WO2002043217A1 - System for reducing excess voltages, comprising a plurality of varistors - Google Patents

System for reducing excess voltages, comprising a plurality of varistors Download PDF

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Publication number
WO2002043217A1
WO2002043217A1 PCT/DE2001/004279 DE0104279W WO0243217A1 WO 2002043217 A1 WO2002043217 A1 WO 2002043217A1 DE 0104279 W DE0104279 W DE 0104279W WO 0243217 A1 WO0243217 A1 WO 0243217A1
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Prior art keywords
varistors
varistor
individual
ptc thermistor
current
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PCT/DE2001/004279
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German (de)
French (fr)
Inventor
Volker Hinrichsen
Kai Steinfeld
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Siemens Aktiengesellschaft
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Priority to AU2002216916A priority Critical patent/AU2002216916A1/en
Priority to DE10195114T priority patent/DE10195114D2/en
Publication of WO2002043217A1 publication Critical patent/WO2002043217A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
    • H02H9/042—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage comprising means to limit the absorbed power or indicate damaged over-voltage protection device
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C1/00—Details
    • H01C1/16—Resistor networks not otherwise provided for
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/10—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material voltage responsive, i.e. varistors
    • H01C7/12—Overvoltage protection resistors

Definitions

  • the invention relates to an arrangement for reducing overvoltages with a plurality of varistors, which are electrically connected in parallel for the joint discharge of a leakage current.
  • Such an arrangement is known, for example, from the article "At home at -50 ° C", Renz, Hinrichsen, EV Report 1/95, Siemens AG, pages 10 to 13.
  • the article describes a series compensation system with a capacitor bank for the compensation of inductive impedances of a transmission line.
  • a plurality of surge arresters are connected in parallel with the capacitor bank.
  • These surge arresters are varistors, the leakage current path of which essentially consists of metal oxide.
  • the parallel connection of several varistors is necessary in order to discharge the high leakage currents to be controlled without overloading the individual varistors.
  • the present invention is therefore based on the object of designing an arrangement for reducing overvoltages with a plurality of varistors in such a way that overloading of individual varistors is avoided in a wide working range.
  • a thermistor element which controls the distribution of the leakage current to the individual varistors is electrically connected in series to at least one of the varistors.
  • the cold resistance of the PTC thermistor element is selected such that the UI characteristic of the varistor is only slightly influenced within its working range.
  • the hot resistance of the PTC thermistor element is adjusted in such a way that when a critical temperature at the PTC thermistor element that jeopardizes the varistor is reached, the voltage drop is so high that the varistor connected in series with the PTC thermistor element is effectively relieved of this voltage and due to the nonlinear voltage UI characteristic the current and power consumption in this varistor decreases sharply.
  • the varistors connected in parallel take on the proportion of the current by which the current through the affected varistor is reduced. In a simple case, for example, two varistors can be connected in parallel, a thermistor element being electrically connected in series with one of the varistors.
  • the varistor provided with the PTC thermistor element is the less powerful of the two connected in parallel
  • the PTC element controls depending on the varistor te temperature the leakage current distribution so that the more powerful varistor carries an increased leakage current component
  • a further advantageous embodiment of the invention provides that the varistor is formed from several layered blocks and at least one of these blocks is a PTC thermistor element.
  • the varistor is formed from several layered blocks, the series connection of the varistor with a PTC element is possible in a structurally very simple manner.
  • the PTC thermistor element is designed as a discrete element and is arranged between the layered blocks of the varistor.
  • the PTC thermistor element forms a structural unit with the varistor.
  • the PTC thermistor element forms a structural unit with the varistor, this results in favorable properties for mounting the varistor. Due to the structural unity, the stor forcibly connected to the PTC thermistor element, so that there are favorable conditions for contacting the varistor and PTC thermistor element.
  • a structural unit can be applied, for example, to a cold-conducting layer on the varistor, for example, by a sintering process.
  • the structural unit results in a large number of possible forms of the combination of PTC element and varistor.
  • FIG. 1 schematically shows a capacitor bank and varistors of a series compensator connected in parallel thereto
  • FIG. 2 shows a schematic construction of a varistor with PTC thermistor elements
  • FIG. 3 shows a further construction of a varistor with PTC thermistor elements.
  • FIG. 1 shows a capacitor bank 1 consisting of a plurality of capacitors 2, 3, 4, 5 connected in parallel and an arrester bank 6 connected in parallel to the capacitor bank 1.
  • Both the capacitor bank 1 and the arrester bank 6 are part of a series compensator, which in the course of an over - Support line is arranged to compensate for inductive impedances. As such, the series compensator is traversed by the current I flowing in the transmission line. In the case of a three-phase transmission line, such a compensation system is provided in each of the phases.
  • the arrester bank 6 consists of a plurality of varistors 7, 8, 9, 10 connected in parallel. Such varistors 7, 8, 9, 10 are also referred to as arresters. In each of the parallel flow paths of the arrester bank 6, a PTC element 11, 12, 13, 14 is connected in series with each of the varistors 7, 8, 9, 10.
  • the operating current I of the transmission line flows through the capacitor bank 6.
  • the capacitor bank 1 partially compensates for the inductive reactive power of the transmission lines.
  • the voltage drop across the capacitor bank 1 is only so great that the variable interference 7, 8, 9, 10 have a very high impedance and only a small leakage current flows through them.
  • the short-circuit energy must be kept away from the capacitor bank 1 in order to protect it from damage.
  • the voltage drop across capacitor bank 1 is such that the impedance of varistors 7, 8, 9, 10 drops sharply in accordance with their UI characteristic and most of the short-circuit current through the parallel current paths of the arrester bank 6 flows. Due to the manufacturing tolerances of the varistors 7, 8, 9, 10, the UI characteristics of the individual varistors 7, 8, 9, 10 vary with one another, so that the impedances of the individual varistors 7, 8, 9, 10 of the arrester bank 6 differ are great.
  • both the varistors 7, 8, 9, 10 and the PTC thermistor elements 11, 12, 13, 14 are at approximately the same temperature.
  • both the varistors 7, 8, 9, 10 and the PTC thermistor elements 11, 12, 13, 14 are heated due to the deviations of the impedances of the varistors 7, 8, 9, 10, individual varistors 7, 8, 9, 10 can already operate at their power limit.
  • the PTC element heats up so strongly that its impedance increases so that the PTC element 11, 12, 13, 14 such a high voltage drop occurs that the varistor 7, 8, 9, 10 is effectively relieved of voltage and due to its non-linear characteristic, the current and thus the power consumption of the affected varistor 7, 8, 9, 10 decrease.
  • the leakage current is now distributed over the individual parallel current paths of the arrester bank 6 in accordance with the impedances that arise.
  • the varistor has several metal oxide blocks 15, 16, 17. These metal oxide blocks 15, 16, 17 are an integral part of the leakage current path of a varistor.
  • the PTC thermistor element is also designed as a discrete block. In order to achieve a precise mapping of the temperature of the metal oxide blocks, the PTC thermistor element is divided into two blocks in this exemplary embodiment.
  • the PTC thermistor blocks 18, 19 are each arranged between two metal oxide blocks 15, 16, 17.
  • a cold-conducting layer 23, 24, 25 is applied to the individual metal oxide blocks 20, 21, 22.
  • the cold-conducting layer 23, 24, 25 and the respective metal oxide block 20, 21, 22 are connected to one another in an electrically conductive manner.
  • Such a connection can be produced, for example, by a sintering, an adhesive process or another joining technique.
  • the metal oxide blocks 20, 21, 22 with the PTC layer 23, 24, 25 are in turn stacked on one another and thus form an essential part of the leakage current path of a varistor.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Emergency Protection Circuit Devices (AREA)
  • Thermistors And Varistors (AREA)

Abstract

A plurality of varistors (7, 8, 9, 10) are connected in parallel in order to distribute the current to be derived to a plurality of varistors (7, 8, 9, 10). Since the UI characteristics of the individual varistors (7, 8, 9, 10) vary due to manufacturing tolerances, the current to be derived is distributed unevenly to the individual varistors (7, 8, 9, 10) and charges the individual varistors (7, 8, 9, 10) to a higher or lesser degree up to an overcharge of individual varistors (7, 8, 9, 10). A PTC resistor element (11, 12, 13, 14) is connected in series to at least one of the varistors (7, 8, 9, 10) in order to control the distribution of the derived current to the individual varistors (7, 8, 9, 10).

Description

Beschreibungdescription
Anordnung zum Abbau von Überspannungen mit mehreren VaristorenArrangement for reducing overvoltages with several varistors
Die Erfindung bezieht sich auf eine Anordnung zum Abbau von Überspannungen mit mehreren Varistoren, welche zur gemeinsamen Ableitung eines Ableitstromes elektrisch parallel geschaltet sind.The invention relates to an arrangement for reducing overvoltages with a plurality of varistors, which are electrically connected in parallel for the joint discharge of a leakage current.
Eine derartige Anordnung ist beispielweise aus dem Aufsatz "Zu Hause bei -50°C", Renz, Hinrichsen, EV Report 1/95, Siemens AG, Seiten 10 bis 13 bekannt. In dem Aufsatz ist eine Serienkompensationsanlage mit einer Kondensatorbank zur Kom- pensation von induktiven Impedanzen einer Übertragungsleitung beschrieben. Um die bei einem Leitungsfehler an der Kondensatorbank abfallende Spannung zu begrenzen, sind parallel zu der Kondensatorbank mehrere Überspannungsabieiter geschaltet . Diese Überspannungsabieiter sind Varistoren, deren Ableit- strombahn im Wesentlichen aus Metalloxid besteht. Die Parallelschaltung mehrerer Varistoren ist notwendig, um die zu beherrschenden hohen Ableitströme ohne Überlastung der einzelnen Varistoren abzuleiten. Um eine möglichst gleichmäßige Verteilung des Ableitstromes auf die einzelnen Varistoren zu erreichen, ist es notwendig, Varistoren mit annähernd identischen elektrischen Eigenschaften zu verwenden. Dazu ist es erforderlich, durch aufwendige Messungen der elektrischen Eigenschaften der Varistoren diese zu kategorisieren und entsprechend aufeinander abgestimmte Varistoren auszuwählen. Diese Methode stellt jedoch lediglich in einem einzigen Arbeitspunkt der nicht linearen UI-Kennlinien der Varistoren eine annähernde Gleichheit der Strom- bzw. Leistungsaufteilung sicher. Der vorliegenden Erfindung liegt daher die Aufgabe zugrunde, eine Anordnung zum Abbau von Überspannungen mit mehreren Varistoren so auszubilden, dass in einem breiten Arbeitsbereich eine Überlastung einzelner Varistoren vermieden wird.Such an arrangement is known, for example, from the article "At home at -50 ° C", Renz, Hinrichsen, EV Report 1/95, Siemens AG, pages 10 to 13. The article describes a series compensation system with a capacitor bank for the compensation of inductive impedances of a transmission line. In order to limit the voltage drop across the capacitor bank in the event of a line fault, a plurality of surge arresters are connected in parallel with the capacitor bank. These surge arresters are varistors, the leakage current path of which essentially consists of metal oxide. The parallel connection of several varistors is necessary in order to discharge the high leakage currents to be controlled without overloading the individual varistors. In order to achieve the most uniform possible distribution of the leakage current to the individual varistors, it is necessary to use varistors with approximately identical electrical properties. To do this, it is necessary to categorize the varistors' electrical properties by means of complex measurements and to select varistors that are matched to one another. However, this method ensures that the current and power distribution is almost identical at only one operating point of the non-linear UI characteristics of the varistors. The present invention is therefore based on the object of designing an arrangement for reducing overvoltages with a plurality of varistors in such a way that overloading of individual varistors is avoided in a wide working range.
Die Aufgabe wird bei einer Anordnung der eingangs genannten Art erfindungsgemäß dadurch gelöst, dass zumindest zu einem der Varistoren ein die Verteilung des Ableitstromes auf die einzelnen Varistoren steuerndes Kaltleiterelement elektrisch in Serie geschaltet ist.The object is achieved according to the invention in an arrangement of the type mentioned at the outset in that a thermistor element which controls the distribution of the leakage current to the individual varistors is electrically connected in series to at least one of the varistors.
Bei einer derartigen Anordnung ist der Kaltwiderstand des Kaltleiterelements so gewählt, dass die UI-Kennlinie des Va- ristors innerhalb seines Arbeitsbereiches nur geringfügig be- einflusst ist. Der Heißwiderstand des Kaltleiterelementes ist dagegen so abgestimmt, dass mit dem Erreichen einer kritischen, den Varistor gefährdenden Temperatur an dem Kaltlei- terelement ein derartig hoher Spannungsfall entsteht, dass der in Serie zu dem Kaltleiterelement geschaltete Varistor wirksam von dieser Spannung entlastet wird und aufgrund der nichtlinearen UI-Kennlinie die Strom- und Leistungsaufnahme in diesem Varistor stark zurückgeht. Gleichzeitig übernehmen die parallel geschalteten Varistoren den Anteil des Stromes, um den sich der Strom durch den betroffenen Varistor verringert. In einem einfachen Fall können beispielsweise zwei Varistoren parallel geschaltet sein, wobei zu einem der Varistoren ein Kaltleiterelement elektrisch in Serie geschaltet ist. Der mit dem Kaltleiterelement versehene Varistor ist da- bei der leistungsschwächere der beiden parallel geschaltetenWith such an arrangement, the cold resistance of the PTC thermistor element is selected such that the UI characteristic of the varistor is only slightly influenced within its working range. The hot resistance of the PTC thermistor element, on the other hand, is adjusted in such a way that when a critical temperature at the PTC thermistor element that jeopardizes the varistor is reached, the voltage drop is so high that the varistor connected in series with the PTC thermistor element is effectively relieved of this voltage and due to the nonlinear voltage UI characteristic the current and power consumption in this varistor decreases sharply. At the same time, the varistors connected in parallel take on the proportion of the current by which the current through the affected varistor is reduced. In a simple case, for example, two varistors can be connected in parallel, a thermistor element being electrically connected in series with one of the varistors. The varistor provided with the PTC thermistor element is the less powerful of the two connected in parallel
Varistoren. Bei einer ansteigenden Belastung des Varistors steuert das Kaltleiterelement in Abhängigkeit der Varistor- te peratur die Ableitstromverteilung so, dass der leistungsstärkere Varistor einen vergrößerten Ableitstromanteil trägtVaristors. When the varistor loads, the PTC element controls depending on the varistor te temperature the leakage current distribution so that the more powerful varistor carries an increased leakage current component
Als günstige Variante hat sich erwiesen, bei der Parallelschaltung mehrerer Varistoren zu jedem der Varistoren ein Kaltleiterelement in Serie zu schalten. Dadurch ist jeder einzelne der Varistoren vor einer Überlastung geschützt und der Ableitstrom kann so sehr gleichmäßig auf die einzelnen Varistoren aufgeteilt werden.It has proven to be a favorable variant to connect a PTC thermistor element in series when several varistors are connected in parallel with each of the varistors. This protects each of the varistors from overloading and the leakage current can be distributed very evenly across the individual varistors.
Eine weitere vorteilhafte Ausgestaltung der Erfindung sieht vor, dass der Varistor aus mehreren geschichteten Blöcken gebildet ist und zumindest einer dieser Blöcke ein Kaltleiterelement ist.A further advantageous embodiment of the invention provides that the varistor is formed from several layered blocks and at least one of these blocks is a PTC thermistor element.
Ist der Varistor aus mehreren geschichteten Blöcken gebildet, so ist die Serienschaltung des Varistors mit einem Kaltlei- terelement in konstruktiv sehr einfacher Weise möglich. Dabei wird das Kaltleiterelement als diskretes Element ausgeführt und zwischen den geschichteten Blöcken des Varistors angeordnet. Bei dieser Lösung ist es möglich, zur Erzielung der notwendigen elektrischen Eigenschaften des Kaltleiterelementes mehrere Blöcke des Kaltleiterelemente in den geschichteten Varistor einzuarbeiten. Dadurch ist es möglich, die elektri- sehen Eigenschaften des Kaltleiterelementes den konstruktiven Forderungen leicht anzupassen.If the varistor is formed from several layered blocks, the series connection of the varistor with a PTC element is possible in a structurally very simple manner. The PTC thermistor element is designed as a discrete element and is arranged between the layered blocks of the varistor. With this solution, it is possible to incorporate several blocks of the PTC thermistor elements into the layered varistor to achieve the necessary electrical properties of the PTC thermistor element. This makes it possible to easily adapt the electrical properties of the PTC thermistor element to the design requirements.
Außerdem kann es vorteilhaft vorgesehen sein, dass das Kaltleiterelement mit dem Varistor eine bauliche Einheit bildet.In addition, it can advantageously be provided that the PTC thermistor element forms a structural unit with the varistor.
Bildet das Kaltleiterelement mit dem Varistor eine bauliche Einheit, so ergeben sich günstige Eigenschaften für die Montage des Varistors. Durch die bauliche Einheit ist der Vari- stor mit dem Kaltleiterelement zwangsweise verbunden, so dass sich günstige Voraussetzungen für die Kontaktierung von Varistor und Kaltleiterelement ergeben. Eine derartige bauliche Einheit kann beispielsweise das Aufbringen einer kaltleiten- den Schicht auf den Varistor beispielsweise durch einen Sin- terprozess erzielt werden. Außerdem ergibt sich durch die bauliche Einheit eine große Anzahl von möglichen Formen der Kombination von Kaltleiterelement und Varistor.If the PTC thermistor element forms a structural unit with the varistor, this results in favorable properties for mounting the varistor. Due to the structural unity, the stor forcibly connected to the PTC thermistor element, so that there are favorable conditions for contacting the varistor and PTC thermistor element. Such a structural unit can be applied, for example, to a cold-conducting layer on the varistor, for example, by a sintering process. In addition, the structural unit results in a large number of possible forms of the combination of PTC element and varistor.
Im Folgenden wird die Erfindung anhand eines Ausführungsbeispiels in einer Zeichnung gezeigt und nachfolgend näher beschrieben. Dabei zeigt dieIn the following, the invention is shown on the basis of an exemplary embodiment in a drawing and described in more detail below. The shows
Figur 1 schematisch eine Kondensatorbank sowie dazu parallel geschaltete Varistoren eines Serienkompensators, Figur 2 einen schematischen Aufbau eines Varistors mit Kalt- leiterelementen und Figur 3 einen weitereren Aufbau eines Varistors mit Kaltlei- terelementen.1 schematically shows a capacitor bank and varistors of a series compensator connected in parallel thereto, FIG. 2 shows a schematic construction of a varistor with PTC thermistor elements, and FIG. 3 shows a further construction of a varistor with PTC thermistor elements.
Die Figur 1 zeigt eine Kondensatorbank 1 bestehend aus mehreren parallel geschalteten Kondensatoren 2 , 3 , 4 , 5 sowie eine parallel zu der Kondensatorbank 1 geschaltete Ableiterbank 6. Sowohl die Kondensatorbank 1 als auch die Ableiterbank 6 sind Teil eines Serienkompensators, welcher im Verlauf einer Über- tragungsleitung zur Kompensation von induktiven Impedanzen angeordnet ist. Als solches ist der Serienkompensator von dem in der Übertragungsleitung fließenden Strom I durchflössen. Bei einer dreiphasigen Übertragungsleitung ist in jeder der Phasen eine derartige Kompensationsanlage vorgesehen.FIG. 1 shows a capacitor bank 1 consisting of a plurality of capacitors 2, 3, 4, 5 connected in parallel and an arrester bank 6 connected in parallel to the capacitor bank 1. Both the capacitor bank 1 and the arrester bank 6 are part of a series compensator, which in the course of an over - Support line is arranged to compensate for inductive impedances. As such, the series compensator is traversed by the current I flowing in the transmission line. In the case of a three-phase transmission line, such a compensation system is provided in each of the phases.
Die Ableiterbank 6 besteht aus mehreren parallel geschalteten Varistoren 7, 8, 9, 10. Derartige Varistoren 7, 8, 9, 10 werden auch als Abieiter bezeichnet. In jedem der Parallelstrom- pfade der Ableiterbank 6 ist ein Kaltleiterelement 11, 12, 13, 14 in Serie zu jedem der Varistoren 7, 8, 9, 10 geschaltet.The arrester bank 6 consists of a plurality of varistors 7, 8, 9, 10 connected in parallel. Such varistors 7, 8, 9, 10 are also referred to as arresters. In each of the parallel flow paths of the arrester bank 6, a PTC element 11, 12, 13, 14 is connected in series with each of the varistors 7, 8, 9, 10.
Im ungestörten Betrieb ist die Kondensatorbank 6 von dem Betriebsstrom I der Übertragungsleitung durchflössen. Die Kondensatorbank 1 kompensiert die induktive Blindleistung der Übertragungsleitungen zu einem Teil. Der Spannungsfall über der Kondensatorbank 1 ist dabei nur so groß, dass die Vari- stören 7, 8, 9, 10 eine sehr hohe Impedanz aufweisen und lediglich ein geringer Leckstrom durch sie hindurchfließt.In undisturbed operation, the operating current I of the transmission line flows through the capacitor bank 6. The capacitor bank 1 partially compensates for the inductive reactive power of the transmission lines. The voltage drop across the capacitor bank 1 is only so great that the variable interference 7, 8, 9, 10 have a very high impedance and only a small leakage current flows through them.
Bei dem Auftreten von Leitungskurzschlüssen muss die Kurz- schlussenergie von der Kondensatorbank 1 ferngehalten werden, um diese vor einer Beschädigung zu schützen. Bei dem Fließen eines Kurzschlussstromes in der Übertragungsleitung entsteht an der Kondensatorbank 1 ein derartig hoher Spannungsfall, dass die Impedanz der Varistoren 7, 8, 9, 10 entsprechend ihrer UI-Kennlinie stark sinkt und der größte Teil des Kurz- Schlussstromes durch die Parallelstrompfade der Ableiterbank 6 fließt. Auf Grund von Fertigungstoleranzen der Varistoren 7, 8, 9, 10 variieren die UI-Kennlinien der einzelnen Varistoren 7, 8, 9, 10 untereinander, so dass die Impedanzen der einzelnen Varistoren 7, 8, 9, 10 der Ableiterbank 6 unter- schiedlich groß sind. Das führt dazu, dass der Varistor mit der geringsten Impedanz den größten Anteil am Ableitstrom trägt und der Varistor mit der größten Impedanz den geringsten Anteil am Ableitstrom führt. Zum Beginn des Ableitvorganges weisen sowohl die Varistoren 7, 8, 9, 10 als auch die Kaltleiterelemente 11, 12, 13, 14 eine annähernd gleiche Temperatur auf. Mit dem Führen des Ableitstromes kommt es zu einer Erwärmung sowohl der Varistoren 7, 8, 9, 10 als auch der Kaltleiterelemente 11, 12, 13, 14. Auf Grund der Abweichungen der Impedanzen der Varistoren 7, 8, 9, 10 können dabei einzelne Varistoren 7, 8, 9, 10 bereits an ihrer Leistungsgrenze arbeiten. Durch den an seiner Leistungsgrenze arbeitenden Varistor 7, 8, 9, 10 und durch den Leistungsumsatz in dem Kalt- leiterelement selbst, erwärmt sich das Kaltleiterelement dabei so stark, dass sich dessen Impedanz so erhöht, dass an dem Kaltleiterelement 11, 12, 13, 14 ein so hoher Spannungsfall entsteht, dass der Varistor 7, 8, 9, 10 wirksam von Spannung entlastet wird und auf Grund seiner nicht linearen Charakteristik die Strom- und damit die Leistungsaufnahme des betroffenen Varistors 7, 8, 9, 10 zurückgeht. Der Ableitstrom verteilt sich nunmehr entsprechend der sich einstellenden Impedanzen auf die einzelnen Parallelstrompfade der Ableiterbank 6.If line short-circuits occur, the short-circuit energy must be kept away from the capacitor bank 1 in order to protect it from damage. When a short-circuit current flows in the transmission line, the voltage drop across capacitor bank 1 is such that the impedance of varistors 7, 8, 9, 10 drops sharply in accordance with their UI characteristic and most of the short-circuit current through the parallel current paths of the arrester bank 6 flows. Due to the manufacturing tolerances of the varistors 7, 8, 9, 10, the UI characteristics of the individual varistors 7, 8, 9, 10 vary with one another, so that the impedances of the individual varistors 7, 8, 9, 10 of the arrester bank 6 differ are great. This means that the varistor with the lowest impedance carries the largest share of the leakage current and the varistor with the largest impedance carries the lowest share of the leakage current. At the beginning of the discharge process, both the varistors 7, 8, 9, 10 and the PTC thermistor elements 11, 12, 13, 14 are at approximately the same temperature. When the leakage current is conducted, both the varistors 7, 8, 9, 10 and the PTC thermistor elements 11, 12, 13, 14 are heated due to the deviations of the impedances of the varistors 7, 8, 9, 10, individual varistors 7, 8, 9, 10 can already operate at their power limit. Due to the varistor 7, 8, 9, 10 operating at its power limit and due to the power conversion in the PTC element itself, the PTC element heats up so strongly that its impedance increases so that the PTC element 11, 12, 13, 14 such a high voltage drop occurs that the varistor 7, 8, 9, 10 is effectively relieved of voltage and due to its non-linear characteristic, the current and thus the power consumption of the affected varistor 7, 8, 9, 10 decrease. The leakage current is now distributed over the individual parallel current paths of the arrester bank 6 in accordance with the impedances that arise.
Eine derartige Steuerung erfolgt dabei in jedem der Parallel- strompfade der Ableiterbank 6, so dass eine Überlastung jedes einzelnen Varistors 7, 8, 9, 10 vermieden wird. Bei einer entsprechenden Anzahl von Varistoren 7, 8, 9, 10 wird die Verteilung des Kurzschlussstromes auf die einzelnen Varistoren 7, 8, 9, 10 der Ableiterbank 6 vergleichmäßigt. Nach dem Ausschalten des Kurzschlusses kühlen die Varistoren 7, 8, 9, 10 und die Kaltleiterelemente 11, 12, 13, 14 ab und sind für weitere Ableitvorgänge bereit.Such control takes place in each of the parallel current paths of the arrester bank 6, so that an overload of each individual varistor 7, 8, 9, 10 is avoided. With a corresponding number of varistors 7, 8, 9, 10, the distribution of the short-circuit current over the individual varistors 7, 8, 9, 10 of the arrester bank 6 is evened out. After the short circuit has been switched off, the varistors 7, 8, 9, 10 and the PTC thermistor elements 11, 12, 13, 14 cool down and are ready for further discharge processes.
Um die Wirksamkeit der Verteilung des abzuleitenden Stromes auf die einzelnen Varistoren 7, 8, 9, 10 genau abzubilden, ist es erwünscht, dass die Kaltleiterelemente 11, 12, 13, 14 die Temperatur des zugehörigen Varistors 7, 8, 9, 10 genau abbilden. Dazu sind in den Figuren 2 und 3 zwei Ausführungs-In order to accurately depict the effectiveness of the distribution of the current to be dissipated to the individual varistors 7, 8, 9, 10, it is desirable that the PTC thermistor elements 11, 12, 13, 14 accurately depict the temperature of the associated varistor 7, 8, 9, 10 , For this purpose, two embodiments are shown in FIGS.
Varianten zur Kombination von Kaltleiterelement und Varistor im Schnitt dargestellt. Der Varistor weist mehrere Metalloxidblöcke 15, 16, 17 auf. Diese Metalloxidblöcke 15, 16, 17 sind wesentlicher Bestandteil der Ableitstrombahn eines Varistors. Das Kaltleiterelement ist ebenfalls als diskreter Block ausgebildet. Um eine genaue Abbildung der Temperatur der Metalloxidblöcke zu erzielen, ist in diesem Ausführungs- beispiel das Kaltleiterelement in zwei Blöcke aufgeteilt. Die Kaltleiterblöcke 18, 19 sind jeweils zwischen zwei Metalloxidblöcken 15, 16, 17 angeordnet.Variants for combining PTC element and varistor shown in section. The varistor has several metal oxide blocks 15, 16, 17. These metal oxide blocks 15, 16, 17 are an integral part of the leakage current path of a varistor. The PTC thermistor element is also designed as a discrete block. In order to achieve a precise mapping of the temperature of the metal oxide blocks, the PTC thermistor element is divided into two blocks in this exemplary embodiment. The PTC thermistor blocks 18, 19 are each arranged between two metal oxide blocks 15, 16, 17.
In der Figur 3 ist auf die einzelnen Metalloxidblöcke 20, 21, 22 jeweils eine kaltleitende Schicht 23, 24, 25 aufgebracht. Die kaltleitende Schicht 23, 24, 25 und der jeweilige Metalloxidblock 20, 21, 22 sind elektrisch leitend miteinander verbunden. Eine derartige Verbindung kann beispielsweise durch einen Sinter-, einen Klebevorgang oder eine andere Fügetech- nik erzeugt werden. Die Metalloxidblöcke 20, 21, 22 mit der Kaltleiterschicht 23, 24, 25 werden wiederum aufeinanderge- stapelt und bilden so einen wesentlichen Teil der Ableit- strombahn eines Varistors . In FIG. 3, a cold-conducting layer 23, 24, 25 is applied to the individual metal oxide blocks 20, 21, 22. The cold-conducting layer 23, 24, 25 and the respective metal oxide block 20, 21, 22 are connected to one another in an electrically conductive manner. Such a connection can be produced, for example, by a sintering, an adhesive process or another joining technique. The metal oxide blocks 20, 21, 22 with the PTC layer 23, 24, 25 are in turn stacked on one another and thus form an essential part of the leakage current path of a varistor.

Claims

Patentansprüche claims
1. Anordnung zum Abbau von Überspannungen mit mehreren Varistoren (7, 8, 9, 10), welche zur gemeinsamen Ableitung eines Ableitstromes elektrisch parallel geschaltet sind, d a d u r c h g e k e n n z e i c h n e t , dass zumindest zu einem der Varistoren (7, 8, 9, 10) ein die Verteilung des Ableitstromes auf die einzelnen Varistoren (7, 8, 9, 10) steuerndes Kaltleiterelement (11, 12, 13, 14) elek- trisch in Serie geschaltet ist.1. Arrangement for reducing overvoltages with a plurality of varistors (7, 8, 9, 10) which are electrically connected in parallel for the joint discharge of a leakage current, characterized in that at least one of the varistors (7, 8, 9, 10) Distribution of the leakage current to the individual varistors (7, 8, 9, 10) controlling thermistor element (11, 12, 13, 14) is electrically connected in series.
2. Anordnung zur Ableitung von Überspannungen nach Anspruch2. Arrangement for the derivation of overvoltages according to claim
1, d a d u r c h g e k e n n z e i c h n e t , dass der Varistor (7, 8, 9, 10) aus mehreren geschichteten Blöcken gebildet ist und zumindest einer dieser Blöcke ein Kaltleiterelement (18, 19) ist.1, so that the varistor (7, 8, 9, 10) is formed from several layered blocks and at least one of these blocks is a PTC thermistor element (18, 19).
3. Anordnung zur Ableitung von Überspannungen nach Anspruch 1 oder 2, d a d u r c h g e k e n n z e i c h n e t , dass das Kaltleiterelement (23, 24, 25) mit dem Varistor eine bauliche Einheit bildet. 3. Arrangement for the derivation of overvoltages according to claim 1 or 2, so that the thermistor element (23, 24, 25) forms a structural unit with the varistor.
PCT/DE2001/004279 2000-11-21 2001-11-14 System for reducing excess voltages, comprising a plurality of varistors WO2002043217A1 (en)

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WO2012140033A1 (en) * 2011-04-12 2012-10-18 Phoenix Contact Gmbh & Co. Kg Two-stage shut-off device
CN103460541A (en) * 2011-04-12 2013-12-18 菲尼克斯电气公司 Two-stage shut-off device
DE102011001977C5 (en) * 2011-04-12 2015-12-03 Phoenix Contact Gmbh & Co. Kg Two-stage switch-off device for a varistor
EP2697881B1 (en) 2011-04-12 2016-11-30 Phoenix Contact GmbH & Co. KG Two-stage shut-off device
FR2986380A1 (en) * 2012-01-31 2013-08-02 Citel Safety device for power line that is utilized for diverting transient over voltages to ground, has thermal bridge for connecting thermal disconnector to varistors to cause opening of thermal disconnector in response to heating of varistors

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