SU1642411A1 - Method of determination of dielectric material parameters - Google Patents

Abstract

The invention relates to electrical measurements and can be used to test dielectric materials. The aim of the invention is to improve the accuracy. The method consists in that a sample of material with a known geometric constant is placed in a cell with a system of two electrodes, an alternating voltage of a known frequency is supplied, active and reactive losses are measured, a constant voltage equal to the effective value of the alternating voltage is measured, and after the absorption current decays, the current through the sample is measured and the current through-conduction losses, the through-conductance, the tangents of the dielectric and through-loss losses, the dielectric constant, the modulus IOOS permittivity, an imaginary part of the complex specific permittivity and conductivity of the active current absorption. The invention allows a more complete investigation of dielectric samples by complex measurement in various types of electric fields. 6 Il. sl C

Description

The invention relates to electrical measuring equipment and can be used to conduct non-destructive tests to diagnose the quality of materials with dielectric properties, in particular, electrical insulation of electrical circuit elements.

The purpose of the invention is to increase accuracy and reliability.

The method consists in that a sample of a material with a known geometric constant is placed in a cell with a system of two electrodes, an alternating voltage of a known frequency is supplied, active and reactive losses are measured, then a constant voltage equal to the effective value of alternating voltage is measured. and after the absorption current decays, the current through the sample is measured and the current through conduction losses, through conductivity, tangents of dielectric and through losses, dielectric constant, modulus com integrated polices permittivity, an imaginary part of the complex dielectric constant and a specific conductance of current absorption by M:

Ei G / AwE tg 5;

ABOUT

4 Yu. &.

/ V

El

 Eivr + tg6

E Eitgd1

 where gdb Rabs / Q; tg6n Rskv / Q;

Pa6s P Rskv;

Rsk ul;

G U / l;

Ei is relative dielectric constant;

I El - module of complex dielectric constant;

E - imaginary part of the complex dielectric constant;

Wabs has specific active conductivity for absorption current;

tg df, tg (tangent angles of dielectric and through losses, respectively;

P, Q - active and reactive losses, respectively;

Slave - active absorption loss;

Rsc - current loss through conduction;

U is the magnitude of the voltage;

I is the value of direct current;

G - through conduction;

L is the geometric parameter of the cell; circular frequency alternating voltage;

EO is dielectric constant.

FIG. 1 shows a block diagram of an apparatus for carrying out the proposed method; in fig. 2 is a vector diagram of the dielectric constant of the substance; in fig. 3 - vector diagram of specific compartments; in fig. 4 - vector current diagram; in fig. 5 is a loss diagram; in fig. 6 is a replacement circuit for a dielectric material.

A device for carrying out the proposed method comprises a source of 1 stabilized direct current, a generator of 2 sinusoidal signals, a switch of 3 measurement modes, a voltmeter 4 of direct and alternating current, a milliammeter 5 of constant and alternating current, a wattmeter 6 and a measured object 7.

The dielectric parameters are measured as follows.

Using switch 3, a constant voltage from source 1 is applied to the measured object 7, a constant voltage value is measured by a voltmeter 4, and a steady-state leakage current value is measured by a milliammeter 5. After that, the through conductivity of the measured object is determined, and the value of the specific through conductivity of the measured cable is found.

y g / a.

Then, using the switch 3, an alternating voltage from the generator 2 is supplied to the measurement object 7, and its effective value LU is set

equal to U-. A voltmeter 4, a milliammeter 5 and a wattmeter 6 measure the effective values of the voltage and the total leakage current LUn l and the active power P dissipated in the dielectric. Reactive power Q, active end-to-end power Rcv, active Rabe absorption power and tangents of dielectric and end-to-end loss tg 5, tg 5 are determined, and then the dielectric

coaxial cable insulation parameters

(El .I1, IEI, oubs).

The validity of the calculated expressions for a dielectric, the replacement circuit of which is shown in FIG. 6. It follows from the analysis of vector diagrams (Fig. 2-5) for this replacement scheme. The following notation is used in the diagrams: a complex of equivalent dielectric constant; Ег EI- according to its imaginary and real parts; E is complex dielectric constant; E1 - its imaginary part; y is the specific through conductivity; EQ is dielectric constant; OU-working frequency; EEC is a complex of equivalent conductivity; complex specific conductivity; у - specific imaginary conductivity; your specific active conductivity; oubs is the specific active conductivity of the absorption current.

From the vector diagrams of the dielectric constant of the substance (Fig. 2) and specific conductivities (Fig. 3) it follows

what is the loss tangent

tg v (E11 + y oG1 EG1); tangents of dielectric and through-loss angles

tg 51 tg (5y y / w E Ei; relative dielectric constant of the substance

Ei y / E0ung (5l1, specific active conductivity Ua uEoEitg (5;

specific active conductivity to absorption current

Wabs u EoEitg 5.

The total loss tangent is defined by

tg d (dubs + G) / (o s Siz, whence

tg 5 (1abs + 1кв) / 1р U / lp И tg d (Рабс + Рскв).

FIG. 4-6, the following designations are accepted: diz, siz, respectively, the conductivity and capacity of the material are active; dubs - active conductance current absorption; G - through (ohmic) conductivity; Sabe, Cr - absorption capacity and geometric capacity, respectively; I is the total leakage current; la, Ip - its reactive and active components; ICKB - current through conduction; 1abs - absorption current; aabs, 1bs active and reactive to the components of the absorption current; CM is the bias current; through hermetic container; 5 eq - equivalent total loss; S - total loss; Q - reactive loss; Р - active losses; Slap - active absorption current losses (active losses from various types of relaxation polarizations); RSw - active losses from the transfer of free charges (current losses through conduction).

Consequently, the tangents of dielectric and end-to-end losses

tg 5 dubs / "Ces; tg shSiz; tg abs / lp; tg (5 1 Sq / 1 p;

tg (3 Pa6c / Q; tg 5 Рскв / 0.

Thus, the values of the tangent angles of total, dielectric, and end-to-end losses, which connect the main characteristics of a material with dielectric properties, can be completely and objectively judged on its conductive and absorption properties and its ability to polarize, and also simply determine its electrical parameters.

The proposed method for determining the parameters of dielectric materials can be applied to control the quality of electrical insulating products, to study the properties of dielectric and insulating materials, laboratory and field studies of the properties of rocks, ores and minerals, studies of the development of prebreakdown conditions, etc.

Claims (1)

The invention The method for determining the parameters of dielectric materials, which consists in placing a sample with a known geometric constant in a cell with a system of two electrodes, is first supplied with a variable with a known frequency, and then constant voltage, determine through-conduction, tangents of angles di5 0 5 0 0 5 Q five 0 electric and end-to-end losses, characterized in that, in order to increase accuracy and reliability, a constant voltage value equal to the effective variable value is taken, reactive and active losses are measured at an alternating voltage, and after constant absorption current is absorbed, the current through the alternating voltage the sample and determine the current loss through conduction, the dielectric constant, the modulus of the complex dielectric constant, the imaginary part of the complex dielectric constant and the specific active conductivity eye of absorption of expression m: Ei G / El Eotg 5; I El E / 1; E Ei tg 5; oubs sh Eo Ei tg (51; where tg 5 Rabbs / Q; tgd PcKB / Q: Rabs R Rskv1 Ei is relative dielectric constant; IE is a module of complex dielectric constant; E11 is the imaginary part of the complex dielectric constant; Wabs has specific active conductivity for absorption current; tg (51, tg 5M are the tangents of the dielectric and through-loss angles, respectively; P, Q - active and reactive losses, respectively; Slap - active absorption loss; RSKV - loss of current through conduction; U is the magnitude of the voltage; I is the value of direct current; L is the geometric parameter of the cell; (about-circular frequency alternating voltage; Ee is the dielectric constant; G - through conductivity. bottom $ 2 gpf Ih , 0 9 , -GPF Ufr2t 9l Editor A. Ogar Compiled by L.Melnikov Tehred M. MorgentalKorrektor A.Ozsulenko h RsnV  R FIG. five I / FIG. 6