Eaton Cutler-Hammer FP-5000 - Page 118

IL17569
Page 8-6
Effective June, 2001
Instantaneous Protection
Instantaneous (short circuit) protection reacts to high level fault
currents. The 50P pickup settings establish the current level at
which the FP-5000 picks up on an instantaneous fault. An optional
time delay may be programmed for coordination purposes.
If an Instantaneous Setting other than “Disable” is selected, the
instantaneous portion of the overall curve can be moved indepen-
dently in a horizontal direction. Figure 8-9 graphically illustrates this
horizontal movement.
Ground Fault Protection
The ground fault protection function can be a composite of the ground:
1. Inverse time overcurrent curve shape pickup and time.
2. 50X-2 and 50R-2 (Short delay) pickup and time.
3. 50X-1 and 50R-1(Instantaneous) pickup.
Its curve shape is independent of the phase curve. The inverse time
overcurrent time multiplier values for the ground function of the
thermal curves are for (1 x I
n
) while the phase function is (3 x I
n
).
Movement of the pickup portion of the curve in a horizontal direction
and the time portion of the curve in a vertical direction is similar to
phase inverse time overcurrent, short delay and instantaneous
functions as previously described. Therefore, the ground fault curve
movement is not graphically illustrated. When programming ground
fault protection, keep in mind that if “Disable” is selected, the ground
fault protection is disabled.
8.3.5 Negative Sequence Current Protection (46)
The FP-5000 provides monitoring and protection based on the
percent of current unbalance or negative sequence. The presence
of negative sequence current identifies either a phase unbalance in
the voltage magnitude or reverse phase rotation condition. The
positive and negative sequence currents are calculated from the
three phase currents. The % unbalance is the ratio of negative
sequence current to positive sequence current (%Unbalance = I
2
/I
1
).
A current unbalance pickup occurs when I
2
/I
1
exceeds the IUB %
Unbalance setting, and I
1
or I
2
magnitude exceeds the IUB
Threshold setting. The Current Unbalance trip is set when the
pickup condition exists for the delay time specified. The current
unbalance pickup and trip is reset when the positive sequence
current drops below the IUB Threshold setting or I
2
/I
1
drops below
the IUB % Unbalance setting minus 1%. The settings associated
with voltage unbalance or negative sequence voltage protection are
listed in Table 8.2.
Figure 8-9. 50P (Instantaneous) Setting Adjustment