GE 850 - Page 276

6–8 850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CURRENT ELEMENTS CHAPTER 6: PROTECTION SETPOINTS
IAC CURVES
The curves for the General Electric type IAC relay family are derived from the formula:
Where:
T = operate time (in seconds)
TDM = Multiplier setting
I = input current
I
pickup
= Pickup Current setting
A to E = constants
t
r
= characteristic constant
T
RESET
= reset time in seconds (assuming energy capacity is 100% and RESET is
“Timed”)
Table 6-8: GE TYPE IAC INVERSE TIME CURVE CONSTANTS
Table 6-9: IAC CURVE TRIP TIMES (IN SECONDS)
0.60 38.400 16.000 6.000 3.200 2.000 1.371 1.000 0.762 0.600 0.485
0.80 51.200 21.333 8.000 4.267 2.667 1.829 1.333 1.016 0.800 0.646
1.00 64.000 26.667 10.000 5.333 3.333 2.286 1.667 1.270 1.000 0.808
IEC SHORT INVERSE
0.05 0.153 0.089 0.056 0.044 0.038 0.034 0.031 0.029 0.027 0.026
0.10 0.306 0.178 0.111 0.088 0.075 0.067 0.062 0.058 0.054 0.052
0.20 0.612 0.356 0.223 0.175 0.150 0.135 0.124 0.115 0.109 0.104
0.40 1.223 0.711 0.445 0.351 0.301 0.269 0.247 0.231 0.218 0.207
0.60 1.835 1.067 0.668 0.526 0.451 0.404 0.371 0.346 0.327 0.311
0.80 2.446 1.423 0.890 0.702 0.602 0.538 0.494 0.461 0.435 0.415
1.00 3.058 1.778 1.113 0.877 0.752 0.673 0.618 0.576 0.544 0.518
MULTIPLIER
(TDM)
CURRENT (I/I
pickup
)
1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
IAC CURVE SHAPE A B C D E t
r
IAC Extremely Inverse 0.0040 0.6379 0.6200 1.7872 0.2461 6.008
IAC Very Inverse 0.0900 0.7965 0.1000 -1.2885 7.9586 4.678
IAC Inverse 0.2078 0.8630 0.8000 -0.4180 0.1947 0.990
IAC Short Inverse 0.0428 0.0609 0.6200 -0.0010 0.0221 0.222
MULTIPLIER
(TDM)
CURRENT (I/I
pickup
)
1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
IAC EXTREMELY INVERSE
0.5 1.699 0.749 0.303 0.178 0.123 0.093 0.074 0.062 0.053 0.046
1.0 3.398 1.498 0.606 0.356 0.246 0.186 0.149 0.124 0.106 0.093
2.0 6.796 2.997 1.212 0.711 0.491 0.372 0.298 0.248 0.212 0.185
4.0 13.591 5.993 2.423 1.422 0.983 0.744 0.595 0.495 0.424 0.370
6.0 20.387 8.990 3.635 2.133 1.474 1.115 0.893 0.743 0.636 0.556
8.0 27.183 11.987 4.846 2.844 1.966 1.487 1.191 0.991 0.848 0.741
10.0 33.979 14.983 6.058 3.555 2.457 1.859 1.488 1.239 1.060 0.926