Study on the remote sensing of the space charge

2000 Fiscal Year Final Research Report Summary

• Project/Area Number: 10650273
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 電力工学・電気機器工学
• Research Institution: Gifu University
• Principal Investigator: TAKAGI Nobuyuki Gifu University Department of Electrical and Electronic Engineering Associate Professor, 工学部, 助教授 (80179415)
• Co-Investigator(Kenkyū-buntansha): WANG Daohong Gifu University Department of Electrical and Electronic Engineering Associate Professor, 工学部, 助教授 (20273120) ; WATANABE Teiji Gifu University Department of Electrical and Electronic Engineering Professor, 工学部, 教授 (20021595)
• Project Period (FY): 1998 – 2000
• Keywords: SPACE CHARGE / SOUND WAVE / REMOTE SENSING / LIGHTNING / THUNDERCLOUD / LIGHTNING ROD / POWER TRANSMISSION LINE

Research Abstract

We developed the new system which measures the space charge density. The space charge is made to vibrate by sound wave, and then the space charge density is estimated from the electric field change associated with the vibration. Scince the space charge distribution can be measured in real time, applications in the various fields is anticipated with this system. For example, this system will make clear the relation between the space charge which occurs from the lightning rod and the circumference of the power transmission steel tower and the progressing feature of lightning stroke, and it becomes possible that a new lightning striking theory is built. And, this system enables to predict the occurrence of lightning if it knows the charge distribution in the thundercloud.
First, a theoretical prediction was done to ascertain the validity of this measurement principle. It was found out that space charge density to about 8000m high can be measured with the resolution of 1nC/m^3 when the frequency and the transmitting output of the sound wave is 1kHz and 900w respectively and the electric field meter has a sensitivity of 1 μ v/m on the ground.
The indoor experiment was done to confirm this result. A sound wave was put on the space charge occurred between the needle-to-plane electrodes applied to a direct current high voltage, and then an electric field change was measured simultaneously. We could detect the space charge density of about a few μ C/m^3.
Furthermore, the observations under winter thunderstorm were done at Mihama in Fukui. We got some results that the space charge densities which occurred at the tip of the tree under a thundercloud were about several 10nC/m^3, and the charge density decreases with increasing altitude. It becomes possible to detect the charge density in the thundercloud if the electric field antenna has a higher detection sensitivity.