What is the standard for SF6 leakage?- 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

What is the standard for SF6 leakage?

发布时间：2020-10-14 来源：ydlcb 浏览次数：25次

The sealing test of sulfur hexafluoride gas equipment is to determine whether the annual gas leakage rate of the gas chamber is qualified by detecting the leakage amount of SF6 gas. The control standard is that the annual gas leakage rate of each independent gas chamber is not more than 0.5%; Two test methods and control standards are proposed in the provisions of the "Electrical Equipment Handover Test Standards" :

1. When the leak detector with sensitivity not less than l×10-6 (volume ratio) is used to detect the sealed part of the gas chamber and the pipe joint, the SF6 leak detector is considered qualified without alarm.

2, the local dressing method is used, and the SF6 content in each dressing chamber is not more than 30 ppm (volume ratio) after 24 hours.

At present, the second test method is more accurate, and its implementation procedure is: vacuum test →SF6 gas → leak test. The specific process is as follows: after the GIS is vacuum detected and SF6 gas is stationary for 5 hours, the flange interface is wrapped with a plastic film, and the test is carried out after 24 hours. If the concentration of SF6 gas in a film is greater than 30 ppm, the gas leakage rate of the air chamber is unqualified. If the concentration of SF6 gas in all wrapped films is less than 30ppm, the gas leakage rate of the chamber is considered acceptable.

Causes of SF6 gas leakage of GIS device

Compared with conventional electrical equipment, SF6 gas insulated switchgear (GIS) has the advantages of small space volume, high operation reliability, low failure rate, low maintenance cost, closed components free from external environment interference and long maintenance cycle, etc., and is widely used in various electrical equipment of power system. The insulating medium adopts SF6 gas with good arc extinguishing performance, high insulation strength and stable chemical properties. From the perspective of long-term operation, various sealing processes and leak detection measures have been taken in time, but because GIS is an integrated assembly and combination equipment, the connection is easy to seal loosely, so SF6 gas leakage is still a common defect in the whole life cycle of GIS, accounting for about 40% of the defects of GIS equipment.

GIS equipment leakage generally occurs at flange joints, welds, gas density relay bonding surfaces, valves, pipelines and sealing surfaces of sealing rings. Common leakage causes are:

01. Equipment manufacturing reasons

GIS equipment can sometimes suffer from SF6 gas leakage defects due to poor manufacturing quality. The uneven flange surface caused by incomplete processing technology will affect the tightness of GIS equipment; Poor casting process will cause the shell to have sand holes, poor welding process will appear weld cracks, sand holes and welds are common inducements for GIS equipment leakage, if this defect is not found in time during the installation process, then it will be difficult to find in operation.

02. Device installation causes

During the installation of GIS devices, the assembly quality is not high. For example, if you do not comply with the requirements of the operation guide, do not select the specified installation parts, or do not follow the specified installation process, SF6 gas may leak. In addition, the environmental cleanliness of the installation site also has an impact on the installation effect. For example, if the ambient humidity is too high, the insulation components will be damp, which will cause adverse effects. Improper installation operation, scratching the surface of the component, or asymmetric force applied to the end face when tightening the flange can also cause SF6 gas leakage. When installing the basin insulator, excessive force and improper assembly will cause the insulator to crack, resulting in SF6 gas leakage. Therefore, it is necessary to strictly follow the construction process of the operation instructions during assembly to ensure that the installation environment and installation methods meet the requirements, check that the flatness of all flanges meet the requirements, ensure that parts are installed and fastened in place, and avoid collision with components.

03. Seal quality reasons

Seal quality is a common factor that causes GIS equipment to leak. Improper tightening of seals, improper placement of sealing rings into sealing slots, or use of defective sealing rings during installation can result in lax sealing and gas leakage. At the same time, with the aging and deformation of the sealing ring, the sealing performance will gradually decrease. Such defects are difficult to find, but it is easy to cause serious defects, so special attention is needed, especially the switch with more operation times, and the sealing ring aging speed is relatively fast, and the GIS equipment should carefully check the seals everywhere when carrying out daily maintenance.