we have actually an approbation running for an 3phase energy meter, realized with an ADE7878. Everything works fine but we have a problem with the energy measurement function in the chip. The system was calibrated with 50Hz, everything works fine. Now the approbation starts to check the active energy measurement on 50Hz, PF=1 and 0,5A current with a symmetric load. These tests are done with PF=0.8 capacitive and 0.5 inductive. If we change the frequency up to 51Hz the active energy values are ok, but if we decrease the frequency to 49Hz, 0.8 capacitive, the active energy is too low compared with the calculated value. Is there a dependency of the active energy register and the frequency in the ADE7878? This issue affects only low current values, if we rise current to e.g. 5A, everything is ok.