Circuit breaker

Description

[0001] The invention relates to the technical field of a protective switching device for a low-voltage circuit with an electronic interruption unit and a method for a protective switching device for a low-voltage circuit with an electronic interruption unit.

[0002] 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.

[0003] A low-voltage circuit, network, or system refers to circuits with nominal or rated currents of up to 125 amps, more specifically up to 63 amps. A low-voltage circuit refers in particular to circuits with nominal or rated currents of up to 50 amps, 40 amps, 32 amps, 25 amps, 16 amps, or 10 amps. 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 power switch. 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.

[0004] Miniature 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 miniature circuit breaker can automatically disconnect the circuit in the event of an overload and / or short circuit. A miniature circuit breaker is a non-self-resetting fuse element.

[0005] 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 (DIN rail, TH35).

[0006] Miniature circuit breakers are electromechanically constructed. They contain a mechanical switching contact or shunt release within 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 arc-quenching devices are provided. Furthermore, connection elements for conductors of the electrical circuit to be protected are used.

[0007] Circuit breakers with an electronic interruption unit are relatively new developments. They feature 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 switched to conduction. Circuit breakers with an electronic interruption unit also often feature a mechanical isolating contact system, in particular with isolating properties in accordance with relevant standards for low-voltage circuits. The contacts of the mechanical isolating contact system are connected in series with the electronic interruption unit, meaning that the current in the low-voltage circuit to be protected is conducted via both the mechanical isolating contact system and the electronic interruption unit.

[0008] The present invention relates in particular to low-voltage alternating current circuits with an alternating voltage, usually with a time-dependent sinusoidal alternating voltage with the frequency f. The time dependence of the instantaneous voltage value u(t) of the alternating voltage is given by the equation: u t = U * sin 2 π * f * t described. Where: u(t) = instantaneous voltage value at time t U = amplitude of the voltage

[0009] 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 revolution of the pointer, and its full angle is 2π (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 2π times its frequency, i.e.: ω = 2 π * f = 2 π / T = Kreisfrequenz der Wechselspannung (T = period of the oscillation)

[0010] Often, the angular frequency (ω) 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 2π: u t = U * sin ωt

[0011] In the case of angular frequencies that are not constant over time, the term instantaneous angular frequency is also used.

[0012] For a sinusoidal, particularly temporally constant, alternating voltage, the time-dependent value of the angular velocity ω and the time t corresponds to the time-dependent angle φ(t), which is also referred to as the phase angle φ(t). This means that the phase angle φ(t) periodically passes through the range 0...2π or 0°...360°. This means that the phase angle periodically assumes a value between 0 and 2π or 0° and 360° (φ = n* (0...2π) or φ = n*(0°...360°), due to periodicity; shortened: φ = 0...2π or φ = 0°...360°).

[0013] The instantaneous voltage value u(t) therefore means the instantaneous value of the voltage at time t, i.e. in the case of a sinusoidal (periodic) alternating voltage, the value of the voltage at the phase angle φ (φ = 0...2π or φ = 0°...360°, of the respective period).

[0014] German utility model DE 20 2009 014 759 U1 discloses a semiconductor relay with an integrated mechanical switching element for load circuit interruption (hybrid relay). A semiconductor relay (1) with an output power switch (4) that can be actuated by a control current or a control voltage via the control inputs (11, 12) and switches contactlessly, and with a mechanical switching element (2) connected in series with the output power switch (4), characterized in that the switching element (2) is integrated into the compact housing, which consists of an upper housing part (16) and a lower housing part (17) and is positively and detachably connected via the snap connections (20), and the switching element's manual operating lever or switch position indicator (3) is led out on the upper side (16a).

[0015] German patent application DE 10 2018 213 354 A1 describes a switching device and method. The invention relates to a switching device for a multi-conductor low-voltage circuit, with a housing, with connection contacts arranged on the housing for connecting conductors of the low-voltage circuit, with a mechanical unit located in the housing with a isolating function and an OFF or ON position, which has isolating contacts for galvanically interrupting the conductors of the low-voltage circuit. An electronic unit is provided, which is connected in series with the mechanical unit on the current flow side, an auxiliary switch is provided which is connected to the mechanical unit and is in turn connected to the electronic unit. The auxiliary switch and the electronic unit are designed such that when the mechanical unit is opened, the electronic unit becomes high-impedance.

[0016] US patent application US 2020 / 0366078 A1 describes a smart circuit breaker. A circuit breaker includes an electromechanical switch, a current sensor, a voltage sensor, and a processor. The electromechanical switch is connected in series between a line input terminal and a load output terminal of the circuit breaker and is configured to be placed in a switched closed state or a switched open state. The current sensor is configured to detect a current flowing in a path between the line input terminal and the load output terminal and generate a current sense signal. The voltage sensor is configured to detect a voltage at a point on the path between the line input terminal and the load output terminal and generate a voltage sense signal.The processor is configured to receive and process the current sense signal and the voltage sense signal to determine operating status information of the circuit breaker and to determine power consumption information of a load connected to the load output terminal.

[0017] The object of the present invention is to improve a protective switching device of the type mentioned at the outset, in particular to propose a new design for a protective switching device in order to improve the safety of such a protective switching device or to achieve greater safety in the electrical low-voltage circuit to be protected by the protective switching device.

[0018] This object is achieved by a protective switching device having the features of patent claim 1 or a method according to patent claim 15.

[0019] According to the invention, a protective switching device for protecting an electrical low-voltage circuit, in particular a low-voltage alternating current circuit, is proposed, comprising: a housing with mains-side connections and at least one load-side connection, a mechanical isolating contact unit connected in series with an electronic interruption unit, wherein the mechanical isolating contact unit is assigned to the load-side connection and the electronic interruption unit is assigned to the mains-side connections, that the mechanical isolating contact unit can be switched by opening at least one contact to prevent a current flow or closing the at least one contact for a current flow in the low-voltage circuit, that the electronic interruption unit can be switched by semiconductor-based switching elements into 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 current sensor unit for determining the level of the current in the low-voltage circuit, a control unit,which is connected to the current sensor unit, the mechanical isolating contact unit and the electronic interruption unit, whereby if current and / or current time limit values ​​are exceeded, avoidance of current flow in the low-voltage circuit is initiated.

[0020] According to the invention, a series connection of a measuring impedance and a switch is provided between conductors of the low-voltage circuit in such a way that when the switch is closed and the electronic interruption unit is switched to low impedance, a measuring current flows through the electronic interruption unit via the mains-side connections.

[0021] This means that a switchable measuring impedance is proposed so that either a measuring current or a defined potential can be generated in the protective switching device.

[0022] The series connection of the measuring impedance and the switch can, for example, be connected to the connection between the mechanical isolating contact unit and the electronic interruption unit. On the other hand, the measuring impedance can be connected to the other conductor, in particular to the other conductor at the mains-side connection.

[0023] Through the mechanical isolating contact unit connected between two conductors upstream of the load-side connection, particularly upstream of the mechanical isolating contact unit assigned to the load-side connection, a measuring current can optionally flow when the contacts of the mechanical isolating contact unit are open, i.e., when the load / consumer is disconnected from the mains side (power source). The measuring current can advantageously be used to test the function of the protective switching device. This design thus enables a safe protective switching device, thereby increasing safety in the low-voltage circuit.

[0024] Thus, when the switch is closed and the contacts of the mechanical isolating contact unit are open and the low-resistance electronic interruption unit is switched, a measuring current can flow through the electronic interruption unit via the mains-side connections.

[0025] Advantageous embodiments of the invention are specified in the subclaims and in the exemplary embodiment.

[0026] In an advantageous embodiment of the invention, the measuring impedance is an electrical resistor and / or capacitor, i.e., a single element or a series or parallel connection of an electrical resistor and a capacitor. Alternatively, a series and parallel connection of two, three, four, five, etc. elements.

[0027] Specifically, the measuring impedance can have a high resistance or impedance value to advantageously keep losses low. With the switchable measuring impedance, i.e. the series connection of a measuring impedance (ZM) and a switch (Smeas), the measuring impedance can advantageously have a lower resistance value, since the losses are limited by a temporary connection via the switch. In particular, the resistance value can be less than 1 MOhm, 500 kOhm, 100 kOhm, 50 kOhm, 10 kOhm, 5 kOhm, 1 kOhm, 500 Ohm, or 100 Ohm. In a 230 volt low-voltage circuit, the use of a measuring resistor of, for example, 1 MOhm leads to approximately 50 mW of losses.

[0028] In an advantageous embodiment, the value of the measuring impedance is dimensioned such that, with a high-impedance electronic interruption unit and the measuring impedance switched on (closed switch), and the contacts of the mechanical isolating contact unit closed, the voltage at the load-side terminals (or at least one load-side terminal relative to the other potential) is less than a first voltage level. For example, the first voltage level can be equal to or less than the maximum value of the protective extra-low voltage (50 volts AC, effective value). This advantageously reduces or defines the voltage at the load-side terminals caused by a leakage current of the electronic interruption unit.

[0029] In an advantageous embodiment of the invention, the switch is a controllable switch. In an advantageous embodiment of the invention, the switch is connected to the control unit so that the switch can be switched on and off by the control unit. For example, the switch can be a relay, such as a reed relay, or a so-called analog switch, i.e. a switch that can be switched (on / off) by a control signal, whereby the switched signal (measuring current) can be an analog (or digital) signal. The switch can also be an electronic switch, such as a TRIC, thyristor, IGBT or MOSFET.

[0030] This has the particular advantage that the control unit can generate a measuring current depending on the state of the electronic interruption unit.

[0031] In an advantageous embodiment of the invention, the protective switching device is designed such that the switch is switched on when the high-impedance electronic interruption unit is activated. This has the particular advantage that when the high-impedance electronic interruption unit is activated and the contacts of the mechanical isolating contact unit are closed, a defined (low) potential is present at the load-side connections. The potential is determined by the level of the (connected) measuring impedance. For example, the lower the resistance value of the measuring impedance, the lower the potential difference at the load-side connections. The potential difference is also determined by the leakage current of the electronic interruption unit. The lower the leakage current of the electronic interruption unit, the lower the potential difference / voltage drop across the (connected) measuring impedance.

[0032] In an advantageous embodiment of the invention, the protective switching device is designed such that the switch is switched off when the low-resistance electronic interruption unit is used.

[0033] This has the particular advantage that with a low-impedance electronic interruption unit and closed contacts of the mechanical isolating contact unit, i.e. usually during normal operation of the protective switching device, usually with a connected consumer / load, the power loss caused by the measuring impedance is reduced because the measuring impedance is switched off.

[0034] In an advantageous embodiment of the invention, the protective switching device is designed such that the switch is switched on when the electronic interruption unit is of high resistance and switched off when the electronic interruption unit is of low resistance.

[0035] This has the particular advantage that a simple (basic) implementation of the switching behavior of the switch coupled to the switching behavior of the electronic interruption unit is provided, so that when the contacts of the mechanical isolating contact unit are closed, on the one hand a defined potential is achieved at the load-side connections and on the other hand a minimized power loss is achieved.

[0036] In an advantageous embodiment of the invention, the protective switching device is designed such that, when the electronic interruption unit is of high impedance and the switch is switched on, the current level is determined by means of the current sensor unit. If a first current threshold is exceeded, it is concluded that the electronic interruption unit is faulty. If a first current threshold is exceeded, the electronic interruption unit can usually no longer be switched off, i.e. a high-impedance state no longer exists. For example, the semiconductor-based switching elements are completely alloyed (permanently conductive / short-circuited). If a first current threshold is exceeded, which concludes that the electronic interruption unit is faulty, the protective switching device can be designed such that the mechanical isolating contact unit cannot be closed or is opened.This has the particular advantage that the (switchable) measuring impedance checks the electronic interruption unit, particularly its high-impedance state. If high impedance is missing or insufficient, appropriate protective measures can be implemented, such as preventing the contacts from closing (if they are not yet closed) or opening them. This condition can also be reported.

[0037] The first current threshold can be in the range of less than 50 mA, advantageously less than 6 mA.

[0038] In an advantageous embodiment of the invention, the protective switching device is designed such that, in order to test the function of the protective switching device with the contacts of the mechanical isolating contact unit open and the electronic interruption unit switched to high impedance and the switch switched on, the electronic interruption unit is switched to a low impedance state for a first period of time without the switch being switched off, so that the measuring current flows through the measuring impedance, in order to test the function of the protective switching device, in particular the electronic interruption unit.

[0039] This means that the electronic interruption unit is switched from the high-impedance state to the low-impedance state for an initial period of time and is then back in the high-impedance state.

[0040] The first time period can be in the range 100 µs to 1 s. For example, 100 µs, 200 µs, ..., 1 ms, 2 ms, ..., 10 ms, 11 ms, ..., 20 ms, 21 ms, ..., 100 ms, ..., 200 ms, ... 1 s.

[0041] For switching times in the range of 1 ms to 2 ms, a voltage change can be detected for functional testing. For time periods of 20 ms to 100 ms or 1 second, it can be checked (multiple times) whether approximately 0 V voltage (instantaneous or effective voltage value) is present across the electronic interruption unit.

[0042] This has the particular advantage that the electronic interruption unit can be checked with regard to its "switchability", whereby the (switched-on) measuring impedance causes a detectable measuring current for functional testing.

[0043] The functional test of the protective switching device can: a determination of the level of the measuring current by means of the current sensor unit, in particular the level of the determined measuring current is compared with a target measuring current level and in the event of a deviation from the target measuring current level which lies outside a first tolerance range, a conclusion is drawn as to a faulty protective switching device (in particular, a conclusion can be drawn as to a faulty electronic interruption unit); the first tolerance range can be a (further) current limit; i.e. if the current is too high, there is a faulty electronic interruption unit; if the current is too low, the measuring impedance could be faulty).

[0044] If there is a deviation from the target measuring current level that lies outside a first tolerance range, for example, the mechanical isolating contact unit cannot be closed or is opened, or ( / and) a determination of the level of a voltage across the electronic interruption unit, in particular that the level of the determined voltage is compared with a target voltage level and in the event of a deviation from the target voltage level which lies outside a second tolerance range, it is concluded that a faulty electronic interruption unit is present, in particular that the mechanical isolating contact unit cannot be closed or is opened.

[0045] Alternatively or additionally, the measured voltage level can also be compared with the target voltage level. If the target voltage level is exceeded, a faulty electronic interruption unit is identified, in particular, that the mechanical isolating contact unit cannot be closed or is opening. This has the particular advantage of allowing a low-resistance test of the electronic interruption unit, verifying the presence of a correct measuring current at low resistance.

[0046] The target measurement current is, for example, equal to the currently applied mains voltage (voltage, low voltage) divided by the measurement impedance. For example, with a currently applied low voltage of 230 V (rms value) and a measurement impedance of 10 kOhm, the target measurement current is 23 mA. The first tolerance range can be, for example, + / - 10% (or + / - 20%) of this value.

[0047] The target voltage level for checking the low resistance of the electronic interruption unit is, for example, values ​​of or less than 1 V, more generally less than 2 VDh. Alternatively, if this target voltage level is exceeded, it is concluded that the interruption unit is faulty.

[0048] The second tolerance range can be, for example, + / - 10% to + / - 100% of this value.

[0049] In an advantageous embodiment of the invention, the protective switching device is designed such that the measuring current is used to calibrate the current level determined by the current sensor unit, in particular after an aforementioned functional test has been carried out (at least partially).

[0050] This has the particular advantage that the (connected) measuring impedance (of known size and thus known measuring current) can be used to calibrate the current sensor unit.

[0051] In an advantageous embodiment of the invention, the protective switching device is designed such that, for functional testing of the protective switching device - with the contacts of the mechanical isolating contact unit closed and the electronic interruption unit switched to low resistance, as well as with the switch off - the switch is switched to a closed state for a first time period, so that an additional current (= supplementary current) caused by the measuring resistor flows through the electronic interruption unit, the magnitude of which (of the additional current = supplementary current) is determined (by means of the current sensor unit and / or control unit), compared with supplementary current values, and if the deviation exceeds a third tolerance range, an additional current fault condition exists. If no consumer or load is connected to the load-side terminals, the underlying output current can have the value zero.In this case, the magnitude of the current is determined by the magnitude of the additional current.

[0052] This has the particular advantage that the current sensor unit or the determination of the current level can be checked when there is no consumer or during operation of the protective switching device.

[0053] The first time range can be in the range 10 ms to 10 s.

[0054] In an advantageous embodiment of the invention, the switch is switched to a closed state for the first time period when the current level determined by the current sensor unit falls below a first current level. The first current level can be less than 5 A, 1 A, or in particular less than 0.5 A.

[0055] This advantageously allows for the detection of a faulty protective switching device, particularly a faulty current sensor unit or current detection device. This allows the current sensor unit or the current detection device to be checked if the load is missing.

[0056] In an advantageous embodiment of the invention, the protective switching device is designed such that (for a conductor) the level of the voltage across the electronic interruption unit can be determined.

[0057] This has the particular advantage that the voltage level between the mains-side connection point and the load-side connection point of the electronic interruption unit can be determined or is determined.

[0058] In an advantageous embodiment of the invention, the protective switching device is designed such that, when the contacts of the mechanical isolating contact unit are open and the switch is switched on, the level of the voltage determined by the switched-on measuring impedance across the electronic interruption unit is determined when the electronic interruption unit is switched to high resistance. If a first voltage threshold is undershot, a first fault condition exists, so that a (possibly renewed or first-time) low-resistance of the electronic interruption unit is prevented and / or the mechanical isolating contact unit cannot be closed or is opened. (Ie. if the first voltage threshold is exceeded, no error condition exists.)

[0059] This serves to check the electronic interruption unit with regard to its "switchability", i.e. the high-resistance of the semiconductor-based switching elements.

[0060] The first voltage threshold depends on the magnitude of the measuring impedance. For example, the voltage across the (functional) switched-off (high-impedance) electronic interruption unit corresponds to the applied mains voltage minus the voltage drop across the measuring impedance. The voltage across the measuring impedance is equal to the leakage current times the magnitude of the measuring impedance. For example, with a leakage current of 0.1 mA and a measuring impedance of 20 kOhm, the voltage drop is 2 V, and thus the first voltage threshold is less than 230 V - 2 V = 228 V (for RMS values).

[0061] This has the particular advantage that a simple check is provided with regard to the switching behavior of the electronic interruption unit, whereby the measuring impedance on the one hand generates a defined potential and on the other hand a defined voltage level is generated by the level of the resistance or impedance value of the measuring impedance in conjunction with (the ascertainable) high-ohm impedance of the electronic interruption unit.

[0062] In an advantageous embodiment of the invention, when the electronic interruption unit is switched to the low-resistance state for the first period of time without the switch being turned off, the voltage level across the electronic interruption unit is determined. If a second voltage threshold is exceeded, a second fault condition exists, so that a further or subsequent low-resistance state of the electronic interruption unit is prevented and / or the mechanical isolating contact unit cannot be closed or is opened. (Ie. if the second voltage threshold is undershot, no error condition exists.)

[0063] The second voltage threshold should be 1 volt or better less than 1 V.

[0064] This has the particular advantage that the electronic interruption unit can be checked more precisely with regard to its "switchability", whereby a defined potential is provided by the switched-on measuring impedance.

[0065] In an advantageous embodiment of the invention, closing of the contacts of the mechanical isolating contact unit is prevented if one (or both) fault conditions are present. In particular, no enable signal is sent to the mechanical isolating contact unit. This means that closing of the contacts of the mechanical isolating contact unit by a handle is not possible.

[0066] Furthermore, the electronic interruption unit can be prevented from becoming low-resistance.

[0067] Alternatively or furthermore, the mechanical isolating contact unit can be opened.

[0068] Other error conditions may exist.

[0069] This has the particular advantage that only a functional protective switching device with a functional electronic interruption unit can be switched on. In the event of a defective protective switching device, which can be determined using the measuring impedance according to the invention, the low-voltage circuit is interrupted. This increases the operational reliability of the protective switching device and thus also of the low-voltage circuit. This ensures that the electronic interruption unit can be switched on and off properly.

[0070] In an advantageous embodiment of the invention, the protective switching device can further be designed such that further embodiments are provided: a housing with a mains-side neutral conductor connection, a mains-side phase conductor connection, a load-side neutral conductor connection, a load-side phase conductor connection of the low-voltage circuit, a mechanical isolating contact unit, in particular a two-pole (especially in a single-phase circuit), with load-side connection points and mains-side connection points, wherein the load-side connection points are connected to the load-side neutral and phase conductor connections, so that the opening of contacts to prevent a current flow or the closing of the contacts to allow a current flow in the low-voltage circuit can be switched, an electronic interruption unit, in particular a single-pole, with a mains-side connection point that is electrically connected to the mains-side phase conductor connection, and a load-side connection point that is connected to a mains-side connection point of the mechanical isolating contact unit,wherein the electronic interruption unit 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 by means of semiconductor-based switching elements, a current sensor unit for determining the level of the current of the low-voltage circuit, a control unit which is connected to the current sensor unit, , the mechanical isolating contact unit and the electronic interruption unit, whereby if current and / or current time limit values ​​are exceeded, avoidance of current flow in the low-voltage circuit is initiated.

[0071] The voltage level between the mains-side connection point and the load-side connection point of the electronic interruption unit can be determined or is determined.

[0072] For this purpose, at least one voltage sensor unit connected to the control unit can be provided. If there are multiple voltage sensor units, these are connected to the control unit.

[0073] According to the invention, a new architecture or structural design of a protective switching device is proposed, with which an increased operational reliability of a protective switching device or of the low-voltage circuit is achieved.

[0074] In an advantageous embodiment of the invention, a first voltage sensor unit connected to the control unit is provided, which determines the level of a / the first voltage across the electronic interruption unit, in particular between the network-side connection point and the load-side connection point of the electronic interruption unit.

[0075] This has the particular advantage of providing a simple solution with only one voltage sensor unit.

[0076] In an advantageous embodiment of the invention, alternatively or additionally, a second voltage sensor unit connected to the control unit is provided, which determines the level of a second voltage between the mains-side neutral conductor connection and the mains-side phase conductor connection.

[0077] Furthermore, a third voltage sensor unit connected to the control unit is provided, which detects the magnitude of a third voltage between the mains-side neutral conductor connection and the load-side connection point of the electronic interruption unit. The protective switching device is designed such that the magnitude of a / the first voltage between the mains-side connection point and the load-side connection point of the electronic interruption unit is determined from the difference between the second and third voltages.

[0078] This has the particular advantage of providing an additional solution based on conventional voltage measurements. It also enables more extensive testing of the protective switching device.

[0079] In an advantageous embodiment of the invention, the current sensor unit is provided on the circuit side between the mains-side phase conductor connection and the load-side phase conductor connection. In particular, the current sensor unit is provided between the mains-side phase conductor connection and the mechanical isolating contact unit, in particular so that the measuring current caused by the switched-on switch can be detected by the current sensor unit.

[0080] This has the particular advantage of providing a compact two-part device, with an electronic interruption unit in the phase conductor along with a current sensor unit on the one hand, and a continuous neutral conductor on the other. Furthermore, a current sensor unit in the phase conductor provides more comprehensive monitoring of currents both in the circuit itself and in the event of earth fault currents.

[0081] In an advantageous embodiment of the invention, the protective switching device is designed such that the contacts of the mechanical isolating contact unit can be opened but not closed by the control unit.

[0082] This has the particular advantage of achieving increased operational reliability, since the contacts cannot be accidentally closed by the control unit.

[0083] In an advantageous embodiment of the invention, the mechanical isolating contact unit can be operated by a mechanical handle in order to switch the opening or closing of contacts.

[0084] This has the particular advantage that the functionality of a classic circuit breaker is provided.

[0085] In an advantageous embodiment of the invention, the mechanical isolating contact unit is designed such that closing of the contacts by the mechanical handle is only possible after an enable, in particular an enable signal.

[0086] This has the particular advantage of providing increased protection and operational reliability as switching on a defective protective switching device is avoided.

[0087] In an advantageous embodiment of the invention, a power supply, particularly for the control unit, is provided, which is connected to the mains-side neutral conductor connection and the mains-side phase conductor connection. Advantageously, the measuring impedance can be connected to the supply conductor connected to the mains-side neutral conductor connection.

[0088] This has the particular advantage of enabling a compact electronic assembly.

[0089] In an advantageous embodiment of the invention, with closed contacts of the mechanical isolating contact unit and low-resistance interruption unit and when a current is determined which exceeds a first current value, in particular when the first current value is exceeded for a first time limit, the electronic interruption unit becomes high-resistance and the mechanical isolating contact unit remains closed, when a current is determined which exceeds a (higher) second current value, in particular for a second time limit, the electronic interruption unit becomes high-resistance and the mechanical isolating contact unit is opened, when a current is determined which exceeds an (even higher) third current value, the electronic interruption unit becomes high-resistance and the mechanical isolating contact unit is opened.

[0090] This has the particular advantage that a graduated shutdown concept is available for a protective switching device according to the invention at increased currents.

[0091] In an advantageous embodiment of the invention, the control unit comprises a microcontroller.

[0092] This has the particular advantage that the functions according to the invention for increasing the safety of a protective switching device or the low-voltage electrical circuit to be protected can be implemented using an (adaptable) computer program product. Furthermore, changes and improvements to the function can be individually loaded onto a protective switching device.

[0093] 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 can be provided.

[0094] The method for a protective switching device for protecting a low-voltage electrical circuit comprising: a housing with mains-side connections and at least one load-side connection, a mechanical isolating contact unit connected in series with an electronic interruption unit, wherein the mechanical isolating contact unit is assigned to the load-side connection and the electronic interruption unit is assigned to the mains-side connections, that the mechanical isolating contact unit can be switched by opening contacts to prevent a current flow or closing the contacts for a current flow in the low-voltage circuit, that the electronic interruption unit can be switched by semiconductor-based switching elements into 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,that the current level of the low-voltage circuit is determined and, if current and / or current-time limit values ​​are exceeded, the prevention of current flow in the low-voltage circuit is initiated, that in the protective switching device, a series connection of a measuring impedance and a switch is provided between conductors of the low-voltage circuit in such a way that, when the switch is closed and the electronic interruption unit is switched to low resistance, a measuring current flows through the electronic interruption unit via the mains-side connections.

[0095] Advantageously, the switch is switched on when the electronic interruption unit is high-impedance and off when the electronic interruption unit is low-impedance. This allows a defined potential to be generated when the electronic interruption unit is high-impedance, and minimizes losses due to the measuring impedance when the electronic interruption unit is low-impedance.

[0096] With a high-impedance electronic interruption unit and the switch switched on, especially with the contacts of the mechanical isolating contact unit open, the current level can be determined using the current sensor unit to test the function of the protective switching device. If a first current threshold is exceeded, a faulty electronic interruption unit is concluded. As a result, the mechanical isolating contact unit cannot be closed or is opened.

[0097] To test the function of the protective switching device, the electronic interruption unit is switched to a low-impedance state for an initial period of time with the contacts of the mechanical isolating contact unit open, the switch closed / switched on, and the high-impedance electronic interruption unit switched to high-impedance. While the electronic interruption unit is switched to the low-impedance state for the initial period of time, the current (measurement current) and / or the voltage across the electronic interruption unit are determined. The determined measurement current is compared with a target measurement current, and if there is a deviation from the target measurement current that lies outside an initial tolerance range, it is concluded that the protective switching device is faulty. The mechanical isolating contact unit cannot be closed or is opened.

[0098] When determining the voltage level across the electronic interruption unit, the detected voltage level is compared with a target voltage level. If the deviation from the target voltage level lies outside a second tolerance range, it is concluded that the electronic interruption unit is faulty. The mechanical isolating contact unit cannot be closed or is opened.

[0099] According to the invention, a corresponding computer program product can be claimed. The computer program product comprises instructions that, when executed by a microcontroller, cause the microcontroller to improve the safety of such a protective switching device or to achieve greater safety in the low-voltage electrical circuit to be protected by the protective switching device.

[0100] The microcontroller is part of the protective switching device, in particular the control unit.

[0101] According to the invention, a corresponding computer-readable storage medium on which the computer program product is stored can be claimed.

[0102] According to the invention, a corresponding data carrier signal which transmits the computer program product can be claimed.

[0103] All embodiments, both in dependent form referring back to patent claim 1 or 15, and referring back only to individual features or combinations of features of patent claims, bring about an improvement in a protective switching device, in particular an improvement in the safety of a protective switching device or, as a consequence, of the electrical circuit, and provide a new concept for a protective switching device.

[0104] The described properties, features and advantages of this invention and the manner in which they are achieved will become clearer and more clearly understood in connection with the following description of the embodiments, which are explained in more detail in connection with the drawings.

[0105] The drawing shows: Figure 1 shows a first representation of a protective switching device, Figure 2 shows a second representation of a protective switching device.

[0106] 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: a grid-side neutral conductor connection NG, a grid-side phase conductor connection LG, a load-side neutral conductor connection NL, a load-side phase conductor connection LL of the low-voltage circuit; an energy source is usually connected to the grid side GRID, a consumer is usually connected to the load side LOAD; a (two-pole) mechanical isolating contact unit MK with load-side connection points APLL, APNL and grid-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 grid-side connection point APNG for the neutral conductor, and a grid-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 contacts KKN, KKL can be opened to prevent a current flow or the contacts can be closed to allow a current flow in the low-voltage circuit, 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 to the mains-side connection point APLG of the mechanical isolating contact unit MK.is connected, wherein the electronic interruption unit has or can be switched by semiconductor-based switching elements to a high-resistance state of the switching elements to prevent a current flow or to a low-resistance state of the switching elements to allow current to flow in the low-voltage circuit, a current sensor unit SI for determining the level of the current in the low-voltage circuit, which is arranged in particular in the phase conductor, a control unit SE which is connected to the current sensor unit SI, the mechanical isolating contact unit MK and the electronic interruption unit EU, wherein if current and / or current time limit values ​​are exceeded, avoidance of a current flow in the low-voltage circuit is initiated. .

[0107] According to the invention, a series connection of a measuring impedance ZM and a switch Smeas is provided between conductors of the low-voltage circuit in such a way that when the switch Smeas is closed and the electronic interruption unit EU is switched to low impedance, a measuring current flows through the mains-side connections LG, NG through the electronic interruption unit EU. Figure 1 When the switch Smeas is closed and the contacts of the mechanical isolating contact unit MK and the low-resistance switched electronic interruption unit EU are open, a measuring current flows via the mains-side connections LG, NG through the electronic interruption unit EU.

[0108] According to Figure 1The series connection of the measuring impedance ZM and the switch Smeas is connected between the mains-side connection points APLG and APNG of the mechanical isolating contact unit MK. The series connection of the measuring impedance ZM and the switch Smeas is connected, on the one hand, to the connection (phase conductor) between the mechanical isolating contact unit MK (APLG) and the electronic interruption unit EU (EUL). The series connection of the measuring impedance ZM and the switch Smeas is connected, on the other hand, to the other conductor (neutral conductor) at the mains-side connection (NG).

[0109] The measuring impedance ZM can, for example, be an electrical resistor and / or capacitor. In particular, the measuring impedance can be a series circuit or / and parallel circuit of a resistor and / or capacitor.

[0110] The switched-on measuring impedance generates a defined potential in the protective switching device, in particular a defined voltage potential across the electronic interruption unit EU, specifically at the load-side connection point EUL.

[0111] Furthermore, a defined measuring current can be generated in the protective switching device, especially when the contacts of the mechanical isolating contact unit MK are open.

[0112] Furthermore, an additional current can be generated by the switched measuring impedance without affecting a connected consumer / load.

[0113] According to the invention, both the measuring current (or additional (measuring) current) and (or / and) the voltage across certain units, such as the electronic interruption unit EU, can be evaluated.

[0114] The evaluation allows the correct behavior of the units, in particular the electronic interruption unit EU, to be recorded.

[0115] The measuring impedance ZM should have a high value (resistance or impedance value) to keep losses low.

[0116] However, the invention also allows medium and smaller values ​​(resistance or impedance values) to be used.

[0117] For example, the resistance value can be less than 1 MOhm, 500 kOhm, 100 kOhm, 50 kOhm, 10 kOhm, 5 kOhm, 1 kOhm, 500 Ohm or 100 Ohm.

[0118] The switch or switchable measuring impedance can reduce the losses, since (larger) losses would only occur when the measuring impedance is switched on and the electronic interruption unit is in a low-resistance state.

[0119] The switch Smeas is controllable, meaning it can be electrically switched on and off. In the example, the switch is connected to the control unit SE, so it can be switched on and off. For example, the switch Smeas can be switched on or off by a control signal Control Smeas, which is indicated by an arrow from the control unit SE to the switch Smeas ("Control Smeas" with "(on / off)") ( Figure 2 The protective switching device is designed such that the switch (Smeas) is switched on when the electronic interruption unit (EU) is high-impedance, and in particular such that the switch (Smeas) is switched off when the electronic interruption unit (EU) is low-impedance. This allows losses due to the measuring impedance to be reduced, even at low values.

[0120] 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.

[0121] For this purpose, in the example according to Figure 1 a first voltage sensor unit SU1 connected to the control unit SE is provided, which determines the level of the voltage between the grid-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU.

[0122] When measuring the voltage by the first voltage sensor unit SU1, 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 1The current sensor unit SI has a very low internal resistance, so that the determination of the voltage level is not affected or only negligibly affected.

[0123] Advantageously, a second voltage sensor unit SU2 can be provided, which determines the level of the voltage between the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG.

[0124] 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 calculating the difference.

[0125] For example, a second voltage sensor unit SU2 connected to the control unit SE can be provided, which 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) connected to the control unit can be provided, which 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 such 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 voltages.

[0126] In the example according to Figure 1The electronic interruption unit EU is designed as a single-pole unit, 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.

[0127] 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 by the control unit SE, but not closed, which is indicated by an arrow with "b.) open" from the control unit SE to the mechanical isolating contact unit MK ( Figure 2 ).

[0128] The mechanical isolating contact unit MK can be operated using a mechanical handle HH on the protective switching device SG to manually open or close the KKL and KKN contacts. The mechanical handle HH indicates the switching state (open or closed) of the contacts of the mechanical isolating contact unit MK.

[0129] 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.

[0130] 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 with "a.) enable" from the control unit SE to the mechanical isolating contact unit MK ( Figure 2 ). 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 is present (from the control unit). Without the release or release signal, the handle HH can be operated, but the contacts cannot be closed ("permanent slip"). An additional release unit LC can be provided for this purpose ( Figure 2 ).

[0131] The protective switching device SG has a power supply NT, for example a power supply unit. In particular, the power supply NT is provided for the control unit SE, which is achieved by a connection between the power supply NT and the control unit SE in Figure 1 is indicated. The power supply NT is (on the other hand) connected to the mains-side neutral conductor terminal NG and the mains-side phase conductor terminal LG. A fuse SS, in particular a fuse, can advantageously be provided in the connection to the mains-side neutral conductor terminal NG (and / or phase conductor terminal LG).

[0132] Alternatively, the measuring impedance ZM can be connected to the mains-side neutral conductor connection NG via the fuse SS.

[0133] A three-pole electronic unit EPART (Figure 2) can advantageously be implemented, for example, as a module with three connection points: one neutral conductor connection point and two phase conductor connection points. The electronic unit EPART comprises, for example, the electronic interruption unit EU, the control unit SE, the power supply NT (especially including the fuse SS), the current sensor unit SI, the first voltage sensor unit SU1, optionally the second voltage sensor unit SU2, and the series circuit consisting of the (electrically switchable) switch Smeas and the measuring impedance ZM.

[0134] High-impedance refers to a state in which only a negligible current flows. In particular, high-impedance 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.

[0135] 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 ​​less than 10 ohms, preferably less than 1 ohm, 100 milliohms, 10 milliohms, 1 milliohm, or less.

[0136] Figure 2 shows an illustration according to Figure 1 , with the difference that the protective switching device is essentially constructed in two parts, with a first (three-pole) part / electronic unit EPART and a second mechanical part / mechanical unit MPART. The first electronic part EPART can, for example, be arranged on a printed circuit board and contains the units mentioned or shown above.

[0137] The first part EPART has only three connections: the mains-side phase conductor connection LG, a connection for or to the mains-side phase conductor connection point APLG of the mechanical isolating contact unit MK, a connection for a connection to the mains-side neutral conductor connection NG.

[0138] The second part MPART can include the mechanical isolating contact unit MK, the handle HH, and a release unit LC. Furthermore, the second part can include a positioning unit POS (not shown) 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).

[0139] Additional, unspecified units may be provided.

[0140] The division into two parts makes it possible to advantageously realize a compact protective switching device according to the invention.

[0141] The protective switching device may further comprise a communication unit COM, a display unit DISP, and an input unit EE. These may be assigned to the control unit SE or connected to it, as shown in Figure 2 indicated.

[0142] The protective switching device SG, for example, operates in principle in such a way that when the contacts of the mechanical isolating contact unit and the low-resistance interruption unit are closed and when a current is determined which exceeds a first current value, in particular the first current value is exceeded for a first time limit, the electronic interruption unit EU becomes high-resistance and the mechanical isolating contact unit MK remains closed, when a current is determined which exceeds a higher second current value, in particular for a second time limit, the electronic interruption unit EU becomes high-resistance and the mechanical isolating contact unit MK is opened, when a current is determined which exceeds an even higher third current value, the electronic interruption unit becomes high-resistance and the mechanical isolating contact unit MK is opened.

[0143] In the following, the invention for the protective switching device SG is further described in other words.

[0144] To test the functionality of the electronic interruption unit EU, a current measurement and / or voltage measurement is provided across the electronic interruption unit EU. If the electronic interruption unit EU is in the high-impedance state, the potential between the electronic interruption unit EU (EUL) and the mechanical isolating contact unit MK (APLG) is undetermined when the contacts are open, or it is co-determined by the connected load / consumer when the contacts are closed. According to the invention, a measuring impedance is provided between this point and the other conductor / neutral conductor in the protective switching device. This (co-)determines the electrical potential at this point. The design of the measuring impedance is problematic because, for an accurate measurement, the value of the measuring impedance (e.g. resistance) should be as small as possible (compared to the resistance of the electronic interruption unit EU in the high-impedance state).On the other hand, the measuring impedance is arranged / connected between the two conductors (phase conductor and neutral conductor), which results in permanent losses, so the measuring impedance value should be as high as possible. To accommodate both, a compromise must be made during the design.

[0145] There is also the problem that a small leakage current flows through the electronic interruption unit EU when it is in the high-impedance state.

[0146] Depending on the connected load / consumer, this leakage current can supply the load with very little power. Especially for loads that require very little power (e.g., LEDs), this can lead to the load being supplied with energy, which is undesirable.

[0147] According to the invention, a series connection of an (electrically) switchable switch Smeas and a measuring impedance, such as a switchable measuring resistor in the protective switching device, is proposed. The measuring impedance ZM can be switched on or off via the (semiconductor) switch Smeas, for example.

[0148] If the electronic interruption unit EU is in the high-impedance (switched off) state (device state: standby), the measuring impedance can be switched on (switch Smeas on or closed) in order to determine the potential at the load-side connection point or connection point EUL of the electronic interruption unit EU and to establish an electrically conductive connection from this point to the mains-side neutral conductor connection. The measuring impedance then forms a high-impedance voltage divider together with the high-impedance / switched off electronic interruption unit EU. The voltage divider is dimensioned such that the majority of the mains voltage is dropped across the switched off / high-impedance electronic interruption unit. A value of the protective extra-low voltage, i.e. a maximum of 50 volts, can advantageously be dropped across the measuring impedance.

[0149] This means that the voltage divider is dimensioned so that a maximum voltage value, e.g. 50 volts AC (effective value), drops across the switched-on measuring resistor (in a 230 volt low-voltage circuit).

[0150] A voltage measurement across the electronic interruption unit EU can be used to check or monitor the functionality of the electronic interruption unit EU.

[0151] The active measuring impedance advantageously diverts a constantly present leakage current, e.g., caused by existing (parasitic) capacitances in the electronic interruption unit (EU), to the mains-side neutral conductor connection. This leakage current is typically less than 1 mA, but can lead to an unwanted energy flow to the load, which is thus avoided.

[0152] The dimensioning / design of the measuring impedance should be carried out based on the following points.

[0153] The measuring impedance, together with the deactivated electronic interruption unit EU, forms a high-impedance voltage divider. This voltage divider should be dimensioned so that the voltage drop across the measuring impedance is less than the protective extra-low voltage (50 Vac), since this voltage is present at the load-side terminals LL and NL. For example, the measuring impedance can be 10% of the impedance of the deactivated electronic interruption unit. If this is 2 MOhm, for example, the value of the measuring impedance ZM should be less than 200 kOhm. A maximum of 23 Vac can then occur at the load-side terminals LL and NL.

[0154] The measuring impedance ZM protects the switch Smeas from overvoltages (e.g., surges). When switched on and with the contacts closed, the switch Smeas and the measuring impedance ZM are located between the phase conductor and the neutral conductor. This means that the switch Smeas would be loaded in the event of mains overvoltages (e.g., triggered by surge events). In this case, the measuring impedance ZM protects the switch Smeas from destruction, as it represents a larger series resistance and thus prevents a higher pulse current in the device.

[0155] Furthermore, the measuring impedance ZM can be dimensioned to protect the protective switching device from thermal destruction in the event of a defective switch Smeas. The current that would flow through the measuring impedance in this case is limited by the measuring impedance to a maximum value, e.g., a few tens of mA.

[0156] In addition to its use for functional testing of the electronic switch and for diverting leakage current, another function of the switchable measuring impedance is conceivable. With appropriate dimensioning or design, the switchable measuring impedance can be used to check and, if necessary, calibrate the included current measurement. The control unit SE switches on the electronic interruption unit EU and the switch Smeas, so that (especially when the contacts of the mechanical isolating contact unit MK are open) a measuring current imeas ( Figure 2) flows, which is detected by the current sensor unit SI. Depending on the dimensioning of the measuring impedance, this can be in the range of a few mA or a few tens of mA, so that the current measurement (current sensor unit SI and control unit SE) can be checked for appropriate functionality. After the functional test, the electronic interruption unit EU is switched back to high impedance. The measurement only takes a few ms, e.g., 10 ms, 20 ms, or a (further) multiple of half the mains period.

[0157] Testing and, if necessary, calibration can advantageously be performed before the closing of the contacts of the mechanical isolating contact unit is enabled using the handle. This allows the functional test or calibration of the current measurement to be performed before the isolating contacts are enabled. Furthermore, the measurement (if appropriately dimensioned) can also be performed with closed contacts and a low-impedance electronic interruption unit EU by briefly closing the switch Smeas and generating an additional (measurement) current through the measuring impedance in the circuit. The additional measurement current imeas is then detected by the current sensor unit and evaluated by the control unit (algorithm), in particular to distinguish it from the normal load current.

[0158] The invention has the following advantages: 1.) Lower resistance values ​​result in more precise voltage measurements across the EU electronic interruption unit for testing the functionality of the EU electronic interruption unit. 2.) Reduced losses in the device because the measuring impedance can be switched off when the EU electronic interruption unit is in a low-resistance state. 3.) Leakage currents from the EU electronic interruption unit are diverted when the EU electronic interruption unit is in a high-resistance state. 4.) Possibility of checking and calibrating the current measurement 5.) Touch voltage at the load-side connections when the EU electronic interruption unit is in a high-resistance state is limited.

[0159] Furthermore, a computer program product or algorithm is proposed which switches the electronic interruption unit EU or the switch Smeas on and off at suitable times (instantaneous values ​​of the mains voltage) and simultaneously evaluates the measured current and voltage values ​​in order to detect whether the electronic interruption unit is functional or not functional.

[0160] The control unit SE can (for this purpose) have a microcontroller. The computer program product can be executed on the microcontroller. The computer program product comprises commands that, when the program is executed by the microcontroller, cause the microcontroller to control the protective switching device, in particular to support, in particular to carry out, the method according to the invention.

[0161] The computer program product may be stored on a computer-readable storage medium, such as a CD-ROM, a USB stick or similar.

[0162] Furthermore, a data carrier signal that transmits the computer program product may exist.

[0163] Although the invention has been illustrated and described in detail by the embodiment, the invention is not limited to the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the appended claims.

Claims

1. Circuit breaker device (SG) for protecting an electrical low-voltage circuit, having: - a housing (GEH) having grid-side connections and at least one load-side connection, - a mechanical isolating contact unit (MK) that is connected in series with an electronic interruption unit (EU), wherein the mechanical isolating contact unit is assigned to the load-side connection and the electronic interruption unit (EU) is assigned to the grid-side connections, - wherein the mechanical isolating contact unit (MK) is able to be switched by opening contacts so as to avoid a current flow or closing the contacts to allow a current flow in the low-voltage circuit, - wherein the electronic interruption unit (EU) is able to be switched by semiconductor-based switching elements to a high-resistance state of the switching elements so as to avoid a current flow or a low-resistance state of the switching elements so as to allow a current flow in the low-voltage circuit, - a current sensor unit (SI) for ascertaining the level of the current of the low-voltage circuit, - a control unit (SE) that is connected to the current sensor unit (SI), the mechanical isolating contact unit (MK) and the electronic interruption unit (EU), wherein, in the event of current or / and current-time limit values being exceeded, avoidance of a current flow in the low-voltage circuit is initiated, characterized in that a series circuit consisting of a measurement impedance (ZM) and a switch (Smeas) is provided between conductors of the low-voltage circuit such that, when the switch (Smeas) is closed and the electronic interruption unit (EU) is switched to the low-resistance state, a measurement current flows through the electronic interruption unit (EU) via the grid-side connections.

2. Circuit breaker device (SG) according to Patent Claim 1, characterized in that, when the switch (Smeas) is closed and the contacts of the mechanical isolating contact unit (MK) are open and the electronic interruption unit (EU) is switched to the low-resistance state, a measurement current flows through the electronic interruption unit (EU) via the grid-side connections.

3. Circuit breaker device (SG) according to Patent Claim 1 or 2, characterized in that the series circuit consisting of the measurement impedance (ZM) and the switch (Smeas) is connected on one side to the connection between mechanical isolating contact unit (MK) and electronic interruption unit (EU).

4. Circuit breaker device (SG) according to Patent Claim 2 or 3, characterized in that the series circuit consisting of the measurement impedance (ZM) and the switch (Smeas) is connected on the other side to the other conductor at the grid-side connection.

5. Circuit breaker device (SG) according to one of the preceding patent claims, characterized in that the measurement impedance is an electrical resistor or / and capacitor.

6. Circuit breaker device (SG) according to one of the preceding patent claims, characterized in that the measurement impedance is a series circuit or parallel circuit consisting of an electrical resistor and capacitor.

7. Circuit breaker device (SG) according to one of the preceding patent claims, characterized in that the measurement impedance has a high resistance or impedance value, in particular in that the resistance value is less than 1 Mohm, 500 kohm, 100 kohm, 50 kohm, 10 kohm, 5 kohm, 1 kohm, 500 ohm or 100 ohm.

8. Circuit breaker device (SG) according to one of the preceding patent claims, <b>characterized in that the switch is connected to the control unit, such that the switch is able to be switched on and off by the control unit; in that the circuit breaker device is designed such that the switch (Smeas) is switched on when the electronic interruption unit (EU) is in the high-resistance state, in particular that the switch (Smeas) is switched off when the electronic interruption unit (EU) is in the low-resistance state.

9. Circuit breaker device (SG) according to one of the preceding patent claims, characterized in that the circuit breaker device is designed such that the level of the current is ascertained by way of the current sensor unit when the electronic interruption unit (EU) is in the high-resistance state and the switch (Smeas) is switched on, in the event of a first current threshold value being exceeded, a faulty electronic interruption unit is inferred, in particular the mechanical isolating contact unit is not able to be closed or is opened.

10. Circuit breaker device (SG) according to one of the preceding patent claims, characterized in that the circuit breaker device is designed such that, in order to test the function of the circuit breaker device when the contacts of the mechanical isolating contact unit (MK) are open and the electronic interruption unit (EU) is switched to the high-resistance state and the switch (Smeas) is switched on, the electronic interruption unit (EU) is switched to a low-resistance state for a first time interval without the switch (Smeas) being switched off, such that the measurement current flows through the measurement impedance in order to test the function of the circuit breaker device, in particular of the electronic interruption unit (EU).

11. Circuit breaker device (SG) according to Patent Claim 10, characterized in that the function test of the circuit breaker device: - comprises ascertaining the level of the measurement current by way of the current sensor unit, in particular comparing the level of the ascertained measurement current with a reference measurement current level and, in the event of a deviation from the reference measurement current level that is outside a first tolerance range, inferring a faulty circuit breaker device, in particular not being able to close or opening the mechanical isolating contact unit, or - comprises ascertaining the level of a voltage across the electronic interruption unit, in particular comparing the level of the ascertained voltage with a reference voltage level and, in the event of a deviation from the reference voltage level that is outside a second tolerance range, inferring a faulty electronic interruption unit, in particular not being able to close or opening the mechanical isolating contact unit.

12. Circuit breaker device (SG) according to Patent Claim 10, characterized in that the measurement current is used to calibrate the level of the current ascertained by the current sensor unit, in particular after a function test according to Patent Claim 11 has been performed.

13. Circuit breaker device (SG) according to Patent Claim 1 to 9, characterized in that the circuit breaker device is designed such that, in order to test the function of the circuit breaker device when the contacts of the mechanical isolating contact unit (MK) are closed and the electronic interruption unit (EU) is switched to the low-resistance state and when the switch (Smeas) is switched off, the switch (Smeas) is switched to a closed state for a first time range such that an additional current caused by the measurement impedance flows through the electronic interruption unit (EU), the level of which additional current is ascertained, is compared with additional current values and, in the event of a deviation outside a third tolerance range, an additional current fault condition is present.

14. Circuit breaker device (SG) according to Patent Claim 13, characterized in that the switch (Smeas) is switched to a closed state for the first time range when the level of the current ascertained by the current sensor unit falls below a first current level, in order in particular to ascertain a faulty circuit breaker device, in particular a faulty current sensor unit or current detection.

15. Method for a circuit breaker device for protecting an electrical low-voltage circuit having: - a housing (GEH) having grid-side connections and at least one load-side connection, - a mechanical isolating contact unit (MK) that is connected in series with an electronic interruption unit (EU), wherein the mechanical isolating contact unit is assigned to the load-side connection and the electronic interruption unit (EU) is assigned to the grid-side connections, - wherein the mechanical isolating contact unit (MK) is able to be switched by opening contacts so as to avoid a current flow or closing the contacts to allow a current flow in the low-voltage circuit, - wherein the electronic interruption unit (EU) is able to be switched by semiconductor-based switching elements to a high-resistance state of the switching elements so as to avoid a current flow or a low-resistance state of the switching elements so as to allow a current flow in the low-voltage circuit, - wherein the level of the current of the low-voltage circuit is ascertained and, in the event of current or / and current-time limit values being exceeded, avoidance of a current flow in the low-voltage circuit is initiated, - wherein, in the circuit breaker device, a series circuit consisting of a measurement impedance (ZM) and a switch (Smeas) is provided between conductors of the low-voltage circuit such that, when the switch (Smeas) is closed and the electronic interruption unit (EU) is switched to the low-resistance state, a measurement current flows through the electronic interruption unit (EU) via the grid-side connections.

16. Method according to Patent Claim 15, characterized in that the switch (Smeas) is switched on when the electronic interruption unit (EU) is in the high-resistance state and is switched off when the electronic interruption unit (EU) is in the low-resistance state.