In a case of a short accident on a distribution line，arc at the short point can move by electromagnetic force，and it causes severe damages of electrical equipment. Thus，it is very important to study moving arc phenomena for the safe installation of electrical equipment. In the view of this，the authors provided a test circuit to study the moving arc phenomena. In this study，arc voltage and arc moving speed were observed when distance between bus bars，circuit voltage and arc current were changed. And the correlation between circuit voltage and arc moving frequency was verified. In addition，the distance between bus bars to prevent moving arc phenomena is estimated. The authors also clarified whether insulation barriers of molded-case circuit breaker can prevent the damage by arc.

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