Short circuit ratio (electrical grid)

In an <a href="/facts/Electrical_grid/RkWPqjmG">electrical grid</a>, the short circuit ratio (or SCR) is the ratio of: the short circuit <a href="/facts/Apparent_power/EXsaw0B9">apparent power</a> (SCMVA) in the case of a <a href="/facts/Electrical_fault/QaCmxu1r">line-line-line-ground (3LG) fault</a> at the location in the grid where some generator is connected, to: the power rating of the generator itself (GMW). 
Since the power that can be delivered by the grid varies by location, frequently a location is indicated, for example, at the point of interconnection (POI):

S
        C
        
          R
          
            P
            O
            I
          
        
        =
        
          
            
              S
              C
              M
              V
              
                A
                
                  P
                  O
                  I
                
              
            
            
              G
              M
              W
            
          
        
      
    
    {\displaystyle SCR_{POI}={\frac {SCMVA_{POI}}{GMW}}}

SCR is used to quantify the system strength of the grid (its ability to deal with changes in <a href="/facts/Active_power/EXsaw0B9">active</a> and <a href="/facts/Reactive_power/EXsaw0B9">reactive</a> power injection and consumption). On a simplified level, a high SCR indicates that the particular generator represents a small portion of the power available at the point of its connection to the grid, and therefore the generator problems cannot affect the grid in a significant way. SCMVA is defined as a product of the voltage before the 3LG fault and the current that would flow after the fault (this worst-case combination will not happen in practice, but provides a useful estimation of the capacity of the circuit). SCMVA is also called a short circuit level (SCL), although sometimes the term SCL is used to designate just the short-circuit current.

Short circuit ratio (electrical grid) open-in-new

Short circuit ratio (electrical grid)