11.10
SEL-751 Relay Instruction Manual Date Code 20170927
Testing and Troubleshooting
Commissioning Tests
Step 5. Use the front-panel METER or the serial port MET command to
verify the results.
Arc-Flash Protection
Tests
Follow the procedures described in Section 2: Installation to complete the
installation of the Arc-Flash Detection (AFD) fiber-optic sensors in the
switchgear equipment to be protected. Make sure the switchgear doors, pan-
els, etc., are closed and in the final operating configuration. This ensures that
the ambient light as measured by the sensors is indicative of the normal oper-
ating condition. DO NOT ENERGIZE the switchgear for the commissioning
tests described in the following text. The relay must have the application set-
tings as necessary, be energized, and be in the ENABLED state. Refer to
Application Guide AG2011-01: Using the SEL-751 and SEL-751A for Arc-
Flash Detection for more details. The SEL-4520 Arc-Flash Test module pro-
vides a convenient way to test the operation of arc-flash detection relays
installed in metal-clad and metal-enclosed switchgear. The SEL-4520 is used
to test the SEL-751 and SEL-751A Feeder Protection Relays and other arc-
flash detection relays that use light and overcurrent to sense an arc-flash event.
Arc-Flash Detection (AFD) System Continuous Self-Testing
The SEL-751 continuously tests (periodic) and monitors all four arc-flash
sensor subsystems with the 2 AVI/4 AFDI card and eight arc-flash sensor
subsystems with the 8 AFDI card and reports the status. The test period is
constant, set to 10 minutes.
1. Point-Sensor AFD Self-Test
Each point-sensor AFD subsystem on the relay has a Transmit
LED channel and a Light Detector channel. The LED
periodically sends a light pulse through the transmit fiber cable,
which is “coupled” into the receive fiber cable in the point
sensor. The light travels back to the light detector on the relay.
The relay uses the light measurement by the detector to
determine the integrity of the point-sensor AFD loop and report
PASS/FAIL status.
2. Clear-Jacketed Fiber Sensor AFD Self-Test
The clear-jacketed fiber sensor is basically a loop, starting from
the Transmit LED and returning to the Light Detector. The
relay self-test involves sending a light pulse around the loop
Table 11.6 Power Quantity Accuracy—Delta Voltages
Apply Currents and Voltages
Real Power
(kW)
Reactive Power
(kVAR)
Power Factor
(pf)
PHROT := ABC
Ia = 2.5 –26
Ib = 2.5 –146
Ic = 2.5 +94
Expected:
P = 0.4677 • CTR • PTR
Expected:
Q = 0.2286 • CTR • PTR
Expected
pf = 0.90 lag
VA (Vab) = 120 +30
VC (Vcb) = 120 +90
Measured: Measured: Measured:
PHROT := ACB
Ia = 2.5 26
Ib = 2.5 +94
Ic = 2.5 146
Expected:
P = 0.4677 • CTR • PTR
Expected:
Q = 0.2286 • CTR • PTR
Expected:
pf = 0.90 lag
VA (Vab) = 120 30
VC (Vcb) = 120 90
Measured: Measured: Measured:
NOTE: The point-sensor diagnostics
signal does not affect the response
time of the sensor. The clear-jacketed
fiber-sensor diagnostics signal can
cause a 1 ms delay if the arc-flash
event occurs at the same time as the
diagnostics test. The clear-jacketed
fiber-sensor diagnostic test injects a
1 ms pulse through the fiber once
every 10 minutes.
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