Single-line-to-ground Fault Research Articles

Evaluating the Voltage Transformer Thermal Stability during Magnetizing Current Inrush Caused by a Single-Line Ground Fault

Evaluating the Voltage Transformer Thermal Stability during Magnetizing Current Inrush Caused by a Single-Line Ground Fault

Control Approach of Grid-Connected PV Inverter under Unbalanced Grid Conditions

In grid-connected photovoltaic (PV) systems, power quality and voltage control are necessary, particularly under unbalanced grid conditions. These conditions frequently lead to double-line frequency power oscillations, which worsen Direct Current (DC)-link voltage ripples and stress DC-link capacitors. The well-known dq frame vector control technique, which is effective under normal conditions, struggles with oscillatory component management in unbalanced grid conditions. To address this issue, this paper presents an advanced control approach designed for grid-connected PV inverters. The proposed approach is effective at reducing oscillations in the DC-link voltage at double the grid frequency, thereby enhancing system stability and component longevity. This method introduces a feedback control method designed to regulate oscillatory components that appeared within the dq frame and suppress the DC-link voltage oscillations under imbalance conditions, including single line-to-ground (SLG) faults. Additionally, the control scheme incorporates a maximum power point tracking (MPPT) controller to optimize PV efficiency. Comprehensive simulations demonstrate the effectiveness of this method in maintaining sinusoidal current injections and stabilizing DC-link voltage during unbalanced grid conditions. Simulation results show that the control scheme effectively stabilizes DC-link voltage, maintains balanced grid current, and ensures constant active power under various conditions, including SLG faults and solar irradiance changes.

Single Line-to-Ground Fault Type Multilevel Classification in Distribution Network Using Realistic Recorded Waveform.

The further identification of fault types for single line-to-ground faults (SLGFs) in distribution networks is conducive to determining the cause of grounding faults and formulating targeted measures for hidden danger treatment and fault prevention. For the six types of SLGFs generated in the actual power grid, this paper deeply studies their fault characteristics. Firstly, the classification criterion of fault transition resistance is derived by the generation mechanism of fault zero sequence voltage (ZSV). At the same time, by comparing and analyzing the same and different characteristics between faults, three criteria for fault classification are obtained. Based on the above four criteria, a multilevel and multicriteria fault classification method is proposed to judge six types of SLGFs. Then, the proposed method is verified by various fault state simulations of the distribution network model with a balanced topology and unbalanced topology. The engineering application of the method is demonstrated by the verification of actual power grid data. Finally, noise and data loss interference test results show the robustness of the method.

Optimize single line to ground fault detection in distribution grid power system using artificial bee colony

The most common power system (PS) distribution network fault, single lineto-ground fault (SLGF), causes residual current (I res) to start an electrical arc and high voltage (HV) three times the rated voltage in other healthy phases. HV from capacitive currents (IC) damages cable insulation and PS appliances. Peterson The neutral point coil (PC) reduces (I res) and extinguishes the electric arc, but the fault current (I fault) remains below the protection devices' threshold. Operations and equipment are riskier. PC adaptive eliminates electrical arcs, making the network safer. This paper detects I faults online using Texas instrument validation in MATLAB and adaptive by artificial bee colony (ABC). This paper discusses Texas instrument fault current detection and MATLAB validation. It improves system reliability, device protection, and copper savings by thousands of tons. ABC intelligently optimizes many mathematical problems. ABC with network neural artificial intelligence (AI) improves algorithm performance (artificial bee colony network neural (ABCNN)). This new method may improve distribution network SLGF detection. This first work can work online in electrical power stations by building the (eZdsp F28335-RS232) into the program to send fault signals to the control when SLGF occurs without damaging devices, equipment, cables, or power outages.

A novel flexible fault eliminator with active disturbance rejection and soft grid-connection in distribution networks

Among the possible fault types in the distribution networks, single-line-to-ground (SLG) fault has the highest probability. The SLG fault current and arc can easily cause personal injury and death. This study proposed a flexible fault eliminator (FFE) based on a cascaded H-bridge topology to limit the SLG fault current and extinguish fault arc in the medium voltage distribution networks. An active disturbance rejection controller for the FFE was designed to improve the current limiting performance of FFE in the presence of insulation parameter measurement errors and sampling errors from potential/current transformers. The controller with good robustness adapts to different ground fault resistances. In addition, a soft grid-connection control scheme based on bistable smooth switching was proposed to avoid the injected current impulse of FFE at the moment of grid connection. Simulation and experimental results showed that the fault current was limited to a small enough value and the fault arc was extinguished effectively. The output current and voltage of FFE at the time of grid connection were in a smooth transition, avoiding the impulse on the power grid system. The FFE can eliminate the SLG fault flexibly and stably.

A novel hybrid arc suppression device for single line-to-ground faults

Traditional passive arc suppression devices (ASDs) do not provide complete compensation for single line-to-ground (SLG) fault currents. Meanwhile, active ASDs are expensive. This study proposes a novel hybrid ASD to balance compensation and cost. The hybrid ASD consists of a passive part and an active part. To reduce the fault voltage to near zero, the passive part uses a single-phase isolating transformer and two sets of phase-selection switches. The active part, which compensates for the residual voltage caused by the transformer's leakage impedance, is connected to the secondary side of the transformer and the ground using a small-capacity inverter. A model predictive control (MPC) method is employed as the controller. We conducted simulations and experiments for various SLG fault cases, which demonstrated the effectiveness and robustness of the hybrid ASD in arc suppression. The hybrid ASD that we propose is independent of the neutral point and has several advantages, including low cost, strong arc suppression capabilities, and high robustness.

A Non-neutral alternate arc suppression method for single phase grounding fault in active distribution network

To fully compensate reactive and active components of the single line-to-ground (SLG) fault current, additional DC power supply devices are usually used for arc suppression devices. Therefore, the alternate arc suppression method is proposed for the non-neutral multi-function arc suppression device (MF-ASD) in this paper, which can achieve energy self-balance in the MF-ASD during the SLG fault without additional DC power supply devices. Firstly, the DC-link charge–discharge characteristic of the MF-ASD is analyzed under different SLG fault conditions. Then, the alternate arc suppression principle and energy flow law between two non-faulty phases of the MF-ASD are described in detail. Further, the relationship between the alternate period, switching time, and the DC-link voltage are deduced as well. Then, the control parameters are reasonably designed for the DC-link voltage stability of two non-faulty phases of the MF-ASD. Finally, the correctness and feasibility of the proposed method are verified by simulation and experiment results.

Control of arc suppression devices for reducing powerline bushfires in resonant grounded power distribution networks using global terminal sliding mode controller

AbstractThis paper proposes a global terminal‐sliding mode controller (GT‐SMC) to compensate powerline bushfires due to electric faults in power distribution networks using arc suppression devices (ASDs). A GT‐sliding surface along with a new quick reaching law is used to design the controller. The major control objective is to compensate the fault current caused by single line‐to‐ground (SLG) faults to a value that cannot ignite fires in bushfire prone areas. A T‐type residual current compensator inverter within an ASD is controlled to achieve the goal. An integral‐sliding mode controller (I‐SMC) is also designed using a conventional reaching law for comparing the performance. Simulations studies and processor‐in‐loop implementations are carried out to investigate the ability of the GT‐SMC over an I‐SMC over a range of fault impedance scenarios. Dynamic properties of the voltage and current due to SLG faults along with the current injection by the ASD are analyzed against the standard criteria, to be followed to get rid of powerline bushfires. Results under different operating scenarios indicate that both controllers are capable to maintain standard criteria for preventing powerline bushfires though the GT‐SMC is proven to exhibit superior transient responses to that of the I‐SMC and integral backstepping controller.

Faulty Feeder Detection for Single Line-to-Ground Fault in Distribution Networks With DGs Based on Correlation Analysis and Harmonics Energy

Faulty feeder detection helps ensure the stable operation after single line-to-ground (SLG) faults in distribution networks. However, the SLG fault currents are weak, the fault conditions are complex, and distortion of fault signals may occur owing to the effect of distributed generators (DGs), which would result in unacceptable performance of the existing detection methods. To improve the accuracy of faulty feeder detection under high penetration of DGs, this paper firstly analyzes the three-sequence networks after SLG faults occur in distribution networks with DGs connection, and points out that the DGs connection does affect the zero-sequence components when DGs are connected to the faulty feeder. Besides, the polarity differences between zero-sequence voltage (ZSV) and zero-sequence currents (ZSC) are revealed. Subsequently, variational mode decomposition is employed to characterize the overall trend of the ZSV and ZSCs, and cross-correlation analysis is applied to capture the polarity characteristics between ZSV and ZSCs. In addition, harmonics characteristics of ZSCs are used as an auxiliary criterion when ZSCs are highly distorted caused by DGs connection. Finally, both of them are utilized to construct the detection scheme. Simulation results and practical data test demonstrate the efficiency of the proposed method.

Effect of Fuel Cells on Voltage Sag Mitigation in Power Grids Using Advanced Equilibrium Optimizer and Particle Swarm Optimization

Integration of Proton Exchange Membrane Fuel Cell (PEMFC) with electrical power grid (EPG) can improve the power quality (PQ) of EPG by injecting the required power. However, this makes the PQ issue more complicated due to the negative impact of voltage sag on EPG. Unfortunately, the classical P-I controllers fail in eliminating the voltage sag. In this context, this paper, attempts to mitigate the voltage sag in an interconnected PEMFC-EPG system by utilizing advanced equilibrium optimizer (AEO) and particle swarm optimization (PSO) controllers, and their efficiency is demonstrated by comparison with conventional P-I controllers. To achieve this goal, the AEO-PEMFC and PSO-PEMFC are employed in the EPG line with different fault scenarios. The obtained results unveil that both AEO-PEMFC and PSO-PEMFC provide the needed boost of voltage in the single line-to-ground faults (SLGF) scenario by 100.00%. For double line-to-ground faults (DLGF) scenario, a voltage boost of 99.56% and 98.39% is achieved while a voltage boost of 98.50% and 97.45% for the three line-to-ground faults (TLGF) scenario is obtained by the AEO-PEMFC and PSO-PEMFC, respectively.

Analysis of transient overvoltages and Self Protection Overvoltage of PV inverters through RT-CHIL

In power systems, Single-Line-to-Ground (SLG) faults are the most common type of fault. When a three-phase four-wire system supplied by an ungrounded synchronous generator is subjected to SLG faults, the unfaulted phases are expected to exhibit significant ground-fault over-voltage (GFOV). Mitigation of this is via effective grounding, as described in IEEE Std 62.92.2. However, for inverter-based resources (IBRs), the physical mechanism that leads to GFOV in synchronous machines is not present. This paper investigates whether GFOV is a problem in IBRs, and whether conventional mitigation requirements, such as providing a grounding transformer (GTF), are suitable for IBR installations. To answer these questions, a Controller Hardware-in-the-Loop (CHIL) based performance analysis is conducted. To this end, different simulation models have been developed to analyze the IBRs control and protection response. The models are comprised of a 13.2 kV, 500 kW distribution system fed by a grid connected PV inverter which was simulated in Typhoon HIL 604 real time simulator, with a IEEE Std 1547-2018 compliant external physical controller connected in the loop. The experimental set-up and tests conducted are explained and results are analyzed, showing that effective grounding requirements are much different than those for traditional generators.

1선 지락 사고시 배전선로 접지저항에 따른 유도전동기 토크 특성 변화에 관한 연구

Customers should be provided with good quality of electricity for stable load operation. Various failures can occur from substations and distribution lines to consumers. The most common failure in distribution lines is single-line ground fault. For distribution lines, grounding resistance is stipulated according to the length of the line and installation conditions. When single-line ground fault occurs, the magnitudes and phase angles of voltage and current change asymmetrically, resulting in unbalance. Three-phase induction motors among customer facilities are greatly affected by these voltage and current imbalances. Imbalance of current and voltage caused by a fault can have a great effect on the torque of the motor.BRIn this study, we analyzed how the pulsating torque of an induction motor appears according to the ground resistance of the line during single-line ground fault in a distribution line. It was confirmed that the higher the ground resistance of the distribution line, the lower the amplitude of the pulsating torque.

Optimal Second-Harmonic Current Injection for Capacitor Voltage Fluctuation Reduction in Hybrid MMCs Under Grid-Side SLG Faults

The second-harmonic injection strategy for modular multilevel converters (MMCs) can effectively suppress the capacitor voltage fluctuation in steady states. However, the capacitor voltage fluctuation under grid-side single-line-to-ground (SLG) faults will be more severe. Moreover, there is no research on the mitigation of capacitor voltage fluctuation under grid-side SLG faults for the hybrid MMC with mixed half-bridge and full-bridge sub-modules. To address this issue for hybrid MMCs, an optimal second-harmonic current injection scheme for mitigating the capacitor voltage fluctuation in the hybrid MMC under grid-side SLG faults is proposed in this paper. The mathematical models of arm power fluctuations of the hybrid MMC are firstly developed under both steady states and grid-side SLG faults. Then, the principle and optimal strategy of the proposed capacitor voltage fluctuation strategy are presented. The capacitor voltage fluctuation under grid-side SLG faults can be reduced by suppressing the three-phase arm power fluctuations. A hybrid MMC model with the proposed scheme has been established in PSCAD/EMTDC to verify its effectiveness and feasibility. Simulation results show that the average voltage fluctuation reduction rate can reach 55.77% with the proposed strategy.

Faulty feeder detection based on image recognition of voltage-current waveforms in non-effectively grounded distribution networks

Faulty-feeder detection is essential for fault location and fault isolation after single line-to-ground (SLG) faults in distribution networks. However, the SLG fault currents are weak, and the fault conditions are complex, thus posing great challenges for faulty-feeder detection. To improve the detection accuracy and reliability, a novel detection method based on waveform recognition is proposed, and it only requires zero-sequence voltage (ZSV) on bus and local zero-sequence current (ZSC), not ZSCs of all feeders. Firstly, the ZSV and local ZSC are superimposed in the same plot, and the ZSV-ZSC image for each feeder is generated. Subsequently, each image is individually identified using the established convolutional neural network with spatial attention residual learning blocks, which has strong discriminative capability. Finally, the fault and non-fault states of each feeder can be distinguished based on the corresponding image identification result. Large amounts of experimental results show that the proposed method with significant simplification of device installation can improve the accuracy of faulty-feeder detection considerably, demonstrating its strong generalization capability and good application prospects.

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.

A linear hybrid active disturbance rejection controller design to extenuate powerline bushfires in resonant grounded distribution power systems

This paper proposes a robust linear hybrid controller by combining the active disturbance rejection and proportional–integral controllers (ADRC+PI) for inverter-based arc suppression coils (ASCs) in resonant grounded distribution power systems (RGDPSs). Resonant grounding techniques are used in real power distribution networks for reducing the fault current in order to reduce the severity of powerline bushfires in the presence of single line-to-ground (SLG) faults. The severity of bushfire hazards due to these SLG faults depends on environmental conditions (e.g., wet or dry grounds) that define the behavior of the system. With respect to these conditions, the fault resistance will be lower for wet grounds for which the system model comprises one dominant pole while dry grounds force the system to have one dominant zero with two dominant poles. By considering the circumstances of such groundings, the behavior of power distribution systems changes when there are SLG faults. This paper investigates a detailed analysis in frequency- and time-domains to design a robust arc mitigator based on the hybrid ADRC+PI controller. Furthermore, the robustness of the proposed hybrid controller against the input disturbances is explored in terms of transient and steady-state stability analysis and the results are compared with the ADRC and PI controllers. In addition, the performance of the proposed hybrid ADRC+PI controller is justified by utilizing virtual- and real-time implementations in a digital signal processor (DSP) through MATLAB/SIMULINK platform on a 22 kV (line-to-line) RGDPS under distinctive grounding conditions.

Study of transient overvoltages on CSI adjustable speed drives under arcing SLGF in the industrial cable grid

Single line to ground fault (SLGF) in MV ungrounded networks is often accompanied by arcing. Most of these arcing faults are unstable and cause transient overvoltages that can exceed the insulation withstand limits of grid equipment. This problem has become especially troublesome in industrial grids widely using power electronics devices, which tend to have lower insulation margins than other power equipment. Typically an arc suppression coil is used to compensate the SLGF capacitive current and reduce the likelihood of arcing in this case. However, as the operating experience shows, arcing ground faults were also recorded in compensated industrial cable grids. This article proposes an original algorithm based on known arc burn theories to simulate the maximum overvoltage values during arcing SLGF. The purpose of this article is to examine the effect of an arc suppression coil on the nature and magnitude of transient overvoltage. The study of transient overvoltages is carried out on the example of an industrial cable grid containing AC adjustable speed drives under arcing SLGF caused by cable insulation breakdown. Simulation results for various grid operating configurations show that the suppression coil can reduce the transient voltage rise intensity but cannot affect the initial voltage pulse during an SLGF. The presented model allows sizing the minimum insulation margins and selecting thresholds of overvoltage protection triggering for grid equipment to ensure its reliable operation.

Protection of Microgrid Interconnection Lines Using Distance Relay With Residual Voltage Compensations

Protection of microgrids at the Point of Interconnection (POI) is a challenging task. Particularly, single-line-to-ground (SLG) faults on interconnection lines are difficult to detect using the fault current detection relays if the microgrid is ungrounded at utility side of its interconnection transformer; such microgrid contributes very low fault current, which disappears once the utility feeder breaker opens. Other common schemes for protection of microgrid interconnection line against SLG faults include Direct Transfer Trip (DTT) and over-voltage relay (59G). The main challenges associated with these methods are installation and maintenance costs of high-speed communication system, sensitivity of relay settings, and delayed fault clearing time due to selectivity requirements. To address such concerns, this paper proposes the use of a distance relay at the microgrid/LV side of the interconnection transformer to provide protection against SLG faults on the interconnection line at the utility/HV side. The designed distance relay executes an enhanced apparent impedance calculation using residual voltage compensation to correctly detect the fault, properly measure the fault location, and timely isolate the fault. In this paper, various scenarios are analyzed using ASPEN and PSCAD simulation tools to demonstrate the effectiveness of the proposed method for protecting the microgrid interconnection line under different fault scenarios.

Suppression Strategy on Neutral Point Overvoltage in Resonant Grounding System Considering Single Line-to-ground Fault

The resonant grounding system (RGS) has problems with neutral point overvoltage and single line-to-ground (SLG) fault. The existing active equipment can only suppress the neutral point overvoltage or the SLG fault arc, which has a single function and low utilization rate. In order to maintain the stable operation of the distribution networks and improve equipment utilization, the research on active equipment integrating the two functions is of great significance. Therefore, this paper proposes active equipment based on a cascaded H-bridge (CHB) inverter that integrates the functions of neutral point overvoltage suppression and arc suppression. The CHB inverter can switch from overvoltage suppression to arc suppression by the characteristics of zero-sequence voltage amplitude during overvoltage suppression. The arc suppression effect of the proposed arc suppression method is better than the existing flexible current arc suppression method in case of asymmetric phase-to-ground parameters. The simulation and experimental results verify the effectiveness of the proposed method under different influencing factors.

Space Vector Pulse-Width Modulation Control Strategy for Four-Leg Inverters Under Single Line-to-Ground Faults in Islanded Microgrids

In this paper, we propose a novel switching modulation scheme for three-phase four-leg inverters that enables the separation of the fault points occurring in AC distribution networks. The proposed method is aimed at continuously supplying normal voltage to the remaining healthy phases while applying zero voltage to any faulty phase when a single line-to-ground (SLG) fault occurs in the distribution network. This modulation scheme allows isolation without physically blocking the point of failure. This can prevent unnecessary continuous outages in the AC distribution network. To this end, we propose a novel coordinate transformation method to extract accurate values for the magnitude of unbalanced three-phase voltages. A novel space vector pulse-width modulation (SVPWM) method for switching schemes that are used under fault conditions is also presented. The proposed coordinate transformation considers a plane lying in a three-dimensional (3-D) space that describes the rotation of a three-phase voltage vector. This transformation converts a physical quantity that rotates in 3-D space into a value that moves in two-dimensional (2-D) space. Subsequently, the use of synchronous reference frame (SRF) transformation enables the detection and control of the voltage magnitude in case of an SLG fault. Additionally, switching vectors are selected to apply zero voltage to the faulty phase by analyzing the switching vector diagram of a four-leg inverter. Mathematical analyses conducted for the entire process are detailed herein. Further, the experimental results of four-leg inverters designed for the 10 kW class verify the proposed strategies.