941MRS751802-MUMProtection RelayTechnical Reference Manual, Standard ConfigurationsREX 5217.1.5. 3U> and 3U>>Abnormal busbar voltages can be caused by faults in the network or a faulty tapchanger or voltage regulator of a power transformer. The function blocks aredesigned for the single-phase, two-phase and three-phase overvoltage protectionwhenever the DT characteristic or, as concerns 3U>, the IDMT (Inverse DefiniteMinimum Time) characteristic is appropriate. Suppression of harmonics is possible.Fig. 7.1.5.-1 Function block symbols of 3U> and 3U>>Three-phase directional overcurrent protection, high-set stage, 3I>>->Start current 0.05…40.00 x InOperate time 0.05…300.00 sOperation mode Not in useDefinite timeInstantaneousBasic angle ϕb 0...90Oper. Direction ForwardReverseEarth fault pr. DisabledEnabledNondir. operat. DisabledEnabledMeasuring mode Mode1 (Phase-to-phase voltages/Peak-to-peak currents)Mode2 (Phase-to-phase voltages/Fund. freq. Currents)Mode3 (Phase-to-earth voltages/Peak-to-peak currents)Mode4 (Phase-to-earth voltages/Fund. freq. Currents)Drop-off time of the operate time counter 0...1000 msNote! The values below apply when f/fn = 0.95...1.05Operation accuracy Current:0.1...10 x In: ±2.5% of set value or ±0.01 x In10...40 x In: ±5.0% of set valueStart timeVoltage:±2.5% of measured value or ±0.01 x UnPhase angle: ±2°Injected currents > 2.0 x start current:internal time < 42 mstotal time < 50 msReset time 40...1000 ms (depends on the minimum pulse width setfor the trip output)Reset ratio, typically 0.95Retardation time < 45 msOperate time accuracy in DT mode ±2% of set value or ±20 msBS1BS2GROUPRESETSTARTTRIP3U>BS1BS2GROUPRESETSTARTTRIP3U>>
