Wind turbine blade maintenance: leading edge erosion, LPS and rope access inspection
A wind turbine blade spends its life cutting through air, rain and whatever comes with it. Over the years, the leading edge wears, and that wear costs energy and, if left untreated, the blade itself. We explain what leading edge erosion is, why the lightning protection system also needs checking, and how this work is done on ropes.
What leading edge erosion is
The leading edge is the edge of the blade that "cuts" the air. It is also the part that takes rain, hail, dust and insects head-on. Because the blade tip moves very fast, every drop of water hits the surface hard. Repeated millions of times, this impact gradually wears away the protective coating, then the filler and, finally, the laminate.
The International Energy Agency, at a technical experts meeting of its wind energy programme, identified leading edge erosion as the main factor reducing blade lifetime and energy output over time, and noted that the phenomenon is still not fully understood. The subject has its own dedicated symposia, such as the one DTU Wind organises every year.
Why it matters
A rough leading edge, or one with material torn away, changes the aerodynamic profile of the blade: the turbine produces less from the same wind. And the wear does not stand still. Surface erosion left untreated lets water in and can reach the laminate, and then the repair is bigger.
That is why it makes sense to inspect regularly and repair early, while the damage is still in the coating.
The lightning protection system (LPS)
Wind turbines are tall, isolated structures, often on hilltops. They get struck by lightning. The blade has its own system to carry the strike to earth without damaging it: receptors on the blade surface, connected to an internal down conductor that runs to the root.
The reference standard is IEC 61400-24, which covers lightning protection of wind turbines, including the blades, and the methods for verifying that the protection meets the requirements. During a rope access inspection, we check the receptors that can be reached from the outside: whether they are in place, whether they show strike or burn marks, and whether the surrounding material is damaged. Electrical tests and acceptance criteria follow the manufacturer's and the operator's procedures.
How a blade is inspected on ropes
The sequence is always the same, and it starts long before anyone leaves the nacelle:
- Preparation: operator procedure, permit to work, wind and weather limits defined, rescue plan and rescue kit on site.
- Stop and lock: the turbine is stopped and the rotor locked, following the manufacturer's and the operator's procedures, with the blade to be inspected pointing down.
- Access: the team anchors to the designated points on the nacelle and descends along the blade, with two ropes per technician.
- Inspection: up close, along the leading edge, the surfaces, the trailing edge and the receptors, with photographs and the location of each defect.
- Report: each defect recorded with its position on the blade, approximate size and a photograph, so the operator can decide what to repair and when.
And the repair
When the damage can be repaired in the field, it is done from the same access: cleaning, removal of degraded material, surface preparation, filling and application of leading edge protection. The materials and method are those specified by the blade manufacturer or the operator, and many products only cure properly within certain temperature and humidity limits. That is why the weather sets the schedule.
Major structural damage, such as deep cracks in the laminate, is beyond the scope of a simple repair and is dealt with as the manufacturer determines.
Ropes, platforms and robots
Today there are three ways to reach the blade: rope access technicians, dedicated suspended blade platforms and, increasingly, inspection robots and drones. Drones are useful for initial screening from the ground, and there are projects, such as Leading Edge Repair in Denmark, developing repair robots. But to see a defect up close, touch it and repair it, you still need someone at the blade. Rope access does that without a high-reach crane or a platform on site.
Before you ask us for an inspection
- Tell us the turbine model, the number of turbines to be inspected and how the wind farm is accessed.
- Send us reports from previous inspections, if there are any.
- Tell us the operator's procedures for stopping, locking out and working at height.
With this, we prepare the work and rescue plan and agree the weather windows with you.
Have a job in this area?
Send us the location, a description and some photographs. We will reply with what is needed to move forward.