GE 850 - Page 278

6–10 850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CURRENT ELEMENTS CHAPTER 6: PROTECTION SETPOINTS
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
T
RESET
= reset time in seconds (assuming energy capacity is 100% and RESET is
“Timed”)
Table 6-11: I
4
T CURVE TRIP TIMES (IN SECONDS)
FLEXCURVES
The custom FlexCurves are described in detail in the FlexCurves section of this chapter.
The curve shapes for the FlexCurves are derived from the formulae:
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”)
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
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 0.1975 0.0625 0.0123 0.0039 0.0016 0.0008 0.0004 0.0002 0.00015 0.0001
0.10 1.9753 0.6250 0.1235 0.0391 0.0160 0.0077 0.0042 0.0024 0.0015 0.0010
1.00 19.753 6.250 1.235 0.391 0.160 0.077 0.042 0.024 0.015 0.010
10.00 197.531 62.500 12.346 3.906 1.600 0.772 0.416 0.244 0.152 0.100
100.00 1975.31 625.00 123.46 39.06 16.00 7.72 4.16 2.44 1.52 1.00
600.00 11851.9 3750.0 740.7 234.4 96.00 46.3 25.0 14.65 9.14 6.00