On the ADE9000 when connected in wye mode (ie 3 phase voltages and a neutral), how do I calculate the line-to-line voltage? I need these values simultaneously withe the line-to-neutral voltages.

Since you are implementing a 3-phase 4-wire wye system, you can derive the line-to-line voltage (Vline) from the line-to-neutral (Vphase). If you can make the assumption that all line-to-neutral voltages are equal and all line-to-neutral angles are equal, then Vline=sqrt(3)*Vphase.

These values are updated at the frequency of the DSP (8ksps) so you need to perform all the reading inside this period of time through the SPI port.

The line-to-neutral voltages are not necessarily balanced.

Even if they were balanced, the calculation doesn't account for voltage distortion or for the phase varying from 120 degrees. It seems odd that the ADE9000 doesn't have a built in method, given how it's the best device on offer.

Since you are implementing a 3-phase 4-wire wye system, you can derive the line-to-line voltage (Vline) from the line-to-neutral (Vphase). If you can make the assumption that all line-to-neutral voltages are equal and all line-to-neutral angles are equal, then Vline=sqrt(3)*Vphase.

These values are updated at the frequency of the DSP (8ksps) so you need to perform all the reading inside this period of time through the SPI port.