Circuit breaker and method

Abstract

The invention relates to a circuit breaker (SG) for protecting a low-voltage circuit for alternating voltage, wherein the current level of a differential current of conductors of the low-voltage circuit is ascertained and wherein: - if first differential current time thresholds (DSG1) are exceeded, current flow in the low-voltage circuit is prevented in that a) switching elements of an electronic breaker unit are in a high-ohmic state with break contacts being in the closed state, or b) in that the break contacts are open; - if a second differential current threshold (DSG2) is exceeded, current flow in the low-voltage circuit is prevented in that the switch elements of the electronic breaker unit are in a high-ohmic state with the break contacts being in the closed state.

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) 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, there are 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 persons while simultaneously ensuring the reliability of supply and availability of electrical systems, i.e., to achieve immunity against technically induced (fault) currents that would lead to false tripping of the protective switching device. This means, on the one hand, ensuring personal protection and, on the other hand, improving the reliability of supply of a low-voltage circuit. 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, as well as by a method according to patent claim 12.

[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 of the conductors of the low-voltage circuit, in particular for recording the time course of the instantaneous value of the differential current

[0026] - 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;

[0027] - 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);

[0028] - 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 first differential current time limit values ​​are exceeded (in particular in terms of amount), avoidance of a current flow in the low-voltage circuit is initiated a) by a high-impedance state of the switching elements of the electronic interruption unit when the isolating contacts are closed or b) by an open state of the isolating contacts.

[0029] Furthermore, if a second differential current limit value is exceeded, the 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.

[0030] This has the particular advantage that two evaluations are provided for the recorded differential current.

[0031] Firstly, with regard to a first residual current time limit, which corresponds to a classic evaluation as used today in state-of-the-art residual current circuit breakers. However, the result of the evaluation can be two possible ways of avoiding a current flow. Firstly, a classic way of avoiding a current flow in the low-voltage circuit by keeping the isolating contacts open, i.e., galvanic isolation. Secondly, a novel way of avoiding a current flow by keeping the switching elements of the electronic interruption unit in a high-impedance state when the isolating contacts are closed.

[0032] The effective value of the residual current can be advantageously used to evaluate the first residual current time limit. For example, by determining the RMS (root mean square) value of the residual current. If the corresponding standard (residual current circuit breaker) current / time limit values ​​are exceeded, one of the two aforementioned current flow prevention measures is implemented.

[0033] On the other hand, a parallel evaluation of a second differential current limit value, advantageously using the instantaneous value of the differential current, so that an immediate shutdown when the amount is exceeded "immediately" initiates a high-resistance state of the switching elements of the electronic interruption unit when the isolating contacts are closed.

[0034] Advantageously, if the second differential current limit is exceeded, the current flow in the low-voltage circuit is prevented by a high-impedance state of the switching elements of the electronic interruption unit within a first break time. The first break time is in particular less than 20 ms, more specifically less than 15 ms, 10 ms, 5 ms, 1 ms, 500 ps, ​​or 100 ps.

[0035] Advantageously, after the current flow in the low-voltage circuit is avoided, caused by the second differential current limit being exceeded, the switching elements of the electronic interruption unit become low-resistance.

[0036] This has the particular advantage that the system is automatically switched back on, thus ensuring high energy supply availability.

[0037] The low-impedance switching occurs particularly when the instantaneous value of the alternating voltage (applied to the protective switching device) is less than a first voltage limit. The first voltage limit is, in particular, less than 10 volts or less than 5 volts. More specifically, the switching elements of the electronic interruption unit can become low-impedance when the alternating voltage passes through zero. This means that the protective switching device switches to the standby state and, for example, automatically returns to the on state at the next voltage crossing through zero.

[0038] This also has the particular advantage that after a faulty differential current event, for example caused by a person touching a (phase) conductor (critical event) or by a technically caused leakage current (not critical for people, i.e. non-critical event) (for example by switched capacitors), an immediate 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.

[0039] After preventing current flow by maintaining a high-resistance state of the switching elements of the electronic interruption unit and closing the contacts due to the second differential current limit values, a low-resistance state is established, allowing further testing for the presence of faulty differential current events. This allows critical events to be distinguished from non-critical events, while providing maximum power supply reliability in the circuit, thus ensuring both personal protection and system availability.

[0040] Thus, the status at the load-side terminals can be further monitored for the presence of differential current limits or differential current time limits. If the status changes, a further action can advantageously be taken, for example, according to the further advantageous embodiments of the invention.

[0041] A completely new protection concept and operating concept of a (FI) protective switching device is presented.

[0042] Further advantageous embodiments of the invention are specified in the subclaims and in the exemplary embodiment.

[0043] The mechanical handle is particularly advantageous because only the mechanical isolating contact unit can be operated. Switching on and off using the electronic interruption unit cannot be operated (directly) on the device.

[0044] In an advantageous embodiment of the invention, after the resistance has become low, a renewed exceedance of the second differential current limit is detected. This is followed by a high resistance, followed by a low resistance. If the second differential current limit is exceeded again (with high resistance and low resistance), this is only carried out until a first number of exceedances has occurred.

[0045] The electronic interrupt unit then remains in a high-impedance state. This can continue until a further time limit is exceeded. Alternatively, or additionally, this state can be communicated via a communication unit.

[0046] Alternatively or additionally, the contacts of the mechanical isolating contact unit can be opened.

[0047] This has the particular advantage of providing a concept for a robust protective switching device that ensures high availability of the power supply.

[0048] In an advantageous embodiment of the invention, the protective switching device is designed such that the second differential current limit is higher in magnitude than a first differential current limit or the first differential current time limit (the differential current component). In particular, the second differential current limit is a value in the range of 2 to 100 times the first differential current limit or first differential current time limit.

[0049] This has the particular advantage that the immediate shutdown is only triggered when an instantaneous residual current value occurs that is always greater than the permanently permissible residual current. In addition, the adjustable second residual current limit allows the limit or threshold to be adapted to the given operating situation and the existing operational events or faults resulting in residual currents.

[0050] In an advantageous embodiment of the invention, a voltage sensor unit connected to the control unit is provided for determining the voltage level of the conductors of the low-voltage circuit, in particular instantaneous voltage values. The protective switching device is designed such that, after the current flow in the low-voltage circuit caused by the second differential current limit being exceeded, is prevented, the switching elements of the electronic interruption unit become low-resistance, wherein the low-resistance occurs in particular when the instantaneous value of the alternating voltage is less than a first voltage limit.

[0051] The first voltage limit is, for example, less than 20 volts, less than 10 volts, or less than 5 volts. In particular, the switching elements of the electronic interruption unit become low-impedance when the alternating voltage passes zero.

[0052] 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.

[0053] 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.

[0054] In an advantageous embodiment of the invention, the mechanical isolating contact unit is assigned to the load-side connections.

[0055] This has the particular advantage of providing an architecture that supports the inventive behavior of the protective switching device. Since, on the one hand, the current flow is interrupted with a high-impedance interruption unit, the protective switching device continues to be supplied with energy even when the contacts are open, so that operation according to the invention can continue. 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 other advantages is claimed.

[0056] 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. In particular,

[0057] - that when the first differential current time limit values ​​are exceeded, the avoidance of a current flow in the low-voltage circuit is initiated a) by a high-resistance state of the switching elements of the electronic interruption unit when the isolating contacts are closed or b) by an open state of the isolating contacts;

[0058] - that when a second differential current limit value is exceeded, the 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.

[0059] The microcontroller is part of the protective switching device, in particular the control unit.

[0060] According to the invention, a corresponding computer-readable storage medium on which the computer program product is stored is claimed.

[0061] According to the invention, a corresponding data carrier signal which transmits the computer program product is claimed.

[0062] All embodiments, both in dependent form referring back to patent claim 1 or 11, and referring back only to individual features or combinations of features of patent claims, in particular also a reference of the dependent 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 as well as the security of supply in low-voltage circuits and provide a new safe concept for a protective switching device.

[0063] 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.

[0064] The drawing shows:

[0065] Figure 1 shows a first schematic diagram of a protective switching device,

[0066] Figure 2 shows a second schematic diagram of a protective switching device

[0067] Figure 3 shows a first representation of a switching behavior,

[0068] Figure 4 shows a second representation of a switching behavior,

[0069] Figure 5 shows a representation of a functional sequence.

[0070] 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:

[0071] - mains-side connections, which usually include a mains-side neutral conductor connection NG and a mains-side phase conductor connection LG,

[0072] - load-side connections, which usually comprise a load-side neutral conductor connection NL and a load-side phase conductor connection LL, - the connections are intended for the low-voltage circuit;

[0073] - an energy source is usually connected to the grid-side connections / the grid side,

[0074] - a consumer is usually connected to the load-side connections / the load side Load;

[0075] - 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.

[0076] - 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),

[0077] - a differential current sensor unit ZCT, for determining the level of a differential current (in particular the time course of the instantaneous value of the differential current) of the conductors of the low-voltage circuit, the differential current sensor unit ZCT is arranged in the example between the electronic interruption unit EU and the mechanical isolating contact unit MK, it can alternatively be provided (arranged) between the mechanical isolating contact unit MK and the load-side neutral and phase conductor connections NL, LL, or alternatively 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 of the conductors of the low-voltage circuit that are led through the protective switching device (to be protected). In the example for a single-phase alternating current circuit, the neutral conductor and the phase conductor.

[0078] 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.

[0079] - (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,

[0080] - a control unit SE, which is connected to the differential current sensor unit ZCT, (optionally) to the current sensor unit SI, to the mechanical isolating contact unit MK and to the electronic interruption unit EU.

[0081] According to the invention, the protective switching device SG, in particular the control unit SE, is designed such that

[0082] - that when the first differential current time limit values ​​DSG1 are exceeded (ie a differential current limit value is exceeded for a first period of time; ie when the level of the differential current exceeds the first differential current limit value for a first period of time), avoidance of a current flow in the low-voltage circuit is initiated a) by a high-resistance state of the switching elements of the electronic interruption unit when the isolating contacts are closed or b) by an open state of the isolating contacts.

[0083] (One of the two variants can be implemented. Alternatively, both variants can be implemented and a user can configure or select an avoidance measure in advance.) For this purpose, for example, the effective value of the residual current can be used to determine when the first residual current time limit values ​​DSG1 are exceeded. A time-based average is already calculated by calculating the effective value.

[0084] According to the invention, the protective switching device, in particular the control unit SE, is further designed such that

[0085] - that when a second differential current limit value DSG2 is exceeded, the 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.

[0086] For this purpose, the instantaneous value of the differential current is advantageously used with regard to the exceedance of the second differential current limit value DSG2.

[0087] Thus, if the second differential current limit DSG2 is exceeded, the current flow in the low-voltage circuit can be prevented by a high-impedance state of the switching elements of the electronic interruption unit within a first shutdown time, which is in particular less than 20 ms, more specifically less than 15 ms, 10 ms, 5 ms, 1 ms, 500 ps, ​​or 100 ps. Thus, a quasi-immediate shutdown is realized.

[0088] 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.

[0089] 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.

[0090] The grid side (GRID), containing the energy source, is normally energized. An electrical consumer is usually connected to the load side (LOAD).

[0091] 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.

[0092] 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.

[0093] The protective switching device can be designed such that the voltage level across the electronic interruption unit can be determined. This means that the level of a first voltage 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.

[0094] For this purpose, in the example according to Figure 1, a first voltage sensor unit SUI is provided which is connected to the control unit SE and which determines the level of the voltage between the network-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU.

[0095] When measuring the voltage by the first voltage sensor unit SUI, the voltage across the series circuit 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.

[0096] The protective switching device can be designed in such a way that a second voltage sensor unit SU2 is provided, which determines the level of the voltage between the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG.

[0097] The first voltage sensor unit can also be replaced by using two voltage measurements (before the electronic interruption unit and after the electronic interruption unit). The voltage across the electronic interruption unit is determined by forming a difference.

[0098] For example, a second voltage sensor unit SU2 can be provided which is connected to the control unit SE and determines the level of a second voltage between the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG. Furthermore, a third voltage sensor unit SU3 (not shown) which is connected to the control unit can be provided and determines the level of a third voltage between the mains-side neutral conductor connection NG and the load-side connection point EUL of the electronic interruption unit EU. The protective switching device is designed in such a way that the level of a first voltage between the mains-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU is determined from the difference between the second and third voltage. A measuring impedance ZM can be connected between the mains-side connection points APLG, APNG of the mechanical isolating contact unit MK.The measuring impedance ZM can, for example, be an electrical resistor and / or capacitor. The measuring impedance can also be an inductance. In particular, the measuring impedance can be a series or parallel circuit of a resistor and / or capacitor and / or inductance.

[0099] 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.

[0100] 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.

[0101] The mechanical isolating contact unit MK can be operated by a mechanical handle HH on the protective switching device SG 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 through a (purely) mechanical connection, on the protective switching device.

[0102] 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, for example, be determined 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). For example, a Hall sensor can be provided in the electronic first part (EPART), which detects and transmits the position of the contacts and / or the handle without contact.

[0103] 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.

[0104] 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").

[0105] 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).

[0106] According to the invention, the NT power supply is normally continuously supplied with power, specifically from the mains-side connections. It is protected by the SS fuse if necessary or can be switched off using the SCH switch. Advantageously, the SCH switch can be designed so that it can only be opened when the contacts are open. This increases the safety of the device, as the electronics (especially the control unit) cannot be switched off when the contacts are closed.

[0107] The purpose of the fuse SS is not only to protect the power supply via the power supply unit NT, but also, particularly in the case of a two-part structure (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.).

[0108] Alternatively, the measuring impedance ZM can be connected to the mains-side neutral conductor connection NG via the fuse SS. This advantageously allows a three-pole electronic unit or an electronic first part EPART (Figure 2) to be implemented, for example as a module that has 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, a position information (from the positioning unit POS), and / or a differential current signal (level of the differential current) from the differential current sensor unit ZCT.

[0109] 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 SUI and / or optionally the second voltage sensor unit SU2.

[0110] 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.

[0111] 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.

[0112] Likewise, current sensor units and voltage detection (e.g. by first voltage sensor units) can be provided.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] The first part EPART can comprise the control unit SE, the first voltage sensor unit SUI, the second voltage sensor unit SU2, the current sensor unit ST, 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.

[0117] The electronic first part EPART has only three connections to the low-voltage circuit:

[0118] - the mains-side phase conductor connection LG as the first connection,

[0119] - a (second) connection for or to the mains-side phase conductor connection point APLG of the mechanical isolating contact unit MK,

[0120] - a third terminal EN for a connection to the mains-side neutral conductor terminal NG .

[0121] 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.

[0122] 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 units supplied, 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 unit 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 the appropriate length and thickness on the circuit board). This has the particular advantage that the lower current carrying capacity in this cable or at this third connection EN ensures safety against a short circuit within the first electronic part (EPART) (or(electronic) units), e.g. on the power supply or control unit side, is improved.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] Furthermore, the communication unit COM can have a display function. A separate display unit can also be provided.

[0127] 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.

[0128] Further, unspecified, units may be provided.

[0129] By dividing it into two parts, a compact protective switching device according to the invention can be advantageously realized with a simplified construction.

[0130] The release unit / release function EG 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 control unit SE) is present. Otherwise, closing is not possible (continuous slipping of the handle HH). 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 control unit SE) is present. The release unit / release function FG then acts as a trigger unit to open the contacts of the mechanical isolating contact unit MK.

[0131] 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.

[0132] The initiation of the prevention of a current flow in the low-voltage circuit is carried out, for example, by a first interruption signal that is sent from the control unit SE to the electronic interruption unit EU.

[0133] The mechanical isolating contact unit MK can be controlled alternatively or additionally by the control unit SE in order to initiate the prevention of current flow in the low-voltage circuit when current limit values ​​or current-time limit values ​​are exceeded. In particular, galvanic isolation is brought about if necessary. The initiation of the prevention of current flow or, if necessary, a galvanic interruption of the low-voltage circuit is initiated, for example, by a second interruption signal that is sent from the control unit SE to the mechanical isolating contact system MK.

[0134] 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.

[0135] The term mechanical isolating contact unit MK particularly refers 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 the 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 - in particular by the handle, trip-free mechanism). For the purposes of the invention, the DIN EN 60947 and IEC 60947 series of standards are relevant for the isolating function and its properties, and reference is made here to them.

[0136] 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 according to DIN 43871 "Small distribution boards for built-in devices up to 63 A," e.g.the width of mounting rails / top-hat rails.

[0137] According to the invention, the protective switching device SG, in particular the control unit SE, is designed such that when first residual current time limit values ​​are exceeded, avoidance of a current flow in the low-voltage circuit is initiated, e.g. by a high-impedance state of the switching elements of the electronic interruption unit when the isolating contacts are closed. The first residual current time limit values ​​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 times for personal protection in North America, 300 mA and the same times for fire protection (230 volt rms value). The second residual current limit value DSG2 can be higher in magnitude than the first residual current time limit value DSG1.In particular, the second differential current limit value DSG2 is a value in the range of 2 to 100 times the first differential current time limit value DSG1.

[0138] The second differential current limit value DSG2 can, for example, be a value of 200 mA. This means, for example, that when a differential current value of 200 mA is reached, the current flow is (virtually) immediately prevented, ie, in particular, for less than 20 ms, more specifically for less than 15 ms, 10 ms, 5 ms, 1 ms, 500 ps, ​​or 100 ps.

[0139] After the current flow in the low-voltage circuit has been avoided due to the second differential current limit value DSG2 being exceeded, in one embodiment the switching elements of the electronic interruption unit become low-resistance. This low-resistance occurs in particular when the instantaneous value of the alternating voltage is less than a first voltage limit. The first voltage limit can be, for example, less than 10 volts or less than 5 volts. More specifically, the switching elements of the electronic interruption unit become low-resistance when the alternating voltage passes through zero. After the low-resistance state has been reached, a further exceedance of the second differential current limit value DSG2 is detected. Then a further high-resistance can occur, followed by a low-resistance state, until a first number (x) of exceedances has occurred.The first number of exceedances can, for example, be a value from the range of 2 or 3 to 20. If this first number (x) of exceedances is exceeded, the contacts of the mechanical isolating contact unit MK (for galvanic isolation) open, for example. Alternatively, the electronic interruption unit can also remain in the high-impedance state.

[0140] The respective states can be reported via the communication unit or displayed via the display unit AE. Figure 3 shows an example of the aforementioned behavior for a differential current if, caused for example by an earth fault current. Figure 3 shows in the upper graphic the level of or the temporal course of the differential current if over time t with the associated avoidance of a current flow OFF by an open state of the isolating contacts (galvanic isolation) or current flow ON (= current flow capability of the protective switching device) for a residual current circuit breaker according to the state of the art.

[0141] In the middle graph the height or the time course of the alternating voltage u G in the (for example 50 Hz) low-voltage circuit at the mains-side connections of the protective switching device over time t (in milliseconds ms).

[0142] In the lower graphic the height or the temporal course of the di f ference current if over time t with corresponding events with the following designation :

[0143] - OFF = Avoidance of current flow by an open state of the isolating contacts (galvanic isolation),

[0144] - STB = prevention of current flow by a high-resistance state of the electronic interruption unit EU,

[0145] - ON = current flow (= current flow capability of the protective switching device) for a protective switching device according to the invention.

[0146] In the upper graphic showing the behavior of a residual current circuit breaker according to the state of the art, an event causing a differential current, for example an earth fault current, occurs at a time t of approximately 5 ms. In the example, the level of the differential current is approximately 400 mA. In a conventional residual current circuit, the current flow is then avoided OFF (switched off) after approximately 17 ms (time approximately 22 ms). This means that from the event until the current flow is avoided, there is a current flow ON in the low-voltage circuit; only then is the current flow OFF avoided by open contacts. In the lower graphic showing the behavior of a protective switching device according to the invention, an event causing a differential current, for example an earth fault current, occurs at a time t of approximately 5 ms.In the example, the level of the differential current would theoretically also reach a value of around 400 mA. According to the invention, a current flow is (virtually) immediately avoided when the second differential current limit value DSG2, for example 200 mA, is reached, so that the possible differential current of, for example, 400 mA is not reached (limitation) within the switch-off time. The current flow is avoided by a high-impedance state of the switching elements of the electronic interruption unit STB. For example, by an instantaneous value evaluation of the level of the differential current by means of the control unit SE. For example, the switching elements of the electronic interruption unit EU then become low-impedance when the instantaneous value of the alternating voltage is less than a first voltage limit.In the example according to Figure 3, the switching elements of the electronic interruption unit become low-impedance at a zero crossing of the alternating voltage, specifically at the next (or next but one) zero crossing of the alternating voltage (for example, depending on the time of occurrence of the event causing the differential current). If the differential current if subsequently reaches the first differential current time limit value DSG1, the current flow in the low-voltage circuit is avoided, as shown. For example, the current flow is avoided at the next zero crossing of the alternating voltage, as shown. The current flow can be avoided by a high-impedance state of the switching elements of the electronic interruption unit with the isolating contacts STB closed. The current flow can be avoided alternatively (classically) by an open state of the isolating contacts OFF. That is,In the protective switching device according to the invention, after the second differential current limit value DSG2 has been exceeded and the current flow in the low-voltage circuit has been virtually immediately avoided, a new (test) low-resistance is achieved to check for the presence of the event causing the differential current.

[0147] Figure 4 shows a representation according to Figure 3, with the difference that the behavior mentioned is shown for a differential current i f , caused for example by an operational pulse differential current.

[0148] In the upper graphic illustrating the behavior of a state-of-the-art residual current device, an event causing a differential current occurs at a time t of approximately 5 ms. This event could be an operational pulse differential current or a technically induced pulse differential current, such as can occur during switching operations, particularly switch-on operations, and in frequency converters in low-voltage AC circuits. Such pulse differential currents are generally uncritical from a personal safety perspective, as they are not caused by people but by non-ideal technical circuits. In the past, considerable effort has been made to make conventional residual current devices resistant to operational pulse differential currents or technically induced pulse differential currents in order to avoid (technically induced) false tripping and to achieve a high level of supply reliability in low-voltage circuits.

[0149] In the example, the level of the differential current is (again) approximately greater than 400 mA. In a conventional residual current device according to the state of the art, the current flow OFF is then avoided (open contacts, switching off) after approximately 17 ms (time approximately 22 ms) - falling edge of the pulse differential current. This means that from the event until the current flow is avoided, there is an ON current flow in the low-voltage circuit; only then is the current flow OFF avoided by open contacts. In the graphic below for the behavior of a protective switching device according to the invention, an event causing a differential current occurs at time t of approximately 5 ms - in the example, the operational pulse differential current or technically induced pulse differential current.

[0150] In the example, the level of the differential current would theoretically also reach a value of approximately or greater than 400 mA. According to the invention, a current flow STB (high-impedance interruption unit) is (virtually) immediately avoided (in particular within the switch-off time) when the second differential current limit value DSG2, for example 200 mA, is reached, so that the possible differential current of, for example, (greater than) 400 mA is not reached (limitation). The current flow is avoided by a high-impedance state of the switching elements of the electronic interruption unit STB. For example, by the instantaneous value evaluation of the level of the differential current using the control unit SE. For example, the switching elements of the electronic interruption unit EU then become low-impedance when the instantaneous value of the AC voltage is less than a first voltage limit.In the example according to Figure 4, the switching elements of the electronic interruption unit become low-resistance in a zero crossing of the alternating voltage, specifically in the next (or next but one) zero crossing of the alternating voltage (for example, depending on the time of occurrence of the event causing the differential current).

[0151] If the differential current i fIf the first differential current time limit value DSG1 is subsequently exceeded, the current flow in the low-voltage circuit would be prevented. If the first differential current time limit value DSG1 or the second differential current limit value DSG2 is not reached, as shown, the electronic interruption unit remains in the low-resistance state for a current flow ON, as shown. Figure 5 shows a representation of a functional sequence with various function and status blocks. A differential current sensor unit ZCT / 10 determines the magnitude of a differential current in the conductors of the low-voltage circuit and records or provides instantaneous values ​​of the differential current, which are then passed on, for example, to a control unit SE.

[0152] The instantaneous values ​​of the differential current of the differential current sensor unit ZCT / 10 are fed to a first evaluation 100, which determines, for example, an effective value (root mean square = rms) of the differential current loifurms , block RMS / 101, and checks for exceedance of the first differential current time limit values ​​DSG1 "I D if ffrms > DSG1" / 102. If the first differential current time limit values ​​DSG1 are exceeded, current flow in the low-voltage circuit is avoided a) by a high-resistance state of the switching elements of the electronic interruption unit with the isolating contacts "Standby" block STB2 / 401 closed b) by an open state of the isolating contacts OFF / 400 => block OFF.

[0153] Whether a) or b) is carried out or / 110 is determined by a device configuration conf / 111 or is set / fixed.

[0154] The instantaneous values ​​of the differential current are, on the other hand, subjected to a second evaluation “ | i D iff,rms (t ) | > DSG2" 200, which in the example uses the magnitude of the instantaneous value of the differential current with regard to the exceedance of the second differential current limit value DSG2. If the second differential current limit value DSG2 is 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 STB are closed => Block STB / 201.

[0155] The avoidance of the current flow in the low-voltage circuit by a high-resistance state of the switching elements of the electronic interruption unit STB takes place within a first switch-off time which is in particular less than 20 ms, more specifically less than 15 ms, 10 ms, 5 ms, 1 ms, 500 ps or 100 ps.

[0156] After the current flow STB / 201 has been avoided, the switching elements of the electronic interruption unit ON / 402 become low-resistance, whereby the low-resistance occurs in particular at an amount of the instantaneous value of the alternating voltage which is smaller than a first voltage limit, for example smaller than 10 volts, "(at | u (t) | < 10 V)" / 402.

[0157] If, after becoming low-impedance, the second differential current limit value DSG2 is exceeded again, this is recorded by a counter 300. If a first number x of exceedances is exceeded, the contacts of the mechanical isolating contact unit MK are opened to prevent current flow OFF => Block OFF / 400. Alternatively, the switching elements of the electronic interruption unit can also assume a permanent or temporarily permanent high-impedance state with the isolating contacts STB2 / 401 closed => Block STB2 / 401.

[0158] If the first number has not yet been reached, the switching elements of the electronic interruption unit become low-resistance to allow current flow ON => Block ON / Block 402.

[0159] 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 test (as described above and below) for a protective switching device.

[0160] The computer program product can advantageously be stored on a computer-readable storage medium, such as a USB stick, CD-ROM, etc., to enable, for example, an upgrade to an enhanced version. Alternatively, the computer program product can also advantageously be transmitted via a data carrier signal.

[0161] The control unit SE can : * with a digital circuit, e . g . with a (further)

[0162] Microprocessor, can be implemented; the (further) microprocessor can also contain an analog part;

[0163] * be implemented with a digital circuit with analog circuit parts.

[0164] 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 the first differential current time limit values ​​(DSG1) are exceeded, the avoidance of a current flow in the low-voltage circuit is initiated a) by a high-resistance state of the switching elements of the electronic interruption unit when the isolating contacts are closed or b) by an open state of the isolating contacts; - that if a second differential current limit value (DSG2) is exceeded, 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.

2. Protective switching device (SG) according to claim 1, characterized in that the effective value of the differential current with respect to the exceeding of the first differential current time limit values (DSG1) is used.

3. 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 second differential current limit value (DSG2).

4. Protective switching device (SG) according to one of the preceding claims, characterized in that when the second differential current limit value (DSG2) is exceeded, the current flow in the low-voltage circuit is prevented by a high-impedance state of the switching elements of the electronic interruption unit within a first switch-off time, which is in particular less than 20 ms, more specifically less than 15 ms, 10 ms, 5 ms, 1 ms, 500 ps or 100 ps.

5. Protective switching device (SG) according to one of the preceding claims, characterized in that after the avoidance of the current flow in the low-voltage circuit, caused by the exceeding of the second differential current limit value (DSG2), the switching elements of the electronic interruption unit become low-resistance, in particular that a voltage sensor unit connected to the control unit is provided for determining the level of a voltage of the conductors of the low-voltage circuit, wherein the low-resistance occurs in particular at an amount of the instantaneous value of the alternating voltage which is smaller than a first voltage limit.

6. Protective switching device (SG) according to claim 5, characterized in that the first voltage limit is less than 20 volts or less than 10 volts or less than 5 volts, in particular that the switching elements of the electronic interruption unit become low-resistance when the alternating voltage passes through zero.

7. Protective switching device (SG) according to claim 5 or 6, characterized in that after becoming low-resistance, a renewed exceedance of the second differential current limit value (DSG2) is detected, a high-resistance followed by a low-resistance occurs until a first number (x) of exceedances occurs, in particular that the contacts of the mechanical isolating contact unit (MK) are then opened.

8. Protective switching device (SG) according to one of the preceding claims, characterized in that the protective switching device is designed such that the second differential current limit value (DSG2) is higher in amount than a first differential current limit value or the first differential current time limit value (DSG1), in particular that the second differential current limit value is a value from the range of 2 to 100 times the first differential current limit value or first differential current time limit value (DSG1).

9. 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 Amount of a current of the conductors 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 first current limit values ​​or first 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.

10. 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 connections (LL, NL). 11 . 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 - that when the first differential current time limit values ​​(DSG1) are exceeded, the avoidance of a current flow in the low-voltage circuit is initiated a) by a high-resistance state of switching elements of an electronic interruption unit with the isolating contacts closed or b) by an open state of the isolating contacts, - that when a second differential current limit value (DSG2) is exceeded, the 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. 12 . Method according to claim 11 , characterized in that an effective value of the difference current with respect to the Exceedance of the first differential current limits or first differential current time limits (DSG1) is used.

13. Method according to claim 11 or 12, characterized in that an instantaneous value of the differential current is used with regard to the exceedance of the second differential current limit value (DSG2).

14. Method according to one of the preceding claims 11 to 13, characterized in that when the second differential current limit value (DSG2) is exceeded, the current flow in the low-voltage circuit is avoided by a high-impedance state of the switching elements of the electronic interruption unit within a first switch-off time, which is in particular less than 20 ms, more specifically less than 15 ms, 10 ms, 5 ms, 1 ms, 500 ps or 100 ps.

15. Method according to one of the preceding claims 11 to 14, characterized in that after the avoidance of the current flow in the low-voltage circuit caused by the exceeding of the second differential current limit value (DSG2), the switching elements of the electronic interruption unit become low-resistance, wherein the low-resistance occurs in particular at an amount of the instantaneous value of the alternating voltage which is less than a first voltage limit.

16. Method according to claim 15, characterized in that after the low-resistance state, a renewed exceedance of the second differential current limit value (DSG2) is detected, a high-resistance state followed by a low-resistance state takes place until a first number (x) of exceedances occurs. , in particular that the contacts of the mechanical isolating contact unit (MK) are then opened.

17. Method according to one of the preceding claims 11 to 16, characterized in that the level of a current in the conductors of the low-voltage circuit is determined and that when first current limit values ​​or first 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. 18 . 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 11 to 17. 19 . Computer-readable storage medium on which the computer program product according to claim 18 is stored . 20 . Data carrier signal which transmits the computer program product according to claim 18 .

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