A lot of people lost their lives in the tremendous earthquake in Tohoku region on March 11. A large capacity of electric power plants in TEPCO area was also damaged and large scale power shortage in this summer is predicted. In this situation, electricity customers are making great effort to save electricity to avoid planned outage. Customers take actions not only by their selves but also by some customers' cooperative movements. All actions taken actually are based on responses to request form the government or voluntary decision. On the other hand, demand response based on a financial stimulus is not observed as an actual behavior. Saving electricity by this demand response only discussed in the newspapers. In this commentary, the events regarding electricity-saving measure after this disaster are described and the discussions on demand response, especially a raise in power rate, are put into shapes in the context of this electricity supply-demand gap.

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It is well known in the numerical simulation of synchronous generator that the damper winding contributes to suppress the three-phase circuit unbalance in power systems. However, experimental study has not been performed yet. In this paper, authors verify experimentally the suppression of the three-phase unbalance by the damper windings. In order to simulate the three-phase unbalance, a 470W dispersed generator of single-phase-two-line type is connected to a three-phase laboratory-scale power system that includes a 6kVA synchronous generator. Authors measured and analyzed line voltages and currents as well as damper bar currents both with and without dispersed generator. The influence of damper windings to the unbalance of three-phase circuit is also investigated. The results show that the damper winding contributes to improve the three-phase unbalance.

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A survey was conducted on power outage cost for industrial customers. 5139 factories, which are designated energy management factories in Japan, answered their power consumption and the loss of production value due to the power outage in an hour in summer weekday. The median of unit cost of power outage of whole sectors is estimated as 672 yen/kWh. The sector of services for amusement and hobbies and the sector of manufacture of information and communication electronics equipment relatively have higher unit cost of power outage. Direct damage cost from power outage in whole sectors reaches 77 billion yen. Then utilizing input-output analysis, we estimated indirect damage cost that is caused by the repercussion of production halt. Indirect damage cost in whole sectors reaches 91 billion yen. The sector of wholesale and retail trade has the largest direct damage cost. The sector of manufacture of transportation equipment has the largest indirect damage cost.

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There are many PWM control apparatuses, which are higher harmonics current sources, in distribution systems. And higher harmonics causes over current by parallel resonance. To avoid the over current, it is necessary to suppress the resonance.
In this paper, a new suppression method, which uses the effect of source connected point in resonance circuit, is proposed. Firstly it shows that the optimal point, which gives a minimum current amplification degree, is orthogonal to static condenser voltage. And then, using eigenvector of state equation, the participation factor is defined. When the participation factor is zero, the orthogonal condition is introduced. Therefore the optimal point is given by using with the participation factor. Finally, adopting numerical examination, it is known that multiple optimal points usually exist. Therefore, we can choose the advantageous point as a source connected node.

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Recently, much attention in Japan has been given to photovoltaic (PV) systems, which are being rapidly installed in ever greater numbers on homes. However, various concerns over potential adverse implications on the secure operation of the power systems that could result from large-scale installation of PV systems have been identified, such as large-scale PV causing frequency variations or causing voltage variations in distribution networks.
This study presents findings on performing direct load control in an artificial climate chamber capable of constant outside air temperature control, and focuses on the potential for using load-variable residential Air-Conditioning (AC) units in order to promote the large-scale introduction of PV. Specifically, measurements were taken of power consumption, room temperature, suction air temperature, and blow air temperature while altering inside air temperature over several minute intervals, and the power consumption variability of AC unit was assessed, while also evaluating the effects on thermal comfort index inside the room.

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With the past high economic growth period in Japan, the power demand has been increasing sharply year by year. Therefore, the Japanese utilities have installed many Shunt Capacitors (SCs) along with the predicted demand in order to keep the voltage profile and stability. Meanwhile, some SCs have aged because they have been used for a long time, and thus, have to be replaced sometime soon. Recently, the usage of the concept of asset managements has been paid attention as economic evaluation techniques in the power system. Therefore we propose a new renewal planning method with cost leveling during the renewal period using the condition age model.

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This paper investigates the modeling method of real earth in an experiment above a conductor plate. This paper advances the method of representation way of grounding electrode on real earth above conductor plate. This paper discusses the basis of representation way and availability of this way. The waveform is different between the case of a real earth and an Al plate after reflection comes back from the return end. The first reflected wave is affected by the impedance of a grounding electrode. This fact indicates that the grounding electrode should be carefully represented in an experiment above a conductor plate. To reduce the difference, the effect of the earth resistivity and the grounding electrode of a real earth is investigated. A simple RL model is proposed to represent a real earth, when an experiment is carried out above the conductor plate. The model circuit gives a reasonable accuracy in comparison with the real earth.

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A new approach of the AC filter design for the SVC (Static Var Compensator) is proposed in this paper. When the SVC consists of TCR(s) (Thyristor Controlled Reactor(s)) or TCT(s) (Thyristor Controlled Transformer(s)) and the AC filter(s), it is required to design AC filter(s) carefully to meet regulation level of harmonic voltage and current at the connection point of the SVC. In general, the AC filter design may require many iterative calculations of the harmonic performance by changing electrical parameters of the AC filter until all the harmonic voltage and current performances at the connection point of the SVC meet the regulation level on various conditions in terms of the filter de-tuning cases and the AC power system conditions. In this respect a new AC filter design approach is proposed, which is innovative on evaluation method of the performance to predetermine the permissible range of the AC filter harmonic impedance on the complex plane. By using this method, the iterations of the calculation can be reduced and it enables more efficient process of the design providing clear accountability of the decision of AC filter parameters.

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To reduce the volume of fuel consumed at Syowa base in Antarctica, we study the proper renewable energy system (RE system) to supply both electrical and thermal energy. Though a lot of photovoltaic power generation systems (PV systems) and wind power generation systems (WG systems) have already been installed all over the world, climate is quite different from other area and we have few experiences on renewable energy system in Antarctica. Moreover, though thermal load is much bigger than electrical load all the year round, both PV system and WG system generate only electrical energy. Therefore we proposed a power supply system composed of PV, WG and heat pump to convert a part of electrical energy to thermal energy. It is important to clear the proper system capacity, operational method of heat pump in this system. As a first step, we studied those items on this system without energy storage system by a simulation. We found that proper operational method of heat pump is affected by capacity of RE system and WG system is useful more than PV system.

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When a stroke of lightning happens in the vicinity of the outdoor high voltage distribution lines, the inductive lightning surge invades to the central line of aerial insulated cables. The creeping discharges can progress along the cable surface from the free end of the binding wire just after the flashover of the insulator at the cable supporting points. If the weak points such as the pin-holes exist in the insulated coating near the cable supporting points, the creeping discharges may give rise to a punch-through breakdown of the insulated coating and melting or snapping accidents of the cable. To prevent these disasters, it is important to clarify the mechanism of the creeping discharge phenomena along the cable surface. The negative creeping discharge along the cable surface depends on the peak value of surge voltage and its progressing process is extremely complicated. We already reported photographically the progressing aspect of the negative creeping discharge using a high-speed image converter camera. In this paper, we consider the progressing mechanism of negative creeping discharge using the discharge models which propose on the basis of the discharge photographs that have been obtained by experimental observations.

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Experimental study was carried out for classified a mechanism of failure of low-voltage electronic Watt-Hour Meters. As the results, the mechanism of failure of electronic meters is clarified into two patterns. One is due to the magnetic field generated by lightning current passing through the inside of an electronic meter. The other is due to the blow out of electric wire caused by lightning current flowing into the power supply circuit for processing unit. For these failure mechanisms, following counter measures were clarified. One is that a magnetic shielding measure using a metallic plate covering the processing unit was effective for reducing the magnetic field. The other measure is that a relocation of the ZnO device in the electronic meter was effective for reducing the lightning current flowing into the power supply circuit.

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