Filtering dispersed harmonic sources on distribution

Telephone company customers reported audible noise in their telephone service. Through measurements, analysis, and simulations, 540 Hz noise was found to be coupling from power distribution to telephone cables in a shared underground right-of-way. The source of the noise was small single-phase electronic loads dispersed throughout the power distribution system in the area. A passive shunt filter was designed using an existing capacitor bank. Installation of this filter reduced the noise to acceptable levels.