Study of vibration and audible noise generated by shunt capacitor banks at substations serving non-linear loads

At the request of a local utility provider, a study was conducted to determine why capacitor banks located at two substations supplying power to a steel mill are creating audible noise. A method to decrease the amount of audible noise was also requested. The construction of the banks and the possible cause of excitation are discussed. Electrical current and acoustic harmonic measurements taken at each substation are presented. Vibration testing of the banks was conducted to determine the mechanical natural frequencies, and the results are given. Possible solutions to reduce the amount of audible noise from the capacitors conclude the discussion.