Calibration and Use of SF6 Gas Density Relay

The SF6 relay can only accurately measure the SF6 gas density value when the circuit breaker is out of operation and after the internal and external temperatures of the circuit breaker achieve balance; when the circuit breaker is in operation, if the circuit breaker leaks SF6 gas, due to the effect of temperature rise, more SF6 gas should be leaked than when the circuit breaker is out of operation to make the electrical contact of the density relay closed.

1. Calibration of SF6 circuit breaker density meter or SF6 relay

It is to use the instrument to automatically calculate the SF6 gas pressure value at 20°C, display the density value at various temperatures and pressures, and compare it with the various pressures simulated by the instrument to observe the contact status of the electrical contacts. Signal or lock the circuit breaker within the specified value to judge the quality of the SF6 circuit breaker density meter or SF6 relay.

In the process of verifying the density meter of SF6 circuit breaker and SF6 relay, it was found that the density relays of multiple circuit breakers were unqualified, but the density meter has not been found to be unqualified. The reason for the unqualified SF6 relay may be SF6 standard air pocket is carrying a long thin copper tube.

In the process of installation or maintenance, the pressure in the standard SF6 air pocket increases due to the bending or collision of the copper tube; it may also be caused by the damage of the corrugated pipe of SF6 relay, causing the standard gas bag of the SF6 relay to leak. When the circuit breaker leaks SF6 gas, the C1-L1 and C2-L2 contacts cannot be connected, causing the SF6 relay to lose its function and seriously threatening the safe operation of the equipment and even the safety of the system.

It is recommended to replace the SF6 relay with a density meter. First of all, it can reduce the SF6 gas pipeline and joints, that is, reduce the probability of SF6 gas leakage; what's more, it can improve the operating reliability of the equipment.

2. SF6 relay is used in actual work on site

When charging the circuit breaker with SF6 gas, some people often think that more SF6 gas can prevent sending signals of supplementing gas and blocking. Indeed, if the gas pressure is higher, it will reduce the probability of sending signals of supplementing gas and blocking, but it will increase the burden on the seals of the circuit breaker, which may damage the seals of the circuit breaker and cause gas leakage. Therefore, it is not recommended to increase the pressure of SF6 gas, which should be strictly controlled within the standard.

SF6 circuit breaker is an important protection and control component 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 frequently monitor the various indicators of the circuit breaker, especially the SF6 relay gas, which must meet the requirements of relevant standards to keep the SF6 circuit breaker in good working condition for a long time.

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