The subject was grounding

Body

Many thanks to Toby Grotz for sharing these two files on the critical 
subject of grounding and bonding of electrical circuitry.    My main 
interest in this stems from personally witnessing a very large 
transformer explode from the ferroresonance phenomenon.  The faulty 
grounding of power distribution systems up in dairy farming area of the 
mid West where cattle were electrocuted added to my interest.  When the 
huge HVDC transmission distribution systems came on line, there seamed 
to be a complex set of problems introduced especially in the single line 
type of system which relies on an earth/ocean return path. I believe you 
can see the unique set of problems here. See

Ole and Fredric Fletcher, pay attention to the polarity and methodology 
of transmission of the HVDC.  Remember the articles regarding the earth 
ground return problems up in dairy country, Wisconsin where cattle were 
being electrocuted by poor grounding systems in rural electric grid.  I 
can recite a real life problem with imposing a potential into the earth 
on the dealing with ground return.  One of our Nursing facilities had 
three separate buildings that shared a two pipe chilled / hot water 
system with buried steel 4 inch lines (supply/ return).   The electrical 
system was 480VAC backbone with delta/Wye step down transformers which 
gave a base 208VAC with center tap ground for 120VAC. The facility 
operated just fine for 50 years.  Along came an Electrical Contractor 
that installed a new distribution transformer (100 KVA) during an 
upgrade to one of the out buildings. After operation for several years 
the buried 4 inch steel AC/heating lines developed leaks and sections of 
the removed lines showed electrolytic (galvanic) erosion.  I discovered 
that the Contractor had installed a delta/delta step-down (100 KVA) 
transformer and grounded one (L-2) of the Secondary terminals to get a 
neutral buss common for 120VAC.  A huge NO,NO cause you had a potential 
of 230V to earth ground.  The difference in ground potential between 
buildings created the galvanic erosion because there was a ground return 
current back to the 480/208VAC backbone in the mains building.  This was 
a huge lesson on the problems encountered with relying on earth ground 
return path.

https://www.electronicshub.org/high-voltage-dc-transmission-system/

https://circuitglobe.com/different-types-hvdc-links.html

See attached files.