Schweitzer Engineering Laboratories SEL-351-5, Instruction Manual

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12.31
Date Code 20070117
Instruction Manual SEL-351-5, -6, -7 Relay
Standard Event Reports, Sag/Swell/Interruption Report, and SER
Example Standard 15-Cycle Event Report
Figure 12.6 Derivation of Phasor RMS Current Values From Event Report
Current Values
In Figure 12.6 , note that two rows of current data from the event report in
Figure 12.3 , 1/4 cycle apart, can be used to calculate phasor rms current
values. In Figure 12.6 , at the present sample, the phasor rms current value is:
IA = 2749 A
∠
–32.6°
The present sample (IA = 2317 A) is a real rms current value that relates to the
phasor rms current value:
2749 A * cos(–32.6°) = 2317 A
IA
t
IA
1474
–2320
–1479
2317
Event Report Column
X = Present Sample
Magnitude =
X = 2317
Y = –1479
Angle = Arctan
= Arctan
Y
X
–1479
2317
=–32.6˚
Real Axis
Axis Imaginary
1/4 cyc.
(–1479)
2
+ (2317)
2
= 2749
Y = Previous
1/4 Cycle