Data Reduction And Error Analysis For The Physical Sciences

Introduction to Electromagnetic Compatibility

Numerical Methods for Scientists and Engineers

Aerosol Measurement Principles Techniques And Applications

In this paper, power electronic transformer (PET)-based railway traction systems are comprehensively reviewed according to the unique application features and requirements. By comparing PET and conventional line frequency transformer (LFT)-based systems, their pros and cons are summarized. By further reviewing all kinds of PET-based designs from the early concepts to the latest ones in the order of their publication dates, the developing trends are highlighted. By synthetically considering the requirements and the state of the art, the key challenges and opportunities are identified and discussed. It shows that although PET-based systems are still developing and far from mature, they are already superior to LFT-based systems in terms of system weight, efficiency, and functionalities especially for 15-kV/16.7-Hz applications. With the advancements on wide bandgap power devices, medium frequency transformers, and converters, PET systems will be even more promising and available for all types of railway tractions in the near future.

Power Electronic Transformer-Based Railway Traction Systems: Challenges and Opportunities

According to the method of moment, a new method to analyze the grid fed by harmonic currents is presented. The method can be used for the condition that the grid is in at least ten-layer soil with a frequency of the injected currents up to 1 MHz. There can be more than one injected current, and the grounding conductor of the grid can be put in any form. Validation of the method is presented by comparing it with other existing methods. As an application of the presented method, breaks in the substation's grounding grid are diagnosed by the measured voltages on the surface of the ground.

Diagnosis of breaks in substation's grounding grid by using the electromagnetic 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 Electric Field and Ion Current Density under Ultra High-voltage Direct-current Transmission Lines Based on Finite Element Method

How to correctly obtain the structure parameters of earth is the precondition of grounding system design. Based on the local searching algorithm, an efficient method for estimating earth structure with any number of layers from the test data by Wenner configuration method is presented. In each iterative procedure, earth apparent resistivities are calculated by complex image method. A new method to directly obtain the partial derivatives of the earth apparent resistivities with respect to the earth parameters from the results of the complex image method is presented, which is more efficient than the conventional methods that arduously calculate the improper integrals with a Bessel's function and an infinite limit of integration. At the same time, a method to determine suitable initial earth parameters for the local searching algorithm is also proposed. The validity of the method is shown by several applications.

Parameter estimation of horizontal multilayer earth by complex image 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.

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

Soil ionization has a great effect on the performance of grounding electrodes fed by currents of high magnitude. In this paper, a numerical method is proposed to analyze the transient performance of grounding system, which takes account of the dynamic and nonlinear effects of soil ionization. The method couples moment method with circuit theory and Fourier transform. The transient performance of grounding system considering the soil ionization effect is compared with that not considering soil ionization effect.

Xiang Cui

Papers

Diagnosis of breaks in substation's grounding grid by using the electromagnetic method

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

Parameter estimation of horizontal multilayer earth by complex image method

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

Numerical analysis of transient performance of grounding systems considering soil ionization by coupling moment method with circuit theory