摘要:

AbstractWhen ground‐fault problems occur on a cable line, immediate fault location and restoration are required. Therefore, various new methods to locate the fault point instantaneously have been investigated to replace such conventional methods as the Murray loop method and the pulse radar method [1]. These methods require a long time to locate the fault point. One possible fault location method is to sense the temperature rise following a ground fault using a fiber optic distributed temperature sensor. Application of this method was found feasible through sensing the temperature rise at a ground‐fault test using a thermocouple as a temperature sensor with test cables [4].A power/optical composite cable was prepared experimentally and after verifying its thermal mechanical performance, the temperature rise at an incidence of a fault was determined and the anticipated performance was demonstrated in a ground‐fault test. This article describes the outline of the

ISSN:0424-7760    

DOI:10.1002/eej.4391140601

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper describes a new approach to the analysis of the back‐swing phenomena in multimachine power systems. When a short‐circuit fault occurs in a power system, some generators decelerate in a short period immediately after the fault in some cases. The phenomenon called back swing is caused by the transient responses in armature winding of synchronous machines and in transmission lines. To represent the back swing in detail by a mathematical model, these transient behaviors have to be described by sets of differential equations. Then not only does the order of differential equations increase, but the convenient expression of the transmission system by a set of node equations becomes useless.In this paper an equivalent power system model for the simple representation of the back swing has been proposed. First, an impedance for each machine that represents the transient of transmission system has been introduced. It is assembled into the differential equations associated with armature winding response. Then the transmission system is represented by a constant impedance matrix. This model makes it possible to calculate the transient behavior of armature flux in multimachine power systems. The transient torque brought to the rotor shaft by the flux is calculated directly and it represents the back‐swing phenomena effect

ISSN:0424-7760    

DOI:10.1002/eej.4391140602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractElectricity markets are experiencing widespread changes that are significantly altering the industry. The purpose of this paper is to analyze the economic consequence of various rules of purchased power pricing and wheeling fees of an electric utility by game theory.A regulator, an electric utility, and a cogenerator are included in this model as players of the game. Consider an extensive game model of an electricity market where a cogenerator sells excess electricity to anelectric utility or an end user. The regulator behaves so as to maximize social welfare. The electric utility and the cogenerator intend to maximize their own profit. The wheeling fee between the electric utility and the cogenerator is adjusted to maximize the sum of incremental profits.We have found that a buy‐back system (the utility purchases cogenerated power) and a cogenerator‐customer wheeling system are equally efficient and are more desirable than a monopoly system. The buy‐back rate should be equal to (in the LP bargaining solution) or less than (in the Nash bargaining solution) the marginal cost of the electric utility. We also conducted an analysis of two‐period electricity

ISSN:0424-7760    

DOI:10.1002/eej.4391140603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe molten carbonate fuel cell (MCFC) power plant is expected to be one of the most promising future power generation systems for the electric utilities because of its high efficiency, environmental suitability and capability of using coal as fuel. To obtain such attractive performance, it is necessary for the plant to adopt the gas‐recycling operation system. The authors tested a 6‐kW class MCFC stack with three types of gas recyclings, i.e., cathode, anode and carbon dioxide ones, including pressurized conditions.This paper describes the test results and the effects of the gas‐recycling operations. Cathode gas recycling is proved to be able to control the stack temperature and give the flexibility for setting oxygen utilization. Anode gas recycling is proved to be able to suppress the methane formation and decrease the deviation of the stacked cell voltages. Including the starting‐up process, it is proved that the electricity can be generated from the stack without supplying carbon dioxide from outside the system by carbon dioxide gas recycling. In such a process using a burner for carbon dioxide gas recycling, burner temperature must be controlled to a certain value. It is important to adjust the fuel supplying rate, load current and cathode gas‐recycling ratio to each other. At the load change process, constant gas utilization operation is not effective in changing the burner te

ISSN:0424-7760    

DOI:10.1002/eej.4391140604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractTo understand a number of power system phenomena and to predict critical conditions in system operation, such as voltage collapse, a real‐time simulator able to model the dynamic behavior of large power systems has been needed for a long time. The need for real‐time simulations stems from the fact that in many practical situations it is desirable to test new equipment and analyze the dynamic behavior of a large power system using the actual pieces of equipment.A new digital simulator was developed based on a hypercube‐type massively parallel computer to achieve this objective. The new simulator features: (1) real‐time simulation of a large power system which covers transient stability through long‐term behavior with constant accuracy level; (2) user‐friendly man‐machine interfaces which mimics an actual operating environment and realtime data presentation on a CRT; and (3) high‐speed digital/analog conversion interfaces which connect the digital simulator to a

ISSN:0424-7760    

DOI:10.1002/eej.4391140605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractOverhead ground wires and surge arresters have been installed to protect high‐voltage power distribution lines and apparatus from overvoltages induced by nearby lightning strokes. The effects of surge arresters for protection of high‐voltage distribution lines against direct lightning strokes have already been investigated using the digital simulation program EMTP (Electromagnetic Transients Program). With regard to the protection of low‐voltage distribution lines from overvoltages induced by lightning strokes, experimental analyses using a scale model line have been reported.This paper reports on the comparison between the experimental analyses and EMTP simulation of power distribution lines, including low‐voltage lines, and the validity of EMTP simulation. Furthermore, this paper analyzes the overvoltages on low‐voltage power distribution lines against direct lightning strokes to overhead ground wire using the digital s

ISSN:0424-7760    

DOI:10.1002/eej.4391140606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper presents a hybrid‐type stability control method based on fuzzy control to improve power system stability. The proposed method consists of a speed deviation input fuzzy controller (F1), an electrical power deviation input analog‐type PSS (ΔP‐type PSS), and a fuzzy judgment mechanism (F2). By using the membership function of the magnitude of speed deviation/acceleration of the generator, the following control schemes are considered. If the magnitude is large, then the supplementary stabilizing signal computed byF1 is used to damp oscillations as fast as possible. Otherwise, the output signal of ΔP‐type PSS is used to avoid undesirable noise effect due to noisy input signal of the speed deviation ofF1. The proposed control method increases the power system stability greatly, and it is simple to implement. The effectiveness of the method is demonstrated by one‐machine infinite‐bus and multi‐machin

ISSN:0424-7760    

DOI:10.1002/eej.4391140607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA new protection system for capacitor banks in the case of a short‐circuiting accident is described. A pulsed power system composed of many capacitor units and closing switches is well known for producing a controlled pulse current of high power as for the power source of a plasma experimental device, etc. According to the increase of capacity of a bank system, it becomes important to protect the whole bank system from a short‐circuiting accident in a capacitor unit.Although some protective ideas have been proposed, these conventional ideas have not been sufficient to absorb the energy flowing into the failure unit from other normal units. Constructing the new 1‐MJ capacitor bank for a plasma experimental device, a newly conceived protective device is designed. The new protection system can absorb the bank energy and suppress the short‐circuiting current flowing into the failure capacitor units, and overcomes the defect in former protection systems. To confirm the utility of a new protection system, a test of a protection resistor imitating the actual bank circuit was made. The test result showed that absorbable energy for the unit ceramic resistor amounted to 1500 Joule/cc. The new system is adopted to the bank system of the TPE‐1RM15 plasma experiment

ISSN:0424-7760    

DOI:10.1002/eej.4391140608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractFor commercial customers with a cogeneration system (CGS), a mixed integer programming model is used to examine effects of time‐of‐use (TOU) rate structure on the optimal operation of the system as well as its optimal capacity. Three case studies are performed for a hotel, a hospital, and an office building (20,000 m2in total floor space, respectively). The optimal capacity of the generator under the flat rate is 50 to 70 percent of peak power demand. Effects of the on‐peak/off‐peak energy charge ratio are saturated at a ratio of 5. It is not until an energy charge ratio of between 2 and 5 that the purchase of off‐peak power increases in summer when price reduction is applied to city gas. As the energy charge ratio is raised, cheaper off‐peak power is substituted for city gas and the sum of electricity energy charge and gas energy charge decreases. The simulation results indicate that properly designed TOU rates may provide commercial customers an incentive to operate a cogeneration system with an appropriate mix of the self‐generation and com

ISSN:0424-7760    

DOI:10.1002/eej.4391140609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe superconducting‐type magnetically levitated railway system (MAGLEV), which is driven directly by variable voltage, variable frequency (VVVF) inverters or cycloconverters, is well known as the new traction system for future super‐rapid mass transportation.Since the frequency converters generate harmonic currents possibly leading to interference problem on utility transmission systems, the conventional ac filter ofLC(reactor‐capacitor) branch and/or the active filter is necessary to prevent the harmonic disturbances.The authors have developed a novel harmonic compensation system consisting of shuntLCfilters on load side, a step‐down transformer on receiving end, and a small‐capacity active filter with one end connected to the secondary winding of the transformer and the other to the load bus.The active filter is current‐controlled to give adequate damping to the harmonic resonance condition between the power system and the passive filter equipment, especially at lower harmonic frequencies.The principle and the characteristics of the new harmonic compensation system are described, and its laboratory test results which show satisfactory performanc

ISSN:0424-7760    

DOI:10.1002/eej.4391140610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY