Vanguard EZCT-2000A - Manual (Page 92)

EZCT-2000A USER’S MANUAL REV 1
88
5.5 Troubleshooting Guide
PROBLEM DESCRIPTION Probable Cause Suggested Solution
When running the
excitation test, the V
x
voltage is always zero.
The excitation current can
be raised during a test.
• The EZCT-2000A X cables are driving a
short circuit. • Check CT shorting screws.
• Check X lead connections.
When running the
excitation test, the V
x
voltage can be raised but
the excitation current is
always zero during a test.
• The EZCT-2000A X cable is driving an
opened circuit.
• Check the CT terminal connection.
CT excitation knee point
voltages and turns ratio
readings are incorrect. • CT may not be completely de-
magnetized.
• If the user runs a dc resistance test,
the CT will be magnetized. The next
test the EZCT-2000A executes is an
excitation test. If the excitation
current did not reach at least 0.8A,
the CT is not completely de-
magnetized.
• Raise the excitation voltage
setting in the test plan.
• Re-run the excitation test.
• You can quickly verify if the CT
was de-magnetized by looking at
the last excitation graph.
When running the
excitation test, the V
x
reading is erratic.
• The EZCT-2000A X cable may be
opened. Each X cable has two
conductors going from the clip end to
the banana jacks. If one of the
conductors is opened, the V
x
readings
will be erratic.
• Remove X cables from the EZCT-
2000A and the CT terminals.
• Check cable integrity using an
Ohm Meter.
Saturation test is correct
but turns ratio test is
erroneous. • V
H
cables problem. • Check the V
H
cable connection.
• Check the V
H
cable integrity with
an Ohmmeter
Turns ratio test of a CT
mounted on a
transformer bushing is
incorrect. • Transformer windings opposite side of
CT windings is not shorted.
• See Figure 4.