Numerical Analysis of Partial Discharge on Multi-Dielectric Insulator Forming Migration-Ohmic Model

Partial discharge characteristics were analyzed on a multi-dielectric insulator in air forming a migration-ohmic model by using fully coupled finite element method. In a HVDC or MVDC system, the electric stress is constantly applied to multi-dielectric insulators resulting in the movement of space or surface charge density. The concentration of surface charge density can cause the partial discharge problem which degrades the breakdown strength of the insulators. To consider an aging effect for dielectric insulators, the conductivity can be a good choice, but it is rarely reported to analyze this migration-ohmic model in discharge analysis. We, therefore, introduced the current continuity equation incorporating with the space charge continuity equations for electron, and positive and negative ions. To verify our numerical setup, we will compare the temporal surface charge decay on the surface of lossy dielectric insulator, obtained from an experiment through the surface charge decay (SPD) measurement with the Kelvin probe.