Ensuring safety, quality, and reliability for wind turbines, railway and aviation

30 August 2022


Don’t worry, Megger’s DLRO series of testers has you covered

The proper operation of electrical equipment greatly depends on the controlled flow of current within that piece of equipment. To prevent long term damage to these electrical assets, and to reduce the amount of energy that is wasted as heat, low resistance testing is made mandatory by many companies worldwide. Low resistance testing helps to identify restrictions in current flow that can prevent a machine from running at full power, or where current flow is too low to activate protective devices.

Low resistance testing is performed mostly in power utility companies, chemical plants, refineries, mines, railroads, telecommunication companies, automotive manufacturers, and aircraft manufacturers, as well as in any company that has UPS battery back-up systems. These tests are performed using a digital low resistance ohmmeter (DLRO), which has become the go-to instrument for many of these industries partly because they can get to hard-to-reach places and work at heights that other instruments simply cannot.

Wind turbines

Take, for instance, the wind power industry. Testing wind turbines can be extremely tricky if you don’t have the right test equipment as not only are they high elevation, but their movement through the air causes ionization, which creates a target for cloud charge that can develop in the atmosphere. As such, the tips of turbine blades are especially susceptible to lightning strikes, which can cause enormous, costly damage to the entire turbine. The only protection these turbines have is a copper conductor that extends from the tip of the blade to its base, and then down the tower to a subterranean grounding electrode. This can provide a low resistance path from cloud to earth without damaging the tower. But, like all electrical assets, in order for it to work properly and protect against lightning strikes, it must be regularly tested and maintained.


Other than lightning strikes, there are many other ways that the turbine blades can be damaged, such as when blades flex in the wind during normal operation. When this happens, the grounding conductor may fracture, and if the fractured conductor is touching at the break, a continuity test will not be able to find it, which can result in the lightning protection failing at a critical time.

To pick up these potential faults, what is needed is a higher test current of 1 A or more. This is because blades can be up to 100 meters long and are tested tip to hub. Test leads that can reach that length must be designed with low enough resistance to not overwhelm the instrument’s capabilities and invalidate the test. Most instruments cannot be used to perform this task, however the DLRO2 and DLRO2X from Megger can.

Megger’s DLRO series of test instruments are all highly accurate and portable pieces of equipment. Megger has taken this to the next level with its two latest iterations: the DLRO2 and DLRO2X. These 2 A low resistance ohmmeters are handheld instruments, providing you with relative high output, accuracy, and repeatability in a compact, handheld design that fits easily into a toolbox and can be used in tight and hard-to-reach spaces. What’s more, both instruments come with a noise rejection mode for improved accuracy and a ‘Difference Meter’ for quick data comparisons.


For turbine-specific tests, Megger’s DLRO2X is the best choice, with the KC-C series long test leads giving you the ability to easily address the challenges of turbine testing.

The DLRO2X can deliver up to 2 A of test current, surpassing the industry standard of 1 A for wind turbines. This instrument also has a dedicated test mode that can measure up to 3.2 Ω while eliminating complicated setup errors.


Tests more than just wind turbines

The DLRO2X is the ideal tool for when you need to repair a wind turbine wing, or for when a maintenance team is testing lightning protection. However, it can also be used by aerospace engineers testing for lightning, static protection, and ground bonds. Not only that, but it can also be used at any number of large industrial sites, in renewable energy applications, in railway maintenance, in manufacturing, and in the oil and gas industry.

The DLRO2X is excellent for these applications because it can store test results by Asset ID, saving full result details for permanent record keeping and for preventive/predictive maintenance. These test results can be shown to clients and oversight authorities and can be directly entered into certifications.

The DLRO2X can also be used to trend operational and environmental effects over time to keep maintenance ahead of deterioration and failure.

The versatility of the DLRO2 and DLRO2X show why Megger’s DLRO family have become the instruments of choice for many power utilities and industries around the world, providing them with confidence in their critical connections.