The SF6 gas density relay can accurately measure the density of SF6 gas only when the circuit breaker is out of operation, and after the temperature inside and outside the circuit breaker reaches equilibrium; when the circuit breaker is running, if the circuit breaker leaks SF6 gas, due to the effect of temperature rise, More SF6 gas leaks than when the circuit breaker is out of service to close the electrical contacts of the density relay.
The calibration of the SF6 circuit breaker density meter or density relay is to use the instrument to automatically convert the SF6 gas pressure value at 20 °C, display the density value at various temperatures and pressures, and compare with the various pressures simulated by the instrument to obtain Observe the contact situation of the electrical contacts, whether it can send a signal or block the circuit breaker within the specified low voltage value, to judge the quality of the SF6 circuit breaker density meter or density relay.
In the process of verifying the density meter and density relay of SF6 circuit breakers, it was found that the density relays of several circuit breakers were unqualified, but the unqualified density meter has not yet been found. The reason for the unqualified density relay may be the SF6 standard gas package Due to a long thin copper tube, the pressure in the standard SF6 gas bag increases due to the bending or collision of the copper tube during installation or maintenance; it may also be due to the corrugation of the density relay The tube is damaged, causing the standard gas bag of the density relay to leak. When the circuit breaker leaks SF6 gas, the C1-L1 and C2-L2 contacts cannot be connected, causing the density relay to lose its function, which seriously threatens the safe operation of the equipment and even system security. It is recommended to replace the density relay with a density meter. On the one hand, it can reduce SF6 gas pipelines and joints, that is, reduce the probability of SF6 gas leakage; on the other hand, it can improve the operational reliability of the equipment.
In the actual work on site, when filling the circuit breaker with SF6 gas, some people often think that filling more SF6 gas can prevent the supplementary gas and the blocking signal. Indeed, if the gas pressure is higher, it will reduce the amount of supplemental gas and The probability of blocking the signal, but it will increase the burden on the seals of the circuit breaker, which may damage the seals of the circuit breaker and cause air leakage. Therefore, it is not advisable to increase the pressure of SF6 gas, and it should be strictly controlled within the standard.
SF6 circuit breaker is an important protection and control element in the power system. If the circuit breaker fails, it will cause great economic losses. To ensure the reliability of the circuit breaker operation, it is necessary to constantly monitor the various indicators of the circuit breaker, especially It is SF6 gas, which must meet the relevant standards to keep the SF6 circuit breaker in good working condition for a long time.
The principle, types and functions of Density Monitors
