WO2001086280A1 - A method of measuring topography in an interface and use of the method for a high-voltage cable - Google Patents

A method of measuring topography in an interface and use of the method for a high-voltage cable Download PDF

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Publication number
WO2001086280A1
WO2001086280A1 PCT/SE2001/000979 SE0100979W WO0186280A1 WO 2001086280 A1 WO2001086280 A1 WO 2001086280A1 SE 0100979 W SE0100979 W SE 0100979W WO 0186280 A1 WO0186280 A1 WO 0186280A1
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WIPO (PCT)
Prior art keywords
insulating layer
cable
interface
layer
voltage cable
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Application number
PCT/SE2001/000979
Other languages
French (fr)
Inventor
Anders Ericsson
Carl-Olof Olsson
Johan Palm
Original Assignee
Abb Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Abb Ab filed Critical Abb Ab
Priority to AU60869/01A priority Critical patent/AU6086901A/en
Publication of WO2001086280A1 publication Critical patent/WO2001086280A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B17/00—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
    • G01B17/06—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations for measuring contours or curvatures
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/34—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor
    • G01N29/348—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor with frequency characteristics, e.g. single frequency signals, chirp signals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/36—Detecting the response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/40—Detecting the response signal, e.g. electronic circuits specially adapted therefor by amplitude filtering, e.g. by applying a threshold or by gain control
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging
    • G01S15/8906—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
    • G01S15/8909—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques using a static transducer configuration
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/023—Solids
    • G01N2291/0231—Composite or layered materials
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/04—Wave modes and trajectories
    • G01N2291/044—Internal reflections (echoes), e.g. on walls or defects
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/26—Scanned objects
    • G01N2291/263—Surfaces
    • G01N2291/2634—Surfaces cylindrical from outside

Definitions

  • the present invention relates to a method, in a high- voltage cable comprising a conductor, an inner semicon- ductive layer and an insulating layer, of measuring the topography in the interface between the inner semicon- ductive layer and the insulating layer.
  • a preferred embodiment relates to a method, in a high- voltage cable which, in addition, comprises an outer semiconductive layer, of measuring the topography in the interface between the outer semiconductive layer and the insulating layer.
  • Cables with a central conductor surrounded by one or more insulating layers have long been an important part of our public power-supply network.
  • an increasing proportion of the distribution network has been laid underground and in that context -.requirements .for an increasing operating voltage, in the cable systems have been a driving force for a development towards both better cable designs and better material and production control .
  • US 1,815,710 describes a method of controlling the thickness of material in a cable, especially the thickness of a metallic sheath surrounding an insulating layer. By means of induction coils, mounted in pairs and connected in a Wheatstone bridge, deviations from symmetry are indicated.
  • US 2,177,528 describes a method of measuring the concentricity of an insulated cable. A sensor, for example a metal roll, is moved over the outer surface of the cable and the capacitance between the conductor of the cable and the sensor is measured.
  • US 2,721,975 describes two sensors diametrically placed at the outer surface of the cable.
  • the capacitance between the conductor of the cable and the sensors is included in two branches in a measuring bridge, the unbalance of which hence indicates the eccentricity of the cable.
  • US 3,407,352 suggests the use of two magnetic coils, mounted at different distances from an object to be measured, to monitor the thickness of an insulating layer over a conductive layer.
  • a high-frequency voltage for example 100 kHz, is applied to the coils and the phase difference is detected by means of a measuring bridge.
  • US 3,500,185 suggests the use of a pair of diametrically placed measuring probes in contact with the surface of a cable in order to measure the eccentricity of the cable and the thickness of the insulation.
  • the probes may be turned around the cable and are connected alternately into an arm in a capacitance bridge.
  • composition of the cable is assumed to be considerably simpler than what is customary today. Instead of one single, hopefully homo- geneous, insulating layer which surrounds a conductor, the current practice is normally to have an inner semiconductive layer around the conductor and an outer semiconductive layer outside the insulating layer. The thickness of each of these layers is significant for the function and service life of the cable. This creates quite new problems and raises new questions to be answered. OBJECT OF THE INVENTION
  • the main object of the present invention is to suggest a simple and reliable method of performing quality control of high-voltage cables during continuous production.
  • a second object is to carry out a corresponding control of test objects on a laboratory scale.
  • a third object is to suggest a simplified method of measuring the topography for an interface between layers in a high-voltage cable.
  • the present invention relates particularly to measurement of the topography in the interface between an inner semiconductive layer and an insulating layer in a high- voltage cable while at the same time being designed to measure also the topography in the interface between an outer semiconductive layer and the insulating layer.
  • the present invention relates to a method, in a high- voltage cable comprising a conductor, an inner semicon- ductive layer and an insulating layer, of measuring the topography in the interface between the inner semiconductive layer and the insulating layer.
  • the present invention proposes a way of contributing to an increased quality and hence reduced costs by suggesting a method for measuring the topography in the interface between an inner semiconductive layer, which surrounds a central conductor, and an insulating layer, which in turn surrounds the semiconductive layer. Outside of the insulating layer, an outer semiconductive layer is advantageously applied.
  • ultrasound with a frequency of between 0.1 MHz and 20 MHz, preferably between 0.5 MHz and 5 MHz , for measuring the topography in the interface.
  • the invention particularly relates to a method, in a high- voltage cable with an outer diameter of between 10 mm and 100 mm, comprising an insulating layer of crosslinked polyethylene (PEX, XLPE) , of measuring the topography in the interface between the inner semiconductive layer and the insulating layer.
  • PEX, XLPE crosslinked polyethylene
  • Other extruded insulating materials including, but not limited to, high-density polyethylene (HDPE) and ethylene-propylene rubber (EPR) , also fall within the scope of the invention.
  • the topography in the interface between the outer semiconductive layer and the insulating layer may also be advantageously measured.
  • the method is, of course, also applicable when a high-voltage cable is built up with several insulating layers or in some other way differs from the cable design described as an example in this application.
  • the method entails considerable advantages if the ultrasound is focussed on the respective interface between semiconductive layers and insulating layers and if the detected ultrasonic signal is amplified selectively such that signals from the respective interface is amplified more than the other signals from intermediate or outside disturbance sources .
  • the radial distance s between the interfaces of the outer and inner semiconductors towards the insulating layer is calculated, and the gradient of s is calculated at varying space coordinates along one of the interfaces or with a cylindrical coordinate system, adapted to the symmetry axis of the cable, at a constant radius defined, for example, for describing the expected position for one of the interfaces .
  • an alarm signal is sent and/or the cable is marked with a colour.
  • the frequency of the ultrasound may be adapted to the outer diameter of the cable, to the diameter of the conductor, or to the thickness of the inner semiconductive layer.
  • the method according to the invention assumes a detection of the outer surface of the high-voltage cable. This can take place by one single ultrasonic probe moving around the high-voltage cable. In use during manufacture, however, the preferred embodiment is probably to have a plurality of probes distributed around ' the cable and possibly also along the cable. By systematically activa- ting a plurality of probes, a considerably improved detection may be achieved.
  • Figure 1 schematically shows the cross section of a high- voltage cable and ultrasonic equipment intended for the method according to the invention
  • Figure 2 shows a first cross section of a high-voltage cable with a non-ideal shape of an inner semiconductive layer
  • Figure 3 shows a second cross section of a high-voltage cable with a non-ideal shape of an inner semiconductive layer
  • Figure 4 shows a third cross section of a high-voltage cable with a non-ideal shape of an inner semiconductive layer
  • Figure 5 schematically shows a device for continuous control of a manufactured high-voltage cable.
  • Figure 1 shows the cross section of a high-voltage cable 1, with a central conductor 2 consisting of a plurality of strands 2a.
  • the conductor 2 is surrounded by an inner, semiconductive layer 3, an insulating layer 4, of cross- linked polymer, and an outer semiconductive layer 5.
  • the semiconductive layers 3 , 5 and the insulating layer 4 are illustrated in an ideal case with a completely circular symmetry.
  • Figure 2 shows, in a corresponding way, the cross section of a high-voltage cable 1, with a central conductor 2, consisting of a plurality of strands 2a.
  • the conductor 2 is surrounded by an inner semiconductive layer 3 , of essentially uniform thickness, but this layer 3 has a wavy shape formed by the strands 2a, with a pattern of valleys 3a winding their way around the conductor 2.
  • Figure 3 shows, in a corresponding way, the cross section of a high-voltage cable 1, with a central conductor 2, consisting of a plurality of strands 2a.
  • the conductor 2 is surrounded by a semiconductive tape 6, with a longitudinal, overlapping joint 6b.
  • An inner semiconductive layer 3, of essentially uniform thickness, has become thicker at the overlapping joint 6b.
  • the thicker portion is interrupted by a steep slope 3b.
  • Figure 4 shows, in a corresponding way, the cross section of a high-voltage cable 1, with a central conductor 2, consisting of a plurality of strands 2a.
  • the conductor 2 is surrounded by a inner semiconductive layer 3 , of essentially uniform thickness, but this layer 3 has been formed, during the extrusion, into irregularities 3c, 3d, 3e, extending into the insulating layer 4, and exhibits longitudinal scores or scratches 3f, 3g.
  • the magnitude of the defects, in this figure as well as in the previous ones, is greatly exaggerated to clearly show possible deviations from the desired appearance.
  • Figure 5 shows the cross section of a high-voltage cable 1 in a measuring box 18 filled with a contact fluid (liquid) 19.
  • a plurality of probes are arranged in the measuring box 18, four of which 21, 22, 23, 24 being shown.
  • the probes 21-24 cooperate with a superordinate control unit 20.
  • the high-voltage cable 1 is inserted into and withdrawn from the measuring box 18 through tightly sealing entries (not shown) in the ends of the measuring box 18.
  • the measurements may be focussed on the desired positions in the cable, radially (in depth) as well as axially and tangentially.
  • a marking member (not shown) , those sections of the high-voltage cable 1, which do not fulfil the quality requirements made on the topography for the interface between an inner semiconductive layer 3 and an insulating layer 4 of crosslinked polyethylene, are marked with a colour.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
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  • Remote Sensing (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Acoustics & Sound (AREA)
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Abstract

A method, in a high-voltage cable (1) comprising a central conductor (2) consisting of one or more strands (2a), an inner semiconductive layer (3) and a surrounding insulating layer (4), of measuring the topography (3a, 3c, 3d, 3e, 3f, 3g) at the interface between the inner semiconductive layer (3) and the insulating layer (4). Ultrasound with a frequency of between 0.1 MHz and 20 MHz, preferably between 0.5 MHz and 5 MHz, is used.

Description

A method of measuring topography in an interface and use of the method for a high-voltage cable
TECHNICAL FIELD
The present invention relates to a method, in a high- voltage cable comprising a conductor, an inner semicon- ductive layer and an insulating layer, of measuring the topography in the interface between the inner semicon- ductive layer and the insulating layer.
A preferred embodiment relates to a method, in a high- voltage cable which, in addition, comprises an outer semiconductive layer, of measuring the topography in the interface between the outer semiconductive layer and the insulating layer.
BACKGROUND ART
Cables with a central conductor surrounded by one or more insulating layers have long been an important part of our public power-supply network. With a view to reducing the network of overhead lines, an increasing proportion of the distribution network has been laid underground and in that context -.requirements .for an increasing operating voltage, in the cable systems have been a driving force for a development towards both better cable designs and better material and production control .
Apparatus and methods for continuous control of cable manufacture were proposed at an early stage.
US 1,815,710 describes a method of controlling the thickness of material in a cable, especially the thickness of a metallic sheath surrounding an insulating layer. By means of induction coils, mounted in pairs and connected in a Wheatstone bridge, deviations from symmetry are indicated. US 2,177,528 describes a method of measuring the concentricity of an insulated cable. A sensor, for example a metal roll, is moved over the outer surface of the cable and the capacitance between the conductor of the cable and the sensor is measured.
US 2,721,975 describes two sensors diametrically placed at the outer surface of the cable. The capacitance between the conductor of the cable and the sensors is included in two branches in a measuring bridge, the unbalance of which hence indicates the eccentricity of the cable.
US 3,407,352 suggests the use of two magnetic coils, mounted at different distances from an object to be measured, to monitor the thickness of an insulating layer over a conductive layer. A high-frequency voltage, for example 100 kHz, is applied to the coils and the phase difference is detected by means of a measuring bridge.
US 3,500,185 suggests the use of a pair of diametrically placed measuring probes in contact with the surface of a cable in order to measure the eccentricity of the cable and the thickness of the insulation. The probes may be turned around the cable and are connected alternately into an arm in a capacitance bridge.
In the methods described above, the composition of the cable is assumed to be considerably simpler than what is customary today. Instead of one single, hopefully homo- geneous, insulating layer which surrounds a conductor, the current practice is normally to have an inner semiconductive layer around the conductor and an outer semiconductive layer outside the insulating layer. The thickness of each of these layers is significant for the function and service life of the cable. This creates quite new problems and raises new questions to be answered. OBJECT OF THE INVENTION
The main object of the present invention is to suggest a simple and reliable method of performing quality control of high-voltage cables during continuous production.
A second object is to carry out a corresponding control of test objects on a laboratory scale.
A third object is to suggest a simplified method of measuring the topography for an interface between layers in a high-voltage cable.
The present invention relates particularly to measurement of the topography in the interface between an inner semiconductive layer and an insulating layer in a high- voltage cable while at the same time being designed to measure also the topography in the interface between an outer semiconductive layer and the insulating layer.
SUMMARY OF THE INVENTION
The present invention relates to a method, in a high- voltage cable comprising a conductor, an inner semicon- ductive layer and an insulating layer, of measuring the topography in the interface between the inner semiconductive layer and the insulating layer. Ultrasound with a frequency of between 0.1 MHz and 20 MHz, preferably between 0.5 MHz and 5 MHz, is used.
GENERAL DESCRIPTION OF THE INVENTION
The desire to achieve increased operational reliability and reduced environmental disruption in the distribution of electric power at present leads to a growing demand for high-voltage cables. At the same time, the quality requirements for high-voltage cables increase continuously . The fundamental requirements that the cable can be produced with a very small eccentricity and without any significant ovality and that the insulation can be manufactured without impurities or blisters can nowadays be fulfilled to such an extent that other parameters are starting to be of decisive importance for the usefulness of the cable. Among these parameters, the topography in the interface between an insulating layer and an inner semiconductive layer has a prominent position.
The present invention proposes a way of contributing to an increased quality and hence reduced costs by suggesting a method for measuring the topography in the interface between an inner semiconductive layer, which surrounds a central conductor, and an insulating layer, which in turn surrounds the semiconductive layer. Outside of the insulating layer, an outer semiconductive layer is advantageously applied.
According to the invention, it is proposed to use ultrasound with a frequency of between 0.1 MHz and 20 MHz, preferably between 0.5 MHz and 5 MHz , for measuring the topography in the interface.
The invention particularly relates to a method, in a high- voltage cable with an outer diameter of between 10 mm and 100 mm, comprising an insulating layer of crosslinked polyethylene (PEX, XLPE) , of measuring the topography in the interface between the inner semiconductive layer and the insulating layer. Other extruded insulating materials including, but not limited to, high-density polyethylene (HDPE) and ethylene-propylene rubber (EPR) , also fall within the scope of the invention.
In a high-voltage cable comprising a conductor, an inner semiconductive layer, an insulating layer and an outer semiconductive layer, the topography in the interface between the outer semiconductive layer and the insulating layer may also be advantageously measured. The method is, of course, also applicable when a high-voltage cable is built up with several insulating layers or in some other way differs from the cable design described as an example in this application.
The method entails considerable advantages if the ultrasound is focussed on the respective interface between semiconductive layers and insulating layers and if the detected ultrasonic signal is amplified selectively such that signals from the respective interface is amplified more than the other signals from intermediate or outside disturbance sources .
In a preferred embodiment of the method, from the detected signals, the radial distance s between the interfaces of the outer and inner semiconductors towards the insulating layer is calculated, and the gradient of s is calculated at varying space coordinates along one of the interfaces or with a cylindrical coordinate system, adapted to the symmetry axis of the cable, at a constant radius defined, for example, for describing the expected position for one of the interfaces . When the value of the gradient of s exceeds a predetermined limit value, an alarm signal is sent and/or the cable is marked with a colour.
Further, the frequency of the ultrasound may be adapted to the outer diameter of the cable, to the diameter of the conductor, or to the thickness of the inner semiconductive layer.
Use of the method for continuous monitoring of cable manufacture, or for laboratory analysis of cables, is also within the scope of the invention.
The method according to the invention assumes a detection of the outer surface of the high-voltage cable. This can take place by one single ultrasonic probe moving around the high-voltage cable. In use during manufacture, however, the preferred embodiment is probably to have a plurality of probes distributed around'the cable and possibly also along the cable. By systematically activa- ting a plurality of probes, a considerably improved detection may be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in greater detail with reference to the accompanying drawings where
Figure 1 schematically shows the cross section of a high- voltage cable and ultrasonic equipment intended for the method according to the invention,
Figure 2 shows a first cross section of a high-voltage cable with a non-ideal shape of an inner semiconductive layer,
Figure 3 shows a second cross section of a high-voltage cable with a non-ideal shape of an inner semiconductive layer,
Figure 4 shows a third cross section of a high-voltage cable with a non-ideal shape of an inner semiconductive layer ,
Figure 5 schematically shows a device for continuous control of a manufactured high-voltage cable.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1 shows the cross section of a high-voltage cable 1, with a central conductor 2 consisting of a plurality of strands 2a. The conductor 2 is surrounded by an inner, semiconductive layer 3, an insulating layer 4, of cross- linked polymer, and an outer semiconductive layer 5. The semiconductive layers 3 , 5 and the insulating layer 4 are illustrated in an ideal case with a completely circular symmetry.
At the outer surface of the high-voltage cable 1, there are schematically shown three probes 11, 12, 13 for the supply of ultrasound and detection of reflected sound from the interfaces between the insulating layer 4 and the respective semiconductive layers 3, 5. The ultrasonic probes 11, 12, 13 are interconnected by a superordinate control unit 10.
Figure 2 shows, in a corresponding way, the cross section of a high-voltage cable 1, with a central conductor 2, consisting of a plurality of strands 2a. The conductor 2 is surrounded by an inner semiconductive layer 3 , of essentially uniform thickness, but this layer 3 has a wavy shape formed by the strands 2a, with a pattern of valleys 3a winding their way around the conductor 2.
Figure 3 shows, in a corresponding way, the cross section of a high-voltage cable 1, with a central conductor 2, consisting of a plurality of strands 2a. The conductor 2 is surrounded by a semiconductive tape 6, with a longitudinal, overlapping joint 6b. An inner semiconductive layer 3, of essentially uniform thickness, has become thicker at the overlapping joint 6b. The thicker portion is interrupted by a steep slope 3b.
Figure 4 shows, in a corresponding way, the cross section of a high-voltage cable 1, with a central conductor 2, consisting of a plurality of strands 2a. The conductor 2 is surrounded by a inner semiconductive layer 3 , of essentially uniform thickness, but this layer 3 has been formed, during the extrusion, into irregularities 3c, 3d, 3e, extending into the insulating layer 4, and exhibits longitudinal scores or scratches 3f, 3g. The magnitude of the defects, in this figure as well as in the previous ones, is greatly exaggerated to clearly show possible deviations from the desired appearance.
The corresponding defects may, of course, occur in the interface between the insulating layer 4 and the outer semiconductive layer 5 although this is not shown in the figures .
Figure 5 shows the cross section of a high-voltage cable 1 in a measuring box 18 filled with a contact fluid (liquid) 19. A plurality of probes are arranged in the measuring box 18, four of which 21, 22, 23, 24 being shown. The probes 21-24 cooperate with a superordinate control unit 20.
The high-voltage cable 1 is inserted into and withdrawn from the measuring box 18 through tightly sealing entries (not shown) in the ends of the measuring box 18. By concurrent activation of a plurality of probes, arranged around the outer surface of the whole high-voltage cable and in several positions along the cable, the measurements may be focussed on the desired positions in the cable, radially (in depth) as well as axially and tangentially. By means of a marking member (not shown) , those sections of the high-voltage cable 1, which do not fulfil the quality requirements made on the topography for the interface between an inner semiconductive layer 3 and an insulating layer 4 of crosslinked polyethylene, are marked with a colour.

Claims

1. A method, in a high-voltage cable comprising a conductor, an inner semiconductive layer and an insulating layer, of measuring the topography in the interface between the inner semiconductive layer and the insulating layer, characterized in that ultrasound' with a frequency of between 0.1 MHz and 20 MHz, preferably of between 0.5 MHz and 5 MHz, is used.
2. A method according to claim 1, in a high-voltage cable with an outer diameter of between 10 mm and 100 mm, comprising an insulating layer of crosslinked polyethylene (PEX, XLPE) , of measuring the topography in the interface between the inner semiconductive layer and the insulating layer .
3. A method according to claim 1, in a high-voltage cable comprising a conductor, an inner semiconductive layer, an insulating layer and an outer semiconductive layer, of measuring the topography in the interface between the outer semiconductive layer and the insulating layer.
4. A method according to claim 3, in a high-voltage cable with an outer diameter of between 10 mm and 100 mm, comprising an insulating layer of crosslinked polyethylene (PEX, XLPE) , of measuring the topography in the interface between the outer semiconductive layer and the insulating layer.
5. A method according to any of the preceding claims, characterized in that the ultrasound is focussed on the respective interface between semiconductive layers and insulating layers.
6. A method according to any of the preceding claims, characterized in that the detected ultrasonic signal is amplified selectively such that signals from the respec- tive interface are amplified more than the other signals from intermediate or outside disturbance sources.
7. A method according to any of the preceding claims, characterized in that, from the detected signals, the radial distance s between the interfaces of the outer and inner semiconductors, towards the insulating layer, is calculated.
8. A method according to any of the preceding claims, characterized in that the gradient of s is calculated, at varying space coordinates along one of the interfaces or at a constant radius in a cylindrical coordinate system, the z-axis of which essentially coincides with the symme- try axis of the high-voltage cable.
9. A method according to claim 8, characterized in that, when the value of the gradient of s exceeds a predetermined limit value, an alarm signal is sent and/or the cable is marked with a colour.
10. A method according to any of the preceding claims, characterized in that the frequency of the ultrasound is adapted to the outer diameter of the cable.
11. A method according to any of the preceding claims, characterized in that the frequency of the ultrasound is adapted to the diameter of the conductor.
12. A method according to any of the preceding claims, characterized in that the frequency of the ultrasound is adapted to the thickness of the inner semiconductive layer.
13. Use of a method according to any of the preceding claims for essentially continuous monitoring of cable manufacture .
14. Use of a method according to any of the preceding claims for laboratory analysis of cables .
PCT/SE2001/000979 2000-05-08 2001-05-04 A method of measuring topography in an interface and use of the method for a high-voltage cable WO2001086280A1 (en)

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SE0001679A SE0001679L (en) 2000-05-08 2000-05-08 Ways of measuring topography in an interface and using the method of a high voltage cable
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010129701A3 (en) * 2009-05-05 2011-01-27 Actuant Corporation Non-contact acoustic signal propagation property evaluation of synthetic fiber rope
CN105738474A (en) * 2016-04-14 2016-07-06 华南理工大学 Needle-shaped ultrasonic guided wave detecting device and method for stranded wire structure damage
US20170082705A1 (en) * 2015-09-17 2017-03-23 Shanghai United Imaging Healthcare Co., Ltd. Rf coil assembly

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US5976449A (en) * 1991-04-09 1999-11-02 Zumbach Electronic Ag Method and apparatus for the cross-sectional measurement of electric insulated conductors
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Publication number Priority date Publication date Assignee Title
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