From: arl_123234@hotmail.com   
      
   On 3/29/19 10:51 AM, Michael Moroney wrote:   
      
   > Often the electrical company will upgrade the lines in stages. The   
   > portion closest to the substation is upgraded first, almost always   
   > Y connected with a neutral. At the end of the upgraded section there   
   > is a transformer bank, connected Y-delta if the older section is   
   > delta. I've noticed one section upgraded 3 times over a decade.   
   > The first Y-Delta transformer bank was just south of an intersection,   
   > later it was just north of the intersection (because they upgraded   
   > the lines on the crossing road fed at the intersection) and now a   
   > smaller bank is several miles north.   
   >   
      
   Hello, and my thanks again for providing further comment.  Just   
   wondering whether delta-delta connected autotransformers are used for   
   the above purpose for interconnecting two 4-wire (Y) MV lines having   
   different voltage ratings.  In this case the neutral wire is   
   pass-through.  I've seen overhead devices on MV lines that at initial   
   glance appear to be MV-LV pole-mounted distribution transformers but on   
   further examination have a total of 6 bushings on the MV side and no LV   
   bushings or obvious connections to LV subscribers.  These units also   
   don't have the footprint of "classic" MV voltage regulators.  So I   
   figure they're either autotransformer voltage boosters/reducers or ...   
   Never saw them as off-the-shelf offerings in old GE, Westinghouse or ABB   
   transformer catalogs.  VTY,   
      
   --   
   J. B. Wood	            e-mail: arl_123234@hotmail.com   
      
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