In order to supply more accurate input voltage to the design of insulation structure for variable frequency wind generator, we took the stator winding of permanent magnet synchronous wind generator as the research object, the equivalent circuit model of cable and motor stator winding coil was built by MATLAB software, and the effects of cable length and the pulse width modulation (PWM) pulse rising edge time output by frequency converter on the transient voltage distribution characteristics of motor winding were analyzed. The results show that with the increase of cable length and the decrease of pulse rising edge time, the maximum voltage to ground and inter turn of motor end and winding increases, and the maximum voltage to ground transfers from the middle coil to the first coil. When the pulse rising edge time is 2.0 µs, the voltage distribution in the winding tends to be uniform.

In order to explore the impact of the performance of silicone dry mica tape on the reliability of insulation system of traction motor, we conducted the material basic performance, laboratory simulation of wire rod, and insulation system reliability evaluation on two imported mica tapes and two domestic mica tapes. The results show that the mica tape with less resin and higher air permeability shows a better compatibility with the silicone impregnating varnish. The formed insulation system has a lower thermal dielectric loss factor and a higher curing rate, which improves the breakdown voltage and improves the reliability of the insulation system.

In order to study the ageing characteristics of cross-linked polyethylene (XLPE) cable and explore the microscopic factors affecting the dielectric properties of materials, the XLPE cables with different ageing states were conducted isothermal relaxation current (IRC) and partial discharge (PD) tests. A pure polyethylene molecular chain P₁, an aged polyethylene molecular chain P₂ containing hydroxyl groups, and a further thermal-oxidative aged polyethylene molecular chain P₃ containing carboxyl groups were established, and polyethylene molecules with different ageing states were carried out quantum chemical calculation. The results show that with the increase of ageing time, the time constant of depolarization current and ageing factor A increase, and the trap number and energy level depth in insulating medium increase. Besides, there are more partial discharges with higher magnitude occurring in the aged cable. The carbon-oxygen group generated by thermal oxygen ageing in polyethylene molecular chain is an important reason for the increase of trap number and energy level depth, and the type of functional group will affect the distribution of trap energy level directly. Under the effect of electric field, the stability of the aged polyethylene molecular chain becomes worse, the dipole moment is larger, and the charge transfer is more obvious, which make the charges in the aged cable insulation more likely to be trapped and accumulate, resulting in electric field concentration and increase of partial discharge level.

In order to study the design and selection of the composite insulated cross arm for 35 kV transmission line, the feasibility analysis was conducted from material technology, electrical scheme, and structural scheme, the finite element stress analysis was conducted on the tension and compression rods of composite insulated cross arm, and the practical application of the composite insulated cross arm was verified. The results show that the composite insulated cross arm of 35 kV transmission line, which adopts the winding forming E-glass fiber/epoxy resin composite and the single strut and single cable-stayed structure, can meet the requirements of mechanical properties. The composite insulated cross arm has been in good operation since it is applied in the pilot project.

The aromatic ketone polymer 4-allyloxy-2-hydroxybenzophenone (AOHBP) was selected as voltage stabilizer. In order to inhibit the migration and precipitation of voltage stabilizer in polymer, dicumyl peroxide (DCP) was used as initiator to graft AOHBP on PP, and an anti-degradation additive styrene derivative (St) was added to inhibit the material degradation caused by the grafting process of voltage stabilizer. The physical and chemical properties of the modified material were characterized, and the electrical treeing initiation characteristics and DC breakdown characteristics of the modified material were studied. The results show that the AOHBP can graft on the PP matrix by the free radical reaction initiated by DCP, and the St and AOHBP can inhibit the macromolecular degradation of PP during the grafting reaction process synergistically. The grafting modified PP insulating material can inhibit the initiation of electrical tree and improve the DC electric strength significantly.

On the basis of a new equivalent topology of oil-paper insulation—hybrid model, a variety of model characteristic parameters were extracted to realize the quantitative evaluation of water content in oil-paper insulation. At first, the polarization branch value range of the hybrid model was determined on the basis of parameter coincidence degree by using the measured frequency domain spectrum of oil-paper insulation equipment. And then, the difference between the hybrid model and extended Debye model in reflecting the damp information of oil-paper insulation was compared combined the experimental data and measured data. At last, the effects of water content in oil-paper insulation on the different branch parameters were studied on the basis of hybrid model, and the quantitative relation expression between the parameters and the damp state of oil-paper insulation were established. The results show that when the total number of polarization branch is 5-7, the identification effect of model parameter is better. The hybrid model can express the dielectric response information of oil-paper insulation system more accurately. The extracted model characteristic parameters can realize the quantitative evaluation of water content in insulating paper preliminarily.

A derived diamine monomer of 1,3-bis(4-aminobenzoyoloxymethyl)-1,2,2-trimethylcyclopentane (BABMT) was synthesized from a biomass small molecule natural-(D)-camphor. It was polymerized with aromatic structure dianhydrides (BPDA and ODPA) to prepare semi-alicyclic structure polyimide (PI) films, respectively, and their thermal properties, mechanical properties, optical properties, and solubility were compared with that of the wholly aromatic structure PI films prepared by alicyclic structure diamine (DMB) polymerizing with alicyclic structure dianhydrides (BPDA and ODPA), respectively. The results show that the semi-alicyclic structure PI films have good thermal properties, the glass transition temperature (T_g) is 281℃ and 236℃, respectively, and the 5% weight loss temperatures (T_d5) is not lower than 390℃. At the same time, the semi-alicyclic structure PI films retain good mechanical properties, the tensile modulus is 2.13 GPa and 2.41 GPa, respectively, the tensile strength is 109 MPa and 97.9 MPa, respectively, and the elongation at break is 7.7% and 11%, respectively. Compared with the wholly aromatic structure PI films, the semi-alicyclic structure PI films show better transparency with the transmittance at 500 nm (T₅₀₀) over 78%, and better solubility in common organic solvents. Wide-angle X-ray diffraction results show that all the semi-alicyclic structure PI films present amorphous structure, and their interchain spacing (d) are larger than that of the wholly aromatic PI films.

The dielectric constant and dielectric loss of composite insulating paper can be reduced by doping different content of aramid 1313 (PMTA) in the natural cellulose pulp, but the mechanical properties of composite insulating paper are greatly reduced due to the poor combining ability of two fibers. In order to solve this problem, we studied the improvement effect of low-temperature plasma treatment on the binding capacity of two kinds of cellulose emphatically, and tested and analyzed the properties of the prepared composite insulating paper. The results show that the low-temperature plasma treatment can effectively improve the binding force between the two kinds of fibers, so as to make up for the loss of mechanical properties, and it has little influence on the dielectric and breakdown characteristics of the composite insulating paper. The results of SEM and XPS show that the surface of PMTA fiber after low temperature plasma treatment become rough, the polarity functional group increases, the binding force with cellulose matrix increases, and the voids of composite insulating paper sample decreases significantly. The power frequency relative permittivity of the composite insulating paper prepared by doping low temperature plasma treated PMTA in natural cellulose pulp is reduced, while the AC/DC electric strength and volume resistivity remain unchanged, and the tensile strength and elongation at break are compensated to the maximum.

Considering the equivalence between sequential stress test and constant stress test, we proposed a mixed stress test method that the sample was applied voltage in the order of sequential advance stress-constant stress-sequential advance stress, and then the voltage withstand index n of XLPE flake sample was evaluated by this method combined with Weibull statistical analysis. The results show that the voltage tolerance index n calculated by the mixed stress test is 16.11, the deviation between it and the n evaluated by the constant stress test is 5.36%, and its total evaluation time is shortened by 98.04% than that of the constant stress test, which proves that this method can evaluate the voltage withstand index of XLPE insulation effectively.

In order to study the high temperature resistance of hydrophobic properties of PRTV coating and the difference of thermal ageing characteristics between epoxy resin coated with PRTV coating (EPTL) and epoxy resin uncoated with PRTV coating (EP). The EPTL and EP were conducted thermal ageing tests at 80, 100, 120℃, and their dielectric properties, internal microstructure, thermal stability, and hydrophobic properties were compared and analyzed. The results show that after the thermal ageing tests under different temperature, the dielectric properties and thermal stability of EPTL are better than that of EP, and the internal microstructure is more complete. Although EPTL still shows strong hydrophobic properties after ageing, the contact angle decreases rapidly, which indicates that the hydrophobicity of PRTV coating is affected by high temperature greatly.