IEEE 487:2015 pdf free download – IEEE Standard for the Electrical Protection of Communications Facilities Serving Electric Supply Locations-General Considerations
metallic member: A non-telecommunications metallic cable component such as a shield,vapor barrier,locating tracer wire, or strength member.
neutralizing transformer (NT) or neutralizing reactor: A device that introduces a voltage into a circuitpair to oppose an unwanted voltage. These devices neutralize extraneous longitudinal voltages resultingfrom ground potential rise(GPR), longitudinal induction, or both,while simultaneously allowing ac and dcmetallic signals to pass. These transformers or reactors are used primarily to protect telecommunications orcontrol circuits at electric supply locations， along routes where exposure to power line induction is aproblem, or both.
optic coupling device: An isolation device using an optical link to provide the longitudinal isolation.Circuit arrangements on each side of the optical link convert the electrical signal into an optical signal fortransmission through the optical link and back to an electrical signal. Various circuit arrangements provideone-way or two-way transmission and permit transmission to the various combinations of voice and/or dcsignaling logic used by the power industry.Single-channel optic coupling devices may be used inconjunction with other isolation devices in protection systems.
optical fiber cable: A telecommunications cable in which one or more optical fibers are used as thepropagation medium.The optical fibers are surrounded by buffers，strength members，and jackets forprotection, stiffness, and strength. An optical fiber cable may be an all-fiber cable or contain both opticalfibers and metallic conductors.
reliability (power system protective relaying): For the purposes of this standard，a combination ofdependability (failure to deliver a valid trip signal) and security (delivery of a false trip or control signal).
solid-state surge protective device (solid-state SPD): A protective device that employs solid-state circuitelements that provide a combination of high-speed voltage and current sensing. These SPDs are acombination of voltage clamps (avalanche diodes) and crowbar devices (multilayer diodes similar tosilicon-controlled rectifiers) and are designed to limit the voltage to a specific value and to reduce currentflow to low values of milliamperes within nanoseconds. These devices are typically integrated into theterminal apparatus.
spark gap: An air dielectric between two electrodes that may be a combination of several basic shapes thatis used to protect telecommunications circuits from damage due to voltage stress in excess of theirdielectric capabilities.It may or may not be adjustable.
surge arrester: A device that guards against dielectric failure of protection apparatus due to lightning orsurge voltages in excess of their dielectric capabilities and serves to interrupt power follow current.
suspension strand: A stranded group of wires supported above the ground at intervals by poles or otherstructures and used to furnish, within these intervals, frequent points of support for cables.
thunderstorm day: A day during which thunder is heard at least once at a specified observation point.
Magnetic (inductive) coupling, particularly under power line fault conditions,is significant when severalkilometers of parallel or close to parallel routing of both systems are considered. The power line faultcurrent flowing to ground is coupled magnetically to the longitudinal circuit of the telecommunicationssystem and results in a distributed longitudinal voltage being induced in the telecommunications circuit.The induced voltage is calculated by multiplying the inducing power line current by the mutual impedancebetween the two systems. The inducing current is a function of the fault location and the power systemcharacteristics. The mutual impedance is a function of such variables as the frequency, length of parallel,separation, soil resistivity, and shielding conductors [see IEEE Std 367 for methods of calculating magnetic(inductive) coupling]. Heterogeneous soil conditions, the presence of shielding conductors, and resistancesto ground of shielding conductors are usually difficult to characterize accurately; however,they have asignificant effect on the resulting level of induced voltage. Therefore, a large spread in values can occurbetween actual and estimated induced voltages because not all parameters can be assessed easily oraccurately.