Wattmetric Ground Fault (32N) - GE 350-A9 Instruction Manual

CHAPTER 6: SETPOINTS

Wattmetric ground fault (32N)

NOTE:
NOTE
350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
The Wattmetric ground fault element, also called Wattmetric Zero-sequence Directional
element, responds to power derived from zero-sequence voltage and zero-sequence
current in a direction specified by the element characteristic angle. The angle can be set
within all four quadrants, so the measured power can be active or reactive or some
combination thereof. Therefore the element can be used to sense either forward or reverse
ground faults in either inductively, capacitively, or resistively grounded networks. The
inverse time characteristic allows time coordination of elements across the network.
Typical applications include ground fault protection in solidly grounded, ungrounded,
resistor-grounded, or resonant-grounded networks, or for directionalizing other non-
directional ground elements.
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) > WATT GND FLT
FUNCTION
Range: Disabled, Alarm, Latched Alarm, Trip, Control
Default: Disabled
For details see Common
VOLTAGE
Range: Calculated Vn, Measured Vx
Default: Calculated Vn
This setting uses neutral voltage (that is, three times the zero-sequence voltage). The
setpoint allows selecting the internally calculated neutral voltage, or externally supplied
voltage (broken delta VT connected to the auxiliary channel of the relay).
When Calculated Vn is selected, the VT CONNECTION setting must be set to wye for the
element to run. When Measured Vx is selected, the AUX VT INPUT under
SYSTEM SETUP > VOLTAGE SENSING
setpoints for the element to run.
VOLTAGE PICKUP
Range: 0.02 to 1.00 x VT in steps of 0.01 x VT
Default: 0.20 x VT
This setpoint specifies the minimum neutral voltage for supervising the power
measurement. This threshold is higher than possible unbalance during normal operation
of the system. Typically, this setpoint is selected at 0.1 to 0.2 x VT for ungrounded or
resonant grounded systems, and at 0.05 to 0.1 x VT for resistor grounded systems.
When the VOLTAGE setpoint value is Measured Vx, 1 x VT is the AUX VT SECONDARY
setpoint value multiplied by the AUX VT RATIO setpoint value.
When the VOLTAGE setpoint value is Calculated Vn, 1 x VT is the VT SECONDARY setpoint
value multiplied by the VT RATIO setpoint value.
CURRENT
Range: Calculated In, Measured Ig
Default: Calculated In
This setting corresponds to the neutral current (that is, three times the zero-sequence
current), either calculated internally from the phase currents or supplied externally via
the ground CT input from more accurate sources such as a core balance CT. This
setpoint selects the source of the operating current.
setpoints.
must be set to neutral voltage (Vn) under the VT bank
S3 PROTECTION
SETPOINTS > S2
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