Why do power lines produce a buzzing sound?

The main reason why the cable makes buzzing sounds after being energized is the electromagnetic induction and resonance caused by the cable structure and laying method.

1.First of all, the structure of the cable is an important factor that causes the humming sound. For example, a three-phase metal armored cable will generate an alternating induced magnetic field after being energized. This magnetic field will cause eddy currents on the steel belt of the cable. The larger the current, the more obvious the eddy current phenomenon and the louder the sound. This phenomenon will not only cause the cable to heat up, but also reduce the current carrying capacity of the cable. In severe cases, it may even cause a fire. In addition, the use of a three-phase four-wire cable can reduce this humming sound to a certain extent. Because the existence of the neutral line can balance the three-phase current and reduce the occurrence of the induced magnetic field.

2.Secondly, the way the cables are laid will also affect the degree of humming. Cable trays and other metal structures generate magnetism when current passes through them, and this electromagnetic wave will produce a humming sound. If the cables are close to these metal structures or the wiring is improper, the humming will increase. To avoid this, you can adjust the spacing of the cable brackets to reduce the occurrence of resonance. 

Finally, in order to solve the problem of humming after the cable is powered on, you can take the following measures: adjust the spacing of the cable brackets to avoid resonance. Use three-phase four-wire cables to reduce the induced magnetic field, check the radiation pattern of the cables, and ensure that the cables are at an appropriate distance from the metal structure. Regularly check the current carrying capacity and temperature of the cables to prevent overheating and fire.