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balanced. Further, the Equivalent VA method may yield better results in the presence of
harmonics, where Total Power Factor will also be reduced from "1". Refer to industry
standards for more information.
6.6 Energy (1-Cycle Update)
Separate values are maintained for both positive and negative Watt-hours, positive and
negative VAR-hours, and VA-hours, for each feeder. These energy quantities are
calculated every cycle from the Total Watts, Total VARs, and Total VAs, and the values
are stored into non-volatile memory every 15 seconds. Energy values may be reset. All
values are reset simultaneously. Refer to the appropriate protocol manual for details.
6.7 Frequency (1-Cycle Update)
Frequency is calculated every cycle for every input. The M57x monitors the change in
Phase Angle per unit time using the Phase Angle measurement for the fundamental
generated by the FFT. The System Frequency is the frequency of the input used for
synchronizing the sampling rate.
Figure 10 - Sign Conventions for Power Measurements
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