Recently, the wholesale electric power exchange has been founded in Japan. With the progress of the electricity market, some management schemes of electricity price risk will be necessary. In financial markets or the preceding electricity markets, various “derivatives" on assets in the markets are often used as management tools to hedge the price risk. This paper gives a short commentary on some fundamental concepts of the derivatives and the pricing theory in the financial engineering, and discusses the problems on the financial engineering approach to electricity derivatives.
This paper presents a constructing Lyapunov function for power system based on solving the Linear Matrix Inequality (LMI) derived from the Lyapunov stability theorem considering with dynamics of load characteristic and AVR control system. The proposed Lyapunov function is constructed as a quadratic form of state variables and an integral term which satisfies the curl equation and the sector condition. An induction machine and a synchronous machine are considered as load characteristics. One machine and one load infinite bus system is considered taking into account the flux decay effects and AVR with one time constant of the generator. To verify the proposed Lyapunov function, the transient stability assessment is shown. The critical clearing times given by the proposed Lyapunov function are compared with those obtained by the numerical integration method, and they are shown to be practical.
Delayed Feedback method for controlling three machines operating onto an infinite-bus system is investigated by computer simulation. Only internal state is necessary for this method. The time series of phase angle of generators with an accident of transmission lines shows the irregular motion and the step-out. It is shown that the irregular motion of the electric power system is controlled onto the stable equilibrium points with the six stable manifolds by delayed feedback control.
Recently, numbers of distributed generators (DGs) connected to distribution systems have been increasing. The system operators should know how large capacity of DGs can be connected without problems to one feeder of the system to control the system appropriately. Conventionally, many studies have presented about the maximum capacity of the DG, but they have been limited results calculated by typical or average value model. However, many DGs will access to one feeder if deregulation of electric power industry is accelerated in the near future. In order to cope with this background, the authors have drawn general formula to calculate the range of the permissible capacity of DGs per one feeder. In order to deal with sets of DGs that are dispersed on distribution line completely, the authors have drawn differential equation of complex power and one of voltage drop which are expressed by function of distance from a substation by transforming. The general formula to calculate the range of the permissible capacity of DGs connected to the feeder is led by solving these equations under the line voltage, the line current, and the power factor of DGs restriction condition. As a numerical analysis, the authors have calculated the maximum capacity of DGs depending on many parameters such as the length of the feeder and DGs power factor etc. In a short length of a feeder, the maximum capacity of DGs is ruled by the current restriction condition, but in a long length of a feeder, it is ruled by the upper voltage restriction condition.
All the phenomena have been solved about the wet rope's melting damage under the power lines. The results are as summarized below. A wet rope acts as a conductor with the same diameter on static induction under the power lines, and if the rope is grounded, the static current is induced on the rope as same as the conductor. The static induction current flowing through the wet rope increases by the ends of the rope, and the half of the induced current on whole rope flows out each end. The cause of wet rope's melting damage under the power lines originates in above-mentioned static induction current, and this damage occurs at the end of the rope which the induction current is maximum. The maximum static induction current, without melting damage to the wet rope is 1mA or less at 12mmφ nylon rope and 5mA or less at 10mmφ aramid rope under 500kV power line. The range (length of the rope, distance between the rope and the power line) on which the wet rope's melting damage occurs can be checked from Table 4 and Fig. 10.
In order to forecast the possibilities of snow accretion on aerial wires, we studied its macroscopic physical mechanism and developed a computer simulation model. We considered aerological temperature in addition to temperature on the ground to assume liquid water content of snowflakes. For calculating cylindrical-sleeve snow growth more adequately, we introduce the following facts to the model, (1) wind speed and its direction were usually unsteady, (2) wind would not necessarily cross wires at right angle, and (3) wires had some snow accretion resistance. We got some sufficient results of the simulated cylindrical-sleeve snow weights between 1/3 and 3 times of the observed weights.
A fault current limiter (FCL) is extensively expected to suppress fault current, particularly required for trunk power systems heavily connected high-voltage transmission lines, such as 500kV class power system which constitutes the nucleus of the electric power system. By installing such FCL in the power system, the system interconnection is possible without the need to raise the capacity of the circuit breakers, and facilities can be configured for efficiency, among other benefits. For these reasons, fault current limiters based on various principles of operation have been developed both in Japan and abroad. In this paper, we have proposed a new type of FCL system, consisting of solid-state diodes, DC coil and bypass AC coil, and described the specification of distribution power system and 66kV model at the island power system and the superconducting cable power system. Also we have made a practical study of 66kV class, which is the testing items and the future subjects of the rectifier type FCL system.
Superconducting generators have many advantages such as increasing generator efficiency and improving power system stability etc. In Japan, national project has been conducted since 2000 which is aimed at the development of fundamental technologies required for a high output density and a large capacity superconducting generators. This paper describes the results of this project, focusing on a “6,000A-class field winding development". A superconducting generator with a high output density and a large capacity has inherent factors that decrease superconducting stability. These are: 1) increase in the magnetic field in the winding which is caused by the increase in winding current density and 2) difficulty in fabricating windings which increases as conductor diameter becomes larger. To secure the stability, we adopted a higher-copper content conductor and a design that increases winding fixing pressure, along with devising a winding method that accommodates larger conductor diameter. These improvements were applied to a partial model of a 600MW field windings. Test results of the model showed a good stability, indicating that design and fabrication technique for a 6,000A-class superconducting field winding has been successfully evaluated.
This paper presents stability and an interactive phenomenon of one SVC, two or more sets of SVC, a SVC and a SVR in distribution systems. In particular, we focus on the saddle-node bifurcation and Hopf bifurcation points. The two local bifurcation points show a boundary of a stable domain.
In order to grasp properly PEFC power generation performances, it is necessary to know factors for water management such as transmissivity and electro-osmotic coefficient of water vapor through the membrane, and factors for power loss such as active and resistive overpotentials. In this study we have measured these factors to analyze our experimental results of PEFC power generation tests by our two-dimensional simulation code. It considers simultaneously the mass, charge and energy conservation equations, and the equivalent electric-circuit for PEFC to give numerical distributions of hydrogen/oxygen concentrations, current density, and gas/cell-component temperatures. The numerical distributions of current density under various operating conditions agreed well with the measured distributions by segmented electrodes, which had grooves for hydrogen/oxygen supply and were mold in our test cell being electrically insulated. Hydrogen/oxygen concentration changes measured by gas chromatography along the gas supply grooves gave also the experimental current distributions, which coincided almost with those by the segmented electrodes. Factors to correct the small difference between the measured and the calculated current density distribution are also discussed from the stand point of the physical meaning of the calculated results considering factors which are not taken into account in our code.
Omitting one phase's current limiting arcing horns on three-phase distribution lines has been applied since 1990's and contributes the costdown for lightning protective countermeasures. Moreover, in order to promote the costdown for the lightning protective countermeasures on single-phase distribution lines, we have investigated the methods omitting one phase's current limiting arcing horns on single-phase distribution lines. When the single-phase distribution line omitting one phase's current limiting arcing horns branches or extends from three-phase distribution line omitting middle phase's current limiting arcing horns, there are possibilities that short circuits are generated between the single-phase distribution line and the three-phase distribution line by a direct lightning stroke. In order to preventing the short circuits outage, we have clarified the conditions that sparkovers generated at some poles and that short circuits continued experimentally and analytically. Based on these conditions, we proposed some effective countermeasures for preventing the short circuits outage on single-phase distribution line omitting one phase's current limiting arcing horns.
A lightning return stroke model is indispensable in calculating electromagnetic field associated with a return stroke. A lot of return stroke models have been proposed, however, no model has ever succeeded in reproducing all the features of typical electromagnetic field waveforms at various distances. In this paper, two return stroke models are proposed. One is a Transmission-Line type model, and the other is modification of Diendorfer-Uman model. These models successfully reproduce all the features of typical electromagnetic field observed on ground.
Various engineering models of return strokes specifying the temporal and special distribution of the currents along the channel have been presented, and these models have been tested for negative subsequent strokes of natural or triggered lightning by comparing measured and model-predicted electric and/or magnetic field waveforms. In this letter, the transmission line model is tested for a negative first stroke of natural lightning by comparing parameters of the magnetic field waveform obtained by LLS with those calculated by using the return-stroke current estimated from the measured electric field.