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350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
S3 PROTECTION
CHAPTER 6: SETPOINTS
Negative sequence
instantaneous
overcurrent
protection
The 350 relay has one Negative Sequence Overcurrent element per protection group. The
negative sequence over-current protection responds to negative sequence current, where
it is calculated as .
The negative sequence over-current elements are uniquely suited to detect phase-phase
faults and are not sensitive to balanced loads. While negative sequence elements do not
respond to balanced load, they do detect the negative sequence current present in
unbalanced load. For this reason, select an element pickup setting above the maximum
expected current due to load unbalance.
PATH
:
SETPOINTS > S3 PROTECTION > SETPOINT GROUP 1(2) > NEG SEQ IOC
NEG SEQ IOC FUNCTION
Range: Disabled, Latched Alarm, Alarm, Trip
Default: Disabled
The selection of the
Latched Alarm
,
Alarm
, or
Trip
setting enables the Negative
Sequence IOC function. The output relay #1 “Trip” will operate if the function
Trip
is
selected, and the negative sequence current computed by the relay, is above the NEG
SEQ IOC PKP setting for a time greater than the selected time under NEG SEQ IOC DELAY.
The LED “ALARM” will not turn on if the neg. sequence IOC function is set to
Trip
. The LED
“ALARM” will flash under the neg. sequence IOC operating condition, with the neg.
sequence IOC function selected as
Alarm
, and will self-reset, when this operating
condition clears. If
Latched Alarm
is selected as a neg. seq. IOC function, the LED
“ALARM” will flash during the IOC condition, and will stay “ON” after the condition clears,
until the reset command is initiated. The output relay #1 “Trip” will not operate if
Latched
Alarm
or
Alarm
setting is selected. Any or all of the output relays 3 to 6 can be selected
to operate with the neg. seq. IOC function selected as
Latched Alarm
,
Alarm
, or
Trip
.
NEG SEQ IOC PKP
Range: 0.05 to 20.00 x CT in steps of 0.01 x CT
Default: 1.00 x CT
This setting defines the negative sequence IOC pickup level.
NEG SEQ IOC DELAY
Range: 0.00 to 300.00 sec in steps of 0.01 sec
Default: 0.00 sec
This setting specifies the time delay before IOC operation. .
OUTPUT RELAY 3 to 6
Range: Do not operate, Operate
Default: Do not operate
Any or all of the output relays 3 to 6 can be selected to operate upon a Neg Seq IOC
condition. Relay outputs operation is available no matter whether the
Latched Alarm
,
Alarm
, or
Trip
function is selected.
BLOCK 1/2/3
Range: Off, Contact Input 1 to 10[8], Virtual Input 1 to 32, Remote Input 1 to 32, Logic
Elements 1 to 16
Default: Off
Three blocking inputs are provided in the Neg. seq. IOC menu. Any one of the assigned
blocking inputs can block the function. The available selections for each block include
Contact input, Virtual Input, Remote Input, or Logic Element.
