A phenomenon known as corona discharge causes the sound you hear from above power wires. Simply put, it’s the noise made by air that surrounds the power lines when electricity passes through them. It’s important to note that this is not the same mechanism that creates the electric hum in transformers.
Why Do Power Lines Buzz
The release of energy that follows when the electrical field intensity on the conductor surface is higher than the ‘breakdown strength’ or the field intensity required to start a flow of the electric current of the air around the conductor causes the audible noise released from high-voltage lines.
The condition of the air, that is, humidity, air density, wind, and water in the form of rain, mist, and fog affects the degree or strength of the corona discharge and the resulting auditory noise. The permeability of the air is increased by water, which increases the strength of the discharge.
Corona activity can also be increased by imperfections on the conductor surface, such as nicks or sharp points, as well as airborne pollutants. The importance of these elements is often reduced when the conductor surface ages or withers.
Modern HV Transmission Lines
Modern transmission lines operate at greater voltages, which has exacerbated the noise problem to the point where it has become a source of concern for the power industry.
As a result, these lines are now planned, built, and maintained in such a way that they function below the corona-inception level during dry conditions, resulting in less corona-related noise.
Water droplets, fog, and snow, on the other hand, can cause corona discharges in bad weather.
Buzzing Sound of High Power Lines
Unless precautions have been taken to restrict the range of the electric field, corona discharge normally happens on its own in high-voltage systems. It emits a bluish radiance in the air surrounding electricity lines in addition to a sluggish, buzzing sound.
In truth, this phenomenon is similar to a lightning strike. You could call it a smaller version of a lightning strike, with the exception that the former causes a dazzling flash of light rather than a delicate bluish glow and a thunderous boom instead of a soft buzz.
The sounds produced by transformers or power lines owing to the passage of alternating current at the frequency of mains electricity are sometimes referred to as “mains hum,” “electric hum,” or “power line hum.”
The frequency response of the buzzing sound you hear is usually 50 or 60 Hertz, based on the frequency of the local power line. It also relies on where you are in the world, as different sections of the world employ different current frequencies.
Addition of The Sound of Transformer Buzzing
There are two basic reasons why transformers hum. They are stray magnetic fields and magnetostriction. Magnetic fields lead the transformer’s internal components to vibrate at a frequency of 50 or 60 Hz.
When a ferromagnetic material meets an alternating magnetic field, it experiences magnetostriction, which causes minute expansion and contraction. A ferromagnetic substance expands and contracts minutely when exposed to an alternating magnetic field.
The Presistency of the Sound
A little amount of vibration is produced as the iron core within the transformer coils extends or contracts due to the magnetic action of alternating current flowing through it. This is the source of the transformer’s persistent buzzing sound. Depending on whether they work at 50 or 60 Hz, transformers emit a somewhat different buzzing sound.
How to Reduce the Buzz?
Certain design adjustments can help to reduce the buzzing sounds of a transformer, but they can’t be fully eradicated. It’s worth noting that the humming sound’s intensity is proportional to the applied voltage. This is why some transformers don’t always produce a buzzing sound.
You’ve probably heard a humming sound coming from high-voltage power lines if you’ve worked on or walked under them. The air condition and various factors included often lead to the corona activity responsible for the noise.