11.11
Date Code 20170927 Instruction Manual SEL-751 Relay
Testing and Troubleshooting
Commissioning Tests
and measuring the light received at the detector. The light
measurement by the detector is used to determine the integrity
of the clear-jacketed fiber sensor AFD loop and report PASS/
FAIL status.
METER LIGHT Report
Use the serial port ASCII command METER L and view the METER LIGHT
report as shown in Figure 5.11.
The report shows the light intensity measurements in percent of full scale (%)
for the four AFD channels. This measurement represents the “background” or
the “ambient” light in the switchgear areas being monitored for arc-flash. Use
this measurement to determine the time-overlight TOL1 to TOL4 settings with
a 2 AVI/4 AFDI card and the TOL1–TOL8 settings with an 8 AFDI card for
arc-flash protection (refer to Section 4: Protection and Logic Functions for
details). If there is excessive background light (any of the Relay Word bits
AFSnEL picks up) or if there is a diagnostic failure (any of the Relay Word
bits AFSnDIAG picks up), the AFALARM Relay Word bit picks up and gives
a WARNING on the relay front panel and asserts the ALARM output contact.
Command AFT (Arc-Flash test)
The relay performs the arc-flash self-test periodically as discussed previously.
Additionally, by using the serial port ASCII command AFT, the relay
performs the self-test on demand in all four channels and reports the status of
each channel. This same test is also available from the Control Window in the
ACSELERATOR QuickSet SEL-5030 Software and the relay front-panel
STATUS sub-menu. Refer to Figure 7.16 for the AFT command response
example. The response shows the light measurements in percent of full scale
and the PASS/FAIL status. The PASS indication means the channel is healthy
and ready to detect an arc-flash event. The FAIL indication means the channel
in question is not healthy and needs repair and testing when a convenient
outage is available for maintenance.
Testing the Arc-Flash Time-Overlight Elements TOL1 to TOL8
Test the TOL elements once the relay has been set, as described in Section 4:
Protection and Logic Functions for the arc-flash protection elements. You
should add the TOL1–TOL4 Relay Word bits with a 2 AVI/4 AFDI card and
the TOL1–TOL8 Relay Word bits with a 8 AFDI card Relay Word bits to the
SER (sequence of events report) settings so that the relay can capture the TOL
element assertion and dropout. Apply a bright light source near the light
sensor (POINT or FIBER type) in the switchgear cabinet and note that the
appropriate TOL element Relay Word bit picks up and drops out as expected.
The arc-flash test can also be captured as a CEV event report by triggering the
event report with the TOLn Relay Word bit. The CEV R (raw data) event
report should be viewed with the
ACSELERATOR Analytic Assistant SEL-5601
Software. You can view the % light intensity analog quantity together with the
TOLn Relay Word bit to verify the correct operation.
Testing the Arc-Flash Overcurrent Elements 50PAF and 50NAF
These current elements are similar to the 50P and 50N elements, except they
use "raw" current input samples and act instantaneously to achieve fast
response. You can test these elements similarly to the 50P and 50N elements.
You can use the CEV R report as described previously to analyze the event.
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