Date Code 20001006 Introduction and Specifications 1-17
SEL-351 Instruction Manual
Processing Specifications
AC Voltage and
Current Inputs
16 samples per power system cycle, 3 dB low-pass filter cut-off frequency
of 560 Hz.
Digital Filtering
One cycle cosine after low-pass analog filtering.
Net filtering (analog plus digital) rejects dc and all harmonics greater than
the fundamental.
Protection and
Control
Processing
4 times per power system cycle
Relay Element Pickup Ranges and Accuracies
Instantaneous/Definite-Time Overcurrent Elements
Pickup Range: 0.25 - 100.00 A, 0.01 A steps (5 A nominal)
1.00 - 170.00 A, 0.01 A steps (5 A nominal - for
phase-to-phase elements)
0.05 - 20.00 A, 0.01 A steps (1 A nominal)
0.20 - 34.00 A, 0.01 A steps (1 A nominal - for
phase-to-phase elements)
0.005 - 1.500 A, 0.001 A steps (0.05 A nominal
channel IN current input)
Steady-State Pickup Accuracy: ±0.05 A and ±3% of setting (5 A nominal)
±0.01 A and ±3% of setting (1 A nominal)
±1 mA and ±5% of setting (0.05 A nominal
channel IN current input)
Transient Overreach: ±5% of pickup
Time Delay: 0.00 - 16,000.00 cycles, 0.25-cycle steps
Timer Accuracy: ±0.25 cycle and ±0.1% of setting
See pickup and reset time curves in Figure 3.5 and Figure 3.6
Courtesy of NationalSwitchgear.com
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