SU1370631A1 - Method of checking quality of wire insulation coating - Google Patents

Abstract

The invention relates to a cable-insulating technique. The purpose of the invention is to increase the reliability of quality control of an insulating coating by measuring the breakdown voltage, taking into account the influence of the internal floor of the insulating coating, the heterogeneity of the structure of impurities in the insulation. An electrical voltage is applied between the living monitored wire and the electrode. The latter increases from zero to wire breakdown. Additionally, a second sample of the monitored wire is taken, to which a constant charging voltage is preliminarily supplied, which is sufficient in magnitude and time of its application to form the maximum internal field. Then, by short-circuiting the electrodes, the charge is removed and a constant voltage is applied, the polarity of which is the opposite of the polarity of the charging voltage. Then, the voltage is increased to the breakdown of the insulation, after which the quality of the insulation coating of the monitored wire is evaluated by the ratio Unp ../ U Ex. 7 2 Il. f. (L

Description

Ca

About 05 WITH

The invention relates to a cable: tyio-insulating technique and can be used to control the electrical strength of an insulating coating of a wire.

The purpose of the invention is to increase the reliability of quality control of an insulation coating by measuring the breakdown voltage, taking into account the influence of the internal floor of the insulation coating, the heterogeneity of the structure and impurities in the insulation.

The method consists in that an electrical voltage is applied between the residential monitored wire and the electrode, increasing the latter from zero.

pr. 1

the dodo insulation of the wire U is completely taken from the second sample

u 5

accurate to form a maximum internal field, the magnitude of which is determined by structural heterogeneity and the presence of various impurities. Then, by briefly shorting the electrodes (the shortening time is not more than 0.5 s), the charge is removed, due to the first high-speed types of polarization, and a constant voltage is applied to the sample, the polarity of which is reversed sample before sample (). Attitude

Unr

 take for quality criteria

and pr;

isolation Since considerable time is required to establish migration polarization, it is natural that depolarization also occurs in

roll wire on which the pre-20 during this time. Therefore, after a constant voltage is applied, a constant charging voltage, which in its magnitude and time of application is sufficient to form the maximum internal voltage, is applied.

35

then, by short-term shorting of the electrodes, the charge is removed and a constant voltage is supplied, the polarity of which is opposite to the polarity of the charging voltage, then the voltage is increased until the insulation is broken, then the quality of the insulation coating of the controlled wire estimated by the ratio of Vnp..i 1 shows a diagram of an apparatus for carrying out the proposed method.

The device contains a source of 1 for-. discharge voltage, discharge resistor 2, breakdown device 3, switching element 4 and test object 5. Q

FIG. Figure 2 shows test object 5, consisting of a sample of a test wire wound onto a metal cylinder, on which the non-insulated end (L) of which is supplied is charged or breakdown voltage.

The method is carried out as follows.

The breakdown voltage of one of the U "samples is determined by applying a voltage between the residential wire and the metal cylinder or between the stripped ends of the twisted sample by gradually increasing the voltage from zero to breakdown. A second sample is prepared for testing. the same voltage U |, which is much smaller than Ur.r,, B, over a time Tj, short-circuiting the plates is short enough; inside the dielectric there is still an electrical internal field opposite to the charge one, and if a constant voltage is again applied to the sample after short-circuiting, the polarity of which is opposite to the charging voltage, in this case the directions of the external field and the field in the dielectric coincide, which leads to dielectric breakdown at a lower voltage - and

Pr.1

Since the charge density in the near-electrode layers is much higher than in the rest of the dielectric, the field strength is maximal exactly at. near-electrode areas.

The increase in the charge density and, consequently, the increase in the potential gradient in the near-electrode regions is also determined by the amount and type of ionic impurities in the dielectric.

To carry out tests on the pre-jjg method, it is necessary to preliminarily determine the values of Uy i necessary for the formation of the maximum internal field in the insulation due to the volume charge.

Claims (1)

Since the values of breakdown voltage and internal field depend, besides the quality of the dielectric, on the diameter of the wire and the features of the technology, the values UT and Co must be determined for each brand of wire separately. Invention Formula The method of quality control of the insulation coating wire consisting of 50 during this time. Therefore, after short-circuiting the plates inside the dielectric still exists an electrical internal field opposite to the charged one, and if a constant voltage is again applied to the sample after short-circuiting, the polarity of which is opposite to the charging voltage, in this case the directions of the external field and the field in the dielectric coincide, leading to dielectric breakdown at lower voltages - and Pr.1 Since the charge density in the near-electrode layers is much higher than in the rest of the dielectric, the field strength is maximal exactly at. near-electrode areas. The increase in the charge density and, consequently, the increase in the potential gradient in the near-electrode regions is also determined by the amount and type of ionic impurities in the dielectric. To carry out tests using the proposed method, it is necessary to preliminarily determine the values of Uy i necessary for the formation of the maximum internal field in the insulation due to the volume charge. Since the values of breakdown voltage and internal field depend, besides the quality of the dielectric, on the diameter of the wire and the features of the technology, the values UT and Co must be determined for each type of wire separately. Invention Formula The method of quality control of the insulation coating wire consisting of The first test object is affected by the increasing test voltage of the first test object before the wire is broken, and the breakdown voltage is measured, in order to increase the reliability of the quality control of the insulation coating, in addition to a constant a charge voltage, the magnitude of which and the duration of the effect are sufficient for | 1) to maximize the maximum internal field in the insulation, short-circuit the electrodes for a short time and the reverse polarity increases the voltage to isolation, the voltage of the insulation is measured, and the quality of the insulation is judged by the ratio of the voltage of the first and second test objects. FIG. 2