Medium-voltage switchgear for rated voltages above 1kV and up to and including 84kV has been widely applied over 50 years. Relevant domestic standards for medium-voltage switchgear have been revised in accordance with IEC standard revision. This brochure reports mainly the following three study items. Firstly, relevant standards were extracted, and revision history was surveyed. Secondly, differences between domestic and international standards for medium-voltage switchgear were described. Lastly, the recent technology trends of evaluation were reviewed.

Under the anticipated high penetration of variable renewable energy generation such as photovoltaic and wind generation, the issue of supply-demand balancing capability should be evaluated and considered in a future power system including the traditional and innovative balancing measures such as traditional centralized generation, generation curtailment of variable renewable generation, demand activation and energy storage and enhanced use of interconnection. Under the situation, a tool for a long-range power system supply-demand analysis and asset optimization should have the capability to evaluate the balancing capability and balancing counter measures.

This paper presents a new methodology for a long-range power system demand-supply analysis and asset planning model with a set of traditional and innovative balancing models featured by the model of import and export of balancing capability between interconnected power systems.

This paper presents verification of capacity for generation control system of central load dispatching center. A dynamic power system model considering a central load dispatching center, load model, power system model and generator model for verification of generation control system is developed. The dynamic power system model is evaluation of validity and consider of optimal LFC system. The application scope of a dynamic power system model is verified.

Authors proposed the method estimating ground fault locations independent of ground fault conditions. Verification of proposed method is carried out using simulator to reproduce ground fault phenomenon. As feature of this simulator, resonance frequency obtained from test using the simulator is different from that of the value calculated from inductance and total capacitor of default value in the simulator. To solve the different point is constructed correction formula of inductance. There is validity that the estimation of ground fault locations using the correction formula is carried out using this simulator. The estimation of ground fault locations is carried out when ground fault condition is inductance. The default value of ground fault locations is almost consistent with calculated value obtained resonance frequency using the simulator. In this paper, Authors report that the estimating ground fault locations by simulator for reproducer ground fault is validity from verification result of the proposed method of estimating ground fault locations.

To know connection phase of transformer and use it for power flow simulation, we proposed a method to determine connection phase of transformer by using smart meter data and optimizing filter. A characteristic of proposed method is that the filter is improved by using previous result of determination and learning where frequency component is useful for it. We clarified that the proposed method is better than a conventional method filter is not optimized.

In the near future, more and more photovoltaic (PV) generation systems are expected to be installed into electric power systems. Since the output of PV varies depending on weather, there is a possibility of causing not only power imbalance but also line overloads. The PV output fluctuations make it impossible to obtain feasible system configurations during outage works by conventional methods. In this paper, therefore, we propose an improved method for determining system configurations, and show several simulation results to demonstrate the effectiveness of the proposed method.

This paper focuses on the minimization of energy costs for a factory with a non-utility generation facility, where exact load following is difficult. The factory purchases any shortfall in energy from utilities under a demand contract. In the demand contract, the amount of energy that can be purchased in a 30 minute period is limited. To reduce energy costs, we propose load follow-up PI control with bias and fuzzy PI control based on the Takagi-Sugeno fuzzy model. The fuzzy PI control method considers the elapsed time and purchasable energy during each 30 minute period. We also optimize the control parameters and the purchasable energy in the demand contract by Particle Swarm Optimization (PSO). The evaluation function in PSO is the increase in monthly costs considering the energy cost per unit for the generation facility, and the purchasing price and basic contract rate for the utilities. The function is estimated by simulation using the available data for the factory. The optimization of the function is carried out using actual load data. The validity of the proposed methods is evaluated by comparing the approximate cost increase with that under fixed energy output from the generation facility.

It is difficult to analyze magnetostatic field problems with multiply connected domains by the direct boundary element method (BEM). On the other hand, there are two methods which can solve magnetostatic field problems with multiply connected domains in double layer charge (DLC) formulation. One uses imaginary loop current to calculate exciting scalar potentials and the other uses the direct BEM to calculate exciting scalar potentials. Thus, in this study, we expand the application scope of the above methods to the direct BEM. The direct BEM is widely used with other analysis methods such as the finite element method (FEM). In that respect, it is also effective to be able to analyze magnetostatic field problems with multiply connected domains by the direct BEM. In addition, results comparing the two methods to analyze multiply connected problems in both the DLC formulation and the direct BEM have not been reported. Therefore, we compare those and systematically clarify their characteristics by calculating a toroidal core model.

When a fault arc occurs in oil-filled electric equipment, it generates a flammable gas and a dynamic pressure rise. In this study, the pressure rises due to the arc are measured in a closed vessel containing air and oil for different arc depths. The pressure rises in air and oil with different depth are measured under experimental conditions involving an arc current 6.6kA, an arc duration of 100 milliseconds. Experimental results show that the frequency of pressure fluctuation varies with the depth of the arc. Our approximate calculation of the pressure fluctuation with consideration of the oil flux is consistent with the experimental results.

This paper proposes a simplified distributed-parameter line model of rails considering frequency dependent effect. Surge characteristic of rails is different from that of overhead line because the rails have sleepers, which are made of wood or concrete. The earth return and space impedance are calculated by the theory of image assuming the zero potential plane is located at the penetration depth. The impedance of the rails vs. frequency characteristics are measured using an impedance analyzer to estimate a shunt admittance of the sleepers and ballast. The rails including many sleepers and ballast are expressed by a Semlyen's line model installed in ATP-EMTP. Its accuracy is confirmed by comparisons between a simulated transient response using the ATP-EMTP and a field test result. The proposed model improves the simulation accuracy in high frequency region and a computation time step of a transient is increased comparing with the conventional model. This model is applicable to the surge analysis on railway signaling system using ATP-EMTP, which is widely used in power system analysis.

When a step voltage regulator (SVR) which is operatable under reverse power flow conditions fails to recognize the substation direction, it is concerned that the SVR may continuously raise or lower the voltage in an abnormal way. In this article, the substation-direction recognition failure is reproduced by an electromagnetic transient simulation to assess this problem.