6 Voltage transformer
6.6 VTElectronics
6.6.1 Test settings
Figure 6-11:VTElectronics test card with test results
Navigate to the parameter fields, and enter the values according to your test requirements:
Pressing the Settings menu key opens the Settings page. The Settings page allows setting the test cards individually. As a rule, do not use the Settings page but the Device Setup tab in the Options view (see "Device Setup" on page 56) to set the test cards. For more information, see "Settings page" on page 50.
Within the Settings menu, you can set correction factors in accordance with IEC 61869-10. The measured transformation ratio of the instrument transformer under test can be adjusted with the provided ratio- and phase-correction values. The correction factors are often available on the asset nameplate.
Vprim: nominal primary voltage with the option "value x 1/√3"
Vsec: nominal secondary voltage with the options value x 1/√3
value x 1/3
Vtest: primary injection voltage.
By default, Vtest = Vprim (with option x 1/√3) if Vprim ≤ 2kV.
If Vprim > 2kV, Vtest = 2kV.
f: output frequency
Auto: select check box for automatic test (default), clear for manual test (refer to 6.6.3 "Automatic test vs. manual test" on page 159).
Amplitude correction: Amplitude correction for corrected transformation ratio calculation Phase correction: Phase error offset for corrected phase error calculation
6.6.2 Measurements
Selecting the check box Manual input lets you enter the value for Vsec manually, for example, when Vsec was measured with an external volt meter rather than at input V1 AC.
Vprim: actual output voltage at 2kV AC output that is injected into the electronic voltage transformer’s primary side
Vsec: secondary voltage measured at V2AC, and its phase angle relative to Vprim nominal Ratio: Vprim /Vsec × CFU1, here: 90.0/√3:10.0071/√32
Note:Results are marked with an exclamation point (!) if a correction factor was used.
1. CFI stands for the amplitude correction. By default, it is set to 1.00 and subsequently no additional ratio error is considered.
2. The value 10.0071/√3 is calculated as follows:
Vsec act × CFU × (V prim nom / V prim act), here: 2.77531 V × 1.001 × (90 V/√3/25.010 V) = 10.0071 V/√3
Ratio error:
where Kn is rated transformation value, here: 90.0 V / 10.0 V
Note:Results are marked with an exclamation point (!) if a correction factor was used.
Phase error: φ = φVsec – φVprim – φPhase correction3
3. By default, the phase correction is set to 0.0000° and subsequently no additional phase error is considered. Here: -0.03°.
Polarity: displays the status of the polarity
OK= phaseVsec - phaseVprim = -45° < 0° < 45°
NOT OK = all other cases ε Kn×Vsec×CFU–Vprim
Vprim
--- 100%×
=
6.6.3 Automatic test vs. manual test 1. Option "Manual input" clear
Automatic test
► Press the I/O (test start/stop) push-button to start the test.
► The test voltage increases from 0V to Vtest in a ramp characteristic within 1 second. Then Vtest is kept for a period of 2.4 seconds, and the measurements are taken. Next, the ramp decreases again within 0.3 seconds.
► The automatic test stops by itself, it can now be assessed.
► To repeat the test, first press Back to Top, if applicable, and then Clear Results.
Manual test
Clearing Auto lets you set the test voltage Vtest manually with the handwheel.
► Press the I/O (test start/stop) push-button to start the test. The focus is set onto the "V test:" entry field.
► Set the value of your choice either by turning the handwheel and/or by entering it with the numerical keys.
► A value set with the numerical keys needs to be fully entered and acknowledged by pressing either Enter or the handwheel before it is applied to the output. If needed, it can then be adjusted using the handwheel.
Values set by turning the handwheel are applied instantaneously.
► Now the measurements are taken and displayed.
► To save the measurement press Keep Results (pressing the I/O push-button has the same effect).
The last measured values are "frozen", the test can now be assessed.
► Stop the manual test by pressing the I/O (test start/stop).
► To repeat the test, first press Back to Top, if applicable, and then Clear Results.
2. Option "Manual input" selected
Note:Select Manual input prior to starting the test. If the test card still contains results, clear them by pressing Clear Results.
When Manual input is selected, there is no phase available. Consequently, neither the polarity nor the phase angle can be calculated.
Since an automatic test only lasts a very short period of time, and a manual measurement is rather difficult, an automatic test with a manual measurement is not useful. Therefore, this Reference Manual will not cover this subject.
Manual test
Clearing Auto lets you set the test voltage Vsec manually with the handwheel.
► Press the I/O (test start/stop) push-button to start the test. The focus is set onto the "V test:" entry field.
► Set the value of your choice either by turning the handwheel and/or by entering it with the numerical keys.
► A value set with the numerical keys needs to be fully entered and acknowledged by pressing either Enter or the handwheel before it is applied to the output. If needed, it can then be adjusted using the handwheel.
Values set by turning the handwheel are applied instantaneously
► Vprim is measured and displayed.
► To save the measurement press Keep Results.
► Navigate to the "V sec" entry field.
► Enter the measured Vsec value either by turning the handwheel or by entering this value with the numerical keys, and press Enter or the handwheel to acknowledge your setting.
► The ratio is calculated and displayed.
► To stop the manual test, press the I/O (test start/stop). The test can now be assessed.
► Alternatively, it is possible to enter the manually measured value into the test card after the test was stopped (for example, if the measurement was carried out at a remote location).
► To repeat the test, first press Back to Top, if applicable, and then Clear Results.
To learn more about test assessment, refer to 10.1 "Test assessment" on page 268.