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Danger! High voltage!
What’s it like to repair a live powerline from a helicopter? We find out from the pros.
By Carrie Connolly
Fort Wayne Reader
During the summer of 2003 the northeast corridor was hit with a blackout of enormous proportions. At 3pm elevators, subways, traffic lights, and your favorite daytime soap all shut down as the lights went out throughout the northeastern United States and Canada. Those of us who still had electricity watched thousands of New Yorkers stream out of offices into the streets of Manhattan.
Terrorism was the first thought that sprang to mind for many people on that hot August afternoon. Fortunately, the truth was less sinister and more akin to a car owner running into trouble after ignoring scheduled maintenance on his vehicle. What sent a good chunk of the Northeastern grid down for the count on August 14, 2003 was, of all things, a tree limb contacting a high voltage power line. It set off a domino effect where various lines tripped out, shutting themselves off one after the other in a well-designed protective measure, and the lights went out from New York to Detroit.
Regular vehicle tune-ups can be put off until they are missed and the engine makes a funny noise or a tire blows on the highway. The same is true with power lines, especially the extra high voltage lines that tower head and shoulders above the rest. These giants are the hard working backbone of the electric grid in the United States and Canada. They transmit power from numerous generation stations to the smaller distribution lines throughout neighborhoods and towns that in turn deliver the power each business and home needs for our many electrical needs. Part of what keeps these EHV lines humming is helicopter-based inspection and maintenance.
With the year anniversary of the blackout just past us, we had a chance to catch up with the aerial crew from Agrotors, Inc of Gettysburg, PA who was the first to inspect the damaged line from a helicopter. Although this job at First Energy was strictly inspection, Agrotors’ Powerline division performs live line maintenance on high voltage transmission lines through out its northeastern U.S. territory. Daniel “Spider “ Lockhart performed the detailed comprehensive inspection of First Energy’s lines once the power was restored.
So, what’s it like to repair an incredibly powerful, high voltage, live power line from a helicopter?
Spider explains what’s called “bonding-on” for the layperson. “First, we put a platform on the skids of the helicopter. Next a wire is attached from the platform to the body of the helicopter. Then hardware and equipment are loaded onto the platform. The lineman and pilot put on hot suits with hoods. Finally a steel wand called a hot stick is attached to the platform.”
A hot suit looks very much like a burlap sack fashioned into a flight suit. Spider explained, “These are to take and distribute the flow of electricity over them as if they were working in a steel cage. This was a theory developed in the late 1880’s by Michael Faraday. He theorized that if you could suspend a man in mid air inside of a steel cage electricity wouldn’t bother him.” What Spider takes for granted after years of working around energized lines is the distinct sensation of pins and needles that one feels while wearing the hot suit. The electricity is literally buzzing all around you.
The pilot takes off with the lineman securely attached to the platform and maneuvers the helicopter into position hovering next to the line. The sequence continues as the lineman prepares to bond on. The lineman touches the wand to the wire and as a result energizes the aircraft. Once energized a bond wire approximately 5 foot long is clamped onto the wire. The length gives the helicopter a certain amount of movement with out pulling off the line. It is a breakaway clamp so that the helicopter can pull off quickly without endangering the crew or the line. The wand is removed and the lineman begins his work.
Bonding on is a precise operation that requires intense concentration from the pilot and the lineman team. But as Spider explained, the phrase,” be quiet I’m concentrating” has little meaning in the charged atmosphere of power line maintenance. “The noise of the helicopter is overridden by the arcing taking place whenever the platform wand is brought into contact with the conductor. Until the wand is physically touching the conductor wire, the noise continues. Once contact is made there is a moderate to loud humming noise. It sounds like a noise you hear at a power transformer station. I describe it as the turning of the generator turbines at a power station, noisy.” The noise is something like the sound of the light saber in Star Wars; hard to describe but unmistakable when you hear it.
The arc is the burst of light created by the transfer of electricity. Electricity streaking between the wand and the wire is incredible. Viewed from the ground the arc appears to shoot from the lineman’s hand like lightning from an electrified comic book hero. For an Agrotors Powerline crew that’s just part of bonding on so they can get to work.
Up in the air with the blades whirling overhead, getting to work is a delicate aerial dance between the pilot and the wires. If he doesn’t get close enough the lineman can’t bond on but getting too close to the wrong wire can cause a flash-over in which electrical clearance is violated.
Spider explains electrical clearance as the minimum distance an object can be from an energized power line to not have the possibility of the electricity arcing over from the line to the object. If the electrical clearance is violated, the line will de-energize, like what happened with the branch that caused the whole problem in the first place.
But what would happen to the helicopter and the people in it? “If we violate the electrical clearance, we have provided the electricity a quick path to ground,” Spider says. “It will dramatically increase the current flow, immediately creating extreme heat. This in turn will melt metal and burn anything in its path to ground.” Line work is clearly not a do-it-yourself project.
The market for this highly focused method of repairing and maintaining extra high voltage power lines is only expected to grow. Publicly traded electric utilities are pushed by shareholders to reduce costs in an effort to increase share price. Cost savings are often attained by scaling back or delaying perceived non-critical projects such as yearly tree trimming or routine inspections.
A vehicle owner experiences the same false sense of security after skipping an oil change; after all the car still drives fine. The utility world is not much different, the lines keep humming and this benign neglect is rewarded through higher earnings. Consumer demand for affordable electricity drives operators to push the maximum voltage through these transmission lines to an ever growing array of smaller distribution lines that feed the suburban sprawl which is partly behind this increasing need for more power. Combine these two variables with line sag, an issue rarely mentioned outside of the power industry, and you have a recipe for future power outages just like the one on August 14, 2003.