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GE
Grid Solutions
869 Motor Protection System
Chapter 6: Metering
869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
Metering
CONVENTION FOR MEASURING PHASE ANGLES
All phasors calculated by 8 Series relays and used for protection, control and metering
functions are rotating phasors, that maintain the correct phase angle relationships with
each other at all times.
For display and oscillography purposes, all phasor angles in a given relay are referred to an
AC input channel pre-selected as the phase A voltage. If there is no voltage input, the
phase A current is used for angle reference. The phase angle of the reference signal always
display zero degrees and all other phase angles are relative to this signal. If the preselected
reference signal is not measurable at a given time, the phase angles are not referenced.
The phase angles in 8 Series relays are always presented as negative values in the lagging
direction as illustrated in the following.
Figure 6-1: Phase Angle Measurement 8 Series Convention
METERING
6–1
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