Study On Large Capacity Power Transmission Method And Influencing Factors Of Transmission Capacity

At present,uhv power cables?overhead lines and GIL are widely used for the transmission of high-capacity power.Power cables are mainly laid underground with mature technology and large transmission capacity,but maintenance is difficult,the technology is relatively complex and the transmission capacity is limited by the thickness of insulation layer;Overhead line is one of the ultrahigh pressure long-distance transmission means of domestic at present mainly adopts,has a large capacity of transmission,the transmission distance is long,simple process etc,but overhead corridor will take up a lot of space resources,make urban power grid construction space more nervous,and produced the corona loss and the additional loss of overhead lines also nots allow to ignore.GIL is a power transmission method based on gas-insulated combined electrical appliances(GIS),which is characterized by safety and reliability,large transmission capacity and environmental friendliness.The electromagnetic wave transmitted by metal waveguide is mainly used in communication radar and other aspects.As a communication means,waveguide transmission performance is stable with minimal loss.In fact,the power capacity transmitted by waveguide can reach the level of megawatt(MW),as a large capacity power transmission method,its transmission capacity is considerable.In this paper,the factors affecting the transmission capacity of uhv power cables and overhead lines are analyzed and calculated,and then the laying environment is adjusted to determine the transmission limit.According to two different power transmission methods,the method to determine the transmission limit is different.For power cables,it is necessary to analyze the source of loss,which is mainly the loss(eddy current loss and circulation loss)that can reach its transmission limit by setting its laying conditions,so as to determine its transmission limit;For the ultrahigh voltage overhead line,the structure is relatively simple.The corona loss and its influence factors such as radio interference and audible noise caused by corona loss are analyzed,so as to determine its transmission limit.Then For the research on the transmission limit of metal waveguide,the transmission characteristic equation should be derived according to Helmholtz equation,and the distribution characteristics of electric field,magnetic field and surface current should be simulated to calculate the loss coefficient,analyze the loss influencing factors and determine the transmission capacity.Finally,the feasibility of metal waveguide as a high-capacity power transmission method is analyzed,and the advantages and disadvantages are analyzed by comparing ultra-high voltage power cable and overhead line.The calculation results show that the load current,sheath grounding mode,phase,arrangement mode,arrangement mode and number of loops have great influence on the circulation loss and eddy current loss of the ultra-high voltage power cable;For the uhv overhead line,the corona loss can be accurately calculated by using the simulated charge method,The corona loss in sunny and dry climate is obviously less than that in wet climate,and has obvious turning point;The radio interference and audible noise caused by corona loss are greatly affected by the type of overhead pylon,phase sequence,splitting number and the distribution of insulator string;For metal waveguide,the distribution of electric field,magnetic field and surface current obtained by simulation calculation basically meets its transmission characteristic equation.Specific wavelength electromagnetic wave is transmitted within cut-off wavelength,size more than(109.22×54.16)mm~2 and the transmission efficiency can reach more than 96%.