Fault Location Scheme Research Articles

A Traveling-Wave-Based Fault Location Scheme for MMC-Based Multi-Terminal DC Grids

This paper presents a novel fault location scheme of DC line in modular multilevel converter (MMC)-based multi-terminal DC (MTDC) grids. Considering the low-inertia characteristics and the meshed topology, the scheme, based on traveling-wave principle, is divided into three steps, namely, faulty pole identification, faulty segment determination and fault-distance calculation. With accurate amplitude, polarities and arrival times of the first arrival current traveling waves (FACTWs) collected from time-synchronized measurements taken just at the converter stations, the proposed scheme can correctly determine the faulty pole, the faulty segment and the precise fault location. The continuous wavelet transform (CWT) is deployed to extract the required features of the input signals at the DC lines. Since the scheme merely needs the features of FACTWs, the practical difficulties of detecting subsequent traveling waves are avoided. A four-terminal MMC-based high voltage direct current (HVDC) grid was built in PSCAD/EMTDC software to evaluate the performance of the fault-location scheme. Simulation results for different cases demonstrate that the proposed fault-location scheme has high accuracy, good adaptability and reliability. Furthermore, the algorithm can be used for a MMC-MTDC grid with any number of meshes.

Analysis on IGBT and Diode Failures in Distribution Electronic Power Transformers

Fault characteristics of power electronic components are of great importance for a power electronic device, and are of extraordinary importance for those applied in power system. The topology structures and control method of Distribution Electronic Power Transformer (D-EPT) are introduced, and an exploration on fault types and fault characteristics for the IGBT and diode failures is presented. The analysis and simulation of different fault types for the fault characteristics lead to the D-EPT fault location scheme.

A novel fault location scheme for power distribution system based on injection method and transient line voltage

This paper presents a novel fault location method by injecting travelling wave current. The new methodology is based on Time Difference Of Arrival(TDOA)measurement which is available measurements the injection point and the end node of main radial. In other words, TDOA is the maximum correlation time when the signal reflected wave crest of the injected and fault appear simultaneously. Then distance calculation is equal to the wave velocity multiplied by TDOA. Furthermore, in case of some transformers connected to the end of the feeder, it’s necessary to combine with the transient voltage comparison of amplitude. Finally, in order to verify the effectiveness of this method, several simulations have been undertaken by using MATLAB/SIMULINK software packages. The proposed fault location is useful to short the positioning time in the premise of ensuring the accuracy, besides the error is 5.1% and 13.7%.

A Submodule Fault Ride-Through Strategy for Modular Multilevel Converters With Nearest Level Modulation

The modular multilevel converter (MMC) with nearest level modulation (NLM) is widely used in the high voltage applications for low switching frequency and easy implementation. Existing literature has not provided a complete submodule (SM) fault ride-through scheme for MMC with NLM. In this paper, a strategy including fault detection, localization, redundancy, and recovery is proposed to ensure continuous operation of MMC under IGBT open-circuit faults conditions. It only requires a few hardware and software resources. The features of MMC and SMs with three types of failures are studied, respectively. Based on these, the fault detection method is proposed by using a simple hardware circuit, thus high computation complexity is avoided. Since current fault localization schemes are limited to MMC with carrier phase shifted pulse width modulation, this paper further proposes a strategy for MMC with NLM to locate the faulty SM and identify the fault type. After this, the fault redundancy and the proposed fault recovery method are applied to eliminate the fault and then exit the failure state. Therefore, the ability of SM fault ride-through can be realized. Analysis of failure characteristics are verified in simulation. Experimental results based on a single-phase MMC prototype with 11 SMs per arm are presented to demonstrate the validity of the proposed fault ride-through strategy.

Research on fault location scheme for inverter AC transmission line of AC–DC hybrid system

As the nonlinear characteristics of converters, the harmonic components of fault information hardly decays with the passage of time, which introduces an estimation error in the fault location in the inverter AC transmission line of an AC–DC hybrid system, especially under commutation failure condition. Therefore, a new fault location scheme, which combines the dynamic synchrophasor measurement algorithm and line equivalent impedance/admittance estimation algorithm, is proposed in this paper. The precision of phasor estimation under harmonic environment has been improved. Based on these, the pre‐fault data of one circle is applied to estimate the line equivalent impedance and admittance. Finally, the traditional fault location formula based on the two‐end information is employed to calculate the fault location. Evaluation results show that the proposed scheme is independent of the fault resistance, fault distance, and fault type. More importantly, it ensures a higher precision of fault location in comparison with the dynamic fault location algorithm, even under commutation failure. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

An artificial neural network-based solution to locate the multilocation faults in double circuit series capacitor compensated transmission lines

During thunder storms, multilocation faults may occur at different locations in different phases of the 3 phase transmission lines at same or different time. This paper proposes an artificial neural network-based solution to locate the multilocation faults in double-circuit series capacitor compensated transmission lines (SCCTLs), unlike previous works that only locate the fault at single location. Although various fault location schemes have been proposed for normal shunt faults occurring at 1 location in SCCTL, nevertheless, finding the locations of multilocation faults in double circuit SCCTL has not been addressed so far. The proposed artificial neural network-based method determines the location of multilocation faults by using current and voltage signals of 1 end of line only, thus avoiding the need of communication link. The signals are preprocessed by using discrete wavelet transform. A comparative study of various neural networks such as feed-forward back-propagation network with Levenberg-Marquardt algorithm, Elman recurrent neural network with gradient descent algorithm, radial basis function neural network has been carried out. The proposed method is not affected by variation in different parameters viz. fault type, fault location, fault inception angle, fault resistance, degree of series compensation, and location of series capacitor. The key advantage of the method is that it correctly estimates the locations of multilocation faults as well as single-location fault, thus making it more reliable and accurate as compared to conventional fault location schemes.

A Practical Approach to Localize Simultaneous Triple Open-Switches for a PWM Inverter-Fed Permanent Magnet Synchronous Machine Drive System

In order to overcome the limitations of conventional diagnosis methods, this paper proposes a reliable and practical on-line fault localization scheme for a pulse width modulation (PWM) inverter-fed permanent magnet synchronous machine (PMSM) drive system even when the inverter has simultaneous open faults in up to three switches. An open-switch fault is usually initiated by an accidental over-current, or electrical and thermal stresses. This fault may induce crucial secondary damage in the drive system since it is easily propagated and produces a continuous harmful effect on other system components. The open-switch faults in inverters often occur in a very complicated manner. Due to this reason, it was only recently that real-time diagnosis schemes under the open-switch faults in multiple switches have been presented in a few references. However, to alleviate the complexity and exactness issues, most of the conventional diagnosis schemes have considered the open faults only in two simultaneous switches until now, which is not generally the case. Even though the fault detection is simple and immediate, the exact fault localization is not a simple task, especially when there are open faults in three simultaneous switches because different open-switch fault locations may develop the same fault signature. To deal with such a problem, free-wheeling mode detection is introduced in this paper for the purpose of identifying the exact fault group and the faulty switch location. Then main objective of this paper is to realize a reliable fault localization algorithm under the condition of simultaneous open-switches (up to three) on an online basis without requiring any extra hardware or sensors in order that the algorithm can be easily installed in main CPU of a commercial drive system. For this purpose, the open faults in simultaneous switches are categorized into seven different fault groups. The entire system is implemented on a digital controller by using TMS320F28335 digital signal processor (DSP). The experimental results are presented under various open fault conditions to validate the usefulness of the proposed open-switch fault localization scheme.

Advanced fault location in MTDC networks utilising optically-multiplexed current measurements and machine learning approach

This paper presents a method for accurate fault localisation of DC-side faults in Voltage Source Converter (VSC) based Multi-Terminal Direct Current (MTDC) networks utilising optically-multiplexed DC current measurements sampled at 5 kHz, off-line continuous wavelet transform and machine learning approach. The technical feasibility of optically-based DC current measurements is evaluated through laboratory experiments using commercially available equipment. Simulation-based analysis through Matlab/Simulink® has been adopted to test the proposed fault location algorithm under different fault types and locations along a DC grid. Results revealed that the proposed fault location scheme can accurately calculate the location of a fault and successfully identify its type. The scheme has been also found to be effective for highly resistive fault with resistances of up to 500Ω. Further sensitivity analysis revealed that the proposed scheme is relatively robust to additive noise and synchronisation errors.

Reliable Open-switch Fault Localization Scheme in Multiple Switches for Inverter-fed Permanent Magnet Synchronous Machine Drives

To improve the reliability of a pulse width modulation inverter-fed permanent magnet synchronous machine drive under open faults in multiple switches, this paper proposes an on-line open-switch fault localization scheme. An open-switch fault which often leads to secondary damage in the entire system arises due to accidental overcurrent as well as electrical and thermal stresses. Especially, the open fault in multiple switches occurs in various types of combination, which prevents a fault localization algorithm from operating reliably. To alleviate the complexity in diagnosis algorithm, this paper classifies the open faults into different categories, which enables the diagnosis algorithm to handle and identify multiple failures in switching devices in more straightforward and systematic way. The decision-making process is simple and easy due to unique fault characteristic in each group. In the proposed scheme, the fault group is simply identified from only non-zero phase current information by using the moving window-based signals instead of the entire electrical periodic data. The proposed scheme detects a fault as well as faulty switches by on-line basis without additional hardware. It is not only immune to false alarms due to inexact detection, but also independent of operating conditions. The practical usefulness of the proposed scheme is verified through the simulations and experiments.

Voltage-Sag-Profiles-Based Fault Location in High-Speed Railway Distribution System

Operation parameters of the high-speed railway distribution system can be obtained from remote terminal units installed in box-type substations. Therefore, the voltage sag profiles may be utilized for fault location. This paper proposes a novel strategy for fault location in a high-speed railway distribution system by measured voltage data of existing box-type substations. The proposed method makes use of the difference between the calculated voltage and measured voltage at the end of the lines to locate the fault. Assuming that the fault occurs at any possible box-type substations along the lines, the faulted line section is identified with the defined difference sequence, and then the exact fault location can be obtained with a searching procedure in the identified fault section. Considering the effect of equivalent capacitance, each line section is modeled with the π model to improve accuracy of fault location. The validity of the proposed method is tested extensively in the simulation model of a real high-speed railway distribution system. The proposed method is not affected by fault type and fault resistance. Furthermore, comparing with the offline detection method of underground cables, it does not need any additional devices and will not interrupt the system operations.

Novel Fault Location in MTDC Grids With Non-Homogeneous Transmission Lines Utilizing Distributed Current Sensing Technology

This paper presents a new method for locating faults in multi-terminal direct current (MTDC) networks incorporating hybrid transmission media, including segments of underground cables and overhead lines. The proposed traveling wave type method uses continuous wavelet transform applied to a series of line current measurements obtained from a network of distributed optical sensors. The technical feasibility of optically-based dc current measurement is evaluated through laboratory experiments using Fiber–Bragg Grating sensors and other commercially available equipment. Simulation-based analysis has been used to assess the proposed technique under a variety of fault types and locations within an MTDC network. The proposed fault location scheme has been found to successfully identify the faulted segment of the transmission media as well as accurately estimating the fault position within the faulted segment. Systematic evaluation of the method is presented considering a wide range of fault resistances, mother wavelets, scaling factors, and noisy inputs. Additionally, the principle of the proposed fault location scheme has been practically validated by applying a series of laboratory test sets.

New fault location scheme for three-terminal untransposed parallel transmission lines

This paper proposes a new fault location scheme in the phase-domain for three-terminal untransposed double-circuit transmission lines utilizing synchronized voltage and current measurements obtained by GPS technique. The proposed scheme is derived taking into consideration the distributed line model and the mutual couplings effect between the parallel lines to obtain accurate results. The proposed scheme is derived based on the transmission line theory and Taylor series expansion of the distributed line model parameters. All fault types including normal shunt faults, evolving faults, and cross-country faults can be discriminated from each other and the fault location can be obtained for all fault types. The evolving faults include earth faults occurring at the same location in two phases of one circuit or two phases of different circuits at different fault inception time. While cross-country faults include earth faults occurring at different locations in two phases of one circuit or two phases of different circuits at same or different fault inception time. The proposed scheme is tested under different fault locations, different fault resistances, different fault inception angles, and all fault types including cross-country and evolving faults. Also, the effect of different sampling rate, measurement and synchronization errors, earth resistivity variations, and transmission line parameters errors on the proposed scheme is considered. Simulations studies conducted by MATLAB software demonstrate that the maximum estimation error in fault location does not exceed 3.06%.

Enhanced Fault-Location Scheme for Double Wye Shunt Capacitor Banks

Determining the location of internal failures in shunt capacitor banks (SCBs) helps to expedite their repair process and, thus, increase the time during which the power system benefits from this crucial component. This paper elaborates on fault location for a common configuration in high-voltage SCBs, which is the double wye connection (Y-Y). The neutral current unbalance protection is adapted to suit the development of an algorithm that detects the location of internal failures in ungrounded and grounded Y-Y SCBs. The proposed method is capable of detecting consecutive failures, and also can mitigate gradual capacitance and temperature change effects. Both internally fused and fuseless banks are considered in the proposed technique. The presented fault-location method is further enhanced by detecting the number of failed elements. Simulations are performed using PSCAD and MATLAB. The results validate the proposed method performance under pre-existing internal unbalances, system voltage unbalance, and faults in the grid. Illustrative simulation scenarios are provided to show the application and significance of the proposed method properties.

Fault location for power grid based on transient travelling wave data fusion via asynchronous voltage measurements

Considering the complex topology of power grids and their important application, finding an effective fault location algorithm is mandatory. This paper presents a fault location method for power grid based on transient travelling wave data fusion and asynchronous voltage measurements. Firstly, the refraction regularity, attenuation rule and main factors affecting the amplitude of the initial travelling wave are analyzed. Then the modulus maxima of detail coefficients, treated as the feature variables of the initial travelling wave, are extracted via wavelet transform. At last, according to the configuration of the measuring points, fault location scheme based on data fusion theory is proposed. In data level fusion, phase-mode and wavelet transform are carried out in order to obtain the feature variables. In feature level fusion, the fault section is determined through the fault feature variables filtered by the network topology and the artificial neural network is used to fit the relationship between the fault distance and the time difference of arrival between single-terminal aerial-mode and zero-mode voltage. In decision level fusion, the double-terminal fault location algorithm based on the single-ended uploaded data is proposed. The IEEE 30-Bus System is simulated in PSCAD/EMTDC and the fault location algorithm is carried out in MATLAB. The simulation results demonstrate that high-precision fault location could be realized and that practicality and economy are improved without requirements on synchronous sampling.

Identification and Localization of non-zero Resistance Short circuit Faults in Distribution Feeders Based on the Theory of Wavelets and Artificial Intelligence

This paper introduces a radial distribution feederprotection scheme based on certain features extraction fromcurrent signals measurement at the substation. The featuresare captured using the discrete wavelet transform (DWT). Twodigital signals processing methods are used to introduce thosefeatures to the 1) fault detection 2) identification and 3)localization schemes; the first one is the energy method and thesecond one is the root mean square method. For the purpose offault type identification, two systems are tested and compared,a Fuzzy Inference System (FIS) and Artificial Neural Network(ANN). Fault location scheme is then built based on ANNs. Aneffort is made to reduce the computational burden and thespeed of detection provided by the fault detection andidentification schemes. Since the short circuit faults are themost likely types of faults that can occur in power systems, theten types of these faults taking into account different faultresistances are simulated in MATLAB environment and theprotection scheme is built based on the idea of overcurrent.The power quality disturbances such as switching transientsevents on the feeder are also taken into account in order to builda reliable and secure protection scheme.

A Comparison Study of Learning Algorithms for Estimating Fault Location

Fault location is one of the important scheme in power system protection to locate the exact location of disturbance. Nowadays, artificial neural networks (ANNs) are being used significantly to identify exact fault location on transmission lines. Selection of suitable training algorithm is important in analysis of ANN performance. This paper presents a comparative study of various ANN training algorithm to perform fault location scheme in transmission lines. The features selected into ANN is the time of first peak changes in discrete wavelet transform (DWT) signal by using faulted current signal acted as traveling wave fault location technique. Six types commonly used backpropagation training algorithm were selected including the Levenberg-Marquardt, Bayesian Regulation, Conjugate gradient backpropagation with Powell-Beale restarts, BFGS quasi-Newton, Conjugate gradient backpropagation with Polak-Ribiere updates and Conjugate gradient backpropagation with Fletcher-Reeves updates. The proposed fault location method is tested with varying fault location, fault types, fault resistance and inception angle. The performance of each training algorithm is evaluated by goodness-of-fit (R<sup>2</sup>), mean square error (MSE) and Percentage prediction error (PPE). Simulation results show that the best of training algorithm for estimating fault location is Bayesian Regulation (R<sup>2 </sup>= 1.0, MSE = 0.034557 and PPE = 0.014%).

A non-unit protection scheme for double circuit series capacitor compensated transmission lines

This paper presents a non-unit protection scheme for series capacitor compensated transmission lines (SCCTL) using discrete wavelet transform and k-nearest neighbor (k-NN) algorithm. All the protective relaying functions such as fault detection, fault classification, faulty phase identification and fault location estimation have been considered in this work. Such a comprehensive work providing all protective relaying functions for protection of double circuit SCCTL utilizing k-NN has not been reported so far. The signal processing and feature extraction are done using discrete wavelet transform due to its capability to differentiate between high and low frequency transient components. For fault detection and classification, only approximate wavelet coefficient of current signal up to level 1 has been used; while for k-NN location estimation, both voltage and current signals of the two circuits are decomposed up to level 3 have been used. Finally, the standard deviation of one cycle pre-fault and one cycle post-fault samples of the approximate wavelet coefficients are calculated to form the feature vector for the k-NN-based algorithm. The performance of the proposed technique is evaluated for large number of fault events with variation in fault type including inter-circuit faults, fault inception angle, fault location and fault resistance. The change in position of series capacitor and different degree of compensation has been discussed. The accuracy of the proposed k-NN-based fault detection and classification module is 100% for all the tested fault cases with a decision period of less than half cycle. The k-NN-based fault location scheme estimates the location of fault with ≤1% error for most of the tested fault cases, which is an exceptional attribute of the proposed scheme as compared with 10–15% error of conventional distance relaying scheme.

Research on FHA Based UAV Fault Locating and Repairing

In response to the failure of safety critical functions that unmanned aerial vehicle (UAV) may happen during the flight phases, fault location scheme was proposed based on function hazard analysis results. And methods about automatically generating repairing strategies were put forward according to the pre-configuration items. Firstly, failure knowledge base, which includes the information about function failure, failure effect, and others, was constructed based on the FHA results combing FMEA analyzing results. And then repair strategies for each failure in the knowledge base combing FTA analyzing results was pre-designed. Finally, abductive reasoning method was applied to search for the cause of failure. And repairing strategies were generated accordingly. An assistant tool was developed to simplify the process of building the knowledge base. Interface for the fault locating and repairing strategies generating was also implemented in the tool. An example was proposed to demonstrate the scheme.

A single-phase earth fault location scheme for distribution feeder on the basis of the difference of zero mode traveling waves

Summary To eliminate the effect of line structure and unbalanced loads on the location of single-phase earth fault in distribution network, a new fault location method is proposed. In this method, the difference of the 2 zero mode traveling waves is taken as the criterion via injecting high voltage pulses into fault phase and nonfault phase, respectively. Through analyzing the transient response characteristic of distribution transformer and the propagation equation of traveling wave at the fault point, it is theoretically proved that the first difference of the 2 zero mode traveling waves is rooted in the reflection of the twice different incident wave of aerial mode voltage at the fault point, and further the fault location formula is obtained. The PSCAD-based simulation results show that the proposed method is effective and accurate to estimate fault distance. Also it has an excellent precision within certain extent.

A new impedance-based fault location scheme for overhead unbalanced radial distribution networks

This paper proposes an analytical impedance-based fault location scheme for distribution systems. The approach is based on voltage and current measurements extracted at only one-end feeding substation. Modal transformation is implemented to decompose the coupled three phase equations due to mutual effects into decoupled ones, and hence directly calculating fault distance in each section without iterative processes. The proposed approach considers various aspects of distribution systems: intermediate loads along the feeder, tapped laterals and sub-laterals at various nodes, time varying loads, and unbalanced operations. The proposed algorithm is extensively investigated on a typical real 11kV distribution system, South Delta electricity sector, Egypt using MATLAB environment. Different cases are studied considering various loading conditions, varied fault resistance values and different fault types. The achieved results ensure the effectiveness of the proposed fault locator irrespective to fault conditions. Besides, the robustness of the proposed scheme against unbalanced loading, network topology change and non-homogenous network sections is also confirmed.