Analysis of water tree using equivalent circuit model

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The technique for measuring the loss current wave form is developed as a technique for diagnosing the water tree deterioration. The distortion with the higher harmonic is seen in the loss current wave form. The relation can be seen between the expansion of water tree and the third harmonic which is the maximum in higher harmonics. Therefore, the loss current analysis is thought as a effective deterioration method that even non-penetration water tree can detect.Then, equivalent circuit model of water tree was constructed in the present research at the first year. As a result, the loss current calculated from the equivalent circuit model proposed by the present research was corresponding to the measurement value.The models were made in consideration of shape and the length of water tree in the next year. Effective data to the water tree detection were calculated by PSpice from these models. It has been understood that the difference is seen in the loss current wave form when shape is different even if the area of the water tree part is the same. Moreover, when shape is different even if the size of water tree is the same, it has been understood that the loss current wave form is different.It was also found that the distortion of the shape of the loss current waves is different depending on applied voltage and frequency, when we detect water tree from the distortion of the loss current.