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WO2003044545A1 - Method for the detection of an earth connection occurring in the vicinity of a neutral point in an electrical device, device for carrying out and application of said method - Google Patents

Method for the detection of an earth connection occurring in the vicinity of a neutral point in an electrical device, device for carrying out and application of said method Download PDF

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Publication number
WO2003044545A1
WO2003044545A1 PCT/CH2002/000611 CH0200611W WO03044545A1 WO 2003044545 A1 WO2003044545 A1 WO 2003044545A1 CH 0200611 W CH0200611 W CH 0200611W WO 03044545 A1 WO03044545 A1 WO 03044545A1
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WO
WIPO (PCT)
Prior art keywords
neutral point
windings
measured
phase currents
earth fault
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.)
Ceased
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PCT/CH2002/000611
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German (de)
French (fr)
Inventor
Göran LINDAHL
Erland Sörensen
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General Electric Switzerland GmbH
GE Vernova GmbH
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Alstom Technology AG
Alstom Schweiz AG
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Priority to AU2002336884A priority Critical patent/AU2002336884A1/en
Publication of WO2003044545A1 publication Critical patent/WO2003044545A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/34—Testing dynamo-electric machines
    • G01R31/346—Testing of armature or field windings
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/06—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric generators; for synchronous capacitors

Definitions

  • the present invention relates to the field of protection technology for electrical devices such as electrical machines or transformers. It relates to a method for detecting an earth fault occurring in the vicinity of a neutral point in a multiphase electrical device operated at a fundamental frequency. It also relates to an apparatus for carrying out the method and an application of the method. STATE OF THE ART
  • the earth fault protection of a generator based on an overvoltage or overcurrent determination results in simple and reliable protection.
  • earth faults that occur in the windings near the neutral point of the generator are not detected.
  • It has therefore already been proposed (Charles S. Mozina, Upgrading Hydroelectric Generator Protection Using Digital Technology, Waterpower '97, Atlanta GA, August 5-8 (1997)) to achieve a 100% earth fault protection by using a conventional surge protection circuit (for 95% of the stator winding) combined with an undervoltage protection circuit tuned to the third harmonic of the generator fundamental frequency (for the remaining 5% of the winding close to the neutral point).
  • the object is achieved by the entirety of the features of claims 1 and 7.
  • the essence of the invention is to measure higher harmonics of the phase currents flowing between the windings and the neutral point according to direction and size, and to infer the occurrence of an earth fault from the measured direction and size of the phase currents.
  • the measured phase currents can be compared with one another in pairs, in particular the measured phase currents are added in pairs and the presence of an earth fault is derived from the change in the sums formed.
  • a preferred embodiment of the device according to the invention is characterized in that second current transformers are arranged within the windings, that the outputs of the second current transformers are likewise connected to the evaluation unit, and that the evaluation unit is a differential current protection circuit.
  • the method according to the invention is used to protect an electrical device or machine from earth faults.
  • Figure 1 shows a schematic representation of a first embodiment of a device according to the invention for earth fault detection by directionally sensitive comparison of different phase currents.
  • Fig. 2 shows a schematic representation of a second embodiment of a device according to the invention for earth fault detection by differential current measurement within the phases.
  • a possible earth fault is detected by a directionally sensitive current measurement of higher harmonics of those currents which are caused by corresponding higher harmonic voltages (for example the third harmonic E 3 ) induced in the windings.
  • FIG. 1 shows a schematic illustration of a first exemplary embodiment of a device according to the invention for detecting earth faults in the windings 11, 12 and 13 of an electrical machine 10.
  • the windings 11, 12, 13 made with high-voltage cables are directly connected to a network (not shown) on one side via network connections 14, 15 and 16.
  • the windings 11, 12 and 13 are connected to a neutral point 22, which can be connected to earth via switches S1, .., S3 either directly, via a resistor 24 or via a filter 25.
  • the windings 11, 12 and 13 have earth capacitances 17 distributed with respect to earth, which are indicated in FIG. 1.
  • a current transformer 19, 20, 21 is arranged in each of the phases R, S and T, the output of which is connected to an evaluation unit 23.
  • the current transformers 19, 20, 21 then measure the third harmonic I 03R , I O3S , l 03 ⁇ of the phase currents .
  • other harmonics can also be used.
  • the capacitive harmonic currents I 03 R and I 03S of the phases not affected circulate in a closed loop, which is formed by the reactance Zx between the neutral point 22 and the location of the earth fault 18 and the reactance of the earth fault itself becomes. Because of the above-mentioned closed loop, the size and direction of the third harmonic phase current I 03 ⁇ in the phase affected by the earth fault (winding 13) differ from the corresponding values in the phases not affected.
  • the neutral point 22 of a rotating machine is either open or grounded via a high impedance, so that an earth fault current to be expected will be small in the fundamental frequency if the earth fault is close to the neutral point. If the three phase currents I03R, IO 3 S, I O3 T measured with the current transformers are added together in pairs in the evaluation unit, it immediately results that one of the sums (I 03 R + lo3s) increases, while the other two sums (I03R + Remove I0 3T and I03R + lo3 ⁇ ). From this it is possible to conclusively conclude the winding in which the earth fault occurs.
  • FIG. 2 shows a schematic representation of a second exemplary embodiment of a device according to the invention for current direction sensitive earth fault detection in the windings 11, 12 and 13 of an electrical machine 10.
  • differential protection is used which is based on current measurements with a first set of current transformers 19,... 21, which is arranged between the windings 11, 12, 13 and the neutral point 22, and a second set of current transformers 26,. ., 28, which are arranged within the windings 11, 12, 13, is based.
  • the capacitive harmonic currents measured in the two current transformer sets 19, .., 21 and 26, .., 28 are fed to a differential current protection circuit 29. If there is no earth fault, the currents measured in both sets are the same. If there is an earth fault, there is a non-zero difference that can be evaluated to protect the machine 10.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Protection Of Generators And Motors (AREA)

Abstract

The invention relates to a method for the detection of an earth connection (18) occurring in the vicinity of a neutral point (22) in a multi-phase electrical device, operated at a base frequency, in particular an electrical motor (10) or a transformer, comprising a number of windings (11, 12, 13) for the individual phases, each connected at one end thereof to the neutral point (22) and at the other end thereof directly to the mains supply by means of a mains connection (14, 15, 16). A simple and reliable detection is achieved, whereby a higher harmonic of the phase current (I03R, I03S, I03T), flowing between the windings (11, 12, 13) and the neutral point (22), is measured for size and direction and the occurrence of an earth contact (18) is established from the measured size and direction of the phase currents (I03R, I03S, I03T).

Description

BESCHREIBUNG DESCRIPTION

VERFAHREN ZUM DETEKTIEREN EINES IN EINER ELEKTRISCHEN EINRICHTUNG IN DER NÄHE EINES NEUTRALEN PUNKTES AUFTRETENDEN ERDSCHLUSSES SOWIE VORRICHTUNG ZUR DURCHFÜHRUNG UND ANWENDUNG DES VERFAHRENSMETHOD FOR DETECTING AN EARTH FAILING APPLICABLE IN AN ELECTRICAL DEVICE NEAR A NEUTRAL POINT, AND DEVICE FOR IMPLEMENTING AND USING THE METHOD

TECHNISCHES GEBIETTECHNICAL AREA

Die vorliegende Erfindung bezieht sich auf das Gebiet der Schutztechnik von elektrischen Einrichtungen wie elektrischen Maschinen oder Transformatoren. Sie betrifft ein Verfahren zum Detektieren eines in der Nähe eines neutralen Punktes auftretenden Erdschlusses in einer mehrphasigen, mit einer Grundfrequenz betriebenen, elektrischen Einrichtung gemäss dem Oberbegriff des Anspruchs 1. Sie betrifft weiterhin eine Vorrichtung zur Durchführung des Verfahrens sowie eine Anwendung des Verfahrens. STAND DER TECHNIKThe present invention relates to the field of protection technology for electrical devices such as electrical machines or transformers. It relates to a method for detecting an earth fault occurring in the vicinity of a neutral point in a multiphase electrical device operated at a fundamental frequency. It also relates to an apparatus for carrying out the method and an application of the method. STATE OF THE ART

Aus dem Stand der Technik ist eine Vielzahl von Verfahren bekannt, mit denen Erdschlüsse oder Erdfehler in den Wicklungen von rotierenden Maschinen wie Synchrongeneratoren detektiert und damit die Maschine vor den negativen Auswirkungen von Erdschlüssen geschützt werden kann. Dazu gehört die Verwendung eines Ueberspannungs- oder Ueberstromrelais am neutralen Punkt, eines Nullspannungs (zero sequence)-Ueberspannungsrelais oder einer Reststromdiffe- rentialschutzschaltung.A large number of methods are known from the prior art with which earth faults or earth faults in the windings of rotating machines such as synchronous generators are detected and the machine can thus be protected against the negative effects of earth faults. This includes the use of an overvoltage or overcurrent relay at the neutral point, a zero voltage (zero sequence) overvoltage relay or a residual current differential protection circuit.

Der Erdfehlerschutz eines Generators auf der Basis einer Ueberspannungs- oder Ueberstrombestimmung ergibt einen einfachen und zuverlässigen Schutz. Er hat jedoch einen wesentlichen Nachteil: Erdschlüsse, die in den Wicklungen nahe dem neutralen Punkt des Generators auftreten, werden nicht erfasst. Es ist des- halb bereits vorgeschlagen worden (Charles S. Mozina, Upgrading Hydroelectric Generator Protection Using Digital Technology, Waterpower '97, Atlanta GA, August 5-8 (1997)), einen hundertprozentigen Erdfehlerschutz dadurch zu erreichen, dass man eine herkömmliche Ueberspannungsschutzschaltung (für 95% der Statorwicklung) mit einer auf die dritte Harmonische der Generatorgrundfrequenz ab- gestimmte Unterspannungsschutzschaltung (für die restlichen 5% der Wicklung nahe dem neutralen Punkt) kombiniert. Dieser Vorschlag basiert auf dem Umstand, dass in vielen Synchrongeneratoren die induzierte elektromotorische Spannung am neutralen Punkt höhere Harmonische enthält, die in der Verbindung des neutralen Punktes zur Erde, in der Regel einem Widerstand, einen entsprechen- den höher harmonischen Strom erzeugen. Tritt in der Nähe zum neutralen Punkt ein Erdschluss auf, wirkt er als Bypass zu diesem Widerstand. Die durch den By- pass hervorgerufene Reduktion des Spannungsabfalls kann dann als Unterspannung detektiert werden. Diese bekannten Erdfehlerschutzverfahren werden unterstützt durch den Einsatz von Aufwärtstransformatoren zwischen Generator und Netz, die im Hinblick auf die Erdung eine Trennung des Generators vom Netz ermöglichen. In jüngster Zeit werden jedoch zunehmend Kraftwerkskonfigurationen eingesetzt, bei denen auf die üblichen Aufwärtstransformatoren verzichtet werden kann, weil die Generatoren die Netzspannung direkt erzeugen. Erreicht wird dies durch eine spezielle Wicklungstechnik, bei der die Wicklungen des Generators mit Hoch- spannungskabeln ausgeführt werden. Derartige Generatoren sind unter der Bezeichnung "Powerformer" bekannt geworden (siehe z.B. M. Leijon, "Powerformer - a radically new rotating machine", ABB review 2/98, pp. 21-26 (1998)).The earth fault protection of a generator based on an overvoltage or overcurrent determination results in simple and reliable protection. However, it has one major disadvantage: earth faults that occur in the windings near the neutral point of the generator are not detected. It has therefore already been proposed (Charles S. Mozina, Upgrading Hydroelectric Generator Protection Using Digital Technology, Waterpower '97, Atlanta GA, August 5-8 (1997)) to achieve a 100% earth fault protection by using a conventional surge protection circuit (for 95% of the stator winding) combined with an undervoltage protection circuit tuned to the third harmonic of the generator fundamental frequency (for the remaining 5% of the winding close to the neutral point). This proposal is based on the fact that in many synchronous generators the induced electromotive voltage at the neutral point contains higher harmonics which, when the neutral point is connected to earth, usually a resistor, generate a corresponding higher harmonic current. If an earth fault occurs in the vicinity of the neutral point, it acts as a bypass to this resistance. The reduction in voltage drop caused by the bypass can then be detected as undervoltage. These known earth fault protection methods are supported by the use of step-up transformers between the generator and the grid, which enable the generator to be disconnected from the grid with regard to grounding. In recent times, however, power plant configurations have increasingly been used in which the usual step-up transformers can be dispensed with because the generators generate the mains voltage directly. This is achieved using a special winding technology in which the generator windings are carried out with high-voltage cables. Such generators are known under the name "Powerformer" (see, for example, M. Leijon, "Powerformer - a radically new rotating machine", ABB review 2/98, pp. 21-26 (1998)).

Es hat sich nun herausgestellt, dass die bekannten Methoden zur Detektion von Erdfehlern bei diesen in der neuen Wicklungstechnik ausgeführten rotierenden Maschinen und Transformatoren nicht hundertprozentig zuverlässig arbeiten.It has now been found that the known methods for the detection of earth faults do not work 100 percent reliably with these rotating machines and transformers implemented in the new winding technology.

DARSTELLUNG DER ERFINDUNGPRESENTATION OF THE INVENTION

Es ist Aufgabe der Erfindung, ein Verfahren und eine Vorrichtung anzugeben, welche die Nachteile bisher bekannter Lösungen vermeiden und insbesondere eine einfache und sichere Detektion von Erdfehlern bzw. Erdschlüssen nahe am neutralen Punkt von mit Kabeln bewickelten bzw. direkt ans Netz angeschlossenen elektrischen Maschinen und Transformatoren ermöglichen.It is an object of the invention to provide a method and a device which avoid the disadvantages of previously known solutions and in particular a simple and reliable detection of earth faults or earth faults close to the neutral point of electrical machines and transformers wound with cables or directly connected to the network enable.

Die Aufgabe wird durch die Gesamtheit der Merkmale der Ansprüche 1 und 7 gelöst. Der Kern der Erfindung besteht darin, höhere Harmonische der zwischen den Wicklungen und dem neutralen Punkt fliessenden Phasenströme nach Richtung und Grosse zu messen, und aus der gemessenen Richtung und Grosse der Phasenströme auf das Auftreten eines Erdschlusses zu schliessen.The object is achieved by the entirety of the features of claims 1 and 7. The essence of the invention is to measure higher harmonics of the phase currents flowing between the windings and the neutral point according to direction and size, and to infer the occurrence of an earth fault from the measured direction and size of the phase currents.

Bevorzugt wird dabei die n-te Harmonische (n=3k+3, k=0,1 ,2,3 ), insbesondere die dritte Harmonische, der Phasenströme zur Messung herangezogen.Preferably, the nth harmonic (n = 3k + 3, k = 0.1, 2.3), in particular the third harmonic, of the phase currents is used for the measurement.

Zur Auswertung können dabei die gemessenen Phasenströme paarweise untereinander verglichen werden, wobei insbesondere die gemessenen Phasenströme paarweise addiert werden und das Vorliegen eines Erdschlusses aus der Veränderung der gebildeten Summen abgeleitet wird.For the evaluation, the measured phase currents can be compared with one another in pairs, in particular the measured phase currents are added in pairs and the presence of an earth fault is derived from the change in the sums formed.

Es ist aber auch möglich, die höhere Harmonische der Phasenströme jeweils zwi- sehen der Wicklung und dem neutralen Punkt sowie an einem Punkt innerhalb der Wicklung zu messen, und zur Feststellung eines Erdschlusses Differenzen aus den innerhalb der Wicklungen und ausserhalb der Wicklungen gemessenen Pha- senstromwerten zu bilden.However, it is also possible to measure the higher harmonics of the phase currents between the winding and the neutral point and at a point inside the winding, and to determine a ground fault, differences from the phase current values measured inside the windings and outside the windings to build.

Eine bevorzugte Ausführungsform der erfindungsgemässen Vorrichtung zeichnet sich dadurch aus, dass innerhalb der Wicklungen zweite Stromwandler angeordnet sind, dass die Ausgänge der zweiten Stromwandler ebenfalls mit der Auswerteeinheit in Verbindung stehen, und dass die Auswerteeinheit eine Differentialstromschutzschaltung ist.A preferred embodiment of the device according to the invention is characterized in that second current transformers are arranged within the windings, that the outputs of the second current transformers are likewise connected to the evaluation unit, and that the evaluation unit is a differential current protection circuit.

Das erfindungsgemässe Verfahren wird zum Schutz einer elektrischen Einrichtung bzw. Maschine vor Erdschlüssen eingesetzt.The method according to the invention is used to protect an electrical device or machine from earth faults.

KURZE ERLÄUTERUNG DER FIGURENBRIEF EXPLANATION OF THE FIGURES

Die Erfindung soll nachfolgend anhand von Ausführungsbeispielen im Zusammenhang mit der Zeichnung näher erläutert werden. Es zeigenThe invention will be explained in more detail below on the basis of exemplary embodiments in connection with the drawing. Show it

Fig. 1 in einer schematisierten Darstellung ein erstes Ausführungsbeispiel einer Vorrichtung nach der Erfindung zur Erdfehlerdetektion durch richtungssensitiven Vergleich unterschiedlicher Phasenströme; undFigure 1 shows a schematic representation of a first embodiment of a device according to the invention for earth fault detection by directionally sensitive comparison of different phase currents. and

Fig. 2 in einer schematisierten Darstellung ein zweites Ausführungsbeispiel einer Vorrichtung nach der Erfindung zur Erdfehlerdetektion durch Differenzstrommessung innerhalb der Phasen. WEGE ZUR AUSFÜHRUNG DER ERFINDUNGFig. 2 shows a schematic representation of a second embodiment of a device according to the invention for earth fault detection by differential current measurement within the phases. WAYS OF CARRYING OUT THE INVENTION

Gemäss der Erfindung wird ein möglicher Erdschluss durch eine richtungssensitive Strommessung höherer Harmonischer derjenigen Ströme detektiert, die durch entsprechende, in den Wicklungen induzierte höherharmonische Spannungen (z.B. die dritte Harmonische E3) verursacht werden. In Fig. 1 ist in einer schematisierten Darstellung ein erstes Ausführungsbeispiel einer Vorrichtung nach der Er- findung zur Erdfehlerdetektion in den Wicklungen 11 , 12 und 13 einer elektrischen Maschine 10 wiedergegeben. Die mit Hochspannungskabeln ausgeführten Wicklungen 11 , 12, 13 sind auf der einen Seite über Netzanschlüsse 14, 15 und 16 direkt an ein (nicht dargestelltes) Netz angeschlossen. Auf der anderen Seite sind die Wicklungen 11 , 12 und 13 mit einem neutralen Punkt 22 verbunden, der über Schalter S1 ,..,S3 entweder direkt, über einen Widerstand 24 oder über ein Filter 25 auf Erde geführt sein kann. Die Wicklungen 11 , 12 und 13 weisen gegenüber Erde verteilte Erdkapazitäten 17 auf, die in Fig. 1 angedeutet sind. Zwischen den Wicklungen 11 , 12, 13 und dem neutralen Punkt 22 ist in jeder der Phasen R, S und T ein Stromwandler 19, 20, 21 angeordnet, dessen Ausgang mit einer Aus- werteeinheit 23 in Verbindung steht. Die aus den Stromwandlern 19, 20,21 und der Auswerteeinheit bestehende Messanordnung ist auf eine höhere Harmonische der Maschinen-Grundfrequenz, insbesondere die n-te Harmonische (n=3k+3 mit k=0, 1 ,2,3...) abgestimmt. Bevorzugt wird eine Abstimmung auf die dritte Harmonische. Die Stromwandler 19, 20, 21 messen dann die dritte Harmonische I03R, IO3S, l03τ der Phasenströme. Es können jedoch auch andere Harmonische verwendet werden.According to the invention, a possible earth fault is detected by a directionally sensitive current measurement of higher harmonics of those currents which are caused by corresponding higher harmonic voltages (for example the third harmonic E 3 ) induced in the windings. 1 shows a schematic illustration of a first exemplary embodiment of a device according to the invention for detecting earth faults in the windings 11, 12 and 13 of an electrical machine 10. The windings 11, 12, 13 made with high-voltage cables are directly connected to a network (not shown) on one side via network connections 14, 15 and 16. On the other hand, the windings 11, 12 and 13 are connected to a neutral point 22, which can be connected to earth via switches S1, .., S3 either directly, via a resistor 24 or via a filter 25. The windings 11, 12 and 13 have earth capacitances 17 distributed with respect to earth, which are indicated in FIG. 1. Between the windings 11, 12, 13 and the neutral point 22, a current transformer 19, 20, 21 is arranged in each of the phases R, S and T, the output of which is connected to an evaluation unit 23. The measuring arrangement consisting of the current transformers 19, 20, 21 and the evaluation unit is based on a higher harmonic of the basic machine frequency, in particular the nth harmonic (n = 3k + 3 with k = 0, 1, 2.3 ...) Voted. Tuning to the third harmonic is preferred. The current transformers 19, 20, 21 then measure the third harmonic I 03R , I O3S , l 03 τ of the phase currents . However, other harmonics can also be used.

Wenn nun ein Erdschluss 18 in der Nähe des neutralen Punktes 22 auftritt (in Fig. 1 in der Wicklung 13), zirkulieren die kapazitiven harmonischen Ströme I03R und l03S der nicht betroffenen Phasen (Wicklungen 11 und 12) in einer geschlossenen Schleife, welche durch die Reaktanz Zx zwischen dem neutralen Punkt 22 und dem Ort des Erdschlusses 18 und der Reaktanz des Erdschlusses selbst gebildet wird. Wegen der o.g. geschlossenen Schleife unterscheiden sich Grosse und Richtung des dritten harmonischen Phasenstromes l03τ in der vom Erdschluss betroffenen Phase (Wicklung 13) von den entsprechenden Werten in den nicht betroffenen Phasen. In den meisten Fällen ist der neutrale Punkt 22 einer rotieren- den Maschine entweder offen oder über eine hohe Impedanz geerdet, so dass ein zu erwartender Erdfehlerstrom in der Grundfrequenz klein sein wird, sofern der Erdschluss nahe am neutralen Punkt liegt. Wenn nun die drei mit den Stromwandlern gemessenen Phasenströme I03R, IO3S, IO3T in der Auswerteeinheit paarweise addiert werden, ergibt sich unmittelbar, dass eine der Summen (I03R + lo3s) zunimmt, während die beiden anderen Summen (I03R + I03T und I03R + lo3τ) abnehmen. Hieraus kann eindeutig auf die Wicklung geschlossen werden, in welcher der Erdschluss auftritt.If an earth fault 18 now occurs in the vicinity of the neutral point 22 (in the winding 13 in FIG. 1), the capacitive harmonic currents I 03 R and I 03S of the phases not affected (windings 11 and 12) circulate in a closed loop, which is formed by the reactance Zx between the neutral point 22 and the location of the earth fault 18 and the reactance of the earth fault itself becomes. Because of the above-mentioned closed loop, the size and direction of the third harmonic phase current I 03 τ in the phase affected by the earth fault (winding 13) differ from the corresponding values in the phases not affected. In most cases, the neutral point 22 of a rotating machine is either open or grounded via a high impedance, so that an earth fault current to be expected will be small in the fundamental frequency if the earth fault is close to the neutral point. If the three phase currents I03R, IO 3 S, I O3 T measured with the current transformers are added together in pairs in the evaluation unit, it immediately results that one of the sums (I 03 R + lo3s) increases, while the other two sums (I03R + Remove I0 3T and I03R + lo3τ). From this it is possible to conclusively conclude the winding in which the earth fault occurs.

In Fig. 2 ist in einer schematisierten Darstellung ein zweites Ausführungsbeispiel einer Vorrichtung nach der Erfindung zur stromrichtungssensitiven Erdfehlerdetektion in den Wicklungen 11 , 12 und 13 einer elektrischen Maschine 10 wiedergegeben. In diesem Fall wird ein Differentialschutz verwendet, der auf Strommessungen mit einem ersten Satz von Stromwandlern 19,..,21 , welche zwischen den Wicklungen 11 , 12, 13 und dem neutralen Punkt 22 angeordnet ist, und einem zweiten Satz von Stromwandlern 26,..,28, welche innerhalb der Wicklungen 11 , 12, 13 angeordnet sind, beruht. Die in den beiden Stromwandlersets 19, ..,21 und 26, ..,28 gemessenen kapazitiven harmonischen Ströme werden einer Differentialstromschutzschaltung 29 zugeführt. Wenn, kein Erdschluss vorliegt, sind die in beiden Sets gemessenen Ströme gleich. Liegt ein Erdschluss vor, ergibt sich eine von Null verschiedene Differenz, die zum Schutz der Maschine 10 ausgewertet werden kann.2 shows a schematic representation of a second exemplary embodiment of a device according to the invention for current direction sensitive earth fault detection in the windings 11, 12 and 13 of an electrical machine 10. In this case, differential protection is used which is based on current measurements with a first set of current transformers 19,... 21, which is arranged between the windings 11, 12, 13 and the neutral point 22, and a second set of current transformers 26,. ., 28, which are arranged within the windings 11, 12, 13, is based. The capacitive harmonic currents measured in the two current transformer sets 19, .., 21 and 26, .., 28 are fed to a differential current protection circuit 29. If there is no earth fault, the currents measured in both sets are the same. If there is an earth fault, there is a non-zero difference that can be evaluated to protect the machine 10.

BEZUGSZEICHENLISTELIST OF REFERENCE NUMBERS

10 elektrische Maschine10 electric machine

11 ,12,13 Wicklung11, 12, 13 winding

14,15,16 Netzanschluss 17 Erdkapazität14,15,16 mains connection 17 Earth capacity

18 Erdschluss18 earth fault

19,20,21 Stromwandler19,20,21 current transformer

22 neutraler Punkt22 neutral point

23 Auswerteeinheit23 evaluation unit

24 Widerstand24 resistance

25 Filter25 filters

26,27,28 Stromwandler26,27,28 current transformer

29 Differentialstromschutzschaltung lθ3R,lθ3S,lθ3T Phasenstrom (höhere (3-te) Harmonische)29 differential current protection circuit lθ3R, lθ3S, lθ3T phase current (higher (3rd harmonic))

S1.S2.S3 Schalter S1.S2.S3 switch

Claims

PATENTANSPRÜCHE 1. Verfahren zum Detektieren eines in der Nähe eines neutralen Punktes (22) auftretenden Erdschlusses (18) in einer mehrphasigen, mit einer Grundfrequenz betriebenen, elektrischen Einrichtung, insbesondere einer elektrischen Maschine (10) oder eines Transformators, welche eine Mehrzahl von den einzelnen Phasen zugeordneten Wicklungen (11 , 12, 13) aufweist, die jeweils mit dem einen Ende an den neutralen Punkt (22) und mit dem anderen Ende über einen Netzan- schluss (14, 15, 16) direkt an ein Stromnetz angeschlossen sind, dadurch gekennzeichnet, dass eine höhere Harmonische der zwischen den Wicklungen (11 , 12, 13) und dem neutralen Punkt (22) fliessenden Phasenströme (I03R, I03S, IO3T) nach Richtung und Grosse gemessen wird, und dass aus der gemessenen Richtung und Grosse der Phasenströme (I03R, IO3S, IO3T) auf das Auftreten eines Erdschlus- ses (18) geschlossen wird.1. A method for detecting an earth fault (18) occurring in the vicinity of a neutral point (22) in a multiphase electrical device operated at a fundamental frequency, in particular an electrical machine (10) or a transformer, which has a plurality of the individual phases has associated windings (11, 12, 13), each of which is connected at one end to the neutral point (22) and at the other end via a mains connection (14, 15, 16) directly to a power supply, characterized that a higher harmonic of the phase currents (I 03 R, I 03S , I O3 T) flowing between the windings (11, 12, 13) and the neutral point (22) is measured according to direction and size, and that from the measured direction and magnitude of the phase currents (I03R, IO 3S , I O3 T) is inferred about the occurrence of an earth fault (18). 2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, dass die n-te Harmonische (n=3k+3, k=0,1 ,2,3 ) der Phasenströme (l03R, IO3S, IO3T) zur Messung herangezogen wird.2. The method according to claim 1, characterized in that the nth harmonic (n = 3k + 3, k = 0.1, 2.3) of the phase currents (I 03R , I O3S , IO 3 T) is used for the measurement , 3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, dass die dritte Harmonische der Phasenströme (I03R, IO3S> IO3T) zur Messung herangezogen wird.3. The method according to claim 2, characterized in that the third harmonic of the phase currents (I03R, IO 3 S > I O3 T) is used for the measurement. 4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass zur Auswertung die gemessenen Phasenströme (I03R, IO3S> IO3T) paarweise untereinander verglichen werden.4. The method according to any one of claims 1 to 3, characterized in that the measured phase currents (I 03 R, IO3S > IO3T) are compared in pairs with one another for evaluation. 5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, dass die gemessenen Phasenströme (I03R, IO3S, IO3T) paarweise addiert werden und das Vorliegen eines Erdschlusses aus der Veränderung der Summen abgeleitet wird. 5. The method according to claim 4, characterized in that the measured phase currents (I 03R , IO 3 S, I O 3T) are added in pairs and the presence of an earth fault is derived from the change in the sums. 6. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass die höhere Harmonische der Phasenströme (I03R, IO3S, IO3T) jeweils zwischen der Wicklung (11 , 12, 13) und dem neutralen Punkt sowie an einem Punkt innerhalb der Wicklung (11 , 12, 13) gemessen wird, und dass zur Feststellung eines Erdschlusses Differenzen aus den innerhalb der Wicklungen (11 , 12, 13) und aus- serhalb der Wicklungen (11 , 12, 13) gemessenen Phasenstromwerten gebildet werden.6. The method according to any one of claims 1 to 3, characterized in that the higher harmonic of the phase currents (I03R, IO3S, IO3T) in each case between the winding (11, 12, 13) and the neutral point and at a point within the winding ( 11, 12, 13) is measured, and that in order to determine an earth fault, differences are formed from the phase current values measured inside the windings (11, 12, 13) and outside the windings (11, 12, 13). 7. Vorrichtung zur Durchführung des Verfahrens nach Anspruch 1 , dadurch gekennzeichnet, dass in den einzelnen Phasen der elektrischen Einrichtung bzw. elektrischen Maschine 10 zwischen den Wicklungen (11 , 12, 13) und dem neutralen Punkt (22) jeweils erste Stromwandler (19, 20, 21) angeordnet sind, und dass die Ausgänge der ersten Stromwandler (19, 20, 21 ) mit einer Auswerteeinheit (23, 29) in Verbindung stehen, in welcher Grosse und Richtung der von den ersten Stromwandlern (19, 20, 21 ) gemessenen Ströme bestimmt und ausgewertet werden.7. The device for performing the method according to claim 1, characterized in that in the individual phases of the electrical device or electrical machine 10 between the windings (11, 12, 13) and the neutral point (22) each have first current transformers (19, 20, 21) are arranged, and that the outputs of the first current transformers (19, 20, 21) are connected to an evaluation unit (23, 29), in which size and direction that of the first current transformers (19, 20, 21) measured currents are determined and evaluated. 8. Vorrichtung nach Anspruch 7, dadurch gekennzeichnet, dass innerhalb der Wicklungen (11 , 12, 13) zweite Stromwandler (26, 27, 28) angeordnet sind, dass die Ausgänge der zweiten Stromwandler (26, 27, 28) ebenfalls mit der Auswerteeinheit (29) in Verbindung stehen, und dass die Auswerteeinheit eine Diffe- rentialstromschutzschaltung (29) ist.8. The device according to claim 7, characterized in that within the windings (11, 12, 13) second current transformers (26, 27, 28) are arranged, that the outputs of the second current transformers (26, 27, 28) also with the evaluation unit (29) are connected, and that the evaluation unit is a differential current protection circuit (29). 9. Anwendung des Verfahrens nach einem der Ansprüche 1 bis 6 zum Schutz der elektrischen Einrichtung bzw. Maschine (10) vor Erdschlüssen. 9. Application of the method according to one of claims 1 to 6 for protecting the electrical device or machine (10) from earth faults.
PCT/CH2002/000611 2001-11-19 2002-11-14 Method for the detection of an earth connection occurring in the vicinity of a neutral point in an electrical device, device for carrying out and application of said method Ceased WO2003044545A1 (en)

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CN100349347C (en) * 2005-03-18 2007-11-14 清华大学 Large-scale steamer generator neutral point lead-out mode and arrangement protecting method
CN102269787A (en) * 2011-05-16 2011-12-07 国网电力科学研究院 Detection method of harmonic characteristic of electronic voltage transformer and detection device thereof
EP2501009A1 (en) * 2011-03-10 2012-09-19 Hitachi, Ltd. Electric rotating machine
WO2013184332A1 (en) * 2012-06-04 2013-12-12 Eaton Corporation System and method for high resistance ground fault detection and protection in power distribution systems
CN103513150A (en) * 2013-09-17 2014-01-15 广东电网公司东莞供电局 Device and method for detecting multipoint earthing of voltage transformer for electric system

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CN100349347C (en) * 2005-03-18 2007-11-14 清华大学 Large-scale steamer generator neutral point lead-out mode and arrangement protecting method
EP2501009A1 (en) * 2011-03-10 2012-09-19 Hitachi, Ltd. Electric rotating machine
JP2012189403A (en) * 2011-03-10 2012-10-04 Hitachi Mitsubishi Hydro Corp Revolving electrical machine
CN102269787A (en) * 2011-05-16 2011-12-07 国网电力科学研究院 Detection method of harmonic characteristic of electronic voltage transformer and detection device thereof
WO2013184332A1 (en) * 2012-06-04 2013-12-12 Eaton Corporation System and method for high resistance ground fault detection and protection in power distribution systems
CN104364989A (en) * 2012-06-04 2015-02-18 伊顿公司 System and method for high resistance ground fault detection and protection in power distribution systems
US9046560B2 (en) 2012-06-04 2015-06-02 Eaton Corporation System and method for high resistance ground fault detection and protection in power distribution systems
CN104364989B (en) * 2012-06-04 2017-11-21 伊顿公司 System and method for high resistance grounding fault detect in a power distribution system and protection
CN103513150A (en) * 2013-09-17 2014-01-15 广东电网公司东莞供电局 Device and method for detecting multipoint earthing of voltage transformer for electric system

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