Simulation and Evaluation of Lightning Overvoltage in Wind Farms Considering Grounding Effects by EMTP Package

This paper is treated with major risks applied by lightning strikes to wind farms. The risks illustrated in this research include overvoltage caused by direct and indirect effects of lightning strikes on any components of wind farm. As demands for electrical energy throughout our world is increased more and more nowadays, wind power plants are extended in every possible locations correspondingly with high isochronic level. So it’s why lightning strikes have come to be important to study. Also as wind farms grow rapidly throughout the world, the grounding system and ground impedance of wind turbine towers under transients have got more important. As a matter of fact, an exact model to testify dynamic properties of grounding system should represent nonlinear effects of soil ionization and be frequency dependent. Some new researches conducted in this issue, all are based circuit theory which does not allow for accurate analysis of aforementioned behaviors. This paper has come to express a new approach to model any grounding system only by few RLC branches in wide frequency range. A new model and some simple formula that is recommended in this work, represent all effects of transient phenomena of lightning strikes and all analysis have got more easier than other approach. By using this method, there’s no difference between those grounding system buried in cylindrical soils or conical one, multi-layer oil or not, humid soil or not and so on, they all are available for transient analysis. Then the outputs of antenna theory and recommended method are compared and finally the RLC branches are implemented in EMTP and get analyzed. So it’s possible to evaluate power systems under lightning strikes with presence of wind farms. Although previous researchers have analyzed some harmful overvoltages created by lightning strikes, but only few of them have reached reasonable outputs. To evaluate some appropriate results, a technical package of simulation must hire first. In this paper some new models of wind farm components such as wind turbine with an interconnecting transformer, different configurations of wind farms, real grounding system with soil ionization based on traveling waves are implemented in Electro-Magnetic Transient Program (EMTP) and some practical case studies are illustrated, too. Due to the complexity of the abovementioned effects, from Electromagnetics point of view, some perfect analysis of overvoltage in wind farms with different configurations is required. Finally the simulations are conducted by RV version of EMTP and evaluated.