Patent ID: 11885843
Assignee: HITACHI ENERGY LTD
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 15:
16. A system for a fault detection in line protection for power transmission system, comprising:
one or more processors;
a non-transitory memory storage coupled to at least one of the processors; and
a set of program instructions stored in the non-transitory memory storage and executable by at least one of the processors to cause the system to:
obtain a sampled value of a voltage at a measurement point on an electrical line, wherein the measurement point corresponds to a location at which a protection device for the line protection is installed;
obtain a sampled value of a current at the measurement point;
calculate an instantaneous measurement point voltage value specified by an operation criterion of the protection device, wherein calculating the instantaneous measurement point voltage value is based on the sampled value of the voltage and the sampled value of the current in accordance with a measurement differential equation corresponding to a time-domain lumped parameter model for the electrical line;
calculate an instantaneous comparison voltage value specified by the operation criterion of the protection device, wherein the instantaneous comparison voltage value is calculated by:, {
  
   
    
     
      
       
        u
        
         
          res
          -
         
         p
         ⁢
         1
         ⁢
         p
         ⁢
         
          2
          -
         
         ⁢
         k
        
       
       =
       
        
         R
         ·
         
          i
          
           p
           ⁢
           1
           ⁢
           p
           ⁢
           
            2
            -
           
           ⁢
           k
          
         
        
        +
        
         L
         ·
         
          
           di
           
            p
            ⁢
            1
            ⁢
            p
            ⁢
            
             2
             -
            
            ⁢
            k
           
          
          dt
         
        
       
      
     
    
   
   
    
     
      
       u
       
        
         res
         -
        
        p
        ⁢
        
         1
         -
        
        ⁢
        k
       
      
      =
      
       
        R
        ·
        
         (
         
          
           i
           
            p
            ⁢
            
             1
             -
            
            ⁢
            k
           
          
          +
          
           
            
             k
             R
            
            ·
            3
           
           ⁢
           
            i
            
             
              0
              -
             
             ⁢
             k
            
           
          
         
         )
        
       
       +
       
        L
        ·
        
         
          d
          ⁡
          (
          
           
            i
            
             p
             ⁢
             
              1
              -
             
             ⁢
             k
            
           
           +
           
            
             
              k
              L
             
             ·
             3
            
            ⁢
            
             i
             
              
               0
               -
              
              ⁢
              k
             
            
           
          
          )
         
         dt
        
       
      
     
    
   
   
    
     
      
       
        k
        R
       
       =
       
        
         
          R
          0
         
         -
         
          R
          1
         
        
        
         3
         ⁢
         
          R
          1
         
        
       
      
     
    
   
   
    
     
      
       
        k
        L
       
       =
       
        
         
          L
          0
         
         -
         
          L
          1
         
        
        
         3
         ⁢
         
          L
          1
         
        
       
      
     
    
   
  
 

wherein p1 and p2 represent first and second phases of a three-phase transmission line of the power transmission system, ures_p1p2_k represents the instantaneous comparison voltage value between phase p1 and phase p2 at instant k, ip1p2_k represents the sampled value of the current between phase p1 and phase p2 at the measurement point at instant k, ip1_k represents the sampled value of the current of phase p1 at the measurement point at instant k, R and L, respectively, represent a resistance value of a resistor and an inductance value of an inductor in the time-domain lumped parameter model,, di
   
    p
    ⁢
    1
    ⁢
    p
    ⁢
    
     2
     -
    
    ⁢
    k
   
  
  dt, represents a differential value of the current ip1p2_k,, d
   ⁡
   (
   
    
     i
     
      p
      ⁢
      
       1
       -
      
      ⁢
      k
     
    
    +
    
     
      
       k
       L
      
      ·
      3
     
     ⁢
     
      i
      
       
        0
        -
       
       ⁢
       k
      
     
    
   
   )
  
  dt, represents a differential value of the value ip1_k+kL·3i0_k, R0 represents a zero sequence resistance of the three-phase transmission line, R1 represents a positive sequence resistance of the three-phase transmission line, L0 represents a zero sequence inductance of the three-phase transmission line, L1 represents a positive sequence inductance of the three-phase transmission line, and i0_k represents a zero sequence current at instant k;
compare the instantaneous measurement point voltage value and the instantaneous comparison voltage value specified by the operation criterion of the protection device; and
trip the electrical line based on a result of the comparison of the instantaneous measurement point voltage value and the instantaneous comparison voltage value specified by the operation criterion of the protection device indicating a fault on the electrical line.