5.11
Date Code 20080213
Instruction Manual
SEL-351A Relay
Trip and Target Logic
Front-Panel Target LEDS
INST Target LED
The
INST
target LED illuminates at the rising edge of trip if SEL
OGIC
control
equation setting FAULT has been asserted for less than 3 cycles. FAULT is
usually set with time-overcurrent element pickups (e.g., FAULT = 51P + 51G)
to detect fault inception. If tripping occurs within three cycles of fault
inception, the
INST
target illuminates.
SEL
OGIC
control equation setting FAULT also controls other relay functions.
See subsection
Control Equation Setting FAULT on page 5.13
COMM Target LED
The
COMM
target LED illuminates at the rising edge of trip if the trip is the
result of SEL
OGIC
control equation setting DTT (see top of
).
Another Application for the COMM Target LED
The Direct Transfer Trip (DTT) SEL
OGIC
setting can also be used to indicate
tripping via remote communications channels (e.g., via serial port commands
or SCADA asserting optoisolated inputs). Use SEL
OGIC
control equation
setting DTT (Direct Transfer Trip) to accomplish this (see
For example, if the
OPEN
command or remote bit RB1 (see
(Control Remote Bit) on page 10.36
) are used to trip via the serial port and
they should illuminate the
COMM
target LED, set them in SEL
OGIC
control
equation setting DTT:
DTT =
… + OC + RB1
Additionally, if SCADA asserts optoisolated input
IN104
to trip and it should
illuminate the
COMM
target LED, set it in SEL
OGIC
control equation setting
DTT also:
DTT =
… + IN104 + …
Relay Word bits set in SEL
OGIC
control equation setting DTT do not have to
be set in SEL
OGIC
control equation setting TR because both settings directly
assert the TRIP Relay Word bit. The only difference between settings DTT
and TR is that setting DTT causes the
COMM
target LED to illuminate.
Many other variations of the above DTT settings examples are possible.
SOTF Target LED
The
SOTF
target LED illuminates at the rising edge of the TRIP Relay Word bit
if the trip is the result of the SEL
OGIC
control equation setting TRSOTF and
associated switch-onto-fault trip logic (see
).
50 Target LED
The
50
target LED illuminates at the rising edge of trip if an instantaneous or
definite-time overcurrent element causes the trip.
51 Target LED
The
51
target LED illuminates at the rising edge of trip if a time-overcurrent
element (51PT, 51AT, 51BT, 51CT, 51NT, 51GT, 51G2T, or 51QT) causes the
trip.
Summary of Contents for SEL-351A
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