GE 889 - Page 289

CHAPTER 4: SETPOINTS PROTECTION
889 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL 4–159
IEC CURVES
For European applications, the relay offers three standard curves defined in IEC 255-4 and
British standard BS142. These are defined as IEC Curve A, IEC Curve B, and IEC Curve C. The
formula for these curves is:
Where:
T = operate time (in seconds)
TDM = Multiplier setting
I = input current
I
pickup
= Pickup Current setting
K, E = constants
t
r
= characteristic constant
T
RESET
= reset time in seconds (assuming energy capacity is 100% and RESET is
“Timed”)
Table 4-26: IEC (BS) INVERSE TIME CURVE CONSTANTS
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
8.0 34.274 14.125 6.031 4.102 3.254 2.756 2.415 2.163 1.967 1.808
10.0 42.842 17.656 7.539 5.127 4.068 3.445 3.019 2.704 2.458 2.260
ANSI MODERATELY INVERSE
0.5 0.675 0.379 0.239 0.191 0.166 0.151 0.141 0.133 0.128 0.123
1.0 1.351 0.757 0.478 0.382 0.332 0.302 0.281 0.267 0.255 0.247
2.0 2.702 1.515 0.955 0.764 0.665 0.604 0.563 0.533 0.511 0.493
4.0 5.404 3.030 1.910 1.527 1.329 1.208 1.126 1.066 1.021 0.986
6.0 8.106 4.544 2.866 2.291 1.994 1.812 1.689 1.600 1.532 1.479
8.0 10.807 6.059 3.821 3.054 2.659 2.416 2.252 2.133 2.043 1.972
10.0 13.509 7.574 4.776 3.818 3.324 3.020 2.815 2.666 2.554 2.465
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
IEC (BS) CURVE SHAPE K E t
r
IEC Curve A (BS142) 0.140 0.020 9.7
IEC Curve B (BS142) 13.500 1.000 43.2
IEC Curve C (BS142) 80.000 2.000 58.2
IEC Short Inverse 0.050 0.040 0.500