With the rapid development of UHV DC transmission projects, a large number of transmission lines need to cross high altitude areas. The reduction of corona inception field strength in high altitude areas makes corona discharge more intense. The resulting electromagnetic environment problems such as audible noise and radio interference are one of the key factors restricting the development of UHVDC transmission projects. In order to study the influence of altitude on the corona effect of negative conductor, four different altitude points in the range of 1120m-4320m were tested by using mobile small corona cage. The current pulse, audible noise and radio interference level of 0.8mm diameter fine copper conductor were collected. Through the analysis of the experimental data, the following conclusions are obtained: with the increase of altitude, the amplitude and number of current pulses increase. The audible noise and radio interference levels increase with the increase of altitude. The conclusions obtained in this paper have certain reference significance for the control of electromagnetic environment of UHVDC transmission project.
High altitude areas often lead to more serious corona discharge, and produce more serious electromagnetic environment problems such as audible noise and radio interference, which greatly restrict the selection of transmission lines and cause certain environmental problems. In order to study the characteristics of audible noise in high altitude areas, Yangbajing Town, Lhasa, Tibet Autonomous Region, China (altitude :4320m) and Wuhan city, Hubei, China(altitude :20m). The audible noise characteristics of three different lengths of discharge fine copper wires in high altitude areas (0.8mm, 1.0mm, 1.2mm) were tested. The influence of applied voltage and wire diameter on corona audible noise in plain area and high altitude area is analyzed. The research can provide important data reference for the study of electromagnetic environment in high altitude areas
In this paper, a magnetic field sensor with simple fabrication, high sensitivity and wide measurement range is proposed. The sensor consists of fiber Bragg grating, sensitivity enhancement structure (SES), magnetostrictive particles and epoxy resin matrix. Metal tube with length of 5 mm is glued onto both sides of the grating as SES, and the mental tube is covered with grooves. The FBG with mental tubes is coated with the matrix made of magnetostrictive particles and resin. During the curing process of matrix, a uniform magnetic field with 200mT and parallel to the fiber is applied to make the orientation of magnetostrictive particles constant. It also can make particles have uniform spatial distribution. Firstly, by comparing the performances of sensors made of three different resin without mental tube with the sensor made by gluing FBG onto Terfenol-D rod directly, it is found that the sensor with epoxy crystal adhesive has the highest sensitivity reaching 0.58 pm/mT. Secondly the sensor based on epoxy crystal adhesive with SES is evaluated. Compared with the sensor without SES and gluing diretly, the sensitivity increases 5.17 times to 3.58 pm/mT and the measurement expands ranging from 0 mT to 226 mT.
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