2.50
SEL-751 Relay Instruction Manual Date Code 20170927
Installation
Field Serviceability
Figure 2.48 Point Sensor Assembly With Two V-Pin Splice Connectors
Field Serviceability
The SEL-751 firmware can be upgraded in the field; refer to Appendix B:
Firmware Upgrade Instructions for firmware upgrade instructions. You may
know when a self-test failure has occurred by configuring an output contact to
create a diagnostic alarm as explained in Section 4: Protection and Logic
Functions. By using the metering functions, you can determine whether the
analog front-end (not monitored by relay self-test) is functional. Refer to
Section 11: Testing and Troubleshooting for detailed testing and
troubleshooting information.
The only two components that can be replaced in the field are the power sup-
ply fuse and the real-time clock battery. A lithium battery powers the clock
(date and time) if the external power source is lost or removed. The battery is
a 3 V lithium coin cell, Ray-O-Vac BR2335 or equivalent. At room tempera-
ture (25°C), the battery will operate nominally for 10 years at rated load.
When the relay is powered from an external source, the battery experiences a
low self-discharge rate. Thus, battery life can extend well beyond 10 years.
The battery cannot be recharged.
Fuse Replacement
To replace the power supply fuse, perform the following steps:
Step 1. De-energize the relay.
Step 2. Remove the eight rear-panel screws and the relay rear panel.
Step 3. Remove the Slot A printed circuit board.
Step 4. Locate the fuse on the board.
Step 5. Remove the fuse from the fuse holder.
Step 6. Replace the fuse with a BUSS S505 3.15A (ceramic),
Schurter T 3.15A H 250V, or equivalent.
Black-Jacketed
Fiber Zipcord
Duplex
V-Pin
Terminators
Sensor
01-35 Meters
A Meters
V-Pin Connector
Splices
Dual V-Pin
Latch
Note: To complete the fiber assembly, you will also need to order two ST connector
splice bushings with P/N 915900148.
Dual V-Pin Latch-V-Pin Terminated
Black-Jacketed Fiber
Zipcord Duplex Cable
P/N C814BVL006
V-Pin to Point Sensor Terminated
Black-Jacketed Fiber
Zipcord Duplex Cable
P/N C814BVP017
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
components, contact SEL about
returning this device and related SEL
equipment for service.
Disconnect or de-energize all external
connections before opening this
device. Contact with hazardous
voltages and currents inside this
device can cause electrical shock
resulting in injury or death.
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