P.3.296
SEL-411L Relay Protection Manual Date Code 20151029
Protection Functions
87L Channel Monitoring and Alarming Logic
Figure 3.206 Channel OK Status
The relay declares an alarm state for a channel if any one of the following is
true (see Figure 3.207).
➤ The channel is not OK for half a second (channel drop out).
➤ The lost packet alarm is asserted.
➤ The channel round-trip alarm is asserted.
➤ Channel asymmetry is exceeded while the channel is required.
➤ The channel is required for the 87L function, but it cannot be
synchronized in terms of aligning the current data.
Figure 3.207 Default Channel Alarm Logic
Table 3.155 87L Channel Alarm Relay Word Bits (Sheet 1 of 2)
Name Description
87CH1T Round-trip delay alarm asserted for the 87L serial Channel 1
87CH2T Round-trip delay alarm asserted for the 87L serial Channel 2
87CH1DT Step change in the round-trip delay alarm asserted for the 87L serial
Channel 1
87CH2DT Step change in the round-trip delay alarm asserted for the 87L serial
Channel 2
87CH1AM Channel asymmetry alarm asserted for the 87L serial Channel 1
a
87CH2AM Channel asymmetry alarm asserted for the 87L serial Channel 2
a
87CH1LP Lost packet alarm asserted for the 87L Channel 1
87CH2LP Lost packet alarm asserted for the 87L Channel 2
87CH3LP Lost packet alarm asserted for the 87L Channel 3 (Ethernet only)
87CH1NB Noise burst alarm asserted for the 87L Channel 1
87CH2NB Noise burst alarm asserted for the 87L Channel 2
87CH3NB Noise burst alarm asserted for the 87L Channel 3 (Ethernet only)
87CH1BR Momentary channel break alarm asserted for the 87L Channel 1
87CH2BR Momentary channel break alarm asserted for the 87L Channel 2
87CH3BR Momentary channel break alarm asserted for the 87L Channel 3
(Ethernet only)
87CH1OK 87L Channel 1 is receiving valid data
Relay
Word Bit
Relay
Word Bit
Valid packet
received
87CHpAC
* packets
87CHpOK
1*
5*
Relay
Word Bits
Relay
Word Bit
87CHpAL
87CHpOK
87CHpAM
87CHpRQ
87CHpLP
87CHpT
87CHpRQ
87CHpNS
0.5 s
0
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