Zongren Peng

Electric field calculation and grading ring optimization of composite insulator for 500kV AC transmission lines

With finite element method, this paper established a static three-dimensional model to calculate the potential and electric field distribution of composite insulator for 500kV AC transmission lines. By changing the mounting height, diameter and caliber of the grading ring installed on the composite insulator, the electric field distribution of the insulator could be controlled visually. After analysis and comparison of the electric field strength on the surface of grading rings and the field distribution curves along the insulator with variable grading ring parameters, the reasonable grading ring configuration was recommended. It can improve the electric field distribution of the composite insulator and also reduce the electric field strength on the surface of grading rings and end-fittings. The conclusions of this paper have important engineering application value for 500kV AC transmission lines construction.

Electric Field Calculation and Structural Optimization of ±800kV Converting Transformer Bushing Outlet Terminal

Converting transformer bushing is the key equipment to develop the ultra-high voltage power transmission project. The electric field distribution in the bushing is correlative to resistivity, temperature and etc. Especially, the electric field distribution relatively centralizes on the bushing outlet terminal for its complex structure. In this paper, finite element analysis (FEA) is used to calculate the electric field distribution of plusmn800 kV converting transformer bushing outlet terminal in the condition of varied structure, varied material resistivity and varied barrier position. The following conclusions could be drawn: (1) Selecting proper materials and using paper, oil and molding with approaching resistivity is useful to improve the electric field distribution on the bushing outlet terminal (2) Further more, the method of setting suitable barrier on the bushing outlet terminal, is effective to improve the electric field distribution on the bushing outlet terminal

Effect of temperature on space charge characteristics in epoxy resin

Epoxy resin has been widely used as the dry-type insulation in high voltage direct current bushing. The temperature of the central conductor can go up to 90-105°C when working at the rated power flow. Thus, the inner insulation made of epoxy resin sustains these high temperatures. In order to study the effect of temperature on the dielectric performance, the space charge characteristics of epoxy resin at different temperatures (21, 40, 60, 80 and 100°C) have been studied with an improved pulsed electro-acoustic set-up. Moreover, the temperature dependence of the volume resistivity has also been measured. Only homocharge close to the electrodes can be found in all tests. The higher the temperature, the more serious the electric field distortion is in the bulk of a sample. The threshold for space charge accumulation decreases remarkably with increasing temperature. Both the apparent trap-controlled charge mobility and the dc conductivity show similar positive temperature dependence, which increases with the elevation of temperature, resulting in different charge decay characteristics at different temperatures. The apparent trap depths corresponding to different temperatures have also been obtained.

The Influence of Charged Sand Particles on the External Insulation Performance of Composite Insulators in Sandstorm Condition

In sandstorm condition, sand particles with different size collide with each other, resulting in electrification of sand particles and a strong electric field will form. When the charged sand particles move to the neighborhood of line insulators, they will impact the external insulation performance of line insulators. In this paper, electric field distribution of composite insulators with the existence of charged sand particles is calculated by means of finite element method. The result indicates that charged sand particles distort the electric field distribution around insulators obviously; the degree of aberration varies with the amount of charge that the sand particles take; when charged sand particles suspend on the surface of sheds or sheaths, these parts will bear very high field stress; when the charge-to-mass ratio of charged sand particles reaches a certain extent, corona discharge will happen in the ambient air, this will accelerate the ageing of composite insulators

Two frameshift mutations of the double-stranded RNA-specific adenosine deaminase gene in Chinese pedigrees with dyschromatosis symmetrica hereditaria

Dyschromatosis symmetrica hereditaria (DSH) (also called ‘reticulate acropigmentation of Dohi’ or ‘symmetric dyschromatosis of the extremities’) (MIM 127400) is characterized by a mixture of hyperpigmented and hypopigmented macules and is localized on the back of the hands and feet. Many patients with DSH also have small freckle-like pigmented macules on their faces. The lesions usually appear in infancy or early childhood, commonly stop spreading before adolescence, and last for life. DSH has been reported mainly in Japan, but a similar condition has been reported among Chinese; about 34 pedigrees including 227 cases and two sporadic cases from China have been reported since 1980. Several cases of DSH have been reported among Koreans, Indians, Europeans and South Americans. No racial difference in the condition has been observed, but the disorder might be distributed mainly in East Asia. The DSH locus has been mapped to chromosome 1q21 and then, in 2003, pathogenic mutations were identified in the double-stranded RNA-specific adenosine deaminase (DSRAD) gene. DSRAD spans 30 kb and contains 15 exons. It encodes RNA-specific adenosine deaminase composed of 1226 amino acid residues, with a calculated molecular mass of 139 kDa. In this study, we performed mutation detection of the DSRAD gene in two typical Chinese families with DSH in which two heterozygous mutations were identified.

Characteristics of dust deposition on suspended insulators during simulated sandstorm

In the present work, we studied the dust deposition characteristics on suspended insulators under the simulated sandstorm conditions in a laboratory. Based on the simulation experiments, the basic dust deposition and distribution characteristics were studied, such as the difference of deposition among sheds at different locations, the difference of deposition between large and small sheds, the relationship between deposition quantity and flow speed of air and dust as well as the relationship between deposition quantity and experimental duration. Our study provides important insights for more advanced studies on this topic in the future.

Investigation of the effects of nano-filler on dielectric properties of epoxy based composites

In this paper, epoxy resin based composites filled with nano-Al<inf>2</inf>O<inf>3</inf> and nano-SiO<inf>2</inf> individually were fabricated. The relationships between the dielectric properties and fillers properties (contents and particle size etc.) were investigated. The results showed that, for nano-SiO<inf>2</inf> filled epoxy, relative permittivity(ɛ<inf>r</inf>) and loss factor(tanδ) increased obviously when filler content was lower than about 0.1wt.%, continue to increase filler content, it appeared a minmium value while filler increased to 0.3wt.%, and above this loading, ɛr and tanδ start to increase again increased with increasing filler content. While for the composites with nanosized Al2O3, a similar phenomenon was observed. The tanδ of epoxy/ micro Al<inf>2</inf>O<inf>3</inf> composites was larger than that of epoxy/ nano Al<inf>2</inf>O<inf>3</inf> composite. Both ɛ<inf>r</inf> and tanδ of Al<inf>2</inf>O<inf>3</inf> filled composites were larger than that of SiO<inf>2</inf> filled composites for its high inherent permittivity.

Study on the voltage-sharing performance of porcelain insulators on 750kV compact double circuit transmission line

Having three-phase conductors arranged in inverted-delta mode in the same tower window,750kV compact double circuit transmission line, which is built in China for the first time, has the seriously distorted voltage and electric field distribution of insulator strings, because of great mutual influence among three phases due to small phase spacing, so it is important to carry out the research on voltage-sharing performance of porcelain insulators on it. In this paper FEA (finite element analysis) method was utilized to calculate the distribution of voltage and electric field of porcelain insulators on 750kV compact double circuit transmission line, and the mutual influence among three phases was considered. Meanwhile, the influence came from the conductors, tower and external environment was fully considered. By optimizing the structure parameters of grading ring, the influence, came from diameter, caliber and position of grading ring, on voltage distribution and electric field was calculated and analyzed. Based on the analysis above, reasonable configuration scheme of grading ring was proposed. Finally the calculation results were compared with the experimental ones, and the results showed the feasibility of FEA method in voltage distribution calculation of porcelain insulator strings, which provided evidence for the design of 750kV compact double circuit transmission line.

Effects of silane coupling agents on the electrical properties of silica/epoxy nanocomposites

Effects of surface modification agents on the properties of silica (SiO2) /epoxy resin (EP) nanocomposites were studied for the significant impacts of the interface structure between the fillers and resin matrix. The surface modification agent of KH550, KH560 and KH570 were grafted to the surfaces of SiO2 fillers. The original and modified SiO2 fillers were characterized by FTIR and TG. Nanocomposite samples were prepared by solution blended process, using 0.3 wt% SiO2 as filler and epoxy resin as polymer matrix respectively. DSC analysis was performed to investigate the glass transition temperature (Tg). Dielectric spectroscopy and breakdown tests were conducted to measure the dielectric permittivity, dielectric loss and breakdown strength. The results show that SiO2 can be grafted with KH550, KH560 and KH570 effectively. Compared with neat epoxy, the Tg and breakdown strength of nanocomposites increased. Influences on the dielectric permittivity were found, depending on the interface between SiO2 fillers and resin matrix. In terms of Tg, breakdown strength and dielectric loss, the KH550 and KH560 modified nanocomposites performed better than the KH570 modified nanocomposites, which is due to the amino and epoxy group on the molecular structure of KH550 and KH560 respectively. These chemical groups played positive roles in cross-linking reaction and building better interfaces for nanocomposites.

Study on law of negative corona discharge in microparticle-air two-phase flow media

To study the basic law of negative corona discharge in solid particle-air two-phase flow, corona discharge experiments in a needle-plate electrode system at different voltage levels and different wind speed were carried out in the wind tunnel. In this paper, the change law of average current and current waveform were analyzed, and the observed phenomena were systematically explained from the perspectives of airflow, particle charging, and particle motion with the help of PIV (particle image velocity) measurements and ultraviolet observations.