Something i've never puzzled out..
If I make a 14kv generator (and I have made a few high voltage generators in my time), I get constant corona from its unattached output.
Why do the 14kv power lines strung around town not do the same? I know sometimes there is just a little bit of discharge around power lines, i've seen and heard it. But thats not what i'm talking about.
Is it because the lines are fully terminated into a load?
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in
No, It has nothing to do with the load. It has to do with the electric field intensity. The field lines converge into conductor. The smaller the radius of that conductor, the higher the field strength is, because of this convergence. The lines get closer and closer together as they converge. Depending on air pressure, humidity and other factors break down of the air causing corona happens at a field strength of about a million volts per meter. That number is easily exceeded with small diameter wires or point sources whereas the power lines are much larger in diameter and never terminate in points that could cause such breakdown. Your bench top supplies have small wires with sharp ends that create the high field intensities. Note that very high voltage lines are always multiple conductors spaced a number inches apart for this very reason. It keeps the converging and increasing electric field in check within allowable limits around such lines. There are equations to determine the expected field intensity around a given conductor.
HV lines do have corona loss. As noted, big conductors and large-radius hardware helps.
Termination doesn't matter, just voltage gradient.
John
s in
ve
Function of the potential and btw 14kv static or DC is less than say
60 hertz. 14 kv. RMS, whre the peak potential is some 1.4 x 14 =3D almost 20 kv.! And yes one can sometimes hear that hissing/corona on 33 kv and higher lines.Thanks for the replies all. That makes sense.
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