Sel 411L - 87 L Channel Monitoring and Alarming Logic; Table 3.154 87 L Channel Alarm Settings

P.3.291
Date Code 20151029 Protection Manual SEL-411L Relay
Protection Functions
87L Channel Monitoring and Alarming Logic
87L Channel Monitoring and Alarming Logic
The line current differential protection function is communications dependent.
It is necessary, therefore, to monitor the status of the communications
channels during in-service operation to detect abnormal or unexpected
conditions and initiate corrective actions. Checking for normal, as specified,
performance of the communications channels is an integral part of a typical
commissioning procedure for the 87L function. In addition, the 87L function
itself responds to some monitored channel characteristics in real time to
maintain proper security and dependability. To serve all these needs, the relay
provides a set of channel monitoring and alarming functions.
This section describes such relay channel monitoring as round-trip channel
delay, channel asymmetry, lost packet counts, etc. These monitoring functions
provide overall assessment of channel quality and feed into the hot stand-by
channel switchover logic and the time fallback logic.
The logic in this section applies to all active channels (87CHpAC asserted),
unless indicated otherwise.
87CH3TS External time-based synchronization in effect for the 87L Channel 3
(Ethernet only)
87CH1NS Data synchronization not possible for the 87L Channel 1
87CH2NS Data synchronization not possible for the 87L Channel 2
87CH3NS Data synchronization not possible for the 87L Channel 3 (Ethernet only)
87CH1LS Low quality of data synchronization over the 87L Channel 1
87CH2LS Low quality of data synchronization over the 87L Channel 2
87CH3LS Low quality of data synchronization over the 87L Channel 3 (Ethernet
only)
87CH1HS High quality of data synchronization over the 87L Channel 1
87CH2HS High quality of data synchronization over the 87L Channel 2
87CH3HS High quality of data synchronization over the 87L Channel 3 (Ethernet
only)
87SYNL Low quality of data synchronization for the 87L scheme
87SYNH High quality of data synchronization for the 87L scheme
Table 3.153 Channel Synchronization Method Relay Word Bits (Sheet 2 of 2)
Name Description
Table 3.154 87L Channel Alarm Settings (Sheet 1 of 2)
Setting Description Range Default
87CH1MT Maximum round-trip channel delay
threshold for the 87L Channel 1 (ms)
OFF, 1–50 OFF
87CH2MT Maximum round-trip channel delay
threshold for the 87L Channel 2 (ms)
OFF, 1–50 OFF
87CH1MD Maximum step change in the round-trip
channel delay threshold for the 87L
Channel 1 (ms)
OFF, 3–50 OFF
87CH2MD Maximum step change in the round-trip
channel delay threshold for the 87L
Channel 2 (ms)
OFF, 3–50 OFF