GE 745 Instruction Manual page 282

PROTECTION SCHEMES
7.5.17.2 Underfrequency 1
Note
NOTE
7–44
As a preliminary step, disable all protection functions except underfrequency 1. Verify that
settings match the in-service requirements. Settings are entered or modified in the
ELEMENTS FREQUENCY

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 for 50 Hz
systems) 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 relay display should remain with no trip indications.
 Slowly decrease the frequency until the output relay(s) operate.
 Check that the operation took place at the selected frequency setting.
 As the frequency is varies, verify that the correct system frequency is
displayed by the
FREQUENCY
 Slowly reduce the voltage and note the voltage at which the output
relay(s) reset.
 Check that this dropout voltage is approximately the voltage supervision
value in the
MINIMUM OPERATING VOLTAGE

If voltage supervision is set to 0.0, then the element remains operated until the voltage is
decreased below approximately 2%, the level at which measurements become unreliable.
 Slowly increase the voltage and check that the element operates when
the voltage reaches 2% above the supervision level.
 Return the voltage to nominal value.
 Slowly decrease the current until the element resets.
FIGURE 7–12: Frequency element testing
UNDERFREQUENCY 1 settings menu.

A2 METERING
actual value.
S4 ELEMENTS FREQUENCY

745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 7: COMMISSIONING
FREQUENCY SYSTEM
 
UNDERFREQUENCY 1

setpoint.
S4