We have set-up the ADE7880 through I2C and everything is functioning correctly when connected to 3-phase calibrator.
However when we connect the ADE7880 to the utility the THDv value rises and falls from 1% to 8% and 8% to 1%, respectively.
We have verified that the utility do not go over 3%. (verified with other power meters).
Something is very weird!
Why when connected to calibrator it gives correct values but not when connected to Utiltity (power provider).
Kindly confirm if the register settings done during utility measurements have been done as recommended in the Quick setup section (page 80) of the datasheet. All the harmonic engine measurements are sensitive to the order and value of these register settings.
We are reading the THDv register. (THDv is not using harmonic registers HX, HY, HZ ?)
The readings are correct when we are using Calibrator (3-phase).
Which inidcates that the settings are correct. (they are constant (do not vary) and accurate)
However when connected to the Utility or Main power supply, the readings start slowly to increasing and then decreasing slowly.
Could this be a noise/aliasing? Does HREADY settling time have an effect?
The default settling time of 750 ms for reading harmonic calculations is fine. The VTHD computations are made from the VRMS and FVRMS measurements. Are you seeing a fluctuation in any of these measurements? Out of curiosity, what is the VLEVEL setting that you have? The VLEVEL setting depends upon the voltage level applied and that might be different for the utility(from the calibration setup).