Design Of Transmission Scheme For Two 220kV Parallel Cables In Phase

With the further improvement of urban land development level and power load density in Shenzhen,industrial development and municipal facilities are increasingly tight.Overhead lines in cities are increasingly being replaced by underground high-voltage cables.On the one hand,the rapid development of urbanization in China is increasing the load density of cities.On the other hand,the skin effect of the cable current limits the maximum allowable cross-section of existing cables,which limits the transport capacity.If a single-phase single cable is used to transform the ground,it is necessary to limit the transmission capacity of the original line,which will inevitably lead to a weak local power grid,which will cause great safety hazards to the power system.Therefore,while ensuring that the transmission capacity of the line meets the requirements,and carrying out the transformation of the cable,the urban land is released and the land utilization rate is improved.Based on the specific examples,this paper studies the parallel transmission of two cables in the same phase.First of all,this paper analyzes the structure,advantages and disadvantages of conventional high-voltage lines,including conventional high-voltage overhead transmission lines and single-phase single power cable lines.The technical and economic comparison analysis of the two transmission schemes was carried out.Secondly,based on the analysis of the status quo of Shenzhen power system,especially the current situation of power load demand and power system transmission capacity requirements,the demand analysis is given for the transformation requirements of a 220 kV overhead line that must be put into the ground.Then,aiming at the requirements of a 220 kV overhead line into the ground,taking a 220 kV high-voltage overhead line migration and reconstruction project as an example,a retrofit scheme based on conventional cable transmission was designed,and the cable type and cable attachment selection scheme were given.And it analyzes the shortcomings of this kind of scheme in terms of economic technicality(the skin effect makes its utilization rate extremely low and not meet the line transportation capacity requirement).After,for the transformation requirements of a 220 kV overhead line into the ground,the transmission scheme of two parallel cables in phase is designed.The cable type selection scheme and the choice of the aluminum sheath wiring method are given.The ATP-EMTP modeling is used to analyze the unbalanced degree of the in-phase cable.Based on the results of the analysis,the optimal layout scheme of two parallel cables is given.Finally,the implementation and operation of the 220 kV overhead line into the ground is briefly described.The collected operational data results show that the transmission scheme of the two parallel cables in phase with the innovative design is not only feasible,but also has good running effect.The contradiction between the rapid development of urbanization in China and the scarcity of urban land resources and the requirements of urban beautification make the entry of overhead transmission lines an inevitable trend in the future development of urban power grids.The research results in this paper show that with the increasing load density of large cities,the innovative transmission scheme of two parallel cables in phase is an effective solution to solve underground power transmission.