There are cross-linked metal sheath and voltage drop in the long distance power cable which make difference between short cables on on-line insulation monitoring technology. In order to solve problem, two terminal synchronous tanδ measurement as a new method of had been put forward paper. The working principle theoretical basis calculation were given. feasibility was demonstrated when there synchronization error system. Matlab software used simulate circuit three-phase calculate insulation....

The fiber loop ring-down spectroscopy technique is introduced into the evanescent-field-based sensing scheme in order to create a new type of fiber-based magnetic field sensor. As consequence, sensitivity and stability system are significantly enhanced. sensor head constructed using section single-mode with its cladding partially etched. process etching described detail, relationship between diameter etched time experimentally investigated. After adopting appropriate size fiber, final...

Traditional thermal sterilization technology is easy to implement and safe, but it will destroy food nutrition change taste. Therefore, people began turn their attention non-thermal sterilization. High-voltage pulsed electric field one of them; has attracted much because its high efficiency little damage food. Different types loads cause serious trailing the pulse falling edge. In view this situation, paper proposes a new topology circuit that combines solid-state switch with half-bridge...

To meet the special requirements of high-voltage pulsed electric field liquid sterilization for pulse power supply, traditional Marx circuit is improved. A bipolar square wave supply designed by combining solid state switch with circuit, which simplifies control strategy and reduces number semiconductor switches. discharge residual charge diverse load designed, makes waveform have steep rising edge fast falling edge, has good clamping function adaptability. An experimental prototype...

To reduce the induction voltage in metal sheath, cross-bonded grounding is a widely adopted method long-distance high power cables, but this introduces challenges to online monitoring and diagnosis of cable insulation. An for insulation based on analysis resistive current proposed paper. A theoretical formula separation between leakage sheath was derived, obtained. equivalent circuit three-phase long distance established using MATLAB/Simulink platform. The simulation used model three typical...

In order to study the influence of trap parameters on dielectric characteristics nano-modified pressboards, pressboards were made using nano doping method with different nanoparticle components. The modified measured, and investigated thermally stimulated current (TSC) method. test results indicated that conductivity initially declined then rose increase nano-Al2O3 content, whereas it solely nano-SiC content. Moreover, exhibited nonlinear enhancement electric field stress at high relative...

The structural, optical and electronic properties of BiFeO3 in ferroelectric paraelectric phases have been investigated using first principles methods within the generalised gradient approximation based on density-functional theory. Several magnetic configurations considered into our calculation, antiferromagnetic state is found to be ground both phases. Electronic at are calculated. band gap 1·198 0.280 eV for analysis structures indicates that O-2p electrons hybridise with Bi-3d Fe-3d...

Partial discharge detection is an important means of insulation diagnosis electrical equipment. To effectively suppress the periodic narrowband and white noise interferences in process partial detection, a interference suppression method based on singular value decomposition (SVD) improved empirical mode (IEMD) proposed this paper. First, signal with x(t) decomposed by SVD. According to distribution characteristics single values signals, corresponding set zero, reconstructed eliminate x(t)....

Abstract In this paper, an improved air discharge fluid model under non-uniform electric field is constructed based on the plasma module COMSOL Multiphysics with artificial stability term, and boundary conditions developed in previous paper are applied to calculation of photoionization rate. Based modified model, characteristics low temperature sub-atmospheric 13 kV direct current voltage discussed, including needle-plate needle-needle electrode structures. Firstly, order verify reliability...

In HVDC transmission systems, the oil and oil-impregnated pressboard insulation of converter transformers is subjected to composite AC DC voltage. Therefore, a study on breakdown characteristics this under AC, voltage essential. paper, tests transformer all kinds those voltages have been completed relationship between peak ratio discussed. It shown that field strength decreases with increases gap any waveform. Breakdown given has little change variation ratio, but evident inflection point...

In this paper, an efficient boundary condition is applied to solve the photoionization rate, and a two-dimensional numerical simulation carried out for development propagation of air streamer at low temperature sub-atmospheric pressure. The results show that new improves calculation accuracy, but influence on discharge process not obvious. current in defined, corresponding expression positive negative given. electric field exceeding threshold value preliminarily introduced. discharge, only...

The water molecule migration and aggregation behaviors in oil-impregnated pressboard are investigated by molecular dynamics simulations combination with Monte Carlo simulation technique. free energy phase diagram of H2O-dodecylbenzene (DDB) H2O-cellulose mixtures calculated technique combined the modified Flory-Huggins model, demonstrating that H2O molecules can hardly dissolved infinitesimal content cellulose system at temperature lower than 650 K, based on which oil/cellulose layered...

In this paper, a modified COMSOL Multiphysics model with artificial stability is adopted, and the boundary condition developed in previous paper are applied to calculation of photoionization rate. The main processes involved air discharge were simulated by 39 plasma chemical reactions composed 12 kinds particles. characteristics low-temperature sub-atmospheric pressure under unipolar square wave pulse voltage 13kV amplitude, 25 kHz-50 kHz frequency duty cycle 50%-75% discussed. results show...

In this paper, the model cables are studied by means of frequency domain spectroscopy (FDS) which involves measurement capacitance, real permittivity and dissipation factor as a function frequency. Firstly, XLPE cable samples were carried out accelerated thermal ageing at 135 °C. Then, was investigated under laboratory condition, including different degree test temperatures. Mechanism analyzed using theory dielectric relaxation in solids. From data curves, it can be shown that capacitance...

In this paper, traveling wave fault location equipment for power cables is designed, and the characteristic waveforms of cable point broken down not are simulated respectively. Then a new method based on wavelet transform presented. Wavelet have good performance in denoising singularity detection, which well solved difficulty identifying initial reflected because local time-frequency characteristic. The distance can be calculated by round-trip times spends cable. only required parameter...

This article analyzes the different types of voltage applied on valve side winding converter transformer. The oil-paper insulation model is established in laboratory order to analyze distribution characteristics electrical field caused by insulation. fields DC voltage, AC superimposed and polarity reversal emulated with FEM (finite element method). It can be concluded from results that resistive distributed will lead high intensity pressboard. capacitive oil. Influenced space charge field,...

This study investigates the electrical aging characteristics of oil-paper composite insulation. In this paper, a coils model and test system for transformer insulation are designed. The tests at room temperature operating performed using step-stress method. A new method estimating unknown parameters in inverse power exponent is proposed, life formula expressed by voltage electric field strength obtained. Considering process temperature, allowable inter-turn oil-immersed transformers can be...

Oil-paper insulation as an irreplaceable system in the electrical power transformer is inevitably suffering water intrusion on working condition, which will make dielectric performance degraded and aging accelerated. In high interest of explaining deterioration effect absorbing moisture properties oil-paper corresponding mechanism, space charge trap level characteristics are investigated for specially prepared oil-impregnated pressboards with different contents. The Pulsed Electro Acoustic...

Abstract To explore the aging assessment method of oil–paper insulation in power transformers, polarization and depolarization current (PDC) characteristics composite samples are investigated under high applied voltage. Based on asymmetry absorption polarity effect pressboard, repeated test is proposed. A novel characteristic parameter, which ratio normalized charge for first second polarization, extracted. The difference between decay rates increases at then decreases with time, increasing...