From: noone@nospam.com   
      
   Στις 18/8/2017 8:47 μμ, ο Richard Chambers έγραψε:   
   > When an EHV transmission line (let's say 345 kV or 400 kV, for example) is   
   > rated at 1,000 MW, is this 1,000 MW:-   
   > a. the rating which should not be exceeded in normal service, with the aim   
   > of eliminating the possibility that a failure on this line might initiate a   
   > cascade failure affecting the entire transmission system, causing a   
   > widespread blackout.   
   > Or is the 1,000 MW   
   > b. the rating that applies under emergency conditions only, for example when   
   > neighbouring parallel lines have already tripped out of service. If this is   
   > the case, the line might be restricted to (for example) 700 MW under all   
   > normal circumstances, and 1,000 MW would be allowed only in an emergency.   
   >   
   > My problem is that I am looking at a technical specification sheet, but I do   
   > not know which interpretation of "MW rating" is the correct one.   
   >   
   > Richard Chambers,       Leeds   UK.   
   > =================================   
   >   
   >   
   >   
   It's been since 2003 I graduated so I'll try my best to answer. A search   
   for my old textbooks was fruitless. Short transmission lines (~60 km)   
   have thermal rating. medium length (~60 km to 220 km) have voltage drop.   
   Long lines (like yours) have stability. So the rating is for the line to   
   be stable. A heavy-duty 400 kV line can go well in 1200 A ballpark.   
      
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