Haruo Kishida

A study of NO removal by packed-beads discharge reactor

Recently, air pollution has become a serious problem; photochemical smog and acid rain are typical phenomena. NO/sub x/ is a serious air pollutant and a toxic gas. In spite of an attempt to reduce the amount of NO/sub x/ emitted, the density of NO/sub x/ in the atmosphere has remained on a stable level, or even become worse. Here, the authors propose a new reactor in which the gap area is filled as a single layer of glass plates and beads. They expect that surface and silent discharges are generated simultaneously in the same space. In this paper, the removal of NO/sub x/ from a dry NO/N/sub 2/ mixed gas by barrier discharge among glass beads in the reactor is experimentally investigated. The experiments are carried out for the frequency 50 Hz, with applied voltage from 0 to 20 kV/sub pp/ and a gas flow rate from 0.4 to 1.4 L/min. The results show that the NO and NO/sub x/ removal rates with glass beads are higher than those without glass beads at the same flow rate or residence time. Thus, the new reactor in which the gap area is filled with glass beads is more effective for NO/sub x/ removal.

Influence of swarming pulsive microdischarge on tree degradation

In treeing degradation, discharges in tree channel through void, it is thought that treeing process is difference between the case of occurrence of SPMD (swarming pulsive microdischarge) before tree inception and no occurrence of SPMD. In this study, treeing samples are separated the SPMD sample and the non-SPMD sample, there are compared discharge magnitude, discharge luminescence, the tree growing rate and the density of tree channels.

Optical and electrical detection of single pulse of partial discharge on electrical treeing

The purpose of this study is to analyze the treeing degradation process by measuring partial discharge pulse and discharge luminous image of single pulse. In the measurement system, PMMA blocks were used with electrodes consisting of a needle and a plate. One cycle of an applied ac voltage was divided into twenty equal phase angle sections, labeled /spl phi//sub 1/,/spl phi//sub 2/,...,/spl phi//sub 20/ in order, from one negative peak to the next negative peak of the applied voltage. A high voltage was applied to the needle electrode, positive discharge pulses and discharge luminescences were measured at the same time between /spl phi//sub 3/ and /spl phi//sub 9/. As a result, the discharge luminescence at /spl phi//sub 3/ and /spl phi//sub 4/ occurred mainly in the void area independently of the discharge magnitude. At /spl phi//sub 7/,/spl phi//sub 8/ and /spl phi//sub 9/, the discharge luminescence was observed in the void area when the discharge magnitude was small, in the tree area when it was comparatively large. The discharge luminescence reached near the tip of tree channel.

Diagnosis of tree initiation by analysis of discharge magnitude and discharge luminescence at each phase angle area

In this study, we present a new method which the diagnosis of tree initiation by measuring discharge magnitude and discharge luminous image at each phase angle area. We measured discharge magnitude and discharge luminous image by the original measurement system to analyze discharge pulses and discharge luminescence at several phase angle areas of applied voltage. As the measuring section, one cycle of applied voltage was divided into twenty areas, which were named from /spl phi//sub 1/ to /spl phi//sub 20/ in order from the negative peak point of applied voltage. Then, we defined effective instantaneous value considered from each equivalent circuit before and after tree initiation, which we took into consideration that the influence of the residual electric charge which stored the tip of void and tree channel. As a result, the product of effective instantaneous value and dv/dt was in proportion to discharge magnitude and luminous quantity. However, each coefficient of correlation differed before and after tree initiation. So, we were able to know the tree initiation by the change of each coefficient of correlation. Therefore, this method facilitated to diagnose the tree initiation only by measuring discharge magnitude at each phase angle area. It was considered to be more useful information for diagnosis of degradation by electrical treeing.

Discharge luminescence and discharge magnitude in treeing degradation

This paper describes results of the discharge luminescence and discharge magnitude measurements performed on the insulation materials exposed to partial discharge. Polymethyl methacrylate (PMMA) with an artificial needle shape void were used as the treeing specimens. The discharge luminescence is observed by image intensifier, and the luminous image is processed by computer. At the same time, the discharge magnitude distribution in relation to phase angle of the applied voltage was measured by a partial discharge measuring system. The mechanism of electric treeing was discussed by not only the measurement of the discharge pulses but also the local luminescence intensity of partial discharge. As a result, the luminescence intensity analysis showed the relation between tree growing length and void length when maximum luminescence intensity moved from the void area to the tree area. Both tree growth and maximum luminescence intensity at the tree area increase with constant ratio. The discharge luminescence intensity at the tree area increases significantly depending on the discharge magnitude in the specific phase angle area in positive and negative.

Analysis of partial discharge phenomena by discharge magnitude and discharge luminescence in each phase angle

This research was carried out to analyze the treeing phenomena from a needle shape void by discharge pulses and a discharge luminescence in each phase angle area. The discharge pulse and the discharge luminescence were measured by a special measuring system to analyze a discharge magnitude and a discharge luminous intensity image according to several phase angle areas of applied voltage. In particular, in this study, we focused on the discharge luminescence in each phase angle area. The luminous image was recorded on a CCD camera, and the image was digitized by a computer after the experiment.