10-6
Line Current Differential Communications
Date Code 20010625
and Serial Port Communications and Commands
SEL-311L Instruction Manual
Relay 2:
Channel X Channel
Y
TIMRX = I
RC422Y = F
TC422Y = R
SEL-311L
CHX
CHY
DWG: M311L084
Relay 1
Relay 2
SEL-311L
CHX
CHY
Network
MUX
MUX
Figure 10.3: Typical Hot-Standby Connection Using Direct Fiber and Multiplexed
EIA-422
In addition, the Channel Monitor settings described below are totally independent of channel
assignment. Set each channel monitor as required by the particular channel application, and per
expected channel performance.
87L C
HANNEL
M
ONITORS AND
C
HANNEL
P
ROBLEM
I
NDICATORS
C
OMMON TO
ALL 87L C
HANNEL
T
YPES
The relay indicates there is a problem with an 87L channel in several ways. The front-panel
LED 87CH FAIL illuminates when the relay detects a problem on either Channel X or Channel
Y. Rear panel TX/RX LEDs illuminate when the relay transmits and receives valid 87L packets
from another SEL-311L Relay. In addition, several Relay Word bits per channel indicate
channel health, and help determine the cause of channel problems. The collection of Relay
Word bits, LEDs, and channel monitor reports collectively form the channel monitors. This
section describes each of the channel problem indicators, and describes settings associated with
them.
Section 13: Testing, Troubleshooting, and Commissioning
describes how to use channel
indicators to troubleshoot a channel problem.
Availability and Delay Monitor Drive Front Panel LED 87CH FAIL
The availability monitor detects channel degradation or failure by counting lost packets. A
packed is lost if it is not received, is received out of order, is corrupted, or contains an incorrect
address. The delay monitor measures round trip channel delay, and alarms if the estimated
one-way delay exceeds a threshold.
Together, the two monitors continuously check each channel for excessive delay, continuous
dropout, and packets lost out of the previous 10,000. Relay Word bits CHXAL and CHYAL
Summary of Contents for SEL-311L
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