In recent years, the user needs have diversified, and transformers adapted to them have been developed. For example, vegetable-based oil immersed transformer, silicone oil immersed transformer, high earthquake resistant transformer, transformer for floating offshore wind farm, mobile transformer and so on. This paper shows an overview of the survey results on these.
Home electric appliances with power electronics devices are increasing. In order to investigate influences due to harmonics currents, grasp of harmonics currents characteristics for appliances. In this study, tablet computers at charging and router using on low voltage distribution system were focused and harmonic currents characteristics were measured. Measured data were compared with limits for harmonic emissions calculated using methods in the standards of JIS C 61000-3-2 (Electromagnetic compatibility (EMC)-Part3-2: Limits). Subsequently, an average harmonic current characteristics profile (AVG profile) from seven types of tablets and routers was obtained. Furthermore, phase values suitable for the AVG profile was derived using a genetic algorithm.
Lithium-ion batteries are becoming practically used for high power applications such as electric vehicles. For this purpose, some estimation technique of battery heat generation is inevitable. The authors, therefore, have already proposed a simple estimation method of the heat generation in lithium-ion batteries during their charge/discharge using internal equivalent resistance and confirmed validity of the method for constant current discharge patterns. The merit of this method is its simplicity but it has already been made clear that its versatility for various current patterns is not enough. Considering these facts, in this study, the authors newly proposed a detailed estimation method of the heat generation in lithium-ion batteries during their charge/discharge using equivalent circuit. The authors compared the estimation results of the heat generation in lithium-ion battery for various constant or pulse current charge/discharge patterns through the newly proposed detailed estimation method with the estimation results through the conventional simple estimation method and measured results through a calorimeter for the corresponding current patterns. The versatility of the newly proposed detailed estimation method was successfully confirmed through these comparisons, indicating the validity and necessity of the proposed method.
Lumps of snow shed from overhead ground wires occasionally damage plastic greenhouses, vehicles and so on. The overhead ground wires are wrapped with PTFE (Poly-tetra-fluoro-ethylene) tape to prevent the accretion of the snow lumps, however, it cannot be prevented completely. In this paper, an artificial snow accretion test was performed to study occasional conditions of the shedding of snow lumps focusing on the wire-surface temperature. When the wire-surface temperature is kept higher than about 2-3 degree Celsius, no accretion of snow lumps is found. And when the wire-surface temperature is kept higher than about 4 degree Celsius, no accretion of snow lumps is found for various outside natural snow conditions. Furthermore, a method for estimation of the wire surface temperature under various environmental conditions is proposed.
The quality of electric power caused by frequency fluctuation and voltage rise will be degraded because of the lightning surge and the mass introduction of distributed power. Thus, it is necessary to improve the peformance of gas circuit breaker in order to maintain the stable supply of electric power. It has been reported that the arc conductance is calculated as the index of the current interruption in numerical analysis. However, few report have the measured value in the current interruption. This is because that the current interruption is the steep phenomenon of micro seconds range. Thus, it is necessary to establish the time-high precision and non-contact measurement method. In this paper, the arc temperature is measured near current zero using the microsecond spectroscopic measurement. As a result, the microsecond spectroscopic measurement which combines the conventional spectroscope and the high speed video camera is 200 times faster than the measurement of conventional spectroscope. For this reason, the microsecond spectroscopic measurement is possible with the high speed video camera. Therefore, it is possible to measure the arc temperature with decreasing the current using the microsecond spectroscope.
Japanese Electrotechnical Committee (JEC) is working on the standardization of JEC, JIS, and IEC. In this article, the history and the activities of Japanese Electrotechnical Committee are reported, and recent topics are also described. Japanese standards like JEC, JIS, etc. are settled and maintained, considering the international standards like IEC. Also, Japanese new technologies and opinions are expected to be reflected in the international standards.