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S3 PROTECTION
Neutral instantaneous overcurrent
6–88
The relay has one Instantaneous Overcurrent protection. The settings of this function are
applied to the calculated neutral current for producing pickup and trip flags. The Neutral
IOC pickup flag is asserted, when the neutral current is above the PKP value. The Neutral
IOC operate flag is asserted if the element stays picked up for the time defined by the
Neutral IOC Delay setting. If the pickup time delay is set to 0.00 seconds, the pickup and
operate flags will be asserted at the same time. The element drops from pickup without
operation, if the neutral current drops below 97-99% of the pickup value.
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 > S3 PROTECTION > NEUTRAL IOC
NTRL IOC1 FUNCTION
Range: Disabled, Latched Alarm, Alarm, Trip
Default: Disabled
The selection of the Latched Alarm, Alarm, or Trip setting enables the Neutral IOC
function. The output relay #1 "Trip" will operate if the Neutral IOC function is selected as
Trip, and the neutral current calculated by the relay satisfies the operating condition set
by the settings. The "ALARM" LED will not turn on if the neutral IOC operates when set to
function Trip. The "ALARM" LED will flash upon Neutral IOC operation with the IOC
function selected as Alarm and will self-reset when this operation clears. If Latched
Alarm is selected as an IOC function, the "ALARM" LED will flash during IOC operation
and will stay "ON" after the operating condition clears, until the reset command is
initiated. The output relay #1 "Trip" will not operate if the Latched Alarm or Alarm
setting is selected. Any assignable output relay can be selected to operate when the
Neutral IOC function - Latched Alarm, Alarm, or Trip - is selected.
NTRL IOC PKP
Range: 0.05 to 20 x CT in steps of 0.01 x CT
Default: 1.00 x CT
This setting sets the neutral instantaneous overcurrent pickup level specified as times
CT.
NTRL IOC DELAY
Range: 0.00 to 300 s in steps of 0.01 s
Default: 0.00 s
This setting provides selection for the pickup time delay, used to delay the protection
operation.
OUTPUT RELAY 4 to 6 / OUTPUT RELAY 5 to 6
Range: Do not operate, Operate
Default: Do not operate
Any assignable output relay can be selected to operate upon Neutral IOC operation.
When the SWITCHING DEVICE is selected as BREAKER, the assignable output relays will
be Output Relay 4 to 6. When the SWITCHING DEVICE is selected as CONTACTOR, the
assignable output relays will be Output Relay 5 to 6.
BLOCK 1 to 3
Range: Off, Contact Input 1 to 10, Virtual Input 1 to 32, Remote Input 1 to 32, Logic
Element 1 to 16
Default: Off
Three blocking inputs are provided for the Neutral IOC feature. When any of the selected
blocking inputs is on, the Neutral IOC function is blocked. The available selections for
each block can be any Contact input, Virtual Input, Remote Input, or Logic Element.
339 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 6: SETPOINTS
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