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Re: HVDC line grounding system question

From	moroney@world.std.spaamtrap.com (Michael Moroney)
Newsgroups	sci.electronics.design
Subject	Re: HVDC line grounding system question
Date	2021-01-06 06:59 +0000
Organization	The World : www.TheWorld.com : Since 1989
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A few things I have learned since posting this:

The grounding area is spread out to decrease the "step charge" voltage 
(voltage between two points on the ground) below a certain level. I saw a 
diagram for a circular grounding system (unsure if it was the same one I 
mentioned) and there were multiple cables leading to the grounding circle, 
to different points evenly spaced along the circle, to ensure the current 
is dissipated evenly.  Important when an irresistable force is pushing 
hundreds or even thousands of amperes into the ground.

A big issue is electrolytic corrosion where metal can be eaten away by
the current. Not as much of an issue with grounded monopolar system
(connect the ground to the negative terminal) but is for bipolar system
where the ground can be either the positive or negative terminal when
operating in monopolar mode. Apparently they can be run this way for days
under a fault situation.  Probably the reason for the coke (carbon) 
mentioned.  p.s. look at the car battery terminals of an older car and
notice the positive terminal is more corroded.

The ground should be somewhat away from human activity since currents can
affect underground water pipes, oil pipelines etc.

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Thread

HVDC line grounding system question moroney@world.std.spaamtrap.com (Michael Moroney) - 2021-01-04 16:09 +0000
  Re: HVDC line grounding system question Joe Gwinn <joegwinn@comcast.net> - 2021-01-04 14:14 -0500
  Re: HVDC line grounding system question legg <legg@nospam.magma.ca> - 2021-01-04 15:01 -0500
  Re: HVDC line grounding system question upsidedown@downunder.com - 2021-01-05 08:13 +0200
    Re: HVDC line grounding system question Cydrome Leader <presence@MUNGEpanix.com> - 2021-01-05 21:38 +0000
      Re: HVDC line grounding system question legg <legg@nospam.magma.ca> - 2021-01-05 18:15 -0500
  Re: HVDC line grounding system question moroney@world.std.spaamtrap.com (Michael Moroney) - 2021-01-06 06:59 +0000

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