High Impedance Ground Fault Research Articles

Faulty section location method for high impedance grounding fault in resonant grounding system based on discrete Fréchet distance

When a High Impedance Fault (HIF) occurs in a resonant grounding system, the differentiation of the current flowing upstream and downstream of the fault point is inconspicuous due to the weak electrical signal. This paper proposes a faulty section location approach based on Discrete Fréchet Distance (DFD) to address this issue. Initially, taking the zero-sequence current as the characteristic quantity, the instantaneous value of the zero-sequence current at each sampling point and its previous sampling moments are accumulated to amplify the fault signal, and furthermore to obtain the cumulative waveform of the zero-sequence current at each monitoring point. The DFD values between the cumulative waveforms of zero-sequence currents flowing through each section are also calculated. For a branchless section, if the Coefficient of Variation (CV) of the DFD in each section does not exceed the threshold value, it is identified as an end-of-line fault, otherwise, the section with the maximum DFD is identified as a faulty section. For a section with branches, the branching coefficient is calculated to determine whether it is a faulty section or not. Finally, MATLAB/Simulink simulation results and field-recorded data demonstrate the validity and robustness of the approach under various fault conditions, despite the connection of Distributed Generators (DGs).

Faulty feeder selection method for high impedance grounding fault in resonant grounding system based on discrete Fréchet distance

Abstract When a high impedance fault (HIF) occurs in a resonant grounding system, the electrical signal is weak and the current distinction between the faulty feeder and non-faulty feeder is inconspicuous. To address this issue, this paper proposes a faulty feeder selection method based on discrete Fréchet distance (DFD). Firstly, the instantaneous value of the zero-sequence current flowing through each sampling point, along with the instantaneous values at its previous sampling moment, is accumulated to enhance the fault signal, and furthermore to magnify the distinction in the amplitude of the accumulated waveforms of zero-sequence current between the faulty feeder and non-faulty feeder. Then, the DFD of the accumulated waveforms of the zero-sequence current for each feeder is calculated, and the Fréchet distance matrix is established to acquire the average DFD (ADFD) value of the accumulated waveform for each feeder. Finally, the relative DFD (RDFD) value is defined as a criterion to distinguish the bus fault from the feeder fault according to the values of the two feeders with the maximum ADFD value and the minimum ADFD value. If the RDFD value is negative, it is identified as a bus fault, otherwise, the feeder corresponding to the maximum ADFD value is identified as a faulty feeder. MATLAB/Simulink simulation results and field measurement data show that the proposed method is not affected by various fault conditions, and the accuracy and reliability in faulty feeder selection are high when detecting an HIF, with good applicability.

Fault Handling and Localization Strategy Based on Waveform Characteristics Recognition with Coordination of Peterson Coil and Resistance Grounding Method

To address challenges in locating high-impedance grounding faults (HIGFs) and isolating fault areas in resonant grounding systems, this paper proposes a novel fault identification method based on coordinating a Peterson coil and a resistance grounding system. This method ensures power supply reliability by extinguishing the fault arc during transient faults with the Peterson coil. When a fault is determined to be permanent, the neutral point switches to a resistance grounding mode, ensuring regular distribution of zero-sequence currents in the network, thereby addressing the challenges of HIGF localization and fault area isolation. Fault calibration and nature determination rely on recognizing neutral point displacement voltage waveforms and dynamic characteristics, eliminating interference from asymmetric phase voltage variations. Fault area identification involves assessing the polarity of zero-sequence current waveforms attenuation during grounding mode switching, preventing misjudgments in grounding protection due to random initial fault angles and Peterson coil compensation states. Field experiments validate the feasibility of this fault location method and its control strategy.

Fault line selection algorithm for single-phase high-impedance ground faults in distribution networks based on the hilbert-huang transform

Fault line selection algorithm for single-phase high-impedance ground faults in distribution networks based on the hilbert-huang transform

A multi-feature fusion algorithm for single-phase high-impedance ground fault line selection in distribution networks based on Hilbert-Huang transform

A multi-feature fusion algorithm for single-phase high-impedance ground fault line selection in distribution networks based on Hilbert-Huang transform

The Research on the Improvement of the Zero-Sequence Relay for the Low Resistance Grounded Power Grid

In the low resistance grounded power grid, when a high-impedance grounding fault occurs at a distribution line, the zero-sequence fault current is not big enough to make the zero-sequence over-current relays trip because of the setting limitations, and thus the earth fault would exist for a long time with no alarm signal. As a result, there would be a hidden danger that the grounding fault might cause further faults or cause harm to personal safety. To solve the problem, in the paper, the characteristics of zero-sequence components when the high-impedance grounding fault occurs are analyzed, and the practicability and the deficiency of the directional zero-sequence over-current relay are pointed out. Based on the analysis, an improved zero-sequence relay with the resistance-capacitance ratio restriction is raised. The resistance-capacitance ratio restriction condition is based on the different structures of the resistant part and the capacitive part of zero-sequence currents, and the faulted line can be identified with the resistance-capacitance ratio criterion. The resistance-capacitance ratio criterion is not influenced by the polarity of the voltage transformer (VT) and current transformer (TA) and can avoid the influence caused by the reversed polarity of the exclusive zero-sequence TA. With the improved zero-sequence over-current relay with the resistance-capacitance ratio restriction, the ability to identify high-impedance grounding faults can be improved, and the fault area can be isolated quickly, to guarantee the reliability and safety of the operation in power grids.

Grounding Protection of flexible grounding systems Based on Polarization of Faulty Phase Voltage

At present, the grounding protection of flexible grounding systems mostly follows the common protection methods of the low-resistance grounding system, and there are problems of insufficient adaptability and utilization of fault information. In the paper, We analyze the fault characteristics of flexible grounding systems after grounding faults, find that when a high-impedance grounding fault happened, after the low-resistance is connected to the Petersen Coil, the phase characteristics between the zero-sequence of voltage and current of flexible grounding system is similar to that of low-resistance grounding system when grounding faults happened, at this time the faulty phase voltage amplitude is far more than the zero sequence voltage and the phases of the two are opposite. Based on this, a flexible grounding system grounding fault location method using the phase relation between zero sequence current of lines and faulty phase voltage is proposed. By taking advantage of the mature phase selection technology of the resonant grounding system, selecting the faulty phase in the compensation stage of the Petersen Coil. When the low-resistance is in parallel, the faulty phase voltage is used to compare the phase with the zero sequence current of lines, which solves the problem that the zero sequence voltage is weak and difficult to measure when the high impedance grounding fault occurs. Simulation experiments and field tests show that this method can improve the reliability of high-impedance grounding protection, and the method can be used as a backup protection for zero sequence overcurrent protection to meet field requirements.

A Faulty Line Selection Method for Flexible Grounding System Based on Transient Fault Data

In view of the problem of high-impedance grounding faults (HIFs) in flexible grounding systems (FGS), a faulty line selection method based on transient waveform slope is proposed in this paper. The change of zero sequence (ZS) current of faulty line and non-faulty line (before and after the neutral point parallel small resistance are put in) are analyzed. After the parallel small resistance is put into operation, the waveform slope curve of the transient zero sequence current of each line is obtained, and the modified Hausdorff distance (MHD) algorithm is used to obtain the transient slope matrix. The faulty line is identified by comparing the sizes of each row of elements in the matrix. Simulation verifies the effectiveness of the proposed faulty line selection method.

High impedance grounding fault location method for power cables based on reflection coefficient spectrum

When a high impedance grounding fault occurs in the power cables, the current at the fault point is extremely low and the fault characteristics are too weak to be detected by the reflectometry. Interfered by the multiple reflections, the fault is hard to be located in the field. In order to solve the problem of conventional frequency domain reflectometry, a high impedance grounding fault location method for 10 kV distribution cables is proposed in this paper, which is based on the reflection coefficient spectrum. Firstly, the equivalent model of cable distributed parameters is established, and the reflection coefficient spectrum at the cable head is derived. Then, according to the theorem of integral transformation and generalized orthogonality, the diagnostic function is built in the spatial domain. Besides, the Kaiser window is introduced to improve the location sensitivity. Finally, the feasibility of the method is verified by simulated and experimental results. It is shown that this method can effectively eliminate the impact of multiple reflections, and precisely locate the single- and multi-point grounding faults. The fault location error is within 0.2%.

Feature extraction of arc high impedance grounding fault of low‐voltage distribution lines based on Bayesian network optimisation algorithm

AbstractIn order to accurately extract the fault features of arc high impedance grounding of low‐voltage distribution lines and judge the fault feature types of arc high impedance grounding of low‐voltage distribution lines, a fault feature extraction method for arc high impedance grounding of low‐voltage distribution lines based on Bayesian network optimisation algorithm is proposed. According to the model of arc high impedance grounding fault based on Thomson’s principle, the parameter information of each transmission signal in arc high impedance grounding fault is extracted. Through the denoising method of arc high impedance grounding signal based on combined filter, the noise information of transmission signal in case of arc high impedance grounding fault is removed and the signal purity is improved. The detection and recognition method for fault characteristics of arc high impedance grounding of low‐voltage distribution lines based on Bayesian network optimisation algorithm is used to detect and judge the fault characteristics of the abnormal characteristics of the denoised transmission signal, and complete the fault feature extraction. After testing, this method can accurately and real‐time extract the fault characteristics of arc high impedance grounding of low‐voltage distribution lines, and has application value.

High impedance grounding fault detection for distribution networks based on fault component principle

High impedance grounding fault detection for distribution networks based on fault component principle

Single-phase-to-ground fault protection based on zero-sequence current ratio coefficient for low-resistance grounding distribution network

Definite-time zero-sequence over-current protection is presently used in systems whose neutral point is grounded by a low resistance (low-resistance grounding systems). These systems frequently malfunction owing to their high settings of the action value when a high-impedance grounding fault occurs. In this study, the relationship between the zero-sequence currents of each feeder and the neutral branch was analyzed. Then, a grounding protection method was proposed on the basis of the zero-sequence current ratio coefficient. It is defined as the ratio of the zero-sequence current of the feeder to that of the neutral branch. Nonetheless, both zero-sequence voltage and zero-sequence current are affected by the transition resistance, The influence of transition resistance can be eliminated by calculating this coefficient. Therefore, a method based on the zero-sequence current ratio coefficient was proposed considering the significant difference between the faulty feeder and healthy feeder. Furthermore, unbalanced current can be prevented by setting the starting current. PSCAD simulation results reveal that the proposed method shows high reliability and sensitivity when a high-resistance grounding fault occurs.

An FTU-Based Method for Locating Single-Phase High-Impedance Faults Using Transient Zero-Sequence Admittance in Resonant Grounding Systems

A novel fault location scheme using feeder terminal units (FTUs) for high-impedance grounding faults in resonant grounding systems (RGSs) is presented. The parallel resonance for a high-impedance fault (HIF) in an RGS with inverter-interfaced distributed generators (IIDGs) is analyzed. The process exhibits unique distribution features for transient zero-sequence components involving underdamped and overdamped states. We conclude that the transient zero-sequence admittances (TZSAs) from FTUs upstream of the fault point have the maximum value, while the TZSAs obtained from FTUs downstream of the fault point are small for HIFs. Therefore, the proposed location scheme uses FTUs to calculate the maximum values of the TZSA. By comparing with action criteria, the distribution automation (DA) master station utilizes the above results of each FTU to locate the faulty feeder section. The accuracy of the fault characteristics and the proposed method are validated by applying a real-time digital simulator (RTDS) and an FTU-based monitoring system. Additionally, the proposed scheme demonstrates an excellent and reliable performance, considering various faulty feeder sections, fault resistances, arcing faults, fault inception angles, imbalances and the presence of IIDGs and noise.

Faulty feeder detection of single phase-earth fault based on fuzzy measure fusion criterion for distribution networks

Faulty feeder detection of single phase-earth fault for medium voltage distribution networks is still challenging since the weak fault feature and diverse fault conditions. A novel single phase-earth fault feeder detection method based on fuzzy measure fusion criterion is proposed in this paper. Various historical feature samples which characterize different fault conditions of the protected feeder are divided into fault group and non-fault group by fuzzy c-means clustering algorithm. The similarity between real time data and the historical feature sample set is quantitatively represented by the fuzzy measure fusion criterion. Fuzzy measure fusion criterion matrix is evaluated through a multi-level evaluation index system to emphasize the effective fault information and reduce the impact of accidental factors. The detection criterion is established by comparing the similarity between the detected feature sample and the historical feature samples to identify the faulty feeder of single phase-earth fault. PSCAD/EMTDC simulation and laboratory fault experiment results have confirmed the effectiveness and adaptability of the proposed detection method. The accurate fault detection can be realized even in the rigorous fault cases of high impedance grounding fault and arc grounding fault.

A novel method for accurate ground parameter estimation in MV networks

This paper presents a novel method for ground parameter estimation that enables the accurate estimation of the total ground capacitance and conductance in MV networks. The novelty of the method is that the effect of the leakage impedance of the inductive voltage transformer can be significantly reduced compared to the prior-art method. The key idea of the novel method is based on dual inductive voltage transformers for resonant earthed neutral networks. Until now, it has been necessary to simplify the equivalent circuit model by neglecting the effect of the inductive voltage transformer leakage impedance to enable ground parameter estimation with the prior-art signal injection-based method. The experimental test results clearly demonstrate the significant effect of the inductive voltage transformer leakage impedance on ground parameter estimation with the prior-art method and show that the proposed method is effective at improving the accuracy of ground parameter estimation, which is beneficial for the security risk assessment of underground cables, the configuration and expansion capacity of the Petersen coil and the detection of high-impedance ground faults.

Interharmonics based high impedance fault detection in distribution systems using maximum overlap wavelet packet transform and a modified empirical mode decomposition

Despite extensive research, high impedance fault (HIF) detection remains challenging because it is always associated with low magnitude, nonlinear, asymmetric and random fault currents. This paper presents a new technique for arcing high impedance ground fault detection in distribution feeders through analysis of interharmonic content of the current signal. The origin of interharmonics is related to the random variation of the electric arc associated with HIF. For effective separation of interharmonic components, a novel method using maximum overlap discrete wavelet packet transform (MODWPT) and a newly developed special knot based empirical mode decomposition (EMD) is presented. The results indicate that the proposed scheme can reliably detect HIFs with a reasonable detection speed and at the same time achieve high security against no-fault cases.

A Cost-Effective Solution for Clearing High-Impedance Ground Faults in Overhead Low-Voltage Lines

Downed distribution conductors in overhead distribution systems may not be a concern for equipment but greatly challenge the safety of persons, as well as the integrity of properties. Standard overcurrent protective devices may not be able to detect the magnitudes of currents resulting from high-impedance ground faults. Sophisticated relays able to detect high-impedance ground faults have been available to electric utilities. However, their implementation is rather uncommon, especially in developing countries, most likely due to their costs. In this paper, the authors formalize the problem, and propose a possible cost-effective solution for low-voltage overhead lines with neutral wire. This solution consists of a metal hook underneath the line conductors, attached to the pole and connected to the neutral wire. In the case of a falling line, the hook would be contacted and a line-to-neutral short circuit would occur; this would positively activate existing standard overcurrent devices, which can therefore disconnect the supply. Costs related to the installation of the device to existing overhead lines are herein analyzed. The effectiveness of the proposed solutions for two different voltage levels (400 V in European countries and 240 V in the USA) is also discussed.

Impacts of Grounding Configurations on Responses of Ground Protective Relays for DFIG-Based WECSs—Part I: Solid Ground Faults

Ground faults are among the major causes of disrupting the safe, secure, stable, and profitable operation of doubly fed induction generator (DFIG) based wind energy conversion systems (WECSs). On one hand, minimizing the possible damage in a DFIG-based WESC, caused by ground faults, requires accurate detection and fast response of ground protective devices. On the other hand, the responses of ground protective devices are highly dependent on ground currents and potentials, especially during high-impedance ground faults. This paper investigates the influences of grounding configurations on the responses of ground protective devices used in DFIG-based WECSs during high-impedance ground faults. Investigated influences are observed through the ability of ground protective devices, used in DFIG-based WECSs, to quickly and accurately respond to high-impedance ground faults for different grounding configurations. In this paper, the solid, low-resistance, high-resistance, and open grounding configurations are tested for DFIG-based WECS in order to establish comprehensive investigations. The results of the investigations show that the responses of ground protective devices vary depending on ground fault currents, which can have different levels due to the grounding configuration. Moreover, the results of the investigations reveal that the frequency-selective grounding configuration can offer a minimum impact on the responses of ground protective devices used in DFIG-based WECSs.

Impacts of Grounding Configurations on Responses of Ground Protective Relays for DFIG-Based WECSs-Part II: High-Impedance Ground Faults

Ground faults are among the major causes of disrupting the safe, secure, stable, and profitable operation of doubly fed induction generator (DFIG) based wind energy conversion systems (WECSs). On one hand, minimizing the possible damage in a DFIG-based WESC, caused by ground faults, requires accurate detection and fast response of ground protective devices. On the other hand, the responses of ground protective devices are highly dependent on ground currents and potentials, especially during high-impedance ground faults. This paper investigates the influences of grounding configurations on the responses of ground protective devices used in DFIG-based WECSs during high-impedance ground faults. Investigated influences are observed through the ability of ground protective devices, used in DFIG-based WECSs, to quickly and accurately respond to high-impedance ground faults for different grounding configurations. In this paper, the solid, low-resistance, high-resistance, and open grounding configurations are tested for DFIG-based WECS in order to establish comprehensive investigations. The results of the investigations show that the responses of ground protective devices vary depending on ground fault currents, which can have different levels due to the grounding configuration. Moreover, the results of the investigations reveal that the frequency-selective grounding configuration can offer a minimum impact on the responses of ground protective devices used in DFIG-based WECSs.

Development of a Novel Protection Device for Bipolar HVDC Transmission Lines

A novel nonunit transient-based protection scheme for bipolar high-voltage direct current (HVDC) lines is proposed. The protection scheme is composed of a starting unit, a boundary unit, a directional unit, a faulty pole identification unit, and a lightning disturbance identification unit. The prototype based on the proposed scheme is developed and its performance is evaluated through a hardware-in-the-loop test using real-time digital simulator (RTDS) and real HVDC control devices. Better than the presently used line protection, the proposed protection not only can detect faults on HVDC lines more rapidly and accurately in different HVDC operation modes, but is also more effective in detecting high-impedance grounding faults. In addition, the novel protection is designed to identify lightning disturbances from short-circuit faults correctly, which avoids the unnecessary restart of HVDC systems due to protection misjudgment.