Research On Key Technologies Of Medium Frequency Ice-Melting On Transmission Lines

Frozen snow or freezing rain will cause electrical or mechanical failures on transmission lines,leading to accidents such as flashover,wire breakage,and pole(tower)failure.Further expansion of the accident may even cause the power system to crack,which will cause incalculable losses to society production and the national economy.Therefore,efficient and economical de-icing technology for transmission line has always been one of the important topics of the power system.Based on the high-frequency de-icing technology,this paper proposes an intermediate frequency selection method which based on sacrificing certain uniformity of the thermal power,and has studied and analyzed the key point of the intermediate frequency ice-melting technology.Based on the principle of the intermediate frequency ice melting technology,this paper proposes an intermediate frequency ice melting system which be comprised of ice-melting power source,transmission lines,intermediate frequency notch filter and wideband wave traps.Equivalent uniform transmission line circuit model also has been gived.This paper takes the transmission line of 30km long,220kV voltage level and whose conductor type is LGJ-300/40 as the research object,and builds a simulation model through the Python programming language,analyzed the voltage,current,power factor,thermal power along the line and the interaction of ice-melting frequency between thermal power.an intermediate frequency ice-melting method based on sacrificing certain uniformity of the thermal power proposed;and the effects of ice dielectric loss tangent,ice thickness and line length on intermediate frequency ice-melting have been analyzed.The simulation results show that according to the intermediate frequency selection method proposed in this paper can greatly reduce the frequency of the ice-melting power source,thereby reducing the cost of the ice-melting device and the harm of high frequency harmonics on the line.Finally,based on the high frequency and high power requirements of the intermediate frequency ice-melting excitation source,a cascade converter based on the single-stage double frequency carrier phase shift(CPS-SPWM)modulation method,double closed-loop control method of voltage effective value and inductor current has been design as the ice-melting excitation source for the transmission line.And the simulation model of the medium frequency ice-melting excitation source was built through MTALAB/Simulink to verify the feasibility of the device.