4.24
SEL-749M Relay Instruction Manual Date Code 20080918
Protection and Logic Functions
Voltage-Based Protection
Voltage-Based Protection
The following information applies to relay models with voltage inputs.
Undervoltage
Function
Overvoltage Function
NOTE: The under- and overvoltage
level settings are in per unit nominal
voltage, Vnm. The relay automatically
calculates Vnm, using the settings
VNOM and Delta_Y as follows:
Vnm = VNOM if DELTA_Y := Delta;
Vnm = VNOM/1.732 if DELTA_Y := Wye.
When you connect the SEL-749M voltage inputs to phase-to-phase connected
VTs, as in Figure 2.10, the relay provides two levels of phase-to-phase
overvoltage and undervoltage elements.
When you connect the SEL-749M voltage inputs to phase-to-neutral
connected VTs, as in Figure 2.10, the relay provides two levels of phase-to-
neutral overvoltage and undervoltage elements.
Each of the elements has an associated time delay. You can use these elements
as you choose for tripping and warning. Figure 4.13 and Figure 4.14 show the
logic diagram for the undervoltage and overvoltage elements, respectively. To
disable any of these elements, set the level settings equal to OFF.
Table 4.21 Undervoltage Settings
Setting Prompt Setting Range Setting Name := Factory Default
UV TRIP LEVEL Off, 0.60–1.00 xVnm 27P1P := 0.80
UV TRIP DELAY 0.0–120.0 sec 27P1D := 0.5
UV WARN LEVEL Off, 0.60–1.00 xVnm 27P2P := OFF
UV WARN DELAY 0.0–120.0 sec 27P2D := 5.0
Table 4.22 Overvoltage Settings
Setting Prompt Setting Range Setting Name := Factory Default
OV TRIP LEVEL Off, 1.00–1.20 xVnm 59P1P := 1.10
OV TRIP DELAY 0.0–120.0 sec 59P1D := 0.5
OV WARN LEVEL Off, 1.00–1.20 xVnm 59P2P := OFF
OV WARN DELAY 0.0–120.0 sec 59P2D := 5.0
Courtesy of NationalSwitchgear.com
To Next Page
Loading...
