Simplified Formulae Method for Estimating Wind Turbine Generators Ground Resistance

Kondylis, Georgios P.; Damianaki, Katerina D.; Androvitsaneas, Vasilios P.; Gonos, Ioannis F.

doi:10.1109/tpwrd.2018.2839061

Cited by 5 publications

(5 citation statements)

References 19 publications

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“…The study [11] aimed to derive simple formulas for predicting the grounding resistance value of wind farms installed in terrains that can be designed with a two-layer grounding system. Different combinations of grounding resistance values for the top and bottom layer of two-layer grounding systems and the depth of the top layer are carefully determined to cover a wide variety of irregularities in the earth.…”

Section: Related Workmentioning

confidence: 99%

An Artificial Neural Network Model Based on Experimental Measurements for Estimating the Grounding Resistance

Kayabaşı

Yildiz

Balci

2022

Advances in Artificial Intelligence Research

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In grounding systems established in rocky and sandy lands where contact resistance with metal electrodes is high, contact resistance is generally the most critical parameter that changes the total grounding resistance value. Therefore, the nonlinear variation of the earth contact resistance according to the soil type cannot be taken into account in determining the grounding resistance with the traditional mathematical formulas given theoretically. This reduces the accuracy of grounding resistance determination. In this study, experimental measurements were made according to soil types and a data set was created. Then, to estimate the total grounding resistance of complex grounding systems, a classification was made using the multi-layer sensor (MLP) type ANN algorithm and the successful results were reported. Thus, according to the data set prepared based on experimental measurements, the proposed general classification algorithm approach can be applied to any grounding system. It presents a different technique from the previous literature as a pre-feasibility study for estimating the grounding resistance, especially before the grounding system installation, which is an early stage of the design process.

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Section: Related Workmentioning

confidence: 99%

An Artificial Neural Network Model Based on Experimental Measurements for Estimating the Grounding Resistance

Kayabaşı

Yildiz

Balci

2022

Advances in Artificial Intelligence Research

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“…where ρ a (1) , ρ a(2) ,... ρ a(n) are the measured apparent soil resistivity values at different electrode spacings and n is the total number of measurements.…”

Section: A Interpretation Of Soil Resistivity Measurementsmentioning

confidence: 99%

“…A common theme in the existing literature is the assumption of uniform soil resistivity, which is unrealistic in practice as measured soil resistivity can vary both horizontally and vertically [1]. Weather conditions [15], especially humidity levels [16], [17], can also cause soil resistivity to change throughout the year.…”

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confidence: 99%

Frequency Domain Analysis of a Wind Turbine Generator Earthing System for Lightning Discharge Currents

et al. 2019

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A safe and cost-effective design of a wind turbine generator (WTG) grounding system requires accurate modeling of local soil resistivity, particularly when wind turbines are spatially distributed across a wide area with different soil types and features. In this paper, three locations at an Australian wind farm were modeled based on measured data. Four soil resistivity models were considered: uniform, multilayer horizontal, vertical, and exponential variation with depth. Full-wave electromagnetic simulations were performed at different lightning discharge current frequencies to find the expected ground potential rise and WTG earthing impedance in the event of a lightning strike. Furthermore, the effect of frequency dependent soil parameters on the WTG earthing was analyzed, along with the effect of foundation rebar on the grounding impedance. Our results show that an accurate soil resistivity model is critical in the design of a WTG earthing system. INDEX TERMS Wind turbine generator, lightning protection, soil resistivity, grounding system, grounding impedance, ground potential rise. The recent proliferation of wind farms as a source of clean energy production calls for an effective design of the grounding system to ensure their safe and reliable operation over their entire life span [1]. Wind turbine generators (WTGs) are extremely vulnerable to lightning strikes due to their size, shape, and location, which is usually in mountainous sites with very high soil resistivity [2], [3]. Moreover, it is worth noting that, according to recent studies [4], elevated terrain can further increase the value of grounding resistance. When lightning strikes a WTG, electrical and electronic components embedded in the WTG are prone to failure and damage as a result of the ground potential rise (GPR) caused by electrical surges [2]. Consequently, WTGs should be provided with a low impedance grounding system to ensure safe and reliable operation. Recommendations for effective grounding and lightning protection of WTGs and wind power systems are provided by IEC 61400-24 [5]. The associate editor coordinating the review of this manuscript and approving it for publication was Huiqing Wen.

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“…The location of an earthing system has a critical effect on the WTG earthing resistance due to the resistivity of the soil [135]. A method was proposed to assess the location of the earthing system to get a low resistance path in [136].…”

Section: Grounding System Of Wind Turbine Generatorsmentioning

confidence: 99%

“…A similarity in the existing literature is the assumption of uniform soil resistivity, which is unrealistic in practice as measured soil resistivity can vary both horizontally and vertically [135]. Weather conditions [164], especially humidity levels [165], [166], can also cause a change in the soil resistivity throughout the year.…”

Section: Introductionmentioning

confidence: 99%

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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Simplified Formulae Method for Estimating Wind Turbine Generators Ground Resistance

Cited by 5 publications

References 19 publications

An Artificial Neural Network Model Based on Experimental Measurements for Estimating the Grounding Resistance

An Artificial Neural Network Model Based on Experimental Measurements for Estimating the Grounding Resistance

Frequency Domain Analysis of a Wind Turbine Generator Earthing System for Lightning Discharge Currents

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

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