Ⅰ. The differences between SF6 density meter relay and pressure gauge
The pressure gauge is used for monitoring, that is, to detect the system pressure. On the one hand, relay relay monitors the change of system pressure, and on the other hand, it plays a role of control and protection. The sf6 density meter relay can be set in different pressure states. The switch signal contact under the bottom.
The sf6 density meter relay usually has an alarm contact and a blocking contact, while the pressure gauge has no contact. This is the difference between the two.
The so-called density refers to the mass per unit volume of a specific substance under specific conditions. The SF6 gas in the SF6 circuit breaker is sealed in a fixed container.
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Under the rated pressure at 20℃, it has a certain density value. Within the range of various allowable conditions for the operation of the circuit breaker, although the pressure of SF6 gas changes with temperature changes, the density value of the sf6 density meter relay remains the same.
Because the insulation and arc extinguishing performance of SF6 circuit breakers depend to a large extent on the purity and density of SF6 gas, the detection and density monitoring of SF6 gas purity are particularly important.
If an ordinary pressure gauge is used to monitor the leakage of SF6 gas, it will be difficult to distinguish whether the pressure change of SF6 gas is caused by the actual leakage or the change of the ambient temperature.
In order to achieve the purpose of frequent monitoring of density, SF6 circuit breakers should be equipped with pressure gauges or SF6 gas density meters and sf6 density meter relays. The pressure gauge or SF6 monitoring system is for monitoring, and the density relay is for control and protection.
The sf6 density meter relay calibrator is an instrument specially used for testing various forms of sf6 density meter relays. Its main function is to measure the contact pressure value of the sf6 density meter relay. And according to the SF6 gas pressure value and temperature value stored in the sf6 density meter relay calibrator at the moment of contact action, it is automatically converted into a standard pressure value corresponding to 20°C.
Ⅱ. SF6 density meter relay measurement performance requirements
1. Pressure indication error
The expression of allowable error of pressure indication Δy is: Δy=±a%F·S
a——Accuracy grade of the tested instrument (according to the provisions of the product technical manual) F·S——The pressure range of the tested instrument
2. Pressure return error
The pressure return error should not be greater than the absolute value of the allowable error of the pressure indication.
3. Temperature measurement error
The temperature measurement error should not exceed ±0.5℃
4. P20 indication error
The P20 indication error displayed by the inspected instrument should not exceed the allowable error of the pressure indication. Note: P20 value refers to the pressure value of SF6 gas at 20°C under the condition of constant SF6 gas density.
5. P20 conversion error
P20 conversion error refers to the difference between the P20 value displayed on the inspected instrument and the P20 value calculated by the standard device based on the pressure value and temperature value of the inspected instrument.
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