VAMP 59 - Page 98

2.14 Inverse time operation
2 Protection functions
Technical description
98
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VM59.EN001
t = Operation delay in seconds
k = User‟s multiplier
I = Measured value
I
PICKUP
= User‟s pick up setting
A,B,C,D = Constant parameter according
Table 2.14.1-4.
Table 2.14.1-4 Constants for IEEE2 inverse delay equation
Delay type
Parameter
A
B
C
D
E
MI
Moderately inverse
0.1735
0.6791
0.8
-0.08
0.1271
NI
Normally inverse
0.0274
2.2614
0.3
-.1899
9.1272
VI
Very inverse
0.0615
0.7989
0.34
-0.284
4.0505
EI
Extremely inverse
0.0399
0.2294
0.5
3.0094
0.7222
Example for Delay type "Moderately inverse (MI)":
k = 0.50
I = 4 pu
I
PICKUP
= 2 pu
A = 0.1735
B = 0.6791
C = 0.8
D = -0.08
E = 0.127
38.0
8.0
2
4
127.0
8.0
2
4
08.0
8.0
2
4
6791.0
1735.05.0
32





































t
The operation time in this example will be 0.38 seconds. The
same result can be read from Figure 2.14.1-11.