Circuit breaker and method

Abstract

The invention relates to a circuit breaker (SG) for protecting an electric low-voltage circuit for an alternating voltage, wherein the level of a differential current of conductors of the low-voltage circuit is ascertained, and if differential current thresholds or differential current time thresholds (DSG1) have been exceeded, a process for preventing the flow of current in the low-voltage circuit is initiated by means of a high-ohmic state of switching elements of an electronic interruption unit in the closed state of separating contacts with a subsequent present value of the differential current which falls below a differential current threshold.

Description

[0001] Description

[0002] Protective switching device and procedure

[0003] The invention relates to the technical field of a protective switching device for a low-voltage circuit with an electronic interruption unit according to the preamble of patent claim 1 and a method for a protective switching device for a low-voltage circuit with an electronic interruption unit.

[0004] Low voltage refers to voltages of up to 1000 volts AC or up to 1500 volts DC. Low voltage refers in particular to voltages greater than extra-low voltage, with values ​​of 50 volts AC or 120 volts DC.

[0005] The term low-voltage circuit, network or system refers to circuits with nominal or rated currents of up to 125 amperes, more specifically up to 63 amperes. The term low-voltage circuit particularly refers to circuits with nominal or rated currents of up to 50 amperes, 40 amperes, 32 amperes, 25 amperes, 16 amperes or 10 amperes. The current values ​​mentioned refer in particular to nominal, rated and / or breaking currents, i.e. the maximum current that is normally carried through the circuit or at which the electrical circuit is usually interrupted, for example by a protective device such as a protective switching device, circuit breaker or circuit breaker. The rated currents can be further staggered, from 0.5 A to 1 A, 2 A, 3 A, 4 A, 5 A, 6 A, 7 A, 8 A, 9 A, 10 A, etc. up to 16 A.

[0006] Circuit breakers are long-established overcurrent protection devices used in low-voltage electrical circuits. They protect cables from damage caused by overheating due to excessive current and / or short circuits. A circuit breaker can automatically disconnect the circuit in the event of an overload and / or short circuit. A circuit breaker is a non-self-resetting fuse element.

[0007] Unlike miniature circuit breakers, circuit breakers are designed for currents greater than 125 A, and in some cases even as low as 63 A. Miniature circuit breakers are therefore simpler and more delicate in design. Miniature circuit breakers typically have a mounting option for mounting on a so-called top-hat rail (support rail, DIN rail, TH35).

[0008] State-of-the-art circuit breakers are electromechanically constructed. They have a mechanical switching contact or shunt release in a housing to interrupt (trip) the electrical current. Typically, a bimetallic protective element or bimetallic element is used to trip (interrupt) the circuit in the event of a prolonged overcurrent (overcurrent protection) or thermal overload (overload protection). An electromagnetic release with a coil is used for brief tripping when an overcurrent limit is exceeded or in the event of a short circuit (short-circuit protection). One or more arc quenching chambers or devices for arc quenching are provided. Furthermore, connection elements for conductors of the electrical circuit to be protected.

[0009] Residual current circuit breakers for electrical circuits, particularly for low-voltage circuits or systems, are well known. Residual current circuit breakers are also known as residual current devices, or RCDs for short. Residual current circuit breakers determine the total current in an electrical circuit, which is normally zero, and interrupt the electrical circuit when a differential current value is exceeded, i.e. a total current that is not equal to zero and exceeds a certain (differential) current value or residual current value. Almost all previous residual current circuit breakers have a summation current transformer, the primary winding of which is formed by the conductors of the circuit and the secondary winding outputs the total current that is used directly or indirectly to interrupt the electrical circuit.

[0010] For this purpose, two or more conductors, usually the forward and return conductors or the line and neutral conductors in a single-phase alternating current system, all three line conductors or all three line conductors and the neutral conductor in a three-phase alternating current system, are passed through a current transformer, usually with a ring-shaped core made of ferromagnetic material. Only the differential current, i.e. a current that differs from the forward and return current, from the conductors is converted. The total current in an electrical circuit is usually zero. This allows fault currents to be detected.

[0011] If, for example, a current flows to earth on the energy sink or consumer side, this is referred to in this context as a fault current. A fault occurs, for example, when there is an electrical connection from a phase conductor of the electrical circuit to earth. For example, if a person touches the phase conductor. In this case, part of the electrical current does not flow back via the neutral conductor as usual, but via the person and the earth. This fault current can now be detected with the help of the summation current transformer, since the recorded sum of the incoming and returning current is not equal to zero. The circuit, e.g. at least one, some or all of the lines, is interrupted via a relay or a holding magnet release, for example with associated mechanics.Residual current circuit breakers for detecting alternating fault currents are generally known from the publication DE 44 32 643 A1.

[0012] The main function of residual current circuit breakers is to protect people from electrical currents (electric shock), as well as systems, machines or buildings from fire caused by electrical insulation faults.

[0013] If the residual current circuit breaker or its summation current transformer is designed in such a way that the secondary energy of the summation current transformer is sufficient to actuate a tripping unit or an interruption unit or a release, then such residual current circuit breakers are said to be mains voltage independent.

[0014] If auxiliary power is required or used for the tripping circuit, which is usually generated by a power supply provided in the residual current device, such residual current devices are called line-voltage-dependent. This means that line-voltage-dependent residual current devices contain a power supply to supply power to a residual current detector (line-voltage-independent devices do not). These power supplies are required, for example, to detect residual currents in DC voltage systems and mixed DC / AC systems, or in high-frequency circuits.

[0015] Protective switching devices with an electronic interruption unit are relatively new developments. They have a semiconductor-based electronic interruption unit. This means that the electrical current flow in the low-voltage circuit is conducted via semiconductor components or semiconductor switches, which interrupt the electrical current flow or can be made conductive. Protective switching devices with an electronic interruption unit also often have a mechanical isolating contact system, in particular with isolating properties in accordance with the relevant standards for low-voltage circuits. The contacts of the mechanical isolating contact system are connected in series to the electronic interruption unit, i.e. the current in the low-voltage circuit to be protected is conducted via both the mechanical isolating contact system and the electronic interruption unit.The present invention relates in particular to low-voltage alternating current circuits with an alternating voltage, typically with a time-dependent sinusoidal alternating voltage with frequency f. The time dependence of the instantaneous voltage value u(t) of the alternating voltage is described by the equation: u(t) = U * sin (2n * f * t). Where: u(t) = instantaneous voltage value at time t.

[0016] U = amplitude of the voltage

[0017] A harmonic alternating voltage can be represented by the rotation of a pointer whose length corresponds to the amplitude (U) of the voltage. The instantaneous deflection is the projection of the pointer onto a coordinate system. One oscillation period corresponds to one full rotation of the pointer, and its full angle is 2n (2Pi) or 360°. The angular frequency is the rate of change of the phase angle of this rotating pointer. The angular frequency of a harmonic oscillation is always 2n times its frequency, i.e.: w = 2n*f = 2n / T = angular frequency of the alternating voltage (T = period of the oscillation)

[0018] Often, the specification of the angular frequency (w) is preferred over the frequency (f), since many formulas of oscillation theory can be represented more compactly using the angular frequency due to the occurrence of trigonometric functions whose period is by definition 2n: u ( t ) = U * sin (wt)

[0019] In the case of circular frequencies that are not constant over time, the term instantaneous circular frequency is also used. For a sinusoidal, in particular temporally constant, alternating voltage, the time-dependent value from the angular velocity w and the time t corresponds to the time-dependent angle cp ( t ) , which is also referred to as the phase angle cp ( t ). This means that the phase angle cp ( t ) periodically passes through the range O...2n or 0°...360°. This means that the phase angle periodically assumes a value between 0 and 2n or 0° and 360° (cp = n* (0...2n) or cp = n* ( 0 °...360 ° ) , due to periodicity; in short: cp = O...2n or cp = 0°...360° ).

[0020] The instantaneous voltage value u(t) or instantaneous current value or instantaneous differential current value therefore means the instantaneous value of the voltage / current / differential current at time t, ie in the case of a sinusoidal (periodic) alternating voltage, the value of the voltage / current / differential current at the phase angle cp (cp = 0...2n or cp = 0°...360°, of the respective period).

[0021] The object of the present invention is to improve a protective switching device of the type mentioned above, in particular to ensure protection against fault currents caused by people while simultaneously reducing the exposure of potentially affected persons due to current-prevention measures of the protective switching device. Alternatively, to create a novel concept for such a protective switching device.

[0022] This object is achieved by a protective switching device having the features of patent claim 1 and by a method according to patent claim 7.

[0023] According to the invention, a protective switching device for protecting an electrical low-voltage circuit, in particular a low-voltage alternating current circuit, is provided, comprising:

[0024] - a housing with mains-side and load-side connections for conductors of the low-voltage circuit,

[0025] - a differential current sensor unit for determining the level of a differential current in the conductors of the low-voltage circuit, - a mechanical isolating contact unit which has a closed state of the contacts for a current flow in the low-voltage circuit or an open state of the contacts for a galvanic isolation in the low-voltage circuit that prevents the flow of current, the mechanical isolating contact unit can be operated and switched in particular by a mechanical handle, so that an opening of contacts to prevent a current flow or a closing of the contacts for a current flow in the low-voltage circuit can be switched (by the handle), thus (in particular) a galvanic isolation in the low-voltage circuit can be switched; in the case of a mechanical isolating contact unit, an opening of contacts is also referred to as being switched off and a closing of contacts is referred to as being switched on;

[0026] - an electronic interruption unit which is connected in series with the mechanical isolating contact unit on the circuit side and which, by means of semiconductor-based switching elements, has a high-resistance (in particular non-conductive) state of the switching elements to prevent a current flow or a low-resistance state of the switching elements to allow current to flow in the low-voltage circuit; in the case of an electronic interruption unit, a high-resistance (in particular non-conductive) state of the switching elements (to prevent a current flow) is also referred to as the switched-off state (process: switching off) and a low-resistance (conductive) state of the switching elements (to allow current to flow) is referred to as the switched-on state (process: switching on);

[0027] - a control unit which is connected to the differential current sensor unit, the mechanical isolating contact unit and the electronic interruption unit. According to the invention, the protective switching device, in particular the control unit, is designed such that when differential current limit values ​​or differential current time limit values ​​(i.e.if a differential current limit value is exceeded for a first period of time) an avoidance of a current flow in the low-voltage circuit is initiated by a high-impedance state of the switching elements of the electronic interruption unit when the isolating contacts are closed and the amount of the instantaneous value of the differential current subsequently falls below a differential current threshold value, in particular that the high-impedance state of the switching elements of the electronic interruption unit (when the isolating contacts are closed) is initiated at the next zero crossing of the differential current.

[0028] This has the particular advantage of providing a new way of preventing current flow in the low-voltage circuit when differential current limits or differential current time limits are exceeded. This avoidance does not occur immediately when the differential current limits or differential current time limits are exceeded, but only after the magnitude of the differential current has been reduced, especially at zero crossing (differential current equal to zero). In a low-voltage alternating current circuit, a faulty differential current (fault current) is also an alternating current. By switching off, for example, at or near zero crossing, ieIf the amount of a differential current falls below a differential current threshold, any repercussions for anyone who may be involved are avoided by immediate current avoidance, in particular by the electronic interruption unit, which can carry out very rapid current avoidance, for example in the (small) millisecond or microsecond range, because current avoidance is carried out at differential current levels that are at least almost reaction-free. This is based on the assumption that during current avoidance processes (switching processes) with small currents through a human body, current avoidance is almost reaction-free, i.e. ventricular fibrillation, for example, is avoided, which could potentially become more severe if the current is abruptly switched off at high currents. Appropriate evaluation and / orProcessing can be carried out using the instantaneous value of the differential current.

[0029] Further advantageous embodiments of the invention are specified in the subclaims and in the exemplary embodiment.

[0030] The mechanical handle is particularly advantageous because only the mechanical isolating contact unit can be operated. Switching the device on and off using the electronic interruption unit cannot be operated (directly) on the device.

[0031] In an advantageous embodiment of the invention, an effective value of the differential current is determined from the magnitude of the detected instantaneous differential current. The effective value of the differential current is compared with an (effective) differential current limit or (effective) differential current time limit, and if this limit is exceeded, the current flow in the low-voltage circuit is prevented, as proposed.

[0032] This has the particular advantage that an evaluation is carried out with regard to an effective residual current time limit value which corresponds to a classic evaluation as used today in residual current circuit breakers according to the state of the art.

[0033] The effective value of the differential current can be advantageously used to evaluate the effective residual current time limit. For example, by determining the RMS value (root mean square) of the differential current. If the corresponding standard (residual current circuit breaker) differential current / time limit values ​​are exceeded, the current flow is prevented according to the invention.

[0034] In an advantageous embodiment of the invention, the instantaneous value of the differential current is used to determine when the differential current limit values ​​or differential current time limit values ​​are exceeded. This has the particular advantage that a faster or (virtually) immediate shutdown occurs when the value is exceeded, with current avoidance occurring immediately after an initial reduction in the differential current.

[0035] In an advantageous embodiment of the invention, a current sensor unit connected to the control unit is provided for determining the magnitude of a current in the conductors of the low-voltage circuit. The protective switching device, in particular the control unit, is designed such that, when first current limit values ​​or first current-time limit values ​​are exceeded, a current flow in the low-voltage circuit is prevented by a high-impedance state of the switching elements of the electronic interruption unit when the isolating contacts are closed.

[0036] This has the particular advantage that in addition to the differential current detection and the associated protective functions, overcurrent / short-circuit current detection is also provided, so that a combined residual current / line protection switching device is advantageously provided.

[0037] In an advantageous embodiment of the invention, after the current limit values ​​or current time limit values ​​are exceeded, the current flow is avoided within a first time period which is in particular less than 1 ms, more specifically less than 100 ps or 10 ps.

[0038] This has the particular advantage that it provides a new, very rapid current avoidance in the event of an overcurrent / short-circuit current detection (event).

[0039] In an advantageous embodiment of the invention, the mechanical isolating contact unit is assigned to the load-side connections.

[0040] This has the particular advantage that an architecture is provided which supports the behavior of the protective switching device according to the invention, since on the one hand the current flow is interrupted in the case of a high-impedance interruption unit, but the protective switching device continues to be supplied with energy even when the contacts are open, so that it can continue to work according to the invention.

[0041] According to the invention, a corresponding method for a protective switching device for a low-voltage circuit with electronic (semiconductor-based) switching elements with the same and further advantages is claimed.

[0042] According to the invention, a corresponding computer program product for a protective switching device is claimed. The computer program product comprises commands which, when the program is executed by a microcontroller, cause the microcontroller to implement or support the inventive embodiments or methods of the protective switching device.

[0043] In particular, when differential current limit values ​​or differential current time limit values ​​are exceeded, avoidance of a current flow in the low-voltage circuit is initiated by a high-impedance state of switching elements of an electronic interruption unit with the isolating contacts closed and the amount of the instantaneous value of the differential current subsequently falling below a differential current threshold value.

[0044] More specifically, the avoidance of current flow is initiated at the next zero crossing of the di f ference current.

[0045] The microcontroller is part of the protective switching device, in particular the control unit.

[0046] According to the invention, a corresponding computer-readable storage medium on which the computer program product is stored is claimed.

[0047] According to the invention, a corresponding data carrier signal which transmits the computer program product is claimed.

[0048] All embodiments, both in dependent form referring back to patent claim 1 or 7, and referring back only to individual features or combinations of features of patent claims, in particular also a reference of the pending arrangement claims to the independent method claim, bring about an improvement in a protective switching device, in particular an improvement in the safety for persons and provide a new concept for a protective switching device for differential currents (fault currents which are usually avoided by conventional residual current circuit breakers).

[0049] The described properties, features and advantages of this invention as well as the manner in which these are achieved will become clearer and more clearly understandable in connection with the following description of the embodiments, which are explained in more detail in connection with the drawing.

[0050] The drawing shows:

[0051] Figure 1 shows a first schematic diagram of a protective switching device,

[0052] Figure 2 shows a second schematic diagram of a protective switching device.

[0053] Figure 1 shows a representation of a protective switching device SG for protecting an electrical low-voltage circuit, in particular a low-voltage alternating current circuit, with a housing GEH, comprising:

[0054] - mains-side connections, which usually include a mains-side neutral conductor connection NG and a mains-side phase conductor connection LG,

[0055] - load-side connections, which usually include a load-side neutral conductor connection NL and a load-side phase conductor connection LL,

[0056] - the terminals are intended for the low-voltage circuit;

[0057] - an energy source is usually connected to the grid-side connections / the grid side GRID,

[0058] - a consumer is usually connected to the load-side connections / the load side LOAD;

[0059] - a (two-pole) mechanical isolating contact unit MK with load-side connection points APLL, APNL and line-side connection points APLG, APNG, whereby a load-side connection point APNL is provided for the neutral conductor, a load-side connection point APLL for the phase conductor, a line-side connection point APNG for the neutral conductor, and a line-side connection point APLG for the phase conductor. The load-side connection points APNL, APLL are connected to the load-side neutral and phase conductor connections NL, LL, so that the opening of contacts KKN, KKL to prevent current flow or the closing of contacts KKN, KKL to allow current flow in the low-voltage circuit can be switched.

[0060] - an electronic interruption unit EU, in particular a single-pole one (which in the case of a single-pole version is arranged in particular in the phase conductor), with a mains-side connection point EUG, which is electrically connected to the mains-side phase conductor connection LG, and a load-side connection point EUL, which is electrically connected or connected to the mains-side connection point APLG of the mechanical isolating contact unit MK, wherein the electronic interruption unit EU has or can be switched between a high-resistance state of the switching elements to prevent a current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit by means of semiconductor-based switching elements (not shown),

[0061] - a differential current sensor unit ZCT for determining the level of a (momentary) differential current in the conductors of the low-voltage circuit. In the example, the differential current sensor unit ZCT is arranged between the electronic interruption unit EU and the mechanical isolating contact unit MK. Alternatively, it can be provided (arranged) between the mechanical isolating contact unit MK and the load-side neutral and phase conductor connections NL, LL, or alternatively, it can be provided (arranged) between the electronic interruption unit EU and the mains-side connections NG, LG. The differential current sensor unit ZCT determines the level of the differential current in the conductors of the low-voltage circuit that are routed through the protective switching device (and are to be protected). In the example, for a single-phase alternating current circuit, this is the neutral conductor and the phase conductor.

[0062] The ZCT residual current sensor unit can be a conventional summation current transformer. The primary side of the summation current transformer is formed by the conductors of the low-voltage circuit (in the example, the phase conductor and neutral conductor). The secondary side of the summation current transformer is connected to the control unit SE.

[0063] - (optional) a current sensor unit SI, for determining the level of the current of the low-voltage circuit, which is arranged in particular in the current path of the phase conductor or phase conductor current path,

[0064] - (optional) a first voltage sensor unit SUA, for determining the voltage level of the low-voltage circuit, in particular the grid-side (GRID) voltage or the voltage in the area of ​​the grid-side connections LG, NG,

[0065] - (optional) a second voltage sensor unit SUB, to determine the level of voltage across the electronic interruption unit EU,

[0066] - a control unit SE, which is connected to the differential current sensor unit ZCT, (optional) to the current sensor unit SI, (optional) to the first voltage sensor unit SUA, (optional) to the second voltage sensor unit SUB, to the mechanical isolating contact unit MK and to the electronic interruption unit EU.

[0067] According to the invention, the protective switching device SG, in particular the control unit SE, is designed such that when differential current limit values ​​or differential current time limit values ​​DSG1 are exceeded, avoidance of a current flow in the low-voltage circuit is initiated by a high-impedance state of the switching elements of the electronic interruption unit when the isolating contacts are closed and the amount of the instantaneous value of the differential current subsequently falls below a differential current threshold value.

[0068] More specifically, if differential current limit values ​​or differential current time limit values ​​DSG1 are exceeded, avoidance of a current flow in the low-voltage circuit can be initiated by a high-impedance state of the switching elements of the electronic interruption unit with the isolating contacts closed at the next zero crossing of the differential current.

[0069] This means that as soon as an exceedance of the differential current limit values ​​or differential current time limit values ​​is detected (a corresponding fault current time limit is exceeded), the electronic interruption unit does not immediately become high-impedance. Instead, it waits until the differential current has sufficiently approached the next zero crossing and only then, when the instantaneous value of the differential current falls below a differential current threshold, does the electronic interruption unit become high-impedance. This means that electronic shutdown can be achieved close to or at the current zero crossing. This reduces or minimizes any reaction on people causing the differential current, which in turn reduces the risk of ventricular fibrillation, for example, because it is assumed that a rapid loss of current could cause the risk of ventricular fibrillation.

[0070] For example, the differential current can be evaluated using a digital algorithm in the control unit, for example, using a microcontroller contained in the control unit. As soon as the algorithm detects that differential current limits or differential current time limits have been exceeded (a fault current is detected), the system waits until the instantaneous value of the differential current falls below a differential current threshold. The electronic interruption unit then becomes high-impedance to prevent current flow in the low-voltage circuit. This can be implemented by a computer program product for a microcontroller or a control unit for a protective switching device.

[0071] The differential current threshold can, for example, be less than 20 mA, less than 10 mA or less than 5 mA.

[0072] The optionally provided current sensor unit SI, which is connected to the control unit SE and is used to determine the level of a current in the conductors of the low-voltage circuit, can design the protective switching device SG in such a way that when first current limit values ​​are exceeded (i.e. when the level of the current exceeds the (amount of) the first current limit value) or first current-time limit values ​​(i.e. the first current limit value is exceeded for a first period of time; i.e. when the level of the (amount of) the current exceeds the first current limit value for a first period of time), avoidance of a current flow in the low-voltage circuit is initiated by a high-resistance state of the switching elements of the electronic interruption unit when the isolating contacts are closed.

[0073] Specifically, the avoidance of the current flow can occur within a first time period which is in particular less than 1 ms, more specifically less than 100 ps or 10 ps.

[0074] In the example, the mechanical isolating contact unit MK is arranged on the load side, while the electronic interruption unit EU is arranged on the mains side according to the invention.

[0075] The grid side (GRID), containing the energy source, is normally energized. An electrical consumer is usually connected to the load side (LOAD).

[0076] This has the advantage that there are no other (especially live) parts or components between the contacts of the mechanical isolating contact unit / load-side connection points (APLL, APNL) of the mechanical isolating contact unit and the two load-side connections (LL, NL). This architecture and design ensures that, when the contacts KKL, KKN are open, there is never any voltage present at the load-side connections LL, NL. This increases the safety of the protective device.

[0077] In contrast, in other architectures where the mechanical isolating contact unit is located on the mains side, there are often (non-galvanically isolated) electronic units in front of the load-side connection.

[0078] The protective switching device can be designed in such a way that the voltage level across the electronic interruption unit can be determined. This means that the voltage level between the mains-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU can be determined or is determined. For this purpose, in the example according to Figure 1, a second voltage sensor unit SUB is provided which is connected to the control unit SE and determines the voltage level between the mains-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU. When the voltage is measured by the second voltage sensor unit SUB, the voltage across the series connection of the electronic interruption unit EU and the current sensor SI can alternatively be determined, as shown in Figure 1.The current sensor unit SI has a very low internal resistance so that the determination of the voltage level is not affected or is negligibly affected.

[0079] The protective switching device can be designed in such a way that a first voltage sensor unit SUA is provided, which determines the level of the voltage of the low-voltage circuit, in particular between the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG, as shown in Figure 1.

[0080] In the example shown in Figure 1, the electronic interruption unit EU is single-pole, in the example in the phase conductor. The mains-side connection point APNG for the neutral conductor of the mechanical isolating contact unit MK is connected to the mains-side neutral conductor connection NG of the housing GEH.

[0081] The protective switching device SG is advantageously designed in such a way that the contacts of the mechanical isolating contact unit MK can be opened but not closed by the control unit SE, which is indicated by an arrow from the control unit SE to the mechanical isolating contact unit MK.

[0082] The mechanical isolating contact unit MK can be operated by a mechanical handle HH on the protective switching device SG in order to manually open or close the contacts KKL, KKN. The mechanical handle HH indicates the switching state (open or closed) of the contacts of the mechanical isolating contact unit MK, in particular by means of a (purely) mechanical connection on the protective switching device. Furthermore, the contact position (or the position of the handle, closed or open) can be transmitted to the control unit SE. The contact position (or the position of the handle) can be determined, for example, using a sensor, such as a position sensor. The contact position or the switching state can be transmitted to the control unit SE. The position sensor can be part of the mechanical isolating contact unit MK. Alternatively, the position sensor can be a component in the electronic first part (EPART, Figure 2). Z .For example, a Hall sensor can be provided in the first electronic part (EPART) which detects and transmits the position of the contacts and / or the handle without contact.

[0083] The mechanical isolating contact unit is, in particular, a standard-compliant isolating contact unit for protective switching devices in installation technology, whereby it complies with the regulations for conventional miniature circuit breakers (MCBs) and residual current devices (RCDs). The mechanical isolating contact unit MK is advantageously designed such that (manual) closing of the contacts by the mechanical handle is only possible after an enable, in particular an enable signal. This is also indicated by the arrow from the control unit SE to the mechanical isolating contact unit MK.

[0084] This means that the contacts KKL, KKN of the mechanical isolating contact unit MK can only be closed by the handle HH when the release or release signal (from the control unit) is present. Without the release or release signal, the handle HH can be operated, but the contacts cannot be closed ("permanent slip").

[0085] The protective switching device SG has a power supply or power supply NT, for example, a switched-mode power supply. In particular, the power supply / power supply NT is provided for the control unit SE, which is indicated by a connection between the power supply / power supply NT and the control unit SE in Figure 1. The power supply / power supply NT is (on the other hand) connected to the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG. A fuse SS, in particular a safety fuse, or a switch Sch (Figure 2) can advantageously be provided in the connection to the mains-side neutral conductor connection NG (and / or phase conductor connection LG).

[0086] According to the invention, the power supply unit NT is normally constantly supplied with power, specifically from the mains-side connections. If necessary, it is protected by the fuse SS or can be switched off using the switch SCH. Advantageously, the switch Sch can be designed so that the switch can only be opened when the contacts are open. This increases the safety of the device, as the electronics (in particular the control unit) cannot be switched off when the contacts are closed. The fuse SS not only serves the purpose of protecting the power supply via the power supply unit NT, but is also intended, particularly in the case of a two-part design (see Figure 2), to protect the "electronic" first part EPART or its entire units (such as the control unit, electronic interruption unit, if applicable voltage sensor unit(s), differential current sensor unit, if applicable current sensor unit, if applicable).measuring impedance, etc.) .

[0087] A measuring impedance ZM can be connected to the mains-side neutral conductor connection NG via the fuse SS.

[0088] This advantageously allows the implementation of a three-pole electronic unit or an electronic first part EPART (Figure 2), for example, as a module having three connections to the low-voltage circuit: a neutral conductor connection and two phase conductor connections. The electronic first part EPART can have additional connections, in particular for control or measurement information, such as an enable signal, an opening signal OEF, positioning information (from the positioning unit POS), and / or a differential current signal (level of the differential current) from the differential current sensor unit ZCT.

[0089] The electronic unit or electronic first part EPART (Figure 2) comprises, for example, the electronic interruption unit EU, the control unit SE, the power supply NT (in particular including fuse SS), the current sensor unit ST, optionally the first voltage sensor unit SUA and / or optionally the second voltage sensor unit SUB.

[0090] With regard to the three connections to the low-voltage circuit of the first electronic part (EPART), this offers the advantage that only two phase conductor connections need to have a high current-carrying capacity (several amperes to carry the load current), and the neutral conductor connection only needs to have a (comparatively) low current-carrying capacity (e.g., less than 1 A, a few mA - depending on the power requirements of the control unit). This simplifies the design and increases the safety of the device, since in the event of a fault in the first electronic part (EPART), no large short-circuit current can flow through this connection.

[0091] The low-voltage circuit can be a three-phase alternating current circuit with a neutral conductor and three phase conductors. The protective switching device can be designed as a three-phase variant for this purpose and, for example, have additional mains-side and load-side phase conductor connections. Electronic interruption units according to the invention and contacts of the mechanical isolating contact unit are provided in a similar manner between the additional mains-side and load-side phase conductor connections. The respective conductors (three phase conductors LI, L2, L3, neutral conductor N) are routed through the differential current unit ZCT.

[0092] Likewise, additional current sensor units / voltage sensor units can be provided.

[0093] High-resistance refers to a state in which only a negligible current flows. In particular, high-resistance refers to resistance values ​​greater than 1 kiloohm, preferably greater than 10 kiloohms, 100 kiloohms, 1 megaohm, 10 megaohms, 100 megaohms, 1 gigaohm, or greater.

[0094] Low-resistance refers to a condition in which the current value specified on the protective device could flow. Specifically, low-resistance refers to resistance values ​​that are less than 10 ohms, preferably less than 1 ohm, 100 milliohms, 10 milliohms, 1 milliohm, or less.

[0095] Figure 2 shows a representation similar to Figure 1, with the difference that the protective switching device is constructed in two parts. It contains an electronic first part (EPART), for example, on a printed circuit board.

[0096] The first part EPART can comprise the control unit SE, the first voltage sensor unit SUA, the second voltage sensor unit SUB, the current sensor unit SI, the electronic interruption unit EU, and the power supply NT. Furthermore, the first part can comprise the fuse SS, a switch SCH, the measuring impedance ZM, a temperature sensor TEM (particularly for the electronic interruption unit EU), a communication unit COM, a display unit AE, and, as a variant, a position sensor unit POS.

[0097] The electronic first part EPART has only three connections to the low-voltage circuit:

[0098] - the mains-side phase conductor connection LG as the first connection,

[0099] - a (second) connection for or to the mains-side phase conductor connection point APLG of the mechanical isolating contact unit MK,

[0100] - a third terminal EN for a connection to the mains-side neutral conductor terminal NG .

[0101] The two connections: to the mains-side phase conductor connection LG and for the or to the mains-side phase conductor connection point APLG have a high current carrying capacity, e.g. several amperes, greater than 10A / 16 A - depending on the nominal current or rated current of the low-voltage circuit, in particular in order to carry the load current even in the event of a short circuit or overload.

[0102] The third connection EN for the connection to the mains-side neutral conductor connection NG has a (comparatively) low current carrying capacity, e.g. less than 1A, a few mA - depending on the energy requirements of the supplied units, especially in the first electronic part EPART. The third connection EN is designed with a low current carrying capacity in order to supply the power supply with power and to measure the voltage between the phase conductor and neutral conductor of the low-voltage circuit. In particular, this third connection EN is protected by a fuse SS. This can be implemented using a melting fuse or a cost-effective conductor track fuse (thin conductor track with appropriate length and thickness on the circuit board).

[0103] This has the particular advantage that the lower current carrying capacity in this line or at this third connection EN improves the safety against a short circuit occurring within the first electronic part (EPART) (or (electronic) units), e.g. on the side of the power supply unit or the control unit.

[0104] This means that in the event of a failure or malfunction of an electronic component of a unit within the first electronic part EPART, no dangerous short-circuit current can occur (fed from the mains-side terminals LG, NG) that could lead to a fire in the device.

[0105] This short-circuit current is fed from the mains via the mains-side connections. An upstream circuit breaker often has a much higher tripping current and feeds parallel low-voltage circuits. If a fault occurs in the circuit breaker (the circuit breaker of the protected low-voltage circuit) and the upstream circuit breaker trips, fault-free parallel circuits would also be switched off, which is thus avoided.

[0106] The communication unit COM can, in particular, be a wireless communication unit. The communication unit COM can have a (manual) input unit on the protective switching device for (manual) acknowledgment of states on the protective switching device SG. Acknowledgment can also be performed (wired and / or wirelessly) via the communication unit COM.

[0107] Furthermore, the communication unit COM can have a display function. A separate display unit can also be provided.

[0108] The protective switching device contains a second part MPART , in particular a mechanical one. The second part MPART can have the mechanical isolating contact unit MK, the handle HH, and a release unit EG . Furthermore, the second part can have a positioning unit POS , for reporting the position of the contacts of the mechanical isolating contact unit MK to the control unit, as well as the (neutral conductor) connection(s). The second part MPART has the differential current sensor unit ZCT , such as a summation current transformer, as is known, for example, from classic residual current circuit breakers.

[0109] Further, unspecified, units may be provided.

[0110] By dividing it into two parts, a compact protective switching device according to the invention can be advantageously realized with a simplified construction.

[0111] The release unit / release function FG enables the actuation of the contacts of the mechanical isolating contact unit by the handle HH when an enable release signal is present. This means that the contacts KKL, KKN can only be closed by the handle when the enable release signal (from the SE control unit) is present. Otherwise, closing is not possible (continuous slipping of the HH handle). The contacts remain in the open position / switching state. Furthermore, the release unit FG can cause the contacts to open (second function of the release unit FG) when an opening signal OEF (from the SE control unit) is present. The release unit / release function FG then acts as a tripping unit to open the contacts of the mechanical isolating contact unit MK.

[0112] The protective switching device SG, in particular the control unit SE, is further configured such that, when current limits or current-time limits are exceeded (i.e., when a current limit is exceeded for a specific period of time), the prevention of current flow in the low-voltage circuit is initiated, in particular to prevent a short-circuit current. This is achieved, in particular, by the electronic interruption unit EU switching from the low-resistance state to the high-resistance state.

[0113] The initiation of the avoidance of a current flow in the low-voltage circuit takes place, for example, by a first interruption signal that is sent from the control unit SE to the electronic interruption unit EU. The mechanical isolating contact unit MK can alternatively or additionally be controlled by the control unit SE in order to initiate the avoidance of a current flow in the low-voltage circuit if current limit values ​​or current-time limit values ​​are exceeded. In particular, a galvanic isolation is brought about here if necessary. The initiation of the avoidance of a current flow or a galvanic interruption of the low-voltage circuit if necessary takes place, for example, by a second interruption signal that is sent from the control unit SE to the mechanical isolating contact system MK.

[0114] The electronic interruption unit EU can comprise semiconductor components such as bipolar transistors, field-effect transistors (FETs), insulated-gate bipolar transistors (IGBTs), metal-oxide-layer field-effect transistors (MOSFETs), or other (self-commutated) power semiconductors. IGBTs and MOSFETs, in particular, are particularly well-suited for the protective switching device according to the invention due to their low forward resistances, high junction resistances, and good switching behavior.

[0115] The term "mechanical isolating contact unit MK" refers in particular to a (standard-compliant) isolating function implemented by the isolating contact unit MK. The isolating function includes the following points: - minimum air gap according to the standard (voltage-dependent) (minimum distance between contacts), - contact position indicator of the contacts of the mechanical isolating contact system, - opening of the mechanical isolating contact system is always possible (no blocking of the isolating contact system - especially by the handle, trip-free mechanism).

[0116] For the purposes of the invention, the DIN EN 60947 and IEC 60947 standards are relevant for the isolating function and its properties, and are incorporated herein by reference. The protective switching device can be designed as a DIN rail-mountable protective switching device SG with a width of, for example, 1 TE, 1.5 TE or 2 TE with two-pole connections (L, N). In electrical installation and switchgear cabinet construction, the width of built-in devices such as protective switching devices, miniature circuit breakers, residual current circuit breakers, etc. is specified in modular units, or TE for short. The width of a modular unit is approximately 18 mm. According to DIN 43880: 1988-12, the installation width of the devices should be between 17.5 and 18.0 mm, or be calculated by multiplying this dimension by 0.5 or an integer multiple thereof, i.e.: k x 0.5 x 18 mm or k x 0.5 x 17.5 mm (with k = 1, 2, 3, ...).For example, a single-pole circuit breaker, according to the state of the art, has a width of 1 module. The components of electrical distribution boards are matched to the module sizes, e.g., the width of mounting rails / top-hat rails, in accordance with DIN 43871 "Small distribution boards for built-in devices up to 63 A."

[0117] According to the invention, the protective switching device SG, in particular the control unit SE, can be designed such that, when effective residual current time limits are exceeded, a current flow in the low-voltage circuit is prevented, e.g., by a high-impedance state of the switching elements of the electronic interruption unit when the isolating contacts are closed. The effective residual current time limits can be limit values ​​according to relevant standards, such as DIN EN 61008-1. For example, 30 mA and a time of 300 ms, 150 ms, 40 ms, or 20 ms for personal protection in Europe in a 230 volt low-voltage circuit; 6 mA and the same time for personal protection in North America; 300 mA and the same time for fire protection (230 volt effective value).

[0118] An instantaneous residual current limit value can be higher in magnitude than the effective residual current time limit value. In particular, the instantaneous residual current limit value is a value in the range of 2 to 100 times the effective residual current time limit value.

[0119] The instantaneous differential current limit can, for example, be a value of 200 mA.

[0120] Furthermore, the protective switching device can be designed such that, for example, upon reaching a differential current value of 200 mA, the current flow is immediately prevented. Thus, in the case of a high differential current, shutdown can occur immediately rather than with a delay (in particular, to increase personal safety (at the risk of possible ventricular fibrillation, but possibly without fatal consequences, since the energy input is reduced)).

[0121] The protective switching device SG, in particular the control unit SE, can have a microcontroller (= microprocessor) on which a computer program product runs, comprising instructions which, when the program is executed by the microcontroller, cause the microcontroller to carry out a tripping behavior (as described above and below) for a protective switching device.

[0122] The computer program product may advantageously be stored on a computer-readable storage medium; such as a USB stick, CD-ROM, etc.; in order to enable, for example, an upgrade to an enhanced version.

[0123] Alternatively, the computer program product can also advantageously be transmitted by a data carrier signal.

[0124] The SE control unit can:

[0125] * be implemented with a digital circuit, e.g. with a (further) microprocessor; the (further) microprocessor may also contain an analog part;

[0126] * be implemented with a digital circuit with analog circuit parts.

[0127] Although the invention has been illustrated and described in detail by the embodiment, the invention is not limited by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the scope of the invention.

Claims

Patent claims 1 . Protective switching device (SG) for protecting an electrical low-voltage circuit for alternating voltage, comprising: - a housing with mains-side and load-side connections (LG, NG, LL, NL) for conductors of the low-voltage circuit, - a differential current sensor unit (ZCT) for determining the level of a differential current of the conductors of the low-voltage circuit, - a mechanical isolating contact unit (MK) which has a closed state of the contacts for a current flow in the low-voltage circuit or an open state of the contacts for a current flow-preventing galvanic separation in the low-voltage circuit, - an electronic interruption unit (EU) which is connected in series with the mechanical isolating contact unit (MK) on the circuit side and which, by means of semiconductor-based switching elements, has a high-resistance state of the switching elements to prevent a current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit, - a control unit (SE) which is connected to the differential current sensor unit (ZCT), the mechanical isolating contact unit (MK) and the electronic interruption unit (EU), characterized in that the protective switching device (SG), in particular the control unit (SE), is designed in such a way that when differential current limit values ​​or differential current time limit values ​​(DSG1) are exceeded, avoidance of a current flow in the low-voltage circuit is initiated by a high-impedance state of the switching elements of the electronic interruption unit when the isolating contacts are closed and the amount of the instantaneous value of the differential current subsequently falls below a differential current threshold value.

2. Protective switching device (SG) according to claim 1, characterized in that when differential current limit values ​​or differential current time limit values ​​(DSG1) are exceeded, avoidance of a current flow in the low-voltage circuit is initiated by a high-impedance state of the switching elements of the electronic interruption unit with the isolating contacts closed in the next zero crossing of the differential current.

3. Protective switching device (SG) according to claim 1 or 2, characterized in that the effective value of the differential current is used with regard to the exceedance of the differential current limit values ​​or differential current time limit values ​​(DSG1).

4. Protective switching device (SG) according to claim 1 or 2, characterized in that the instantaneous value of the differential current is used with regard to the exceedance of the differential current limit values ​​or differential current time limit values ​​(DSG1).

5. Protective switching device (SG) according to one of the preceding claims, characterized in that a current sensor unit (SI) connected to the control unit (SE) is provided for determining the level of a current of a conductor, in particular a phase conductor, of the low-voltage circuit, that the protective switching device (SG), in particular the control unit (SE), is designed in such a way that when current limit values ​​or current-time limit values ​​are exceeded, avoidance of a current flow in the low-voltage circuit is initiated by a high-resistance state of the switching elements of the electronic interruption unit when the isolating contacts are closed, wherein after exceeding the current limit values ​​or current-time limit values, avoidance of the current flow within a first time period which is in particular less than 1 ms, more specifically less than 100 ps or 10 ps.

6. Protective switching device (SG) according to one of the preceding claims, characterized in that the mechanical isolating contact unit (MK) is assigned to the load-side terminals (LL, NL).

7. Method for a protective switching device (SG) for protecting an electrical low-voltage circuit for alternating voltage, in which the level of a differential current of conductors of the low-voltage circuit is determined and, if differential current limit values ​​or differential current time limit values ​​(DSG1) are exceeded, avoidance of a current flow in the low-voltage circuit is initiated by a high-impedance state of switching elements of an electronic interruption unit with the isolating contacts closed and subsequent undershoot of the amount of the instantaneous value of the differential current below a differential current threshold value.

8. Method according to claim 7, characterized in that when differential current limit values ​​or differential current time limit values ​​(DSG1) are exceeded, an avoidance of a current flow in the low-voltage circuit is initiated by a high-resistance state of switching elements of an electronic interruption unit with the isolating contacts closed in the next zero crossing of the differential current, 9. Method according to claim 7 or 8, characterized in that the effective value of the differential current is used with regard to the exceedance of the differential current limit values ​​or differential current time limit values ​​(DSG1).

10. Method according to claim 7 or 8, characterized in that the instantaneous value of the differential current is used with regard to the exceedance of the differential current limit values ​​or differential current time limit values ​​(DSG1).

11. A computer program product comprising instructions which, when the program is executed by a microcontroller, cause the microcontroller to support or carry out the method according to one of claims 7 to 10.

12. Computer-readable storage medium on which the computer program product according to claim 11 is stored.

13. Data carrier signal which the computer program product according to Patent claim 11 is transferred.

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