Schweitzer Engineering Laboratories SEL-787 - Figure 9.5 Derivation of Phasor RMS Current Values from Event Report Current Values

9.13
Date Code 20081022 Instruction Manual SEL-787 Relay
Analyzing Events
Event Reporting
Figure 9.5 Derivation of Phasor RMS Current Values From Event Report
Current Values
Digital Event Report
(EVE D Command)
The digital event report includes:
➤ Digital states of control and protection elements, including
overcurrent and voltage elements (if voltage inputs are
available), plus status of digital inputs and outputs and RTD
status
➤ Event Summary
➤ Relay Settings
Use the EVE D n command to view the normal digital report with 4 samples/
cycle for report n (if not listed, n is assumed to be 1). EVE D R gives the
RAW report with 16 samples/cycle.
Refer to the example event report in Figure 9.6 to view the digital event report
columns.
IA (RMS)
t
IA
Event Report Column
Magnitude =
X = 940.7
Y = —750.3
Angle = Arctan
= Arctan
Y
X
—750.3
940.7
= –38.6˚
Real Axis
Axis Imaginary
1/4 cyc.
(—750.3)
2
+ (940.7)
2
= 1204
Y = Previous
1/4 Cycle
•
•
•
752.0
—941.0
—750.3
940.7
•
•
•
X = Present Sample
NOTE: The arctan function of many
calculators and computing programs
does not return the correct angle for
the second and third quadrants (when
X is negative). When in doubt, graph
the X and Y quantities to confirm that
the angle that your calculator reports
is correct.