Download Report

A new industry standard
within lightning protection
of wind turbine blades
The Lightning Interception Blade Implant® adheres to the international lightning
protection standard IEC 61400-24 Ed. 1. for wind turbines and ensures complete
protection from damages due to direct lightning strikes to wind turbine blades.
Lightning protection of wind turbine
blades has never been safer
nor easier to implement than now.
The Lightning Interception Blade Implant® is setting new industry
standards by ensuring that lightning strikes are captured with high
efficiency and safely directed down through the wind turbine blades
without causing any damages or downtime. Lightning-related damages
are a major concern to the wind power industry and one of the main
reasons for longer outages. Depending on location, topography, weather
conditions and wind turbine height, lightning can strike a wind turbine
more than 25 times a year. This problem is growing in line with the height
of wind turbines. The taller the wind turbine, the higher the risk of direct
lightning strikes. The tendency of moving wind turbines even further
offshore, simply results in increased maintenance and repair costs.
Due to such extended lightning exposures, the operation and maintenance costs increase, while the Annual Energy Production decrease,
resulting in a higher Cost of Energy (CoE) than expected. Enhancing
wind turbine lightning protection systems will help alleviate this problem.
Our solution
The Lightning Interception Blade Implant® provides a cost-effective
solution to lightning protection of the outermost 5m of a blade, which
covers Lightning Zone 0A1 and 0A2 as seen in the fact box. This ensures
high interception effectiveness when exposed to direct lightning strikes.
The innovative blade concept has been designed using state-of-the-art
technology and tested in excess of 200 kA using our in-house testing
facilities, guaranteeing that it can withstand the expected high impact
from lightning strikes.
Furthermore, our concept adaptation process ensures quick and effective
adaptation to the geometry of every specific blade design.
Down conductor
Tip receptor
Tip receptor base
Side receptor
Cut-out of GLPS blade tip with tip receptor,
side receptor, and internal connection.
The Blade Zoning Concept
Data from numerical modelling and field
inspections shows that approx. 70% of lightning
attachments on fiberglass blades occur within the
first 1 m of the tip and approx. 90% occur within
the first 2m. The results have led to the Blade
Zoning Concept.
The Blade Zoning Concept is used to assess the
possible strike amplitudes to different section
of the blade, and describes which parts of the
blade that are most exposed and to which
lightning current amplitudes (see illustration)
Tests conducted to assess the impact of impulse
currents of 3-10kA attaching directly to inboard
blade sections (Zone 0A4), have provided evidence
of only limited cosmetic damages to the blade.
For zone 0A3, strikes of up to 50kA will in some
instances attach outside the air terminations and
result in damage. However, once the probabilities
of having such strikes are assessed for the
different blade radii, it becomes obvious that the
risk of failure (probability x consequence) in the tip
region of the blade is very high.
The results show that it is simply not feasible
to protect Zone 0A3 or Zone 0A4 against direct
attachment. Conversely, the importance of
protecting the tip section (Zone 0A1 and Zone 0A2)
cannot be emphasized enough, why our design
focuses on the protection of these most exposed
parts of the blade.
Overall design
The overall design consists of a single assembly from the tip receptor,
following the blade geometry, towards the main down conductor cable
traced to the blade root. Along this path, a single pair of side receptors
is implemented in the tip region, flush with the blade surface, with the
insulation coordination of the different parts ensuring high interception effectiveness. The overall concept is illustrated in previous page.
The tip receptor is a solid metal tip, which is machined to the designed,
aerodynamic shape of the blade tip. The tip can be produced using various metals having different electrical and thermal properties tailored to
the specific application.
The tip receptor is then attached to the receptor base, and via the special insulated conductor cable to the side receptor and further to the
main down conductor, ensuring that lightning current intercepted by the
tip or side receptors is safely conducted to the blade root. The first pair
of side receptors is a fixed and integrated part of the tip implant, and
consists of an internal part – the side receptor base – and an external
part, the side receptor itself. The internal metal parts are covered with
suitable insulation material, to ensure maximum interception effectiveness of the air termination for strikes attaching to the tip zones.
Both the tip and side receptors are easily replaceable, should they erode
due to high level of lightning charge content.
The insulation system is the mechanical interface between the internal
metal parts and the blades inner surface. The main purpose of the
insulation system in the tip section of fibreglass blades is to delay the
processes of forming partial discharges from inner metallic parts. By
lowering the field enhancement and delaying these discharges in time,
the insulation system prevents the lightning discharge to attach the
blade down conductor through the blade shell, and thereby causing
structural damage.
Zone 0A1
Zone 0A4
Zone 0A3
XX m
15m
Zone 0A2
4m
1m
The Blade Zoning Concept – The blade consists
of 4 lightning zones, each with an upper current
amplitude (0A1<200kA, 0A2<100kA, 0A3<50kA,
0A4<10kA).
1. IEC 62305-1 Ed.2 Protection against lightning
– Part 1: General Principles,” IEC, 2011.
By developing well-engineered machined
and moulded parts for each of the LPS
components using state-of-the-art FEM
based simulation tools, and testing the final
product thoroughly according to IEC6140024, with extended test levels, our insulation
system has been optimized to secure
optimal insulation coordination.
Easy certification and installation process
The Lightning Interception Blade Implant® is a pre-manufactured
system, designed for production with robust tolerance design and
delivered with inherently high level of quality assurance. The benefits
are decreased assembly time and consistent high quality.
Once the implant has been tailored to the specific blade geometry,
where the tip geometry represents the exact curvature of the blade
tip and the side receptors are designed and shaped to fully protect the
in-board blade sections, the installation in blade production becomes
very simple.
The Blade implant can be delivered as one component including the
complete down conductor system or in sections to accommodate a
specific blade manufacturing process, if required.
During the mould layup, the Lightning Interception Blade Implant®
is fitted into one side of the blade aligning the tip parts and the down
conductor system to coordinated fix points and structural blade
components. The customization ensures that the Lightning Interception
Blade Implant® fits perfectly into the mould. The down conductor
system is rolled out to the entire blade length terminating at the
customized root termination solution.
Once the blade is cured and demoulded, the tip receptor and side
receptors are easily installed using the simple receptor concept.
All components and tools are provided as a part of the concept.
The Lightning Interception Blade Implant®
can bring substantial savings to your business.
Your benefits
The Lightning Interception Blade
Implant® gives you the following
unique advantages:
• A blade tip lightning protection system
designed for production with robust
tolerance design - reducing production
time and ensuring consistently high quality
• A lightning protection system with
replaceable tip and side receptors
• A blade tip where insulation coordination
and receptor spacing have been optimised
to ensure maximum interception
effectiveness of the strikes attaching
to the blade
• A blade tip, which is pretested and that
meets the highest requirements in the
IEC 61400-24 concerning the blade tip
design
• A blade tip, which is certified by a
third party, documenting the overall
performance and documentation of the
system.
This ensures optimal lightning protection of
your wind turbine blades, reducing the CoE,
and ensures compliance and certification
according to required standards.
Therefore, the Lightning Interception Blade
Implant® can bring substantial savings to
your business.
www.global-lightning.com
Global Lightning Protection Services A/S
HI-Park 445
DK-7400 Herning
Denmark
[email protected]
+45 70 26 02 11