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8.4 PROTECTION SCHEMES
8.4PROTECTION SCHEMES
The Active setpoint group is indicated by a continuously illuminated LED, and the Edit group by an intermittently illuminated
LED on the relay faceplate. When changing settings for testing be careful to check the correct group is adjusted and
selected as the active group.
Verify that settings in a particular setpoint group are being used by the protection elements when the particular group is
selected to be active. There are three alternative strategies that can be used to provide this verification:
•
Test any one protection element that has different settings in different groups
•
Test a random selection of protection elements in different groups
•
Test all protection elements that are not disabled in every group
Once one of the above strategies is selected, the following procedures are used to test protection elements.
a) PHASE TOC 1
For these tests, refer to the figures on page 8–3 for test connections.
The following procedures, other than the check for Linear Reset Timing, are based on the "Instantaneous" reset
time characteristic. If the "Linear" reset time characteristic is required, ensure that there is sufficient time between
test current injections, or cycle relay power OFF and ON to discharge the energy measurement accumulator to 0.
NOTE
The following procedure checks Pickup with one phase for operation:
1.
Inject current at a level below the pickup level into Phase A.
2.
Slowly increase the current until the Pickup LED comes on. Note the pickup value.
3.
Slowly reduce the current until the Pickup LED goes out. Note the dropout level, which should be 2% of CT less than
pickup when pickup ≤ CT or 97 to 98% of pickup when pickup > CT.
4.
Repeat Steps 1 through 3 for Phases B and C.
The following procedure checks indications and operations caused by a Trip function, with front panel
1.
Inject current to cause a pickup and wait until the element times to Trip.
2.
Check that the Trip and Message LEDs are flashing, the Last Trip message is displayed, and the Output Relay 1 and
any others programmed to operate (as well as their associated LED indicators) operate.
3.
Slowly reduce the current until the Pickup LED goes out. Check that the Trip and Message LEDs are flashing, and that
the Output Relay 1 and any others programmed to operate (as well as their associated LEDs) reset.
4.
Press the front panel
displayed. Turn current off.
The following procedure checks indications and operations caused by a Trip function, with Logic Input resetting:
1.
Ensure that the reset logic input control function has been assigned to a logic input.
8
2.
Inject current to cause a pickup and wait until the element times to Trip.
3.
Check that the Trip and Message LEDs are flashing, the Last Trip message is displayed, and the Output Relay 1 and
any others programmed to operate (as well as their associated LED indicators) operate.
4.
Slowly reduce the current until the Pickup LED goes out. Check that the Trip and Message LEDs are flashing, and that
the Output Relay 1 and any others programmed to operate (as well as their associated LEDs) reset.
5.
Assert a logic input to provide a reset. Check that the Trip and Message LEDs are now off, and the Last Trip message
is no longer displayed. Turn current off.
The following procedure checks indications and operations caused by an Alarm function:
1.
Inject current to cause a pickup and wait until the element times to Alarm.
2.
Check that the Alarm and Message LEDs are flashing, the Active Alarm message is displayed, and any output relays
programmed to operate (as well as their associated LEDs) operate.
8-16
Courtesy of NationalSwitchgear.com
key. Check that the Trip and Message LEDs go off, and the Last Trip message is no longer
RESET
750/760 Feeder Management Relay
8 COMMISSIONING TESTS
8.4.1 SETPOINT GROUPS
8.4.2 PHASE OVERCURRENT
key resetting:
RESET
GE Multilin
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