CN103412197A - Laser induced thermal pulse polymer dielectric space charge measuring device and method - Google Patents

Abstract

The invention relates to a laser induced thermal pulse polymer dielectric space charge measuring device and a laser induced thermal pulse polymer dielectric space charge measuring method. The technical scheme of the invention is that a high direct voltage is applied to two sides of an organic polymer dielectric sample for a certain time, the power supply is disconnected and the two sides are grounded simultaneously so as to dissipate surface charges of the sample, a pA-level current detection system is connected, the whole system is arranged in a shielded environment, a measuring space without electromagnetic interference is formed, laser pulses are irradiated on a fuel rod with a certain position away from the lower surface of the sample, so that quantitative fuel combusts and releases heat instantaneously, a high-energy thermal pulse is produced, current response signals are obtained in an external circuit through a pA-level current detection device, and the sampling and recording are conducted by a computer. Therefore, the electric field distribution and space charge distribution in the dielectric can be obtained, and coordinate graphs of the electric field distribution and space charge distribution can be obtained.

Description

A kind of induced with laser thermal pulse polymer dielectric space charge measurement apparatus and method

Technical field

The present invention relates to a kind of research of induced with laser thermal pulse polymer dielectric space charge measurement apparatus and method.

Background technology

Along with the continuous progress of industrialized development and science and technology, the Polymers solid dielectric material high-voltage engineering, power electronics, microelectronics insulation and all kinds of dependence electric charge is resident and the special sensor of the behavior such as polarization in application more and more extensive.The polymkeric substance of particularly take in recent years is a dark horse as the polymer nanocomposites of basic material, becomes the study hotspot in electric insulation and relevant speciality field.Be subjected to electric power and electronics miniaturization and the impact required such as integrated, had higher requirement in the aspects such as high temperature resistant, the anti-high electric field of Polymers solid dielectric material, resistant to partial discharges and electric branch.Yet also there are some outstanding problems in the Polymers solid dielectric material in application process, one of them is exactly the accumulation of space charge.As long as have various interfaces, defect or impurity in the Polymers solid dielectric, cause the interfacial polarization behavior, or, due to the injection of electric charge, at fault location, form the space charge phenomenon just inevitable.

For a long time, problems with space charge never is well solved, and, along with the widespread use of polymer dielectric material becomes more outstanding, has even become crucial bottleneck problem in some dielectric applications field.Space charge exerts an influence to dielectric characteristic, and the most direct reason is its caused electric field distortion.Therefore study the space charge characterizing method, purpose is to obtain the distribution of space charge in the polymer solids medium, further analyzes Electric Field Distribution wherein.And, by the description of defect states, can from the approach that improves or reduce deep energy level defect amount polymeric media, reduce space charge, homogenizing medium internal electric field, reach the serviceable life that extends dielectric material and the purpose that improves equipment dependability.In addition, space charge, even can be for the assessment of medium degree of aging as a kind of the most direct method that characterizes defect.

Due to the space charge in the polymer solids medium for the research of dielectric material and apply most important, so the research development of the measurement of space charge and characterization technique.Modern space charge measurement technology adopts nondestructive method usually.These methods roughly are divided three classes: (1) thermology method; (2) pressure wave method; (3) pulse electroacoustic method.

The thermal pulse current method is a special kind of skill grown up on the medium physical basis, is widely used in recent years research medium conductivity mechanism and charge storage phenomenon, is widely used in the research of defect states of polymeric media material.The concrete steps of thermal pulse current method detection space electric charge are, apply a thermal pulse for the tested sample that contains space charge, temperature wave is in the Propagation process, can cause the medium contraction or expansion, also can make local specific inductive capacity that small variation occurs, this can break the equilibrium relation that the space charge in medium has established, impels space charge from new distribution.Simultaneously, the induced charge on two electrodes also can change, and reacting externally circuit is exactly a small capacitance current (pA level) to have occurred, is called as the thermal pulse electric current.The thermal pulse electric current is that the space charge variation institute in medium causes, has therefore comprised the distributed intelligence of space charge, can calculate Electric Field Distribution and the distribution of space charge situation in medium by analyzing the thermal pulse electric current.The applicable scope of thermal pulse current method is more extensive, for the insulating material of any shape, as long as can calculate the thermal pulse propagation condition of section within it, can apply the thermal pulse current method and detect its inner space charge.The thermal pulse current method can have a lot of application, and the people such as A.Toureille utilize the thermal pulse current method to study the impact that poly structure is assembled space charge.The people such as S.Agnel utilize the thermal pulse current method to study the impact of the polymkeric substance of different materials on space charge.The people such as M.Aboud carry out aging to tygon under dry, wet condition, and utilize the distribution situation of thermal pulse current method detection space electric charge in various sample, have studied the ambient humidity impact aging on tygon.The thermal pulse current method can also be for detection of the Dynamic Accumulation situation of space charge in insulating medium, the people such as M.Aboud utilize the thermal pulse current method to study the accumulation of space charge in crosslinked polyethylene and EP rubbers section, and bi-material is contrasted.

Yet, control about the thermal pulse temperature and time in the thermal pulse current method is still a difficult problem, how to obtain the thermal pulse of a temperature fast rise and decline, what impact is the length of thermal pulse duration have to measurement result, and the temperature difference has what impact etc. these problems still without final conclusion for electronic wave.And precision and the Sampling of the pA level electric current of surveying are also needed solution badly.

Purpose

The object of the present invention is to provide a kind of induced with laser thermal pulse polymer dielectric space charge measurement apparatus and method.

Technical scheme

The technical solution adopted for the present invention to solve the technical problems is:

1, with laser pulse generator, manufacture thermal pulse, the laser pulse generator of using in experiment is that power is the red laser generator of 250mW.Laser generator forms the laser pulse fire fuel, as thermal source formation thermal pulse, adds to sample one side with the fuel of quantitatively burning.In this experiment, fuel is one to one potpourri of potash chlorate and sulphur, and quantitatively 1g is for each experiment altogether, and the surface of sample one side is directly over fuel, certain according to its positional distance, and in this experiment, fixed its distance is 11.5cm.In experiment, the instantaneous high heat Ear Mucosa Treated by He Ne Laser Irradiation fuel produced with laser generator, because being heated, potash chlorate very easily is decomposed into potassium chloride and oxygen, and sulphur is heated and a large amount of oxygen reactions that produce, burning generates sulphuric dioxide and produces amount of heat, fuel can burn moment, and makes environment temperature sharply raise.

2, (relating to high direct voltage is positive and negative direct current in polymer dielectric sample both sides, to apply the high direct voltage certain hour, amplitude is 2kV-20kV, be pressing time: 5 minutes to 60 minutes), the complete disconnecting power switch that pressurizes, and by both sides simultaneously ground connection make the specimen surface electric-charge-dissipating.

3, sample and pA level reometer are formed to series circuit, whole circuit is in the environment of metallic shield, forms a measurement space that there is no electromagnetic interference (EMI).

4, open generating laser, fire fuel, fuel can be at a fixed time in after-flame extinguish, produce at short notice a strong thermal pulse, the sample underlaying surface temperature over time relation as shown in Figure of abstract 3.For example, can produce in this experiment the temperature difference is 50 ℃, and the time is the thermal pulse of 1.5s.Thermal pulse can make external circuit demonstrate the subtle change of electric current.This electric current is recorded by pA level reometer, and, by the computer sampling record, can obtain current data.

5, in medium, the Potential distribution of each point can be calculated by formula (1):

$V\left(x\right)=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{b}_i\cos \frac{\mathrm{i\πx}}{L}---\left(1\right)$

B wherein _iCan be calculated by survey electric current and formula (2):

$I\left(t\right)=\underset{1}{\overset{\∞}{\mathrm{\Σ}}}{I}_n\left(t\right)=-\mathrm{A\ϵ}\frac{{\mathrm{\π}}^2}{2L}\underset{1}{\overset{\∞}{\mathrm{\Σ}}}{n}^2{b}_n\exp \frac{-t}{{\mathrm{\τ}}_n}---\left(2\right)$

The medium internal electric field distributes and distribution of space charge can calculate according to formula (3) formula (4):

$E\left(x\right)=\frac{\∂V\left(x\right)}{\∂x}---\left(3\right)$

$\mathrm{\ρ}\left(x\right)=-\mathrm{\ϵ}\frac{{\∂}^{2}V\left(x\right)}{\∂x^2}---\left(4\right)$

Can obtain thus Electric Field Distribution and distribution of space charge in medium, and obtain the coordinate diagram of Electric Field Distribution and distribution of space charge.

Beneficial effect

Advantage of the present invention and beneficial effect:

1. significantly improve the certainty of measurement space electric charge, and clear and definite experimental implementation;

2. for the non-damage type experiment, to the properties of product not damaged, keep the product original appearance;

3. can effectively obtain space charge and the Electric Field Distribution of sample.

The accompanying drawing explanation

Fig. 1 is the process flow diagram of experimental implementation in the present invention;

Fig. 2 is the experimental procedure schematic diagram of using thermal pulse current method measurement space electric charge in the present invention;

Fig. 3 is experimental provision image before and after high speed thermal pulse that infrared video camera is clapped of the present invention applies;

Fig. 4 is sample underlaying surface temperature temporal evolution figure in the present invention;

Fig. 5 be in the present invention the electric current of surveying and the graph of a relation of time;

Fig. 6 calculates the graph of a relation of gained space charge density and sample thickness in the present invention.

Preferred forms

1, with laser pulse generator, manufacture thermal pulse, the laser pulse generator of using in experiment is that power is the red laser generator of 250mW.Laser generator forms the laser pulse fire fuel, as thermal source formation thermal pulse, adds to sample one side with the fuel of quantitatively burning.In this experiment, fuel is one to one potpourri of potash chlorate and sulphur, and quantitatively 1g is for each experiment altogether, and the surface of sample one side is directly over fuel, certain according to its positional distance, and in this experiment, fixed its distance is 11.5cm.In experiment, the instantaneous high heat Ear Mucosa Treated by He Ne Laser Irradiation fuel produced with laser generator, because being heated, potash chlorate very easily is decomposed into potassium chloride and oxygen, and sulphur is heated and a large amount of oxygen reactions that produce, burning generates sulphuric dioxide and produces amount of heat, fuel can burn moment, and makes environment temperature sharply raise.

2, (relating to high direct voltage is positive and negative direct current in polymer dielectric sample both sides, to apply the high direct voltage certain hour, amplitude is 2kV-20kV, be pressing time: 5 minutes to 60 minutes), the complete disconnecting power switch that pressurizes, and by both sides simultaneously ground connection make the specimen surface electric-charge-dissipating.

3, sample and pA level reometer are formed to series circuit, whole circuit is in the environment of metallic shield, forms a measurement space that there is no electromagnetic interference (EMI).

4, open generating laser, fire fuel, fuel can be at a fixed time in after-flame extinguish, produce at short notice a strong thermal pulse, the sample underlaying surface temperature over time relation as shown in Figure of abstract 3.For example, can produce in this experiment the temperature difference is 50 ℃, and the time is the thermal pulse of 1.5s.Thermal pulse can make external circuit demonstrate the subtle change of electric current.This electric current is recorded by pA level reometer, and, by the computer sampling record, can obtain current data.

5, in medium, the Potential distribution of each point can be calculated by formula (1):

$V\left(x\right)=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{b}_i\cos \frac{\mathrm{i\πx}}{L}---\left(1\right)$

B wherein _iCan be calculated by survey electric current and formula (2):

$I\left(t\right)=\underset{1}{\overset{\∞}{\mathrm{\Σ}}}{I}_n\left(t\right)=-\mathrm{A\ϵ}\frac{{\mathrm{\π}}^2}{2L}\underset{1}{\overset{\∞}{\mathrm{\Σ}}}{n}^2{b}_n\exp \frac{-t}{{\mathrm{\τ}}_n}---\left(2\right)$

The medium internal electric field distributes and distribution of space charge can calculate according to formula (3) formula (4):

$E\left(x\right)=\frac{\∂V\left(x\right)}{\∂x}---\left(3\right)$

$\mathrm{\ρ}\left(x\right)=-\mathrm{\ϵ}\frac{{\∂}^{2}V\left(x\right)}{\∂x^2}---\left(4\right)$

Can obtain thus Electric Field Distribution and distribution of space charge in medium, and obtain the coordinate diagram of Electric Field Distribution and distribution of space charge.

Claims (1)

1. Patent of the present invention relates to a kind of induced with laser thermal pulse polymer dielectric space charge measurement apparatus and method, and he comprises:

   1. the present invention is by adopting after organic polymer dielectric sample both sides apply the high direct voltage certain hour, deenergization makes the specimen surface electric-charge-dissipating by both sides while ground connection, rear access pA level current detecting system, whole system is placed in to the shielding environment, form a measurement space that there is no electromagnetic interference (EMI), by laser pulses irradiate on the fuel rod of test coupon lower surface certain position, make quantitative fuel moment burning heat release, produce a high energy thermal pulse, then in external circuit, obtain current responsing signal by pA level current sensing means, by the computer sampling record.Can obtain thus Electric Field Distribution and distribution of space charge in medium, and obtain the coordinate diagram of Electric Field Distribution and distribution of space charge.

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