Schweitzer Engineering Laboratories SEL-351A - Figure 12.6 Derivation of Phasor RMS Current Values from Event Report Current Values

12.29
Date Code 20080213 Instruction Manual SEL-351A Relay
Standard Event Reports 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
=–30.0˚
Real Axis
Axis Imaginary
1/4 cyc.
(–1479)
2
+ (2317)
2
= 2749
Y = Previous
1/4 Cycle
Courtesy of NationalSwitchgear.com