Sulfur hexafluoride gas common unit conversion process- SF6在线监测系统_SF6检漏仪_SF6传感器_SF6密度继电器

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Sulfur hexafluoride gas common unit conversion process

发布时间：2015-07-20 来源：ydlcb 浏览次数：249次

GIS, SF6 circuit breakers, SF6 transformers and other equipment will be filled with a certain pressure (density) of SF6 gas, the pressure unit used in the domestic industry is Mpa, and the European, Japanese joint venture manufacturers often use bar and psi and other gas pressure units, which will cause some trouble to everyone. Weavers Xiaobian collection of several units of conversion formulas, listed out for everyone's reference.

In engineering, megapascals (MPa) are commonly used: 1MPa=1,000,000Pa. A standard atmospheric pressure =1.00336×0.098MPa= 0.1010mpa ≈0.1Mpa. The legal unit of pressure for 1bar=0.1MPa is the PASCAL (Pa) : 1Pa=1N/㎡ (Newtons/m2). Pressure unit conversion: 1MPa=1000kPa, 1kPa=10mbar=101.9716 mmH2O = 4.01463imH2O 10mWC = 1bar = 100kPa, bar = 0.987 atmospheric pressure = 1.02 kg/cm2 = 100 kPa= 14.5 psi 1psi=6.895kPa=0.06895bar, 1 MPa =145 LBS /cm2 (psi)=10.2 kg/cm2 (kg/cm2) =10 bar (bar)=9.8 atmospheres (atm) 1 lb/inch 2(psi)=0.006895 MPa =0.0703 kg/cm2 (kg/cm2) =0.0689 bar (bar)=0.068 atmospheric pressure (atm) 1 bar (bar)=0.1 MPa =14.503 LBS/inch2 (psi)=1.0197 kg/cm2 (kg/cm2) =0.987 atmospheric pressure (atm) 1 atmospheric pressure (atm)=0.101325 MPa =14.696 Pounds per inch 2(psi)=1.0333 kg/cm2 (kg/cm2) =1.0133 bar Note: PSI is Pounds per square inch. P is pound pound, S is square square, I is inch inch. Convert all units into metric units and you can calculate: 1bar≈14.5psi, psi is often used in Europe and the United States.

The state parameters of sulfur hexafluoride and the temperature of liquefaction or solidification can be calculated easily by using the state parameter curve. 1. Calculate the inflatable volume of sulfur hexafluoride gas in the circuit breaker. For example, a sulfur hexafluoride circuit breaker, the working pressure is 0.45MPa at 20 ° C (gauge pressure), and the sulfur hexafluoride gas filling amount is 31kg.

When the working pressure is 0.45MPa at 20℃, the absolute pressure is 0.55MPa. The working point S in the break linear cluster can be obtained from the pressure of 0.55MPa at 20℃. It is estimated that the density of the oblique line parallel to the oblique linear cluster passing through the point S is 35kg/ m3

The gas filling volume of the sulfur hexafluoride circuit breaker is: 31/35=0.886 m3. 2. For sulfur hexafluoride circuit breaker internal inflation pressure changes with the external temperature allowed range for example, at 20℃, the above inflation working pressure is 0.45MPa, the absolute pressure is 0.55MPa sulfur hexafluoride circuit breaker. When the ambient temperature rises to 30 ° C and the density =35 kg/ m3 is kept unchanged, the absolute pressure is 0.58 MPa and the working pressure is 0.48MPa when 30 ° C is obtained along the diagonal line to the right of point S in Figure 1-4. When the temperature drops to -10℃, along the density =35 kg/ m3 oblique line can be found on the left side of point S at -10℃, the absolute pressure is 0.49 Mpa, and the working pressure is 0.39MPa. The results show that when the external temperature changes between -10℃ and 30℃, the working pressure of sulfur hexafluoride circuit breaker can change between 0.39 MPa and 0.48 MPa. (Inflation pressure 0.45MPa at 20℃).

3. Understand the temperature of sulfur hexafluoride gas liquefaction under different working pressures in the example of sulfur hexafluoride circuit breaker, the working pressure is 0.45MPa at 20℃, the density is 35 kg/ m3, the operating point S, the oblique line of the point S intersects with the AMB curve at T point, the temperature at this point t=-33℃, the corresponding working pressure is 0.35MPa. That is, the sulfur hexafluoride gas in this circuit breaker begins to liquefy at -33 ° C. The T point indicates the liquefaction point where condensation occurs as the temperature drops.

Once the sulfur hexafluoride gas begins to liquefy, as the temperature continues to drop, the sulfur hexafluoride gas continues to condense into a liquid, the density of the gas no longer remains constant but constantly decreases, and the pressure of the gas drops faster. When the temperature drops to the liquefaction point, it does not mean that all the gas is immediately condensed into a liquid, but only the beginning of condensation. However, when the temperature continues to decrease and the pressure and density of the gas decline faster, the insulation and arc extinguishing performance of the sulfur hexafluoride gas decline rapidly, so the sulfur hexafluoride circuit breaker does not allow the operating temperature to be lower than the liquefaction point.

It can be seen from the curve AMB that the higher the working pressure (gauge pressure) of the sulfur hexafluoride circuit breaker, the higher the liquefaction temperature. The liquefaction temperature is related to the working pressure of the circuit breaker. If the liquefaction temperature is not high and -20℃ is calculated, the corresponding absolute pressure at 20℃ should not be higher than 0.82 MPa, and the working pressure (gauge pressure) should not be higher than 0.72 MPa.

When the operating pressure of the circuit breaker is very low, the temperature may not be liquefied and directly condensed into a solid. It can be seen that the operating environment conditions of SF6 circuit breaker are -30℃ ~ +40℃, the rated pressure is 0.45MPa, and the locking pressure is 0.4MPa. The analysis results can also be calculated and verified by Boil-Mallott gas equation of state PV/T=P1V1/T1. Where: P is pressure; V is the volume; T is the temperature (absolute temperature); P1 is the pressure after the change; V1 is the changed volume; T1 is the temperature after the change. When the volume is unchanged and the SF6 gas pressure changes with the change of temperature, the SF6 gas pressure change value of LW8-35 circuit breaker can be calculated, and the parameters are substituted into the formula to obtain: P1=P×T1/T0.45MPa×(273℃-39℃)/(273℃+20℃)=0.36MPa When SF6 gas temperature changes from 20℃ to -39℃, SF6 gas pressure changes from 0.45MPa to 0.36MPa, which is lower than the locking pressure of 0.4MPa.

The common specifications of domestic sulfur hexafluoride: 8L/10kg, 15L/20kg and 40L/50kg, the common purity is the following: 99.99%, 99.995% and 99.999%. The higher the purity of sulfur hexafluoride gas, the lower the impurity content.