Sel 411L - Figure 3.36 Disturbance Detection Logic Responding to Remote Currents

P.3.63
Date Code 20151029 Protection Manual SEL-411L Relay
Protection Functions
87L Differential Elements
the 87L base, or the data are unavailable because of lost communications for
two power cycles, the remote disturbance detection asserts to maintain
dependability.
Once asserted, the 87DDR Relay Word bit stays asserted for at least 10 power
cycles, using the dropout timer to ensure reliable operation of the supervised
87L elements and the 87DTT logic.
Note that the remote disturbance detection logic executes in the master or
outstation mode; no differential quantities are necessary. Moreover, none of
the channels is necessary in the permanent outstation mode (E87CH = 3SS),
and the bottom portion of the 87DDR logic of Figure 3.36 results in
permanent assertion of the 87DDR Relay Word bit. This in turn, effectively
makes the 87DD logic of Figure 3.34 respond to local signals only. As a
result, 87DTT in outstation relays effectively receives supervision only from
disturbance in local currents and voltages.
Figure 3.36 Disturbance Detection Logic Responding to Remote Currents
The local and remote disturbance detection schemes work with the same
adaptive algorithm for detecting disturbance in a given current or voltage
phasor. Figure 3.37 presents the applied algorithm.
First, the logic calculates the instantaneous increase in the input phasors, IN,
compared with its one-power-cycle-old value. The magnitude, DX, of that
change signifies changes in magnitude, angle, or a combination of magnitude
and angle change in the input phasor. Note that the input phasor, even for input
signals distorted with harmonics or under off-nominal frequency, will be
periodic with respect to a power cycle. The DX signal, therefore, will be very
small.
DD Algorithm
87IQ1AFR
DD Algorithm
DD Algorithm
Relay
Word
Bit
87DDR
87I11AFR
...
mag
87I11AFR
0.1 pu
+
−
mag
87I1pAFR
+
−
2 cyc
0
87CH1RQ
DD Algorithm
87IQpAFR
DD Algorithm
DD Algorithm
87IGpAFR
87I1pAFR
87CHpRQ
...
...
...
87CH1RQ
87CHpRQ
Settings
E87L = N
87IG1AFR
0.1 pu
Remote 1
Currents
Remote p
Currents
Remote 1
Currents
Remote p
Currents
E87CH = N
10 cyc
0
Relay
Word
Bit
87DDRD