Lightning protection of Wind Turbines Hans V. Erichsen [email protected] 2011-10-14 Serec,, Zurich,, Switzerland www.testinglab.dk Requirements for lightning protection of wind turbines All wind turbine manufactures claims that they fulfill the IEC 61400 61400-1; 1; Wind turbine generator systems - Part 1: Safety requirements . This standard claim that the wind turbine need to have a LPS (Li ht i Protection (Lightning P t ti System) S t ) These demands can be found in: • IEC 61400-24, 2010 Wind Turbines – Part 24: Lightning Protection. Requirements for lightning protection is based on both direct and indirect effects. Lightning flash parameters for wind turbine • The Lightning Protection Level (LPL) is recommended by IEC 61400-24 61400 24 to be LPL I. Level I is the highest level of protection, where the maximum values of lightning current parameters relevant to LPL I will not be exceeded with a probability of 99 %. Lightning flash parameters Lightningflashparameters LPL I LPLI Currentparameter Symbol Unit Peakcurrent I kA 200 Flashcharge Qshort C 300 Specificenergy W/R MJ/Ω 10 Averagesteepness di/dt kA/μs 200 According A di to t IEC 62305-1 62305 1 and d IEC 61400-24, 61400 24 LPL 1 goes from f 3 kA to t 200 kA. kA This Thi means that th t 1% off allll lightning li ht i has h a peak k currentt lower that 3 kA and 1% higher than 200 kA. The IEC 62305-1 and IEC 61400-24 do not consider the lower levels of the other parameters such as Energy, Charge and di/dt. This also means that the wind turbine blades are not protected at the direct strike points against lightning flashes with a peak current lower that 3kA! Blade damages & Performance criteria • Blade damages – Cosmetic – Wind turbine can run until next scheduled maintenance – Blade damages need to be repaired before next scheduled maintenance • Wind turbine performance criteria – – – – Run with out any disturbance's R t t itself Restart it lf after ft Lightning Li ht i eventt Can not restart itself after Lightning event Need repairment before it can run again Lightning flashes to wind turbine • Ground flash property – 90% downward – 10% upward d • Wind turbine (>100m height) flash property – 20% downward – 80% upward D Downward d lilightning ht i Multiple p strokes The four towers in the picture are separated with a distance of 2.9 km, ranging in height from 121 to 191 m, developed upward leaders following a nearby positive cloud-to-ground (+CG) flash on 7/16/09 UT in Rapid City, South Dakota, USA +CG return stroke channel and self-propagating upward leaders developed from all four towers. Source: Observations of simultaneous multiple upward leaders from tall structures. Tom A. Warner -South Dakota School of Mines and Technology, Rapid City, SD, USA. ICLP 2010. Attachment point – point of stroke By use of the rolling sphere model, Lightning attachment points to the wind turbine will be defined. • Blades attachment • Hub attachment • Nacelle attachment Lightning protection blades Wearing of attachment point The charge [C] or [As] of the lightning current wearing the attachment points. Blade receptors / attachment point can be particular exposed to charge wearing Down conduction Components and connections between different part of systems and main components is a part of the direct lightning protection system. system Lightning current will be distribute in all electrical conducting parts through the entire Wind Turbine. Requirements for protection of sub systems Mechanical parts • Blade and blade bearings • Nacelle and other Structural components • Mechanical drive train and yaw system Focus is particular on: – Main bearing(s) – Gearbox – DD Generator Lightning protection zoning (LPZ) LPZ can be divided into two categories • LPZ for conducted surges – Ideal location and integration of SPD’s • LPZ for induced effects – Definition of equipment immunity levels – Definition of required equipment shielding IEC 61400-24 Requirements for protection of sub systems Electrical low low-voltage voltage systems and electronic systems and installations • Surge protection • Isolation withstand voltage level • Induced effects – Cables (Installation technique) – Cabinets ((Shielding g technique) q ) • Wires entering cabinet • Electronic equipment Electronic equipment needs to have a immunity corresponding to the present environment (As minimum to fulfil EMC requirements, recommend to follow TR 50373 – wind turbine; Electromagnetic Compatibility ) Surge Protection Device (SPD) IEC 61400-24 Figure F2. IEC 62305-4 Figure C1. Indirect d ect e effects ects IEC 61400-24 Requirements for protection of sub systems Electrical El t i l hi high-voltage h lt (HV) power systems t • In configurations g operating p g on higher g voltage levels the fundamental protection principles must remain the same same. – Transformer – Generator G – Switchgear Earthing systems and its integration with lightning protection The purpose of a external earthing systems is the following: • Personal safety – • Step and tough voltage Functional safety – • Short circuit clearance Lightning Protection – Current dissipation to earth Personal safety • Personal safety – Thunders storm warning – Safe stay doing thunderstorms Verification Of The Safe Locations In A Wind Turbine During Thunderstorms; ICOLSE 2009 Lightning Sensors • Electricon is designing measurement systems to measure and analyze y lightning g g events. • Sensors can be integrated into wind turbine applications Blade inspections Test and verification methods blades High-voltage strike attachment tests • Initial leader attachment test • Swept p channel attachment test High-current physical damage tests Arc entry test High-current physical damage tests High-voltage strike attachment tests High-voltage strike attachment tests Tak for opmærksomheden Spørgsmål er meget velkommen! 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