The objective of this paper is to propose a new method for the optimal design of HV equipments. In this method, a shape function called NURB-spline (Non-Uniform Rational B-spline) is introduced to represent the contour of the electrode or insulator. NURB-spline has much better controllability, locality and continuity than other shape functions. The first two properties can significantly reduce the number of geometric variables and the last is a necessary condition for the smoothness of a field.
There are two distinctive processes in this algorithm. One is the determination of an optimal desired field which should be the smallest and uniformly implemented value. The other is the adaptive addition of a geometric variable to a region where the uniformity fails. Due to the abovementioned features, the entire process guarantees stable convergence. IEM (Integral Equation Method) is used for field calculations. Three examples are chosen from the conventional researches and simulated to verify the advantages of the proposed method.

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Numerical analysis of electric field is performed by several practical methods. The surface charge simulation method is used for three-dimensional analysis of static electric field in the medium with constant and homogeneous permittivity. The number of unknowns becomes large in practical problems, and large memory storage and long computation time are required. Therefore, when a computation model where the electric field distribution is known is given and a small conductor is added to the computation model, we propose an efficient method superposing the known electric field distribution. In the proposed method, the surface charges induced by the added small conductor are used as unknowns. By using the proposed method, the area to be analyzed becomes small and the number of unknowns is reduced. The formula for the proposed method and how the area to be analyzed is determined are shown. Furthermore, some numerical examples and an application for the power cable with defect are presented.

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CuBr vapor lasers are expected to be used instead of copper vapor lasers because of their small size and low cost. ASE (amplified spontaneous emission) intensity distributions are measured as a function of CuBr reservoir temperature in a CuBr vapor laser equipment. The ASE intensity distributions are dependent on the spatial distributions of excited copper vapor. This paper reports a simulation code by which can be calculated excited copper vapor distributions in the discharge tube from the ASE intensity distributions. The main equation of this simulation code consists of spontaneous emission and stimulated emission terms only and is solved by using finite difference method. We have investigated the spatial distributions of excited copper vapor in a CuBr vapor laser by ASE intensity distribution analysis. These results show concentration of excited copper vapor in the center of the discharge tube as increasing the CuBr reservoir temperature.

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The design of arc rupturing parts of molded case circuit breakers depends upon the strength and distribution of the magnetic blowout field by which the arc is forced. The magnetic blowout field causes the arc to move into a set of V-slotted iron grids, where the arc is extinguished rapidly. Thus, the first step in the calculation of the motion of the arc is the prediction of the magnetic blowout forces. In many cases, however, it was not easy to calculate the forces owing to the complicated three dimentional structure of arc chutes and contact systems.
In this paper, a developed method which can calculate the distribution of magnetic blowout forces along arc lying in the arc rupturing parts of a circuit breaker is described. The magnetic blowout forces have been calculated by using the flux densities in the arc which are obtained by 3-D finite element method taking into account magnetic saturation.

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This paper describes a new method for simulating protection coordination of a network distribution system with dispersed-generators by using the Electro-Magnetic Transients Program (EMTP). This method includes detail models of the network protector that consist of network relays, protector circuit-breakers and protector fuses. This method can easily simulate the protection coordination for various faults at any point on the network distribution system. The results obtained by this simulation method were corroborated by an analog simulator. An example of the short-circut fault on the spot network system with a generator was discussed in the simulation.

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This paper presents an approximate calculation method of cable surges considering the effect of cleats. A theory developed by L. M. Wedepohl is applied to obtain an equivalent wave propagation characteristic using admittance parameters in the system cascaded by distributed-parameter lines and lumped-parameter elements which express cleats to fix power cables.
A cable system including many cleats is represented by an equivalent homogeneous line in the paper. An equivalent wave deformation is expressed by Semlyen's line model, and its parameters are evaluated from an equivalent amplitude of a travelling wave given by Wedepohl's theory. An equivalent characteristic impedance and a propagation velocity are calculated by an approximate formula proposed by the authors. Calculated results using the equivalent homogeneous lines agree well with measured results in a scale model and field test results in an actual tunnel-installed cable.

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A new parallel algorithm for time domain transient stability analysis is proposed. It is built over a framework in which an interlaced partitioned scheme for the transient stability problem is assumed and the network equations are solved by LDU factorization and sparse vector techniques. The parallelization approach is based on the factorization path tree and its main feature is the switching from direct factor to inverse factors to best exploit the parallelism during the solution of the network equations. The task scheduling procedure assumes a computational model that exhibits both global and local memories. A tutorial example and application results showing the effectiveness of the algorithm are also presented.

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Power system dynamic equivalents play an important role in the effort to reduce the computational burden of the transient stability analysis of power systems. In this paper, the author 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 highly improved by converting a coordinate system representing the subsystem from the R-J coordinate system of the main system to the reference generator's D-Q coordinate 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. So the equivalent obtained by proposed method can be used for both steady-state and transient stability analysis studies.
In order to verify the dynamic equivalent's performance, stability simulation results for model power system composed of 16 generators are also shown.

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This paper describes development of the reliability analysis system for transmission systems from primary substations on high voltage trunk line systems to distribution substations. This system has been developed on an engineering workstation. User can input the network data of power systems from primary substations to distribution substations and the structure of buses and connections of transformers in substations using graphics. This analysis system can evaluate reliability at each distribution substation by simulating outage and recovery process for all faults modes which can be occurred, defining capacity of facilities, probability of fault at each facilities, value of load at each bank and the points where switching elements are turn off in the network as input data. In the calculation of recovery pocess of each fault mode, the constraints of operation of radial power systems are considered.

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This paper proposes new demand-side reliability indices and useful computational techniques for reliability evaluation of composite power systems. These new indices are based on the active power which can reach at 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 load curtailment area is defined, and the estimate method of load curtailment area is indicated. In case the reachable power exceed the demand, system reliability is evaluated by the demand-side reserve, and the power system is devided 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 and practicalness.

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A high-temperature superconductor is investigated to be applied to a fault current limiter. However, a current carrying capacity of a single element is too low for a practical use. So parallel connection of superconducting elements is required to increase the current capacity. This paper discusses an a. c. current distribution between two YBa₂Cu₃O_7-x superconducting elements connected in parallel that differ in electrical aspects such as a critical current level and voltage-current characteristic. As the instantaneous value of the current rises from zero to peak, the following processes are observed: (1)The transition from superconducting to normal conducting state is initiated in the element with the smaller critical current. (2) The current value in the element is kept constant until the other element with the larger critical current level becomes normal conducting state. (3) Only when the instantaneous value of the a. c. current exceeds the summation of the individual critical current values of each element, the voltage across parallel-connected elements appears. These results are caused by quick recovery characteristic of our YBCO superconductors from normal conducting state to superconducting state.

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We have studied the multivariable optimal control system, which coordinates excitation and governing system of a generator, and this control system is applied a self-tuning adaptive control scheme.
This paper describes the field test results of a TAGEC practical model, which is installed on a hydro-power generator connected with a long-distance transmission line, and which is capable of operating automatically. This paper also describes the test results on controllability of TAGEC using in the large-scale analogue simulator of APSA (Advanced Power System Analyzer) owned by the Kansai Electric Power Co., Inc.
The field test results verify the applicability of TAGEC to actual plants and the control performance of the various faults in power system. And also the TAGEC improves power system stability of multi-machine system compared with conventional control.

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With today's global environmental and energy problems, high expectations exist for solar power generation to reduce carbon dioxide generated by the consumption of fossil fuels.
On the other hand, power consumption in residential homes is increasing every year. Among the many household appliances, the power demand for air conditioners increases dramatically during the summer, particularly in the afternoons. As this pattern closely matches the output pattern of solar cells, it should be possible to combine a photovoltaic array with an air conditioner to decrease the energy consumption within the home.
We have developed a residential solar-powered air conditioner that operates through a combination of photovoltaic array and commercial power.
In this paper, the configuration and specification of the solar-powered air conditioner are described. And the performance characteristics of the solar-powered air conditioner are examined by the analysis of the characteristics of the solar cell.

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