Study On The Influence Of AC Electric Field Strength On Conductor Icing Performance

The icing on transmission lines is one of the most serious threatens to the safety ofpower system. Researchers in various countries have carried out large numbers ofinvestigations on conductor icing performance through artificial icing tests. However,most of these tests do not consider the effects of transmission line operation electricfield on ice amount and ice density, which apparently reduce the application value.Besides, the mechanism of the influence of AC electric field on icing performance is notclear. Thus, the study on the conductor energized icing characteristics and the ACelectric field influence mechanism is valuable both academically and practically.This study conducted plenty of energized icing tests in the multifunctional artificialclimate chamber. Single smooth conductor, single LGJ-185,2×LGJ-120, and3×LGJ-120are chosen as the specimen. The influence of AC electric field strength onicing performance is attained. The electric field distribution on ice surface during itsgrowth is calculated using FEM software, COMSOL Multiphysics. The mechanism ofthe effects of AC electric field strength on conductor icing tests is analyzed, whichcontains the force from dielectrophoresis and the Coulomb force created by the chargingof droplet under AC corona. The following conclusions are found:①Conductor icing performance as ice amount and ice density are significantlyeffected by AC electric field strength. The amount values of glaze and rime onconductors both increase first and then decrease with the rise of AC electric fieldstrength. When the field strength is10kV/cm, the weight of glaze and rime are greaterthan that of0kV/cm by35%、30%respectively. When the field strength is20kV/cm,the weight of glaze and rime are less than that of0kV/cm by30%、40%respectively.The density of rime also increases at first then decreases when filed strength lifted.While, the change of glaze density with varying filed strength is not obvious.②The energized icing performance is influenced by the liquid water content.When the values of liquid water content is24g/m~3、36g/m~3, the ice amount differencebetween the energized and non-energized icing test is smaller than that under8g/m3ofliquid water content.③The types and bundle pattern do not have considerate influence on glaze icingperformance. However, on different sub-conductor, the change of glaze morphology andamount with AC electric field strength are not the same. ④The electric field of the droplet surface and the space field distribution duringthe ice growth procedure is calculated. The corona discharge quality is measured. Whendroplet reaches the conductor surface, the filed strength on its surface reaches thecorona onset value. When conductor surface field strength reaches10kV/cm, thecorona discharge could exist stably on ice surface, which is consitant with themeasurement results. When applied voltage is further increased, the corona dischargequality and power increased rapidly.⑤The effect from dielectrophoresis and the Coulomb force created by the dropletcharging on the movement of droplet are calculated. It is found that thedielectrophoresis tend to pull the droplet to the conductor, which will increase the iceamount and density if the corona is weak. Under the AC corona, the charging of thedroplet and its Coulomb force are both alternative values. The Coulomb force is mainlydecided by the space ion density and the field strength. When corona activity is strong,the values of electric field strength and space charge density are large. The Coulombforce from the droplet charging will apparently obstruct the droplets from approachingthe conductor. This obstruction effect may be the reason of the decline of the ice amountand rime density when field strength is intense.