How drone-based lightning protection inspection works

Structure of the lightning protection system on a wind turbine

Every rotor blade on a wind turbine carries a lightning protection system (LPS). At defined locations on the blade (typically the blade tip and/or at receptors along the blade) sit metallic air-termination components that capture the lightning current. From there the down conductor runs through the blade interior via the hub into the tower and down to the tower earthing. The entire path from air-termination to earth is referred to as the conductor path. Any interruption or elevated transition resistance along this path can mean the lightning current is not safely discharged, with the potential for severe follow-on damage to the laminate or the bearings.

Why measure by drone?

The conventional method measures the down conductor resistance from the tower base. A defined test voltage is applied and the resistance between a blade injection point and the tower earthing is measured. This base-point measurement reliably captures the lower half of the conductor path. Interruptions in the upper blade section, where lightning strikes occur most frequently, are however easily missed, because fault currents find alternative paths or the measurement uncertainty remains below the damage threshold. A measurement directly at the air-termination component closes this gap because it captures the full conductor path from air-termination to earth.

The DDI method: Voliro T with 4-pole measurement and high-voltage testing

For lightning protection measurement DDI uses the Voliro T: a specialised inspection drone that can position itself at the blade tip and physically dock with air-termination components and the tip. The 4-pole measurement for resistance determination is integrated into the Voliro T as standard. DDI supplements this with a proprietary high-voltage testing method that makes all common turbine types reliably testable, including those where conventional methods reach their limits, for example because the down conductor configuration of the blade places specific demands on test voltage and measurement range. The result: all common turbine types are testable with the DDI method.

What exactly is measured?

The measurement captures the down conductor resistance across the entire path from the docked air-termination component (or blade tip) through the down conductor, through the hub and the tower and down to the tower earthing. Every measurement result is logged with a timestamp, GPS coordinates and an operator identifier. Per rotor blade, all defined air-termination components and the blade tip are visited individually. The result is a complete resistance profile of the lightning protection system per turbine.

Which turbine types are testable?

Thanks to the combination of 4-pole measurement and the DDI high-voltage testing method, all common onshore and offshore turbine types from major manufacturers are testable, regardless of blade size and down conductor configuration. For unclear or very old turbine types we clarify testability in advance based on the available documentation.

Drone vs. rope access

• Base-point measurement: fast and inexpensive, but captures primarily the lower half of the down conductor path; faults in the upper blade section remain uncertain.
• Rope access: complete measurement possible, but logistically demanding, season-dependent, with high downtime and personnel costs.
• DDI drone method: complete measurement of the conductor path from all air-termination components and blade tips, approx. 30 minutes downtime per turbine, a single operator, no platform, no rope access team. Result: standards-compliant to IEC 61400-24.

Standards basis

The measurement is carried out to IEC 61400-24, the international standard for lightning protection on wind turbines. The German version is published as DIN EN 61400-24. In addition, the BWE guideline applies for periodic inspection. Every measurement protocol produced by DDI contains an explicit standards reference with version information. More on the regulatory framework under /en/technik/normen-richtlinien.