Sf6 Circuit Breaker Operating Mechanism Composition

sf6 circuit breaker operating mechanism uses compressed SF6 gas as arc extinguishing and insulating medium, and uses the energy of the arc to generate SF6 compressed gas to extinguish the arc. It is used to cut off the rated current and fault current, convert lines, and realize the control and protection of high-voltage transmission and transformation lines and electrical equipment, and is equipped with an operating mechanism for opening, closing and automatic reclosing. sf6 circuit breaker spring mechanism consists of three stages, each of which is driven by a spring operating mechanism. The circuit breaker mainly consists of three parts: the bracket, the operating mechanism, and the pole of the circuit breaker (including the arc extinguishing chamber, the support, and the transmission box). 1. Characteristics of SF6 gas SF6 gas is a colorless, odorless, non-toxic, non-flammable and transparent gas. It is an inert gas at room temperature and generally does not react with other materials. Its electrical strength is 2.5 times that of nitrogen at the same pressure, its breakdown voltage is 2.5 times that of air, and its arc extinguishing ability is 100 times that of air. It is a new generation of ultra-high voltage insulating medium material that is superior to air and oil. 2. SF6 gas online monitoring device - density relay
The density of the gas on the SF6 electrical equipment is expressed by the pressure of the SF6 gas after temperature compensation, that is, the pressure value at 20℃. The density relay is mainly composed of pressure sensing parts, temperature compensation parts, transmission elements, contact devices, junction boxes and shells. When the SF6 pressure drops to the alarm pressure value, the relay outputs a pair of contacts (alarm signal); when it drops to the locking action pressure value, the relay outputs another contact (locking signal) to lock the corresponding control system of the equipment. In order to protect the safety of the equipment and the power grid, the equipment is prohibited from opening and closing operations.
SF6 gas absolute pressure and alarm parameters:
Our factory's density relay is an absolute pressure type density relay (i.e., a density relay with absolute vacuum as the reference pressure). During operation, the rated pressure of SF6 is 0.75Mpa, and the circuit breaker is in normal state; when the pressure value is less than 0.64 Mpa, the circuit breaker will issue a pressure reduction alarm, and the circuit breaker can be opened and closed normally; when it is less than 0.61 Mpa, the opening and closing circuit will lock the circuit breaker and prohibit operation. It must be isolated and shut down for leakage detection and gas replenishment.
2.1 Density relay verification
Due to the drift of the action value or poor contact of the contacts caused by long-term operation, the density relay needs to be calibrated regularly to ensure the accuracy of its display and action. During the verification process, pay attention to protection to prevent SF6 gas poisoning and ensure indoor ventilation.
When disassembling the density relay, avoid loosening other parts and breaking the pipeline. To prevent leakage, a new gasket must be replaced each time the equipment is reinstalled. After the work is completed, a leak test is required.
2.2 SF6 gas micro-water measurement
During the SF6 equipment, a trace amount of water will enter the switch along with the SF6 when it is inflated. During the operation, high-pressure electricity will cause chemical reactions, and water will be generated. The amount of water content will directly affect the life and safety of the equipment, so the micro-water content in SF6 should be checked regularly.
SF6 gas can be tested 24 hours after it is filled into the electrical equipment. The allowable water content in the arc extinguishing chamber of the circuit breaker (volume ratio at 20℃) requires: no more than 150µL/L at the time of handover and after overhaul, and no more than 300µL/L during operation. The annual leakage rate of SF6 gas circuit breakers is no more than 0.5% (the standard of the group company is 1%).