A finite element simulating model of stator bar end was established by COMSOL software, and the influences of electrical properties parameters of insulating material on the electric field and potential distribution of bar end were analyzed. The results show that with the increase of relative permittivity of main insulation, the maximum electric field on stator bar end surface increases, therefore it is better to choose smaller relative permittivity of main insulating material. The resistivity of main insulation material has no significant effect on the maximum electric field on bar end surface. The relative permittivity of each anti corona layer has little effect on the maximum electric field on bar surface. It is better to choose larger nonlinear resistance coefficient of medium resistance anti corona layer. The nonlinear resistance coefficients of medium and high resistance anti corona layer have little effect on the maximum electric field on bar surface, and it is best to choose 1. The nonlinear resistance coefficient of high resistance anti corona layer has no effect on the maximum electric field on bar surface. The influence degree of initial resistivity of different anti corona layers on the maximum electric field of bar surface is different. Through partial correlation analysis, the influence degree of electrical properties parameters of insulating material on the maximum electric field at bar end is ranked, and the initial resistivity and nonlinear resistance coefficient of the medium resistance anti corona layer are the dominant factors.

Internal water seepage is one of the common faults of cable. The accurate detection, identification, and location of internal water seepage defect in cable play a vital role in improving power safety and stability. On the basis of time-domain reflection technology (TDR) theory, the effects of injection pulse frequency and amplitude attenuation on the effective positioning distance of TDR were analyzed by simulation. The characteristic waveforms of different impedance points were obtained, the resolution method of water seepage defect waveforms was summarized, and the effect of complex reflection wave on the positioning accuracy was studied. The results show that the TDR technology can detect the water seepage defect in cable, and the effective detection distance is about 3.76 km. Different types of defects will return different characteristic waveforms, and when the degree of water seepage is different, the waveform amplitude and wave tail oscillation will also change.

A monitoring method for the operating state characteristics of bushing in UHV converter valve hall was proposed from the perspective of intelligent image processing and three-dimensional modeling technology. This method mainly included using intelligent image processing technology to identify and classify the databases of infrared thermal imager and ultraviolet imager, using Kalman filtering technology to realize on-line measurement in real time for the insulation distance of typical metal fittings, and using three-dimensional modeling technology based on finite element method to build the electric field simulation model of typical main equipment bushing in valve hall, and the electric field distribution on the surface of key metal fittings was obtained. Combined with the image database information, insulation distance information, and electric field distribution information of typical main equipment bushing, its operation state parameters were obtained effectively, and its operation state was evaluated by the intelligent algorithm automatically. The results show that when the Kalman filtering technology is not used, the prediction deviation of the distance at key positions changes severely in 0‒160 s. After using the Kalman filtering technology, the jump amplitude of prediction deviation decreases and is basically controlled at the same error level. The neural network has good learning effect, the fitness function tends to be stable after 100 iterations, and the local weight of fuzzy neural network shows typical nonlinear characteristics. The research conclusion can explore potential hidden dangers and locate positive faults effectively, which provide effective data support and protection strategies for the operation and maintenance of main equipment bushing.

From the perspective of the particle size of pollution particles, the particle size characteristics of the insulator surface pollution under two typical dust pollution sources of nickel plants (metal) and chemical plants were tested and analyzed, and the influence mechanism of the pollution particle size on the pollution accumulation was studied by establishing a pollution particle deposition model. The results show that the average particle size of pollution particles on insulator surface in chemical plant area is only 6.67 μm, while the average particle size of pollution particles on insulator surface in nickel plant area attains 24.5 μm. The deposition rate is the largest when the particle size of pollution particles is 20‒30 μm, therefore the surface of insulator in nickel plant area is polluted seriously. The simulation results based on the pollution particle deposition model can confirm with the on-site pollution accumulation phenomena, which explains the influence of pollution particle size on the insulator pollution accumulation.

Under the sinusoidal, bipolar square wave, and bipolar short impulsive voltage with 50 Hz of frequency, three typical corona-resistant turn-to-turn insulated twisted pairs for new energy vehicles were used to experiment, and the influences of three voltages on their partial discharge inception voltage (PDIV) characteristics were studied. The results show that within the effective bandwidth after frequency domain filtering, the discharge frequency domain energies under bipolar repetitive short pulse and square wave voltage distribute in 0.5‒0.9 GHz mainly. Keeping other test environments unchanged, the PDIVs under sinusoidal and bipolar repetitive square wave voltage are almost equal. The PDIVs under sinusoidal and square wave are about 20% lower than under bipolar repetitive short pulse voltage, and with the increase of pulse width, the PDIV decreases under bipolar repetitive short pulse voltage. According to the research results, when conducting PDIV test on turn-to-turn insulation, the sinusoidal and square wave voltage are more conservative test voltages for evaluating the PDIV of inverter-fed motor turn-to-turn insulation. When conducting PDIV test on capacitive sample of twisted pairs, the sinusoidal voltage can be considered to replace pulse voltage.

The main insulation of cross-linked polyethylene (XLPE) HVDC cable was sliced at radial inner, middle, and outer layers to as samples, and their equivalent thermal history was modeled by differential scanning calorimetry (DSC). The changes of chemical and electrical properties of each layer in cable insulation after type test were analyzed by infrared spectroscopy (FTIR), space charge, and DC electrical strength test. The results show that after type test, the equivalent heat treatment temperatures of each layer in cable main insulation are about 70℃, there is a small difference between the equivalent heat treatment time of the middle layer and the outer layer, while the equivalent heat treatment time of the inner layer is about 581 times bigger than that of the middle layer. There are little changes in DC electric strength and chemical properties of each layer in cable main insulation. Due to the equivalent heat treatment time of each layer is different, the impurities, polar small molecules, and other substances in inner insulation layer continue to diffuse from the inner layer to the middle layer, which results in the significant accumulation of heteropolar space charges.

This review mainly discusses the insulating materials adapted in chip packaging process from the perspective of the application of current silicon-based and next-generation silicone carbide (SiC) and other wide-bandgap semiconductor in power electronics packing, and prospects its future research trends towards requirements of high thermal conductivity and high temperature resistance.

Compared with other dielectric materials, polymer-based all-organic composite dielectric materials have the advantages of high electrical strength, low dielectric loss, light weight, and excellent mechanical processing performance, and is more suitable for practical applications. In this article, the research progress of polymer-based all-organic composite dielectric materials with the matrix of pure polyvinylidene fluoride (PVDF), PVDF copolymers, and other polymers is reviewed. Some problems still faced in capacitor energy storage and practical application are discussed, and its future development is prospected.

Insulating paper is an important insulating material that produced by papermaking technology and widely used in electrical equipment such as transformers, capacitors, motors, wires and cables. According to its composition, insulating paper can be divided into cellulose paper and non-cellulose paper. With the sustainable development of China’s power industry, motors and other electric equipment are gradually getting more efficient and smaller. Therefore, higher property requirements are put forward to insulating paper, especially high-temperature resistant performance. Although cellulose papers have a long history, their heat resistance is not high enough to meet the operating requirements of electrical insulation systems, which need the thermal class of F or above. Non-cellulose papers with higher heat resistance have sprung up. This article briefly introduces the development history, performance characteristics, main uses, production status, and development trends of various high-temperature resistant non-cellulose insulating papers in China.

Ceramizable silicone rubber composites were prepared by using kilchoanite as ceramic filler, glass frit as flux, and nano silica as reinforcing agent. The effect of the content and size of kilchoanite on the tensile properties of the composites was studied. The ceramic specimens were obtained by sintering the composites at 1 000℃, and then the microstructure of its fracture surface was observed. The phase change of ceramic specimens was analyzed by X-ray diffraction, and its linear contraction and flexural strength were measured. The results show that the increase of the kilchoanite with the same particle size can reduce the tensile strength of the composites, while increase the elongation at break. Under the same content, the kilchoanite with a smaller size can improve the tensile strength of the composites. When the content of kilchoanite is too high or too low, the flexural strength and density of the ceramic specimens decrease. With the decrease of the size of kilchoanite, the flexural strength of the ceramic specimens increases, while the linear contraction also increases. The maximum flexural strength of the ceramic specimens can reach to 58.57 MPa by changing the content and size of kilchoanite.