User's Guide

28 A c l a r a R F E l e c t r i c I - 2 1 0 + c U s e r G u i d e
Supported Messages
Generators create, and transmission lines carry, three phases. Most parts of the
country call these A, B, and C. The rotation of the phases may be defined to be
clockwise ABCABC… or counterclockwise CBACBA… Each of the three phases
are displaced in time by 120° as depicted in the following image.
Figure 5.9 Phases A, B, and C
Transformer connections are able to shift the phase relationship. A single-phase
transformer with its primary connection across A and B will cause the timing
observed at the secondary to be AB. It will follow the BA waveform in the
preceding image rather than AN or BN. In this way, an LV electrical service can
be shifted to a different phase, or phasor than the source. In a similar manner, a
polyphase delta-wye transformer will by its construction, shift power at the
secondary by either +30° or -30°. Thus, a simple measurement of the phases
delivered to a service can be transformed to be different than the phases that
originate at power source. The phase detection feature will measure the phasor
delivered to each service location relative to the phasor at the power source.
For the phase detection feature to work, at least one meter must be placed in or
near a substation yard somewhere in the service territory, where the phase
connection is known with good authority. This meter is known as a reference
meter. The installer must note the connection of the reference meter, and this
configuration must be entered into the headend. The reference meter must be
within radio range of a DCU, and the same DCU must be within range of other
meters in the network. There may be more than one reference meter installed at the
utility, but they should all be on the same phasor. An AN connection is preferable.
Once the system is activated, the headend will issue a phase detect beacon message
to each DCU. Each DCU will broadcast the message to all meters within range.