4.6
SEL-751 Relay Instruction Manual Date Code 20170927
Protection and Logic Functions
Group Settings (SET Command)
VNOM Range Check
The relay performs a range check for the VNOM setting that depends upon the
voltage-input delta or wye configuration. When the setting DELTA_Y is DELTA,
then the allowed range of the VNOM is OFF, 20–250 V (l-l). When the setting
DELTA_Y is WYE, then the allowed range of VNOM is OFF, 20–480 V (l-l).
Note that the VNOM setting is always in line-to-line voltage, even when set
for a wye configuration. You should be careful to use a solidly-grounded wye
system for VNOM inputs greater than 250 V (l-l) to avoid a 1.73 increase in
terminal voltages from a line-to-ground fault.
EXAMPLE 4.4 VNOM Setting Calculation for Standard Voltage
Inputs
Consider a 10 kV (phase-to-phase) system with wye-connected VTs rated
7200:120 (PTR := 60).
The setting for VNOM would be VNOM := 10000/60 := 166.67.
In the case of LEA sensors, the calculated VNOM should be scaled by
37.5 (300/8) to set VNOM at the 300 V base as shown in the following exam-
ple. The scaling (37.5) is explained in Low-Energy Analog (LEA) Voltage
Inputs.
Enable Settings
EDIR Setting may be forced to OFF
and hidden
See Table SET.1: Range
Dependencies for the EDIR
Setting.
ELOAD, EFLOC Forced to N and hidden These functions require
three-phase voltage.
Directional Element Settings (available when EDIR := Y or AUTO)
ORDER Refer to Table SET.2: Range
Dependencies for the ORDER
Setting for the ORDER setting
dependencies on the SINGLEV
setting.
Associated directional ele-
ment requires three-phase
voltage.
50PDIRP, Z2F, Z2R,
a2, k2, 50QFP, 50QRP
Hidden Associated voltage ele-
ments require three-phase
voltage.
Overvoltage Elements
59G1P, 59G2P,
59Q1P, 59Q2P
Forced to OFF and hidden These functions require
three-phase voltage.
27InOQ (n=1, 2) Refer to Table SET.3: Range
Dependencies for 27I Operating
Quantities
These functions require
three-phase voltages.
59InOQ (n=1, 2, 3, 4) Refer to Table SET.4: Range
Dependencies for 59I Operating
Quantities
These functions require
three-phase voltages.
Vector Shift Settings
E78VS Hidden Element enable requires
three-phase voltages
Table 4.4 Effect on Group Settings When SINGLEV := Y (Sheet 2 of 2)
Identifier Settings
Group Setting Change Reason
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