AC Icing Flashover Characteristics and Maximum Withstand Voltage Gradient of 220 kV Polluted Composite Insulators

In light ice-covered areas, icing of composite insulators with different pollution degrees has a great influence on their insulation performance. In this article, the solid layer pollution method was adopted to realize different degrees of pre-pollution for six kinds of FXBW-220/160 composite insulators. Then, with the reference ice thickness of 10 mm as the standard, icing and ac flashover tests were carried out on insulators under the multifunctional artificial climate chamber. The ice weight and minimum flashover voltage (
${U}_{\textit {mf}}{)}$
of insulators under different pollution degrees were obtained, and the path of the flashover arc was recorded. In addition, the maximum withstand voltage gradient equation of insulators under different discharge probabilities was established. The results show that when insulators are energized icing, the ice weight decreases with the increase of salt deposit density (SDD), which in turn causes the
${U}_{\textit {mf}}$
to decrease. The relationship between the
${U}_{\textit {mf}}$
and SDD is a negative power function regardless of whether the insulators are energized icing or not. The differences in arc path, residual ice layer resistance, and the ratio of air gap arc to ice surface arc are the main reasons for affecting the flashover voltage. In addition, the maximum withstand voltage gradient
${E}_{\alpha }$
at discharge probability
$\alpha $
% of 10%, 5%, and 0.13% when the insulators are energized icing decreases with the increase of SDD, and
${E}_{{10}} > {E}_{{5}} > {E}_{{0}.{13}}$
. Increasing the spacing and diameter of the largest shed of composite insulators and reasonably cooperating with medium/small sheds can help to significantly improve their flashover performance. The results of this article can provide data support for the selection and optimal design of insulators for 220 kV transmission lines in light ice-covered areas.