Electromagnetic Compatibility in Underground Mining

Preface. 1. Introduction. 2. General Principles, Concepts and Terms. The technological environment - environmental protection. Hazards and interferences induced by the use of electric mining equipment. The electromagnetic field. Electromagnetic interferences - electromagnetic compatibility. The causes, nature and propagation of industrial electromagnetic interferences. General principles of electromagnetic interference measurement. 3. Electromagnetic Interactions due to Alternating Current Power Networks. Types and range of interaction. Theoretical principles of calculating the electromotive force of electromagnetic induction. Principles of calculating the included voltages in the auxiliary cores of mining power cables. Values of voltages induced in the pilot (auxiliary) cores of power cables and flexible mining cables. The influence of screens used in power cables and flexible mining cables. The influence of the operation of thyristor convertors on interference in high-voltage power networks. Examples of the results of measurements of electromagnetic interference in the underground low-voltage networks and their immediate vicinity. 4. Sources and Propagation of Electromagnetic Interference in Electric Traction Networks. Preliminary Remarks. Rectifier stations as sources of electromagnetic interference. Electric locomotives as a source of interference. Transmission of interference by contact lines. The storage-battery locomotive as a source of radio noise. The electric field of a contact wire in a heading. Examples of the electric interaction of a contact line. The mutual impedance of earth return circuits. The influence of rails on the mutual impedance of earth return circuits in headings. The magnetic interaction between a traction (contact) line and the earth return circuit. The magnetic interaction between a contact line and a symmetrical line. 5. Electromagnetic Interference in Mine Communications Networks. Communication and dispatching systems in underground mines. Telephone communication. Radio-telephone communication. Wire teletransmission lines - types of cables used and principal parameters. Circuit resistance and its asymmetry, and cable circuit insulation resistance. Circuit resistance. Circuit insulation resistance. Attenuation and capacity asymmetry of a circuit. Effective attenuation of circuits. Cross-talk attenuation. Asymmetry of circuit capacity. Psophometric voltages and their measurement in underground telephone networks and some requirements. Internal interference in telephone communication - cross-talk in call signals. The influence of dispatching alarm and warning sytems on the level of the interference voltage in telecommunication lines. The influence of an electric mine traction system on the level of interference in telephone lines. Interference produced by operation of radiotelephones. The influence of electric traction systems on the level of the interference voltage in radio-telephone loop antennas. The influence of interference on the operation of radiotelephone receivers. Methane monitoring systems. Some requirements and general principles of the protection of telecommunication lines against electromagnetic interference. Basic requirements for reducing the interference produced in power lines. The symmetry of transmission lines. Requirements concerning the design of telecommunication lines. References. Subject Index.