DIYbanter - View Single Post

Bud--

wrote:
In alt.engineering.electrical Timothy Daniels wrote:

| As always, "w_tom" ignores that the high voltages that short out
| "3 miles of sky" will short out the underground power lines which
| enter my building and buildings all over America. Anything able to
| leap "3 miles of sky" will leap the fraction of an inch between the
| power lines and the earthed metal conduit. What is left will be a
| much lower voltage spike that can be handled by the average
| "plug-in protector".

It does not always make the 2nd leap to ground. There is not always a metal
conduit available. I've seen such strikes.

With no service panel suppressor it is well accepted that at about 6kV
there will be arc-over from bus to enclosure for (US) circuit breaker
panels. While arcing, the voltage will be hundreds of volts. Since the
panel/system ground is connected to the earth electrode (US) most of
surge energy is dumped to earth.

If talking about a plug-in suppressor, Experiments by Martzloff (the
idiot/member-of-the-IEEE) show surprisingly little energy reaches the
suppressor. Circuit impedance greatly limits the current, and thus
energy. Surprisingly, there is more energy at the MOV for lower surge
currents (on short branch circuits) because the MOV can hold the panel
voltage below the 6kV breakover voltage. With up to 10kA surges, the max
energy at the MOV was 34J with most cases below 1.2J.

--
bud--