In this paper, I will explain recent trends of the laws and regulations about environment. Furthermore, I will describe the environmental activities in the electric wire and cable industry such as material recycling, promotion of environmental conscious design, and so on.

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A voltage rise problem in distribution network has been discussed as the foremost concern against the penetration of large amount of photovoltaics (PVs). The authors focus on latent ability of the present distribution network and PVs to find a low cost solution against the problem and consider a solution to mitigate the voltage rise using PV's constant leading power factor operation. So far, as a result of having simulated with an aggregated model of real distribution network, we proposed that a combination of PV's constant leading power factor operation and LDC makes it possible to maintain the line voltage and LTC tap position adequately.
In this paper, additionally, the authors confirmed some effects of the proposed method in an aggregated model of distribution network and trunk power system. One of them is the proposed method reduces the frequency of restricting output power from PVs and changing LTC and SVR tap position, although PVs are rapidly fluctuated. Another is the proposed method can't make a great impact for trunk power system of a voltage class exceeding 6.6kV.

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In this paper, we propose a new decentralized multi-agent approach for detecting fault equipment in power system. The proposed method consists of several Substation agents (SSAGs), Distribution substations (DSAGs) and Line agents (LAGs). SSAG is installed each substation and controls its substation. DSAG is installed each distribution substation and receives instruction from SSAG or LAG. LAG is installed any substation and controls the transmission line. In order to demonstrate the capability of proposed multi-agent system, it has been applied to a model power system that has 7 substations and 8 distribution substations. The simulation results show that the proposed multi-agent approach is effective and promising.

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Penetration of photovoltaic generation (PV) system into the power system may give some negative impacts to stable operations of power system; for example, to the frequency control. Therefore, investigation on the short-term fluctuation of PV generation is important as a precaution against further PV penetration. Since the PV generation is almost proportional to the incident solar radiation, this paper develops static and dynamic characteristic models for short-term fluctuation in the global solar radiation. The static characteristic model is a set of standard deviations which have been statistically estimated based on the past observed data. The dynamic characteristic model is autoregressive models which are designed for the actually observed time sequential short-term fluctuation data. In both models, the clearness index is used to eliminate seasonal variation of solar radiation.

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This paper analyzes Japan's optimal power generation mix considering massive deployment of solar photovoltaic (PV) system and wind power generation. The extensive introduction of PV system and wind power system are expected to play an important role in addressing energy security and climate change concern in Japan. Considering this expected large-scale deployment of PV system in electric power system, it is necessary to investigate the optimal power generation mix which is technologically capable of controlling and accommodating the intermittent output-power fluctuation inherently derived from PV and wind energy system. On these backgrounds, we develop optimal power generation mix model, explicitly analyzing the impact of output fluctuation in variable renewable in detailed resolution of time interval like 10 minutes at consecutive 365 days, with the role of stationary battery technology incorporated. Simulation results reveal that considerable deployment of those variable renewables do not necessarily require the scale of battery capacity similar as that of variable renewable capacity, due to quick load following treatment by thermal power plants, pumped-storage hydro power and battery technology over renewable output fluctuation.

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There are many PWM control apparatuses, which are higher harmonics current sources, in distribution systems. And higher harmonics causes over current by parallel resonance. To avoid the over current, it is necessary to suppress the resonance.
In this paper, a new suppression method, which inserts a damping resistance in resonance circuit, is proposed. Firstly using the participation factor of state equation and condenser capacitance, the condenser current is defined. And, the damping resistance position becomes the maximum current condenser. Then, to determine the damping resistance value, a natural frequency characteristic to current amplification degree is introduced using with eigen value. Finally, adopting numerical examination, it is known that the damping resistance is effective in any case. Moreover, the hybrid method of the damping resistance and the optimal harmonic source point method is more effective in multi resonance circuits problem.

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A fault that occurs near a power station may cause a loss of synchronism of generators in the power station against the remaining generators and result in a widespread blackout. When swing of generators in the power station with respect to the remaining generators is similar to that of a generator in one machine and an infinite bus system, a power-angle curve (P-δ curve) is often used for studying the stability of the system and deciding the number of generators to be shed for stabilization. In operation, power system stabilizers predict loss of synchronism, determine the number of generators to be shed, and then shed them in a very short time period. Such stabilizers use data measured during a period of about 200 ms after fault occurence. The voltage and current measured on the bus and line connected to a power station are used to compute the P-δ curve. When a line is removed to clear a fault, the current in the damper circuit of a generator decays significantly in a very short period. This causes significant changes in the line current. However, when the P-δ curve is estimated using these data, and is applied to a stability study, the number of generators to be shed sometimes exceeds the optimum number. This is caused by the practice of measuring the current immediately after a fault is cleaed. Therefore, the authors propose a current detection method in which the portion of current that decays immediately after a fault is cleared. Such current has three distinct terms. Two are exponential functions in which one has extremely short time constant, while the other has a longer time constant. By using these estimated functions, the fast decaying component is removed from the measured current, which can then be used to estimate the P-δ curve more precisely. The method was verified via simulations using an infinite bus system model and the EAST10 model of IEEJ.

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An electric vehicle includes more electronic parts than a gasoline-powered vehicle. Not only control but also driving circuits of electric vehicles are electrical at variance with those of gasoline-powered vehicles. It means that there is higher possibility of malfunctions on an electric vehicle due to electromagnetic disturbances caused by a lightning stroke. Therefore, it is important to establish lightning protection methodologies for electric vehicles. To solve the mechanisms that the lightning current following through the vehicle body and some other parts causes the malfunctions, it is important to clarify transient magnetic fields and current distributions in electric vehicles. In this paper, the transient magnetic fields and the current distributions in an electric vehicle are simulated using the FDTD method, and the probability of lightning damages is discussed.

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Recently, it is desired to develop energy control technologies for environmental issues such as global warming and exhaustion of fossil fuel. Power fluctuations in large power consumers may cause the instability of electric power systems and increase the cost of the electric power facility and electricity charges. Developing the electric power-leveling systems (EPLS) to compensate the power fluctuations is necessary for future electric power systems.
Now, EPLS with an SMES have been proposed as one of the countermeasures for the electric power quality improvement. The SMES is superior to other energy storage devices in response and storage efficiency. The authors proposed the EPLS based on fussy control with the SMES. For this practical implementation, optimizing control gain and SMES capacity is an important issue.
This paper proposes a new optimization method of the EPLS. The proposed algorithm is novel particle swarm optimization based on taper-off reflectance (TRPSO). The proposed TRPSO optimizes the design variables of the EPLS efficiently and effectively.

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Interconnection of the grounding system of wind turbines reduces steady-state grounding resistance, however, the transient behavior during a lightning strike to an interconnected wind turbine grounding system remains to be discussed. This paper investigates the influence of interconnection on the lightning surge response of wind turbine grounding system. Two different numerical methods, Numerical Electromagnetics Code (NEC-4) based on Method of Moments (MoM), and Virtual Surge Test Lab (VSTL) based on Finite Difference Time Domain (FDTD) method, are used for lightning surge analysis of wind turbine grounding systems. Comparison of results using NEC-4 and VSTL are made to clarify the usefulness of these methods for transient analysis of a large grounding system. The influence of soil parameters, front time of injected current, and the type of a conductor employed for interconnection, on the response of interconnected wind turbine grounding is discussed.

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We examined the lightning frequency reported by Eriksson and the lightning current distribution shown in IEC 62305-1. The lightning striking coefficient is assumed to be related to height of structures. The lightning current distribution to ground which was applicable to the electro-geometric model is estimated. Using the assumption of lightning striking distance coefficient and the estimated lightning current distribution, we calculated the lightning frequency and the lightning current distribution, concerning lightning shielding effect in transmission lines. The calculation results of the lightning frequency and the lightning current distributions were compared with the observation results, and agree satisfactorily with them.

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