GE Multilin G650 Manual page 179

5.4 PROTECTION ELEMENTS
5.4.2.4 ANSI CURVES
This family of curves complies with the American Standard ANSI C37.90 for Extremely inverse, Very inverse, Normally
inverse and Moderately inverse curves. The formulas that define these curves are as follows:
where:
T = Operation time (in seconds).
Dial = Multiplying factor
I = Input current
I = Current pickup setting
pickup
A, B, C, D, E = Constants
T = Reset time (in seconds) assuming a 100% of power capacity and that the reset is activated
reset
T = Characteristic constant
r
5
The different constants that define the above-mentioned curves are:
Table 5–35: CONSTANTS FOR ANSI CURVES
ANSI CURVE SHAPE
ANSI Extremely Inverse
ANSI Very Inverse
ANSI Normally Inverse
ANSI Moderately Inverse
5-36
A B
0.0399 0.2294
0.0615 0.7989
0.0274 2.2614
0.1735 0.6791
G650 Generator Protection & Control System
C D E
0.5 3.0094 0.7222
0.34 -0.284 4.0505
0.3 -4.1899 9.1272
0.8 -0.08 0.1271
5 SETTINGS
TR
5.67
3.88
5.95
1.08
GEK-113285A