| The icing on the transmission line threatens the safe operation of the grid system,for instance,serious icing may lead to accidents including collapse of the tower and rupture of conductor,and ice-shedding could cause deicing jump of conductors resulting in burning of conductors and tripping.Study of overhead transmission lines on icing and dynamic response of ice-shedding is of great significance to ensure the safety and reliability of the transmission system.In this paper,the de-icing response of a icing 220 kV single circuit transmission tower-line system was simulated basing on the finite element software ABAQUS.The variable density method was used to simulate the inertial effect of ice without shedding,and the shedding of ice was realized by changing the inertial acceleration.The influence of line types,locations of de-icing spans,locations of de-icing sites,de-icing rates,and de-icing orders of conductors and ground wires on dynamic effects of tower-line system were analyzed.The safe solutions of deicing were given for single ground wire and conductor,and the safe solutions of simultaneous deicing and step-by-step deicing were also given for double bundled conductors.The results show,when the span length is 300 meters,that terminal de-icing once method with initial de-icing rate less than 20% should be selected for single conductor,and with initial de-icing rate less than 30% for single ground wire,and for double bundled conductors,that the middle de-icing method with initial de-icing rate less than 10%and terminal de-icing method with initial de-icing rate less than 30% should be selected,and when the step-by-step de-icing method is used in the same span,temporary spacers are needed for the de-iced conductors,and the de-icing rate is needed to reduce stepwise,and the de-icing rate is needed to reduce when conductors have different heights.If power-off deicing wereallowed,the stress of towers,ground wires and conductors could meet the strength requirement,and 100% complete de-icing could be adopted,regardless of the collision of the conductors.For de-icing once method of single conductor and ground wire,symmetric de-icing should be selected to prevent adjacent span having an excessive tension difference.The deicing experiment was planed to carry out according to the program described above.The method of suspending concentrated load was used to simulate icing,and releasing load simulate deicing.Considering the experimental site with deicing strategy during power outage,the experimental scheme was developed at the beginning,in which 12 masses were simultaneously released in two conditions that the weights were 3.5 kg and 5 kg respectively.Meanwhile,the finite element model of the 2-tower and 3-span tower-line system was established in the ABAQUS software in accordance with the actual line.The wires were simulated respectively by using the three-demensional beam element and truss element whose material was set to be ‘No Compression’.The dynamic response of the tower-line system under different conditions of deicing were analyzed under the given experimental scheme.The results show that,with the increase of the suspended weight,the stress of towers,conductors and insulators,of the tower-line system increases correspondingly,yet not exceeds the yield strength of the material and the tower-line system is safe under the concentrated load;also,the deicing jump of the conductor has characteristics of low frequency and large amplitude,and the jump height of the conductor is maximum at the moment lumped mass released,and then the amplitude gradually decreases to the equilibrium position due to the presence of damping.The jump height of the conductor of adjacent span is lower than the experimental conductor;the jump height of the conductor and the tension difference between adjacent conductors increase with the suspended weight.The dynamic stress during the conductor jump is less than the initial stress under static load.The stress of the two insulators is large after loading and when the load is released,the stress is smaller than that under the static load.The stress of transmission towers varies little after the load is released,and the stress value is small,far below the yield strength of structural components,all of which are still in the elastic state.Combined with the experimental scheme,the simulated deicing experiment was carried out outdoor in actual tower-line system.By changing the ice thickness,the galloping rules of the conductor under different deicing conditions were studied.Time history curves of displacement and acceleration at the point of the experimental conductor were obtained by using the pull-line displacement sensor and the acceleration sensor respectively.Comparative analysis of experimental results and simulation results is consistent,which verifies the correctness of the model and the numerical simulation method used. |
