Dielectric gas is used in industrial applications as an electrical insulator, with air being the preferred option due to its ubiquity. The type of gas used depends on voltage level, thermal properties, and toxicity. Sulfur hexafluoride is commonly used in power plants but has significant environmental and health risks. Attempts are being made to combine it with safer gases.
Dielectric gas is a form of gas used in industrial applications as an electrical insulator. Common types of gases used include air, nitrogen, and sulfur hexafluoride. Various types of electrical components such as transformers and switches require the presence of a dielectric gas to prevent damage to a circuit in the event of an electrical discharge. In routine applications, air is often the preferred dielectric gas because it does not require a sealed, pressurized system and is ubiquitous.
The type of dielectric gas used depends largely on the voltage level of the device and circuit, as well as the fundamental properties of the gas, such as its inert chemical nature, and thermal properties, such as boiling point and ability to transfer heat . The level of toxicity and flammability of the dielectric gas under certain conditions must also be considered. An electrical short can cause a component such as a high voltage transformer to physically degrade to the point that the gas is released into the surrounding environment. For this reason, gaseous air and nitrogen are often used as they are largely inert and non-reactive.
Sulfur hexafluoride is used as a dielectric gas in high voltage switchgear such as industrial circuit breakers connecting generators to step-up voltage transformers. It is also used in areas of high voltage electrical power systems that require gas insulators, such as transmission lines, transformers and substations. Approximately 80% of all produced sulfur hexafluoride is commonly used in power plants and substations worldwide due to its superior insulating qualities and ability to suppress the transmission of radio and sound waves from electrical equipment. It also has the highest breakdown voltage level for any insulating gas, which is the voltage level required for a dielectric gas to start conducting current and fail to act as an insulator.
However, the disadvantages of using sulfur hexafluoride as a dielectric gas are significant and, for this reason, attempts are being made to combine it with safer gases, such as nitrogen, carbon dioxide or perfluorocarbon compounds. Sulfur hexafluoride is estimated to be 22,800 to 23,900 times more of a contributing factor to global warming when released into the atmosphere than an equivalent amount of carbon dioxide. It also lingers in the atmosphere as a stable greenhouse gas much longer than other greenhouse gases, lasting anywhere from 800 to 3,200 years before degrading. The compound also poses serious health risks upon human exposure, such as causing respiratory problems, and often combines with other compounds when released into the air which can lead to fluoride contamination of the body and a variety of ailments.
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