With the development of modern electrical equipment toward miniaturization, high-degree integration, and multi-functionalization, a large amount of heat accumulation will lead to insulation failure of electrical equipment. In order to develop a composite that can achieve high thermal conductivity even with low filler content (mass fraction<50%) and meet the strict requirement of current electrical equipment for heat dissipation, a composite insulating paper composed of aramid nanofibers and hydroxylated boron nitride nanotubes （BNNT-OH） was synthesized in this paper, and the effects of BNNT-OH content on the properties of composite insulating paper were studied. The results show that when the mass fraction of boron nitride nanotubes is 20%, the thermal conductivity of composite insulating paper is as high as 15.92 W/(m·K). The excellent thermal conductivity is due to the high intrinsic thermal conductivity of boron nitride nanotubes, and that the strong interaction between hydroxylated boron nitride nanotubes and aramid nanofibers reduces the interfacial thermal resistance.

An ANF/mica composite insulating paper was prepared by vacuum assisted filtration and hot pressing technology taking aramide nanofiber (ANF) as matrix and natural mica (mica) as filler. The microscopic morphology, tensile strength, electrical insulation properties, and temperature resistance of the composite insulating paper were studied systematically. The results show that the mica and ANF are superimposed in order during vacuum filtration process, and the mica fragments fill the gaps in paper effectively, creating a dense "brick-and-mortar structure", which significantly enhances the electric strength and insulating properties of the composite insulating paper. Furthermore, the glass transition temperatures of pure ANF insulating paper and ANF/mica-10 composite insulating paper are higher than 300℃, exhibiting excellent thermal stability. Although the addition of mica slightly reduces the tensile properties of pure ANF insulating paper, its insulation strength and tensile performance remain superior to traditional mica paper.

A high heat resistant o-allylphenol-dicyclopentadiene epoxy resin was synthesized using dicyclopentadiene, o-allylphenol, and epichlorohydrin as raw materials, and its structure was characterized by infrared spectrum and gel chromatography. Then the epoxy resin was cured with bisphenol-A phenolic resin, benzoxazine resin, and active ester respectively, and a PCB substrate was pressed. The curing behavior of the system was studied by differential scanning calorimetry and thermogravimetric analysis. The mechanical properties, dielectric properties, and water absorption properties of the PCB substrate were tested, and compared with the curing system of phenol-dicyclopentadiene epoxy resin. The results show that compared with phenol-dicyclopentadiene epoxy resin, the o-allylphenol-dicyclopentadiene epoxy resin has higher heat resistance (glass transition temperature T_g and 5% thermogravimetric temperature T_d5% are higher), bending strength, impact strength, high temperature bending strength retention, and better dielectric properties, lower water absorption.

A new type of ceramifiable intumescent fire protection coating was prepared by using epoxy resin as the matrix, ammonium polyphosphate as the flame retardant, zinc borate as the flux, and raw vermiculite powder and wollastonite as the refractory fillers. The effects of the compound of four fillers on the properties of ceramifiable intumescent fire protection coating were studied by scanning electron microscope (SEM) and fire resistance test. The results show that ammonium polyphosphate can significantly improve the expansion multiplication rate and thermal insulation performance, zinc borate can effectively enhance the strength and density of the charcoal layer, and raw vermiculite powder and wollastonite can enhance the burn-resistant performance of the charcoal layer and increase the fire resistance time limit at high temperature. When the mass ratio of ammonium polyphosphate, raw vermiculite, zinc borate, and wollastonite is 11∶5∶6∶10, the tensile shear strength is 7.8 MPa, the refractory performance is the best, the fire resistance time limit reaches 10 min, the maximum backsheet temperature is 393℃, and the charcoal layer after burning can withstand a voltage of 1.0 kV.

A glass fiber winding reinforced epoxy resin composite with high thermal conductivity was prepared by filling the bisphenol A type epoxy resin system with a mixture of alumina and silica powder fillers. The effects of filler content on the mechanical properties, electrical properties, and thermal conductivity of composite were studied. The results show that the addition of mixed fillers is beneficial for improving the thermal stability and thermal conductivity of the composite. When the mass fraction of the fillers is 62% (of which the mass fraction of silicon powder is 48% and the mass fraction of alumina is 14%), the tensile strength (0° and 90° directions), bending strength, and NOL ring tensile strength of the composite are 160.25, 24.50, 245.40, and 134.30 MPa, respectively. The dielectric constant is 1.889, the dielectric loss factor is 0.673×10^-2, the volume resistivity is 3.36×10¹⁶ Ω·cm, and the thermal conductivity is 1.257 W/(m·K), which is 155% higher than the thermal conductivity before addition.

In the partial discharge test and detection of power transformers, multi-source pulse overlap seriously affects the identification of partial discharge signals. In this paper, a clustering separation method of partial discharge signals based on multi-terminal pulse amplitude ratio was proposed. Firstly, the partial discharge test of 220 kV transformer was carried out, and the pulse overlapping phenomena in PRPD and T-F spectra under different test voltages were analyzed. Then, based on the propagation attenuation law of different types of pulses in transformer, a three-dimensional amplitude ratio pulse clustering separation method based on multi-terminal detection of transformer was proposed, and the method was realized by DBSCAN algorithm. Finaly, multi-terminal detection was carried out during the partial discharge test of 220 kV transformer, and the clustering separation and pulse source analysis of the pulse were carried out. The results show that utilizing the multi-terminal amplitude ratio clustering separation method can accurately divide the multi-source overlap pulses during partial discharge process in to interference pulse and two kinds of discharge pulse, and the initial location of the pulse source can be realized according to the amplitude ratio . The multi-terminal pulse amplitude ratio clustering separation method realizes the extraction of transformer partial discharge pulse, and its development and application will be conductive to improve the anti-interference capability and detection accuracy in transformer partial discharge testing.

To improve the insulating properties of machinable ceramic brush holders in high humidity environment, different types of organosilane film layers were formed on the surface of machinable ceramic, and their microstructure, contact angle, surface bonding strength, and moisture absorption rate were tested. The effects of the film layers containing KH-560, KH-570, and fluorosilane on the adhesion strength and moisture absorption of epoxy adhesive were studied. The mechanism of the films enhance the moisture resistance of machinable ceramic brush holder was concluded. The results show that the film layer thickness of KH-560 organosiliane on the surface of the machinable ceramic brush holder is about 40 μm. At the same time, the water contact angle of the brush holder product treated by KH-560 coupling agent increases from 9.2° to 42.8°, the moisture absorption rate reduces by more than 58.3%, and the hydrophobicity increases significantly. Even in the environment with relative humidity of 90%, the insulation resistance can still reach more than 220 MΩ, showing excellent insulation performance, which makes its insulation reliability improve significantly in high humidity environment.

In recent years, with the rapid development of new energy vehicles and flexible direct current transmission projects, and other fields, there was an increasing demand for the metallized film capacitors with high volume ratio and high temperature resistance. Especially under extreme conditions such as high temperature and high electric field, higher requirements were put forward for the electrical performance of dielectric films in capacitors. In this paper, the current research status and development trend of dielectric film materials for metallized film capacitors in recent years were summarized. Firstly, the key factors affecting the energy storage performance of dielectric films were introduced and the failure reasons of metallized film capacitors under operating conditions were analyzed. Secondly, the modification methods of energy storage performance for dielectric films designed on the basis of four aspects, such as molecular chain structure, aggregation state structure, doping of functional fillers, and surface modification were summarized. Finally, the strategies to improve the energy storage performance of dielectric films of metallized film capacitors were summarized and prospected.

The motor is the key drive component of new energy vehicles, and the insulation system is an important guarantee for motor reliability. Once the motor insulation fails, it will pose a threat to the safe operation of the vehicle. The severe electric heating stress is the main factor causing insulation failure, so it is of great significance to test the motor insulation level under complex pulse parameters and environmental conditions. This paper had reviewed the latest research results at home and abroad from several aspects of performance evaluation methods and influencing factors, voltage distribution calculation, and weak spot location of new energy vehicle drive motor insulation system. Combined with the development trend of voltage level improvement, power density improvement, breaking frequency improvement, and switching speed increase, the problems and challenges faced by insulation evaluation of variable frequency motor were pointed out, which provided reference for the future research in this field.

The one-dimensional ANF and two-dimensional edge-hydroxylated BNNS (BNNS-OH) were mixed to prepare ANF/BNNS-OH composite insulating papers with “brick -mud” structure by vacuum filtration technology. The mechanical properties, thermal conductivity, dielectric properties, and breakdown properties of the composite insulating paper were studied. The results show that the BNNS-OH arranges in ANF orderly, and the structure is dense. The ANF/BNNS-OH composite insulating paper has excellent mechanical properties, thermal conductivity, and breakdown properties. When the mass fraction of BNNS-OH is 10%, the tensile strength and electric strength of the composite insulating paper are 242.4 MPa and 312.9 kV/mm, respectively. When the mass fraction of BNNS-OH is 40%, the thermal conductivity of the composite insulating paper reaches 6.76 W/(m·K), which is 158.02% higher than that of pure ANF insulating paper. At same time, the composite insulating paper has excellent high temperature wideband dielectric stability.