Measurement of Ion Flow Fields Generated by Positive DC Corona Discharge based on E-FISH

To accurately measure the ion flow field of atmospheric DC corona discharges is important for optimizing the electromagnetic environment of HVDC overhead transmission lines. Since the distribution of ion flow field may be distorted by the inserting of electric field sensor, existing methods are inadequate for the measurement of electric field generated by corona discharges. In this paper, a non-invasive method based on the electric field induced second harmonic effect (E-FISH) is developed to measure the ion flow field produced by positive dc corona discharges and compare with numerical simulations. Firstly, an electric field measurement system is established according to the principle of E-FISH. Secondly, a calibration procedure for the measurement of non-uniform electric field is proposed by adopting FEM simulation under corona free condition. Finally, the electric field generated by positive DC corona discharge in a rod-plate air gap is measured quantitatively and compared with the results obtained by numerical simulations. The experimental results are in good agreement with the numerical simulation results of corona ion flow field in the rod-plate air gap, which verifies the applicability and accuracy of this method. By comparing experimental results with computational ones, it is demonstrated that the E-FISH method has the potential to be applied in the ion flow field measurement of HVDC transmission lines.