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Delegates are invited to meet and discuss with the poster presenters in this topic directly after the session 'Advanced electrical systems: From megabyte to megawatt' taking place on Wednesday, 12 March 2014 at 09:00-10:30. The meet-the-authors will take place in the poster area.

Zeljko Djurisic University of Belgrade, Serbia
Co-authors:
Zeljko Djurisic (1) F P Danka Todorovic (1) Milena Milinkovic (3)
(1) University of Belgrade, Belgrade, Serbia (2) Siemens Belgrade, Belgrade, Serbia

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Abstract

Wind farm lightning protection system with a kite

Introduction

Height of tips of the high power wind turbine blades reaches over 200m. The objects of this height, either offshore or onshore, are often targets of direct atmospheric discharges. The existing concept of protection is not capable of providing a complete protection of all wind turbine elements against lightning currents and induced over-voltages, thus lightning strikes constitute a very frequent cause of wind turbine failures and outages. A novel concept of wind turbine protection against direct lightning strikes is presented.

Approach

The idea is to place a protective system, in the form of grounded conductive wires, in close vicinity and within the area of a wind farm, the tips of the wires being kept by kites at a desired height. Height of a protective wire has to be significantly above the topmost point of any wind turbine. Stormy clouds, carried by the wind, approach first the very high tips of the protective wires, which usually results in an upward discharge, relieving charge from the clouds, thus making the probability of lightning strikes at the wind turbines considerably smaller.

Main body of abstract

This work develops a new idea of lightning protection, conceptually different from the existing protection system since it is based on protection of the wind farm as a whole, not on protection of individual wind turbines. The essence of this innovative concept is putting, at selected points of a wind farm area, the receiving systems consisting of grounded conductive wires whose tips are lifted sufficiently high above the ground, thus being exposed to atmospheric discharges when clouds approach the wind farm zone.
The idea is to place in the vicinity of a wind farm very tall lighting receptors at a height which considerably exceeds the topmost point of any wind turbine (e.g. 1000m). If a sufficiently charged cloud approaches, it will discharge itself into the protective wires. In this process, taking into account heights of the wire tips, the discharge will be upwards (from the wire toward cloud). After this discharge, the cloud will be considerably less charged and its potential for a new discharge will be significantly lower. Carried by the wind, the cloud eventually comes above wind turbines. Taking into account that wind turbines are considerably lower compared to the protective wires, which have taken the initial charge from the cloud, the probability of lightning strikes at the wind turbines is significantly lowered.

Conclusion

The proposed system for wind farm protection is very efficient, simple, and inexpensive. It can be installed in already built wind farms which have problems associated with atmospheric discharges. The existing protection systems integrated with wind turbines obtain the role of secondary protection against lightning strikes.
The realization and control of a kite system is an up-to-date topic in so far as using such system as high altitude wind power systems is concerned. Compared to a kite wind generator system, this sistem is much simpler since the only function of the kite is to maintain the wire at the desired height.



Learning objectives
The basic question is: Is it possible to reduce potential of a cloud before it comes above the object which is to be protected against atmospheric discharge?