The partial discharge (PD) waveform reflects the evolution process of electron avalanche in the discharge space. The authors expect to estimate the condition of the discharge space based on the PD waveform characteristics. The semi-conductive sheet was attached to the insulator to simulate the decrease in surface resistance due to deterioration. With the reduction of the surface resistivity, the shoulder appeared on the rising part of the PD waveform and the rise time of the PD waveform became longer. In addition, we simulated the change in the rise time using an equivalent circuit model. The displacement current was calculated from the surface potential distribution estimated by the diffusion equation, and the PD current was simulated by summing up all the current components. As a result, the shoulder was reproduced at the rising part of the PD waveform in the simulation as well. The surface resistance was estimated from the PD waveform by fitting with the experimental results.

A minute air gap may result in a successive partial discharge in an insulation system. Here, the partial discharge inception voltage (PDIV) in a half-pipe-type insulating material-air gap-insulating material electrode system with or without bridging between insulating materials was measured to investigate the influence of the bridging between insulating materials on the PDIV. The PDIV under the DC ramp voltage (DC-PDIV) with bridging between insulating materials using Al tape is higher than that without bridging. The DC-PDIV after cutting the bridging Al tape between insulating materials also corresponds to that without bridging. In addition, the PDIV under a surge voltage application (Surge-PDIV) is almost the same despite the bridging change. These results indicate that the inverse field due to the charge traveling via the Al tape for bridging between insulating materials relaxes the external field.

This paper describes a numerical study about influence of time duration of intermittent feedstock feeding on Si nanoparticle formation using the pulse-modulated induced thermal plasma (PMITP) with the time controlled feedstock feeding (TCFF). The PMITP+TCFF method has been developed originally by our group to synthesize large amounts of nanoparticles. We have also developed a numerical model for Si nanoparticle synthesis including nanoparticle nucleation and growth in thermal plasma temperature and gas flow fields in PMITP+TCFF method. Using this model, we investigated the temperature variation in the PMITP, and then the particle size distribution of synthesized nanoparticles for different feeding time durations of the feedstock for Ar-PMITP. As a result, it was found that shorter feeding time durations of the feedstock decreases the size of the produced nanoparticles and increases the amount of nanoparticles produced.