REFPDIFI3PW1CT1I3PIdN/II3PW1CT2ProtectedwindingIEC09000113-3.vsdIEC09000113-3 V2 EN-USFigure 38: Connection of Restricted earth fault, low impedance functionREFPDIF in multi-breaker arrangements6.2.2.6 CT earthing direction M13048-29 v13To make the restricted earth fault protection REFPDIF operate correctly, the mainCTs are always supposed to be star -connected. The main CT's neutral (star)formation can be positioned in either way, ToObject or FromObject. However,internally REFPDIF always uses reference directions towards the protectedtransformers, as shown in Figure 38. Thus the IED always measures the primarycurrents on all sides and in the neutral of the power transformer with the samereference direction towards the power transformer windings.The earthing can be freely selected for each of the involved current transformers.6.2.3 Setting guidelines IP14942-1 v16.2.3.1 Setting and configuration M13052-3 v3Recommendation for analog inputs M13052-8 v10I3P: Neutral point current ( All analog inputs connected as 3Ph groups in ACT).I3PW1CT1: Phase currents for winding 1 first current transformer set.I3PW1CT2: Phase currents for winding1 second current transformer set for multi-breaker arrangements. When not required configure input to "GRP-OFF".I3PW2CT1: Phase currents for winding 2 first current transformer set. Used forautotransformers.Section 6 1MRK 504 169-UEN ADifferential protection98 Transformer protection RET650 2.2 IECApplication manual
