Sel 551 - Figure 7.3 Derivation of Event Report Current Values and RMS Current Values from Sampled Current Waveform

7.15
Date Code 20110408 Instruction Manual SEL-551 Relay
Standard Event Reports and SER
Example Standard 15-Cycle Event Report
Figure 7.3 Derivation of Event Report Current Values and RMS Current Values From Sampled Current Waveform
In Figure 7.3, note that any two rows of current data from the event report in
Figure 7.2, one quarter (1/4) cycle apart, can be used to calculate rms current
values.
IA
cyc
1
8
IA
= 3217 A
peak
peak
t
99
2342
3215
2205
–98
–2342
–3216
–2203
1559
–1558
–2274
–1656
–69
2273
1656
70
multiply by
1
2
multiply by
2
1
2
peak
3217 A
= 2275 A rms
IA
1559
–69
–1656
–2274
–1558
70
1656
2273
1656
70
–1558
-2274
–1656
–69
1559
(–1656)
2
+ (-1558)
2
= 2274
event report column
(–69)
2
+ (-2274)
2
= 2275
(1559)
2
+ (-1656)
2
= 2274
(–2274)
2
+ (70)
2
= 2275
(–1558)
2
+ (1656)
2
= 2274
(70)
2
+ (2273)
2
= 2274
2273