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 106 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.