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Re: Ground strike currents and time...
Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
Would you like to try a 300 MHz scope?? Its analog with no storage,
but it might reveal something more.
Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
I got to looking at currents involved in ground strikes. Apparently
the current is real high and the time is real fast in order to drain
the secondary so quickly. But, How high and how fast?
I tried a Pearson 101 and 110 current probe side by side on the
ground wire from the strike target for just a little 3.7 inch
108,000 volt spark from the top terminal of my SISG.
The 4MHz #101 probe just sort of "misses it all". The 20MHz 110
sees something, but it is pretty garbled. The cores just don't
react to super fast currents...
So I thought about Rogowski coils... But from the above, we are
looking at like 50,000 A/uS signals and Rogowski Coils just don't do that.
So I made the fastest Inductive current loop I could with the parts I had:
It's just a loop of wire and a low inductance 50 ohm resistor on a
50 ohm BNC cable. The other end of the cable is also terminated
into 50 ohms. This is the signal:
40V at 10nS rise times!!! That is the limit of the scope
now!!! And the real signal is obviously "faster still"...
That puts the current pulse in the range of 10 - 20 nS and the
current in the 1000 to 2000 amp range!! For a 108kV 3.7 inch spark
off a 31.1pF toroid!!! Goodness only knows what a 5 foot streamer
to ground is =:O The streamer resistance is roughly 100 ohms in that case.
The peak power for a few nS is over 100,000,000 watts!!!! For
just a "little" spark...