CN109239463A - A kind of dielectric loss measurement method based on linear correction algorithm - Google Patents
A kind of dielectric loss measurement method based on linear correction algorithm Download PDFInfo
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Abstract
The present invention relates to a kind of dielectric loss measurement method based on linear correction algorithm, this method improves realization on the basis of plesiochronous DFT, includes the following steps: the current signal I for sampling the voltage signal V applied on test specimen simultaneously He flowing through；Alive fundamental wave phase angle is applied using the humorous phase angle linear correction method acquisition of plesiochronous DFTThe current signal fundamental wave initial phase angle flowed through in test specimen is obtained using the humorous phase angle linear correction method of plesiochronous DFTAccording to formula
Description
The application be application No. is: 201510258036.4, invention and created name be " a kind of dielectric loss measurement method ",
The applying date are as follows: the divisional application of application for a patent for invention on May 19th, 2015.
Technical field
The present invention relates to a kind of high-precision dielectric loss measurement methods.
Background technique
Intelligent medium loss measurent instrument is the self-reacting device of measuring medium loss angle tangent and capacitance, can be in work
Under frequency high voltage, the high pressures such as the various insulating materials of in-site measurement, insulating sleeve, power cable, capacitor, mutual inductor, transformer
The dielectric loss angle tangent and capacitance of equipment.The instrument be also applied for workshop, laboratory, R&D institution measurement High-Voltage Electrical Appliances set
Standby dielectric loss angle tangent and capacitance；Being equipped with insulation lubricating cup can measure insulation oil loss.
The working principle of intelligent medium loss measurent instrument: the voltage when applying alternating voltage on dielectric, in dielectric
At in phase angle difference between electric currentComplementary angle δ be known as dielectric loss angle, the tangent tg δ of δ is known as dielectric loss angle tangent.tgδ
Value is the parameter for measuring dielectric loss.The measurement route of the instrument is including standard loop (Cn) all the way and is tested back all the way
Road (Cx).Standard loop is made of built-in high stability standard capacitor and measurement route, is tested circuit by test item and measurement
Route.Measurement route is made of sample resistance and preamplifier and A/D converter, before being connected in parallel on sample resistance both ends
It sets amplifier input resistance and is far longer than sample resistance, it can thus be assumed that loop current all flows through sample resistance.Pass through measurement
Current signal is converted to digital signal by route, then is measured standard respectively with digitlization real-time collecting method by single-chip microcontroller and returned
Road electric current and subject loop current amplitude and its phase difference can show that the capacitance of test product and medium are damaged by vector calculus
Consumption.
Frequency analysis technology is answered in various fields such as electric energy quality monitoring, electronic product production testing, electric appliances monitorings
It is the important technical for carrying out power system monitor, quality inspection, monitoring of tools with extensive.Frequency analysis is most widely used at present
Technology be discrete Fourier transform (DFT) and Fast Fourier Transform (FFT) (FFT).Quasi-synchronous sampling technique is mutually tied with DFT technique
The frequency analysis technology of conjunction can be improved the precision of frequency analysis, formula are as follows:
In formula: k is the number (such as fundamental wave k=1,3 subharmonic k=3) for needing the harmonic wave obtained；Sin and cos are positive respectively
String and cosine function；And akAnd bkThe respectively real and imaginary parts of k subharmonic；N is the number of iterations；W is determined by integration method, is adopted
When with muiltiple-trapezoid integration method, W=nN；γiFor a weighting coefficient；For the sum of all weighting coefficients；f(i)
For the ith sample value of analysis waveform；N is sampling number in the period.
In engineer application, frequency analysis always carry out the sampling of finite point be difficult to stricti jurise synchronize adopt
Sample.In this way, when the plesiochronous DFT of application carries out frequency analysis, will exist the leakage of the long range as caused by truncation effect and
The short range leakage as caused by fence effect, so that analysis result precision is not high or even insincere.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of high-precision dielectric loss surveys based on linear correction algorithm
Amount method, to be efficiently modified the analytical error of plesiochronous DFT frequency analysis technology, obtain high-precision frequency analysis as a result, from
And improve the reliability of dielectric loss measurement.
Realize that the technical solution of the object of the invention is to provide a kind of dielectric loss measurement method based on linear correction algorithm,
It comprises the following steps:
(1) the W+2 sample point data for the voltage signal V and current signal I that synchronized sampling is applied on test specimen at equal intervals:
{fV(i),fI(i), i=0,1 ..., W+1 }；
(2) plesiochronous DFT formula is applied since the sampled point i=0 of the voltage signal V:
W+1 data of analysis obtain the base of the voltage signal V
Wave informationWith
Plesiochronous DFT formula is applied from the sampled point i=1 of the voltage signal V:
W+1 data of analysis obtain the base of the voltage signal V
Wave informationWith
Using formula:Calculate the frequency drift μ of the voltage signal VV；
Using formulaCalculate the fundamental wave initial phase angle of the voltage signal V；
Using formulaLinearly correct the fundamental wave initial phase angle of the voltage signal V.
(3) plesiochronous DFT formula is applied since the sampled point i=0 of the current signal I:
W+1 data of analysis obtain the base of the current signal I
Wave informationWith
Plesiochronous DFT formula is applied from the sampled point i=1 of the current signal I:
W+1 data of analysis obtain the base of the current signal I
Wave informationWith
Using formula:Calculate the frequency drift μ of the current signal II；
Using formulaCalculate the fundamental wave initial phase angle of the current signal I；
Using formulaLinearly correct the fundamental wave initial phase angle of the current signal I.
(4) according to formulaCalculation medium loss angle tangent.
The main reason for plesiochronous DFT frequency analysis can effectively inhibit long range and leak, spectrum leakage is signal
Short range leakage caused by frequency drift, the present invention, which discloses one kind, can effectively inhibit the humorous phase angle of short range leakage linearly to correct
Method, to obtain high-precision humorous phase angle information and dielectric dissipation factor.
N is the sampling number in an ideal period.The equal interval sampling is according to the ideal for carrying out frequency analysis
The cycle T and frequency f (such as power frequency component frequency f is 50Hz, period 20mS) of signal, sample N point in one cycle, that is, adopt
Sample frequency is fs=Nf, and N >=64.
Described W+2 sample point data of sampling is accordingly selected according to selected integration method, according to multiple
Change trapezoidal integration method, then W=nN；According to complexification rectangular integration method, then W=n (N-1)；According to iterative Simpson product
Divide method, then W=n (N-1)/2；Then according to sample frequency fs=Nf obtains sample point data sequence；N is the number of iterations, one
As n >=3.
An iteration coefficient gammaiIt is determined by integration method, ideal period sampled point N and the number of iterations n, specific derivation process
Referring to document [wear some problem [J] the electrical measurement and instrument in the application of quasi-synchro sampling in elder generation, 1988, (2): 2-7.].
For the sum of all weighting coefficients.
The drift μ of signal frequencyVAnd μIIt is according to sampling number N in neighbouring sample point fundamental wave phase angle difference and ideal period
Fixed relationship and obtain, the drift of signal frequency can also be used for amendment fundamental wave and higher hamonic wave frequency f1With higher hamonic wave
Frequency fk。
The present invention has the effect of positive: (1) present invention has high-precision dielectric loss measurement result.
(2) method of the present invention fundamentally solves the problems, such as that the humorous phase angle analysis precision of plesiochronous DFT is low, and nothing
Complicated inverting and amendment need to be carried out, algorithm is simple.
(3) relative to plesiochronous DFT, frequency analysis technology of the present invention only needs to increase a sampled point and just solves
Plesiochronous DFT analytical error big problem, it is easy to accomplish.
(4) existing instrument and equipment is improved using the present invention, be technically feasible, and do not need to increase any hard
Part expense can be such that analysis result can be improved to 10-8Grade.
(5) this method is similarly also applied for carrying out successive ignition rather than the frequency analysis process of an iteration, at this time only
Needing an iteration to resolve into successive ignition realization can.As an iteration with successive ignition is substantially, only
It is that when calculating, successive ignition carries out decoupled method, and an iteration is that the process of successive ignition is merged into iteration coefficient γi
In once calculate complete, so the present disclosure applies equally to successive ignition processes.
Specific embodiment
(embodiment 1)
A kind of dielectric loss measurement method based on linear correction algorithm of the present embodiment, comprising the following steps:
(1) the W+2 sample point data for the voltage signal V and current signal I that synchronized sampling is applied on test specimen at equal intervals:
{fV(i),fI(i), i=0,1 ..., W+1 }.W is accordingly selected according to selected integration method, according to the trapezoidal product of complexification
Divide method, then W=nN；According to complexification rectangular integration method, then W=n (N-1)；According to iterative Simpson integration method, then
W=n (N-1)/2；Then according to sample frequency fs=Nf obtains sample point data sequence；N is the number of iterations, general n >=3.
(2) plesiochronous DFT formula is applied since the sampled point i=0 of the voltage signal V:
W+1 data of analysis obtain the base of the voltage signal V
Wave informationWithAn iteration coefficient gammaiIt is determined by integration method, ideal period sampled point N and the number of iterations n；For the sum of all weighting coefficients；
Plesiochronous DFT formula is applied from the sampled point i=1 of the voltage signal V:
W+1 data of analysis obtain the base of the voltage signal V
Wave informationWith
Using formula:Calculate the frequency drift μ of the voltage signal VV；
Using formulaCalculate the fundamental wave initial phase angle of the voltage signal V；
Using formulaLinearly correct the fundamental wave initial phase angle of the voltage signal V.
(3) plesiochronous DFT formula is applied since the sampled point i=0 of the current signal I:
W+1 data of analysis obtain the base of the current signal I
Wave informationWith
Plesiochronous DFT formula is applied from the sampled point i=1 of the current signal I:
W+1 data of analysis obtain the base of the current signal I
Wave informationWith
Using formula:Calculate the frequency drift μ of the current signal II；
Using formulaCalculate the fundamental wave initial phase angle of the current signal I；
Using formulaLinearly correct the fundamental wave initial phase angle of the current signal I.
(4) according to formulaCalculation medium loss angle tangent.
Those skilled in the art it should be appreciated that more than embodiment be intended merely to illustrate the present invention, and
It is not intended as limitation of the invention, the present invention can also be changing into more modes, as long as in connotation model of the invention
In enclosing, variation, the modification of embodiment described above will all be fallen within the scope of claims of the present invention.
Claims (2)
1. a kind of dielectric loss measurement method based on linear correction algorithm, it is characterised in that the following steps are included:
(1) the W+2 sample point data for the voltage signal V and current signal I that synchronized sampling is applied on test specimen at equal intervals: { fV
(i),fI(i), i=0,1 ..., W+1 }；Described W+2 sample point data of sampling is to use muiltiple-trapezoid integration method, then W
=nN；
(2) plesiochronous DFT formula is applied since the sampled point i=0 of the voltage signal V:
W+1 data of analysis obtain the fundamental wave letter of the voltage signal V
BreathWith
Plesiochronous DFT formula is applied from the sampled point i=1 of the voltage signal V:
W+1 data of analysis obtain the fundamental wave letter of the voltage signal V
BreathWith
Using formula:Calculate the frequency drift μ of the voltage signal VV；
Using formulaCalculate the fundamental wave initial phase angle of the voltage signal V；
Using formulaLinearly correct the fundamental wave initial phase angle of the voltage signal V；
(3) plesiochronous DFT formula is applied since the sampled point i=0 of the current signal I:
W+1 data of analysis obtain the fundamental wave letter of the current signal I
BreathWith
Plesiochronous DFT formula is applied from the sampled point i=1 of the current signal I:
W+1 data of analysis obtain the fundamental wave letter of the current signal I
BreathWith
Using formula:Calculate the frequency drift μ of the current signal II；
Using formulaCalculate the fundamental wave initial phase angle of the current signal I；
Using formulaLinearly correct the fundamental wave initial phase angle of the current signal I；
(4) according to formulaCalculation medium loss angle tangent；
In formula: k is the number for needing the harmonic wave obtained；Sin and cos is respectively sine and cosine functions；And akAnd bkRespectively k
The real and imaginary parts of subharmonic；N is the number of iterations；W is determined by integration method；γiFor a weighting coefficient；For
The sum of all weighting coefficients；F (i) is the ith sample value of analysis waveform；N is sampling number in the period；
The equal interval sampling is adopted in one cycle according to the cycle T and frequency f of the ideal signal for carrying out frequency analysis
Sample N point, i.e. sample frequency are fs=Nf, and N >=64.
2. a kind of dielectric loss measurement method based on linear correction algorithm according to claim 1, it is characterised in that: institute
W+2 sample point data of the sampling stated accordingly is selected according to selected integration method, then according to sample frequency fs
=Nf obtains sample point data sequence；N is the number of iterations, n >=3.
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| CN110231515B (en) * | 2019-06-19 | 2021-04-09 | 桂林理工大学 | Real-time online measurement method for dielectric loss factor of insulation life test |
| CN112904088B (en) * | 2021-01-15 | 2022-03-04 | 南方电网科学研究院有限责任公司 | Dielectric loss tangent calculation method in broadband dielectric loss detection device |
| CN114184845B (en) * | 2021-11-05 | 2022-08-09 | 西南交通大学 | Vehicle-mounted cable service state evaluation method based on variable-temperature dielectric performance |
| CN115508671B (en) * | 2022-11-10 | 2023-03-28 | 国网天津市电力公司电力科学研究院 | Fault positioning method and system based on line voltage lowest point calculation |
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| CN109270357A (en) | 2019-01-25 |
| CN104849569B (en) | 2018-11-23 |
| CN104849569A (en) | 2015-08-19 |
| CN109030957B (en) | 2020-12-25 |
| CN109239463B (en) | 2020-07-31 |
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