Ice accretions on high–voltage conductors and insulators and related phenomena

Abstract

This paper proposes to survey a good part of the research work accomplished to date on the atmospheric icing of conductors and insulators in the presence of high voltage, with emphasis laid on the studies carried out at the University of Québec in Chicoutimi. The review covers laboratory testing and mathematical modelling.The role of several electrical parameters, such as electric eld strength and polarity, corona discharge, water droplet charge and ionic wind velocity, on the structure and amount of ice accretion on high-voltage conductors, is discussed.Concerning the icing of insulators, the initiation of electrical discharge on the ice surface, the formation of local arcs along the air gaps and their development to a ®ashover arc along the insulators are discussed. Basic experiments on the role of several major parameters relating to ice accretion, insulator characteristics and voltage type and polarity, on the maximum withstand voltage of short insulators, are also discussed. Finally, several measures for improving the withstand voltage of insulators are brie®y recalled.

Modeling of AC arc inside wet snow =

“…The snow cover compacts rapidly as wind speed grows ( Table 2.2); temperature has little effect on snow cover compaction: at -2 °C the density of freshly fallen snow is 0.1-0.11 g/cm 3 , while at -10 °C density is 0.07-0.08 g/cm 3 . …”

“…Different authors based their calculations on different values for K and b, but these were generally set at 800 and 0.5 respectively, for polluted insulators [21], and 1118 and 0.53 respectively, for iced insulators [3]. It should be noted that this relationship was obtained using a combination of experimental results and analytical evaluation.…”

“…These constants may vary in accordance with the arc medium material and ambient conditions. A survey of the literature shows that the values of A and n, as measured or utilized by different investigators, vary over a wide range for different types of arc (see Table 2.3) [3,21,23,38,40,41,50,51,52,53]. These values depend not only on the arc medium but also on the electrolyte used to form the resistive layer.…”

“…where R is the density in g/cm 3 Although initiated by wind action, this time-densification of snow is also influenced by condensation, melting and other processes. Table 2.1 lists the densities of snow cover subjected to different levels of wind action [28].…”

“…La comparaison des résultats obtenus par le modèle mathématique avec ceux obtenue expérimentalement montre une très bonne concordance. Variation of dc conductivity by using of regression method of experimental data under heating process and 8 = 0.35 g/cm 3 Variation of dc conductivity by using of regression method of experimental data under heating process and ô = 0.51 g/cm 3 Variation of dc conductivity by using of regression method of experimental data under cooling process and 5 = 0.24 g/cm 3 Variation of dc conductivity by using of regression method of experimental data under cooling process and 8 = 0.35 g/cm 3 Variation of dc conductivity by using of regression method of experimental data under cooling process and 5 = 0.51 g/cm 3 Effect of K on the snow conductivity under heating process for snow sample of ô = 0.51 g/cm 3 , a = 146 uS/cm, K, = 0.14 ''C'and K 2 snowfall is between 70 and 300 inches [1][2][3]. In cold climates, the accumulation of glaze ice or wet snow on the outdoor insulators of power networks may considerably affect their electric performance, as well as cause structural damage.…”