GE 339

CHAPTER 6: SETPOINTS S3 PROTECTION
339 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL 6–67
electromechanical units. With this setpoint, the energy capacity variable is
decremented according to the following equation.
where: T
RESET
= reset time in seconds; E = energy capacity reached (per unit); M = curve
multiplier; CR = characteristic constant (5 for ANSI, IAC, Definite Time, and FlexCurves™; 8
for IEC curves)
ANSI Curves
The ANSI time overcurrent curve shapes conform to industry standards and the ANSI
C37.90 curve classifications for extremely, very, normally, and moderately inverse. The
ANSI curves are derived from the following formula:
Eq. 17
where:T = trip time (seconds); M = multiplier value; I = input current; I
pu
= pickup current
setpoint; A, B, C, D, E = constants
Table 6-3: ANSI Curve Constants
Table 6-4: ANSI Curve Trip Times (in seconds)
ANSI Curve Shape A B C D E
ANSI Extremely Inverse 0.0399 0.2294 0.5000 3.0094 0.7222
ANSI Very Inverse 0.0615 0.7989 0.3400 –0.2840 4.0505
ANSI Normally Inverse 0.0274 2.2614 0.3000 –4.1899 9.1272
ANSI Moderately Inverse 0.1735 0.6791 0.8000 –0.0800 0.1271
Multiplier (TDM) Current (I/Ipickup)
1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
ANSI Extremely Inverse
0.5 2.000 0.872 0.330 0.184 0.124 0.093 0.075 0.063 0.055 0.049
1.0 4.001 1.744 0.659 0.368 0.247 0.185 0.149 0.126 0.110 0.098
2.0 8.002 3.489 1.319 0.736 0.495 0.371 0.298 0.251 0.219 0.196
4.0 16.004 6.977 2.638 1.472 0.990 0.742 0.596 0.503 0.439 0.393
6.0 24.005 10.466 3.956 2.208 1.484 1.113 0.894 0.754 0.658 0.589
8.0 32.007 13.955 5.275 2.944 1.979 1.483 1.192 1.006 0.878 0.786
10.0 40.009 17.443 6.594 3.680 2.474 1.854 1.491 1.257 1.097 0.982
ANSI Very Inverse
0.5 1.567 0.663 0.268 0.171 0.130 0.108 0.094 0.085 0.078 0.073
1.0 3.134 1.325 0.537 0.341 0.260 0.216 0.189 0.170 0.156 0.146
2.0 6.268 2.650 1.074 0.682 0.520 0.432 0.378 0.340 0.312 0.291
4.0 12.537 5.301 2.148 1.365 1.040 0.864 0.755 0.680 0.625 0.583
6.0 18.805 7.951 3.221 2.047 1.559 1.297 1.133 1.020 0.937 0.874
8.0 25.073 10.602 4.295 2.730 2.079 1.729 1.510 1.360 1.250 1.165
10.0 31.341 13.252 5.369 3.412 2.599 2.161 1.888 1.700 1.562 1.457
ANSI Normally Inverse
0.5 2.142 0.883 0.377 0.256 0.203 0.172 0.151 0.135 0.123 0.113
1.0 4.284 1.766 0.754 0.513 0.407 0.344 0.302 0.270 0.246 0.226
2.0 8.568 3.531 1.508 1.025 0.814 0.689 0.604 0.541 0.492 0.452
4.0 17.137 7.062 3.016 2.051 1.627 1.378 1.208 1.082 0.983 0.904
6.0 25.705 10.594 4.524 3.076 2.441 2.067 1.812 1.622 1.475 1.356