User manual 09/2009 - Schneider Electric

The Metering FunctionMeasuring the Current and Voltage Phase UnbalancesMicrologic trip units calculate the current unbalance for each phase (3 values).The current unbalance is expressed as a % compared to the average current:I1- Iavg I2 - Iavg I3 - Iavg< 0 > 0 < 0I1 I2 I3 IavgMicrologic trip units calculate the:• Phase-to-phase voltage unbalance for each phase (3 values)• Phase-to-neutral (if present) voltage unbalance for each phase (3 values)The voltage unbalance is expressed as a % compared to the average value of the electrical quantity(Vavg):U12 - Vavg U23 - Vavg U31- Vavg> 0 < 0 < 0U12 U23 U31 VavgNOTE: The unbalance values are signed (relative values expressed as a %).The maximum/minimum unbalance values are absolute values expressed as a %.Maximum/Minimum ValuesThe Micrologic A trip unit determines in real time the maximum (MAX) and minimum (MIN) value of thecurrent for each phase reached for the current period (1)(2).The Micrologic E trip unit determines in real time the maximum (MAX) and minimum (MIN) value reachedby the following electrical quantities organized in groups for the current period (1). The groups of electricalquantities measured in real time are:• Current (2): Phase and neutral currents, average currents and current unbalances• Voltage: Phase-to-phase and phase-to-neutral voltages, average voltages and voltage unbalances• Power: Total power and power for each phase (active, reactive, apparent, and distortion)• Total harmonic distortion: The total harmonic distortion THD for both current and voltage• Frequency(1) The current period for a group is initialized by the last reset of one the maximum values in the group(see below).(2) Micrologic A and E trip units also determine the maximum value (MAXMAX) of the maximum (MAX)values and the minimum (MINMIN) value of the minimum values (MIN) of the phase currents.76 LV434104 09/2009