Measuring 400V three phase large consumer power
It depend on contract, usualy only real power is charged, the instrumen shall count real, reactive, apparent.
3 current transformers and 3 volatages is the exact measuring, but you can use one current and one voltage with asumption that network and motor are balanced (that would be rathere an estimation than measuring).
Any power meter for rated voltage for your country is ok, let's say 400VAC nominal.


Industrial power meters, there are a lot of them. I can just give you one example: https://www.youtube.com/watch?v=ggDtJWUbkJ4