Re: [EVGRAY] High Voltage DC Transmission System

Body

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 seperate 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 electrolyitic (galvanic) errosion.  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 errosion 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.

On 12/7/2018 3:58 AM, Norman Wootan [email protected] [EVGRAY] wrote:
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