CN101435734A

CN101435734A - Method for detecting transformer on-load tap changer insulating oil leakage by SF6 gas

Info

Publication number: CN101435734A
Application number: CNA2008102309832A
Authority: CN
Inventors: 王俊良; 曾定文; 白慧芳; 王振方; 段利伟; 郑俊阳; 杨海峰; 牛宇干
Original assignee: Pingdingshan Power Supply Co of State Grid Henan Electric Power Co Ltd
Current assignee: Pingdingshan Power Supply Co of State Grid Henan Electric Power Co Ltd
Priority date: 2008-11-11
Filing date: 2008-11-11
Publication date: 2009-05-20

Abstract

The invention relates to a method for detecting leakage of insulating oil in an on-load tapping switch of a transformer by using SF6 gas, which comprises the following steps: firstly, calculating volume of the SF6 gas in the insulating oil added to the on-load tapping switch; adding the SF6 gas to the insulating oil for the on-load tapping switch according to a calculated value; selecting an oil sample of transformer body oil; and using a gas chromatograph to carry out chromatographic analysis for the selected oil sample of the transformer body oil. If the SF6 gas is detected out, which proves that the on-load tapping switch leaks the insulating oil; and if no SF6 gas is detected out, which proves that the on-load tapping switch does not leak the insulating oil. The method determines the problem of oil leakage of the on-load tapping switch by using an indirect method to avoid occurrence of misjudgment accidents, can judge failure property and approximate position inside equipment to provide reliable scientific basis for maintenance work, reduce unplanned power failure and limited loading time of a transformer, greatly reduce economic expenditure on manpower, physical resources and materials, and reduce labor intensity, insecurity factors and the like.

Description

Utilize SF 6The method of gas detection transformer on-load tap changer insulating oil leakage

Technical field

The present invention relates to a kind of detection method, refer to a kind of SF of utilization especially ₆The method of gas detection transformer on-load tap changer insulating oil leakage.

Background technology

The visual plant that transformer is regulated as electric pressure in the electric system, along with development of electric power industry, the above power transformer major part of 35kV has all been installed on-load tap changer, its action accurately rapidly, can reduce with the fluctuation of burning voltage, can force the distribution load electric current, thereby guarantee the power grid security reliability service.

But because some load ratio bridging switch has defective at aspects such as design, technology, material, installation, maintenances, its fault probability is increased, wherein the insulating oil in the shunting switch all has generation to transformer body seepage phenomenon at many power departments, easily cause accident illusions such as transformer internal discharge, brought many troubles for work about electric power person, correct judgement transformer internal operation situation caused have a strong impact on, influenced normal electric power safety production.The method of judging the transformer internal leak at present mainly is to adopt the method for the back manual detection breakthrough that has a power failure, and has not only increased unplanned frequency of power cut, has also increased corresponding maintenance cost.

Summary of the invention

The purpose of this invention is to provide the unplanned frequency of power cut of a kind of minimizing, avoid judging by accident disconnected generation, the differentiating transformer internal fault utilizes SF accurately ₆The method of gas detection sub-connecting switch of transformer insulating oil leakage.

For achieving the above object, the technical solution used in the present invention is: a kind of SF that utilizes ₆The method of gas detection transformer on-load tap changer insulating oil leakage, step is as follows:

Step 1, according to transformer body oil, on-load tap changer insulating oil weight in the transformer, according to SF ₆Add SF in gas stable detection concentration 20 μ L/L and the insulating oil ₆The maximum volume number percent of gas is 6%, is calculated as follows respectively to add SF in the on-load tap changer insulating oil ₆The minimum volume of gas and maximum volume:

V＝(M ₁+M ₂)÷0.89×20×10 ^-6

V′＝M ₂÷0.89×6％

In the formula: minimum volume, the L of unit of adding of V-SF6 gas;

M ₁-be transformer body weight of oil, unit K g;

M ₂-be transformer loaded switch weight of oil, unit K g;

Maximum volume, the L of unit of adding of V '-SF6 gas;

Step 2, select qualified, new SF for use ₆Gas joins in the on-load tap changer insulating oil, and its addition is less than or equal to the maximum adding quantity that calculates in the step 1 greater than the minimum addition of calculating in the step 1;

Step

3,2 add SF set by step ₆The transformer operation of gas was got the oil sample of transformer body oil after one month;

Step 4, the transformer body oil oil sample that step 3 is chosen carry out stratographic analysis;

When using gas chromatographic analysis, select the stainless-steel tube of long 2m, internal diameter 3mm for use, inner filling 60～80 purpose GDX～104 carriers are made into into SF ₆The gas analysis chromatographic column; Select for use hydrogen to do carrier gas, use gas chromatograph to analyze.

Use liquid-phase chromatographic analysis, directly the sample oil sample is analyzed.

Step 5, judge according to the testing result of step 4:

If detect SF ₆Gas illustrates on-load tap changer insulating oil leakage in transformer body oil, simultaneously according to detected SF ₆Gas concentration can be judged the speed of seepage;

If do not detect SF ₆Gas illustrates that on-load tap changer insulating oil does not leak in the transformer body oil.

The above-mentioned SF that utilizes ₆The method of gas detection transformer on-load tap changer insulating oil leakage, the described SF of step 1 ₆Gas stable detection solubility 20 μ L/L determine as follows:

SF in a, the carrier gas ₆Determining of minimum detectable concentration:

Choose the 100mL syringe of 7 smooth, cleanings, good seal, get hydrogen 100mL respectively, use the micro syringe of 10 μ L then, in 7 syringes, add the pure SF of 5 μ L, 4 μ L, 3 μ L, 2.5 μ L, 2 μ L, 1.5 μ L, 1 μ L respectively ₆Gas, being mixed with concentration respectively is 50 μ L/L, 40 μ L/L, 30 μ L/L, 25 μ L/L, 20 μ L/L, 15 μ L/L, 10 μ L/L SF ₆Sample gas extracts the gas sample of 0.5mL then respectively, and utilizing chromatograph to identify the minimum detection limit is 20 μ L/L.

SF in b, the insulating oil ₆Determining of minimum detectable concentration:

Choose the 100mL syringe of 7 smooth, cleanings, good seal, get new insulating oil 100mL respectively, use the micro syringe of 10 μ L then, the concentration that adds 5 μ L, 4 μ L, 3 μ L, 2.5 μ L, 2 μ L, 1.5 μ L, 1 μ L respectively in 7 syringes is 10 ⁶The pure SF of μ L/L ₆Gas, being mixed with concentration respectively is 50 μ L/L, 40 μ L/L, 30 μ L/L, 25 μ L/L, 20 μ L/L, 15 μ L/L, 10 μ L/L SF ₆Sample solution extracts the oil sample of 0.5mL then respectively, and utilizing chromatograph to identify the minimum detection limit is 20 μ L/L.

Add SF in the described insulating oil ₆The maximum volume number percent of gas is 6% to be to determine according to following method: according to " transformer analysis and diagnosis " as can be known, the volume content of gas is about 10% of insulating oil volume in the oil; The volume ratio of gas content of oil of insulating after tested is 4%, determines the SF that adds in on-load tap changer insulating oil ₆The volume of gas mostly is 6% most.

The above-mentioned SF that utilizes ₆The method of gas detection transformer on-load tap changer insulating oil leakage is characterized in that: the described adding of step 2 SF ₆The purity of gas 〉=99.99%.

The invention has the beneficial effects as follows:

Because SF ₆Gas has good physicochemical property, not so, strong, the arc extinguishing ability height of not quick-fried, insulating capacity, and stable chemical performance, under red-hot temperature, do not react with other many materials such as oxygen, argon gas, aluminium, its decomposition temperature: 2000 ℃, being 19 times of 105 ℃ of insulating oil decomposition temperatures, is a kind of UHV (ultra-high voltage) insulating medium material of new generation that is better than the sky G﹠O.So SF ₆Gas is the optimal gas of differentiating the load ratio bridging switch seepage.

Utilize SF ₆The method of gas detection transformer internal leak defines the on-load shunting switch leakage problems, and electrical network economy, safe operation are had far reaching significance, can carry out under situation about not having a power failure, and is time saving and energy saving:

1, avoided the generation of the disconnected accident of erroneous judgement;

2, unplanned power failure of transformer and restriction duration of load application have been reduced;

3, greatly reduce the economy expenditure of human and material resources, material power;

4, labour intensity and unsafe factor etc. have been reduced.

The present invention is described in further detail below in conjunction with the drawings and specific embodiments:

Description of drawings

Fig. 1 is a process chart of the present invention

Fig. 2 is SF of the present invention ₆Gas standard specimen stratographic analysis spectrogram

Fig. 3 is SF of the present invention ₆Sample gas is prepared 20 μ L/L stratographic analysis spectrograms

Fig. 4 is SF of the present invention ₆Sample solution is prepared 20 μ L/L stratographic analysis spectrograms

Embodiment

As shown in Figure 1, a kind of SF that utilizes ₆The method of gas detection transformer on-load tap changer insulating oil leakage, step is as follows:

V＝(M ₁+M ₂)÷0.89×20×10 ^-6

V′＝M ₂÷0.89×6％

In the formula: minimum volume, the L of unit of adding of V-SF6 gas;

M ₁-be transformer body weight of oil, unit K g;

M ₂-be transformer loaded switch weight of oil, unit K g;

Maximum volume, the L of unit of adding of V '-SF6 gas;

Step

Step 5, judge according to the testing result of step 5:

The described SF of step 1 ₆Gas stable detection solubility 20 μ L/L determine as follows:

SF in a, the carrier gas ₆Determining of minimum detectable concentration:

Choose the 100mL syringe of 7 smooth, cleanings, good seal, get hydrogen 100mL respectively, use the micro syringe of 10 μ L then, in 7 syringes, add the pure SF of 5 μ L, 4 μ L, 3 μ L, 2.5 μ L, 2 μ L, 1.5 μ L, 1 μ L respectively ₆Gas, being mixed with concentration respectively is 50 μ L/L, 40 μ L/L, 30 μ L/L, 25 μ L/L, 20 μ L/L, 15 μ L/L, 10 μ L/L SF ₆Sample gas; Extract the gas sample of 0.5mL then respectively, utilizing chromatograph to identify the minimum detection limit is 20 μ L/L.

SF in b, the insulating oil ₆Determining of minimum detectable concentration:

Choose the 100mL syringe of 7 smooth, cleanings, good seal, get new insulating oil 100mL respectively, use the micro syringe of 10 μ L then, the concentration that adds 5 μ L, 4 μ L, 3 μ L, 2.5 μ L, 2 μ L, 1.5 μ L, 1 μ L respectively in 7 syringes is 10 ⁶The pure SF of μ L/L ₆Gas, being mixed with concentration respectively is 50 μ L/L, 40 μ L/L, 30 μ L/L, 25 μ L/L, 20 μ L/L, 15 μ L/L, 10 μ L/L SF ₆Sample solution; Extract the oil sample of 0.5mL then respectively, utilizing chromatograph to identify the minimum detection limit is 20 μ L/L.

The described adding of step 2 SF ₆The purity of gas 〉=99.99%.

Determine to add in the transformer insulation oil SF ₆Gas is to realize prerequisite of the present invention to the influence of oil and the amount of adding, for implementing the present invention, at first determines SF in the insulating oil ₆Gas partition coefficient, gas chromatograph are to SF ₆The minimum detection limit of gas sample is identified to add SF simultaneously ₆Gas is to the oil of insulating oil.

At first as follows to SF in the insulating oil ₆The partition factor of gas is measured:

1, gets new insulating oil 500mL as blank oil.

2, draw blank oily 20mL, the SF of the 20mL that reinjects with the 100mL syringe ₆Gas is placed in constant temperature and is in 50 ℃ the shaker, after the vibration balance, takes out whole balanced gas, and analyzes SF ₆Gas concentration sees table one for details.

3, after first time balance, inject the 20mL pure hydrogen in the syringe oil sample and do carrier gas, be placed in constant temperature and be in 50 ℃ the shaker and carry out vibration second time, after the balance of vibrating, take out whole balanced gas, and read gas volume accurately, analyze SF then ₆Gas concentration sees Table one mutually.

4, measure formula according to gas partition coefficient in the insulating oil in the GB/T 17623-1998 gas Chromatographic Determination method and calculate SF ₆Gas is partition factor in insulating oil, sees table one for details.

SF in table one insulating oil ₆The mensuration table of gas partition coefficient

According to different SF ₆Gas concentration is measured gas chromatograph to SF ₆The minimum detection limit of gas sample:

According to law:

(1) equivalent theorem: M ₁V ₁=M ₂V ₂

(2), gas molecule diffusion theory: as can be known by molecular motion of material, because the molecule of the object that is in contact with one another is irregularly to move, so these molecules will be crossed the contact of object naturally and infiltrate each other, spontaneously mix up mutually, form diffusion phenomena.

(3) distribution law: when solute is dissolved in two kinds of immiscible or mixing materials of mixing hardly simultaneously respectively, its concentration ratio in the solvent of two kinds of liquid has a definite value or approaches a definite value, this definite value approximates the ratio of solute solubleness in two kinds of liquid fluxs, wherein said proportionate relationship is called partition factor.

With reference to Fig. 2

Determine the SF of purity 〉=99.99% with SP-3430 type gas chromatograph ₆The appearance time of gas, go out peak area and concentration.

With reference to Fig. 3, table two

SF to variable concentrations ₆The gas sample carries out stratographic analysis:

Choose the 100mL syringe of 7 smooth, cleanings, good seal, get hydrogen 100mL respectively, use the micro syringe of 10 μ L then, in 7 syringes, add the pure SF of 5 μ L, 4 μ L, 3 μ L, 2.5 μ L, 2 μ L, 1.5 μ L, 1 μ L respectively ₆Gas, being mixed with concentration respectively is 50 μ L/L, 40 μ L/L, 30 μ L/L, 25 μ L/L, 20 μ L/L, 15 μ L/L, 10 μ L/L SF ₆Sample gas.Extract respectively then in the gas sample injecting chromatograph of 0.5mL, identifying the minimum detection limit is 20 μ L/L.

The SF6 gas sample stratographic analysis of table two variable concentrations is table as a result

By table two and Fig. 3 as can be seen:

1, SF ₆The data deviation that gas sample concentration and chromatograph test out is bigger.According to the gas molecule diffusion theory as can be known, the object molecule that is in contact with one another can infiltrate each other, spontaneously mix up mutually, but because SF ₆Molecular weight gas is big, easily sinks, and works as SF ₆When gas and diluents mix up mutually, the skewness phenomenon will occur, and cause the test figure deviation.

2, the minimum detection limiting concentration of SF6 gas sample should be 20 μ L/L.

With reference to Fig. 4, table three

SF to different volumes concentration ₆The insulating oil sample solution carries out stratographic analysis:

Choose the 100mL syringe of 7 smooth, cleanings, good seal, get new insulating oil 100mL respectively, use the micro syringe of 10 μ L then, in 7 syringes, add the pure SF of 5 μ L, 4 μ L, 3 μ L, 2.5 μ L, 2 μ L, 1.5 μ L, 1 μ L respectively ₆(concentration is 10 to gas ⁶μ L/L), being mixed with concentration respectively is 50 μ L/L, 40 μ L/L, 30 μ L/L, 25 μ L/L, 20 μ L/L, 15 μ L/L, 10 μ L/L SF ₆Sample solution.Extract respectively then in the oil sample injecting chromatograph of 0.5mL, identifying the minimum detection limit is 20 μ L/L.

The SF of table three different volumes concentration ₆The insulating oil sample solution carries out the stratographic analysis result

By table three and Fig. 4 as can be seen:

1, SF ₆Sample solution concentration and chromatograph are analyzed data error and are met the guide rule regulation, and this illustrates SF ₆Gas is in solvable and the insulating oil.

2, as shown in Table 3: SF ₆The minimum detection limit of gas sample should be 20 μ L/L.

According to the test result of above gas sample and oil sample, can determine that gas chromatograph is to SF ₆The minimum detection limiting concentration of gas sample is about 20 μ L/L.

The SF of variable concentrations ₆The oily situation of oil sample sees Table four:

Table four: the oily situation of the SF6 oil sample of variable concentrations

By the oily test figure of table four as can be known: the SF that in oil, mixs up variable concentrations ₆During gas, its SF ₆Oil sample meets the requirement of insulating oil GB.

Embodiment 1

With 50 tons of transformer body oil, shunting switch insulating oil is example for 500 kilograms:

Step 1, determine the SF that in load ratio bridging switch, adds ₆Gas flow:

According to SF ₆Add SF in gas stable detection solubility 20 μ L/L and the insulating oil ₆The maximum volume number percent of gas is 6%, is calculated as follows SF in the on-load tap changer insulating oil respectively ₆The minimum volume of gas and maximum volume:

V＝(M ₁+M ₂)÷0.89×20×10 ^-6

＝(50000+500)÷0.89×20×10 ^-6＝1.1(L)

V′＝M ₂÷0.89×6％＝500÷0.89×6％＝33.7(L)

In the formula: minimum volume, the L of unit of adding of V-SF6 gas;

M ₁-be transformer body weight of oil, unit K g;

M ₂-be transformer loaded switch weight of oil, unit K g;

Maximum volume, the L of unit of adding of V '-SF6 gas;

Owing to add the SF of minimum volume in the on-load tap changer insulating oil ₆During gas, the insulating oil in the load ratio bridging switch all leaks in the transformer body oil, SF in the transformer body oil ₆The volumetric concentration of gas is 20 μ L/L, but this in practice situation is impossible, therefore, in real work, adds SF ₆To be far longer than the minimum volume amount during gas, general near or equal the maximum volume amount.

Add 33.7L SF in the 500kg loaded tap switch oil ₆During gas, its concentration is: 60000 μ L/L.

Step 2, to select qualified purity for use be 99.99% new SF ₆Gas adds 33.7L in on-load tap changer insulating oil;

Step

3,2 add SF set by step ₆The transformer operation of gas was got the oil sample of transformer body oil after one month; And according to one month serial sampling interval time 3 times;

Determine that how many times are leakage be, chromatograph just has response: promptly: the transformer of 50 tons of transformer body oil, and needing how many mL content of seepage is the shunting switch oil of 60000 μ L/LSF6, chromatograph just has response:

According to equivalent law M ₁V ₁=M ₂V ₂Can calculate minimum leakage V ₁:

60000×V1＝20×50000÷0.89

Minimum leakage V ₁=18.7L

So when load ratio bridging switch oil seepage amount was 18.7 liters, chromatograph just had response, that is to say in 18.7 liters of transformers that are dissolved in 50 tons of oil the SF of 50 tons of oil ₆Content is 20 μ L/L, sampling this moment, and chromatograph can detect SF ₆Content determines that shunting switch has breakthrough.

Step 4, select the stainless-steel tube of long 2m, internal diameter 3mm for use, inner filling 60～80 purpose GDX～104 carriers are made into into SF ₆The gas analysis chromatographic column; Select for use hydrogen to do carrier gas, use gas chromatograph, the transformer body oil oil sample that step 3 is chosen carries out gas chromatographic analysis;

Earlier chromatograph is demarcated, to the oil sample degassing of vibrating, after the vibration balance, taken out whole balanced gas, and read gas volume accurately again, get 0.5mL gas sample injecting chromatograph then,, differentiate SF by thermal conductance assessor at last through chromatographic column ₆Whether gas exists, and calculates SF accurately ₆Content.

Serial sampling 3 times, analysis result is: 0 μ L, 0 μ L, 15 μ L;

Step 5, judge according to the testing result of step 4:

The result of the testing result of step 4 shows: all do not detect SF preceding twice ₆Gas illustrates that on-load tap changer insulating oil does not have or SF is seldom arranged ₆Gas permeation detects SF the 3rd time in transformer body oil ₆Gas illustrates on-load tap changer insulating oil leakage in transformer body oil, in case detect SF from transformer body oil ₆Gas just needs to shorten the sample interval, and one month the time interval changes 10 days into takes a sample once or took a sample once in 1 day, analyzes the speed of determining seepage.

Embodiment 2

Select 110kV to build transformer station, the transformer model is: SFZLB-31500/110, appearance is numbered: 818L06-1.This transformer put into operation from 8 or three years, found that at run duration the heavy 400kg of the oil of load ratio bridging switch suspects that the loaded tap switch oil chamber is toward the body seepage;

Step 1: determine SF ₆The addition of gas:

The volume of load ratio bridging switch: 400 * 0.89=449L

The addition of SF6 gas: 449 * 6%=27L

Step 2: the SF that in loaded tap switch oil, injects 27L ₆Gas:

Selecting purity is 99.99% SF ₆Gas and minute adjustment valve connect with stainless-steel tube, an edge joint SF ₆The reduction valve delivery outlet, Yi Bian link to each other with the gas relay deflating valve of load ratio bridging switch.Regulate accurate needle-valve, make SF ₆Gas flow rate is controlled at 125ml/min, is convenient to SF ₆Gas slowly is dissolved in the oil uniformly.Continuous charge 4 hours reaches SF ₆The quantitative really 27L of gas.

Step 3: gather oil sample, prepare SF ₆Gas permeation is analyzed, and injects SF ₆Gas begins sampling after one day, according to one day time interval serial sampling 10 times;

Step 4: make SF ₆The gas analysis chromatographic column; The transformer body oil sample that step 3 was gathered in continuous 10 days carries out gas chromatographic analysis, and concrete analysis the results are shown in following table:

Date of test	2008. 03.04—10	2008. 03.11	2008. 03.12	2008. 03.13
Date of test	2008. 03.04—10	2008. 03.11	2008. 03.12	2008. 03.13	SF6 gas content μ L/L	0	Trace	Trace	13.6

Step 5: by the analysis result of step 4 as can be known, the on-load tap changer insulating oil of transformer is seepage in transformer body oil.

The present invention utilizes round-about way to define the on-load shunting switch leakage problems, and electrical network economy, safe operation are had far reaching significance: avoided the generation of erroneous judgement accident; Can be according to test data, judgment device internal fault character and Position Approximate are for service work provides reliable scientific basis; Unplanned power failure of transformer and restriction duration of load application have been reduced; Greatly reduce the economy expenditure of human and material resources, material power; Labour intensity and unsafe factor etc. have been reduced.

Along with improving constantly of gas chromatographic analysis precision, utilize SF ₆The minimum detectable concentration of the method for gas detection transformer on-load tap changer insulating oil leakage will be reduced gradually by 20 μ L/L, and so, the mensuration of the minimum leakage of on-load tap changer insulating oil will reduce.Even if a small amount of seepage is arranged also can be measured.More help of the present invention applying.

Claims

1, a kind of SF that utilizes ₆The method of gas detection transformer on-load tap changer insulating oil leakage is characterized in that: step is as follows:

V＝(M ₁+M ₂)÷0.89×20×10 ^-6

V′＝M ₂÷0.89×6％

In the formula: minimum volume, the L of unit of adding of V-SF6 gas;

M ₁-be transformer body weight of oil, unit K g;

M ₂-be transformer loaded switch weight of oil, unit K g;

Maximum volume, the L of unit of adding of V '-SF6 gas;

Step 3,2 add SF set by step ₆The transformer operation of gas was got the oil sample of transformer body oil after one month according to certain time interval;

Step 5, judge according to the testing result of step 5:

2, according to the described SF that utilizes of claim 1 ₆The method of gas detection transformer on-load tap changer insulating oil leakage is characterized in that: the described SF of step 1 ₆Gas stable detection solubility 20 μ L/L determine as follows:

SF in a, the carrier gas ₆Determining of minimum detectable concentration:

Choose the 100mL syringe of 7 smooth, cleanings, good seal, get hydrogen 100mL respectively, use the micro syringe of 10 μ L then, in 7 syringes, add the pure SF of 5 μ L, 4 μ L, 3 μ L, 2.5 μ L, 2 μ L, 1.5 μ L, 1 μ L respectively ₆Gas, being mixed with concentration respectively is 50 μ L/L, 40 μ L/L, 30 μ L/L, 25 μ L/L, 20 μ L/L, 15 μ L/L, 10 μ L/L SF ₆Sample gas extracts the gas sample of 0.5mL then respectively, and utilizing chromatograph to identify the minimum detection limit is 20 μ L/L;

SF in b, the insulating oil ₆Determining of minimum detectable concentration:

Choose the 100mL syringe of 7 smooth, cleanings, good seal, get new insulating oil 100mL respectively, use the micro syringe of 10 μ L then, the concentration that adds 5 μ L, 4 μ L, 3 μ L, 2.5 μ L, 2 μ L, 1.5 μ L, 1 μ L respectively in 7 syringes is 10 ⁶The pure SF of μ L/L ₆Gas, being mixed with concentration respectively is 50 μ L/L, 40 μ L/L, 30 μ L/L, 25 μ L/L, 20 μ L/L, 15 μ L/L, 10 μ L/L SF ₆Sample solution extracts the oil sample of 0.5mL then respectively, and utilizing chromatograph to identify the minimum detection limit is 20 μ L/L;

3, according to the described SF that utilizes of claim 1 ₆The method of gas detection transformer on-load tap changer insulating oil leakage is characterized in that: the described adding of step 2 SF ₆The purity of gas 〉=99.99%.