p2 p Re K1( ) Re K2( ) RF Re K3( ) 0=×–+×–EQUATION107 V1 EN-US (Equation 36)p Im K1( ) Im K2( ) RF Im K3( ) 0=× ×–×+× ×–EQUATION108 V1 EN-US (Equation 37)If the imaginary part of K3 is not zero, RF can be solved according to equation 37,and then inserted to equation 36. According to equation 36, the relative distance tothe fault is solved as the root of a quadratic equation.Equation 36 gives two different values for the relative distance to the fault as asolution. A simplified load compensated algorithm, which gives an unequivocalfigure for the relative distance to the fault, is used to establish the value that shouldbe selected.If the load compensated algorithms according to the above do not give a reliablesolution, a less accurate, non-compensated impedance model is used to calculatethe relative distance to the fault.10.9.7.3 The non-compensated impedance model M14983-121 v3In the non-compensated impedance model, IA line current is used instead of IFAfault current:UA p Z1 L IA RF IA×+× ×=EQUATION109 V1 EN-US (Equation 38)Where:IA is according to table 348.The accuracy of the distance-to-fault calculation, using the non-compensatedimpedance model, is influenced by the pre-fault load current. So, this method isonly used if the load compensated models do not function.10.9.7.4 IEC 60870-5-103 M14983-135 v2The communication protocol IEC 60870-5-103 may be used to poll fault locationinformation from the IED to a master (that is station HSI). There are two outputsthat must be connected to appropriate inputs on the function block I103StatFltDis,FLTDISTX gives distance to fault (reactance, according the standard) andCALCMADE gives a pulse (100 ms) when a result is obtainable on FLTDISTXoutput.Section 10 1MRK 511 424-UEN BMonitoring448 Bay control REC650 2.2 IECTechnical manual
