9.21
Date Code 20171006
Instruction Manual
SEL-400 Series Relays
Reporting
Event Reports, Event Summaries, and Event Histories
Step 3. Calculate the reference phase angle. Usually, you compare power
system angles to a reference phasor (positive-sequence A-Phase volt-
age, for example):
Repeat
for the row data in the VA column that correspond
to the IA column data values you used in
The angle calculation for the VA data is the following:
Equation 9.3
(This is an example of an arctan calculation that yields the
incorrect answer from some calculators and math programs.)
Step 4. Calculate the absolute phase angle:
Subtract the IA angle from the VA angle to obtain the A-Phase-
referenced phasor angle for IA.
Equation 9.4
IA leads VA; thus, the rms phasor for current IA at the present
sample is 277.0 A
21.9°, referenced to VA.
In the procedure above, you use two rows of current data from the event report to
calculate an rms phasor current. At the first sample pair of Cycle [1], the rms pha-
sor is I
A
= 277.0 A
–105.9°.
The present sample of the sample pair (X = –76) is a scaled instantaneous current
value (not an rms quantity) that relates to the rms phasor current value by the
expression.
Equation 9.5
Polar Calculator Method
A method for finding the phasor magnitude and angle from event report quarter-
cycle data pairs is to use a polar-capable calculator or computer program. Many
calculators and computer programs convert Cartesian (X and Y) coordinate data
to polar data. Key or enter the X value (present value or lower value of a column
pair) and the Y value (later value or upper value in a column pair) as Cartesian
(rectangular) coordinates. Perform the keystrokes necessary for your calculator
or computing program to convert to polar coordinates. This is the phasor value
for the data pair.
Digital Section of the Event Report
The second portion of an event report is the digital section. Inspect the digital
data to evaluate relay element response during an event. See
for an
example from the SEL-411L. If you want to view only the digital portion of an
event report, use the
EVE D
command. In the digital portion of the event report,
the relay indicates deasserted elements with a period (.) and asserted elements
with an asterisk (*) character.
VA
=
arctan
Y
X
----
=
arctan
288.0
–
223.7
–
----------------
=
127.8
–
=
VA
IA
127.8
–
105.9
–
21.9
–
=
–
=
–
X
76
–
277.0
105.9
–
cos
=
=
Содержание SEL-421-4
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