필드밀과 루프안테나를 이용한 뇌경보시스템 개발에 관한 연구

Abstract

This thesis deals with the development of a lightning warning system which can predict the possibility of lightning strike and the position of lightning discharge. Lightning warming system plays an important role in protecting human life and other facilities from lightning strikes. The system uses the electric field intensity at the ground as a parameter to warn the possibility of lightning strike. A planar-shutter type electric field mill(EFM) with a rotating-vanes is studied to measure the electric field intensity.

Calibration of the developed EFM was performed in a vertically symmetrical arrangement which consists of two-parallel round plates to form homogeneous electrical fields. The sensitivity of the EFM was adjusted to 0.15[V/kV/m], and this covers the ranges from 200[V/m] to 20[kV/m]. After the calibration, the field mill was installed on the roof of a building to measure the changes of electric field intensity caused by thunderclouds.

The position of lightning discharges in useful information to know the movement and the activity of thunderclouds. Electric field component produced by lightning discharge is detected by the configuration of a whip antenna and a narrow-band resonance amplifier with 300 [kHz] center frequency. Magnetic field waveform in detected by a crossed-loop coil and an integral amplifier. Frequency bandwidth of the circuit ranges form 5 [kHz] to 1.2[MHz].

The polarity of lightning discharges is discriminated by electric field component. After fixing the polarity, we can calculate the direction and distance of lightning discharge by the peak and the zero-cross time of the detected magnetic field waveform.

From the field test on the ground, it was confirmed that the system has the good performance necessary for the measurement of electric field and the position of lightning discharges.