Owing to recent progress of the lightning protection design, the total number of the faults on a power line has decreased however the proportion of faults caused by lightning is still high with often reaching beyond 30%. The mechanism of the lightning damage changes with the development of the protection design, and lightning current parameters, required for the protection design, also changes. For the efficient accumulation, estimation of the lightning current parameters from the measurement of the electric and magnetic field is effective. In this report, the author reviews the recent observation of the fields for the purpose of lightning protection.

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The subject of this study is to propose a power interchange system in a collective housing with residential solid oxide fuel cells (SOFCs) and a robust operation planning method for integrated SOFCs against uncertain energy demand forecast. In this method, the future operation plan for multiple SOFCs is optimized and determined to minimize the expected total primary energy consumption in the collective housing considering uncertainty in demand forecast. If the forecast energy demand includes forecast errors, the result of SOFCs operation will corrupt from the viewpoint of the primary energy consumption. Thus, the output decision problem for SOFCs is formulated by considering the corruption caused by forecast errors, so that the decided SOFC outputs have the robustness against uncertainty in demand forecast. The validity of the proposed method is examined based on numerical simulations from the perspective of the robustness.

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Smart Grid and Demand Response had been attracted attentions and evaluated in several demonstration projects. Many demand response experimental results for residential and large scale buildings had been evaluated, while evaluation for small size buildings seems to be not enough. In this paper, a new energy service combined EMS method is proposed for small size buildings. Then results of its application to Miyako Island All-Islands EMS Demonstration Project are introduced. The experimental services include not only demand responses but also peak cutting recommendations and energy analysis reports. The results show combination of services can realize more effects than individual service. Especially the peak cutting recommendations and energy analysis reports help energy consumers to learn and understand how to save and manage energy usages that lead to effective demand response potentials. Also the experimental system developed for energy data measurement and demand response management as an island community EMS is introduced.

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This paper proposes a new operational planning method for residential PEFC (Polymer Electrolyte Fuel Cell) cogeneration system considering the periodical boundary conditions concerning hot water in storage tank. It can be easily expected that residential PEFC cogeneration system is likely to produce more hot water than needed, because heat efficiency of PEFC is higher than its electrical efficiency. In that case, the surplus hot water would be discarded, and it might deteriorate total operational cost. However, previous researches have not discussed and focused on how to deal with the surplus hot water, and when to discard it. Therefore, we introduce periodical boundary conditions concerning hot water amount in storage tank, and include the cost of disposal hot water as the penalty into our objective function in order to consider them in the operational planning. We simulate the operational planning in the conditions of 3 seasons by using 2 methods, which are proposed method considering periodical boundary constraints and conventional method of operational planning. The study system is configured of PEFC, commercial grid, storage tank, and auxiliary gas boiler. The simulation results show the efficacy of proposed method in many cases. In addition, the bird's-eye view figures composed of optimal solutions reveal some information about the way to decide the appropriate periodical boundary conditions.

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Although computer simulation is certainly a powerful tool for power system stability assessment, manual analysis is more helpful for understanding mechanism of unstable phenomena. Among unstable phenomena, oscillatory stability must be the most complex one. The paper analyzes the impact of recently developed Japanese RE's standard active anti-islanding function named “frequency feedback with step injection” on power system oscillatory stability.  Since active anti-islanding makes islanded system unstable, it also makes stability of large interconnection worse. The question is how serious is the impact and how the impact can be mitigated. The paper presents a method for oscillatory stability analysis considering induction motor load, RE, and anti-islanding function on RE so minutely as readers can reproduce. Analyses are performed as case studies on aggregated power sending and receiving systems in existing interconnection of Japan. The analyses results are verified by simulation results on the same case studies.

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About 50% of the high-voltage (HV) static capacitors (SC) have been operating for more than 30 years by the beginning of the 2010s. Most of them are oil-immersed paper capacitors. For their efficient maintenance and management, it is necessary to establish an on-site partial-discharge (PD) diagnosis of the capacitors. In this paper, acoustic emission (AE) method is selected from the view point of PD detection sensitivity for SC and applicability for the on-site PD diagnosis without any interruption for continuous SC operation. PD localization technique for SC using plural AE sensors is developed in this paper. PD localization method utilizing information of internal structure of SC is proposed to improve the accuracy of PD localization by AE sensors in concrete terms. This proposed method applied to PD test for an aged SC operated for 48 years and removed from the actual substation. A number of carbonizations formed by PD were found inside the aged SC at the dismantled test after the PD test. Then, As compared with the accuracy of proposed PD localization method and traditional one, accuracy of proposed one improves by 60% to the traditional one.

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This paper describes two types of Rotary Loop Flow Controller, one is series type and the other is UPFC type. Both of them can maintain the suitable voltage level of distribution system even with a large and uneven penetration of distributed generation (DG). The configurations of proposed controllers are essentially same as wound rotor induction machine with no slip rings. The proposed controllers are less costly, more efficient, more tolerant to over voltages/currents as compared to power electronics type controllers. Further, UPFC type rotary loop flow controller has additional advantages like relatively smaller capability, ability to control reactive power than the series type of rotary loop flow controller. The proper functioning of the proposed controllers is confirmed through simulations and experiments.

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Recently, with the expansion of communication network areas, the number of radio communication stations, built in the neighborhood of customer houses, has increased. If lightning strikes a communication radio tower, part of the lightning current flows into the distribution line and into customer houses. This may cause the failure of distribution lines or customer equipment. To protect distribution lines and customer equipment from lightning faults, it is necessary to analyze the surge phenomena in distribution lines and customer equipment and take appropriate protection measures. In this study, we examined the effect of lightning protection measures for distribution lines and customer equipment against lightning strikes to a communication tower. First, using an actual-scale test distribution line, we measured the lightning current flowing into distribution lines and customer equipment. Secondly, we quantitatively examined the effect of lightning protection measures by lighting surge analysis while changing each parameter. From the experimental and analytical results, we show that the proposed protection measures can reduce the lightning current flowing into distribution lines and customer equipment.

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Currently, the IEC (International Electrotechnical Commission) standard (IEC62271-100) requires that the transformer limited fault (TLF) shall be verified in the test duty T10, the amplitude factor of which is defined as 1.7 for the transient recovery voltage (TRV). But, the TRV measurements for the TLF at various transformers show that the factor is mostly lower than 1.7. The reason for the low values is considered to be that the short-circuit inductance of transformer at the TRV frequency region is lower than that at the power frequency, and consequently the factor is lower than the standard value 1.7. But, the frequency-dependence of the short-circuit inductance of transformer has not been clarified yet.  We measured the short-circuit inductances of model transformers with and without iron core. The short-circuit inductance with the iron core becomes small and equals to one without the iron core at the TRV frequency region. We concluded that this is the reason for the phenomena of low amplitude factor. In addition we showed, by taking eddy current within an iron core and Cu windings into consideration, that the frequency-dependence of the short-circuit inductance could be explained.

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This paper presents the new design method of power transformer for reduction of inrush current and losses. This method was developed using design procedure of winding structure, analysis of inrush currents and genetic algorithm with real coding. Characteristics calculated by this method were compared with them of an actual transformer for customers' facilities. Especially, restrained inrush currents were obtained by EMTP-ATP simulation using machine parameters calculated by the design method developed in this study.

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This paper proposes an equivalent circuit at a transition point of distribution line for lightning-induced voltage analysis. The lightning-induced voltages caused by a piecewise linearly varying lightning current are expressed by analytical formulas. The equivalent circuit is represented by resistors and current sources, which are known from past history and given by the lightning-induced voltage on an infinite-length line. Transient voltages and currents at the transition point are accurately obtained in small computation time using the equivalent circuit. Thus, the proposed equivalent circuit is very convenient for analyzing the lightning induced effect in complicated electric power networks. This paper presents an example of EMTP data cards to use the proposed equivalent circuit in the EMTP.

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