Effects of electric field distribution and water drop ejection on flashover of icicles in plane-to-plane gaps

Abstract

Ice morphology was established from field failure observations on electrical insulators, considering partial and full bridging conditions. Small scale laboratory simulations showed an important effect of droplet ejection on the probability of flashover. During the experiments, factors including applied water conductivity, icicle length, combinations of air gap and icicle length and duration of melting period were investigated using typical in-service stress levels. According to the experimental results, applied water conductivity and icicle length affected the residual ice layer resistance. Flashover voltage decreased by 33% as the conductivity increased from 150 S/cm to 750 μS/cm and reduced by 10% as icicle length declined from 6 to 4 cm for constant 2-cm air gap. Fully bridged icicles required extra energy for ice melting, leading to higher flashover voltage compared to partially bridged icicles of the same morphology. A single 3-cm air gap had 14% higher flashover voltage than a pair of 1.5 cm air gaps.

Dynamic interactive characteristics between icicle growth and corona discharge on HVDC outdoor insulators during icing accretion

“…The field strength at the maximum E ic point was 41.2 kV/ m, which exceeded the air breakdown field strength at this temperature and produced discharge activity to inhibit icicle growth. During the discharge phase of icicle growth, the majority of the corona discharge is located between the icicle tip and the droplet [18]. Therefore, the time of corona appearance was used as the duration of corona discharge in the energised state.…”

“…Especially, when the insulator was seriously ice‐covered, corona discharge became the primary factor inhibiting its growth. The corona discharge at the tip of the icicle could be equated to a needle‐plate electrode discharge [18]. Moreau et al.…”

“…Especially, when the insulator was seriously ice-covered, corona discharge became the primary factor inhibiting its growth. The corona discharge at the tip of the icicle could be equated to a needle-plate electrode discharge [18]. Moreau et al conducted an experimental study on the corona discharge of needle-plate electrodes and revealed the physical mechanism and flow characteristics of the corona discharge process [19].…”

Ion Migration in the Process of Water Freezing under Alternating Electric Field and Its Impact on Insulator Flashover

“…Combing the References [8,28], when local arc discharge appears, some air gaps are short connected, resulting in body resistance decreasing and higher current. Based on the principle of Joule's law, heating effect will be produced, which may affect the temperature of ice surface and slow down the icing rate; (2) According to the simulation and experimental measuring in References [7,17,29], the icicle tips make the electric field deform because of the large curvature of the icicles. The electric field strength around the icicle tips increases so that point corona discharge may occur and its heat effect may melt ice.…”

Ice flashover performance and its characterization parameter of composite insulator with booster sheds

“…Gap length d and residue ice layer R(x) were both important factors to flashover [21]. On the one side, the gap length d affected the electrical field strength especially at the icicle tip to determine the arc initiation.…”