Xiang Cui

Analysis of the Electric Field and Ion Current Density under Ultra High-voltage Direct-current Transmission Lines Based on Finite Element Method

The corona generated from high-voltage direct-current transmission lines can induce the ion around the lines, which will increase the electric field and the ion current density and influence the environment nearby. Based on the finite-element method, an iterative algorithm to analyze the electric field and the ion current density at the ground level generated from the bundled conductors of bipolar lines is proposed. After the validity of the method is testified, some examples are analyzed. The method has been used to design plusmn800 kV transmission lines system in China

Analysis of the Ionized Field Under HVDC Transmission Lines in the Presence of Wind Based on Upstream Finite Element Method

Corona phenomenon generated from high voltage direct current (HVDC) transmission lines can affect the environment nearby. Based on the upstream finite element method, an iterative algorithm is used to analyze the ionized electric field and the ion current density at the ground level with the wind velocity taken into consideration. The algorithm is efficiently convergent. The proposed method is testified by measurement results of a unipolar line in the presence of wind and a bipolar test line. Finally some examples are analyzed to predict the effect of the wind and to determine the transmission corridor of ±800 kV HVDC transmission line.

Grounding Performance Analysis of the Substation Grounding Grids by Finite Element Method in Frequency Domain

Based on finite-element method (FEM) of 1-D conductor element coupled with 3-D soil element, we take into account the frequency dependent characteristic of the discretized elements to analyze the grounding performance of the substation grounding grids. Compared with A-V formulation of 3-D FEM, the proposed method can greatly save the CPU time, and the frequency can be considered during FEM modeling. In comparison with the method of moment (MoM) and the measured results, the presented method is proved to be correct and effective. Furthermore, we can calculate the H-field generated by the substation grounding grids with both currents in the underground conductors and leakage currents flowing in the soil. The results show slight difference between FEM and MoM, which can be explained by the fact that the leakage currents in the soil are not taken into account for MoM

Analysis of corona onset electric field considering the effect of space charges

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.

Calculation of the 3-D Ionized Field Under HVDC Transmission Lines

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 Deutschs 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.

Detailed characteristics of intermittent current pulses due to positive corona

In order to get detailed characteristics of intermittent current pulses due to positive corona such as the repetition rate of burst-pulse trains, the peak value ratio of the primary pulse to the secondary pulse, the number of pulses per burst, and the interval of the secondary pulses, a systematic study was carried out in a coaxial conductor-cylinder electrode system with the conductor electrode being set with a discharge point. Empirical formulae for the number of pulses per burst and the interval of the secondary pulses are first presented. A theoretical model based on the motion of the space-charge clouds is proposed. Analysis with the model gives explanations to the experimental results and reveals some new insights into the physical mechanism of positive intermittent corona.

Impact Factors in Measurements of Ion-Current Density Produced by High-Voltage DC Wire's Corona

The reduced-scale model of HVDC transmission lines in the laboratory is widely used to investigate the ionized fields. This paper is aimed at analyzing impact factors of the ion-current density measurement system based on Wilson plates in the laboratory. Both experimental and numerical simulation methods are used to obtain the characteristics of the measurement system. The results show that measurement data can be calibrated with different Wilson plates, and suitable parameters are proposed in this paper to meet the requirement of measurements. The measurement system described in this paper can be used in other similar applications.

Simulation of Electromagnetic Transients of the Bus Bar in Substation by the Time-Domain Finite-Element Method

In order to analyze the electromagnetic interference (EMI) generated from the aerial bus bars in substation, the transient electromagnetic wave process on the bus bars is calculated by using the time-domain finite-element (TDFE) method. The TDFE method is preferable to both the commonly used finite-difference time-domain (FDTD) method, which has difficulties in dealing with the multiconductor transmission lines (MTLs) with lumped parameter networks, and the universal software electromagnetic transient program (EMTP), which is not effective for the calculation of the whole electromagnetic wave processes along the MTLs. The feasibility and efficiency of the proposed TDFE method have been demonstrated by comparing the numerical results with experimental measurements. Furthermore, we have performed a successful case study on the numerical prediction of the EMI in the secondary cable in substation by using the TDFE method.

Shielding Effect of HVAC Transmission Lines on the Ion-Flow Field of HVDC Transmission Lines

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 ±800-kV HVDC and 500-kV HVAC transmission lines running on the same tower are calculated.

The Ionized Fields and the Ion Current on a Human Model Under

The ultra-high-voltage direct-current (UHVDC) system has many advantages in long-distance power transmission. This paper is aimed at analyzing the distributions of the ionized fields and the ion current on the human model under ±800-kV UHVDC transmission lines; therefore, a numerical method which combines the 3-D charge simulation method and Deutschs assumption is used. And the validity of the presented method is demonstrated through a test in the laboratory. For ±800-kV UHVDC transmission lines, the ionized fields and the ion current on the human model are calculated, and numerical results show that the ionized fields and the ion current density on the top of the human model increase evidently when the human model stands under ±800-kV UHVDC transmission lines. And the total ion current flowing on the human model is far lower than the permitted limit.