What is the main function of SF6 gas density micro- 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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What is the main function of SF6 gas density micro-water online monitoring device?

发布时间：2017-05-27 来源：ydlcb 浏览次数：38次

SF6 gas density micro-water online monitoring device is mainly used for online monitoring of the circuit breaker SF6 gas micro-water, temperature and its change trend. When SF6 gas indicators change, the change curve is given, and when the indicators exceed the standard and reach dangerous conditions, the alarm device is automatically started, and the monitoring data is uploaded to the upper monitoring host and the management center station in real time to ensure the safe operation of the equipment and the entire system of the substation.

SF6 gas is widely used in high voltage electrical equipment because of its stable physical and chemical properties, excellent insulation properties and excellent arc extinguishing performance. When SF6 electrical equipment is running, SF6 gas in the electrical equipment will inevitably leak out; At the same time, the external moisture of the electrical equipment will also penetrate into the interior of the high-voltage electrical equipment, resulting in a decrease in the SF6 gas density in the electrical equipment and a decrease in the water content of the SF6 gas in the equipment exceeding the specified standard, so that the high-voltage electrical equipment has a safety hazard.

Generally, the leakage of SF6 gas and the infiltration of external moisture into the interior of the electrical equipment occur simultaneously. The leakage reduces the density of SF6 gas in the equipment, which will reduce the insulation performance and arc extinguishing performance inside the equipment, and the increase of the moisture content of SF6 gas inside the equipment will lead to condensation. Under the action of the arc, trace H2O will hydrolysis with SF6 and metal. Produces highly toxic and corrosive gases, damages insulation and endangers safe operation. SF6 gas and highly toxic corrosive gas inside the equipment leak out together, endangering human health, but also increasing the greenhouse gas in the environment.

In orde to ensure the safe operation of SF6 high-pressure equipment, SF6 gas density, water content and other parameters must be strictly monitored, if these devices leak, SF6 gas density is reduced, it will have extremely serious consequences, such as the voltage strength of the switching equipment is reduced, or the breaker breaking capacity is reduced.

The allowable moisture content of SF6 electrical equipment is an important performance index. Excessive moisture will produce condensation, which will cause SF6 gas decomposition and hydrolysis reaction under the action of arc and partial discharge, seriously damage insulation parts and reduce insulation performance. Online detection of moisture content should be carried out. Due to the good long-term stability of the high polymer film humidity capacitance sensor, it can be used to detect the moisture content of SF6 gas in GIS/GCB enclosed complete sets of electrical appliances online.

When the gas chamber of the high-pressure equipment is filled with SF6 gas to determine whether it has met the requirements of insulation or arc extinguishing, the concept of SF6 gas density is often used to measure, because the insulation strength of the SF6 gas chamber depends on the size of the SF6 gas density value, that is, the number of molecules of SF6 gas per unit volume, and has nothing to do with temperature. The size of the density value is reflected by the inflation pressure at 20℃. In order to ensure the safe and reliable operation of SF6 gas insulation equipment, it is necessary to monitor the SF6 gas density value, not the gas pressure.

① When the gas density is constant, the breakdown strength of SF6 gas is independent of temperature;

When the pressure is constant, the breakdown strength of SF6 gas decreases with the increase of temperature (due to the increase of temperature, SF6 gas density gradually decreases).

Because in the case of a certain density, when the temperature changes, the pressure also changes, and the corresponding change curves of different densities are also different. Therefore, in order to correctly reflect whether the change in pressure is due to leakage or caused by temperature change, it is necessary to pass the temperature compensation or correction method, so that the reading of the pressure indicator instrument regardless of how the temperature in the natural environment changes, the indicated result is always the standard pressure value at 20℃, and the value is equivalent to the SF6 gas density value in the gas room. When the leakage occurs, the density relay can immediately indicate the density change caused by the leakage. When the density indication value of SF6 gas is lower than the preset alarm value, the density relay will give the contact signal of the alarm for aeration, that is, the leakage is not too much, and the air should be aerated, and the equipment can continue to run to prevent the insulation performance from being reduced. If the leakage is serious, give a pair of locking contact signals, and lock the switch operation, indicating that the equipment can not operate normally at this time, once the operation, there will be an accident.

SF6 gas density micro-water online monitoring operation of SF6 gas insulation equipment no matter how strictly controlled in the installation and operation and maintenance, there will always be water vapor in the equipment, at room temperature, SF6 gas even if it contains more water, there will be no chemical reaction, so in the compartment without arc or corona, the harm of water is mainly to reduce the pressure level. For example, when the moisture content of SF6 gas is above 30%, the discharge voltage along the surface decreases significantly, and can be reduced to 60% to 80% of the dry time; In the compartment with arc or corona, in addition to reducing the insulation capacity, under the action of arc, trace H2O will hydrolysis with SF6 gas and metal materials to produce highly toxic substances and corrosive gases, damaging insulation and corroding metal. Due to the high humidity of SF6 gas caused by GIS high voltage electrical equipment accidents have been reported, such as China in the 1990s, a factory in the south of the 126kV GIS lightning arrester interval put into operation soon, it was found that the internal discharge sound, and then run for a period of time, disintegration found in most of the contacts there are dense white powder, etc. The white powder is the product of hydrolysis reaction. Another example: It has been reported that the high humidity of SF6 gas caused the explosion of high voltage transformer.