14
TRT33A Getting Started
5.1.3 Current transformer Testing
The largest number of windings are on the „‟X‟‟ or “S” (secondary) side of the current transformer. The
primary has only one or two turns, or you have to make one using the test cables. Therefore, when
testing current transformer the „‟H” leads are connected to the secondary CT terminals. TRT33A applies
the vol
tage from the „‟H‟‟ leads and measures induced voltage (in the primary of the CT) through the „‟X‟‟
leads.
Connect the H and X cables as on the figure 5-4 described below.
Press
UP/DOWN
in
CONFIGURATION
menu to choose CT option. This option enables measurement of
CT transformers, and is available in HV CONFIG field. In that case LV CONFIG and PH
DISPLACEMENT fields become automatically inactive.
In some cases, where the inductance of the current transformer is lower than the power available from
TRT33A, an over current error will be displayed. To avoid that, choose a lower test voltage for testing
current transformers.
Current transformers with multiple secondary taps are tested similar to single secondary taps. After each
specific ratio is tested, the HV leads can be moved to the next pair of secondary contacts of the
transformer.
Polarity of a CT can be checked. From the measured phase angle, we can see the polarity of a CT. If the
phase angle is close to 0 degrees, polarity is correct. If the phase angle is close to 180 degrees, then the
polarity is not correct.
5.1.3.1 Unmounted CT
Connect ground cable of the device to the earth ground.
Use the TRT33A H and X leads to connect as shown in figure 5-5.
5.1.4 Autotransformer
To test a single-phase autotransformer, perform the following setup procedure:
Connect ground cable of the device to the earth ground.
Connect the H and X test cables to the corresponding H and X connectors of the TRT33A.
Connect clip 1U (H1; A) to the lower numbered terminal and 1N (H0; N) to the higher
numbered terminal of the high-voltage winding.
2U (X1; a) and 2N (X0; n) clips connect to the lower-voltage winding.
Figure 5-5:
Connection of
unmounted CT
transformer
