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350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
S3 PROTECTION
CHAPTER 6: SETPOINTS
Phase timed overcurrent (51P)
The relay has one Phase Time Overcurrent protection element per protection group. The
settings of this function are applied to each of the three phases to produce trip or pickup
per phase. The TOC pickup flag is asserted, when the current on any phase is above the
PKP value. The TOC trip flag is asserted if the element stays picked up for the time defined
by the selected inverse curve and the magnitude of the current. The element drops from
pickup without operation, if the measured current drops below 97-98% of the pickup value,
before the time for operation is reached. The selection of Definite Time has a base time
delay of 0.1 s, multiplied by the selected TD multiplier. For example the operating time for
TOC set to Definite Time and a TDM set to 5 will result in 5*0.1 = 0.5 s.
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 > SETPOINT GROUP 1(2) > PHASE TOC
PH TOC FUNCTION
Range: Disabled, Latched Alarm, Alarm, Trip
Default: Disabled
For details see
PH TOC PKP
Range: 0.05 to 20.00 x CT in steps of 0.01 x CT
Default: 1.00 x CT
This setting sets the time overcurrent pickup level. For example, a PKP setting of 0.9 x CT
with 300:5 CT translates into 270A primary current.
PH TOC CURVE
Range: ANSI Extremely/Very/Moderately/Normally Inverse, Definite Time, IEC Curve A/B/C
and Short Inverse, IAC Extremely/Very/Inverse/Short, User Curve, FlexCurve A, FlexCurve
B
Default: Extremely Inverse
This setting sets the shape of the selected TOC inverse curve. If none of the standard
curve shapes is appropriate, a custom User curve, or FlexCurve can be created. Refer to
the User curve and the FlexCurve setup for more detail on their configurations and
usage.
PH TOC TDM
Range: 0.05 to 50.00 in steps of 0.01
Default: 1.00
This setting provides selection for Time Dial Multiplier by which the times from the
inverse curve are modified. For example if an ANSI Extremely Inverse curve is selected
with TDM = 2, and the fault current was 5 times bigger than the PKP level, the operation
of the element will not occur before an elapsed time from pickup, of 495 ms.
PH TOC RESET
Range: Instantaneous, Linear
Default: Instantaneous
The “Instantaneous” reset method is intended for applications with other relays, such as
most static relays, which set the energy capacity directly to zero when the current falls
below the reset threshold. The “Timed” reset method can be used where the relay must
coordinate with electromechanical relays.
