From: null@void.com   
      
   On 7/14/2015 2:11 PM, gfretwell@aol.com wrote:   
   >   
   > The other principle reason for the ground is stated in NEC 250.4(A)(1)   
   >   
   > ."Electrical systems that are grounded shall be connected to earth in   
   > a manner that will limit the voltage imposed by lightning, line   
   > surges, or unintentional contact with higher-voltage lines and that   
   > will stabilize the voltage to earth during normal operation"   
   >   
      
   I have typical US urban overhead power distribution.   
      
   If the primary wire falls on the secondary conductors, earthing at my   
   house helps trip the utility overcurrent protection (damage is less than   
   it might otherwise be).   
      
   If the neutral from my house to the pole opens, the my earthing gives   
   some (often not much) protection from 120-120V unbalance. Actually we   
   have an all-metal water supply system, so earthing to the water pipe   
   gives a lot of protection, with the neutral current riding on the water   
   pipe to adjacent houses and on their supply neutral back to the utility   
   transformer.   
      
   The utility primary wire is 8kV to a primary neutral. The primary   
   neutral is the same wire as the secondary neutral. The neutrals and   
   transformer case are earthed at the transformer pole (and at some other   
   poles). The utility earthing electrodes are similar to a ground rod   
   (which is about the worst electrode). Many of the wires down to the   
   earthing electrodes have been stolen for copper. My earthing electrodes   
   help earth the utility system.  If the primary/secondary neutral opens,   
   my earhing electrode helps keep the "ground" at my house from going to   
   8kV with respect to the earth.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)