Lightning Surge Analysis of a Wind Farm

Abstract

The rapid expansion of wind power generation has brought problems involving lightning strikes to the fore. Many such incidents have damaged not only the wind turbine that was actually struck but also other turbines that were not, a phenomenon that is yet to be fully explained. In this chapter, the author presents a case study using a wind farm model with multiple wind turbines connected to a power system. The aim is to clarify the influence of the earthing system on surge propagation from a wind turbine that has been struck to others which have not, during a winter lightning strike. When one of the wind turbines in a wind farm is struck by lightning, the phenomenon of surge invasion to the collection system is categorised as “back-flow surge”. It has been reported that this back-flow surge sometimes burns out surge protection devices (SPDs) or breaks low-voltage circuits even far from the point where the lightning struck. In practice, many such incidents that have occurred not only involved the wind turbine that was actually struck but also other affected wind turbines that had not been struck. This chapter will analyse incidents of burnout to SPDs resulting from winter lightning at wind farms using ARENE and PSCAD/EMTDC. Calculations were performed to clarify the mechanism of how the back-flow surge propagates to other turbines from the directly struck wind turbine. The calculations also clarified that burnout incidents could easily occur even in a turbine that had not been struck by the lightning. It also became evident that burnout incidents can be reduced when interconnecting earthing wires are installed between wind turbines.