Sensitive Ground Instantaneous Overcurrent Protection (50Sg) - GE Multilin 850 Instruction Manual

PROTECTION
Sensitive Ground
Instantaneous
Overcurrent
Protection (50SG)
4–152
The 850 relay is equipped with Sensitive Ground Instantaneous Overcurrent protection
element. The settings of this function are applied to the measured Sensitive Ground
current for producing Pickup and Trip flags. The Sensitive Ground IOC Pickup flag is
asserted when the Sensitive Ground current is above the PKP value. The Sensitive Ground
IOC Operate flag is asserted if the element stays picked-up for the time defined by the
Sensitive Ground IOC PKP Delay setting. If the Pickup time delay is set to 0.00 seconds, the
Pickup and Operate flags are asserted at the same time. The element drops from Pickup
without operation if the Sensitive Ground current drops below 97 to 98% of the Pickup
value.
Path:
Setpoints > Protection > Group 1(6) > Current > Sensitive Ground IOC 1(X)
FUNCTION
Range: Disabled, Trip, Alarm, Latched Alarm, Configurable
Default: Disabled
PICKUP
Range: 0.005 to 3.000 x CT in steps of 0.001 x CT
Default: 1.000 x CT
This setting sets the instantaneous Sensitive Ground overcurrent pickup level specified
as a multiplier of the nominal CT current for sensitive CT input. For example, a PKP
setting of 0.9 x CT with 300:5 CT translates into 270A primary current.
DIRECTION
Range: Disabled, Forward, Reverse
Default: Disabled
This setting defines the operation direction of the Sensitive Ground time overcurrent
element. Entering the direction for the Sensitive Ground IOC element, does not
automatically apply the selection. The direction detection is performed by the element
Sensitive Ground Directional OC, which must be enabled and configured according to
the directionality criteria of the feeder currents.
PICKUP DELAY
Range: 0.000 to 6000.000 s in steps of 0.001 s
Default: 0.000 s
This setting provides the selection for the pickup time delay used to delay the operation
of the protection.
DROPOUT DELAY
Range: 0.000 to 6000.000 s in steps of 0.001 s
Default: 0.000 s
This setting provides the selection for the dropout time delay used to delay the dropout
of the detection of the overcurrent condition.
BLOCK
Range: Off, Any FlexLogic operand
Default: Off
The Sensitive Ground IOC is blocked, when the selected operand is asserted.
OUTPUT RELAY X
For details see Common
EVENTS
Range: Enabled, Disabled
Default: Enabled
TARGETS
Range: Self-reset, Latched, Disabled
Default: Self-reset
Setpoints.
850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS