Hmmm,
Could it be the meter that is not EMC safe?
It's been quite some time since I had to do with EMC correct grounding, but I remember something about closing the ground loop and not closing it and in the latter case in what end of the cable should it be grounded. But I would say normally ground the cable in the end at the PLC, but then again that could make the cable work as an antenne for noise that is then "broadcast" in the ungrounded end i.e. at the mater. You'll have to ask the expert about when to use what method, as I never really got that part under my skin.
Michal