DK142664B - FAULT POWER PROTECTION SWITCH - Google Patents

Description

(11) PRESENTATION WRITING 1 4266

DENMARK <"> lnt.CI.’H 01 H 83 / U

«(21) An * # enrng nr. 4084/71 (2¾ IraHove ·» den 20. 8Ug. I971 (24) Lobadag 20. aug. 1971 'h (44) Aneogningen fremlagt og fremlsBggeiseeekriftet publigt den 8. d.6C. 198Ο

DIRECTORATE FOR

PATENT AND TRADEMARK SYSTEM (30) Priority requested from dan

Sep 8 I97O, 2044302, BE

Dec 19 I97O, 2062694, BE

(71) SIEMENS AKTIENGESKItLSCHAFT, Berlin und Muenchen, 8 Muenchen 2, Wit- = Telsbacherplatz 2, BE.

(72) Inventor: Helmut Roes eh, Adalhert-Stif ter-Str. 29a, Regene burg, BE.

(74) Agent under consideration:

The engineering company Giersing & Stelllnger.

(54) Faulty current protection circuit breaker.

The invention relates to a residual current circuit breaker with a sum current transformer which has a magnetic core with primary windings for connection to a circuit intended for monitoring and with a secondary winding which supplies the excitation winding of a tripping magnet acting on a switch for a switching device.

If an AC fault current occurs in the monitored circuit, a voltage is generated in the secondary winding, as a result of which the tripping magnet reacts so that the switch device is operated over the switch lock to interrupt the monitored circuit.

Such a residual current circuit breaker could not hitherto be used for monitoring circuits in which direct current fault currents can also be expected. The residual current circuit breaker is not tripped at all if it is passed through by a direct current fault current, since, as is known, a voltage in the primary winding is required to induce a voltage in the secondary winding of the sum current transformer. Not even the flux change which a pulsating DC fault current produced in the primary winding of the primary current transformer, produced by one-way alignment of 4 alternating current, causes in the transformer is so great that a voltage sufficient to trip the residual current circuit breaker is induced in the secondary current transformer.

The object of the invention is to provide a residual current circuit breaker of the above-mentioned type which also responds to direct current fault currents.

To solve this problem, a residual current circuit breaker of the type indicated in the introduction is characterized in that the material of the magnetic core is chosen such that it has a markedly large induction fluctuation in connection with a markedly large impulse permeability, the residual being preferably small.

The invention is thus based on the recognition that the reason why the known residual current circuit breakers do not trip at the prescribed DC fault currents at alternating current fault currents is that both the induction fluctuation and the impulse permeability are too small for the materials used. , so that, consequently, the present problem can be solved simply by appropriate selection of a suitable magnetic core material. This is all the more surprising since such materials with the required properties have long been known.

Suitably, the magnetic core of the current transformer has an induction fluctuation of over 3000 Gauss, preferably of at least 4000 Gauss, and a relative impulse permeability of at least 1000.

Due to the high pulse permeability, small dimensions are obtained for the transformer and thereby also for the residual current circuit breaker, as only a relatively small magnetic activation is required for tripping the residual current circuit breaker and because the number of primary turns on the current transformer can be kept small.

The magnetic core may suitably be a cut tape core or a ferrite with suitably selected properties.

The invention is explained in more detail in the following with reference to the drawing, in which fig. 1 shows hysteresis loops for cores of magnetic material, fig. 2 shows a residual current circuit breaker according to the invention, fig. Fig. 3 shows the excitation characteristic of a hitherto common residual current circuit breaker and of a residual current circuit breaker according to the invention; Fig. 4 shows a further embodiment of the residual current circuit breaker according to the invention; 5 shows the excitation characteristic of the residual current circuit breaker according to FIG. 4.

FIG. 1 shows a hysteresis loop 1 (induction B as ordinate with the field strength H as abscissa) for a core of magnetic material with large induction oscillation and a hysteresis loop 2 for a core of magnetic material with small induction fluctuation ΔΒ. By the induction oscillation is meant the difference between saturation induction B1 and remanence induction. respectively Br_.ΔΗ is the field strength fluctuation until the saturation induction is obtained · The quotient ^ (p0 = permeability in the empty space) is referred to as impulse permeability.

The residual current circuit breaker J according to fig. 2 serves for o-monitoring of the wires R / TJ and Mp in an electrical system. It has a sum current transformer 4 with a magnetic core 5. The magnetic core 5 is a ring core, preferably a ring band core consisting of a wound band of soft magnetic material. The tape thickness can e.g. amount to 0.006 to 0.3 mm. On this magnetic core they sit in fig. 2 primary windings 6 shown as a single winding and a secondary winding 7 * The primary windings 6 are interposed in the lines R / u and Mp intended for monitoring. The secondary winding 7 is connected to a magnetizing winding 9 for a release magnet 8. This release magnet 8, which may be a holding magnet or a working magnet, acts through a mechanical connecting part 8a on a switch lock 10, which through a coupling rod 10a operates switch contacts 11 inserted in the monitored wires R / TJ and Mp.

The magnetic core 5 of the sum current transformer oren 4 suitably has an induction fluctuation of more than 3000 Gauss and an impulse permeability of at least 1000 Ga. The induction fluctuation is suitably at least 4000 Gauss.

A suitable material for the magnetic core 5 is e.g. a known iron-nickel alloy containing 61-67% by weight of nickel and 2-4% by weight of molybdenum as well as small deoxygenation and processing additives (silicon and manganese up to 1% by weight) and the balance iron. This alloy or one of the alloy ring core cores was fertilized for 4-6 hours at 950-1200 ° C and then heated to a temperature of 400-500 ° C for 3-5 hours. The heating to 400-500 ° C suitably takes place in a magnetic field whose field lines extend transversely or perpendicularly to the direction which the magnetic flux has in the material, when this is built in in the form of the magnetic core in the sum current transformer.

* 142664 The saturation induction of * a thus treated annular core of this alloy amounts to approx. 12500 Gauss, the induction fluctuation is at 6000-11000 Gauss, and the impulse permeability at 4000-1000.

Another known iron-nickel alloy suitable for the magnetic core of the sum current transformer in the residual current circuit breaker according to the invention may contain 75-82% by weight of nickel, 2-5> 5% by weight of molybdenum and 0-5% by weight of 9. copper as well as up to 1% by weight of de-blotting and processing additives (silicon and manganese) and the rest iron. The iron content is suitably at least 6.5% by weight. This alloy and a ring band core made therefrom were fertilized for 2-6 hours at 950-1220 ° C and then heated to 450-600 ° C for 1-3 hours. Finally, the alloy and core, respectively, were further tempered for 1-50 hours at 250-400 ° C. The tempering at 250-400 ° C suitably takes place in a magnetic field whose field lines run transversely or perpendicular to the direction which the magnetic flux island has in the alloy, when this is built in in the form of the magnetic core in the sum current transformer. A thus treated annulus core of this alloy has a saturation induction of about 8000 Gauss and an induction fluctuation of 50OO-65OO Gauss as well as an impulse permeability of 15000-5000.

The magnetic core 5 of the sum current transformer may also consist of corresponding ferrites made with the aforementioned values for induction fluctuations and pulse permeability.

The operation of the residual current circuit breaker is explained in more detail with reference to fig. 3 · In the embodiment shown in FIG. The diagram of the diagram shown in Fig. 3 is plotted for the flux f and the time t, respectively, and in the abscissa the residual current 1 If an alternating current current corresponds to the punctured curve 12 in FIG. 3 through the sum current transformer 4, it is magnetized according to the excitation characteristic 13. At a suitable magnitude of this alternating current, the whole excitation characteristic 13 will be traversed during a period of the alternating current fault current, and the flux change occurring is very large so that the voltage induced in the secondary current transformer , that it exceeds the activation voltage of the tripping magnet 8, so that the residual current circuit breaker is tripped without difficulty.

On the other hand, the residual current has the character of a pulsating direct current corresponding to the solid curve 14 in fig. 3 (one-way direct current), the magnetization characteristic 13 is traversed by the magnetization of the magnetic core 5 in the sum current transformer 3 only up to the residual point 15. However, the induction fluctuation of the magnetic current transformer's magnetic core in the residual current circuit breaker according to the invention is large enough to change the flux. the secondary winding of the sum current transformer, which is 14266Λ j larger than the activation opening of the induction magnet 8, so that the residual current »protection circuit breaker is tripped. For s menu comparison, in fig. 3 »dotted lines show the excitation characteristic 16 which would exist if the induction oscillation of the magnetic core did not have the size required to trigger the residual current circuit breaker. With the occurrence of a residual current consisting of pulsating direct current corresponding to the curve 1 * in Fig * 3, the excitation characteristic 16 will only be passed to the residue point 17 »which is significantly higher than the residue point 15» so that the corresponding flux change & is less than the flux change and is not sufficient inducing a voltage in the sum current transformer h 'e secondary winding 7 »which exceeds the activation value of the tripping magnet 8.

If the magnetic core of the sum current transformer in the residual current circuit breaker according to the invention further has a large impulse permeability, the increase of the excitation characteristic 13 in FIG. 3 very steep, i.e. the flux change A j) ^ required to trigger the switch is obtained already at relatively small fault currents.

The residual current circuit breaker according to the invention has in particular the advantage that the difference between the activation values of the alternating current residual current and the direct current residual current is relatively small. This difference is all the smaller the smaller the residual induction of the magnetic core of the sum current transformer.

The residual current circuit breaker 13 according to fig. h is also used to monitor the R / U cables and in an electrical system.

It has a sum current transformer ih with a magnetic core 15 * This magnetic core 15 is a cutting band core which consists of two halves which are held together by a clamping band 15a and between which there are two air gaps 15b. The band of this cut-core core may consist of an iron-nickel alloy which has no particular composition and which has not been subjected to any particular pretreatment. The tape thickness in the cut tape core can amount to e.g. 0.06-0.3 mm. This sectional tape core encloses the two wires 16, which represent the two primary windings, and which are interposed in the lines R / U and Mp intended for monitoring. Furthermore, a magnetic winding 17 »which is connected to the magnetizing winding 19 in a tripping magnet . This release magnet 18, which may be a holding magnet or a working magnet, acts through a mechanical connecting part 18a on a switch lock 20, which through a coupling rod 20a operates switch switches 21 which are inserted in the lines R / XJ and M 2 intended for monitoring.

The magnetic core 15 designed as the cut tape core has as a rim of the two air gaps 15b in comparison with an annular band core of the same construction (see hysteresis loop 51 in Fig. 5) a cropped hysteresis loop (see hysteresis loop 52 in Fig. 5) and thus a significantly larger induction fluctuations, which are defined as the difference between the saturation induction and the residue induction. The residual current circuit breaker according to fig. 4 is tripped when the lines 16 are traversed by an alternating current fault current. Due to the air gaps 15b, the induction oscillation of the section strip core 15 is sufficiently large that also the change of the magnetic flux induced by a pulsating direct current fault current flowing in the lines 16 is sufficient to induce a voltage in the secondary current transformer 18 which exceeds the activation voltage 18. and that the residual current circuit breaker is also triggered by the passage of such a pulsating direct current residual current ·