GB2556141A

GB2556141A - Arrangement for detecting and clearing fault currents

Info

Publication number: GB2556141A
Application number: GB1712980.0A
Authority: GB
Inventors: Adlhoch Manfred
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2016-09-14
Filing date: 2017-08-14
Publication date: 2018-05-23
Anticipated expiration: 2037-08-14
Also published as: DE102016217470A1; CN107819319B; GB201712980D0; CN107819319A; GB2556141B; DE102016217470B4

Abstract

Arrangement for detecting and clearing fault currents, where a first switching contact 13 is arranged in a first line 10 between a first input terminal 11 and a first output terminal 12, and a second switching contact 23 is arranged in a second line 20 between a second input terminal 21 and a second output terminal 22, the switching contacts are connected to magnetic release 5 that has a yoke having a first field winding 8 and a second field winding 9 respectively that are attuned to one another such that during fault-current-free operation the magnetic fluxes produced in the yoke cancel one another out. The yoke has a sensor winding 41 that can be used to determine a magnetic flux difference so that in the event of a magnetic flux difference exceeding a threshold value a tripping current is passed to the sensor winding 41, so a magnetic flux is produced that causes tripping of the magnetic release, so that at least one switching contact opens.

Description

(54) Title of the Invention: Arrangement for detecting and clearing fault currents Abstract Title: Detecting and clearing fault currents (57) Arrangement for detecting and clearing fault currents, where a first switching contact 13 is arranged in a first line 10 between a first input terminal 11 and a first output terminal 12, and a second switching contact 23 is arranged in a second line 20 between a second input terminal 21 and a second output terminal 22, the switching contacts are connected to magnetic release 5 that has a yoke having a first field winding 8 and a second field winding 9 respectively that are attuned to one another such that during fault-current-free operation the magnetic fluxes produced in the yoke cancel one another out. The yoke has a sensor winding 41 that can be used to determine a magnetic flux difference so that in the event of a magnetic flux difference exceeding a threshold value a tripping current is passed to the sensor winding 41, so a magnetic flux is produced that causes tripping of the magnetic release, so that at least one switching contact opens.

1/6

FIG 1A

L

FIG 1B

L

2/6

3/6

FIG 3

Wq

5/6

ό 41 0

6/6

FIG 6

FIG 7

Arrangement for detecting and clearing fault currents

Field of Invention

The invention relates to an arrangement that is designed to detect and clear fault currents, and to a residual current breaker having such an arrangement.

Background

Conventional residual current breakers, which are designed to detect and clear fault currents, do so using the transformer principle, which cannot be applied to DC fault currents, however. AC-sensitive residual current breakers have a summation current transformer through which a first line to a load and the associated second line returning from the load are routed. When a current drains to ground on the load side, reference is made in this context to a fault current. This fault current can now be detected using the summation current transformer, since the sum of the flowing and returning currents that is detected in terms of absolute value is not equal to zero in the case of a fault current. A relay is used to set off a tripping mechanism that causes an interruption in the supply line and optionally in the return line. Residual current breakers for detecting AC fault currents are known generally from the document DE 44 32 643 A1.

The laid-open specification DE 10 2010 034 001 A1 discloses an arrangement for detecting and clearing DC fault currents. This arrangement has a first switching contact that is arranged in a forward line between a grid-side first input terminal and a load-side first output terminal. In addition, the arrangement has a second switching contact that is arranged in a return line between a grid-side second input terminal and a load-side second output terminal. In this arrangement, the first and the second switching contact are operatively connected to a magnetic release that has a yoke having two limbs, wherein each of the limbs has an associated field winding, said field windings being attuned to one another such that during fault-current-free operation the magnetic fluxes produced in the yoke by the field windings cancel one another out. In addition, a first measuring shunt is connected in the forward line and a second measuring shunt is connected in the return line. In this arrangement, the first field winding is connected to the connections of the first measuring shunt and the second field winding is connected to the connections of the second measuring shunt, so that in the event of a load-side DC fault current the magnetic fluxes induced in the yoke no longer cancel one another out, so that tripping of the magnetic release opens at least one of the two switching contacts.

It would be desirable to provide a DC- and AC-sensitive residual current breaker that is distinguished by good dependability.

Summary of Invention

According to an aspect of the invention, a first switching contact is arranged in a first line between a grid-side first input terminal and a load-side first output terminal. A second switching contact is arranged in a second line between a grid-side second input terminal and a load-side second output terminal. The first and the second switching contact are operatively connected to a magnetic release that has a yoke. By way of example, the yoke can have a first limb and a second limb. The yoke has a first and a second field winding that are attuned to one another such that during fault-current-free operation the magnetic fluxed produced in the yoke by the field windings cancel one another out. The first field winding carries at least one current element of the first line and the second field winding carries at least one current element of the second line. At least one current element means that either a portion of the current of the line or the entire current of the line can be carried. That is to say, by way of example, that the complete current of the line is carried by the field winding.

Field winding also means a winding having only one turn or half a turn. That is to say, by way of example, that just one conductor could be carried by the magnetic release or the yoke or, respectively, the magnetic flux circuit.

The yoke has a sensor winding that is connected to a control unit. These are configured such that a magnetic flux difference can be ascertained. In the event of a magnetic flux difference that exceeds a first threshold value, a tripping current is passed to the sensor winding, so that a magnetic flux is produced in the magnetic release that causes tripping of the magnetic release, so that at least one switching contact opens.

An arrangement of such design for detecting and clearing fault currents has the advantage that it can be used for both DC and AC voltage. Further, only one magnetic circuit is used, which realizes functions both for a retaining magnetic circuit and of a summation current transformer. Further, embodiments are distinguished by a high level of robustness, since the current difference or, respectively, magnetic flux difference is not used directly for tripping, i.e. for interrupting the electrical circuit of the first and second lines. Instead, the magnetic flux difference is detected electronically, possibly processed further electronically, compared with threshold values or period threshold values, i.e. a threshold value must exist for a certain period, and tripping is prompted in the event of said threshold value being exceeded or predefined tripping criteria being satisfied. This is effected, according to the invention, such that the magnetic circuit for the detection is also simultaneously used for the tripping or clearing. This can be effected by virtue of the sensor winding also simultaneously being used as a tripping winding by virtue of a current that causes a magnetic flux in the magnetic release being impressed into the sensor winding, so that the magnetic release trips and opens at least one switching contact. Hence, brief magnetic flux differences do not necessarily result in tripping, but rather tripping is effected only after electronic evaluation and satisfaction of predetermined criteria.

Hence, a compact design and robust operation can be achieved. The structural design means that the arrangement of simple design is moreover distinguished by a high level of availability, which further contributes to a high level of dependability of the arrangement.

In the case of DC use or AC/DC-sensitive use, care should be taken to ensure that the first field winding and the second field winding are connected with the correct polarity.

In one embodiment of the invention, the yoke has a tripping winding. The tripping current is passed to the tripping winding instead of to the sensor winding. In this way, a magnetic flux is produced in the magnetic release that causes tripping of the magnetic release, so that at least one switching contact opens.

This has the particular advantage that even the tripping process can be monitored by the sensor winding. As such, it is possible, by way of example, to check whether the tripping winding is in order and produces an adequate magnetic flux for the magnetic release to open the switching contact.

In one embodiment of the invention, a first measuring shunt is connected in the first line and a second measuring shunt is connected in the second line. The first field winding is connected to the connections of the first measuring shunt, and the second field winding is connected to the connections of the second measuring shunt.

This has the particular advantage that embodiments provide for routing a current element via the field coils. Even in the event of large currents in the circuit, i.e. in the first and second lines, it is therefore possible to realize small arrangements for detecting and clearing fault currents.

In one embodiment of the invention, the first switching contact and/or the second switching contact are operable via a switching mechanism and tripping of the switching mechanism via the magnetic release is initiable.

This has the particular advantage that, using the arrangement, smaller magnetic fluxes also reliably result in tripping. As such, a magnetic release is realizable with relatively small forces. The switching mechanism that is arranged between the magnetic release and the switching contacts and is operatively connected to the magnetic release and the switching contacts can be used to transmit the comparatively small forces of the magnetic release in a manner amplified - by an energy store (energy store spring) on hand in the switching mechanism - such that fast and reliable tripping of the switching contacts is realizable.

In one embodiment of the invention, the magnetic fluxes induced in the yoke are adjustable by virtue of the dimensioning of the measuring shunts and/or by virtue of the geometric design of the field coils.

This has the particular advantage that the operability of the arrangement is adjustable by virtue of the dimensioning or design. The magnetic fluxes induced in the yoke are intended to cancel one another out in the fault-current-free state. This can be realized in multiple ways, for example by virtue of appropriate dimensioning of the measuring shunts, but also by virtue of the geometric design of the field coils, for example by virtue of the number of turns; the direction of winding can be used to vary the polarity.

In one embodiment of the invention, the magnetic release has a permanent magnet.

This has the particular advantage that cohesion of the magnetic circuit or magnetic release is realizable by virtue of a constant magnetic flux, which is advantageous particularly for DC applications. It is thus possible to keep an armature, for example.

In one embodiment of the invention, the magnetic release has an armature via which the magnetic fluxes of the yoke flow.

This has the particular advantage that the armature can be used as a tripping element of the magnetic release, for example when the magnetic flux difference, particularly in the case of direct current, is so great that it is intended to directly cause tripping or opening of the switching contact. For tripping by tripping current, it may be the tripping element of the magnetic release.

In one embodiment of the invention, the armature is connected to at least one spring.

This has the particular advantage that an armatured magnetic release without a permanent magnet is realizable, in which the armature is pushed against the yoke by the spring.

In one embodiment of the invention, the yoke has further field windings in order to carry at least current elements of a three-phase AC circuit, so that fault currents can be detected and cleared.

This has the particular advantage that embodiments according to the invention can also be used for three-phase AC systems. In the case of a yoke having multiple limbs, it is also possible for all field windings to be arranged on one limb. The yoke may also be designed as a singlelimb yoke.

In one embodiment of the invention, the control unit is configured such that it has a filter and an analog-to-digital converter that is used to process the signal from the sensor winding, and also a microprocessor having memory that checks the processed sensor signal for whether it exceeds the first threshold value, and, if it does exceed it, allows an electric current to flow through the sensor winding or the tripping winding.

This has the particular advantage that electronic processing or digital processing of the sensor signal is made possible, as a result of which it is possible to realize, for example with microprocessor assistance, many evaluations, detections and functions.

Advantageously, the arrangement can be used in a residual current breaker that allows the aforementioned advantages to be realized. In particular, a residual current breaker for direct and/or alternating current can be realized, as a result of which an AC/DC-sensitive protective element is available.

All of the configurations, both in terms of single features or combinations of features, cause an improvement for the detection and clearance of fault currents.

Description of the Figures

The described properties, features and advantages of this invention and the manner in which they are achieved will become clearer and more distinctly comprehensible in conjunction with the description of the exemplary embodiments that follows, said exemplary embodiments being explained in more detail in conjunction with the drawings, in which:

Figures 1A and 1B show schematic depictions of the measurement principle of the arrangement according to the invention for detecting and clearing fault currents;

Figure 2 shows a schematic depiction of a first arrangement;

Figure 3 shows a schematic depiction of a second arrangement;

Figure 4 shows a schematic depiction of a third arrangement;

Figure 5 shows a schematic depiction of a fourth arrangement;

Figure 6 shows a schematic depiction of a fifth arrangement; and

Figure 7 shows a schematic depiction of a sixth arrangement.

In the various figures of the drawing, like parts are always provided with the same reference symbols. The description applies to all figures of the drawing in which the relevant part is likewise identifiable.

Detailed Description

Figures 1A and 1B schematically depict the measurement principle of the arrangement according to the invention for detecting and clearing fault currents. In this regard, figure 1A shows a highly simplified circuit diagram of the arrangement during fault-free operation. To ascertain a fault current, the principle of the current or voltage difference is used in this case: the input side of the arrangement has a first input terminal 11 and a second input terminal 21, which are designed for connecting the arrangement to a supply grid 60. The output side of the arrangement has a first output terminal 12 and a second output terminal 22, which are designed for connecting a load 50. A first measuring shunt 14 is electrically connected between the first input terminal 11 and the first output terminal 12, and a second measuring shunt 24 is electrically connected between the second input terminal 21 and the second output terminal

22. During fault-free operation, i.e. so long as no fault current occurs, a current I flows from a supply grid 60 (not depicted in figure 1) via the first input terminal 11, said current being able to be measured both at the first measuring shunt 14 as h and at the load 50 as l_v, and also at the second measuring shunt as U. In the fault-free operating state, it thus holds that:

If the first measuring shunt 14 now has a nonreactive resistance value R1 that is dimensioned to be of exactly the same magnitude as the nonreactive resistance value R2 of the second measuring shunt 24, i.e. the relationship

R1 - R2 applies, then, according to Ohm’s law, the voltage U1 present across the first measuring shunt 14 corresponds to the voltage U2 present across the second measuring shunt 24. It therefore holds that:

R1 — R2 <-> U1 — U2

This is the characteristic of fault-free operation of the arrangement. In this state, no fault current If drains to ground on the load side.

Figure 1B depicts a faulty operating state of the arrangement in which a fault current If drains to ground on the load side 50. The basic design of the arrangement in this case corresponds to the design described in figure 1 A. By contrast, the equation 11 = I_v = I2 that is valid for faultfree operation is no longer valid in this case. Instead, it now holds that:

Ii - I2 + If

The potential of the second input terminal 21 is in this case grounded on the supply grid side, for example.

Since the relationship Ri = R2 still holds for the two measuring shunts 14 and 24, but at the same time is h > I2 in the case of a fault current (see above), it follows that the voltage U1 present across the first measuring shunt 14 must be larger than the voltage U2 present across the second measuring shunt 24. The relationship

U1 > U₂ or AU = U1 - U₂ applies, which is conditional upon the draining fault current If. The resultant voltage difference AU or the current difference between the first measuring shunt 14 and the second measuring shunt 24 can therefore be used to trip the arrangement.

Figure 2 shows the operating principle for the monitoring and tripping in an arrangement in a schematic depiction. The input terminals 11 and 21 are in turn provided for connecting the arrangement to a power supply grid; the output terminals 12 and 22 are used for connecting an electrical load. In the first line 10, the first measuring shunt 14 and the first switching contact 13 are arranged in a series connection between the first input terminal 11 and the first output terminal 12; in the second line 20, the second measuring shunt 24 and the second switching contact 23 are accordingly arranged in a series connection between the second input terminal 21 and the second output terminal 22. The first switching contact 13 and the second switching contact 23 are operatively connected to a switching mechanism 3 of the arrangement, which is provided for the purpose of opening the switching contacts 13 and 23 in the event of a fault current occurring.

For monitoring and tripping, the arrangement has a magnetic release 5 that is mechanically connected to the first switching contact 13 and the second switching contact 23 via the switching mechanism 3. The magnetic release 5 is connected to the switching mechanism 3 via an operative connection, for example via a tripping lever (not depicted), and has an armature 2, a permanent magnet 4 and a yoke having a first limb 6 and a second limb 7. The yoke is of two-piece design in this case, with separate limbs 6 and 7. It may also be embodied as one piece, however. The yoke can also have just one limb. Any configuration is conceivable in this case, so long as a closed magnetic circuit or magnetic flux is realizable.

In the deenergized state, a magnetic flux Φ appears in the yoke on account of the permanent magnet 4, said magnetic flux being dimensioned to be sufficiently large to keep the armature 2 at the ends of the two limbs 6 and 7 counter to the oppositely directed force of a spring 31.

To detect the voltage difference AU or current difference that allows a fault current to be inferred, the first limb 6 has a first field winding 8 arranged on it that is connected to the connections of the first measuring shunt 14. The second limb 7 has a second field winding 9 arranged on it that is connected to the connections of the second measuring shunt 24. On account of the voltage Ui present across the first measuring shunt 14 or by virtue of the current through the first field winding 8, a magnetic flux Φι is produced in the first limb 6 of the yoke; similarly, the voltage U2 present across the second measuring shunt 24 or the current through the second field winding 9 produces a magnetic flux Φ₂ in the second limb 7 of the yoke. In this case, for the DC case (or for AC/DC-sensitive cases), the field windings 8 and 9 are electrically connected to the respective measuring shunt 14 or 24 in such a way, or polarized in such a way, that the two induced magnetic fluxes Φ1 and Φ₂ are oriented oppositely to one another in the magnetic circuit. As a result, the magnetic fluxes Φ1 and Φ₂ produced in the yoke by the voltages U1 and U₂ on account of the relationship U1 = U₂ cancel one another out during faultfree operation - the armature 2 therefore continues to be kept at the ends of the two limbs 6 and 7.

In the case of a fault current If, a current drains to ground on the load side, which means that the current l₂ returning via the return line 20 is smaller than the current h routed via the forward line 10. It holds that:

h > l₂

Since the nonreactive resistance values R1 and R2 of the two measuring shunts 14 and 24 are dimensioned identically, it follows directly that the voltage U₂ falls accordingly in comparison with U1 in the case of a fault current If. Therefore, the relationship:

Ui > U₂ applies. If a smaller voltage U₂ is present across the second measuring shunt 24, it follows that a smaller magnetic flux Φ₂ is also induced via the second field winding 9. Therefore, in the case of a fault current, it holds that:

Φΐ > φ₂

If the magnetic flux Φι produced via the first field winding 8 is larger than the magnetic flux Φ₂induced via the second field winding 9, then the magnetic flux Φ is attenuated, and the magnetic circuit of the magnetic release 5 is therefore out of equilibrium.

This change in the magnetic flux or the magnetic flux difference in relation to the magnetic flux of the permanent magnet for the DC case or the magnetic flux difference for the AC case is now detected by a sensor winding 41. The sensor winding 41 is connected to a control unit 61, which is not depicted in figure 2. Said control unit compares the ascertained magnetic flux difference with a first threshold value and, if it exceeds it, a tripping current is passed to the sensor winding 41, so that a higher third magnetic flux or a decrease in the magnetic flux Φ is produced that is so large that tripping of the magnetic release is caused, so that at least one switching contact opens. By way of example, a third magnetic flux is produced or the magnetic flux Φ is attenuated such that the magnetic retaining force is no longer sufficient to keep the armature 2 against the force of the spring 31. A deflection in the armature 2 causes the switching mechanism 3 to be tripped as a result, which opens the switching contacts 13 and

23.

By way of example, the magnetic flux difference can be ascertained for alternating currents directly from the current induced in the sensor winding 41. For direct currents, an alternating current flowing in the sensor winding or sensor coil 41 and impressed by the control unit 61, for example by an oscillator, can be used to ascertain a change in the magnetic flux or magnetic flux difference. Filters in the control unit 61 can be used to ascertain magnetic flux differences both for DC cases and for AC cases, which means that an AC/DC-compatible arrangement is realizable.

Figure 3 shows an arrangement as shown in figure 2 with the difference that the first and second measuring shunts 14, 24 are not provided, but instead the first and second lines 10, 20 directly form a field winding by being routed through the magnetic release 5, more precisely through the yoke, for example with the two limbs 6, 7. The two conductors therefore directly form the field winding 8, 9. In the case shown in figure 3, the field windings electrically each have one half-turn.

Furthermore, the magnetic release 5 has a tripping winding 42. This is arranged on the yoke, on the first limb 6 in the example. Said tripping winding is likewise connected to the control unit 61, which is not depicted in figure 3. In this example, the tripping current of the control unit 61 is passed not to the sensor winding 41 but rather to the tripping winding 42. The magnetic flux produced thereby or the attenuation of the magnetic flux Φ causes tripping of the magnetic release by virtue of the armature 2 lifting, for example, i.e. the magnetic circuit of the magnetic release 5 being opened. The switching mechanism 3 can be used to open the contacts 13, 23.

Figure 4 shows an arrangement as shown in figure 2 with the difference that in this case too the magnetic release 5 has a tripping winding 42. In the example, on the yoke, in particular on the first limb 6.

The field windings, the sensor winding and if appropriate the tripping winding may be situated at any location in the magnetic release. The depictions with the first and second limbs are chosen only by way of example. For the DC voltage case, further, only the direction of winding or direction of magnetic flux is crucial, which can be prescribed by the polarity of the DC voltage or can be changed or adapted on the winding if need be by changing the connection polarity.

Figure 5 shows an arrangement as shown in figure 2 with the difference that the magnetic release 5 has a single-piece yoke. Furthermore, there is no permanent magnet 4 provided. Instead of the permanent magnet 4, which attracts the armature 2 by virtue of its magnetic flux Φ, a second or a second and third spring 32, 33 is/are provided. These push the armature 2 against the yoke of the magnetic release 5.

When a tripping current is passed to the sensor winding 41, the magnetic flux repels the armature 2 and hence trips the magnetic release, as a result of which the switching mechanism 3, for example, is used to cause opening of the switching contacts 13, 23.

In figure 5, the yoke may also further have a tripping coil 42 arranged on it. The field coils 8, 9 may be arranged on any section of the yoke, as already set out.

Figure 6 shows a schematic arrangement with a supply grid 60 and a load 50, between which an arrangement according to the invention is provided. In this case, the magnetic release 5 along with lines 10, 20 are combined in a summation current unit 63. The latter is operatively connected to the contacts 13, 23. The summation current unit 63 has, according to the invention, a sensor winding 41 and a tripping winding 42. The sensor winding 41 is connected to the control unit 61. The tripping winding 42 is likewise connected to the control unit 61. Figure 6 shows a further exemplary interfacing of the tripping winding 42 with a resistor R, a thyristor and a capacitor. The gate connection of the thyristor is connected to the control unit 61 in this case.

The control unit 61 is in turn connected to a power supply unit 62 for supplying power, which is in turn connected to the first and second lines 10, 20 on the supply grid side 60.

Figure 7 shows an arrangement as shown in figure 6 with the difference that the tripping winding 42 is connected to the power supply unit 62, for example by means of a transistor, thyristor, triac or other switching element, the control connection of which is in turn connected to the control unit 61. As such, in the case of a fault, a tripping current can be passed to the tripping winding 42.

The control unit 61 has further assemblies, such as an amplifier 71, a filter 72, such as a lowpass filter, high-pass filter, bandpass filter or band rejection filter, for example, an analog-todigital converter 73, a microprocessor 74 and/or a memory 75.

The magnetic release 5, particularly the yoke, is advantageously made of ferromagnetic material.

The invention will be explained again below in other words.

According to the invention, there is provision for a retaining magnet or magnetic release also to be used as a summation current transformer. Particularly for residual current breakers in low-voltage systems. In this case, the functional parts retaining magnet and summation current sensor use a common magnetic circuit with a ferromagnetic core. This invention can be used both for AC voltage applications and for DC voltage applications, as in low-voltage systems of this kind.

Figure 3 depicts a two-pole arrangement, as in a residual current breaker, with the functional assemblies (primary) lines, switching contacts/contact system, breaker mechanism, retaining magnet and summation current transformer. The special feature is the embodiment of the magnetic circuit. These have the (primary) lines routed directly through the magnetic circuit. At least one sensor winding is provided. As an alternative to this, a tripping winding.

The sensor winding is used for detecting the summation current (sinusoidal oscillation current, pulsed current and/or smooth direct current) through the electrical tripping circuit/the control unit.

In this example, the tripping winding is used for the two functions: a) internal test function = ‘test’ and b) the tripping function = ‘trip’.

The function of the tripping winding can also be realized as well, i.e. combined, in one winding, for example the sensor winding.

The particular advantage of the invention is the use of only one common magnetic circuit for at least two functions, tripping/retaining magnetic circuit and summation current transformer. This allows space and costs to be saved. A further advantage is the increase in device reliability, since fewer parts need to be used, including connecting lines. Furthermore, there is the possibility of monitoring the tripping process live via the sensor winding when the tripping winding is activated, so as to introduce an additional measure of certainty. In this case, the sensor winding detects the tripping process from actuation through to lifting of the armature of the retaining magnetic circuit/magnetic release, which interrupts the magnetic circuit and hence the induction on the sensor winding.

The residual retaining force of the armature against the retaining magnet/magnetic release is in such a powerful form that it is overcome (as tripping) only by activation of an input of energy on the tripping winding or sensor winding.

Tripping purely as a result of magnetic flux production/induction brought about by the primary windings of the (primary) lines 10, 20 is impossible.

An alternative design is depicted in figure 4. In the course of further space savings, the primary windings can be provided by means of resistor taps. This embodiment makes it possible to realize a very compact design, but this requires a much higher sensor sensitivity/measurement accuracy for the magnetic fluxes or magnetic flux differences of the control unit 61.

Figure 5 shows an advantageous configuration with only one sensor winding or secondary winding, and a dispensation with a permanent magnet for realizing the residual retaining force on the armature. The residual retaining force is alternatively realized by one or two springs 32, 33.

Embodiments according to the invention that have been explained can be used as a residual current breaker, for example as a 1+N, 3-phase, 3+N or purely DC type.

A depiction of the electrical principle or of one realization is depicted in figure 6. What is shown is the control unit 61, which is supplied with power by a power supply unit 62. A microprocessor 74 in the control unit 61 reads in the summation difference current via the sensor winding and rates the type and level of the summation (fault) current.

The summation current sensor is arranged in the magnetic system of the retaining magnet/magnetic release. When a defined tripping threshold is exceeded, electronic tripping is caused by microprocessor 74, for example by means of thyristor, and the tripping winding 42 is energized or actuated. The actuation of the tripping winding subsequently opens the contacts, which isolates a load 50 from the supply or source 60.

An alternative depiction of the electrical principle or of one realization is depicted in figure 7. In this, the functional assemblies of the control unit 61 are apparent. In this case, the tripping function alternately occurs via a bipolar transistor, supplied with power via the power supply unit.

The invention combines a magnetic release circuit with a summation current transformer function while using a common magnetic system.

The overall result is an inexpensive design, a higher level of reliability with extended life, a saving on the number of components and parts needed, a saving on space in the device and an increase in certainty as a result of a monitored tripping process.

Although the invention has been illustrated and described in more detail by virtue of the exemplary embodiment, the invention is not limited by the examples disclosed and other variations can be derived therefrom by a person skilled in the art without departing from the scope of the invention as defined by the appended claims.

of reference symbols

Armature

Switching mechanism Permanent magnet Magnetic release with yoke first limb second limb first field winding second field winding first line first input terminal first output terminal first switching contact first measuring shunt second line second input terminal second output terminal second switching contact second measuring shunt first spring second spring third spring

Sensor winding Tripping winding electrical load

Supply grid

Control unit

Power supply unit

Summation current unit

Amplifier

Filter

Analog-to-digital converter

Microprocessor

Memory

Claims

1. An arrangement for detecting and clearing fault currents, in which a first switching contact (13) is arranged in a first line (10) between a grid-side first input terminal (11) and a load-side first output terminal (12), in which a second switching contact (23) is arranged in a second line (20) between a grid-side second input terminal (21) and a load-side second output terminal (22), wherein the first and the second switching contact (13, 23) are operatively connected to a magnetic release (5) that has a yoke, wherein the yoke has a first field winding (8) and a second field winding (9) that are attuned to one another such that during fault-current-free operation the magnetic fluxes (Φ1, Φ2) produced in the yoke by the field windings (8, 9) cancel one another out, wherein the first field winding (8) carries at least one current element of the first line (10) and the second field winding (9) carries at least one current element of the second line (20), and wherein the yoke has a sensor winding (41) that is connected to a control unit (61) that is configured such that the sensor winding (41) can be used to ascertain a magnetic flux difference, in the event of a magnetic flux difference that exceeds a first threshold value a tripping current is passed to the sensor winding, so that a magnetic flux is produced in the magnetic release that causes tripping of the magnetic release (5), so that at least one switching contact (13, 23) opens.

2. The arrangement as claimed in patent claim 1, wherein the yoke has a tripping winding (42) and in that the tripping current is passed to the tripping winding, so that a magnetic flux is produced in the magnetic release that causes tripping of the magnetic release (5), so that at least one switching contact (13, 23) opens.

3. The arrangement as claimed in patent claim 1 or 2, wherein the arrangement is configured such that the magnetic flux difference cannot cause tripping of the magnetic release (5).

4. The arrangement as claimed in patent claim 1, 2 or 3, wherein a first measuring shunt (14) is connected in the first line (10), a second measuring shunt (24) is connected in the second line (20), the first field winding (8) is connected to the connections of the first measuring shunt (14), and the second field winding (9) is connected to the connections of the second measuring shunt (24).

5. The arrangement as claimed in one of the preceding patent claims, wherein the first switching contact (13) and/or the second switching contact (13) are operable via a switching mechanism (3) and tripping of the switching mechanism (3) via the magnetic release (5) is initiable.

6. The arrangement as claimed in one of the preceding patent claims, wherein the first measuring shunt (14) is electrically connected between the first input terminal (11) and the first switching contact (13), and the second measuring shunt (24) is electrically connected between the second input terminal (21) and the second switching contact (23).

7. The arrangement as claimed in one of the preceding patent claims, wherein the magnetic fluxes (Φ1, Φ2) induced in the yoke are adjustable by virtue of the dimensioning of the measuring shunts (14, 24) and/or by virtue of the geometric design of the field coils (8, 9).

8. The arrangement as claimed in one of the preceding patent claims, wherein the magnetic release (5) has a permanent magnet (4).

9. The arrangement as claimed in one of the preceding patent claims, wherein the magnetic release (5) has an armature (2) via which the magnetic fluxes of the yoke flow.

10. The arrangement as claimed in patent claim 9, wherein the armature (2) is connected to at least one spring (32, 33).

11. The arrangement as claimed in one of the preceding patent claims, wherein the yoke has further field windings in order to carry at least current elements of a three-phase AC circuit, so that fault currents can be detected and cleared.

12. The arrangement as claimed in one of the preceding patent claims, wherein a power supply unit (62) is provided that is connected firstly to the first and second lines (10, 20) and secondly to the control unit (61).

13. The arrangement as claimed in one of the preceding patent claims, wherein the control unit (61) is configured such that it has a filter (72) and an analog-to-digital converter (73) that is used to process the signal from the sensor winding, and also a microprocessor (74) having memory (75) that checks the processed sensor signal for whether it exceeds the first threshold value, and, if it does exceed it, allows an electric current to flow through the sensor winding (41) or the tripping winding (42).

14. The arrangement as claimed in one of the preceding patent claims, wherein the yoke has a first limb (6) and a second limb (7), and the first limb (6) has a first field winding (8) and the second limb (7) has a second field winding (9), which are attuned to one another such that during fault-current-free operation the magnetic fluxes (Φ1, Φ2) produced in the yoke by the field windings (8, 9) cancel one another out.

15. A residual current breaker, having an arrangement for detecting and clearing fault currents as claimed in one of claims 1 to 14.

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Application No: GB1712980.0 Examiner: Jonathan Huws