From: petergrantfisher@gmail.com   
      
   Hi Richard,   
      
   Before I retired I was an Infrastructure Planning Engineer for a UK DNO. Our   
   aim was to 'make the asset sweat'.  At 132kV, the rating of a circuit was the   
   minimum continuous rating. Why minimum, you ask? The circuit rating changes   
   with ambient    
   temperature, so the Summer Rating is less than the Winter Rating. The rating   
   can also be pushed by the shape of the load curve. You can supply a higher   
   maximum demand if the load factor is low.   
      
   You can also push the rating, by as much as two, for short term switching   
   transients.    
      
   The circuit rating is likely to be set by one, or a few pinch points. For   
   example, I had one 132kV circuit which crossed a railway line. The maximum   
   line sag at that crossing, set the rating for whole 25km circuit. I was able   
   to raise the circuit rating    
   by 10MW, by changing the insulator strings on the bottom phase on each of the   
   two circuits, on the two adjacent towers, from suspension sets to semi-tension   
   sets. Under £10k, and out of the maintenance budget!   
      
   Regards   
      
   Peter   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)