| Research Abstract |
Pulsed electro-acoustic method, which is able to measure space charge distribution accumulated in cvlindral power cable insulation, has been developed in our laboratory. The purpose of this research is to improve the spatial measurement resolution of space charge distribtion within 5%. To achieve this purpose, the following techniques have been developed.
(1) Low impendance, high voltage nanosecond pulse generator
Hg reed relay, the high voltage swich, is used to protect from the chattering noise. Fast response, high voltage divider has been improved by arranging the divider impendances in a coaxial array. Furthemore, the high voltage pulse generator are wholly shielded in a metal box to protect from electro-magnetic noises. As the results, the expected the high voltage, nanosecond pulse generator (rising time : 3ns, pulse width : 50ns, peak value : 4kV) has been developed.
(2) Detection of nanosecond pressure pulse wave
To improve the spatial measurement resolution, pizeo-electrical polymer (PVDF : thickness of 4-9 mum) has been used to detect the pressure pulse wave. In this case, the pressure pulse wave propagates in multi-layr materials. The acoustic impendance of every material has been measured and the optimum acoustic matching of multi-layr materials has been made. As the results, the primary purpose of the spatial measurement resolution within 5% of space charge distribution has been achieved.
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