According to the characteristics of series resonance circuit, a new model for calculating the dielectric dissipation factor of high-voltage power cable was established, and a new dielectric loss factor calculating formula derived from the differential power of the series resonance circuit was proposed. On the basis of test model, the dielectric dissipation factor of XLPE power cable was calculated by the step-up or step-down process of the series resonance to solve the problem of dielectric dissipation measuring of high voltage and large capacity cable. The results show that the simulation calculating values of circuit parameters and field test results match with the actual values. Compared with conventional electric bridge method, the test method for calculating dielectric dissipation factor based on the resonance characteristic is more accurate to a certain extent. This provides a reference for testing the dielectric dissipation factor of high voltage and high capacity power cable.

In this paper, three metal-organic framework (MOF) materials MOF-505, Cu-BTC, and MIL-100(Fe) were prepared by solvothermal method, and Cu-BTC with the highest adsorption capacity was selected. The equilibrium adsorption capacity of Cu-BTC, activated carbon, 13X molecular sieve, and activated clay at different initial concentrations and adsorption temperatures was systematically studied. The difference among the adsorption characteristics for aminophenazone of the MOFs was explained by simulation calculations using simulation software. The results show that the adsorption capacity for aminophenazone of Cu-BTC is much higher than that of the other three adsorbents. Under different temperature, the equilibrium adsorption capacity of BTC for aminophenazone at different initial concentrations has much difference, thus the appropriate adsorption temperature should be selected to achieve the optimal adsorption capacity.

In order to study the effects of different damping paths on cables, we set up a variety of endogenous and exogenous damping paths according to operating experience. Accelerated damping test were conducted on cables for 90 cycles, and the insulation resistance, partial discharge, and depolarization current were measured regularly. Then the moisture state of the cable was comprehensively evaluated by TOPSIS method. The results show that during cable operation, moisture can enter and rapidly spread inside the cable through the broken body, cable joints, and various interface structures of the cable terminals. The degradation effects of moisture through cable joints and endogenous moisture on the insulation is the most prominent, which should be prevented and taken seriously. Furthermore, the comprehensive evaluation of electrical properties based on insulation resistance, partial discharge, and depolarization current can effectively explore the damping process and identify the moisture state, which can be applied to practical engineering to evaluate the damp problem of distribution network cables in warm-damp environment.

The typical defects model of heat-shrinkable and cold-shrinkable cable accessories were established, and partial discharge tests were carried out at 0.1 Hz ultra-low frequency and oscillatory wave voltage. The differences in the partial discharge inception voltage (PDIV), the PD quantity, the number of PD and other parameters of the typical defects under the two voltages were measured and compared, and the formation mechanism of these differences was analyzed. The results show that for most of the measured defects, compared with under 0.1 Hz ultra-low frequency voltage, the PDIV under the oscillating wave voltage is lower, the PD quantity is larger, and the number of partial discharge pulses is more. The difference in the voltage distribution mechanism and the voltage recovery rate at the defect location is the main reason for the above-mentioned difference.

According to isotope tracing technology, we used stable isotope tracer ¹⁸O₂ to carry out SF₆ partial over-thermal decomposition experiments to simulate the decomposition of SF₆ under sustained high temperature. The influence mechanism of trace O₂ on the overheating decomposition of SF₆ was analyzed by obtaining the changes in the volume fractions of the main oxygen-containing products labeled by ¹⁸O. The results show that under overheating conditions, trace O₂ preferentially reacts with SF₃, SF₂, and SF to generate SOF₃, SOF₂, and SOF, followed by generating a small amount of SO₂F₂. It is said that O₂ is the main source of oxygen for the formation of SOF₂. Besides, under overheating conditions, SF₆ can be completely decomposed to generate elemental S, which reacts with trace O₂ to generate SO₂.

The relationship between the withstand voltage and the thickness of the sheath was studied when the air gap distance is 0, 5, 10, 15 cm, respectively. The influence of the length of sheath on the development of creeping discharge was studied when the sheath surface is dry, wet, and dirty, respectively. The results show that with the increase of the length and thickness of gap, the breakdown voltage of the insulating sheath-air combined gap increases nonlinearly, and the increase rate of the breakdown voltage also increases. The surface flashover electric field intensity of the insulating sheath decreases obviously in dirty state, the average flashover electric field intensity is 1.2 kV. Based on the above research, the configuration of anti bird droppings flashover insulating sheath was obtained. The thickness of the sheath is determined according to the line voltage level, and then the covering length is determined by the maximum surface flashover distance. It is recommended that the thickness and covering length of sheath in 110 kV transmission line is 6 mm and 60 cm, respectively; while the thickness and covering length of sheath in 220 kV transmission line is 8 mm and 110 cm, respectively.

Crosslinked polyethylene/organic montmorillonite (XLPE/OMMT) nanocomposites were prepared by melting blending method. The performance of samples before and after thermal ageing were characterized by small angle X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), and mechanical properties test. The results show that with the mass fraction of 0.5%, OMMT can be well dispersed in the matrix before ageing. However, OMMT agglomerates when the filler doping amount increases. There are only a few chemical bonds between OMMT and XLPE matrix, they mainly coexist in the form of physical entanglement. The crystallinity of nanocomposites decreases due to the space steric effect of OMMT lamella. After ageing, the layer spacing of XLPE/OMMT-0.5% samples decreases and the crystallinity increases. With the increase of OMMT doping amount, the interlayer spacing of OMMT increases due to the breakdown of XLPE molecular chain and the thermal rearrangement of OMMT in matrix. Due to thermal ageing, the completeness of crystal structure of nanocomposites gets worse, the crystal size distribution becomes wider, and the crystallinity decreases significantly. The molecular chain structure of nanocomposites is seriously damaged by thermal oxidation and thermal cracking. The mechanical property of XLPE/OMMT-0.5% decreases slightly after ageing, and when the content of OMMT exceeds 0.5%, the mechanical properties of nanocomposites decrease seriously. And the samples become brittle and hard.

The effect of different contents of bis-triethoxysilylpropyl tetrasulfide (Si69) and bis(tert-butylperoxy diisopropyl) benzene (BIBP) on vulcanization characteristics, mechanical properties, and electrical insulation property of EPDM were compared and analyzed. The results show that with the increase of Si69 and BIBP content, the curing speed increases, the process positive curing time decreases, the maximum torque increases, the crosslinking density of the rubber increases and the mechanical properties are improved. With the increase of Si69 content, the electrical insulation property of the rubber decreases; with the increase of BIBP content, the electrical insulation property of the rubber increases gradually.

The accumulation test of metal particles in oil between spherical electrodes under different ratios of AC/DC composite voltage was carried out, the partial discharge (PD) signals at different moments were collected simultaneously. And then the discharge frequency and average discharge quantity were counted, and the correlation between the aggregation behavior of metal particles and PD characteristics was analyzed. The results show that the accumulation area of metal particles under DC voltage is the largest, and the metal particles aggregated the most closely under 3:1 AC/DC composite voltage. The discharge frequency decreases with time, while gradually increases with the increase of AC component in AC/DC composite voltage. It is considered that the collision frequency between metal particles and electrodes and the closeness of particle accumulation are the main factors affecting the frequency of partial discharge and the average discharge quantity.

The simulation model of 35 kV prefabricated cable terminal was established to simulate and calculate the electric stress, thermal stress, and mechanical stress distribution of the cable terminal under the impulse voltage. The electric field, temperature, and stress of body insulation, semi-conductive layer, and shielding layer were calculated and analyzed, and the influence of harmonic wave with different frequency on the electric field distribution was considered. The results show that the influence of high frequency signal on permittivity does not lead to large distortion of electric field intensity, and the change of electric field intensity is not obvious. At the same time, the temperature rise of cable terminal caused by impulse voltage is small, and its influence can be ignored. The impulse voltage increases the mechanical stress at the intersection of the semi-conductive layer and the stress cone, and the maximum radial strain reaches to 2.54%, which makes the position of the semi-conductive layer prone to produce air gap and is the main cause of cable terminal damage. It is concluded that not only the electric field optimization but also the elastic strain of the material should be considered in the material selection and structural design.