How to determine negative current (L1, L2, L3)

[1MartinHerzog]

Imagine you have a Balkonkraftwerk which produces 800 Watt and is pluged in to phase L1. When there is no device consuming energy on L1 then a negative current 3,48 Ampere (800W/230A) should be the output. Unfortunately I get 3,48 Ampere instead of -3,48 Ampere. Is there a possibility to get the direction of the electrical current? Thank you