CN103884818A - Method for measuring activation energy of transformer insulating paper and method for predicting service life of transformer insulating paper - Google Patents

Abstract

The invention relates to a method for measuring the activation energy of transformer insulating paper. In the method, accelerated aging test is performed on the transformer insulating paper at multiple temperatures, and the polymerization degree of the transformer insulating paper is measured periodically; when the polymerization degree is less than 250, the accelerated aging test is ended to obtain the aging time of the transformer insulating paper when the polymerization degree is 250 at multiple temperatures, and the activation energy is calculated through a service life prediction module and the aging time of the transformer insulating paper when the polymerization degree is 250 at multiple temperatures; the service life prediction module is lnTau=ln A+Ea/(RT), wherein A is a proportional constant, Ea is activation energy, R is a Boltzman constant, T is temperature, and Tau represents the working life of a product when the temperature is T. According to the method, the activation energy of the insulating paper is obtained by calculating in order to obtain the service life prediction module suitable for the insulating paper, so that the service life estimation result of the insulating paper is more accurate.

Description

A kind of assay method of transformer insulating paper energy of activation and the life-span prediction method of transformer insulating paper

Technical field

The present invention relates to a kind of assay method of transformer insulating paper energy of activation and the life-span prediction method of transformer insulating paper.

Background technology

Nuclear power station main-transformer mostly is large capacity oil-immersed power transformer, and due to the difference of practical operation situation and load variations, its actual residual life has suitable uncertainty.The operation of exceeding the time limit without foundation will cause nuclear power station major safety risks, simultaneously, because the volume and weight of main-transformer is huge, change workload large, long in time limit, cost is high and the manufacturing cycle is long, interimly need to carry out Aging Assessment and predicting residual useful life to it in the nuclear power station longevity, thereby formulate in advance buying and change plan, avoid blindly maintenance or change.

Nuclear power station designed life is 40 years, and the aging and life-span management requirement current according to power station, also needs to study the problem of lengthening the life for 60 years.This just need to determine by the aging and life status of assessment and analysis main-transformer replacing strategy and the plan in its period suitable in power station.

The insulation system of large capacity oil-immersed power transformer is mainly made up of the cellulosic materials such as insulating paper (plate) and naphthenic hydrocarbon mineral insulating oil two large divisions.The hydraulic performance decline causing after deteriorated due to solid insulating materials such as insulating oil can purify, regenerate and change processing according to aging conditions, insulating paper (plate) is in good time irreversible, and generally all cannot directly change.Aging and unavailable the unavailable of whole transformer that just substantially mean of these solid insulating materials.Therefore, the aging and life-span of transformer depends primarily on its insulating paper using (plate).

Abroad there are some researches show, the degree of polymerization is an important parameter that characterizes insulating paper physical strength, be determine the aging and residual life of insulating paper the most directly, the most reliable index.Common degree of polymerization method of testing comprises:

1) by furfural content estimation degree of polymerization numerical value in test oil, but there is following defect in the method:

There are the processes such as the filtration of existence, renewal due to on-the-spot transformer, can cause furfural content in oil to change;

Relation between furfural content before furfural content and oil strain after oil strain needs research;

Between furfural content and the insulating paper degree of polymerization, relation needs further to be studied;

Above-mentioned some all can cause degree of polymerization estimation numerical value inaccurate.

2) obtain average degree of polymerization by the method for measuring viscosity.

In transformer insulating paper residual life evaluation field, existing achievement in research mostly is carries out accelerated aging test under a certain temperature conditions, regularly gather the degree of polymerization of insulating paper, and what use for the key factor (energy of activation) of life appraisal is empirical data, this can cause assessment result inaccurate.

Summary of the invention

Technical matters to be solved by this invention is to provide a kind of assay method of transformer insulating paper energy of activation.

Another technical matters to be solved by this invention is to provide a kind of life-span prediction method that utilizes above-mentioned energy of activation this transformer insulating paper to be carried out to life prediction.

For solving above technical matters, the present invention takes following technical scheme:

A kind of assay method of transformer insulating paper energy of activation, at multiple temperature, transformer insulating paper is carried out to accelerated aging test, the degree of polymerization of the transformer insulating paper described in results of regular determination, in the time that the degree of polymerization is less than 250, finish described accelerated aging test, the degree of polymerization that obtains at multiple temperature described transformer insulating paper is the digestion time of 250 o'clock, and the digestion time that is 250 o'clock by the degree of polymerization of transformer insulating paper described at Life Prediction Model and described multiple temperature calculates described energy of activation; Described Life Prediction Model is: ln τ=ln A+Ea/ (RT), and wherein, A is proportionality constant, and Ea is described energy of activation, and R is the graceful constant of bohr thatch, and T is temperature, τ represents the mission life of product in the time that temperature is T.

Preferably, described multiple temperature are at least 2.

Preferably, measure the degree of polymerization of described transformer insulating paper by viscosimetry.

Particularly, because Arrhenius model thinks that degradation with aging is the result of temperature action, and can obtain to the prediction residual life under fixed temperature, also can derive the residual life at another temperature according to the residual life at a certain temperature, heat ageing is a kind of chemical reaction occurring under temperature action, this chemical reaction is the function of temperature, therefore adopts Arrhenius model inference to go out described Life Prediction Model.The derivation method of Life Prediction Model is:

Formula (1) is Arrhenius model, and formula (1) is expressed as:

K(t)=A _a exp(-Ea/RT) （1），

Wherein: K(t): reaction rate; Aa: proportionality constant; Ea: described energy of activation; R: the graceful constant of bohr thatch; T: working temperature;

Formula (1) deformable is formula (2):

ln K(t)=ln A _a-Ea/(RT) （2）；

If τ is the mission life of product under temperature T, obtain described Life Prediction Model: ln τ=ln A+Ea/ (RT), wherein: A=1/Aa.

Preferably, be the digestion time of 250 o'clock according to the degree of polymerization of transformer insulating paper described at described Life Prediction Model and described multiple temperature, utilize least square method to calculate described energy of activation.

More preferably, described Life Prediction Model is arranged, make y=ln τ, x=1/T, a=Ea/R, b=ln A, can draw: y=ax+b;

Be the digestion time of 250 o'clock according to the degree of polymerization of transformer insulating paper described at described multiple temperature, utilize least square method can directly calculate parameter a and b, computing method are suc as formula (5) and formula (6):

$a=\frac{\mathrm{N\Σxy}-\mathrm{\Σx\Σy}}{\mathrm{N\Σ}{x}^2-{\left(\mathrm{\Σx}\right)}^2}---\left(5\right);$

$b=\frac{\mathrm{\Σy}-\mathrm{a\Σx}}{N}---\left(6\right);$

Can obtain described activation energy and proportionality constant A according to parameter a and b.

A kind of life-span prediction method of transformer insulating paper, adopt said determination method to obtain described energy of activation and described proportionality constant A, by described energy of activation and described proportionality constant A again the Life Prediction Model described in substitution obtain the Life Prediction Model of described transformer insulating paper, then according to the actual motion temperature of described transformer insulating paper, can calculate the bimetry of described transformer insulating paper at this actual motion temperature.

Due to the enforcement of above technical scheme, the present invention compared with prior art tool has the following advantages:

The present invention by carrying out accelerated aging test to insulating paper of the same race under many temperature spots, regularly gather the degree of polymerization of insulating paper, according to experimental result, calculate the energy of activation of insulating paper, thereby obtain being applicable to the Life Prediction Model of this kind of insulating paper, and then make the result of insulating paper life appraisal more accurate.

Brief description of the drawings

Accompanying drawing 1 is the variation relation figure of the degree of polymerization and digestion time and aging temperature.

Embodiment

Below in conjunction with specific embodiment, the present invention will be further described in detail, but the present invention is not limited to following examples.The implementation condition adopting in embodiment can require to do further adjustment according to the difference of concrete use, and not marked implementation condition is the normal condition in the industry.

Embodiment

(1) adopt under 3 temperature spots insulating paper of the same race is carried out to accelerated aging test, regularly gather the degree of polymerization of insulating paper, in the time that the degree of polymerization reaches by condition, (be less than 250), accelerated aging test finishes, and obtains the variation tendency of 3 groups of degree of polymerization with digestion time.

1 life-span prediction method

The selection of 1.1 Life Prediction Models

Use Arrhenius model as Life Prediction Model, this model thinks that degradation with aging is the result of temperature action, and can obtain to the prediction residual life under fixed temperature, also can derive the residual life at another temperature according to the residual life at a certain temperature.

Heat ageing is a kind of chemical reaction occurring under temperature action, and this chemical reaction is the function of temperature, can represent with following formula:

K(t)=A _a exp(-Ea/RT) （1）；

Wherein: K(t): reaction rate; Aa: proportionality constant; Ea: the energy of activation (eV) of chemical reaction, represents the susceptibility of certain material aging; R: the graceful constant of bohr thatch (0.816*10-4eV/K); T: working temperature (K).

Formula (1) is deformed into formula (2):

ln K(t)=ln A _a-Ea/(RT) （2）；

If τ be the mission life of product under temperature T (hour), Life Prediction Model can be reduced to:

lnτ=ln A+Ea/(RT) （3）

Wherein: A=1/Aa.

Determining of 1.2 life model parameters

Formula (3) is arranged, make y=ln τ, x=1/T, a=Ea/R, b=ln A, can draw:

y=ax+b （4）

Suppose to carry out accelerated aging test under 3 different temperatures (T1, T2, T3), the off-test time is respectively (τ 1, τ 2, τ 3).Utilize least square method can directly calculate parameter a and b, computing method are suc as formula (5) and formula (6):

$a=\frac{\mathrm{N\Σxy}-\mathrm{\Σx\Σy}}{\mathrm{N\Σ}{x}^2-{\left(\mathrm{\Σx}\right)}^2}---\left(5\right)$

$b=\frac{\mathrm{\Σy}-\mathrm{a\Σx}}{N}---\left(6\right)$

Can obtain activation energy Ea and proportionality constant A according to parameter a and b, and then obtain Life Prediction Model.

Life prediction under 1.3 actual motion conditions

Obtain after Life Prediction Model, can obtain Arrhenius figure, obtain the serviceable life at actual condition temperature thereby can extrapolate.But extrapolation method is limited in 30～50 DEG C of overstep of end point data conventionally, because chemical reaction at high temperature may be replaced by the different reaction of another kind, makes aging curve occur linear deviation.

2. sample calculation analysis

Under 105 DEG C, 110 DEG C, 115 DEG C conditions, respectively three groups of Oil-Paper Insulations are carried out to accelerated aging test, regularly gather the degree of polymerization of insulating paper, test figure is in table 1, table 2, table 3, and the degree of polymerization is with the variation tendency of digestion time and temperature as shown in Figure 1.

Table 1

Digestion time (hs)	The degree of polymerization	Digestion time (hs)	The degree of polymerization	Digestion time (hs)	The degree of polymerization
						0	1228	3360	598	7080	352
120	1088	3480	586	7260	347
						240	1018	3600	577	7440	343
360	968	3720	567	7620	337
						480	936	3840	557	7800	332
600	908	3960	550	7980	328
						720	880	4080	542	8160	322
840	860	4200	533	8340	318
						960	837	4320	520	8520	315
1080	820	4440	515	8700	310
						1200	801	4560	506	8880	304
1320	776	4680	493	9060	301
						1440	760	4800	473	9240	297
1560	750	4920	465	9420	294
						1680	734	5040	459	9600	291
1800	725	5160	452	9780	288
						1920	713	5280	446	9960	282
2040	706	5400	442	10140	275
						2160	698	5520	427	10320	271
2280	684	5640	422	10500	269
						2400	679	5760	413	10680	267
2520	674	5880	405	10860	263
						2640	660	6000	393	11040	260
2760	653	6180	389	11220	257

2880	644	6360	381	11400	254
						3000	624	6540	372	11580	252
3120	615	6720	366	11760	251
						3240	606	6900	360	11940	250

Table 2

Digestion time (hs)	The degree of polymerization	Digestion time (hs)	The degree of polymerization	Digestion time (hs)	The degree of polymerization
						0	1240	3060	555	6000	328
180	1067	3180	538	6180	319
						360	967	3300	528	6360	307
540	899	3420	516	6540	299
						720	864	3540	494	6720	293
900	833	3660	483	6900	285
						1080	799	3780	477	7080	279
1260	777	3900	470	7260	273
						1440	746	4020	462	7440	269
1620	724	4140	455	7620	266
						1740	710	4260	443	7800	262
1860	680	4380	431	7980	259
						1980	671	4500	420	8160	257
2100	656	4620	409	8340	255
						2220	635	4740	398	8520	254
2340	621	4920	388	8700	253
						2460	610	5100	375	8880	252
2580	601	5280	369	9060	251
						2700	589	5460	356	9240	250
2820	571	5640	349	9420	249
						2940	563	5820	339

Table 3

Digestion time (hs)	The degree of polymerization	Digestion time (hs)	The degree of polymerization	Digestion time (hs)	The degree of polymerization
						0	1236	2040	577	4200	368
120	1075	2160	568	4380	355

240	972	2280	556	4560	341
						360	902	2400	538	4740	332
480	865	2520	526	4920	321
						600	834	2640	512	5100	312
720	800	2760	500	5280	299
						840	766	2880	485	5460	289
960	744	3000	473	5640	281
						1080	713	3120	461	5820	274
1200	691	3240	450	6000	267
						1320	677	3360	439	6180	262
1440	647	3480	428	6360	258
						1560	638	3600	419	6540	255
1680	623	3720	410	6720	254
						1800	602	3840	400	6900	252
1920	588	4020	380	7080	250

According to the regulation of standard U.S. transformer diagnostic techniques standard (FIST-3-31)-2003, can select the insulating paper degree of polymerization to reach 250 discrimination standards as end of life.According to the test figure of table 2～table 4, can obtain respectively the insulating paper degree of polymerization under different aging temperatures and reach 250 digestion time, the results are shown in Table 4.

Table 4

Test temperature (DEG C)	105	110	115
				The end-of-life time (h)	11940	9240	7080

The disposal route of introducing according to 1.2 joints, establishes x=1/T, and y=ln τ, utilizes least square method can calculate coefficient a and b, and result of calculation is as shown in table 5.

Table 5

Numbering	1	2	3	Σ
					Test temperature (DEG C)	105	110	115
Absolute temperature T (K)	378.15	383.15	388.15
					The end-of-life time (h)	11940	9240	7080
x	0.002644453	0.002609944	0.002576324	0.007830721
					x 2	6.99313E-06	6.81181E-06	6.63744E-06	2.04424E-05
y	9.387649387	9.131297165	8.865029187	27.38397574

y 2	88.12796101	83.38058791	78.58874248	250.0972914
					xy	0.0248252	0.023832173	0.022839184	0.071496557

Coefficient substitution formula (5), formula (6) that table 6 is calculated, can obtain:

$a=\frac{\mathrm{N\Σxy}-\mathrm{\Σx\Σy}}{\mathrm{N\Σ}{x}^2-{\left(\mathrm{\Σx}\right)}^2}=7669.8645,b=\frac{\mathrm{\Σy}-\mathrm{a\Σx}}{N}=-10.8922$

By a=E _a/ R can obtain activation energy E _a=a × R=0.6611eV, can obtain constant A=1.86E-5 by b=ln A.

Therefore can obtain Life Prediction Model, Life Prediction Model is converted, to obtain final product:

τ=A·e ^Ea/(RT)=1.86×10 ^-5·e ^{7669.8645/(273.15+T)}

Can calculate different running temperature T(DEG C according to this model) the bimetry τ of lower insulating paper, specifically in table 6.

Table 6

Running temperature	50℃	60℃	70℃	80℃
					Bimetry (year)	43.14	21.16	10.82	5.74

(2) measure the transformer insulating paper degree of polymerization in real work by viscosimetry, can assess the ageing state of this insulating paper according to table 7.

Table 7

The insulating paper degree of polymerization	Residual life
		1000～1200	New insulating paper
500	60%～66% designed life
		300	30% designed life
200	End of life

Above the present invention is described in detail; its object is to allow the personage who is familiar with this art can understand content of the present invention and be implemented; can not limit the scope of the invention with this; the equivalence that all Spirit Essences according to the present invention are done changes or modifies, and all should be encompassed in protection scope of the present invention.

Claims (6)

1. the assay method of a transformer insulating paper energy of activation, it is characterized in that: at multiple temperature, transformer insulating paper is carried out to accelerated aging test, the degree of polymerization of the transformer insulating paper described in results of regular determination, in the time that the degree of polymerization is less than 250, finish described accelerated aging test, the degree of polymerization that obtains at multiple temperature described transformer insulating paper is the digestion time of 250 o'clock, and the digestion time that is 250 o'clock by the degree of polymerization of transformer insulating paper described at Life Prediction Model and described multiple temperature calculates described energy of activation; Described Life Prediction Model is: ln τ=ln A+Ea/ (RT), and wherein, A is proportionality constant, and Ea is described energy of activation, and R is the graceful constant of bohr thatch, and T is temperature, τ represents the mission life of product in the time that temperature is T.

2. assay method according to claim 1, is characterized in that: described multiple temperature are at least 2.

3. assay method according to claim 1, is characterized in that: the degree of polymerization of measuring described transformer insulating paper by viscosimetry.

4. assay method according to claim 1, it is characterized in that: be the digestion time of 250 o'clock according to the degree of polymerization of transformer insulating paper described at described Life Prediction Model and described multiple temperature, utilize least square method to calculate described energy of activation.

5. assay method according to claim 4, is characterized in that: the calculation procedure of described energy of activation is as follows:

(1), described Life Prediction Model is arranged, make y=ln τ, x=1/T, a=Ea/R, b=ln A, can draw: y=ax+b;

(2), be the digestion time of 250 o'clock according to the degree of polymerization of transformer insulating paper described at described multiple temperature, utilize least square method can directly calculate parameter a and b, computing method as shown in the formula:

(3), can obtain described activation energy and proportionality constant A according to parameter a and b.

6. the life-span prediction method of a transformer insulating paper, it is characterized in that: adopt the assay method described in any one in claim 1 to 5 to obtain described energy of activation and described proportionality constant A, by described energy of activation and described proportionality constant A again the Life Prediction Model described in substitution obtain the Life Prediction Model of described transformer insulating paper, then according to the actual motion temperature of described transformer insulating paper, can calculate the bimetry of described transformer insulating paper at this actual motion temperature.