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Re: HVDC line grounding system question

From	Cydrome Leader <presence@MUNGEpanix.com>
Newsgroups	sci.electronics.design
Subject	Re: HVDC line grounding system question
Date	2021-01-05 21:38 +0000
Organization	PANIX Public Access Internet and UNIX, NYC
Message-ID	<rt2m81$2n2$1@reader1.panix.com> (permalink)
References	<rsrmo1$fdn$1@pcls7.std.com> <rsvej8$84d$1@pcls7.std.com> <tnv7vf9jlabd0nc9e0uuomcm2ago8i88id@4ax.com>

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upsidedown@downunder.com wrote:
> On Mon, 4 Jan 2021 16:09:12 +0000 (UTC),
> moroney@world.std.spaamtrap.com (Michael Moroney) wrote:
> 
>>
>>There is a long HVDC power line from northern Quebec Canada to Ayer, 
>>Massachusetts USA. It operates at either +/- 375 kV or +/- 450 kV
>>depending on source.  As I understand it, it is grounded at exactly one
>>point, near Saint-Claude, Quebec. You can see it on this Google
>>satellite view: https://goo.gl/maps/bnsYcbv9Q3ewmkG49  where the power 
>>line ROW runs diagonally on the right side, and the actual grounding
>>point is the weird circular shape at the upper left.  Additionally,
>>multiple conductors (6) run from the ROW to the circle.  The street
>>view at https://goo.gl/maps/K94ZceiRfUL2ePaU7 near the grounding poing 
>>shows the huge towers as well as 4 conductors, two at the top of the 
>>towers and two others on wooden poles.  They are on rather substantial 
>>insulators.
> 
> Old unipolar SCR based under sea HVDC systems have grounding
> electrodes at each shore and only one conductor runs from coast to
> coast. Those SCR based systems also require a line potential reversal
> if energy is to be transferred in the opposite direction.
> 
> Newer IGBT based systems are usually bipolar and two conductors are
> required. What is the point to ground the midpoint except electric
> safety ? In these systems one conductor is always positive and the
> other negative, regardless in which direction energy is transferred.

Any idea what the resistance of the sea and earth are as measured for this 
applications?

What might the ground currents be into the coke pile?

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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