Underfrequency 2 - GE 745 TRANSFORMER MANAGEMENT RELAY Instruction Manual

10 COMMISSIONING
11. 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.
The blocking from logic input, if enabled, can be tested as described in earlier tests for other
elements.
NOTE
1. Disable all protection functions except the Underfrequency 2 function.
2. Verify that settings match in-service requirements. Enter/modify settings and logic under:
SETPOINTS/S4 ELEMENTS/FREQUENCY/UNDERFREQUENCY 2/...
3. Repeat the appropriate steps of Section 10.6.17: UNDERFREQUENCY 1 on page 10–35 for this element.
The results must be compared to the settings for the Underfrequency 2 element.
a) PRELIMINARIES
Disable all protection functions except Overfrequency. Verify that settings match in-service requirements.
Overfrequency settings are modified under:
SETPOINTS/S4 ELEMENTS/FREQUENCY/OVERFREQUENCY/...
b) VOLTAGE INPUT FUNCTION (VOLTAGE INPUT ENABLED)
1. 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.
2. Slowly increase the frequency until the output relay(s) operate. Check that the frequency at which opera-
tion took place is the selected frequency setting. As the frequency is varied, verify that the display indicates
the correct value of system frequency under:
ACTUAL VALUES/A2 METERING/FREQUENCY/SYSTEM FREQUENCY
3. Slowly reduce the voltage. Note the voltage at which the output relay(s) reset. Check that this dropout volt-
age is equal to the voltage level set under:
SETPOINTS/S4 ELEMENTS/FREQUENCY/OVERFREQUENCY/MINIMUM OPERATING VOLTAGE
Note that this level can be set down to 0.00 A, in which case the element remains operated to a voltage
level of approximately 2% of nominal.
4. Slowly increase the voltage and check that the element operates when the voltage reaches 2% above the
set level. Return the voltage to nominal value.
5. Slowly decrease the current until the element resets. Check that this dropout current level is equal to the
setting under:
SETPOINTS/S4 ELEMENTS/FREQUENCY/OVERFREQUENCY/MINIMUM OPERATING CURRENT
If current sensing has not been enabled for this element, the element remains operated for current levels
down to 0.00 A.
6. Slowly increase the current and check that the element operates when the current reaches a value just
above the setting. Set the current to rated CT secondary.
GE Power Management 745 Transformer Management Relay
10.6 PROTECTION SCHEMES

10.6.18 UNDERFREQUENCY 2

10.6.19 OVERFREQUENCY
10
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