Protective switching device and method

Abstract

The invention relates to a protective switching device for a low-voltage circuit, in which the magnitude of the current and voltage of the low-voltage circuit is determined periodically. On the one hand, the magnitude of the current determined in a first cycle is compared with a first current threshold value, in the case of which the first time window with a first duration is started, in which the effective value of the determined voltage is compared with a first voltage threshold value, in the case of which, in the case of undershooting the first voltage threshold value, a first information display is carried out. On the other hand, the effective value of the magnitude of the current determined in a second cycle is compared with a second current threshold value, in the case of which the second time window is started, in which, after the start of the second time window and after the first duration has elapsed, the effective value of the determined voltage is compared with the first voltage threshold value, in the case of which, in the case of undershooting the first voltage threshold value, a second information display is carried out.

Description

TECHNICAL FIELD

[0001] The invention relates to the technical field of a protective switching device, for example a fire protection switch or a line protection switch, for low voltage circuits according to the preamble of claim 1 and a method for a protective switching device for low voltage circuits according to the preamble of claim 13. BACKGROUND

[0002] Low voltage means a voltage of up to 1000 volts AC voltage or up to 1500 volts DC voltage. Low voltage in particular means a voltage which is greater than a small voltage, the value of which is 50 volts AC voltage or 120 volts DC voltage.

[0003] Low voltage circuit or low voltage network or low voltage device means a circuit with a rated current of up to 125 amperes, more particularly up to 63 amperes.

[0004] Fault arc means an arc which occurs in the event of a fault, that is to say an arc which is caused by a fault in the circuit. For example by a poorly clamped, faulty or poorly conducting connection or contact in the circuit, for example in a junction box, a switch or a socket of a low voltage circuit. Not an (interference) arc which occurs for example in the normal operation of the network, for example when a switch is operated or at the brushes of an electric motor.

[0005] Series fault arc means an arc which occurs in the current path of the circuit, that is to say for example the current which also flows through the consumer flows through the arc. That is to say, if the current flows in a conductor which is "almost interrupted", a so-called series fault arc occurs at the point of interruption.

[0006] Fire protection switch is a relatively new protective device for circuits or voltage networks and serves to identify such (in particular series) fault arcs. The fire protection switch can in particular be used in domestic installation devices, for example in a fuse box, in order to identify such faults and to cause a circuit interruption, self-interruption or to output a fault arc identification signal in the event of a fault or if a fault arc limit value is exceeded.

[0007] Line protection switch is a long-known overcurrent protection device which is used in the electrical installation technology in low voltage circuits. The line protection switch protects the line from damage due to heating as a result of an excessively large current and / or a short circuit. The line protection switch can automatically interrupt the circuit in the event of an overload and / or a short circuit. The line protection switch is a safety element which does not reset automatically.

[0008] In contrast to the line protection switch, the circuit breaker is designed for currents greater than 125 A, sometimes also starting from 63 amperes. The line protection switch is therefore designed more simply and more finely.

[0009] Line protection switches are usually designed electromechanically. Line protection switches have switch contacts or working current triggers for interrupting (triggering) the current, bimetallic protection elements or bimetallic elements for triggering (interrupting) in the case of long-lasting overcurrent or in the case of thermal overload, electromagnetic triggers with coils for short-term triggering in the case of exceeding an overcurrent limit value or short circuit, and one or more arc chambers or means for extinguishing arcs. There are also connection elements for the conductors of the circuit to be protected.

[0010] Line protection switches essentially monitor the current size in the circuit and interrupt the circuit when an overcurrent limit value or a current-time period limit value is exceeded. SUMMARY

[0011] The technical problem addressed by the present invention is to improve a protection switch device, in particular a fire protection switch or a line protection switch, in particular to be able to identify the triggering cause.

[0012] The technical problem is solved by a protection switch device having the features of claim 1 or a method according to claim 13.

[0013] According to the invention, a protection switch device for interrupting a low-voltage circuit when an overcurrent limit value or a current-time limit value is exceeded is provided, having

[0014] - a housing having terminals for the conductors of the low-voltage circuit,

[0015] - an interrupting unit having contacts and for interrupting the low-voltage circuit in the housing,

[0016] - a bimetallic trigger connected to the interrupting unit,

[0017] - a magnetic trigger connected to the interrupting unit,

[0018] - a current measuring device for periodically determining the current size of the low-voltage circuit, wherein the current size or a corresponding effective value of the current size is periodically determined,

[0019] - a voltage measuring device for periodically determining the effective value of the voltage of the low-voltage circuit,

[0020] - a display device for displaying information of the protection switch device,

[0021] - a control unit connected to the current measuring device, the display device and the interrupting unit.

[0022] According to the application, the protective switch device is designed in such a way that, on the one hand, the determined current magnitude in a first cycle is compared with a first current threshold value, and in the event of an excess of the first current threshold value, a first time window having a first duration is started, in which the determined voltage effective value is compared with a first voltage threshold value, and in the event of a fall below the first voltage threshold value, a first information display is effected.

[0023] On the other hand, the determined current magnitude effective value in a second cycle is compared with a second current threshold value, and in the event of an excess of the second current threshold value, a second time window is started, and after the start of the second time window and after a first duration, the determined voltage effective value is compared with the first voltage threshold value, and in the event of a fall below the first voltage threshold value, a second information display is effected.

[0024] By selecting the first and second cycles, the first duration, the current threshold values and the voltage threshold value, different operating situations or triggering causes can advantageously be displayed.

[0025] Advantageous design options of the application are specified in the dependent claims.

[0026] In an advantageous design option of the application, the first cycle lies in the range of 1 millisecond, so that the determined current magnitude is compared with the first current threshold value approximately every millisecond.

[0027] This has the particular advantage that there is an optimum time period for displaying a short-circuit state or a short-circuit triggering.

[0028] In an advantageous design option of the application, the first duration lies in the range of 200 milliseconds, so that a first time window having a duration of approximately 200 milliseconds is started each time the first current threshold value is exceeded.

[0029] This has the particular advantage that there is an optimum first duration for displaying a short-circuit state or a short-circuit triggering.

[0030] In an advantageous design option of the application, the protective switch device has a rated current. The rated current is the maximum current which flows in the protective switch device in a normal situation or operating situation when the device is supplied with a rated voltage. This is not a reference to an overcurrent or short-circuit current here. The rated current of the protective switch device is usually 6 A, 10 A, 13 A, 16 A, 20 A, 25 A, 30 A, 40 A, 50 A, 63 A, 80 A, 100 A, 125 A, etc.

[0031] The first current threshold is a multiple of the rated current. In particular, the first current threshold is three or five times the rated current, or a value in or near this range. The current threshold can be set depending on the characteristics (B, C, D, etc.) of the protective switching device.

[0032] This has the particular advantage that a solution is given in which the size of the first current threshold depends on the rated current on the side of the protective switch, in particular for short-circuit situations.

[0033] In an advantageous design of the application, the protective switching device has a rated current, wherein the second current threshold is a multiple of the rated current. In particular, the second current threshold is 1.15 times the rated current.

[0034] This has the particular advantage that a solution is given in which the size of the current threshold depends on the rated current on the side of the protective switch, in particular for overcurrent situations.

[0035] In an advantageous design of the application, the second period lies in the range of one second, so that the determined effective value of the current is compared to the second current threshold approximately every second.

[0036] This has the particular advantage that there is an optimal time period for determining the overcurrent state or the overcurrent trigger.

[0037] In an advantageous design of the application, the second time window starts in the event of an excess of the second current threshold and ends in the event of a drop below the second current threshold.

[0038] This has the particular advantage that there is a solution for optimally determining the overcurrent state or the overcurrent trigger.

[0039] In an advantageous design of the application, the determined current magnitude is converted in parallel by two analog-digital converters. The first analog-digital converter has a resolution of, for example, 12 bits or 16 bits, which provides the current magnitude determined with the first period. The second analog-digital converter has a resolution of, for example, 24 bits, which provides the current magnitude determined with the second period.

[0040] This has the particular advantage that, on the one hand, in particular for high (short-circuit) currents, a fast conversion is provided with sufficient accuracy (12 bits or 16 bits), and on the other hand, in particular for overcurrents, a higher accuracy (24 bits) is provided at sufficient speed.

[0041] In an advantageous design of the application, the protective switching device has a rated voltage. The first voltage threshold is a fraction of the rated voltage. In particular, the first voltage threshold is less than 0.4 times the rated voltage, more particularly less than or equal to 0.35 times the rated voltage.

[0042] In the case of a rated voltage of, for example, 230 volts, the first voltage threshold may, for example, be 80 volts or lie in the range of 80 volts.

[0043] This has the particular advantage that a solution is given in which the size of the voltage threshold depends on the rated voltage of the protective switching side.

[0044] In an advantageous design of the application, a measurement resistor is provided for the current measurement.

[0045] This has the particular advantage that it is possible to determine the current size particularly simply and linearly.

[0046] In an advantageous design of the application, the control unit has a microprocessor.

[0047] This has the particular advantage that a flexible, computer program-supported implementation is possible.

[0048] According to the application, a parallel method for a low-voltage circuit is also claimed, in which method the size of the current and the voltage of the low-voltage circuit is determined at least periodically. According to the application, on the one hand, the size of the current determined in a first cycle is compared with a first current threshold, in the case of which first current threshold being exceeded, a time window having a first duration begins, in which first duration the effective value of the determined voltage is compared with a first voltage threshold, in the case of which first voltage threshold being undershot, a first information display is made. On the other hand, the effective value of the current size determined in a second cycle is compared with a second current threshold, in the case of which second current threshold being exceeded, a second time window begins, in which second time window begins and after a first duration has elapsed, the effective value of the determined voltage is compared with a first voltage threshold, in the case of which first voltage threshold being undershot, a second information display is made.

[0049] All the design solutions, whether they are referred to in dependent form to the independent claim or only to individual features or feature combinations of the claim, lead to an improvement of the protective switching device. BRIEF DESCRIPTION OF DRAWINGS

[0050] The features, characteristics and advantages described of the application and the implementation thereof are more clearly and more precisely understood in connection with the description of embodiments, which are explained in more detail below in connection with the drawings.

[0051] Herein in the drawings:

[0052] Figure 1 Figures are shown for illustrating the protective switching device of the present invention,

[0053] Figure 2 Figures are shown for illustrating the line diagram of the present invention. DETAILED DESCRIPTION

[0054] Figure 1 Figures are shown for illustrating the protective switching device SG (e.g. a fire protection switch, a line protection switch or a combined fire protection switch / line protection switch) for a low voltage circuit, in the example for a single-phase alternating current circuit, with:

[0055] - a housing (not shown) with input side terminals Ne, Le and output side terminals Na, La for conductors of the low voltage circuit, in the example an energy source is connected at the input side terminals Ne, Le and one or more consumers are connected at the output side terminals Na, La.

[0056] - a current measuring device SH, in the example a shunt, a shunt resistor, a measuring resistor or a resistor, for periodically determining the current magnitude of the low voltage circuit,

[0057] - a voltage measuring device (not shown) for periodically determining the effective value of the voltage of the low voltage circuit,

[0058] - a display device (not shown) for displaying information of the protective switching device,

[0059] - a control unit SE, which is connected with the current measuring device SH and the display device.

[0060] Furthermore, an interrupt unit UB with a contact KT is provided, which is connected with the control unit SE, for interrupting the low voltage circuit.

[0061] Furthermore, a bimetallic trigger BM or a bimetallic or bimetallic protection element is provided, through which the current of the low voltage circuit flows, and which is connected with the interrupt unit UB. That is, in the case of an excessively high current in the low voltage circuit for a certain duration, the bimetallic trigger BM heats up and deforms as a result of the heating, which deformation leads to a triggering of the interrupt unit UB, which therefore opens the contact KT and leads to an interruption of the circuit. That is, in the case of an exceeding of a current-time boundary value, the interruption by the bimetallic is carried out, which is referred to as the so-called thermal triggering.

[0062] Furthermore, a so-called magnetic trigger MR is provided. This magnetic trigger is also connected with the interrupt unit UB. The magnetic trigger MR has a coil, through which the current of the low-voltage circuit flows. If the current exceeds a certain current limit value, the magnetic field of the coil becomes so great that the iron part of the magnetic trigger MR is attracted, so that the interrupt unit UB is triggered and thus the contact KT is opened and a disruption of the circuit is caused. This is referred to as magnetic triggering, which causes an almost immediate interruption of the low-voltage circuit in the event of an excess of the current limit value or a short circuit in the low-voltage circuit.

[0063] The contact KT can have an arc extinguishing device ARC, which extinguishes the electric arc that is generated when the contact is opened. The arc extinguishing device can have a so-called arc runner AR.

[0064] According to Figure 1 The input-side connection Ne (input-side neutral conductor connection) for the neutral conductor, for example, is connected with the output-side connection Na (output-side neutral conductor connection) via the first sub-contact of the contact KT. The input-side connection Le (input-side phase conductor connection) for the phase conductor, for example, is connected with the output-side connection La (output-side phase conductor connection) via the magnetic trigger MR, the second sub-contact of the contact KT, the bimetal BM and the current measuring device SH. The arc extinguishing device ARC with the arc runner AR is connected in parallel with the second sub-contact of the contact KT.

[0065] The control unit SE is connected on the one hand with both connections of the current measuring device (in the example the resistor SH) and on the other hand with the output-side connection Na (output-side neutral conductor connection).

[0066] According to the application, the protective switching device is designed in such a way that, on the one hand, the magnitude of the current determined with the aid of the current measuring device SH in a first period (for example 1 millisecond) is compared with a first current threshold value, in the event of an excess of this first current threshold value, a time window with a first duration (for example 200 milliseconds) is started, within which the effective value of the determined voltage is compared with a first voltage threshold value, in the event of a fall below this first voltage threshold value, a first information display is carried out. On the other hand, the effective value of the magnitude of the current determined or present in a second period (for example 1 second) is compared with a second current threshold value, in the event of an excess of this second current threshold value, a second time window is started, after the start of the second time window and after the first duration (for example 200 milliseconds) has elapsed, the effective value of the determined voltage is compared with the first voltage threshold value, in the event of a fall below this first voltage threshold value, a second information display is carried out.

[0067] The first period lies in the range of 1 millisecond (0.5 to 1.5 milliseconds), so that the determined current magnitude is compared to the first current threshold approximately every millisecond. Then the absolute value of the current (approximately) every millisecond and the (approximately) every millisecond root mean square (RMS) value can be used.

[0068] The first duration lies in the range of 200 milliseconds (150 to 250 milliseconds), so that a time window with a duration of approximately 200 milliseconds starts each time the first current threshold is exceeded. That is, a time window of 200 milliseconds length can start, for example, every millisecond. Thus, there can be multiple parallel (temporally overlapping) time windows. After, for example, 200 milliseconds, the first time window ends.

[0069] The protective switching device has a rated current, wherein the current threshold is a multiple of the rated current. In particular, the first current threshold is three or five times the rated current. In particular, the second current threshold is 1.15 times the rated current.

[0070] The second period lies in the range of 1 second, so that the determined current root mean square value is compared to the second current threshold approximately every second. The second time window starts in case the second current threshold is exceeded and ends in case the second current threshold is undershot. That is, the second time window can start and end consecutively. There are no parallel second time windows.

[0071] The determined current magnitude can be converted in parallel by two analog-to-digital converters. The first analog-to-digital converter can have a resolution of 12 or 16 bits and can provide the determined current magnitude (or its root mean square value) every millisecond.

[0072] The second analog-to-digital converter can have a resolution of 24 bits and can provide the determined current magnitude or its root mean square value every second. Alternatively, the second analog-to-digital converter can also calculate the root mean square value more frequently, for example, with respect to a time period of 80 milliseconds or every 80 milliseconds. Therein, only every second, for example, the root mean square value of 80 milliseconds is used, i.e., approximately every twelfth value.

[0073] The protective switching device has a rated voltage. The first voltage threshold is a fraction of the rated voltage. In particular, the first voltage threshold is less than 0.4 times the rated voltage, more particularly less than or equal to 0.35 times the rated voltage. In case of a rated voltage of, for example, 230 volts, the first voltage threshold can be, for example, 80 volts or lie in the range of 80 volts (60 or 70 volts to 90 or 100 volts).

[0074] The control unit (SE) or the current measuring device (SH) can have an analog-to-digital conversion for digitizing the current values. The control unit (SE) can have a microprocessor for implementing the mentioned functions.

[0075] A protective switching device such as a line protection switch or a fire protection switch can be triggered for different reasons. The reason for the triggering can be an overcurrent (exceeding a current-time limit value), which leads to a thermal triggering, or a short circuit (exceeding a current limit value), which leads to a magnetic triggering, as set out in the introduction. Until now, it has not been possible to identify the reason for the triggering. The present application solves this problem by evaluating the current rise. By implementing a current measuring device, which can be based on a shunt / (measuring) resistor or a (current) transformer, the current is sampled, for example by means of an analog-digital converter, and processed by a microcontroller of the control unit.

[0076] Figure 2 A line diagram is shown in which the time t is plotted on the horizontal X axis and the current over time on the vertical Y axis.

[0077] A first curve BMA is shown, which represents the current over time for a triggering by a bimetal BM, and a second curve MRA, which represents the current over time for a triggering by a magnetic trigger MR.

[0078] The rise of the second curve MRA is greater than the rise of the first curve BMA. By means of the evaluation of the current value, the comparison and the duration according to the present application, the respective triggering can be determined and displayed.

[0079] By means of the protective switching device according to the present application, the current course is continuously collected within a time window and continuously compared with a threshold value, if necessary, so that the type of triggering (bimetal, magnetic trigger) can be displayed.

[0080] This implementation can be realized by means of a method or computer program product, which is run, for example, in a microcontroller of the control device. The method can store, for example, the current current value and compare it within a time window or within a time interval. If the respective threshold value is exceeded, a corresponding display is made.

[0081] Furthermore, a manual triggering of the protective switching device can also be collected and displayed. A distinction can be made between a thermal triggering, a magnetic triggering and possibly a manual triggering by means of the control unit, for example a method / computer program product in a microcontroller.

[0082] Based on the recognition of different triggering causes, it is possible to better predict the maintenance needs of the protective switching device. This information can be used to warn the customer about possible overload triggers in the system or to show the number of replacements to be made due to short-circuit triggers or thermal triggers. The electrical installer or electrician has valuable information about the triggering cause at the time of fault detection. The protective switching device can have a communication device, for example by means of wired and / or wireless communication, by means of which the determined triggering cause can be transmitted. For example to a superiorly arranged management system or monitoring system. The communication device can have a communication, for example ZigBee, Bluetooth, WLAN, Thread or other such like.

[0083] The transmission of the data can take place (almost) in real time. The data can be used to estimate the service life of the device. Also for triggering (effective) maintenance of the device.

[0084] While the application has been illustrated and described in more detail by way of example, the application is not restricted to the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the scope of the application.

Claims

1. A protective switching device for interrupting a low-voltage circuit when a current boundary value or a current-time boundary value is exceeded, comprising: - A housing having connectors (Ne, Na, Le, La) for conductors used in the low-voltage circuit. - An interrupt unit (UB) having contacts (KT) for interrupting low-voltage circuitry within the housing. - A bimetallic trigger (BM), which is connected to the interrupt unit (UB). - A magnetic trigger (MR), which is connected to the interrupt unit (UB). - A current measuring device (SH) for periodically determining the magnitude of the current in the low-voltage circuit. - A voltage measuring device for periodically determining the effective value of the voltage in the low-voltage circuit. - A display device for displaying information about the protective switch device. - A control unit (SE), which is connected to the current measuring device (SH), the display device, and the interrupt unit (UB). The protective switch device (SG) is designed to be, This allows for the following process: Firstly, the current magnitude determined in the first cycle is compared with a first current threshold. If the current exceeds the first current threshold, a first time window with a first duration begins. During this first duration, the effective value of the determined voltage is compared with a first voltage threshold. If the voltage is below the first voltage threshold, first information is displayed. On the other hand, the effective value of the current determined by the second cycle is compared with the second current threshold. If the current exceeds the second current threshold, the second time window begins. After the second time window begins and the first duration has elapsed, the effective value of the determined voltage is compared with the first voltage threshold. If the voltage is below the first voltage threshold, the second information is displayed.

2. The protective switch device according to claim 1, Its features are, The first cycle is within a 1-millisecond range, thus comparing the determined current magnitude with the first current threshold approximately every millisecond.

3. The protective switch device according to claim 1 or 2, Its features are, The first duration is within the range of 200 milliseconds, so that whenever the first current threshold is exceeded, a first time window with a duration of approximately 200 milliseconds begins.

4. The protective switch device according to claim 1 or 2, Its features are, The protective switch device has a rated current such that the first current threshold is a multiple of the rated current, specifically, the first current threshold is three or five times the rated current.

5. The protective switch device according to claim 1 or 2, Its features are, The protective switch device has a rated current such that the second current threshold is a multiple of the rated current, specifically such that the second current threshold is 1.15 times the rated current.

6. The protective switch device according to claim 1 or 2, Its features are, The second cycle is within a one-second range, thus comparing the determined effective value of the current with the second current threshold approximately every second.

7. The protective switch device according to claim 1 or 2, Its features are, The second time window begins when the current exceeds the second current threshold and ends when the current falls below the second current threshold.

8. The protective switch device according to claim 1 or 2, Its features are, The determined current magnitude is converted in parallel using two analog-to-digital converters. The first analog-to-digital converter has a 12-bit or 16-bit resolution and provides a current magnitude determined in the first cycle. The second analog-to-digital converter has a 24-bit resolution and provides a current magnitude determined in the second cycle.

9. The protective switch device according to claim 1 or 2, Its features are, The protective switch device has a rated voltage such that the first voltage threshold is a small fraction of the rated voltage, particularly such that the first voltage threshold is less than 0.4 times the rated voltage, and more particularly less than or equal to 0.35 times the rated voltage.

10. The protective switch device according to claim 1 or 2, Its features are, The protective switch device is: - Line protection switch, or - A device for identifying faulty arcs in series, or - Combined line protection switches and devices for identifying series fault arcs.

11. The protective switch device according to claim 1 or 2, Its features are, The current measuring device has a resistor (SH).

12. The protective switch device according to claim 1 or 2, Its features are, The control unit (SE) has a microprocessor.

13. A method for a low-voltage circuit, wherein the magnitudes of the current and voltage of the low-voltage circuit are periodically determined. Its features are, On one hand, the current magnitude determined in the first cycle is compared with a first current threshold. If the current exceeds the first current threshold, a time window with a first duration begins. During the first duration, the effective value of the determined voltage is compared with a first voltage threshold. If the voltage is below the first voltage threshold, first information is displayed. On the other hand, the effective value of the current determined by the second cycle is compared with the second current threshold. If the current exceeds the second current threshold, the second time window begins. After the second time window begins and the first duration has elapsed, the effective value of the determined voltage is compared with the first voltage threshold. If the voltage is below the first voltage threshold, the second information is displayed.

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