Induction from street lighting circuits: Effects on telephone circuits

This paper discusses series street lighting circuits from the point of view of their relations to nearby telephone circuits. These lighting circuits often hare a much greater inductive influence in proportion to the amount of power transmitted than have most other types of power distribution or transmission circuits. This is due to the relatively large distortion in wave shape of voltage and current on certain types of these lighting circuits, and to the unbalanced voltages to ground which occur with series layouts. Three general types of lighting circuits are discussed. These are a-c. arc circuits, d-c. arc circuits supplied by mercury arc rectifiers, and alternating-current incandescent circuits. Of these, the incandescent type of circuit, in which the lamps are equipped with individual series transformers or auto-transformers, is the most important in this respect. Measures for reducing interference from these circuits are discussed. It is hoped that the information given in the paper will be useful to power and telephone engineers in their cooperative efforts to solve these difficulties.