The “PASS” or “FAIL” message is generated using the PT accuracy class (see
Section 13.9.1
)
and the selected error limit from the User Preferences menu. If no PT nameplates are selected in
the Site Editor, the PowerMaster
®
estimates a nameplate according to the readings and a default
accuracy class of 0.3. Once the measured ratio is displayed, the PowerMaster
®
calculates the
error to see if it is within limits. For example, if the measured ratio is 3.76:1, the nameplate is 4:1,
the accuracy class is 0.1, and the error limit is set to “2.0x Specification Accuracy,” then the
PowerMaster
®
will display a “FAIL” message. Here is how it is calculated:
[(3.76-4) / 4]*100 = -6.0% error
(Accuracy class = 0.1) * (Error limit = 2) = ±0.2%
6.0% > 0.2% = FAIL
Testing Tips:
1. Verify the probe is rated for the voltage being tested. Only use probes meeting the
manufacturer’s specifications. Using probes that do not meet the manufacturer’s
specifications may lead to a safety hazard.
2. Never connect a voltage probe around a conductor before terminating it to its cable and to
the PowerMaster
®
.
3. For Litewire probes, verify the optic cable is clean to prevent surface arcing.
4. Position the probe as far as practical from other voltage carrying conductors.
5. IN GENERAL, if a PT Ratio test has an erroneous ratio result or a phase angle greater
than ±1°, check the installation of the voltage probe before suspecting a PT problem.
Using the Volt Litewire Probe
PowerMaster
®
Connections:
1. Connect the 3-Phase Probe Adapter Cable to either SET 1 or SET 2.
2. Connect the HV Signal Cable (stamped with the Volt Litewire serial number) to the red
connector on the 3-Phase Probe Adapter Cable.
Connection to the Service:
Refer to the Volt LiteWire manual provided on page 7 (“Making Phase to Ground
Measurements”). Please note that when doing phase to ground measurements, using a “hot tap
clamp” is simply referring to any clamp device (i.e. vice grips) to tie the Phasing Electrode to earth
ground (refer to page 14 of the Volt Litewire manual for a picture of the Phasing Electrode).
The user also has the option to view phase to phase measurements (see page 9 for “Making
Phase to Phase Measurements With two Hot Sticks”). These measurements can be viewed and
saved in any hot screen. However, performing a PT Ratio Test can only be done with phase to
ground measurements.
Rev 1.5
106
