I’m often asked why are there red, orange and white balls on some electrical transmission lines?
The following anecdote serves as a vivid answer to that question.
In 1987, while serving in the U.S. Navy, one of our HS-85 squadron crews stationed at Naval Air Station Alameda flew an H-3 Sea King helicopter through a set of 60,000 volt transmission lines on a hazy afternoon. The electrical lines crossed the North Fork of the American River between Weimar and Foresthill in the foothills of the Sierra Nevada east of Sacramento.
The momentum of the helicopter caused each of the three lines to snap in half. The first line — or phase — hit the helicopter’s ice shield that covered the intakes to its jet engines. The ice shield and engines are located just below the helicopter’s main rotor blades. As the power line snapped in half, the electrical arc that developed between two broken ends left a large, black carbon scorch mark.
The second line hit a little lower on the aircraft, right across the windshield. The external temperature probe built into the glass popped back into the helicopter’s cabin, hitting the air crewman in the helmet. The third line struck below the windshield across the nose of the helicopter and left the largest scorch mark.
Thankfully, the helicopter was able to fly to McClellan Air Force Base near Sacramento and landed safely. Nobody was hurt. However, the broken power lines left parts of Foresthill without electrical service until PG&E crews were able to re-string the lines across the river.
That brings us back to the colorful balls that hang on some transmission lines. The balls are called aerial spherical markers and make the transmission lines more visible to low-flying planes and helicopters. If you happen to be on a low-level flight, power lines can be difficult to see, especially if you’re flying facing the sun or other low visibility conditions such as fog, drizzle or rain.
The markers are often installed on wires near approach paths to airports or helicopter pads and where they cross rivers and canyons. The markers can also be found on guy wires for radio and television masts and meteorological towers, as well as other overhead spans like cable-car and communications lines. According to the Federal Aviation Administration, this aerial marker should not have a diameter less than 36 inches. Smaller spheres are permitted on power lines below 50 feet above the ground. When installed, each marker should alternate between aviation orange, white and red and be spaced not more than 200 feet from each other.
However, in some instances only one color is used to contrast the most with the surrounding terrain. The markers have a spherical shape because they have same amount of visibility from every angle. The spheres are hollow — composed of two hemispheres snapped together by stainless steel clamps — and are usually installed by aircrews in helicopters.
CLIMATE CHANGE TALK
I will be giving a presentation about climate change, and what it means for our local weather at the Santa Maria Public Library, 421 S McClelland St. in Santa Maria on Friday, Jan. 24, from 3 to 4 p.m. with time for questions afterwards. All are welcome, including families. This talk is sponsored by the Santa Maria branch of the American Association of University Women.
John Lindsey’s is PG&E’s Diablo Canyon marine meteorologist and a media relations representative. Email him at email@example.com or follow him on Twitter: @PGE_John.