Contents I. Introduction
A vacuum interrupter is widely used for circuit breaker at medium voltage power system. When short circuit occurs, pair of electrodes in vacuum interrupter is separated and an arc occurs. The electrodes are heated by the arc and the electrode temperature remain high for several ms after the fault current interruption[1][2]. In this period, It is assumed that a lot of thermal electrons and metal vapors, which is considered to have a significant effect on interruption ability, are produced from the high temperature electrode surface. Therefore the measurement of electrode temperature is important for explication of interruption phenomenon in vacuum, but it is difficult because the temperature distribution is not uniform at the entire electrode and it changes transiently[3]. Since high voltage is applied to the electrode, a non-contact method is more appropriate for temperature measurement than a contact method. The fiber-type radiation thermometer, which is one of the non-contact methods, could not acquire the temperature distribution because the measurement area was small[4]. Therefore, we develop two color pyrometer method with a high-speed camera which can measure transiently changing electrode temperature distribution.
