Calculation and experimental validation of impedance of buried single-core bonding leads

The development of digital twins for high‑voltage (HV) and extra‑high‑voltage (EHV) cable systems requires accurate electromagnetic modelling, particularly for predicting overvoltages and electrical stresses arising during transient events. A key parameter in these simulations is the impedance of bonding leads, whose evaluation becomes non-trivial when single‑core cables are buried and arranged in irregular loop geometries. This paper investigates the frequency‑dependent input impedance of buried single‑core bonding leads through a combined analytical, numerical, and experimental approach. Two loop configurations—a circular loop and a rectangular loop, each 20 m in total length—were modelled using analytical inductance formulae, Finite Element Method (FEM), and Method of Moments (MoM). Field measurements of input impedance were performed with a Vector Network Analyzer (10 kHz to 10 MHz). Results show that simplified analytical models and magnetostatic FEM accurately describe the impedance up to approximately 500 kHz, while MoM simulations exhibit very good agreement with measurements across the entire frequency range up to 10 MHz. These findings identify the frequency ranges in which different modelling approaches remain valid and provide practical guidance for selecting appropriate models in transient analyses of HV and