Electrical discharge occurring from a space charge cloud formed with charged particles

To investigate the discharge phenomenon occurring in a space charge cloud, a charged cloud generator using solid particles was constructed. Charged powder particles with diameters from 50 to 250 μm are ejected with a speed of 40 m/s from the outlet of the corona charger to form a charged cylindrical cloud in a cubic space with a side length of 5.4 m. The time variation of the electric field strength around the charged cloud was measured with four field mills simultaneously. Brush-like discharge intermittently occurs and a number of streamers widely extend from the grounded electrode toward the cloud. The maximum length of the streamer channel reached 0.7 m and the magnitude of the discharge current exceeded 4 A.