What is harmonics in electrical power system?

Harmonics are signs that tell the power system to indicate that there is something wrong. Detecting harmonics can be a useful method of determining the health of your power source as well as its equipments that are used to aid in the process.

As you are aware of the significance of Harmonics Let me tell you what they are(I prefer to explain the subject in simple terms instead of using the jargons)

We are aware that the whole power system is operating at the same frequency, 50 Hz in normal well-balanced conditions. Thus every phase is balanced i.e the phase angle, voltage and current are both balanced. But when the system is not balanced i.e when a fault is discovered within the system, or an abnormality is observed, Harmonics are produced within the system.

What is Harmonics? ?

When the system is not balanced due to an abnormality, the current, the voltage and the angle will cease to be in balance and when the system is not balanced, there is Harmonics.When the system is in balance, it represent current and volatge as a pure sine waves, but when it is not balanced, the oscillations of the current and the volatge don’t have the sine quality anymore and are distorted.Now when you understand the fundamentals of the fourier series, you are aware that every waves can be represented by a combination of cosine and sine. Therefore, if the current and the volatge are not sine-soidal, they can be assumed to represent a combination of various sine and cosine waves with different frequencies.These additional frequencies that are multiples that of the basic frequency, are more than HARMONICS.

Ideally, there should be no harmonics in the system , however in reality, it’s not possible because there are always tiny errors and leakages in our measurement instruments(CT,PT etc.) that are unavoidable.Thus some harmonics will always be present and is acceptable.

Let’s look at some examples of applications where HARMONICS detection is used to identify problems.

Earth fault in a transmission line, The breakers for the residual circuit that you have in your home also operates on the same principle , but it doesn’t really analyze harmonics, it simply assures the entire system remains in balance.

When you see harmonics in your system , be careful.


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