Sel 411L - Page 346

P.3.238
SEL-411L Relay Protection Manual Date Code 20151029
Protection Functions
Trip Logic
Trip SELOGIC Control
Equations
You select the appropriate relay elements for unconditional, direct transfer
tripping, switch-onto-fault, and communications-assisted tripping. Set the
following SEL
OGIC control equations for tripping:
➤ TR—Unconditional tripping
➤ DTA, DTB, DTC—Direct transfer tripping
➤ TRSOTF—SOTF tripping
➤ TRCOMM/TRCOMMD—Communications-assisted tripping
Include the instantaneous and time-delayed tripping elements in the TR
SEL
OGIC control equation. You would typically set instantaneous high-set
current level detectors and Zone 2 distance protection in the TRSOTF
SEL
OGIC control equation. You would also set instantaneous Zone 2 distance
protection in the TRCOMM SEL
OGIC control equation.
TR
The TR SELOGIC control equation determines which elements trip
unconditionally. You would typically set all instantaneous and time-delayed
tripping elements (step-distance protection plus instantaneous and time-
overcurrent protection) in the TR SEL
OGIC control equation.
87LQGSP Enable 87L negative-sequence/residual diff. SPT Y
EWFC
a
Weak infeed trip SP
b
a
In POTT and DCUB settings.
b
SP = single-pole.
The E87DTT setting allows for receiving direct transfer tripping over the 87L
communications channel. This logic only pertains to a three-terminal scheme
with one master and two outstation relays (see 87DTT Direct Transfer
Tripping Logic for more details). If a outstation relay receives a direct transfer
trip from the master relay, the outstation relay will single-pole trip if its
Zone 2 directional negative-sequence/residual-directional overcurrent
elements are asserted and the FIDS logic gives an indication of the faulted
phase, otherwise the slave relay will trip three poles.
The Z2GTSP setting is used to single-pole trip during ground faults within the
last 20 percent of the protected line when the communications channel is not
available.
The 67QGSP setting is used to single-pole trip during high-resistance ground
faults such that the fault impedance lies outside of the ground distance
protection characteristics. In this case, the FID logic selects the faulted phase
and Zone 2 negative-sequence/residual-directional overcurrent elements
provide communications-assisted tripping.
The 87LQGSP setting allows the relay to single-pole trip on the more
sensitive negative-sequence and zero-sequence differential elements. Note
that the 87OP Relay Word bit needs to be added to the TR, unconditional trip,
equation to trip on an 87LQ or 87LG element assertion.
With the EWFC setting set to SP, a relay at a weak terminal converts echo to a
single-pole trip (see Weak-Infeed Logic for more details).
Table 3.123 Additional Settings for Single-Pole Tripping (SPT) (Sheet 2 of 2)
Setting Description Selection