EP0603857B1 - Ring core transformer with parasitic voltage shielding - Google Patents

Ring core transformer with parasitic voltage shielding Download PDF

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Publication number
EP0603857B1
EP0603857B1 EP93120690A EP93120690A EP0603857B1 EP 0603857 B1 EP0603857 B1 EP 0603857B1 EP 93120690 A EP93120690 A EP 93120690A EP 93120690 A EP93120690 A EP 93120690A EP 0603857 B1 EP0603857 B1 EP 0603857B1
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EP
European Patent Office
Prior art keywords
winding
magnetic core
current transformer
shielding
metallic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP93120690A
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German (de)
French (fr)
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EP0603857A1 (en
Inventor
Ingmar Dr. Grambow
Holger Dr.-Ing. Däumling
Hans Elsner
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Ritz Messwandler GmbH and Co KG
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Ritz Messwandler GmbH and Co KG
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Publication of EP0603857A1 publication Critical patent/EP0603857A1/en
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    • 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
    • H01F38/28—Current transformers
    • H01F38/30—Constructions
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
    • H01F27/36—Electric or magnetic shields or screens
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
    • H01F27/36—Electric or magnetic shields or screens
    • H01F27/363—Electric or magnetic shields or screens made of electrically conductive material
    • 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
    • H01F38/28—Current transformers
    • H01F38/30—Constructions
    • H01F2038/305—Constructions with toroidal magnetic core

Definitions

  • the invention relates to a toroidal current transformer for installation in a metal encapsulation which is at ground potential and surrounds a high-voltage conductor and has at least one toroid which has a winding with leads passing through the metal encapsulation and a metallic shield surrounding the winding and which has an insulating gap to avoid a short-circuit winding .
  • Such a toroidal current transformer is known from DE-A-34 14 366.
  • the metallic shield consists of an electrically conductive material with an insulating gap.
  • transient overvoltages can occur within a switchgear in which such a toroidal current transformer is installed, for example when actuating disconnectors, which lead to disturbances in the form of traveling waves within the metal encapsulation.
  • Such transient overvoltages can generate high interference voltages in a current transformer, which can lead to considerable interference in the connected measuring electronics during operation of the current transformer.
  • the invention is therefore based on the object of a current transformer of the type mentioned train that the interference potential is further reduced by transient overvoltages.
  • the metallic shield is low-resistance and low-inductance and is formed as a conductive layer consisting of film or fabric, which is shaped as a winding of a meandering tape with changing winding direction, preferably after almost every complete turn.
  • the shielding and its low impedance and low inductance effectively prevent the formation of transient overvoltages, which are induced in the supply lines as a result of electrical converter waves. This also means that there are no overvoltages at the measuring connections, which can damage the connected instruments.
  • the protective circuits of the measuring instruments otherwise provided can advantageously be omitted.
  • Such a shielding film which can be formed either by a metallized plastic film or a metal film, for example, provides an ideal seal and metallic encapsulation of the windings against disturbing electromagnetic influences.
  • the foil must have an insulated gap in order to avoid a short circuit turn around the toroid in which high currents would flow.
  • the film can have a gap at which the winding of the current transformer is exposed.
  • the film may have an insulating layer above its electrically conductive layer.
  • a particularly good protection against overvoltages results from the fact that the layer of metallic shielding is designed as a meandering band winding with a changing winding direction. This results in a low inductance.
  • the supply lines have a metallic shielding cover, the first end of which is arranged directly on the metallic shielding and connected to it in a conductive manner, and that the metallic shielding cover is connected to the earth potential at its second end in the region of a measuring connection.
  • the first end of the metallic shielding sheath it is necessary for the first end of the metallic shielding sheath to be arranged directly on the shielding and to be conductively connected to it. In the area of the exit of the leads from the winding, there is no section in which electrical disturbances penetrate the leads. It is also important that the metallic shield cover is connected to the earth potential at its second end in the area of a measuring connection, so that a defined reference potential is available at this second end.
  • the metallic shield has an interference voltage potential with respect to the metal encapsulation due to the influence of the electrical interference. It is important that the differential voltage to be measured between the leads and the metallic shield is as great as the voltage between the leads and the metal encapsulation in the area of the measuring connection.
  • the electrical interference potentials on the metallic shield and the metallic shield cover equalized by currents flowing along the metallic shield and the metallic shield cover to the measuring connection and from there via the mass back to the metal enclosure of the switchgear. Such compensating currents have no influence on the voltages to be measured.
  • the invention can be advantageously designed in such a way that the supply lines have a shielding jacket which at least partially surrounds the metallic shielding cover, which is conductively connected to a grounded shielding electrode surrounding the current transformer and is likewise connected to the ground potential in the area of the measuring connection.
  • This additional shielding jacket is insulated from the shielding cover and has the effect that electrical disturbances only lead to interference potentials on the shielding cover and not to interference potentials on the metallic shielding cover, so that the equalizing currents flow through the shielding cover to compensate for the interference potential and not through the metallic shielding cover.
  • the film is designed as a tape winding with a winding layer on the toroidal core that is insulated from one another.
  • a metallized tape can be used as the film, which is provided on one side with an adhesive layer and on the other side with an insulating layer. The winding must not be closed to avoid a short circuit current around the toroid.
  • Such a tape winding can be easily applied in terms of production technology.
  • Interference voltages are also further reduced in that the metallic shield is applied in a partially overlapping manner and consists of a band whose surface conducts.
  • the measure that a semiconducting sheath is additionally provided also has a positive effect on the suppression of interference voltages.
  • the semiconducting layer can be provided both below and above the metallic shield.
  • windings are in contact with the flat semiconducting sheath in a conductive, preferably flat, manner.
  • a further reduction in the interference voltages is achieved if a shield made of metal tape which is insulated on all sides is additionally provided, at least in the area of the supply line.
  • a cylindrical toroidal current transformer 2 is arranged within a tubular part of a metal encapsulation 1. For the sake of clarity, only one toroidal core 3 is shown in FIG. 1.
  • the ring cores surround a conductor 4 carrying high voltage and are shielded from the electric field by a shield electrode 5, 28.
  • the shield electrode 5 has a gap 6, through which the shield electrode 5 with the metal encapsulation 1 is prevented from forming a short-circuit turn around the ring core 3, in which a ring current would be induced through the current flowing through the high-voltage conductor 4. However, electrical interferences still enter the area of the ring cores 3 through the gap 6.
  • Each toroidal core is surrounded by a secondary winding 7 symbolically represented in the figure, in which an electrical signal dependent on the current in the high-voltage conductor 4 is generated by induction. the electrical signal is fed through the leads 8, 9 to a measuring connection 10.
  • the ring cores are each surrounded by a shield 11 in the form of a shielding film, which is interrupted by a schematically illustrated gap 12 in order to avoid a short-circuit winding.
  • the feed lines 8, 9 have a metallic shield sleeve 13, which directly at its first end 14 is conductively connected to the film 11. At its second end 15, the shield cover 13 is grounded in the area of the measuring connection 10. It is taken into account that the connection of the shielding sleeve 13 or the shielding sleeve 16 to the earth potential of the measuring connection 10 is designed such that the leads 8, 9 are also shielded as well as possible in this area and that the earth connection of the shielding sleeve 13 or the shielding sleeve 16 is as short as possible.
  • a shielding jacket 16 surrounding the shielding sleeve 13 is provided, which surrounds the feed lines 8, 9 and the shielding sleeve 13 and is grounded in the area of the measuring connection 10. As a result, no compensating currents are induced in the shield cover 11. This results in a further reduction in the interference voltage potential.
  • the shield 11 is shown as a meandering winding from tape 17 over the lower left sector. This becomes visible when the outer tape insulation 25 and the covering protective winding 24 (FIG. 4) are removed in the sector mentioned.
  • the winding is clearer in Figure 3, which shows a view according to arrow III in the area of the feed line.
  • the shield 11 consists of a metallic tape 17, for example a metallic fabric tape, the surface of which is elastically conductive.
  • the winding is meandering.
  • band 17 is first laid with a certain pitch around the ring core with winding and protective fuse, which is of a customary construction, until it reaches a split band 18. It is passed under the insulating split tape and then on edge 19 of the split tape 18 deflected in the opposite direction and again guided around the ring core until it reaches the slit band 18 again. The next partial turn then follows in the opposite direction as described above.
  • the individual turns 20, 21 thus each have an opposite winding direction and do not touch at the deflection points. In this way, short-circuit turns are avoided.
  • the end of the tape is conductively connected to the shield sleeve 13 of the leads.
  • the shield cover 13 ideally consists of the individual shield covers 22, 23, which surround each supply line separately.
  • a further lowering of the interference voltage potential results if, at least in the area of the feed lines 8, 9, the shield 11 is additionally provided with a protective winding 24, which is made, for example, from mutually insulated winding layers of a metallized strip.
  • This tape can, for example, be provided on one side with an adhesive layer and on the other side with an insulating layer. The windings must not be closed to avoid a short-circuit current around the toroid.
  • an insulating layer can then be applied on the outside in a generally known manner.
  • this additional protective winding 24 is shown from a metal tape insulated at least on one side.
  • Each feed line 8, 9 initially has its own individual shield cover 22, 23, which in turn is surrounded by the shield cover 13.
  • the secondary winding of the toroidal core 3 is first provided with protective insulation (not shown), on which an additional semiconducting layer may also be applied.
  • This semiconducting layer then forms the base 27 (FIGS. 4 and 1) for the metallic shield 11, the individual turns of which are applied to the surface of the semiconducting layer and touch it in a conductive manner.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Regulation Of General Use Transformers (AREA)
  • Transformers For Measuring Instruments (AREA)
  • Coils Or Transformers For Communication (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

The invention relates to a toroidal-core (annular-core) current transformer for mounting in an earthed metal enclosure which surrounds a high-voltage conductor, having at least one toroidal core which has a winding using the feed wires passing through the metal enclosure and a metal shielding which surrounds the winding. In order to prevent interference voltages in the measurement signal, the metal shielding is designed with low resistance and low inductance. The metal shielding is formed by a conducting layer, in particular foil or fabric which has an insulating gap in order to prevent short-circuit winding. A shielding in the form of a strip winding changes the winding direction after each turn. <IMAGE>

Description

Die Erfindung bezieht sich auf einen Ringkernstromwandler zum Einbau in eine auf Erdpotential liegende, einen Hochspannungsleiter umgebende Metallkapselung mit wenigstens einem Ringkern, der eine Wicklung mit die Metallkapselung durchsetzenden Zuleitungen und eine die Wicklung umgebende metallische Abschirmung aufweist, die zur Vermeidung einer Kurzschlußwicklung einen isolierenden Spalt aufweist.The invention relates to a toroidal current transformer for installation in a metal encapsulation which is at ground potential and surrounds a high-voltage conductor and has at least one toroid which has a winding with leads passing through the metal encapsulation and a metallic shield surrounding the winding and which has an insulating gap to avoid a short-circuit winding .

Ein derartiger Ringkernstromwandler ist aus der DE-A-34 14 366 bekannt. Bei dem bekannten Stromwandler besteht die metallische Abschirmung aus elektrisch leitendem Material mit einem isolierenden Spalt.Such a toroidal current transformer is known from DE-A-34 14 366. In the known current transformer, the metallic shield consists of an electrically conductive material with an insulating gap.

Aufgrund der Induktivität der Abschirmung können innerhalb einer Schaltanlage, in die ein derartiger Ringkernstromwandler eingebaut ist, beispielsweise bei der Betätigung von Trennschaltern, transiente Überspannungen auftreten, die zu Störungen in Form von Wanderwellen innerhalb der Metallkapselung führen. In einem Stromwandler können durch solche transienten Überspannungen hohe Störspannungen erzeugt werden, die beim Betrieb des Stromwandlers zu erheblichen Störungen in der angeschlossenen Meßelektronik führen können.Due to the inductance of the shield, transient overvoltages can occur within a switchgear in which such a toroidal current transformer is installed, for example when actuating disconnectors, which lead to disturbances in the form of traveling waves within the metal encapsulation. Such transient overvoltages can generate high interference voltages in a current transformer, which can lead to considerable interference in the connected measuring electronics during operation of the current transformer.

Der Erfindung liegt daher die Aufgabe zugrunde, einen Stromwandler der eingangs genannten Art derart auszubilden, daß das Störpotential durch transiente Überspannungen weiter reduziert wird.The invention is therefore based on the object of a current transformer of the type mentioned train that the interference potential is further reduced by transient overvoltages.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß die metallische Abschirmung niederohmig und niederinduktiv und als leitende, aus Folie oder Gewebe bestehende Schicht ausgebildet ist, die als Wicklung eines meandrierend geführten Bandes geformt ist mit sich änderndem Wickelsinn, vorzugsweise nach annähernd jeder vollständigen Windung.This object is achieved in that the metallic shield is low-resistance and low-inductance and is formed as a conductive layer consisting of film or fabric, which is shaped as a winding of a meandering tape with changing winding direction, preferably after almost every complete turn.

Durch die Abschirmung und deren Niederohmigkeit und niedrige Induktivität wird die Entstehung von transienten Überspannungen, die infolge elektrischer Wandlerwellen in den Zuleitungen induziert werden, wirkungsvoll vermieden. Dadurch entstehen auch keine Überspannungen an den Meßanschlüssen, die zu Schäden an den angeschlossenen Instrumente führen können. Die sonst vorgesehenen Schutzbeschaltungen der Meßinstrumente können vorteilhaft entfallen. Durch eine solche Abschirmfolie, die beispielsweise entweder durch eine metallisierte Kunststoffolie oder durch eine Metallfolie gebildet sein kann, ist eine ideale Abdichtung und metallische Kapselung der Wicklungen gegen störende elektromagnetische Einflüsse gegeben.The shielding and its low impedance and low inductance effectively prevent the formation of transient overvoltages, which are induced in the supply lines as a result of electrical converter waves. This also means that there are no overvoltages at the measuring connections, which can damage the connected instruments. The protective circuits of the measuring instruments otherwise provided can advantageously be omitted. Such a shielding film, which can be formed either by a metallized plastic film or a metal film, for example, provides an ideal seal and metallic encapsulation of the windings against disturbing electromagnetic influences.

Die Folie muß einen isolierten Spalt aufweisen, um eine Kurzschlußwindung um den Ringkern zu vermeiden, in der hohe Ströme fließen würden. Zu diesem Zweck kann die Folie einen Spalt aufweisen, an dem die Wicklung des Stromwandlers freiliegt. Es ist aber auch denkbar, die Folie im Bereich des Spaltes unter Zwischenlage einer Isolierschicht überlappen zu lassen, um auf diese Weise den Spalt möglichst klein zu gestalten. Es kann beispielsweise die Folie oberhalb ihrer elektrisch leitenden Schicht eine Isolierschicht aufweisen.The foil must have an insulated gap in order to avoid a short circuit turn around the toroid in which high currents would flow. For this purpose, the film can have a gap at which the winding of the current transformer is exposed. However, it is also conceivable to have the film overlap in the area of the gap with the interposition of an insulating layer, in order in this way to make the gap as small as possible. For example, the film may have an insulating layer above its electrically conductive layer.

Ein besonders guter Schutz gegen Überspannungen ergibt sich aber aus dem Umstand, daß die Schicht der metallischen Abschirmung als meandrierende Bandwicklung mit sich änderndem Wickelsinn ausgebildet ist. Hierdurch wird eine niedrige Induktivität erreicht.A particularly good protection against overvoltages results from the fact that the layer of metallic shielding is designed as a meandering band winding with a changing winding direction. This results in a low inductance.

In einer Weiterbildung der Erfindung ist vorgesehen, daß die Zuleitungen eine metallische Schirmhülle aufweisen, deren erstes Ende direkt an der metallischen Abschirmung angeordnet und mit dieser leitend verbunden ist und daß die metallische Schirmhülle an ihrem zweiten Ende im Bereich eines Meßanschlusses mit dem Erdpotential verbunden ist. Zur Vermeidung von Überspannungen am Meßanschluß ist es notwendig, daß das erste Ende der metallischen Schirmhülle direkt an der Abschirmung angeordnet ist und mit dieser leitend verbunden ist. Im Bereich des Austritts der Zuleitungen aus der Wicklung ergibt sich dadurch kein Abschnitt, in dem elektrische Störungen die Zuleitungen durchsetzen. Dabei ist es weiterhin wichtig, daß die metallische Schirmhülle an ihrem zweiten Ende im Bereich eines Meßanschlusses mit dem Erdpotential verbunden ist, so daß an diesem zweiten Ende ein definiertes Referenzpotential zur Verfügung steht.In a further development of the invention it is provided that the supply lines have a metallic shielding cover, the first end of which is arranged directly on the metallic shielding and connected to it in a conductive manner, and that the metallic shielding cover is connected to the earth potential at its second end in the region of a measuring connection. To avoid overvoltages at the measuring connection, it is necessary for the first end of the metallic shielding sheath to be arranged directly on the shielding and to be conductively connected to it. In the area of the exit of the leads from the winding, there is no section in which electrical disturbances penetrate the leads. It is also important that the metallic shield cover is connected to the earth potential at its second end in the area of a measuring connection, so that a defined reference potential is available at this second end.

Hierfür ist es ohne Belang, ob die metallische Abschirmung durch den Einfluß der elektrischen Störungen ein Störspannungspotential gegenüber der Metallkapselung aufweist. Wichtig ist, daß die zwischen den Zuleitungen und der metallischen Abschirmung auftretende, zu messende Differenzspannung ebenso groß ist wie im Bereich des Meßanschlusses die Spannung zwischen den Zuleitungen und der Metallkapselung.For this it is irrelevant whether the metallic shield has an interference voltage potential with respect to the metal encapsulation due to the influence of the electrical interference. It is important that the differential voltage to be measured between the leads and the metallic shield is as great as the voltage between the leads and the metal encapsulation in the area of the measuring connection.

Die elektrischen Störpotentiale auf der metallischen Abschirmung und der metallischen Schirmhülle werden durch Ströme ausgeglichen, die entlang der metallischen Abschirmung und der metallischen Schirmhülle bis zum Meßanschluß und von dort über die Masse zurück zur Metallkapselung der Schaltanlage fließen. Auf die zu messenden Spannungen haben solche Ausgleichsströme keinen Einfluß.The electrical interference potentials on the metallic shield and the metallic shield cover equalized by currents flowing along the metallic shield and the metallic shield cover to the measuring connection and from there via the mass back to the metal enclosure of the switchgear. Such compensating currents have no influence on the voltages to be measured.

Die Erfindung kann dadurch vorteilhaft ausgestaltet werden, daß die Zuleitungen einen die metallische Schirmhülle wenigstens zum Teil umgebenden Schirmmantel aufweisen, der mit einer den Stromwandler umgebenden geerdeten Schirmelektrode leitend verbunden und im Bereich des Meßanschlusses ebenfalls mit dem Erdpotential verbunden ist.The invention can be advantageously designed in such a way that the supply lines have a shielding jacket which at least partially surrounds the metallic shielding cover, which is conductively connected to a grounded shielding electrode surrounding the current transformer and is likewise connected to the ground potential in the area of the measuring connection.

Dieser zusätzliche Schirmmantel ist gegenüber der Schirmhülle isoliert und bewirkt, daß elektrische Störungen lediglich zu Störpotentialen auf dem Schirmmantel und nicht zu Störpotentialen auf der metallischen Schirmhülle führen, so daß die Ausgleichsströme zum Ausgleich der Störpotentiale durch den Schirmmantel fließen und nicht durch die metallische Schirmhülle.This additional shielding jacket is insulated from the shielding cover and has the effect that electrical disturbances only lead to interference potentials on the shielding cover and not to interference potentials on the metallic shielding cover, so that the equalizing currents flow through the shielding cover to compensate for the interference potential and not through the metallic shielding cover.

Eine Weiterbildung der Erfindung sieht vor, daß die Folie als Bandwicklung mit gegeneinander isolierter Wicklungslage auf dem Ringkern ausgebildet ist. Es kann beispielsweise ein metallisiertes Band als Folie verwendet werden, das auf einer Seite mit einer klebenden Schicht und auf der anderen Seite mit einer isolierenden Schicht versehen ist. Die Wicklung darf nicht geschlossen werden, um einen Kurzschlußstrom um den Ringkern herum zu vermeiden. Eine solche Bandwicklung läßt sich fertigungstechnisch einfach aufbringen.A further development of the invention provides that the film is designed as a tape winding with a winding layer on the toroidal core that is insulated from one another. For example, a metallized tape can be used as the film, which is provided on one side with an adhesive layer and on the other side with an insulating layer. The winding must not be closed to avoid a short circuit current around the toroid. Such a tape winding can be easily applied in terms of production technology.

Störspannungen werden auch dadurch weiter verringert, daß die metallische Abschirmung teilweise überlappend gewickelt aufgebracht ist und aus einem Band besteht, dessen Oberfläche leitet.Interference voltages are also further reduced in that the metallic shield is applied in a partially overlapping manner and consists of a band whose surface conducts.

Die Maßnahme, daß zusätzlich eine halbleitende Hülle vorgesehen ist, wirkt sich ebenfalls positiv auf die Unterdrückung von Störspannungen aus. Die halbleitende Schicht kann sowohl unterhalb als auch oberhalb der metallischen Abschirmung vorgesehen werden.The measure that a semiconducting sheath is additionally provided also has a positive effect on the suppression of interference voltages. The semiconducting layer can be provided both below and above the metallic shield.

Dabei wirkt sich günstig aus, wenn die Windungen mit der flächigen halbleitenden Hülle leitend, vorzugsweise flächig, kontaktiert sind.It has a favorable effect if the windings are in contact with the flat semiconducting sheath in a conductive, preferably flat, manner.

Eine weitere Verringerung der Störspannungen erreicht man, wenn zusätzlich eine Abschirmung aus allseitig isoliertem Metallband, mindestens im Bereich der Zuleitung, vorgesehen ist.A further reduction in the interference voltages is achieved if a shield made of metal tape which is insulated on all sides is additionally provided, at least in the area of the supply line.

Die Erfindung wird in einer bevorzugten Ausführungsform unter Bezugnahme auf eine Zeichnung beschrieben, wobei weitere vorteilhafte Einzelheiten den Figuren der Zeichnung zu entnehmen sind. Funktionsmäßig gleiche Teile sind dabei mit denselben Bezugszeichen versehen.The invention is described in a preferred embodiment with reference to a drawing, with further advantageous details being shown in the figures of the drawing. Functionally identical parts are provided with the same reference numerals.

Die Zeichnungen zeigen im einzelnen:

Fig. 1
stellt schematisch einen Axialschnitt durch den erfindungsgemäßen Stromwandler dar,
Fig. 2
eine axiale Ansicht auf einen Ringkern mit teilweise freigelegter Abschirmung,
Fig. 3
ein Detail als Ansicht gemäß Pfeil III in Figur 2 in einem früheren Arbeitsschritt,
Fig. 4
stellt die Ansicht gemäß Figur 3 in einem späteren Arbeitsschritt dar und
Fig. 5
ein Detail der Zuleitung.
The drawings show in detail:
Fig. 1
schematically represents an axial section through the current transformer according to the invention,
Fig. 2
an axial view of a toroid with partially exposed shield,
Fig. 3
3 shows a detail as a view according to arrow III in FIG. 2 in an earlier work step,
Fig. 4
shows the view of Figure 3 in a later step and
Fig. 5
a detail of the supply line.

Innerhalb eines rohrförmigen Teils einer Metallkapselung 1 ist ein zylindrisch ausgebildeter Ringkernstromwandler 2 angeordnet. Der Übersichtlichkeit halber ist nur ein Ringkern 3 in Figur 1 dargestellt.A cylindrical toroidal current transformer 2 is arranged within a tubular part of a metal encapsulation 1. For the sake of clarity, only one toroidal core 3 is shown in FIG. 1.

Die Ringkerne umgeben einen Hochspannung führenden Leiter 4 und sind gegenüber dem elektrischen Feld durch eine Schirmelektrode 5, 28 abgeschirmt. Die Schirmelektrode 5 weist eine Spalt 6 auf, durch den verhindert wird, daß die Schirmelektrode 5 mit der Metallkapselung 1 eine Kurzschlußwindung um die Ringkern 3 herum bildet, in dem durch den Hochspannungsleiter 4 durchfließenden Strom ein Ringstrom induziert würde. Durch den Spalt 6 gelangen jedoch noch elektrische Störungen in den Bereich der Ringkerne 3.The ring cores surround a conductor 4 carrying high voltage and are shielded from the electric field by a shield electrode 5, 28. The shield electrode 5 has a gap 6, through which the shield electrode 5 with the metal encapsulation 1 is prevented from forming a short-circuit turn around the ring core 3, in which a ring current would be induced through the current flowing through the high-voltage conductor 4. However, electrical interferences still enter the area of the ring cores 3 through the gap 6.

Jeder Ringkern ist von einer in der Figur symbolisch dargestellten Sekundärwicklung 7 umgeben, in der ein von dem Strom im Hochspannungsleiter 4 abhängendes elektrisches Signal durch Induktion erzeugt wird. das elektrische Signal wird durch die Zuleitungen 8, 9 einem Meßanschluß 10 zugeführt.Each toroidal core is surrounded by a secondary winding 7 symbolically represented in the figure, in which an electrical signal dependent on the current in the high-voltage conductor 4 is generated by induction. the electrical signal is fed through the leads 8, 9 to a measuring connection 10.

Die Ringkerne sind von je einer Abschirmung 11 in Form einer Abschirmfolie umgeben, die durch einen schematisch dargestellten Spalt 12 unterbrochen ist, um eine Kurzschlußwicklung zu vermeiden.The ring cores are each surrounded by a shield 11 in the form of a shielding film, which is interrupted by a schematically illustrated gap 12 in order to avoid a short-circuit winding.

Die Zuleitungen 8, 9 weisen eine metallische Schirmhülle 13 auf, die an ihrem ersten Ende 14 direkt leitend mit der Folie 11 verbunden ist. An ihrem zweiten Ende 15 ist die Schirmhülle 13 im Bereich des Meßanschlusses 10 geerdet. Dabei ist berücksichtigt, daß die Verbindung der Schirmhülle 13 bzw. des Schirmmantels 16 mit dem Erdpotential des Meßanschlusses 10 so gestaltet ist, daß die Zuleitungen 8, 9 auch in diesem Bereich möglichst gut abgeschirmt sind und daß der Erdanschluß der Schirmhülle 13 bzw. des Schirmmantels 16 möglichst kurz gefaßt ist.The feed lines 8, 9 have a metallic shield sleeve 13, which directly at its first end 14 is conductively connected to the film 11. At its second end 15, the shield cover 13 is grounded in the area of the measuring connection 10. It is taken into account that the connection of the shielding sleeve 13 or the shielding sleeve 16 to the earth potential of the measuring connection 10 is designed such that the leads 8, 9 are also shielded as well as possible in this area and that the earth connection of the shielding sleeve 13 or the shielding sleeve 16 is as short as possible.

Es ist ein die Schirmhülle 13 umgebender Schirmmantel 16 vorgesehen, der die Zuleitungen 8, 9 und die Schirmhülle 13 umgibt und im Bereich des Meßanschlusses 10 geerdet ist. Hierdurch werden in der Schirmhülle 11 keine Ausgleichsströme induziert. Dies ergibt eine weitere Absenkung der Störspannungspotentiale.A shielding jacket 16 surrounding the shielding sleeve 13 is provided, which surrounds the feed lines 8, 9 and the shielding sleeve 13 and is grounded in the area of the measuring connection 10. As a result, no compensating currents are induced in the shield cover 11. This results in a further reduction in the interference voltage potential.

In Figur 2 ist über den linken unteren Sektor die Abschirmung 11 als meandrierende Wicklung aus Band 17 dargestellt. Diese wird sichtbar, wenn die äußere Bandisolierung 25 und die abdeckende Schutzwicklung 24 (Fig. 4) im genannten Sektor entfernt wird. Die Wicklung wird deutlicher in Figur 3, die eine Ansicht gemäß Pfeil III im Bereich der Zuleitung zeigt. Die Abschirmung 11 besteht aus einem metallischen Band 17, beispielsweise einem metallischen Gewebeband, dessen Oberfläche elastisch leitend ist.In Figure 2, the shield 11 is shown as a meandering winding from tape 17 over the lower left sector. This becomes visible when the outer tape insulation 25 and the covering protective winding 24 (FIG. 4) are removed in the sector mentioned. The winding is clearer in Figure 3, which shows a view according to arrow III in the area of the feed line. The shield 11 consists of a metallic tape 17, for example a metallic fabric tape, the surface of which is elastically conductive.

Die Wicklung ist meandrierend ausgeführt. Dazu wird Band 17 zunächst mit einer bestimmten Steigung um den üblich aufgebauten Ringkern mit Wicklung und Schutzsicherung gelegt, bis es ein Spaltband 18 erreicht. Es wird unter dem isolierenden Spaltband hindurchgeführt und dann an Kante 19 des Spaltbands 18 in entgegengesetzte Richtung umgelenkt und wieder um den Ringkern geführt, bis es erneut das Spaltband 18 erreicht. Anschließend folgt die nächste Teilwindung wie zuvor beschrieben in entgegengesetzter Richtung. Die einzelnen Windungen 20, 21 haben somit jeweils einen entgegengesetzten Wickelsinn und berühren sich an den Umlenkstellen nicht. Auf diese Weise werden Kurzschlußwindungen vermieden. Das Ende des Bandes wird mit der Schirmhülle 13 der Zuleitungen leitend verbunden. Dabei besteht die Schirmhülle 13 idealerweise aus den Einzelschirmhüllen 22, 23, die jede Zuleitung extra umgeben.The winding is meandering. For this purpose, band 17 is first laid with a certain pitch around the ring core with winding and protective fuse, which is of a customary construction, until it reaches a split band 18. It is passed under the insulating split tape and then on edge 19 of the split tape 18 deflected in the opposite direction and again guided around the ring core until it reaches the slit band 18 again. The next partial turn then follows in the opposite direction as described above. The individual turns 20, 21 thus each have an opposite winding direction and do not touch at the deflection points. In this way, short-circuit turns are avoided. The end of the tape is conductively connected to the shield sleeve 13 of the leads. The shield cover 13 ideally consists of the individual shield covers 22, 23, which surround each supply line separately.

Eine weitere Absenkung der Störspannungspotentiale ergibt sich, wenn mindestens im Bereich der Zuleitungen 8, 9 die Abschirmung 11 zusätzlich mit einer Schutzwicklung 24 versehen ist, die beispielsweise aus gegenseitig isolierten Wicklungslagen eines metallisierten Bandes gefertigt ist. Dieses Band kann beispielsweise auf einer Seite mit einer klebenden Schicht und auf der anderen Seite mit einer isolierenden Schicht versehen sein. Die Wicklungen dürfen nicht geschlossen werden, um einen Kurzschlußstrom um den Ringkern herum zu vermeiden.A further lowering of the interference voltage potential results if, at least in the area of the feed lines 8, 9, the shield 11 is additionally provided with a protective winding 24, which is made, for example, from mutually insulated winding layers of a metallized strip. This tape can, for example, be provided on one side with an adhesive layer and on the other side with an insulating layer. The windings must not be closed to avoid a short-circuit current around the toroid.

Abschließend kann dann außen eine Isolierschicht in allgemein bekannter Weise aufgebracht werden. In Figur 4 ist diese zusätzliche Schutzwicklung 24 aus einem mindestens einseitig isolierten metallischen Band dargestellt.Finally, an insulating layer can then be applied on the outside in a generally known manner. In Figure 4, this additional protective winding 24 is shown from a metal tape insulated at least on one side.

In Figur 5 ist in vergrößerter Darstellung das Ende der Zuleitungen gezeigt. Jede Zuleitung 8, 9 weist zunächst eine eigene Einzelschirmhülle 22, 23 auf, die ihrerseits wiederum von der Schirmhülle 13 umgeben sind.The end of the feed lines is shown in an enlarged representation in FIG. Each feed line 8, 9 initially has its own individual shield cover 22, 23, which in turn is surrounded by the shield cover 13.

In üblicher Weise wird die Sekundärwicklung des Ringkerns 3 zunächst mit einer nicht dargestellten Schutzisolierung versehen, auf der ggf. zusätzlich eine halbleitende weitere Schicht aufgebracht wird. Diese halbleitende Schicht bildet dann die Unterlage 27 (Fig. 4 und 1) für die metallische Abschirmung 11, deren einzelne Windungen flächig auf der halbleitenden Schicht aufgebracht sind und diese leitend berühren.In the usual way, the secondary winding of the toroidal core 3 is first provided with protective insulation (not shown), on which an additional semiconducting layer may also be applied. This semiconducting layer then forms the base 27 (FIGS. 4 and 1) for the metallic shield 11, the individual turns of which are applied to the surface of the semiconducting layer and touch it in a conductive manner.

BEZUGSZEICHENLISTEREFERENCE SIGN LIST

11
MetallkapelMetal chapel
22nd
RingkernstromwandlerToroidal current transformer
33rd
RingkernToroid
44th
Leiterladder
55
SchirmelektrodeShield electrode
66
Spaltgap
77
SekundärwicklungSecondary winding
88th
ZuleitungSupply
99
ZuleitungSupply
1010th
MeßanschlußMeasuring connection
1111
Abschirmungshielding
1212th
Spaltgap
1313
SchirmhülleUmbrella cover
1414
erstes Endefirst end
1515
zweites Endesecond end
1616
SchirmmantelUmbrella coat
1717th
Bandtape
1818th
SpaltbandSlit band
1919th
KanteEdge
2020th
WindungSwirl
2121
WindungSwirl
2222
EinzelschirmhülleSingle screen cover
2323
EinzelschirmhülleSingle screen cover
2424th
SchutzwicklungProtective winding
2525th
BandisolierungTape insulation
2727
Halbleitende UnterlageSemiconductive base
2828
SchirmelektrodeShield electrode

Claims (8)

  1. A magnetic core current transformer (2) for installation in a metal encapsulation lying at earth potential and surrounding a high voltage conductor with at least one magnetic core (3) which comprises a winding with leads interspersing the metal encapsulation, and a metallic shielding which surrounds the winding and comprises an insulating gap (6) for preventing a squirrel-cage winding, characterised in that the metallic shielding (11) is formed low ohmed and of low inductance by a conducting layer which consists of foil or tissue and which is formed as a winding of a meanderingly guided tape (17) with a changing direction of winding, preferably after approximately each complete winding (20, 21).
  2. A magnetic core current transformer (2) for installation in a metal encapsulation lying at earth potential and surrounding a high voltage conductor, with at least one magnetic core (3) which comprises a winding with the leads interspersing the metal encapsulation, and a metallic shielding which surrounds the winding and comprises an insulating gap (6) for preventing a cage winding, according to claim 1, characterised in that the leads (8, 9) comprise a metallic screen cover (13) of which the first end is arranged directly on the metallic shielding and is conductingly connected to this metallic shielding and that the metallic screen cover is connected to earth potential at its second end in the region of a measuring connection (10).
  3. A magnetic core current transformer according to at least one of the preceding claims, characterised in that the leads comprise a screen coating (16) which surrounds the metallic screen cover (13) at least in part and which is conductingly connected to an earthed screen electrode (28) surrounding the current transformer (2) and which is conductingly connected in the region of the measuring connection (10) likewise to the earth potential.
  4. A magnetic core current transformer according to claim 1, 2 or 3, characterised in that the foil is formed as as a tape winding (24) with mutually insulated winding layers on the magnetic core.
  5. A magnetic core current transformer according to claim 1, 2, 3 or 4, characterised in that the metallic shielding (11) is mounted in an overlappingly wound manner and consists of a tape (17) whose surface conducts.
  6. A magnetic core current transformer according to claim 1, 2, 3, 4, or 5, characterised in that additionally a semi-conducting cover (27) is provided.
  7. A magnetic core current transformer according to claim 1, 2, 3, 4, 5, or 6 characterised in that the windings (20, 21) are contacted conductingly, preferably flatly, with the flat semi-conducting cover (27).
  8. A magnetic core current transformer according to claim 1, 2, 3, 4, 5, 6, or 7, characterised in that there is provided at least in part, a shielding (24) of metal tape insulated on all sides, preferably in the region of the supply line.
EP93120690A 1992-12-24 1993-12-22 Ring core transformer with parasitic voltage shielding Expired - Lifetime EP0603857B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE9217807U DE9217807U1 (en) 1992-12-24 1992-12-24
DE9217807U 1992-12-24

Publications (2)

Publication Number Publication Date
EP0603857A1 EP0603857A1 (en) 1994-06-29
EP0603857B1 true EP0603857B1 (en) 1997-09-10

Family

ID=6887663

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93120690A Expired - Lifetime EP0603857B1 (en) 1992-12-24 1993-12-22 Ring core transformer with parasitic voltage shielding

Country Status (3)

Country Link
EP (1) EP0603857B1 (en)
AT (1) ATE158103T1 (en)
DE (2) DE9217807U1 (en)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4344183A1 (en) * 1993-12-23 1995-06-29 Ant Nachrichtentech High voltage transformer and use
EP0825447B1 (en) * 1996-08-23 2008-04-02 ABB Schweiz AG Measuring device for a metal-encapsulated gas-insulated high voltage installation
EP0825448A3 (en) * 1996-08-23 1999-12-29 Asea Brown Boveri AG Measuring device for a metal-encapsulated gas-insulated high voltage installation
DE102005007334B4 (en) * 2005-02-17 2007-02-08 Siemens Ag Summation current transformer for the universal current-sensitive detection of an electrical differential current
EP1693943A3 (en) * 2005-02-17 2015-10-28 Siemens Aktiengesellschaft Device for the AC/DC sensitive detection of differential currents
CN114050041A (en) * 2021-11-17 2022-02-15 许昌许继软件技术有限公司 High-voltage bushing integrated with low-power-consumption current transformer coil

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH660262A5 (en) * 1982-12-10 1987-03-31 Bbc Brown Boveri & Cie POWER CONVERTER.
CH662215A5 (en) * 1983-09-08 1987-09-15 Sprecher Energie Ag METAL-ENCLOSED, GAS-INSULATED SWITCHGEAR.
FR2564594B1 (en) * 1984-05-21 1986-09-12 Merlin Gerin CURRENT SENSOR WITH AMAGNETIC CORE
DE4106034A1 (en) * 1991-02-22 1992-08-27 Siemens Ag POWER CONVERTER

Also Published As

Publication number Publication date
ATE158103T1 (en) 1997-09-15
DE9217807U1 (en) 1993-04-08
DE59307337D1 (en) 1997-10-16
EP0603857A1 (en) 1994-06-29

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