Prof. Akihiro AMETANI, Naoto NAGAOKA, Yoshihiro BABA Power System Analysis Laboratory http://istc.doshisha.ac.jp/course/electrical/labo_17.html Research Topics Analysis of phenomena and characteristics in lifelines/infrastructure systems: Intelligent buildings, wind-power generation, electric railroads, solar-power generation, etc. Analysis of transient/steady-state phenomena in electrical/electric systems Developing numerical analysis methods and modeling methods for transient/steady-state phenomena: Fourier/Laplace transform, EMTP, numerical electromagnetic field analysis, etc. Different types of modeling methods, transient/steady-state characteristic research: cars, railway, airplanes, lithium-ion batteries, transformers, electrical appliances, semiconductor elements, measuring instruments, machinery lifetime estimation, etc. Research Contents Introduction Virtually most of the lifelines (water lines, railroads, telecommunications, etc.) and infrastructure (buildings, roads, etc.) of modern society run on electricity. If electricity were shut off, water would not run when the water taps were turned on, building doors would not open, ATMs would shut down, cell phones would not recharge, and their base stations would stop transmitting before that anyway. The technologies of "electrical energy as a power source" and "electrical signals for telecommunications and control" are indispensable to modern society. The Power System Analysis Laboratory conducts research related to the electrical energy (electrical power) that supports lifelines and infrastructure. Its ultimate goal is stable supply of electrical power. Electrical power systems must therefore be designed, built, and operated with "safety," "high reliability," "efficiency," and "economic considerations" in mind. Since electrical power systems are also very large systems, however, it is not possible to fully verify them through experimentation. The main topics of our laboratory are the development of numerical analysis methods for electrical power systems and the development of numerical models for power equipment to be used in this. Fig. 1 shows an overview of our research topics.
Modeling Insulation levels in electrical power systems are dictated by the voltage of switching surges generated by breakers and lightning surges caused by lightning. It is therefore important to predict overvoltage precisely when designing economical electrical power systems. To do this, we first need very precise numerical analysis models to represent power equipment. Our laboratory develops models of different equipment used in electrical power systems. The primary components of transmission and distribution systems are the overhead power lines and cables, which are distributed-parameter lines. In overhead power lines with considerable length, which are affected by earth, wave propagation characteristics have frequency characteristics. In cables, sheaths are thin, so their propagation characteristics also are a function of frequency. Our laboratory has devised numerical analysis models that consider the frequency dependence of these homogeneous lines with great precision. We are also developing a finite-length line model that considers grounding and vertical conductors, as typified by steel towers, which must be treated as non-homogeneous lines. When developing these models, we conduct theoretical electromagnetic field analysis and develop functional approximation method suited to represent line models; we then conduct measurements using scale models to confirm the precision of the analytical model. We are also developing devices that measure high voltages precisely without contact by applying the induction characteristics of multi-phase distributed-parameter lines. Substations are built by organically combining an array of equipment such as transformers, bus lines, breakers, and arrestors. Models of these are widely available for low-frequency domains, but we are developing the broadband numerical models needed for surge analysis. Since this equipment has nonlinear voltage-current characteristics, these characteristics must be adequately expressed in model development. For breakers, it is particularly necessary to consider arc characteristics, which are a discharge phenomenon. The model developed by our laboratory can take these characteristics into account with an extremely simple function and has notably short calculation times. The model developed by our laboratory was also improved jointly with Mr. Ichiro FUJITA of the Plasma Application Laboratory, and we developed a discharge lamp model that has achieved good results. A paper on this model was presented and awarded a prize at a conference.