In this text, it introduces the result of the outline of the Kitakyushu Smart Community Creation Project and the dynamic pricing society proof of summer in fiscal year 2012. The effect of the peak cutting of about 9-13% was achieved by the Variable Critical Peak Pricing.
This paper proposes a novel method for the management of EV fast charging stations from the viewpoint of voltage quality in distribution networks. In the future, EV's coincident charging possibly impacts on voltage profiles of distribution networks. The proposed method determines how many EVs can be charged by EV fast chargers with fast charging stations on distribution networks under constraints of voltage fluctuation. The proposed method is based on a solution of the linear programming (LP) with an objective function of maximizing the number of available fast chargers and constraints of linearized power flow equations. The proposed method can improve calculation precision of the number of available fast chargers by repeating modification of the linearized power flow equations with AC power flow and recalculation of the linear programming problem. In addition, the proposed method can be applied to PV connected distribution networks and easily estimate the reactive power required for the increase of the available fast chargers by using duality of LP. As a result, the proposed method can determine the maximum number of available fast chargers while keeping voltage profiles within the regulated range.
The traded volumes in Japan Electric Power Exchange (JEPX) are desired to increase. However, few studies have clarified what factors have contributed to impacting the traded volumes, including the time-wise changes of these contributions. In this study, the authors analyzed the traded volume using error correction models. As a result, a cointegration relationship was found where the traded volume of 1GWh was mainly associated with the buying bids of 2.8-4.0GWh, while such association with the selling offers was minor. In addition, the traded volume was also influenced by short-term disturbances that reverted to this cointegration equilibrium in about three weeks. However, much of such short-term disturbances were based on the past deviation from the cointegration equilibrium, implying the importance of buying bid increases.
The partial discharge characteristics in Oil Filled (OF) cable were studied by using miniature model in order to clarify deterioration mechanism of OF cable with partial defects. It was found out that partial discharge may occur continuously when following three factors are caused together. One is the existence of the overlapped oil gap in the insulation papers of OF cable. The second is invasion of surge voltage superimposed on AC working voltage. The third is the reduced gas-absorption capacity of oil due to the large amount of dissolved gas in the oil. The paper covers the experimental results in the miniature model on the required conditions and development process of partial discharge in OF cables.
About 70% of overhead transmission line faults have been caused by natural forces. Above all, more than 60% of those faults are due to lightning. As transmission line arresters (TLAs) are effective to prevent the faults caused by lightning, we have installed them in many of our transmission lines. Nevertheless, TLAs have been damaged by a very large electric charge of lightning, particularly in winter. Through investigation of the damaged TLAs collected from our transmission lines, we found some of the internal zinc oxide (ZnO) elements of TLAs were damaged. But it is difficult to detect those damaged TLAs by the conventional measurement of insulation resistance between terminals of TLAs. Therefore, this paper proposes a new detection method for the damaged TLAs using the frequency characteristics of its equivalent series resistance. The detection rate of the damaged TLAs by the new method is remarkably higher than that by the conventional method.
The Tokyo Electric Power Company, Inc (TEPCO) plans UHV power network system in Japan in order to meet the steadily increasing demand for electricity. Four-hundred kilometer UHV-designed double-circuit transmission lines have already been constructed and are now operated at 500kV. Double-circuit flashovers on the UHV minami-iwaki transmission line occurred the first time with successful re-closing of the circuit in 2006. In this paper, we report on the melted OPGW500mm2, lightning location system (JDLN), oscillograph, and the phenomenon analyzed by using EMTP. The results are as follows: (1) Double-circuit flashovers on the UHV minami-iwaki transmission line occurred for the first time. The overhead ground wire (OPGW500mm2) was melted by lightning. (2) According to the oscillograph, the fault was occurred at the phase of 270 degrees. (3) Lightning peak current was about +265kA by using JLDN. The melted component wires of OPGW500mm2 were caused by the lightning, and the amount of melted wires was estimated at 3 wires in 1L, 4 wires in 2L. (4) From the result of EMTP analysis, the lightning peak current was +265kA, and the rise time was 2.5µs∼3.5µs. It shows that EMTP result doesn't contradict the lightning current estimated by JLDN.