Date Code 20001006 Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements 3-1
SEL-351 Instruction Manual
SECTION 3: OVERCURRENT, VOLTAGE, SYNCHRONISM
CHECK, FREQUENCY, AND POWER ELEMENTS
INSTANTANEOUS/DEFINITE-TIME OVERCURRENT ELEMENTS
Phase Instantaneous/Definite-Time Overcurrent Elements
Four levels of phase instantaneous/definite-time overcurrent elements are available. Two addi-
tional levels of phase instantaneous overcurrent elements (Levels 5 and 6) are also available. The
different levels are enabled with the E50P enable setting, as shown in Figure 3.1, Figure 3.2, and
Figure 3.3.
Level 2 element 67P2S in Figure 3.3 is used in directional comparison blocking schemes (see
Directional Comparison Blocking (DCB) Logic in Section 5: Trip and Target Logic). All the
other phase instantaneous/definite-time overcurrent elements are available for use in any tripping
or control scheme.
Settings Ranges
Setting range for pickup settings 50P1P through 50P6P:
0.25 - 100.00 A secondary (5 A nominal phase current inputs, IA, IB, IC)
0.05 - 20.00 A secondary (1 A nominal phase current inputs, IA, IB, IC)
Setting range for definite-time settings 67P1D through 67P4D:
0.00 - 16000.00 cycles, in 0.25-cycle steps
Setting range for definite-time setting 67P2SD (used in the DCB logic):
0.00 - 60.00 cycles, in 0.25-cycle steps
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)
Timer: ±0.25 cycles and ±0.1% of setting
Transient Overreach: ±5% of setting
Courtesy of NationalSwitchgear.com
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