A Generating Method for UHF Maps of Epoxy Surface Discharge Based on the Multiscale Simulation System

The ultrahigh-frequency (UHF) maps are often used as an important basis to evaluate the insulation status. However, the current research is mostly driven by pure data, making it difficult to judge the actual status of defects through UHF maps. Multiscale simulation technologies are adopted to simulate the UHF maps of surface defects from physical mechanisms. The microprocess of surface discharge is simulated using the plasma model, and the electromagnetic (EM) signal amplitudes are calculated based on the finite-difference time-domain (FDTD) method, using the current in the microsimulation as an excitation. Then, the segmented equivalent parameters of the circuit model are solved using the microsimulation results. The phases of the UHF pulses are simulated in the circuit model, and the UHF maps are obtained combined with the signal amplitude. It is found that the undischarged segment resistance determines the voltage recovery time, which is a key parameter that affects the UHF maps. The random settings of the simulation are important factors making the simulation results more reasonable. The relationship between the microprocess of surface discharge and the UHF maps is established theoretically, providing a basis for the accurate assessment of the insulation defect status of power equipment.