Modular Wind Turbine Blade Lightning Shield
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Solution Overview
Problem
Modular wind turbine blades face challenges in ensuring that lightning current is transferred across the joint between adjacent blade modules without causing damage, as the connection joint breaks electrical continuity in conductive spar caps.
Innovation Solution
The implementation of an electromagnetic shield positioned on and in electrically conductive contact with the spar cap portions at the connection joint, which extends across the joint in the spanwise direction to divert lightning current and prevent voltage flashovers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If modular blade design is used to facilitate transportation, then ease of transport is improved, but electrical continuity in the spar cap is broken at connection joints
Solution Approach 1:
The blade is divided into multiple modular sections that can be transported separately and assembled on-site. The spar cap is segmented into corresponding portions at each module, with connection joints allowing mechanical assembly while maintaining electrical continuity through conductive materials and overlapping configurations.
Solution Approach 2:
The spar cap connection joint utilizes composite construction combining conductive fibres (such as carbon fibres) with metallic strips or meshes. This composite approach maintains electrical continuity across the joint while providing mechanical strength for module connection, resolving the conflict between modular transportability and electrical continuity.
2Reliability
If conductive fibres are used in spar cap for lightning protection, then lightning protection capability is improved, but voltage flashovers may occur at connection joints
Solution Approach 1:
A metallic strip or mesh is introduced as an intermediary element at the connection joint between conductive fibre portions. This metallic intermediary provides a controlled low-impedance path for lightning current, preventing uncontrolled voltage flashovers while maintaining overall lightning protection capability. The metallic strip acts as a mediator that safely bridges the electrical connection across the joint.
Solution Approach 2:
The connection joint design ensures equipotential connection between adjacent spar cap portions using conductive materials and overlapping configurations. By maintaining equal potential across the joint, voltage differences that could cause flashovers are eliminated, while lightning current can still flow continuously through the equipotential path.
3Reliability
If lightning current flows across connection joint, then lightning protection function is maintained, but damage to blade at joint may occur
Solution Approach 1:
The impedance of the connection joint is deliberately modified by introducing metallic strips or meshes with lower electrical resistance compared to the conductive fibres alone. This parameter change creates a preferred current path through the joint with controlled impedance, allowing lightning current to flow while preventing excessive heating and damage to the joint structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The electromagnetic shield effectively mitigates the risk of voltage flashovers and damage at the connection joint by providing a low-impedance path for lightning current, thereby protecting the blade from overheating and structural damage.
Implementation Method 1
The electromagnetic shield locally shields the connection joint in the conductive spar cap. The electromagnetic shield is in intimate contact with the surfaces of the spar cap portions. The electromagnetic shield is not intended to protect the spar cap portions from direct lightning attachment. Instead, the electromagnetic shield provides local shielding at the joint area by preventing the formation of high electric fields at the joint and thus minimising the risk of any flashovers.
Implementation Method 2
The electromagnetic shield extends across the connection joint in the spanwise direction. The electromagnetic shield is positioned on and in electrically conductive contact with at least one surface of the first spar cap portion and at least one surface of the second spar cap portion. In the event of a lightning strike, lightning current may flow in the spar cap. The current in the spar cap will be diverted into the electromagnetic shield as this has a lower impendence than the spar cap, in particular due to the skin effect.
Implementation Method 3
The current in the spar cap will be diverted into the electromagnetic shield as this has a lower impendence than the spar cap, in particular due to the skin effect.
Data Source
AI summary
A wind turbine blade having at least two blade modules extending in the spanwise direction of the blade and being configured for connection end-to-end at a connection joint An electromagnetic shield is positioned in electrically conductive contact with the blade modules and extending across the connection joint in the spanwise direction.