Transient Electric Field Evolution in a 220 kV Cable Joint Under Switching Overvoltage Considering Measured Dielectric Dispersion

Abstract

Switching energization imposes wideband transient voltages on cable joints, whereas conventional simulations often use frequency-independent properties for semiconductive field-control components. This study develops a measurement-informed time-domain workflow for a 220 kV cable joint. A 13.976 km route containing 31 joints was evaluated at 20 closing angles, yielding a maximum positive overvoltage of 493.65 kV at 90°. Full-spectrum analysis placed 99.67% of the Hann-windowed record energy at or below 20 kHz, supporting dielectric measurements over 10–20 kHz. At 25 °C, the relative permittivity, polarization-loss tangent, and DC conductivity of semiconductive silicone rubber were measured. One- to six-pole Debye models were compared, and a five-pole representation was selected using the minimum Bayesian information criterion, with a combined weighted relative root-mean-square error of 8.17%. The causal model was implemented in a two-dimensional time-dependent electric-currents model for the stress-control cones and the inner and outer semiconductive shielding layers. A whole-domain search located the global maximum, 12.82 kV/mm at 6.90 ms, at the inner shielding-tube termination; the stress-cone-adjacent insulation reached 5.67 kV/mm at 8.80 ms. The results identify the inner shielding-tube termination as the dominant field-concentration region and establish a reproducible link between measured dielectric dispersion and transient-field analysis.