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VOLTAGE TRANSFORMERS ROUTINE TEST PROCEDURE

VOLTAGE TRANSFORMERS ROUTINE TEST PROCEDURE
C57.13.5 Test procedures for voltage transformers.

Applied voltage test on the neutral terminal
With the ground link temporarily removed from the neutral terminal of the transformer, a voltage of 19 kV (r.m.s.) shall be applied between the neutral terminal and the ground for 60 s.

The gas pressure of the gas-filled transformer may be at any setting equal to or less than the pressure given in Clause 5 for the test.

The transformer shall be considered as having met the requirements if no external and internal disruptive discharge or collapse of voltage is observed.

Accuracy test
The test shall be performed in accordance with 8.1 of IEEE Std C57.13-1993.
The calibration of the test system given in 4.3 shall apply.

The gas pressure of the gas-filled transformer may be at any setting for the test.
The transformer shall be considered as having met the requirements if the performance is within the limits of
the accuracy class.

Excitation characteristics with respect to rated voltage factor
The excitation current of the voltage transformer shall be measured in accordance with 8.3.2 of IEEE Std C57.13-1993, with the voltage corresponding to the rated voltage factor applied to one of the windings and
with the other windings open-circuited.

The impressed voltage shall be measured with both the r.m.s.-voltmeter and the average-voltmeter (but r.m.s. calibrated). The form factor, defined as:

where
Vrms = voltage measured with the r.m.s.-voltmeter, and
Vavg = voltage measured with the average-voltmeter.

The exciting current and the form factor shall be included in the routine test report.

The gas pressure of the gas-filled transformer may be at any setting equal to or less than the pressure given in Clause 5 for the test.

The measured excitation current shall be compared with the design value to ensure proper construction.

Resistance measurement of windings
The resistance of all the windings including tapped portions of the windings shall be measured in accordance with 8.5 of IEEE Std C57.13-1993. The measured values shall be corrected to 75 °C.

The gas pressure of the gas-filled transformer may be at any setting for the test.

The resistance data obtained shall be compared with the design values to ensure proper construction.
source: C57.13.5 IEEE Trial-Use Standard of Performance and Test Requirements for Instrument Transformers of a Nominal System Voltage of 115 kV and Above
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