GE 750 Instruction Manual page 402

CONTROL SCHEMES
7.6.6 Underfrequency
Restoration
7 - 74
 Inject V
relay.
 Reduce the injected voltages to cause an undervoltage trip, then set V
to nominal.
 Slowly raise V
This is the operating level of
Make the test connections specified in FIGURE 7–1: Relay Test Wiring – Wye Connection or
FIGURE 7–2: Relay Test Wiring – Delta Connection on page 7–5. The following procedure
checks Logic and Timers for Underfrequency Restoration:
 Program the
and
UNDERFREQ 2 FUNCTION
 Assert or De-assert a logic input to simulate a closed breaker.
 Inject a voltage at nominal voltage and frequency into the bus voltage
Phase A input.
 Initially set
setpoints as required.
 Reduce the frequency to below the underfrequency pickup level.
After the programmed delay Underfrequency 1 should cause a trip,
which should not initiate underfrequency restoration as the breaker is
closed.
Diagnostic message "Ufreq Restore Init" should not be displayed.
 Assert or De-assert a logic input to simulate an open breaker, which
should initiate underfrequency restoration.
The diagnostic alarm message and LED should be displayed, and any
output relays programmed to operate for this condition should operate.
 Change the
the diagnostic message should change to control and the Alarm LED
should turn off.
Return this setpoint to "Alarm".
 Assert logic input Block Restoration.
The diagnostic alarm message and LED should be removed from the
display, and any output relays that operated should reset.
 De-assert the logic input.
The alarm message and LED should again be displayed and output
relays operated. After the delay programmed in Incomplete Sequence
Time, the alarm message and LED should be removed from the display
and output relays reset.
 Return the reduced frequency to nominal, resetting both the
underfrequency trip condition and underfrequency restoration.
 Reduce frequency until Underfrequency 1 trips, then immediately return
the frequency to nominal.
The diagnostic alarm message and LED should be displayed, and output
relays operated.
= V = nominal voltage into the bus voltage input of the
ab cb
until the Close Relay operates.
cb
UNDERVOLT RESTORE MIN VOLTS
UNDERFREQ 1 FUNCTION
as "Disabled".
UNDERFREQ RESTORATION
UNDERFREQ RESTORE FUNCTION
750 FEEDER MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 7: COMMISSIONING
for V
as "Trip", as "0",
MIN VOLTAGE
setpoint to Alarm, and other
setpoint to "Control", and
ab
.
cb