Search Results (140)

This paper presents a model-based parameter estimation approach for high-voltage circuit breaker operating mechanisms using the dynamic model and stroke curves. First, an equivalent dynamic model of the mechanism is established, and its fidelity is validated through comparison with a virtual prototype model built in ADAMS, confirming the validity of the modeling assumptions. Then, the parameter estimation task is formulated as an optimization problem that minimizes the discrepancy between model predictions and actual stroke curves, and the Covariance Matrix Adaptation Evolution Strategy (CMA-ES) algorithm is adopted to search for the optimal parameter set. Subsequently, to ensure estimation reliability, a thorough identifiability analysis is conducted, including sensitivity and correlation analyses, which collectively indicate that the key parameters are well identifiable. Afterward, experimental tests are performed on a 252 kV circuit breaker under various operating conditions, and the results demonstrate that the parameter identification errors are consistently below 6.3%. Finally, we compare the proposed method with three representative data-driven classifiers on the same dataset for a classification task. The comparison shows that our method achieves higher accuracy than others. Furthermore, the proposed method yields physically interpretable parameters directly linked to mechanical components, providing valuable information for condition assessment and maintenance planning in engineering applications. Full article

A systematic investigation of how different circuit and arc parameters affect the threshold value for the $R500$ interruption limit ($R{500}_{th}$) has been provided. These parameters include the breaker cooling power, arc time constant, time delay of the transient recovery voltage (TRV), parallel capacitance, and network impedance. The results are obtained through black-box model calculations based on Mayr’s arc model. Our findings suggest that the interruption limit for the $R500$ method has negligible dependency on the cooling power used in Mayr’s arc model. On the other hand, it is shown that larger values of parallel capacitance and TRV time delay led to a decrease of the $R{500}_{th}$. On the contrary, $R{500}_{th}$ rises by increasing the network impedance. These results imply that the influence of arc–circuit interaction must be considered when applying this approach for assessing the interruption limit. As a validation step, the numerical findings have been cross validated by selected measurement results provided in the literature. Full article

With increasingly stringent restrictions on SF₆ greenhouse gas emissions, C₄F₇N-based gas mixtures have attracted considerable attention as promising alternatives for high-voltage circuit breakers; however, their relatively weaker arc-quenching capability poses significant challenges for interruption chamber design at high voltage levels. In this study, a 3.5% C₄F₇N/83.5% CO₂/13% O₂ gas mixture was used as the arc-extinguishing medium in a 550 kV environmentally friendly gas circuit breaker. Based on a magnetohydrodynamic (MHD) model considering PTFE nozzle ablation effects, systematic optimization studies were conducted on key structural parameters of the puffer-type interruption chamber, including the exhaust hole diameter, nozzle throat diameter and length, arcing contact diameter, and downstream expansion angle. Simulations under arcing times of 9.9 ms and 11.4 ms were performed to evaluate chamber pressure, axial temperature, extinction peak voltage, and post-arc conductance characteristics. The results indicate that extending the nozzle throat straight section to 70 mm, enlarging the exhaust hole, and increasing the moving contact radius can effectively enhance pressure buildup, reduce arc-core temperature, and improve dielectric recovery capability. Under the 11.4 ms arcing condition, the optimized structure achieved an extinction peak voltage of 6972.4 V and a G200 value of 0.731 ms, demonstrating substantially improved interruption performance. These findings reveal the synergistic relationship between arcing time and structural parameters and provide theoretical guidance for the engineering design of environmentally friendly high-voltage gas circuit breakers. Full article

Multiple-fault events can initiate overload propagation and cascading outages, resulting in severe load loss and reduced system resilience. Therefore, beyond conventional protection concepts based on the (n − 1) criterion, there is also a need to address multiple-fault events to minimize loss of load. This paper presents an optimized overload tripping scheme to mitigate cascading outages in high-voltage grids under multiple-fault conditions, where selected line switches or circuit breakers are opened in a controlled manner to isolate limited grid sections, minimize interrupted load, and prevent further overload propagation. The method combines inverse definite minimum time relay modeling with a heuristic graph-search algorithm implemented in pandapower to identify feasible switching actions that minimize load loss while preventing overload propagation. The approach is demonstrated on SimBench high-voltage urban and mixed benchmark grids under double-line fault scenarios. In the urban grid, the proposed scheme reduces the maximum load loss from 34.0% to 2.4%, while in the mixed grid, the reduction is from 50.3% to 5.2%. A SAIFI-inspired resilience proxy is introduced to quantify the reduction in customer/load interruptions, showing a resilience improvement factor of about 3.6 for cascading scenarios. In addition, thermal inertia analysis indicates that corrective switching must be completed within approximately 5 min to remain within line-temperature limits. The analysis is based on quasi-steady-state power-flow and relay simulations; transient stability effects are outside the scope of this study. The results demonstrate that the optimized overload tripping scheme is a promising adaptive protection strategy for improving grid resilience under severe contingency conditions. Full article

High-voltage self-blast circuit breakers feature complex gas flow field dynamics during the arc interruption process due to the multiple gas chambers and valves in the interrupter. The structure of key interrupter components and the characteristics of the operating mechanism significantly influence the gas flow field behavior, thereby affecting the breaking performance. The C₄F₇N gas mixture is currently the most promising alternative to SF₆. However, the influence mechanisms of various factors on its breaking performance remain unclear, which limits the design of C₄F₇N-based self-blast interrupter chambers. This paper investigates the impact of nozzle throat length and mechanism stroke on the breaking performance of a 126 kV double-motion self-blast circuit breaker prototype by establishing a magnetohydrodynamic (MHD) arc model for C₄F₇N gas mixtures. The results indicate that a longer throat length can enhance the pressure-buildup capability in the expansion chamber to some extent, but its effect on short arcing times is limited, whereas it has a more pronounced influence on medium and long arcing times. However, it also impedes arc energy dissipation, potentially reducing the breaking capability for short and medium arcing times while improving performance for long arcing times. A larger mechanism stroke not only ensures a greater contact gap at current zero for long arcing times but also accelerates the gas flow velocity between the contacts, facilitating arc energy dissipation and enhancing the thermal interruption performance. Full article

The SF₆ circuit breaker is an essential piece of high-voltage equipment in ensuring the safe operation of the power grid. Regarding the arc-extinguishing chamber, as the most essential component, its performance is directly related to the breaking capacity of the circuit breaker. This study applies the Double Distribution Function Lattice Boltzmann Method (DDF-LBM), combined with the Smagorinsky sub-grid scale (SGS) model, to systematically simulate the dynamic breaking process of a 252 kV SF₆ arc-extinguishing chamber under 50 kA breaking current conditions. Two independent distribution functions are employed to describe the fluid field and the temperature field, respectively, thereby simulating the physical flow–heat coupling process. A dynamic simulation framework is constructed using the D2Q9 model to describe the mechanical motion of the contacts and the fluid flow. The description of contact movement is achieved by dynamically updating the geometric mesh, thereby realizing fluid–solid transformation. The research results indicate that the proposed method can simulate the pressure variation of the fluid field during the breaking process. The value of the Smagorinsky constant (C_s) exhibits a non-negligible influence on the pressure field predictions. The optimal value of C_s = 0.10 is determined through analysis, and the peak pressures at the upstream and throat measurement points reach 1.11 MPa and 1.37 MPa, respectively. Numerical simulations are conducted on the dynamic breaking process of the arc-extinguishing chamber, revealing the evolution of the pressure field upstream of the nozzle and at the throat regions. This study provides new numerical simulation methods for the investigation of SF₆ arc-extinguishing chambers and establishes a foundation for the application of the Lattice Boltzmann Method in the field of high-voltage electrical appliances. Full article

To address the turn-off overvoltage challenge arising from the rapid interruption of Low Voltage DC Solid-State Circuit Breakers (SSCBs), this paper proposes a high-precision behavioral modeling method for domestic SiC MOSFETs. The model is constructed based on the physical structure of the device, integrating a modified EKV-based static current model and a voltage-dependent nonlinear parasitic capacitance model described by piecewise functions. Model parameters are efficiently extracted from datasheets and measurement data using a composite optimization strategy combining the Genetic Algorithm and the Levenberg–Marquardt algorithm. The model is implemented in LTspice, and its accuracy in both static and dynamic characteristics is validated by comparing the simulation waveforms with experimental results. Based on the validated model, the turn-off process is subdivided into four distinct stages, with an equivalent circuit established for each. A systematic analysis reveals the intrinsic physical mechanism of the voltage spike and oscillation, which results from interaction among the drive circuit parameters, system parameters, and the nonlinear capacitances of the device. The research outcomes provide effective theoretical guidance and a design tool for simulation modeling, turn-off stress assessment, and snubber circuit optimization for SSCBs utilizing SiC MOSFETs. Full article

High-voltage circuit breakers (HVCBs) are critical switching devices whose mechanical reliability directly affects power system safety and operational continuity. Accurate fault diagnosis remains challenging due to nonlinear vibration characteristics and the sensitivity of support vector machines (SVMs) to hyperparameter selection. To address this issue, a multi-strategy improved dung beetle optimization–support vector machine (MIDBO–SVM) framework is proposed for vibration-based mechanical fault diagnosis. Frequency-domain features are extracted from vibration signals using the fast Fourier transform to characterize fault-related spectral variations. A multi-strategy improved dung beetle optimization (MIDBO) algorithm incorporating chaotic initialization, adaptive search regulation, and mutation enhancement is developed to improve population diversity, global exploration, and convergence stability. The optimized MIDBO is used to determine the penalty and kernel parameters of the SVM, constructing a robust and well-generalized diagnostic model. Experimental results show that MIDBO–SVM achieves a diagnostic accuracy of 96.67%, outperforming conventional SVM (86.25%) and random forest (89.17%). The proposed method also demonstrates faster convergence and maintains accuracy above 86% under imbalanced sample conditions, confirming its robustness and generalization capability. These advantages contribute to more reliable mechanical condition assessment and improved maintenance decision support for HVCBs. Full article

To address the practical engineering challenges of limited fault samples for high-voltage circuit breaker spring operating mechanisms and the inability of single features to fully reflect equipment status, this paper proposes a small-sample fault diagnosis method based on multi-source feature fusion and Stacking ensemble learning. First, a multi-source sensing system containing MEMS (Micro-Electro-Mechanical System) pressure and travel, coil, and motor current was constructed to achieve comprehensive monitoring of the mechanical and electrical states of a 220 kV circuit breaker; in particular, the introduction of non-invasive MEMS sensors effectively solves the difficulty of capturing static spring fatigue characteristics inherent in traditional methods. Second, a high-dimensional feature space was constructed using Savitzky–Golay filtering and physical feature extraction techniques. To address the characteristics of small-sample data distribution, a two-layer Stacking ensemble learning model based on 5-fold cross-validation was designed. This model utilizes the SVM (Support Vector Machine), RF (Random Forest), and KNN (K-Nearest Neighbors) as base classifiers and Logistic Regression as the meta-learner, achieving an adaptive fusion of the advantages of heterogeneous algorithms. True-type experimental results show that the average diagnostic accuracy of this method under normal conditions and four typical fault conditions reaches 96.1%, which is superior to single base models (the RF was 94.2%). Feature importance analysis further confirms that closing and opening pressures are the most critical features for distinguishing mechanical faults. This study provides effective theoretical basis and technical support for condition-based maintenance of high-voltage circuit breakers under small-sample conditions. Full article

Ultra-high voltage (UHV) power transmission has become a prerequisite for the development of clean energy. However, arcs generated by UHV circuit breakers can easily lead to safety incidents, and developing arc-extinguishing gases with low global warming potential (GWP) presents certain challenges. It is a fact that fluorolefins, as a class of fluorinated compounds with low GWP, show high application potential in replacing traditional arc-extinguishing agents. In this study, all six conjugated perfluorinated compounds, including C₆F₆ and C₆F_8, were calculated within the density functional theory (DFT) framework at the B3LYP/6-311+G(d,p) level. The dipole moments, HOMO/LUMO energy gaps, and the inherent aromaticity of annular molecules under external electric fields of these fluorinated molecules are investigated accordingly. By analyzing these results, it is found that the influence of the conjugated structure on the stability of arc-extinguishing gases under high-voltage conditions was partially elucidated, providing useful insights for the subsequent development of environmentally friendly and high-performance arc-extinguishing gases. Full article

To address the reclosing failures in the distribution networks (DNs) with high penetration of distributed energy resources (DERs), this paper proposes a communication-free cooperative fault recovery control method based on staged active power injection of an energy storage (ES) system. First, during the initial phase of a fault, a back-electromotive force (b-EMF) suppression arc extinction control strategy was designed for the ES converter, promoting fault arc extinction. Subsequently, the ES switches to grid-forming (GFM) control, providing active power injection to the network following the circuit breaker (CB) tripping. A time-limited variable power control of ES converter is also designed to establish voltage characteristics for fault state detection. And a fault state criterion based on voltage relative entropy is designed, helping reliable reclosing. Simulation results demonstrate that the proposed method achieves coordination solely through local measurements without the need for real-time communication between ES and CB, and can shorten the recovery time of transient faults to hundreds of milliseconds. Full article

The development of high-performance DC circuit breakers (DCCBs) and rapid fault detection schemes is a crucial and challenging part of advancing Modular Multilevel Converter (MMC) HVDC grids. This paper introduces a new current-limiting DCCB that uses the differential discharge times of shunt capacitors to generate artificial current zero-crossings, thus facilitating arc quenching. This mechanism significantly reduces the effect of fault currents on the MMC. The shunt capacitors and arresters in the proposed breaker also offer voltage support during faults, effectively stopping transient traveling waves from spreading to nearby non-fault lines. This feature creates an effective line protection boundary in multi-terminal HVDC systems. Additionally, a fast fault detection scheme with primary and backup protection is proposed. A four-terminal MMC-HVDC (±500 kV) simulation model is built in PSCAD/EMTDC to validate the scheme. The results demonstrate the excellent fault detection performance of the proposed method. The voltage and current behavior during the interruption process of the new DCCB is also analyzed and compared with that of a hybrid DCCB. Full article

The global phase-out of sulfur hexafluoride (SF6), an insulating gas with high global warming potential (GWP), has driven the search for eco-friendly alternatives in high-voltage equipment. Perfluoroisobutyronitrile (C4F7N) emerges as a promising candidate due to its low GWP and high dielectric strength. However, its chemical stability under circuit breaker conditions, especially when interacting with vaporized contact materials such as silver, remains a key concern. This study investigates the decomposition mechanisms of C4F7N in the presence of silver vapor using quantum chemical calculations at the B3LYP/LanL2DZ level. A reaction network comprising 35 pathways and 12 transition states were identified. All structures were confirmed as valid stationary points via frequency analysis and intrinsic reaction coordinate (IRC) calculations. Three primary reaction pathways between C4F7N and Ag were delineated, leading to secondary reactions that generate low-weight molecules and Ag-containing species such as AgF and AgCN. Key energy barriers and temperature-dependent equilibrium constants (K_eq) were determined to evaluate pathway feasibility. This work provides fundamental insights into the high-temperature interfacial chemistry of C4F7N with Ag, offering essential data for assessing its material compatibility and long-term reliability as a sustainable insulation medium in power systems. Full article

This paper presents a data-driven probabilistic framework for analysing power system faults using Monte Carlo simulations. The study evaluates the operational reliability of multiple high-voltage switchgear topologies—including single-busbar systems, double-busbar systems, and ring-type configurations—by modelling the stochastic behaviour of disconnectors, circuit breakers, busbars, and withdrawable switching elements with bypass arrangements. Realistic unavailability parameters derived from statistical reliability data are used to generate fault intervals for each device, enabling the simulation of millions of operational scenarios and capturing both full and partial outage events. The proposed methodology quantifies outage probabilities, identifies critical components, and reveals how devices count, switching logic, and system redundancy influence overall resilience. Results show significant reliability differences between topologies and highlight the importance of optimized substation design for fault tolerance. The developed probabilistic framework provides a transparent and computationally efficient tool to support planning, modernization, and predictive maintenance strategies in transmission and distribution networks. Findings contribute to improved fault diagnosis, enhanced grid stability, and increased reliability in both conventional and renewable-integrated power systems. Full article

Vacuum circuit breakers (VCBs) have been extensively employed in switching shunt capacitor banks. However, research on the prestrike characteristics of double-break VCBs in making power frequency voltage remains limited. This study aims to investigate the influence of different closing time differences on the prestrike characteristics of double-break VCBs in making power frequency voltage, and to compare these influences with those of single-break VCBs. Experiments were conducted using vacuum interrupters rated at 24 kV, with contacts made of CuCr40 alloy doped with 1 wt% graphene. Taking the closing time of the high-voltage break as the time zero point, three closing time differences (0 ms, 0.727 ms, and −0.347 ms) were set, and experiments were carried out at six closing phase angles (from 0° to 150° in 30° increments) for each condition. The experimental results demonstrate that when the closing of the high-voltage break lags behind that of the low-voltage break by 0.347 ms, the double-break VCB exhibits optimal prestrike performance, where prestrike is almost entirely suppressed except at the 90° phase angle. Furthermore, the prestrike performance during the closing of the double-break VCB is significantly superior to that of the single-break VCB, characterized by a steeper RDDS curve. These findings provide a theoretical basis for the design of control-switching double-break VCBs. Full article