Study On Lightning Overvoltage Protection Of Wind Turbines

Wind power is a kind of clean and renewable energy, development and utilization of wind power resource is an effective way to adjust the energy structure and promote sustainable energy development. China is rich in wind energy resources which has a great potential in development and utilization. Nowadays the total installed capacity of wind turbines in China ranks first in the world. With the development of wind power generation technology, the wind turbines are vulnerable to lightning accidents because of the height increases ceaselessly. The blade of wind turbines is apt to be stroke by lightning. When the wind turbines struck by lightning, the lightning current injects in blade and flows through its root. Then lightning current along the bearing and cabin into tower. Finally the lightning current injects into earth device and flows to the soil. In the process of lightning, overvoltage may appear on the three-phase cable and power electronic equipment by the coupling effect of electromagnetic field when the lightning current flows through the wind tower, the normal operation of wind turbines will be affected by these transient overvoltage as well. When the lightning current flow through earth, the earth potential will arise and equipment is likely to be damaged. Wind farm is consist by many wind turbines, all the parallel unit may be damaged when one of them stroke by lightning. Therefore, this paper aims to calculate and analyze the transient overvoltage in wind turbine, to discuss the various factors impact on the overvoltage and provide a reference on lightning protection design for wind turbine operation safety.The study builds a comprehensive wind turbine electrical model including blade model, cabin model, tower model, power cable model, transformer model, earthing device model and arrestor model. The electrical model convert wind turbine into an electric network. Overvoltage of each node in the network can be obtained by solving transient response of circuit. This paper focuses on the calculation of the electrical parameters of the wind turbine tower model and advantages and disadvantages between the existing models. There is designing a reduced-resize model of the tower of wind turbine for simulating the process of lightning struck in tower. Comparing the experimental results, the paper shows the accuracy of calculation between different models and verifies the correctness of the models. Various ground resistances are simulated with consideration to whether the tower and cable are individual or interconnected ground systems, whether to install arrester to observe transient phenomena in wind tower, cable and transform. Lightning transient overvoltage calculation can provide references on the selection of arrester, and help judging the rationality of design, so as to ensure the safety of the wind turbine operation, and achieve optimization design of cost saving.