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.

Experience with the detection of faulty composite insulators on high-voltage power lines by the electric field measurement method

Abstract: Hydro-Quebec's experience with polymer insulators began in 1977. A sixteen km section of a 735 kV transmission line near Quebec City was then re-insulated with 282 composite insulators of three different makes in equal proportions. The objective was to study them under real service conditions in order to evaluate their performance and to assess the relative merits of each make. This experimentation was later extended to some other lines and/or voltage levels and has continued up to now. During all these years, various methods of testing composite insulators in-service have been experimented with and early in the 1990s, the first device developed at IREQ for the in-situ testing of porcelain insulators by the electric field method was modified and adapted for use on composite suspension insulators. This paper presents a few cases of insulators having a particularly dangerous type of failure mode and found on the lines by the use of the electric field method. Some background information on the detection of defects by this method is also given and some of the experiments done in the laboratory on composite insulators to define the limits of the method are described.

Probabilistic forecasting from ensemble prediction systems: Improving upon the best‐member method by using a different weight and dressing kernel for each member

Abstract: Ensembles of meteorological forecasts can both provide more accurate long-term forecasts and help assess the uncertainty of these forecasts. No single method has however emerged to obtain large numbers of equiprobable scenarios from such ensembles. A simple resampling scheme, the ‘best member’ method, has recently been proposed to this effect: individual members of an ensemble are ‘dressed’ with error patterns drawn from a database of past errors made by the ‘best’ member of the ensemble at each time step. It has been shown that the best-member method can lead to both underdispersive and overdispersive ensembles. The error patterns can be rescaled so as to obtain ensembles which display the desired variance. However, this approach fails in cases where the undressed ensemble members are already overdispersive. Furthermore, we show in this paper that it can also lead to an overestimation of the probability of extreme events. We propose to overcome both difficulties by dressing and weighting each member differently, using a different error distribution for each order statistic of the ensemble. We show on a synthetic example and using an operational ensemble prediction system that this new method leads to improved probabilistic forecasts, when the undressed ensemble members are both underdispersive and overdispersive. Copyright © 2006 Royal Meteorological Society.

Double-multiple streamtube model for Darrieus in turbines

Abstract: An analytical model is proposed for calculating the rotor performance and aerodynamic blade forces for Darrieus wind turbines with curved blades. The method of analysis uses a multiple-streamtube model, divided into two parts: one modeling the upstream half-cycle of the rotor and the other, the downstream half-cycle. The upwind and downwind components of the induced velocities at each level of the rotor were obtained using the principle of two actuator disks in tandem. Variation of the induced velocities in the two parts of the rotor produces larger forces in the upstream zone and smaller forces in the downstream zone. Comparisons of the overall rotor performance with previous methods and field test data show the important improvement obtained with the present model. The calculations were made using the computer code CARDAA developed at IREQ. The double-multiple streamtube model presented has two major advantages: it requires a much shorter computer time than the three-dimensional vortex model and is more accurate than multiple-streamtube model in predicting the aerodynamic blade loads.

Optimal scheduling of thermal generating units

Abstract: Scheduling the operation of thermal generating units involves the selection of units to be placed in operation and the allocation of the load among them- These two decisions must be taken so as to minimize the sum of tile startup, banking, and expected riming costs subject to the demand, spinning-reserve, and minimum down-time and up-time constraints and, sometimes, to the following two additional limitations: a unit should not be started up more than once a day; and no more than two units of the same plant should be started up simultaneously. This optimization problem is formulated in this paper as a mixed-integer nonlinear programming problem. Then, by following the Bender's approach, the problem is partitioned into a nonlinear and a pure-integer nonlinear programming problem- The First problem, which represents the economic dispatch problem, is not solved here. The second problem, usually called the unit commitment problem, is solved by a variational method and a branch-and-bound algorithm. Numerical results obtained for a network of ten generating units are presented.