When many people come into contact with equipment such as GIS and SF6 circuit breakers, they often have a question: What is SF6 gas? Why are power equipment not directly using air but instead specially filling SF6 gas? In fact, the reason why SF6 gas can be widely used in high-voltage and ultra-high-voltage power equipment is mainly related to its excellent insulation performance, arc-extinguishing performance, and high chemical stability. At the same time, as the operating years of the equipment increase, the problem of SF6 gas leakage has also received more attention.
The Chinese name of SF6 gas is sulfur hexafluoride, with the chemical formula SF6. It is a compound composed of one sulfur atom and six fluorine atoms. At normal temperature and pressure, SF6 gas is a colorless, odorless, non-flammable gas, and it has good chemical stability. Due to these characteristics, SF6 gas has been used in high-voltage switchgear, GIS combined electrical equipment, circuit breakers and other power equipment for a long time, mainly to undertake insulation and arc-extinguishing functions.
Why do power equipment need SF6 gas? First of all, it is the insulation performance. As the voltage level of the power grid continues to increase, the electric field strength between different charged bodies inside the equipment will also increase. Simply relying on air for insulation requires a larger electrical gap and equipment space. However, SF6 gas has a higher insulation strength and can provide a better gas insulation effect under certain pressure conditions. Therefore, in the same voltage requirements, using SF6 gas as the insulation medium can help reduce the internal space of the equipment.
This is also one of the important reasons why GIS equipment can achieve a compact design. GIS, or gas-insulated metal enclosed switchgear, arranges circuit breakers, disconnectors, grounding switches, busbars, current transformers and other equipment or functional units in a metal enclosed shell, and uses SF6 gas for insulation. Compared with traditional outdoor air-insulated equipment, GIS has a smaller overall占地面积， and is particularly suitable for scenarios with limited land resources such as urban substations and industrial parks.
In addition to insulation performance， SF6 gas has another very important characteristic， which is good arc-extinguishing performance. When a high-voltage circuit breaker performs opening operation， a spark will be generated between the contacts. If the spark cannot be extinguished quickly， it may cause the current to continue flowing， affecting the normal opening of the circuit breaker. SF6 gas can absorb electrons during the arc-extinguishing process and has a strong inhibitory effect on the arc， thus helping the circuit breaker to cut off the fault current more effectively.
Because of its insulation and arc-extinguishing characteristics， SF6 gas has formed a relatively mature application system in high-voltage and ultra-high-voltage power equipment. Especially in GIS and SF6 circuit breakers， SF6 gas is a very important medium. Parameters such as gas pressure， density and sealing state will also become the focus of maintenance personnel after the equipment is put into operation.
However， SF6 gas is not “filled and then there is no need to worry”. During the long-term operation of power equipment， due to factors such as aging of sealing parts， changes in the state of flange connection areas， mechanical vibration and equipment maintenance operations， SF6 gas leakage may occur. When the leakage is small， on-site personnel may not be able to directly detect it through observation. This requires the use of professional detection equipment for judgment.
Why is SF6 gas leakage important to pay attention to？ On the one hand， after SF6 gas leakage， the internal gas pressure or density of the equipment will decrease. When the gas content is lower than the requirements of the equipment， it may affect the insulation and arc-extinguishing performance of the equipment. For GIS and SF6 circuit breakers， the normal state of the gas directly relates to whether the equipment can maintain the designed performance. Therefore， SF6 gas leakage detection is not only an environmental protection requirement， but also an important part of the safe operation management of power equipment.
On the other hand, SF6 gas itself is a greenhouse gas with a high greenhouse effect potential. Therefore, while using SF6 gas in the power industry, it is necessary to ensure proper equipment sealing, leak detection, maintenance management, and recycling treatment to minimize the disorderly emission of the gas. For power equipment already in operation, timely detection of leakage points is more proactive than waiting for a significant drop in gas pressure before handling.
In actual operation and maintenance, SF6 gas leakage detection mainly includes portable detection and online monitoring methods. Portable SF6 leak detectors are suitable for personnel to conduct point-by-point inspections of equipment exteriors, flanges, valves, joints, etc. This method is highly flexible, but the detection effect is related to personnel experience, detection routes, and on-site conditions.
Online monitoring is another approach. By configuring monitoring devices in the equipment area or related installation locations, continuous collection of SF6 gas concentration and other information is carried out. When the monitoring value reaches the set alarm conditions, the system promptly issues an alarm signal to remind maintenance personnel to check the equipment status. For relatively enclosed places such as GIS rooms and SF6 switch rooms, continuous monitoring is particularly significant.
The LD70 SF6 gas leakage online monitoring and alarm system produced by Wuhan Guodian Xigao Electric Co., Ltd. is a device designed for SF6 gas leakage monitoring needs. This system can be used for SF6 gas leakage monitoring in related power equipment areas and promptly alarms when abnormal situations are detected, helping maintenance personnel to detect potential leakage problems as early as possible. For substations and related power places that use SF6 gas as an insulating or arc extinguishing medium, continuous monitoring can serve as an important auxiliary means for daily operation management.
It should be noted that SF6 gas leakage online monitoring cannot completely replace on-site leak detection. Online monitoring is more suitable for continuous monitoring and abnormal alarm functions, and when the system indicates an abnormal situation, it is still necessary to combine portable leak detection equipment, equipment gas pressure or density data, and on-site inspections to further confirm the specific leakage location. The combination of the two methods is usually more suitable for actual operation and maintenance work.
From the perspective of the development of power equipment, the reason why SF6 gas can be used for a long time is mainly due to its excellent insulation and arc extinguishing performance. For high-voltage and ultra-high-voltage switchgear equipment, these properties can help the equipment achieve a high electrical safety margin within a limited space and meet the requirements for high-voltage breaking. However, at the same time, the use of SF6 gas also poses higher requirements for equipment sealing, operation monitoring, and maintenance management.
In simple terms, SF6 gas is not an ordinary “filling gas”, but a medium that performs important electrical functions in high-voltage power equipment. Understanding what SF6 gas is, why SF6 gas is used, and why SF6 gas leakage needs to be monitored is of practical significance for personnel engaged in substation operation and maintenance, GIS equipment maintenance, and high-voltage electrical testing.
As the monitoring of the operating status of power equipment continues to strengthen, SF6 gas leakage detection will increasingly focus on continuous, digital, and intelligent aspects. For power equipment using SF6 gas, it is necessary to manage the gas state, conduct leak detection, and issue abnormal alarms during the equipment operation process, promptly handle potential problems, and reduce the impact of equipment failures and gas leakage. The LD70 SF6 gas leakage online monitoring and alarm system produced by Wuhan Guodian Xigao Electric Co., Ltd. can be used as a device option for SF6 gas leakage online monitoring scenarios. When selecting, it should be configured based on the equipment type, installation environment, and monitoring requirements.
Post time: Sep-21-2026