Rockwell Automation 865 Differential Protection Relay - Manual (Page 86)

3-42 Protection
Functions
865-UM001A-EN-P – July 2009
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 . 0 5 . 0
3 2
=
⎥
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛ −
+
⎟
⎠
⎞
⎜
⎝
⎛ −
−
+
⎟
⎠
⎞
⎜
⎝
⎛ −
+ ⋅ = t
The operation time in this example will be 0.38 seconds. The same result
can be read from Figure 3.26.
Figure 3.26 – IEEE2 Moderately Figure 3.27 – IEEE2 Normal
Inverse Delay Inverse Delay