# Questions Regarding ADE7880 Harmonics Calculations

Question asked by karens on Nov 18, 2014
Latest reply on Nov 24, 2014 by dlath

Hello

Using ADE7880 to do the harmonics calculations, here are THD values on the voltage and current:

Phase A: THD on voltage is 0.8496; THD on current is 0.8488

Phase B: THD on voltage is 0.8363; THD on current is 0.849

Phase C: THD on voltage is 0.8401; THD on current is 0.8529

The load is resistance load, line voltage frequency is 60Hz (actually measured frequency is 61Hz, don't know why?). I am not sure if these are reasonable values or not. Upon the equations shown on data sheet page 59, I was expected that the THD values should be much smaller. Based on your experience, how could I estimate those THD values? I want to make sure the harmonics calculation I did are correct.

I use the default settings of HX, HY, and HZ.

Phase A: Harmonic X distortion on voltage is 0.000764

Harmonic Y distortion on voltage is 0.001344

Harmonic Z distortion on voltage is 0.000052

Harmonic X distortion on current is 0.321839

Harmonic Y distortion on current is 0.001433

Harmonic Z distortion on current is 0.000050

Phase B: Harmonic X distortion on voltage is 0.000188

Harmonic Y distortion on voltage is 0.001620

Harmonic Z distortion on voltage is 0.000024

Harmonic X distortion on current is 0.000585

Harmonic Y distortion on current is 0.001660

Harmonic Z distortion on current is 0.000016

Phase C: Harmonic X distortion on voltage is 0.001041

Harmonic Y distortion on voltage is 0.001591

Harmonic Z distortion on voltage is 0.000020

Harmonic X distortion on current is 0.000543

Harmonic Y distortion on current is 0.001588

Harmonic Z distortion on current is 0.000083

Here are some related setups:

1. HREADY line is used to trigger MCU to read harmonics data

2. Since ADE7880 monitors one phase at a time, MCU sets to do 10 readings on one phase, then switch to next phase, read 10 readings, and so on. Is it a good practice, or  I should do more readings at one phase?

3. HCONFIG register, set the update rate to 512 ms (closed to 750 ms initial setting time)

Thank you very much for the help!

Karen