Edward W. C. Lo

Calculations of Eddy Current, Fluid and Thermal Fields in an Air Insulated Bus Duct System

In this paper, a 3-D eddy-current field model for calculating the eddy current losses in an air insulated bus duct system (AIBDS) is proposed. The temperature rises in the AIBDS, including its long linear section and connecting unit, are evaluated using a coupled fluid field and thermal field model. The contact resistance between the copper conductors and the temperature rise in those contact areas are measured and compared with the simulation results in order to validate the proposed methodology

Analyses of three-dimensional eddy current field and thermal problems in an isolated phase bus

In this paper, a three-dimensional eddy current field model to calculate the eddy current losses in an isolated phase bus (IPB) is proposed. The rise in temperature of the conductors and enclosures in the IPB are evaluated using the proposed set of thermal equations. Computation results of a 20-kV/12.5-kA IPB scheme are reported to validate the algorithm. The withstand voltage ability and short-circuit stress of the IPB are also verified. The agreement between the computation and test results confirm that the design scheme being studied is successful and practical.

Integrated RBF network based estimation strategy of the output characteristics of brushless DC motors

The circuit-field coupled model is very accurate but it is computationally inefficient in studying the output performance of brushless DC motors. In order to resolve the problem, an estimation strategy based on an integrated radial basis function (RBF) network is proposed in this paper. The strategy introduces new conceptions of the network group that are being realized by three steps, namely: (1) an adaptive RBF network is proposed for modeling the center network; (2) the RBF network group is then used to build the base networks; and (3) an integrated RBF network based on the base network group is used subsequently to predict the nontrained output characteristics of the brushless DC motor.

Refinement computations of electromagnetic fields using FE and meshless methods

A refinement algorithm for electromagnetic field computations using a combination of finite element and meshless methods is introduced. Bridging scales are used to separate the finite element and meshless shape functions to make the refinement hierarchical and to uphold the mathematical properties such as consistency and linear independence for all the bases. To facilitate the application of the proposed algorithm, details about the node addition, requirements for the node distribution, and relationships between the finite element and meshless shape functions, as well as the determination of the stop criterion are also fully addressed. Primary numerical results are reported to demonstrate and validate the applicability and advantages of the proposed algorithm over traditional ones.

Harmonic simulation of MTR traction system by EMTP

The proliferation of nonlinear loads resulting from new technologies has increased the levels of harmonics in power systems, and traction systems represent large nonlinear loads. This paper presents results of a simulation and site measurement study of the harmonics related to Mass Transit Railway (MTR) in Hong Kong. Simulation results from the ATP Electromagnetic Transient Program (EMTP) are compared with the site measurements so as to verify the simulation model of the network. Summaries of the parameters affecting the harmonic performance of the traction system and estimates of the most predominant harmonics in a network are also presented and recommendations are made for the improvement of the power quality.

Recent Projects of Building Integrated Photovoltaic in Hong Kong

In Hong Kong, a number of medium-scale building integrated photovoltaic (BIPV) systems were completed in last few years. These BIPV projects included government building, commercial building, schools, institutional building. The power rating the BIPV system for each project is in the order of tens of kilowatts. Most of these BIPV systems are grid-connected type to eliminate the bulky and troublesome battery banks. Some of these projects are retrofitting on existing buildings; while some are parts of a new building. The paper gives details on the design of these PV systems in Hong Kong, including system configurations, design considerations, protections, grid-connection interfacing, power quality issues, their performance, technical difficulties encountered, and experience gained.

Niched Genetic Simulated Annealing Algorithm in the Optimization Design of a Permanent Magnetic Actuator for a 40.5kV Vacuum Circuit Breaker

A new algorithm combining genetic algorithm (GA) and simulated annealing (SA) algorithm with significant improvements on efficiency is proposed. Based on the calculation of the electromagnetic field, the optimization design of a bi-stable permanent magnetic (PM) actuator for a 40.5 kV vacuum circuit breaker (VCB) is developed

An experimental study of Engineering-Science-Mathematics Approach in elementary engineering and science education

A learning model of Engineering-Science-Mathematics Approach (ESMA) is designed and experimented for engineering pre-college outreach to K-6 students and teachers. It is evidenced that the learning efficiency and outcome are significantly higher than traditional learning approach of Mathematics-Science-Engineering at college level. This design utilizes the minimum resources of engineering and science specialists in school district and materials available on the market. The ESMA model can be applied to a wide audience with trained in-school science teachers. The study shows that K-6 is the optimal age period for engineering pre-college outreach.

Unit Transient Based Protection for High Voltage Wind Power Transmission Lines

Based on the wavelet transform results of the transient signals from all ends of the line, a unit protection for high voltage power transmission line is presented. The attenuation effects of high voltage transmission line and busbar capacitance to high-frequency current signals are analyzed. The Transient Current Content Ration(TCCR), Transient Voltage Content Ratio (TVCR) and Transient Voltage Singularity Ratio (TVSR) are deduced according to the analysis of the differences during high frequency voltage transients at each end of the transmission line when in-zone faulted and out-zone faulted. Protection criterion using TCCR and protection criterion using TVSR are proposed, and the principles of protection settings are given. The wavelet modulus maxima of transient signals are used to calculate TCCR and TVSR. Simulation experiments of different faults with EMTP are carried out to test and analyze the protection criteria. A 100kHz sampling rate is used in the simulation experiments. According to the simulation results, the protection criteria prove to be simple, reliable and good for whole line protection.