ISA T 2000 - CT Tests: Ratio, Polarity and Burden

DOC. MIE11110 Rev. 5
Page
16
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110
Having verified that there is no saturation, you can return and
press SAVE to save the test result; then, slowly reduce the
voltage: the test can be stopped only after knob (6) is in its zero
position. This is because the transformer under test cannot be left
with some remaining magnetization. So, if the test is broken during
the generation, and the output has not been adjusted to zero
prior to stop, the following message is displayed.
In this instance, you have to start again the test, slowly reach
the same test value and slowly decrease to zero.
NOTE: if CT’s are located on the primary side and on the
secondary side of a power transformer, the test of the CT ratio
can be performed with the voltage mode, as follows:
. Connect the CT secondary to the test set voltage output;
. Connect the PT winding on which the CT is inserted to the low
voltage measurement input.
The PT winding is not crossed by any current, so the secondary
voltage can be measured on the PT terminals (primary or
secondary).
1 .1.2. CT tests : ratio, polarity and burden
When this test is selected, the following menu is displayed.
Purpose of the test is to measure the actual CT ratio, to verify its
polarity, to measure the burden in terms of VA. This test is
performed applying current (and not voltage, as in the former