Single-line-to-ground Fault Research Articles

Active arc suppression device based on voltage‐source convertor with consideration of line impedance in distribution networks

In the non-effectively grounding distribution system, residual current under single-line-to-ground (SLG) fault threatens the safety of human being and power supply equipment. Active arc suppression device has been proved to be effective for SLG fault arc suppression when the line impedance is ignored. However, in practice, line impedance varies with the fault location and the load current flowing through the impedance brings about additional voltage drop, which increases the fault current and is not dealt with by the conventional methods. To achieve accurate SLG fault arc suppression with the existence of line impedance, the neutral-to-ground voltage reference for full ground-fault current compensation is firstly derived and a detection method is then proposed. The pre-fault and post-fault line currents are used to eliminate the influence of load current on the line impedance voltage drop. A dual-loop voltage and current controller is then designed. The prototype of active arc suppression device was developed. The results of simulation and prototype experiment validate the effectiveness of the proposed method.

Single line to ground fault detection and location in medium voltage distribution system network based on neural network

<p>The aim of this project was to detect and locate the single ground failure lines that occurs in medium voltage (MV) networks on the transmission lines (TL). Compared with anther faults, single line-to-ground (SLG) is the most frequent. The neural network (NN) algorithm was advanced in order to discover and locate SLG faults. The network is simulated through simulated numerous defects at various locations, as well as changing earth resistance from (or 100 Ω) to TL to gather all of the data. In the electromagnetic transients’ program (EMTP) program software, the existing fault have been measured. In addition, the waves were evaluated by utilize MATLAP's fastfourier-transform to calculate the waves of top three of them, On the MV network are fifty hundred faults are simulated all data in the neural network at MATLAB were trained and examined to improve the NN algorithm according to this data. Comparing all the simulated location faults that have been applied with those all locations detected in the NN algorithm, the overall error between them has been found to be very low and not to exceed 0.7. The Simulink circuit was created from this algorithm and checked in order to predict each failure could occur in the future in the MV network.</p>

Directional element evaluation applied to half-wavelength transmission lines

In this paper, a careful analysis of directional element behavior applied to a half-wavelength transmission line (HWL) is presented. Single line-to-ground (SLG) faults were applied, varying loading conditions and fault resistance. A commercial relay was used. Two directional elements were considered: 32QG and 32V. With the aim of obtaining directional element setting parameters, a Python program based on two-port network theory was developed. The simulations were also performed in a hardware-in-the-loop (HIL) environment. It was observed that only the element 32V operated properly throughout the system during SLG fault conditions. It can be concluded that the conventional directional element algorithm can be applied to a system with a half-wavelength transmission line under the above-mentioned fault condition.

Analysis of Voltage Stability Index under Stressed Operating Conditions in Bus Power Systems

In stressed operating conditions, several types of voltage stability indices (VSI) are used for the assessment of voltage stability at specific operating points. The performance of various available VSIs are compared in this paper. The one generation unit tripped effects, single line to ground (SLG) fault and inductive loading variations occur in combinational format with such operating conditions. Voltage collapse occurs in the lines or nodes due to the stressed operating conditions (SOC). SLG fault, loading effects, power margin, line continency ranking, and line number are some of the performance parameters of VSI analysed in this paper. For utilization of reactive power compensation, the proper location can be chosen with the help of critical line and node analysis (CLNA) that makes use of VSIs. For any SOC, accurate voltage instability prediction is performed using VSI as per the simulation results. Under voltage collapse due to multiple causes, the voltage stability assessment of any specific line can be performed using this information.

IEC 61850-Based Centralized Protection against Single Line-To-Ground Faults in Ungrounded Distribution Systems

We developed an International Electrotechnical Commission (IEC) 61850-based centralized protection scheme to prevent single line-to-ground (SLG) faults in the feeders and busbars of ungrounded distribution systems. Each feeder intelligent electronic device (IED) measures its zero-sequence current and voltage signals and periodically transmits zero-sequence phasors to a central IED via a Generic Oriented Object Substation Event message. Using the zero-sequence phasors, the central IED detects SLG faults in feeders and busbars. To achieve centralized protection, angle differences between the zero-sequence currents and voltage phasors are exploited, and their calculation compensates for data desynchronization. The feeder IEDs were implemented using the MMS-EASE Lite library, while the transmitted zero-sequence phasors were calculated based on fault signals simulated by Power System Computer Aided Design / Electro-Magnetic Transient Design and Control (PSCAD/EMTDC). The central IED determined if the SLG fault was in a feeder or busbar by aggregating and analyzing the zero-sequence phasors received from the feeder IEDs. The results confirmed the validity and efficiency of our centralized protection scheme.

Low-Voltage Ride Through Strategy for MMC With Y₀/Y₀ Arrangement Transformer Under Single-Line-to-Ground Fault

In the offshore wind farm high-voltage direct-current (HVDC) system, the power delivery capability of the onshore modular multilevel converter (MMC) decreases severely under grid fault, which makes the DC-bus voltage increase rapidly and threatens the safe operation of the system. This paper proposes a low-voltage ride through (LVRT) strategy for MMC with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{Y}_{0}/\text{Y}_{0}$ </tex-math></inline-formula> arrangement transformer under single-line-to-ground (SLG) fault. The influence of different transformer arrangements to the MMC under SLG fault is analyzed. On this basis, a power delivery capability enhanced method is proposed for MMC with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{Y}_{0}/\text{Y}_{0}$ </tex-math></inline-formula> arrangement transformer to take advantage of its control ability on zero sequence current. In addition, an optimized LVRT strategy based on resonant controller is proposed, which has simple control structure and can ride through the SLG fault without DC chopper. The offshore wind farm MMC-HVDC simulation system is established in PSCAD/EMTDC and simulation studies are conducted to validate the effectiveness of the proposed LVRT strategy.

Single-Line-to-Ground Fault Location in Resonant Grounded Systems Based on Fault Distortions

Under single-line-to-ground (SLG) faults, the voltages and currents in resonant grounded systems will inevitably be distorted. To locate the faults quickly and accurately, this paper proposes a location method based on fault distortions. The faulty phase is firstly detected according to the first SLG fault feature below, and then the faulty feeder and section are detected according to the second feature below. 1) On the bus, one of the following distortions occurs. One dropped faulty-phase voltage (FPV) and two raised normal-phase voltages (NPVs). One dropped FPV and two NPVs (in which one rises and the other drops), where the product of FPV amplitude distortion and its phase-angle distortion is unique among three phase voltages. 2) On the faulty phase, the current on faulty feeder upstream rises, while the currents on faulty feeder downstream and normal feeders drop. Compared to existing methods, simulation tests show that the proposed method is robust under high impedance faults, and has a simple algorithm and easy engineering implementation. Also, it is effective under harmonics, three-phase imbalance, and different fault positions.

A Research on Selection of Appropriate Stability Index under Adverse System Conditions for the Assessment of Voltage Stability of an IEEE 14 Bus Power System

For voltage stability assessment at a given operating point, various types of voltage stability indices (VSIs) have been proposed in the literature. In this paper, the voltage stability assessment of an IEEE-14 bus system is done for performance comparison of different types of VSIs available, under certain critical and practical stressed operating conditions (SOCs). The performance comparison of various VSIs under the considered SOCs is not reported in the literature. Such SOCs include the combinational occurrence of – variation in inductive loading, single line to ground (SLG) fault and effect of one generation unit tripped. These SOCs are the prime cause of voltage collapse of any node/line. The results show the performance of various VSIs with respect to line number, contingency ranking of the line, power margin, effects of loading and SLG fault. These VSIs are also instrumental in critical line and node analysis (CLNA) which is useful in the choice of proper location for reactive power compensation required. The simulated results provide the best performing VSI for accurate prediction of voltage instability under any considered SOC. This information is essential for voltage stability assessment of a particular line under multiple causes of voltage collapse.

Feature‐clustering‐based single‐line‐to‐ground fault section location using auto‐encoder and fuzzy C‐means clustering in resonant grounding distribution systems

Many sensors like digital fault indicators (DFIs) have been applied and promoted in distribution systems. The sensors can provide a technical mean for single-line-to-ground (SLG) fault section location, but there are still some feature extraction and fault diagnosis problems. A novel SLG fault section location method utilizing auto-encoder (AE) and fuzzy C-means (FCM) clustering is presented in this work. Taking advantage of abundant information provided by DFIs, striking features can be extracted by the AE network, which is different from the artificially designed features that rely on prior knowledge. Compared with the learning-based methods requiring massive training data, the proposed method only requires the data from one SLG fault. By applying the AE network to the zero-sequence current measured by DFIs, the SLG fault section location's striking features could be obtained. Through feature classification by FCM clustering without setting threshold, the positional relationship between each detection node and the fault point would be distinguished to locate the fault section. Considering the abnormal communication of DFIs, the experiment proves that the proposed method can work effectively under various fault conditions.

An Identification Method for Asymmetric Faults With Line Breaks Based on Low-Voltage Side Data in Distribution Networks

Faults with line breaks occur more and more frequently and are difficult to detect by relay protection device in small-current grounding distribution networks. However, faults with line breaks are more likely to cause security accidents such as fires, overvoltages and electric shocks. Considering the low cost and high reliability of collecting data on the low-voltage (LV) side in distribution networks, this paper proposes a method for distinguishing between faults with line breaks and short-circuit faults on the medium-voltage (MV) side. Voltage amplitude and phase on the LV side of distribution transformer (DT) are analyzed through symmetrical component method. The amplitudes are used to identify two-phase faults with line breaks (TPFs-LBs) and two-phase short-circuit faults (TPFs-SCs); while the phases are selected to distinguish single-line-to-ground faults with line breaks (SLGFs-LBs) from single-line-to-ground faults (SLGFs). The effects of network parameters, operation conditions and external factors on the proposed method have been discussed. Simulation results verified the effectiveness of the proposed method.

Optimization of detection of a single line to ground fault based on ABCNN algorithm

One of the most faults found in the electrical distribution network is a single line to ground fault (SLGF). It can be detected and rectified through many methods. The utilization of Peterson coil (PC), reduces the electrical arcs and make the distribution network safe from damage in contrast to the cost value. This paper focuses on the method for its detection on higher and lower values of the ground fault current (GFC). Moreover, it will identify the capacitance and earth leakage of earthling network lines as well as calculate the opposing inductance to compensate for the cause. It also presents the selfextinguishing of GFC by controlling PC through one of the novel optimization techniques called adaptive and artificial bee colony with network neural (ABCNN) to improve the algorithm's performance, like optimization efficiency, speed, solution, and iteration. As a result, the determination of the GFC equals the sound phase current. Also, the extinguishing of an electric arc results in a short time compared with classical methods. The significant advantage of this research is the increment in the system's reliability, protection of devices as well as saving in copper cost. MATLAB was used to carry out this research. For the validity, the proposed algorithm results were compared with the classical method by creating faults on separate phases also.

Analysis and Control of an MMC-HVDC System Under an Unbalanced Grid Condition

Modular multilevel converter (MMC)-based high voltage direct current (HVDC) systems have been increasingly researched and installed in recent years. During operation, systems may be subjected to various unbalanced conditions, the single-line to ground (SLG) fault is one of the most common unbalanced faults. When a SLG fault occurs in a three-phase alternating current (AC) system, the double-line frequency positive- and zero-sequence harmonic components will be produced besides the double-line frequency negative-sequence harmonic component. And if the control system cannot suppress these harmonic components, they can propagate into the direct current (DC) side of the HVDC system and cause ripples in DC-line voltage and current as well as other unwanted consequences. Among the proposed controllers in the published papers on this topic, rarely controllers can both effectively suppress the circulating current and completely eliminate ripples in the DC-line voltage and current while still keeping the AC-side current balanced under unbalanced grid conditions. Therefore, this paper first analyses the propagation of harmonic components in a two-terminal MMC-HVDC system under a SLG fault. Then, based on the mathematical analysis, a proposed controller including an inner current controller for controlling the negative- and positive-sequence components and a controller for suppressing the zero-sequence component is designed to eliminate harmonic propagation from the faulty three-phase AC system to the DC side of the HVDC system, resulting in suppressing ripples in DC-line voltage and current. The theoretical analysis and proposed controller are verified by a simulation model in PSCAD platform.

Faulty phase recognition method based on phase-to-ground voltages variation for neutral ungrounded distribution networks

Faulty phase recognition under single-line-to-ground (SLG) fault condition is critical for some arc suppression methods in medium voltage (MV) distribution networks. Conventional methods tend to be invalid due to network asymmetry in high-resistance ground-fault condition and the difficulty of detecting phase-to-ground parameters in practice. In this paper, the variation of the three phase-to-ground voltages with the change of SLG fault resistance is analyzed in detail, and the magnitude and phase angle variation rules of the voltages are obtained. Then, the unique variation rules on SLG fault for each phase are separately and strictly discussed in theory and numerical analysis. Furthermore, a faulty phase recognition method is proposed based on the variation rules of three-phase voltages. Simulation results in PSIM verify the proposed variation rules and validate the effectiveness of the proposed faulty phase recognition method, which ensures accurate recognition of faulty phase in high-resistance ground fault.

Optimization of detection of single line to ground fault by controlling peterson coil through ANFIS

The most common fault in the distribution network is the single line to ground fault (SLGF). With earthling in the distribution network, it causes electrical arc as well as a high voltage in the faulted phase compared to other two healthy phases. It increases the danger of separation and isolation in the power network. One of the classical technique to control the arc is through Peterson Coil (PC), which detects and turns off/reduces the electrical arc making the network safer, increasing its reliability and device's safety. To control the PC, some of the techniques used in this research area are PID, FL, NN etc. This paper presents Adaptive Neural-Fuzzy Inference System (ANFIS) technique to controlling the PC. It gives the best results by detecting the fault, reducing the electrical arc and minimizing the fault current to the rated current in a very short time. Moreover, this research focuses on suppressing fault current by looking at its higher and lower peaks. Also, it calculates the opposing inductance to compensate the capacitance caused. It will save thousands of tons of copper costs. This research was conducted using MATLAB. For the validity of the proposed technique results, PID control technique was used.

Modulation Index Design of Full-Bridge MMC for Capacitor Voltage Ripples Reduction Under Single-Line-to-Ground Faults Conditions

The energy storage requirements of full-bridge submodule (FBSM)-based modular multilevel converters (FB-MMCs) can be reduced more than 50% compared to conventional half-bridge SM-based MMCs (HB-MMCs) when negative voltage states of FBSMs are used. However, under single-line-to-ground (SLG) faults conditions, the FBSM voltages ripples increase significantly, which is quite different from HB-MMCs. This article analyzes the characteristics of the FBSM voltage fluctuations under both steady-state and SLG faults conditions, and the impact of modulation index, power factor angle and inductance at the grid side on the FBSM voltage fluctuations is also analyzed. Results indicate that the peak-to-peak value of the FBSM voltage fluctuations has strong correlation with the modulation index. It is also found that the fundamental frequency components become dominant when SLG faults occur, and the ripples are almost twice of the steady-state operations, which may threaten safe operation of FB-MMCs. Based on these analysis, a modulation index design method is proposed for the purpose of balancing the FBSM voltage fluctuations of the FB-MMC under SLG faults conditions. The validity of the proposed modulation index design method is verified by simulation results on a ±200 kV/800 MW FB-MMC.

Location of Single-Line-to-Ground Fault Using 1-D Convolutional Neural Network and Waveform Concatenation in Resonant Grounding Distribution Systems

Nowadays, smart monitoring devices such as digital fault indicator (DFI) have been installed in distribution systems to provide sufficient information for fault location. However, it is still a challenge to extract effective features from massive data for single-line-to-ground (SLG) fault-section location. This work proposes a novel method of fault-section location using a 1-D convolutional neural network (1-D CNN) and waveform concatenation. After SLG fault occurs, DFI measures the transient zero-sequence currents at double-ends of the line section, which could be concatenated to construct characteristic waveform. The features of characteristic waveforms would be extracted adaptively by 1-D CNN to locate the fault section. Furthermore, the problem where the on-site recorded data are hard to collect would be solved because 1-D CNN only needs a small number of samples for training in practical applications. The experimental results verified that the proposed method could work effectively under various fault conditions, even if a few DFIs are out of order.

Informational Fundamentals of the Multiparameter Differential Protection of Busbar Generators against Single Line-to-Ground Faults

The multiparameter differential protection of busbar generators against single line-to-ground faults (SLGF) is studied in accordance with information theory of protection. Such protection is based on the use of the individuality property of harmonic groups. Moreover, it controls many parameters of the higher harmonics of differential currents and is shown to have absolute selectivity. Given the properties of the harmonics of some groups, this perfection is achieved to maintain the aggregate information support of protection at a high level with SLGF in areas where the harmonics of other groups are insufficient. Depending on network parameters and modes, multiparameter differential protection does not require settings or adjustments. This advantage is provided by using relative characteristic values that are generated by the protection during operation. Such protection is sensitive due to a special active-adaptive recognition path, which can measure low-level harmonics against a background of the predominant component of the fundamental harmonic in the current.

Two-Phase Current Injection Method for Single Line-to-Ground Fault Arc-Suppression With Revised STATCOM

To suppress the arc current in the single line-to-ground (SLG) fault in neutral isolated distribution network, a two-phase current injection method is proposed for the revised static synchronous compensator (STATCOM), as an extra function during the SLG fault. Therefore, the traditional roles of the dedicated passive coil or power electronic based arc-suppression devices can be taken by this multi-purpose STATCOM. This article first introduces the principles and the models of the arc-suppression current injection during SLG fault. Then, different options of arc-suppression current injection by the revised STATCOM are analyzed in terms of stabilizing the floating dc capacitor voltages of the cascaded H-bridges (CHB) converter. It is discovered that the two-phase current injection is the only viable option to maintain the floating dc capacitors voltages. Then, the arc-suppression current controller and the dc capacitors voltages controller are proposed, and the design process of the control parameters adapting to the varying transitional (grounding) resistances computed online is also introduced. The proposed methods are first validated by simulations. Then, an MVA-rating CHB converter prototype is constructed, and 10 kV feeder SLG fault and arc-suppression experiments are performed to demonstrate the effectiveness of the proposed method.

Fault line detection using waveform fusion and one-dimensional convolutional neural network in resonant grounding distribution systems

Effective features are essential for fault diagnosis. Due to the faint characteristics of a single line-to-ground (SLG) fault, fault line detection has become a challenge in resonant grounding distribution systems. This paper proposes a novel fault line detection method using waveform fusion and one-dimensional convolutional neural networks (1-D CNN). After an SLG fault occurs, the first-half waves of zero-sequence currents are collected and superimposed with each other to achieve waveform fusion. The compelling feature of fused waveforms is extracted by 1-D CNN to determine whether the fused waveform source contains the fault line. Then, the 1-D CNN output is used to update the value of the counter in order to identify the fault line. Given the lack of fault data in existing distribution systems, the proposed method only needs a small quantity of data for model training and fault line detection. In addition, the proposed method owns fault-tolerant performance. Even if a few samples are misjudged, the fault line can still be detected correctly based on the full output results of 1-D CNN. Experimental results verified that the proposed method can work effectively under various fault conditions.

Analysis of the Jeju Island Power System with an Offshore Wind Farm Applied to a Diode Rectifier HVDC

The Jeju Island power system consists of two-unidirectional high voltage direct current transmission systems (HVDC), thermal power plants, and renewable energy sources. The local government’s policy states that a 100 MW offshore wind farm should be constructed in the future. Due to the small size and sensitivity of the Jeju Island power system, power system analysis must be carried out before the installation of the new facility. Therefore, the objective of this study was to analyze the Jeju Island power system with a new wind farm applied to uncontrolled diode rectifier HVDC. Although there are many studies about the grid connection method of offshore wind farms, its small grid connection analysis has been rarely investigated, especially in the diode rectifier HVDC method. Diode rectifier HVDC is a new grid connection method for offshore wind farms, which reduces the costs and increases the reliability of the offshore platform. To verify the accuracy and effectiveness of simulation models, steady and transient state scenarios were conducted using the PSCAD/EMTDC program. First, the model of the Jeju Island power system without a new wind farm was compared with measured power system data. Second, its power system connected with a diode rectifier HVDC was simulated in a steady state. Finally, disconnection and single line ground fault occurred at the offshore wind farm, respectively. From the simulation results, the grid stability of the Jeju Island power system was confirmed considering a new facility.