directional OC protection, and so on). The following loops are used for different types offaults:• for 3 phase faults: loop A-B.• for 2 phase faults: the loop between the faulted phases.• for 2 phase-to-ground faults: the loop between the faulted phases.• for phase-to-ground faults: the phase-to-ground loop.LMBRFLO function indicates the distance to fault as a percentage of the line length, inkilometers or miles as selected on the local HMI. LineLengthUnit setting is used to selectthe unit of length either, in kilometer or miles for the distance to fault. The distance to thefault, which is calculated with a high accuracy, is stored together with the recordeddisturbances. This information can be read on the local HMI, uploaded to PCM600 and isavailable on the station bus according to IEC 61850–8–1.The distance to fault can be recalculated on the local HMI by using the measuringalgorithm for different fault loops or for changed system parameters.18.8.3 Setting guidelinesThe parameters for the Fault locator function are set via the local HMI or PCM600.The Fault locator algorithm uses phase voltages, phase currents and residual current inobserved bay (protected line) and residual current from a parallel bay (line, which ismutual coupled to protected line).The Fault locator has close connection to the Disturbance report function. All externalanalog inputs (channel 1-30), connected to the Disturbance report function, are availableto the Fault locator and the function uses information calculated by the Trip valuerecorder. After allocation of analog inputs to the Disturbance report function, the user hasto point out which analog inputs to be used by the Fault locator. According to the defaultsettings the first four analog inputs are currents and next three are voltages in the observedbay (no parallel line expected since chosen input is set to zero). Use the Parameter Settingtool within PCM600 for changing analog configuration.The measured phase voltages can be fine tuned with the parameters VAGain, VBGain andVCGain to further increase the accuracy of the fault locator.The list of parameters explains the meaning of the abbreviations. Figure 398 also presentsthese system parameters graphically. Note, that all impedance values relate to theirprimary values and to the total length of the protected line.Section 18 1MRK 506 369-UUS -Monitoring846 Line distance protection REL670 2.2 ANSIApplication manual
