GE D90 Plus Instruction Manual page 572

METERED VALUES
562
For display and oscillography purposes, all phasor angles in a given device are referred to
an AC input channel pre-selected by the
Settings > Protection > Power System > Frequency menu. This setting defines a
particular AC signal source to be used as the reference.
Plus
The D90 will first determine if any phase VT bank is indicated in the source. If it is,
voltage channel VA of that bank is used as the angle reference. Otherwise, the
Plus
D90 determines if any auxiliary VT bank is indicated. If it is, the auxiliary voltage channel
of that bank is used as the angle reference. If neither of these two conditions are satisfied,
then two more steps of this hierarchical procedure to determine the reference signal
include the phase CT bank and the ground CT bank.
If the AC signal pre-selected by the D90
phase angles are not referenced. The phase angles are assigned as positive in the leading
direction and negative in the lagging direction to more closely align with power system
metering conventions. These are illustrated below.
Figure 489: D90
Plus
The D90 calculates voltage symmetrical components for the power system phase A
line-to-neutral voltage, and symmetrical components of the currents for the power system
phase A current. Owing to the above definition, phase angle relations between the
symmetrical currents and voltages stay the same irrespective of the connection of
instrument transformers. This is important for setting directional protection elements that
use symmetrical voltages.
For display and oscillography purposes the phase angles of symmetrical components are
referenced to a common value specified by the
The following voltages and currents are measured for wye-connected instrument
transformers in the ABC phase rotation.
Frequency and Phase Reference
Plus
upon configuration is not measurable, then the
Plus
phase angle measurement convention
Frequency and Phase Reference
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 11: METERING
setting in the
setting.
Eq. 54
Eq. 55
Eq. 56