Dimitris Tzortzakakis <no...@nospam.com
>Στις 3/1/2021 8:03 π.μ., ο/η Michael Moroney έγραψε:
>> 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 right. Additionally,
>> multiple conductors (6) run from the ROW to the circle. The street
>> view at https://goo.gl/maps/K94ZceiRfUL2ePaU7
shows the huge towers
>> as well as 4 grounding leads, two at the top of the towers and two
>> others on wooden poles. They are on rather substantial insulators.
>> Does anyone know any details for this rather odd setup? Why multiple
>> grounding conductors, and any details of the circular structure?
>> Do the grounding conductors carry current during normal operation,
>> perhaps with the line at half power with one side out of service and
>> the grounding (neutral?) carrying the return current?
>the ground wires on top of the poles are lightning arresters. they
>normally carry no current.
I don't think they are lightning arrestors. Near the south end, this
line has an insulated conductor and a pair of (uninsulated) lightning
arrestor lines. https://goo.gl/maps/LGNiEYMcC7rrtjMQA
> the other two on the wooden poles seem to
>carry too high a potential to being ground wires. they probably could be
>a MV feed for a nearby town.
I followed these lines to the circular ground point using Google Satellite
View zoomed in. They are two of the 6 conductors which go there.
Two others are the two conductors on top of the pylons. It appears the
other two are also the two conductors on top of the pylons but from the
ones continuing past the point where the lines go to the circle.
They are not the feed for a town. I have never seen a delta distribution
system using the ground as a conductor in the US (although this is