Measurement method of ionic mobilities in direct current corona discharge in air

Ionic mobilities are characteristic parameters for describing the motion of charges in electric field and also basic parameters for the calculation of ionized field and ion current density of ultra high voltage direct current (UHVDC) transmission lines. This paper presents a measurement method of ionic mobilities in air. The analytical solution of ion mobility was derived from the equations of the ionized field and the ion current density. A circular parallel plate apparatus was applied to measure the ionic mobilities. Experimental results show that in direct current corona discharge of room temperature, the measured result of negative ion mobility was 2.23 to 2.51 ×10 −4 m 2 ·V −1 s −1 , and the average value was 2.39 ×10 −4 m 2 -V −1 ·s −1 ; the measurement of positive ion mobility was 1.54 to 1.93 × 10 −4 m 2· V −1· s −1 , with the average of 1.71 × 10 −4 m 2· V −1· s −1 .