4.52
SEL-700G Relay
Instruction Manual
Date Code 20170814
Protection and Logic Functions
Group Settings (SET Command)
The voltage-controlled phase time-overcurrent element, 51C, operates when
its torque-control setting, 51CTC, is equal to logical 1. Typically, the torque-
control setting should include the Relay Word bit for an undervoltage element,
such as 27PPX1. This way, the 51C element operates only when generator
terminal voltage is less than 27PPX1P setting. This element works properly
whether or not a step-up transformer is present and regardless of the
connection of the step-up transformer—delta/wye, wye/wye, etc.
The 51V element in the SEL-700G Relay is intended for applications in which
the generator is directly connected to a bus, to the delta side of a delta-wye
transformer, or to a wye-wye or delta-delta transformer. The voltage-
restrained phase time-overcurrent element, 51V, also includes a torque-control
setting, 51VTC. However, the 51V element operation is fundamentally
different in that the element pickup setting is reduced automatically as the
generator phase-to-phase voltage decreases during a fault. When the generator
voltage is 100 percent of the VNOM_X setting, the 51V element operates
based on 100 percent of its pickup setting, 51VP. As the generator phase-to-
phase voltage drops, the relay decreases the element pickup by a like amount,
down to 12.5 percent of nominal phase-to-phase voltage. For voltages below
12.5 percent, the relay uses a pickup that is 12.5 percent of the 51VP setting.
The element automatically determines fault type and appropriate phase-to-
phase restrain voltage based on the compensation angle setting 51VCA; it will
not operate if the relay cannot determine the fault type. This element operates
for phase-to-phase and three-phase faults. Use other elements (for example,
neutral/residual overcurrent 50N, 51N, 50GX, 51GX) for the ground
overcurrent protection.
When a step-up transformer is present, the generator phase-to-phase voltage is
compensated for the phase shift across the transformer. There is no
compensation for the voltage drop across the step-up transformer.
Table 4.9
Voltage Controlled/Restraint Time OC Protection Settings
Setting Prompt
Setting Range
Setting Name := Factory Default
Voltage-Controlled TOC (EBUP := C or DC_C)
V-CTRL TOC LVL
OFF, 0.50-16.00 A
a
a
Ranges and default settings shown are for 5 A CT. Divide by 5 for 1 A rated CTs.
51CP := 3.00
V-CTRL TOC CURVE
U1–U5, C1–C5
51CC := U2
V-CTRL TOC TDIAL
0.50-15.00
b
b
Setting Range shown is for US Curves. Range is 0.05-1.00 for the IEC Curves.
51CTD := 3.20
V-CTRL TOC EM RST
Y, N
51CRS := Y
51C TOC TRQCTRL
SEL
OGIC
51CTC := 27PPX1 AND NOT
LOPX
Voltage-Restraint TOC (EBUP := V or DC_V)
V-RESTR TOC LVL
OFF, 2.00–16.00 A
51VP := 8.00
COMPEN ANGLE
0, -30, 30
51VCA := 0
V-RESTR TOC CURV
U1–U5, C–C5
51VC := U2
V-RES TOC TDIAL
0.50–15.00
b
51VTD := 3.00
V-RES TOC EM RST
Y, N
51VRS := Y
51V TOC TRQCTRL
SEL
OGIC
51VTC := NOT LOPX
Summary of Contents for SEL-700G Series
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