9-22
Event Reports and Sequential Events Reporting
Date Code 20010521
SEL-387E Instruction Manual
Figure 9.7: Derivation of Phasor RMS Current Values From Event Report Current Values
In Figure 9.7 note that two rows of current data one-quarter cycle apart can be used to calculate
phasor RMS current values. At the time of interest the present sample is used as the Real Axis,
or “X,” component, while the value from one-quarter cycle before is used as the Imaginary Axis,
or “Y” component. Plotting the components as shown, and noting that the angle of the phasor is
Arctan (Y/X), the complete phasor quantity can be derived and compared with other current
phasors calculated from other current pairs selected from the same two rows of the Event Report.
In Figure 9.7, at the present sample, the phasor RMS current value is:
IA = 2749 A
µ
-30.0
The present sample (IA = 2380 A) is a real RMS current value that relates to the phasor RMS
current value:
2749 A • cos(-30.0
) = 2380 A
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