GE 845, Instruction Manual

Page: 287 / 552

CHAPTER 4: SETPOINTS PROTECTION
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL 4–159
I
2
T CURVES
The curves for the I
2
t are derived from the formula:
Where:
T = operate time (in seconds)
TDM = Multiplier setting
I = input current
I
pickup
= Pickup Current setting
T
RESET
= reset time in seconds (assuming energy capacity is 100% and RESET is
“Timed”)
Table 4-32: I
2
T CURVE TRIP TIMES (IN SECONDS)
I
4
T CURVES
The curves for the I
4
t are derived from the formula:
Where:
T = operate time (in seconds)
TDM = Multiplier setting
I = input current
I
pickup
= Pickup Current setting
10.0 11.552 7.494 5.320 4.426 3.922 3.597 3.369 3.201 3.072 2.969
IAC SHORT INVERSE
0.5
0.072 0.047 0.035 0.031 0.028 0.027 0.026 0.026 0.025 0.025
1.0 0.143 0.095 0.070 0.061 0.057 0.054 0.052 0.051 0.050 0.049
2.0 0.286 0.190 0.140 0.123 0.114 0.108 0.105 0.102 0.100 0.099
4.0 0.573 0.379 0.279 0.245 0.228 0.217 0.210 0.204 0.200 0.197
6.0 0.859 0.569 0.419 0.368 0.341 0.325 0.314 0.307 0.301 0.296
8.0 1.145 0.759 0.559 0.490 0.455 0.434 0.419 0.409 0.401 0.394
10.0 1.431 0.948 0.699 0.613 0.569 0.542 0.524 0.511 0.501 0.493
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
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
0.01 0.44 0.25 0.11 0.06 0.04 0.03 0.02 0.02 0.01 0.01
0.10 4.44 2.50 1.11 0.63 0.40 0.28 0.20 0.16 0.12 0.10
1.00 44.44 25.00 11.11 6.25 4.00 2.78 2.04 1.56 1.23 1.00
10.00 444.44 250.00 111.11 62.50 40.00 27.78 20.41 15.63 123.5 10.00
100.00 4444.44 2500.00 1111.1 625.00 400.00 277.78 204.08 156.25 123.46 100.00
600.00 26666.7 15000.0 6666.7 3750.0 2400.0 1666.7 1224.5 937.50 740.74 600.00