EP0691662B1 - Differential transformer for electronic protection device - Google Patents

Differential transformer for electronic protection device Download PDF

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Publication number
EP0691662B1
EP0691662B1 EP95109486A EP95109486A EP0691662B1 EP 0691662 B1 EP0691662 B1 EP 0691662B1 EP 95109486 A EP95109486 A EP 95109486A EP 95109486 A EP95109486 A EP 95109486A EP 0691662 B1 EP0691662 B1 EP 0691662B1
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EP
European Patent Office
Prior art keywords
core
current transformer
differential
winding
transformer according
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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.)
Expired - Lifetime
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EP95109486A
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German (de)
French (fr)
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EP0691662A1 (en
Inventor
Markus Dipl.-Ing. Brunner
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Vacuumschmelze GmbH and Co KG
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Vacuumschmelze GmbH and Co KG
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F3/00—Cores, Yokes, or armatures
    • H01F3/08—Cores, Yokes, or armatures made from powder
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
    • H01F38/20—Instruments transformers
    • H01F38/22—Instruments transformers for single phase ac
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H83/00—Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current
    • H01H83/14—Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current operated by imbalance of two or more currents or voltages, e.g. for differential protection
    • H01H83/144—Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current operated by imbalance of two or more currents or voltages, e.g. for differential protection with differential transformer

Definitions

  • the invention relates to a total current transformer with a wound, self-contained core made of highly permeable, soft magnetic material for detecting the total current of power lines passing through the core, in which the winding of the core is connected to a circuit breaker via an amplifier.
  • Such a total current transformer is described in WO 93/16479.
  • the core for this known summation current transformer can optionally consist of sintered, ferromagnetic material, of stacked disks or wound strips or wires.
  • US 5 235 488 describes a total current transformer with a wound core made of an iron-nickel alloy. All these cores have in common that insulating layers are provided either by small air gaps in the material or by the division into disks or by winding, which reduce eddy currents induced in the material by the alternating field acting on them. The consequence of this is that such cores - particularly because of their small dimensions - have a low mechanical strength and are therefore sensitive to shock loads and also have a low strength for the winding.
  • a summation current transformer is connected to the input of an amplifier, i.e. the power for switching a relay is not taken from the core itself, it requires a relatively low transmission power and can therefore be designed with small dimensions.
  • the reduction in size is essentially limited by the associated mechanical weakening of the summation current transformer core and by the inevitable Increasing the ohmic resistance of the winding, since this must then consist of relatively thin wires.
  • this ohmic resistance of the winding of the summation current transformer core is decisive, among other things, for the amplification factor of the downstream amplifier. Since the ohmic resistance changes with the temperature, the amplifier will also have a temperature response, so that the accuracy of the tripping characteristic suffers.
  • EP 0 392 204 A2 describes the use of a finely crystalline iron alloy as a material for a magnetic core of a residual current circuit breaker.
  • a nickel-iron alloy with approx. 77 percent nickel is used as the material.
  • the material is subjected to an extensive annealing treatment.
  • the object of the present invention is now to provide a summation current transformer which can have relatively small dimensions and nevertheless has a mechanically firm core and a low temperature response.
  • the core is solid, that is, without insulating intermediate layers or air gaps that divide the core cross section, that the material of the core consists of a metallic alloy with a content of at least 40 percent nickel, which is a positive Has temperature coefficient of electrical resistance, and that the wall thickness in relation to the average geometric diameter of the core is chosen so that it is not less than 0.01 times and not greater than 0.5 times the average geometric diameter.
  • the total current transformer 1 in FIG. 1 consists of a core 2 with a winding 3. Power lines 5 and 6 are passed through the core and connect an AC voltage source 8 to a consumer 9 via a circuit breaker 7.
  • the supply lines of an amplifier 10 are connected to the power lines 5 and 6, the input lines of which are connected to the winding 3 of the summation current transformer 1 and the output lines of which are connected to the turn-off winding 11 of the circuit breaker 7.
  • FIG. 2 When using a solid core made of a metallic alloy with a high nickel content, an equivalent circuit diagram for the circuit results, as shown in FIG. 2.
  • Metallic nickel-iron alloys containing high nickel have a magnetic permeability, the values of which are orders of magnitude higher than are required for use as the core of a summation current transformer.
  • the core 2 thus has a very high inductance.
  • a flow in the core 2 causes eddy currents to spread, since they are not prevented by air gaps or other insulating layers that divide the core cross section. These eddy currents generate an opposing field to the alternating field in the core 2 caused by the total current; they are only limited by the electrical resistance of the material from which the core 2 is made.
  • core 2 is therefore represented by an ohmic resistor R2 and an inductor L2.
  • the winding 3 is divided into an inductor N3 and a resistor R3, which characterizes the copper resistance of the winding.
  • the circuit in FIG. 2 is tuned so that the protective switch 7 is triggered by the amplifier 10 at the desired maximum total current value. If the ambient temperature now increases, the copper resistance R3 of the winding 3 also increases, so that the input voltage at the amplifier 10 would decrease. On the other hand, the resistance R2 also increases, since the material of the core 2 has a positive temperature coefficient of the electrical resistance. However, the increase in the resistance R2 means that the eddy currents in the core 2 decrease and the field generated by the total current is less weakened. This necessitates a higher AC permeability of the core 2 and leads to an increase in the induced voltage in the winding 3 and thus at the input of the amplifier 10.
  • the core 2 can be produced, for example, by cutting it off a tube or by extrusion.
  • Fig. 3 shows a divided core in a circular shape
  • Fig. 4 such a rectangular shape
  • Fig. 5 shows a core of two U-halves, which are to be assembled overlapped.
  • These cores have the advantage that the winding is known Way is easier to apply and that it can be pushed wrapped over the core parts.
  • the overlap area in FIG. 5 does indeed cause an air gap, albeit small, to be present on part of the core. A significant reduction in the eddy currents does not occur as a result, so that the level of the eddy currents is still determined almost completely by the conductivity of the core material and the temperature-compensating effect is retained.
  • Fig. 6 for an embodiment of a core according to the invention with 1000 turns for winding 3 and a winding resistance of 50 ohms and a core cross section of 0.03 cm 2 and an iron length of 4.15 cm
  • the output voltage of the amplifier 10 that is Voltage on the winding 11 of the circuit breaker 7 shown depending on the AC permeability, which can result from different core material, different annealing treatments.
  • the solid curve is the output voltage at room temperature, the dashed curves are obtained if a temperature of + 70 ° or -20 ° C is used.
  • the use of the summation current transformer according to the invention means that, on the one hand, one has a mechanically very strong, practically directly wound core and, moreover, the temperature response can be compensated for by the ohmic resistance of the winding of the summation current transformer core.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Transformers For Measuring Instruments (AREA)
  • High-Tension Arc-Extinguishing Switches Without Spraying Means (AREA)

Description

Die Erfindung betrifft einen Summenstromwandler mit einem bewickelten, in sich geschlossenen Kern aus hochpermeablem weichmagnetischen Material zur Erfassung des Summenstromes von durch den Kern hindurchtretenden Stromleitungen, bei dem die Wicklung des Kerns über einen Verstärker an einen Schutzschalter angeschlossen ist.The invention relates to a total current transformer with a wound, self-contained core made of highly permeable, soft magnetic material for detecting the total current of power lines passing through the core, in which the winding of the core is connected to a circuit breaker via an amplifier.

Ein derartiger Summenstromwandler ist in WO 93/16479 beschrieben. Der Kern für diesen bekannten Summenstromwandler kann wahlweise aus gesintertem, ferromagnetischem Material, aus aufeinandergestapelten Scheiben oder gewickelten Bändern oder Drähten bestehen. In US 5 235 488 ist ein Summenstromwandler mit einem gewickelten Kern aus einer Eisen-Nickel-Legierung beschrieben. Allen diesen Kernen ist gemeinsam, daß entweder durch kleine Luftspalte im Material oder durch die Aufteilung in Scheiben oder durch Wickeln Isolierschichten vorgesehen sind, die durch das einwirkende Wechselfeld induzierte Wirbelströme im Material vermindern. Dies hat zur Folge, daß derartige Kerne - besonders wegen ihrer kleinen Abmessungen - eine geringe mechanische Festigkeit aufweisen und daher gegen Schockbeanspruchungen empfindlich sind und auch für die Bewicklung eine geringe Festigkeit aufweisen.Such a total current transformer is described in WO 93/16479. The core for this known summation current transformer can optionally consist of sintered, ferromagnetic material, of stacked disks or wound strips or wires. US 5 235 488 describes a total current transformer with a wound core made of an iron-nickel alloy. All these cores have in common that insulating layers are provided either by small air gaps in the material or by the division into disks or by winding, which reduce eddy currents induced in the material by the alternating field acting on them. The consequence of this is that such cores - particularly because of their small dimensions - have a low mechanical strength and are therefore sensitive to shock loads and also have a low strength for the winding.

Wenn ein Summenstromwandler an den Eingang eines Verstärkers angeschlossen wird, die Leistung für das Schalten eines Relais also nicht dem Kern selbst entnommen wird, so benötigt er eine relativ geringe Übertragungsleistung und kann daher mit kleinen Abmessungen ausgeführt werden. Die Verkleinerung der Abmessungen wird im wesentlichen begrenzt durch die damit verbundene mechanische Schwächung des Summenstromwandlerkerns und durch die unvermeidliche Erhöhung des ohmschen Widerstandes der Wicklung, da diese dann aus relativ dünnen Drähten bestehen muß. Dieser ohmsche Widerstand der Wicklung des Summenstromwandlerkerns ist aber unter anderem maßgebend für den Verstärkungsfaktor des nachgeschalteten Verstärkers. Da der ohmsche Widerstand sich mit der Temperatur ändert, wird auch der Verstärker einen Temperaturgang aufweisen, so daß die Genauigkeit der Auslösecharakteristik darunter leidet.If a summation current transformer is connected to the input of an amplifier, i.e. the power for switching a relay is not taken from the core itself, it requires a relatively low transmission power and can therefore be designed with small dimensions. The reduction in size is essentially limited by the associated mechanical weakening of the summation current transformer core and by the inevitable Increasing the ohmic resistance of the winding, since this must then consist of relatively thin wires. However, this ohmic resistance of the winding of the summation current transformer core is decisive, among other things, for the amplification factor of the downstream amplifier. Since the ohmic resistance changes with the temperature, the amplifier will also have a temperature response, so that the accuracy of the tripping characteristic suffers.

In EP 0 392 204 A2 wird die Verwendung einer feinkristallinen Eisenlegierung als Material für einen Magnetkern eines Fehlerstrom-Schutzschalters beschrieben. Um eine geringe Temperaturabhängigkeit der magnetischen Eigenschaften des Kerns zu erzielen, wird als Material eine Nickel-Eisen-Legierung mit ca. 77 Prozent Nickel eingesetzt. Das Material wird einer aufwendigen Glühbehandlung unterzogen.EP 0 392 204 A2 describes the use of a finely crystalline iron alloy as a material for a magnetic core of a residual current circuit breaker. In order to achieve a low temperature dependence of the magnetic properties of the core, a nickel-iron alloy with approx. 77 percent nickel is used as the material. The material is subjected to an extensive annealing treatment.

Aufgabe der vorliegenden Erfindung ist es nun, einen Summenstromwandler anzugeben, der relativ kleine Abmessungen haben kann und trotzdem einen mechanisch festen Kern und einen geringen Temperaturgang besitzt.The object of the present invention is now to provide a summation current transformer which can have relatively small dimensions and nevertheless has a mechanically firm core and a low temperature response.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß der Kern massiv, das heißt ohne isolierende Zwischenlagen oder Luftspalte, die den Kernquerschnitt aufteilen, ausgebildet ist, daß das Material des Kerns aus einer metallischen Legierung mit einem Gehalt von mindstens 40 Prozent Nickel besteht, das einen positiven Temperaturkoeffizienten des elektrischen Widerstandes besitzt, und daß die Wandstärke im Verhältnis zum mittleren geometrischen Durchmesser des Kerns so gewählt ist, daß sie nicht kleiner als das 0,01-fache und nicht größer als das 0,5-fache des mittleren geometrischen Durchmessers beträgt.This object is achieved in that the core is solid, that is, without insulating intermediate layers or air gaps that divide the core cross section, that the material of the core consists of a metallic alloy with a content of at least 40 percent nickel, which is a positive Has temperature coefficient of electrical resistance, and that the wall thickness in relation to the average geometric diameter of the core is chosen so that it is not less than 0.01 times and not greater than 0.5 times the average geometric diameter.

Vorteilhafte Weiterbildungen der Erfindung sind in den Unteransprüchen beschrieben.

  • Fig. 1 zeigt die Schaltung des Summenstromwandlers beim Einsatz für eine elektronische Schutzeinrichtung;
  • Fig. 2 enthält ein Ersatzschaltbild zur Erläuterung der Wirkungsweise;
  • in den Fig. 3 bis 5 sind mögliche weitere Kernformen dargestellt und
  • in Fig. 6 ist der Temperaturgang eines erfindungsgemäßen Kerns dargestellt.
Advantageous developments of the invention are described in the subclaims.
  • Fig. 1 shows the circuit of the summation current transformer when used for an electronic protective device;
  • 2 contains an equivalent circuit diagram to explain the mode of operation;
  • 3 to 5 possible further core shapes are shown and
  • 6 shows the temperature response of a core according to the invention.

Der Summenstromwandler 1 in Fig. 1 besteht aus einem Kern 2 mit einer Wicklung 3. Durch den Kern sind Stromleitungen 5 und 6 hindurchgeführt, die über einen Schutzschalter 7 eine Wechselspannungsquelle 8 mit einem Verbraucher 9 verbinden. An die Stromleitungen 5 und 6 sind die Versorgungsleitungen eines Verstärkers 10 angeschlossen, dessen Eingangsleitungen mit der Wicklung 3 des Summenstromwandlers 1 und dessen Ausgangsleitungen mit der Ausschaltwicklung 11 des Schutzschalters 7 verbunden sind.The total current transformer 1 in FIG. 1 consists of a core 2 with a winding 3. Power lines 5 and 6 are passed through the core and connect an AC voltage source 8 to a consumer 9 via a circuit breaker 7. The supply lines of an amplifier 10 are connected to the power lines 5 and 6, the input lines of which are connected to the winding 3 of the summation current transformer 1 and the output lines of which are connected to the turn-off winding 11 of the circuit breaker 7.

Wenn der Summenstrom, der durch die in den Stromleitungen 5 und 6 fließenden Ströme beispielsweise infolge eines Erdschlusses nicht Null ist, so wird in dem Kern 2 des Summenstromwandlers 1 ein Wechselfluß erzeugt, der eine Spannung in der Wicklung 3 induziert, die ihrerseits über den Verstärker 10 die Auslösung des Schutzschalters 7 bewirkt.If the total current, which is not zero due to the currents flowing in the power lines 5 and 6, for example due to an earth fault, an alternating current is generated in the core 2 of the total current transformer 1, which induces a voltage in the winding 3, which in turn via the amplifier 10 triggers the circuit breaker 7.

Bei Verwendung eines Massivkerns aus einer metallischen Legierung mit hohem Nickelgehalt ergibt sich ein Ersatzschaltbild für die Schaltung, wie es in Fig. 2 dargestellt ist. Hochnickelhaltige metallische Nickel-Eisen-Legierungen besitzen eine magnetische Permeabilität, deren Werte um Größenordnungen höher sind, als sie für den Einsatz als Kern eines Summenstromwandlers benötigt werden. Der Kern 2 besitzt damit eine sehr hohe Induktivität. Da er jedoch massiv ausgeführt ist, bewirkt ein Fluß in dem Kern 2, daß sich Wirbelströme ausbreiten können, da sie durch Luftspalte oder andere isolierende Schichten, die den Kernquerschnitt aufteilen, nicht gehindert werden. Diese Wirbelströme erzeugen ein Gegenfeld zu dem durch den Summenstrom bedingten Wechselfeld in dem Kern 2; sie werden nur begrenzt durch den elektrischen Widerstand des Materials, aus dem der Kern 2 besteht. Im Ersatzschaltbild ist der Kern 2 daher durch einen ohmschen Widerstand R2 und eine Induktivität L2 dargestellt. Die Wicklung 3 ist im Ersatzschaltbild nach Fig. 2 aufgeteilt in eine Induktivität N3 und einen Widerstand R3, der den Kupferwiderstand der Wicklung kennzeichnet.When using a solid core made of a metallic alloy with a high nickel content, an equivalent circuit diagram for the circuit results, as shown in FIG. 2. Metallic nickel-iron alloys containing high nickel have a magnetic permeability, the values of which are orders of magnitude higher than are required for use as the core of a summation current transformer. The core 2 thus has a very high inductance. However, since it is solid, a flow in the core 2 causes eddy currents to spread, since they are not prevented by air gaps or other insulating layers that divide the core cross section. These eddy currents generate an opposing field to the alternating field in the core 2 caused by the total current; they are only limited by the electrical resistance of the material from which the core 2 is made. In the equivalent circuit diagram, core 2 is therefore represented by an ohmic resistor R2 and an inductor L2. In the equivalent circuit diagram according to FIG. 2, the winding 3 is divided into an inductor N3 and a resistor R3, which characterizes the copper resistance of the winding.

Es wird angenommen, daß die Schaltung in Fig. 2 so abgestimmt ist, daß bei dem gewünschten maximalen Summenstromwert eine Auslösung des Schutzschalters 7 über den Verstärker 10 erfolgt. Wenn sich nun die Umgebungstemperatur erhöht, erhöht sich auch der Kupferwiderstand R3 der Wicklung 3, so daß die Eingangsspannung am Verstärker 10 sinken würde. Andererseits erhöht sich aber auch der Widerstand R2, da das Material des kernes 2 einen positiven Temperaturkoeffizienten des elektrischen Widerstandes besitzt. Die Erhöhung des Widerstandes R2 bedingt aber, daß die Wirbelströme in dem Kern 2 abnehmen und das durch den Summenstrom erzeugte Feld weniger schwächen. Dies bedingt eine höhere Wechselstrompermeabilität des Kernes 2 und führt zu einer Erhöhung der induzierten Spannung in der Wicklung 3 und damit am Eingang des Verstärkers 10. Hieraus ist ersichtlich, daß durch die bewußte Inkaufnahme von nennenswerten Wirbelströmen durch Verwendung eines Massivkerns eine Temperaturkompensation der Schaltung möglich ist; in der Praxis hat sich herausgestellt, daß die Kompensation optimal ist, wenn - abhängig von dem jeweils verwendeten Material und der Kernform - die Wandstärke des Kernes 2 im Verhältnis zu dem mittleren Durchmesser einen Wert im Bereich von 0,01 bis 0,5 aufweist. Die besonders hohe statische Permeabilität der erfindungsgemäß verwendeten hochnickelhaltigen Legierung gestattet es außerdem, den Kern in verschiedenen geometrischen Formen und auch geteilt aus zwei oder mehr Kernteilen zusammenzusetzen.It is assumed that the circuit in FIG. 2 is tuned so that the protective switch 7 is triggered by the amplifier 10 at the desired maximum total current value. If the ambient temperature now increases, the copper resistance R3 of the winding 3 also increases, so that the input voltage at the amplifier 10 would decrease. On the other hand, the resistance R2 also increases, since the material of the core 2 has a positive temperature coefficient of the electrical resistance. However, the increase in the resistance R2 means that the eddy currents in the core 2 decrease and the field generated by the total current is less weakened. This necessitates a higher AC permeability of the core 2 and leads to an increase in the induced voltage in the winding 3 and thus at the input of the amplifier 10. From this it can be seen that by consciously accepting significant eddy currents by using a solid core, temperature compensation of the circuit is possible ; In practice it has been found that the compensation is optimal if - depending on the material used and the core shape - the wall thickness of the core 2 has a value in the range of 0.01 to 0.5 in relation to the average diameter. The particularly high static permeability of the high-nickel alloy used according to the invention also allows the core to be assembled in different geometric shapes and also divided from two or more core parts.

Der Kern 2 kann zum Beispiel durch Abtrennen von einem Rohr oder durch Fließpressen hergestellt werden.The core 2 can be produced, for example, by cutting it off a tube or by extrusion.

Fig. 3 zeigt einen geteilten Kern in Kreisform, Fig. 4 einen solchen in Rechteckform und Fig. 5 einen Kern aus zwei U-Hälften, die überlappt zusammenzusetzen sind. Diese Kerne besitzen den Vorteil, daß die Wicklung in bekannter Weise leichter aufzubringen ist und daß sie fertig gewickelt über die Kernteile geschoben werden kann. Der Überlappungsbereich in Fig. 5 bewirkt zwar, daß auf einem Teil des Kerns ein wenn auch kleiner Luftspalt vorhanden ist. Eine wesentliche Verminderung der Wirbelströme tritt dadurch nicht ein eintreten, so daß nach wie vor die Höhe der Wirbelströme nahezu vollständig von der Leitfähigkeit des Kernmaterials bestimmt wird und der temperatur-kompensierende Effekt erhalten bleibt.Fig. 3 shows a divided core in a circular shape, Fig. 4 such a rectangular shape and Fig. 5 shows a core of two U-halves, which are to be assembled overlapped. These cores have the advantage that the winding is known Way is easier to apply and that it can be pushed wrapped over the core parts. The overlap area in FIG. 5 does indeed cause an air gap, albeit small, to be present on part of the core. A significant reduction in the eddy currents does not occur as a result, so that the level of the eddy currents is still determined almost completely by the conductivity of the core material and the temperature-compensating effect is retained.

In Fig. 6 ist für ein Ausführungsbeispiel eines erfindungsgemäßen Kerns mit 1000 Windungen für die Wicklung 3 und einem Wicklungswiderstand von 50 Ohm sowie einem Kernquerschnitt von 0,03 cm2 und einer Eisenlänge von 4,15 cm, die Ausgangsspannung des Verstärkers 10, also die Spannung an der Wicklung 11 des Schutzschalters 7 abhängig von der Wechselstrompermeabilität dargestellt, die sich durch unterschiedliches Kernmaterial, unterschiedliche Glühbehandlungen ergeben kann. Die ausgezogene Kurve ist damit die Ausgangsspannung bei Raumtemperatur, die gestrichelten Kurven ergeben sich, wenn man eine Temperatur von +70° bzw. -20°C zugrundelegt. Man sieht hier einerseits, daß eine sehr gute Kompensation des Temperaturganges ermöglicht wird, und daß andererseits bei einer Wechselstrompermeabilität von mehr als 15 000 oder 20 000 keine wesentliche Änderung der Ausgangsspannung mehr auftritt, so daß bei diesem Anwendungsfall ohne weiteres die zur Temperaturkompensation verwendete Schwächung der statischen Permeabilität des Kernmaterials durch die im Massivkern auftretenden Wirbelströme in Kauf genommen werden kann.In Fig. 6 for an embodiment of a core according to the invention with 1000 turns for winding 3 and a winding resistance of 50 ohms and a core cross section of 0.03 cm 2 and an iron length of 4.15 cm, the output voltage of the amplifier 10, that is Voltage on the winding 11 of the circuit breaker 7 shown depending on the AC permeability, which can result from different core material, different annealing treatments. The solid curve is the output voltage at room temperature, the dashed curves are obtained if a temperature of + 70 ° or -20 ° C is used. It can be seen here on the one hand that a very good compensation of the temperature response is made possible, and on the other hand that with an AC permeability of more than 15,000 or 20,000 no significant change in the output voltage occurs, so that in this application the weakening of the temperature compensation used without further notice static permeability of the core material can be accepted due to the eddy currents occurring in the solid core.

Dies gilt umso mehr, als tatsächlich Verluste durch Wirbelströme nur auftreten, wenn ein Fehlerfall, d. h. ein Summenstrom verschieden von Null, vorliegt, so daß also nur kurzzeitig vom Auftreten des Fehlers bis zum Abschalten des Schutzschalters 7 ein Fluß im Kern 2 vorhanden ist. Eine Aufheizung des Kerns 2 im Normalbetrieb des Summenstromwandlers findet also nicht statt. Durch die Verwendung des erfindungsgemäßen Summenstromwandlers wird erreicht, daß man einerseits einen mechanisch sehr festen, praktisch direkt bewickelbaren Kern besitzt und außerdem den Temperaturgang bedingt durch den ohmschen Widerstand der Wicklung des Summenstromwandlerkerns ausgleichen kann.This is all the more true since losses due to eddy currents actually only occur when there is a fault, ie a total current other than zero, so that there is only a short time in the core 2 from the occurrence of the fault until the circuit breaker 7 is switched off. A The core 2 is therefore not heated during normal operation of the summation current transformer. The use of the summation current transformer according to the invention means that, on the one hand, one has a mechanically very strong, practically directly wound core and, moreover, the temperature response can be compensated for by the ohmic resistance of the winding of the summation current transformer core.

Claims (4)

  1. Differential-current transformer (1) with a wound, self-contained core (2) made from high-permeability soft magnetic material for monitoring the differential current flowing in conductors (5, 6) passing through the core (2), the winding of the core (2) being connected to a protective switch (7) via an amplifier (10), characterised in that:
    - the core (2) is made solid, that is without intermediate insulating layers or air gaps, which divide up the cross section of the core,
    - the material of the core (2) consists of a metallic alloy with at least 40 percent nickel content, which has a positive temperature coefficient of electrical resistance,
    - the wall thickness in comparison to the average geometrical diameter of the core (2) is chosen such that it is not less than 0.01 times and not greater than 0.5 times the average geometrical diameter.
  2. Differential-current transformer according to Claim 1, characterised in that the core (2) is made up of several parts.
  3. Differential-current transformer according to Claim 1, characterised in that the core (2) is made in the form of a circle and is manufactured by cutting from a tube.
  4. Differential-current transformer according to Claim 1, characterised in that the core (2) is manufactured by extrusion.
EP95109486A 1994-07-06 1995-06-20 Differential transformer for electronic protection device Expired - Lifetime EP0691662B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4423622 1994-07-06
DE4423622A DE4423622A1 (en) 1994-07-06 1994-07-06 Total current transformer for electronic protective devices

Publications (2)

Publication Number Publication Date
EP0691662A1 EP0691662A1 (en) 1996-01-10
EP0691662B1 true EP0691662B1 (en) 2001-09-19

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US (1) US5576921A (en)
EP (1) EP0691662B1 (en)
DE (2) DE4423622A1 (en)
ES (1) ES2164123T3 (en)

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CN101847502B (en) * 2010-06-10 2012-07-25 中国西电电气股份有限公司 Preparation method of TPY-level current transformer with secondary current of being 5A
EP3026443B1 (en) 2014-11-27 2018-01-31 ABB Schweiz AG An electronic device for measuring a differential current in an electric line.

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DE4423622A1 (en) 1996-01-11
ES2164123T3 (en) 2002-02-16
DE59509601D1 (en) 2001-10-25
EP0691662A1 (en) 1996-01-10
US5576921A (en) 1996-11-19

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