CN106324450B - Characteristic impedance matching method in cable transmission attenuation characteristic test - Google Patents
Characteristic impedance matching method in cable transmission attenuation characteristic test Download PDFInfo
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- CN106324450B CN106324450B CN201610637774.4A CN201610637774A CN106324450B CN 106324450 B CN106324450 B CN 106324450B CN 201610637774 A CN201610637774 A CN 201610637774A CN 106324450 B CN106324450 B CN 106324450B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
- G01R31/1263—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
- G01R31/1272—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation of cable, line or wire insulation, e.g. using partial discharge measurements
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Abstract
The invention relates to a characteristic impedance matching method in a cable transmission attenuation characteristic test, which comprises the following steps: a signal generator capable of outputting variable-frequency sinusoidal voltage signals is connected to the head end of the cable, a noninductive adjustable resistor is connected in series between a conductor core at the tail end of the cable and the metal sheath, and voltage signals of a signal output end and the noninductive adjustable resistor are accessed into measuring equipment; the signal generator sequentially inputs sinusoidal voltage waves with different frequencies, an oscilloscope is used for measuring a voltage signal of the non-inductive adjustable resistor and a tail end voltage wave amplitude value under each frequency sinusoidal voltage wave, and when the amplitude value of the tail end voltage wave and the change of the input sinusoidal voltage peak value are not more than +/-3%, the non-inductive resistance value at the moment is recorded; and performing linear regression analysis on the noninductive resistance values under different frequencies, and eliminating singular points to obtain the terminal matching impedance. The invention can accurately measure the characteristic impedance value of the coiled cable under high frequency and improve the test precision.
Description
Technical Field
The invention relates to a characteristic impedance matching method, in particular to a characteristic impedance matching method in a cable transmission attenuation characteristic test.
Background
Partial Discharge (PD) is a phenomenon that repeated breakdown and extinction occur locally in an insulating medium, the discharge occurs in a local defect of the insulation, the discharge amount is small, the insulation capability is not affected in the initial stage of the occurrence of the partial discharge, but the insulation is slowly damaged and the service life of the insulation is shortened when the PD occurs for a long time under the action of voltage. PD is the primary manifestation of early insulation failure in cable accessories, and is one of the primary causes of insulation degradation, as well as the primary characteristic quantities that characterize the insulation condition. Both operating experience and research show that: the PD quantity of the power cable is closely related to the insulation condition of the power cable, and the change of the PD quantity indicates that the insulation of the cable reflects the existence of potential hidden trouble defects to a certain extent, so that the method is one of effective methods for quantitatively analyzing the insulation degradation degree.
At present, high-voltage cable partial discharge detection is mostly carried out by using a high-frequency current sensor to carry out signal coupling on a grounding lead-out wire or a cross interconnection wire of accessories such as a cable intermediate joint, a cable terminal and the like, a cable line can be dozens of kilometers long, the geographical position span is large, and the interval between adjacent intermediate joints is often more than 400 m. The partial discharge signal is a high-frequency weak amplitude signal, and the characteristic impedance of the power cable line at high frequency presents pure resistance characteristics, so that the field accurate test is not easy to be performed.
Disclosure of Invention
The present invention has been made in view of the deficiencies in the prior art to provide a method for matching characteristic impedance in a cable transmission attenuation characteristic test that overcomes or at least partially solves the above mentioned problems.
A characteristic impedance matching method in a cable transmission attenuation characteristic test, the method comprising the steps of:
a signal generator capable of outputting variable-frequency sinusoidal voltage signals is connected to the head end of the cable, a noninductive adjustable resistor is connected in series between a conductor core at the tail end of the cable and the metal sheath, and voltage signals of a signal output end and the noninductive adjustable resistor are accessed into measuring equipment;
the signal generator sequentially inputs sinusoidal voltage waves with different frequencies, an oscilloscope is used for measuring a voltage signal of the non-inductive adjustable resistor and a tail end voltage wave amplitude value under each frequency sinusoidal voltage wave, and when the amplitude value of the tail end voltage wave and the change of the input sinusoidal voltage peak value are not more than +/-3%, the non-inductive resistance value at the moment is recorded;
and performing linear regression analysis on the noninductive resistance values under different frequencies, and eliminating singular points to obtain the terminal matching impedance.
Further, the resistance range of the non-inductive adjustable resistor is 30
~100
。
Further, the frequencies of the input sine voltage waves are respectively 0.1kHz, 0.5kHz, 1kHz, 2kHz, 5kHz, 10kHz, 20kHz, 50kHz, 100kHz, 200kHz, 500kHz and 1 MHz.
Furthermore, the detection bandwidth of the oscilloscope is 1kHz-100 MHz.
The testing method can accurately test the characteristic impedance value of the coiled cable under high frequency, improves the testing precision of the local discharge signal of the on-site high-voltage cross-linked cable line, increases the reliability of the subsequent data analysis result, and lays a foundation for the discharge type identification and cable state evaluation work.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive labor.
Fig. 1 is a schematic structural diagram of a characteristic impedance matching method in a cable transmission attenuation characteristic test according to an embodiment of the present invention.
Detailed Description
Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
As shown in FIG. 1, the invention provides a field measurement method for characteristic impedance values of high-frequency high-voltage cross-linked cables, which is suitable for field matching of characteristic impedance in transmission attenuation characteristic tests of coiled high-voltage and ultrahigh-voltage cross-linked cables.
The invention provides a field matching method of characteristic impedance in a transmission attenuation characteristic test of a coiled high-voltage and ultrahigh-voltage cross-linked cable, which comprises the following steps:
(1) in the transmission attenuation characteristic test of a coiled high-voltage and ultrahigh-voltage cross-linked cable, a signal generator capable of outputting variable-frequency sinusoidal voltage signals is connected to the head end of the coiled cable, and a resistance value range of 30 ~ 100 is connected in series between the tail end conductor wire core of the coiled cable and the metal sheath
The voltage signal of the signal output end and the noninductive adjustable resistor is accessed into the measuring equipment.
(2) The signal generator is input with a sinusoidal voltage wave u of different frequencyi(t) respectively measuring the voltage signals of the non-inductive adjustable resistor by using an oscilloscope and recording terminal voltage waves u under different frequencieso(t) of (d). The signal generator can input the frequency of 0.1kHz, 0.5kHz, 1kHz, 2kHz, 5kHz, 10kHz, 20kHz, 50kHz, 100kHz, 200kHz, 500kHz and 1MHz in sequence, as shownThe detection bandwidth of the wave filter is 1kHz-100 MHz.
(3) Adjusting the non-inductive adjustable resistance value in the range of measurement, repeating the step (2) in sequence, and recording the output signal uo(t) with the input signal ui(t)。
(4) The voltage signal amplitude u detected by the resistance end in the step (3)o(t) with the input signal uiWhen the peak value of (t) does not vary by more than. + -. 3%, the non-inductive resistance value at that time is recorded.
(5) And performing linear regression analysis on the noninductive resistance values under different frequencies, and removing singular points to determine the tail end matching impedance required by the coiled cable test. Specifically, firstly, a rectangular coordinate system is established, and a frequency-resistance value scatter diagram is drawn in the coordinate system; secondly, performing straight line fitting on scattered points in the graph, and eliminating points which deviate too far from a straight line; and finally, a straight line formed by the removed scattered points is the matched impedance value.
The method provided by the invention adopts an off-line detection means to carry out on-site matching on the characteristic impedance of the coiled high-voltage and ultrahigh-voltage cross-linked cable, obtains an optimal resistance value by comparing and analyzing the relation between sine wave signals injected under different frequency bands and measurement signals so as to obtain the characteristic impedance value of the cable line, ensures the accuracy of partial discharge signal measurement under high frequency, and provides reliable guarantee for subsequent signal analysis and processing.
The invention has the following advantages:
1. the method used by the patent has the advantages of simple wiring, convenient operation and no change of the original cable structure.
2. The method designed according to the patent can accurately match the characteristic impedance under high frequency suitable for testing the partial discharge signal of the coiled cable, and further improve the detection capability of the partial discharge signal in the test of the transmission attenuation characteristic of the cable.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for apparatus or system embodiments, since they are substantially similar to method embodiments, they are described in relative terms, as long as they are described in partial descriptions of method embodiments.
The above description is only for the preferred embodiment of the present invention, and should not be used to limit the scope of the claims of the present invention. While the foregoing description will be understood and appreciated by those skilled in the relevant art, other equivalents may be made thereto without departing from the scope of the claims.
Claims (4)
1. A characteristic impedance matching method in a cable transmission attenuation characteristic test, the method comprising the steps of:
a signal generator capable of outputting variable-frequency sinusoidal voltage signals is connected to the head end of the cable, a noninductive adjustable resistor is connected in series between a conductor core at the tail end of the cable and the metal sheath, and voltage signals of a signal output end and the noninductive adjustable resistor are accessed into measuring equipment;
the signal generator sequentially inputs sinusoidal voltage waves with different frequencies, an oscilloscope is used for measuring a voltage signal of the non-inductive adjustable resistor and a tail end voltage wave amplitude value under each frequency sinusoidal voltage wave, and when the amplitude value of the tail end voltage wave and the change of the input sinusoidal voltage peak value are not more than +/-3%, the non-inductive resistance value at the moment is recorded;
carrying out linear regression analysis on the noninductive resistance values under different frequencies, eliminating singular points and obtaining the terminal matching impedance, wherein the method comprises the following steps:
establishing a rectangular coordinate system, and drawing a scatter diagram of the frequency-resistance value in the coordinate system;
performing straight line fitting on scattered points in the graph, and eliminating points which deviate too far from a straight line;
and the straight line formed by the removed scattered points is the matching impedance value.
2. The method for matching the characteristic impedance in the cable transmission attenuation characteristic test according to claim 1, wherein: the resistance range of the non-inductive adjustable resistor is 30-100 omega.
3. The method for matching the characteristic impedance in the cable transmission attenuation characteristic test according to claim 1, wherein: the frequency of the input sine voltage wave is 0.1kHz, 0.5kHz, 1kHz, 2kHz, 5kHz, 10kHz, 20kHz, 50kHz, 100kHz, 200kHz, 500kHz and 1MHz respectively.
4. The method for matching the characteristic impedance in the cable transmission attenuation characteristic test according to claim 1, wherein: the detection bandwidth of the oscilloscope is 1kHz-100 MHz.
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| CN106885975A (en) * | 2017-04-10 | 2017-06-23 | 华北电力大学（保定） | A kind of high-tension cable ageing testing method and device based on impulse response |
| CN107064761B (en) * | 2017-05-08 | 2023-08-11 | 南京电力工程设计有限公司 | Method and system for detecting internal wave velocity characteristics of alternating current cable |
| CN107743041A (en) * | 2017-09-28 | 2018-02-27 | 杭州电子科技大学 | Coaxial cable decay analogy method |
| CN114371324B (en) * | 2021-12-03 | 2024-06-25 | 北京无线电计量测试研究所 | Method for measuring source impedance of spike signal generator |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103792462A (en) * | 2014-01-15 | 2014-05-14 | 国家电网公司 | Power transformer winding turn-to-turn short circuit failure detecting method based on resistance frequency curve |
| CN104407272A (en) * | 2014-12-16 | 2015-03-11 | 国家电网公司 | Cable identification device |
| CN205229440U (en) * | 2015-12-15 | 2016-05-11 | 国网北京市电力公司 | A detecting system for detecting partial discharge detector |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103792462A (en) * | 2014-01-15 | 2014-05-14 | 国家电网公司 | Power transformer winding turn-to-turn short circuit failure detecting method based on resistance frequency curve |
| CN104407272A (en) * | 2014-12-16 | 2015-03-11 | 国家电网公司 | Cable identification device |
| CN205229440U (en) * | 2015-12-15 | 2016-05-11 | 国网北京市电力公司 | A detecting system for detecting partial discharge detector |
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