摘要:

AbstractIn the field of high‐voltage engineering, it has been desired for a long time to improve the internal PD resistance of epoxy resin without lowering other properties. Recently, the authors discovered that some sulfur compound as curing agents or simple additives improved the PD resistance of rubber markedly, and here an attempt has been made to apply this fact to the case of epoxy resin.As was expected, some sulfur compounds containing SS‐bond suppress the deterioration of epoxy resin due to internal partial discharges, and the larger the molecular weight of organic group combining the SS‐bond, the longer the effective life of additives. Moreover, to make full use of these additives, it is very important to restrict moisture in the insulation systems.From this study, the authors have proposed the chemical formulation of the suppressive effect of additives for deterioration of epoxy resin due to internal partial disch

ISSN:0424-7760    

DOI:10.1002/eej.4391140701

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

年代:1994

数据来源: WILEY

摘要:

AbstractOptimal switching pattern planning is the main subject of distribution network reconfiguration to recover from a blackout or to avoid a blackout due to maintenance and construction. This is a combinatorial optimization problem, and an enumerative check of every pattern is necessary to obtain the optimal solution.In practice, successive heuristic search methods are adopted to obtain the quasi‐optimal solution within a limited computation time. However, a very long computing time is still required when the problem size becomes slightly larger. The step‐by‐step nature of the methods results in many iterations, although it ensures satisfaction of the constraints. Reduction of the iterations is considered to be necessary to enhance processing speed.In this paper, “supply adequacy” is introduced as a new criteria index to guess the solution, which is obtained by fuzzy inference for each possible pair of source and load zone. The reconfiguration pattern is obtained at once or in a few processing steps by assigning to each zone the source with the highest adequacy. Numerical examples show that the proposed method can obtain the solution faster than the ordinary method, more remarkably with the increase of pro

ISSN:0424-7760    

DOI:10.1002/eej.4391140702

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

年代:1994

数据来源: WILEY

摘要:

AbstractWhen combined with a magnet having a magnetic field gradient (for example, a permanent magnet), a Y‐based oxide superconductor is capable of forming a noncontact bearing with a strong levitational force. Since this bearing exhibits low rotational loss, it is very likely to form a highly efficient power storage system in combination with a flywheel.In this paper, an 8‐MWh power storage system utilizing a flywheel was designed conceptually to examine its applicability and the possible effects of its introduction. It was found that this system was an effective power stor

ISSN:0424-7760    

DOI:10.1002/eej.4391140703

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe possibility of laser‐induced lightning has been investigated for the future application in the protection of electric power systems from lightning strokes. This technique induces lightning strokes artificially along a laser‐produced breakdown plasma channel and conducts them to a harmless place on the ground.To clarify the plasma formation mechanism and the discharge (sparkover) induction process, sparkover induction experiments are performed for two types of long‐gap electrode configurations, plate‐to‐rod and plate‐to‐plate, with a 50‐J TEA CO2laser.In the present paper, the sparkover voltage characteristics and interferometric measurement on laser‐produced plasma mainly are described, together with sparkover induction for a series of metal beads arranged equidistantly which simulate

ISSN:0424-7760    

DOI:10.1002/eej.4391140704

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper investigates the voltage stability in a single OLTC (On‐Load Tap Changer) system, which consists of a single OLTC and multiple generators as well as loads. It is shown that the sensitivity of the load voltage to tap positiondV/dn=(I1= exact value) plays an important role, independently of the existence of the equilibrium of the tap position. That is, when the equilibrium exists, the region whereI1>O is in the stability region; if the equilibrium disappears, the stability region also disappears but the voltage is still recovering in the region whereI1>O. Based on these results, the region of reverse control action of OLTC is defined as the region whereI1>O. It is proved that another sensitivityI2, which is defined asdV/dnwhen constant power characteristics are assumed for loads, can be used to estimate the region of reverse control action when the exact load characteristics are not availabl

ISSN:0424-7760    

DOI:10.1002/eej.4391140705

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

年代:1994

数据来源: WILEY

摘要:

AbstractPower system dynamic equivalents play an important role in the effort to reduce the computational burden of the transient stability analysis of power systems. This paper proposes a new efficient practical algorithm for forming linear dynamic equivalents for power systems based on modal analysis. The main feature of the proposed method is that the accuracy of the equivalent model is greatly improved by converting a coordinate system representing the subsystem from theR‐Jcoordinate system of the main system to the reference generatorD‐Qcoordinate system of the subsystem. The order reduction is based on aggregation of similar modes and elimination of the inferior modes without significant effect on the frequency response of the subsystem. Thus the equivalent obtained by the proposed method can be used for both steady‐state and transient stability analysis studies.To verify the dynamic equivalent performance stability simulation results for a model power system composed of 16 generators also are

ISSN:0424-7760    

DOI:10.1002/eej.4391140706

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper proposes new demand‐side reliability indices and useful computational methods for reliability evaluation of composite power systems. These new indices are based on the active power which can reach each demand spot under generating and transmission network constraints. This conception is defined as “reachable power,” and it leads the reserve margin on each demand spot, which is called as “demand‐side reserve.” If the reachable power is insufficient to satisfy the demand, load curtailment is required.In the proposed approach, the conception of the load curtailment area is defined, and the estimate method of load curtailment area is indicated. In case the reachable power exceeds the demand, system reliability is evaluated by the demand‐side reserve, and the power system is divided into several reliability zones according to the demand‐side reserve levels. Small system examples are used to illustrate principles of the proposed approach, and middle system examples show the effectiveness a

ISSN:0424-7760    

DOI:10.1002/eej.4391140707

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

年代:1994

数据来源: WILEY

摘要:

AbstractIt has been clarified that a superconducting magnetic energy storage (SMES) is very effective for power system stabilization. The control methods proposed for power system stabilization by SMES are the pole assignment, the optimal control, and so on, each of which, however, has its drawbacks.This paper is concerned with the power system stabilization by neural network control of the active power of SMES. First, the optimal stabilizing control of the SMES power for the model power system is calculated for various power system operating conditions and fault conditions. Then these optimal controls are used as training data for the neural network. The neural network used is a multilayer type with a feedback from the output layer to the input layer. The trained neural network is examined by untrained operating conditions and faults.

ISSN:0424-7760    

DOI:10.1002/eej.4391140708

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe load of a dc railway has very large peaks while the average power is low. This makes the capacity of wayside power equipment larger. Recently, the ratio of peak power to average power has become even higher because of the introduction of a large number of electric multiple units with a regenerative brake system. This has also made the contact system unreceptiveness of the regenerated energy a significant problem. To solve these problems, researchers are attempting to add intelligence to the power system.This paper describes a novel method of intelligently controlling the traction power of trains. In this system the trains reduce their accelerating power to cut current peaks in wayside substations. With the proposed method the load peaks can be reduced by up to 31 percent, which means that the characteristics of the railway load have been changed drastically. The delays of the trains involved are negligible. Also, the unreceptiveness of the regenerated power can almost be eliminated.In the first part of this paper, the idea of traction power control is described. Then a description is given of how the idea is applied to wayside substation load peak suppression or receptiveness improvement, with some simulation results to prove the method. Finally, the possibility is discussed of further improvement of the system by adding communication capability between trains and wayside equipment.

ISSN:0424-7760    

DOI:10.1002/eej.4391140709

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

年代:1994

数据来源: WILEY

摘要:

AbstractWhen magnetic fields in electrical machines with moving conductors such as linear induction motors are analyzed, eddy currents due to the movement of conductors should be taken into account. Although two kinds of coordinate systems (moving and fixed coordinate systems) can be applicable to the analysis of eddy currents in moving conductors, the advantages and disadvantages of both coordinate systems are obscure.In this paper, methods for analyzing magnetic circuits with moving conductors are classified systematically, and the moving and fixed coordinate systems are compared with each other from the standpoints of accuracy, memory requirement, and CPU time. It is shown that the moving coordinate system is superior to the fixed coordinate system for transient analysis.

ISSN:0424-7760    

DOI:10.1002/eej.4391140710

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

年代:1994

数据来源: WILEY