Calculation Of Ion Flow Field Research Articles

A Fast Ion Flow Field Calculation Method of UHVDC Transmission Lines Based on Adaptive Iteration Factor and Half-error Term

A Fast Ion Flow Field Calculation Method of UHVDC Transmission Lines Based on Adaptive Iteration Factor and Half-error Term

Ion Flow Field Calculation Considering the Influence of Water Drops and Wind Flow

In this work, an effective calculation method of the ion flow field that considers the impact of wind flow and water drops is presented. To be explicit, the nominal electric field is solved by the charge simulation method (CSM) whilst the space charge density is calculated adopting a second order upwind finite volume method. In addition, a method that determines the roughness factor of a conductor surface is used to enhance calculation accuracy. The influence of various properties of the water drops exerting on an ion flow field is analyzed. Eventually, a practical experiment is conducted to verify the calculated result, and the effectiveness and reliability of this method are then proved via comparing calculated and measured results.

High Effective Calculation and 3-D Modeling of Ion Flow Field Considering the Crossing of HVDC Transmission Lines

The 3-D calculation method of the ion flow field is required for the crossing issue of high-voltage direct-current (HVDC) transmission lines. Appropriate computational regions and boundary conditions are critical to the calculation. In this article, a novel method combining charge simulation method-flux tracing method (CSM-FTM) and finite-element method (FEM) is proposed to optimize the ion flow field calculation. The advantage of CSM-FTM in dealing with the opening domain is fully utilized. Quadratic charges are applied in CSM to ensure the calculation accuracy of the space-charge-free electric field. In addition, a hemisphere calculation region is adopted in order to model the HVDC lines with an arbitrary cross angle. The Dirichlet boundary condition on the spherical surface in the FEM calculation is obtained based on FTM. Finally, the electric field of ±800 and ±500 kV lines at a cross angle of 60° is analyzed as an example. By utilizing the proposed method, the calculation area is substantially reduced and the calculation accuracy is significantly improved.

Calculation of Ion Flow Field of Monopolar Transmission Line in Corona Cage Including the Effect of Wind

In this work, the ion flow field of a monopolar transmission line inside the corona cage of a square cross-section is iteratively calculated concerning the effects of wind. The electric field distribution is solved analytically using the charge simulation method (CSM). Meanwhile, the upwind finite volume method (UFVM) with 2nd order accuracy is presented for the distribution of space charge density. Additionally, a dual mesh grid is established in the calculation domain, the interlaced geometric construction of the mesh assures a quick and effective convergence rate. In the final part, a reduced-scaled experiment is designed to examine the feasibility and accuracy of this approach, electric field and ion current density on the bottom side are measured by field mills and Wilson plates. The data numerically computed fits well with that acquired by measurement.

Calculation of Ion-Flow Field Near the Crossing of HVdc Transmission Lines Using Equivalent Corona Conductors

The crossing of two-circuit high-voltage direct current (HVdc) overhead lines will happen with the increasing number of HVdc transmission projects. The 3-D calculation is needed to predict the ion-flow field near the crossed HVdc lines. In order to decrease the difficulty of meshing near the bundle conductors, the equivalent single conductors are applied in the modeling. A roughness coefficient converting approach for equivalent conductor in Peek’s formula is presented. Thus, the corona degree of bundle conductors can be reflected by the equivalent single conductor. Afterward, the effectiveness of equivalent corona conductors in ion-flow field calculation is checked by a series of experiments and simulation. Finally, the 3-D ion-flow field distribution near the crossing of ±800 and ±500 kV HVdc overhead lines is calculated using equivalent corona conductors.

Calculation of Ion Flow Field Around Metal Building in the Vicinity of Bipolar HVDC Transmission Lines by Method of Characteristics

In this paper, a 3-dimensional method of characteristics is used to calculate the ion flow field around a metal building in the vicinity of bipolar HVDC transmission lines. The surface charges are introduced to make sure that the surface of the metal building is equipotential. An improved iterative method is proposed to solve the ion flow field. A reduced-scale test under laboratory conditions is carried out to verify the calculation results. Comparison of the results with those by Deutsch Assumption shows that although the two groups of results on the ground are in good agreement, the electric fields in space are different because the method of characteristics considers the effect of space charges on the direction of the electric field. The ion flow field around a metal building in the vicinity of a 800 kV transmission line was calculated with the method and discussed.

Calculation of Ion-Flow Field of HVdc Transmission Lines in the Presence of Wind Using Finite Element-Finite Difference Combined Method With Domain Decomposition

A combined method adopting the domain decomposition is proposed for analyzing the ion-flow field of high-voltage direct current transmission lines, including the effect of the transverse wind. The upstream finite-element method is used with a dense triangle mesh in the vicinity of bundle conductors to guarantee the accuracy. The upstream finite-difference method is proposed and the larger uniform quadrilateral grid is applied to simulate the ion-flow field in the rest of the region with a satisfactory precision. The calculation process of the Poisson equation is iterated with the Dirichlet–Neumann algorithm to coordinate the solution between adjacent subdomains. The proposed approach improves the efficiency and remains stable with high wind speed. Finally, the influence of wind on the ion-flow field is analyzed and calculations are in good agreement with experimental data and results in the previous literature.

Calculation of Ion Flow Field Around HVdc Bipolar Transmission Lines by Method of Characteristics

The ion flow fields around high voltage direct current (HVdc) transmission lines due to corona are nonlinear, which can be simulated by calculating the electric field distribution and ion density distribution iteratively. In this paper, an application of the method of characteristics is presented to calculate the ion densities around bipolar HVdc transmission lines based on a pair of first-order partial differential equations of the ion densities. The electric field is calculated directly by accumulating all the contributions from the ions in the air and charges on the conductors. No large-scale system of equations needs to be solved, which means that the requirement for computer memory is low, and the method is suitable for large-scale calculation. The results are in good agreement with the measured data.

Improved Coupled Ion-Flow Field Calculation Method for AC/DC Hybrid Overhead Power Lines

The conversion of multicircuit ac transmission lines to hybrid ac/dc lines is a promising way of substantially increasing transmission capacities in areas where it is difficult to obtain new rights of way. Critical questions related to such a conversion include the impact on the electric fields and ion currents at the ground level, as well as the dc current coupling into the ac phases. In this paper, a new procedure based on the method of characteristics is proposed for solving the fully coupled ion-flow problem. The method does not make the Deutsch assumption and is fast and stable even for high assumed wind speeds. A hybrid tower is simulated with different voltages and wind speeds. The results show the influence of the onset gradient, the dc line voltage, and the wind speed on the current coupling as well as the electric field and ion current density at the ground level. It is shown that the new proposed method can serve as the tool for dimensioning real hybrid towers.

Discussion on the Deutsch Assumption in the Calculation of Ion-Flow Field Under HVDC Bipolar Transmission Lines

Deutsch assumption greatly simplified the calculation of the ion-flow field under HVDC transmission lines. However, its applicability remains to be proved for the 800-kV HVDC projects in contemplation in China. The ground-level electric field and ion current density are calculated with an upwind differential-based 2-D method and a Deutsch assumption based on the 1-D method to analyze the errors of the ion-flow field caused by Deutsch assumption. A dc bipolar line laboratory model is established to verify the methods. The parameters indicating the corona discharge intensity and the field distortion degree are introduced to evaluate the errors caused by Deutsch assumption. Then, the applicability of the Deutsch assumption is discussed on the 800-kV HVDC test line established in China. The relationship of the corona discharge intensity, the field distortion degree, and the errors caused by Deutsch assumption are analyzed. Using the corona discharge intensity to evaluate the errors caused by Deutsch assumption seems to be reasonable.

Calculation of Ion Flow Field Under HVdc Bipolar Transmission Lines by Integral Equation Method

The electric fields under high-voltage direct current (HVdc) transmission lines and the ions produced by corona affect each other greatly. This paper presents an iterative method to calculate ion flow fields under HVdc bipolar transmission lines in the presence of wind. Both the electric fields and the ion densities are calculated by integral equation method. The method is fast and stable. The results are in good agreement with the experimental data. The ion flow fields under a plusmn 800-kV bipolar direct current (dc) transmission line are analyzed

Accurate calculation of ion flow field under HVDC bipolar transmission lines

Ions produced by corona on overhead HVDC transmission lines drift through the air under the action of the electric field and wind. Knowledge of the ion-flow characteristics is essential for the performance evaluation of existing and planned lines. An iterative method for accurate bipolar lines is introduced. The calculations can also be applied to monopolar lines by settling appropriate quantities to zero in the equations. The procedure pioneers the use of a charge simulation method for calculation of the ion-flow field and a weighted residual method for calculation of space-charge densities. Examples show the application of the computational technique to HVDC bipolar lines in corona. The method is fast and reliable in comparison with previous methods, and the computed results compare well with experimental data.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>