Abstract
Considering the ice shedding phenomena on ice-covered outdoor insulators, this paper conducted the artificial experiments by using a five-unit suspension ceramic insulator string covered with wet-grown ice to investigate the effects of ice shedding on the icing discharge characteristics. According to IEEE Standard 1783/2009, the minimum flashover voltage (VMF), propagation of discharges to flashover and related leakage current (LC) were measured. It was found that VMF after ice shedding can be increased by about 17% as compared with that before ice shedding. The initiation and formation of discharge arcs across ice-free regions caused by ice shedding become difficult, showing an unstable propagating path, indeterminate arc shape and longer arc column. Although VMF under ice shedding conditions is higher than that without ice shedding, the fundamental component, and harmonics show lower amplitudes for the latter case. The ratios of harmonics to the fundamental are well in accordance with discharge characteristics during the flashover for which the ratios show a relatively stable varying tendency in the absence of ice shedding, but show changeable and indeterminate variation under ice shedding conditions. The obtained results are helpful to understand the icing state and its influence on surface discharges for preventing the icing flashovers.
Highlights
Icing flashover of outdoor insulators has already been considered as a major factor affecting the stable and safe operation of the power grid in cold climate areas [1,2,3,4,5]
As spectrum analysis of leakage current (LC) on ice-covered insulators shows that the low-frequency components can be the major LC content to have a significant influence on the distortion of LC waveforms associated with discharge phenomena [32], this paper analyzes the fundamental component, and the 3rd, 5th and 7th harmonics of LC to reflect the discharge characteristics with and without ice shedding during the flashover process
The ratios of harmonics to the fundamental component are well in accordance with discharge behaviors and characteristics observed during the flashover process, which can be used as a tool for understanding and monitoring the impact of the icing state on the ice-covered outdoor insulators
Summary
Icing flashover of outdoor insulators has already been considered as a major factor affecting the stable and safe operation of the power grid in cold climate areas [1,2,3,4,5]. It has been found that water film, air gaps, contamination level, atmospheric pressure and ambient temperature are significant factors that affect the icing flashover. In these studies, ice shedding has been mentioned to happen during the ice accretion or ice flashover process [13,14,15,16,17,18,19,20,21,22]. Based on time-frequency analysis of leakage current, the propagation characteristics of surface discharges to flashover were acquired for discussing the influence of ice shedding on discharge characteristics of ice-covered outdoor insulators
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