3-16 Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements Date Code 20001006
SEL-351 Instruction Manual
Figure 3.13: Levels 5 Through 6 Negative-Sequence Instantaneous Overcurrent Elements
TIME-OVERCURRENT ELEMENTS
Phase Time-Overcurrent Elements
Four phase time-overcurrent elements are available. The elements are enabled with the E51P
enable setting as follows:
Table 3.1: Available Phase Time-Overcurrent Elements
Time-Overcurrent
Element
Enabled with
Setting
Operating Current See Figure
51PT E51P = 1 or 2 I
P
, maximum of A-, B-, and
C-phase currents
Figure 3.14
51AT E51P = 2 I
A
, A-phase current Figure 3.15
51BT E51P = 2 I
B
, B-phase current Figure 3.16
51CT E51P = 2 I
C
, C-phase current Figure 3.17
The following is an example of 51PT element operation. The other phase time-overcurrent
elements operate similarly (note the similarity among the logic in Figure 3.14, Figure 3.15,
Figure 3.16, and Figure 3.17).
Courtesy of NationalSwitchgear.com
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