1.18
SEL-421 Relay Instruction Manual Date Code 20171021
Introduction and Specifications
Specifications
Zones 4 and 5
5 A Model: OFF, 0.05 to 150 secondary, 0.01 steps
1 A Model: OFF, 0.25 to 750 secondary, 0.01 steps
Sensitivity
5 A Model: 0.5 A secondary
1 A Model: 0.1 A secondary
Accuracy (Steady State): ±3% of setting at line angle for SIR < 30
±5% of setting at line angle for
30 SIR 60
Transient Overreach: <5% of setting plus steady-state accuracy
Mho Ground-Distance Elements
Zones 1–5 Impedance Reach
Mho Element Reach
5 A Model: OFF, 0.05 to 64 secondary, 0.01 steps
1 A Model: OFF, 0.25 to 320 secondary, 0.01 steps
Sensitivity
5 A Model: 0.5 A secondary
1 A Model: 0.1 A secondary
(Minimum sensitivity is controlled by the
pickup of the supervising phase and residual
overcurrent elements for each zone.)
Accuracy (Steady State): ±3% of setting at line angle for SIR < 30
±5% of setting at line angle for
30 SIR 60
Zone 1 Transient
Overreach: <5% of setting plus steady-state accuracy
SEL-421-5 Maximum
Operating Time: 0.8 cycle at 70% of reach and SIR = 1
SEL-421-4 Maximum
Operating Time: 1.5 cycle at 70% of reach and SIR = 1
Quadrilateral Ground-Distance Elements
Zones 1–5 Impedance Reach
Quadrilateral Reactance Reach
5 A Model: OFF, 0.05 to 64 secondary, 0.01 steps
1 A Model: OFF, 0.25 to 320 secondary, 0.01 steps
Quadrilateral Resistance Reach
Zones 1, 2, and 3
5 A Model: OFF, 0.05 to 50 secondary, 0.01 steps
1 A Model: OFF, 0.25 to 250 secondary, 0.01 steps
Zones 4 and 5
5 A Model: OFF, 0.05 to 150 secondary, 0.01 steps
1 A Model: OFF, 0.25 to 750 secondary, 0.01 steps
Sensitivity
5 A Model: 0.5 A secondary
1 A Model: 0.1 A secondary
(Minimum sensitivity is controlled by the
pickup of the supervising phase and residual
overcurrent elements for each zone.)
Accuracy (Steady State): ±3% of setting at line angle for SIR < 30
±5% of setting at line angle for
30 SIR 60
Transient Overreach: <5% of setting plus steady-state accuracy
Instantaneous/Definite-Time Overcurrent Elements
Phase, Residual Ground, and Negative-Sequence
Pickup Range
5 A Model: OFF, 0.25–100.00 A secondary,
0.01 A steps
1 A Model: OFF, 0.05–20.00 A secondary,
0.01 A steps
Accuracy (Steady State)
5 A Nominal: ±0.05 A plus ±3% of setting
1 A Nominal: ±0.01 A plus ±3% of setting
Transient Overreach: <5% of pickup
Time-Delay: 0.00–16000.00 cycles, 0.125 cycle steps
Timer Accuracy: ±0.125 cycle plus ±0.1% of setting
Maximum
Operating Time: 1.5 cycles
Time-Overcurrent Elements
Pickup Range
5 A Model: 0.25–16.00 A secondary, 0.01 A steps
1 A Model: 0.05–3.20 A secondary, 0.01 A steps
Accuracy (Steady State)
5 A Model: ±0.05 A plus ± 3% of setting
1 A Model: ±0.01 A plus ± 3% of setting
Time Dial Range
US: 0.50–15.00, 0.01 steps
IEC: 0.05–1.00, 0.01 steps
Curve Timing Accuracy: ±1.50 cycles plus ± 4% of curve time (for
current between 2 and 30 multiples of
pickup)
Reset: 1 power cycle or Electromechanical Reset
Emulation time
Ground Directional Elements
Neg.-Seq. Directional Impedance Threshold (Z2F, Z2R)
5 A Model: –64 to 64
1 A Model: –320 to 320
Zero-Seq. Directional Impedance Threshold (Z0F, Z0R)
5 A Model: –64 to 64
1 A Model: –320 to 320
Supervisory Overcurrent Pickup 50FP, 50RP
5 A Model: 0.25 to 5.00 A 3I0 secondary
0.25 to 5.00 A 3I2 secondary
1 A Model: 0.05 to 1.00 A 3I0 secondary
0.05 to 1.00 A 3I2 secondary
Undervoltage and Overvoltage Elements
Pickup Ranges
Phase Elements: 2–300 V secondary, 0.01 V steps
Phase-to-Phase
Elements: 4–520.0 V secondary, 0.01 V steps
Accuracy (Steady State): ±0.5 V plus ± 5% of setting
Transient Overreach: <5% of pickup
Underfrequency and Overfrequency Elements
Pickup Range: 40.01–69.99 Hz, 0.01 Hz steps
Accuracy, Steady State
Plus Transient:
±0.005 Hz for frequencies between 40.00
and 70.00 Hz
Maximum Pickup/
Dropout Time: 3.0 cycles
Time-Delay Range: 0.04–400.0 s, 0.01 s increments
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