Arc Grounding Research Articles

Extended Pantograph–Catenary Arc Modeling and an Analysis of the Vehicular-Grounding Electromagnetic Transients of Electric Multiple Units

As the operating speed of electric multiple units (EMUs) in high-speed railways increases, pantograph–catenary (PC) detachment arcing occurs frequently. The resulting vehicular-grounding electromagnetic transients are related to the dynamic characteristics of the arc length. During large detachment, the processes of arc extinction and arc reignition may occur, resulting in more severe train body (TB) over-voltages and adverse effects on some vehicular electronic devices. As an extension of the previous works, this paper aims to establish a suitable PC arc model to examine the TB transient voltages. To begin with, the arc length dynamic characteristics are reasonably analyzed to deduce the relationship between the detachment distance and the arc length via the chain arc model. Then, the dynamic characteristics of the arc length are introduced, and an arc modeling scheme is proposed to elaborate the vehicle-grid electric power model for EMUs encountering various arcing scenarios. Based on this, the transient over-voltages are analyzed, accounting for both the arc extinction and arc reignition, as well as the mutual influences of multiple detachments in a short time. The influential factors, including arc length characteristics, phase angle, excitation inductance, and grounding parameters, are also involved in the performed analyses.

Arc Grounding Fault Identification Using Integrated Characteristics in the Power Grid

Arc Grounding Fault Identification Using Integrated Characteristics in the Power Grid

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.

Detection of arc grounding fault based on the features of fault voltage

Arc grounding faults commonly occur in power grids, causing extensive power outages and significant economic losses. In this paper, we propose a novel method for detecting arc grounding faults that utilizes a time-frequency-phase mixed feature extraction approach. The mathematical expression for the arc grounding fault voltage is detailed in this paper, and from this, time-domain features that are unaffected by fault transition resistance are extracted. Furthermore, features with clear physical interpretation are extracted from the frequency and phase domains of the fault signal. Our method is able to avoid the subjective feature selection problem that exists in current methods. We conduct fault detection experiments using a topology designed for the purpose and a 10 kV setup to obtain voltage data of arc grounding faults. We then train a fault recognition model using a classic backpropagation neural network. Experimental results demonstrate that the proposed method achieves an accuracy of 98.22% in identifying arc grounding faults. Additionally, we apply this method to identify corona discharge and surface discharge, achieving accuracies of 90.68% for corona discharge and 92.9% for surface discharge.

Fault type identification of arc grounding based on time-frequency domain characteristics of zero sequence current

Different types of faults pose different degrees of threat to the distribution network. Accurate identification of fault types is essential for distribution network maintenance and hazard prevention. The simulation of a typical single-phase arc grounding fault in a distribution network is carried out based on a 10 kV test platform, and the zero-sequence current of cable fault, tree touch, line break, and insulator flashover is obtained. The BP neural network is established and trained to recognize the feature data, which is extracted by Fourier transform and wavelet transform. The identification results prove the effectiveness of the proposed method for single-phase arc grounding fault type identification in distribution networks.

Modelling and control of current full compensation system‐based controllable voltage source

AbstractCurrent active suppression technology of arc overvoltage in distribution network has small capacity of controllable voltage source and complex control and cannot flexibly adjust the zero‐sequence voltage of neutral point. This study proposes a controllable voltage source system to fully compensate the arc current of ground fault for solving these problems. A controllable voltage source model based on passive supply voltage converter is established, utilising Dyn transformer to carry unbalanced load for a long time. The model output voltage is the same amplitude and frequency as that of single‐phase ground fault phase, but opposite phase. The compensation switch is operated when a ground fault occurs. The output voltage amplitude of the controllable voltage source is controlled, the fault phase voltage is controlled to be 0 in the closed loop, the grounding fault arc current is eliminated and the arc grounding overvoltage is suppressed. The control strategy was verified by the PSCAD/EMTDC simulation model of single‐phase grounding fault arc in 10 kV distribution network and the real single‐phase fault experiment platform of 0.4 kV distribution network. Results proved the model and strategy's accuracy and effectiveness. It provides an engineering practical method for active suppression of arc grounding overvoltage in distribution network.

Adaptive Active Voltage-Type Arc Suppression Strategy Considering the Influence of Line Parameters in Active Distribution Network

The reliable extinguishment of a single phase-to-ground (SPG) arc is the key issue for safe and reliable operation in the distribution network. However, Since the existing arc suppression methods are normally affected by the line parameters, the residual current (RC) at the grounding point still exists, then the grounding arc is hard to be extinguished reliably. Thus, an adaptive active voltage-type arc suppression (AAVAS) strategy that can reliably inhibit the RC at the grounding point is proposed in this paper. Firstly, the mechanism of the traditional voltage-type arc extinguishing method affected by the line parameters is proved, and the variation rules are given for the RC under different fault distances and grounding resistance. Secondly, the variation characteristics are analyzed for the faulty line current before and after arc extinguishing. On this basis, it is proposed to add the residual voltage (RV) compensation ring to the traditional voltage-type control strategy, which can effectively offset the influence of voltage drop on faulty-phase line impedance. Then, the Bode diagram analysis shows that the presented strategy performs well regardless of ground-fault conditions. Finally, the feasibility and effectiveness of the proposed AAVAS strategy are verified by the simulation and experiment results.

Research on arc grounding identification method of distribution network based on waveform subsequence segmentation-clustering

The traditional method of detecting fault current based on threshold judgment method is limited by the current size and is easily disturbed by noise, and it is difficult to adapt to the arc ground fault detection of the distribution network. Aiming at this problem, this paper proposes a single-phase arc-optic ground fault identification method based on waveform subsequence splitting fault segmentation, combined with three-phase voltage-zero sequence voltage waveform feature extraction clustering. First of all, the waveform fault segment is segmented and located, secondly, the characteristic indexes of the time domain and frequency domain of the combined three-phase voltage-zero sequence voltage waveform are established, and the multidimensional feature distribution is reduced by the principal component analysis method, and finally, the characteristic distribution after the dimensionality reduction is identified by the K-means clustering algorithm based on the waveform subsequence. Experimental results show that the arc light grounding fault identification method proposed in this paper achieves 97.12% accurate identification of the test sample.

A Single-Phase-to-Ground Fault Detection Method Based on the Ratio Fluctuation Coefficient of the Zero-Sequence Current and Voltage Differential in a Distribution Network

Because the traditional zero-sequence overcurrent protection method is not effective in detecting single-phase-to-ground faults (SPGF) in a low-resistance grounded system (LRGS), this paper analyzes the fault characteristics of a 10-kV LRGS in detail. From the perspective of the time domain, the relationship between zero-sequence current and zero-sequence voltage is deduced, and the characteristics corresponding to faulty lines and nonfaulty lines are analyzed. The analysis reveals that the ratio fluctuation coefficients of the zero-sequence current to the differential zero-sequence voltage corresponding to faulty lines and nonfaulty lines have notably different characteristics; consequently, a high-sensitivity SPGF detection method is proposed. This method considers the existence of unbalanced loads and asymmetric parameters in the distribution network, can effectively identify high-impedance faults as high as 5000 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> and nonlinear arc grounding faults, and can resist noise interference with a signal-to-noise ratio of 20 dB. Finally, many simulations and comparisons based on PSCAD/EMTDC verify that the proposed detection method has better applicability than the existing methods in detecting high-impedance SPGFs.

Single-Phase to Ground Fault Line Identification for Medium Voltage Islanded Microgrids With Neutral Ineffectively Grounded Modes

Considering single-phase to ground (SPG) faults accounting for more than 80% of all faults, neutral ineffectively grounded mode (NIGM) is the most promising choice for medium voltage (MV) islanded microgrids (MGs) to enhance operation reliability. But due to the weak fault current and flexible network topology of islanded MGs, it is difficult to detect SPG fault lines. To solve this issue, this paper firstly analyzes the SPG fault characteristics of the MV islanded MGs with different NIGMs and network topologies. It is found that the looped MGs have a virtual terminal, i.e., the point where zero-sequence current (ZSC) is zero. And the feature differences between fault and non-fault lines are revealed. Based on that, an SPG fault line identification method is proposed. The main criterion is constructed based on the skewness signs of high frequency zero-sequence voltage (ZSV) and ZSC. Additionally, the fundamental amplitude of the difference between the actual ZSC received from another terminal and the ZSC calculated from local ZSV and ZSC is used to formulate an auxiliary criterion. Finally, the effectiveness of the proposed method is validated in a 10kV islanded MG model considering different NIGMs, different fault conditions, arc grounding faults, and the influences of the line parameter, operating point and measurement noises.

A faulty section location method for distribution grid based on grounding fault transfer device

In the distribution grids, grounding fault transfer devices have been widely used to suppress the transient arc grounding fault. Based on the grounding fault transfer device, a high sensitivity faulty section location method is proposed in this paper. When an arc grounding fault occurs, the fault phase bus is earthed by the grounding fault transfer device, which can simultaneously realize arc suppression and faulty section location. There are two grounding transient processes in this method, including fault grounding and active grounding of the faulty phase bus. During the aforementioned processes, the similarity degree of the zero mode current on both directions of the faulty section varies from low to high, whereas there is almost no change in the healthy section. The ratio of S transform energy relative entropy is used to represent the level of change of the similarity degree on both directions of each section. The section with the maximal entropy ratio is determined as the faulty section. The proposed method does not need to set the threshold and presents higher sensitivity for an arc fault. Simulation proves the sensitivity and accuracy of the proposed method.

Arc Grounding Fault Monitoring and Fire Prediction Method Based on EEMD and Reconstruction

To solve the problem of the single-phase ground fault and occurrence of electrical fires due to the residual current in substation AC power systems, a residual current intelligent sensing technology is proposed based on ensemble empirical modal decomposition (EEMD), sample entropy (SE) reconstruction, and fire warning technology using a beetle antennae search algorithm. First, through the residual current monitoring device to collect residual current information, EEMD and SE reconstruction for arc-earth fault diagnosis and an analysis of the differences in the current characteristics of each line after reconstruction are used to determine the fault line. Second, residual current, temperature, and operating voltage as input parameters and fire probability are the output parameters. The input–output relationship is established by a back-propagation neural network (BPNN) and optimized by the beetle antennae search (BAS) algorithm to speed up the convergence and improve the prediction accuracy to establish a substation fire warning scheme. Through simulation experiments, this paper proposes the residual current as a monitoring object method can effectively diagnose ground faults and accurately predict the probability of fire occurrence to ensure the safe and stable operation of substations.

Faulty Section Location Method Based on Dynamic Time Warping Distance in a Resonant Grounding System

When a single-phase grounding fault occurs in a resonant grounding system, the determination of the fault location remains a significant challenge due to the small fault current and the instability of the grounding arc. In order to solve the problem of low protection sensitivity when a high-resistance grounding fault occurs in a resonant grounding system, this paper proposes a fault location method based on the combination of dynamic time warping (DTW) distance and fuzzy C-means (FCM) clustering. By analyzing the characteristics of the zero-sequence current upstream and downstream of the fault point when a single-phase grounding fault occurs in the resonant grounding system, it is concluded that the waveform similarity on both sides of the fault point is low. DTW distance can be used to measure the similarity of two time series, and has the characteristics of good fault tolerance and synchronization error tolerance. According to the rule that the DTW value of faulty section is much larger than that of nonfaulty sections, FCM clustering is used to classify the DTW value of each section. The membership degree matrix and cluster centers are obtained. In the membership degree matrix, the section corresponding to the data in a class of their own is the faulty section, and all other data correspond to the nonfaulty section; otherwise, it is a fault occurring at the end of the line. The simulation results of MATLAB/Simulink and the field data test show that the method can accurately locate the faulty section.

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.

Method for Line Selection of Single-phase Arc Grounding Fault in Distribution Network Based on Extracting Fault Arc Characteristics

Single-phase arc grounding fault is the most important fault form of the medium voltage in distribution network. Once the arc grounding fault occurs, the faulty point generates an arc, and the system generates an arc grounding over-voltage, so it is very necessary to analyze the faulty arc. The faulty arc current has obvious “zero rest phenomenon” at the zero point, and the voltage at this time rises suddenly. This characteristic can be used to analyze the fault. This paper analyzes the current of the faulty arc in MATLAB/Simulink, and extracts transient information of arc current through wavelet transform. According to the singular characteristics, the line selection is carried out by comparing the maximum value of the fourth scale of zero-sequence current of fault line and non-fault line under different “zero rest ratio”. The result shows that the extraction of the arc feature is participating in the arc grounding fault to correctly select the fault line, and the principle is reliable, accurate and suitable for distribution networks in different grounding methods.

Application of 66kV Active Intervention Grounding Arc Suppression Device

The energy supply is mainly based on electric energy at present, and power supply reliability is an important indicator for evaluating power supply services. In view of the 66kV transmission voltage level unique to Northeast my country, the neutral point of the transmission system directly affects the stable operation of the power system. First, the composition of the substation in the system and the working principle of the arc suppression device are analyzed. Secondly, when a single-phase grounding fault occurs in a 66kV neutral point ungrounded system, an active intervention grounding arc suppression device is designed. Finally, the operating characteristics of the designed grounding arc suppression device are demonstrated based on the simulation results.

Analysis on burning failure of main transformer in 220kV substation

Neutral point ungrounded three-phase system is widely used in 10kV and 35kV low-voltage systems because of its higher power supply reliability. When the single-phase grounding short-circuit fault occurs in the system, the other two phases can continue to operate for a period of time to ensure the reliability of power supply. However, when the system operates under single-phase grounding fault, arc grounding overvoltage is easy to occur, which may damage electrical equipment or develop into phase-to-phase short circuit. This paper analyses a burning accident of main transformer caused by arc grounding overvoltage in 220kV substation, obtains fault recording information, points out fault causes and puts forward corresponding preventive measures.

Experimental Research and Numerical Simulation of Single Soil‐Arc‐Grounding‐Fault in Distribution Networks

Among the distribution network faults, single‐phase grounding faults have the greatest probability. The faults are often accompanied by arcs in the grounding point soil. This type of fault current has a small amplitude and seldom can obtain field record data. A soil arc grounding fault is tested on a realistic‐distribution‐network‐experimental‐platform (RDNEP), and it is concluded that the soil‐arc‐grounding‐fault (SAGF) has three main characteristics: hysteresis, nonlinearity, and asymmetry. By comparing with the characteristics of common arc models, it is pointed out that common arc models cannot accurately fit the characteristics of SAGF. This paper proposes and establishes a double exponential function arc model. Through the comparison of simulation waveforms with experimental data, it is verified that the numerical simulation method proposed in this paper can simulate the development process of SAGF more accurately. Furthermore, the equivalence of RDNEP is verified on the real distribution network system (RDNS). On this basis, analyzed the arc characteristic changes of different SAGF development cycles. Finally, by studying the applicability of the proposed model in simulating ground faults in grass and gravel roads, it is verified that the model proposed in this paper has a strong generalization capability. The research has laid a theoretical foundation for a detection algorithm that is based on the characteristics of SAGF.

Simulation of a single-phase arc grounding fault on a 220-kV cable transmission system

Cable tunnel fires are mainly caused by single-phase arc grounding faults. The massive energy generated by arc can threaten the safety of the densely laid cable tunnels. In this study, a digital arc fault model with a 220-kV cable transmission system was established on Power Systems Computer Aided Design(PSCAD). The arc model was improved because the parameters were acquired from the experimental results. The arc fault can be divided into two stages: a primary arc at the initiation of the fault and a secondary arc after the tripping of the circuit breakers. The primary arc contains few nonlinear components because of the large arc currents. The secondary arc voltages exhibit nonlinear characteristics because of arc elongation. The secondary arc power continues to increase, however, its amplitude is considerably smaller than the primary arc. The lifetime of the primary arc is dependent on the action of the relaying protection system. Further, some limits based on the energy balance theory were introduced to obtain the extinction time of the secondary arc. In addition, the total energy generated by the arc fault in the 220-kV cable transmission system will eventually become 4891 kJ. This digital arc fault model will significantly contribute to future research with respect to the mechanism of cable tunnel fires.

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.