Search Results (36)

Recurrent catastrophic inverter failures significantly undermine the reliability and economic viability of utility-scale photovoltaic (PV) power plants. This paper presents a comprehensive investigation of severe inverter destruction incidents at the Kopli Solar Power Plant, Estonia, by integrating controlled laboratory simulations with extensive field monitoring. Initially, detailed laboratory experiments were conducted to replicate critical DC-side short-circuit scenarios, particularly focusing on negative DC input terminal faults. The results consistently showed these faults rapidly escalating into multi-phase short-circuits and sustained ground-fault arcs due to inadequate internal protection mechanisms, semiconductor breakdown, and delayed relay response. Subsequently, extensive field-based waveform analyses of multiple inverter failure events captured identical fault signatures, thereby conclusively validating laboratory-identified failure mechanisms. Critical vulnerabilities were explicitly identified, including insufficient isolation relay responsiveness, inadequate semiconductor transient ratings, and ineffective internal insulation leading to prolonged arc conditions. Based on the validated findings, the paper proposes targeted inverter design enhancements—particularly advanced DC-side protective schemes, rapid fault-isolation mechanisms, and improved internal insulation practices. Additionally, robust operational and monitoring guidelines are recommended for industry-wide adoption to proactively mitigate future inverter failures. The presented integrated methodological framework and actionable recommendations significantly contribute toward enhancing inverter reliability standards and operational stability within grid-connected photovoltaic installations. Full article

The Wenchuan earthquake (Ms8.0), which struck Sichuan Province, China, on 12 May 2008, was one of the most devastating seismic events in recent Chinese history. It resulted in the deaths of nearly 90,000 people, left millions homeless, and caused widespread destruction of infrastructure across a vast area. In addition to the severe ground shaking and surface rupture, a variety of unusual atmospheric/ionospheric and geophysical phenomena were reported in the days and hours leading up to the earthquake. Notably, iridescent clouds were observed just before the earthquake at three distinct locations approximately 450–550 km northeast of the epicenter. These clouds appeared as fragmented rainbows located beneath the sun and were characterized by their short lifespan, lasting only 1–10 min. Moreover, they exhibited striped patterns within the iridescent regions, suggesting the influence of an external electric field. These features cannot be adequately explained by the well-known meteorological phenomenon of circumhorizontal arcs, raising the possibility of a different origin. The formation mechanism of these clouds remains unclear. In this study, we explore the hypothesis that the iridescent clouds were precursory phenomena associated with the impending earthquake. Specifically, we examine a potential causal relationship between the appearance of these clouds and the geological environment of the earthquake source. We propose a novel model in which electrical disturbances generated along the fault system immediately before the mainshock propagated upward and interacted with the ionosphere, resulting in the creation of a localized electric field. This electric field, in turn, induced electro-optic effects that altered the scattering of sunlight and projected iridescent patterns onto cirrus clouds, leading to the observed phenomena. Full article

Recently published marine geophysical and seafloor drilling data permit a substantive reappraisal of the rifting and spreading that formed the South China Sea (SCS). The SCS rifted margins are different from those of the Atlantic type, having higher strain rates, younger orogenic crust, and distributed syn-rift magmatism. Rifting ~66–11 Ma and spreading 30–14 Ma split a Cretaceous Andean arc and forearc, producing >700 km of seafloor spreading in the east and a ~2000-km-wide rifted margin in the west. Luconia Shoals–Dangerous Grounds–Reed Bank–north Palawan–SW Mindoro were separated from China when the SCS opened. Brittle faulting of the upper crust was decoupled from ductile flow and magmatic intrusion of the lower crust, producing wide rifting with thin spots held together by less extended surrounds. Sediments accumulated in inter-montane lakes. Transform faults formed at/after breakup to link offset spreading segments. Spreading in the eastern subbasin from C11n to C5AD was at rates averaging 62 mm/yr, 30–24 Ma, decreasing to 38.5 mm/yr younger than 23 Ma. Spreading reorganization was common as margin segments broke up to the SW and spreading directions changed from ~N-S before 23 Ma to NW-SE after 17 Ma. Full article

The distribution network line has the risk of an unsuccessful three-phase blind reclosing in permanent fault. Based on the response of the inverter of the distributed generation (DG) to the short-term low-frequency voltage disturbance to the line to be detected, this paper proposes a non-fault identification method for the distribution network before three-phase reclosing, based on model parameter identification. During the disturbance period, when there is no fault after the arc is extinguished, the detection line is three-phase symmetrical, and each phase-to-ground loop is its own loop resistance and inductance linear network, which is independent of the fault location, transition resistance and other factors. Furthermore, the R–L network without fault is used as the identification reference model, and the least squares algorithm is used to identify the resistance and inductance parameters of each phase loop of the detection line by using the voltage and current response information of the line side during the excitation period so as to identify the fault state. The non-fault criterion before three-phase reclosing, characterized by the difference between the calculated value of resistance and inductance and the corresponding actual value, is designed. Finally, PSCAD is used to build a distribution network with DG for verification, and simulations under different fault locations and transition resistances are carried out. The results show that when the line is in a non-fault state, the parameter identification results of the three phase-to-ground circuits are highly consistent with the true value; that is, the non-fault state is determined. When the fault continues, there is a large deviation between the parameter identification results of at least one phase-to-ground loop and the corresponding real value, which does not meet the condition of the non-fault criterion. The method in this paper is more sensitive than the detection method using response voltage. Moreover, it is not necessary to add additional disturbance sources, which is expected to improve the economy and feasibility of three-phase adaptive reclosing applications for distribution lines with a large number of DGs. Full article

Fault detection, classification, and precise location identification in power transmission lines are critical issues for energy transmission and power systems. Accurate fault diagnosis is essential for system stability and safety as it enables rapid problem resolution and minimizes interruptions in electrical energy supply. The characteristic parameters of mixed-conductor power transmission lines connected to the grid were calculated using the relevant line data. Based on these parameters, a dataset was created with computer-derived values. This dataset included variations in arc resistance and the short circuit power of the corresponding bus, facilitating the performance testing of various machine learning algorithms. It was observed that the correct determination of the faulty phase was of high importance in the correct determination of the fault position. For this reason, a gradual structure was preferred. It was achieved with a 100 percent success rate in fault detection with the ensemble bagged algorithm. It was obtained with the neural network algorithm with a 99.97 percent success rate in faulty phase detection. The most successful location results were obtained with the interaction linear algorithm with 0.0066 MAE for phase-to-phase faults and the stepwise linear algorithm with 0.0308 MAE for phase ground faults. Using the proposed algorithm, fault locations were identified with a maximum error of 26 m for phase-to-ground faults and 110 m for phase-to-phase faults on a transmission line with a mixed conductor of approximately 178 km. Additionally, we compared the training and testing results of several machine learning algorithms metrics including the accuracy, total error, mean absolute error, root mean square, and root mean square error to provide informed recommendations based on their performance. The findings aim to guide users in selecting the most effective machine learning models for predicting failures in transmission lines. Full article

When a single-phase grounding fault occurs in a resonant grounding system, due to the compensation effect of the arc coil on the system, there are problems such as the fault signal amplitude and the signal waveform being close, which leads to difficulties in line selection. This paper proposes a fault line selection discrimination method based on MCEEMD-MPE normalization and a k-means clustering analysis algorithm. The method is applied to the single-phase grounding fault of a resonant grounding system. The zero-sequence current is obtained and decomposed by MCCEEMD to obtain a number of components. The components with obvious characteristics are selected for normalization calculation by multi-scale permutation entropy, which not only avoids mode aliasing, but also highlights the characteristics of the fault signal at different scales. Finally, the k-means clustering analysis algorithm is used to correctly distinguish the fault and non-fault lines. The effectiveness of the method is verified in a real test field case. The results of the calculation show that the method can accurately identify the fault line under different faults when a single-phase grounding fault occurs. The recognition accuracy is 100%, which effectively improves the grounding fault line selection rate of the resonant grounding. Full article

The direct current (DC) cable serves as the link for energy output in photovoltaic (PV) systems. Its degradation can cause arcs, which easily lead to fire accidents. Locating arc faults, however, is challenging. To cope with it, this paper proposes an arc location method based on time reversal. The method has been tried to locate system fault. However, its application in the arc fault location of photovoltaic systems is seldom discussed and needs further research. For this purpose, the voltage waveforms of an arc fault collected at one of the cable ends is reversed. This transformation derives a symmetrical arc fault signal. Afterwards, the reversed signal is injected back into the cable to trace the fault location, which is a symmetrical process of the arc fault signal travelling from its origin to the detection point. Utilizing the energy-focusing characteristics of time reversal, the position with the highest energy in the derived waveform corresponds to the actual fault location. To verify the proposed method, a DC arc fault test is performed to obtain the wave characteristics. The Paukert arc model is chosen based on the tested result. A PV system containing a DC cable with an arc fault is simulated with Simulink with the affecting factors, i.e., grounded resistance, cable length, fault location and sampling frequency. The simulated results demonstrate that the localization error is within 5% in the worst case. Full article

The development of a single-phase grounding fault arc is influenced by various environmental factors, which can result in the rapid extinction and reignition of the arc. This phenomenon can lead to accidents, such as resonant overvoltage. Current grounding arc models inadequately account for the effects of grounding current, arc length, environmental wind speed, and other variables on the characteristics of the arc. In response to this issue, this article establishes a three-dimensional single-phase grounding arc mathematical model grounded in magnetohydrodynamics. It simulates and analyzes the effects of arc length and environmental wind speed on both arc ignition and extinguishing. Furthermore, an artificial single-phase grounding test platform is constructed within the actual distribution network to validate the accuracy of the simulation model. Research has demonstrated that, under identical operating conditions for both simulation and experimentation, the error range between the simulated arc voltage and the measured data is within 8%. The three-dimensional single-phase grounding arc mathematical model effectively describes the dynamic development process of the grounding arc. At a gap of 12 cm, under windless conditions and with a grounding current of 40.0 A, the temperature of the arc column at the peak of the current reaches 2600 K, while the conductivity decreases to 2.1 × 10⁻⁴ S/m, resulting in the inability of the arc to sustain a burning state. At a gap of 2 cm and a wind speed of 7 m/s, the temperature of the arc column at the peak of the current reaches 2900 K, the conductivity drops to 4.3 × 10⁻³ S/m, leading to the extinction of the arc. Full article

In order to investigate the characteristics and typical influential factors of wildfires caused by accidental faults in high-voltage transmission lines, a bespoke platform was constructed for the purpose of conducting simulation experiments. Discharge and ignition experiments were conducted on a variety of substrates, including kidney fern fragments, cedar needle fragments, poplar sawdust, and eucalyptus leaf fragments, to investigate the effects of different gaps on the initiation and propagation of wildfires. The results demonstrate that the discharge-inducing ignition stages can be succinctly summarized as “two phases and two points” (the discharge induction period, the gap breakdown point, the arc induction period and the fault removal point) when a suitable gap is maintained between the simulated falling lines and the vegetation surface. In the event of direct contact, the removal of the fault is not possible. The potential for ignition of the aforementioned vegetation types by the discharge is as follows: cedar needles > eucalyptus leaf fragments ≈ poplar sawdust > kidney fern fragments. As the water content increases, eucalyptus leaf fragments can still be ignited, and the breakdown voltages required for discharge-inducing ignitions gradually decrease. In the case of different forest ground vegetation types, when ignited by the discharge between the falling lines and the vegetation under conditions of proper gap and moisture content, the resulting ignition and sustained flames will promote the formation of streamer channels and further aggravate the discharges and burning processes, potentially leading to the ignition of a wildfire. Full article

Reliable fault line selection technology is crucial for preventing fault range expansion and ensuring the reliable operation of distribution networks. Modern distribution systems with neutral earthing via arc extinguishing coil face challenges during single-phase ground faults due to indistinct fault characteristics and system sequence networks influenced by the grounding methods on the distributed generation side. These factors increase the difficulty of fault line selection. By analyzing the differences between the zero-sequence currents of feeder lines and neutral lines in active distribution networks with neutral earthing via arc extinguishing coil, a method for single-phase ground fault line selection has been proposed in this paper. This method involves switching from a neutral point ungrounded mode to a low-resistance neutral grounding mode using distributed generation grid-connected transformers under permanent fault conditions. Criteria based on the differences in zero-sequence current ratios before and after the grounding mode switch are established. Simulation validation using the Power Systems Computer Aided Design (PSCAD) platform has been conducted. The proposed method demonstrates strong tolerance to transition resistance, simple extraction of fault characteristic signals, and accurate fault line selection results. Full article

When a single-phase grounding fault occurs in resonant ground distribution network, the fault characteristics are weak and it is difficult to detect the fault line. Therefore, a fast fault line selection method based on MCECA-CloFormer is proposed in this paper. Firstly, zero-sequence current signals were converted into images using the moving average filter method and motif difference field to construct fault data set. Then, the ECA module was modified to MCECA (MultiCNN-ECA) so that it can accept data input from multiple measurement points. Secondly, the lightweight model CloFormer was used in the back end of MCECA module to further perceive the feature map and complete the establishment of the line selection model. Finally, the line selection model was trained, and the information such as model weight was saved. The simulation results demonstrated that the pre-trained MCECA-CloFormer achieved a line selection accuracy of over 98% under 10 dB noise, with a remarkably low single fault processing time of approximately 0.04 s. Moreover, it exhibited suitability for arc high-resistance grounding faults, data-missing cases, neutral-point ungrounded systems, and active distribution networks. In addition, the method was still valid when tested with actual field recording data. Full article

A single-phase grounding fault often occurs in 10 kV distribution networks, seriously affecting the safety of equipment and personnel. With the popularization of urban cables, the low-resistance grounding system gradually replaced arc suppression coils in some large cities. Compared to arc suppression coils, the low-resistance grounding system features simplicity and reliability. However, when a high-resistance grounding fault occurs, a lower amount of fault characteristics cannot trigger the zero-sequence protection action, so this type of fault will exist for a long time, which poses a threat to the power grid. To address this kind of problem, in this paper, a hybrid grounding system combining the low-resistance protection device and fully controlled power module is proposed. During a low-resistance grounding fault, the fault isolation is achieved through the zero-sequence current protection with the low-resistance grounding system itself, while, during a high-resistance grounding fault, the reliable arc extinction is achieved by regulating the neutral-point voltage with a fully controlled power module. Firstly, this paper introduces the principles, topology, and coordination control of the hybrid grounding system for active voltage arc extinction. Subsequently, a dual-loop-based control method is proposed to suppress the fault phase voltage. Furthermore, a faulty feeder selection method based on the Kepler optimization algorithm and convolutional neural network is proposed for the timely removal of permanent faults. Lastly, the simulation and HIL-based emulated results verify the rationality and effectiveness of the proposed method. Full article

Aiming at the problems of low equipment utilization and the high-capacity requirements of existing arc-suppression devices, a multi-functional reactive power compensation device with the capability of grounding fault regulation (MF-RPCD) is proposed. Firstly, the topology and operation mechanism of MF-RPCD are introduced in this paper. MF-RPCD works in a reactive power compensation mode when a power grid is under normal operation to ensure the unit power factor operation of the power-grid side. When a single line-to-ground fault occurs in the power grid, MF-RPCD works in a fault-regulation mode to effectively suppress the ground-fault current. Secondly, the parameters of the active and passive parts of MF-RPCD are optimally designed to ensure the stable operation of MF-RPCD. Finally, the correctness, feasibility and effectiveness of the proposed topology and functions are verified using simulations and experiments. Full article

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. Full article

In order to improve the performance of an arc suppression coil grounding system in handling cross-line two-point successive grounding faults (CTSGs), the applicability of the transient quantity method and the steady-state quantity method for assessing CTSGs is analyzed. Then, a novel method for line selection for CTSGs was proposed, which comprehensively utilizes transient and steady-state information. Specifically, this method adopts a continuous line selection process, with priority given to the transient quantity method, and a supplementary line selection process, with priority given to the steady-state quantity method. After accurately selecting some faulty lines, such lines are tripped, and then, the process proceeds with continuous line selection again. When the number of cycles exceeds the set value, and the fault line cannot be completely cut off, they are tripped one by one according to the degree to which they are approaching the steady-state method criterion, from large to small. Furthermore, in response to the dramatic increase in computing volume that is caused by the continuous application of the transient method in on-site applications and the impact of current transformer accuracy on the steady-state method, this paper proposes corresponding solutions. PSCAD simulation, full-scale tests, and field recording data tests verify that this paper’s method can accurately detect a CTSG. Full article