1.19
Date Code 20170927 Instruction Manual SEL-751 Relay
Introduction and Specifications
Specifications
Frequency (81)
Setting Range: Off, 15.00–70.00 Hz
Accuracy: ±0.01 Hz (V1 >60 V) with voltage
tracking
±0.05 Hz (I1 >0.8 • I
NOM
) with current
tracking
Time Delay: 0.00–240.00 seconds, 0.01 second steps
Pickup/Dropout Time: <4 cycles
Rate-of-Change of Frequency (81R)
Setting Range: OFF, 0.10–15.00 Hz/s
Accuracy: ±100 mHz/s, plus ±3.33% of pickup
Time Delay: 0.10–60.00 seconds, 0.01 second steps
Synchronism Check (25)
Pickup Range, Secondary
Voltage: 0.00–300.00 V
Pickup Accuracy, Secondary
Voltage:
±1% plus ±0.5 volts (over the range of
2–300 V)
Slip Frequency Pickup Range: 0.05 Hz–0.50 Hz
Slip Frequency Pickup
Accuracy: ±0.02 Hz
Phase Angle Range: 0–80°
Phase Angle Accuracy: ±4°
Load-Encroachment Detection
Setting Range
5 A Model: 0.10–128.00 ohms secondary,
0.01 ohms steps
1 A Model: 0.50–640.00 ohms secondary,
0.01 ohms steps
Forward Load Angle: –90° to +90°
Forward Load Angle: +90° to +270°
Accuracy
Impedance Measurement: ±5% plus ±0.5 ohms
Angle Measurement: ±3°
Station Battery Voltage Monitor
Operating Range: 0–350 Vdc (300 Vdc for UL purposes)
Pickup Range: 20.00–300.00 Vdc
Pickup accuracy: ±2% of setting plus ±2 Vdc
Timers
Setting Range: Various
Accuracy: ±0.5% of setting plus ±1/4 cycle
RTD Protection
Setting Range: Off, 1–250°C
Accuracy: ±2C
RTD Open-Circuit Detection: >250°C
RTD Short-Circuit Detection: <–50°C
RTD Types: PT100, NI100, NI120, CU10
RTD Lead Resistance: 25 ohm max. per lead
Update Rate: <3 s
Noise Immunity on RTD
Inputs:
As high as 1.4 Vac (peak) at 50 Hz or
greater frequency
RTD Trip/Alarm Time Delay: Approx. 6 s
Metering
Accuracies are specified at 20C, nominal frequency, ac currents within
(0.2–20.0) • I
NOM
A secondary, and ac voltages within 50–250 V
secondary (1.33–6.67 V secondary with 8 V LEA option), unless
otherwise noted.
Phase Currents: ±1% of reading, ±1° (±2.5° at 0.2–0.5 A
for relays with I
NOM
= 1 A)
Three-Phase Average Current: ±1% of reading
IG (Residual Current): ±2% of reading, ±2° (±5.0° at 0.2–0.5 A
for relays with I
NOM
= 1 A)
IN (Neutral Current): ±1% of reading, ±1° (±2.5° at 0.2–0.5 A
for relays with I
NOM
= 1 A)
±1.6 mA and ±1% (0.04–4.0 A) (0.2 A
nominal channel IN current input)
I1 Positive-Sequence Current: ±2% of reading
3I2 Negative-Sequence
Current: ±2% of reading
System Frequency: ±0.01 Hz of reading for frequencies
within 15–70 Hz (V1 > 60 V)
Line-to-Line Voltages: ±1% of reading, ±1° for voltages
Three-Phase Average
Line-to-Line Voltage:
±1% of reading for voltages within
24–264 V
Line-to-Ground Voltages: ±1% of reading, ±1° for voltages within
24–264 V (0.64–7.04 V for LEA
inputs)
Three-Phase Average
Line-to-Ground Voltages:
±1% of reading for voltages within
24–264 V (0.64–7.04 V for LEA
inputs)
Voltage Imbalance (%): ±2% of reading
V1 Positive-Sequence
Voltage:
±2% of reading for voltages within
24–264 V (0.64–7.04 V for LEA
inputs)
3V2 Negative-Sequence
Voltage:
±2% of reading for voltages within
24–264 V (0.64–7.04 V for LEA
inputs)
Real Three-Phase Power
(kW): ±3% of reading for 0.10 < pf < 1.00
Reactive Three-Phase Power
(kVAR): ±3% of reading for 0.00 < pf < 0.90
Apparent Three-Phase Power
(kVA): ±3% of reading
Power Factor: ±2% of reading
RTD Temperatures: ±2°C
Energy Meter
Accumulators: Separate IN and OUT accumulators
updated once per second, transferred
to nonvolatile storage 4 times per day.
ASCII Report Resolution: 0.001 MWh
Accuracy: The accuracy of the energy meter
depends on applied current and power
factor as shown in the power metering
accuracy specifications above. The
additional error introduced by
accumulating power to yield energy is
negligible when power changes slowly
compared to the processing rate of
once per second.
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