2.50
SEL-421 Relay Instruction Manual Date Code 20171021
Installation
AC/DC Connection Diagrams
Several types of STP bulk cable and patch cables are available for use in Ethernet
networks. If noise in your environment is severe, you should consider using fiber-
optic cables. We strongly advise against using twisted-pair cables for segments
that leave or enter the control house.
If you use twisted-pair cables, you should use care to isolate these cables from
sources of noise to the maximum extent possible. Do not install twisted-pair
cables in trenches, raceways, or wireways with unshielded power, instrumenta-
tion, or control cables. Do not install twisted-pair cables in parallel with power,
instrumentation, or control wiring within panels, rather make them perpendicular
to the other wiring.
You must use a cable and connector rated as Category 5 (Cat 5) to operate the
twisted-pair interface (10/100BASE-T) at 100 Mbps. Because lower categories
are becoming rare and because you may upgrade a 10 Mbps network to
100 Mbps, we recommend using all Cat 5 or better components.
Some industrial Ethernet network devices use 9-pin connectors for STP cables.
The Ethernet card RJ45 connectors are grounded so you can ground the shielded
cable by using a standard, externally shielded jack with cables terminating at the
Ethernet card.
AC/DC Connection Diagrams
You can apply the SEL-421 in many power system protection schemes.
Figure 2.55 shows one particular application scheme with connections that repre-
sent typical interfaces to the relay for a single circuit breaker connection.
Figure 2.56 depicts typical connections for a dual circuit breaker protection
scheme.
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