9.12
SEL-787 Relay
Instruction Manual
Date Code 20081022
Analyzing Events
Event Reporting
Figure 9.4
Derivation of Analog Event Report Current Values and RMS
Current Values From Sampled Current Waveform
In
, note that two rows of current data from the analog event report,
1/4 cycle apart, can be used to calculate phasor rms current values. In
, at the present sample, the phasor rms current value is:
Equation 9.1
The present sample (IA = 940.7 A) is a real rms current value that relates to
the phasor rms current value:
Equation 9.2
(752.0)
2
+ (–941.0)
2
= 1204
(–750.3)
2
+ (940.7)
2
= 1204
(–941.0)
2
+ (–750.3)
2
= 1204
Event Report Column
752.0
–941.0
–750.3
940.7
IA
1
2
2
2
Multiply by
1
Multiply by
940.7
–941.0
–750.3
752.0
–1061.1
–1330.8
1063.5
1330.4
t
IA (peak)
1/4 cyc.
IA
peak
= 1703A
peak
1703 A
peak
= 1204 A
RMS
•
•
•
752.0
—941.0
—750.3
940.7
•
•
•
IA
1204 A
38.6
°
–
∠
=
1204 A
cos
38.6
°
–
(
)
• 940.7
A
=
Summary of Contents for SEL-787
Page 1: ...20081022 SEL 787 Transformer Protection Relay Instruction Manual PM787 01 NB ...
Page 6: ...This page intentionally left blank ...
Page 12: ...This page intentionally left blank ...
Page 18: ...This page intentionally left blank ...
Page 78: ...This page intentionally left blank ...
Page 206: ...This page intentionally left blank ...
Page 280: ...This page intentionally left blank ...
Page 334: ...This page intentionally left blank ...
Page 376: ...This page intentionally left blank ...
Page 388: ...This page intentionally left blank ...
Page 474: ...This page intentionally left blank ...
Page 508: ...This page intentionally left blank ...