5.32
SEL-311C Relay Instruction Manual Date Code 20060320
Trip and Target Logic
Front-Panel Target LEDs
TIME Target LED
The TIME target LED illuminates at the rising edge of trip if SELOGIC control
equation setting FAULT has been asserted for more than three cycles. FAULT
is usually set with distance and time-overcurrent element pickups (e.g.,
FAULT = 51G + 51Q + M2P + Z2G) to detect fault inception. If tripping
occurs more than three cycles after fault inception, the TIME target illuminates.
SEL
OGIC control equation setting FAULT also controls maximum/minimum
metering. If FAULT is asserted, maximum/minimum metering is blocked (see
Maximum/Minimum Metering on page 8.29). Fault current values are not to be
accrued as maximum current values in maximum/minimum metering.
COMM Target LED
The COMM target LED illuminates at the rising edge of trip if the trip is the sole
and direct result of SEL
OGIC control equation setting TRCOMM and
associated communications-assisted trip logic, Relay Word bit ECTT, or
SEL
OGIC control equation setting DTT (see Figure 5.1, top half of figure).
Another Application for the COMM Target LED
If none of the traditional communications-assisted trip logic is used (i.e.,
SEL
OGIC control equation setting TRCOMM is not used), consideration can
be given to using the COMM target LED 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 Figure 5.1).
For example, if the OPEN command or remote bit RB1 [see CON Command
(Control Remote Bit) on page 10.37] 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 SELOGIC control equation setting DTT do not have to
be set in SEL
OGIC control equation setting TR–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 sole and direct result of the SEL
OGIC control equation setting
TRSOTF and associated switch-onto-fault trip logic (see Figure 5.3).
79 Target LEDs
If the reclosing relay is turned off (enable setting E79 = N or 79OI1 = 0), all
the Device 79 (reclosing relay) target LEDs are extinguished.
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