Through adding 2-methyimidazolium cobalt (ZIF-67) nano-fillers into 3,3′,4,4′-biphenyltetracarboxylic anhydride (BPDA) - 4,4′-diaminodiphenyl ether (ODA) type polyimide (PI) matrix, we prepared a PI/ZIF-67 three-layer composite films with sandwich structure. The structure of ZIF-67 and PI/ZIF-67 three-layer composite films were characterized by FTIR, XRD, and SEM, and the effect of ZIF-67 content on the thermal stability and dielectric property of the composite films was studied. The results show that when the mass fraction of ZIF-67 is less than 10%, the initial decomposition temperature of composite film is higher than 500℃, which shows good thermal stability. The dielectric constant of PI/ZIF-67 composite films is obviously lower than that of PI. When the mass fraction of ZIF-67 is 10%, the dielectric constant of PI/ZIF-67 composite film decreases by 50%. When the mass fraction of ZIF-67 is 5%, the dielectric constant of PI/ZIF-67 composite film decreases by 71%. When the mass fraction of ZIF-67 is less than 10.0%, the dielectric loss of PI/ZIF-67 composite film is slightly higher than that of pure PI.

Partial discharge (PD) caused by interface defects is one of the main causes of interface breakdown, but the initiation and evolution of interface PD of cable accessories is not clear now. In this paper, the electric field distribution of actual cable accessory interface was simulated and analyzed. According to the calculation results of electric field, an interface test unit was designed and manufactured using the built-in electrode method, and then the test unit were conducted partial discharge initiation experiments. The results show that the electric field distribution of the interface test unit is similar to that of the actual cable accessory interface, and the PD development law obtained by the interface test unit is the same to that of the actual cable accessory interface. The interface test unit can effectively simulate the electric field of actual cable accessory interface, and at the same time, the introduction of metal electrodes were avoided into the test interface. It is concluded that the test unit can be used to study the initiation and evolution of PD at the cable accessory interface.

Three typical stator defect models were fabricated using the generator stators in actual operation, and then conducted accelerated thermal ageing tests. The difference on partial discharge characteristics of the three typical defects before and after ageing was studied using pulse current method. The results show that after ageing, the partial discharge inception voltage (PDIV) of the model with internal defect increases, while the PDIV of the model with slot discharge and end discharge decrease, this is because there are large number of cracks on the epoxy mica tape insulation surface due to thermal ageing. The phase resolved partial discharge (PRPD) pattern of internal discharge model is symmetrical, and the width of discharge phase becomes narrow after thermal ageing; the PRPD pattern of slot discharge model changes from hill shape to semi ellipse shape after thermal ageing, and the discharge density increases significantly; the PRPD pattern of end discharge model shows the characteristics of corona discharge, and the discharge characteristics at the positive and negative half-cycle of alternating current is obvious asymmetry.

Fog chamber is an indispensable part of artificial simulation for insulator pollution test. In this paper, the influence of pollution degree and humidity on the discharge characteristics of porcelain insulator in fog chamber environment was studied in combination with simulation and test. At first, the electric field distribution of clean and dirty insulators in 110 kV transmission line with and without fog chamber was simulated by the software Comsol Multiphysics. And then a scheme to make the electric field near the high voltage end of insulator with and without fog chamber approximate by reducing the test voltage with fog chamber was proposed. At last, tests were carried out with the voltage obtained by simulation. The results show that compared with the condition without fog chamber, the electric field around the clean insulator is larger at the high voltage end and smaller at the low voltage end under the condition with a fog chamber. Moreover, the electric field around the insulator in the fog chamber increases with the increase of pollution degree. The simulation results are verified by the test results, with the increase of the insulator pollution degree and the humidity, the number of discharge photons increases. This paper proposes a scheme to re-duce the test voltage in the artificial fog chamber to optimize the insulator pollution discharge test, and the test effect is more consistent with the actual field application status.

In view of the burning loss and fire risk of T-type cable plug used in high voltage devices when the conductor is overheating, we built an experimental platform for the pyrolysis of rubber material for T-type cable plug , and the pyrolysis behavior of T-type cable plug was studied based on FTIR method. The results show that in the temperature range of 80-260℃, the pyrolysis characteristic components of T-type cable plug are silicone grease, CO₂, and H₂O. The escape temperature of CO₂ and H₂O is 80℃, and their concentration reaches the maximum value at 200℃, while the escape temperature of silicone grease is above 200℃, and the escape temperature increases with the increase of temperature. The results of non-isothermal thermogravimetric analysis show that the weight loss rate at 305℃ is 2.50%.

An aramid 1313 fibrid was prepared by precipitation method, and its morphology structure and properties were characterized by fiber length test, thermogravimetric analysis (TGA), X-Ray diffraction (XRD), scanning electrical microscopy (SEM). The dewaterability of aramid 1313 fibrids and chopped fibers in the papermaking process was evaluated by dewatering time, and the mechanical properties and electrical insulation properties of the paper were studied. The results show that with the increase of molecular weight of aramid 1313 fibrid, the average length of fibrids increases, and the tensile strength, elongation at break, tearability, and insulating properties of the paper increase. The fibrid is non-crystalline structure. With the increase of molecular weight, it becomes to film structure, and the thermostability increases. However, the thermostability of chopped meta-aramid fiber is still higher than that of aramid 1313 fibrids.

In order to discover the bonding mechanism of self-adhesive silicone rubber tape, we prepared a self-adhesive silicone rubber tape through the reaction of boric acid and methyl-vinyl silicone rubber. The variation of bonding force at interface of self-adhesive silicone rubber tape with temperature and soaking time was traced by tensile tests, and the self-fusion effect was verified. A physical model of self-fusion effect was proposed with the help of infrared spectrum test. The results show that when the content of boric acid in the reaction system is 2.5%, the self-adhesive tape has the highest initial bonding force. When silicone rubber has the molecular structure of short chain boron-containing siloxanes imbedded in long chain siloxane network, the well contacted silicone rubber interfaces can bond through complexation between boron and oxygen atoms in the boron-containing siloxanes, and the bonding force is stronger than the cohesion among polysiloxane molecules. The complexation can not complete instantly, and the higher the temperature of interface, the shorter the time of complexation. Under 60℃, the complexation strength can reach the optimum value within 12 hours.

Natural contamination tests were conducted on insulators from ultra-high voltage (UHV) converter stations under four typical climate conditions, including extreme arid, semi-arid, semi-humid, humid. The inhomogeneous coefficient characteristics of contamination of the insulators were obtained, and the effects of diameter, layout, and AC/DC voltage on the contamination performance of insulators for converter stations were analyzed. The results show that the equivalent salt density (ESDD) ratio of the top and bottom surface of the insulator from Tianshan station, Lingzhou station, Zhongzhou station and Suzhou station is 1.56, 0.41, 1.26 and 1.45, respectively. Compared with the vertical post insulator, the horizontal arrangement of the wall bushing insulator has a larger area exposed to the rain, and there is obvious washing effect by the rain on the pollution of the insulator surface. The ESDD of insulators arranged horizontally at Lingzhou Station and Suzhou Station is 0.64 and 0.63 times smaller than that of insulators arranged vertically. The difference of AC/DC insulator pollution accumulation is mainly determined by electric field force, pollutant particle size, and wind speed. The AC/DC pollution accumulation ratio of post insulators from Tianshan Station, Zhongzhou Station, and Suzhou Station is 1.12, 0.84 and 0.52, respectively. With the increase of the diameter of post insulator, the ESDD increases gradually. The research results can provide data support for the external insulation design of UHV converter stations in China.

SF₆ is often used in GIE as an insulating medium, it will decompose when overheating or appearing partial discharge inside GIE, the decomposition products, such as SO₂, SOF_2, SO₂F₂, H₂S, and CO will produce after further reaction. In this paper, the components H₂S and CO were quantitatively measured by photoacoustic spectroscopy detection technology, and the factors affecting photoacoustic signal were discussed theoretically. A photoacoustic spectrum experiment platform was built, and the gas was measured quantitatively based on the photoacoustic effect. Appropriate gas absorption lines were chosen as characteristic spectrum line to avoid the potential cross-interference of other gas components. According to the results of HITRAN simulation, the characteristic spectrum line of H₂S was chosen as 6 336.6 cm^-1, and the characteristic spectrum line of CO was chosen as 6 380.3 cm^-1. The results show that the linearity between the gas concentration of CO and H₂S and the amplitude of pure photoacoustic signal is extremely high, which suggests that the gas concentration can be accurately calculated through the measurement of photoacoustic signal value of gas. With the background gas of SF₆, the lower limit of detection for CO is 9.88×10^-6, and the lower limit of detection for H₂S is 1.75×10^-6.

Basin insulator is the core component of gas insulated metal transmission line (GIL) equipment. A large amount of charge will accumulate on the surface of insulators under long-term effect of unipolar DC electric field, resulting in the electric field distortion at the solid-gas interface, which leads to surface flashover of insulators easily and reduces the insulation performance of equipment. On the basis of relevant research results of DC insulators, this study restrains the accumulation of surface charges by reasonably controlling the surface field strength of insulators and increasing the resistivity of insulating materials. The structure design was optimized by simulation methods, and the insulator was prepared by casting, then dielectric tests and mechanical performance tests under AC and DC stress was carried out and passed, which verified the correctness of design.