5-152 G30 Generator Protection System GE Multilin5.6 GROUPED ELEMENTS 5 SETTINGS55.6.3 TRANSFORMER PERCENT DIFFERENTIAL (ANSI 87GT)PATH: SETTINGS GROUPED ELEMENTS SETTING GROUP 1(6) TRANSFORMER PERCENT DIFFERENTIALThe calculation of differential (Id) and restraint (I r) currents for the purposes of the percent differential element is describedby the following block diagram, where “Σ” has as its output the vector sum of inputs, and “max” has as its output the input ofmaximum magnitude; these calculations are performed for each phase.The differential current is calculated as a vector sum of currents from all windings after magnitude and angle compensation.(EQ 5.25)The restraint current is calculated as a maximum of the same internally compensated currents.(EQ 5.26)The element operates if Id > PKP and Id / Ir > K, where PKP represents a percent differential pickup setting and K is arestraint factor defined by the relays settings Slope 1, Slope 2, and a transition area between breakpoint 1 and breakpoint 2settings. PERCENT DIFFERENTIALPERCENT DIFFERENTIALFUNCTION: DisabledRange: Disabled, EnabledMESSAGE PERCENT DIFFERENTIALPICKUP: 0.100 puRange: 0.050 to 1.000 pu in steps of 0.001MESSAGE PERCENT DIFFERENTIALSLOPE 1: 25%Range: 15 to 100% in steps of 1MESSAGE PERCENT DIFFERENTIALBREAK 1: 2.000 puRange: 1.000 to 2.000 pu in steps of 0.001MESSAGE PERCENT DIFFERENTIALBREAK 2: 8.000 puRange: 2.000 to 30.000 pu in steps of 0.001MESSAGE PERCENT DIFFERENTIALSLOPE 2: 100%Range: 50 to 100% in steps of 1MESSAGE INRUSH INHIBITFUNCTION: Adapt. 2ndRange: Disabled, Adapt. 2nd, Trad. 2ndMESSAGE INRUSH INHIBITMODE: Per phaseRange: Per phase, 2-out-of-3, AverageMESSAGE INRUSH INHIBITLEVEL: 20.0% foRange: 1.0 to 40.0% of f0 in steps of 0.1MESSAGE OVEREXCITN INHIBITFUNCTION: DisabledRange: Disabled, 5thMESSAGE OVEREXCITN INHIBITLEVEL: 10.0% foRange: 1.0 to 40.0% of f0 in steps of 0.1MESSAGE PERCENT DIFF BLOCK:OffRange: FlexLogic operandMESSAGE PERCENT DIFFERENTIALTARGET: Self-resetRange: Self-reset, Latched, DisabledMESSAGE PERCENT DIFFERENTIALEVENTS: DisabledRange: Disabled, EnabledI d I1comp I2comp+=I r K max I1comp I2comp( , )×=
