CN104502488A - Method for evaluating insulation aging degree of oil-immersed type power transformer - Google Patents

Abstract

The invention provides a method for evaluating the insulation aging degree of an oil-immersed type power transformer. By comprehensive consideration for multiple aging parameters such as the operating temperature, the content of gas in oil, the content of furfural and the concentration of corrosive sulfide of the transformer, the accuracy of a discrimination result is guaranteed. The method mainly comprises the following steps: detecting the content of gas dissolved in the oil and calculating the polymerization degree; measuring the content of the furfural in the oil and calculating the polymerization degree; determining the operating temperature and calculating the polymerization degree; measuring the initial content of dodecanethiol and DBDS in the oil and calculating the influence and the action on the decreasing rate of the polymerization degree of insulation paper; weighting and calculating the polymerization degree calculated according to all aging characteristic quantities, thus obtaining the polymerization degree of the insulation paper, and evaluating the insulation-aging condition. The method provided by the invention has the advantages that the basic principle is simple, the operability is strong, and the problems of inaccuracy and limitation of aging evaluation by single characteristic parameter are effectively solved; multiple parameters are introduced for combined evaluation of the aging, so that the accuracy and the truth of the result are guaranteed, and the method has important practical application significance for evaluating the insulation aging and the service life of oiled paper.

Description

A kind of method of oil-immersed power transformer insulation ag(e)ing scale evaluation

Technical field

The present invention relates to transformer oil paper insulation life appraisal and Forecasting Methodology, particularly a kind of method of oil-immersed power transformer insulation ag(e)ing scale evaluation.

Background technology

Power equipment safety is the most important thing of defeated change distribution network even running, and device security is mainly insulation safety.Huge economic loss is brought in order to avoid blindly changing, and without running the potential safety hazard caused according to continuation, be necessary to utilize modern technologies and analysis means to carry out real-time assessment to the degree of aging of in-service Electric Power Equipment Insulation and residual life, realize power equipment and guaranteeing to extend its serviceable life to greatest extent under safe operation reliability prerequisite.

Paper oil insulation is one of primary insulation form of current power equipment employing, the impact that can be subject to the various factors such as electric field, temperature, oxygen, moisture, mechanical stress in During Process of Long-term Operation occurs aging gradually, causes the electric property of insulation and mechanical property to decline.Show in practical operating experiences, insulating oil is after Long-Time Service is aging, and can process even renew oil by the purification of oil or regeneration and solve, therefore it is not the principal element affecting the transformer insulated life-span.And form the fibrous paper of solid insulation, the hydraulic performance decline caused after its deterioration is then irreversible, therefore paper insulated aging be the key factor determining insulation life in transformer.

The characteristic quantity that current evaluation insulating paper is aging mainly contains CO/CO in the degree of polymerization, oil ₂concentration, furfural content.The degree of polymerization passes judgment on insulating paper life-span the most direct also the most reliable characteristic quantity at present, but insulation paper polymerization degree can only off-line measurement, is difficult to application in engineering reality; CO/CO ₂affected by environment comparatively large, and insulating paper has suction-operated to it, can affect degree of aging and differentiate result; In oil, furfural easily reacts with antioxidant in oil and can decompose under high temperature, depends merely on furfural content and assesses insulation ag(e)ing and unreliable.Therefore need a kind of method proposing oil-immersed power transformer insulation ag(e)ing scale evaluation badly, include appraisement system in by the aging relevant multiple characteristic quantities of paper oil insulation, improve the accuracy of Aging Assessment.

Summary of the invention

The invention provides a kind of method of oil-immersed power transformer insulation ag(e)ing scale evaluation, include appraisement system in by the aging relevant multiple characteristic quantities of paper oil insulation, improve the accuracy of Aging Assessment.

The present invention realizes by the following technical solutions: a kind of method of oil-immersed power transformer insulation ag(e)ing scale evaluation, is characterized in that, comprise the following steps: step S01: draw oil sample to transformer, carry out degassed to described oil sample; By the gas sample inject gas chromatograph obtained degassed from oil, obtain the content C of CO _cOand the content C of total hydrocarbon _c,H, the computing formula that CO content asks for the degree of polymerization is DP (C _co)=-295.3ln (C _cod)-875.7 (1), and the computing formula that total hydrocarbon content asks for the degree of polymerization is DP (C _c,H)=-429.6ln (C _c,Hd)-2325 (2), wherein C _cOand C _c,Hunit is μ L/L; Step S02: be dissolved in 25mL toluene by 25mg furfural, makes the furfural lean solution of 1000mg/L, by new transformer oil dilution furfural lean solution, and the furfural standard solution of preparation desired concn; Extract 4.5mL normal concentration oil sample, put into test tube, then extract 0.5mL methyl alcohol and put into same test tube, test tube mouth is clogged and puts into mechnical oscillator and to vibrate 5min; Then take out described invisible spectro liquid to be placed in hydro-extractor and to be separated and to be extracted liquid, get the nonpolar chromatographic column of extract liquid chromatography C18 described in 5 μ L and be separated, and detect the content C of furfural by UV-detector _fur, the content C of furfural _furthe computing formula asking for the degree of polymerization is: DP (C _fur)=-160ln (C _furd)-243.4 (3), the wherein content C of furfural _furunit is mg/L;

Step S03: calculate the mean value T monitored, deduct transformer normal operating temperature 65 DEG C and obtain temperature increase △ T, the computing formula that temperature and time asks for the degree of polymerization is dP wherein ₀be the initial polymerization number of degrees value of insulating paper, t runs the cumulative time exceeding 65 DEG C, and unit is year.Step S04, according to benzyl disulfide and lauryl mercaptan (DBDS) initial concentration in the oil sample that gas chromatography-quality analysis combined instrument (GC-MS) records, C _dBDSand C _{lauryl mercaptan}unit is mol/L, calculating DBDS and lauryl mercaptan are to the acceleration multiple of insulating paper degradation rate respectively, are in oil sample containing finite concentration DBDS (or lauryl mercaptan) and containing insulation paper polymerization degree fall off rate ratio time DBDS (or lauryl mercaptan).K ₁=74.551c _dBDS+ 1 (5), by k ₁and k ₂be applied to (4) to obtain $\mathrm{DP}\left(\mathrm{t\ΔT}\right)=D{P}^{\′}\left(\mathrm{t\ΔT}\right)/k_1{k}_2=D{P}_0{e}^{-\frac{3\×2^{\frac{\mathrm{\ΔT}}{6}}}{50}t}/k_1{k}_2\left(7\right).$

The degree of polymerization of each aging expressed as parameters that step S05:. calculates according to step S01, step S02, step S03 and step S04, insulation paper polymerization degree numerical value DP is asked in weighting, formula

DP＝0.35DP(C _furd)+0.32DP(C _cod)+0.1DP(t△T)+0.23DP(C _C，Hd)(8)

DP=0.6DP (C _cod)+0.4DP (C _{c, H}d) (9), formula (8) is applied to the degree of polymerization and equals 250 greatly, and formula (9) is applied to the degree of polymerization and is less than 250; Described Transformer Insulation Aging degree can be judged with reference to DP numerical values recited.

In an embodiment of the present invention, in described step S01, the sample cock that described transformer sampling point is equipment bottom is drawn oil sample.

In an alternative embodiment of the invention, airtight good glass syringe is adopted to carry out hermetically sealed sampling when drawing oil sample to described transformer in described step S01.

In still another embodiment of the process, if the mean value T of transformer running temperature is lower than 65 DEG C in described step S03, △ T peek value " 0 ".

Adopt the method for oil-immersed power transformer insulation ag(e)ing scale evaluation provided by the invention, compared with prior art there is following benefit: with the most reliable characteristic amount of this paper oil insulation degree of aging of the degree of polymerization for Appreciation gist, and consider multiple aging parameters such as temperature, oilpaper gas content, furfural content, ensure that the accuracy differentiating result.

Accompanying drawing explanation

Fig. 1 is the computation structure figure of the degree of polymerization in the present invention.

Embodiment

Below in conjunction with accompanying drawing, the present invention is further described.

With reference to figure 1, the calculating of the degree of polymerization of the present invention has considered multiple aging character parameters such as time, temperature, oil dissolved gas content, furfural content and corrosivity sulfide concentration, ensure that the accuracy differentiating result.

In the specific embodiment of the invention, to the method for oil-immersed power transformer insulation ag(e)ing scale evaluation, mainly comprise the following steps:

1, dissolved gases content in oil is detected

The standard of this method of testing reference has GB/T 7252-2001 " Gases Dissolved in Transformer Oil analysis and judge directive/guide ", GB/T 7597-2007 " oil for electric power (transformer oil, steam turbine oil) sampling method ", GB/T17623-1998 " Gas Chromatographic Determination of Dissolved Gases in Insulating Oil component concentration ", DL/T 703-1999 " Gas Chromatographic Determination of gas content in insulating oil ".

1) sample: the position of sampling should notice that got oil sample can represent the oil of oil tank body, and preferably should draw oil sample at the sample cock of equipment bottom in sample position, under special circumstances, can sample at different sampling points.Sampling amount, can be 50mL-60mL to the transformer of large oil mass, will get less as far as possible, be limited with enough to the equipment of few oil mass.Airtight good glass syringe should be used when sampling to transformer oil to sample;

2) degassed: this method adopts the machinery concussion mode of dissolution equilibrium method, and its Repeatability and Reproducibility can meet the demands;

3) analytical gas: the gas sample inject gas chromatograph of the dissolved gas obtained from oil through degasser, by carrier gas, gas sample is brought in chromatographic column, the distribution of each component gas phase in the chromatography column and solid phase in gas sample and adsorption coefficient difference is utilized to be separated, isolated simple substance component is detected by detecting device, carries out qualitative and quantitative analysis according to the retention time of each component of recording device records and response.

Cellulose is the principal ingredient of insulation Paper or cardboard, and cellulose can produce multiple gases under aging conditions, wherein CO and CO ₂shared proportion is larger, and CO in oil ₂impact by air is comparatively large, and CO is primarily of the aging generation of insulating paper, and obviously relevant to the degree of polymerization.So experimentally go out with engineering operation data fitting by the degree of polymerization corresponding to CO content, computing formula is DP (C _co)=-295.3ln (C _cod)-875.7 (1);

Cellulose when aging except produce CO and CO ₂outward, also produce based on the hydrocarbon compound of methane, ethane, ethene, and obviously relevant to the degree of polymerization, therefore experimentally go out by total hydrocarbon content C with engineering operation data fitting _c,Hthe corresponding degree of polymerization, computing formula is DP (C _c,H)=-429.6ln (C _c,Hd)-2325 (2); Wherein CO content C _cOand total hydrocarbon content C _c,Hunit be μ L/L.

2, the furfural content in oil is measured:

The standard of this method of testing reference has GB 7597-2007 " oil for electric power (transformer oil, steam turbine oil) sampling method ", DL/T 984-2005 " oil-filled transformer insulation ag(e)ing judges directive/guide ".

1) preparing standard solution: be dissolved in 25mL toluene by 25mg furfural, makes the furfural lean solution of 1000mg/L.By new transformer oil dilution furfural lean solution, obtain desired concn furfural standard solution (as 0.5,1.0,5 or 10mg/L);

2) extraction of sample: extract 4.5mL furfural normal concentration oil sample with 10mL syringe, put into test tube.Extract 0.5mL methyl alcohol with 1mL syringe and put into same test tube, clogged by test tube mouth and put into mechnical oscillator and to vibrate 5min, then the liquid taken out in test tube is placed in hydro-extractor and is separated and is extracted liquid;

2) analysis of extract: get 5 μ L extract liquid chromatography C18 (nonpolar) chromatographic columns and be separated, and the content C detecting furfural by UV-detector _fur, and calculate the content C of furfural _furdegree of polymerization formula be: DP (C _fur)=-160ln (C _furd)-243.4 (3), the wherein content C of furfural _furunit is mg/L.

3, the determination of running temperature

The standard of this method reference is DL/T 572-2010 " power transformer operating standard ".What in the method, temperature adopted is Celsius temperature, and its method determined is: the mean value T calculating the transformer running temperature monitored, deducts transformer normal operating temperature 65 DEG C and obtain temperature increase △ T, and the formula that temperature and time calculates the degree of polymerization is dP wherein ₀be the initial polymerization number of degrees value of insulating paper, t runs the cumulative time exceeding 65 DEG C, and unit is year, if try to achieve temperature averages lower than 65 DEG C, and △ T peek value " 0 " in formula.

4, the influence of lauryl mercaptan and DBDS

Benzyl disulfide (DBDS) and lauryl mercaptan initial concentration in the oil sample that this method uses gas chromatography-quality analysis combined instrument (GC-MS) to record, C _dBDSand C _{lauryl mercaptan}unit is mol/L, calculating DBDS and lauryl mercaptan are to the acceleration multiple of insulating paper degradation rate respectively, are namely the insulation paper polymerization degree fall off rate ratios when containing finite concentration DBDS (or lauryl mercaptan) in oil sample and do not contain DBDS (or lauryl mercaptan).

K ₁=74.551c _dBDS+ 1 (5), k ₂=4535.538c ² _{lauryl mercaptan}+ 49.406c _{lauryl mercaptan}+ 1 (6), by K ₁and K ₂be applied to (4) to obtain $\mathrm{DP}\left(\mathrm{t\ΔT}\right)=D{P}^{\′}\left(\mathrm{t\ΔT}\right)/k_1{k}_2=D{P}_0{e}^{-\frac{3\×2^{\frac{\mathrm{\ΔT}}{6}}}{50}t}/k_1{k}_2\left(7\right).$ 5, weighting ask for the degree of polymerization assessment aging

Try to achieve the degree of polymerization numerical value under different characteristic parameter according to above-mentioned steps, degree of polymerization assessment insulation ag(e)ing is asked in weighting

DP＝w ₁DP(C _furd)+w ₂DP(C _cod)+w ₃DP(t△T)+w ₄DP(C _C,Hd)(8)，

DP=w ₅dP (C _cod)+w ₆dP (C _c,Hd) (9), wherein w ₁, w ₂, w ₃, w ₄, w ₅, w ₆for weight coefficient, and w ₁+ w ₂+ w ₃+ w ₄=1, w ₅+ w ₆=1; Formula (8) is applied to the degree of polymerization and equals 250 greatly, and formula (9) is applied to the degree of polymerization and is less than 250.

For trying to achieve weight coefficient, constructed fuction

$\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{[D{P}_i-w_{1}D{P}_i\left(C_{\mathrm{fur}}d\right)-w_{2}D{P}_i\left(C_{\mathrm{co}}d\right)-w_3{\mathrm{DP}}_i\left(\mathrm{t\ΔT}\right)-w_{4}D{P}_i\left(C_{C,H}d\right)]}^2\left(10\right)$

$\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{[D{P}_i-w_{5}D{P}_i\left(C_{\mathrm{co}}d\right)-w_{6}D{P}_i\left(C_{C,H}d\right)]}^2\left(11\right)$

Function S (the w of structure ₁, w ₂, w ₃, w ₄), S (w ₅, w ₆) are all the true degree of polymerization numerical value DPi using experiment measuring, deduct the degree of polymerization calculated value that four are multiplied by weight coefficient respectively, required w value should make S minimum.In formula, n represents the data group number brought into, brings 7 groups of experimental datas into formula (10), (11) obtain function S (w ₁, w ₂, w ₃, w ₄), S (w ₅, w ₆).At w ₁+ w ₂+ w ₃+ w ₄=1, w ₅+ w ₆under=1 condition, the conditional extremum method in Practical Higher Mathematics, and in conjunction with actual operating data matching, try to achieve w ₁, w ₂, w ₃, w ₄, w ₅, w ₆numerical value be 0.35,0.32,0.1,0.23 respectively, 0.6,0.4.

Transformer degree of aging is assessed again according to the transformer insulating paper degree of polymerization criterion of table 1.

Table 1 transformer insulating paper degree of polymerization criterion

Its general principles is simple, workable, efficiently solve single features parameter and assess aging inaccuracy and confinement problems, introduce aging accuracy and the authenticity that ensure that result of multiple parameter joint assessment, paper oil insulation Aging Assessment and life appraisal are had important practical application of significance.

Be more than preferred embodiment of the present invention, all changes done according to technical solution of the present invention, when the function produced does not exceed the scope of technical solution of the present invention, all belong to protection scope of the present invention.

Claims (4)

1. a method for oil-immersed power transformer insulation ag(e)ing scale evaluation, is characterized in that, comprises the following steps:

Step S01: draw oil sample to transformer to be measured, carries out degassed to described oil sample; By the gas sample inject gas chromatograph obtained degassed from oil, obtain the content C of CO _cOand the content C of total hydrocarbon _c,H, the computing formula that CO content asks for the degree of polymerization is DP (C _co)=-295.3ln (C _cod)-875.7 (1), and the computing formula that total hydrocarbon content asks for the degree of polymerization is DP (C _c,H)=-429.6ln (C _c,Hd)-2325 (2), wherein C _cOand C _c,Hunit is μ L/L, and d is oilpaper ratio, the ratio of the volume (mL) of oil and quality (g) numerical value of paper;

Step S02: 25mg furfural is dissolved in 25mL toluene, make the furfural lean solution of 1000mg/L, by new transformer oil dilution furfural lean solution, preparation furfural chromatographic peak demarcates the standard solution of desired concn, to obtain furfural quantitative correction factor, for the measurement of actual sample; Extract 4.5mL normal concentration oil sample, put into test tube, then extract 0.5mL methyl alcohol and put into same test tube, test tube mouth is clogged and puts into mechnical oscillator and to vibrate 5min; Then take out described invisible spectro liquid to be placed in hydro-extractor and to be separated and to be extracted liquid, get the nonpolar chromatographic column of extract liquid chromatography C18 described in 5 μ L and be separated, and detect the content C of furfural by UV-detector _fur, the content C of furfural _furasking for degree of polymerization computing formula is: DP (C _fur)=-160ln (C _furd)-243.4 (3), the wherein content C of furfural _furunit is mg/L;

Step S03: monitoring transformer running temperature, and ask for the mean value T of running temperature, T deducts transformer normal operating temperature 65 DEG C and obtains temperature increase △ T, and the computing formula that temperature and time asks for the degree of polymerization is dP wherein ₀be the initial polymerization number of degrees value of insulating paper, t runs the cumulative time exceeding 65 DEG C, and unit is year, if try to achieve temperature averages lower than 65 DEG C, and Δ T peek value " 0 " in formula;

Step S04, according to Qi Xiang Se Pu ?quality analyze benzyl disulfide (DBDS) and lauryl mercaptan initial concentration in the oil sample that combined instrument (GC ?MS) records, C _dBDSand C _{lauryl mercaptan}unit is mol/L, calculating DBDS and lauryl mercaptan are to the acceleration multiple of insulating paper degradation rate respectively, are in oil sample containing finite concentration DBDS (or lauryl mercaptan) and containing insulation paper polymerization degree fall off rate ratio time DBDS (or lauryl mercaptan).K ₁=74.551c _dBDS+ 1 (5), by k ₁and k ₂be applied to (4) to obtain $\mathrm{DP}\left(\mathrm{t\ΔT}\right)={\mathrm{DP}}^{\′}\left(\mathrm{t\ΔT}\right)/k_1{k}_2=D{P}_0{e}^{-\frac{3\×2^{\frac{\mathrm{\ΔT}}{6}}}{50}t}/k_1{k}_2---\left(7\right).$

Step S05: the degree of polymerization calculating each aging characteristics sign obtained according to step S01, step S02, step S03 and step S04, insulation paper polymerization degree numerical value DP is asked in weighting, and its computing formula is DP=0.35DP (C _furd)+0.32DP (C _cod)+0.1DP (t △ T)+0.23DP (C _{c, H}d) (8), DP=0.6DP (C _cod)+0.4DP (C _{c, H}d) (9), formula (8) is applied to the degree of polymerization and reaches and equal 250 greatly, and formula (9) is applied to the degree of polymerization and is less than 250; Described Transformer Insulation Aging degree can be judged with reference to DP numerical values recited.

2. the method for a kind of oil-immersed power transformer insulation ag(e)ing scale evaluation according to claim 1, is characterized in that: draw oil sample to the sample cock that described transformer sampling point is equipment bottom in described step S01.

3. the method for a kind of oil-immersed power transformer insulation ag(e)ing scale evaluation according to claim 1, is characterized in that: adopt airtight good glass syringe to carry out hermetically sealed sampling when drawing oil sample to described transformer in described step S01.

4. the method for a kind of oil-immersed power transformer insulation ag(e)ing scale evaluation according to claim 1, is characterized in that: if the mean value T of transformer running temperature is lower than 65 DEG C in described step S03, △ T peek value " 0 ".