Power circuit interference with telegraphs and telephones

Abstract
The subject is of interest to the designer, the power engineer and the communication engineer, and the time appears to be ripe for a review of the situation. The paper is a general survey of the position, describing the features in the modern generation and distribution of electrical energy which are responsible for interference with telegraph and telephone circuits, emphasizing the importance of harmonics in this connection, and indicating some known remedies which may be applied to power plant at its source when trouble is experienced.The improvements to be expected by the transposition of wires forming overhead power and telephone circuits are described and also the practical applications. The separating distance and length where power lines and communication circuits run parallel is next considered with reference to inductive effects from (a) the balanced voltages and currents, (b) the residual voltages and currents, and (c) the abnormal occurrences due to short-circuits, etc.The balance of telephone circuits is then dealt with. Telephone circuits in this country are designed to be free from disturbance from telegraph circuits and telephone circuits carried on the same routes. It is considered that a balance which will ensure this is the most that can be expected in such a system as a public telephone service, and if disturbance from power circuits is experienced with such balanced conditions on the telephone circuits, then the injurious affection is excessive. Remedies which may be applied to telephone and telegraph circuits are described.A review of the problem and general experience in this country is then given under the headings of tramways, railways (direct-current and single-phase), and electric light and power systems, with an account of certain remedies and a discussion of the lay-out of power systems as influencing interference. In the author's opinion the solution of the inductive problem is mainly one for the designer; the power engineer, the telephone engineer and the protective-gear engineer are also concerned in that order.In an appendix Prof. E. W. Marchant describes a method of removing ripples from mercury-arc rectifiers.

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