Schweitzer Engineering Laboratories SEL-701 - Page 87

Date Code 20010719 701 Motor Protection Relay
Settings Calculation
Basic Motor Protection
4.23
Overcurrent Elements
Table 4.14 Ove rc urrent Elemen t S ettings
If the SEL-701 Relay is connected to a motor protected by a fused contactor,
disable the phase overcurrent elements by setting their pickups to OFF. If the relay is
connected to a device capable of interrupting fault current, use the Level 1 phase
overcurrent element to detect and trip for short circuit faults. Set the Level 1 pickup
equal to 1.2 to 1.5 times the motor locked rotor current with a 0.10 second time delay.
Set the Level 2 pickup equal to 2.0 times the locked rotor current with a 0.00 second
time delay.
The relay offers two types of ground fault detecting overcurrent elements. The
neutral overcurrent elements (50N1T and 50N2T) operate using current measured by
the IN input. The residual overcurrent elements (50G1T and 50G2T) operate using the
sum of the measured phase currents.
When a ground fault CT is connected to the relay IN input, as in Figure 2.6 on
page 2.7 in Section 2: Installation, use the Level 1 ground overcurrent element to
detect motor ground faults. Calculate the pickup setting based on the available ground
fault current and the neutral CT ratio.
Table 4.14 Overcurrent Element Settings
Setting Prompt Setting Range
Setting Name =
Factory Default
Level 1 Phase O/C Pickup OFF, 0.25–100.00 A
a
50P1P = OFF
Level 1 Phase O/C Time Delay 0.00–400.00 s 50P1D = 0.60
Level 2 Phase O/C Pickup OFF, 0.25–100.00 A
a
50P2P = OFF
Level 2 Phase O/C Time Delay 0.00–400.00 s 50P2D = 0.50
Level 1 Residual O/C Pickup OFF, 0.25–100.00 A
a
50G1P = OFF
Level 1 Residual O/C Time Delay 0.00–400.00 s 50G1D = 0.60
Level 2 Residual O/C Pickup OFF, 0.25–100.00 A
a
50G2P = OFF
Level 2 Residual O/C Time Delay 0.00–400.00 s 50G2D = 0.50
Level 1 Neutral O/C Pickup OFF, 0.025–10.000 A
b
50N1P = 0.500
Level 1 Neutral O/C Time Delay 0.00–400.00 s 50N1D = 0.10
Level 2 Neutral O/C Pickup OFF, 0.025–10.000 A
b
50N2P = OFF
Level 2 Neutral O/C Time Delay 0.00–400.00 s 50N2D = 0.50
Negative-Seq. O/C Pickup OFF, 0.25–100.00 A
b
50QP = OFF
Negative-Seq. O/C Time Delay 0.10–400.00 s 50QD = 0.60
a
Setting range shown for ITAP = 5 A. Range is 0.05–20.00 A when ITAP = 1 A.
b
Setting range shown for INTAP = 5 A. Range is 0.005–2.000 A when INTAP = 1 A.