Re: grounding NST's

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Esondrmn@xxxxxxx 

Phil,

I have the low voltage wires that run out to my coil inside a thick 
walled pvc pipe then inside a square metal tube (rain gutter down 
spout).  The metal tube is grounded to the main RF ground.

Ed Sonderman

In a message dated 3/21/2006 8:14:23 PM Pacific Standard Time, 
tesla@xxxxxxxxxx writes:
So let me throw this *new* question out there:
     Even if you put the NST at the coil proper (in "high voltage
land"), you still have to run power (LV) wires to it. So how do you
ground things in case of a secondary strike to these LV wires?
     I'm running my LV wires in a flexible metal gooseneck conduit,
so a secondary strike will hit the conduit instead of the power
wires. These power wires include the "hot" to the NST from the
variac, the "hot" to run the SRSG from the phase control, the "hot"
to run the gap cooling fans, and a neutral common to all three.
Obviously, a secondary strike to any of these would be bad. But the
conduit will be a relatively large piece of tubular metal laying on
the floor, so I'm hoping it will have low impedance to RF ground and
thus protect the wiring inside.
     So far so good? But how do we bond it to ground? After all, a
short of any of the hots to the conduit will make the whole thing
hot, and a long piece of flexible metal conduit on a concrete floor
isn't necessarily going to trip any breakers or blow fuses to
indicate the fault. And it isn't safe, either, since the conduit is
connected at the panel end and therefore accessible during normal
(plugged in) operation. So we can't leave the conduit floating.
     One end (at the coil?) to RF ground? Remember, the theory is to
have low impedance to RF ground. But we have other concerns as well.
So other end (at the control panel?) to house ground? But then what
if it takes a streamer hit?
     And we can't bond it to *both* house and RF ground, because that
would be like tying both together. Maybe if the conduit was itself an RF choke?
     Perhaps the conduit should be nonmetallic up to the point of the
maximum expected reach of RF and streamer hits, but metallic and tied
to RF ground in the vicinity of the coil?

-Phil LaBudde