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Ionized field strength on the ground level is one of the fundamental electromagnetic environment parameters of ultrahigh voltage direct current (UHVdc) transmission lines. An algorithm of an upstream boundary element method is presented in this paper to calculate the ionized field on the boundary with a high accuracy. The ionized field is generated and measured in an experimental platform with an HV conductor to a grounded cylindrical corona cage. The relations between ionized field strength and applied voltage, conductor position, and conductor diameter are investigated. Calculations show that the relative error of the ionized field on the HV electrode could be reduced to 0.1% when compared with the analytical solution. Ionized field distribution under the typical ±1100 kV UHVdc transmission lines is also analyzed as the application. [ABSTRACT FROM AUTHOR]

The prediction and control methods of radio interference (RI) for HVdc transmission lines passing through high-altitude region are main key factors in design of the HVdc transmission lines. In order to obtain the altitude effect and correction of RI for HVdc transmission lines, four HVdc reduced-scale test lines with the same parameters were built up at 50, 1700, 3400, and 4300 m elevation, respectively. Simultaneously, two HVdc full-scale test lines with the same conductor type of 4 × JL/G1A-500/45 had been set up at altitude 50 and 4300 m as well, respectively. Using these test facilities, a lot of RI measured data were accumulated in a long time span, from Jan. 2010 to Jul. 2014. By analyzing the RI measurement data at different altitude regions, it is indicated that the altitude correction of RI has a nonlinear relation to the altitude. Meanwhile, the RI altitude correction formula for HVdc transmission lines has been proposed in this paper. Using the proposed RI altitude correction formula, the RI levels at high altitude are lower than that predicted by using the RI correction formula of ac transmission lines, which means that it could save a lot of investments at high altitudes. [ABSTRACT FROM PUBLISHER]

The calculation of voltages induced by external electromagnetic fields on multiconductor transmission lines (MTLs) has been the subject of several studies. In this paper, discrete equations for MTLs exposed to incident fields are derived based on the time-domain finite-element method and the backward differentiation formula. Based on these equations, a value-delivery table characterizing the MTLs is presented. Combining this table with modified node analysis formulation, it is convenient for analyzing the responses of transmission lines composed of complex termination networks or complex transmission-lines networks. The validity and efficiency of the proposed algorithm is demonstrated using several examples. Finally, a 1-km 35 kV overhead line above an imperfectly conducting ground is studied, and the influences of ground wire and a metal-oxide arrester to the lightning-induced voltage are both discussed. [ABSTRACT FROM PUBLISHER]

Audible noise (AN) is very important for the construction of transmission lines for the sake of the environment. Especially, at high-altitude areas, it has become a key technical factor deciding conductor types and tower structures. In order to determine the altitude effect and the correction of AN for HVdc transmission lines, four reduced-scale test lines with the same parameters were built up at elevations of 50, 1700, 3400, and 4300 m in China, respectively. Simultaneously, two full-scale test lines were set up in Beijing and Tibet, whose altitudes were 50 m and 4300 m, respectively. Using the test facilities, the AN of HVdc transmission lines had been measured for a four-year period, from January 2010 to July 2014. Through a statistical analysis of a large amount of data, AN characteristics of HVdc transmission lines at different altitudes are obtained. By comparing the statistical results from different altitude areas, it is found that AN of HVdc transmission lines is nonlinearly dependent on altitude. Finally, an AN altitude correction formula of HVdc transmission lines is proposed. It shows that from 0 to 4300 m, the AN correction value of HVdc lines is far less than the predicted value by an HVac method. [ABSTRACT FROM AUTHOR]

A modified method based on the optimized charge simulation method (CSM) is used to predict the corona onset voltage and electric field when the space charges due to the corona are considered. Based on the streamer model of corona discharge, space charges generated near the conductors are predicted. In order to calculate the electric field at the conductor surface, space charges are replaced by some equivalent line charges near the conductor. Because of the existence of space charges, the corona onset electric field is changed a little. After a simplified model of actual power transmission lines is introduced with the help of rough coefficient, the corona onset voltage and corona onset electric field are calculated for different types of conductors finally. [ABSTRACT FROM PUBLISHER]

With the growing public awareness of environmental protection, the dc ground-level total electric field (TEF) is attracting increasing attention. Especially in high-altitude areas, it has become a key technical factor in deciding conductor types and the height of the transmission line. To determine the altitude effect and correction of the ground-level TEF for HVdc transmission lines, four short bipolar test lines with bundle conductors with the same parameters were built in China at altitudes of 50, 1700, 3400, and 4300 m. Using the test facilities, the dc ground-level TEF was measured over a long period of time, from Jan. 2010 to Nov. 2015. Through a statistical analysis of a large amount of data, the ground-level TEF characteristics of short bipolar test lines at different altitudes were obtained. By comparing the statistical results from different altitudes, it is determined that the dc ground-level TEF and corona inception field strength are linearly dependent on the altitude. Finally, the ground-level TEF and corona inception field strength altitude correction formulas of HVdc transmission lines are proposed. [ABSTRACT FROM AUTHOR]