9.17
Date Code 20171006 Instruction Manual SEL-400 Series Relays
Reporting
Event Reports, Event Summaries, and Event Histories
Obtaining RMS Phasors From 4-Samples/Cycle Event Reports
Use the column data in an event report to calculate rms values. You can use a cal-
culator to convert rectangular data to phasor data, or use hand-calculations to sep-
arately determine the magnitude and angle of the rms phasor.
Hand Calculation Method
The procedure in the following steps explains a method for obtaining a current
phasor from the IA channel data in the event report of Figure 9.6. You can pro-
cess voltage data columns similarly. The drawings in Figure 9.7 and Figure 9.8
show 1 cycle of A-Phase current in detail. Figure 9.7 shows how to relate the
event report ac current column data to the sampled waveform and rms values.
Figure 9.8 shows how to find the phasor angle. If you use the larger 8-samples/
cycle event report, take every other sample and apply those values in this procedure.
This examples assumes you have captured an event report and are prepared to
calculate phasors from it.
Step 1. Calculate the phasor magnitude:
a. Select a cycle of data from the IA column of the event report.
Figure 9.6 Cycle [1] data for this example are shown in Figure 9.7.
There are three pairs of scaled instantaneous current samples
from Cycle [1].
Compute phasor magnitude using the following expression:
Equation 9.1
b. In Equation 9.1, Y is the first row of IA column current of a data
pair, and the next row is X, the present value of the pair.
For this example, the computation shown in Figure 9.7 yields 277.0 A.
c. Compute phasor magnitudes from the remaining data pairs for
Cycle [1].
d. Confirm that all values are similar.
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