From: noone@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. 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 read that in HVDC feeds there are no   
   fround wires and the ground current flows through, the well, ground,   
   from the starting point of the transmission line to the end point. and   
   there are cases like submerged feeds where the current has to flow   
   through earth (and I suppose the cable's shield, but that would be very   
   thick for 1200+ amperes).   
      
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