Guide to Lightning Protection System (LPS) Testing

Each year, over 2.1 billion lightning bolts strike around the world — a massive natural electric force we cannot keep at bay. Most hit the ground and dissipate, but a fraction also lands on industrial assets.

Some American wind farms experience over 1,000 lightning strikes annually and between 8 and 14 hits per blade. High-voltage exposure, especially repeated exposure, causes significant damage.

Fortunately, there’s a fix. To minimize the environmental impacts, most industrial assets are equipped with a lightning protection system (LPS), a proven solution for intercepting and diffusing even high-voltage currents.

Lightning Protection Systems (LPS) Are a Must for Industrial Sites

Lightning flashes generate 300M Volts and 30K Amps, heating the air by 27k °C. Tall industrial facilities are a prime target for the electric zap. When exposed to such voltage and heat, unprotected assets short-circuit, catch fire, or get damaged. In 2023, lightning strikes destroyed $76 billion worth of assets across North America and Europe and caused 60% of wind blade losses.

Lightning protection systems (LPS) come to the rescue, intercepting lightning currents and re-directing them safely to the ground. Governments, regulators, and even insurance companies mandate LPS installation for industrial assets.

Types of Industrial Assets Requiring LPS

• Power distribution facilities
• Solar farms
• Radar antennas
• Telecom and airport towers
• Storage tanks with hazardous contents
• Oil and gas facilities (drilling equipment, pumping stations)
• Construction sites
• Wind turbines

Not installing and maintaining an LPS may lead to lightning-induced damages, downtime, and costly repairs. Non-compliance can also lead to penalties.

Australian wind farm operator SWF2 failed to install protection systems for the wind turbines. In 2016, a “once-in-50-year storm” with 80,000 lightning strikes hit Australia, causing the wind farm to fail under high voltage fluctuations. The blackout affected over 850,000 residents. Legal proceedings ended in 2020, with SWF2 facing a $1 million fine.

The takeaway: Don’t skimp on LPS installation. Regularly inspect the system to avoid unsavory surprises due to a faulty component.

How Often Do You Need to Test a Lightning Protection System?

Lightning protection standards, notably IEC 62305, NFPA 780, and UL 96A, recommend periodic inspections by certified agencies. The testing frequency depends on the LPS tech specs, protected asset type, previous repairs, and weather conditions.

As a rule, the older the asset, the more lightning-prone the area, or the more flammable the asset, the more frequent inspections you should conduct.

Generally, the standards specify the following intervals. As per IEC 62305, the testing frequency depends on the asset type or the LPS’s lightning protection levels (LPL):

• For level 1 & 2 LPSs (max current 200 and 150 kA), visual inspections should occur annually, and a full inspection every 2 years.
• For level 3 & 4 LPSs (max current 100 kA), the visual inspection should take place every 2 years, and complete inspection – every 4 years.
• LPSs on high-risk, flammable assets should be inspected every 6 months.
• every year. LPS in areas with extreme environmental conditions should undergo a full inspection

According to NFPA 780, you should test a lightning protection system immediately following installation and after each repair. The standards also specify the following intervals:

• Visual inspection – every year
• Visual inspection in areas with severe weather conditions – every 6 months
• Complete, in-depth inspections – every 3-5 years
• Complete inspection of LPSs on critical systems – every 1-3 years
• Earth resistance testing – during significant temperature & humidity fluctuations (extremely hot and cold months)
• For explosive assets, the electrical testing of LPS should be every 17 months, and the surge protection device should be inspected every 7 months.

Finally, UL 96A mandates inspections post-installation and requires a five-year re-inspection program to renew the certification.

Lightning Protection Testing Methods Overview

Regular inspection and proactive maintenance are essential for lightning protection systems to operate effectively 24/7 all year round. Both IEC 62305 and NFPA 780 mention visual, continuity, ground resistance, and surge protection testing as reliable methods for analyzing operating conditions and locating defects.

During an LPS test, inspectors will look for signs of:

• Deterioration and corrosion of air terminals, conductors, and components
• Corrosion of earth electrodes
• Poor earthing resistance in the grounding electrode system
• Discontinuities of connections, equipotential bonding, and fixings
• Surge detection device defects

Inspectors must document all findings upon completion. The report will be used as a point of comparison during the next inspection.

Visual LPS Inspection

Visual inspection is one of the simplest, non-destructive testing methods for detecting readily apparent defects. Both certified inspectors and asset owners can conduct this type of testing. Direct access to all LPS elements is necessary, so consider using a cherry-picker or a drone.

For instance, with Voliro T drone, you can inspect wind turbine elements for wear or damage using a 4K 12 MP camera with a 30/60fps frame rate and 80° field of view. All collected data is stored on a microSD card and can be exported to inspection software for analysis.

A visual LPS inspection verified the following:

• Proper assembly and compliance with all standards.
• No breaks, color changes, rough surfaces, or burrs formed.
• Securely attach all LPS components to the mounting surface.
• No corrosion or vibration weakens the system.
• Grounding electrodes are still attached.

A drawback of visual inspection is that it only identifies physical defects without assessing the LPS functionality. Therefore, it should be combined with other NDT methods for conclusive qualitative data.

Continuity Testing

Continuity testing determines if the lightning protection system components are properly installed, run uninterrupted, and have low resistance. This method also verifies the integrity of fuses, wires, connections, and switches. New wind turbine elements require continuity tests to ensure equipotential connection with the LPS.

During a continuity test, a digital multimeter sends a current through the circuit. If the current flows smoothly, the system is closed-circuited. The multimeter shows resistance indicators, reflecting the current’s ease of flow. Lower resistance reduces the risk of lightning damage.

Recommended equipment for continuity testing:

• Digital multimeters measure voltage, resistance, and currents and show the results on screens. The test current supplied ranges from 10A (standard) to 200 mA (high-precision models).
• Specialized continuity testers are more affordable devices that detect circuit continuity by lighting up when the current flows smoothly.
• Low resistance ohmmeters (LRO) measure the lowest resistance values in circuits (0.1 mΩ or lower).

Tall wind turbines are challenging to test for continuity because you must access the LPS and schedule lengthy service interruptions.

It’s possible to reduce downtime to 20-30 minutes using a drone equipped with a LPS payload. With 360° mobility, Voliro T can access wind blades up to 250 m at any angle. Voliro mountable LPS probe features a Micro-Ohmmeter VG-BAT-150, providing a single solution for various tasks:

• Ground resistance testing and inspection of grounding electrodes
• Inspecting resistance between LPS components (lightning rods, down conductors, and grounding electrodes).
• Continuity testing and conductor resistance measurements

The LPS probe can measure currents as small as 0.30 A and resistances as low as 0.001 Ω. Using Voliro T, Skyspecs inspected LPS on over 210 wind turbines in the USA and Germany in just two weeks. We analyzed each receptor in detail and measured its resistivity 10 times faster than conventional methods.

Surge Protection Device (SPD) Testing

A surge protection device (SPD) shields assets against extreme, transient overvoltages coming both from direct and indirect lightning strikes. When voltage levels are too high, SPD acts like a conductor, redirecting electrical currents to the earth and preventing damage to electrical installations and equipment.

According to NFPA 70 standard, SPDs are required at all power service entrances, and all components must be easily accessible for inspection. Typically, SPDs are inspected during setup, after installation, upon repairs, and after severe lightning strikes. When installed on flammable assets, SPDs should be tested no less than every seven months.

SPD inspection typically aims to verify the following conditions:

• Integrity of bonding conductors and cable shields
• Line routings operation
• Absence of unaccounted installations
• SPD connectivity with the power supply (circuit continuity)
• Peak safe discharge current for the SPD
• Minimize the current path impedance to the ground

Digital multimeters or individual ohmmeters help perform continuity and resistance testing. Specialized surge protection testers can also be used to measure surge capacities and the current leakage (i.e., whether current passes from a protective ground conductor to the ground).

Ground Resistance Testing

Ground resistance test measures the resistance between grounding electrodes and the earth. When there is a good connection and low resistance, lightning current can safely disperse to the ground. Ideally, the resistance should be less than 5.0 ohms.

Types of ground resistance testing include:

• Soil resistivity testing: Determines where to install your new earthing electrodes or if the existing grounding system is adequate for the soil conditions.
• Fall-of-potential test: Checks whether an individual electrode can disperse lightning currents. For this test, disconnect the electrode from the grounding system.
• Selective method: Tests electrode resistivity without disconnecting them from the grounding system, increasing the safety of personnel.
• Stakeless method: Measures the resistance or grounding electrodes by fixing current clamps on the grounding electrode (no need to remove electrodes from the loop).

High ground resistance may indicate insufficient electrode depth or quantity. Readings may also be higher due to significant changes in soil humidity, salinity, and temperature.

According to NFPA 70, ground resistance testing requires certified testing tools — handheld devices equipped with high-precision ohmmeters. In essence, they work like usual multimeters, testing the resistance and circuit continuity by supplying the current to the electrodes. However, their design and setup are better suited to testing grounding electrodes (stakes with sharp points to penetrate the ground and clamps that fit around the electrode).

In the aftermath of a lightning strike, however, the surrounding area around a wind blade may still be charged and dangerous to personnel. To perform ground resistance testing in this case, you can opt for Viloro drones with current measurement capabilities of 0.30 A and a resistance measurement range of 0.001-1000 ohms.

Streamline LPS Testing with Voliro

Voliro eliminates the dangers of LPS testing, reducing the risk of personnel exposure to electrical currents. Purpose-built for work at heights, the Voliro drone minimizes cherry-picker operations and accelerates the inspection process — up to 18 wind turbines can be inspected per day!

Voliro also includes 3 days of pilot training with every subscription, while AI-assisted autonomy further reduces piloting risks risks. Reduce LPS inspection time by 90% with Voliro!