Impedance-based Fault Location Research Articles

Combination effects of fault resistance and remote in feed current on simple impedance based fault location

There are many types of fault location algorithms and one of it is simple impedance based fault location algorithm which is still widely used by power system utilities around the world mainly because of no communication channel exists between local and remote substations. The aim of this research is to study the combination effects of remote in feed current and fault resistance on the accuracy of simple impedance based fault location algorithm which is used to estimate fault location when the transmission line is connected to equivalent Thevenin sources from both ends. Simulation has been carried out using Matlab Simulink software for single line-to-ground fault and line-to-line fault. For each type of fault, fault location and fault resistance were varied for two conditions which were when remote breaker in open and remote breaker in close conditions. From the results, it can be concluded that remote in feed current will add additional error to the error due to the existence of fault resistance when fault resistance not equal to zero.

A new single end wideband impedance based fault location scheme for distribution systems

This paper proposes an improved impedance based fault location scheme based on system analysis at non-fundamental frequencies. The fault is treated as a voltage source that injects high frequency components into the system and the analysis is carried out using these injected components. The proposed method only requires local measurements at the substation and therefore is classified as a single end method. The new contribution is that the proposed method uses the distributed parameter line model to account for inductive and capacitive effects of the line. It has been evaluated on the IEEE 34-bus feeder which is based on an actual distribution system which has the typical features such as non-homogeneous feeder sections, asymmetrical line configurations, unbalanced loads and single and three-phase laterals. The fault point, fault resistance and fault inception angle have been varied to check their influence on the accuracy of the method. The simulation results demonstrate the accuracy of the proposed method where for most cases, the error in fault location is less than 50m.

Dynamic state estimation for double-end traveling wave arrival identification in transmission lines

A dynamic state estimation (DSE) approach is proposed to improve the accuracy to identify the front-wave arrival times of a two-terminal traveling wave protection scheme for a transmission line with low sampling rates. The solution is implemented as an offline method aiming to use existing infrastructure measurements. The work presents the principles of traveling wave (TW) theory and legacy protection schemes with this methodology. The proposed method requires GPS synchronized measurements at both ends of the line and a high fidelity model of the protected line. The paper presents comparisons between the differentiator smoother for arrival time identification, traditional impedance based fault location using 1 or 2 terminals and the proposed DSE-TW. The performance is also assessed with the Bergeron model and the frequency dependent parameter model of the transmission line. Numerical simulations and laboratory tests demonstrate that the method can correctly identify the front-wave arrival time at each end with better accuracy and different sampling rates. This work illustrates the advantages of DSE-TW such as high accuracy of arrival time identification, the minimum error of fault location and better performance with different (lower) sampling rates.

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.

Adaptive Impedance-Based Fault Location Algorithm for Active Distribution Networks

Modern fault location methods are robust; however, they depend strongly on the availability of the measurements given by Distributed Energy Resources (DER). If the communication or synchronism of this information is lost, the fault location is not possible. This paper proposes an adaptive impedance-based fault location algorithm for active distribution systems. The proposal combines information provided by Intelligent Electronic Devices (IEDs) located at the substation, the knowledge of the network topology and parameters, as well as the distributed power sources, to estimate the fault location. Its adaptive feature is given by the use of a Distributed Energy Resources (DER) electrical model. This model is used to estimate the DER current contribution to the fault, in case the information provided by a local IED is not available. The method takes two types of DER technologies into account: Inverter non-interfaced DER (INIDER) and Inverter-interfaced DER (IIDER). The proposed method is validated on a modified IEEE 34-node test feeder, which was simulated with ATP/EMTP. The results obtained using the IEDs information, presented a maximum error of 0.8%. When this information is not available, the method’s performance decreases slightly, obtaining a maximum error of 1.1%. The proposed method showed better performance when compared with two state of the art methods, indicating potential use for real-life applications.

Impact of an inverter‐based DG on a double‐ended fault location method

This paper describes the influence of Distributed Generation (DG) on a double ended fault location based on measuring the high frequency fault transients. The additional non-fundamental frequency current components from DG will influence the accuracy of an impedance based fault location technique based on non-fundamental frequencies. A double-ended impedance based fault location technique that utilizes the high frequency content (up to 5 kHz) is studied. The study showed that double-ended method is still able to locate a fault with a maximum error of 4% compared to the case without DG which showed a percentage error up to 2%.

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.

Assessment of impedance based fault locator for AC micro-grid

This paper proposes an impedance-based fault location determination scheme for the 3-phase micro-grid. The paper describes how voltage and current data during a fault event can be leveraged to accurately locate a fault in the micro-grid including distributed generation (DG). The proposed method uses voltage and current measurements from both ends of the line section in order to determine the fault location. This method is devised in such a way that it evades the requirement of fault type identification by using only one fault location equation. The method is applicable to all types of shunt faults. In the proposed formulation of fault location, the effect of mutual inductance and capacitance of distribution line is also considered. The method is tested on a simulated medium-voltage (MV) micro-grid with doubly fed induction generator (DFIG) and permanent magnet synchronous generator (PMSG) wind turbines connected to specific nodes. The test results indicate that the proposed fault locator can reliably locate faults in the micro-grid with high accuracy.

Influence of instrument transformers and anti-aliasing filters on the performance of fault locators

Anti-aliasing filters are used in cascade with instrument transformers (IT) as part of protective relay data acquisition systems for providing input signals to fault locators. Due to IT and anti-aliasing filters transient responses, the fault locators input data may not be replicas of the power network voltage and current waveforms, and incorrect information may be transferred to protection devices. In this paper, the performance of traveling wave-based and impedance-based fault location techniques are evaluated by extensive short-circuit simulations considering different IT topologies and anti-aliasing filters. The total amount of fault location estimated errors were combined to generate an error function and an original study about a thorough statistical analysis was performed. From the obtained results, the errors can be approximated by a function with normal probability distribution, and the fault location performances are directly affected by the fault-induced amplification and attenuation of the highest frequencies at the IT spectrum and the oscillations presented in the anti-aliasing filters bandpass.

High Frequency Impedance Based Fault Location in Distribution System With DGs

Distributed generations (DGs) with power electronic devices and their control loops will cause distortion to the fault currents and result in errors for power frequency measurement based fault locations. This might jeopardize the distribution system fault restoration and reduce the grid resilience. The proposed method uses high frequency (up to 3 kHz) fault information and short window measurement to avoid the influence of DG control loops. Applying the DG high frequency impedance model, faults can be accurately located by measuring the system high frequency line reactance. Assisted with the DG side recorded unsynchronized data, this method can be employed to distribution systems with multiple branches and laterals.

Impedance-Based Fault Location Algorithm for Ground Faults in Series-Capacitor-Compensated Transmission Lines

Locating a fault in a series-capacitor-compensated transmission line (SCCTL) is a challenging task due to the action of a metal-oxide varistor a nonlinear element present as a part of the protection system of the series capacitor. In this paper, an accurate fault-location algorithm that uses synchronized measurements from both ends of the SCCTL is presented which provides fault-location results without using the model of MOV or natural fault loop for single-phase-to-ground, and double-phase-to-ground faults. Another salient feature of the proposed technique is that the subroutines for locating faults in different sections transmission line yield almost identical fault-location results regardless of which section the transmission line is faulted. The proposed technique could also be extended to the double-circuit transmission lines. First, the proposed technique is introduced and its features are elaborated through detailed mathematical analysis. Thereafter, a 500- $\text{kV}$ system with an SCCTL is designed in PSCAD, while the fault-location algorithm is modeled in MATLAB. The proposed algorithm is tested through simulations covering various fault scenarios in an SCCTL. For performance evaluation, the comparative analysis of the proposed technique with a well-known existing technique is performed in this paper.

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.

A threshold free synchrophasor measurement based multi-terminal fault location algorithm

A new impedance based fault location algorithm is proposed for a generic multi-terminal transmission network consisting of a main line and tapped branches with no direct measurements available at the intermediate tapping nodes. The core of the algorithm is a threshold free faulted branch search algorithm that systematically compares the multiple estimates of voltages for the tapping nodes, computed using synchrophasor measurements at the terminals. Once the faulted branch is identified, multi-terminal fault location problem is reduced into a two-terminal fault location problem to determine the exact location of fault within the branch. The proposed algorithm is simple and does not involve resource intensive mathematical operations such as matrix inversion. The proposed algorithm was implemented as a module in an in-house developed real-time synchrophasor application software program, and its performance was evaluated using a test setup consisting of a real-time simulator, an actual synchrophasor network, and a phasor data concentrator. The tests showed that the proposed algorithm is capable of correctly determining the faulted branch, except for few faults that are very close to tapping nodes. When the algorithm is used with practical synchrophasor measurements, the fault location error was within a typical tower span for most cases.

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.