For the insulation diagnosis of stator windings of generators, sampling surveys are conducted on the coils to estimate the dielectric strength of the stator winding. Previous research has relied on inferring the breakdown voltage of the stator winding from the value 3σ away from the mean value of the breakdown voltage of the coil. However, this conventional method exhibits a significant estimation error when the sample size is small. Therefore, we propose a method for estimating the breakdown voltage of the stator winding based on the maximum value of the partial discharge magnitude and minimum value of the breakdown voltage of the sample coil. We verify this method by Monte Carlo simulation assuming a sampling survey of coils.

This paper describes measurements of progression velocity and electric field intensity at the head of plasma bullet in atmospheric pressure argon plasma jets (APJs) using two-typed probe. The probe used firstly is consisted with a fine stainless-steel wire and a resistor. Observed probe current waveforms contain both of displacement and conduction currents, then our interesting in this paper is focused with the latter current waveform. We observed a rapidly growth of pulse height in the discharge current along the APJs. The increase of pulse height is attributable to isolated charged particles progressing to downstream side in the APJ which may be a plasma bullet. The velocity of the plasma bullet is estimated, and the results are identified by the second probe which is consisted with a ring made of copper with a coil wound several turns. The new probe acts as a current detector to capture the discharge current which penetrate the center of the ring on the basis of the “expanded Ampere's law”. From the results, the velocity of the plasma bullet was measured to be v=1∼3 km/s. This value is proved the results obtained by the wire probe. The electric field intensity at the head of plasma bullet is also measured and we estimated to be 1∼10 kV/cm. The value is acted as a driven source for the plasma bullet, as like as a streamer in the APJ.

Characterizations of pulsed power output for pulsed power generator using GaN FET have been evaluated and compared with using SiC-MOS FET. The fast rise/fall time of output voltage without the dependance on the dummy load has attractive feathers. However, the surge voltage between drain and source terminals, exceeding the maximum rating occurred due to the fast turn-off speed feathers of GaN FET, which has limited the power capability. The inductive energy storage pulsed power generator using GaN FETs as opening switches has developed, and the output obtains a maximum voltage of ∼900V with rise/fall time of <20 ns. The fast current interruption characteristics by the turn-off of GaN FET lead to high voltage-pulsed output.

G-value of hydrogen peroxide irradiated by pulsed intense relativistic electron beam (PIREB) was demonstrated. The PIREB with a kinetic energy of up to 2 MeV and pulse duration of 100 ns (FWHM) was generated using the intense pulsed power generator “ETIGO-III”. The G-value after PIREB irradiations was estimated as 1.25 molecules/100eV with 68.9 kGy of average dose accumulated by 9 shots and 20 mg/L of hydrogen peroxide concentration. The result indicated that the G-value of PIREB irradiation was higher than that by high LET radiation irradiations.