Ground strike currents and time...

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi All,

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.

http://drsstc.com/~sisg/files/scantesla/DanQ-1.JPG

http://drsstc.com/~sisg/files/scantesla/DanQ-02.gif

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:

http://drsstc.com/~sisg/files/scantesla/DanQ-07.JPG

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:

http://drsstc.com/~sisg/files/scantesla/DanQ-08.gif

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...

Cheers,

	Terry