Study on corona current measurement with probe suspended in the vertical static electric field

At the time of sounding of static electric field, measuring devices can not be rested on the ground, which are suspended in the air. To study the relationship between corona current and electric field in the air, current detection unit with probe suspended in the vertical electric field has been tested in the laboratory. The experimental results show that probes suspended in a vertical electric field can still generate corona discharge and the waveform of corona impulse current is double exponential wave and the peak value of corona impulse current can reach milliampere level. Furthermore, the distance between current probes and the upper electrode plate makes a difference in onset voltage of corona discharge. The value of onset voltage decreases with decreasing the distance. By calibrating shorter probes, it was established that the waveform of corona current suspended in a vertical electric field is the same as that of a singlepointed probe resting on and perpendicular to a flat plane ground electrode. However, to the longer probes, the closer distance between current detection unit and the upper electrode plate is, the larger the waveform of corona current will change. With the limit of test space, the upper electrode plate has great influences on the waveform of corona impulse current.