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Re: [TCML] X-ray cable best practices for feeder cable

Hi DC, all, 

I am not going to try and say that the resonance 

won't affect the x-ray cable when used as a trans- 

mission line from the pole pig to the base of the 

coil, as it's pretty obvious from the statements of 

others far more veteran in this subject matter than 

myself that it very well could. However, I have per- 

sonally never had this problem with my x-ray cable 

transmission line and I'm sure many of you remember 

my bringing my Green Monster coil to the 2007 

Cheesehead Teslathon and firing it off. I ended 

up using DC's "Big Bruiser" power supply to po- 

wer it, as my power suply/control cabinet weighs 

over 1000 lbs. and I do not have access to a fork 

lift truck. At the Cheesehead T'thon (as I do at 

home with my power supply), I ran the power from 

DC's Big Bruiser power supply to the base of the 

Green Monster via that single ~ 60 ft. strand of x- 

ray cable, running the "hot" end through the central 

core conductor and the "return" through the outer 

mesh shielding jacket. I HAVE, however, had an 18 

kV distribution arrestor one time and more recently, 

the .1 uFd, 50 kV rated Hipotronics pulse cap (yep, 

the primary cap) :^( to fail on me, but never the trans- 

former. Fortunately, I had another .1 uFd, 25 kVAC 

rated Plastic Capacitors pulse cap as a standby 

to replace the dead Hipotronics cap (thanks Bill 

Limeaux) ;^). Maybe this resonance issue IS what 

took out these secondary components.?? Maybe 

these components "sacraficed" thereselves for the 

pig, as that was the intended purpose of the distribution 

arrestor, anyway (safety gap substitute). Was not in- 

tending on "sacraficing" the Hipotronics cap, though ;^(( 

Comments, anyone? 

David Rieben 

----- Original Message ----- 
From: "DC Cox" <resonance@xxxxxxxxxxxx> 
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx> 
Sent: Tuesday, January 6, 2009 1:07:18 PM GMT -06:00 US/Canada Central 
Subject: Re: [TCML] X-ray cable best practices for feeder cable 

Resonance can be quite wonderful, or, as Phil explains in his examples, very 

Resonance in your HV feeder cable is not something you want, so I avoid 
using any feeder cable that is coaxial in nature, ie, has a ground 
shield around it.  X-ray cables were designed strictly for DC power 
transmission and not for transferring AC power. 
Been there, done that ----- and it cost me a pole xmfr! 

Dr. Resonance 

On Mon, Jan 5, 2009 at 9:25 PM, <FIFTYGUY@xxxxxxx> wrote: 

> In a message dated 1/5/09 10:37:26 P.M. Eastern Standard Time, 
> sparktron01@xxxxxxxxxxx writes: 
> >I am now in the world of "Power Engineering", and I  absolutely 
> >concur with DC; I've seen evidence of it in Medium  Voltage 
> >(>600V, <15kV) systems. 
> Dave, how about repeating your story of the  direct current power cable 
> with 
> a pinhole burned through the insulation every  foot? :) 
> >One of our companies clients had a bad substation ground  at 
> >2.4kV L-L to a 1000 HP motor.  Interesting to see a 45  deg 
> >"crucifix" burned around a bonding bushing on a 600A 
> >feeder  conduit entering the MV MCC.  MCC/Motor Ground 
> >missing to  substation ground, EXCEPT for MV cable shields 
> >(not there from original  installation, not our companies 
> >installation); length of "burn/arc"  flashing at least 3" long. 
> >So this situation is EXACTLY like using a  shielded X-Ray 
> >cable in Tesla service. 
> Switching (and other transients) can excite  resonances in shielded cables 
> and other stray capacitances which of course can  cause the damage you 
> describe. 
> Worse is the problem of these resonances being  excited by harmonics from 
> non-linear loads. 
> >On a delta system (no ground) with a "capacitive" single  phase 
> >arcing fault to ground, transient over voltages can  exceed 
> >8X V applied.  If you doubt, check the IEEE "Buff"  Technical 
> >reference for details.  I trust we all understand the  implications 
> >of applying ~1kVAC to a 120VAC branch  circuit.... 
> That's why you stick arrestors and transient  devices all over the place 
>    BTW, Dave, do you still have all those  MOV's? 
> >Proper grounding is important in house wiring, but MUST 
> >be  installed correctly at MV; a fire, catastrophic equipment 
> >damage (even  collateral to unrelated systems), or electrocution 
> >will result if  improperly installed. 
> > 
> >Imagine what would happen if a plant  technician 
> >had his bare hand on 1000HP motor while running, and a  single 
> >phase (or capacitive gradient) current occurred.  At a  minimum 
> >a severe shock, or more likely death would have  occurred. 
> >I have made it a personal rule to never touch high  horsepower 
> >medium voltage motors while running for this  reason... 
> The root cause is the bad grounding. A 1/20  horsepower motor at 60V, or 
> even 
> less, can kill you just as dead. 
>    The worrisome part is the high-resistance  grounding utilized in many 
> medium voltage systems, or the intentional lack of  grounding in many 
> systems 
> where downtime is more costly than safety. Then  monitoring devices are 
> supposed 
> to prevent disasters. But I wonder if  facilities with ungrounded systems 
> change their procedures when they know they  have a ground fault ("Don't 
> touch 
> anything until we can shut down next  Saturday!"). Bad Things have happened 
> when 
> one ground fault a while later  precipitates a second fault, and then a 
> line-line fault occurs... 
>    Or in an electrolytic cell room, where grounding  is also intentionally 
> avoided to prevent accidents. Now *there's* a  low-impedance source for 
> you! 
> -Phil LaBudde 
> Center for the Advanced Study of Ballistic  Improbabilities 
> **************New year...new news.  Be the first to know what is making 
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