Urumqi Nantianya Electrical Complete-sets Equipment Co.,Ltd.
Add : 366 Tongbaishan Street, Economic and Technological Development Zone, Urumqi
Phone : 86-:13809951165
Service Phone :0991-4653766


Talking about SF6 load switch and inflatable cabinet switchgear

SF6 load switch

SF6 load switch is a kind of load switch, isolating switch and grounding switch. It is sealed in a box filled with SF6 gas. It uses SF6 excellent insulation and arc extinguishing performance to meet the functions of closing, isolation and grounding. Switching device. The utility model has the advantages of simple structure, reliable interlocking, small volume, less maintenance, safety and easy installation, and is suitable for different applications.

Because the SF6 load switch cooperates with the current limiting fuse to better protect the transformer, it has been widely used abroad. In industrialized countries (such as Europe, Japan), the ratio of circuit breakers to load switches is 1:5-6. In China, with the continuous development of urban network construction and transformation, the load switch equipment is in the ring of 12kV power distribution system. There are more and more applications for network power supply and terminal power transmission. At present, most of the domestic SF6 load switches are mainly occupied by foreign companies (such as ABB, Schneider, etc.), and dozens of domestic manufacturers have developed and produced various types of SF6 load switches (such as Wenzhou Kaiyuan and Ningbo Tianan). , Zhenjiang Longyuan, etc.). Domestic manufacturers have gained a more comprehensive understanding of the SF6 load switch by digesting and absorbing foreign rich design, manufacturing and operation experience. The quantity and quality of domestic SF6 load switches have been steadily improved.

C-GIS inflatable cabinet

Cabinet type SF6 gas insulated switchgear (referred to as C-GIS inflatable cabinet) is a new high-tech series product newly developed in foreign countries in the past decade, and has gradually become an important variety of metal-enclosed switchgear. China has only started in recent years.

The C-GIS inflatable cabinet is a medium-pressure equipment that encloses all high-voltage components such as bus bars, circuit breakers (or load switches), disconnectors, transformers, etc. in a stainless steel housing filled with a lower pressure SF6 gas. Its outstanding features are safety, high reliability, simple operation, maintenance-free, and easy installation. Its greatest feature is that it is not affected by external environmental conditions, such as condensation, pollution, small animals and chemicals, and can be used in places with harsh environments. Another important feature is that the use of excellent SF6 insulation greatly reduces the size of the cabinet, which is conducive to the development of miniaturization. Compared with air insulation, the SF6 inflatable cabinet has a mounting area of 26% and a volume of 27%. At the same time, because the air tank is equipped with a good oil-free switch, the maintenance and repair work is greatly reduced. It is suitable for the requirements of network nodes or user terminals, and meets the needs of flexible use of compact switchgear for various secondary substations. It is especially suitable for occasions with high electricity requirements such as airports, subways, railways, etc. C-GIS adapts to the requirements of miniaturization and intelligence.

At present, several large-scale research institutes and switch manufacturers in China have developed a new type of cabinet type SF6 gas-insulated switchgear by introducing, digesting and cooperating, such as Xigao Institute, Xi'an Senyuan, Zhenjiang Longyuan, Tianshui Great Wall Switch Factory, Shanghai Tian Ling Switch Factory, Guangdong Shunde Switch Factory, etc. All products have passed the type test, and have now entered the stage of small batch trial production and product improvement and serialization. Due to the high requirements on the process equipment and the difficulty in processing, the C-GIS inflatable cabinet is not very popular in China.

The extensive use of SF6 gas in switchgear has driven the rapid development of the switch manufacturing industry. However, when SF6 gas is arc-discharged, it decomposes to form sulfur-low fluoride, which is both toxic and corrosive to many insulating materials and metallic materials. In addition, SF6 gas also has a certain influence on the ambient temperature (greenhouse effect). In 1991, the former Ministry of Electrical and Mechanical Services issued a notice on the “Requirements for SF6 High-voltage Switchgear Production Plant” to ensure the quality of SF6 switchgear. The relevant requirements for the SF6 high-voltage switch production plant of 35kV and below are put forward. Briefly said:

a. There should be air purification with a purity of 1 million or more, a relative humidity of less than 75%, and good ventilation conditions.

b. SF6 leak detection chamber, parts cleaning room and drying device.

c. There are reliable SF6 charge and discharge and recovery devices.

d, hydraulic test and air tightness test device.

e, necessary testing conditions and equipment: 1, physical and chemical testing; 2, insulation testing; 3, SF6 gas detection;

f. Improve quality management and process management system.

The high-voltage switch production plant should produce SF6 load switch and inflatable cabinet switchgear, mainly to solve the following technical problems:

1, the sealing problem:

Air leakage rate has always been the focus of attention of manufacturers and users. The annual leakage rate of SF6 load switch and inflatable cabinet is below 1%/year. The service life of the switch is generally around 30 years. The sealing takes into account factors such as the amount of compression of the sealing member, life, aging, and reliability.

When the pressure of the SF6 gas in the tank drops to atmospheric pressure, it seems that the internal and external pressures are equal and there is no leakage of the gas. However, from the perspective of penetration, the concentration of SF6 gas in the tank is obviously higher than that outside the cabinet, and the SF6 gas still oozes out. Otherwise, the air concentration outside the tank is higher than that in the tank, and the air will enter the tank through the gap. For a long time, although the gas pressure in the tank is still atmospheric, the gas composition changes. The percentage of SF6 gas is reduced. When the proportion of SF6 is reduced to 40%, there is a possibility that the insulation performance may cause an accident, so the sealing problem must be taken seriously.

SF6 load switches generally use seals to achieve dynamic and static sealing of gases (such as ABB's SFG, Schneider's SM6 switch); there are also very few seals that combine stainless steel welding and sealing rings (VEI SF6 switch); C-GIS Inflatable cabinets are sealed by welded seals, seal seals and metal bellows seals. Welding seals are used to ensure the airtightness of the welds. Generally, the welding equipment and welding technology cannot meet the requirements. At least argon arc welding or laser welding equipment is required for welding. At present, several welding robots have been introduced from abroad. Equipment) to ensure the quality of the welding.

There are two commonly used SF6 gas leak detection methods: one is qualitative leak detection, that is, the leak point; the second is quantitative leak detection, that is, the gas concentration in the sealed volume is measured after 24 hours of sealing to estimate the annual leak rate.

Also consider the impact of environmental factors on the sealing performance, such as whether the sealing performance meets the requirements under high temperature or low temperature conditions.

2. Gas moisture content:

The moisture content of SF6 gas is one of the main detection indexes of SF6 switch quality, and its size directly affects the insulation level of the switch.

The water in the SF6 gas, when its content is lower than the saturation value at the state temperature, the water exists in a gaseous state.

The content is one of the main detection indexes of SF6 switch quality, and its size directly affects the insulation level of the switch.

When the water content in the SF6 gas is lower than the saturation value at the state temperature, the water is present in the SF6 gas in a gaseous state. The test proves that the insulation performance of the SF6 switch is not affected at all; if the gas moisture When the content exceeds the saturation value, part of the water vapor will condense on the surface of the solid insulator inside the switch, thereby reducing the creeping voltage of the creeping surface, which also affects the arc extinguishing performance of the switch. Therefore, DL/T596-1996 "Procedure Test Procedures for Electrical Equipment" stipulates that the water content of SF6 switch after new commissioning and overhaul shall not exceed 150ppm, and shall not exceed 300ppm during operation. For new SF6 gas, first check the moisture of the gas itself. The content does not exceed the specified value (generally the moisture content is 15 ppm).

The sealed box is filled with an appropriate amount of dried adsorbent, and the adsorbent is mainly used to adsorb moisture to ensure that the moisture content in the sealed box does not exceed the standard. All parts in the sealed box (including sealed box, transmission parts, contact blades, etc.) and standard parts must be baked strictly according to the baking temperature and baking time of each component, and the moisture of the parts themselves should be strictly controlled. The content and the packaging time of the parts are guaranteed.

When the SF6 switchgear is vacuumed and inflated, the gas pipeline is cleaned with high-purity nitrogen or sulfur hexafluoride gas to control the moisture content in the pipeline, and the production process of the standardized SF6 switchgear is established.

3, parts quality problems: the quality of parts is directly related to the quality of the product. The SF6 load switch and the air-filled cabinet are maintenance-free or maintenance-free switchgear. Once the components in the sealed box have quality problems, it is highly likely that the entire switchgear will be scrapped.

To ensure the quality of parts, it is necessary to strictly control the materials, processing technology and inspection methods of the parts, and the mechanical strength, electrical performance and other aspects of the parameters meet the requirements of the product. More rigorous inspection of the parts required to be loaded, and stricter control of process control and process inspection are required for the entire assembly process to ensure the correctness and consistency of the assembly. In particular, the lubrication of the drive link and the surface of the contact in the sealed box should be permanently effective throughout the life of the product. The contact pressure of the contact should be strictly controlled. The resistance of the main circuit of the switch meets the technical requirements of the product during the life cycle.

With the rapid development of the social economy, the city's electricity load is growing, the requirements for power supply reliability are getting higher and higher, and high-performance ring network power distribution, multi-loop power distribution, opening and closing, etc. have become secondary power distribution. One of the important non-replaceable devices in the system, especially the compact and scalable SF6 switchgear, has become the dominant device in secondary distribution systems. With the wide application of digital technology, integrated technology and mechatronics technology, SF6 switchgear will be further developed.

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