Detection method and treatment measure of sulfur hexafluoride gas 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

Detection method and treatment measure of sulfur hexafluoride gas leakage

发布时间：2019-12-16 来源：ydlcb 浏览次数：34次

Abstract: At present, high voltage switchgear generally uses SF6 gas with excellent arc extinguishing performance and high insulation strength as the arc extinguishing and insulation medium, but from the running situation, SF6 gas leakage is still one of the main defects of such equipment. This paper uses a combination of various leak detection methods to carry out leak detection work on the equipment to determine the specific leak point, summarizes the experience of SF6 gas leakage management of the power substation equipment in operation, combined with the problems in the field leak detection and gas supplement, puts forward the corresponding precautions, and examples the practical problems encountered in the maintenance work, and then analyzes the corresponding treatment measures.

Key words: sulfur hexafluoride; Air leakage; Detection

introduction

High voltage SF6 circuit breakers, combined electrical appliances currently occupy the field of high voltage and ultra-high pressure, SF6 gas is an excellent arc extinguishing and insulating medium, colorless, tasteless, non-toxic, will not burn, stable performance, and has a good arc extinguishing performance, so it is widely used in the power grid. From the perspective of operation, at the beginning of operation, despite the adoption of various detection means and sealing processes, SF6 gas leakage is still a major defect, which may cause insulation breakdown and equipment rejection. Therefore, leak detection and treatment of leak points have become important maintenance items of SF6 equipment. This paper analyzes the detection methods and treatment measures on actual cases.

1. Air leakage caused by damaged gaskets

1.1 Event Process

220kV combined electrical equipment in a substation was put into operation on September 24, 2014. On January 1, 2015, the pressure of the 220kV high pressure casing chamber of the No. 2 main transformer was reduced to the alarm value, and the alarm was lifted after the maintenance personnel made up the pressure to the rated pressure. On January 6, 2015, the pressure of the air chamber fell below the alarm value again, and the maintenance personnel judged that there was gas leakage in the air chamber. Through various methods to verify the gas leakage location, it is determined that there is a gas leakage phenomenon at the D-type inflation junction of the B-phase high-pressure casing gas chamber on the 220kV side of the No. 2 main transformer. The position of air leakage is analyzed carefully, and the causes of air leakage and corresponding elimination schemes are determined. After opening the inflation interface, it is found that the valve gasket is badly sealed and the gasket is damaged. After replacing the gasket, the air leakage defect disappears.

1.2 Detection Methods

When the maintenance personnel used SF6 infrared imaging detector to detect the leakage of the connected part of the equipment body, the suspected gas leakage image appeared at the D-type inflation interface of the B-phase high-pressure casing gas chamber on the 220kV side of the No. 2 main transformer, as shown in Figure (1) and (2).

The suspected points were further analyzed and confirmed, and various verification methods were used to determine the specific gas leakage points. The traditional contact leak detector is used again to detect the leak in the high pressure casing gas chamber. After a comprehensive leak detection on the site, an alarm signal also appeared at the D-type inflation junction of the B-phase high-pressure casing gas chamber on the 220kV side of the No. 2 main transformer.

Then the foam method was used to verify it, as shown in Figure (3). Apply soapy water in the suspected location, and judge the leakage point of the equipment by using the characteristics of soapy water that is easy to bubble. As a result, bubbling phenomenon appeared, which verified the gas leakage phenomenon again.

1.3 Defect Treatment

After determining the location of the air leakage point, the maintenance personnel first tighten the interface screws at this place with pipe pliers. After tightening this place to check, there is still an alarm signal, indicating that the field leakage phenomenon has not been eliminated. It indicates that the cause is not unsecured. Secondly, open the air chamber inlet seal and observe the sealing ring. Breakage of the sealing ring was observed on site, such as (4)

After replacing the sealing ring, the equipment runs normally, no air leakage occurs, and the equipment defect is eliminated. Therefore, it can be determined that the defect of the equipment leakage is caused by the damage of the sealing ring. According to the analysis of the damage of the sealing ring, the sealing ring may be stressed unevenly during the installation process, and the sealing ring will gradually age and be damaged after one year of operation due to weather changes and poor operating conditions.

Figure (1) Gas leakage point Figure (2) visible light image of gas leakage

Figure (3) Foam method to verify the leak point Figure (4) broken seal ring

2. The circuit breaker has air leakage caused by sand holes

2.1 Event Process

From June 2015 to September 2015, the substation maintenance personnel dealt with the low pressure alarm of the porcelain pillar circuit breaker outside the 110kV room of a substation. The conventional contact leak detection equipment was used to detect the leakage of the equipment, but the leak point was not found. Thirdly, the trachoma defect at the bottom of C-phase porcelain column was detected successfully through the mutual application of other leak detection methods, and the treatment measures and programs were developed in turn to successfully eliminate the defect.

2.2 Detection Method

The initial maintenance personnel used the traditional contact leak detector to detect the leakage of the circuit breaker, but failed to find the leakage defect of the circuit breaker. However, the equipment frequently appears low pressure alarm, suspected of air leakage defects.

After arriving at the site, the equipment will be tested from the bottom up, as shown in Figure (5). From the lower side of the circuit breaker, the gas valve, the connecting pipe, and the whole porcelain column casing body, the leak detection work has been carried out, but there is no alarm signal. Then the circuit breaker is tested by bandaging method. The casing bonding part on the upper side, the circuit breaker connecting the pipe on the lower side, the density relay, the inflation interface, and the porcelain column are respectively arranged

Figure (5) Casing body inspection Figure (6) trachoma defect inspection at the bottom

Wrap the bottom. After standing for a period of time, the gas in the dressing is detected. An alarm signal appears in the inner wrap at the bottom of the C-phase porcelain column. In order to further determine the specific position, the foam method was used to detect the part, as shown in FIG. (6), the foaming phenomenon appeared at the bottom side of the C-phase porcelain column. It was also confirmed by the leak detector that there was a gas leakage phenomenon.

2.3 Defect Treatment

After determining the location of the air leakage, the cause is analyzed according to the phenomenon. The air leakage is the plane poured at the bottom, not the sealing surface or the connection part, so it can be judged that there is an air leakage defect in the plane position of the pouring. The surface of the poured plane is flat without cracks, and it is suspected that there is a sand hole defect causing air leakage. Because the position of the air leak and the C-phase circuit breaker body is cast in one piece, the parts can not be replaced, it is recommended to replace the porcelain column of the circuit breaker as a whole. In December, according to the reported plan, the circuit breaker was replaced as a whole. After the replacement, the equipment was tested and no alarm signal was found. After running for a period of time, the equipment does not appear low pressure alarm signal, indicating that the equipment defect has been eliminated.

3. Combination of multiple leak detection methods

According to the practical experience of field work, the daily leak detection methods are summarized, respectively: SF6 leak detector, soap bubble method, local bandage method. Each leak detection method has its own advantages, but all have related limitations. However, each leak detection method can be used together to ensure the normal development of our work.

3.1 The SF6 leak detector is used for leak detection

The common SF6 leak detector is a contact leak detector. The air inlet of the leak detector is placed in different positions of the electrical equipment to detect the SF6 concentration in the gas near it. After reaching the alarm value, the alarm shows that there is gas leakage.

At present, the SF6 infrared gas leak detection imager has begun to be popularized, which can realize the detection of SF6 gas operating equipment at a distance and realize the on-line detection. At the same time, the leak scene is directly displayed on the screen, which is easy to observe and judge.

3.2 Apply the soap bubble method to detect leaks

Soap bubble method for leak detection is to apply soapy water to the suspected location of the equipment, and use the soapy water easy to bubble to determine the leakage point of the equipment. But the soap leak detection method can only find more obvious leakage defects. It is usually used in conjunction with the leak detector, that is, the leak point is detected by the leak detector (SF6 leak detector alarm) and then the leak is detected by soap bubbles.

3.3 Local bandaging method is adopted for leak detection

Local bandage method leak detection, that is, the equipment is wrapped with a complete film, so that the equipment is in a sealed environment, after a period of time, the leak detector is used to detect the gas in the film to determine whether there is leakage. However, this detection method can not measure the leakage rate, which is very difficult in practice. The volume value of each part is not easy to obtain accurately; The uncertainty of the volume must mislead the measurement results of the annual gas leakage rate.

3.3 Summary and application

Practice has proved that the actual effect of only one leak detection method is not satisfactory, so several methods can be used for comprehensive detection. The leak detector, soap bubble method and local dressing method are combined to find out an ideal leak detection program step by step. Choose a leak detector to detect the leak, detect the leak point (leak detector alarm) with soap bubble to detect the leak, if still can not detect the leak point, and then use the local bandage method to detect the leak. And began to use a new type of leak detector to judge gradually.

Closing remarks

Through the use of different detection methods, the equipment can be effectively detected by air leakage. Therefore, when testing the equipment, it is necessary to cooperate with each other to make up for the complete detection of the equipment. And in practical application, all kinds of difficult defects are effectively dealt with. With the progress of science and technology, more and more advanced technologies will be applied to gas detection work. In the future, there will be a variety of detection means and equipment, and various detection methods and methods will gradually complete the detection work of the equipment.

References:

[1] "High Pressure SF6 equipment supplementary gas working procedure (J)" CAI Zhenwen Electric World 2009 (4) : 26 ~ 27

[2] "Circuit Breaker leakage and water exceeding standard treatment (J)" Chen Guoqing Shanghai Electric Power 2003 (3) : 267-268

[3] "Substation Maintenance" Human Resources Department of State Grid Corporation organized China Electric Power Press 442-449.