Novel HVDC spacers by adaptively controlling surface charges – part ii: experiment

Charge accumulation on the surface of high voltage direct current (HVDC) spacers decreases their surface flashover voltage and affects the reliability of the insulation systems. In part I of this study, a novel HVDC spacer in which the surface charges can be adaptively controlled is proposed, and the aim of this paper is to experimentally verify the design. The experimental results of three kinds of model spacers, including a regular spacer, a spacer with a novel shape, and a spacer with charge adaptively controlled are provided. AC and DC surface flashover experiments and a polarity reversal test were performed. The effect of surface charges on triggering the surface flashover phenomenon are discussed. The results show that the surface flashover voltage increases both for the novel shaped spacer and the charge-adaptivelycontrolled spacer under application of AC bias, owing to a modification of the spacer shape that increases the creep distance. However, the surface breakdown voltage is the lowest for the novel shaped spacer under DC application and polarity reversal test. The charge adaptive control spacer displayed more advantages than the other samples under application of DC bias and in polarity reversal tests owing to its superior surface charge dissipation properties. It is hoped that this work could offer a new perspective for the design of a suitable spacer to avoid surface flashover when implementing HVDC energy transmission systems.