An AAIR drone or unmanned aerial system (UAS) begins turbine blade inspections at a Texas wind farm. According to Navigant Research, cumulative global revenue for turbine UAS sales and inspection services is expected to reach nearly $6 billion by 2024.

By Grant Leaverton, Vice President & General Manager
Advanced Aerial Inspection Resources (AAIR)

Commercial-grade drones are proving to be more than a novelty. Advanced optics, cameras, battery life, data analytic systems, and the ability to remain stable in strong winds means these machines can provide a valuable service at wind farms.

Drone inspections of turbine towers and blades can save a wind-farm owner time, cost, and safety risks over rope-based inspections. Now drones are proving even more useful at wind site, and the safer option for aerial inspection of power lines and transmission infrastructure.

The commercial drone industry is evolving at a rapid pace. Each change or advancement means application of Unmanned Aircraft Systems (UAS) can enter another market and provide a service that typically cuts costs and enhances safety. To date, UASs have provided service in industries such as military, security, search and rescue, construction, agriculture, real estate and land surveying, insurance, and others.

The wind-power industry is no different, and many wind-farm owners capitalized on drone use early with unmanned inspections of their turbines. In some instances this eliminated the need for traditional climbing, and rope-based or platform inspections by wind technicians. UAS have led to significant operations and maintenance savings and, most importantly, reduced safety risks at many wind sites.

While adoption of UAS is increasing, so are the machines, which is leading to new ways and reasons for using them. It is also leading to new techniques and skillsets required for proper and safe drone operation. For example, in the wind industry, turbine and blade inspections are no longer the only useful purpose for UAS. Wind-farm owners are starting to employ them for aerial inspection of power lines and transmission interconnects.

As the reasons for using drones evolve, it is imperative to keep track of the regulatory framework governing their use and maintain skills to operate the new and upgraded machines.

Turbine blades to transmission lines
New drones are entering the marketplace every week. Advancements in autonomous flight, sense-and-avoid features, and feature recognition technologies are now available in many off-the-shelf units.

A commercial-grade UAS, handled by an experienced operator, can provide safer and typically higher-resolution visual assessments than ground or rope-based inspections. For this reason, drones are increasingly becoming the method of choice for turbine blade inspections at wind farms and even for comprehensive aerial inspections (CAIs) of transmission assets.

Drone sensors are getting smaller and smarter. At the same time, the data sets drones are capable of collecting remotely are only getting bigger. This benefits some users who can attain greater use and data, employing drones for more than one task.

The wind industry is a prime example where drones have increased their reach and value. Wind-farm owners are now able to employ drones for tower, blade, and transmission inspections. This is no small accomplishment: where regular blade inspections might prevent an unexpected failure that could bring down a single asset, failure of a wind site’s transmission line could potentially bring the entire park offline.

Today’s commercial drones are ideal for performing comprehensive aerial inspections (CAIs) of transmission assets. A CAI is a highly detailed inspection meant to spot the smallest of defects, such as loose or missing cotter pins on a conductor attachment. UAS-driven CAIs can even detect hairline cracks in critical welds.

This type of inspection reaches far beyond basic aerial patrol and yields a much higher probability of defect detection. The detail and data obtained lets site owners determine the overall health of their system and make early O&M and repair decisions to prevent unplanned outages. In addition to the higher quality of data provided by UAS, drone inspections eliminate the need for helicopters and climbing patrols and provide a safer and more cost-effective option.

Routine transmission-line inspections are just one application where drones are proving useful at wind sites. Storm damage assessment is another. Mother nature can wreak havoc on transmission lines. This is especially true at wind farms, which are purposely situated in high-wind regions. Whether it is 200-plus mile-per-hour winds or an ice or lightning storm that hits a wind site, preventing failure is not always an option. A post-storm assessment is routine O&M protocol at wind farms, and drones can also make this process simpler, safer, and less costly.

A CAI is a highly detailed transmission line inspection meant to catch the smallest defects, such as loose or missing cotter pins on a conductor attachment or hairline cracks in critical welds.

For example, downed lines present unique hazards for repair crews, and the ability of UAS to bypass these hazards and provide a real-time view of a work area is of high value for linemen. It lets a repair team identify hazards before workers enter an area and helps them decide on the right tools and equipment for the job. This insight keeps workers safer and expedites the restoration process.

Rule changes
As regulations change, the use of UAS for transmission line inspections will likely become more common. As it currently stands, drones must fly only within visual line of site (VLOS) of the operator. This limits the range of flight to 1,000 to 2,000 feet on average, depending on how large the UAS.

It is expected Federal Aviation Administration (FAA) regulations will change and eventually let beyond visual line of site (BVLOS) operations of UAS. When this happens, users can add long-range aerial patrol to the list of viable uses for transmission line inspection by drones. This provides for a much higher-level inspection of the asset, and is a critical function of managing a right-of-way from possible encroachment and vegetation management.

The FAA’s recent Part 107 “small rules” release moves the industry a step closer to long-distance flights. Part 107, which takes effect August 29, 2016, permits commercial flight of drones weighing less than 55 pounds, at a maximum speed of 100 mph, below 400 ft. AGL (above-ground level) during daytime (and as long as they remain within the line of sight of the operator). Although the new rule does not permit BVLOS operations, it opens discussions by stating that consideration of certain waivers of operational restrictions would take place if the operator could prove an equivalent level of safety.

Current rules state that drones must fly only within visual line of site of the operator, which limits flight range to about 1,000 to 2,000 feet. It is expected FAA regulations will eventually change so users can add long-range aerial patrol to the list of viable uses and transmission line inspections by drones.

This means that the line of site restriction may be waived in certain situations. Experts in the utility industry are predicting that certain BVLOS waivers for overhead line inspection will be granted within the next 12 months.

Part 107 has another significant ruling as well. The regulation eliminates the once-required FAA pilot’s license to fly a commercial drone. A UAS pilot certificate is still required but much easier to obtain and can even be done online. This change is significant because it lowers the qualification standards for drone operation and opens the door to new talent.

This may seem unfavorable except that the original regulations were extremely prohibitive to would-be drone operators. Benefits of the new rules include reduced costs to get licensed for drone operation and increased operational flexibility for owners. There are other minor changes in the regulations that are available on FAA’s website.

The advancements in drone capabilities and new regulations for commercial drone use mean it is imperative for users to keep up with the ever-changing UAS industry. These changes also open the door for new industries to take advantage of the many potential benefits drones can offer, and for older industries to research new uses for UAS. As the capabilities of drones advance and the opportunities increase, one thing remains clear, drones are here to stay. 

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AAIR is a conditional assessment firm that uses drones to provide aerial inspections and asset management to the wind and utility industries.

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Paul Dvorak / Editor

Quadcopters and similar remote-controlled air vehicles have been available for years. YouTube is full of hobbyists flying quad-copters with GoPros showing the world what their neighborhood looks like. Entrepreneurs immediately saw the potential: inspect wind-turbine blades and other not-easy-to-inspect facilities using high-resolution cameras mounted on Unmanned Aerial Vehicles, UAVs. Of course, the whole point of doing so is to inspect more blades in a shorter period and chip away at wind-farm operating expenditures.

The AAIR drone will carry a camera capable of 25-megapixel images. The frame is wider at one end to accommodate an unobstructed view for the camera.

Until recently, a reliable blade inspection was done by a wind tech hanging from a rope, and he might take six hours to inspect one turbine. An alternative might have been to use a crane or man bucket. But both options are expensive. And ground-based cameras need wind to manipulate the turbine rotor for a best shot. Even a telescope on the ground does not yield good imagery.

The basics and then some

Drones, for our purposes, are really UAVs capable of carrying high-resolution images and video, and soon sensors that might spot a range of problems in wind-turbine blades.

AAIR’s Grant Leaverton, the new breed of wind tech, flies a drone for a wind turbine inspection. He says that blade inspections are just the first of the services drones will provide to take cost out of wind farm O&M.

A wind technician with his new robot buddy will perform the inspection job, all three blades with guidance, in about 90 minutes, say technicians with WindSpect,

A wind technician with his new robot buddy will perform the inspection job, all three blades with guidance, in about 90 minutes, say technicians with WindSpect, one company flying drones. At the end of a flight, the technician will remove an SD card from the drone and put it into the company computer for a detailed report on what the inspection found. Specialized software has the capability to recognize flaws in the blade, mark their location as meters from the tip or ground, and identify the type of flaw, such as surface impact, cracks, or leading-edge erosion and more.

The WindSpect drone will capture high-resolution images and video during inspection flights.

“We will release Version 1.0 of the AirFusion Wind Edition software mid-summer,” says AirFusion CEO Dennis Chateauneuf. He said that the solution has generated an extraordinary amount of interest and “dozens of productive conversations are taking place with owner-operators, wind-turbine manufacturers, and many of the service companies with a great deal of interest coming from Europe and Asia.”

“We are largely agnostic about the drone used in the inspection. Many platforms can carry the appropriate sensors, and meet the overall need for accurate flight, durability, and so on. We will suggest a variety of UAV choices that will be technically suitable to the task,” says AirFusion Chief Strategy Officer Kevin Wells.

An enormous advantage is that the software’s accuracy improves over time. “The more images it ‘sees’ and learns from, the better the end result. For example, if after using the AirFusion platform a company has archival footage that spans two or more years, the system may be able to indicate there is a crack in this location today that was not present a year ago. Was there a precursor we might have picked up to predict this problem? It could be something subtle, perhaps something under the surface of the blade. This temporal analysis is another benefit we will exploit to constantly improve the performance of the software. The system is smart today, but will become smarter over time,” says Greg Pepus, AirFusion’s SVP of Software Development.

Collision avoidance

UpWind Solutions, an independent operations and maintenance service provider for the wind industry, recently added blade inspections using UAVs to its services by partnering with SkySpecs. Both companies say the partnership will deliver high-quality images for reports, improving safety and reducing inspection costs.

SkySpecs says it provides an advanced UAV for easy completion of turbine blade inspections. What’s more, SkySpecs’ collision avoidance technology lets technicians with minimal flight training or experience conduct high-quality inspections from only a few feet away from the blade without risk of collision.

UpWind said a few other benefits of the technology include autonomous flight software that lets the company rapidly complete high-quality, low-risk inspections. High-definition images and video are produced for reports and to let users zoom in closely to problem points identified throughout the inspection. A technician can take control over the automated UAV any time to capture more images of a specific blade area.

25-mega-pixel images

Grant Leaverton, General Manager with UAV inspection company Advanced Air Inspection AAIR, has readied 6 and 8-rotor UAVs that can carry 25-mega-pixel cameras aloft, and conduct research on several other useful diagnostic sensors.

The blade image from AAIR shows sever trailing edge damage. The image is typical for those captured by drone carried cameras.

“Typically the more rotors the more stable the platform. Weight extracts its cost in flight time. The heavier the payload, the shorter the flight time. But what we can do now is the tip of an iceberg for industrial infrastructure inspections. For the time being, most will focus on the high-resolution inspection of blades, nacelles, and towers — the places that are not easy to reach,” he said.

The number of blades examined in a day depends on the type of inspection, “When focused on a particular feature, say the leading edge and looking for erosion, you can do 12 to 20 blades in a day depending on the height of the tower. But that is better than two per day with rope access or cranes. And if you want to cover every inch of blade, that of course takes more time,” said Leaverton.

SkySpecs drone got airborne at the AWEA WINDPOWER 2015 Conference.

Another plus: You can fly the UAV regardless of where the turbine rotor stops. “This is more of a personal preference issue. However, because we are taking pictures, we get the best lighting for photography with the blades pointing straight down. However, in a no-wind situation, you cannot turn or position the rotor but you can still do the inspection,” he said. The platform is easier to fly without wind.

While visual inspections are the obvious application, other sensors are getting auditions. One intriguing technology is infra-red. “If you are looking for internal defects that are barely subsurface, an infrared camera might reveal them. That’s the theory. Also, if the blade has delaminations, subsurface cracks, or wrinkles in the fiberglass, that will show up as a heat signature. The thinking is that such flaws will have to be close to the surface to show up, and depend on the sensitivity of the equipment,” explained Leaverton. “It’ is an interesting potential because internal defects are huge issues for owners. The defects are hard to detect and they can propagate and turn into catastrophic failures. So detecting internal defects will be a curious proposition.”

A typical screen from AirFusion shows a portion of an inspection report possible from a Windspect flight. Developer Greg Pepus says the software will provide analysis of images such as severity of damage and location indicators. IR cameras may soon provide other possibilities, such as internal blade damage.

There is also more around the wind farm that needs inspection. “A lot of wind-farms owners operate their own transmission lines and substations. The visual inspections are a big deal, along with infrared thermal imaging for detecting hot spots or broken insulators. Another sensor to detect corona discharges would indicate broken hardware such as insulators.”

For utilities, keeping the right-of-way open is critical. For example, it’s important to keep transmission lines free of vegetation, trees over lines, overgrowth, and encroachment. Infrared is also good for looking for vegetation.

Ideas for improvement

Leaverton suggests improving a few things. For example, knowing where one picture out of hundreds came from is important. “Before starting an inspection, you must know which blade you are looking at, and identify the hub. So before the inspection, we find a way to ID the blade. We use a light board on which we write, Blade 1.” This issue is handled different from company to company.

Because where you are on the blade is also an issue, industry guidelines would prove useful. “A problem is that blades have no reference lines on them. Some have markings and others have lightning protection that serves as a landmark. In absence of reference marks, we use geo tagging in each photo so we know the altitude at which each picture was taken. That works best when the blade is straight down.

Measuring defects is also more art than science at this time. You have go on the relative features of the blade and understand the width of the frame. “It’s necessary to maintain a steady distance from the blade so you know, for instance, that each frame represents one meter. But that is imperfect so in the report, we relate damages with respect to each other rather than absolute measurement.”

When a pilot of the UAV has a video screen to see what UAV is seeing, “You get a first person video perspective of what the camera sees. When using a two-man crew, one might use goggles, so both would look at a blemish and discuss the problem. Once you get the picture on the computer you can look even closer because the high resolution allows zooming in on the area of interest,” he said.

In the end, the goal is to better allocate repair dollars. “Wind-farm owners won’t fix everything, but if we can identify the worst of things, that is useful. And that is a value-add,” said Leaverton.

On the horizon

More sensors in development might identify water in the blade or spot where the laminations are coming apart, or to carry RFID sensors if it is necessary to do some sort of inventory management.

“We are hard at work evaluating a wide variety of sensor types in our lab today,” said AirFusion’s Chateauneuf. “The ultimate goal is to be able look under the surface, to look inside the blade. So we’re working on that and other sensor-based techniques to add functionality for future releases like truly automated flight control where the UAV effectively “flys itself” around the blade to collect the data automatically.”

Later, an automated flight control feature will let the drones fly themselves in a pattern around the blades. This is subject to FAA regulations because flight control is one of those things that are only done with permission. “But we are working on that because of its great potential,” added Wells.

Fly-it-yourself is another possibility said Leaverton. “If a wind farm wants to buy a UAV, we’ll be glad to provide flight instructions.”

In addition to inspections, it’s not hard to imagine the drones doing cosmetic repair in a year or two and more serious repairs after that. This is all good news for the wind industry because the speed, accuracy, and detail will shave more off O&M costs making wind-generated power all the more competitive with other generators of electricity.

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