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

Claim 0:
1. A method for a fault detection in line protection for a power transmission system, comprising:
obtaining 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;
obtaining a sampled value of a current at the measurement point;
calculating an instantaneous measurement point voltage value specified by an operation criterion of the protection device, wherein the instantaneous measurement point voltage value is calculated by:, {
  
   
    
     
      
       
        u
        
         
          q
          -
         
         ⁢
         p
         ⁢
         1
         ⁢
         p
         ⁢
         
          2
          -
         
         ⁢
         k
        
       
       =
       
        
         u
         
          p
          ⁢
          1
          ⁢
          p
          ⁢
          
           2
           -
          
          ⁢
          k
         
        
        -
        
         (
         
          
           R
           ·
           
            i
            
             p
             ⁢
             1
             ⁢
             p
             ⁢
             
              2
              -
             
             ⁢
             k
            
           
          
          +
          
           L
           ·
           
            
             di
             
              p
              ⁢
              1
              ⁢
              p
              ⁢
              
               2
               -
              
              ⁢
              k
             
            
            dt
           
          
         
         )
        
       
      
     
    
   
   
    
     
      
       u
       
        
         q
         -
        
        ⁢
        p
        ⁢
        
         1
         -
        
        ⁢
        k
       
      
      =
      
       
        u
        
         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, respectively, of a three-phase transmission line of the power transmission system, uq_p1p2_k represents the instantaneous measurement point voltage value between phase p1 and phase p2 at instant k, uq_p1_k represents the instantaneous measurement point voltage value of phase p1 at instant k, up1p2_k, ip1p2_k respectively, represent the sampled value of the voltage and the sampled value of the current between phase p1 and phase p2 at the measurement point at instant k, up1_k, ip1_k, respectively, represent the sampled value of the voltage and 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 a 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;
calculating an instantaneous comparison voltage value specified by the operation criterion of the protection device, wherein the calculating the instantaneous comparison voltage value is based on the sampled value of the voltage and the sampled value of the current in accordance with a comparison differential equation corresponding to the time-domain lumped parameter model;
comparing the instantaneous measurement point voltage value specified by the operation criterion of the protection device and the instantaneous comparison voltage value; and
tripping the electrical line based on a result of the comparison of the instantaneous measurement point voltage value specified by the operation criterion of the protection device and the instantaneous comparison voltage value indicating a fault on the electrical line.