P.3.283
Date Code 20151029 Protection Manual SEL-411L Relay
Protection Functions
87L Active and Required Channel Logic
At any given time, an active channel may or may not be required. Whether we
can consider an active channel to be required depends upon usage of the
remote current data for protection in the master mode.
The 87CHpRQ relay word bit flags the requirement for the p-th channel.
These bits assert as follows.
In the 3SS outstation application, no active channels are required. In any
application over Ethernet (2E, 3E, or 4E) all active channels are required in
the absence of a stub bus condition assertion (ESTUB Relay Word bit). Under
the stub bus condition, no channels are required; the 87L zone only extends to
the opened line disconnect switch and, therefore, includes local currents only.
Figure 3.195 and Figure 3.196 cover other, more complex, applications.
Figure 3.195 applies to the 2SS and 3SM 87L configurations. The relay
selects active channels per Table 3.148 and uses the 87CHpAC Relay Word
bits to signal its selection. The active channel(s) in this application remains
required (87CHpRQ asserted) as long as the relay is not in the stub bus
configuration.
For example, assume E87CH = 3SM (three-terminal master application over
serial channels). Both channels are active (87CH1AC = 87CH2AC = 1). Both
channels are required (87CH1RQ = 87CH2RQ = 1) as long as the stub bus
condition is not present (ESTUB deasserted), or the relay is not in single-
ended test mode (87TESTT = S) and the characteristic is under test
(87CHART asserted).
Figure 3.195 87CHpRQ Logic for the 2SS and 3SM 87L Configurations
Figure 3.196 applies to the 2SD configuration. Both channels are active,
facilitating instantaneous switchover upon a channel failure.
If you select the first channel as primary (87PCH = 1), Channel 1 is required if
the switchover logic requests no channel switchover (87HSB Relay Word bit
deasserted, see 87L Standby Channel Switchover Logic) and Channel 2 is
required if the switchover logic calls for switching to the standby channel
(87HSB asserted).
If you select the second channel as primary (87PCH = 2), Channel 2 is
required if the switchover logic requests no channel switchover (87HSB Relay
Word bit deasserted) and Channel 1 is required if the switchover logic calls for
switching to the standby channel (87HSB asserted).
Neither of the two channels is required in the stub bus condition, or under
certain testing conditions as explained previously.
Settings
E87CH = 2SS
87CH1AC
E87CH = 3SM
87CH2AC
ESTUB
87CH2RQ
87CH1RQ
Relay
Word
Bits
87CHART
87TESTT = S
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