User manual 09/2009 - Schneider Electric

The Metering FunctionPower Calculation AlgorithmPresentationThe algorithms are given for both calculation methods (2 wattmeters and 3 wattmeters). The powerdefinitions and calculation are given for a network with harmonics.All the calculated quantities are delivered by the Micrologic E trip unit (on-screen and/or via thecommunication network). With the 2-wattmeter calculation method, it is not possible to deliver powermetering for each phase.Input DataThe input data are the voltages and currents for each phase (for more information on calculatingharmonics, see Harmonic Currents, page 87):Using this data, the Micrologic E trip unit calculates the various power ratings according to the sequencedescribed below.Active PowersMetering on a 3-Pole or 4-Pole Circuit Breaker WithENVT OptionThe active power for each phase and total active poweris calculated.Metering on a 3-Pole Circuit Breaker Without ENVTOptionOnly the total active power can be calculated.—Pw1 and Pw2 are the fictional active powers calculated by the 2-wattmeter method.Apparent Powers for Each PhaseMetering on a 3-Pole or 4-Pole Circuit Breaker WithENVT OptionThe apparent power is calculated for each phase. ——Metering on a 3-Pole Circuit Breaker Without ENVTOptionLV434104 09/2009 83