Wednesday, April 18, 2012

Why do power lines buzz?

            Most of the time while roaming around Bangalore I do remember a funky statement which I read in news paper article “people who spend half of their income in food/apparels and rest on to digest it” are so called Americans aka white color jobs. Now we Bangaloreans have gradually adopted it. So I have a hobby to go walk upon my dinner only if I felt it was heavy but not regularly. Cool breeze! It was really calm environment without any noise of honking. Especially walking on Bangalore fly over you could enjoy the night city view. I’m sure at least that moments we been open minded like having felt out of nest and imagine how differently our mundane in the city goes on and on…..
In that calm was able to hear some humming noise and it was from the high tension cable passed over there. What is that? Way back to school days physics class …. Discharge of electricity! Basically we're hearing corona discharge. The strong electric field at the surface of a high voltage power line conductor ionizes the nearby air and causes a partial breakdown of its dielectric strength. The audible noise we hear is caused by the local sound-pressure level changes due to the individual corona discharges that in turn occur as part of electron avalanches. During wet weather the noise level is much higher due to the presence of drops of water on the underside of the conductors. These weather drops break up and the departing portions cause discharges in the water-to-water gap.
The predominant frequency of the corona hum noise is double (100 Hz or 120 Hz) the commercial frequency.

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