Rockwell Automation 865 Differential Protection Relay User Manual
Page 81
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Protection Functions
3-37
865-UM001A-EN-P – July 2009
Table 3.23 – Constants for IEC Inverse Delay Equation
Parameter
Delay type
A
B
NI Normal
inverse
0.14
0.02
EI Extremely
inverse
80
2
VI Very
inverse
13.5
1
LTI Long
time
inverse
120
1
Example for Delay type "Normal inverse (NI) ":
k
=
0.50
I
=
4 pu (constant current)
I
pickup
=
2
pu
A
= 0.14
B
= 0.02
0
.
5
1
2
4
14
.
0
50
.
0
02
.
0
=
−
⎟
⎠
⎞
⎜
⎝
⎛
⋅
=
t
The operation time in this example will be 5 seconds. The same
result can be read from Figure 3.16.
Figure 3.16 – IEC Normal Inverse Delay
Figure 3.17 – IEC Extremely Inverse Delay
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