Recently, with the progress in energy management system (EMS), better understanding of the detailed mechanism of energy demand occurrence becomes an important subject in energy efficiency research. One of the effective measures is the development of energy end-use simulation model. Firstly in this paper, component of energy demand formative mechanism in building sector is explained. Secondly, researches on energy end-use modeling are reviewed. In the final part, example of electricity load curve simulation in city block is introduced.
Renewable energies having little effect on the global environment have been attracting much attention. Among them, wind power has been introduced widely. However, output power of wind power generation is unstable, and thus it can have bad influence on power system operation. Therefore, control of the introduction or battery system for smoothing the unstable output is required. In this paper, a new method of power system frequency control is proposed which is based on the output frequency band control of wind farm by using variable speed wind generators.
In this paper, a cooperative control of three energy storage systems (ESSs) and biogas generation for a stabilization of renewable energy generation output is developed considering the difference of characteristics such as the ratio of energy capacity to power capacity (energy/power ratio) and the dynamic response. The purposes of this system are 30-minute balancing between the actual and scheduled output based on weather forecasts and absorption of the short-term (less than 30 minutes) output fluctuation. This paper presents the basic study about an efficacy and best portfolio of a cooperative control of multiple ESSs and BG. This paper also describes ESS capacity and control parameters design procedure. Evaluation results of required ESS capacity conduces a planning method of scheduled output for SOC recovery. Additionally, it is understood that BG is effective as the substitute of sodium-sulfur battery (NAS).
The Fault Current Interrupting Arcing Horns (FCIAH) is a new type of arcing horns, which operates to break fault current within one cycle of alternating current and contributes to reducing the instantaneous power interruption due to the opening of a circuit breaker. However, reportedly the transmission line is often tripped by the line protection relay in some power utilities, even though the FCIAH successfully could break fault current. In this paper, we have investigated primary factors in the unwanted operation of the line protection relays at the current interruption by the FCIAH, and have proposed effective installation strategies of the FCIAH considering the operational coordination with the responses of the line protection relays.
On a 66kV overhead transmission line equipped with arcing horns, a two-phase short-circuit fault between an upper and a lower line caused by a lightning strike turned into a three-phase short-circuit fault. And, a round inspection after the fault revealed that there were many partially-melted spots on a jumper wire of middle line. In order to clarify the mechanism of the fault experimentally, the short-circuit tests were carried out by using the full scale apparatus considering the installation conditions of the arcing horns on the actual lines. The arc was ignited between arcing horns installed on the lower line, and the aspects of the phase-to-phase short-circuit fault between the lower and the middle line were observed by using the high speed videos. As a result, the arc jets spouted upwards from the arcing horns of the lower line, and the arc showed a tendency of rising easily due to the arc jets. These results suggested that the hot gas generated by the arc and the arc jets caused the breakdown between the lower and the middle line, and the phase-to-phase short-circuit fault occurred. Considering the breakdown phenomena, a countermeasure against the short-circuit fault was investigated.
Load bearing deterioration of existing transmission towers due to base displacement is estimated by numerical analyses and on-site measurements. However, the accuracy and efficiency improvement of the practical analysis technique is inevitably requested, because of a lot of anxiety towers that should be diagnosed. The purpose of this paper is to propose incremental and direct iteration methods considering bolt slip, paying attention to the most appropriate ratio of construction error to total base displacement and bolt slipping stress. It is clarified that the proposed methods are remarkably improved from the viewpoint of accuracy and efficiency improvement compared with the conventional method not considering bolt slip. And it is also clarified that the direct iteration method is worth using from the practical standpoint, such as computer run-time and on-site computation, compared with the incremental method.
It was reported so far that degradation of varistor voltage of metal-oxide varistors (MOVs) was observed when short-tailed impulse currents such as 4/10µs or 8/20µs impulses were applied, whereas after application of impulse currents having rather long duration such as 2ms rectangular current, degradation of varistor voltage was not observed. In this study, it is found that degradation of varistor voltage occurs after application of 10/350µs impulse current having longer duration than short-tailed impulses. The charge transfer value per unit cross section area is found to be related to degradation of varistor voltages, though its effect is dependent on impulse current waveforms. The behaviour of degradation of varistor voltage inside of MOV elements stressed by short-tailed impulse currents is partially explained by non-uniformity of current distribution in the elements, which is confirmed by numerical electromagnetic analysis.
In this paper, the performance of Liao's second-order absorbing boundary condition in representing a semi-infinite wire in surge simulations using the finite-difference time-domain method has been studied. It has been confirmed that the precision type, single or double precision, influences the performance of this absorbing boundary condition and the use of double precision type yields more accurate results. The use of stabilization coefficient, which is often set to d=0.0075, yields less accurate results when a semi-infinite conductor is represented. The working volume should be large in radial direction of a semi-infinite conductor, but could be smaller in the axial direction.
Two types of lightning flashes, which are upward lightning and downward lightning, have been observed at Tokyo Skytree. Relationship between upward lightning occurrence and meteorological conditions has been investigated with the data obtained by Japan Meteorological Agency. It has been found that when the altitude of -10°C is lower than 6000m, most of lightning flashes are upward and vice versa.