An experimental study of large ion density under the Shiobara HVDC test line

The characteristics of large ions under the Shiobara HVDC (high-voltage direct current) test line found in experiments on their voltage characteristics and lateral profiles described. Applied voltage has less influence on large-ion density than on small-ion density. It is shown that large-ion density increases gradually downwind, reaches a maximum value at 67 m from the line center, and then decreases gradually; but it is 2 to 3 times larger than its BGL (background level) even at a point 200 m from the line. The empirical equations representing the characteristics of large-ion density attenuation are derived. The maximum large-ion density becomes nearly equal to 4×BGL and accounts for about 40% of the density of aerosol less than 1 μm in diameter