From: dhky@shaw.ca   
      
   On 21/11/2013 3:38 AM, J.B. Wood wrote:   
   > On 11/20/2013 07:23 PM, Don Kelly wrote:   
   >> You may find that the surge arrestor is not necessarily mounted on the   
   >> transformer but is a separate unit near it (typically looks like an   
   >> insulator between the fuse and the transformer but there will be a lead   
   >> to ground (probably to the ground on the transformer).   
   >   
   > Thanks for the informative reply, Don.  I looked again and all I can   
   > observe between the transformer HV (primary) terminal and the MV feeder   
   > is the usual series combination of a manual-reset cutout and a fuse.   
   > Also, the replacement transformers, unlike those they replaced, have a   
   > (plastic?) shroud that covers about half the length of the transformer's   
   > HV terminal insulator.   
   >   
   > The surge arrester's principal function is to protect against lightning   
   > strikes (or perhaps induced potential from unusual sunspot/auroral   
   > activity) so I suppose it could be left out without undue risk for power   
   > outages and equipment damage.  Or perhaps the replacement units are more   
   > robust and don't require an arrester.  Sincerely,   
   >   
   The setup can vary from utility to utility- Here only an arrester and a   
   fuse are used-no cutout. The fuses are in tubes and, if I recall   
   correctly the fuse holder acts as a cutout. Some appear to have the   
   arrestor and fuse on a common mount. An  underground MV cable has fuse   
   and arrester on the pole where the cable goes down.   
      
   --   
   Don Kelly   
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