Measurement method of charge densities at ground level under high-voltage direct current conductor

Ions generated by corona discharge of high-voltage direct current (HVDC) transmission lines exist in the space between conductors and the ground. Electric field strength, ion current density, and space charge density are significant electromagnetic environment parameters of HVDC transmission lines. To measure the charge densities at ground level under the HVDC power lines, an aspirator-type charge meter is designed and utilised. The charge meter is calibrated in the ionised field generated by parallel metal mesh and plate. Charge densities on the ground under the unipolar HVDC conductor are measured by the calibrated devices in the laboratory. Experimental results show that reasonable agreement between measured data by the devices and the ones by field mills and ion current plates could be obtained, which establishes a foundation to research the charge characteristics of ions near the ground.