9.18
SEL-387-0, -5, -6 Relay
Instruction Manual
Date Code 20050919
Event Reports and SER
Standard 15-, 30-, or 60-Cycle Event Reports
Figure 9.7
Derivation of Phasor
RMS Current Values From Event Report Current Values
, 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
at the present sample the
phasor rms current value is:
Equation 9.1
IA
t
IA
1379
–2376
–1375
2380
event report column
X=present sample
Y =
previous
1/4 cycle
Magnitude =
X = 2380
Y
=
–13
75
Angle
= Arctan
= Arctan
Y
X
(
)
–
2380
(
)
=–30.0˚
Real Axis
A
xi
s
Ima
g
inary
1/4 cyc.
(–1375)2 + (–2380)2 = 2749
IA
2749 A
30.0
°
–
∠
=
Содержание SEL-387-0
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