Operation: CP1SD/T/L Version
72
CENTRON® Polyphase Meter Technical Reference Guide
SiteScan Diagnostic #1
The purpose of this diagnostic is to verify that all meter elements are sensing and receiving
the correct voltage and current for each phase. This diagnostic may indicate one or more of
the following problems:
Cross-phasing of a voltage or current phasing
Incorrect polarity of a voltage or current circuit
Reverse energy flow of one or more phases
Internal meter measurement malfunction
Faulty site wiring
This error will not be reported when the meter is in a serial test configuration since this is
considered as a “valid” 3-element 4-wire Y service.
The voltage and current angles are determined with respect to phase A voltage, and
compared to a pre-established service diagram, according to the current meter service in use.
A lag and lead tolerance is entered as a parameter for the current and voltage angles.
Current Angle Tolerance
The SiteScan Current Angle Tolerance configurations in PC-PRO+ Advanced are the lead
and lag tolerances for current angles associated with Diagnostic #1. The range of adjustment
is from 90 to 120 degrees both lag and lead direction.
Cross-Phase, Polarity, and Energy Flow Check
Although the diagnostic checks occur every 5 seconds, once every second the meter
determines the angle of each voltage and current phasor with respect to VA. The meter will
not only display this information in the Toolbox Mode, but will determine each phasor angle
for validity with respect to the meter’s form and service type. Diagnostic #1 will take the
“typical” phasor diagram for a particular form number and service type and place an
envelope around each phasor where the actual phasor must be found for the diagnostic
check to pass. The envelope for the voltage vectors is fixed at ±10° and the envelope for the
current vectors is fixed at ±100°. The meter will recognize ABC or CBA phase rotation and
will adjust the SiteScan expected values.
For example, if a typical diagram has the B phase voltage angle at 120°, and the envelope
around that phasor is ±10°, then the actual phasor must be between 110° to 130° from VA
for the diagnostic check to pass. The system will check each phasor in a similar fashion. The
system will define the phasor envelope for each phase.
Figure 7.4 through Figure 7.13 show the ideal phasor diagrams for all possible form
numbers and service types. These vector relationships assume site wiring as shown and the
special case of unity power factor with balanced phase loading.
