Fair weather induced charges and currents on tall wind turbines and experiments with kites

Abstract

Abstract-Earth's atmospheric potential rapidly increases up to few tens of kilovolts below 200 m altitude. This potential drop will induce charge to tall objects at ground by virtue of electrostatic induction. In this work we investigate the induced electric charges in fair weather to a 1.5 MW and 5 MW wind turbines. The effect of rotation is included and the current calculated result in currents of few micro-amps. The production of point discharge and corona is investigated and some experiments are conducted by means of instrumented kites.

On the Induced Currents to Wind Turbines by the Earth’s Atmospheric Electric Potential: Experiments With Drones

“…However, ESD is triggered mainly by the electrification of the tall conductive structure when exposed to atmospheric electric fields and does not require wind presence. In addition to ESD hazards, this electrification can lead to induced currents on tall structures that can produce interferences in sensors, increasing the noise level or causing false readings [9].…”

“…During thunderstorms, the electromagnetic environment can lead to significant sensor-disturbances due to lightning strikes or simply from the high quasi-electrostatic fields in the presence of thunderclouds [13], [14]. However, since wind turbines are very tall conductive towers, intense electric fields can develop at the tips of the blades even under fair-weather conditions [9]. That is because, under fair-weather, the Earth's atmospheric potential rapidly increases up to a few tens of kilovolts below 200 m altitudes, as measured by Hy-wire balloon experiments [15].…”

“…This potential drop induces charge to grounded tall objects by electrostatic induction, where the maximum induced charge is found at the tip of the grounded object. State-of-the-art wind turbines of more than 10 MW can reach altitudes of more than 200 m. This can result in electric field amplification at sharp edges [9], leading to point/corona discharge [16]. In addition, there is a periodic variation in the induced electrical charge due to the movement of the rotor, which induces currents, as explained in [9].…”

“…State-of-the-art wind turbines of more than 10 MW can reach altitudes of more than 200 m. This can result in electric field amplification at sharp edges [9], leading to point/corona discharge [16]. In addition, there is a periodic variation in the induced electrical charge due to the movement of the rotor, which induces currents, as explained in [9]. This same work presents an experimental study using kites tethered by conductive wires to simulate fair-weather induced charges and currents on the tall wind turbine.…”

“…Although blades are made of nonconductive glass fiber, the standard addition of carbon-reinforced components (e.g., spars) [18] as well as the required Lightning Protection System (LPS) [19] ensures the existence of a conductive path from the tip to the root. For that reason, prior works used tethered kites [9], and tethered balloons [17], to simulate the electrical behavior of wind turbines. However, a significant shortcoming with both platforms is the difficulty of maintaining a fixed position and keeping the tether oriented in the vertical direction.…”