3 ms·
#5 bothers me. There is no technical reason that a downed power line should start a fire. As far as I know, a certain amount of energy will be more or less un
by amluto 3y ago
#5 bothers me. There is no technical reason that a downed power line should start a fire.
As far as I know, a certain amount of energy will be more or less unavoidably discharged when a power line hits the ground: the power line has some capacitance to ground, and it has a voltage (which varies with time) relative to ground, and the stored energy (1/2 C V^2) isn’t going to just disappear. This isn’t all that much energy.
But there is no real reason that the power station needs to keep delivering more power to an arc after the capacitance discharges. Avoiding it is somewhat complicated, but the technology is available off the shelf:
http://www.swedishneutral.se/main.php?name=gfn http://www.swedishneutral.se/main.php?name=gfn
IIRC some Australian customers have tested this system by intentionally dropping a live power line onto dry grass, and nothing catches fire!
- notatoad 3y agonot necessarily to the ground, a power line going down could short with any number of structures, or other power lines. i've seen a grass fire start when a bird touched its wingtips to two lines on the same pole, and the smoking carcass hitting the ground was enough to ignite it.
- amluto 3y agoA short to a structure is likely to be a ground fault, and it will trip an RCD, and the arc current and energy can be controlled. A short to another phase wire can happen, but it’s less common.