Where:1) shows how to connect the secondary side of the open delta VT to one VT input on the IED.+3U0 shall be connected to the IED2) is the TRM where this voltage input is located. It shall be noted that for this voltage input thefollowing setting values shall be entered:3 6.6 11.43VTprim kV= × =EQUATION1923 V1 EN-US (Equation 4)110sec 3 1103VT V= × =EQUATION1924 V1 EN-US (Equation 5)Inside the IED, only the ratio of these two parameters is used. It shall be noted that the ratio ofthe entered values exactly corresponds to ratio of one individual open delta VT.6.63 6.6 3110110 3× =EQUATION1925 V1 EN-US (Equation 6)3) shows that in this example the first three input channel of the preprocessing block is notconnected in SMT tool or ACT tool.4) shows the connection made in Signal Matrix Tool (SMT), Application configuration tool (ACT),which connect this voltage input to the fourth input channel of the preprocessing function block5).5) is a Preprocessing block that has the task to digitally filter the connected analog input andcalculate:• fundamental frequency phasors for all four input channels• harmonic content for all four input channels• positive, negative and zero sequence quantities by using the fundamental frequencyphasors for the first three input channels (channel one taken as reference for sequencequantities)These calculated values are then available for all built-in protection and control functions withinthe IED, which are connected to this preprocessing function block in the configuration tool. Forthis application most of the preprocessing settings can be left to the default values.If frequency tracking and compensation is required (this feature is typically required only for IEDsinstalled in the generating stations ) then the setting parametersDFTReference shall be setaccordingly.4.2.4.6 Example how to connect the open delta VT to the IED for low impedanceearthed or solidly earthed power systems SEMOD55055-199 v6Figure 19 gives an example about the connection of an open delta VT to the IED for lowimpedance earthed or solidly earthed power systems. It shall be noted that this type of VTconnection presents secondary voltage proportional to 3U0 to the IED.In case of a solid earth fault close to the VT location the primary value of 3Uo will be equal to:1MRK 504 158-UEN A Section 4Analog inputs49Application manual
