ITU-T Recommendations

Recommendation ITU-T K.147 considers the overvoltage and overcurrent protection of information technology equipment including IEEE 802.3 Ethernet. This Recommendation describes how surges are coupled into the system and what surge mitigation measures are used, considering the differences in implementations and network configurations. Furthermore, it contains the different surge and power fault test circuit approaches and conditions under which the specified tests are applied.
Networked equipment can be subject to overvoltage and overcurrent transients. Both data and powering services should be resistant to expected environmental transients. Where equipment has multiple independent ports, such as central hubs, switches, or repeaters, then testing for inter-port resistibility is required.
Resistibility testing needs to identify lightning transients coupled into a network by magnetic induction, earth potential rise, resistive coupling, and transient coupling by a voltage-limiting operation of surge protective functions or flashover. Voltage limitation may convert common-mode surges into differential-mode surges in the signal path. Depending on local installation practices, it is also possible for alternating current mains power faults to couple into the network, which can necessitate the use of overcurrent protection.