Reasearch On The Key Technologies Of High-efficiency Operation Of Transmisson Lines Based On Dynamic Line Rating

With continuous construction and improvement of the power grid, thermal rating of overhead transmission lines, especially the overload capacity on N-1 operation mode has been the bottleneck of power grid. By improving the existing line capacity, equipment efficiency will increase and shortage of power supply will be eased.In this paper, domestic and international line rating standards including calculation models, boundary conditions and emergency ratings are compared. Static and transient heat balance models are built to calculate conductor current capacity. Main factors effecting max capacity are discussed. Rating methods on different operation modes including normal operation, special operation and emergency operation are proposed. According to local environmental climate in Grangdong Province, overhead transmission line overload capacity is analyzed and maximum current capacity is calculated on three different operation modes. A new rating method for wind farm outgoing transmission line based on combined consideration of wind turbine power characteristic and transmission line permissive carrying current characteristics is proposed. By dynamically matching the power curve of wind turbine and transmission line, the proposal of transmission line capacity improvement for operation and design is raised. Besides, economic benefit of transmission line capacity improvement is analyzed, and a risk assessment method based on conductor temperature is proposed.At last, A DLR monitoring system based on line catenary angle is disigned. Conductor temperature can be calculated using catenary angle and wind deflection angle. Based on Conductor Temperature Model(CTM), dynamic line max capacity can be calculated using conductor temperature, environment temperature, solar radiation and load capacity. The system hardware design is introduced and field experiment has proved its feasibility and reliability.