Transient surface charging of tri‐post insulator in SF6‐filled direct current gas‐insulated transmission lines: Effects of electric conductivity, gas pressure, and voltage amplitude

Abstract

Abstract The transient surface charging characteristics of a tri‐post insulator in a ± 500 kV direct current gas‐insulated transmission lines (DC‐GIL) filled with sulfur hexafluoride (SF)6 gas are investigated. An improved method is introduced to calculate the surface charge distribution with satisfactory efficiency and accuracy, which involves applying weak form partial differential equation (PDE), simplifying ion transport equation and geometric model. The influence of volume and surface conductivity, gas pressure, voltage amplitude on the transient surface charging is discussed with the method. The charge density shows non‐synchronously increasing pace in different regions. The transient surface charging shows non‐monotonic tendency in some regions. With increasing volume conductivity, the transient surface charging is accelerated obviously. With increasing surface conductivity, the charge density near the enclosure increases. With varying electric conductivity, the dominant conduction changes. Thus, the volume and surface conductivity should be concerned in the design of DC‐GIL tri‐post insulators. With increasing gas pressure, slight acceleration in surface charging is observed. The acceleration in charging with high voltage amplitude cannot be employed to improve the efficiency in measurement. The result indicates that the simulation of transient surface charging is beneficial in evaluating the insulating characteristics of tri‐post insulators with flexibility and reasonability.