Peng Zongren

Research on transient electric field distribution of converter transformer valve side winding under polarity reversal

Converter transformer is the most important equipment in DC transmission system. Polarity reversal is a special working condition of converter transformer in service, and the polarity reversal test is also generally regarded as the most important experiment for converter transformer. In the calculation of the polarity reversal field, the permittivity and conductivity of the each dielectric material should be given. The insulation materials of converter transformer are oil and pressboard. The resistivity of pressboard is anisotropic, there is a great difference value between the directions of through and along the paper layer. Different polarity reversal durations have different experiment results during polarity reversal test process. In this paper, the electric field distribution of converter transformer valve side winding in a practical ±800 converter transformer under polarity reversal test voltage was calculated with field-circuit coupling method. The anisotropism of paperboard resistivity was taken into account during the calculation process. In order to analyse the influence of polarity reversal duration to the distribution of electric field, several different polarity reversal durations were set to contrast. The results of this paper could provide references for the research and design of converter transformer.

Formation and Distribution of Space-Charge in Cross-Linked Polyethylene

The formation and distribution of space-charge in a cross-linked polyethylene (XLPE) sample are investigated by means of pressure wave propagation, infrared spectroscopy and electrostatic force microscopy (EFM). The related mechanism of space-charge distribution and the structure of XLPE are discussed. The EFM images show that quite large quantitative space-charges locate at the surface of spherulites.

Aging Characters Analysis of Composite Insulators

In this paper, a composite insulator with seven years running history at power grid was taken into account. At first, an electric field was computed through finite elements method and electric field difference at different shed was compared. Secondly, through SEM photos of silastic sections from different sheds, microcosmic structure character of silastic aging under electric and ultraviolet effect was analyzed; through contrasting microcosmic structure of side surface with top and bottom surface of shed, the rules of electric aging and electric erosion was studied; through energy spectrum analysis, the possibility of surface contamination moving into inner of silastic was studied. The results gotten from this paper are positive and helpful for advanced aging studying of composite insulator and optimization design of insulator for anti-aging.

Influence of addition of hydroxyl-terminated liquid nitrile rubber on dielectric properties and relaxation behavior of epoxy resin

Epoxy resin is one of the most popular insulation materials used in power equipment, whereas it is easy to crack when used in some large equipment due to its poor toughness. In order to increase the toughness of epoxy resin, adding liquid rubber into epoxy resin is a common way employed in industrial production. However, the dielectric properties of epoxy resin changes while the toughness increases. In this paper, hydroxyl-terminated liquid nitrile rubber (HTBN) was used as the filler to toughen the epoxy resin. Through comparing and analyzing the glass transition temperature and permittivity of composites with different filler contents, the influence of rubber particles on the mechanical and dielectric properties of epoxy resin was studied. The results indicate that the glass transition temperature decreases with the increase of filler content. When HTBN content is more than 15%, the toughness of composites is enhanced. With the increasing content of HTBN, the volume resistivity decreases, while the relative permittivity and dielectric loss tangent increase. The breakdown strength reveals little change. The addition of HTBN has a certain effect on the dielectric relaxation behaviors of epoxy resin, and the dielectric relaxation which caused by the interfacial polarization between rubber particles and epoxy matrix appears at the temperature above 5 °. Therefore, the influences of fillers on the dielectric properties should be considered while toughening the epoxy through adding liquid rubber during the formula design.

Voltage-sharing performance of MOA for 1000kV UHV GIS

In this paper, the voltage-sharing performance of MOA (Metal-oxide Surge Arrester) for 1000kV UHV GIS is discussed using the secondary development of the finite element and boundary element numerical method by 3D simulation, ensuring the non-uniform rate of the voltage distribution can be controlled within 10%, reaches the requirements of electric field distribution and the voltage distribution on the resistors for the Ultra-high Voltage project. In the end, the reasonable configuration parameter of grading ring of tank type MOA for Ultra-high Voltage GIS is provided.

Electrical field influence of metallic particles and inner voids on UHV AC GIS spacer

Gas insulated switchgear (GIS) has been widely applied in substation because of its high reliability and compactness. GIS spacers are critical components which influence the insulation level of GIS, playing supporting conductor, isolating chamber and electrical insulation roles. Defects in spacer like voids, metallic particles, protrusions or pits introduced during manufacturing, installation and operating process are considered to contribute to degradation of GIS. The defects are more likely to cause insulation failure when considering UHV AC GIS spacer. In this paper, a basic calculation model of a part of GIS was established using ANSYS with an epoxy spacer included. Two kinds of defects were studied. Metallic particles with different sizes sticking to or floating on the surface of spacer were simulated. The laws of electrical field distribution with size and position of metallic particles were summarized. Voids of different sizes were modeled in different positions in the epoxy body of spacer to investigate how they affect electrical field distribution. Results indicated that electrical field would be enhanced at the three point of epoxy, metal and SF6 for sticking particles. Floating particles would enhance electrical field of nearby surface of spacer. Sizes and positions hardly influenced the enhancement degrees of inner voids.