U.2.46
SEL-421/SEL-421-1 Relay
User’s Guide
Date Code 20020501
Installation
Connection
➤
You should keep the length of the communications cables as
short as possible to minimize communications circuit
interference and also to minimize the magnitude of hazardous
ground potential differences that can develop during abnormal
power system conditions.
➤
EIA-232 communications cable lengths should never exceed
50 feet, and you should always use shielded cables for
communications circuit lengths greater than 10 feet.
➤
Modems provide communication over long distances and give
isolation from ground potential differences that are present
between device locations. (Examples are the SEL-28XX-series
transceivers.)
➤
Lower data speed communication is less susceptible to
interference and will transmit greater distances over the same
medium than higher data speeds. You should use the lowest
data speed that provides an adequate data transfer rate.
Summary of Contents for SEL-421
Page 8: ...This page intentionally left blank ...
Page 30: ...This page intentionally left blank ...
Page 110: ...This page intentionally left blank ...
Page 204: ...This page intentionally left blank ...
Page 284: ...This page intentionally left blank ...