Charge Simulation Based Electric Field Analysis of Composite Insulators for HVDC Lines

This paper illustrates a charge simulation method based computation of electric potential and field of composite insulators for HVDC lines. The electric field is calculated under both dry and wet conditions and compared to AC line insulators. The results indicate that for the same nominal voltage, the electric field for DC lines is higher than for ac lines, thereby necessitating larger field control devices (corona and grading rings) for DC insulators. A process for optimizing corona and grading ring dimensions is described and applied for 500 kV HVDC lines.