Positive dc corona inception on dielectric-coated stranded conductors in air

In this study, the positive inception voltage of bare and dielectric-coated stranded conductors has been researched by numerical calculations and corona cage experiments. The charge simulation method is used to calculate the potential gradient distribution of the coated stranded conductors. Then, based on the positive inception criterion, the photoionisation inception model considering the effective radiation wavelength is proposed and employed to evaluate the inception voltage of the coated stranded conductors. In addition, in the laboratory, the inception voltage test platform is build up to measure the inception voltage. The results reveal that with the increase of the coating layer thickness, the inception voltage increases. For the same thickness, the inception voltage reduces slightly with the increase of relative permittivity. The calculated values are in good agreement with experimental results of the laboratory corona cage. The conclusion lays a foundation for studying the effect of the coating layer on the corona performance.