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.

Identification of a chemical indicator of the rupture of 1,4-β-glycosidic bonds of cellulose in an oil-impregnated insulating paper system

Abstract: In this study, headspace gas chromatography/mass spectrometry has been used to assess the volatile by-products generated by the ageing of oil-impregnated paper insulation of power transformers. Sealed-glass ampoules were used to age under oxidative conditions 0.5-g specimens of insulating paper in 9 mL of inhibited mineral oil in a temperature range of 60–120 °C and moisture of 0.5, 1 and 2% (w/w). A linear relationship between one of the oil-soluble degradation by-products, i.e. methanol, and the number of ruptured 1,4-β-glycosidic bonds of cellulose, regardless of the type of paper (ordinary Kraft or thermally-upgraded (TU) Kraft paper), was established for the first time in this field. Ageing at 130 °C of model compounds of the Kraft paper constituents (α-cellulose, hemicellulose and lignin) and two cellulosic breakdown by-products (D-(+)-glucose and 1,6-anhydro-β-d-glucopyranose) confirmed that the α-cellulose degradation was mostly responsible for the presence of this molecule in the system. Furthermore, additional 130 °C-tests with six different papers and pressboard samples under a tight control of initial moisture indicated that at least one molecule of methanol is formed for each rupture of 1,4-β-glucosidic bond of the molecular chains. Stability tests showed that the ageing indicator is stable under the oxygen and temperature conditions of open-breathing transformers. The presence of methanol was detected in 94% of oil samples collected from over than 900 in-service pieces of equipment, confirming the potential for this application. Lastly, the tests have shown that oil-oxidation by-products and TU-nitrogenous agents modify the methanol partitioning coefficients in the paper/oil/air system, which makes their study essential over a range of field conditions encountered by power transformers. Results are presented and discussed in comparison with 2-furfuraldehyde, which is the current reference in the domain.

Surface effects on electrochemical properties of nano-sized LiFePO4

Abstract: LiFePO4 has won the challenge to be the active element for the positive electrode of Li-ion batteries for electromobility. In an attempt to optimize the electrochemical performance, efforts have been made to reduce the size of the particles, so that the electrons and Li+ ions have a reduced path to travel inside the material. However, when the size decreases below 100 nm, surface effects become increasingly important, and can eventually dominate the physical and the chemical properties. The purpose of this work is to review them and their implications, involving sensitivity to exposure to humidity, and separate between surface disorder effects, impurities and intrinsic properties. This goal is achieved by the combination of different techniques to characterize the particles, including X-ray diffraction, electron microscope imaging, optical spectroscopy, and magnetism.

Compliance Analysis of PMU Algorithms and Devices for Wide-Area Stabilizing Control of Large Power Systems

Abstract: For the first time, IEEE Std. C37.118.1-2011 now provides metrics for PMU dynamic performance in terms of classes P and M filter designs. This paper attempts to determine whether fulfilling these requirements makes the PMU inherently well suited for stability control applications such as wide-area power system stabilizers (PSSs). In this aim, we considered two different frequency-adaptive approaches for class-P and -M compliance to ensure operation over a wide frequency range. The first is based on a finite-impulse response (FIR) with no overshoot in either the phase or the amplitude step responses, while the second is Kalman filter-based (EKF), which allows for a more refined out-of-band interference rejection at the cost of a phase step response with overshoot. These two approaches are benchmarked against Hydro-Quebec`s existing PSS requirements and the conclusion is that the total vector error-based response time is not indicative of the phase lag within the frequency band of interest, nor of the 3-dB bandwidth under sinusoidal amplitude/frequency modulation phenomena, which are key criteria when specifying PSS PMUs. Using simulated and field-recorded network fault responses, we also show that a class-M PMU is unsatisfactory for wide-area stabilizing control, unless its performance is improved during the fault period, which is not covered by Std. C37.118.1-2011.

State-space system identification-toward MIMO models for modal analysis and optimization of bulk power systems

Abstract: This paper provides an introduction to a reduced-order, small-signal identification approach to modal analysis and control of large power systems. Being based on system-wide responses to low-energy pulse excitations generated using conventional time-domain simulation software such as PSS/E or EMTSP, it readily takes full advantage of the large built-in model database. The proposed multi-input-multi-output (MIMO) minimal realization reveals naturally the dominant modes attached specifically to a given device, as well as the transfer functions relating selected measurement and observation sites. It plays a complementary role to direct computation of the full-scale linearized model using a comprehensive program such as MASS, after a summary of the theoretical work initiated at Hydro-Quebec in the early 1990s to promote this approach and put it into routine use, we present the main challenges in developing a production grade computer code. Detailed examples inspired by actual network studies at Hydro-Quebec are discussed, the most complex of them involving the identification of a 125th order MIMO model with 26 inputs and 26 outputs.