Frequency Domain Analysis of a Wind Turbine Generator Earthing System for Lightning Discharge Currents (original) (raw)
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Electric Power Systems Research, 2019
The impact of frequency-dependent soil electrical parameters on the lightning response of typical wind turbine grounding systems is investigated. It is shown that the frequency dependence of soil parameters is responsible for decreasing the ground potential rise and, thus, the impulse impedance and impulse coefficient of the grounding systems. This effect is more pronounced for high-resistivity soils and fast current pulses. It is also shown that, considering typical dimensions of actual wind turbine grounding systems and soils with resistivity higher than 300 Ωm, the impulse impedance seen by each single wind turbine is expected to be lower than the low-frequency grounding resistance.
2018 IEEE PES Asia-Pacific Power and Energy Engineering Conference (APPEEC), 2018
As a result of the growing supply and demand for wind power, wind turbine generators are increasingly being installed at sub-optimal sites that have high soil resistivity and high incidence of lightning strikes. This means that lightning protection systems for wind turbines are becoming a critical component of wind farm design. Not only do effective lightning protection systems ensure the safety of the physical wind turbine structure and human operators, they also protect the electrical and control systems installed inside wind turbine generators and safeguard the lives of human operators. This work presents a framework to assess the effectiveness of wind turbine lightning protection systems at the wind farm design phase. Performing the analysis at this early stage reduces lightning-induced downtime, which leads to increased energy yield. Our results show that the grounding system plays a critical role in the wind turbine lightning protection system. For this reason we also analyse various influential parameters of a grounding system design. We present results from full-wave electromagnetic simulations of the complete wind turbine grounding system, including the foundation.
Analysis of ground potential distribution under lightning current condition
2017
The grounding system of a lightning protection scheme is designed basically to avoid arcing and dangerous step potentials. The grounding impedance of the system varies depending on soil structure and frequency. This paper describes the effect of harmonic impedance (also called frequency dependence of soil) on potential distribution under lightning strike to a metal tower with single grounding path, for different soil types. The results show that the peak value of ground potential rise (GPR) and step voltage (SP) may reach extremely hazardous values even at distances in the order of 90 m from the tower footing, especially when soil resistivity is high. Hence, we emphasise that, in contrast to power grounding, when designing of grounding systems that are meant to handle transient or high frequency currents as well, the frequency dependent soil parameters should be considered to avoid hazardous situations, especially at locations with a high probability of lightning strikes such as met...
Frequency response of grounding system of wind turbine generators
This paper examines the frequency response of several grounding systems of wind turbine generators, as they are currently used in wind parks in Greece. Several cases were studied depending on the grounding system and the soil structure. For every given frequency of the fault current the following magnitude have been calculated: the complex grounding resistance, the step and the touch voltages on the ground surface. Also, the effect of the point from which the fault current is diffused in the grounding system of several connected wind turbine generators has been examined. Furthermore, cases for the grounding system, which was energized each time from a different wind turbine, have been separately studied. The effect of the soil structure on the response of a grounding system has been also investigated. Cases of uniform soil model and two-layer soil model with different specific resistivity values for the first and second soil layers, in combination with altering the thickness of the first layer, have been studied. Moreover, the frequency response of a grounding system in each of the above cases has been examined. The soil structure has been computed using soil resistivity measurements and specialized genetic algorithm software, which has been developed in our lab.
Transient response of grounding systems of wind turbines under lightning strikes
The paper focuses on the transient analysis of grounding systems of wind turbines. The analysis is carried out in the frequency domain and it uses a recently proposed hybrid approach based on circuit theory and Method of Moments, in order to fully account for resistive, inductive and capacitive couplings. The corresponding transient response is obtained by means of the Inverse Fourier Transform. A typical wind turbine grounding system arrangement based on ring electrodes is analyzed.
Novel Formulation to Determine the Potential on the Soil Surface Generated by a Lightning Surge
IEEE Transactions on Magnetics, 2016
This paper presents the development of an analytical formulation for estimating the potential on the soil surface, caused by electric current calculated on a grounding conductor. The formulation has great significance in its use in conjunction with one-dimensional numerical methods, which are not able to determine such potentials directly. The proposed study focuses on lightning surges taking into account the frequency dependence of the soil properties. First, the subject is introduced emphasizing important aspects related to the analysis and representation of grounding systems against lightning. Afterwards, the proposed analytical formulation is introduced with a focus on the computational implementation of the transmission line modeling method in one dimension (TLM-1D). Simulations were carried out considering a typical horizontal electrode used as grounding in the power electric system. The formulation was validated by comparing the results with the solution based on the Electromagnetic Model (CDEGS Software), which is considered the most stringent for the solution of full Maxwell equations due to their minimum approaches. The results demonstrate that the generalized formulation presents good accuracy, contributing to an improved representation of grounding systems based on numerical techniques in one dimension.
Evaluation of Transient Response of Different Earthing Configurations due to Lightning Impulses
International Journal of Recent Technology and Engineering (IJRTE), 2019
Earthing system is very important in order to protect the electrical equipment as well as the human’s safety against over voltages. The main function of the earthling system is to remove unwanted excessive electrical currents caused by unusual conditions such as fault and lightning or switching over voltages by providing a low resistance path to the earth. Researchers had studied the behaviour of the earthling system to improve its performance for the past few years. There are few factors that influence the performance of the earthling system such as soil resistivity and soil ionization which need to be focused in order to improve the earthling. Thus, this paper evaluates on the factors that affect the behaviour of the earthling system based on simulation works using MATLAB and Safe Grid Software. Some analytical calculations are used to obtain the soil resistivity and resistance as well as the touch and step voltages. The simulation results were validated based on comparison with o...
Energies, 2021
This paper presents an optimum earthing system design for improving the lightning performance of a 500 kV transmission line for its sustainable operation. The study includes an interpretation of the soil profile and compares the results between default and new earthing arrangements for improving tower footing resistance and tower footing impedance. An evaluation of the tower footing resistance (TFR) and impedance (Ri) before and after earthing improvement was carried out. Moreover, the effects of TFR and Ri, also known as low and high-frequency earthing, respectively, based on a specification of TFR and soil resistivity (SR) ranges at various sites were also considered. The analysis was carried out using the SESCAD tool of Current Distribution Electromagnetic Field Grounding and Soil Structure Analysis software (CDEGS) and PSCAD/EMTDC software for low and high frequency earthing, respectively. From the analysis, the results showed that the new earthing arrangement reduced the TFR by...
Frequency and Time Response of Power Plant Grounding System Exposed to Lightning Strike
International Journal of Electrical and Computer Engineering (IJECE), 2016
This paper examines the frequency response of power plant grounding system exposed to the lightning current. Large amount of current generated by the stroke flow in the grounding system of power plant and dissipate in the soil. The electric and magnetic field generated by such high voltages and currents may cause damage of equipment and may be dangerous for the personnel in power plant. For the every given frequency obtained using Fast Fourier Transformation (FFT) of lightning current impulse, electromagnetic field theory approach is used to solve Maxell’s equation and compute scalar potential, electric and magnetic field. Also, the influence of the point in which lightning current is diffused in the grounding system is presented. Three dimensional plots of spatial distribution of scalar potential, electric and magnetic field are presented. The time domain response of scalar potential, electric and magnetic field on one profile is also presented.