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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]

Ionic mobilities are characteristic parameters for describing the motion of charges in electric field and also basic parameters for the calculation of ionized field and ion current density of ultra high voltage direct current (UHVDC) transmission lines. This paper presents a measurement method of ionic mobilities in air. The analytical solution of ion mobility was derived from the equations of the ionized field and the ion current density. A circular parallel plate apparatus was applied to measure the ionic mobilities. Experimental results show that in direct current corona discharge of room temperature, the measured result of negative ion mobility was 2.23 to 2.51 ×10−4 m2·V−1 s−1, and the average value was 2.39 ×10−4 m2-V−1·s−1; the measurement of positive ion mobility was 1.54 to 1.93 × 10−4m2·V−1·s−1, with the average of 1.71 × 10−4 m2·V−1·s−1. [ABSTRACT FROM PUBLISHER]

The sound pressure level (SPL) has been generally accepted in the measurement and evaluation of degree of nuisance to the corona-generated audible noise from transmission lines. Quite many scholars have studied the spectrum and statistical characteristics of the SPL from transmission lines through the long-term frequency measurement. In fact, the corona sources on the transmission lines usually act as sound sources emitting sound pressure pulses with random amplitudes and random time intervals, yet the statistical characteristics of the random sound pressure pulses and their correlation to the SPL have barely been investigated. In this paper, a series of experiments with single positive corona source in a coaxial cylindrical structure were carried out to investigate the statistical characteristics of the pulse amplitudes and time intervals of sound pressure pulses. In the experiment, time-domain measurement for the audible noise was employed. Based on the statistical results, a stochastic model was developed to simulate the sound pressure pulses. The validity of the stochastic model was testified by comparing the simulated and measured A-weighted sound pressure levels. On the basis of the stochastic model, the influence of random pulse amplitudes and time intervals of the sound pressure pulses on the resultant SPL was demonstrated. [ABSTRACT FROM AUTHOR]

The corridor of the high-voltage direct current transmission lines in China is very complex and there may be buildings near the lines. The conductivity of the building material may influence the electric field in the building. In this paper, based on the upstream FEM, a method is proposed to solve the coupled problem of the ion flow field in the air and the current field in the building model. The numerical results coincide with the analytic results and measurement results. The electric field in and on the building model is analyzed considering different conductivities. [ABSTRACT FROM PUBLISHER]

The HVDC and HVAC transmission lines running on the same tower is a promising technology to improve the transmission capacity of an existing corridor. The ions generated by corona discharge of HVDC transmission lines will strengthen the ground-level electric field, which may endanger human exposure. To investigate how the presence of HVAC transmission lines changes the ion-flow field, experiments are carried out on an indoor test model with bipolar dc and three-phase ac lines. The experiment results are then compared with the simulation results. The experiment and simulation results show that the HVAC transmission lines have a shielding effect on the ion-flow field from the HVDC transmission lines running above. Finally, the ground-level electric field and ion current density of the \pm 800–kV HVDC and 500-kV HVAC transmission lines running on the same tower are calculated. [ABSTRACT FROM PUBLISHER]

This paper aims at investigating the mechanism of hybrid ac/dc corona which is usually accompanied with the hybrid HVAC/HVDC power transmission lines. A coaxial wire-cylinder corona cage is designed in this paper, and the combined ac/dc voltage is applied to the wire and cage. The low-frequency component of corona current from the hybrid ac/dc corona in this corona cage with five types of wires is measured. To obtain the detailed characteristic of the interaction between the space charge and ionized electric field, a 1-D method is developed to simulate the hybrid ac/dc corona in the symmetrical corona cage. This method is validated through the comparison with measurement results. Based on this simulation method, analysis of the evolution of space charge and ionized electric field in one time cycle is presented. The regular pattern of charge injection from the discharge electrode is summarized, where the charge injection is found not linearly dependent on the applied voltage. Finally, the corona loss of hybrid ac/dc corona is calculated, and the similar result with the quadratic law in ac corona is found from the calculation results. This research provides useful knowledge for the engineering computation of the effects of hybrid ac/dc corona. [ABSTRACT FROM AUTHOR]

As many high voltage direct current (HVDC) projects are constructed in China, the ionized field problem is of wide concern. The upstream finite element method (Upstream FEM) has good adaptability and is widely used to analyze the ionized field under HVDC lines. Galerkin's scheme is used to improve the charge density precision. Poisson's equation solution technique and charge density updating strategy are adopted to accelerate the calculation. The charge density precision and the calculation efficiency is remarkably improved. For the 15\,000-nodes-scale ionized field problem of bipolar-6-bundled HVDC lines, the calculation time is less than 5 s. The algorithm also shows good robustness to the charge density initial value in the numerical cases. [ABSTRACT FROM PUBLISHER]

The ac-dc hybrid transmission line is an effective way to enhance the transmission capacity of a power corridor. However, the corona discharge of ac and the dc transmission lines may interact with each other, which makes the electric field at the ground level difficult to be predicted. This paper presents a simulation method for the calculation of the field effects caused by the corona activities of hybrid ac-dc transmission lines. This approach can simulate the convection and recombination of the space charge generated by ac or dc corona without improper simplifications, and the conductor surface gradient strictly kept to the onset value. The calculated electric field and ion current density at the ground level agree well with the measurement results of a hybrid line model. [ABSTRACT FROM PUBLISHER]

The ionized field under HVDC transmission lines is actually a 3-D field with considering the influence of wires sag, towers, up-and-downs on the ground, surrounding buildings and other situations and little of its calculation method has been reported. In this paper, a method to calculate the 3-D ionized field under HVDC transmission lines is proposed based on Deutsch's assumption which is simple, fast, and easy to use and the computation cost of which is low. After the validity of the method is testified, some examples are analyzed and some conclusion are given. [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]

An improved method to simulate the ion-flow field generated from the corona discharge on HVDC transmission lines is proposed. To remove the oscillations in simulation of charge conservation law, an upwind weighting function is adopted in the finite-element method. The Poisson's equation and the charge conservation law are solved simultaneously through Newton's method of iterations, which accelerates the convergence of the algorithm. A rule for charge density on boundary in the bipolar problem is proposed in this paper, which ensures the stability of the iterations. The computation time, convergence rate, and accuracy of the proposed method are analyzed. The proposed method is verified by analytical and experimental results, and then it is applied to the prediction of the ion-flow field from a \pm1100-kV HVDC transmission line. [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]

The corona-generated electromagnetic interference commonly known as radio interference (RI) has become a limiting factor for the design of high voltage direct current transmission lines. In this paper, a time-domain measurement system is developed to measure the time-domain characteristics of corona-generated RI from a single corona source under a positive corona source. In the experiments, the corona current pulses are synchronously measured through coupling capacitors. The one-to-one relationship between the corona current pulse and measured RI voltage pulse is observed. The statistical characteristics of pulse parameters are analyzed, and the correlations between the corona current pulse and RI voltage pulse in the time-domain and frequency-domain are analyzed. Depending on the measured corona current pulses, the time-domain waveform of corona-generated RI is calculated on the basis of the propagation model of corona current on the conductor, the dipolar model for electric field calculation, and the antenna model for inducing voltage calculation. The well matched results between measured and simulated waveforms of RI voltage can show the validity of the measurement and calculation method presented in this paper, which also further show the close correlation between corona current and corona-generated RI. [ABSTRACT FROM AUTHOR]

Based on the second-order wave equation of voltage, discrete equations for multiconductor transmission lines (MTLs) are derived by using finite-element time-domain (FETD) method and Newmark-Beta formulation. And then, the time-domain method to process lumped elements is also given based on the node admittance method of circuit analysis. Combining all the discrete equations and lumped elements, the global FETD equation is obtained based on the single iteration variable voltage. Finally, by means of the coupled equations between current and voltage, the iteration formulas of current along MTLs are derived. Compared with EMTP program by numerical examples, the proposed method in this paper is proved to be correct and effective. Furthermore, the simulation result demonstrates that the proposed method is better than the existing FETD methods in computation efficiency and convenience for the treatment of complex lumped networks. [ABSTRACT FROM AUTHOR]

Abstract: Making use of EMTP, the transient simulation of the currents along the towers and ground wires is performed when the lightning strikes the tower of the power transmission line. The investigation shows that the currents along the towers and ground wires dramatically decrease and can be ignored after 5 spans. And the effect on them for different impulse ground impedances, lightning current injection locations, tower spans, lightning wave impedances and so on are obtained when lightning strike on tower. With the help of Fourier transform, the method of moment is adopted to calculate the transient coating stress voltage of the pipeline and total electric field in the earth when the underground pipeline runs parallel to or crosses the power transmission line. The approximate formulas of the maximum coating stress voltage along the pipeline are proposed for the situation of crossing, which involve the lightning current, soil resistivity, pipeline models, tower grounding structure sizes and separation distance between the pipeline and tower grounding structure. Then, the proposed method can be used to evaluate the safety distance between the pipeline and tower grounding structure with the lightning electrical strength of the anti-corrosion coating of the pipeline. Eventually, if actual distance is less than the calculated value, modeling and analysis of protection measures in the pipeline can be carried out to protect the coating. [Copyright &y& Elsevier]