The technical progress and its reflection in the construction of the medium voltage metal enclosed switchgear for secondary distribution of electricity

This article presents the results of the research carried out for modernization of the medium voltage metal enclosed switchgear for secondary distribution of electricity. The metal enclosed switchgear upgrading is based on the patent proposal no. A/00230/14.03.2013 for this purpose and aims at increasing the reliability in the supply of electricity. The modernization consists in eliminating the existing deficiencies of secondary distribution metal enclosed switchgear by replacing the air or SF6 switching devices with vacuum switching devices, by merging the separation and interruption functions (of nominal currents, excess currents or fault currents) in the same multipurpose vacuum switching device, supplemented by the use of another vacuum switching device, for the earthing function. In this way it will be possible for the remote controls to be assigned to all the functions of the metal enclosed switchgear [separationinterruption (simultaneously) or earthing] with vacuum switching devices, thus providing a mechanical endurance with at least a size grade greater than the existing ones. Due to the possibility for remote control of all the functions of the metal enclosed switchgear, the maintenance costs for the entire lifespan will be lower, and the duration of network reconfiguration will be significantly reduced as opposed to current duration, ensuring a higher performance of the supply of electricity to the customers. By using silicone and composite insulation for the general bars of the metal enclosed switchgear and the vacuum switching devices of its equipment, with a leakage path to the mass higher than the existing ones, it will be possible for the metal enclosed switchgears, which have their cable outgoing insulated with sealed potheads to operate in severe environmental conditions, and to be tested and certified according to CEI/ST62271-304/2008.