K3IF AIA ZL×---------------- ZA ZB+Z1 ZA DD+--------------------------- 1+è øæ ö×=EQUATION106 V1 EN (Equation 71)and:• ZADD = ZA + ZB for parallel lines.• IA, IFA and VA are given in the above table.• KN is calculated automatically according to equation 67.• ZA, ZB, ZL, Z0L and Z0M are setting parameters.For a single line, Z0M = 0 and ZADD = 0. Thus, equation 68 applies to both single andparallel lines.Equation 68 can be divided into real and imaginary parts:p2 p Re K1( ) Re K2( ) RF Re K3( ) 0=×–+×–EQUATION107 V1 EN (Equation 72)p Im K1( ) Im K2( ) RF Im K3( ) 0=× ×–×+× ×–EQUATION108 V1 EN (Equation 73)If the imaginary part of K3 is not zero, RF can be solved according to equation 73, and theninserted to equation 72. According to equation 72, the relative distance to the fault issolved as the root of a quadratic equation.Equation 72 gives two different values for the relative distance to the fault as a solution.A simplified load compensated algorithm, which gives an unequivocal figure for therelative distance to the fault, is used to establish the value that should be selected.If the load compensated algorithms according to the above do not give a reliable solution,a less accurate, non-compensated impedance model is used to calculate the relativedistance to the fault.12.14.7.3 The non-compensated impedance modelIn the non-compensated impedance model, IA line current is used instead of IFA faultcurrent:Section 12 1MRK 511 287-UUS AMonitoring514Technical manual
