Discussion on the Deutsch Assumption in the Calculation of Ion-Flow Field Under HVDC Bipolar Transmission Lines

Deutsch assumption greatly simplified the calculation of the ion-flow field under HVDC transmission lines. However, its applicability remains to be proved for the +/- 800-kV HVDC projects in contemplation in China. The ground-level electric field and ion current density are calculated with an upwind differential-based 2-D method and a Deutsch assumption based on the 1-D method to analyze the errors of the ion-flow field caused by Deutsch assumption. A dc bipolar line laboratory model is established to verify the methods. The parameters indicating the corona discharge intensity and the field distortion degree are introduced to evaluate the errors caused by Deutsch assumption. Then, the applicability of the Deutsch assumption is discussed on the +/- 800-kV HVDC test line established in China. The relationship of the corona discharge intensity, the field distortion degree, and the errors caused by Deutsch assumption are analyzed. Using the corona discharge intensity to evaluate the errors caused by Deutsch assumption seems to be reasonable.