C60 BREAKER PROTECTION SYSTEM – INSTRUCTION MANUAL 8-1C60 Breaker Protection SystemChapter 8: Theory of operationTheory of operationThis chapter outlines advanced information on operation.8.1 Fault locator8.1.1 Fault type determinationFault type determination is required for calculation of fault location. The algorithm uses the angle between the negativeand positive sequence components of the relay currents. To improve accuracy and speed of operation, the faultcomponents of the currents are used; that is, the pre-fault phasors are subtracted from the measured current phasors. Inaddition to the angle relationships, certain extra checks are performed on magnitudes of the negative and zero-sequencecurrents.The single-ended fault location method assumes that the fault components of the currents supplied from the local (A) andremote (B) systems are in phase. The figure shows an equivalent system for fault location.Figure 8-1: Equivalent system for fault locationThe following equations hold true for this equivalent system.Eq. 8-1wheremZ (1-m)ZR FZ A Z BE A E BV A V BV FI A I BLocal busRemotebusdistance to fault842780A1.CDRV A m Z I A R F I A I B+ +=
