Sel 411L - Figure 3.214 87 L Master (87 MTR) Logic; Figure 3.215 87 L Outstation (87 SLV) Logic

P.3.307
Date Code 20151029 Protection Manual SEL-411L Relay
Protection Functions
87L Master, Outstation, and Loss of Protection Logic
The 87L function is a master when it receives all required and properly
synchronized current data. As Figure 3.214 shows, the 87L function is not in
the master mode (87MTR deasserts) if any of the required channels (signaled
by 87CHpRQ Relay Word bits) is as follows:
➤ Unhealthy (not OK), as deassertion of the 87CHpOK Relay
Word bit (see 87L Channel Monitoring and Alarming Logic)
signals.
➤ Incapable of providing usable data because the 87CHpNS
Relay Word bit (see 87L Channel Synchronization Logic and
Status) detected a lack of synchronization.
➤ Forced out, or intentionally marked as unusable, by the
87CHpFO Relay Word bit (typically because of suspected
current data synchronization problems, see 87L Time Fallback
Logic).
Note that the three-terminal outstation application with a single channel
(E87CH = 3SS) becomes a master in the stub bus mode (when the 87L
function needs no remote currents).
Figure 3.214 87L Master (87MTR) Logic
As Figure 3.215 shows, the 87L function is in the outstation mode if at least
one of its active channels is receiving valid data. This means that the relay is
connected to at least one other relay in the 87L scheme, but it is not in the
master mode.
Figure 3.215 87L Outstation (87SLV) Logic
As Figure 3.216 shows, the relay loses the 87L function in either of the
following two cases.
➤ 87L blocking logic, either locally or remotely, is blocking the
function (as the 87BLK Relay Word bit signals), even if the
87L function is a master.
➤ Either 87DTT is disabled in the relay while it is in outstation
mode, or none of the relays connected on the active channels is
a master.
Relay
Word Bits
Relay
Word Bit
87CHpFO
87CHpNS
87CHpOK
Relay
Word Bit
87CHpRQ
E87CH = 3SS
87MTR
To all remote
relay
terminals as a
MASTER bit
(all required channels) ...
Setting
ESTUB
SEL
OGIC
Relay
Word Bits
Relay
Word Bit
87CHpAC
87CHpOK
Relay
Word Bit
87MTR
87SLV
(all active channels) ...