GE D90 Plus Instruction Manual page 182

POWER SYSTEM
NOTE:
Voltage inputs
172
Ground CT Secondary
Range: 1 A, 5 A
Default: 5 A
This setting selects the ground CT secondary value. It is used to derive secondary current
values from per-unit settings used in protection elements.
Current Cutoff Level
Range: 0.002 to 0.020 pu in steps of 0.001
Default: 0.020 pu
This setting modifies the current cut-off threshold. Very low currents (1 to 2% of the
rated value) are very susceptible to noise. Some customers prefer very low currents to
display as zero, while others prefer the current be displayed even when the value reflects
noise rather than the actual signal. The D90
and angles of the measured currents. If the magnitude is below the cut-off level, it is
substituted with zero. This applies to phase and ground current phasors as well as true
RMS values and symmetrical components. The cut-off operation applies to quantities
used for metering, protection, and control, as well as those used by communications
protocols. Raw current samples available via oscillography are not subject to cut-off.
Lower the
Current Cutoff Level
valid measurements. Unless dictated otherwise by a specific application, the default
setting of "0.020 pu" is recommended.
Select the Settings > Protection > Power System > AC Inputs - Voltage menu item to
open the voltage input configuration window.
Figure 152: Voltage input configuration settings
This menu allows the user to specify the parameters for each voltage input. The
and
Ratio Auxiliary VT Ratio
matching primary voltage in a synchrocheck application. The
settings are used to derive secondary voltage values from the per-
Auxiliary VT Secondary
unit settings used in protection elements. Protection functions that require phase-to-
neutral or zero-sequence quantities will not function correctly for delta VT configurations.
The following voltage input settings are available.
Phase VT Connection
Range: Wye, Delta
Default: Wye
This setting specifies the phase VT connection type for the corresponding voltage input.
An open-delta source VT connection would be entered as "Delta".
Plus
applies a cut-off value to the magnitudes
setting with care as the D90
settings are used for calculation of primary metering values or
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 7: PROTECTION
Plus
accepts lower signals as
Phase VT
Phase VT Secondary and