Status of joint development and research on low-frequency induction

This paper deals with coordination of power and telephone systems with respect to induction at power system frequency, usually 60 cycles. The principal problem in this field relates to effects produced under abnormal conditions on power systems. The factors controlling the magnitude, frequency of occurrence, duration, and effects, of induced voltages, are discussed. Different types of protective measures, some applicable to power systems and others to communication systems, are outlined, including their respective advantages, limitations, and fields of application. The reaction on this problem of lightning and of situations involving liability of contacts between telephone wires and power wires is touched upon. The whole matter is treated from the standpoint of the comprehensive joint investigation of the interference problem which is being conducted by the N.E.L.A. and the Bell System.