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Transient performance of interconnected wind turbine grounding systems DOI:10.15199/48.2015.06.13

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We analyze the transient grounding characteristics of interconnected wind turbine grounding systems, for fast rising current pulses. By increasing the number of wind turbines, influences on harmonic impedance and transient potential are examined for different soil characteristics and different locations of excitation. Simulations are performed using simple model of grounding system that neglects the foundation reinforcement. The influence of such simplification for isolated wind turbines is analyzed in previous papers. Here we extend the previous analysis for interconnected wind turbines and we look at the possibilities for optimization of the transient analysis of extended grounding systems in wind farms. Streszczenie. Przeanalizowano w pracy charakterystyki stanów przejściowych uziemień turbin wiatrowych dla szybkiego narastania impulsów prądowych. Przy wzroście liczby turbin wiatrowych zbadano wpływu na impedancje harmoniczną oraz stan przejściowy dla różnych charakterystyk gleby i różnych lokalizacji wzbudzenia. Przeprowadzono symulacje przy użycie prostego modelu uziemienia, który zaniedbuje wzmocnienie fundamentów. Wpływ takiego uproszczenia dla pojedynczych turbin przebadany został w e wcześniejszych publikacjach. W tym artykule rozszerzono poprzednia analizę na połączone turbiny oraz skierowano uwagę na możliwości optymalizacji analizy stanów przejściowych rozbudowanych systemów uziemienia na farmach wiatrowych. (Wyznaczenie stanu przejściowego w systemie uziemienia elektrowni wiatrowej ). Keywords: grounding system, lightning, transient analysis, wind turbine. Słowa kluczowe: systemy uziemienia, wyładowania atmosferyczne, analiza stanu przejściowego, turbina wiatrowa. Introduction Recently a number of papers have been devoted to the transient performance of isolated wind turbine grounding systems [1-4]. In practice, wind turbines are often spread across large areas, electrically interconnected by buried medium voltage cables. Me[...]

Improving Efficiency of Full-Wave Electromagnetic Analysis of Grounding Systems Within Homogeneous Earth DOI:10.15199/48.2019.05.03

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The frequency dependent and transient characteristics of grounding systems are of interest in many engineering analyses related to electric power safety and lightning protection, where frequencies of interest range from dc to few MHz [1], and electromagnetic compatibility related studies, with frequencies of interest up to tens of MHz [2]. Different methods for modelling of grounding systems have been developed in the past few decades, based on electric circuit [3, 4], transmission line [5] and electromagnetic theory [6]. Among them, electromagnetic model provides most accurate results for all frequencies of interest. The most popular electromagnetic model is based on antenna theory and solution of electric field integral equations by the method of moments (MoM) [6, 7]. One difficulty in implementation of the mathematically exact solution for the electric field for semi-infinite conducting medium in practical problems is the numerical evaluation of singular, oscillatory and slow converging Sommerfeld integrals, which is numerically unstable and extremely time consuming procedure. To circumvent this problem in practical analysis, quasi-static [8, 9] or complex-images approximations [10, 11] are often employed, however, the governing approximations limit their validity to a certain upper frequency and system dimensions. Due to the lack of efficient full-wave model, the domain of applicability of these approximations as well as other approximate models has not been rigorously tested for wide range of parameters and complex configurations. Another common problem in the application of antenna theory based methods for analysis of buried conductors is that they may not provide exact solutions for low frequencies approaching 0 Hz. This is either due to improper treatment of the images of currents in conductors [9], or due to numerical instabilities often referred to as “low frequency breakdown". This paper presents efficien[...]

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