Transient Grounding Characteristics of an Actual Wind Turbine Generator System at a Low‐resistivity Site

Abstract

In order to exploit high wind conditions, wind turbine generator systems are often constructed in places where few tall structures exist; therefore, they are often struck by lightning. Much of the damage caused by lightning is from the resulting breakdown and malfunction of the electrical, communication, and control systems inside the wind turbine generator system; these breakdowns can be attributed to a rise in electric potential both within the system and in the surroundings due to lightning. Impulse tests were conducted on a wind turbine generator system at a disposal site where the conductivity of the ground was very low, like that found on the surface of the sea. The rise in ground potential of the system, and around its foundation, was measured. When a wind turbine generator system is constructed at a site where the grounding resistivity is very low, the potential rise at the wave front typically becomes larger than that of the steady state because of the inductivity of the grounding system. Therefore, it is very important that the transient characteristics of the grounding system are well understood. 

A Review of Current Issues in State-of-Art of Wind Farm Overvoltage Protection

“…The data needed for these models are sometimes difficult to obtain; the reason for this is that it often consists of several different components, each needed to be appropriately modeled for the lightning surge analysis [15,16,21,[36][37][38][39][40][41]. Moreover, wind farm component models are often frequency-dependent, non-linear or otherwise involve proprietary data belonging to the manufacturers.…”

“…Firstly, the EMTP software package-which is almost universally applied to the wind farm lightning-initiated transient analysis-has some limitations, which should be borne in mind. One important limitation has been pointed out by Ametani, for example, is concerned with the TEM mode of lightning surge propagation [41]. Namely, it is a well-known but often "forgotten" fact that the EMTP software package is based on the circuit theory approach-assuming the TEM mode of wave propagation-where the parameters of a circuit need to be provided for the simulation.…”

“…Namely, it is a well-known but often "forgotten" fact that the EMTP software package is based on the circuit theory approach-assuming the TEM mode of wave propagation-where the parameters of a circuit need to be provided for the simulation. However, there are some phenomena that include non-TEM mode of wave propagation, which would not be tackled by the circuit approach [41].…”

“…Hence, soil ionization features prominently in lightning surge analysis and subsequently derived models of the TW grounding systems should account for it. Due to the inherent difficulty in analysing grounding system behavior under lightning strikes, various authors have resorted to different approaches, whose complexity varies significantly, from basic ones to quite elaborate ones, e.g., [15,16,[41][42][43]. Table 1 provides a general comparison between different possible approaches in the transient grounding system analysis, with some of their merits and demerits [43].…”

Evaluating the High Frequency Behavior of the Modified Grounding Scheme in Wind Farms

“…As a result, the electrical potential is increased in both the grounding system and the soil, which makes the grounding system unreliable and reduces the wind tower generator system's reliability and safety [8][9][10]. Therefore, one of the effective ways to increase a wind tower's stability and reliability during lightning strikes is to analyze the transient behavior of wind turbine grounding systems [11,12].…”