2.2.1.3.
IAC CURVES
The curves for the General Electric type IAC relay family are derived from the formulae:
where: T =
TDM =
I =
Ipkp =
A to E =
IAC Curve Shape
IAC Extremely Inverse
IAC Very Inverse
IAC Inverse
IAC Inverse Long
IAC Inverse Short
GEK-106273L
PRODUCT DESCRIPTION
⎛
⎜
⎜
⎜
=
+
T
TDM
*
A
⎜
⎛
⎜
⎜
⎜
⎜
I
⎝
⎝
Operate time in seconds
Multiplier setting
Input current
Pickup Current Setting
Constants
Table 2.1: GE TYPE IAC INVERSE TIME CURVE CONSTANTS
HMI
Extr Inverse
Very Inverse
Mod Inverse
Inverse Long
Inverse Short
MIF Digital Feeder Protection
B
D
+
⎞
⎛
⎛
⎞
I
⎟
I
−
⎜
⎜
⎟
−
C
⎟
C
⎜
⎟
⎜
⎠
I
⎝
⎠
⎝
pkp
pkp
A
B
0.0040
0.6379
0.0900
0.7955
0.2078
0.8630
0.3754
17.8307
0.0442
0.0482
⎞
⎟
⎟
⎟
E
+
⎟
2
3
⎞
⎛
⎞
⎛
⎞
I
⎟
⎟
⎜
⎟
⎜
⎟
−
C
⎜
⎟
⎟
⎜
⎟
⎟
I
⎝
⎠
⎠
⎝
⎠
⎠
pkp
C
D
0.6200
1.7872
0.1000
-1.2885
0.8000
-0.4180
0.32
-23.7187
0.34
0.0223
E
0.2461
7.9586
0.1947
23.8978
0.0697
2-5