Ground Fault Resistance Research Articles

A high resistance grounding fault identification method for distribution network considering topological connection

Abstract Traditional high resistance grounding fault identification in distribution networks fails to meet load demands, demanding optimization for reliability and economics. A novel approach considers topological connections, applies the Hilbert-Huang transform for signal decomposition, refines components, and utilizes particle swarm optimization to enhance feature vectors. This defines an association matrix and leverages zero sequence current features, accurately pinpointing suspected high resistance ground faults through filtered second derivative concavity and zero crossing point analysis. Experimental data underscores the design method’s exceptional calculation efficiency, capping at 40 milliseconds, and maintaining over 90% fault recognition accuracy. Recognition time notably diminishes, shrinking from 0.91 seconds for 10 iterations to 0.28 seconds for 50 iterations.

Arc Suppression Control With Adaptive Parameters of Active Grounding Device Considering Ground Fault Resistance Uncertainty

Active grounding device (AGD) is an effective device to eliminate grounding arcs and prevent disasters caused by ground faults in distribution networks. However, due to the uncertainty of the ground fault resistance, the traditional arc suppression control cannot guarantee the suppression effect and the control stability simultaneously under the fixed control parameters. In this paper, an arc suppression control method based on adaptive parameters is proposed. According to the dual-loop control model of the AGD connected to the fault distribution network, the relationship between the model input and the fault voltage is derived. Then in two extreme cases of the ground fault resistance, the suppression effect and the system stability are analyzed using the amplitude-frequency curve and the root locus, respectively. Further, a control method is proposed to make control parameters self-adaptive through the feedback information of the residual fault voltage. Finally, the effectiveness of the proposed control method is verified by the simulation model of MATLAB/Simulink and the low-voltage experiment of the prototype, which can realize arc suppression with high, low or dynamic resistance ground fault.

On line monitoring of transmission line

Continuous online monitoring of transmission line is required for proper functioning of power system. This paper presents two simulink model one for single transmission line, singly fed and the other for parallel transmission line doubly fed and presents the simulation result which shows the continuous variation in transmission line impedance before, during and after the fault. This paper shows the effect of different factors like prefault system condition, ground fault resistance, series compensation effect individually and then taking together on impedance plot under line to ground fault and three phase to ground fault. In case of parallel transmission line the paper have taken into account of mutual coupling effect also.

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.

A new method for single‐phase high resistance grounding fault protection in low resistance grounded distribution networks

AbstractThe neutral point of the distribution network is grounded with low resistance, which can quickly remove single‐phase grounding fault and effectively suppress overvoltage. However, the existing zero‐sequence overcurrent protection has a high setting value. In the case of large fault resistance and weak fault current, the existing protection methods may refuse to operate. Based on the waveform characteristics of the zero‐sequence current of each outgoing line in the distribution network, this article proposes a new method for single‐phase high resistance grounding fault protection in low resistance grounded distribution network, which combines cosine distance and improved K‐means algorithm. First, the cosine distance between zero‐sequence current of every two outgoing lines is obtained, and the cosine distance matrix used to describe the fault characteristics is constructed. Then the improved K‐means algorithm is used to cluster the row vectors of the cosine distance matrix to obtain the convergent cluster center and cluster label, so that the fault line can be determined. This protection method does not need to set the threshold value manually, and has strong ability to handle large fault resistance. It can effectively deal with noise interference and intermittent arc grounding fault, and still has good adaptability in scenarios such as change of fault initial phase angle, change of fault location, access of distributed generations and occurrence of two outgoing lines in phase to grounding fault. Finally, a model is built, and the effectiveness of the proposed method is proved by the simulation of grounding fault.

Enhanced sensitive phase alpha plane scheme against high resistance ground faults

Abstract Phase-based Alpha (α) Plane Relaying (APR) scheme has numerous advantages over the Current Differential Relay (CDR) for transmission line protection. Since the large Restraining Region (RR) in the APR makes high security against CT saturation, channel delay, line charging current and synchronization error. However, the APR loses its sensitivity for high resistance ground faults, especially single line to ground faults under outfeed conditions. Also, losing its dependability under close-in low resistance three-phase faults. Thereby, the sequence-based APR provides enhanced sensitivity with the cost of computational burden and complexity. Hence, in this paper, the concept of the average value (I Avg) of both end instantaneous currents is used as an auxiliary logic. In which, the polarity of I Avg is incorporated as an add-on logic to the conventional APR to confirm high resistance internal faults. Thereby, the requirement of sequence components can be avoided (negative and zero). To validate the proposed auxiliary logic, it is tested for the WSCC (Western System Coordinating Council) 9-bus, 110 kV, 50 Hz. System. The simulated results under various fault cases found authenticated results. In addition, the comparative assessment and validation with real-world data reveal the enhanced sensitivity of the proposed logic under high-resistance ground faults.

Fault location method for MMC-HVDC transmission line based on adaptive optimal feature reconstruction

Applying the regression mechanism of intelligent algorithm to transmission line fault location is a new research direction in recent years.The location accuracy of such methods largely depends on the feature selection of the training samples of the algorithm model.This paper proposes a feature extraction method that combines regression algorithm, waveform decomposition and optimization algorithm, which can adaptively extract optimal features according to training samples, thereby ensuring the location accuracy of the algorithm model to the greatest extent. Through the test in a MMC-HVDC transmission line simulation model, the optimal feature reconstruction method proposed in this paper can greatly improve the fault location accuracy of transmission line, and has good location performance in case of high resistance grounding fault.

A Single-Phase High-Impedance Ground Faulty Feeder Detection Method for Small Resistance to Ground Systems Based on Current-Voltage Phase Difference

At present, the small resistance to ground system (SRGS) is mainly protected by fixed-time zero-sequence overcurrent protection, but its ability to detect transition resistance is only about 100 Ω, which is unable to detect single-phase high resistance grounding fault (SPHIF). This paper analyzes the zero-sequence characteristics of SPHIF for SRGS and proposes a SPHIF feeder detection method that uses the current–voltage phase difference. The proposed method is as follows: first, the zero-sequence current phase of each feeder is calculated. Second, the phase voltage root mean square (RMS) value is used to determine the fault phase and obtain its initial phase as the reference value. The introduction of the initial phase of the fault phase voltage can highlight the fault characteristics and improve the sensitivity and reliability of feeder detection, and then CVPD is the difference between each feeder ZSC phase and the reference value. Finally, the magnitude of CVPD is judged. If the CVPD of a particular feeder meets the condition, the feeder is detected as the faulted feeder. Combining the theoretical and practical constraints, the specific adjustment principle and feeder detection logic are given. A large number of simulations show that the proposed method can be successfully detected under the conditions of 5000 Ω transition resistance, –1 dB noise interference, and 40% data missing. Compared with existing methods, the proposed method uses phase voltages that are easy to measure to construct SPHIF feeder detection criteria, without adding additional measurement and communication devices, and can quickly achieve local isolation of SPHIF with better sensitivity, reliability, and immunity to interference.

Faulty Phase Detection Method Under Single-Line-to-Ground Fault Considering Distributed Parameters Asymmetry and Line Impedance in Distribution Networks

Accurate faulty phase detection under single-line-to-ground (SLG) fault is the basis of the emerging voltage-based fault arc suppression technology. Most conventional faulty phase recognition criteria assume the distributed line-to-ground parameters are symmetrical, therefore suffering invalidity in actual distribution networks especially under high-resistance ground-fault conditions. This paper firstly analyzes the magnitude and phase angle variation models of the phase-to-ground voltages before and after the SLG fault. Considering the asymmetrical distributed parameters and the line impedance, the specific phase-to-ground voltage variation rules corresponding to SLG fault on each phase are then discussed. Based on the voltage variation rules, a robust and practical method for faulty phase identification is proposed, which does not need the distributed parameters. Finally, the correctness of the variation rules and the availability of the proposed method is verified by simulation. Comparative study shows the proposed method has better accuracy and applicability with the conventional methods when the asymmetry and ground-fault resistance are high.

Faulty feeder detection of single phase-to-ground fault for distribution networks based on improved K-means power angle clustering analysis

High-resistance ground faults often occur in distribution networks, and the fault current can be as low as 0.1A, making it extremely difficult to realize faulty feeder detection. The application of traditional faulty feeder detection methods based on single fault characteristic is limited. Thus, a method of single-phase grounding fault feeder detection based on improved K-means power angle clustering analysis was proposed. First, collect various fault characteristic quantities of each feeder under different operation and fault conditions, and establish a historical sample database. Then, the improved K-means clustering algorithm is used to quickly classify the historical sample database, and the cluster center is optimized through the spatial density and maximum neighbor distance principle. Finally, the power angle similarity is calculated according to the relative position of the real-time feature sample and the cluster center in the fault space, so as to realize the sensitive detection of the fault feeder. The PSCAD simulation and the 10 kV distribution network test field showed that the proposed method effectively eliminates the misjudgment of a single fault characteristic caused by external interference. And without a fixed setting value, the accurate fault feeder detection of intermittent arc grounding, high resistance grounding and other fault conditions can be realized.

An accurate algorithm of PMU-based wide area measurements for fault detection using positive-sequence voltage and unwrapped dynamic angles

Modern power system requires advanced and intelligent sensors-based protection such as a Phasor Measurement Unit that can provide faster, accurate, and real-time data acquisition. The aim is to allow accurate action-based performance for analysts in monitoring the transmission lines so that rapid actions can be taken during abnormal circumstances before the blackout occurs. Among different algorithms, this study focuses on modelling the non-recursive phasor estimation method in a power Simulink environment for a standard test system equipped with a developed algorithm to detect the fault zone. The algorithm includes an index for faulty bus classification based on the positive-sequence voltage measurements of the pre-fault and post-fault conditions, where the bus with a maximum differential percentage is identified as a faulted bus. An important differentiation of this work is that the proposed algorithm can coordinate with all phasor measurement units to accurately determine the faulty line using the index of unwrapped dynamic phase angles. Furthermore, the robustness of the indices is analyzed in the presence of sudden load change, measurement noise, and during nonlinear high-impedance faults. The performance of the comprehensive algorithm is investigated on the IEEE 9-bus and 39-bus standard test systems by applying different faults scenarios, considering several factors such as fault inception angles, line-fault resistance, ground-fault resistance. The comparative studies have shown that the proposed indices can play a significant role in segregating the fault and non-fault conditions, as they are needed to supervise the appropriate relays for enhancing the overall security of the power grid.

Wavelet packet coefficient of transient first half wave line selection method for single-phase grounding fault

Overvoltage will occur after single-phase grounding fault in distribution network, endangering system insulation. It is of great significance to find out the fault line as soon as possible to ensure the safe operation of the system. Wavelet modulus maxima can be used to detect the sudden change singularity of transient current. However, the judgement of single mode maximum value is easily influenced by the form of fault and interference, leading to misjudgement. In this paper, the transient characteristics of single-phase grounding fault are analyzed, and the magnitude and phase characteristics of the first half wave are given; Based on wavelet packet algorithm, several key problems such as boundary effect, wavelet selection and decomposition scale are explored; Taking the zero sequence voltage as the reference to determine the fault interval, the zero sequence current of each line is decomposed by three-scale wavelet packet using db6 wavelet, and the wavelet coefficients of the characteristic frequency band are extracted for comparison. The fault line is the one with the largest amplitude and different phase from others. The distribution system model of neutral grounding through arc suppression coil is built. Simulation is carried out for several cases with great difficulty in line selection, such as short circuit when phase voltage crosses zero, high resistance grounding and long line fault. The experimental results prove the reliability of this method.

Fault Current Constrained Impedance-Based Method for High Resistance Ground Fault Location in Distribution Grid

Fault Current Constrained Impedance-Based Method for High Resistance Ground Fault Location in Distribution Grid

The resistive ground fault of PWM voltage inverter in the EV charging station

During the direct touch of the inverter output voltage or with the ungrounded shield of the cable connecting the inverter to the motor or other type of load, the nonsinusoidal ground currents with a basic harmonic frequency between 1.5 and 16 kHz, flow via a human’s body. Here was proved that Residual Current Device (RCD) (I_{triangle n} = 30 mA) does not switch off the power supply when a ground current with a value of about some hundred milliamps occurs. Because RCDs do not disconnect the power supply, the touch on the inverter’s voltage is dangerous to health and life. For the authors, the RCD usage in the Voltage Frequency Converters (VFCs) is not a good engineer practice when high-frequency common-mode distortion currents flow through it. The paper presents tests of RCD operation in the event of a resistance ground fault (via human body) during EV battery charging where the PWM voltage inverter is connected to the external rectifier to provide DC charging battery voltage. Finally, the authors propose a method of eliminating common-mode (CM) current from short protection system by using a separate circuit in which the parasitic leakage current omits an RCD.

활선 DC선로 절연상태 모니터링을 통한 스마트 그리드 시스템 성능유지

With the development of distributed power generation using solar power and renewable energy, smart grid-type DC power distribution is gradually spreading. However, DC distribution has a disadvantage in that the electric corrosion phenomenon of the ground electrode is prominent compared to the AC distribution system. The destruction of the stability of the ground electrode due to the electrostatic phenomenon deteriorates the reliability of the distribution system by causing electric shock accidents to human life, failure and malfunction of equipment. Therefore, the main issues of DC distribution are the electric corrosion of the ground electrode and the need to increase the reliability of the distribution system for smooth power supply. In this paper, the insulation resistance measurement device (IMD: Insulation Monitoring Device) is to be researched and developed to measure the insulation resistance in the live state and monitor the insulation state of the power line in order to secure the insulation resistance of the line and to secure electrical safety through monitoring. Based on this study, we intend to analyze the reliability of equipment safety according to IT (non-grounding) ground fault and power line insulation resistance degradation.

Voltage Correlation Based Single Pole-to-Ground Fault Detection of MMC-HVDC Transmission Line

Through analysis of various fault voltage characteristics of modular multilevel converter high voltage direct current (MMC-HVDC) transmission system, it shows that the positive and negative voltage relationships of direct current transmission lines with single pole-to-ground faults are obviously different from other faults. Hence, Pearson correlation coefficient is used to describe the degree of difference in this work. In the case of single pole-to-ground fault, correlation coefficient is positive and close to 1, while as for other failures, correlation coefficient is negative and close to −1. This article analyzes the mechanism of correlation coefficient to withstand transition resistance and verifies the effectiveness of the proposed method under high resistance grounding fault. A novel scheme is proposed by combining the quantity sum of voltage variation characteristics, which can effectively identify fault pole. The proposed scheme needs smaller time window and owns high efficiency, as well as great robustness to transition resistance.

Proposed High-Performance Digital Distance Relay (Dept.E)

This paper proposes a new design for high-performance digital distance relay. It is equipped with a dedicated decaying dc component estimation algorithm and a new method for compensation of ground fault resistance. The proposed relay algorithm can estimate and eliminate the dc decaying component from fault current signals within one cycle from the fault instant. Then, it uses fast Fourier transform to extract accurate phasor quantities of fault currents. Also, an innovative algorithm for compensation of fault resistance is introduced. The later technique is based on supposing a virtual distance relay at the other end of the line. Using the preliminary estimation of the apparent relay-to-fault impedance at both sides, the unknown fault resistance and its related error are determined. Hence, this error can be compensated in computing the actual relay-to-fault impedance. Many test cases are performed under different fault locations and several values of ground fault resistance to confirm the efficacy of the proposed relay.

Rotor ground-fault diagnosis methods for synchronous condensers based on amplitude and phase-angle of voltage

A single ground fault of the rotor windings in a synchronous condenser can cause serious damage if the fault is not eliminated in time. This paper proposes a new rotor ground-fault diagnosis method for synchronous condensers based on the amplitude of the 150 Hz component of the voltage across a grounding resistance (GR) placed in the neutral of an excitation transformer. It can be seen that the amplitude of the 150 Hz component of the voltage across the GR increases with a decrease of the ground-fault resistance (GFR). This method is an improvement of existing algorithms for rotor ground-fault detection that requires less analyzing and can achieve online detection of the severity of a rotor ground fault at any point of the excitation winding. In addition, the influence of different excitation voltages on the algorithm based on phase-angle is analyzed considering actual working characteristics. Moreover, a model is built in the MATLAB/Simulink platform using the real parameters of a TTS-300-2 synchronous condenser to verify the effectiveness of the proposed method. Finally, a dual diagnostic criterion is given according to the results of simulations. The research conclusions can have a great significance on the healthy running of synchronous condensers and they can help to drastically reduce both cost and repair time.

Analysis of Internal Overvoltages in Transformer Windings during Transients in Electrical Networks

Due to the increasing requirements for the reliability of electrical power supply and associated apparatus, it is necessary to provide a detailed analysis of the overvoltage risk of power transformer insulation systems and equipment connected to their terminals. Exposure of transformer windings to overvoltages is the result of the propagation condition of electromagnetic waves in electrical networks and transformer windings. An analysis of transformer winding responses to transients in power systems is of particular importance, especially when protection against surges by typical overvoltage protection systems is applied. The analysis of internal overvoltages in transformers during a typical transient related to switching operations and selected failures is of great importance, particularly to assess the overvoltage exposure of insulation systems in operating conditions. The random nature of overvoltage phenomena in electrical networks implies the usage of computer simulations for the analysis of overvoltage exposures of electrical devices in operation. This article presents the analysis of the impact of transient phenomena in a model of a medium-voltage electrical network during switching operations and ground faults on overvoltages in the internal insulation systems of transformer windings. The basis of the analysis is simulations of overvoltages in the windings, made in the Electromagnetic Transients Program/Alternative Transients Program (EMTP/ATP) using a model with lumped parameters of transformer windings. The analysis covers the impact of the cable line length and the ground fault resistance value on internal overvoltage distributions.

A novel pilot directional backup protection scheme based on transient currents for HVDC lines

For HVDC transmission lines, the backup protection cannot respond to internal faults quickly. To solve this problem, a novel pilot directional backup protection scheme is proposed in this paper. Firstly, the fault characteristic of transient currents on both sides of DC bus is analyzed. When forward traveling-wave of current reaches a DC bus, the transient current integration at the back side of the bus over a short time is larger than that at the front side. However, when backward traveling-wave reaches the bus, the current integration at the back side is smaller than that at the front side. Therefore, fault direction can be determined by comparing the transient currents on both sides of DC bus. Then, internal faults can be distinguished from external faults by comparing fault directions at two ends of DC lines, and faulty poles can be selected by comparing the transient currents of two poles. Lastly, to test the performance of the novel protection proposed in this study, a ±800 kV HVDC system is built in PSCAD/EMTDC. Comprehensive test studies show that the proposed protection scheme not only can identify internal faults and select faulty poles correctly and quickly, but also can respond to high resistance ground faults.