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Characterization of the Electrical Environment

Characterization of the Electrical Environment

David W. Bodle
Axel J. Ghazi
Moinuddin Syed
Ralph L. Woodside
Series: Heritage
Copyright Date: 1976
Pages: 324
  • Book Info
    Characterization of the Electrical Environment
    Book Description:

    Characterization of the Electrical Environmentis a current reference on the design factors required to ensure reliable performance of communication facilities under field operating conditions.

    eISBN: 978-1-4426-3217-2
    Subjects: Technology, Physics

Table of Contents

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  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-x)
    (pp. xi-xi)
    (pp. xii-xii)
    (pp. 1-10)

    The purpose of this document is to characterize the electrical environmental conditions to which communication facilities are exposed. Consideration is given both to present electrical environmental conditions and to anticipated future conditions. The environmental information which is presented is intended to facilitate the development of system protection requirements. These requirements will be determined after input is analysed from all of the other related factors as shown in Figure 1-1.

    Environmental information presently available adequately defines many of the areas of principal concern-, however, critical voids do exist, particularly in areas of a quantitative nature. These less defined areas are identified...

    (pp. 11-84)

    Lightning is a major environmental hazard to communication systems and will be covered in détail in this section. The material is presented from an engineering standpoint and has been selected on the basis of its usefulness to the protection engineer. Attention is directed exclusively to the effects of lightning on land-based facilities. Those interested in such aspects of the subject as cloud formation, separation of charge, and other atmospheric details should consult other texts.¹

    Lightning is an electrical discharge from cloud to cloud or between cloud and earth. Cloud-to-cloud discharges are by far the more numerous but are of minor...

  7. 3. POWER INTERFERENCE (Under Abnormal Conditions)
    (pp. 85-207)

    The Power network is an important environmental factor affecting communication facilities. Steady state induction at fundamental and harmonic frequencies often causes signal interference (noise) in communication systems.

    Paralleling telephone wires and cables may also be exposed, during power line phase-to-ground faults, to induced voltages of sufficient magnitudes to damage connected apparatus and to be a shock hazard to field personnel.

    In joint-use aerial construction and at Power-Telephone crossovers, there exists the possibility of direct contacts.

    Although good plant practices minimize such occurrences, direct contacts must still be recognized as a significant factor because of the associated high levels of voltages...

    (pp. 208-250)

    Electric shock from power facilities is most frequently the result of direct contact with an energized conductor. However, a direct contact is not necessarily required. For example, electric shock may also result from the following types of exposure:

    1) Leakage currents through insulation.

    2) Flashover along surfaces.

    3) Discharge through air as a result of close proximity to a high voltage conductor.

    In modern society, man is seldom unexposed to the possibility of electric shock. However, due to a concerned safety effort, cases of fatal electric shock have been kept small in comparison to fatalities from many other common hazards....

    (pp. 251-288)

    When a substance conducts electric current, a potential difference occurs. The gradient of such a potential is the rate of increase or decrease of its magnitude with distance from some point of reference.

    The scope of this section is limited to the consideration of potential gradients appearing in the earth in the vicinity of grounding electrodes. Earth potentials may create a shock hazard, damage communication plant and apparatus, and interrupt service because of permanent grounding of carbon block protectors. Major sources of hazardous earth potentials are lightning discharges to earth or to buried conducting objects, and earth return power fault...

  10. 6. CORROSION
    (pp. 289-307)

    In the past century, engineering progress has been largely dependent upon the development of materials that better withstand stresses. As the margins of safety were gradually reduced through improved mathematical techniques, design engineers were able to make corresponding reductions in initial costs. However, increased failures due to metal fatigue also began to become evident, directly confronting engineers with the problem of corrosion.

    Metals have always been subject to corrosion, especially in areas close to salt water. However, rising chemical influences in the environment in the form of industrial pollution, pesticides, agricultural fertilizers, and other agents that cause or accelerate corrosion...

    (pp. 308-321)

    Communication operating companies have recognized for many years that telecommunication apparatus, radio facilities, tower lighting, and electronic equipment powered from external sources can be damaged by over-voltage surges originating on primary and secondary power distribution circuits. Some measurements, but chiefly experience, have established that these over-voltage surges do attain magnitudes many times greater than normal operating voltages. They are inherently associated with the operation of a power distribution network and cannot be prevented by practical means. Sources of over-voltage surges are many and varied; some of the more important of them are listed below.

    a) Lightning strokes to primary and...

    (pp. 322-323)

    Electromagnetic Pulse (EMP) occurs when a nuclear explosion at or near the surface of the earth causes an electromagnetic field to propagate outward from the point of explosion. Depending on its intensity, EMP can temporarily block or permanently damage components of a communication system. Solid state devices and magnetic memories are particularly susceptible. The degree to which communication facilities are exposed to EMP effects depends on such factors as the type and size of the explosive device, its position with respect to earth, and the proximity of communication plant to ‘point zero’.

    EMP protection engineering requires the following kind of...