Sel 411L - Figure 3.203 Lost Packet Alarm Logic; Figure 3.204 Noise Burst Alarm Logic; Figure 3.205 Momentary Channel Break Alarm Logic

P.3.295
Date Code 20151029 Protection Manual SEL-411L Relay
Protection Functions
87L Channel Monitoring and Alarming Logic
Apply the 87CHpPC setting on a per-channel basis to monitor packets lost
among the last 10,000 scheduled packets. The 87CHpLP Relay Word bit
signals an alarm.
Figure 3.203 Lost Packet Alarm Logic
Noise Burst and
Momentary Channel
Break
This section applies to all active channels, both serial and Ethernet. These
alarms have no associated settings.
The relay defines a noise burst according to Figure 3.204. This logic counts
packets it receives as expected but which failed a data integrity check, and it
asserts only if the newest packet passes a data integrity check signifying that
channel noise has subsided.
This alarm can fail to trigger in some situations because, in addition to failing
the BCH, the noise can affect packet framing and the ability of the relay to
identify the packet. When this alarm does assert, however, it signifies channel
noise—the relay is receiving 87L packets, but these packets are temporarily
failing a data integrity check.
Figure 3.204 Noise Burst Alarm Logic
The relay defines momentary channel break according to Figure 3.205. The
logic arms itself only if the relay resumes reception of valid packets within
0.1 s. If more than three consecutive packets time out within that 0.1-second
window, the alarm asserts. This logic can trigger either for channel switching
or channel noise.
Figure 3.205 Momentary Channel Break Alarm Logic
Overall Channel
Status
You can use the variety of available Relay Word bits to program custom
channel status logic with SEL
OGIC control equations. The relay provides for a
default overall channel status indication.
The relay declares a given active channel as OK (87CHpOK Relay Word bit)
if this channel receives more than one valid packet in a row, as in
Figure 3.206. Validity depends upon a consecutive sequence number
compared with the last packet, expected arrival time, and data integrity
(BCH). The 87CHpOK Relay Word bit deasserts if five consecutive packets
fail to meet the criteria.
Setting
Analog
Relay
Word Bit
87CHpPC
87CHpLX
87CHpLP
0
0.1 s
Relay
Word Bit
4
8
Number of packets
received but corrupted
among the last 10 packets
Valid packet
received
87CHpNB
0
0.1 s
Relay
Word Bit
Valid packet
received
Packet
timed out
* packets
87CHpBR
0
0.1 s
0
0.1 s
3*
0.12 s