Experiment Study On Ice Shedding From Transmission Lines

Accreted ice shedding from transmission lines can easily lead to flashover between conductors and the damage of fittings,and unbalanced tensile force caused by nonuniform ice shedding can also give rise to tower fall and conductor breaking accidents,which are great threats to the security operation of electrical power system and peoples' daily life.Transmission line hazards caused by ice shedding occur occasionally since a lack of knowledge of the ice shedding mechanism,thus it's necessary to study the dynamic effects of the conductor after ice shedding.In this paper,the models of ice shedding from single-span,double-span and triple-span with a total span length 50 m are designed in which accreted ice is simulated by lumped loads hanging on the conductor and the ice shedding sequence and speed are controlled by time relay.The tensile forces on both ends and the midpoint displacement of the conductor are measured under different cases,and simulations by using ANSYS are done to verify the results.The main research content and conclusions are as follows:(1)When ice sheds from single-span conductors,the maximum jump height at the conductor midpoint increases with the increase of ice thickness.The maximum dynamic tension on both the conductor ends has minor difference with the maximum static tension,that is,ice shedding has no amplification effect on the tension on conductor ends.(2)As a whole,the maximum jump height of the conductor midpoint increases with the increase of ice shedding ratio;the largest jump height occurs when ice sheds from the middle part of the conductor under the same shedding ratio;the maximum dynamic tension on both the conductor ends is slightly larger than the maximum static tension only under relatively low shedding ratios.No mechanical damage is done to transmission lines under different shedding rations and locations.(3)The jump height at the midpoint of the single-span conductor has its maximum value when ice sheds from both end to the middle simultaneously,and minimum value when ice sheds from middle to both ends.The jump height reaches its smallest value when ice sheds from both end to the middle at a high speed.(4)For multi-span conductors,the minimum dynamic response occurs when all the accreted ice on the conductor sheds simultaneously,which is also the safest shedding mode.When all the accreted ice on one of the spans sheds and the other remain icing,the jump height of the conductor reaches its maximum value,which is most likely to cause the flashover between conductors,(5)The dynamic response of double and triple span conductors after ice shedding under different shedding sequences differs considerably.Ice shedding from the middle to the ends and ice shedding from both the ends to the middle are relatively safe shedding sequences for double-span conductor,but dangerous shedding sequences for triple-span conductor.