Electrical Power Engineering Systems Co.

Yokosuka, Japan

Electrical Power Engineering Systems Co.

Yokosuka, Japan
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Tadokoro T.,Japan Central Research Institute of Electric Power Industry | Kotari M.,Japan Central Research Institute of Electric Power Industry | Ohtaka T.,Japan Central Research Institute of Electric Power Industry | Iwata M.,Japan Central Research Institute of Electric Power Industry | Amakawa T.,Electrical Power Engineering Systems Co.
IEEJ Transactions on Power and Energy | Year: 2017

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 6.6 kA, 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. © 2017 The Institute of Electrical Engineers of Japan.


Kotari M.,Japan Central Research Institute of Electric Power Industry | Tadokoro T.,Japan Central Research Institute of Electric Power Industry | Tanaka S.-I.,Japan Central Research Institute of Electric Power Industry | Iwata M.,Japan Central Research Institute of Electric Power Industry | Amakawa T.,Electrical Power Engineering Systems Co.
IEEJ Transactions on Power and Energy | Year: 2017

To develop an alternative test method for internal arc in SF6-insulated power equipment, we have systematically obtained experimental data on SF6 arc to calculate the pressure rise in power equipment. In this study, we carried out experiments on SF6 arc in a closed container. The arcs were ignited between rod electrodes by applying a current with a peak of 10.7 kA and a duration of 40ms. The rod electrodes were made of copper, iron, and aluminum. It was found that the maximum pressure rise was highest in the case of the aluminum electrode. Additionally, to determine the energy balance resulting from a SF6 arc in the container, the energy balance was discussed on the basis of input energies and consumption energies. The input energy components are the arc energy and the energies of the decomposition reaction of SF6, the oxidation reaction of metal vapor, and the fluoridation reaction of metal vapor. On the other hand, the consumption energy components are the energy contributing to the internal pressure rise and the energies associated with the melting of electrodes, the vaporization of electrodes, and the radiation emitted from the SF6 arc. It was found that the input energies approximately agreed with the consumption energies. The energy of the fluoridation reaction of the metal vapor was highest in the case of the aluminum electrode, and the energy accounted for about 20% of the total input energy. Also, the radiation energy in the case of the aluminum electrode was comparable with that for the iron electrode, and the energy contributing to the internal pressure rise was highest in the case of the aluminum electrode. © 2017 The Institute of Electrical Engineers of Japan.


Kotari M.,Japan Central Research Institute of Electric Power Industry | Miyagi T.,Japan Central Research Institute of Electric Power Industry | Iwata M.,Japan Central Research Institute of Electric Power Industry | Amakawa T.,Electrical Power Engineering Systems Co.
IEEJ Transactions on Power and Energy | Year: 2017

In this paper, we present an analysis of the pressure rise caused by combusting of oil resulting from a fault arc, assuming that the arc occurs in oil-filled equipment in a large electric room with an opening. In the analysis, we clarified that the location and volume of the arc fault and the location of the opening affected the pressure rise and the propagation around the arc fault. We found that the initial pressure rise (P1st) at the floor adjacent to the wall and equipment was greater than those at other locations. In particular, P1st was largest at the corner of the electric room owing to a superimposed pressure wave. Moreover, the value of P1st at the floor adjacent to the equipment was independent of the location of the opening. It was also found that P1st decreased inversely propositionally to the distance between the floor adjacent to the wall and equipment and the location where the fault occurred. Also, the time to reach P1st was decided by the distance in spite of part of arc fault, arc fault volume and location of the opening, and the pressure wave which occurs from the arc fault is propagated in air at sonic speed, The results would be utilized for a strength design of wall in an electric room. © 2017 The Institute of Electrical Engineers of Japan.


Li Y.,Japan Atomic Energy Agency | Hasegawa K.,Japan Atomic Energy Agency | Miura N.,Japan Central Research Institute of Electric Power Industry | Hoshino K.,Electrical Power Engineering Systems Co.
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2015

When a crack is detected in a piping line during in-service inspections, failure estimation method provided in ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be applied to evaluate the structural integrity of the cracked pipe. The failure estimation method in the current codes accounts for the bending moment and axial force due to pressure. The torsion moment is not considered. Recently, analytical investigations have been carried out by several authors on the limit load of cracked pipes considering multi-axial loads including torsion and two failure estimation methods for multi-axial loads including torsion moment with different ranges of values have been proposed. In this study, to investigate the failure behavior of cracked pipes subjected to multi-axial loads including the torsion moment and to provide experimental support for the failure estimation methods, failure experiments were performed on 20 mm diameter stainless steel pipes with a circumferential surface crack or a through-wall crack under combined axial force and bending and torsion moments. Based on the experimental results, the proposed failure estimation methods were confirmed to be applicable to cracked pipes subjected to multi-axial loads. Copyright © 2015 by ASME.


Li Y.,Japan Atomic Energy Agency | Hasegawa K.,Japan Atomic Energy Agency | Miura N.,Japan Central Research Institute of Electric Power Industry | Hoshino K.,Electrical Power Engineering Systems Co.
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2015

Piping lines in nuclear power plants may experience multiaxial loads including tensile force, bending and torsion moments during operation. There is a lack of guidance for failure evaluation under the multi-axial loads including torsion moment. ASME B&PV Code Section XI Working Group is currently developing fully plastic failure evaluation procedures for pressurized piping items containing local wall thinning subjected to multi-axial loads. A failure estimation method for locally wall thinned pipes subjected to multi-axial loads including torsion moment has been proposed through numerical analyses. In this study, in order to investigate the failure behavior of the pipes with local wall thinning subjected to multi-axial loads including the torsion, failure experiments were performed on 20 mm diameter carbon steel pipes with a local wall thinning. Based on the experimental results, the proposed failure estimation method is confirmed to be applicable to pipes with local wall thinning. Copyright © 2015 by ASME.


Seki S.,Japan Central Research Institute of Electric Power Industry | Ohno Y.,Japan Central Research Institute of Electric Power Industry | Ohno Y.,Electrical Power Engineering Systems Co. | Mita Y.,Japan Central Research Institute of Electric Power Industry | And 3 more authors.
ECS Electrochemistry Letters | Year: 2012

Relationships between the lithium salt concentration in a low-volatility solvent (room-temperature ionic liquid) and lithium secondary battery performance characteristics were investigated by using [LMOpositive electrode |DMPIm-TFSA+LiTFSA binary electrolyte | lithiummetal negative electrode] cells. Charge/discharge cycle and rate performance characteristics and various changes in resistance (lithium salt concentration and cycle number dependences) were examined, and the necessity of a suitable lithium salt concentration (0.32-0.64 mol kg?1) for good capacity retention and rate capability was concluded. © 2012 The Electrochemical Society.


Li Y.,Japan Nuclear Energy Safety Organization | Hasegawa K.,Japan Nuclear Energy Safety Organization | Miura N.,Japan Central Research Institute of Electric Power Industry | Hoshino K.,Electrical Power Engineering Systems Co.
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2013

When a crack is detected in a stainless steel pipe during in-service inspections, the failure estimation method given in codes such as the ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be applied to evaluate the structural integrity of the cracked pipe. In the current codes, the failure estimation method includes the bending moment and tensile force due to pressure. The torsion moment is assumed to be relatively small and is not considered. Recently, analytical investigations considering multiaxial loads including torsion were conducted in several previous studies by examining the limit load for pipes with a circumferential crack. A failure estimation method for the combined bending moment, torsion moment, and internal pressure was proposed. In this study, the failure behavior of pipes with a circumferential crack subjected to multiaxial loads including the torsion is investigated to provide experimental support for the failure estimation method. Experiments were carried out on small size stainless steel cylinders containing a circumferential surface or through-wall crack, subjected to the combined tensile load and torsion moment. Based on the experimental results, the proposed failure estimation method was confirmed to be applicable to cracked pipes subjected to combined tensile and torsion loads. Copyright © 2013 by ASME.


Kobayashi T.,Japan Central Research Institute of Electric Power Industry | Kobayashi Y.,Japan Central Research Institute of Electric Power Industry | Tabuchi M.,DAISO Co. | Shono K.,Japan Central Research Institute of Electric Power Industry | And 3 more authors.
ACS Applied Materials and Interfaces | Year: 2013

The all solid-state lithium battery with polyether-based solid polymer electrolyte (SPE) is regarded as one of next-generation lithium batteries, and has potential for sufficient safety because of the flammable-electrolyte-free system. It has been believed that polyether-based SPE is oxidized at the polymer/electrode interface with 4 V class cathodes. Therefore, it has been used for electric devices such as organic transistor, and lithium battery under 3 V. We estimated decomposition reaction of polyether used as SPE of all solid-state lithium battery. We first identified the decomposed parts of polyether-based SPE and the conservation of most main chain framework, considering the results of SPE analysis after long cycle operations. The oxidation reaction was found to occur slightly at the ether bond in the main chain with the branched side chain. Moreover, we resolved the issue by introducing a self-sacrificing buffer layer at the interface. The introduction of sodium carboxymethyl cellulose (CMC) to the 4 V class cathode surface led to the suppression of SPE decomposition at the interface as a result of the preformation of a buffer layer from CMC, which was confirmed by the irreversible exothermic reaction during the first charge, using electrochemical calorimetry. The attained 1500 cycle operation is 1 order of magnitude longer than those of previously reported polymer systems, and compatible with those of reported commercial liquid systems. The above results indicate to proceed to an intensive research toward the realization of 4 V class "safe" lithium polymer batteries without flammable liquid electrolyte. © 2013 American Chemical Society.


Kobayashi Y.,Japan Central Research Institute of Electric Power Industry | Kobayashi T.,Japan Central Research Institute of Electric Power Industry | Shono K.,Japan Central Research Institute of Electric Power Industry | Ohno Y.,Japan Central Research Institute of Electric Power Industry | And 3 more authors.
Journal of the Electrochemical Society | Year: 2013

A precise and simple temperature measurement technique during charge and discharge is applied to 5 Ah Al-laminated lithium-ion batteries (LiMn 2O4/LiNi0.8Co0.15Al 0.05O2 cathode and graphite anode) using a quasi-adiabatic cell holder. The obtained temperature profiles are described in terms of the reactions of the anode and cathode. This technique is applied to a cycled cell, and the capacity fading mechanism is also indicated by the temperature profiles. From the comparison between the cell temperature profiles and the reaction heat flows of the half cells in each electrode obtained by an isothermal microcalorimeter, we find that the capacity fading of the cycled cell can be derived from the capacity fading of the cathode and also from the upward shift in the operated state of charge (SOC) of the cathode in the cell. The latter shift is derived from the irreversible loss of lithium at the anode, and it leads to the misalignment of the cathode and anode operation windows. The proposed temperature measurement technique has the potential to be applied to various types of large lithium-ion batteries during operation, thus providing a new approach to analyzing the degradation of lithium-ion batteries. © 2013 The Electrochemical Society. All rights reserved.


Miura N.,Japan Central Research Institute of Electric Power Industry | Hoshino K.,Electrical Power Engineering Systems Co. | Li Y.,Japan Nuclear Energy Safety Organization | Hasegawa K.,Japan Nuclear Energy Safety Organization
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2014

When a crack-like-flaw is detected in piping during in-service inspection, the limit load criterion given in the codes such as JSME Rules on Fitness-for-Service for Nuclear Power Plants or ASME Boiler and Pressure Vessel Code Section XI can be applied to evaluate the structural integrity of the piping. However, in-service piping is generally subjected to combined tensile, bending, and torsional loading, and a methodology to evaluate the limit moment for torsion has not yet been established because of inadequate experimental validation. In this study, fracture tests were conducted for circumferentially cracked cylinders subjected to torsional moment. The experimental maximum moments were compared with the limit moments, which were evaluated on the basis of the net-section-collapse criterion for torsional moment. The maximum moments can be conservatively predicted by the net-section-collapse criterion. Copyright © 2014 by ASME.

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