Search Results (9)

Accurate non-invasive voltage measurement is critical for the stable operation of ultra-high-voltage direct-current (UHVDC) grids. In practical converter valve environments, voltage inversion based on the charge simulation method (CSM) may be affected by nearby charged conductors. To address this problem, this paper proposes a non-invasive voltage measurement method combining radially aligned near-conductor two-sensor differential electric-field measurement with three-dimensional electrostatic finite-element modelling. The differential electric field between two radial sensing positions is used for voltage inversion, which suppresses distant common-mode interference. When a nearby interference conductor exists, a weighted differential correction coefficient k is introduced to compensate for the residual radial interference component. Theoretical and simulation results show that k is a scenario-dependent coefficient affected by the measured voltage, sensor spacing, interference voltage, and geometric configuration. In an ultra-high-voltage (UHV) converter valve bridge-arm scenario with a 400 kV interference conductor, the absolute voltage inversion error is reduced from 0.50–1.57% FS before correction to below 0.20% FS after correction. Experiments on a 30 kV-scaled platform further verify the method under different measured voltages, sensor spacings, and interference-voltage levels, with the best-tested case reducing the maximum error from 0.93% FS to 0.16% FS. Full article

Electrostatic traveling wave (ETW) methods have shown promising performance in dust mitigation of solar panels, particle transport and separation in in situ space resource utilization, cell manipulation, and separation in biology. The ETW field distribution is required to analyze the forces applied to particles and to evaluate ETW design parameters. This study presents the numerical results of the ETW field distribution generated by a parallel electrode array using both the charge simulation method (CSM) and the boundary element method (BEM). A low accumulated error of the CSM is achieved by properly arranging the positions and numbers of contour points and fictitious charges. The BEM can avoid the inconvenience of the charge position required in the CSM. The numerical results show extremely close agreement between the CSM and BEM. For simplification, the method of images is introduced in the implementation of the CSM and BEM. Moreover, analytical formulas are obtained for the integral of Green’s function along boundary elements. For further validation, the results are cross-checked using the finite element method (FEM). It is found that discrepancies occur at the ends of the electrode array. Finally, analyses are provided of the electric field and dielectrophoretic (DEP) components. Emphasis is given to the regions close to the electrode surfaces. These results provide guidance for the fabrication of ETW systems for various applications. Full article

Resin-impregnated paper (RIP) bushing has gained significant interest due to its extended application in Extra High Voltage (EHV) and Ultra High Voltage (UHV) electricity transmission systems. However, the design criterion of its overall structure, the geometry parameters of the condenser layers, and stress release devices, etc., are still not fully understood. This article proposes a unique electric field optimization technique to integrate both the analytical and the numerical methods. The charge simulation method (CSM) is employed to create the overall equipotential surface, within which the finite element analysis (FEA) is adapted to study the localized field enhancement effects, taking into consideration the multi-physics coupled fields. A case study is performed on an actual UHV bushing. The results are compared to the traditional methods, to demonstrate the benefit of the hybrid method. Full article

Global warming is the greatest challenge faced by humankind, and the only way to reduce or totally eliminate its effects is by minimizing CO₂ emissions. Electrostatic precipitators are very useful as a means to reduce emissions from heavy industry factories. This paper aims to examine the performance of wire-duct electrostatic precipitators (WDESP) as affected by high-temperature incoming gases with a varying number of discharge wires while increasing their radius. The precipitator performance is expressed in terms of the corona onset voltage on the stressed wires and the corona current–voltage (I–V) characteristic of the precipitators working with incoming gases at high temperatures. The start of the corona onset voltage on the surface of the discharge wires is calculated for the precipitators under high temperatures based on the standard of the self-repeat of avalanches’ electrons developing on the surface of the stressed wires at high temperatures. For this, calculating the electrostatic field in the precipitators with single- and multi-discharge wires due to the stressed wire with the use of the well-known charge simulation method (CSM) with high-temperature incoming gases is important. The modeling of corona I–V characteristics is adopted using the finite element method (FEM) for single- and multi- (3-, 5-, and 7-) discharge wires of WDESP with high-temperature incoming gases. Additionally, the electrostatic field, potential, and space charge of WDESP are calculated by a simultaneous solution of equations of Poisson, current density, and the continuity current density. A WDESP was set up in the Laboratory of High Voltage Engineering of Czech Technical University (CTU) in Prague, the Czech Republic, to measure the corona onset voltage values and corona I–V characteristics for different WDESP configurations at high temperatures with a varying number of discharge wires while increasing their radius. The calculated values of the corona onset voltage based on CSM and the calculated corona I–V characteristics based on FEM agree reasonably with those measured experimentally with high-temperature WDESP. Full article

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. Full article

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. Full article

The accurate calculation of electric field intensity under transmission lines is more and more important with the expansion of high voltage engineering, which largely determines the site selection and design of transmission projects. In order to get more accurate results, a methodology of a charge simulation method (CSM) combined with an intelligent optimization algorithm for a 3D calculation model is proposed in this paper. Three key points are emphasized for special mention in this optimized charge simulation method (OCSM). First, the number of sub-segments on the finite length conductor, the position and number of the simulating charge set on a sub-segment are taken as the optimization parameters for unified calculation. Secondly, the fitness function of optimization algorithm is constructed by two values, voltage relative error and electric field intensity relative error. Thirdly, a finite element method (FEM) was used to obtain the electric field intensities, which are compared with the results of the proposed algorithm. A simulation case is carried out on a 3D calculation model of 220 kV transmission lines, which verify the effectiveness of the optimization algorithm. The proposed OCSM solves the parameter optimization problem of CSM in the 3D computational model, which considers physical shape of wire span, and has the advantages of strong global search ability and higher calculation accuracy. Full article

Scheduling EV user’s charging behavior based on charging price and applying renewable energy resources are the effective methods to release the load pressure of power grids brought about by the large-scale popularity of electric vehicles (EVs). This paper presents a novel approach for EV charging scheduling based on price negotiation. Firstly, the EV charging system framework based on price negotiation and renewable energy resources is discussed. Secondly, the price negotiation model is presented, including the initial price models and the conditions of transactions. Finally, an EV charging scheduling mechanism based on price negotiation (CSM-PN), including the price adjustment strategies of both the operator and EV users is proposed to seek a final transaction during multi-round price negotiation. Simulation results show that this novel approach can effectively improve the charging station operator’s income, reduce the EV users’ costs, and balance the load of the power grid while improving the efficiency of the EV charging system. Full article

To investigate the microphysics mechanism and the factors that influence arc development along a polluted surface, the arc was considered as a plasma fluid. Based on the image method and the collision ionization theory, the electric field of the arc needed to maintain movement with different degrees of pollution was calculated. According to the force of the charged particle in an arc plasma stressed under an electric field, a calculation model of arc velocity, which is dependent on the electric field of the arc head that incorporated the effects of airflow around the electrode and air resistance is presented. An experiment was carried out to measure the arc velocity, which was then compared with the calculated value. The results of the experiment indicated that the lighter the pollution is, the larger the electric field of the arc head and arc velocity is; when the pollution is heavy, the effect of thermal buoyancy that hinders arc movement increases, which greatly reduces the arc velocity. Full article