Date Code 20171021 Instruction Manual SEL-421 Relay
Instruction ManualInstruction Manual
SECTION 3
Testing
This section contains guidelines for determining and establishing test routines for
the SEL-421 Relay. Follow the standard practices of your company in choosing
testing philosophies, methods, and tools. Section 10: Testing, Troubleshooting,
and Maintenance in the SEL-400 Series Relays Instruction Manual addresses the
concepts related to testing. This section provides supplemental information spe-
cific to testing the SEL-421.
Topics presented in this section include the following:
➤ Low-Level Test Interface on page 3.1
➤ Relay Test Connections on page 3.3
➤ Checking Relay Operation on page 3.8
➤ Technical Support on page 3.23
The SEL-421 is factory calibrated; this section contains no calibration informa-
tion. If you suspect that the relay is out of calibration, contact your Technical Ser-
vice Center or the SEL factory.
Low-Level Test Interface
You can test the relay in two ways: by using secondary injection testing, or by
applying low-magnitude ac voltage signals to the low-level test interface. This
subsection describes the low-level test interface between the calibrated input
module and the processing module.
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
J24, the analog or low-level test interface connection. Receptacle J24 is on the
right side of the main board; for a locating diagram, see Figure 2.19 on
page 2.18.
Figure 3.1 shows the low-level interface connections. Note the nominal voltage
levels, current levels, and scaling factors listed in Figure 3.1 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 J24 receptacle.
Step 5. Substitute a test cable with the signals specified in Figure 3.1.
Equipment components are sensitive
to electrostatic discharge (ESD).
Undetectable permanent damage can
result 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 compo-
nents, contact SEL about returning
this device and related SEL equip-
ment for service.
To Next Page
Loading...
