Megger Three-Phase TTR, Инструкция по эксплуатации

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Service
AVTMTTR330 Rev 3 March 2010
35
TTR330 – Self check
A customer may want to make sure that the test set is functioning properly
before testing a transformer. Traditionally, for the transformer turns ratio testers,
a customer performed this test by connecting H1-X1 and H2-X2 test leads. The
1:1 turns ratio was expected to be measured. Additionally, the displayed test
results were interpreted as a test set calibration check.
The 3-phase TTR test set is designed and optimized for the transformer turns
ratio testing. It uses a mixed analog-digital technique to provide the high accurate
readings of the tested transformer turns ratio. The test set measurement
approach is based on high impedance input and output transformer voltage
monitoring circuits. The high impedance of the monitoring circuits is optimized
for the accurate transformer turns ratio testing.
When performing a 3-phase TTR functional test, the H and X test leads
interconnect the input and output monitoring circuits without a transformer
being connected. Such connection cause an impedance mismatch and, as a result
of the mismatch, the displayed turns ratio reading is not exactly 1:1 as it may be
expected. A customer should be aware that a functional test is not a real
transformer turns ratio test. Due to the intrinsic and inevitable impedance
mismatching, the 3-phase TTR functional test readings may be from 0.9980 to
1.0020. The TTR functional test readings do not represent its calibration. It
simply shows that the TTR test set circuitry functions properly. To check the 3-
phase TTR calibration, a customer should use the Calibration Standards
mentioned in
Calibration heading above.
To perform a 3-phase TTR functional test proceed as follows:
1. Turn TTR test set power off.
2. Connect H1 lead to X1 lead, H2 lead to X2 lead, H3 lead to X3 lead, and H0
lead to X0 lead. Make sure the leads are properly connected and that H/X
pairs are not electrically in contact with each other.
3. Turn TTR test set power on.
4. After self-test is complete and a QUICK TEST.
5. Enter transformer type DIAG 07 YNyn0.
F
WARNING
Do not continue functional test if the diagram type
DIAG 07 YNyn0 transformer type is not listed.
Keep the leads, which are energized, clear of ground,
and personnel and each of the other lead-pair sets.