Sel 411L - 87 L Channel Synchronization Logic and Status; Figure 3.196 87 Chprq Logic for the 2 SD 87 L Configuration; Table 3.149 Active and Required Channel Relay Word Bits

P.3.284
SEL-411L Relay Protection Manual Date Code 20151029
Protection Functions
87L Channel Synchronization Logic and Status
Figure 3.196 87CHpRQ Logic for the 2SD 87L Configuration
Use the 87CHpAC and 87CHpRQ Relay Word bits when testing or when
developing custom 87L alarm logic. These Relay Word bits are inputs to many
relay logic diagrams. An understanding of the concepts of active and required
channels is therefore beneficial for comprehending the remainder of this
section and other sections in this manual.
87L Channel Synchronization Logic and Status
This section explains settings and associated operating and status logic for
87L data synchronization.
We first provide details regarding clock offset calculations for the channel-
based synchronization method and other auxiliary usage such as channel
monitoring and alarming or when engaging time fallback logic in external
time-based data synchronization.
We then provide details for the estimation of time quality for the external
time-based synchronization method and other auxiliary usage such as channel
monitoring and alarming.
Finally, the section describes logic schemes that drive the method of data
synchronization and indicate the status and estimated accuracy of
synchronization. User settings determine the method of synchronization, but
this method can change dynamically in the external time-based
synchronization mode according to the time fallback method in effect.
Synchronization accuracy helps control sensitivity of the 87L function and
supervises the multi-ended fault location algorithm.
Table 3.149 Active and Required Channel Relay Word Bits
Name Description
87CH1AC 87L Channel 1 is active
87CH2AC 87L Channel 2 is active
87CH3AC 87L Channel 3 is active (Ethernet only)
87CH1RQ 87L Channel 1 is required for the current-based 87L elements
87CH2RQ 87L Channel 2 is required for the current-based 87L elements
87CH3RQ 87L Channel 3 is required for the current-based 87L elements
(Ethernet only)
Setting
E87CH = 2SD
Setting
87PCH = 1
Setting
87PCH = 2
ESTUB
87CH2RQ
87CH1RQ
SELOGIC
87HSB
Relay
Word Bit
Relay
Word
Bits
87CHART
87TESTT = S
NOTE: To ensure proper
communication and protection,
please refer to the firmware
compatibility in Table A.2.