Telephone interference caused by harmonics in distribution systems: Analysis and simulations

The subject of this paper is telephone interference caused by harmonics in distribution systems. The first part of the paper presents a theoretical analysis of the phenomenon with a detailed discussion of the role of ground currents and harmonic sequence order. Applicable standards, acceptable interference levels and mitigating solutions are also summarized. The second part of the paper describes modeling and simulations of a typical distribution system. Simulation results show the importance of controlling harmonics on the feeder to limit telephone interference concerns.