Wind farm earthing

Hatziargvriou, N.; Lorentzou, M.I.; Jenkins, Nick

doi:10.1049/ic:19971016

Cited by 10 publications

(4 citation statements)

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“…Research using simulations of the transient and steady-state grounding a Correspondence to: Kazuo Yamamoto. E-mail: kyamamoto@mem.iee.or.jp * Department of Electrical Engineering, Kobe City College of Technology, 8-3 Gakuenhigashi-machi, Nishi-ku, Kobe, Hyogo 651-2194, Japan * * Techno Center, Shoden Co. 365, Sanoucho, Inage-ku, Chiba, Chiba 263-0002, Japan * * * Faculty of Engineering, Shonan Institute of Technology, 1-1-25, Tsujidonishikaigan, Fujisawa, Kanagawa 251-8511, Japan * * * * Electric Power Engineering Research Lab, CRIEPI, 2-6-1 Nagasaka, Yokosuka-shi, Kanagawa 240-0196, Japan characteristics of wind turbine foundations has already been presented [12][13][14][15][16][17][18][19][20][21][22]. However, studies using an actual wind turbine generator system to study transient grounding characteristics are very few in number [23].…”

Section: Introductionmentioning

confidence: 99%

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

Yamamoto

Yanagawa²,

Sekioka

et al. 2009

IEEJ Transactions Elec Engng

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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. 

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Section: Introductionmentioning

confidence: 99%

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

Yamamoto

Yanagawa²,

Sekioka

et al. 2009

IEEJ Transactions Elec Engng

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“…The resistance is the only component to be considered for designing a grounding system at the power frequencies. However, the grounding system behaviour is different for lightning discharge currents due to the high-frequency components [142]. At higher frequencies, the inductive component of the impedance is a dominant factor compared to the resistance.…”

Section: Grounding System Of Wind Turbine Generatorsmentioning

confidence: 99%

“…Cotton [140] presented a wind farm earthing system with a uniform soil resistivity of 500 Ωm, which is not a representative value in practice [156]. Hatziargvriou et al [142] also analysed a wind farm earthing system with a uniform soil resistivity value of 100 Ωm. Visacro et al [162] considered the reaction of grounding systems to lightning discharge currents by considering a uniform soil resistivity value.…”

Section: Introductionmentioning

confidence: 99%

“…WTG grounding systems commonly serve two purposes: power system fault protection and lightning protection [137]. However, grounding sys-tem behaviour is different for lightning discharge currents compared to fault currents due to the high-frequency components present in lightning discharge currents [142]. At higher frequencies the reactive component of the impedance is dominant compared to the low-frequency resistance.…”

Section: Introductionmentioning

confidence: 99%

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Design and Analysis of Earthing System for Wind Turbine Generators from Lightning Discharge Currents

Deshagoni¹

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<p>Currently, wind power production is undergoing rapid growth due to the escalating interest in green energy generation. As a result, generators are now choosing to locate wind turbine generators (WTGs) in areas where there is more lightning activity, and earthing problems can be exacerbated further by the soil resistivity being higher than where turbines are usually located. In addition, the desire to capture more energy from the wind has given way to larger WTGs, further increasing the probability of lightning strikes to the structure. This heightened regularity has emphasized the need for an effective grounding system, capable of dissipating the large currents discharged by the lightning into the lightning protection system. This “effective grounding system” must offer a low impedance by limiting the ground potential rise, which is critical due to the wider frequency content of the lightning discharge currents (ranging from DC to several MHz). The design of an effective grounding system for WTGs depends on the calculation of the minimum length of the earth electrodes, soil resistivity and its frequency-dependency, and the impact of WTG foundation. The calculation of the length of earth electrodes needs an accurate measurement of soil resistivity and modeling of the measured resistivity. Hence, this research considers the measured soil resistivity values of an Australian wind farm and presents an analysis of the soil stratification to identify the optimum soil models. The influence of the soil layers on the WTG grounding system is also investigated to install the earth electrodes. As the resistivity of the soil is frequency-dependent, an analysis is performed to evaluate the effect of the frequency-dependent soil parameters on the WTG grounding system at various frequencies of lightning discharge current. In addition, the impact of the rebar of the WTG foundation on the grounding system is evaluated as the rebar shares the lightning discharge currents. The effective length of the earth electrodes is frequency-dependent, and rebar determines the impedance of the grounding system at high-frequencies. The next step in the grounding design is the design of earth electrodes. The current dissipating capacity of the earth electrodes depends on soil resistivity, dimensions of the earth electrodes, and burial depth of the electrodes. However, the traditional practice of designing earth electrodes is based on the soil resistivity alone, considering the uniform soil resistivity model. The conventional method of designing earth electrodes based on the uniform soil resistivity is not practical due to non-homogeneous behavior of the soil resistivity. To enhance the WTG earthing system design, this research proposes a novel method to calculate the minimum length of an earth electrode for uniform and two-layer based soil models considering electrode dimensions and burial depth. The grounding impedance achieved when electrode lengths are calculated using the proposed method is compared to grounding impedance values computed using the conventional method. This comparison shows that the proposed method is an improvement on the current convention. In particular, the proposed method gives a grounding impedance value of less than 10 Ω at low frequencies for all soil resistivity values. This results in a reduction in the potential rise of up to 64% compared to the peak potential value in the conventional method. The benefits offered by the proposed method mean that it can be employed to calculate electrode lengths for the required resistance values based on soil resistivity, electrode dimensions, and burial depth. Such a design may serve as a starting point for an engineer wishing to design a WTG earthing system. Another challenge noted is the practice of assessing the effectiveness of the WTG grounding system. The conventional method is based on achieving a low-frequency resistance of 10 Ω according to the standard IEC 61400-24 and the performance of the grounding system at high frequencies is not considered. Hence, identification of the high-frequency components of the relevant lightning discharge currents is important to understand the performance of the grounding system. An analysis of the wind turbine earthing system for different lightning discharge current wave shapes is performed considering the lightning current waveforms and parameters mentioned in the IEC 61400-24 standard and evaluated the various frequency components and their influence on the WTG grounding system. It is identified that the impedance of the grounding system is minimum for the first short positive stroke current parameters for all the soil resistivity values compared to the first short negative and the subsequent short current wave shapes, although the peak current magnitude is highest for this wave shape. From the analysis of WTG grounding system based on various parameters, this research presents a procedure for assessing the effectiveness of WTG lightning protection system with a focus on the grounding system. It is identified that the effectiveness of the grounding system can be improved by proper design of earth electrodes, optimum soil stratification, and selecting low resistivity soil sites. Finally, various earth electrode configurations are evaluated to identify the better electrode configuration for WTG grounding system. This thesis provides an in-depth analysis of WTG grounding systems to protect WTGs from lightning strikes. The contributions of this research will help wind farm architects to design effective grounding systems leading to effective lightning protection systems. Finally, the contributions will help to increase the adoption of wind power, resulting in more renewable energy generation. The outcome of this research can be realized to reduce the downtime of WTGs by incorporating the effectiveness of lightning protection system component into the wind farm optimization process. Also, a generalized procedure for calculating the minimum length of earth electrodes for all the soil models can be developed in the future.</p>

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Transient Analysis of Grounding Systems

2018

Computational Method in Electromagnetic Compatibility

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Wind farm earthing

Cited by 10 publications

References 1 publication

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

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

Design and Analysis of Earthing System for Wind Turbine Generators from Lightning Discharge Currents

Transient Analysis of Grounding Systems

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