4.54
SEL-700G Relay
Instruction Manual
Date Code 20170814
Protection and Logic Functions
Group Settings (SET Command)
by the phase current transformer ratio, CTRX, to find the element pickup
current in secondary amps.
Select a curve shape and time-dial that allow this element to coordinate with
the system primary protection.
Apply electromechanical reset emulation if the system phase overcurrent
relays are induction disk relays; otherwise, electromechanical reset emulation
is not necessary.
By definition, this element should be torque controlled by an undervoltage
element. To prevent misoperation if a potential transformer fuse blows, the
element is also torque controlled by the NOT LOPX Relay Word bit.
To enable and set the undervoltage element, set
With the previous settings, the 51C element is enabled whenever the generator
voltage is less than 80 percent of nominal, as long as there is no simultaneous
loss-of-potential condition. You can choose to use a different undervoltage
element pickup setting.
Voltage-Restrained Time-Overcurrent Settings.
When using the 51V
element, set the 51VP pickup setting greater than the maximum generator
phase current expected under full voltage, nonfault conditions. Divide this
current by the phase current transformer ratio, CTRX, to find the element
pickup current in secondary amps.
Select a curve shape and time-dial that allow this element to coordinate with
the system primary protection.
Apply electromechanical reset emulation if the system phase overcurrent
relays are induction disk relays; otherwise, electromechanical reset emulation
is not necessary.
Because this element reduces its pickup setting automatically as generator
voltage decreases, the element should not be permitted to operate if there is a
blown potential transformer fuse condition. To prevent misoperation if a
51CP
IP
CTRX
-----------------
51CC
U2
=
51CTD
3.00
=
51CRS
N
=
51CTC
27PPX1 AND NOT LOPX
:=
27PPX1P
0.8 • Vnom volts
=
where
Vnom
VNOM_X • 1000/PTRX
=
51VP
max load current
CTRX
----------------------------------------
amps
51VC
U2
=
51VTD
3.00
=
51VRS
N
=
Summary of Contents for SEL-700G Series
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