Load switch 3p 400A VNA 10/400 L z I2 UHL2 KEAZ 145590

VNA series load switch (auto-gas load switch) is a switching device designed for operation in AC three-phase electrical networks with voltage of 10 (6) kV. It occupies an intermediate position between a disconnector and a power circuit breaker, as it is capable of disconnecting load currents but is not intended for breaking short-circuit currents. Purpose and scope of application The main purpose of VNA switches is the switching on and off of electrical circuit sections under load with voltage up to 10 kV, frequency 50-60 Hz, with rated current in accordance with the designation structure. Structurally, the VNA switch is installed in the following types of switchgear: Complete switchgear (KSU) Stationary single-sided maintenance chambers (KSO) Complete transformer substations (KTP) indoor installation Important feature: these devices provide a visible circuit break in the disconnected position and safe grounding of the disconnected section for work execution. Principle of operation and design features Auto-gas arc extinction The VNA switch belongs to switching devices with an auto-gas arc extinguishing device. The principle of operation is based on extinguishing the electric arc that arises during contact opening by the flow of gases released from the walls of the arc-extinguishing chamber under the influence of the high temperature of the arc. In the arc-extinguishing chamber, special inserts made of polymethyl methacrylate (organic glass) are installed. During arc combustion, the material of the inserts intensively decomposes with the release of a large amount of gases, the pressure in the chamber increases, the arc is cooled and extinguished. Construction The main elements of the VNA switch construction: Frame - load-bearing metal structure Insulators - support and tension Main contacts (stationary and moving) - ensure the passage of load current Arc-extinguishing contacts - open after the main ones, taking the arc upon themselves Arc-extinguishing chambers - one for each pole Control shaft - transmits movement from the drive to the contacts Spring mechanism - ensures the speed of switching on and off operations Kinematics features When switching on, the main contacts first close, then the arc-extinguishing ones. When switching off, the sequence is reversed: first the main contacts open (without an arc, as the circuit is still closed through the arc-extinguishing ones), then the arc-extinguishing contacts, on which the arc arises and is extinguished in the chamber.