500 pounds of ice; the added pressure on power lines this week
AUSTIN (KXAN) - After a couple of days of freezing rain and temperatures below 32 degrees, one of the main concerns is lingering ice and its impact on power lines. Ice can be heavy and cause lines to snag or snap.
Half and inch of ice can add 500 pounds of weight to a power line. According to the Omaha Public Power District, on a 920 foot long transmission line, that much ice will cause the line to sag four feet lower than normal.
Make that 3/4 an inch of ice and it will cause a power line to sag six feet. An inch of ice will cause a power line to sag nine feet and make it 12 feet with slightly more than an inch of ice.
One of the main issues with ice forming on power lines is that it freezes in a teardrop shape. Why is this an issue? The wind.
When strong winds hit the lines, that teardrop shape causes the line to become less aerodynamic. The line will act sort of like an airplane wing. It will then begin to flop around in the air. This is called a "gallop".
Power companies tie twisted wire or metal pieces to the power lines to help prevent galloping.
According to the Omaha Public Power District, older power lines are designed to handle half and inch of ice and 40 mile an hour winds. Some newer lines, however, can handle over an inch of ice and 90mph winds.
Austin Energy hasn't reported many downed power lines because of ice at the time of publishing. They have said that trees falling on lines have been the primary cause of downed lines. Ice can increase a tree branch's weight by thirty times its normal weight.