EP1386132A2 - Procede et dispositif pour detecter des endroits defectueux dans des systemes de conduites isoles - Google Patents

Procede et dispositif pour detecter des endroits defectueux dans des systemes de conduites isoles

Info

Publication number
EP1386132A2
EP1386132A2 EP02727410A EP02727410A EP1386132A2 EP 1386132 A2 EP1386132 A2 EP 1386132A2 EP 02727410 A EP02727410 A EP 02727410A EP 02727410 A EP02727410 A EP 02727410A EP 1386132 A2 EP1386132 A2 EP 1386132A2
Authority
EP
European Patent Office
Prior art keywords
line system
magnetic field
wire
detected
alternating current
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP02727410A
Other languages
German (de)
English (en)
Inventor
Rainer Becker
Christoph Rodner
Ifrit Kiselmann
Michael Disqu
Wolfgang Herz
Frieder Neumann
Reiner Primke-Engel
Peter SCHÖNHERR
Ernst-Hermann Wolf
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Prokoning GmbH
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Original Assignee
Prokoning GmbH
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
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.)
Filing date
Publication date
Application filed by Prokoning GmbH, Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV filed Critical Prokoning GmbH
Publication of EP1386132A2 publication Critical patent/EP1386132A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M3/00—Investigating fluid-tightness of structures
    • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
    • G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
    • G01M3/16—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using electric detection means
    • G01M3/165—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using electric detection means by means of cables or similar elongated devices, e.g. tapes

Definitions

  • the invention relates to a method for the detection of fault locations within a line system provided with a sheath, in the sheath of which at least one wire is arranged at a distance from the line system and running longitudinally to the line system.
  • Pipe systems with jackets relate to a large number of differently designed pipe systems, which are used for the transmission of electrical energy, in the form of electrically insulated cable arrangements, and extend to the transport of material flows in natural gas pipes or district heating pipes. All piping systems have in common that they have to be protected against external mechanical, thermal or weather-related influences, which is why they are usually provided with a moisture-proof jacket. However, if the sheathing protecting the internal line system is damaged, its protective effect is locally considerably impaired, as a result of which the line system is exposed to the above-mentioned external influences without protection. It is precisely these defects that need to be detected before the line system suffers irreversible damage.
  • District heating pipes are surrounded in a manner known per se with a foam-filled plastic jacket and are laid a few meters underground.
  • water circulates in the pipes between a central heating station and the various consumers.
  • the district heating pipes which are designed as steel pipes and have different diameters, are used in the flow and return, which are adapted to the size of the respective network or network section.
  • the pipes are provided with a jacket made of insulating rigid foam to reduce heat loss and with an outer plastic jacket pipe to protect them from external mechanical influences and moisture from the ground.
  • the pipes When operating a district heating network, the pipes are generally monitored for leaks. In addition to damage to the outer jacket, leaks in the media pipes, which are often caused by weld defects, can also lead to moisture. As these moisture points can lead to energy loss and destruction of the piping system, they must be detected, located and remedied immediately.
  • the leak detection must be done in another way. This takes advantage of the fact that the inside of the pipe jacket always remains dry when the pipe system is intact, while a leak is associated with a substantial accumulation of moisture in the rigid foam. If it is possible to detect and localize this moisture with a suitable method, the detection and location of the cause of the leakage is also achieved indirectly. Moisture inside the casing can also be caused by soil water that has penetrated due to damage to the outer cladding tube. Here, too, there is a serious disturbance situation, since in addition to the heat losses associated with moisture penetration of the foam, the penetrating soil water with the salts dissolved therein forces pipe corrosion and the dissolution of the pipe-foam-jacket pipe combination. As with moisture ingress as a result of a leak in the media pipe, the actual leakage monitoring of the other pipe sections is deactivated by the moisture error.
  • monitoring wires or metallic conductors are already arranged in the hard foam on both sides of the pipes at the factory, which are looped through when the pipes are laid in the weld seam sockets and carried on to the house connections, where they are accessible at all times.
  • a previously known possibility of detecting moisture is by measuring the direct current resistance between the two monitoring wires. Because of its albeit low ion concentration due to dissolved salts, locally available water reduces the insulation resistance of the rigid foam. This Ohm 'specific resistance is measured on the monitoring wires from the feed from. In the case of dry and therefore faultless cables, the measured resistance is in the M ⁇ range and is limited by the leakage losses in the insulating foam. In the case of a wet cable, the measured resistance represents the total value of the wire resistance over the length to the wet point and the contact resistance between the wires there. This method has a high sensitivity and works from resistances below 500 k ⁇ . However, only a yes / no decision as to whether moisture is present or not is possible.
  • So-called time-domain reflectometry is also used to localize moisture spots.
  • a voltage pulse is applied to the monitoring wires, which spreads along the wires, is reflected at the location of the moisture due to the jump in electrical conductivity, and runs back to the feed point.
  • the sensitivity of the method is lower than that of the DC resistance measurement, since interference due to reflections add up over the entire length of the line and raise the noise background. The process only works reliably from higher moisture levels.
  • the measured transit time of the voltage pulse is a measure of the pipe length between the leak at which the reflection took place and the feed point. The implementation of the transit time measurement in a location determination is only possible if the course of the pipes in the ground is exactly known.
  • the commercially available metal detectors and inductive proximity switches are based on the eddy current method.
  • the test object to be detected is brought into the effective range of an eddy current sensor through which alternating current flows, in the simplest case a coil.
  • the test object is a metallic conductor, semiconductor or ion conductor, that is to say electrically conductive
  • eddy currents are induced in it by the alternating magnetic field that surrounds the sensor, the intensity of which depends on the electrical, magnetic and geometric parameters of the test object.
  • the eddy currents in turn are magnetic Secondary field concatenated, which overlaps with the primary sensor field to form the overall magnetic field and is mapped and measured in the impedance, the so-called AC resistance of the sensor.
  • the course of the underground pipelines can be tracked precisely by the operator, from a known starting point, with a manual or mechanically performed pivoting movement of the sensor over the ground to determine the location of the maximum interaction, i.e. determines the smallest distance between the sensor and the pipeline and progresses along the pipeline in pursuit of this location.
  • This can reduce the uncertainty of the location of the damage site in the direction transverse to the pipe run.
  • the location of the damage in the longitudinal direction of the pipeline is not possible.
  • the measuring sensitivity is not sufficient to directly detect corrosion in the pipe or the weld seam (classic eddy current error check).
  • the measuring effects of a faultless and a defective pipe differ in the range of fluctuation of the effective disturbance parameters, such as depth, pipe wall thickness, weld seam formation, soil moisture, etc. only a little.
  • the method is fundamentally suitable for determining moisture and gradients thereof in the ground, it is not possible to distinguish whether the detected moisture is a sign of a damage location inside the pipe shell or outside in the surrounding earth, where it is always more or is less abundant.
  • the eddy current sensor's area of action simultaneously detects the inside and the outside of the pipe casing. An improvement in the lateral resolution is not possible due to the large depth and the associated relatively large-area sensor.
  • the known displacement current method is the dielectric analogue to the magnetic eddy current method.
  • Metal electrodes of various shapes come into consideration as capacitive sensors.
  • the The method is sensitive to the dielectric properties ( ⁇ r ) of the test object. In the present case, these are the dielectric constants of the insulating foam, the soil, and in particular that of the water to be detected there.
  • the lateral resolution is not sufficient to distinguish whether the detected moisture is inside or outside the pipe jacket.
  • Metal surfaces or bodies that are in the effective range of the capacitive sensor cause shielding effects and are the cause of interference signals.
  • alternating current is fed into the line system and into the at least one wire or into two or more wires which are spaced apart from one another. Furthermore, the magnetic field generated by the alternating current through the line system and the wire or through the wires is detected in a spatially resolved manner along the line system, and finally, on the basis of the detected magnetic field, a magnetic field evaluation is carried out, by means of which the fault locations can be detected precisely.
  • two monitoring wires running parallel to each other are drawn inside the plastic jacket. The following considerations start from this case, but systems that deviate from this are also dealt with.
  • the resistance measured at the feed point is purely real in the case of direct current measurement, with current and voltage being in phase along the entire two-wire line.
  • inductive and capacitive resistance components are added in the AC case.
  • the resistance measured at the infeed point is thus complex - one also speaks of the AC resistance or the impedance in this context - so that a corresponding phase shift between current and voltage occurs.
  • an equivalent circuit diagram which shows a two-wire line with an alternating current feed and a moist point as a fault location.
  • the two-wire line symbolizes the arrangement of a district heating pipeline within the sheath of which two parallel monitoring wires are provided. Both monitoring wires are electrically insulated from each other by the rigid foam inside the plastic sheathing.
  • an alternating current voltage U_ is applied to the two-wire line, which leads to an alternating current I in connection with the total impedance Z ⁇ _ of the line arrangement.
  • the following therefore applies to the total impedance ZL:
  • ZL RQ + s (2R D raht + j ⁇ L ra ht) + RFeuc te / G ⁇ s -C wire)
  • the total length S L of the pipeline is included in the capacity value of the wire. This capacitance is parallel to the contact resistance R F eu chte in the area of the moisture point. This means that the current flow does not decrease completely after the wet point, but a capacitive current remains until the end of the pipeline.
  • the entire line is split into several individual sections, each with only one moisture point, for which the load resistances result in accordance with the above relationship and the parameters given in the subsections.
  • the total resistance of the route to the last wet point is calculated as the parallel connection of the impedances of the individual sections. This means that the current along the route gradually decreases after each wet point.
  • the step amplitude depends on the ratios of the contact resistances at the various moisture points.
  • two separate monitoring wires are not provided in all piping systems, but in some manufacturers only a single monitoring wire is laid in the rigid foam.
  • the extensive amplitude and phase information available with AC excitation is queried as a function of the location along the line.
  • the magnetic field which is linked to the line current and surrounds the conductor on closed paths, is used as an information carrier.
  • the amplitude and phase of the magnetic field is the exact image of the amplitude and phase distribution of the current on the line below at any distance above the line.
  • the sought-after central scanning position is modeled, as it were, on the eddy current method, in that the operator determines the signal maximum in a manual or mechanically executed pivoting movement of the sensor transverse to the pipe run.
  • the evaluation for example by merely observing the signal changes with respect to the amplitude and phase of the magnetic field as it progresses in the direction of the pipe run, leads to the point at which moisture is present in the interior of the pipe jacket. As long as the operator is between the feed point and the wet point, the signal maximum remains almost constant. If the moisture point is exceeded, the signal maximum collapses and the phase direction of the purely capacitive line current is displayed.
  • the magnetic field is preferably scanned with an inductive sensor which, due to the large distance between the sensor and the pipeline, typically of up to 2 m, meets the high requirements for signal dynamics.
  • the signal processing is connected downstream, which processes the recorded measurement signals in such a way that an operator is able to interpret the measurement signals in a simple, reliable and comprehensible manner.
  • the complex received signal at the sensor is amplified and converted by means of a quadrature demodulator into two rectified signal components, the so-called real and imaginary part of the received voltage, which ultimately represent the amplitude and phase of the current on the line.
  • the amplification and rectification of the measurement signals can be extremely narrow-band. A bandwidth of 3 Hz is typical for one Excitation frequency of 30 kHz. This corresponds to a relative bandwidth of 100 ppm. Interfering interference signals can thus be effectively suppressed. Interference signals can be caused by high-current or data lines with high signal activity, which run close to the heating pipe and are sometimes laid in the same floor duct.
  • adjustable phase directions can be hidden or selected in order to systematic interference signals such. B. to suppress the measuring effects of the capacitive leakage and residual currents behind the wet area.
  • the phase selection can preferably be carried out in such a way that only the real signal component is displayed at the signal output, which is caused by the cross current that flows between the monitoring wires at the wet point.
  • the moisture point is noticed as an abrupt drop in signal when the operator exceeds it and leaves it behind. If there are multiple moisture points along the pipeline, the signal drop when the individual points are exceeded is less clear. Here, however, the additional phase shift that occurs can be used to confirm the display of the wet point.
  • a test device suitable for carrying out the method according to the invention accordingly consists of the following main components which are connected or communicate with one another:
  • inductive sensors that can be optimized with regard to the depth range, as well as fluxgate, GMR and SQUID sensors come into question.
  • the magnetic field sensor is moved along the line course and at the same time swiveled transversely to the line course.
  • the deflection in the transverse direction is typically ⁇ 1 m and must clearly show the signal maximum in this direction. This enables the line to be detected and tracked in the transverse movement.
  • the fault location is characterized by significant signal changes in the longitudinal movement. Both movements can be realized either by walking and manually swiveling the sensor or automatically with a mobile test system, for example rolling on wheels, as well as a motor-driven swivel arm that carries the sensor.
  • Analog electronics with amplifier and phase-selective rectifier for processing the sensor receive voltage Because of the low signal level, a high gain of up to 100 dB should be adjustable. For the same reason, a very small signal bandwidth of typically 3 Hz bandwidth is required in order to be able to reliably suppress interfering interference signals. This can be achieved using a narrow-band quadrature demodulator or a PLL circuit, both of which require a synchronous signal connection to the AC voltage generator at the feed point. This can be done using a cable that the operator carries with him when walking down the line or wirelessly using radio and telemetry.
  • High pass filtering in the local area to suppress influencing variables that are slowly changing with regard to the location, e.g. variable depth of the pipeline.
  • Interactive marking options for the test site by setting time stamps when recording data.
  • the method explained above which is based on the phase-selective and spatially resolved magnetic field scanning, can also be used for the detection of fault locations of a very general nature, such as the detection of cable breaks or short circuits between two cables.
  • the method offers the exact determination of the course of a pipeline system, which runs buried under a thick layer of earth, for example, even without the presence of defects. This is particularly important for the planning and construction of route layouts in areas where all types of piping systems have already been installed.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)

Abstract

La présente invention concerne un procédé pour détecter des endroits défectueux au sein d'un système de conduites pourvu d'une gaine. Au moins un fil passe le long du système de conduites, à distance de ce système, à l'intérieur de ladite gaine. Cette invention est caractérisée en ce que le système de conduites et ledit fil ou deux ou plusieurs fils éloignés les uns des autres sont alimentés en courant alternatif, en ce que le champ magnétique produit par le courant alternatif à travers le système de conduites et le fil ou les fils est détecté avec une haute définition spatiale le long du système de conduites, et en ce qu'une analyse du champ magnétique est réalisée sur la base du champ magnétique détecté et permet de détecter les endroits défectueux.
EP02727410A 2001-04-06 2002-03-13 Procede et dispositif pour detecter des endroits defectueux dans des systemes de conduites isoles Withdrawn EP1386132A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE2001117238 DE10117238A1 (de) 2001-04-06 2001-04-06 Verfahren und Vorrichtung zur Detektion von Fehlerstellen in isolierten Leitungssystemen
DE10117238 2001-04-06
PCT/EP2002/002797 WO2002082034A2 (fr) 2001-04-06 2002-03-13 Procede et dispositif pour detecter des endroits defectueux dans des systemes de conduites isoles

Publications (1)

Publication Number Publication Date
EP1386132A2 true EP1386132A2 (fr) 2004-02-04

Family

ID=7680667

Family Applications (1)

Application Number Title Priority Date Filing Date
EP02727410A Withdrawn EP1386132A2 (fr) 2001-04-06 2002-03-13 Procede et dispositif pour detecter des endroits defectueux dans des systemes de conduites isoles

Country Status (3)

Country Link
EP (1) EP1386132A2 (fr)
DE (1) DE10117238A1 (fr)
WO (1) WO2002082034A2 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102007025494A1 (de) * 2007-06-01 2008-12-04 Schilli, Bernd, Dipl.-Ing. (FH) Leistungsstarker elektrischer Leitungssucher für Kabel und Rohre zur Ortung, Verfolgung und Tiefenmessung. Einbringen eines Metalldrahts in Kunststoffrohre zur Möglichkeit der späteren Leitungsverfolgung
TWI546520B (zh) * 2015-03-30 2016-08-21 大同股份有限公司 流體偵測裝置及流體偵測方法
DE102020003135A1 (de) 2020-05-26 2021-12-02 Curt Reichert Sensoreinrichtung zur Funktionsüberwachung einer Rohrleitung

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DE4104216A1 (de) * 1991-02-12 1992-08-13 Bernd Brandes Leitungsrohr zum transport eines mediums
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GB9414847D0 (en) * 1994-07-22 1994-09-14 Radiodetection Ltd Identification of buried cables
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Also Published As

Publication number Publication date
DE10117238A1 (de) 2002-10-17
WO2002082034A3 (fr) 2003-11-27
WO2002082034A2 (fr) 2002-10-17

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