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When the SF6 density meter is not installed, if the ambient temperature is20℃, the pointer deviates towards0MP. However, if the ambient temperature is not20℃, due to the compensation of the two steel strips based on the difference between the ambient temperature and20℃, when the ambient temperature is higher than20℃, the two steel strips expand and push the pointer towards a smaller density or pressure indication value, resulting in a reading lower than0MP; on the contrary, when the ambient temperature is lower than20℃, the gear mechanism and pointer will move towards a larger density or pressure indication value, resulting in a reading higher than0MP.
When filling SF6 gas density into the SF6 circuit breaker, as the gas pressure gradually increases, the top of the spring metal bellows moves in a certain direction, and the two steel strips compensate based on20℃, pushing the gear mechanism and pointer to move towards a larger density or pressure indication value, resulting in an increase in indication value. The indication value of the density or pressure meter not only depends on the pressure, but also on the temperature. When filling SF6 gas into the SF6 circuit breaker, the gas rapidly expands and cools, and the temperature usually drops below0℃, but the two steel strips cannot compensate for the temperature difference between the actual temperature of the SF6 gas and the ambient temperature. Therefore, in this case, the indication value in theSF6 density meter cannot represent the density or pressure value at the actual temperature of the SF6 gas, nor can it represent the density or pressure value at ambient temperature.
After the SF6 circuit breaker is operated, wait for a period of time to allow the internal temperature of the circuit breaker to rise to a balance with the external ambient temperature, and adjust the SF6 gas to the rated density or pressure value. At this time, regardless of whether the pressure of the SF6 gas increases or decreases due to the influence of the ambient temperature, the temperature compensation function of the two steel strips in theSF6 density meter will keep the pointer biased towards the rated value after20℃, without changing.
After the circuit breaker stops operating, if the temperature of the SF6 gas density inside the circuit breaker reaches a balance with the external ambient temperature, the indication of the density or pressure value will not change with the variation of the external ambient temperature. When the ambient temperature rises, the temperature of the SF6 gas inside the circuit breaker also rises, and the pressure also increases, but due to the expansion of the two steel strips with the increase of ambient temperature, the indication value of the pointer will not change. Conversely, when the ambient temperature decreases, the indication value of the pointer will also maintain the original density or pressure value.
SF6 gas density meters and relays are important components to ensure the normal operation of SF6 circuit breakers. Understanding their structure and working principles can help better maintain and manage these devices to ensure the stable operation of power supply systems. When using and maintaining SF6 circuit breakers, close attention should be paid to the indications of the SF6 gas density meters and density relays, as well as their response to the ambient temperature and SF6 gas, in order to ensure the normal operation of the equipment.
