In less than 100 years, the power and telecommunications industries have become highly technological and competent in servicing the growing electrical power and communication needs of a complex, modern society. This tremendous advancement has not been without problems of mutual compatibility, however.  In the early days of power and telecommunication transmission, fundamental incompatibilities existed between the two systems since both used the earth as a ground return conductor.

As the length of both systems' lines grew and the number of subscribers increased, the inductive interference problems became more severe. Further expansion of both industries was seriously threatened when it became necessary to refer these problems to the courts and commissions for resolution, such as California's General Order 52 issued in 1912.  As a consequence, representatives from both industries joined in cooperative efforts to study and resolve the main causes of incompatibility.  This joint effort, primarily between the Edison Electric Institute and the Bell System, resulted in over fifty engineering reports during the 1920's and 30's.  This cooperation resulted in numerous advances and innovations, with the primary development being paired conductors enclosed in metallic shielded cables for telecommunications transmission. Developments such as drainage reactors, longitudinal chokes, neutralizing transformers and isolation transformers also occurred and were applied to open wire lines to suppress power line interference.

The above practices and procedures were usually adequate in solving most electromagnetic and electrostatic induced voltage and current problems.  However, in the 1960's and 70's certain design features and trends in the environment occurred that presented new and challenging problems in the area of incompatibility.  As a result, the Institute of Electrical and Electronic Engineers (IEEE) formed the Inductive Coordination and Electrical Protection (ICEP) Committee to provide effective execution of the following considerations:

1) Design of systems to minimize inductive interference and susceptibility.

2) Adopt standards and guidelines relating to interference.

3) Establish a continuing dialog between interested parties to provide a medium for exchanging information in the advanced planning stages of new facilities.

In the meantime, some manufacturers have responded to the industry's need for equipment similar to that used in the open wire days, but better designed and more economical for cable applications.  Information on these devices is provided in the later chapters of this manual.