Transient behavior of wind towers grounding systems under lightning strikes

Abstract

Wind turbines, because of their height and localization, are frequently subject to direct lightning strikes. Thus, the investigation on the performance of their grounding system is of paramount interest for the prediction of the potential threats either for people working in (or animals passing through) the wind farm area and for the power and control units installed in close proximity of the turbine towers. In this paper,we perform a comprensive study of the transient behavior of the earthing systems of wind turbines. The analysis is conducted in the frequency domain and an hybrid approach, based on circuit theory and Method of Moments, is adopted to fully account for resistive, inductive and capacitive couplings between elements of the ground system. The actual transient behavior is obtained by means of an Inverse Fourier Transform. The results, computed considering a typical wind turbine grounding system configuration, provide more insight on the nature of the early-time transient response of grounding systems and allow to draw up useful design guidelines.

Transient lightning response to grounding grids buried in horizontal multilayered earth model considering time domain quasi-static complex image method and soil ionization effect

“…With the above considerations, according to other studies (Papalexopoulos and Meliopoulos, 1987; Li et al , 2012, 2014a, 2020; Araneo1 and Celozzi, 2016; Cidras et al , 2000; Joao and Carlos, 2008; Yutthagowith et al , 2011), the formula of the frequency domain hybrid methods based on PI basis function can be given directly as equations (1) and (2): where true[Vptrue¯true] was a N p × 1 vector for scalar electrical potentials (SEP) of nodes on discrete conductor segments of grounding grids in frequency domain, true[trueF¯true] was a N p × 1 vector for a lightning current in frequency domain; true[trueZb¯true¯true] was a N b × N b diagonal matrix, who owns internal impedance of the discrete conductors in frequency domain, true[trueMb¯true¯true] was a N b × N b matrix, who owns zero diagonal elements and gives mutual induction interactions between arbitrary two pieces of discrete conductors in frequency domain; true[trueZs¯true¯true] was a N b × N b matrix, which gives mutual conduction interaction between arbitrary two pieces of discrete conductors in frequency domain. true[trueA¯true¯true]…”

“…The average SEP true[Uatrue¯true(ttrue)true] and branch voltage true[Ubtrue¯true(ttrue)true], leakage current true[Istrue¯true(ttrue)true] and branch current true[Ibtrue¯true(ttrue)true] can also be calculated. In addition, SEP, electric field strength E and magnetic field strength B can be obtained anywhere (Li et al , 2012, 2014a, 2020; Araneo1 and Celozzi, 2016).…”

“…In recent years, combined with appropriate fast Fourier transform methods, many different theories based on frequency domain have been proposed. For example, the electric circuit methods (Liew and Darveniza, 1974; Wang et al , 2005; Geri et al , 1992; Mousa, 1994; Geri, 1999), the transmission line methods (TLM) (Liu et al , 2001; Liu et al , 2005; Jardines et al , 2014; Jamali et al , 2019), the electromagnetic field methods (Grcev and Dawalibi, 1990; Grcev, 1996; Grcev and Heimbach, 1997; Sheshyekani et al , 2011) and the hybrid methods (Papalexopoulos and Meliopoulos, 1987; Li et al , 2012, 2014a, 2020; Araneo1 and Celozzi, 2016; Cidras et al , 2000; Joao and Carlos, 2008; Yutthagowith et al , 2011). Meanwhile, the numerical methods based on difference methods in time domain have also been developed, for example, the finite difference time domain (FDTD) methods (Baba et al , 2005; Ala et al , 2008; Li et al , 2011), the electric circuit methods (Ramamoorty et al ,1989; Mokhtari et al , 2015), the hybrid methods (Yutthagowith et al , 2013; Chen and Du, 2019; Li et al , 2014a; Li and Rao, 2019) and the TLM (Lorentzou et al , 2003; Andre and Mattos, 2005).…”