IEEE 776-2018 pdf free.IEEE Recommended Practice for Inductive Coordination of Electric Supply and Communication Lines.
While inductive interlerence may occur at any time the above conditions are satisfied, the majority olcases and the principal concern of this recommended practice involve interference in telecommunication systems as a result of their proximity to electric power systems. Therefore, subsequent discussion is limited to that general case, although the principles and practices could apply to other cases as well.
4.1.1 Inductive Influence
Inductive influence is defined as those characteristics of an electric supply circuit that determine the character and intensity of the inductive field that it produces. The voltage and current present on an operating power system produce electric and magnetic fields in the vicinity of the system. The character and intensity of those fields dcterminc the inductive influence. Character is related primarily to the frequencies present. while intensity is related to the magnitude of voltages and currents modified by line configuration, current distribution, and any shielding structures in the immediate vicinity, excluding the shield of a telecommunications cable.
NOTE— When buried or underground telecommunications cables are bcaied in the proximity of buried or underground power cables the effects of electromagnetic interference (EM I) should be carefully considereiL4
4.12 Coupling
Coupling is defined as the transfer of energy from one system to another. For the inductive influence of a power system to affect another system or circuit, there has to be coupling between the two. The coupling mechanism consists of the mutual impedance between circuits in proximity to each other. This coupling has resistive, capacitive, and inductive components. Electric induction, via capacitive coupling, is often consequential when the exposed circuit is composed of unshielded conductors above ground. However. when the exposed circuit conductors are within a grounded metallic sheath or shield, capacitive coupling generally is considered negligible. Therefore, the coupling mechanism of primary concern will generally be the mutual inductance between an electric supply circuit or circuits and a telecommunications facility.
The primary factors affecting coupling are separation of the systems, frequency of the magnetic field, and earth resistivity.
4.1.3 Susceptiveness
Susceptiveness is defined as those characteristics thai determine the extent to which the service rendered by a teleco,nmunications circuit can be adversely affected by a given longitudinal voltage or current. The existence of an inductive field and coupling with a metallic telecommunication circuit will cause longitudinal voltage to be induced in the telecommunication circuit. However, interference does not occur unless the circuit is susceptible to the induced voltage and resulting current. One kind of interference is the introduction of an unwantcd signal (noise) into thc circuit. The sinccptivcncss of the circuit to noise depends on the quality of the cable shield, the amplitude and frequency of the signal normally transmitted, circuit impedances and the longitudinal habnce of the circuit and its associated equipment. Longitudinal balance detennines the extent to which longitudinal (common-mode) voltage is converted to metallic (differentialmode) voltage. Interference is often also manifested as a malfunction in the operation of the circuit. The malfunction is usually caused by electrical or thermal overstrcss of a circuit component by the induced voltage or resulting current. In addition, safety thresholds are to be considered.
4.2 Need for coordination
The continued successful coexistence of systems for the transmission, distribution, and utilization of electric power and telecommunications depends upon the ability of their providers to resolve problems of interference between the systems. The need for coordination between providers of electric supply and telecommunications lines has existed since the early days of the industries. At various times, cooperative studies have been undertaken, resulting in the dissemination of a large body of technical information on the subject. This information continues to grow with the expansion of these industries and the introduction of new technology. However, this growth and change introduces new concerns that should be addressed if continued compatibility of the systems is to be accomplished. Some of these concerns are as follows:
a) Ecological considerations, which encourages the placement of facilities on joint or adjacent rights- of-way
b) Higher-capacity power systems serving larger loads.IEEE 776 pdf download.