Analysis of the Field Circuit Model for the Suspension Potential of Conductors in Single‐Circuit Outage of Double‐Circuit DC Transmission Lines on the Same Tower

ABSTRACT In the de‐icing process of double‐circuit direct current (DC) transmission lines on the same tower, an operational condition exists in which one circuit is de‐energised and utilised as part of the de‐icing current path, specifically designed for grounding line de‐icing purposes. Accurate calculation of the floating potential of the out‐of‐service line is crucial for the design of de‐icing devices. This study employs the upstream finite element method combined with a potential prediction correction approach to determine the floating potential of de‐energised conductors. A field‐circuit model is proposed for calculating conductor floating potentials under single‐circuit outage conditions in double‐circuit DC transmission lines. The charge dissipation process through grounding resistors with varying values is also analysed. In a ± 500 kV case study, the relative errors between the circuit model and electric field model calculations for the positive and negative conductor floating potentials are merely 3.66% and 0.89%, respectively, verifying the validity of the circuit model. The equivalent resistance of ion flow fields reaches magnitudes of 10 6 Ω, significantly exceeding the intrinsic resistance of the conductors. When using voltage‐limiting resistors, conductor voltages decrease significantly with a 0.5‐MΩ resistor, and the calculated floating potentials become 8.702 kV and −5.849 kV, reflecting reductions of 84.8% and 88.4%, respectively. This research demonstrates that the proposed method provides an effective solution for floating potential calculation during single‐circuit outages in double‐circuit DC lines. The analysis of charge dissipation through voltage‐limiting resistors offers technical support for designing DC de‐icing devices.