Influence of Humidity and Salinity on the Discharge Characteristics of a Short Rod-Plane Gap Under Negative DC Voltage

In this article, the effects of air humidity and salinity on the discharge characteristics of a short rod-plane gap under negative dc voltage are investigated experimentally. The discharge of the rod-plane gap was recorded using a measuring resistance, photomultiplier tube, and ultraviolet imager. The experimental results show that corona discharge of rod electrode can be observed in the rod-plane gap when the relative humidity is lower than 70%, and furthermore, partial discharge of water molecules in the air can also be observed in the rod-plane gap when the relative humidity is higher than 70%. The partial discharge inception voltage (PDIV) decreases with the increase of air humidity and salinity, and the corona discharge inception voltage (CDIV) increases slightly with the increase of humidity. The average discharge current increases with the increase of applied voltage and humidity. The repetition rate of the optical pulse and the Trichel pulse increases with the increase of applied voltage. The discharge repetition rate of water molecules in the air can be estimated from the repetition rate difference between the optical pulse and the Trichel pulse. The amplitude of the Trichel pulse in clean air is higher than that in the salty air, while the repetition rate of the Trichel pulse in clean air is lower than that in the salty air, which is due to the charging of NaCl particles during discharge.