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A circuit model of an oil‐immersed transformer for use in surge analyses in the high‐frequency region is proposed, and its effectiveness is evaluated by comparison with measurements on a model winding. The circuit model is used for lightning surge analyses of a 500‐kV substation, and the effect of transformer modeling on the lightning surge voltage at the transformer terminals is investigated. When the new circuit model is used for transformer modeling, the peak value of the surge voltage is lower but the rate of voltage rise is higher than in conventional transformer modeling by a lumped capacitance. This difference can be explained in terms of the charging of capacitances in the transformer model. © 2000 Scripta Technica, Electr Eng Jpn, 134(1): 28–35, 2001

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HideyukiNIIZATO and Sumio TAKEDA New permeable type breakwater with low wave reflection performance is developed. This breakwater consists of a slit wall and reservoirs, in which L-type impermeable walls are set up, in front of a permeable vertical wall.As the results of hydraulic model tests on the wave reflection, it is found that the breakwater has very low wave reflection performance for wide frequency range. Furthermore, the experiments on the water exchange performance are carried out, and it is found that the breakwater is effective in water quality improvement of an inner bay.