Study On Ice-melting Method By Channel Load Current Of Bundled Conductor Transmission Line

Icing disaster taken place on transmission line is one of the most serious problemscompared with other natural disaster. In recent years, because of the global climatewarming, kinds of extreme weather were taken place frequently. When continuouscold-air were outbreak, the formation of icing on the outdoor transmission line isinevitable. The icing disaster will cause serious losses, such as overloading, conductorgalloping, tower collapsing, and insulator string flashover accident. It will not onlydamage the grid structure, but also threat to the security of the gird, even failures of thegrid. When the icing disasters were happened, they are always accompanied withinclement weather. Therefore, traffic blocked by the snow and communication was alsodisrupted. So that it is very difficult to repair the damaged power grid, thus resulting inextended power outage, causing serious losses to industrial and agricultural production,affecting the daily life of the people and to the national economy caused huge losses.There are more than30anti-icing and de-icing methods reported in home and abroad.But the de-icing method which used the Joule heating of the current is the fastest andmost effective de-icing method. However, many methods of these kinds are carried outwhen the transmission line is outage. The outage will bring economic losses, reducingthe safety factor of the gird, but also causing great inconvenience to peoples’ living.With the increase requirement of safe reliability of the gird and developing of smart grid,in order to ensure the safe and reliable operation of the power system, the developmentof an uninterruptible, real-time anti-icing and de-icing method is of great significance.Because of the bundled conductors are widely used in HV and EHV transmission,the paper propose a novel, uninterruptible, and real-time de-icing methods, i.e.icing-melting method by channel load current of bundled conductor into sub-conductorscircularly(IMCLC), based on the special structure of bundled conductors. Thefundamental principle and control scheme of this method were represented in detail.Based on the six-bundled conductor, this paper calculated electrical inductance atdifferent condition and the voltage difference between sub-conductors with and withoutcurrent. The calculated results reveal that this voltage difference corresponding to theload current, ice-melting model and the distance far away from the short point. In orderto reduce the voltage on the insulation spacer and the switch, the ice-melting distance ofconductor should be reduced. Through the analysis of thermal balance of icing conductor, this paper establishedthe critical ice-melting model and current ice-melting model, and their impact factorswere also studied. At the same time, the COMSOL Multiphysics was used to simulatethis model. The simplified calculation formula of ice-melting time was proposed bysimplifying this current ice-melting model. According to the control demand of IMCLCand the simplified ice-melting time, the grouping method of the sun-conductor wasdesigned.Many ice-melting experiments were carried out in the artificial climate chamberand the natural icing test station. The test results reveal that the calculated results ofcritical ice-melting current and simulated results were in a line with test results, thegrouping method of sub-conductor was also be examine to be correct. The fieldice-melting test show that the ice layer on the conductor can be removed effectively byusing the IMCLC method, the ice-melting time is dispersed, and the jumping caused bythe ice shedding will generate huge displacement of the conductor which affected by theamount of ice layer on the conductor. Therefore, the ice-melting work should be carriedout when the ice thickness reach a threshold to limit the jumping magnitude.Based on the test results in the artificial climate chamber and field test at thenatural icing station, this paper proposed a Fuzzy Expert control method of CMCLCwhich based on multiple parameters. The input and output parameter, membershipfunction, and fuzzy rules were also designed.