CHAPTER 6: SETPOINTS
S4 CONTROLS
350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
6–125
Local Mode is set if the input for the LOCAL MODE setpoint is asserted. In this mode, the
REMOTE OPEN and REMOTE CLOSE setpoints are deactivated, regardless of the status of
their selected inputs.
Breaker Open
and
Breaker Close
commands from the KEYPAD BKR
OPEN and KEYPAD BKR CLOSE setpoints will be active, if the breaker operation is set to
Local Mode (i.e. the selected input under the LOCAL MODE setpoint asserted).
Cold load pickup
The 350 can be programmed to block the instantaneous over-current elements, and raise
the pickup level of the time over-current elements, when a cold load condition is detected.
The cold load condition is detected during closing of the breaker on a feeder that has been
de-energized for a long time. The feeder inrush current and the motor accelerating current
during breaker closing may be above some over-current protection settings. The diagram
shows the slow decaying of the cold load current starting at about 500% of the nominal
current at the time of breaker closing, decaying down to 300% after 1 second, 200% after
2 seconds, and 150% after 3 seconds.
Figure 43: Cold load pickup
The relay detects Cold Load condition (Cold Load Pickup armed), if the currents on all three
phases drop below 3% of the CT nominal rating for the period of time greater, than the
Outage Time Before Cold Load setting. The Cold Load condition can be immediately
initiated (Outage Time Before Cold Load timer bypassed), by asserting a contact input
selected for External CLP Initiate.
The second timer Cold Load Pickup Block is used to specify the time of blocking the
instantaneous over-current elements, and the time of raised pickup levels of the time over-
current elements, after breaker closing. The timer starts when at least one of the three
phase currents is above 10% of CT nominal. Upon timer expiration, the settings return to
normal.
The following path is available using the keypad. For instructions on how to use the
keypad, please refer to
Chapter 3 - Working with the Keypad
.
PATH
:
SETPOINTS > S4 CONTROLS > COLD LOAD PICKUP
Time (seconds)
Current
(%
of
nominal)
0
100
200
300
400
500
-1
0
1
2
3
4
5
6
OUTAGE
PICKUP
PICKUP
LOAD ENERGIZED
X
NORMAL TRIP SETTING
898750.CDR
