Abstract: Service conditions, electrical ratings, thermal ratings, and environmental testing requirements are defined for communications networking devices to be installed in electric power substations. This standard establishes a common reproducible basis for designing and evaluating communications networking devices and the communications ports of protective relays for use in this harsh environment. Keywords: auto dialers, bridges, communications networking device, communications ports, derating, dielectric test, electrostatic discharge (ESD) test, environmental requirements, Ethernet hubs, fast transient test, firewalls, humidity, IEEE 1613, impulse test, insulation test, modems, power apparatus, radio frequency (RF) test, routers, serial device, surge withstand capability (SWC) test, switches, temperature range, temperature rise, voltage rating.