I've been trying to make a 3phase energy measuring device using the ADE7880. I made a custom PCB with a host microcontroller. I had problems with reading the correct frequency. The ADE7880 was reporting 100Hz instead of 50Hz. One of the forum member identified that the neutral was not grounded as specified in the Figure 5 of the UG-356. The ADE7880 then started to report correct frequency. But I don't understand the reason behind grounding the neutral. In case of unbalanced 3-phase network, the current would be flowing back into the neutral. Is this safe for the PCB? I was trying out with single phase loads and I accidentally connected the phase of the load to the neutral of the board and the chip blew. Please suggest if I can provide any protection to avoid the chip from damaging in such cases.