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摘要：The electrical insulation performance of series reactors is a crucial guarantee for their safe operation, and lightning impulse testing serves as a significant means to evaluate this performance. Currently, the lightning impulse testing methods for reactors in China's standards JB/T5346-2014 and DL/T462-2025 differ, leading to varying degrees of insulation damage to the reactors. In response, this paper employs experimental and simulation methods to study the lightning impulse testing of reactor phase-to-phase insulation based on the aforementioned standards. The experimental and simulation results indicate that the induced peak voltages for dry-type air-core and iron-core reactors in standard JB/T5346-2014 are 312.09 kV and 270.35 kV, respectively, exceeding the standard values by 56% and 35%; the maximum field strength values are 1.75 kV/mm and 1.64 kV/mm, respectively. In standard DL/T462-2025, the induced peak voltage aligns with the standard value, and the maximum field strength value remains at 1.19 kV/mm. The lightning impulse testing method for reactors in standard JB/T5346-2014 results in higher induced overvoltages and local field strengths, necessitating higher margin requirements for insulation design.关键词：reactor;phase to phase;lightning impulse test;electric field intensity;insulation6|0|0更新时间：2026-09-15 -
摘要：To analyze the frequency-response characteristics of a capacitor voltage transformer (CVT) under harmonic and broadband voltage conditions, a broadband equivalent circuit model of a 110 kV CVT considering multi-source stray parameters is established. On the basis of the conventional CVT equivalent circuit, the model incorporates the broadband parameters of the capacitive divider, stray capacitance of the compensation reactor, winding-to-ground capacitances of the intermediate transformer, equivalent interlayer capacitances, interwinding coupling capacitance, and secondary burden parameters. A frequency sweep from 1 Hz to 2 MHz is carried out to investigate the influence of different stray parameters on the CVT transfer characteristics. The results show that the stray capacitance of the compensation reactor and the primary-side interlayer capacitance of the intermediate transformer have significant effects on resonance peaks and valleys in the low-frequency and harmonic ranges. The interwinding coupling capacitance mainly changes the amplitude distribution in the middle-frequency range, while the secondary-side stray capacitances, equivalent series inductances of the capacitive divider, and secondary burden mainly affect the high-frequency response. The results indicate that multi-source stray parameters are important factors influencing the broadband transfer characteristics of CVTs and should be considered in broadband equivalent modeling.关键词：capacitor voltage transformer;multi-source stray parameters;frequency response;broadband equivalent model;parameter sensitivity analysis1|0|0更新时间：2026-09-15 -
摘要：Aiming at prominent voltage fluctuation, insufficient dynamic stability support in power systems with high penetration of new energy, as well as delayed response and large power loss caused by step-up transformers equipped in conventional distributed synchronous condensers, dynamic simulation models of 15Mvar-35kV high-voltage direct-connected synchronous condenser and traditional distributed synchronous condenser are established based on structural characteristics of high-voltage cable winding motors. Dynamic simulation analysis under sudden voltage variation conditions is carried out, and dynamic operating performances of the two types of condensers are compared. The dynamic characteristics of high-voltage direct-connected synchronous condenser are thoroughly analyzed, the design merits of transformer-free structure are clarified, and its deep phase modulation capability is verified.In accordance with performance requirements of excitation control, PID, fuzzy PID and variable universe fuzzy PID excitation control strategies are designed and tested. The results show that high-voltage direct-connected synchronous condenser can supply dynamic reactive power support rapidly. Variable universe fuzzy PID control accelerates excitation response and restrains overshoot, effectively improving dynamic reactive power support and voltage stability of power systems.关键词：high-voltage direct-connected synchronous condenser;transient characteristics;excitation control;reactive power compensation;variable universe fuzzy PID;new energy station1|0|0更新时间：2026-09-15 -
摘要：Vacuum circuit breakers, as the core switching devices for switching capacitor banks in distribution networks up to 35kV, frequently generate high-amplitude, high-frequency closing inrush currents when energizing unloaded capacitor banks.These currents can easily lead to the burnout of switch contacts and failures of capacitor banks, seriously threatening grid safety.As the ideal switch model fails to consider practical parameters like closing speed, dielectric recovery strength, and contact materials, it can't precisely depict the transient characteristics during vacuum circuit breaker closing operations.This study takes a 40.5kV vacuum circuit breaker switching parallel capacitor banks as the research scenario and uses the PSCAD simulation platform to build a customized simulation model integrating pre-breakdown characteristics, dielectric recovery properties, and high-frequency arc-quenching ability.The simulation carried out closing inrush current tests by setting up vacuum circuit breakers under various typical closing situations, including different closing velocities, contact materials, existence of residual voltage in capacitor banks, back-to-back switching, and series reactors.The findings of the research show that the pre-breakdown phenomenon is the main reason for the closing inrush current.Raising the closing speed speeds up the restoration of dielectric strength in the contact gap, which can effectively decrease both the peak value of the inrush current and the dispersion of three-phase closing times. Reverse residual charges in capacitor banks greatly increase the closing inrush current and overvoltage.Under back-to-back closing circumstances, the peak of the inrush current can reach dozens of times that of a single-capacitor bank, which is the most serious switching situation for capacitor banks.The optimal solution for suppressing closing inrush current in 35kV distribution networks (dominated by the fifth harmonic) is the 5%-7% reactance range.It can offer stable suppression under conventional, residual-voltage, and back-to-back closing conditions, and it also has high reliability and engineering applicability.This research finding offers theoretical foundation and data support customized to actual operational scenarios for optimizing the closing speed of vacuum circuit breakers, designing inrush current suppression schemes, and improving the engineering performance of reactive power compensation devices.关键词：vacuum circuit breaker;PSCAD modeling;parallel capacitor bank;closing inrush current;simulation analysis1|0|0更新时间：2026-09-15 -
摘要：This paper analyzes the causes of inter-turn short circuits in dry-type air-core reactors, which are mainly summarized into five types: local overheating, overvoltage, vibration, insulation weakness or aging, and partial discharge, etc. And for several fault conditions, specific cause analysis and judgment are carried out. To quantitatively analyze the physical quantities that change significantly after inter-turn short circuits, the circuit equations after inter-turn short circuits are listed with current as the variable, and a formula for calculating inductance is given. A program is written to calculate the magnitude of the short-circuit current when inter-turn short circuits occur at different positions of the reactor. The calculation results show that the total loop current almost remains unchanged, while the total loop active current changes significantly; when the short-circuit position is in different branches, the change is the largest in the middle (where the minimum number of turns is located), slightly smaller in the outermost layer, and the smallest in the innermost layer; when the short-circuit position is in the same branch, the change is the largest in the middle and the smallest at the top. Finally, the correctness of the calculation results was verified through experiments.关键词：dry-type air-core reactor;inter-turn short circuit;inductance;Bartky transformation;short-circuit current;active current;active power1|0|0更新时间：2026-09-15 -
摘要：According to the existing standards for electrical factory tests of medium-frequency Induction heating capacitors, the tests are carried out under power frequency or direct current conditions. However, the capacitors actually operate under medium-frequency voltage, so routine factory tests cannot accurately evaluate the operation reliability of products under medium-frequency conditions.The simulated medium-frequency operation test can verify relevant product parameters economically and effectively, and guide product development and design. In this paper, a simulated test platform is built to carry out the operation test of capacitors under medium-frequency conditions.The test results show that the test at 50Hz power frequency cannot accurately reflect the adverse effects on capacitor performance caused by the superposition of dielectric loss, eddy current loss of aluminum foil and lead resistance.The conclusions of this research can provide technical support for factory inspection, structural design and performance verification of medium-frequency heating capacitors.关键词：medium-frequency induction heating capacitor;routine factory test;simulated operation;temperature rise characteristic1|0|0更新时间：2026-09-15 -
摘要：Breakdown strength is a key indicator for evaluating the insulation performance of polypropylene films used in capacitors. However, the results are not only determined by the intrinsic properties of material, but are also significantly affected by the testing method. To enable iterative performance comparison of domestic polypropylene films and objective benchmarking against imported products, it is necessary to select a breakdown strength test method that can accurately reflect the material performance. This paper conducts a comparative study of different testing methods using domestic polypropylene films. By varying the electrode configuration and other relevant experimental conditions, breakdown strength data of the films under different methods were obtained. Statistical analysis was then performed to compare the test results. The results show that the breakdown strength values obtained by different testing methods differ significantly. Considering testing accuracy, repeatability, operational simplicity and engineering applicability, this paper recommends the fifty-point electrode method as the preferred method for evaluating the breakdown strength of polypropylene films for capacitors. The results provide a reference for quality evaluation of domestic polypropylene films, performance comparison among different batches, and benchmarking tests against imported film products.关键词：metallized film capacitor;biaxially oriented polypropylene film;Import substitution;breakdown strength;test method1|0|0更新时间：2026-09-15 -
摘要：Metallized film capacitors (MFCs) exhibit pronounced nonlinear, multistage capacitance degradation under coupled electrical, thermal, and humidity stresses, while sample-to-sample variability and measurement errors further increase the uncertainty in lifetime assessment. To improve the accuracy of remaining useful life (RUL) prediction for MFCs, accelerated aging tests under superimposed AC–DC electrical stress were conducted at 85 °C and 85% relative humidity (RH), and a three-stage nonlinear Wiener degradation model was established according to the stage-dependent characteristics of the capacitance degradation trajectories. Change-point locations and stage-specific drift forms were identified using a procedure combining the Bayesian information criterion with iterative search, yielding power-law, exponential, and power-law drift models for the three stages, respectively. Rauch–Tung–Striebel smoothing and the expectation–maximization algorithm were subsequently employed to estimate model parameters and derive prior information. As sequential observations were progressively incorporated, variational Bayesian inference was used to update the latent states, random variables, and associated model parameters, from which the probability distribution of the RUL was derived. Leave-one-out cross-validation results show that the predicted lifetime gradually approaches the actual lifetime as incremental degradation data become available, indicating that the proposed model can capture stage transitions and sample-to-sample variability during MFC degradation and validating the effectiveness of the sequential-data-driven probabilistic RUL assessment method.关键词：metallized film capacitors;Wiener process;nonlinear multi-phase model;remaining useful life;reliability assessment1|0|0更新时间：2026-09-15 -
摘要：To address the issues of a sharp increase in voltage imbalance at the grid connection point of wind turbines, intensified reactive power fluctuations, and potential overvoltage damage to reactive power compensation equipment such as shunt capacitor banks when asymmetric faults (e.g., single-phase grounding, two-phase short circuit) occur on offshore wind farm transmission lines, this paper takes the SWT-4.0-146 squirrel-cage asynchronous wind turbine at Rudong Offshore Wind Farm as the research object and investigates the grid-connected stability mechanism of the full-power converter under asymmetric faults. First, mathematical models of the squirrel-cage asynchronous generator and its full-power converter in the three-phase stationary coordinate system, two-phase stationary coordinate system, and synchronously rotating coordinate system are established, and the influence laws of negative sequence components on DC bus voltage and grid-connected current are derived. Second, based on the symmetrical component method, the coupling relationship between positive and negative sequence components during asymmetric faults is analyzed, revealing the mechanism of double-frequency fluctuations in active/reactive power and their impact on DC bus voltage stability. Then, a comprehensive simulation model including the wind turbine, LCL filter, grid-connected transformer, and fault point is built in MATLAB/Simulink to simulate a single-phase grounding fault condition where phase A voltage drops to 0.2 pU. Finally, the system response before and after negative sequence current suppression is compared and analyzed. Simulation results show that when an asymmetric fault occurs, the grid-connected phase A current surges from the rated value of 1.2 kA to 2.8 kA, with a negative sequence current content of 11.15 A. After adopting positive-negative sequence decoupling control, the negative sequence current can be reduced to 0.46 A, a reduction of 95.9%, and the double-frequency fluctuation of the DC bus voltage is suppressed within 1% of the set value. The research demonstrates that the proposed positive-negative sequence decoupling control strategy can effectively suppress negative sequence current and DC bus voltage fluctuations, significantly enhance the stability of wind power grid-connected systems under asymmetric faults, and reduce the overvoltage risk of shunt capacitor banks during fault periods, providing a theoretical basis for the protection configuration and fault ride-through strategy optimization of reactive power compensation equipment in offshore wind farms.关键词：asymmetric fault;squirrel-cage asynchronous wind turbine;full-power converter;grid-connected stability;negative sequence component;voltage imbalance;reactive power compensation1|0|0更新时间：2026-09-15 -
摘要：The main challenge in the industrial production of low-ash polypropylene lies in achieving a high level of product quality consistency. This study discusses several key aspects involved in the industrial preparation of low-ash polypropylene, including the sources of ash, residual metal elements, and the implementation of an integrated process-cleanliness strategy. Based on a catalytic system employing MgCl₂/TiCl₄-type Ziegler–Natta catalyst as the primary catalyst, the effects of trace impurities in polypropylene feedstocks, triethylaluminum cocatalyst, external electron donors, polymerization process stability, additive cleanliness, and post-treatment operations on the ash content of polypropylene were systematically evaluated. The results show that residual Ti and Mg are primarily associated with the utilization efficiency of the primary catalyst, whereas Al residue is related to both the dosage of cocatalyst and the consumption of organoaluminum species by impurities in the reaction system. Abnormal levels of Ca, Fe, and other metallic elements are closely associated with additives and externally introduced contaminants.关键词：low-ash polypropylene;Ziegler-Natta catalyst;element source tracing;additive;clean equipment;process-wide control1|0|0更新时间：2026-09-15 -
摘要：As a key internal factor inducing transformer magnetizing inrush current, core remanence faces insufficient online identification accuracy in engineering due to strong coupling between nonlinear hysteresis and closing phase angles. Addressing traditional methods' shortcomings in feature characterization, this paper selects closing phase angle and inrush current peak as dual features, proposing a remanence identification scheme based on Relevance Vector Machine (RVM). Based on Jiles–Atherton dynamic hysteresis theory, a single-phase transformer field-circuit coupled model is established in COMSOL Multiphysics. Different initial remanence states are generated via DC pulse injection, and steady-state remanence data are obtained by a flux probe in the core center. The nonlinear mapping between remanence and dual features is constructed with verified physical consistency. A sparse RVM regression model is built, realizing adaptive parameter adjustment via Bayesian automatic relevance determination (ARD) to reduce manual tuning dependency. Simulation results show high inversion accuracy with R²=0.998, demonstrating effectiveness in modeling complex nonlinear relationships and accurate remanence identification.关键词：Transformer core remanence;Inrush current;Closing phase;Relevance Vector Machine;finite element simulation3|0|0更新时间：2026-03-12 -
摘要：High-voltage AC SF6 circuit breakers in ultra-high-voltage DC transmission systems are responsible for reactive power compensation and harmonic filtering. Due to the high voltage level and large switching capacity, frequent operations of AC filter circuit breakers can cause contact erosion and even lead to failures. Based on the actual line configuration of a converter station, this paper uses PSCAD to model and analyze possible operating conditions, investigates the in-fluence of closing resistance on switching transients and the current characteristics under different resistance states, and proposes fault diagnosis methods and electrical life assessment approaches. The results show that a closing resistance in the range of 300–400 Ω provides excellent comprehensive performance across four types of filters, effectively sup-pressing overvoltage across the main capacitor, inrush currents, and arrester overvoltages. By applying criteria such as harmonic analysis, inrush current peak timing, and three-phase closing consistency, faults in the closing resistor can be accurately identified. Three electrical life assessment methods are proposed: the dynamic resistance method combined with neural networks, SF6 decomposition product analysis, and historical switching data correction. The dynamic re-sistance method achieves a prediction error within 4%. A developed online monitoring system enables real-time con-dition assessment of circuit breakers and recommends graded maintenance strategies, providing technical support for enhancing grid reliability.关键词：AC filter;closing resistor;Inrush current and overvoltage suppression;Circuit breaker electrical life assessment;Online monitoring system3|0|0更新时间：2026-03-12 -
摘要：After a series reactor is connected to the busbar of the step-up substation, the system parameters change, which in turn affects the propagation process and distribution law of overvoltages. To implement the capacity expansion project of a power plant, it is necessary to calculate and analyze the overvoltages related to the 220kV busbar series reactor. An electromagnetic transient model (including components such as generators, transformers, series reactors, arresters, and transmission lines) was established using ATP/EMTP. The lightning overvoltages and switching overvoltages at the reactor and key in-station equipment installation locations were calculated, and the safety of insulation coordination was analyzed. The results show that the existing arrester configuration can effectively ensure the insulation safety of the equipment.关键词：series reactor;lightning incoming wave;switching overvoltage;surge arrester;circuit breaker0|0|0更新时间：2026-03-12 -
摘要：When a resistive capacitive DC voltage divider experiences capacitor self resonance or overall resonance, high-frequency harmonic voltage can lead to overheating or sustained partial discharge of the resistive capacitors. resulting in internal thermal and malfunction of the voltage divider. The paper analyzes the discharge erosion damage fault of capacitor core connection caused by resonance in ± 500kV DC converter station. Through methods such as disassembly inspection, residual electron microscopy analysis, fracture energy spectrum analysis, harmonic measurement, temperature rise test, LCR sweep frequency test ，, the fault mechanism and causes are thoroughly investigated. . The study examines the impact of resonance on the insulation performance of the capacitor core and proposes preventive and improvement measures. . It has important reference and the significance for the harmonic mechanism, new equipment development, material insulation and other fields of DC converter station.关键词：direct current transmission;DC voltage divider;Resistance capacitance type;resonance;harmonic9|0|0更新时间：2026-03-12
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