Re: [EVGRAY] High Voltage DC Transmission System

Body

Ole, thank you for the photos of the HV components of the HVDC systems. 
Take a look at this attachment from Seimens.. These systems are 
certainly impressive and they have to use huge halls for totally indoor 
operation at such high potentials ( one million V) vs the old HVAC 
outdoor yards.

On 12/7/2018 6:28 AM, Norman Wootan wrote:
>
> 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:
>> https://www.electronicshub.org/high-voltage-dc-transmission-system/
>>
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