WO2006117033A1 - Capacitive sensor for recording oil level with guard electrode and heating - Google Patents

Capacitive sensor for recording oil level with guard electrode and heating Download PDF

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Publication number
WO2006117033A1
WO2006117033A1 PCT/EP2006/001401 EP2006001401W WO2006117033A1 WO 2006117033 A1 WO2006117033 A1 WO 2006117033A1 EP 2006001401 W EP2006001401 W EP 2006001401W WO 2006117033 A1 WO2006117033 A1 WO 2006117033A1
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WO
WIPO (PCT)
Prior art keywords
sensor according
housing
measuring
sensor
wall
Prior art date
Application number
PCT/EP2006/001401
Other languages
German (de)
French (fr)
Inventor
Dieter Dohnal
Karsten Viereck
Norbert Reindl
Axel Seikowsky
Original Assignee
Maschinenfabrik Reinhausen Gmbh
Micro-Epsilon Messtechnik Gmbh & Co. Kg
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 Maschinenfabrik Reinhausen Gmbh, Micro-Epsilon Messtechnik Gmbh & Co. Kg filed Critical Maschinenfabrik Reinhausen Gmbh
Publication of WO2006117033A1 publication Critical patent/WO2006117033A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/26—Oils; viscous liquids; paints; inks
    • G01N33/28—Oils, i.e. hydrocarbon liquids
    • G01N33/2888—Lubricating oil characteristics, e.g. deterioration
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
    • G01N27/226—Construction of measuring vessels; Electrodes therefor

Definitions

  • the invention relates to a capacitive sensor for detecting the oil condition, in particular the oil condition of insulating oils electrical equipment.
  • a capacitive sensor is in principle suitable for detecting any non-electrical quantity that can be attributed to a change in the dielectric; Such a sensor is therefore also applicable to the measurement of oil quality, which is also characterized by the dielectric constant of the oil.
  • a capacitive sensor for detecting the oil condition has a sensor cell surrounded by an outer tube.
  • the sensor cell itself has a level sensor and, independently, an oil quality sensor.
  • the outer tube is immersed in the oil to be examined; The oil fills a between sensor cell and outer tube existing interior.
  • the outer tube has on its inner side a concentric counter electrode for the capacitive measurement with the mounted on the outside of the sensor cell capacitor surface of the oil quality sensor.
  • a disadvantage of this known sensor is that the measurement result is highly temperature-dependent, since the dielectric constant of the oil under investigation changes with temperature.
  • the known sensor For the determination of the oil quality of oil-filled electrical equipment, eg. B. the insulating oil of power transformers, which in operation a strongly fluctuating, u. a. From the respective electrical load and the selected type of cooling of the respective transformer depending on the temperature, the known sensor is not suitable.
  • Another disadvantage of the known sensor is the dependence of the measurement result of the impedance of the oil and thus the loss factor tan ⁇ .
  • the object of the invention is therefore to present a capacitive sensor, in which the temperature dependence of the measurement result as well as the influence of the loss factor tan ⁇ are eliminated with a simple structural design.
  • the invention is based on a sensor which is designed in the form of a capacitive voltage divider, the measurement being carried out to ground.
  • an electric heater is provided in the sensor according to the invention, which is regulated and ensures that the temperature between the Measuring electrodes is kept constant and thus the measurement result no longer depends on the respective temperature of the oil.
  • the electrodes of the sensor and the heater are completely embedded in a both transformer oil-resistant and temperature-resistant plastic.
  • suitable plastics may be, for example, PTFE or PEEK.
  • PEEK stands for the material of the semi-crystalline thermoplastic polyether ether ketone. This polyetheretherketone having the chemical formula [- (C 6 H 4 ) -CO- (CSHA) -O- (C 6 HA) -O-] n is known to the person skilled in the art. This material has been used above all in engine construction and in sports and leisure equipment in various unreinforced than fiber-reinforced variants.
  • Fig. 1 shows a sensor according to the invention in a side sectional view
  • Fig. 2 shows this sensor in a lateral view
  • FIG. 4 shows a detail from FIG. 1 with the effective electrode regions
  • FIG. 5 shows a schematic representation of the effect of the sensor according to the invention as a cylindrical capacitor.
  • FIG. 6 shows a schematic representation of the effect of the sensor according to the invention as a stray field capacitor.
  • the sensor according to the invention consists for example of an outer, tubular housing 1; From Figure 1 it can be seen that the individual components in the interior of the housing 1, which will be explained in more detail below, are arranged rotationally symmetrical. In the context of the invention, other embodiments are conceivable instead of the tubular housing 1 described here and the rotationally symmetrical structure explained in more detail below.
  • the sensor according to the invention can also be designed rectangular with rectangular or segmented electrodes.
  • the housing 1 itself can z. ß. be coated with glisscoat.
  • Above the housing 1 is closed by a cover 2 with screw 3.
  • an outer circumferential cover tube 4 In the lower part of the housing 1 is an outer circumferential cover tube 4, which is particularly advantageous from the already described PEEK material.
  • an inner housing 5 Centrally in the interior of the tubular housing 1, an inner housing 5, also particularly advantageous from PEEK material arranged.
  • the inner housing 5 rests with an upper circumferential flange 6 on an inner, likewise circumferential collar 7 of the housing 1.
  • a circumferential seal 8 is inserted into a groove.
  • the inner housing 5 is cup-shaped and dimensioned such that in its lower region, ie below the flange 6, an annular measuring gap 9 between the outer wall of the housing 5 and the inner wall of the housing 1 remains.
  • This measuring gap 9 is in connection with horizontally penetrating the housing 1 and outwardly leading holes 10. The oil whose condition is to be detected, completely fills the measuring gap 9 and can circulate through these holes 10.
  • a measuring electrode -11 is arranged concentrically, the connection region 12 leads upwards.
  • insulators 13, 14, which, like the measuring electrode 11 itself, are concentrically formed circumferentially.
  • guard electrodes 15, 16 are arranged on both sides of these insulators 13, 14, in each case on the side facing away from the measuring electrode 11, again concentrically surrounding guard electrodes 15, 16 are arranged.
  • the one guard electrode 15 is formed as the entire lower portion of the cup-shaped housing 5 filling center part, while the other guard electrode 16 has a concentric annular shape.
  • a circumferential electric heating coil 17 is provided between the inner wall of the cover tube 4 and the inner region of the housing 1.
  • an electronic temperature sensor 18 preferably a specialist known type PT100, arranged. Further technical information about this type of PT100 can be found eg. For example, www.mercatio.com, www.nagy-instruments.de or www.burster.de. From above, the housing 5 is closed by a cover 19, which is fastened centrally with a screw 20 on the guard electrode 15.
  • the components are arranged concentrically around each other, wherein, as described, the two guard electrodes 15, 16 and the intermediate measuring electrode 11, each spatially and electrically separated from each other by insulators 13, 14, with their electrically effective areas abut the inner wall of the housing 5.
  • the outer wall of this housing 5 forms the inner wall of the measuring gap 9 through which the oil flows.
  • the circulating heating coil 17 is arranged in the outer wall of the concentric measuring gap 9. Not shown are the electrical leads of the measuring electrode 11, the guard electrodes 15, 16 and the temperature sensor 18. These leads are guided by a not shown passage to the outside.
  • a plug 22 is provided for the connection of the measuring line.
  • the heating coil 17 ensures that the oil in the measuring gap 9, whose state is detected by the capacitive arrangement of the described components, always has the same temperature.
  • changes in the dielectric constant due to temperature changes of the transformer oil o. ⁇ . In the environment, eg. B. in the transformer tank, excluded.
  • FIG. 5 shows, schematically with indicated field lines, the effect of the described sensor according to the invention as a guard ring capacitor.
  • the measuring electrode 11 is gapped by the guard electrodes 15, 16 arranged on both sides and the field is homogenized between the measuring electrode 11 and the housing 1 acting as the counterelectrode. Thus, practically only the dielectric in the region of the measuring electrode 11 is evaluated.
  • the sensor according to the invention thus allows a temperature-independent detection of the relative dielectric constant as a measure of the state of the oil, d. H. its (dielectric) insulating properties. Furthermore, the disturbing influence of the loss factor tan ⁇ is eliminated in the sensor according to the invention.
  • the sensor has a stable measuring signal in sufficient amplitude; typical values are an operating temperature of 75 degrees C, a sensor array capacitance of 1.8 pF at a frequency of 35 kH.
  • FIG. 6 also schematically shows, with indicated field lines, the possible effect of the described sensor according to the invention as stray field capacitor.

Abstract

The invention relates to a capacitive sensor for recording oil level, in particular the oil level of insulating oil in electrical equipment. An inner housing is arranged within an outer housing such that a measuring gap remains between the two. A measuring electrode is arranged in the measuring gap with a guard electrode arranged to both sides thereof and insulated therefrom. An electrical heating coil is provided in the wall of the outer housing in the region of the measuring gap.

Description

KAPAZITIVER SENSOR ZUR ERFAS SUNG DES ÖLZUSTANDES MIT CAPACITIVE SENSOR FOR CAPTIVATING THE OIL CONDITION WITH
GUARDΞLEKTRODE UNDGUARDΞLECTRODE AND
HEIZUNGHEATER
Die Erfindung betrifft einen kapazitiven Sensor zur Erfassung des Ölzustandes, insbesondere des Ölzustandes von Isolierölen elektrischer Betriebsmittel.The invention relates to a capacitive sensor for detecting the oil condition, in particular the oil condition of insulating oils electrical equipment.
Ein kapazitiver Sensor eignet sich prinzipiell für die Erfassung jeder nichtelektrischen Größe, die sich auf eine Änderung des Dielektrikums zurückführen lässt; ein solcher Sensor ist somit auch für die Messung der Ölqualität, die ebenfalls durch die Dielektrizitätskonstante des Öls gekennzeichnet ist, anwendbar.A capacitive sensor is in principle suitable for detecting any non-electrical quantity that can be attributed to a change in the dielectric; Such a sensor is therefore also applicable to the measurement of oil quality, which is also characterized by the dielectric constant of the oil.
Aus WO 2004/109269 ist bereits ein solcher kapazitiver Sensor zur Erfassung des Ölzustandes bekannt. Er besitzt eine Sensorzelle, die von einem Außenrohr umgeben ist. Die Sensorzelle selbst weist einen Füllstandssensor und, unabhängig davon, einen Ölqualitätssensor auf. Das Außenrohr wird in das zu untersuchende Öl eingetaucht; das Öl füllt dabei einen zwischen Sensorzelle und Außenrohr bestehenden Innenraum aus. Das Außenrohr weist an seiner Innenseite eine konzentrische Gegenelektrode für die kapazitive Messung mit der an der Außenseite der Sensorzelle angebrachten Kondensatorfläche des Ölqualitätssensors auf. Dieser bekannte kapazitive Sensor ist für die Anwendung in Motoren, Getrieben sowie Hydrauliksystemen vorgesehen.From WO 2004/109269 such a capacitive sensor for detecting the oil condition is already known. It has a sensor cell surrounded by an outer tube. The sensor cell itself has a level sensor and, independently, an oil quality sensor. The outer tube is immersed in the oil to be examined; The oil fills a between sensor cell and outer tube existing interior. The outer tube has on its inner side a concentric counter electrode for the capacitive measurement with the mounted on the outside of the sensor cell capacitor surface of the oil quality sensor. This known capacitive sensor is intended for use in engines, transmissions and hydraulic systems.
Ein Nachteil dieses bekannten Sensors besteht darin, dass das Messergebnis stark temperaturabhängig ist, da sich die Dielektrizitätskonstante des untersuchten Öles mit der Temperatur ändert. Für die Ermittlung der Ölqualität ölgefüllter elektrischer Betriebsmittel, z. B. des Isolieröles von Leistungstransformatoren, die in Betrieb eine stark schwankende, u. a. von der jeweiligen elektrischen Belastung und der gewählten Kühlungsart des jeweiligen Transformators abhänge Temperatur aufweisen können, ist der bekannte Sensor nicht geeignet. Ein weiterer Nachteil des bekannten Sensors besteht in der Abhängigkeit des Messergebnisses von der Impedanz des Öls und damit dem Verlustfaktor tanδ.A disadvantage of this known sensor is that the measurement result is highly temperature-dependent, since the dielectric constant of the oil under investigation changes with temperature. For the determination of the oil quality of oil-filled electrical equipment, eg. B. the insulating oil of power transformers, which in operation a strongly fluctuating, u. a. From the respective electrical load and the selected type of cooling of the respective transformer depending on the temperature, the known sensor is not suitable. Another disadvantage of the known sensor is the dependence of the measurement result of the impedance of the oil and thus the loss factor tanδ.
Aufgabe der Erfindung ist es demnach, einen kapazitiven Sensor vorzustellen, bei dem die Temperaturabhängigkeit des Messergebnisses ebenso wie der Einfluss von dem Verlustfaktor tanδ bei einfachem konstruktivem Aufbau eliminiert sind.The object of the invention is therefore to present a capacitive sensor, in which the temperature dependence of the measurement result as well as the influence of the loss factor tanδ are eliminated with a simple structural design.
Diese Aufgabe wird durch einen Sensor mit den Merkmalen des ersten Patentanspruches gelöst. Die Unteransprüche betreffen besonders vorteilhafte Weiterbildungen der Erfindung.This object is achieved by a sensor having the features of the first claim. The subclaims relate to particularly advantageous developments of the invention.
Die Erfindung geht von einem Sensor aus, der in Form eines kapazitiven Spannungsteilers ausgeführt ist, wobei die Messung gegen Masse erfolgt.The invention is based on a sensor which is designed in the form of a capacitive voltage divider, the measurement being carried out to ground.
Nach einem weiteren Merkmal der Erfindung ist beim erfindungsgemäßen Sensor eine elektrische Heizung vorgesehen, die geregelt ist und sicherstellt, dass die Temperatur zwischen den Messelektroden konstant gehalten ist und damit das Messergebnis nicht mehr von der jeweiligen Temperatur des Öles abhängt.According to a further feature of the invention, an electric heater is provided in the sensor according to the invention, which is regulated and ensures that the temperature between the Measuring electrodes is kept constant and thus the measurement result no longer depends on the respective temperature of the oil.
Durch den konstruktiven Aufbau des erfindungsgemäßen Sensors konnte der störende Einfluss des Verlustfaktors tanδ auf das Messergebnis vermieden werden.Due to the structural design of the sensor according to the invention, the disturbing influence of the loss factor tanδ on the measurement result could be avoided.
In einer besonders vorteilhaften Ausführungsform der Erfindung sind die Elektroden des Sensors und die Heizung vollständig in einen sowohl trafoölbeständigen als auch temperaturbeständigen Kunststoff eingebettet. Solche geeigneten Kunststoffe können beispielsweise PTFE oder auch PEEK sein. PEEK steht dabei für das Material des teilkristallinen Thermoplast Polyether-Etherketon. Dieses Polyetheretherketon mit der chemischen Formel [- (C6H4)- CO - (CSHA) -O- (C6HA) - O-] n ist dem Fachmann bekannt. Dieses Material wird bisher vor allem im Motorenbau und bei Sport- und Freizeitgeräten in verschiedenen unverstärkten als aus faserverstärkten Varianten verwendet.In a particularly advantageous embodiment of the invention, the electrodes of the sensor and the heater are completely embedded in a both transformer oil-resistant and temperature-resistant plastic. Such suitable plastics may be, for example, PTFE or PEEK. PEEK stands for the material of the semi-crystalline thermoplastic polyether ether ketone. This polyetheretherketone having the chemical formula [- (C 6 H 4 ) -CO- (CSHA) -O- (C 6 HA) -O-] n is known to the person skilled in the art. This material has been used above all in engine construction and in sports and leisure equipment in various unreinforced than fiber-reinforced variants.
Es hat sich überraschend gezeigt, dass durch die beschriebene Einbettung in einen geeigneten Kunststoff am erfindungsgemäßen Sensor der störende Einfluss der Impedanz über den Verlustfaktor tanδ des Öles beseitigt werden kann. Ein solcher Kunststoff ermöglicht zudem eine besonders glatte, homogene und isolierende Oberfläche, die z. B. durch Aufsputtem oder Lackieren erzeugt werden kann.It has surprisingly been found that the interfering influence of the impedance on the loss factor tanδ of the oil can be eliminated by the described embedding in a suitable plastic on the sensor according to the invention. Such a plastic also allows a particularly smooth, homogeneous and insulating surface, the z. B. by sputtering or painting can be generated.
Die Erfindung soll nachfolgend an Hand von Zeichnungen beispielhaft noch näher erläutert werden. Die Figuren zeigen:The invention will be explained in more detail by way of example with reference to drawings. The figures show:
Fig. 1 einen erfindungsgemäßen Sensor in seitlicher SchnittdarstellungFig. 1 shows a sensor according to the invention in a side sectional view
Fig. 2 diesen Sensor in seitlicher DarstellungFig. 2 shows this sensor in a lateral view
Fig. 3 wiederum diesen Sensor von obenFig. 3, in turn, this sensor from above
Fig. 4 ein Detail aus der Figur 1 mit den wirksamen Elektrodenbereichen4 shows a detail from FIG. 1 with the effective electrode regions
Fig. 5 eine schematische Darstellung der Wirkung des erfindungsgemäßen Sensors als Zylinderkondensator Fig. 6 eine schematische Darstellung der Wirkung des erfindungsgemäßen Sensors als Streufeldkondensator.5 shows a schematic representation of the effect of the sensor according to the invention as a cylindrical capacitor. FIG. 6 shows a schematic representation of the effect of the sensor according to the invention as a stray field capacitor.
Der erfindungsgemäße Sensor besteht beispielsweise aus einem äußeren, rohrförmigen Gehäuse 1 ; aus Figur 1 ist zu sehen, dass die einzelnen Bauteile im Inneren des Gehäuses 1 , die anschließend noch näher erläutert werden, rotationssymmetrisch angeordnet sind. Im Rahmen der Erfindung sind an Stelle des hier beschriebenen rohrförmigen Gehäuses 1 und dem nachfolgend noch näher erläuterten rotationssymmetrischen Aufbau auch andere Ausführungsformen denkbar. Beispielsweise kann der erfindungsgemäße Sensor auch rechteckig mit rechteckigen oder auch segmentierten Elektroden ausgeführt sein. Das Gehäuse 1 selbst kann z. ß. mit Glisscoat beschichtet sein. Oben ist das Gehäuse 1 durch einen Deckel 2 mit Verschraubungen 3 abgeschlossen. Im unteren gereich des Gehäuses 1 befindet sich ein außen umlaufendes Abdeckrohr 4, das besonders vorteilhaft aus dem bereits beschriebenen PEEK-Material besteht. Zentrisch im Inneren des rohrförmigen Gehäuses 1 ist ein inneres Gehäuse 5, ebenfalls besonders vorteilhaft aus PEEK-Material, angeordnet. Das innere Gehäuse 5 liegt mit einem oberen, umlaufenden Flansch 6 auf einem inneren, ebenfalls umlaufenden Kragen 7 des Gehäuses 1 auf. Zur zusätzlichen Abdichtung ist zwischen äußerem Gehäuse 1 und innerem Gehäuse 5 eine umlaufende Dichtung 8 in eine Nut eingelegt. Das innere Gehäuse 5 ist topfförmig ausgebildet und derart dimensioniert, dass in seinem unteren Bereich, d. h. unterhalb des Flansches 6, ein ringförmiger Messspalt 9 zwischen der Außenwand des Gehäuses 5 und der inneren Wand des Gehäuses 1 verbleibt. Dieser Messspalt 9 steht in Verbindung mit horizontal das Gehäuse 1 durchdringenden und nach außen führenden Bohrungen 10. Das Öl, dessen Zustand erfasst werden soll, füllt den Messspalt 9 vollständig aus und kann durch diese Bohrungen 10 zirkulieren. An der Innenwand des topfförmigen Gehäuses 5 ist konzentrisch eine Messelektrode -11 angeordnet, deren Anschlussbereich 12 nach oben führt. Beidseitig vertikal, d. h. ober- und unterhalb der Messelektrode 11 , befinden sich an der Innenseite des Gehäuses 5 Isolatoren 13, 14, die, wie auch die Messelektrode 11 selbst, konzentrisch umlaufend ausgebildet sind. Wiederum beidseitig dieser Isolatoren 13, 14, jeweils an deren der Messelektrode 11 abgewandten Seite, sind wiederum konzentrisch umlaufende Guardelektroden 15, 16 angeordnet. Dabei ist die eine Guardelektrode 15 als den gesamten unteren Bereich des topfförmigen Gehäuses 5 ausfüllendes Mittelteil ausgebildet, während die andere Guardelektrode 16 eine konzentrische, ringförmige Form aufweist. Zusätzlich ist zwischen der Innenwand des Abdeckrohres 4 und dem inneren Bereich des Gehäuses 1 eine umlaufende elektrische Heizspule 17 vorgesehen. Innerhalb des Gehäuses 5 ist noch ein elektronischer Temperatursensor 18, vorzugsweise ein dem Fachmann bekannter Typ PT100, angeordnet. Nähere technische Informationen zu diesem Typ PT100 sind z. B. unter www.mercatio.com, www.nagy-instruments.de oder www.burster.de erhältlich. Von oben ist das Gehäuse 5 durch einen Deckel 19 verschlossen, der mit einer Schraube 20 an der Guardelektrode 15 zentrisch befestigt ist.The sensor according to the invention consists for example of an outer, tubular housing 1; From Figure 1 it can be seen that the individual components in the interior of the housing 1, which will be explained in more detail below, are arranged rotationally symmetrical. In the context of the invention, other embodiments are conceivable instead of the tubular housing 1 described here and the rotationally symmetrical structure explained in more detail below. For example, the sensor according to the invention can also be designed rectangular with rectangular or segmented electrodes. The housing 1 itself can z. ß. be coated with glisscoat. Above the housing 1 is closed by a cover 2 with screw 3. In the lower part of the housing 1 is an outer circumferential cover tube 4, which is particularly advantageous from the already described PEEK material. Centrally in the interior of the tubular housing 1, an inner housing 5, also particularly advantageous from PEEK material arranged. The inner housing 5 rests with an upper circumferential flange 6 on an inner, likewise circumferential collar 7 of the housing 1. For additional sealing between the outer housing 1 and the inner housing 5, a circumferential seal 8 is inserted into a groove. The inner housing 5 is cup-shaped and dimensioned such that in its lower region, ie below the flange 6, an annular measuring gap 9 between the outer wall of the housing 5 and the inner wall of the housing 1 remains. This measuring gap 9 is in connection with horizontally penetrating the housing 1 and outwardly leading holes 10. The oil whose condition is to be detected, completely fills the measuring gap 9 and can circulate through these holes 10. On the inner wall of the cup-shaped housing 5, a measuring electrode -11 is arranged concentrically, the connection region 12 leads upwards. On both sides vertically, ie above and below the measuring electrode 11, are located on the inside of the housing 5 insulators 13, 14, which, like the measuring electrode 11 itself, are concentrically formed circumferentially. Again, on both sides of these insulators 13, 14, in each case on the side facing away from the measuring electrode 11, again concentrically surrounding guard electrodes 15, 16 are arranged. In this case, the one guard electrode 15 is formed as the entire lower portion of the cup-shaped housing 5 filling center part, while the other guard electrode 16 has a concentric annular shape. In addition, a circumferential electric heating coil 17 is provided between the inner wall of the cover tube 4 and the inner region of the housing 1. Within the housing 5 is still an electronic temperature sensor 18, preferably a specialist known type PT100, arranged. Further technical information about this type of PT100 can be found eg. For example, www.mercatio.com, www.nagy-instruments.de or www.burster.de. From above, the housing 5 is closed by a cover 19, which is fastened centrally with a screw 20 on the guard electrode 15.
Es ist also zu sehen, dass beim beschriebenen Ausführungsbeispiel die Bauteile konzentrisch um einander herum angeordnet sind, wobei, wie beschrieben, die beiden Guardelektroden 15, 16 und die dazwischenliegende Messelektrode 11 , jeweils durch Isolatoren 13, 14 räumlich und elektrisch voneinander getrennt, mit ihren elektrisch wirksamen Bereichen an der Innenwand des Gehäuses 5 anliegen. Die Außenwand dieses Gehäuses 5 bildet die Innenwand des vom Öl durchströmten Messspaltes 9. In der äußeren Wandung des konzentrischen Messspaltes 9 ist die umlaufende Heizspule 17 angeordnet. Nicht dargestellt sind die elektrischen Anschlussleitungen der Messelektrode 11 , der Guardelektroden 15, 16 sowie des Temperatursensors 18. Diese Anschlussleitungen werden durch eine nicht dargestellte Durchführung nach außen geführt. Oben im Deckel 2 ist ein Stecker 22 für den Anschluss der Messleitung vorgesehen. Figur 4 zeigt noch einmal im Detail die wirksamen Bereiche der Messelektrode 11 und der Guardelektroden 15, 16, wie beschrieben jeweils getrennt durch die Isolatoren 13, 14, an der inneren Wandung des Gehäuses 5, parallel zum Messspalt 9 verlaufend. Durch die Heizspule 17 wird erreicht, dass das im Messspalt 9 befindliche Öl, dessen Zustand durch die kapazitive Anordnung der beschriebenen Bauelemente erfasst wird, stets die gleiche Temperatur aufweist. Dadurch sind Veränderungen der Dielektrizitätskonstante durch Temperaturänderungen des Transformatorenöles o. ä. in der Umgebung, z. B. im Transformatorenkessel, ausgeschlossen.It can thus be seen that in the described embodiment, the components are arranged concentrically around each other, wherein, as described, the two guard electrodes 15, 16 and the intermediate measuring electrode 11, each spatially and electrically separated from each other by insulators 13, 14, with their electrically effective areas abut the inner wall of the housing 5. The outer wall of this housing 5 forms the inner wall of the measuring gap 9 through which the oil flows. The circulating heating coil 17 is arranged in the outer wall of the concentric measuring gap 9. Not shown are the electrical leads of the measuring electrode 11, the guard electrodes 15, 16 and the temperature sensor 18. These leads are guided by a not shown passage to the outside. Top in the lid 2, a plug 22 is provided for the connection of the measuring line. FIG. 4 again shows in detail the effective regions of the measuring electrode 11 and the guard electrodes 15, 16, as described in each case separated by the insulators 13, 14, running on the inner wall of the housing 5, parallel to the measuring gap 9. The heating coil 17 ensures that the oil in the measuring gap 9, whose state is detected by the capacitive arrangement of the described components, always has the same temperature. As a result, changes in the dielectric constant due to temperature changes of the transformer oil o. Ä. In the environment, eg. B. in the transformer tank, excluded.
Figur 5 zeigt schematisch mit angedeuteten Feldlinien die Wirkung des beschriebenen erfindungsgemäßen Sensors als Schutzringkondensator. Die Messelektrode 11 wird durch die beidseitig angeordneten Guardelektroden 15, 16 umfassend geguarded und das Feld zwischen Messelektrode 1 1 und dem als Gegenelektrode wirkenden Gehäuse 1 homogenisiert. Somit wird praktisch nur das Dielektrikum im Bereich der Messelektrode 11 ausgewertet.FIG. 5 shows, schematically with indicated field lines, the effect of the described sensor according to the invention as a guard ring capacitor. The measuring electrode 11 is gapped by the guard electrodes 15, 16 arranged on both sides and the field is homogenized between the measuring electrode 11 and the housing 1 acting as the counterelectrode. Thus, practically only the dielectric in the region of the measuring electrode 11 is evaluated.
Der erfindungsgemäße Sensor gestattet damit eine temperaturunabhängige Erfassung der relativen Dielektrizitätskonstante als Maß für den Zustand des Öles, d. h. seine (dielektrischen) Isoliereigenschaften. Weiterhin ist beim erfindungsgemäßen Sensor der störende Einfluss des Verlustfaktors tanδ eliminiert. Der Sensor besitzt ein stabiles Messsignal in ausreichender Amplitude; typische Werte sind eine Betriebstemperatur von 75 Grad C, eine Kapazität der Sensoranordnung von 1 ,8 pF bei einer Frequenz von 35 kH.The sensor according to the invention thus allows a temperature-independent detection of the relative dielectric constant as a measure of the state of the oil, d. H. its (dielectric) insulating properties. Furthermore, the disturbing influence of the loss factor tanδ is eliminated in the sensor according to the invention. The sensor has a stable measuring signal in sufficient amplitude; typical values are an operating temperature of 75 degrees C, a sensor array capacitance of 1.8 pF at a frequency of 35 kH.
Figur 6 schließlich zeigt schematisch ebenfalls mit angedeuteten Feldlinien die mögliche Wirkung des beschriebenen erfindungsgemäßen Sensors als Streufeldkondensator. Finally, FIG. 6 also schematically shows, with indicated field lines, the possible effect of the described sensor according to the invention as stray field capacitor.

Claims

Patentansprüche claims
1. Kapazitiver Sensor zur Erfassung des Ölzustandes, insbesondere des Ölzustandes von1. Capacitive sensor for detecting the oil condition, in particular the oil condition of
Isolieröl elektrischer Betriebsmittel, wobei in einem äußeren Gehäuse (1 ) ein inneres Gehäuse (5) derart angeordnet ist, dass zwischenInsulating oil electrical equipment, wherein in an outer housing (1), an inner housing (5) is arranged such that between
Innenwand des äußeren Gehäuses (1 ) und Außenwand des inneren Gehäuses (5) ein Messspalt (9) verbleibt, wobei an der inneren Wandung des Messspaltes (9) eine Messelektrode (11 ) angeordnet ist, wobei sich an der inneren Wandung des Messspaltes (9) oberhalb und unterhalb der MesselektrodeInner wall of the outer housing (1) and outer wall of the inner housing (5) remains a measuring gap (9), wherein on the inner wall of the measuring gap (9) a measuring electrode (11) is arranged, wherein on the inner wall of the measuring gap (9 ) above and below the measuring electrode
(11), jeweils durch Isolatoren (13, 14) von dieser elektrisch isoliert, jeweils eine Guardelektrode (15,(11), in each case by insulators (13, 14) of this electrically isolated, in each case a guard electrode (15,
16) befindet und wobei in der Wandung des äußeren Gehäuses (1 ), zumindest teilweise im Bereich des16) and wherein in the wall of the outer housing (1), at least partially in the region of
Messspaltes (9) angeordnet, eine elektrische Heizspule (17) vorgesehen ist.Measuring gap (9) arranged, an electric heating coil (17) is provided.
2. Sensor nach Anspruch 1 , dadurch gekennzeichnet, dass Messelektrode (11) und/oder die Guardelektroden (15, 16) horizontal, senkrecht zur Längsachse des Messspaltes (9), umlaufend ausgebildet sind.2. Sensor according to claim 1, characterized in that the measuring electrode (11) and / or the guard electrodes (15, 16) are formed horizontally, perpendicular to the longitudinal axis of the measuring gap (9), circumferentially.
3. Sensor nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das Gehäuse (1 ) rohrförmig ausgebildet ist und das innere Gehäuse (5) rotationssymmetrisch ausgebildet und zentrisch angeordnet ist, derart, dass der Messspalt (9) ringförmig ist.3. Sensor according to claim 1 or 2, characterized in that the housing (1) is tubular and the inner housing (5) is rotationally symmetrical and arranged centrally, such that the measuring gap (9) is annular.
4. Sensor nach Anspruch 3, dadurch gekennzeichnet, dass Messelektrode (1 1 ) und/oder die Guardelektroden (15, 16) konzentrisch und ringförmig ausgebildet sind.4. Sensor according to claim 3, characterized in that the measuring electrode (1 1) and / or the guard electrodes (15, 16) are concentric and annular.
5. Sensor nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass der Messspalt (9) mit mindestens einer das äußere Gehäuse (1 ) durchdringen Öffnung (10) in Verbindung steht.5. Sensor according to one of claims 1 to 4, characterized in that the measuring gap (9) with at least one outer housing (1) penetrating opening (10) is in communication.
6. Sensor nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass im unteren Bereich des äußeren Gehäuses (1 ) ein außen umlaufendes Abdeckrohr (4) angeordnet ist, das aus einem trafoölbeständigen und temperaturbeständigen Kunststoff besteht.6. Sensor according to one of claims 1 to 5, characterized in that in the lower region of the outer housing (1) an outer circumferential cover tube (4) is arranged, which consists of a transformer oil-resistant and temperature-resistant plastic.
7. Sensor nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, dass das innere Gehäuse (5) aus einem trafoölbeständigen und temperaturbeständigen Kunststoff besteht.7. Sensor according to one of claims 1 to 6, characterized in that the inner housing (5) consists of a transformer oil-resistant and temperature-resistant plastic.
8. Sensor nach Anspruch 6 oder 7, dadurch gekennzeichnet, dass als Kunststoff PTFE oder PEEK verwendet ist.8. Sensor according to claim 6 or 7, characterized in that is used as a plastic PTFE or PEEK.
9. Sensor nach der Ansprüche 1 bis 8, dadurch gekennzeichnet, dass im Inneren des Sensors, vorzugsweise im Bereich des Messspaltes (9), ein Temperatursensor (18) vorgesehen ist.9. Sensor according to claims 1 to 8, characterized in that in the interior of the sensor, preferably in the region of the measuring gap (9), a temperature sensor (18) is provided.
10. Sensor nach einem der Ansprüche 1 bis 9, dadurch gekennzeichnet, dass die beiden Guardelektroden (15, 16) und die dazwischenliegende Messelektrode (1 1 ), die jeweils durch die Isolatoren (13, 14) räumlich und elektrisch voneinander getrennt sind, mit ihren elektrisch wirksamen Bereichen an der Innenwand des inneren Gehäuses (5) anliegen. 10. Sensor according to one of claims 1 to 9, characterized in that the two guard electrodes (15, 16) and the intermediate measuring electrode (1 1), which are spatially and electrically separated from each other by the insulators (13, 14), with their electrically effective areas abut against the inner wall of the inner housing (5).
PCT/EP2006/001401 2005-05-04 2006-02-16 Capacitive sensor for recording oil level with guard electrode and heating WO2006117033A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102005020809.6 2005-05-04
DE200510020809 DE102005020809B3 (en) 2005-05-04 2005-05-04 Capacitive sensor for detecting oil level, especially insulating oil for electrical operating arrangements, has measurement electrode on inner measurement gap wall, insulated guard electrodes, electrical heating coil in outer housing wall

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WO2006117033A1 true WO2006117033A1 (en) 2006-11-09

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US10514025B2 (en) * 2014-12-10 2019-12-24 Daikin Industries, Ltd. Preheater for compressor

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DE102015200203A1 (en) * 2015-01-09 2016-07-14 Zf Friedrichshafen Ag Measuring arrangement for detecting foreign particles in a medium

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Publication number Priority date Publication date Assignee Title
US10514025B2 (en) * 2014-12-10 2019-12-24 Daikin Industries, Ltd. Preheater for compressor
WO2019049430A1 (en) * 2017-09-11 2019-03-14 Ｋｙｂ株式会社 Fluid property detection device

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