Crawling along a simulated overhead transmission line shield wire at roughly 1 mph (1.6 kmph), a robot called “Ti” is moving us closer to realizing the promise of the smart grid. Ti is fully armed with an array of remote-sensing technologies, including LiDAR, high-definition cameras, RF sensors, an electromagnetic interference detector and GPS. This mechanical inspector is collecting critical data on the state of the transmission grid.
Today, Ti is crawling along a line in EPRI's High-Voltage Test Laboratory in Lenox, Massachusetts, U.S. In the future, Ti might be crawling along energized lines at your utility.
Ti, one of EPRI's more complex attempts, is intended to be a permanent fixture on transmission lines, making two circuits of an approximately 80-mile (129-km) loop per year. Because Ti will draw power directly from the line, it is expected to have a life expectancy on the order of a decade, although routine maintenance will be performed every two years.
When fully operational, Ti will be on the job 24/7, 365 days a year, replacing both ground patrols and flybys, and providing more and better quality data. With its suite of sensors, the robot will be able to pick up subtle abnormalities often missed by living and breathing inspectors, and, as such, can be considered a transmission line inspector itself.
Ti's suite of sensors offers many features:
High-definition visual and infrared cameras that not only will determine clearances between conductors, trees and other objects in the right-of-way, but also will be able to compare present and historical images of components to spotlight dangerous changes.
A Light Detection and Ranging (LiDAR) sensor that measures exact distances, such as conductor height and position, vegetation height, nearby structures and obstructions in the right-of-way.
An electromagnetic interference detector that will collect data on discharge activity, such as arcing or corona.
Bringing It All Together
A communications system that will pick up and relay data to system operators from both the on-board sensors and any number of RF sensors (lightning, vibration, leakage current) along the transmission line right-of-way, providing a real-time assessment of conditions and actionable information on components such as insulators, conductors and compression connectors. Histograms will be available to help system operators enable assessment and set limits that trigger maintenance.
A weather station to measure temperature, humidity, wind speed and direction, and barometric pressure.
A microphone to listen for line audible noise.
A GPS and inertial tracking system to identify both the robot's location and speed, as well as the location of existing and potential problem areas and components along the ling.
Of necessity, in addition to all its “smartness,” the robot is designed to be very agile. While its primary home is a transmission line shield wire, it can glide by structures and travel over armor rod splices and other obstacles, such as marker balls, relatively easily by automatically disconnecting itself from the shield wire, moving onto a pre-installed bypass system, then re-engaging the shield wire to continue inspecting. Further, if an outage occurs farther down the transmission line, the robot can be accelerated up to 5 mph (8 kmph), in many cases getting to the outage site to assess the situation before field crews arrive.
Composite insulators can flash under due to moisture ingress, then dry out again to give the appearance of a good insulator. When investigating the cause of outages, Ti can be sent to the flashover location (typically within a few hours) and also monitor subsequent activity when the line is re-energized. The robot can do a detailed visual survey to find flash marks or the carcass of a bird before the coyotes take it away. It also can sit at the outage location and do some monitoring for a few days to identify intermittent causes.
Using a smart phone, system operators or line workers can control where Ti goes, how long it stays there and what is does in the process. If Ti is probing a transmission line in some truly remote regions of the Rockies or Southwestern desert, for example, then controllers could operate the robot using satellite communications. Of course, if Ti encounters severe ice, a broken strand wire or some other obstacle that prohibits movement, it is smart enough to stay put and call for help, just like any other commuter heading to work.
We, indeed, have a lot of work yet to do to make our power grids truly “smart.” Sensing devices like our industry robot, Ti, will be one of the many as we look to truly understand and appropriately respond to the health of our network.
Andrew Phillips (firstname.lastname@example.org) is the director of transmission and substations research at EPRI.