The development has already received a gold medal at the prestigious International Innovation Exhibition "HI-TECH" and is ready to be put into production.
It is well known that the electricity tariff is made up of a great many components. Among them is the cost of natural gas production or other primary energy resource, its transportation costs, the cost of maintenance and construction of new cogeneration plants, power substations, distribution networks and other equipment. Increasing production efficiency at all of the above stages can lead to staggering economic results. Experts say that due to energy saving the domestic GDP can grow by at least 2 times. And in a relatively short time.
One of the components necessary to implement such a strategy is to increase the time between repairs of gas transformers, which slowly but surely are replacing their oil-fired counterparts. The unique insulating properties of gas-insulated gas (SF₆, sulfur fluoride), which allow using it in high-voltage switchgear, were discovered by Soviet scientists. Their innovation made it possible to reduce the weight and size of the products required for the reliable operation of power plants and substations. Plus, it increased their safety by eliminating the possibility of fires and explosions.
Gradually this technology began to be used as a dielectric not only in the USSR, but all over the world, and is now considered the most progressive. However, nothing is perfect.
"The transformer case is made of aluminum, it is a sealed structure, where gas is pumped in. The problem is that in the process of welding it forms a natural oxide film, the melting temperature of which is 4 times higher than the aluminum itself - about 2 thousand degrees. Because of this, it does not melt, but stays in the edge of the weld, automatically turning it into a weak link of the entire device. This is where depressurization most often occurs due to internal pressure, leading to additional costs for repair or replacement of equipment, as well as to atmospheric emissions of dangerous greenhouse gas, which is sulfur fluoride, " explained Irina Filipenko, a fourth-year graduate student at St. Petersburg Mining University.
In co-authorship with her colleagues from the Department of Mechanical Engineering, she developed a method that allows to improve the quality of the edges of products made of aluminum materials through magnetic-abrasive processing. The innovation has already passed all necessary tests, received several patents for the invention and positive feedback from customers producing electrical equipment.
"At the moment, the " old-fashioned" methods are often used in edge finishing. Often workers grind the seams by hand with a sandpaper. Of course, this does not give the effect that the business expects. In addition, the higher the temperature is, and with friction, as you know, it increases significantly, the more voluminous the oxide film becomes. Magnetic abrasive treatment before welding is carried out at 30-40 degrees, that is, the method is cold, which gives additional advantages, "- said Irina Filipenko.
The efficiency indicators of the St. Petersburg scientists' development speak for themselves. The strength of welded joints, due to its application in practice is 1.6 times higher, and the fracture liability, that is the time required for the pressure to crack the equipment and cause its depressurization is 4.5 times higher.
Of course, the area of application of the innovation is not limited to transformers. At the moment, the Mining University is developing a machine that will make it possible to study the impact of the technique on aluminum products of all sizes, which in the future will allow using it to improve the quality of performance surfaces in various sectors of the national economy, up to aircraft and rocket production.
There is one more component of this project, which is no less important than the economic one. As is known, the introduction of gas-insulated transformers at the end of the 20th century not only minimized the number of fires and explosions in substations, but also significantly reduced the cases of oil spills, leading to soil contamination. At the same time, SF₆ leaks have a detrimental effect on the Earth's atmosphere, which means that in this case, solving one environmental problem automatically led to the emergence of a new one, which also requires an urgent solution.
"Initially, no one thought about the fact that sulfur fluoride decomposes during operation and inevitably enters the air. But, most surprisingly, few people even think about its negative impact on the environment today. Eco-activists, for example, have never held a rally against the use of sulfur hexafluoride as an insulating material in wind turbines. And in vain, because its emissions from the EU and Great Britain are equivalent to one and a half million more cars with internal combustion engines on the roads. Emissions are on the rise due, in part, to the development of green energy. At the same time, each molecule of sulfur hexafluoride remains in the Earth's atmosphere for a very long time, heating the planet for thousands of years. I am glad that the implementation of the results of our scientific research into production will make it possible to reduce the acuteness of this problem," Vyacheslav Maksarov, Dean of the Mechanical Engineering Department of the Mining University, summarized the head of the project.
It should be noted that in May the St. Petersburg Mining University was awarded three gold and three silver medals of the XXVIII International Exhibition of Innovations "HI-TECH", which was held in St. Petersburg. One of its winners was the development "Technological improvement of the quality of the edges of products made of aluminum materials before welding by means of magnetic-abrasive processing" (authors: V. Maksarov, A. Keksin, I. Filipenko, R. Sheglova).