CHAPTER 10: THEORY OF OPERATION FAULT LOCATORL90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL 10-6110If the FAULT REPORT 1 VT SUBSTITUTION setting value is “I0” and the VTs are connected in a wye configuration, the faultlocation is performed based on the actual phase to ground voltages. If the VTs are connected in a delta configuration, faultlocation is performed based on the delta voltages and zero-sequence voltage approximated based on the zero-sequencecurrent:Eq. 10-84where ZSYS0 is the equivalent zero-sequence impedance behind the relay as entered under the fault report setting menu.Figure 10-20: Fault locator schemeSince the fault locator algorithm is based on the single-end measurement method, in three-terminal configurationthe estimation of fault location may not be correct at all three terminals especially if fault occurs behind the line'stap respective to the given relay.
