Vanguard EZCT-2000A - Manual (Page 16)

EZCT-2000A USER’S MANUAL REV 1
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3.2 EZCT-2000A X Input Voltage Warning
The EZCT-2000A X output terminals are rated to 2,000 Vac working voltage. Any voltage present
at these terminals above 2,000 Vac may damage the X sense circuitry, cause false readings, or
both. An example of a typical situation where this may occur is shown in Figure 5 below.
Figure 5. Sample CT Name Plate
For the above example CT, the turns ratio between X1-X4 is 3150 to 1. The turns ratio between
X1-X2 is 400 to 1. The turns ratio between X1-X4 and X1-X2 is 7.88 (3150/400). If a test voltage
of 300 Vac is applied to the X1-X2 terminals, a voltage of 2,364 Vac (300 Vac x 7.88) will be
induced at the X1-X4 terminals. If all the test leads are connected to the EZCT-2000A and the
excitation test is performed on the X1-X2 terminals, the voltage induced at the X1-X4 terminals
will exceed 2,000 Vac as the voltage across the X1-X2 terminals increases above 250 Vac. A
“Flash-Over” condition may occur and damage the EZCT-2000A. In this case, the user should
only connect the X1-X2 leads and run its excitation test, then connect the X4 lead before
running the X1-X4 excitation test.