CN111579879B - Dielectric infinite high frequency relative dielectric constant measuring method - Google Patents
Dielectric infinite high frequency relative dielectric constant measuring method Download PDFInfo
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- CN111579879B CN111579879B CN202010461207.4A CN202010461207A CN111579879B CN 111579879 B CN111579879 B CN 111579879B CN 202010461207 A CN202010461207 A CN 202010461207A CN 111579879 B CN111579879 B CN 111579879B
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- surface potential
- dielectric constant
- time domain
- insulating dielectric
- relative dielectric
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- G—PHYSICS
- 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
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2617—Measuring dielectric properties, e.g. constants
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/16—Spectrum analysis; Fourier analysis
Abstract
The invention discloses a principle for measuring infinite high-frequency relative dielectric constant of an insulating dielectric medium based on polarization current and surface potential time domain spectrum, belonging to the field of dielectric constant measurementThe dielectric parameter measurement field of the edge dielectric medium solves the defect that the infinite high frequency relative dielectric constant of the existing insulating dielectric medium is difficult to accurately measure. The basic principle of the invention is as follows: the method comprises the steps of adopting an acquisition system consisting of an electrometer, an electrostatic voltmeter and a computer to realize the acquisition and recording of a polarization current time domain spectrum of the measured insulating dielectric medium under the action of direct current voltage and a surface potential attenuation time domain spectrum under the condition of open circuit, accurately obtaining the surface potential change rate of the surface potential attenuation initial moment through a least square fitting method, and obtaining the surface potential change rate according to the surface potential attenuation initial moment change rate
And a polarization current I (t) 1‑ ) By the formula
Realizing infinite high frequency relative dielectric constant epsilon ∞ The measurement of (2).
Description
Technical Field
The invention relates to the field of dielectric parameter measurement of insulating dielectrics, in particular to an infinite high-frequency relative dielectric constant measurement principle of the insulating dielectrics based on polarization current and surface potential time domain spectrum.
Background
Insulating dielectrics serve as electrical insulation, mechanical support, and outer encapsulation in electronic devices and electrical equipment. Relative dielectric constant ε r Is one of the important technical indexes for characterizing the polarization performance of the insulating dielectric. Debye relaxation polarization theory states that the relative permittivity ε of insulating dielectrics r The size can be determined by the relative dielectric constant epsilon of infinite high frequency ∞ Static relative dielectric constant ε s CornerThe frequency omega and the relaxation time tau are determined, and the specific relation is as follows
In the electric frequency range, the relative dielectric constant epsilon of infinite high frequency ∞ Is the result of instantaneous displacement polarization such as electron displacement polarization and atom displacement polarization. Static relative dielectric constant ε s Is the appearance after all polarization mechanisms (including transient displacement polarization and relaxation polarization) in the insulating dielectric medium are fully established under the action of a direct current electric field. If the infinite high frequency relative permittivity ε of the insulating dielectric can be obtained ∞ And static relative dielectric constant ε s Then the relative permittivity epsilon of the insulating dielectric in the electric frequency range can be calculated according to the Debye relaxation polarization theory or the extended Debye relaxation polarization theory r . Wherein the relative dielectric constant ε of infinite high frequency ∞ Is measured as the relative dielectric constant ε r Important basis for theoretical calculation.
For transparent gas, liquid and solid insulating dielectrics, the relative permittivity ε of an infinite high frequency ∞ Equal to the square of the light refraction coefficient n, and the relative dielectric constant epsilon of infinite high frequency can be obtained by measuring the light refraction coefficient n ∞ . However, it is difficult to obtain the optical refractive index by an optical test method using a non-transparent insulating dielectric. In general, the dielectric constant epsilon of an insulating dielectric is approximate to infinite high frequency obtained by adopting a broadband dielectric spectrum method ∞ . For example, a broadband dielectric spectrometer is set at the highest frequency of 10 7 Relative permittivity obtained in Hz as the relative permittivity ε of an infinitely high frequency ∞ But at a frequency much lower than that of light (of the order of 10 14 Hz), that is, an infinitely high frequency relative dielectric constant can hardly be obtained by the dielectric spectroscopy method.
Disclosure of Invention
In order to overcome the defect that the infinite high frequency relative dielectric constant of the insulating dielectric is difficult to accurately obtain by the existing method, the invention aims to provide a measuring principle of the infinite high frequency relative dielectric constant of the insulating dielectric based on a polarization current and a surface potential time domain spectrum.
The invention is realized by the following technical scheme:
a principle for measuring the infinite high-frequency relative dielectric constant of an insulating dielectric medium based on polarized current and surface potential time domain spectrums is characterized in that a switch is switched from a polarized current test state to a surface potential test state, the polarized current time domain spectrums before the switch is switched and the surface potential time domain spectrums after the switch is switched are collected and recorded, and the change rate of the surface potential at the initial moment is determined according to the change rate of the surface potential
And a polarization current I (t) 1- ) By the formula
Calculating to obtain the infinite high-frequency relative dielectric constant epsilon ∞ 。
Further, the influence of thermal noise on the measured surface potential time domain spectrum of the insulating dielectric is eliminated through a least square fitting method, and therefore the surface potential change rate of the insulating dielectric at the initial open circuit moment is accurately obtained.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides an infinite high-frequency relative dielectric constant measuring principle of an insulating dielectric medium based on polarization current and surface potential time domain spectrums, belongs to an electrical measuring method, and can more effectively represent the infinite high-frequency relative dielectric constant of the insulating dielectric medium (including transparent and non-transparent insulating dielectric media) in an electrical frequency range compared with an optical refractive index measuring method.
The principle of the infinite high-frequency relative dielectric constant measurement of the insulating dielectric medium based on the polarized current and surface potential time domain spectrum is simple and easy to realize, the influence of thermal noise on the surface potential change rate is eliminated through a least square fitting method, and the application range is wide.
Drawings
FIG. 1 is a schematic diagram of a system for joint testing of polarization current and surface potential time domain spectra of an insulating dielectric;
FIG. 2 is the results of a response current test of an insulating dielectric under a DC voltage in the examples;
FIG. 3 is a surface potential time domain spectrum test result of the insulating dielectric before and after the DC voltage is removed in the example;
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. a high voltage electrostatic probe; 9. a high voltage electrostatic voltmeter; 10. an electrometer; 11. A direct current high voltage power supply; 12. a switch; 13. computer data communication 1; 14. computer data communication 2.
Detailed Description
The present invention will be described in detail with reference to the following embodiments and examples. It should be emphasized that this summary is intended to be illustrative, and not limiting, of the invention.
Detailed description of the invention
A principle for measuring the infinite high-frequency relative dielectric constant of an insulating dielectric medium based on polarized current and surface potential time domain spectrums is characterized in that a switch is switched from a polarized current test state to a surface potential test state, the polarized current time domain spectrums before the switch is switched and the surface potential time domain spectrums after the switch is switched are collected and recorded, and the change rate of the surface potential at the initial moment is determined according to the change rate of the surface potential
And a polarization current I (t) 1- ) By the formula
Calculating to obtain the infinite high-frequency relative dielectric constant epsilon ∞ 。
Detailed description of the invention
On the basis of the first embodiment, specifically, the influence of thermal noise on the measured surface potential time domain spectrum of the insulating dielectric is eliminated by a least square fitting method, so that the surface potential change rate of the insulating dielectric at the initial open circuit time is accurately obtained.
Detailed description of the invention
In a first embodiment, the switch is switched from a polarization current test state to a surface potential test state (t ═ t) 1 ) The response current I (t) of the insulation dielectric to be tested under the action of the DC voltage 1- ) And initial time rate of change of surface potential
In a relationship of
Specific address, epsilon in said fitting formula 0 D is the thickness of the insulating dielectric to be measured, and S is the area of the insulating dielectric to be measured.
Detailed description of the invention
Based on the first and third embodiments, specifically, the infinite high frequency relative permittivity ∈ of the insulating dielectric ∞ Is calculated by the formula
Detailed description of the invention
On the basis of the second embodiment, specifically, the least square fitting formula of the surface potential u (t) is:
U(t)＝A 0 +A 1 exp(-t/τ 1 )+A 2 exp(-t/τ 2 )+A 3 exp(-t/τ 3 )
specific address, parameter A in said fitting formula 0 、A 1 、A 2 、A 3 Are respectively constant, parameter tau 1 、τ 2 、τ 3 Respectively, relaxation time constants.
Examples
The insulating dielectric of this example is a 10 wt% silicon carbide/polyethylene composite insulating dielectric, and the electrode area S is 452.16mm 2 The thickness d is 0.25mm, the applied direct current voltage U is 5kV, the electrometer model is Gishili 6517B, the high-voltage electrostatic voltmeter model is Tak 341B, the applied voltage time is 0-1800 s, the variation curve of the response current I along with the time t is shown in figure 2, the variation curve of the surface potential U along with the time is shown in figure 3, and the variation curve of the surface potential U along with the time is shown in t 1 Removing the DC high voltage at all times t 1 Response I (t) at time 1800s 1 )＝7.82pA。
The fitting parameter obtained in this example is A 0 ＝252.31709V、A 1 ＝2042.28V、A 2 ＝302.13V、A 3 ＝2179.85V、τ 1 ＝57585.37s、τ 2 ＝1822.67s、τ 3 ＝57839.73sm，t 1 Surface potential rate dU (t) of the insulating dielectric at time 1800s 1 ) (dt) — 0.23V/s, infinite high frequency relative dielectric constant ε ∞ Was 2.12.
Claims (1)
1. The method for measuring the infinite high-frequency relative dielectric constant of the insulating dielectric medium based on the polarized current and the surface potential attenuation time domain spectrum is characterized in that a switch is switched from a polarized current test state to a surface potential attenuation test state, the polarized current time domain spectrum before the switch is switched and the surface potential attenuation time domain spectrum after the switch is switched are collected and recorded, and the initial time change rate of the surface potential attenuation is determined according to the initial time change rate of the surface potential attenuation
And polarization current
By the formula
Calculating to obtain infinite high-frequency relative dielectric constant
；
Is a dielectric constant of a vacuum, and is,dto measure the thickness of the insulating dielectric,Sis the area of the insulating dielectric being tested; the influence of thermal noise on the measured surface potential attenuation time domain spectrum of the insulating dielectric medium is eliminated through a least square fitting method, so that the change rate of the surface potential attenuation initial moment of the insulating dielectric medium at the open circuit initial moment is accurately obtained;
surface potential U (t) 1+ ) The least squares fit equation of (a) is:
parameter A in the fitting formula 0 、A 1 、A 2 、A 3 Are respectively constant, parameter tau 1 、τ 2 、τ 3 Respectively, relaxation time constants; relative permittivity of insulating dielectric
Relative dielectric constant of magnitude passing through infinite high frequency
Static relative dielectric constant
The angular frequency omega and the relaxation time tau are determined,
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