A frequency-based RF partial discharge detector for low-power wireless sensing

Partial discharge (PD) monitoring has been the subject of significant research in recent years, which has given rise to a range of well-established PD detection and measurement techniques, such as acoustic and RF, on which condition monitoring systems for highvoltage equipment have been based. This paper presents a novel approach to partial discharge monitoring by using a low-cost, low-power RF detector. The detector employs a frequency-based technique that can distinguish between multiple partial discharge events and other impulsive noise sources within a substation, tracking defect severity over time and providing information pertaining to plant health. The detector is designed to operate as part of a wireless condition monitoring network, removing the need for additional wiring to be installed into substations whilst still gaining the benefits of the RF technique. This novel approach to PD detection not only provides a low-cost solution to on-line partial discharge monitoring, but also presents a means to deploy wide-scale RF monitoring without the associated costs of wide-band monitoring systems

Distributed active transformer - a new power-combining andimpedance-transformation technique

In this paper, we compare the performance of the newly introduced distributed active transformer (DAT) structure to that of conventional on-chip impedance-transformations methods. Their fundamental power-efficiency limitations in the design of high-power fully integrated amplifiers in standard silicon process technologies are analyzed. The DAT is demonstrated to be an efficient impedance-transformation and power-combining method, which combines several low-voltage push-pull amplifiers in series by magnetic coupling. To demonstrate the validity of the new concept, a 2.4-GHz 1.9-W 2-V fully integrated power-amplifier achieving a power-added efficiency of 41% with 50-Ω input and output matching has been fabricated using 0.35-μm CMOS transistor

Multimodal electromechanical model of piezoelectric transformers by Hamilton's principle

This work deals with a general energetic approach to establish an accurate electromechanical model of a piezoelectric transformer (PT). Hamilton’s principle is used to obtain the equations of motion for free vibrations. The modal characteristics (mass, stiffness, primary and secondary electromechanical conversion factors) are also deduced. Then, to illustrate this general electromechanical method, the variational principle is applied to both homogeneous and nonhomogeneous Rosen-type PT models. A comparison of modal parameters, mechanical displacements, and electrical potentials are presented for both models. Finally, the validity of the electrodynamical model of nonhomogeneous Rosen-type PT is confirmed by a numerical comparison based on a finite elements method and an experimental identification

A Novel Digital Image Processing Technique to Detect Power Transformers Internal Faults using Frequency Response Analysis Polar Plot Signature

This thesis introduces a new application, which aims to improve the current approach to interpretation of the Frequency Response Analysis (FRA) signature. In contrast to current FRA practice (conventional approach), the newly proposed application develops various Digital Image Processing techniques to overcome most of the drawbacks of the conventional FRA approach. By automating and standardising FRA interpretation, its detection accuracy is enhanced so that incipient mechanical and non-mechanical faults within power transformers can be detected

Perfomance and Efficiency in Colombia's Power Distribution Sistem: Effects of the 1994 Reform

We asess evolution in perfomance, efficiency and productivity of Colombia's power distribution utilitiesbefore and after the 1994 regulatory reform that introduced electricity market activities for the power sector in 12 distribution companies from 1985 to 2001. Perfomance is evaluated contrasting changes in meanand median by Wilcoxon Rank Sum and Pearson test on financial and other perfomance indicators. Technical efficiency is measured by means of Data Envelopment Analysis (DEA). The nature of the dataset allows the the estimation of Malmquist productivity index and its evolution in time. Results show a recovery after thereform in the mains perfomance indicators of profitability, parcial input productivity, and output. Plantefficiency and productivity increased after de reform, mainly in the largest utilities used as benchmarks inthe DEA efficiency scores measures. Meanwhile, the less efficient power distribution companies did not improve after the reform and were not able to undertake plant restructuring to chatch up in plant efficiency with respectto the Pareto efficient input allocation. Econometric results on DEA efficiency scores suggest a positive effectof policy reform.Electricity distribution, productive efficiency, power sector Colombia, Malmquist productivity index

Low voltage dc to dc converter-regulator with minimum external magnetic field disturbance final report, 1 jun. 1954 - 30 jun. 1965

Engineering developments for low voltage dc to dc converter-regulator with minimum external magnetic field disturbanc