Switchgear and Protection - Methods of arc extinction
1 Answer
In electrical systems, an arc is an electric current that passes through the air between two conductive surfaces. Arcs can occur due to various reasons, such as short circuits or faults, and they can be dangerous and damaging. Switchgear and protection systems are designed to manage and control these arcs to ensure the safety and proper operation of electrical systems. There are several methods of arc extinction used in switchgear to quickly and safely extinguish these arcs. Here are some common methods:
High Resistance Method (Series Resistance): This method involves inserting a high resistance in series with the circuit. The resistance limits the current, reducing the energy of the arc. As the energy decreases, the arc voltage drops below the level required to sustain the arc, leading to its extinction. However, this method is not very efficient and is mostly used in low-voltage systems.
Oil Immersion Method: In this method, the switchgear equipment is immersed in oil. When an arc occurs, the oil cools and quenches the arc, thereby extinguishing it. Oil also provides insulation and helps in preventing re-striking of the arc. This method is commonly used in high-voltage and medium-voltage switchgear.
Air Blast Method: In air blast circuit breakers, high-pressure air is blown across the arc path. The high-velocity air cools and removes ionized particles from the arc, leading to its extinction. Air blast circuit breakers are commonly used in outdoor substations.
Magnetic Blowout Method: This method utilizes the principle of the magnetic field. When a fault occurs, a magnetic field is generated around the fault current. This magnetic field interacts with the arc, creating a force that pushes the arc away from the contacts, and thus extinguishing it.
Vacuum Method: Vacuum circuit breakers create a vacuum between the contacts where the arc forms. Without the presence of ionized particles in the medium, there is no medium for the arc to continue. Vacuum circuit breakers are compact, have fast operation times, and are suitable for medium to high voltages.
SF6 Gas Method: SF6 (sulfur hexafluoride) is a highly effective insulating and arc-quenching gas. When an arc occurs, SF6 gas is released into the arcing chamber, creating a high-temperature environment that quickly extinguishes the arc. SF6 circuit breakers are commonly used in high-voltage systems.
Hydrogen Gas Method: Hydrogen gas has high thermal conductivity, allowing it to cool and extinguish arcs rapidly. Hydrogen gas circuit breakers are mostly used in generator protection systems.
Each of these methods has its advantages and disadvantages, and their selection depends on factors like voltage level, application, environmental considerations, and safety requirements. The goal is to ensure a rapid and reliable method of arc extinction to protect the electrical system and those who work with it.
High Resistance Method (Series Resistance): This method involves inserting a high resistance in series with the circuit. The resistance limits the current, reducing the energy of the arc. As the energy decreases, the arc voltage drops below the level required to sustain the arc, leading to its extinction. However, this method is not very efficient and is mostly used in low-voltage systems.
Oil Immersion Method: In this method, the switchgear equipment is immersed in oil. When an arc occurs, the oil cools and quenches the arc, thereby extinguishing it. Oil also provides insulation and helps in preventing re-striking of the arc. This method is commonly used in high-voltage and medium-voltage switchgear.
Air Blast Method: In air blast circuit breakers, high-pressure air is blown across the arc path. The high-velocity air cools and removes ionized particles from the arc, leading to its extinction. Air blast circuit breakers are commonly used in outdoor substations.
Magnetic Blowout Method: This method utilizes the principle of the magnetic field. When a fault occurs, a magnetic field is generated around the fault current. This magnetic field interacts with the arc, creating a force that pushes the arc away from the contacts, and thus extinguishing it.
Vacuum Method: Vacuum circuit breakers create a vacuum between the contacts where the arc forms. Without the presence of ionized particles in the medium, there is no medium for the arc to continue. Vacuum circuit breakers are compact, have fast operation times, and are suitable for medium to high voltages.
SF6 Gas Method: SF6 (sulfur hexafluoride) is a highly effective insulating and arc-quenching gas. When an arc occurs, SF6 gas is released into the arcing chamber, creating a high-temperature environment that quickly extinguishes the arc. SF6 circuit breakers are commonly used in high-voltage systems.
Hydrogen Gas Method: Hydrogen gas has high thermal conductivity, allowing it to cool and extinguish arcs rapidly. Hydrogen gas circuit breakers are mostly used in generator protection systems.
Each of these methods has its advantages and disadvantages, and their selection depends on factors like voltage level, application, environmental considerations, and safety requirements. The goal is to ensure a rapid and reliable method of arc extinction to protect the electrical system and those who work with it.