Abstract
A pole-mounted transformer on a power distribution line is vulnerable to lightning overvoltages, and is one of the most frequently damaged instruments in Japan. Therefore, the response of transformers to the overvoltage draws great concern. By incorporating the modeling for the secondary windings proposed by Mr. Honda et al., the authors develop equivalent circuits of distribution transformers of 10kVA, 20kVA and 30kVA rated capacity based on modal analysis of measured admittance whereby one can evaluate its response to overvoltages on a low-voltage line as well as on a medium-voltage line. The validity of calculated results obtained by using the developed circuits is demonstrated by comparison with experimental results. The response of transformers made by the same manufacturer to the lightning impulse voltage waveforms is influenced by the rated capacity, and the phase and the degree of such influence is demonstrated.
