Trystan Casey
Electrical corona, also known as corona discharge, is an electrical phenomenon that occurs when there is a high-voltage conductor that ionizes the surrounding air, resulting in a visible bluish, violet, or coloured glow and an audible hissing sound. This phenomenon can lead to power losses and has detrimental effects on electrical insulation systems. Given the potential for damage, it is important to understand the appearance and characteristics of electrical corona to implement effective mitigation strategies, such as corona rings and improved insulation.
| Characteristics | Values |
|---|---|
| Visual appearance | A bluish, violet, or colored glow |
| Sound | Audible hissing noise |
| Odor | Ozone, an unstable form of oxygen, is produced during this process |
| Impact on materials | Ozone can destroy rubber. Nitric acid can be created if there is sufficient moisture. These can degrade and embrittle nearby materials, including electrical insulators. |
| Impact on power systems | Power loss, reduced efficiency of transmission lines, and interference with neighboring communication circuits |
| Impact on aircraft electrical systems | Corona can happen around terminations within an insulated system (such as wires and cables) that are exposed to air or can happen within the insulation itself. |
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What You'll Learn
Corona discharge is an electrical phenomenon
The formation of corona discharge is influenced by several factors, including atmospheric conditions, conductor condition, and spacing between conductors. It commonly occurs at locations with sharp points, edges, or corners, where the electric field strength is higher. The critical voltage for corona discharge is typically around 30 kV, but it can vary depending on atmospheric pressure and temperature.
The impact of corona discharge includes power losses in the form of light, heat, sound, and
Corona discharge can also lead to the generation of corrosive gases such as ozone, nitric oxide, and nitric acid if water vapour is present. These gases can degrade and damage nearby materials, including electrical insulation. In addition, corona can cause degradation to insulation systems, leading to equipment failure over time.
To mitigate the effects of corona discharge, various strategies can be employed, including improved insulation, the use of corona rings, and designing high-voltage electrodes with smooth, rounded shapes. These measures help reduce the formation of corona discharge and minimize its impact on power transmission equipment and electrical systems.
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It causes degradation to insulation systems
Electrical corona is a luminous discharge that occurs when there is an excessive localized electric field gradient on an object, causing the ionization and possible electrical breakdown of the air adjacent to it. It is often seen as a bluish or violet glow in the air next to pointed metal conductors carrying high voltages.
Corona discharge can cause degradation to insulation systems. It can occur within the insulation of wires and cables exposed to air, leading to equipment failure. The high voltage applied to a transmission line creates an electric field around the conductors, and the magnitude of the current flowing through the line is proportional to the severity of the corona discharge. As the current increases, the corona discharge becomes more intense, leading to power loss in the form of light, heat, sound, and ozone production.
Ozone, an unstable form of oxygen generated during this process, is detrimental to electrical insulators and can cause rubber to deteriorate. The gases produced by corona discharges, such as ozone, nitric oxide, and nitrogen dioxide, can also lead to the formation of nitric acid if water vapour is present. These gases are corrosive and can degrade and embrittle nearby materials, causing lasting damage to insulation systems.
To mitigate the impact of corona on insulation systems, several strategies can be employed. These include improved insulation techniques, the use of corona rings, and the implementation of smooth, rounded shapes for high-voltage electrodes. By understanding the processes of insulation degradation, engineers can develop methods to assess and counter the effects of corona discharge on insulation systems.
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It can be suppressed by improved insulation
A corona discharge is an electrical phenomenon that occurs when a high-voltage conductor ionizes the air surrounding it. This is often visible as a bluish or violet glow and audible as a hissing sound. The phenomenon is characterized by a luminous glow and a humming or hissing noise that increases in intensity with increasing output voltage.
Corona discharges can cause damage to electrical systems by progressively degrading insulation systems. This can lead to equipment failure and economic losses. The degradation of insulation systems can be indicative of microscopic air bubbles trapped within the insulation. The formation of corona discharges is more likely at highly curved regions on electrodes, such as sharp corners, projecting points, edges of metal surfaces, or small-diameter wires.
To suppress and mitigate the effects of corona discharges, improved insulation can be used. This involves employing insulation materials that can withstand higher voltages and designing insulation systems that minimize the formation of corona discharges. Additionally, the use of corona rings, which are toroidal devices, can help spread the electric field over larger areas and decrease the field gradient below the corona threshold.
Another strategy to suppress corona formation is to design terminals on high-voltage equipment with smooth, large-diameter, rounded shapes like balls or toruses. This reduces the sharpness of the conductor surface and distributes the charge over a wider area, thereby reducing the likelihood of corona discharge. Increasing the diameter of the conductor or bundling conductors can also help reduce the electric field around the conductor and mitigate the corona effect.
By implementing these improved insulation techniques and design modifications, the impact of corona discharges on electrical systems can be significantly reduced, preventing equipment failure and minimizing economic losses.
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It can be identified by a bluish/violet glow and hissing sound
Electrical corona discharge is a phenomenon that occurs when a high-voltage conductor ionizes the surrounding air, resulting in a visible bluish/violet glow and an audible hissing sound. This usually happens at sharp points, edges, and corners of metal conductors with high voltages. The phenomenon gets its name from the characteristic corona, or halo, of coloured light that it produces.
The corona discharge process involves the creation of a region of plasma around the conductor. This occurs when the electric field surrounding the conductor is strong enough to ionize the insulating fluid, usually air. The resulting plasma has a lower dielectric strength than the original fluid, allowing charge to leak off the conductor into the air. This leakage can cause a subtle hissing sound, which increases in intensity with higher voltages.
The corona effect is influenced by various factors, including the atmospheric conditions, conductor condition, and spacing between conductors. It is more likely to occur at high altitudes and during stormy weather, when there is an increased number of ions in the air. The effect can be mitigated through the use of corona rings, which effectively ''round out'' the conductors, reducing sharp points that are more susceptible to corona discharge.
While the corona effect can be utilized in processes such as air filtration and photocopiers, it is often an unwanted side effect in high-voltage applications. The current leakage caused by corona discharge can lead to energy loss and reduced efficiency in power transmission systems. Additionally, the corrosive gases produced, such as ozone and nitric oxide, can degrade and embrittle nearby materials, causing damage to equipment over time.
To summarize, electrical corona damage can be identified by a bluish/violet glow and hissing sound. This phenomenon is caused by the ionization of air surrounding high-voltage conductors, leading to current leakage and potential equipment degradation over time. Strategies such as improved insulation, corona rings, and rounded conductor designs can be employed to minimize the occurrence and impact of the corona effect.
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It wastes energy and damages equipment
Electrical corona discharge is an electrical phenomenon that occurs when a high-voltage conductor ionizes the surrounding air, resulting in a visible bluish, violet, or coloured glow and an audible hissing sound. This phenomenon leads to power losses in the form of light, heat, sound, and
The energy dissipated due to the corona effect is known as corona loss. Power loss due to corona is undesirable and uneconomical, reducing the efficiency of transmission lines. The power loss, or corona loss, is defined by the rate at which energy is drawn from the high-voltage power source by the corona. This loss is caused by the movement of positive and negative ions in the electric field. The energy supplied by the high-voltage power source is used to sustain the corona discharges, with most of the energy being converted to thermal energy, heating the air around the conductors.
The magnitude of the current flowing through the transmission line directly impacts the severity of the corona discharge. Higher current levels generate a stronger electric field, leading to increased ionization and a higher likelihood of corona discharge. As the current increases, the corona discharge becomes more intense, resulting in greater power loss. Therefore, managing the current in high-voltage systems is crucial for controlling and mitigating corona discharge.
Additionally, the corona effect can cause degradation and damage to insulation systems. Long-term exposure to high voltage can impact system components and interconnection systems. The gases produced by corona discharges, such as ozone, nitric oxide, and nitric acid, are corrosive and can degrade and embrittle nearby materials, including electrical insulators. This corrosion can lead to equipment failure and impact the durability and functionality of electrical equipment.
To mitigate these issues, various strategies can be employed, such as improved insulation, the use of corona rings, and designing high-voltage electrodes with smooth, rounded shapes to reduce the occurrence of corona discharges and their detrimental effects on energy efficiency and equipment damage.
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Frequently asked questions
Electrical corona damage can manifest as physical degradation to insulation systems. This can lead to equipment failure.
Electrical corona, also known as corona discharge, is an electrical phenomenon where a high-voltage conductor ionizes the surrounding air, resulting in a visible violet or bluish glow and an audible hissing sound.
Electrical corona is caused by the ionization of air surrounding high-voltage transmission lines or conductors. This occurs when the electric field intensity exceeds a certain threshold, typically around 30 kV/cm at normal pressure and temperature.
