Copyright (c) 2008 Berkeley Electronic Press All rights reserved. http://www.bepress.com/ijeeps Recent documents in International Journal of Emerging Electric Power Systems en-us Fri, 25 Apr 2008 02:46:33 PDT 3600 http://www.bepress.com/ijeeps/vol9/iss3/art5 http://www.bepress.com/ijeeps/vol9/iss3/art5 Wed, 23 Apr 2008 06:37:06 PDT Recently, fuzzy logic control has widely received attention in various power system applications, despite difficulties of obtaining its control rules and membership functions. Nowadays, power systems consist of multiple areas where load variations with abrupt changes always exist, and proper control rules and membership functions could hardly be achieved. This paper proposes a practical design of fuzzy logic controllers for superconducting magnetic energy storage (SMES) based on a wide area synchronized phasor measurement for enhancing the stability of an interconnected power system. Moreover, a heuristic method is applied for determining control rules and membership functions. The estimated model is determined via a simplified oscillation model for detection and assessment of an approximated inter-area oscillation mode. Finally, some simulation studies based on a two-area four-machine power system are carried out to examine the performance and effectiveness of the designed fuzzy SMES controller. Sanchai Dechanupaprittha Power System Stability and Control http://www.bepress.com/ijeeps/vol9/iss3/art4 http://www.bepress.com/ijeeps/vol9/iss3/art4 Wed, 23 Apr 2008 06:36:38 PDT Experimental studies are carried out to investigate the effectiveness of solving the electromagnetic interference (EMI) problem in power line communication (PLC) networks. A test bed is designed to study the effectiveness of the method. Measurements are carried out in a semi-anechoic chamber using a clamp-on current probe, a rod antenna and a loop antenna to compare the conducted and radiated emissions for the various cases. It is well known that the dominant mode of radiation is common mode (CM). The experimental results show that both the conducted and radiated emissions can be reduced by 15dB. This is achieved by increasing the impedance between the noise source and the power line network across the alternative noise path. Lin Biao Wang Power line communications http://www.bepress.com/ijeeps/vol9/iss3/art3 http://www.bepress.com/ijeeps/vol9/iss3/art3 Wed, 23 Apr 2008 06:36:32 PDT Large generators have high effective X/R ratios and combined with other generator time constants and parameters, a current zero may not be obtained at the time of contact parting, i.e., the dc component of the short-circuit current at the contact parting time is higher than the peak ac component. This is well documented in the current literature. The paper presents calculations of the generator source short-circuit currents of a 234 MVA generator using ANSI/IEEE and IEC standards and EMTP simulation. The results are compared and the application of a generator breaker to meet the requirements of calculated duties are discussed. It shows considerable differences in the results, depending upon the method of calculation. J. C. Das Generator Source short-Circuit Currents Selection of Generator Breakers http://www.bepress.com/ijeeps/vol9/iss3/art2 http://www.bepress.com/ijeeps/vol9/iss3/art2 Wed, 23 Apr 2008 06:36:19 PDT A load modeling method based on wide area trajectory sensitivity of a power system is presented in this paper. A generator angle as wide area information is used to identify load parameters. Load parameters of wide area identification can fit the dynamic behaviors of a power system more accurately than that of local identification can. Compared with the local-sensitivity of the load parameter, wide-area-sensitivity can reflect the character of power oscillation more clearly. The local sensitivity trajectories of load parameters are obvious only a short time after the disturbance and they are close to zero after about two seconds and can't describe the oscillation character of a power system more clearly. The simulation results proved the feasibility and validity of the wide area load modeling method. It is expected that the method will be used widely in a large scale power system in the future. Xiupeng Guan power system http://www.bepress.com/ijeeps/vol9/iss3/art1 http://www.bepress.com/ijeeps/vol9/iss3/art1 Wed, 23 Apr 2008 06:36:01 PDT For advanced, non-destructive on-site condition monitoring of HV power cables up to 150kV by partial discharge detection and dielectric losses measurement it is necessary to energize the disconnected cable system. One of the methods available for this purpose is based on applying damped AC voltages up to 150kV. In this paper, the use of modern technological solutions in power electronics and signal processing as well as in technical design and production methods will be discussed on the basis of the ultra light system (300kg) which is able to test cables up to 20km lengths. Edward Gulski Condition monitoring HV power cables http://www.bepress.com/ijeeps/vol9/iss2/art7 http://www.bepress.com/ijeeps/vol9/iss2/art7 Wed, 23 Apr 2008 06:34:38 PDT The power transformer is a complex and critical component of the power transmission and distribution system. System abnormalities, loading, switching and ambient condition normally contribute to accelerated aging and sudden failure. In the absence of critical components monitoring, the failure risk is always high. For early fault detection and real time condition assessment, an online monitoring system in accordance with the age and conditions of the asset would be an important tool. Power loss, heat generation and heat distribution evaluations in a large-scale oil immersed power transformer are presented here, along with the details of computer implementation and experimental verification. Core power losses are approximately constant with temperature variation or may decrease with that. Over the temperature range of 20 to 100°C the change in hysteresis loss Ph with temperature was negligible. Since the total core loss PT decreased with increasing temperature over this range, almost all the loss reduction was due to a reduction in the eddy current loss component Pe that was inversely proportional to the resistivity. Winding and oil temperature will increase with the load increasing and may create a hot spot. This is caused by degradation insulation and the loss of life in the power transformer. Hottest spot temperature and temperature profiles in radial and height coordinates were found using three different methods in this paper. The finite element method (FEM), finite difference method (FDM) and discrete furrier transform methods (DFT) are used to analyze algorithms in this paper. Computational results based on theoretical considerations and using the DFT method are shown to be in good agreement with FDM and FEM. Two mathematical formulae are proposed for temperature distribution in both radial and horizontal axes of core and windings. COMSOL for FEM, GEMINI for FDM and MATLAB for DFT are used. Kourosh Mousavi Takami power transformer