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F.3 ANALYSIS OF A PRACTICAL CASE
F.3ANALYSIS OF A PRACTICAL CASE
Using the values from the real case previously mentioned, we can prepare a table, where:
* Theoretical Pickup = Set Value * 1.05, in order to avoid undesired trips.
** Adjusted Time:
This table shows the relation between current accuracy
The current error is below 3%, as stated in the specifications, and the timing error will depend on it, according to the general
F
formula.
Though the example is for a 3 phase relay, the same is applicable to single phase ones.
F-4
=
T
⎛
MeasuredCu
⎜
⎝
Theoretical Pickup * (A)
Practical Pickup (A)
Estimated Current Error (%)
Injected Current (A)
Measured Current (A)
Theoretical Time (s)
Adjusted Time ** (s)
Real Time (s)
Timing Error (s)
Timing Error (%)
(Estimated Current
MIFII Digital Feeder Relay
13
5 .
*
. 0
45
1
⎞
rrent
−
⎟
1
⎠
3
5 .
PHASE A PHASE B PHASE C
3.675
3.675
3.675
3.61
3.63
3.59
-1.77
-1.22
-2.31
4
4
4
3.93
3.95
3.91
42.52
42.52
42.52
49.45
47.25
51.86
50.1
50.2
50.2
-0.65
-2.95
+1.66
-1.29
-5.88
+3.31
Accuracy) and timing accuracy
APPENDIX F
(Timing
Error).
GEK-106237P
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