Number of phase reference locations

The number of phase reference locations required depends on the density of meters and the ability of RF communications to travel between clusters of transformers. Groups of transformers with no RF connectivity to a reference location (regardless of the number of hops) will need to have at least one phase reference point.

Even for clusters of transformers with good RF communications, Itron recommends multiple phase reference points for redundancy as described in the following list:

  • Clusters with three or more substations:

    • Recommend at least one phase reference per substation

  • Clusters with one or two substations

    • Recommend three or more phase references (with at least one per substation)

    • Three or more enables redundancy and potential location of input error or phase change

  • Clusters that consist of a single feeder or large tap (less than one substation)

    • Recommend three references but two may be adequate for smaller clusters

  • Very small clusters (generally a tap serving distant loads such as remote vacation homes)

    • Establishing reference is not strictly required

    • Location Awareness will distinguish transformers on different phases even without system-wide reference

    • Very small, isolated clusters have small impact on most phase-related analyses where system-wide reference is necessary.

Choosing phase reference locations

These are general guidelines to simplify analysis and review. If these criteria are inconvenient or not available, any location can be used.

  • Choose a singlephase service point on wye-connected (phase-neutral) transformers.

  • Choose a location close to a substation on a 3-phase trunk where the likelihood of a routine phase change is less (that is, avoid a 1-phase lateral where changes are more likely).

  • To reduce complexity, the transformer connection will directly reflect the phase angle supplied by the substation. For example, if a delta-connected transformer is selected or a wye-connected transformer downstream of a delta-wye stepdown bank is selected, the +/- 30° phase shift must be discerned and accounted for when entering the phase angle.