CN102062746A - Method for measuring oiled paper insulated micro water content on basis of dielectric response - Google Patents

Abstract

The invention discloses a method for measuring oiled paper insulated micro water content on the basis of dielectric response, which fully utilizes the inherent characteristic that the dielectric constant of an insulating material changes along with voltage frequency change, and obtains the complex dielectric constant Epsilon * of a sample by measuring the relevant characteristic parameters of the output voltage gain M and the phase difference of samples with different temperatures and different micro water contents and carrying out mathematical calculation by combining with an equivalent circuit of a tester. An interactional rule between an oiled paper micro water content m and the complex dielectric constant Epsilon * and between temperature T and applied voltage frequency f is analyzed, the variation rule of tested data is fitted by a mathematical software tool to finally obtain the general function relational expression between the oil paper micro water content m and the complex dielectric constant Epsilon * and between the temperature T and the applied voltage frequency f, and finally, the function relational expression is utilized to calculate the insulated micro water content of the unknown oiled paper.

Description

A kind of paper oil insulation micro-water content measuring method based on the dielectric response

Technical field

The present invention relates to a kind of paper oil insulation micro-water content measuring method, belong to assessment of power equipment state of insulation and life prediction field based on the dielectric response.

Background technology

The safe operation of power equipment is the first road system of defense of avoiding the electrical network major accident, and power transformer is the key equipment in this road system of defense.Present most widely used power transformer is an oil-immersed type transformer, the good and bad electric property and the operation life that directly influences transformer of its paper oil insulation performance.Moisture is a key factor that influences insulating oil and insulating paper insulating property.Minor amount of water branch reduces the voltage breakdown of insulation system and the dielectric loss of increase insulation system in the insulating oil, and when moisture in the insulating oil surpasses certain threshold value, the insulating property of equipment will reduce greatly.Moisture also will be participated in the chemical degradation reaction of macromolecular materials such as oilpaper fiber directly, impel these material degradations aging, thereby quicken the deterioration of the every performance of insulation system.The heat ageing rate of insulating paper is directly proportional with moisture wherein, and water cut whenever doubles and will reduce by half its mechanical life in the paper.Can cause accidents such as insulation breakdown, burning apparatus when serious, this is an irreversible process that develops gradually with transformer working time.Therefore, the detection of paper oil insulation water cut has great importance to transformer safety, stable operation.Most moisture concentrates in the insulating board, and the moisture in the transformer insulation oil can be analyzed by customary oil sample collection and testing laboratory and detect at present, and the method that is adopted is generally coulometric titration.But also can't directly record for the micro-water content in the insulating board, can only obtain the information of micro-water content in the insulating board by the corresponding relation of little water in little water and the insulating board in the transformer insulation oil.The little water method of testing of these traditional paper oil insulations is confined to single information, the insulation information that provides is very few, the content information that has only comprised little water, and suffered on-the-spot disturbing factor is many, has the limitation that can't set up transformer insulation state and test result corresponding relation.

Summary of the invention

For addressing the above problem, the invention provides a kind of paper oil insulation micro-water content measuring method based on the dielectric response, can realize the effective, quick of paper oil insulation micro-water content detected.

The present invention solves the problems of the technologies described above the specific inductive capacity that the know-why that is adopted is based on insulating material and changes this inherent characteristic that changes with electric voltage frequency, find out the generic function relational expression between its micro-water content and complex permittivity and test voltage frequency, the probe temperature, then, with complex permittivity, test voltage frequency and the probe temperature substitution generic function relational expression of the paper oil insulation of unknown micro-water content, obtain unknown micro-water content again.The present invention may further comprise the steps according to the concrete technical scheme that above-mentioned know-why adopted:

First step, at first prepare insulating board sample to be measured with the different micro-water contents of a kind of model, respectively each sample is placed in the plate electrode sensor then, carrying out artificial ageing handles, and with the sinusoidal voltage of the after-applied frequency adjustable of transformer insulated oil-impregnated as input signal, test the voltage gain M and the phase differential of every kind of input signal and output signal

Second step with the following formula of above-mentioned test data substitution, is calculated the complex permittivity ε of tested sample ^*:

Complex permittivity ε ^*Form by two parts, wherein, ε ', ε " be the real part and the imaginary part of complex permittivity,

For the phase differential between input voltage and the output voltage, M are voltage gain amplitude M, R _T, C _TBe test cell model parameter, R _L, C _LBe known load branch road parameter, d is the spacing of plate electrode sensor, and A is a plate electrode sensor drive electrode surface area.

Third step is according to the complex permittivity ε that obtains in above-mentioned second step ^*And apply electric voltage frequency f, environment temperature (T) is carried out data fitting, determines paper oil insulation micro-water content m and complex permittivity ε ^*, apply the general purpose function relational expression of electric voltage frequency f, environment temperature T:

First formula is:

$m={[f^{r_2\left(T\right)}\·\left(\frac{{\mathrm{\ϵ}}^{\′}-{\mathrm{\ϵ}}_{\∞}}{{\mathrm{\ϵ}}_0}\right)\·{10}^{-c_1-f_{T1}\left(T\right)}]}^{\frac{1}{r_1\left(f\right)}}$

Second formula is: $m={[f^{r_4\left(T\right)}\·\left(\frac{{\mathrm{\ϵ}}^{\′\′}}{{\mathrm{\ϵ}}_0}\right)\·{10}^{-c_2-f_{T2}\left(T\right)}]}^{\frac{1}{r_3\left(f\right)}}$

C in above-mentioned two formulas ₁, c ₂Be related coefficient, r (T) is for comprising the expression formula of temperature T, and r (f) is for comprising the expression formula of frequency f, and f (T) is the function relevant with temperature T.Wherein, related coefficient c ₁, c ₂, expression formula r (T), r (f), f (T) carry out the data linear fit by the different micro-water content samples of the same model complex permittivity separately of preparation with its voltage signal frequency f, environment temperature T that is applied when the measurement to obtain.The related coefficient c that the insulating paper match of each model obtains ₁, c ₂, expression formula r (T), r (f), f (T) difference.

The 4th step, to put into the plate electrode sensor of first step with the insulating paper of unknown micro-water content of the same model of sample of preparation in advance, injection insulating oil dipping, and on the plate electrode sensor, apply between the 0.01Hz-10000Hz any one sinusoidal voltage as input signal, the voltage gain M and the phase differential of Test input signal and output signal

And then carry out data processing by formula and relational expression that above-mentioned second step and third step are confirmed, calculate the micro-water content of paper oil insulation; Wherein, the micro-water content m that first formula and second formula calculate in by above-mentioned third step is all less than 2% the time, adopt the micro-water content value of the first formula calculated value as final unknown paper oil insulation, other situations all adopt the micro-water content value of the mean value of two values as unknown paper oil insulation.

Above-mentioned first step specifically comprises the steps:

(1) the insulating board method of sample preparation to be measured of different micro-water contents is: earlier will new insulating board be placed on such as drying in the thermal vacuum chamber between 70 ℃ to 90 ℃ to handle to moisture and fully separate out, insulating board exposure with oven dry is placed in the room air then, allow it absorb the water in air branch, reach predetermined value up to its weight.Micro-water content percentage computing method are:

$m=\frac{m_0-m^{\′}}{m_0}\×100\%$

Wherein, m ' is an insulating board oven dry back quality, m ₀It is quality after insulating board makes moist.

(2) because the paper oil insulation system of unknown micro-water content actual be aged, for carrying out artificial burin-in process to the sample of preparation with actual conforming to.Sample is carried out the method that heat ageing handles is: sample is positioned in a certain fixed temperature value between 100 ℃-150 ℃ handled 500-800 hour.Temperature in the heat treatment process should evenly distribute, and for to make the degree of aging of each part of sample identical, the position of sample in processing procedure will clocklike change.After artificial ageing is finished, measure the degree of polymerization (DP) of each sample, judge the ageing state of aging sample with this.

(3) after sample is put into the plate electrode sensor, on the drive electrode of sensor, connect input voltage signal, after the induction electrode output signal, insert intelligent oscillograph, voltage gain M and phase differential between Test input signal and the output signal

Change the test environment temperature T, another test more than sample repetition is changed in the frequency f repeated test of input voltage signal after all testing from the low frequency to the high band.

The formula principle of the complex permittivity of establishing in above-mentioned second step is with reference to Fig. 3, to set up mathematical model according to the circuit voltage divider principle.

(1) according to each the paper oil insulation sample that records in the first step at different temperatures T, voltage gain M and phase differential under the different frequency f

Calculate the real part ε ' and the imaginary part ε of complex permittivity respectively with following calculating formula " value:

The original calculation formula of the real part of complex permittivity and imaginary part is:

${\mathrm{\ϵ}}^{\′}=\frac{{\mathrm{dC}}_T}{A},$ ${\mathrm{\ϵ}}^{\′\′}=\frac{d}{R_T\mathrm{A\ω}}$

Therefore require ε ', ε " value will calculate the measuring unit parameters R earlier _TAnd C _TValue.Here defining the admittance of measuring branch road and load branch among Fig. 3 is respectively Y _T=1/R _T+ i ω C _TAnd Y _L=1/R _L+ i ω C _LCan get according to voltage divider principle:

In low-frequency range, promptly ω leveled off to 0 o'clock, and voltage gain M equals R _L/ (R _L+ R _T).High-frequency range, promptly ω levels off to ∞, and voltage gain M equals C _T/ (C _T+ C _L).R _TAnd C _TWith known load branch R _L, C _LValue and the M that records,

Value is expressed as follows:

With the measuring unit parameters R _TAnd C _TCalculating formula substitution ε ', ε " the original calculation formula in can obtain comprising characteristic parameter M that the dielectric test obtains and

The real part and the imaginary part calculating formula of complex permittivity.

In the calculating formula, " be the real part and the imaginary part of complex permittivity, real part is represented the specific inductive capacity of material, and imaginary part has reflected the power loss characteristic of material for ε ', ε.R _L, C _LBe known load branch parameter, d is the spacing of plate electrode sensor, and A is a plate electrode sensor drive electrode surface area;

Paper oil insulation micro-water content m that establishes in the above-mentioned third step and DIELECTRIC CONSTANT, the general purpose function that applies electric voltage frequency f, environment temperature T concern that the principle of formula is:

(1) with the different micro-water content samples of same model complex permittivity real part and imaginary part ε ', the ε separately that calculates in second step " carry out logarithm conversion, promptly get log (ε '/ε ₀), log (ε "/ε ₀).Wherein, ε ₀It is permittivity of vacuum.The reason of taking the logarithm is to help follow-up data analysis match, draws paper oil insulation micro-water content m and environment temperature T, the mutual Changing Pattern between electric voltage frequency f and the complex permittivity.

(2) micro-water content m and complex permittivity ε ^*, the relation of environment temperature T and voltage signal frequency f is set up can use for reference the semiempirical computing formula:

$\log \left(\frac{{\mathrm{\ϵ}}^{\′}-{\mathrm{\ϵ}}_{\∞}}{{\mathrm{\ϵ}}_0}\right)=c_1-\mathrm{\γ}\{f_T\left(T\right)-\log \left(f\right)+\log \left(m\right)+c_m\}$

$\log \left(\frac{{\mathrm{\ϵ}}^{\′\′}}{{\mathrm{\ϵ}}_0}\right)=c_2-\mathrm{\γ}\{f_T\left(T\right)-\log \left(f\right)+\log \left(m\right)+c_m\}$

Wherein, f _T(T), log (m)+c _mDifference representation temperature and moisture effects subfunction, γ, c ₁, c ₂Represent real part and the imaginary part linear transformation function of each factor of influence to complex permittivity.For ease of pressing the following formula form analysis, utilize following formula to get ε _∞/ ε ₀≈ 2.4, with the complex permittivity real part log that calculates in second step (ε '/ε ₀) convert to log ((ε '-ε _∞)/ε ₀) form:

$\log \left(\frac{{\mathrm{\ϵ}}^{\′}-{\mathrm{\ϵ}}_{\∞}}{{\mathrm{\ϵ}}_0}\right)=\log (\exp (2.306*\log \left(\frac{{\mathrm{\ϵ}}^{\′}}{{\mathrm{\ϵ}}_0}\right))-\frac{{\mathrm{\ϵ}}_{\∞}}{{\mathrm{\ϵ}}_0})$

The complex permittivity of the different micro-water content samples of same model of preparation and its voltage signal frequency f, environment temperature T that is applied when measuring are carried out the data linear fit obtain related coefficient c ₁, c ₂, expression formula r (T), r (f), these actual numerical values of f (T), the substitution semiempirical formula is also carried out the calculating formula that inverse operation obtains this model paper oil insulation micro-water content.

The corresponding relation formula that the utilization of above-mentioned the 4th step is set up calculates unknown paper oil insulation micro-water content.

As seen, the present invention is based on the dielectric response theory, by measuring different electric voltage frequencies, varying environment temperature, different micro-water content input and output voltage signal gain M with a kind of insulating paper sample, and phase differential

Calculate the complex permittivity ε of sample ^*Again the data in the test are analyzed, drawn known paper oil insulation micro-water content m and the complex permittivity ε that calculates ^*, the rule that is mutually related between temperature T and these data of electric voltage frequency f of applying, and utilize mathematical tools such as MATLAB that the Changing Pattern of data is carried out reasonable process of fitting treatment, finally obtain paper oil insulation micro-water content m and complex permittivity ε ^*, temperature T and apply the general purpose function relational expression of electric voltage frequency f; Thereby utilize this functional relation to realize that unknown paper oil insulation micro-water content to model insulating paper of the same race calculates at last.Thus, advantage of the present invention is to be theoretical foundation with the dielectric response, utilize the complex permittivity of insulating material to change this inherent characteristic that changes with electric voltage frequency, can simplify the calculating of the micro-water content of paper oil insulation to a great extent, and can have higher reliability, economy and practicality at the specific inductive capacity that does not record paper oil insulation under the special proving installation situation by dielectric loss etc.Wherein, paper oil insulation micro-water content m that finally obtains and complex permittivity ε ^*, temperature T and the general purpose function relational expression that applies electric voltage frequency f can be used for carrying out reliable and accurately assessment to the paper oil insulation system of unknown micro-water content.

Description of drawings

Further specify the present invention below in conjunction with drawings and Examples.

Fig. 1 measures paper oil insulation micro-water content schematic flow sheet for the present invention

Fig. 2 measures the measurement mechanism synoptic diagram of paper oil insulation micro-water content for the present invention

Fig. 3 is the equivalent circuit diagram of entire measuring device

1-oscillograph among the figure, the 2-power supply that wears out, the 3-baking oven; 4-plate electrode sensor drive electrode, 5-valve, 6-oil pump; the 7-oil pipeline, 8-insulating oil, 9-insulating paper sample; 10-plate electrode sensor protection electrode; the 11-temperature sensor, 12-plate electrode sensor sensing electrode, the organic container of 13-; 14-tests branch road, 15-load branch.

Embodiment

Hereinafter with reference to accompanying drawing, embodiments of the present invention is described in detail.

Paper oil insulation micro-water content measuring method based on the dielectric response of the present invention is seen Fig. 1, may further comprise the steps:

First step is placed on temperature maintenance in 80 ℃ thermal vacuum chamber 2 to 3 days with the new insulating board of same model.In this process, for judging whether fully oven dry of sample, must use the continual weight of fine measuring instrument to measure to sample, no longer change up to the weight of measuring.After the oven dry, insulating board exposed fully be placed on (in indoor air) in the air, from air, absorb moisture with this.The accurate check weighing apparatus measures of whole same use, insulating board weight reaches predetermined value m in continuous variation up to its weight ₀, m ₀Be that insulating board absorbs the quality after moisture makes moist.m ₀Value need and need the micro-water content value of preparation to calculate according to the quality behind the sample drying, and the computing method of predetermined value are:

$m_0=\frac{m^{\′}}{1-m}$

Wherein, m ' is an insulating board oven dry back quality; M is the micro-water content that needs preparation, is respectively 0.3%, 0.6%, 1%, 2% and 4% 5 group of micro-water content from low to high.

And then, utilizing device shown in Figure 2 to carry out artificial ageing handles and tests.This device is seen Fig. 2, and it has the characteristics of the capacity plate antenna formula sensor of electrode opposing parallel, and its capacitive structures mainly is made up of plate electrode sensor drive electrode 4 and induction electrode 12, is guard electrode 10 around the induction electrode 12; The direct ground connection of guard electrode has been eliminated parallel stray capacitance and resistance, has played the interference effect of shielding external electrical field to test electrode; The plate electrode sensor is positioned over the inside of organic container 13, the organic glass container top is connected through oil pipeline 7 with the bottom, oil pump 6 is installed at the top makes transformer insulation oil 8 be in recurrent state, simulation real transformer running status, and bottom mounting temperature sensor 11 is the interior temperature of monitoring container in real time.Whole organic glass container is positioned in the baking oven 3 that temperature can regulate.

Test preceding drive electrode 4 and induction motor 12 with pure washed with methanol organic glass container 13 and flat panel sensor, having cleaned the back dries it in the time of 80 ℃, open top cover after having dried, rapidly the insulating board sample for preparing is placed in the middle of the plate electrode sensor.Elder generation was with K switch when artificial ageing was handled ₁, K ₃Closure, K ₂Disconnect, the voltage of aging power supply 2 is 200V (can select in the scope of 100V-300V), temperature is controlled at 130 ℃ (can select 100 ℃-150 ℃ scope) in the baking oven 3, and the insulating paper sample was carried out burin-in process 600 hours (can select 500 hours-800 hours scope).Temperature in the baking oven should evenly distribute, and measures with infrared detecting set.For obtaining identical degree of aging, the test container position in baking oven clocklike changes.After artificial ageing was finished dealing with, measuring micro-water content according to IEC60450 was that the degree of polymerization (DP) of 0.6% and 4% sample is as shown in table 1.

The sample state	DP (degree of polymerization)	Aging factor
			New sample	1340	/
Aging back 0.6% micro-water content	470	39％
			Aging back 4% micro-water content	320	72％

As shown in Table, the sample aging factor that micro-water content is low is starkly lower than the high test product of micro-water content.The aging factor of the sample of micro-water content 4% almost is 2 times of 0.6% sample.This result shows little water having a strong impact on insulation ag(e)ing clearly.

To being positioned over after sample 9 burin-in process in the middle of the plate electrode sensor finish cut-off switch K ₁, K ₃, by top portion valve 5 insulating oil is injected in organic container, place certain hour (best above time in 1 week), allow the little water in the paper oil insulation system reach equilibrium state.Temperature in the baking oven is controlled at 30 ℃, Closing Switch K after reaching equilibrium state ₁And K ₂, applying frequency at the drive electrode end of dielectric tests sensor respectively is 0.01Hz, voltage magnitude is 5V; The output voltage signal of induction electrode connects intelligent oscillograph 1, directly obtains voltage gain amplitude M and phase differential between input signal and the output signal And data are carried out record.After the sinusoidal voltage input signal test that single micro-water content sample is applied 0.01Hz finishes, again it is applied 0.1Hz one by one, 1Hz, 10Hz, 100Hz, 1000Hz and 10000Hz seven kinds of sine voltage signals are altogether from low to high measured voltage gain amplitude M and phase differential that record measures at every turn

Value.Single micro-water content sample applied frequency voltage signal test from low to high when 30 ℃ (can select) and all finish in 20 ℃ of-100 ℃ of scopes after, temperature in the baking oven is raise and remain on 70 ℃ (can in 20 ℃ of-100 ℃ of scopes, select), place certain hour (best above time in 1 week) and make the little water in the paper oil insulation reach equilibrium state again.Again apply 0.01Hz respectively, 0.1Hz, 1Hz, 10Hz, 100Hz, the sine voltage signal of 1000Hz and 10000Hz is tested, voltage gain amplitude M and phase differential that record measures at every turn Value.After the sample of single micro-water content applied frequency voltage signal test from low to high when 30 ℃ and 70 ℃ and all finish, voltage gain amplitude M and phase differential when changing different micro-water content samples and when 30 ℃ and 70 ℃, testing the sinusoidal voltage input signal that applies 7 kinds of different frequencies respectively between input signal and the output signal

Value, and each voltage gain amplitude M and the phase differential that obtains of testing of record Value.Duplicate measurements is all tested up to all micro-water content samples and to be finished.Above-mentioned 30 ℃ and 70 ℃ is a pair of selection temperature value, and these two temperature can be selected arbitrarily between 20 ℃-100 ℃, as long as twice temperature is different.If for to make the micro-water content computing formula of final acquisition more accurate, can select two or more temperature to test respectively.

Second step, the complex permittivity real part ε ' of paper oil insulation sample and imaginary part ε " calculation procedure as follows:

The original calculation formula of the real part of complex permittivity and imaginary part is:

${\mathrm{\ϵ}}^{\′}=\frac{{\mathrm{dC}}_T}{A},$ ${\mathrm{\ϵ}}^{\′\′}=\frac{d}{R_T\mathrm{A\ω}}$

Therefore require ε ', ε " value will calculate the measuring unit parameters R earlier _TAnd C _TValue.Here defining the admittance of measuring branch road and load branch among Fig. 3 is respectively Y _T=1/R _T+ i ω C _TAnd Y _L=1/R _L+ i ω C _LAs shown in Figure 3, can get according to voltage divider principle:

In low-frequency range, promptly ω leveled off to 0 o'clock, and voltage gain M equals R _L/ (R _L+ R _T).High-frequency range,

Be that ω levels off to ∞, voltage gain M equals C _T/ (C _T+ C _L).R _TAnd C _TWith known load branch R _L, C _LValue and the M that records,

Value is expressed as follows:

With the measuring unit parameters R _TAnd C _TCalculating formula substitution ε ', ε " the original calculation formula in can obtain comprising characteristic parameter M that the dielectric test obtains and

The real part and the imaginary part calculating formula of complex permittivity.

In the calculating formula, " be the real part and the imaginary part of complex permittivity, real part is represented the specific inductive capacity of material, and imaginary part has reflected the power loss characteristic of material for ε ', ε.R _L, C _LBe known load branch parameter, d is the spacing of parallel pole sensor, and A is a parallel pole sensor drive electrode surface area;

Third step, with the characteristic parameter M that records and Be worth complex permittivity real part and imaginary part computing formula in substitution second step, get the logarithm log (m) of little quality mark respectively, the real part log of complex permittivity ((ε '-ε _∞)/ε ₀) and imaginary part log (ε "/ε ₀) the logarithm and the logarithm log (f) of each frequency, the computational data in the time of 30 ℃ is as shown in the table

The contrast computational data can draw different in moisture under the uniform temp to the influence of complex permittivity.ε ', ε more as can be known " value all along with moisture and temperature increase and increase, and its variation tendency is basic identical under different temperatures and moisture.These variation tendencies are generally speaking near linear.Therefore can pass through linear fit, the complex permittivity real part when drawing 30 ℃, 70 ℃ respectively and the expression formula of imaginary part:

From above four expression formulas as can be seen, little water m of the real part of complex permittivity and the size of imaginary part and paper oil insulation, apply electric voltage frequency f and temperature T relevant.First of each expression formula is little with the temperature T variation, and preceding two variations then are bigger.It is linear to suppose that temperature T changes with the logarithm of complex permittivity, so just can average for first by carrying out the temperature linearity match to back two, can obtain:

$\log \left(\frac{{\mathrm{\ϵ}}^{\′}-{\mathrm{\ϵ}}_{\∞}}{{\mathrm{\ϵ}}_0}\right)=(-0.0851\log \left(f\right)+1.7780)\log \left(m\right)-(0.0011T+0.2320)\log \left(f\right)+0.0081T-0.6499$

$\log \left(\frac{{\mathrm{\ϵ}}^{\′\′}}{{\mathrm{\ϵ}}_0}\right)=(-0.2797\log \left(f\right)+2.1328)\log \left(m\right)-(0.0032T+0.2265)\log \left(f\right)+0.0177T-1.2571$

According to top two formulas, can write out the general expression formula that comprises temperature:

$\log \left(\frac{{\mathrm{\&epsiv;}}^{\&prime;}-{\mathrm{\&epsiv;}}_{\&infin;}}{{\mathrm{\&epsiv;}}_0}\right)=r_1\left(f\right)\log \left(m\right)-r_2\left(T\right)\log \left(f\right)+f_{T1}\left(T\right)+{\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HSA00000338779200022.png"\; state="\{\{state\}\}">c</figure-callout>}}_1$

$\log \left(\frac{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}{{\mathrm{\&epsiv;}}_0}\right)=r_3\left(f\right)\log \left(m\right)-r_4\left(T\right)\log \left(f\right)+f_{T2}\left(T\right)+{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HSA00000338779200021.png"\; state="\{\{state\}\}">c</figure-callout>}}_2$

Just can derive the expression formula of micro-water content by inverse operation:

$m={[f^{r_2\left(T\right)}\&CenterDot;\left(\frac{{\mathrm{\&epsiv;}}^{\&prime;}-{\mathrm{\&epsiv;}}_{\&infin;}}{{\mathrm{\&epsiv;}}_0}\right)\&CenterDot;{10}^{-c_1-f_{T1}\left(T\right)}]}^{\frac{1}{r_1\left(f\right)}}$

$m={[f^{r_4\left(T\right)}\&CenterDot;\left(\frac{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}{{\mathrm{\&epsiv;}}_0}\right)\&CenterDot;{10}^{-c_2-f_{T2}\left(T\right)}]}^{\frac{1}{r_3\left(f\right)}}$

C in the formula ₁, c ₂, being related coefficient, r (T) is for comprising the expression formula of temperature T, and r (f) is for comprising the expression formula of frequency f, and f (T) is the function relevant with temperature T, ε _∞/ ε ₀=3.The substitution computational data obtains paper oil insulation micro-water content m and its complex permittivity ε ^*, the functional relation that applies electric voltage frequency f and environment temperature T is as follows:

$m={(f^{0.0011T+0.2330}\&CenterDot;(\frac{{\mathrm{\&epsiv;}}^{\&prime;}}{{\mathrm{\&epsiv;}}_0}-3)\&CenterDot;{10}^{0.6499-0.0081T})}^{\frac{1}{-0.0851\log \left(f\right)+1.7780}}$

$m={(f^{0.0032T+0.2265}\&CenterDot;\left(\frac{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}{{\mathrm{\&epsiv;}}_0}\right)\&CenterDot;{10}^{-0.0177T+1.2571})}^{\frac{1}{-0.2797\log \left(f\right)+2.1328}}$

The 4th step is prepared respectively to measure and verify accuracy than two kinds of insulating papers of low 0.2% and higher 5% as the insulating paper of unknown micro-water content with the micro-water content of the same model of sample for preparing in advance.At first unknown micro-water content insulating paper (actual micro-water content is known) is put in the middle of the plate electrode sensor, after the injection transformer oil-impregnated temperature in the baking oven is kept 50 ℃ (can select the arbitrary temperature between 20-100 ℃), and on the plate electrode sensor, applying the sinusoidal voltage that frequency is 0.1Hz (can between 0.01Hz-10000Hz, select any one sinusoidal voltage) input signal, the voltage between Test input signal and the output signal duplicates gain M and phase differential

The voltage of testing is duplicated gain M and phase differential

Calculate in substitution second step in the formula of complex permittivity real part and imaginary part and calculate, calculate the real part ε ' and the imaginary part ε of complex permittivity ", real part ε ' and imaginary part ε " paper oil insulation micro-water content m and its complex permittivity ε in the 3rd step of substitution again ^*, apply the micro-water content that the functional relation of electric voltage frequency f and environment temperature T calculates, and verify calculated value and actual value as follows:

Also can effectively assess little quality by the real part and the imaginary part of complex permittivity as can be seen from top form.With two computing formula determining in the third step micro-water content value that first kind of unknown paper oil insulation system-computed goes out be there are differences, these two calculated values are all less than 2% as can be seen from the table, so adopt the value of the calculated value of first formula as final micro-water content m, be m=0.213, error is 6.5%; With two computing formula determining in the third step micro-water content value that second kind of unknown paper oil insulation system-computed goes out be there are differences, these two calculated values are all greater than 2% as can be seen from the table, so adopt the micro-water content value m of the mean value of the first and second formula calculated values as this paper oil insulation system, be m=(5.33+5.245)/2=5.2875, error is 5.7%.As seen, utilize the present invention to set up the funtcional relationship formula and can calculate unknown paper oil insulation micro-water content, the error between its income value and the actual value is less.

Claims (4)

1. the paper oil insulation micro-water content measuring method based on the dielectric response is characterized in that it comprises the steps:

First step, the insulating board sample for preparing the different micro-water contents of same model, respectively each sample is placed in the plate electrode sensor then, carrying out artificial ageing handles, and with the sinusoidal voltage of the after-applied frequency adjustable of transformer insulated oil-impregnated as input signal, test the voltage gain M and the phase differential of every kind of input signal and output signal

Second step is with voltage gain M and the phase differential of testing in the first step

The following formula of value substitution, the complex permittivity (ε of calculating tested sample ^*):

In the formula, ε ', ε " be the real part and the imaginary part of complex permittivity,

For the phase differential between input voltage and the output voltage, M are the voltage gain amplitude, R _T, C _TBe test cell model parameter, R _L, C _LBe known load branch road parameter, d is the spacing of plate electrode sensor, and A is a plate electrode sensor drive electrode surface area;

Third step is according to the complex permittivity ε that obtains in above-mentioned second step ^*And apply electric voltage frequency f, environment temperature T and carry out data fitting, determine paper oil insulation micro-water content m and complex permittivity ε ^*, apply the general purpose function relational expression of electric voltage frequency f, environment temperature T:

First formula:

$m={[f^{r_2\left(T\right)}\&CenterDot;\left(\frac{{\mathrm{\&epsiv;}}^{\&prime;}-{\mathrm{\&epsiv;}}_{\&infin;}}{{\mathrm{\&epsiv;}}_0}\right)\&CenterDot;{10}^{-c_1-f_{T1}\left(T\right)}]}^{\frac{1}{r_1\left(f\right)}}$

Second formula: $m={[f^{r_4\left(T\right)}\&CenterDot;\left(\frac{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}{{\mathrm{\&epsiv;}}_0}\right)\&CenterDot;{10}^{-c_2-f_{T2}\left(T\right)}]}^{\frac{1}{r_3\left(f\right)}}$

C in above-mentioned two formulas ₁, c ₂Be related coefficient, r (T) is for comprising the expression formula of temperature T, and r (f) is for comprising the expression formula of frequency f, and f (T) is the function relevant with temperature T;

The 4th step, to put into the plate electrode sensor of first step with the insulating paper of unknown micro-water content of the same model of sample of preparation in advance, injection insulating oil dipping, and apply between the 0.01Hz-10000Hz any one sinusoidal voltage as input signal, the voltage gain M and the phase differential of Test input signal and output signal

And then carry out data processing by formula and relational expression that above-mentioned second step and third step are confirmed, calculate the micro-water content of paper oil insulation; The micro-water content m that first formula and second formula calculate in by above-mentioned third step is all less than 2% the time, adopt the micro-water content value of the first formula calculated value as final unknown paper oil insulation, other situations all adopt the micro-water content value of the mean value of two values as unknown paper oil insulation.

2. the measuring method of paper oil insulation micro-water content according to claim 1, it is characterized in that in described first step, the insulating paper method of sample preparation to be measured of its different micro-water contents is: the insulating board that will not carry out any processing earlier is placed in the thermal vacuum chamber oven dry and handles to moisture and fully separate out, insulating board exposure with oven dry is placed in the air then, allow it absorb the water in air branch, reach predetermined value up to its weight.

3. the measuring method of paper oil insulation micro-water content according to claim 1 is characterized in that artificial ageing in the described first step is handled to be meant sample is positioned in 100 ℃-150 ℃ the temperature and to handle 500-800 hour.

4. the measuring method of paper oil insulation micro-water content according to claim 1 is characterized in that in the first step that input signal and output signal all insert oscillograph, measures characteristic parameter voltage gain M and phase differential

To calculate complex permittivity in the characteristic parameter substitution complex permittivity computing formula in second step again.

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