Tips For Making Precise Ratio Measurements - Chauvin Arnoux DTR 8510 Manual De Instrucciones

1. Connect the Primary (H) cable to the appropriate connectors on the DTR
Secondary (X) cable as a loop through the current transformer hole as shown in the figure.
2. Press the TEST button. During the Ratio test, the instrument will check for H/X reverse polarity, short (excessive current) etc.
before conducting Ratio test.
NOTE:
„ If the H/X is reversed, the instrument will display the error message (see Fig. 5-5) as in VT/PT test and terminate the test.
„ If there were a polarity reversal, the Ratio would be blinking with a negative sign. This means either the connections are re-
versed on a given side or the transformer is wound backwards relative to the marking.
„ The test can be cancelled at any time by pressing the TEST button during the operation.
„ The CT test ramps up the voltage in steps. At the end of the test, it ramps down the voltage.
„ There are certain low mass, low ratio CT's for which the DTR
sage will be "High Excitation Current".
As in VT/PT, the CT test may be run as many times as needed by pressing the TEST button.
The measurement records can be saved in Manual or Auto mode as in VT/PT mode.
The CT remains active until the configuration is changed. Powering the instrument down and turning it back on will not change
the Test Type.

5.3. TIPS FOR MAKING PRECISE RATIO MEASUREMENTS

The DTR 8510 is designed for step-down transformers. It sources low voltage on the primary. It starts with a fraction of the final
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source voltage and checks the secondary voltage.
If it exceeds the primary by a pre-determined value, the safety feature stops the measurement. The recommended procedure is to
reverse the leads in these circumstances so that the primary of the transformer is connected to the H cables and the secondary
of the transformer is connected to the X cables.
CAUTION: It is important to check that the H cables are connected to the primary side and the X cables are connected
to the secondary side of the transformer before the test begins.
„ Always verify the integrity of the cable connections and reposition the clips as necessary for robust and low-resistance con-
nections. Inspect the transformer terminals for dielectric coatings, fungus, dirt or corrosion.
„ Running a continuity test before the ratio test will provide a useful way to check windings and connections.
„ When testing polyphase transformers, keep in mind that in some cases, the measured ratios must be multiplied or divided by
√3. Refer to § 6 for polyphase connection diagrams and associated ratio equations.
H
RED
X
BLACK
Figure 5-7
8510 may not be able to provide correct ratio. The error mes-
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63
8510 and the transformer under test. Connect the
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H
BLACK
X2 X1
X
RED