Cold Load Pickup Blocking; Undervoltage Restoration - GE 750 Instruction Manual

Control Schemes
Undervoltage Restora-
tion
GE Multilin
blocking. Wait until the element operates, as shown by the Pickup LED coming
on at the end of the programmed
3. Turn the current off. The time interval can be checked in the Event Recorder.
For Neutral IOC 1 Blocking, Ground IOC Blocking, Sensitive Ground IOC Blocking,
and Neg Seq IOC Blocking, follow the procedure described above for Phase IOC 1
Blocking, injecting current as appropriate.
The following procedure checks Phase TOC 1 Raised Pickup for Cold Load Blocking:
1. Ensure all other overcurrent features are "Disabled".
2. Cold Load Pickup Blocking will raise the pickup setting of the curve normally
used by the programmed percentage. Set a test current to a level between the
normal pickup setting and the raised setting, (at least 5% of nominal current)
then turn the current off.
3. Assert a Cold Load Pickup logic input and immediately inject the test current
into the relay. Phase TOC 1 will not pickup as the pickup current is raised.
Increase the injection current until the Pickup LED comes on, before the cold
load pickup blocking feature times-out and returns the pickup to normal. Check
that the raised pickup level is correct. Turn current off, and wait until the alarm
is removed from the display.
4. Set a test current to a level between the normal pickup setting and the raised
setting, then turn the current off.
5. Assert a Cold Load Pickup logic input and immediately inject the test current
into the relay. Phase TOC 1 will not pickup as the pickup current is raised.
6. At the end of the programmed
should come on, as the pickup setting has returned to normal. When this
happens, reduce the injection current until the Pickup LED goes out. The
LOAD PICKUP BLOCK TIME
For Neutral TOC 1 Raised Pickup, Ground TOC Raised Pickup, Sensitive Ground TOC
Raised Pickup, and Neg Seq TOC Raised Pickup, follow the procedure outlined for
Phase TOC 1 Raised Pickup, injecting current as appropriate.
To check the Select Setpoint Group for Cold Load Blocking, apply a Cold Load Pickup
logic input and verify that the selected setpoint group becomes active. Verify that
settings return to the previous setpoint group after the Cold
interval expires.
a) Description
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 7–4. The
following procedure checks Logic and Timers for Undervoltage Restoration:
1. Program the Undervoltage 1 function as "Trip" and the Undervoltage 2 function
as "Disabled".
2. Assert or De-assert a logic input to simulate a closed breaker.
3. Inject a balanced three-phase voltage at nominal voltage and frequency into
the bus voltage input.
4. Initially set the undervoltage restoration function setpoint to Alarm, and other
setpoints as required.
5. Turn the voltage off. After the programmed delay Undervoltage 1 should cause a
trip, which should not initiate undervoltage restoration as the breaker is closed.
Diagnostic message "Uvolt Restore Init" should not be displayed.
6. Assert or De-assert a logic input to simulate an open breaker, initiating
undervoltage restoration. The diagnostic alarm message and LED should be
displayed, and output relays programmed to operate for this condition should
operate.
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COLD LOAD PICKUP BLOCK
COLD LOAD PICKUP BLOCK TIME
interval can be checked in the Event Recorder.
750/760
Feeder Management Relay
time.
the Pickup LED
COLD
LOAD PICKUP BLOCK TIME
7–49