IEEE 1692-2011 pdf free.IEEE Guide for the P rotection of Communication Insta | lations from Lightning Effects.
High differential ground potentials between local equipment and remote power grounds make the power serviec conductors a favored discharge path for LGPR currents. Soil conditions havc a significant effect on differential ground potentials. Higher soil resistivity will result in higher differential ground potentials from lightning strikes to earth. With cloud to ground electric potentials in the magnitude of tens of millions of volts, an earth strike can be characterized as a current source. When the stroke discharge occurs the current traveling in the earth will flow regardless of the soil impedance. General application of ohm’s law will indicate the higher soil resistivity will result in a higher differential ground potential lbr a given discharge current.
Sites without towers may experience LGPR efl’ects as much, if not more, than sites with towers as they are less likely to have extensive grounding infrastructure, Sites at most risk are areas with a higher occurrence of lightning and high soil resistivity.
5.1 Surge protective devices (SPD) and wire-line
The standard surge protective devices (SPD) in the telecommunications industry, for the termination of communication wire-line services is the gas discharge tube (GDT). GDTs are also called gas tubes. GDTs can be found on virtually every telephone pair terminated in homes, buildings, and similar locations, GDTs arc designed to shunt most current to ground. lithe magnitude shunted does not exceed a certain threshold the SPD will help protect equipment, and personnel. from harm.
Most shunting devices, however, do not fully protect network electronic equipment from a GPR or “outgoing current,” whether induced from lightning or from a faulted power line. When shunting devices are connected to an elevated ground (outgoing current) during a GPR event, they merely otTer an additional current path ol’f the site to remote earth (the other end),
When SPDs (GDTs, MOVs, ARDs, SCRs, SADs, SASs, etc.) are used as ground shunting devices, they will not protect equipment from GPR. These devices merely offer an additional path to remote earth through the communication pairs for any and all outgoing currents.
When there is a GPR event the SPI) provides a connection of the communication path in the reverse direction from which they were intended to operate and increases the possibility of equipment damage to telephone and power installations.
The most susceptible locations arc those where the equipment is located near, or under, towers andor are located at a higher altitude than the surrounding area.
Some of the susceptible locations to equipment damages include the Public Safety Answering Point locations (also called 911 PSAP) The typical 911 PSAP center is a relatively small building under, or near, a radio tower. This tower is a likely target for lightning. Personnel taking emergency calls coming into the PSAP may be at a higher risk since they must be at the phones at all times and cannot be oIl’ the phones during lightning storms, as recommended in virtually every telephone book in the United States. For additional information see ATIS 0600321 [B2].IEEE 1692 pdf download.