Jian Wang

North China Electric Power University | NCEPU · School of Electrical and Electronic Engineering

As high-voltage and high-power electronic devices such as insulated gate bipolar transistors (IGBTs) develop towards higher levels, the generated heat and operating temperature rise rapidly, causing the problem of insulation packaging failure to become more serious. In this paper, to study the gas production mechanism of the high-temperature therma...

Power electronic transformer insulation systems endure extended periods of operation under challenging conditions characterized by the interaction of electrical and thermal factors. Current numerical models of space charge inadequately replicate the charge evolution in actual operational circumstances. In this paper, a high-frequency heating model...

The air cavities at the interface are an important cause of partial discharge (PD) in SST composite insulation. Therefore, it is of great practical significance to study the partial discharge and breakdown characteristics of composite insulation air cavities under high frequency electric stress. In this paper, the interface breakdown strength and p...

Low and medium speed magnetic levitation traffic with short power supply distance and complex grounding network structure, prone to power supply rail grounding faults. However, the existing fault location methods do not accurately locate the fault point, making it difficult for the protective device to act to cut off the fault. To address the above...

The Wire metal particles in gas-insulated equipment such as GIS (Gas-Insulated Substation) and GIL (Gas-Insulated transmission lines) under DC stress present a special firefly motion behaviour, namely a long-term levitation on the surface of conductors. However, the electrode coating, as a key device available to suppress the movement of particles,...

High temperature tends to be one principal failure cause of silicone gel package insulation in high-power electronic devices, even leading to equipment damage under severe conditions. To clarify the aging characteristics and failure mechanism of silicone gel package insulation of high-power IGBT devices under the high-temperature scenario, this pap...

A particle motion excitation and observation platform was established to physically simulate the actual online operating conditions of HVAC/HVDC GIS/GIL as well as study the capture mechanism of particle traps. Experimental results illustrated that, the collision motion style was a principal factor to affect the particle capturing capability, and t...

Surface coating technology is an effective way to solve the interface insulation problem of DC GIS/GIL basin insulators, while the performance of the coating will change greatly, and the insulation strength will be completely lost after long-term service in the extreme conditions of corona erosion. In this research, the multi-needle-plate electrode...

In outer space’s extreme electron radiation environment, the insulating medium will experience a deep dielectric charging effect. As an excellent insulating medium, polyimide is widely used in spacecraft. In practical use, glass microspheres and glass fibers are often added to increase its mechanical strength. However, the influence of glass micros...

In molecular dynamics simulation, the cross-linked epoxy resin model can well simulate the performance of epoxy resin in actual use. We have established a cross-linked epoxy resin model and a composite model of epoxy resin and aluminum at the molecular level. Based on ReaxFF, the reaction molecular dynamics simulation of pyrolysis aging was carried...

In order to introduce fluorine-containing functional groups into epoxy resins to stably enhance the surface electrical properties of thin films, the trifluoromethyl group containing diglycidyl ethers bisphenol A (F-DGEBA) monomer was prepared by a simple and environmentally friendly method. Further, the film was obtained by blending the prepared mo...

The movement of metal particles is effectively inhibited when a DC GIL’s (gas-insulated transmission line) electrode is coated. This article aims to study the problem of coating falling off during GIL operation and the change in the particle-inhibitory effect after coating ageing. A closed constant temperature heating platform and a particle motion...

Polyimide, which is widely used to insulate power equipment operating in a vacuum environment, is prone to insulation failure due to surface flashover. Using POSS to modify it is an effective solution. This paper focuses on the study of DC surface flashover characteristics in vacuum of POSS/polyimide composite film, by introducing 1%, 3%, 5% equiva...

Insulation failure usually occurs in AC gas-insulated transmission (AC GIL) in field operation, in which the primary cause is the charged motion of metal particles in the electric filed. At present, the particle inhibition method applied is to design particle traps on the inner wall of the GIL shell. However, due to the large randomness of the char...

To explore the influence of curing agents on the oxygen participated thermal decomposition mechanisms of the epoxy resin, the epoxy-O2 models, cured by 3,3-DDS, 3,3-SDA, 3,3-SSDDS, and 4,4-DDS, respectively, were first established. The ReaxFF-based MD simulation is applied to track the initial reactions of the pyrolysis. The results show that the O...

The deep dielectric charging of the slip ring assembly caused by high-energy electron radiation leads to the failure of the solar array drive assembly (SADA), which accelerates the failure of the whole satellite. It is necessary to optimize the structure of the slip ring assembly according to the deep dielectric charging characteristics to reduce t...

Four crosslinked epoxies, agented by ODA, SDA, DDS, and SSDDS, were constructed, followed by DFT calculations and MD simulations to assist the selection of coatings for the quick repairment of GIL. The DFT-based ground-state charge density results indicate that the core group and molecular length impact the reactivity of diamine curing agents. Base...

Environment-friendly gas insulating mediums adapted to a DC gas-insulated transmission line (GIL) electric field condition is the key to the next generation of Environment-friendly HVDC GILs. In this paper, we review the literature on sulfur hexafluoride (SFö) alternatives including the scientific understanding, control, and implementation of gas-s...

Aluminum dust adsorbed on insulator surface may induce discharge or even flashover in DC GIL. So, it is of great significance to suppress dust’s adsorption to improve reliability of gas-solid insulation system. In this study, two kinds of nanocomposite coatings doped with different fillers, nano-SiC and montmorillonite (MMT) with nano-TiO2, were de...

In this study, a series of polyimide (PI) films containing both phenyl sulfide and phenyl ether functional groups in different ratios were prepared via a two-step thermal imidization method. The creepage discharge behaviors, including creepage discharge inception voltages (CDIVs), as well as phases, amplitudes, and numbers of discharges in the init...

A large amount of metal dust is often generated during production and operation of Gas Insulated Switchgear/Gas‐Insulated Transmission Line, and insulating fibres are very easy to mix in during assembly. The discharge phenomenon induced by these two impurities remains unknown. By setting up a test rig with parallel electrodes, the discharge charact...

The ReaxFF SFO force field for a SF 6 −O 2 system is developed based on the density functional theory (DFT) calculation data. Then, a series of molecular dynamics (MD) simulations were performed. The results show that the main oxygen-containing compounds that appeared in the MD simulation include SOF 4 , SOF 2 , and SO 2 F 2. The relative quantitat...

When DC GIL in operation endures the lightning impulse voltage, the charge accumulation at the gas-solid interface area will seriously affect the insulation performance of the spacer. Considering that gas side conduction is one of the important factors affecting charge accumulation, for the purpose of clarifying of the insulation characteristics of...

To investigate the effect of fluorination on surface electrical performance of ethylene propylene rubber (EPR), four pieces of EPR are prepared and fluorinated for different duration ranging from 120 min to 480 min. The surface morphology and element compositions of experimental specimens are tested. The surface potential decay (SPD) and complex pe...

Polyimides containing diphenyl sulfide units were directly coated on the Aluminum electrodes via solution polycondensation-thermal imidization method, which is important for suppression of the free metal particle motion in the Direct Current Gas Insulation Transmission Line (DC GIL). The micro-structures were identified by Fourier-transform infrare...

The metal particle contamination in gas-insulated switchgear (GIS) or gas-insulated transmission line (GIL) is an important factor leading to the decline of insulation performance. Exploring the deterioration mechanism and suppression measures of metal particles on insulation is a key technical problem in enhancingimproving the dielectricinsulation...

The present work aims at investigating the single excessive hydrogen (SEH) mechanism in the current transformers (CTs) by reactive force field molecular dynamics (ReaxFF MD) simulations. The chemical components in the CTs, i.e. mineral insulating oil, insulating paper, nickel crystal and moisture were established. Temporal evolutions of dissolved-g...

Polyimides (PIs) and their nanocomposites may render quite high dielectric loss under high frequency (HF) electrical stresses, which will significantly affect the insulation properties and operating lifetime of the equipment when the composite materials are used in the high-voltage and large-capacity power electronics transformers (HFPTs). In this...

With the combination of the phenyl thioether group into the molecular chain of polyimide, the high frequency dielectric loss of the modified polyimide film can be effectively reduced, which will avail this insulating material of application in high frequency electrical equipment. In the proposed study, polyimide films containing different proportio...

The electrical performance of DC gas insulation transmission line (GIL) using SF6 gas mixture or alternative gas as insulation medium will be deteriorated by free metal particles. The analysis of the factor affecting the insulation strength of SF6/N2 and C4F7N/CO2 gas mixtures is mainly performed in this paper. The breakdown experiments with partic...

This study aims to restrain free conducting wire-type particles which are commonly and dangerously existing within DC gas-insulated transmission lines. A realistic platform of a coaxial cylindrical electrode was established by using a high-speed camera and a partial discharge (PD) monitor to observe the motion, PD, and breakdown of these particles....

This paper investigates the influence of tip corona of free linear particle on the partial discharge pattern. The reduced scale apparatus of 126 kV GIS is set up in the laboratory. Linear particles with the same radii, same length and different tip radii are respectively placed in the experimental tank. The discharge signal, ultrasonic signal and m...

This paper analyzes the electromechanics of the spherical metal particles in AC gasinsulated lines (GIL) with a pragmatic test rig comprising coaxial cylindrical electrodes. Analysis on fluid resistance during the particle moving process is presented based on fluid mechanics as well as the kinetic parameters of the SF₆/N₂ mixt...

Based on the Maxwell equations, surface charge accumulation on the post-insulator was analyzed. The particle pollution, as well as the generating, recombination, migration and diffusion of the positive and negative ions in the gas were taken into account. Furthermore, from the microcosmic perspective, two surface charge accumulation models of the p...

With the superiority of compactness, high reliability and the great transmission capacity, gas-insulated lines (GIL) has been widely used especially in certain regions. However, free metal particles may be brought into the closed structure inevitably. To study the problem of metal-particles pollution in AC GIL, the electromechanics of one spherical...

In this study, mechanical analysis of the air-gap breakdown with free spherical metal particle is conducted in a DC uniform field to address the problem of metal-particle pollution in DC gas insulation. The criterion and spacing of micro-discharge between the particle and electrode is calculated based on the analysis of electric-field distortion wi...

To address the problem of metal-particle pollution in DC gas insulation, an experimental platform is built for observing the particle's motion and discharge. And the breakdown process is observed using a high-speed camera. Based on the platform, the mechanical analysis of the air-gap breakdown with free spherical metal particles is conducted in a D...

To solve the problem of metal-particles pollution in DC gas insulated metal enclosed transmission line (GIL), in a more realistic situation of coaxial cylindrical electrodes, the motion analysis of spherical metal particle was made in DC GIL structure. Based on the theory of fluid mechanics and considering the SF6/N2 mixtures parameters, analysis o...

To solve the problem of metal-particle pollution in DC GIL, in a more realistic situation of coaxial cylindrical electrodes, the motion analysis of spherical metal particles is done based on DC GIL structure. Based on the theory of fluid mechanics and considering the SF 6 /N 2 mixtures parameters, analysis of the flow resistance in the process of p...

Western blotting analysis of transgenic plants expressing myc-tagged NBR1 or mNBR1 transgene. Total proteins were extracted from the leaves and equal amounts of proteins were subjected to SDS-PAGES, probed with an anti-myc monoclonal antibody or stained with Coomassie brilliant blue. (PPT)

Induction of ATG8 genes by heat stress. Five-week-old Arabidopsis wild-type Col-0 plants were placed in a 45°C growth chamber and total RNA was isolated from leaf samples collected at 0 and 10 hours of heat stress. Transcript levels were determined using real-time qRT-PCR and fold induction of an ATG8 gene by heat stress was calculated from the rat...

Structure and mutants for the NBR1 gene. (A) Exon and intron structure of NBR1. The exons are indicated with rectangles and the introns with lines. The location of T-DNA insertions for the nbr1-1 and nbr1-2 mutants as well as the two primers for PCR genotyping of the mutants (P1 and P2) are indicated. (B) PCR identification of homozygous nbr1 mutan...

Primers for qRT–PCR. (DOCX)