Schweitzer Engineering Laboratories SEL-751 - Table 4.34 Undervoltage Function

4.97
Date Code 20170927 Instruction Manual SEL-751 Relay
Protection and Logic Functions
Group Settings (SET Command)
Under- and
Overvoltage
Functions
When you connect the SEL-751 voltage inputs to phase-to-phase connected
VTs (single-phase or three-phase), as in Figure 2.20 or Figure 2.21, the relay
provides two levels of phase-to-phase overvoltage and undervoltage elements.
When you connect the SEL-751 voltage inputs to phase-to-neutral connected
VTs (single-phase or three-phase), as in Figure 2.20 or Figure 2.21, the relay
provides two levels of phase-to-neutral, phase-to-phase overvoltage and
undervoltage elements. Two levels of negative-sequence overvoltage elements
are available when the VTs are connected in three-phase as shown in
Figure 2.21. Two levels of zero-sequence overvoltage elements are available
when the voltage inputs are connected in wye configuration
(DELTA_Y := WYE) as shown in Figure 2.21. When a synchronism voltage
input is present (e.g., VS input shown in Figure 2.21) the SEL-751 provides
two levels of VS under- and overvoltage elements. You can use these elements
to control reclosing logic described later.
Each of the elements has an associated time delay, except the three-phase
under- and overvoltage elements, 3P27 and 3P59. You can use these elements
as you choose for tripping and warning. Figure 4.61 and Figure 4.62 show the
logic diagrams for the undervoltage and overvoltage elements, respectively. To
disable any of these elements, set the level settings equal to OFF.
ALARM DO RATIO 0.01–0.99 PU THLADRn := 0.98
MAXIMUM TMP 80–300°C TMAXn := 155
RESET THML SEL
OGIC RSTTHn := 0
a
n = 1–3 and x = 1–2.
Table 4.33 IEC Thermal Element Settings (Sheet 2 of 2)
Setting Prompt Setting Range
Setting Name :=
Fac to ry De fault
a
Table 4.34 Undervoltage Function
Setting Prompt Setting Range
Setting Name :=
Factory De fault
UV TRIP1 LEVEL OFF, 2.00–300.00 V 27P1P := OFF
UV TRIP1 DELAY 0.00–120.00 sec 27P1D := 0.50
UV TRIP2 LEVEL OFF, 2.00–300.00 V 27P2P := OFF
UV TRIP2 DELAY 0.00–120.00 sec 27P2D := 5.00
PP UV TRIP1 LEVEL OFF, 2.00–300.00 V
a
a
Setting range shown is for DELTA_Y := DELTA.
27PP1P := OFF
PP UV TRIP1 LEVEL OFF, 2.00–520.00 V
b
b
Setting range shown is for DELTA_Y := WYE.
27PP1P := OFF
PP UV TRIP1 DELAY 0.00–120.00 sec 27PP1D := 0.50
PP UV TRIP2 LEVEL OFF, 2.00–300.00 V
a
27PP2P := OFF
PP UV TRIP2 LEVEL OFF, 2.00–520.00 V
b
27PP2P := OFF
PP UV TRIP2 DELAY 0.00–120.00 sec 27PP2D := 0.50
UVS LEVEL 1 OFF, 2.00–300.00 V 27S1P := OFF
UVS DELAY 1 0.00–120.00 sec 27S1D := 0.50
UVS LEVEL 2 OFF, 2.00–300.00 V 27S2P := OFF
UVS DELAY 2 0.00–120.00 sec 27S2D := 0.50