Wind Turbine Generator Towers

Wind turbine generator towers are frequently struck by lightning. In order to optimize lightning protection means of wind turbine generator systems, it is important to know the mechanism of lightning overvoltages generated in the systems. 

3D view of a 3/100-scale model of a wind turbine generator tower, blades, nacelle, current lead wire, and a voltage reference wire. (Reprinted from Yamamoto, K., A study of overvoltages caused by lightning strokes to a wind turbine generation system, PhD thesis, Doshisha University, Kyoto, Japan, 2007. With permission.) 

Numerical solution of initial value problems involving Maxwell s equations in isotropic media. IEEE Trans. Antennas Propagation 14(3) 302-307. 

Courant, R., K. Friedrichs, and H. Lewy. 1965. On the partial difference equations of mathematical physics. IBM Journal ll(2) 215-234. 

Yokoyama. 2002. Thin wire representation in finite difference time domain surge simulation. IEEE Trans. Power Deliv. 17(3) 840-847. 

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The potential of wind energy to produce large-scale electric power is focused on the development of wind-turbine tower technology from current sizes of 1 to 3 MWe to turbines that will produce 3 to 5 MWe. The number of 5 MW wind turbines that could produce 9 PWh/a by 2050, estimated for an average electricity generating ratio of 3 GWh per installed MW (American Wind Association, 2007), would be about 600 000. These would be located in areas of sufficient mean annual wind speeds for commercial operation and as an auxiliary resource in other locations. 

The basic principles of wind energy have been used for centuries. Windmills existed in the 7th century in Persia. An older image closely associated with wind power is Don Quixote and the wooden towers with cloth-covered sails turning in the wind. Today s wind turbines use a giant propeller on a tall metal pole. As it rotates, the propeller drives a generator to supply nearby users or send power to the grid. 

Each wind turbine in a wind farm generates power independently and sends its power to a transformer located at the base of the tower. Submarine cable interconnects each turbine with up to a dozen other turbines to create an array. Specialized cable installation vessels and underwater cable installation equipment connect the turbines and embed the electrical cable up to 2 meters below the seabed. Each array is then connected to the central substation or an ESP. The power... 

Small wind generators. People living in isolated hill farms may find benefit from a wind turbine, but not everyone will live or work in a location which has sufficient wind resources. There are issues of local wind turbulence from buildings and trees which will impede the efficient operation of a wind turbine. Lots of people will object to the erection of a tall tower with a wind turbine at the top. Planning permission will be required. Financial payback for a 100 kW installation will be in the region of 15 to 20 years. 

While many different design solutions have been considered in the early stages, for commercial use the modem wind industry has now stabilized on horizontal axis wind turbines (HAWT). A typical example is shown in Fig. 1 a land-based tower with a nacelle mounted on the top, containing the generator, a gearbox, and the rotor. Typically, three-bladed upwind rotors are used. 

Commercial wind turbines are composed of several parts on the top of a tower that can be in excess of 100 m tall, three giant blades of 30 meters or more in length rotate a horizontal shaft, turning a generator that converts mechanical energy into roughly 3 MW electricity. Inside the tower there is a cable that carries electricity to transmission lines and a computer system that controls the rotation and direction of the blades. 

A smaii wind generator shouid not be fixed to a building because the wind blowing onto the building causes turbulence which reduces the efficiency of generation. Similarly, nearby buildings or trees will reduce efficiency. A turbine fitted to a mast or tower is by far the best method of installation and the higher the turbine the better it will perform. 

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