Taking 1,3,5-tri(4-aminophenoxy) benzene (TAPOB) as crosslink agent, a micro-branched crosslinked structure was constructed in 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-diaminodiohenyl ether (ODA) polyimide (PI) film, and a series of PI films with different TAPOB content were prepared. The effects of TAPOB content on the mechanical properties, thermomechanical properties, dielectric properties, and water absorption were studied. The results show that the addition of TAPOB can improve the comprehensive properties of BPDA/ODA PI films significantly. The existence of crosslinked structure is conductive to improve the mechanical properties, decrease the coefficient of thermal expansion (CTE) and water absorption of the film, and the micro-branched structure has a certain effect on reducing the dielectric constant.

LDHNSs dispersion was obtained by ultrasonic stripping of hydrotalcite assisted with intercalation agent. PI/LDHNSS composite films were prepared by in-situ polymerization, and their electrical properties were studied. The results show that the LDHNSs disperse uniformly in PI matrix without obvious agglomeration and stacking, which show good interfacial compatibility with the matrix. Compared with pure PI film, the volume resistivity and electric strength of the composite films decrease slightly to some extent with the addition of LDHNSs. However, it should be note that the corona resistance life of the composite film is improved significantly. When the mass fraction of LDHNSs is 0.5%, the corona resistance life of the composite film is the longest, which is about 8 times longer than that of pure PI, realizing the maximum improvement of corona resistance performance for composite at a relatively low addition amount.

A novel dianhydride monomer containing alicyclic ring and amide group was synthesized and further polymerized with several diamine monomers to prepare a series of transparent polyimide films. The properties of the films were tested and characterized. The results show that the synthesized polyimide films have excellent optical properties (T₅₅₀>89%), low coefficient of thermal expansion (CTE<17×10^-6 K^-1), and higher glass transition temperature (T_g>320℃) because of introducing trans cyclohexane and amide into the structure of dianhydride at the same time. The introduction of alicyclic structure decreases the formation of charge transfer complex, which increases the transparency of the polyimide films. On the other hand, the introduction of amide structure decreases the coefficient of thermal expansion.

This article started from the composition and classification of silicone grease to get access to the performance requirements according to the demand of cable accessories. And then the two typical common grease used in cable accessories was described, including normal silicone grease and silicone fluoride grease. At last, the research status of coated silicone grease used for cable accessories and the selecting method of silicone grease were summarized.

The ageing failure of composite insulators in coastal areas has always brought great hidden danger to the safe and stable operation of power grid in coastal areas, and it is also the key and difficult point in the operation and maintenance management of composite insulators. In this paper, the post composite insulators used in substations with different operation years were studied, and the relationship between the hydrophobicity and the operation years was analyzed. The results show that the hydrophobicity is closely related to the high voltage environment, insulator surface orientation, and other factors, and when the operation time of insulators reaches 7 years, the hydrophobicity declines sharply.

A triethoxyacetylenic silane (TEOAS) was synthesized to treat the surface of hydroxylated multiwalled carbon nanotubes (MWCNTs), and then the MWCNTs-T was obtained and characterized. PSA/MWCNTs and PSA/MWCNTs-T composite resins were prepared using solution method by mixing silicon-containing polyarylacetylene (PSA) with MWCNTs and MWCNTs-T, respectively. The thermal conductivity, thermal stability, electric insulation, and bending properties of the PSA/MWCNTs and PSA/MWCNTs-T composites were investigated. The results show that TEOAS was grafted on the surface of MWCNTs successfully, and MWCNTs-T is compatible with PSA matrix. The thermal conductivity of the composites increases with the increase of the mass fraction of MWCNTs and MWCNTs-T. The effect of MWCNTs-T is more obvious, with the mass fraction of 2%, the thermal conductivity of PSA/MWCNTs-T reaches 0.62 W/(m·K), which is 3 times as higher as that of PSA. The introduction of MWCNTs and MWCNTs-T can decrease the thermal stability and bending properties of PSA, the effect of MWCNTs-T is smaller than that of MWCNTs. The glass transition temperature of the PSA/MWCNTs is higher than 500℃, the electrical resistivity of the composite resin decreases linearly with the increase of frequency, while is still higher than 10⁸ Ω·cm at 10⁶ Hz.

Due to artificial operation and poor sealing performance during the assembly of oil-related equipment in some substation, the shed on composite insulator used in the auxiliary equipment may deform due to the contact with insulating oil. In order to further study the influence of insulating oil on the composite insulator shed and analyze the cause of its deformation, we used insulating oil to treat silicone rubber for shed, and investigated its volume change, chemical structure, hydrophobicity, mechanical properties, and electrical properties. The results show that the insulation oil increases the volume of silicone rubber, while decreases its elongation at break, tensile strength, tear strength, and hardness, which relates to the swelling of silicone rubber. According to the study, using oil dropping device and insulator to simulate the deforming process of the shed, we propose a method of recovering the deformation of the shed by heat treatment.

During the operation of high-frequency transformer, oil-paper insulation bears severe electric and thermal stress, and the insulation system is easy to fail prematurely. In order to study the effect of high frequency pulse voltage on the discharge characteristics of oil-paper insulation, we built a partial discharge (PD) test platform under high frequency pulse voltage to conduct partial discharge tests. The characteristics of partial discharge of oil-paper insulation under highfrequency voltage was studied and compared with the characteristics under power frequency voltage. The results show that under high frequency voltage, partial discharge mainly occurs at the rising and falling edge of voltage, the PD amplitude is much higher than that under power frequency, and there is an frequency-induced inflection point near the frequency of 10 kHz. Moreover, oil-paper insulation is punctured under high frequency impulse. The reason is that the rapid voltage rise rate caused by high frequency changes the local field strength and high frequency electrothermal coupling effect at the defect position, resulting in the change of the partial discharge intensity.

Optical fiber sensing technology has the advantages of anti-electromagnetic interference, small volume, multiplexing, etc. Intelligent on-line monitoring for power equipment by optical fiber sensing technology has become a new trend of power grid development. In this paper, the research progress of several optical fiber sensing technologies in the field of power equipment monitoring were reviewed, including fiber grating sensing technology, scattering distributed optical fiber sensing technology, fluorescent optical fiber sensing technology, and interferometric optical fiber sensing technology. From the aspects of temperature monitoring, strain monitoring, partial discharge monitoring, fiber-optic current sensor, pollution monitoring, and hydrogen monitoring, the application as well as the advantages and disadvantages of different sensing technologies in different power equipment were explained. At last, the development direction of the engineering and networking application of optical fiber sensing technology was proposed.

In order to study the effect of stress cone on the accumulation of space charge, we designed a cable model with stress cone structure. A platform was built to perform the combined electric and thermal ageing on the model cable. The distribution of space charge before and after ageing was measured by pulse electro-acoustic method, and the accumulation of space charge at different axial and radial positions was compared. The results show that more space charge accumulates at the root of the stress cone, and the accumulated space charge mainly distributes on the outside of the insulation layer of the cable. To make a preliminary explanation of this phenomenon, it is believed that the electric field distortion caused by the stress cone makes the space charge easy to accumulate in this area.