Hydro-Québec

About: Hydro-Québec is a government organization based out in Montreal, Quebec, Canada. It is known for research contribution in the topics: Electric power system & Dielectric. The organization has 2596 authors who have published 4433 publications receiving 100878 citations.

Triggering and guiding high-voltage large-scale leader discharges with sub-joule ultrashort laser pulses

Abstract: The triggering and guiding of leader discharges using a plasma channel created by a sub-joule ultrashort laser pulse have been studied in a megavolt large-scale electrode configuration (3–7 m rod-plane air gap). By focusing the laser close to the positive rod electrode it has been possible, with a 400 mJ pulse, to trigger and guide leaders over distances of 3 m, to lower the leader inception voltage by 50%, and to increase the leader velocity by a factor of 10. The dynamics of the breakdown discharges with and without the laser pulse have been analyzed by means of a streak camera and of electric field and current probes. Numerical simulations have successfully reproduced many of the experimental results obtained with and without the presence of the laser plasma channel.

Wide Frequency Range Adaptive Phasor and Frequency PMU Algorithms

Abstract: The paper deals with developing and testing frequency-adaptive PMU algorithms with wider linearity range than specified in IEEE Std C37.118-1. This goal is achieved by means of three different concepts encompassing robust state-of-the-art design approaches: 1) FIR bandpass filtering, 2) extended Kalman filtering (EKF), and 3) discrete Fourier transform (DFT) demodulation with FIR low-pass smoothing. While FIR-based PMUs are linear phase with no overshoot in either phase or amplitude step responses, the adaptive EKF PMU is more computer-intensive but allows for a reduced group delay and better out-of-band interference rejection at the cost of a phase step response with overshoot. Frequency measurement performances of the various PMUs are assessed in detail. It turned out that FIR PMUs are best for meeting Std C37-118-1 metrics but they are outperformed by EKF under changing harmonics. Test results on three recent commercial PMU models further confirm that PMU algorithms meeting standard C37-118-1 can behave quite differently under dynamic conditions.

Effect of Graphite Particle Size on Irreversible Capacity Loss

Abstract: Electrolyte decomposition and irreversible capacity loss (ICL) occur on carbon electrodes in Li‐ion cells. The nature of the surface sites and their role in the amount of electrolyte decomposition on carbon electrodes is not fully understood. Therefore, a study was undertaken to analyze the relationship between the ICL and the active sites on natural graphite of prismatic structure. The ICL was measured on natural graphite of predominantly two‐dimensional platelets of average particle size varying from 2 to 40 μm. The fraction of edge and basal plane sites was determined for ideal prismatic structures of different particle size and used as a model for the natural graphite particles. This analysis permitted an analysis of the relationship between the electrolyte decomposition and the distribution of surface sites. From this analysis we conclude that these sites play an important role in the magnitude of the irreversible capacity loss on natural graphite. © 2000 The Electrochemical Society. All rights reserved.