Isolated vs. interconnected wind turbine grounding systems : effect on the harmonic grounding impedance, ground potential rise and step voltage

Sunjerga, Antonio (Electromagnetic Compatiblity Laboratory, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland) ; Li, Quanxin (Electromagnetic Compatibility Laboratory, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland ; School of Electrical Engineering, Wuhan University, Wuhan, China) ; Poljak, Dragan (Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Split, Split, Croatia) ; Rubinstein, Marcos (School of Management and Engineering Vaud, HES-SO // University of Applied Sciences Western Switzerland) ; Rachidi, Farhad (Electromagnetic Compatibility Laboratory, Swiss Federal Institue of Technology (EPFL), Lausanne, Switzerland)

Wind turbines are very vulnerable to lightning strikes due to their height, sharp edges and remote locations often with high soil resistivity. In this paper we present numerical simulations of the impedance of a typical wind turbine grounding geometry. We analyze the influence of interconnecting grounding systems of different wind turbines. IEC TR61400-24 suggests interconnection of grounding electrodes of wind turbines through horizontal electrodes (in the form of insulated or bare conductors) to achieve low steady-state grounding resistance. The analysis takes into account the frequency dependence of the soil electrical parameters. We show that the low frequency grounding impedance can be reduced by a factor of two or more as a result of interconnecting grounding systems. However, the reduction is significantly lower at higher frequencies because of the interconnection wire’s inductance. We analyze the spatial distribution of the ground potential rise and step voltage in response to typical first and subsequent lightning return stroke current waveforms. It is shown that both, ground potential rise and step voltage can be significant along the wire, especially for high resistivity soil, and placing sensitive equipment near the interconnecting wire should be either avoided, or insulated wire should be used.


Keywords:
Article Type:
scientifique
Faculty:
Ingénierie et Architecture
School:
HEIG-VD
Institute:
IICT - Institut des Technologies de l'Information et de la Communication
Date:
2019-08
Pagination:
10 p.
Published in:
Electric Power Systems Research
Numeration (vol. no.):
2019, vol. 173, pp. 230-239
DOI:
ISSN:
0378-7796
Appears in Collection:

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 Record created 2019-10-29, last modified 2019-10-29

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