Understanding the Corona Effect and Plasma in High-Voltage Systems

by | Sep 7, 2023 | Theory

When discussing high-voltage power systems, two terms that frequently come up are the “corona effect” and “plasma.” While they might sound complex, with a little unpacking, these phenomena can be understood more intuitively.

1. The Basics: What is an Ion?

Before we delve into plasma and the corona effect, let’s start with a fundamental building block: the ion. At its core, an ion is just an atom or molecule that has gained or lost one or more electrons. Atoms are made up of protons, neutrons, and electrons. Typically, atoms have an equal number of protons (positively charged) and electrons (negatively charged), making them electrically neutral.

However, under certain conditions, atoms can lose or gain electrons. When an atom loses an electron, it has more protons than electrons, making it positively charged. On the other hand, if it gains an electron, it becomes negatively charged. Such charged atoms or molecules are called ions.

2. Plasma: The Fourth State of Matter

Plasma is often termed the fourth state of matter, the other three being solid, liquid, and gas. When a gas is provided with enough energy, either through heat or another energy source, the atoms in the gas can become ionized, creating a mix of free-floating electrons and ions. This state, where the gas becomes electrically conductive and full of these charged particles, is called plasma.

While plasma sounds exotic, it’s more common than one might think. Lightning and neon signs are examples of naturally occurring and man-made plasmas, respectively. In both cases, an electrical discharge or strong electric field ionizes the gas, making it glow and conduct electricity.

3. The Corona Effect: Plasma in Action on Power Lines

The corona effect is a phenomenon that occurs in high-voltage power systems. In simple terms, it’s the ionization of air surrounding a conductor due to the strong electric field emanating from the conductor.

Here’s what happens: When the voltage is very high, the electric field around the conductor becomes strong enough to ionize the nearby air, turning it into plasma. As the air gets ionized, tiny pockets or regions of plasma form around the conductor. These pockets of plasma are areas where the air has turned into a mix of ions and free electrons.

However, unlike a full-blown electrical arc or discharge, the corona effect is more localized. The ionized pockets don’t create a continuous path for a lot of electricity to flow to the ground. Instead, they cause tiny amounts of current to “leak” from the conductor into the surrounding air. This “leakage” of electricity is what leads to the characteristic buzzing or hissing sound often heard around high-voltage lines.

One key thing to note about the corona effect is its transient nature. The ions and free electrons created during the process quickly recombine to form neutral atoms once again. This recombination releases energy, which can manifest as a faint, often bluish glow, and the aforementioned buzzing sound.

4. The Implications and Importance of Understanding the Corona Effect

While the corona effect might seem like just a curious phenomenon, it has practical implications. The small amount of current that “leaks” due to the corona effect represents a loss in the power transmission system. Additionally, the corona effect can lead to the production of ozone, a compound that can corrode conductors over time.

Understanding the corona effect and plasma is crucial for engineers and professionals working in the power industry. By minimizing the corona effect, power transmission efficiency can be improved, and the lifespan of the infrastructure can be extended.


The world of high-voltage power systems is filled with intriguing phenomena, with the corona effect and plasma being two of the most captivating. By breaking down these concepts into their basic elements and understanding the role of ions, we can better appreciate the complexities and wonders of the electrical world around us.

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