SF6 gas concentration online monitoring and alarm system assists in electrical safety work

With the continuous development of the power system, SF6 electrical equipment is becoming more and more widely used, especially GIS composite appliances, which are widely used due to their advantages of greatly reducing the footprint and spatial volume of electrical equipment, easy installation, safe and reliable operation, and convenient maintenance.

SF6 is a strongly electronegative gas, and its molecules easily adsorb free electrons to form massive negative ions, weakening the collision ionization process in the gas. Therefore, its electrical insulation strength is very high, about 2.5 times that of air insulation strength in a uniform electric field. SF6 gas exhibits a peak in thermal decomposition at t ≈ 2000K, therefore, when the AC arc current crosses zero, SF6 has a much stronger cooling effect on the arc channel than air, and its arc extinguishing ability is about 100 times that of air. Due to its excellent arc extinguishing and insulation properties, as well as good chemical stability, SF6 gas has been used as an arc extinguishing medium for high-voltage circuit breakers since the late 1950s. SF6, as an arc extinguishing medium, has replaced oil and has largely replaced compressed air in ultra-high voltage and extra high voltage circuit breakers.

Pure SF6 gas is colorless, odorless, non-toxic, and non flammable, with a specific gravity five times that of air. When the distribution equipment room equipped with SF6 equipment, such as GIS, leaks, SF6 gas accumulates to a certain concentration in the lower space. If workers enter the room, serious personal safety accidents such as cerebral hypoxia and even rapid suffocation may occur. In addition, under the influence of arc, partial discharge, high temperature and other factors, SF6 gas will produce highly toxic decomposition products such as SF4, S2F2, SOF2, and some decomposition products will produce corrosive electrolytes when they come into contact with water. These not only pose a serious threat to personal safety, but also endanger the normal operation of electrical equipment. The "Electricity Safety Work Regulations" (for power plants and substations) specifically stipulate that the distribution equipment room equipped with SF6 equipment must ensure that the SF6 concentration is less than 1000ppm. In addition to installing strong ventilation devices, monitoring devices such as oxygen meters and SF6 gas concentration detection alarms that can sound an alarm must also be installed.

The SF6 gas concentration online monitoring and alarm system is an intelligent online monitoring system designed and developed to provide personal health and safety protection for workers in distribution equipment rooms equipped with SF6 equipment, based on the current emphasis on safety production in the power system.