抄録
The neutral points of the transformers in substations are grounded and connected by the power lines. By measuring the current which flows through the neutral points, the telluric current between substations could be measured. We have monitored this current in order to detect anomalies before and after earthquakes since 1996. Although the neutral current is theoretically zero, it is generated by various factors, such as temperature and geomagnetic changes, and artificial noises. A very large change of the neutral current, unexplainable by these factors, was observed before and after the M3.0 earthquake which occurred under the power lines on September 22, 1999. However, so far, we have never observed any anomalies for other earthquakes.
