7.1.7.1 Filtering GUID-16B5060B-101C-402A-BF25-06E70FDD7836 v2Practically all voltage, current and impedance quantities used within the ZMFPDISfunction are derived from fundamental frequency phasors filtered by a half cyclefilter.The phasor filter is frequency adaptive in the sense that its coefficients are changedbased on the estimated power system frequency.A half cycle filter will not be able to reject both even and odd harmonics. So, whileodd harmonics will be completely attenuated, accuracy will be affected by evenharmonics. Even harmonics will not cause the distance zones to overreachhowever; instead there will be a slightly variable underreach, on average in thesame order as the magnitude ratio between the harmonic and fundamentalcomponent.7.1.7.2 Distance measuring zones GUID-74B12BB1-FE0A-4DE4-BDBE-159A438D396B v4The different fault loops within the IED are of full scheme type, which means thatearth fault loop for phase-to-earth faults and phase-to-phase faults for forward andreverse faults are executed in parallel.Figure 43 presents an outline of the different measuring loops for the six distancezones.IEC05000458-2-en.vsdL1-N L2-N L3-NL1-N L2-N L3-NL1-N L2-N L3-NL1-N L2-N L3-NL1-L2 L2-L3 L3-L1L1-L2 L2-L3 L3-L1L1-L2 L2-L3 L3-L1L1-L2 L2-L3 L3-L1L1-N L2-N L3-N L1-L2 L2-L3 L3-L1Zone 1Zone 2Zone 3Zone 4Zone 5L1-N L2-N L3-N L1-L2 L2-L3 L3-L1Zone RVIEC05000458 V2 EN-USFigure 43: The different measuring loops at phase-to-earth fault and phase-to-phase faultEach distance protection zone performs like one independent distance protectionfunction with six measuring elements.Transients from CVTs may have a significant impact on the transient overreach ofa distance protection. At the same time these transients can be very diverse innature from one type to the other; in fact, more diverse than can be distinguishedby the algorithm itself in the course of a few milliseconds. So, a setting (CVTtype)is introduced in order to inform the algorithm about the type of CVT applied andSection 7 1MRK 505 394-UEN AImpedance protection118 Line differential protection RED650 2.2 IECTechnical manual
