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.

Partial discharge inception voltage (PDIV) detection is an essential test method for evaluating the insulation performance of random wound inverter-fed motor stators. As an important parameter of pulse-width modulation voltage, the effects of pulse width on the PDIV of interturn insulation and interphase insulation in random wound inverter-fed motors are noteworthy. In this paper, the PDIV distribution laws of interturn insulation and interphase insulation in motor under different pulse widths were studied in the frequency of 50 Hz, rise time of 75 ns, and pulse widths within of 0.5-20 μs. The results show that when unipolar pulse square waves are input into random wound inverter-fed motors for PDIV testing, the overall trend of PDIV decreases as the input pulse width increases. Due to the combined effect of overvoltage from the rising and falling edges of short pulses, a turning point occurs in PDIV at a pulse width of 4 μs. It is necessary to consider the effects of pulse width and overvoltage and select appropriate pulse widths to obtain conservative values of stator insulation PDIV when conducting the PDIV test of interturn insulation and interphase insulation in random wound inverter-fed motor under unipolar pulse.

In order to improve the solution processability of traditional thermoplastic polyimide (TPI) and enhance its adhesion and heat resistance, several soluble thermoplastic polyimide (TPI) resins were prepared from different commercial dianhydride monomers and self-made diamine monomers with pyridine and diphenyl ether structures and active phenol side groups or benzene side group in the main chain through the two-step method. And then the corresponding TPI films and flexible copper clad laminates (FCCLs) were prepared. The properties of TPI resins were analyzed by solubility test and gel permeation chromatography (GPC). The structure, water absorption, mechanical properties, and dielectric properties of TPI films were tested, and the related properties of the FCCLs were also tested. The results show that all the TPI resins can dissolve in strong polar organic solvents such as NMP, and the glass transition temperature (T_g) and 5% thermal weight loss temperature (T_5%) of the corresponding films are in the range of 236.8-325.6℃ and 508.7-553.7℃, respectively, and the residue rate at 800℃ (R₈₀₀) is higher than 64%. The coefficient of thermal expansion (CTE), tensile strength, elongation at break, and water absorption is in the range of 56.36×10^-6-78.30×10^-6℃^-1, 64.93-109.18 MPa, 9.09%-24.60%, and 0.74%-3.75%, respectively. The dielectric constant and dielectric loss of TPI-4 with better comprehensive properties are also lower than that of other samples, and the peeling strength of the corresponding FCCL reaches 0.95 N/mm, but it can only pass the floating welding test at 288℃ for 10 seconds. In addition, the polar phenol side group in TPI-4 not only ensures its organic solubility, but also significantly enhances its heat resistance and mechanical strength, and also reduce its CTE. The existence of reactive phenol side groups provides great convenience for the subsequent chemical modification of TPI. By adding a small amount of cyanate ester resin (CE01) to modify the TPI, the peel strength and the floating welding resistance of the responding FCCLs can be obviously improved.

Photosensitive polyimide (PSPI) is widely used in electronics, microelectronics, optical display, and other fields. Foreign companies attach great importance to the patent protection of PSPI material formulas and applications. In this paper, the PSPI patents applied by Toray Industries Inc. in China were taken into research, and the changes in the number of patent applications, legal status, technical subject distribution, and other key information were analyzed in detail. Through combining with Toray's representative PSPI products and their applications, the technical development, patent protection strategy, key points of patent technology of Toray were clarified. Based on the above analysis, the technology development trends and application direction of PSPI materials were explored and presented.

Four kinds of copolymerized polyimide (PI) membranes were prepared through thermal imidization method after solution polymerization between two kinds of self-made diamine monomers 9,9′-bis[4-(4-amino-3-hydroxyphenoxy) phenyl] fluorene (BAHPPF) and 4-(4′-tertbutyl)phenyl-2,6-di(4′-aminophenyl)pyridine (TPAPP) and 4,4′-(hexafluoroisopropene)phthalic anhydride (6FDA), and the molar ratio of BAHPPF and TPAPP is 9∶1, 8∶2, 7∶3, and 6∶4, respectively. Then the corresponding copolymerized thermal rearrangement (TR) membranes were obtained after heat treatment at 450℃. The thermal, mechanical, and gas separation properties of the membrane materials were measured. The results show that the glass transition temperature of the copolymerized PI membranes is around 350℃. As the molar ratio of TPAPP increases, the tensile strength of the copolymerized PI membranes decreases. After thermal rearrangement, the mechanical properties of the copolymerized TR membranes decrease significantly, while the d values increase. When the molar ratio of BAHPPF and TPAPP is 8∶2, the copolymerized TR membrane exhibits the best gas permeability, and the permeation coefficients for H₂, CO₂, O₂, and N₂, is 346.4, 304.5, 72.43, and 13.34 Barrer respectively. Meanwhile, the O₂/N₂ separation performance of the four TR membranes is close to the Robeson upper limit in 2008.

A series of fluorinated polythioetherimide films were synthesized by copolymerization using 4,4′-diaminodiphenyl sulfide (SDA) and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP) as diamine monomers, and 4,4′-biphenylene ether dianhydride (ODPA) as dianhydride monomer. The thermal, electrical, optical properties, and water absorption of the PI films were tested. The results show that the PI films have good thermal, dielectric properties and optical transparency. The glass transition temperature of the film is in the range of 240.7-251.6℃, the 5% and 10% heat loss temperature is above 480℃ and 514℃, respectively, and the residual carbon rate reaches 50% at 800℃. Under the frequency of 1 MHz, the dielectric constant of the PI films are 2.27-2.99, the dielectric loss factors are 0.004 7-0.005 6. The highest transmittance of the films reaches 88.75% in the range of visible light, and the water absorption rate is 0.95%-2.26%.

Firstly, a Y-shape diamine monomer 4-(4′-tertbutyl)phenyl-2,6-di(4′-aminophenyl)pyridine (TPAPP) containing pyridine ring structure and tertbutyl group was synthesized. Then, it was polymerized with 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6FAP) and 4,4′-(4,4′-isopropyldiphenyloxy)bis(phthalic anhydride) (BPADA), and a series of copolyimide (PI) films were prepared by thermal imidization. The structure and optical, mechanical, and thermal properties as well as solubility of the PI films were investigated by infrared spectroscopy, X-ray diffraction, UV visible spectra, tensile tests, dynamic thermo-mechanical analysis, thermogravimetric analysis, and solubility tests. The results show that as the molar ratio of TPAPP increases, the optical transparency and glass transition temperature of the copolyimide films exhibit an increasing trend. When the molar ratio of diamine and dianhydride is 5:5, the copolyimide film shows the best mechanical properties, with the tensile strength of 144.9 MPa, the Young's modulus of 3.4 GPa, and the elongation at break of 9.3%. In addition, these copolyimides demonstrate good solubility in aprotic polar solvents.

In order to study the influence of different interface pressure on the electric field distortion of the composite interface of crosslinked polyethylene/silicon rubber (XLPE/SR) insulation in the cold shrinkable cable intermediate joint, a simulation model of 35 kV cold shrinkable cable intermediate joint was established by the finite element simulation software. The electric-thermal-force field of the composite interface without defects and with metal impurities, circumferential scratches, and longitudinal scratches was simulated and calculated. The results show that the interface pressure has different effects on the joint deformation and electric field strength distortion under different conditions. The joint deformation with longitudinal scratch is more significant, and the field strength distribution at the defect is more obviously affected by the interface pressure. The field strength of the shielding tube is inversely proportional to the interface pressure, and the field strength of the stress cone in the joint with longitudinal scratches is directly proportional to the interface pressure. The overall field strength of the insulation composite interface except for the defects decreases with the increase of the interface pressure.

With the constant updating of flexible display devices, the researches on colorless transparent polyimide (CPI) films as substrate materials have attracted considerable attention. In order to solve the inherent contradictions among optical performance, high-temperature resistance, dimensional stability, and mechanical properties of CPI, we synthesized a series of semi-aromatic CIP films with side chains containing benzimidazole by copolymerization using cyclobutanetetracarboxylic dianhydride (CBDA) as the dianhydride monomer, 2,2′-bis(trifluoromethyl)-4-diaminobiphenyl (TFMB) and 2-(3,5-diaminophenyl)-benzimidazole (BBIA) as diamine monomers. The influence of hydrogen bonding, free volume, and main chain structure on the properties of films was systematically investigated by the Materials Studio software simulation and experimental results. The results show that the prepared CPI films have excellent optical transparency, thermal resistance, and mechanical properties. The average transmittance of CPI films in wave length of 380-780 nm is higher than 85%, the glass transition temperature (T_g) is above 400℃, the linear coefficient of thermal expansion (CTE) is 15×10^-6-17×10^-6 K^-1, the maximum tensile strength is 165 MPa, and the modulus is in the range of 3.7-5.2 GPa.

In order to improve the solubility and meltability of polyimide (PI), a series of addition thermosetting fluorinated poly(imide-siloxane) copolymer resins (ABIS) were prepared from two kinds of synthesized trifluoromethyl-containing aromatic diamine monomers and 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA), besides, aminopropyl-terminated polydimethylsiloxane (APPS) was chosen as flexible segment, and 3-aminophenyl acetylene (APA) was used as reactive end-capping agent. The structure of ABISs were characterized by proton nuclear magnetic resonance spectroscopy (¹H NMR) and Fourier transformation infrared spectroscopy (FTIR). The solubility, rheological behavior of ABIS and the thermal stability of the cured ABIS were further studied. Moreover, ABIS films were prepared by solution filming, and their physical properties were studied. ABIS resin matrix composites (T300CF/ABIS) were prepared by hot pressing using T300 carbon cloth as reinforcement, and their mechanical properties were also tested. The results show that the introduction of siloxane segment and trifluoromethyl group can significantly increase the flowability and solubility of PI resin systems. The introduction of fluorinated diamine decreases the 5% weight loss temperature (T_d5) of the cured ABIS, but its T_d5 is still higher than 425℃. At the same time, the residual yield at 800℃ (Y_r800℃) of ABIS resins reach 26%. The tensile strength and elongation at break of ABIS films are as high as 15.8 MPa and 65.3%, respectively. In the frequency range of 40 Hz-10⁷ Hz, the dielectric constant (ε) and dielectric loss factor (tanδ) of the PI films are 3.21 and 0.01, respectively, which keep unchanged basically. The contact angle of water on the cured ABIS film is 94°. The flexural strength and interlaminar shear strength (ILSS) of T300CF/ABIS composites can be 137.6 MPa and 16.6 MPa, respectively. The synthesized ABIS resin has promising applications in microelectronic devices and flexible heat-protective composites.