. The numerical results confirm the high accuracy and validity of the proposed method.

Impedance-Based Fault Location Method for Four-Wire Power Distribution Networks

Fault location techniques play an essential role in system recovery and repair. Therefore, numerous methods have been presented for fault location in power transmission and distribution networks. The contribution of this paper is to extend the state-of-art impedance-based fault location methods to support four-wire power distribution. To make this possible an algorithm is developed. The method is obtained using the principles of circuit theory and overcomes the challenges which prevent the use of most fault location methods for distribution networks in practice. This paper presents the detailed equations which are used in the algorithm and how they are obtained. The satisfactory performance of the algorithm is confirmed with numerical examples using MATLAB software.

Impedance-based fault location methods: Sensitivity analysis and performance improvement

This paper deals with analysis and improvement of two-terminal impedance based fault location methods for transmission lines. Firstly, a customised sensitivity analysis (CSA) for this class of methods is discussed, which allows a more comprehensive analysis than those so far used for evaluating the robustness to uncertainties of the input parameters (such as phasors and electrical line parameters). Second, a customised modal transformation (CMT) is derived from CSA, aiming to improve impedance-based fault location methods for performance. Such an approach uses the Park transformation along with a cost function obtained from the CSA. To assess the effectiveness of the developed approach, four two-terminal fault location methods from the literature, using both distributed parameter line model and only fault data, are considered. Evaluation tests based on Alternative Transients Program (ATP) simulations have shown that the proposed approach presents results quantitatively superior than other approaches from the literature confirming its applicability.

Low Voltage Zones to Support Fault Location in Distribution Systems With Smart Meters

This paper proposes to combine the voltage monitoring capability of smart meters with impedance-based fault location methods to provide an efficient fault location approach improving service restoration. The first step of the proposed methodology is to apply an impedance-based method to obtain a rough estimation of fault location. Since the result is an estimated distance to the fault, multiple branches can be indicated due to the typical distribution systems topologies. Therefore, the challenge is: how to recognize the actual fault location? To solve this problem, voltage measurements from smart meters are used to build the low voltage zones (LVZs). The main contributions of the proposed fault location technique are to decrease the multiple estimations associated with impedance-based methods, to propose a systematic approach to build the LVZs, and to explore the presence of smart meters for fault location. The proposed method was tested through intensive and extensive simulations in a real distribution system, proving its efficiency.

Robustness of a generalized impedance based fault locator considering distorted measurements

Power quality is a relevant aspect in power distribution systems, which among others, considers service continuity and distortion of the current and voltage waveforms. This paper proposes a generalized application strategy of an impedance-based fault location method for power distribution systems and also analyses the effects of the waveform distortion on its performance, by comparing the location errors in the case of distorted and not distorted measurements of voltages and currents. Different sources of waveform distortion, such as transformer saturation, low resolution of the measuring devices, harmonics, low sampling frequency, signal noise and DC offset are analysed. According to the obtained results, the worst performance of the fault location method is obtained in the case of distortions caused by current transformer saturation. An additional circumstance of reduced performance is in such cases of simultaneous presence of low sampling rate and high harmonic distortion. Finally, the analysed values of resolution, signal noise, presence of DC offset and potential transformer saturation, cause a negligible reduction on the locator performance.

Experimental studies on impedance based fault location for long transmission lines

In long transmission lines, the charging current caused by the shunt capacitance decreases the accuracy in impedance based fault location. To improve the accuracy of fault location, this paper presents a novel scheme, where two Digital Fault Recorders (DFRs) are installed in a line. They can send the transient data of the faults to the both ends of a line. To estimate the distance of a fault, impedance based fault location methods are applied with transient fault data of both ends protection relays and both DFRs installed in a line. To evaluate the proposed scheme, a laboratory setup has been developed. In the lab, several faults have been simulated and associated voltages and currents are injected to a relay IED to compare experimental results.

A Comparison of Impedance-Based Fault Location Methods for Power Underground Distribution Systems

In the last few decades, the Smart Grid paradigm presence has increased within power systems. These new kinds of networks demand new Operations and Planning approaches, following improvements in the quality of service. In this sense, the role of the Distribution Management System, through its Outage Management System, is essential to guarantee the network reliability. This system is responsible for minimizing the consequences arising from a fault event (or network failure). Obviously, knowing where the fault appears is critical for a good reaction of this system. Therefore, several fault location techniques have been proposed. However, most of them provide individual results, associated with specific testbeds, which make the comparison between them difficult. Due to this, a review of fault location methods has been done in this paper, analyzing them for their use on underground distribution lines. Specifically, this study is focused on an impedance-based method because their requirements are in line with the typical instrumentation deployed in distribution networks. This work is completed with an exhaustive analysis of these methods over a PSCADTM X4 implementation of the standard IEEE Node Test Feeder, which truly allows us to consistently compare the results of these location methods and to determine the advantages and drawbacks of each of them.

Time-based fault location method for LV distribution systems

Due to the utilization of fundamental frequency, current impedance-based fault location methods are able to locate only permanent and linear faults. The duration of the arc in low and medium voltage systems can be as short as a quarter of a cycle. This period, which is normal for intermittent faults, is insufficient for fundamental frequency-based fault location algorithms. Therefore, available methods are not applicable for intermittent arcing fault location. In this paper, the time-based method previously proposed by the authors has been developed to locate short duration faults in LV distribution systems. The advantage of the proposed method over available methods is its capability for locating faults using fewer samples, which enable the user to locate both arcing faults as well as normal faults in the network. The main characteristics of an arcing fault, i.e., non-linearity and short duration, have been addressed in the proposed algorithms methodology. Various characteristics of a LV distribution system (i.e., heterogeneity, unbalanced load and line, etc.) have been taken into account in the current enhanced algorithm. The validity of the devised algorithm is studied within PSCAD-EMTDC environment and the obtained results show a good accuracy.

Improved Fault Location Through Analysis of System Parameters During Autoreclose Operations on Transmission Lines

This paper describes a novel single-ended impedance-based fault-location method for transmission lines, which is based upon the analysis of voltage and current during discrete system states that arise during the operation of single- and three-phase autoreclose schemes. A fault-location estimation algorithm, using the data measured during various system states and is capable of locating the fault types involving one fault resistance (i.e., single-line-to-ground fault or line-to-line fault), is developed and presented. The proposed fault-location technique is shown to have high accuracy; results are presented and compared with the well-established Takagi method and the performance of the algorithm is analyzed and discussed. The proposed technique can reduce or negate limitations associated with conventional single-ended methods and can also estimate other factors associated with the fault (e.g., fault resistance and remote source impedance). In addition, it is a potentially economic solution, since it is relatively straightforward to implement on a standard protection relay hardware platform. The proposed method is demonstrated using Electromagnetic Transients Program/Alternate Transients Program simulation models for a variety of different cases. This paper concludes with an overview of ongoing and future work that has the intention of moving the work forward toward implementation within commercially available relay hardware.

One-end impedance based fault location in double-circuit transmission lines with different configurations

• One-end impedance based fault location method for double-circuit transmission lines with eight different configurations. • Developed in phase coordinates and does not require six-order sequence component transformation. • Fault data for verification are obtained using MATLAB – Simulink. • Results shown that the method is accurate and robust. A one-end impedance based fault location method suitable for double-circuit transmission lines with different end configurations is presented in this paper. The effect of mutual coupling of the circuits is taken care of in developing the algorithm. The method is developed in phase coordinates and hence it does not require the complicated six-order sequence component transformation. It is applicable to both symmetrical and unsymmetrical lines. Depending on the terminations at both ends of the line, eight different cases are discussed. The fault data required to evaluate the effectiveness of the method are obtained by simulating faults in different types of double circuit lines using MATLAB/Simulink. The accuracy of the proposed technique is evaluated by comparing the computed fault location with the actual fault location in the simulated models. It is shown that the method is accurate and robust for small errors in estimated equivalent source impedances.