Research On New Technology Of Online Ice Mmelting In Distribution Network

The icing of overhead lines can cause problems such as falling towers,disconnections,and vibration,which will not only cause large-scale power outages,but even threaten the personal safety of residents near the lines.Existing ice melting methods at home and abroad are currently mainly based on AC short-circuit ice melting technology and DC short-circuit ice melting technology.Although good results have been achieved,the current engineering applications of ice melting technology mainly target the main network and are used in ice melting.During this period,power outages are still required,and there is no engineering precedent for online ice melting.At present,distribution network mainly uses artificial bamboo poles to de-icing.Not only the road icing during the winter icing period often prevents the staff from reaching the site smoothly,but also there is a great personal safety hazard.Therefore,it is urgent to design an online ice melting device to solve the power outage during ice melting.Based on this,this paper studies the online ice melting principle and device design one by one.This article first studies the mathematical model of ice coating on overhead lines and introduces the principle of the new online ice melting technology.The grounding transformer and the adjustable reactor are combined into a zero-sequence reactor.The grounding transformer is used to provide the neutral point and the adjustable reactance is used to adjust the melting current value.In the case of non-stop line,by adjusting the inductance value of the adjustable reactor connected to the neutral point of the ice-coated line,the end of the line is used as a zero-sequence circuit,and the zero-sequence current component is superimposed to make the coating.The ice melting current of the ice section line exceeds its specified minimum melting current to achieve the ice melting effect,and the voltage and current on the load side will not be affected during the ice melting operation,thereby realizing online ice melting.The equivalent circuit model is established based on the transformer nameplate,wire type,length and other data obtained from the field survey in the mountainous area of northern Guangdong,and the main parameters such as the iron core and winding turns of the grounding transformer are preliminarily designed based on the ice melting current.Maxwell3 D combine with external circuits is used as the simulation Tools,built the designed grounding transformer model,verify its zero-sequence impedance and melting data by connecting to the online ice melting external circuit.Thereby it can determinine the gear distribution of the adjustable reactor according to the melting current,and provide guidance for its specific parameter design.Based on the online ice melting principle and the above-mentioned parameterized simulation results,a grounding transformer with a capacity of 2500 k VA and a seven-turn adjustable reactor with adjustable impedance are manufactured.The zero-sequence impedance of the designed grounding transformer and the impedance of the adjustable reactor are tested.The test shows that the key parameters of the two meet the design requirements.The designed grounding transformer,adjustable reactor,and related equipment such as the knife switch required for ice melting are carried out on the pilot line for the network ice melting test.The results of the observation and analysis of the voltage,current and other data during the ice melting process show that the device has the function of melting ice without power failure.Not only can it effectively solve the problem of partial ice coating in the distribution network,but also further reduces the economic loss caused by power outage during ice melting.