Tsunayoshi Ishii

A Field Study of Lightning Surges Propagating Into Residences

In the highly information-based society of today, lightning damage to home electric appliances, such as personal computers and facsimile machines is having a greater impact, indicating a growing public interest in countermeasures for lightning. However, many things remain unknown about lightning surges that propagate into residences. The Tokyo Electric Power Company had observed the patterns of intrusion of lightning surges into residences using lightning surge waveform detectors installed at ordinary residences and obtained observation data on 18 lightning strokes between 2003 and 2006. These observation results can be used to examine the patterns of propagation of lightning surges into residences. In some observation cases of lightning strokes to the ground, lightning surge currents were estimated to flow from the ground into residences. These valuable data will be useful for elucidating the lightning surge propagation in the low-voltage distribution system including residences.

Hierarchical Decentralized Autonomous Control in Super-Distributed Energy System

This paper deals with a decentralized autonomous control strategy of a super-distributed energy system with a hierarchical structure in order to reduce the complexity of control. In this paper, distribution systems are assumed to be composed of multiple small-scale power systems in which many customers with dispersed generators exist. A small-scale power system can be considered as a unit with a generator state and a load state, or as a customer with dispersed generators. Control components of small-scale power systems are interconnected with each other and are used to operate distribution systems. An expanded decentralized autonomous control method for a super-distributed energy system with a hierarchical structure is proposed based on the Hopfield neural network. It is demonstrated that super-distributed energy systems with a hierarchical structure can be controlled autonomously by applying the proposed method.

Decentralized autonomous control of super distributed energy systems

This paper focuses on a super distributed energy system that consists of a number of dispersed generation systems such as fuel cells, micro gas-turbines, and so on. The behavior of a customer with a dispersed generation system is modeled on the Ising spin model in statistical mechanics. The validity of the modeling of the behavior of a customer is verified based on the Monte Carlo simulation. The feasibility of the decentralized autonomous control using the vicinity information is also investigated on the basis of the stability analysis of the Hopfield neural network model.

Observational and experimental study of the lightning stroke attraction effect with ground wire system constructions

Although power distribution lines are protected by ground wire systems, there are fears that these ground wires may break at their corrosion points. For practical purposes, they have therefore been removed to avoid maintenance in certain areas. The Tokyo Electric Power Company (TEPCO) has continuously observed lightning strokes and obtained 321 datasets to date. The present study has determined the potential for an anticipated lightning stroke attraction effect based on the observed data, despite the fact ground wires are eliminated while ground wire caps are left in place. Furthermore, a verification experiment using facilities simulating the power distribution system has confirmed the problem of insulated wires being struck by lightning and the extent of the impact of the ground wire cap on the lightning stroke attraction effect. These results are expected to provide a new facility-construction menu, which will help rationalize the lightning protection design.

A Field Study of Lightning Phenomena on Low-Voltage Distribution Lines Including Residences

As society becomes ever more dependent on electronics, interest in the patterns of lightning hazards in low-voltage distribution lines including residences is growing. However, there have been few studies on low-voltage distribution lines and many things remain unknown about the propagation patterns of lightning surges in the field, particularly the intrusion of lightning surges into residences. The Tokyo Electric Power Company has conducted field research of phenomena accompanying lightning flashes to actual distribution systems using lightning-activated cameras as well as lightning surge waveform detectors, obtaining invaluable 101 datasets of lightning flashes between 2002 and 2007. This paper analyzes typical observation examples and estimates the lightning surge propagation routes in low-voltage distribution lines. In some examples, it is inferred that a lightning current flowed in the reverse direction from the residence to the low-voltage distribution line caused by ground potential rise due to the nearby lightning to the ground. These results will be useful for clarifying lightning surge propagation patterns in low-voltage distribution lines.

Analysis and autonomous distributed control of super distributed energy systems

This paper focuses on a super distributed energy system that consists of a number of dispersed generation systems such as fuel cells, micro gas-turbines, and so on. The behavior of a customer with a dispersed generation system is modeled on the Ising spin model in statistical mechanics. The validity of the modeling of the behavior of a customer is verified based on the Monte Carlo simulation. The feasibility of autonomous distributed control using vicinity information is also investigated on the basis of stability analysis of the Hopfield neural network model.