P.11.43
Date Code 20151029 Protection Manual SEL-411L Relay
Testing and Troubleshooting
Relay Troubleshooting
Relay Troubleshooting
Inspection Procedure
Complete the following inspection procedure before disturbing the system.
After you finish the inspection, proceed to Troubleshooting Procedures.
Step 1. Confirm that the power is on. Do not turn the relay off.
Step 2. Measure and record the control power voltage at the relay
POWER terminals marked + and – on the rear-panel terminal
strip.
Step 3. Measure and record the voltages at all control inputs.
Step 4. Measure and record the state of all control outputs.
Step 5. Inspect the serial communications ports cabling to be sure that
a communications device is connected to at least one
communications port.
Troubleshooting
Procedures
Troubleshooting procedures for common problems are listed in Table 11.15.
The table lists each symptom, possible causes, and corresponding diagnoses/
solutions. Related relay commands are listed in bold capitals. See Section 15:
ASCII Command Reference for details on relay commands and Section 5:
Settings for details on relay settings.
Table 11.14 Channel Statistics Section
Packets lost—24 hours A count of the number of packets lost over the last
24 hours. Increasing packet loss is an indication of a
failing channel.
Maximum channel delays—
round-trip, transmit, receive and
maximum channel asymmetry
The worst-case values of these delays are recorded
along with the time of occurrence. These values may
be an indicator that a channel is out-of-tolerance or
that switching is occurring on the communications
network.
Round trip delay and asymmetry
histograms
These histograms tabulate how frequently the
measurements of round-trip channel delay and
asymmetry fall within specified ranges. Histograms
provide an alternative way of monitoring the
behavior of a channel. For instance if the round trip
channel delay is 4–6 ms for 85% of the time and
15–20 ms for 15% of the time then it may be that the
channel is regularly switching from a low latency
path to a higher latency path and working in the
higher latency path for 15% of time.
Channel Usage (Primary versus
hot stand-by)
In dual redundant channel applications these values
are measures of the time that each of the primary and
secondary channels are active—expressed as
percentages. In a healthy network the primary
channel is expected to be near 100% and the
secondary is expected to be near 0%.
NOTE: To ensure proper
communication and protection,
please refer to the firmware
compatibility in Table A.2.
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