Vanguard TRM-203_403 - Manual (Page 6)

TRM-203 AND TRM-403 USER’S MANUAL REV 1
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1.0 INTRODUCTION
1.1 General Description and Features
The TRM-203 and TRM-403 are three phase transformer winding resistance meters that allow
the user to connect all test cables to the transformer bushings. The unit will then measure the
transformer resistance value for each of the phases without the need to disconnect and
reconnect cables for each phase.
The TRM-203 and TRM-403 can provide a fast and stable reading of very large transformers by
utilizing a 60Vdc power supply. The TRM-203 is capable of outputting a selectable test current
from 1A to 20A while the TRM-403’s test current is selectable from 1A to 40A.
Since both units can accurately measure resistance from 1 micro-ohm to 500 Ohms (up to 2000
Ohms for the TRM-203), they can be used as micro-ohm meters to measure EHV circuit breaker
contact resistance, or for any low resistance measuring application.
For a Delta transformer, the TRM-203/403 can measure the phase resistance readings and
provide the individual Delta winding resistance values. The TRM-203/403 can also provide the
individual winding resistance values for a Wye transformer without the neutral terminal.
If the transformer winding resistance temperature is available at the time of testing, the TRM-
203/403 can calculate the equivalent resistance value at any temperature value. This useful
feature can be used to compare the field readings against the factory test resistance values.
The TRM-203/403 can perform a special test to collect data automatically for up to 90 minutes
(at 60-second sampling intervals) or 45 minutes (at 30 second sampling intervals). The test data
is recorded with a time stamp.
All test results can be printed on the unit’s built-in 2.5” wide thermal printer. Test record
header information including the company, substation name, transformer information, and
operator information can also be entered using the rugged, 44–key “QWERTY”-style membrane
keypad.
The TRM-203/403 can automatically demagnetize the inductive device under test, eliminating
the manual task of demagnetizing the transformer core after a resistance test.
The TRM-203/403 also has a “make-before-break” test mode that can be used to test the Load
Tap Changer (LTC) or Voltage Regulator contact test sequence. The TRM-203/403 produces a
“Dynamic-Resistance” graph of the LTC or Voltage regulator contact under operation. An
opened contact can be detected visually from this resistance chart.
The TRM’s built-in LTC/Voltage regulator can be used to conveniently change the LTC/voltage
regulator tap position from the TRM-203/403 front panel.
User Interface
The TRM-203/403 features a back-lit graphic LCD screen (128 x 64 pixels) that is clearly visible in
both bright sunlight and low light levels. A 44-key “QWERTY”-style membrane keypad is used to
enter test information and operate the unit.