In this paper, the estimation of local loss in a reactor with new type of structure of yoke and air-gapped core leg is discussed. The local loss evaluation is carried out by using the magnetic field analysis, and the local loss measurement of reactor model is performed by the initial temperature rise method using thermocouples. Methods for taking account of anisotropy of grain-oriented silicon steel and the modeling of lamination of core are examined. The effectiveness of analysis is validated by comparing with measurement. It is illustrated that the eddy current loss due to the fringing flux near gaps is more than 100 times larger than the material loss. The method for analyzing magnetic field precisely can be applied for developing a highly efficient and reliable reactor.

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Currently, the way of measuring earthing resistance is the fall of potential method which is used extensively both in Japan and worldwide. However, in overcrowded areas particularly in urban districts there is not enough space for taking measurements due to limited sites，the greater size of buildings and asphalt and concrete paving. Furthermore, there is the difficulty of inserting an auxiliary electrode. There are examples where large building sites with various underground obstacles （materials） such as piping，electric wise and concrete settlement, influence the measured earthing resistance. The present stste requires an improvement in earthing resistance measurement technology. Hence, the fall of potential method is used to simulate the earthing resistance measurement at the points of inserting the auxiliary electrode.

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