Estimated reading time 16 minutes, 36 seconds.
Photos by Lloyd Horgan
Providing electrical power across the U.K. is far from a simple task. Since its creation in 1928, the grid that carries electricity from the point of generation to the point of use has been growing, shifting, and morphing to keep pace with both demand and geography.
While National Grid takes electricity from power stations and transmits it at up to 400kV (400,000 volts) across the whole of the U.K., it is the Distribution Network Operators like Western Power Distribution (WPD) that must bridge the gap between that high-voltage grid and the customer.
Robin Tutcher is the accountable manager at WPD’s Helicopter Unit: a specialist team that operates the company’s helicopters at treetop height for up to five hours every day. Their job is to survey, inspect and report on the condition of almost every piece of equipment involved in getting electricity from the grid to the end user.
“The customer is at the heart of everything we do,” explained Tutcher. “And given the size of the area we cover, we effectively have over 23 million customers.”
The team’s beat covers 21,600 square miles (56,000 square kilometers) from the far southwest corner of England, across Southern Wales, and up to the east coast. But it is the sheer number of towers, poles and transformers — known to the professionals as “assets” — that provides the challenge.
Walking the line
With almost every property in the country connected to electricity, looking at a map of the distribution network highlights the scale of the task.
While the high voltage distribution lines on large steel towers connect the main regions relatively logically, the smaller poles are scattered seemingly at random, with some circuits threading their way between large built-up areas, while other spurs run out to individual cottages in the middle of nowhere.
“The customer is at the heart of everything we do, and given the size of the area we cover, we effectively have over 23 million customers.”
“It’s a spider’s web — there are around 17,000 towers and 1.3 million wooden poles,” said Tutcher. “A defect on any of them could develop into a fault which presents a risk to the public, or a potential power outage.”
Each of these towers must be inspected every year, and the poles every four years. Using the traditional method, a foot and vehicle team can expect to cover about three miles (five kilometers) every day. By contrast, one helicopter can cover that distance in as little as 15 minutes. With such quick response times, the helicopters are often used to investigate faults where the precise location and nature of the defect is not known. It is little wonder that helicopters were being pressed into service almost as soon as they became available to civilian operators.
In fact, WPD’s Helicopter Unit began its life before the company itself. In 1963, while the British electricity infrastructure was still under national control, contractor-operated Bell 47Js flew linesmen to inaccessible areas to carry out repairs. With the privatization of the electricity sector from 1990, the companies that eventually became WPD modernized the helicopter operation that they had inherited (by then a mixed fleet of Bell 206 JetRangers and Eurocopter AS355 Twin Squirrels). In 2011, the unit transitioned to an Airbus Helicopters fleet with the purchase of two EC135 P1 variants, later supplementing them with two more, and adding a P2e in 2015. The unit is kept busy, as Tutcher explained.
“It’s a spider’s web — there are around 17,000 towers and 1.3 million wooden poles. A defect on any of them could develop into a fault which presents a risk to the public, or a potential power outage.”
“We inspect around 2,500 assets every day,” he said. “In the time we have operated them, we’ve flown over 27,000 hours on the EC135.”
Unsurprisingly, most of this flying is at very low level. An 11kV pole is only 25 feet (7.5 meters) tall.
“We will usually position just a few meters away from the pole,” said Dominic Brachet, one of the five pilots at the WPD Helicopter Unit. “You need to be able to see defects like cracks on the insulator, which are very small.”
Each asset will have around 50 inspectable items, from the placement of danger signage to the physical integrity of the pole, conductor, and insulators. However, this doesn’t mean that the helicopter will necessarily enter the hover. Seated in the front left seat, the observers are trained to conduct a full inspection at breathtaking pace, only needing to pause if an item isn’t immediately visible or a problem requires further investigation.
“We will try to keep moving,” said Brachet. “But we can hover or orbit if we need to go back for another look.”
Defects are logged by the observer on a touchscreen display as they go. The infrastructure needs to be constantly maintained as water ingress, vegetation growth, wildlife and even human interference can all cause damage.
“The primary inspection is a visual inspection,” explained Brachet. “We will place the observer so that they can assess the general condition of the asset and we’ve then got various sensors to add value to that. If we need to move away from the pole because of livestock or other hazards, then we will go to the sensors.”
Those sensors are housed on the left skid and feed into a customized mission system, all integrated by Babcock. On the skid’s leading edge is a TrakkaCam SWE-400 Quad from Trakka Systems. This allows the mission system operator (MSO) seated in the rear left of the helicopter to bring high-definition video, thermal or ultraviolet (UV) cameras to bear either manually, or by selecting a specific asset on the mission system map.
“The UV [camera] gives us the potential to detect discharge,” explained Scott Robinson, one of the MSOs at the Helicopter Unit. “Most of the time, though, we’ll be using the thermal camera to pick out hot spots.”
These thermal inconsistencies are not always indicative of a fault, but contribute to the overall assessment that the crew make about an asset. While on-task there is a constant flow of communication between the pilot, the observer and the MSO. Not only to safely navigate in close proximity to the wires, but also to aid each other’s wider situational awareness. It is often instinct that leads them to uncovering defects.
Robinson described how during a recent survey of a line, the observer’s eyes were drawn to another asset on a line that crossed over the one being surveyed. While the pilot repositioned the aircraft to allow a second look, Robinson corroborated the observer’s hunch with the thermal camera. Upon closer inspection, the crew discovered that a wooden pole had nearly been burned through by electricity from an 11kV line that had become earthed through the supporting structure.
The fusion of the various sensors and systems within the aircraft is certainly powerful, but arguably the most impressive piece of equipment on the WPD EC135 fleet is the Riegl VUX-1LR lidar (light detection and ranging) sensor. Utilizing a scanning laser, this pod is mounted on the rear of the left skid and continuously measures the distance to its surroundings to produce a georeferenced “point-cloud” — in essence, a three-dimensional model of anything within a swathe of space that the aircraft has flown over. While the LiDAR does not require in-flight monitoring, it produces around 1GB of data per minute for processing once back on the ground, so its usage must be managed to reduce redundancy. Once uploaded, an algorithm differentiates power distribution equipment from the ground and vegetation, and automatically searches the swathe for hazards such as tree encroachment or conductors sagging too close to objects or the ground.
The challenges of processing that quantity of information pay off once it is fused with other data from the company, as Tutcher explained.
“It’s a huge amount of data, and we are only just scratching the surface of what we can do with it at the moment,” he said. “For example, lines sag when they get hot. We can use the LiDAR data along with ambient temperature and line load to calculate whether it will still be a safe distance from the ground when the conductor is at its hottest or under its maximum load.”
Observer Pete Galvin said the system has also increased the crew’s efficiency, reducing the time spent trying to estimate the proximity of trees to power lines.
“From the aircraft, it’s almost impossible to judge whether a tree is one meter from the conductor or three meters away,” he said. “We will still report where we see a hazard from vegetation, but the lidar provides much better accuracy.”
In contrast to the sensors, the aircraft might be considered relatively low tech.
“Our aircraft are very manual,” said Brachet. “The P1s only have a stability augmentation system, but that makes them ideal for this job as it requires a lot of manual flying.”
The lack of advanced avionics or an autopilot also means a lower basic weight of the machine, which confers additional benefits.
“Given that we can operate down to 200 feet in urban environments, having an OEI (one engine inoperative) flyaway capability is essential,” explained Brachet. “We can take three people and all the kit, and still have the power and the maneuverability to operate safely at low level. There aren’t any other light twins that can do that with such a small footprint.”
Staying safe at low level is something that occupies a great deal of thought at the WPD Helicopter Unit. Most technology integrated into modern helicopters is designed to keep them as far away from the ground as practicable, but those avionics are less helpful when the job demands flying next to the wires and towers that the computers are telling you to avoid. However, at WPD’s frequently held safety meetings, wires are not considered the top risk. Alongside the inherent risk of fatigue when spending five hours a day in such a high-workload environment is the risk of getting too used to it.
“All your training as a helicopter pilot is to stay away from the wires,” said Brachet. “And yet our job is to get as close as them as possible. Actually, our main risk is complacency, because of the amount of time that we spend at very low level among the wires. It becomes very normal, and it could become easy to underrate the threats and/or hazards. There is a really heavy focus on the three-way communication, and everyone in the cockpit depends on one another to do the job and stay safe.”
Power to the people
It’s a job that the WPD Helicopter Unit is evidently energized about doing. And it’s sometimes hard to tell whether they are more excited about the undoubtedly thrilling experience of flying around the countryside at 30 feet, or the gadgets that they get to work with.
However, Tutcher said it’s the highly experienced and professional people working the aircraft and technology that allows the unit to work as efficiently as it does.
And the team expects it will only get busier in the future. With demand for electricity increasing, the maintenance of that infrastructure will be more important than ever.
One constant will be the WPD’s yellow helicopters and their crews, flitting between the poles and lines that connect cities, towns and villages, doing their bit to keep Great Britain’s lights on.