This article discusses topics such as Corona Effect, Skin Effect, Proximity Effect, Ferranti Effect, Critical Disruptive Voltage, Visual Critical Voltage, and more.
Table of Contents
Corona Effect
Corona Effect: When two conductors are spaced at a distance greater than their diameter, and an AC voltage is gradually applied, a special stage is reached.
At this stage, the air surrounding the conductors becomes ionized due to electrostatic stress, causing the air insulation to break down. A faint purple glow appears, and ozone gas is produced, which is known as the Corona Effect.
Effect of Corona
1. A purple glow is observed around the conductor.
2. Ozone gas is produced.
3. Power loss occurs.
4. Harmonic currents are generated.
Advantage of Corona:
1. It limits the transient effects caused by surge voltage, acting as a safety valve for switchgear.
2. The electrostatic stress between the conductors is reduced due to the air around the conductor acting as a conductor, effectively increasing the virtual diameter of the conductor.
Disadvantage of Corona:
1. Power loss occurs.
2. Efficiency decreases.
3. Ozone gas is produced.
4. Conductors are corroded due to chemical reactions.
5. It causes interference with nearby communication lines.
6. Flashover voltage is created between the insulator and the conductor.
7. A large amount of harmonics is generated.
Critical Disruptive Voltage
Critical Disruptive Voltage: The minimum phase-to-neutral voltage at which corona occurs is called the Critical Disruptive Voltage.
Visual Critical Voltage
Visual Critical Voltage: The minimum phase-to-neutral voltage at which the corona glow becomes visible around the conductor is called the Visual Critical Voltage.
Skin Effect
Skin Effect
When AC electricity flows through a conductor, it tends to flow along the surface of the conductor rather than penetrating it. This phenomenon is known as the Skin Effect. Due to the Skin Effect, the resistance of the line increases, resulting in increased line losses.
Influence of Skin Effect in Transmission Line:
Due to the Skin Effect, the resistance of the line increases, leading to higher losses when current flows through the line. The Skin Effect also increases as the diameter of the line increases. In addition, the size of the conductor affects the Skin Effect in the transmission line.
Ways to Reduce the Skin Effect:
1. By reducing the diameter of the conductor.
2. By using non-magnetic materials.
3. By using hollow cylindrical conductors.
4. By using barrel-shaped conductors.
5. By using stranded conductors.
6. By using aluminum conductors.
Proximity Effect
When a current-carrying conductor is placed near another current-carrying conductor, the flux from one conductor induces a current in the neighboring conductor. This flux is more intense on the closer side of both conductors than on the farther side, leading to unequal current distribution and increased resistance similar to the Skin Effect. This phenomenon is known as the Proximity Effect.
(Note: During the Proximity Effect, if the current in both conductors flows in opposite directions, the current density increases towards the adjacent portions of the conductors. Conversely, if the current flows in the same direction, the current density increases towards the distant portions of the conductors.)
Influence of Proximity Effect:
Due to the Proximity Effect, uneven current distribution occurs in the conductor, leading to increased resistance and reduced self-reactance.
Ways to Reduce the Proximity Effect:
1. By maintaining a low frequency range.
2. By increasing the spacing between conductors.
3. By using stranded conductors.
Ferranti Effect:
In medium and long transmission lines, when there is no load or very little load connected, a leading charging current flows, resulting in a higher voltage at the receiving end compared to the sending end. This phenomenon is known as the Ferranti Effect.
