U.6.6
SEL-421 Relay User’s Guide Date Code 20090715
Testing and Troubleshooting
Testing Features and Tools
TEST DNP Command
Use the TEST DNP command to test the serial DNP3 interface. Values you
enter in the DNP3 map are override values. Use the TEST DNP command to
write override values in the serial DNP3 map. The TEST DNP command does
not affect data on the DNP3 LAN/WAN interface. For more information on
serial DNP3 and the SEL-421, see DNP3 Communications on page R.6.1.
TEST FM Command
Use the TEST FM command to override normal Fast Meter quantities for
testing purposes. You can only override “reported” Fast Meter values (per-
phase voltages and currents). You cannot directly test Fast Meter values that
the relay derives from the reported values (power, sequence components, and
so on). For more information on Fast Meter and the SEL-421, see SEL
Communications Protocols on page R.5.1.
Low-Level Test
Interface
The SEL-421 has a low-level test interface between the calibrated input
module and the processing module. You can check the relay in two ways: by
using secondary injection testing, or by applying low-magnitude ac voltage
signals to the low-level test interface.
Connection
Equipment components are sensitive
to electrostatic discharge (ESD).
Undetectable permanent damage
can reuslt if you do not use proper
ESD procedures. Ground yourself,
your work surface, and this
equipment before removing any
cover from this equipment. If your
facility is not equipped to work with
these components, contact SEL
about returning this device and
related SEL equipment for service.
!
CAUTION
The top circuit board is the relay main board and the bottom circuit board is
the input module board. At the right side of the relay main board (the top
board) is the processing module. The input to the processing module is
multipin connector J20, the analog or low-level test interface connection.
Receptacle J20 is on the right side of the main board; for a locating diagram,
see Figure 2.19.
Figure 6.1 shows the low-level interface connections. Note the nominal
voltage levels, current levels, and scaling factors listed in Figure 6.1 that you
can apply to the relay. Never apply voltage signals greater than 6.6 Vp-p
sinusoidal signal (2.33 Vrms) to the low-level test interface.
To use the low-level test interface, perform the following steps:
Step 1. Remove any cables connected to serial ports on the front panel.
Step 2. Loosen the four front-panel screws (they remain attached to the
front panel), and remove the relay front panel.
Step 3. Remove the 34-pin ribbon cable from the front panel by
pushing the extraction ears away from the connector.
Step 4. Remove the ribbon cable from the main board J20 receptacle.
Step 5. Substitute a test cable with the signals specified in Figure 6.1.
Step 6. Reconnect the cables removed in Step 4 and replace the relay
front-panel cover.
Step 7. Replace any cables previously connected to serial ports on the
front panel.
Courtesy of NationalSwitchgear.com
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