Measurement Computing WavePort 312P rev.1.0 - Manual (Page 38)

4-4 Device Configuration PowerVista/312 User’s Manual
4.1.3 Three Phase Grounded Wye
System Configuration PT Connection: Wye
To accurately measure a three phase Grounded Wye system, connections need to be made so that per phase
power calculations can be performed. This insures inclusion of any ground effects in calculated power.
External voltage and current connections should be made as shown
in Figure 4-2 . In the System Configuration,
the PT connection should be set as Wye.
A Delta PT connection can alternately be specified if the user desires to calculate line-to-line voltages and use
the Two Wattmeter Method for power calculations. By definition however, the Two Wattmeter Method is out
of scope for systems that have ground currents flowing. For this reason, the Delta PT connection should be used
for observational purposes only and not for critical power measurements.
Note: The user can expect incorrect power measurements if a Delta PT connection is used on a Grounded Wye
system with ground currents flowing.
Figure 4-2. Connection Arrangement for Three Phase Grounded System.
The safety ground connection must be made to a solid ground connection so that the instrumentation is
referenced. If there is a possibility of a loose ground connection, make sure that the safety ground is on the
“ground” and not the neutral side of the suspect lead. To be safe, avoid connecting the safety ground to the
neutral, and seek to locate a bonafied system ground.
For this system arrangement, note that EasyPower Measure will automatically calculate the neutral return
current as the sum of the phase currents. Though the extra channel E1 could be used to explicitly measure this
current, it is recommended to use E1 for an additional signal such as a ground current instead.