CHAPTER 7: COMMISSIONING PROTECTION SCHEMES
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL 7–47
Provided that the operate times are not scattered over a wide range, it
may be desirable to repeat this test several times and average the results.
If there is a wide scatter, verify the test setup and ensure the signal
source behaves in a consistent manner.
Note
The blocking from logic input, if enabled, can be tested as described in earlier tests for
other elements.
7.5.17.3 Underfrequency 2
Disable all protection functions except the underfrequency 2 function.
Verify that settings match in-service requirements. Enter/modify
settings and logic in the
S4 ELEMENTS FREQUENCY
UNDERFREQUENCY 2
setpoints menu.
Repeat the appropriate steps of Underfrequency 1 on page 7–44 for this
element.
Compare the results to the settings for the underfrequency 2 element.
7.5.17.4 Overfrequency
Disable all protection functions except overfrequency.
Verify that settings match in-service requirements.
Overfrequency settings are modified in the
S4 ELEMENTS
FREQUENCY
OVERFREQUENCY settings menu.
Voltage input function (voltage input enabled):
Using the variable-frequency voltage/current source connected to terminals C11 and C12
for the voltage signal and H1 and G1 for the current signal,
Set the frequency to 60.00 Hz (or 50.00 Hz) and the voltage amplitude
to the rated VT secondary voltage.
Set the current amplitude to rated CT secondary.
Monitor the appropriate trip and auxiliary relays.
Reset all alarms and indications on the relay.
The 745 display should remain unchanged with no trip indications.
Slowly increase the frequency until the output relay(s) operate.
Check that the frequency at which operation took place is the selected
frequency setting.
As the frequency is varied, verify that the A2 METERING
FREQUENCY
SYSTEM FREQUENCY actual value indicates the correct
value of system frequency.
Slowly reduce the voltage.
Note the voltage at which the output relay(s) reset.
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