GE D90 Plus Instruction Manual page 298

GROUPED PROTECTION ELEMENTS
288
Figure 249: Wattmetric ground fault configuration window
The following settings are available for each wattmetric zero-sequence directional ground
fault element.
Function
Range: Enabled, Disabled
Default: Disabled
This setting enables and disables the wattmetric zero-sequence directional ground fault
protection element.
Source
Range: LINE (SRC 1), BKR 1 (SRC 2), BKR 2 (SRC 3)
Default: LINE (SRC 1)
This setting selects the signal source for the wattmetric zero-sequence directional
ground fault protection element.
Voltage
Range: Calculated VN, Measured VX
Default: Calculated VN
The wattmetric zero-sequence directional ground fault element uses neutral voltage
(that is, three times the zero-sequence voltage). This setting allows selecting between the
internally calculated neutral voltage or the externally supplied voltage (broken delta VT
connected to the auxiliary channel bank of the relay). When the latter selection is made,
the auxiliary channel must be identified by the user as a neutral voltage under the VT
bank settings. This element operates only if the auxiliary voltage is configured as neutral.
OV Pickup
Range: 0.02 to 1.10 pu in steps of 0.01
Default: 0.20 pu
This setting specifies the minimum zero sequence voltage supervising the directional
power measurement. This threshold needs to be higher than possible unbalance during
normal operation of the system. Typically, this setting is selected at 0.1 to 0.2 pu for the
ungrounded or resonant grounded systems, and at 0.05 to 0.1 pu for solidly or resistor-
grounded systems. When using externally supplied voltage via the auxiliary voltage
channel, 1 pu is the nominal voltage of this channel as per VT bank settings. When using
internally calculated neutral voltage, 1 pu is the nominal phase to ground voltage as per
the VT bank settings.
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 7: PROTECTION