
3-18
Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements
Date Code 20001006
SEL-351 Instruction Manual
Figure 3.14: Phase Time-Overcurrent Element 51PT (With Directional Control Option)
Accuracy
Pickup:
±
0.05 A secondary and
±
3% of setting (5 A nominal phase current inputs, IA, IB, IC)
±
0.01 A secondary and
±
3% of setting (1 A nominal phase current inputs, IA, IB, IC)
Curve Timing:
±
1.50 cycles and
±
4% of curve time for currents between (and including)
2 and 30 multiples of pickup
Logic Outputs (51PT Element Example)
The resultant logic outputs in Figure 3.14 are the following Relay Word bits:
Table 3.3: Phase Time-Overcurrent Element (Maximum Phase) Logic Outputs
Relay Word Bit
Definition/ Indication
Application
51P
Maximum phase current, I
P
, is
greater than phase time-
overcurrent element pickup setting
51PP.
Element pickup testing or other
control
applications. See
Trip
Logic
in
Section 5: Trip and
Target Logic
.
51PT
Phase time-overcurrent element is
timed out on its curve.
Tripping and other control
applications. See
Trip Logic
in
Section 5: Trip and Target Logic
.
51PR
Phase time-overcurrent element is
fully reset.
Element reset testing or other
control applications.
Summary of Contents for SEL-351
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