Sulfur hexafluoride gas density relay and gas density meter operation precautions- SF6在线监测系统_SF6检漏仪_SF6传感器_SF6密度继电器

韦弗斯新闻动态

最新动态

SF6安全保障专家

专注于SF6气体检测的专业化

135 85763546

Sulfur hexafluoride gas density relay and gas density meter operation precautions

发布时间：2020-08-17 来源：ydlcb 浏览次数：20次

1. The sulfur hexafluoride gas density relay and gas density meter can accurately measure the density (or pressure) value of SF6 gas only after the SF6 equipment is withdrawn from operation and the temperature inside and outside the equipment is balanced.

2, sulfur hexafluoride gas density relay and gas density meter temperature compensation function of the double-layer metal strip, can only compensate for the change in density (or pressure) value caused by the change of ambient temperature, but can not compensate for the change in density (or pressure) value caused by the internal temperature rise of the equipment. 3. The main function of sulfur hexafluoride gas density relay and gas density meter is to monitor whether SF6 gas leaks, and only when the equipment exits the operation, and after the temperature inside and outside the equipment reaches the balance, it can determine whether the gas leaks according to the change in the density (pressure) reading. 4, when the circuit breaker is put into operation, due to the load current of the circuit breaker through the conductor resistance and contact resistance of the conductive circuit, the electrical power consumed will be all converted into heat energy, heating SF6 gas and producing temperature rise, and then producing pressure increment, the density (or pressure) meter will read larger, which is a normal phenomenon of this gas density meter. If the reading of the table is small at this time, it is necessary to judge whether the equipment is because of air leakage or its own gas filling quality is less. 5, according to the sulfur hexafluoride gas density relay and gas density meter configuration in the circuit breaker location, the reading is also biased. The so-called ambient temperature generally refers to the temperature of the air without sunlight, if the density (pressure) meter is installed on the back of the sunshine side of the circuit breaker, the density (pressure) reading will be larger; If the density (pressure) meter is installed on the sunny side of the circuit breaker, the temperature will be higher after sunlight exposure, and the density (pressure) reading will be smaller. The deviation depends on the temperature difference. 6, when the circuit breaker is running, the size of the sulfur hexafluoride gas density relay and gas density meter reading error depends on the temperature rise caused by the load current of the circuit breaker and the circuit resistance, and the size of the error is independent of the ambient temperature. Strictly speaking, this reading can neither represent the actual pressure value of SF6 gas nor the actual density value of SF6 gas. According to the Technical Guidelines for Ordering Gas Insulated Metal Enclosed Switchgear (DL/T728-2013), the temperature rise of GIS enclosures easily accessible to operators shall not exceed 40K; For parts not touched by the operator, the allowable temperature rise can be increased by 65K. 7, the use of sulfur hexafluoride gas density relay and gas density table, according to its structure, principle, use conditions and other specific analysis, such as the northwest is a typical temperate continental climate, winter and summer temperature difference between the average 10-15℃, can not be because the actual density of SF6 gas does not change with the temperature change, It is considered that the reading of the density (pressure) meter does not change with the change of temperature. In actual work, if the reading error of the table is found to be large, it can not be sure that there is a problem with the quality of the density table. 8. According to the statistical analysis results of nearly 500 SF6 density tables of a power supply bureau in winter and summer, the greater the load current, the greater the error, and the error can reach 10% to 20%. In this case, sulfur hexafluoride gas density relays and gas density tables should not be judged as having problems.

According to the ideal gas equation of state pv=nRT, it can be seen that the pressure p is a linear relationship of temperature. As shown in the figure below, when the gas temperature in the sulfur hexafluoride equipment changes, the value of the pressure gauge changes with the change, and it is not ready to show the state of the equipment.

Sulfur hexafluoride gas density relay Structure Principle Sulfur hexafluoride gas density relay (table) is an indispensable and important accessory of sulfur hexafluoride circuit breaker and sulfur hexafluoride combined electrical apparatus (GIS). Its basic function is to monitor the sealing status of SF6 appliances in operation and whether there is gas leakage. As shown in the figure below, the structure of the compensation chip type sulfur hexafluoride density relay

Sulfur hexafluoride density relay structure Temperature compensation principle SF6 gas density relay is actually a pressure relay with temperature compensation, and its density value is expressed by the corresponding pressure value of 20℃. When the temperature changes, the elastic Bourdon tube and metal band change at the same time, so that the pointer displays unchanged. In the case of constant volume, any pressure change due to temperature change alone can be compensated by the corresponding change of Bourdon tube and metal sheet at the same time, so as not to cause the deflection of the pointer and ensure the correctness of the pressure indication value. As shown in the following picture.

The response of the pressure element to any pressure change that is not caused by a temperature change is translated into the gas density relay pointer action and reflected on the dial, and the pressure value beyond the minimum or maximum pressure allowed by the system can be monitored. Air leakage as shown below.

The requirements of the new 18 anti-measures of the State Grid on the structure of sulfur hexafluoride density relay: The density relay should be installed in the same operating ambient temperature position as the monitored gas chamber. Explanation: If the operating environment temperature is different, the compensation temperature of Bourdon tube and metal strip is inconsistent, resulting in inaccurate values. General requirements for sulfur hexafluoride electrical appliances According to DL/T728-2013 "Gas insulated metal enclosed Switchgear ordering Technical Guidelines" and the former Ministry of Energy issued "High voltage circuit breaker operating Regulations" and other standards, the general requirements for sulfur hexafluoride electrical appliances (for convenience, the sulfur hexafluoride electrical appliances described in this article basically refer to SF6 circuit breakers and GIS) are: 1, monitoring the change of SF6 gas pressure, should be set up density relay or gas density meter. 2. The density monitoring device can be a density meter or a density relay. When a density relay is selected, a gas density meter should also be installed. 3. Check and record the pressure and temperature of SF6 gas regularly every day. Sulfur hexafluoride appliances use gas density relays according to Weifers' statistics of nearly 500 SF6 density tables in a power supply bureau, including imported Swiss ABB tables, German WIKA, CBS, Xi 'an Huawei, Shanghai Keli and other origin instruments are in this situation, that is, spring tube pressure gauges with gas leakage caused by pressure drop alarm and blocking electrical contacts. The SF6 gas density relay is formed. Density relays are used for monitoring with gas density gauges and for alarm and latching elements. Based on the existing experience and theoretical analysis, the SF6 gas density relay with this structure is adopted on the following basis: 1. Although the pure pressure-temperature curve of SF6 gas (i.e., the three-phase physical diagram of SF6 gas, liquid and solid) is more complex, the relationship between the pressure of SF6 gas and the change of temperature is still linear within a certain temperature range. Therefore, each equipment manufacturer adopts the actual use of SF6 gas pressure-temperature curve, that is, the pressure of SF6 gas changes with the change of temperature, and there is a 10%-15% error allowed by the standard, but in a fixed and unchanged container, as long as there is no leakage phenomenon, the density value of SF6 gas is always unchanged. The density value of SF6 gas is proportional to the function of the pressure value. Therefore, it is theoretically feasible to monitor whether the equipment leaks gas with the pressure value. 2, the spring tube pressure gauge has the characteristics of simple structure, mature manufacturing process and technical standards, accurate measurement, low cost, etc., suitable for large-scale manufacturing and use. When the circuit breaker is filled with sulfur hexafluoride gas, generally 24 hours later, the internal temperature of SF6 circuit breaker rises to reach a balance with the external ambient temperature, regardless of whether the SF6 gas is affected by the ambient temperature, its pressure increases or decreases, due to the temperature compensation effect of the double-layer metal strip. The needle of the gas density meter should always point to the actual density (pressure) value of SF6 gas at 20 ° C. When the SF6 device reduces the mass of SF6 gas and the pressure due to gas leakage or test taking, the pointer moves in the direction of the decrease of the density (or pressure) indicator value, the result is that the density (or pressure) value indicated by the pointer becomes smaller.