The high-voltage distribution box is noisy

Yes, high-voltage distribution boxes can produce audible noise, typically a humming or buzzing sound caused by electrical discharges and transformer vibrations. High-voltage distribution boxes and substations often emit a humming or buzzing sound due to several electrical phenomena. One primary cause is corona discharge, which occurs when the electric field around a conductor ionizes the surrounding air, creating small electrical discharges that produce a soft buzz or crackle.

This effect is more pronounced in humid, rainy, or foggy conditions because moisture increases air conductivity, intensifying the noise. Another source of noise is transformer hum, caused by magnetostriction, where the iron core of a transformer slightly changes shape as the alternating current passes through it. This vibration produces a steady hum at a frequency double that of the mains electricity—typically 120 Hz in North America—with higher harmonics adding to the sound.

Distribution lines themselves can generate a raspy buzz, often modulated at low harmonics of the power line frequency, due to small arcs forming on insulators or pins. These arcs usually occur twice per cycle near the voltage peaks of the AC waveform, creating a characteristic 120 Hz buzz in a 60 Hz system. Environmental factors such as humidity, wind, rain, and airborne contaminants can amplify these sounds.

Sharp points or nicks on conductors, weathering, and surface irregularities can also increase corona discharge and associated noise. In summary, hearing a steady hum, buzz, or faint crackle from a high-voltage distribution box is generally normal and indicates standard electrical activity. However, unusually loud or irregular noises may warrant inspection to ensure there are no faults or deteriorating components.