täällä on mittarina E450
"Summation by magnitude separates the positive from the negative values
of the individual phases. Measured quantity +A therefore only includes the
positive values of the individual phases (+A1 and +A2 in example 1),
measured quantity -A only the negative values of the individual phases
(-A3 in example 1), provided any are present.
In case of a connection error, the meter measures the real import and
export energy correctly in the +A and -A registers.
With this method the meter adds exported and imported energy. This
method should only be used if the utility is sure there is no energy export.
The absolute magnitude summation can be used as an anti-tampering
measure. Here negative magnitudes of A1, A2, A3 are added to the positive
magnitudes of A1, A2, A3. See example above. "