Electricite De France Research Articles

Quelques remarques sur l'utilisation des modèles mathématiques pour la prévision en hydrologie et météorologie

Practical forecasting models applied by Electricite de France are described. The multiple regression computation is applied to the following two types of forecast : 1. Long-term forecasting of runoff volumes and the subsequent evaluation of low-water flows, based on monthly rainfall and temperature. 2. Short-term flood forecasting, based on antecedent daily or hourly rainfall, antecedent runoff and eventually a seasonal parameter. 3. Extreme floods' probability is evaluated by the method, in which extreme daily (or hourly) flow and extreme daily (or hourly) rainfall distributions are extrapolated together, being both assumed to decrease exponentially according to e-(x/a) (a is called Gradex ). 4. Local daily rainfall is forecast, one and two days ahead, by multiple correlation of rainfall versus pressure at ground level, and 1000-700 mb thickness, inside a sample of analog days, selected by pattern recognition of the 700 millibars level over western Europe-North atlantic. Graphical correlation methods-including co-axial relations are considered to be subjective and ineffective. The main point in computing multiple regression is that it allows rapid selection of the most useful variables for the forecast and the principal part of the natural model to be isolated, even if it is non-linear. A satisfactory linear approximation can be achieved by means of simple transformations. Deterministic models are merely considered to be inventories of links pointing to possible correlations, rather than as representing actual forecasting models. There is nothing to be gained in relying exclusively on over-detailed physical schemes of debatable usefulness : a reliable choice of variables is much more critical than the exact analytical form of relations.

The “Investment '85” Model of Electricite de France

The purpose of the “Investment 85” model is to shed light on the evolution, up to 1985, of the optimal structure of electricity production equipment in France and to outline its geographical distribution by main regions. The model fits into the general pattern of theoretical studies which contribute to the preparation of investment decisions by Electricité de France. It was solved in 1965 and represents the status then current in the application of mathematical programming methods to investment decision problems faced by Electricité de France. A detailed description of the model including the production and consumption features is provided. The various components of the total cost and the constraints are discussed. A treatment of the problem under uncertainty is given and the main results of the model are summarized. In addition the paper contains a historical review of the main stages in the development of the model and its solution.

Direct supply of a large pulsed load from the e.h.v. transmission network

The paper describes the results of design studies examining the possibility of supplying a large pulsating load of ±160MW directly from the national Grid. The pulse load considered is that of the proposed 300 GeV European particle accelerator; however, the study treatment and results are also relevant to the more general problem of step load and generation changes and their effect on power-system operation and design. Several methods of suppression of the pulse-induced voltage fluctuation are outlined and an account is given of the theoretical investigations into the expected dynamic behaviour of the power system when subjected to a cyclic pulse load of this magnitude. Practical support tests on the supply system are described and the collaborative tests with Electricite de France and other Continental supply systems, via the cable across the English Channel, are given special emphasis. The novel application of time-series-analysis techniques to frequency measurement is also demonstrated. The results of the study show that the direct connection of such a pulse load to the public-supply network is a practical possibility.

Methods of choosing equipment at Electricite de France: Development and present-day concept

In 1950 Electricité de France (EDF) began to use a method of relative profitability in choosing its production equipment. This was the so-called Blue Note method. However, the size of the investments put into play, the variety of techniques which could be used, and the major uncertainties concerning long-term development of sources of energy required the simultaneous use of aggregate programming methods. Use in the last five years of nonlinear programming has confirmed the usefulness of these methods. The problem of coherence between this aggregate (or “global”) approach and the “analytical” approach (the Blue Note) then became of great importance. This is why an extensive effort at theoretical research has been devoted to this problem, at the time when development of the economic context made it necessary to update the Blue Note. Now, following this theoretical research, EDF is able to fuse the two approaches into a single method ensuring coherence of all the decisions for choosing equipment, whether it is a matter of general management (centralized decisions) or of the multitude of small decisions taken in a decentralized way by the regional managers.

Rejets en mer des eaux résiduaires faiblemhent radioactives du centre de la Hague

The construction of a large chemical treatment plant for radioactive Electricite de France reactor fuel has brought with in an effluent disposal problem, for which the possibility of disposal of slightly radioactive decontaminated effluent at sea has been investigated in the absence of a big river carrying a regular flow. The attractive feature about the selected dumping area off Cap de la Hague is its powerful Raz Blanchard current which it was thought could be relied on to rapidly disperse the radioactive elements within a very substantial body of sea water. The project authorities considered it desirable to aim at minimum possible specific sea water contamination in the immediate vicinity of the disposal channel outlet. This meant studying contaminated water movements and establishing the safety margin attached to the scheme by tracing the radioactive effluent's route back to Man and calculating likely radiation therefrom. This safety margin was found to be very high. A further purpose of the preliminary studies was to deterrnine the optimum site for the channel outlet and appropriate times at which to discharge the effluent (3 hours during each tide.) The disposal duct runs overland for a short distance, followed by an underwater run 5,500 m in length. Technical design and pipe-laying problems have all been solved, especially as associated with the altitude of the Centre, the ground features and the strong local sea currents. Despite all the difficulties encountered, the undersea duct was laid in six months. An original experiment with dye designed to simulate normal operating conditions during a fortnight was carried out as a check on the accumulation possibilities observed on the model. Thus, the general problem was dealt with by alternating model and real-life tests, which seemed to be the only way to do the job in view of the very numerous parameters on which dispersion depends in this region. The experimental data were found to agree very closely with the initial data observed in real life, Careful systematic supervision of the area is ensuring that contamination of the sea water within the limits laid down by the local authorities (which are based on the preliminary studies carried out on site) does not endanger human life, i.e.that it is well within the limits specified by the International Commission for Protection against Radiation.

Development of automatic digital control of a power system from the laboratory to a field installation

Progress of automatic power-system control in the CEGB is outlined briefly from its consideration before the d.c. cross-Channel link with Electricite de France to the present, when it has been applied experimentally to part of the CEGB system. The predictive nature of the automatic-control scheme tested is discussed, together with the objectives of this scheme. An experiment in the laboratory, using a model power system controlled by a digital computer, and the subsequent application of the control techniques and their development for field use are described.

Analyse des contraintes relevées sur une pale du groupe A 3 N de la Rance

A study of the behavior of the main mechanical parts of a machine under actual operational conditions can contribute valuable information towards the manufacturer's and designer's development studies. A bulb unit at the Rance power plant, which had been in service under a wide range of different conditions provided an interesting subject of investigation into the behavior of its main mechanical components in industrial service. A major investigation was successfully carried out by close collaboration between Electricite de France and Neyrpic, a Division of Alsthom, one of the manufacturers of these units. This development research enabled more economical low-head plant operation to be achieved. The author describes the results of strain gauge measurements on a runner blade, in which the results were transmitted through the sea water by raclio. The results provided a check on the design calculations and helped towards a better understanding of stresses arising under transient operating conditions. Characteristic operating conditions were covered with the sets operating as direct reverse pumps and turbines. The average stress measured in the blade mounting under peak operating conditions was 14 kg/sq.mm with the unit running as a turbine. The blade vibrated under the excitation of the fixed components and cavitation but at no time did this vibration assume dangerous proportions. No abnormal effects were observed when the machine cut out. This analysis will require completing with a study of the hydrodynamic pressure distribution, for which a special measurement programme has been carried out.

Quelques exemples de dégradation des bétons par cavitation dans des ouvrages hydroélectriques

In 1965 the Hydraulic Production Section of Electricite de France carried out a survey of cavitation damage to concrete among operational structures. Twenty cases were observed, resulting in the following findings:- 1) Cases of erosion were fairly infrequent; 2) Comparatively major damage usually occurred after exceptionally prolonged operation (e.g. after passing part or the whole of the flow diverted through the relief arrangements during staggered starting-up of power sets; 3) More severe damage seems liable to occur with the two following types of flow:- a) Moderate mean flow velocities (10-20 m/sec) with considerable turbulence, b) High mean flow velocities (above 30 m/sec) with little turbulence. Relief works belong to category (a). Their energy dissipation arrangements frequently seem to require full sheeting protection. Where high flow velocities are experienced, e.g. in bottom outlets, careful surface outline design and a smooth finish are important factors in preventing rapidly spreading damage.

Ordenación hidráulica, en Provenza (Francia)

French Provence has an irregular rainfall and a large need of water, both for urban use and for the irrigation of its fertile soil. Local needs, the general progress and the development of the Electricite de France (E.D.F.) have led to the formation of the Canal Society of Provence, from which important improvements in the existing canal network are to be expected, and also in the provision of new sources of water. As the number of works and reforms are large, the author has limited himself to a description of the more outstanding ones. In relation to the construction machinery used in these works, special mention should be made of a jumbo which drills and clears away the debris after firing the charges. This is a very important problem, which appears to be finally solved, so that in the near future the rate of drilling in galleries will be substantially improved. Another important feature, which could be usefully applied to hydraulic projects with shortage of water, is the use of pressurized irrigation networks and aspersion type watering.

Évolution de la méthode thermodynamique de détermination du rendement des machines hydrauliques

Évolution de la méthode thermodynamique de détermination du rendement des machines hydrauliques

Marginal Cost Pricing in Practice

In the late forties and in the fifties a number of French economists connected with Electricite de France were actively engaged in thinking about pricing policy and investment criteria. In contrast to most of their English speaking colleagues, who addressed themselves to their fellow economists, these Frenchmen were concerned to formulate proposals for practical implementation. Thus their work on marginal cost pricing led to the new tariff structure for high-voltage supplies introduced in 1957. Similarly, their work on long-term programming has been directly applied in formulating the investment plans of Electricite de France. In view of their practical importance and intellectual quality, it is extremely valuable to have a selection of these writings brought together and made available to a wider public. Professor Nelson has compiled a most interesting book. It contains, apart from his introduction, twelve chapters (some of them joint products) by a total of seven authors, Marcel Boiteux and Pierre Masse being the who have contributed the lion's share. Chapter 1 offers a bird's-eye view of the economic problems of Electricite de France; the next six chapters deal with price policy, including Boiteux's famous paper on peak pricing; chapter 8 is about the optimal management of seasonal reservoirs, and the last four chapters relate to the choice of investments. There is a certain amount of duplication between some of the chapters, but at least this reassures the reader that he faces a coherent body of doctrine and not a collection of unrelated pieces. In France, the unit-charge of the high-voltage tariff (the tarif vert) varies with time of day, time of year and geographically; in addition there is a peak kilowatt charge. This tariff, which reflects marginal costs, though of necessity only in an approximate way, is given its justification and has its derivation explained in chapters 2 to 7. Many of the complications in the exposition are necessitated by the mixed hydro/thermal character of French electricity supply. The following remarks gloss over these complications in order to concentrate on a key theoretical point in public utility pricing which has bothered a number of writers, namely the relation between longand short-runmarginal cost pricing. The authors' position, as stated by Boiteux, is that provided there is an optimal investment policy, short-term pricing is also long-term pricing and there is no longer any contradiction between the two (p. 70).

La stabilité des tranchées profondes forées en présence de boue

Considerable progress has been made in Europe during the last ten years with the slurry trenching technique of excavating trench panels of length L by drilling with mud (Fig. 1), the trench then being filled with concrete fed through a tremie-pipe. The author analyses the stability conditions for a single trench element. The stabilising pressure Ph of the mud must be such as to balance the passive thrust of the ground σIII (Equation 1). The first step in calculating this thrust is an examination of equilibrium conditions in a plane parallel to the panel faces (Figs 2 and 3). Arch effects in this plane are assumed to be similar to those in a storage silo. A similar calculation to the one by Caquot for silos yields values for σI and σII ; the equilibrium limit occurs in the plane containing σI and σII which latter is found from σI (Equation 2 and Fig. 4). Theoretical considerations show that σIII does not increase indefinitely with depth, but that it tends to a finite value depending on the width of the panel. (Equation 3). Possible cohesion of the ground is easily allowed for by applying the corresponding states principle (Equation 4). The theory is applied to data observed at an Electricite de France construction site at Gerstheim (Figs 6, 7 and 8), and both sets of results are found to agree satisfactorily.

Étude sur modèle réduit de la coupure de la Rance

Étude sur modèle réduit de la coupure de la Rance

The Green Tariff of the Electricite de France

Editor's Note. In submitting this article in its English translation the translators wrote: We have sought to adhere to the meaning of the original French but also have taken some editorial license in clarifying the meaning for the reader. The 'Tariff Vert' or Green tariff, instituted late in 1956 by Electricite de France, the nationalized electric utility system of France represents the most advanced and sophisticated application of marginal cost pricing yet attempted. Regardless of whether the principles are specifically applicable to American conditions, the work of Boiteux, Dessus and others associated together in the formulation and implementation of the tariff are worthy of study and have been receiving increasing attention from American economists. This article first describes the impact of inflation on the electric tariff set up in France in the 1935-38 period which was still in effect in 1956. As will become apparent, the original tariff became completely irrational as a result of inflation. The later part of the translation is given to the Green Tariff. It is noted that this tariff is applicable to wholesale service at voltages ranging upward to 220 kv, an extremely high service voltage. Customers apparently furnish their own transformation equipment. Any rates quoted in American currency are at the approximate exchange rates prevailing at the time and have been computed by the translators. Readers are referred to the paper by Professor James R. Nelson at the American Economic Association meetings of December 1962 in which the tariff was analyzed. It is understood that Professor Nelson will bring out a book which will contain translations of numerous French articles and papers on the subject.

Presa de Migoelou

This hydroelectric installation is on the higher section of the Gave d'Arrens, in the French Pyrenees. The dam has been constructed by the Electricite de France. The power station takes advantage of a hydraulic fall of 1840 ms, and its power is 124,000 kVA, with a yearly energy output of 400 million kWh. The main project is situated at a height of 2255 ms, so that it has been constructed during four successive summer periods. The height of the dam is 25 ms, and consists of a series of vaults. The volume of water it can hold is very considerable, being of the order of 17 x 10 6 m 3 . The foundations of the dam are granite, covered by a moraine of 20 ms maximum depth. The vaults of the dam, of 25 ms span, form two straight lines in planform, following the configuration of the ground. The thickness of these vaults is 2 m, and on the upstream side the slope is 0.6. The abutments have a constant thickness of 2 ms, and the one situated at the meeting point of the two straight sections has been designed to meet the most adverse possible situations. Statical calculations are based on the assumption of a temperature range between —15 and 35 C, and the thrust of ice formations has been disregarded. The project includes other smaller dams. Considerable work Was done in the initial stages in preparing access to the site, for which purpose it became necessary to install an aerial cable transport system.

Presa de Grandval

This important project is situated on the top section of the river Truyere, within the region of the French Central Massif. The dam has been constructed by the Electricite de France. The total hydroelectric development project in this zone involves six dams and six power stations, to exploit an overall hydrostatic head of 520 ms. The water accumulated by these dams has a maximum volume of 540.10 6 cubic metres, and will produce a yearly output of 1450 .10 6 kWh. The Grandval dam rests on strong microschistous rock folds. Its length is 330 ms, and its maximum height 88 ms, measured from the foundation base. Structurally it is formed by a series of vaults supported by abutments, which are spaced at 50 ms intervals. The mean thickness of the vaults at the base is 4.90 ms, and 1.50 at the crown. The vertical slope on the upstream side is 0.70. A feature of this design is that the vaults are not uniformly cylindrical up to the top, as is customary. The top part of the dam consists, in fact, of a small gravity dam, resting on the underlying vaulted structure. The dam is straight at the top, and a road runs along it, on an overhanging structure. The dam has a surface spillway, which is ski jump shaped, and runs over the two abutments on either side of the power station.

Capital Budgeting and Pricing in the French Nationalized Industries

IT IS only recently that American economists have begun major efforts to apply welfare economics to the decisions of specific public enterprises. They have principally chosen the difficult field of water-resource policy, one of the few important areas of American public enterprise where such efforts are feasible.' Jn France, on the other hand, where the postwar public sector includes important basic industries, a major share of economists' output since the war has concerned the application of welf areeconomics principles to policy-making in these industries. The French economists have concentrated on two major problems: (a) the formulation of criteria for choice, by public enterprises, among proposed investment projects, the criteria to be applied ini allocating fixed capital budgets assigned to the enterprises; and (b) the pricing of products so as to approximate the prices of a welfare optimum in the face of complications such as a no-deficit requirement for each enterprise, peaked demand, many joint products, and production uncertainties. The French theoretical work on investment choice parallels recent American discussion; the work on peak-load pricing antedates recent American results; and some of the work on optimal pricing under the no-deficit constraint has no American counterpart. We shall examine the major French results in this paper. A survey seems particularly worthwhile because the work has had a practical impact, which we shall describe, on policy in the French nationalized industries. A majority of French economic theorists are associated in one capacity or another with the nationalized industries, some in the highest managerial posts.2 The industries themselves have sponsored much of the theoretical work, and their recent investment and pricing policies show its influence. The French economists' practical success ought to encourage those American economists who have been urging American public enterprises to adopt policies closer to those which the efficiency conditions of welfare economics imply. We shall be concerned, specifically, with the studies (many of them unpublished) performed by members of, or at the request of, Electricite de France, Charbonnages de France (coal mines), Societe Nationale des Chemins de Fer (railways), and Gaz de France.3 Under-

“Electricite de France” faces expansion problems

“Electricite de France” faces expansion problems

Hydroelectric Power in France: Plans and Projects

THE production of electric energy has been one of the major problems facing the planners of Europe's economic reconstruction since World War II. The fact that several of the leading industrial nations of Western Europe are importers of coal, dependent on outside supplies for that most important source of thermoelectric power, brought the necessity for new sources of hydroelectric power sharply into focus. France has pushed the development of hydroelectric power more than any other country in Western Europe; for French domestic supplies of coal have been inadequate to cover the needs of both industry and the production of electric energy. In I95 I, France needed a total of 75 million tons of coal a year. At least onethird of this was required for the production of electricity in the great industrial regions of northern and northeastern France and in the Paris metropolitan area. The Monnet Plan, drawn up shortly after World War II (I946) to organize the reconstruction of France's economy, entrusted the task of planning in the field of electric power to Electricite de France, the state agency that now controls the majority of the power plants and the entire high-tension grid. Most of the thermoelectric power is generated in three regions: northern France, eastern France, and the Paris area. Hydroelectric power, on the other hand, is generated in the Pyrenees, the Central Massif, the Alps, and the valleys of the Rhone and the Rhine. Planning and construction of hydroelectric installations are under way in four regions: the Central Massif, the Alps, the Rhone Valley, and the upper valley of the Rhine. In each of these regions dams are being built, powerhouses equipped with turbines and generators, and high-tension lines strung across the countryside to carry power to the industries, railroads, and homes of France. The four regions present different environmental conditions, and thus the problems confronting the planner and the engineer also differ. This study is intended to illustrate the planning and construction techniques cur-