The Research On Increasing Transmission Capacity Of 220kv Overhead Transmission Lines

With the continuous and rapid increase of the national economy, the power consumption demand is gradually increasing, power shortage has become a bottleneck restricting the development of economy, especially in the developed district. Therefore, it is of significance in the economy to enhance the current capacity of transmission lines.In this paper we discuss some key measures on increasing the capacity of transmission lines, including enhancing the transmission voltage, using the lines with larger section area or heat-resistant lines. In addition, we analyze the advantages and disadvantages of them, and propose the measure of improving the allowing temperature of transmission lines; according to the solution of increasing capacity of environmental temperature changing real-time dynamic. Based on this solution, we design the manual on increasing capacity of 220kV transmission lines so that it could provide Hubei Province Power Corporation.the guidance with operation of increasing capacity.Studying the methods of calculating current carrying capacity, they are the Morgan formula and the revised Morgan formula. We analyze the advantages and disadvantages of them, and point out their respective application conditions. The Morgan formula is applied to the case of non-zero wind speed. On the contrary, the revised Morgan formula is applied to the case of zero wind speed. In this paper we propose a new method on calculating current carrying capacity, called ANSYS simulation method. Based on principle of finite element and temperature field, this method could be applied to the case of any wind speed.There are two methods on calculating sag of overhead transmission lines, which are the Catenary formula and the Parabola formula. The former one is based on the unit load uniformly distributed along the length of transmission lines, the later one is based on the unit load uniformly distributed along the straight line of two suspension points of transmission lines. In above two methods, how to calculate the level of stress of transmission lines is the core of calculating sag. Moreover, Condition formula and Strain-summation method are the methods to calculate the level of stress.We develop a graphical user interface software which could meet the demand of increasing capacity of 220kV transmission lines based on Visual C++ 6.0. With the help of this user interface, we can easily calculate current and sag values which provide a theoretical basis to increase the capacity of dynamic line rating of 220kV transmission lines.