Fumitoshi Noto

Development of automatic measurement system for growth and shape of tree by image processing

A system to automatically measure the tree degradation phenomenon in organic insulating materials using an optical microscope is discussed. Cross-linked polyethylene was used as the sample material. A video-graphic processing method made it possible to examine the initialization period of the treeing phenomenon and to measure the tree length, surface area, and form of propagation using serial video images. As a result, it was possible in a long-time breakdown test, to demonstrate characteristic difference in tree length and surface area according to the size of the applied voltages in the period immediately after initialization. When the voltage was low the tree shape resembled the branches of a tree. As the voltage increased, the shape of the breakdown area formed a round chestnut-like tree. In a short-time breakdown test, it was shown that length and surface area were greatly influenced by the radius of curvature of the needle electrode. This difference was evident 20 s after the initialization of the tree. When the radius of the needle electrode tip was large, the tree took on a bushlike shape. When the radius was small the tree went from a tree-branch shape to a bushlike shape.<<ETX>>

Investigation of tracking degradation by DC voltage application

Tracking tests of organic insulating materials of power apparatus for outdoor use have previously been carried out by AC voltage application using stainless steel electrodes. AC voltage has been used for all power engineering apparatus, namely, generation, transmission and household electric products. Recently, this type of apparatus using DC voltage has appeared in various fields. As a result, a solution seemed to be needed for tracking degradation under DC voltage application. This paper describes the investigation of tracking degradation of organic insulating materials for power engineering application. The following results were obtained. Time to tracking breakdown under DC voltage application was long than under AC voltage application. At plus polarity of top electrode, discharge phenomena were stronger than minus polarity. Time to tracking breakdown using a platinum electrode was shorter than that using a stainless steel electrode.<<ETX>>

Study on radiation aging of polymeric insulating material by positron annihilation

Structure changes of fluoropolymer, a heat-resistant insulating material, after /spl gamma/-ray irradiation, were investigated using positron annihilation. The correlation between structure changes and dielectric breakdown strength was studied. The dielectric breakdown strength is found to decrease with increasing dose. Positron lifetime data showed that crystallinity increased with irradiation. As the crystalline region is increased by irradiation, it is easy to accelerate electrons when impulse voltage is applied. It is then that dielectric breakdown occurs.<<ETX>>

Investigation on tracking deterioration using electron spin resonance

A tracking deterioration test using polycarbonate (PC) as a sample was carried out by means of the modified IEC 587 test method. The structure of residual carbon was investigated with the measurement of electron spin resonance. It was shown that carbon radicals increase noticeably in accordance with the applied voltage and applied time. It is found that carbon radicals are generated in proportion to the product of the square of the applied voltage and the applied time. Analysis of the X-ray diffraction pattern indicates that carbon radicals do not form a graphite structure.<<ETX>>

Influence of irradiation on electrical properties of conducting polymer

Electrical properties of electron beam irradiated polypyrrole films, which are conducting polymer, were studied. Conductivity increased with increasing the temperature from -190/spl deg/C to 180/spl deg/C. The conductivity was constant from 0 Gy to 50 MGy irradiation, then rapidly decreased from 50 MGy to 150 MGy irradiation. Moreover, free radicals decreased with dose. From the results of chemical analysis, it was found that the numbers of C=C, C-C and C-N bonds decreased with dose.

Investigation on dielectric properties of /spl gamma/-ray irradiated poly(ether ether ketone) by positron annihilation

Dielectric properties of /spl gamma/-ray irradiated poly(ether-ether-ketone) were investigated under impulse voltage and AC voltage. Irradiation between 0 Gy and 10 MGy did not affect dielectric breakdown strength at room temperature, however, structural changes of the irradiated specimen were observed by positron annihilation. The intensity, I/sub 3/ of ortho-positronium decreased with increasing the dose, therefore, it was clarified that the amount of cavities in amorphous region decreased.<<ETX>>