CN111562440B - Method for measuring resistivity of insulating dielectric medium based on time domain least square fitting - Google Patents
Method for measuring resistivity of insulating dielectric medium based on time domain least square fitting Download PDFInfo
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- CN111562440B CN111562440B CN202010461194.0A CN202010461194A CN111562440B CN 111562440 B CN111562440 B CN 111562440B CN 202010461194 A CN202010461194 A CN 202010461194A CN 111562440 B CN111562440 B CN 111562440B
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
Abstract
The invention discloses a measuring principle of the resistivity of an insulating dielectric medium based on time domain least square fitting, belongs to the field of dielectric parameter measurement of the insulating dielectric medium, and solves the problems that the existing measuring method of the resistivity of the insulating dielectric medium is low in efficiency and easy to be subjected to polarization absorptionReceiving current and thermal noise. The method comprises the following steps of testing and recording a polarization current time domain spectrum of a tested insulating dielectric medium under the action of direct-current voltage, performing time domain least square fitting on polarization current by respectively adopting a universal relaxation polarization current model and an extended Debye model, determining an optimal polarization absorption current model by taking a residual time sequence which is irrelevant to time and a residual average value which is not more than one percent of a steady-state conduction current component as criteria, and accurately obtaining a steady-state conduction current I dc And conducting current density J from steady state dc And calculating the electric field intensity to obtain the resistivity rho.
Description
Technical Field
The invention belongs to the field of dielectric parameter measurement of insulating dielectrics, and particularly relates to a measuring principle of resistivity of the insulating dielectrics based on time domain least square fitting.
Background
The excellent insulating properties of insulating dielectrics are an important basic guarantee for the safe operation of electrical equipment and electronic devices. Volume resistivity is one of the important dielectric parameters that characterize the insulating properties of insulating dielectrics. The volume resistivity of an insulating dielectric is generally measured using a test system as shown in fig. 1, which is mainly to apply a dc high voltage to the insulating dielectric for a certain time and measure the quasi-steady state leakage current flowing through the insulating dielectric. In the initial stage of the applied voltage, the polarization absorption current component caused by relaxation polarization is large. The sink current component gradually decreases with increasing time. After a sufficiently long time, the component of the absorbed current is almost zero, at which time the current through the insulating dielectric is mainly a quasi-steady state leakage current. In engineering, a value of a current flowing through the insulating dielectric at 1 minute of applied voltage is generally taken as a quasi-steady state leakage current value to save test time, but is easily affected by a polarization absorption current. In order to accurately obtain the leakage current flowing through the insulating dielectric sample, a method is generally adopted in which the time for reading the leakage current flowing through the insulating dielectric is prolonged, the efficiency is low, and the influence of thermal noise is large. Under the action of the direct-current high voltage, the polarization absorption current component of the insulating dielectric needs a long time to decay to zero, but the specific time required for the polarization absorption current component to decay to zero is difficult to define, so the leakage current obtained by prolonging the reading time usually also comprises the polarization absorption current component, which affects the accuracy of the volume resistivity.
SUMMARY OF THE PATENT FOR INVENTION
In order to overcome the defects that the existing method for measuring the resistivity of the insulating dielectric is low in efficiency and is easily influenced by polarization absorption current and thermal noise, the invention aims to provide a measuring principle of the resistivity of the insulating dielectric based on time domain least square fitting.
The invention is realized by the following technical scheme:
the insulation dielectric resistivity measuring principle based on time domain least square fitting is characterized in that the influence of polarization absorption current and thermal noise is eliminated through a least square fitting method, and therefore steady-state conduction current I is accurately obtained dc And the current density J is conducted from the steady state dc And calculating the electric field intensity to obtain the resistivity rho.
Further, a universal relaxation polarization current model and an expanded Debye model are respectively adopted to carry out time-domain least square fitting on the polarization current, and an optimal polarization absorption current model is judged according to the fitting effect.
Further, the criterion for the least squares best fit effect is that the residual time series is time independent and the residual mean does not exceed one percent of the steady state conduction current component.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a measuring principle of the resistivity of an insulating dielectric medium based on time domain least square fitting, which is based on the time domain characteristic of a universal relaxation polarization absorption current and eliminates the influence of the polarization absorption current and thermal noise on steady-state conduction current and the resistivity by a least square fitting method.
The insulating dielectric resistivity measurement principle based on time domain least square fitting disclosed by the invention is easy to realize, can improve the measurement efficiency of the insulating dielectric resistivity, is generally suitable for insulating dielectrics with universal relaxation polarization characteristics, and has a wide application range.
Drawings
FIG. 1 is a schematic diagram of an insulation dielectric response current test system under the action of a DC electric field;
FIG. 2 is a test current and a fitted current for an insulating dielectric of an embodiment;
FIG. 3 is a residual of the insulating dielectric test current and the fitted current of the embodiment;
in the figure: 1. an insulating dielectric; 2. a high voltage electrode; 3. a measuring electrode; 4. a guard electrode; 5. a high voltage electrode lead; 6. a measurement electrode lead; 7. a guard electrode lead; 8. an electrometer; 9. computer data communication line.
Detailed Description
The present invention will be described in detail with reference to the following embodiments and examples. It is emphasized that this summary is provided to explain the invention and not to limit it.
Detailed description of the invention
A measurement principle of insulation dielectric resistivity based on time domain least square fitting specifically eliminates the influence of polarization absorption current and thermal noise by a least square fitting method, thereby accurately obtaining steady state conduction current I dc And the current density J is conducted from the steady state dc And calculating the electric field intensity to obtain the resistivity rho.
Detailed description of the invention
On the basis of the first specific embodiment, specifically, a universal relaxation polarization current model and an extended debye model are respectively adopted to perform time-domain least square fitting on the polarization current, and the optimal polarization absorption current model is judged according to the fitting effect.
Detailed description of the invention
On the basis of the second embodiment, specifically, the criterion of the least square best fit effect is that the residual time series is independent of time and the residual average value is not more than one percent of the steady-state conduction current component.
Detailed description of the invention
On the basis of the first embodiment, specifically, the calculation formula of the resistivity is
Specifically, in the formula, U is an externally applied dc voltage, S is an area of the insulating dielectric, and d is a thickness of the insulating dielectric.
Detailed description of the invention
On the basis of the second embodiment, specifically, the calculation formula of the residual Δ I is
ΔI i (t)＝I i (t)-I fi (t)
In particular, the residual mean value Δ I av Is calculated by the formula
In particular, I in the formula i (t) is the ith test value of the response current flowing through the insulating dielectric, I fi (t) is the ith fitted value for the response current flowing through the insulating dielectric.
Examples
The insulating dielectric medium of the embodiment is a 10wt% silicon carbide/polyethylene composite insulating medium, and the electrode area S =2122.64mm 2 The thickness d =0.2mm, the externally applied direct current voltage U =1kV, the electrometer model is Gekkeli 6517B, the test time t is 0-1000 s, and the variation curve of the response current I along with the time t is shown in figure 2.
The fitted currents obtained using the current fitting method are shown in fig. 2. The fitting parameters obtained in this example were a =909.74pa, n = -0.96,i, respectively dc =0.87pA. As shown in fig. 3, the residual Δ I time series is time independent. Residual mean value Δ I av ＝-0.794×10 -3 pA, less than I dc One hundredth of the embodiment, the relaxation polarization mechanism of the insulating dielectric conforms to the universal relaxation polarization law, and the resistivity p =7.90 × 10 13 Ω · m, and resistivity ρ extending the test time to t =7000s alone 0 ＝8.05×10 13 The relative error of omega m is 1.9 percent and is within the allowable range of test error.
Claims (1)
1. The method for measuring the resistivity of the insulating dielectric based on time domain least square fitting is characterized in that a pervasive relaxation polarization current model and an extended Debye model are respectively adopted to carry out time domain least square fitting on polarization current, an optimal polarization absorption current model is judged according to a fitting effect, the influence of polarization absorption current and thermal noise is eliminated, and therefore steady-state conduction current I is accurately obtained dc And the current density J is conducted from the steady state dc And calculating the electric field intensity to obtain resistivity rho; the criterion of the least square best fitting effect is that the residual time sequence is irrelevant to time and the average value of the residual does not exceed one percent of the steady-state conduction current component;
the calculation formula of the resistivity rho is as follows:
wherein U is an externally applied DC voltage, S is an area of the insulating dielectric, and d is a thickness of the insulating dielectric;
the residual mean value is expressed as:
wherein, I i (t) is the I-th test value of the response current flowing through the insulating dielectric, I fi (t) is the ith fitted value for the response current flowing through the insulating dielectric;
the measurement method is suitable for the insulating dielectric medium which is 10wt% of silicon carbide/polyethylene composite insulating medium.
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| US5391994A (en) * | 1992-12-31 | 1995-02-21 | At&T Corp. | Method for measuring surface resistivity using square electrodes and multiplying surface resistance measurements by a correction factor |
| CN102508774A (en) * | 2011-10-28 | 2012-06-20 | 哈尔滨工程大学 | Modeling method for software reliability growth model based on novel environmental factor function |
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