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REV 1.0 TRF-100 USER’S MANUAL
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1.0 INTRODUCTION
1.1 General Description and Features
The TRF-100 is Vanguard’s third generation, microprocessor-based, automatic, three phase,
transformer turns-ratio tester. This lightweight, portable unit is designed for testing
transformers at utility power substations.
The TRF-100 determines the transformer turns-ratio using the IEEE C57.12.90 measurement
method. The transformer turns-ratio (ranging from 0.8 to 50,000) is determined by precisely
measuring the voltages across the unloaded transformer windings. To ensure accuracy, the TRF-
100’s measuring circuitry self-calibrates before each measurement. It requires neither
adjustment nor temperature compensation. The TRF-100’s turns-ratio measurement accuracy
is 0.1% or better.
The TRF-100 can perform a specific test for each transformer type (such as single phase, delta
to Y, Y to delta, delta to delta, or Y to Y) without the need to switch test hookup cables. Also,
the unit’s automatic transformer phase detection feature can detect different transformer
vector diagrams. The TRF-100 can automatically detect and test 67 transformer types defined
by ANSI, CEI/IEC and Australian standards.
To prevent an accidental wrong test-lead hook-up (e.g., when the operator reverses H and X
leads), the TRF-100 outputs a low-level test voltage to verify the hook-up condition before
applying the full test voltage to the transformer.
In addition to measuring a transformer’s turns-ratio, the TRF-100 can also measure a
transformer’s excitation current (in milli-amperes) and its winding phase angle.
Three test voltages (4 Vac, 40 Vac, 100 Vac) allow the TRF-100 to test CT’s and PT’s, as well as
power transformers.
The TRF-100 can also calculate the turns-ratio percentage error if the transformer’s nameplate
voltages are provided. The baseline turns-ratio is calculated using the nameplate voltages, and
the test results are compared to the baseline turns-ratio. The percentage error is then
calculated from the difference between the baseline and test turns-ratios.
User Interface
The TRF-100 features a back-lit LCD screen (20 characters by 4 lines) that is viewable in both
bright sunlight and low-light levels. The test results screen displays the transformer turns-ratio,
excitation current, and turns-ratio accuracy. The unit is controlled via a rugged "QWERTY"-style
membrane keypad.
Computer Interface
The TRF-100 can be computer-controlled via the USB interface using the supplied Vanguard
TTRA S2 turns ratio analysis PC software. The TTRA S2 software can be used to run a test and to
store test results on a PC. Test results can also be exported to Excel, PDF, and XML formats for
further analysis.