what is the electrical component symbol in datasheet ABB M1M 10
They look like surge arrestors. The odd thing is that they only appear on the three-phase 3-wire connection and not on the other two. This makes me think that they should be used when the three-phase supply is floating.
In this way the arrestors will break down if the floating supply drifts above a certain voltage for some reason. The reason for it may be so as not to exceed the CAT III insulation rating of the meter itself.