CIRCUIT BREAKER AND METHOD

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 low-voltage circuit comprising multiple conductors, 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 above, in particular 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 and by a method according to patent claim 16.

[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 at least one mains-side connection and 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 connection, 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, a current sensor unit for determining the level of the current in the low-voltage circuit, a control unit 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, the avoidance of current flow in the low-voltage circuit is initiated.

[0020] According to the invention, a measuring impedance is provided between two conductors of the low-voltage circuit. The measuring impedance is connected, on the one hand, to the connection between the mechanical isolating contact unit and the electronic interruption unit. On the other hand, the measuring impedance is connected to the other conductor, in particular to the other conductor at the mains-side connection.

[0021] According to the invention, the protective switching device is designed such that, in order to test the function of the protective switching device, the electronic interruption unit (EU) is switched to a low-impedance state for a first period of time when the contacts of the mechanical isolating contact unit are open and the electronic interruption unit is switched to a high-impedance state.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] This has the particular advantage that the electronic interruption unit can be checked with regard to its "switchability and switched-on state".

[0026] Advantageous embodiments of the invention are specified in the subclaims and in the exemplary embodiment.

[0027] 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.

[0028] 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.

[0029] In an advantageous embodiment of the invention, the voltage level across the electronic interruption unit is determined during the switching (action) of the electronic interruption unit to the low-resistance state for the first period of time. If a second voltage threshold is exceeded, a second fault condition exists, preventing the electronic interruption unit from becoming further or subsequently low-resistance and / or the contacts from closing. (I.e., if the voltage falls below the second threshold, no fault condition exists.)

[0030] The first voltage threshold should preferably be less than 1 V. The first voltage threshold can be between 0 volts (or greater than 0 volts) and less (e.g., 10% less) than the instantaneous value of the currently applied AC voltage (especially when monitoring or comparing instantaneous values).

[0031] This has the particular advantage that the electronic interruption unit can be checked more precisely with regard to its "switchability" or switched-on state.

[0032] 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, the voltage level across the electronic interruption unit is determined when the electronic interruption unit is switched to high impedance. If the voltage falls below a first voltage threshold, a first fault condition exists, thus preventing the electronic interruption unit from becoming low impedance (possibly again or for the first time) and / or closing the contacts. (I.e., if the first voltage threshold is exceeded, no fault condition exists.)

[0033] The first voltage threshold could be an effective / mean / rms value of the AC voltage. The first voltage threshold could be an instantaneous voltage value. The comparison can be made using effective values ​​or instantaneous values ​​over time.

[0034] This serves to check the electronic interruption unit with regard to its "switchability or switched-off state", i.e. the high-resistance or high-resistance of the semiconductor-based switching elements.

[0035] The first voltage threshold is advantageously 5-15% of the nominal voltage or applied voltage of the low-voltage circuit, for example, 10%. This applies to both effective values ​​and instantaneous values ​​of the AC voltage, depending on the selected comparison method. For example, the instantaneous value of the AC voltage can also be measured at specific times. For example, at the time when the instantaneous value of the AC voltage is +300 V or -300 V.

[0036] This has the particular advantage of allowing a simple check of the switching behavior of the electronic interruption unit.

[0037] 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.

[0038] Furthermore, the electronic interruption unit can be prevented from becoming low-resistance.

[0039] Other error conditions may exist.

[0040] This has the particular advantage that only a functional protective switching device with a functional electronic interrupter unit can be switched on. This increases operational reliability in the low-voltage circuit. This ensures that the electronic interrupter unit can be switched on and off properly.

[0041] In an advantageous embodiment of the invention, the protective switching device can further be designed in such a way that further refinements 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 prevent a 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, wherein if current and / or current time limit values ​​are exceeded, an avoidance of a current flow in the low-voltage circuit is initiated.

[0042] According to the invention, the level of the voltage between the mains-side connection point and the load-side connection point of the electronic interruption unit can be determined or is determined.

[0043] 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.

[0044] By determining the voltage level across the electronic interruption unit, the functionality of the electronic interruption unit can be determined according to the invention. According to the invention, increased operational reliability of a protective switching device is thus achieved. Furthermore, a new architecture or structural design of a protective switching device is proposed.

[0045] 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.

[0046] This has the particular advantage of providing a simple solution with only one voltage sensor unit.

[0047] In an advantageous embodiment of the invention, a second voltage sensor unit connected to the control unit is alternatively provided, which determines the level of a second voltage between the mains-side neutral conductor connection and the mains-side phase conductor connection. Furthermore, a third voltage sensor unit connected to the control unit is provided, which determines the level 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 level 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] In an advantageous embodiment of the invention, a measuring impedance is connected, in particular, between the mains-side connection points of the mechanical isolating contact unit. In particular, the measuring impedance is an electrical resistor and / or capacitor, i.e., a single element or a series or parallel connection of two elements.

[0052] In particular, the measuring impedance should have a high resistance or impedance value to minimize losses. In particular, resistance values ​​greater than 100 kOhm, preferably 1 MOhm, 2 MOhm, 3 MOhm, 4 MOhm, or 5 MOhm, especially greater than 5 MOhm, are recommended. In a 230-volt low-voltage circuit, the use of a measuring resistor of, for example, 1 MOhm, results in approximately 50 mW of losses.

[0053] This has the particular advantage of allowing for better verification of the functionality of the electronic interruption unit, particularly when the isolating contacts are open, especially with the circuit breaker architecture according to the invention.

[0054] In an advantageous embodiment of the invention, the low-voltage circuit is a three-phase alternating current circuit. The protective switching device has several or additional mains-side and load-side phase conductor connections to protect the phases of the electrical circuit. Between each of the mains-side and load-side phase conductor connections, an electronic interruption unit with a voltage detection device according to the invention, in particular first voltage sensor units, is provided. Furthermore, a contact of the mechanical isolating contact unit is provided between each of the mains-side and load-side phase conductor connections. This has the particular advantage of enabling protection for three-phase alternating current circuits.

[0055] 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.

[0056] This has the particular advantage of achieving increased operational reliability, since the contacts cannot be accidentally closed by the control unit.

[0057] 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.

[0058] This has the particular advantage that the functionality of a classic circuit breaker is provided.

[0059] 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.

[0060] This has the particular advantage of providing increased protection and operational reliability as switching on a defective circuit breaker is avoided.

[0061] 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. Specifically, a fuse, particularly a melting fuse, is provided in the connection to the mains-side neutral conductor connection. Advantageously, the measuring impedance can be connected to the mains-side neutral conductor connection via the fuse.

[0062] This has the particular advantage of enabling a compact electronic assembly. Furthermore, there is only one cross-connection between the phase conductor and the neutral conductor in the protective switching device. A fault in the protective switching device that causes a short circuit between the phase conductor and the neutral conductor can thus be easily protected, secured, and located.

[0063] 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.

[0064] This has the particular advantage that a graduated shutdown concept is available for a protective switching device according to the invention at increased currents.

[0065] In an advantageous embodiment of the invention, the control unit comprises a microcontroller.

[0066] 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.

[0067] According to the invention, a corresponding method for a protective switching device for a low-voltage circuit with electronic (semiconductor-based) switching elements with the same and further advantages is claimed.

[0068] The method for a protective switching device for protecting a low-voltage electrical circuit with: a housing with at least one mains-side connection and one load-side connection, a mechanical isolating contact unit which is 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 connection, 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 for current flow in the low-voltage circuit, that the level of the current in the low-voltage circuit, in particular between the mains-side phase conductor connection and the load-side phase conductor connection,it is determined that if current and / or current-time limit values ​​are exceeded, an avoidance of current flow in the low-voltage circuit is initiated, that a measuring impedance is provided between two conductors of the low-voltage circuit, whereby the measuring impedance is connected on the one hand to the connection between the mechanical isolating contact unit and the electronic interruption unit.

[0069] To test the function of the protective switching device, the electronic interruption unit is switched to a low-resistance state for an initial period of time when the contacts of the mechanical isolating contact unit are open and the electronic interruption unit is switched to a high-resistance state.

[0070] The polarity of the applied instantaneous value of the alternating voltage, i.e. the measurement time, can be used to determine whether a first semiconductor-based switching element (for a first voltage polarity) or a second semiconductor-based switching element (for a second voltage polarity) is being tested.

[0071] When the electronic interrupt unit is switched to the low-resistance state for the first period of time, the voltage across the electronic interrupt unit is determined. If a second voltage threshold is exceeded, a second fault condition is present, preventing the electronic interrupt unit from becoming low-resistance again and / or closing the contacts.

[0072] With the contacts of the mechanical isolating contact unit open and the electronic interruption unit (EU) switched to high resistance, the voltage level across the electronic interruption unit can also be determined. If the voltage falls below a first voltage threshold, a first fault condition is present, preventing the electronic interruption unit from becoming low-resistance and / or closing the contacts.

[0073] According to the invention, a corresponding computer program product is 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.

[0074] The microcontroller is part of the protective switching device, in particular the control unit.

[0075] According to the invention, a corresponding computer-readable storage medium on which the computer program product is stored is claimed.

[0076] According to the invention, a corresponding data carrier signal which transmits the computer program product is claimed.

[0077] All embodiments, both in dependent form referring back to patent claim 1 or 16, and referring back only to individual features or combinations of features of patent claims, in particular also a reference of the pending arrangement claims to the independent method claim and vice versa, bring about an improvement of a protective switching device, in particular an improvement of the safety of a protective switching device or of the electrical circuit, and provide a new concept for a protective switching device.

[0078] 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.

[0079] The drawing shows: Figure 1 a first representation of a protective switching device, Figure 2 a second representation of a protective switching device, Figure 3 a third representation of a protective switching device with first voltage curves, Figure 4 a fourth representation of a protective switching device with second voltage curves, Figure 5 a fifth representation of a protective switching device.

[0080] 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. .

[0081] According to the invention, the protective switching device is 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.

[0082] 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.

[0083] 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.

[0084] According to the invention, a measuring impedance ZM is further 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 circuit or parallel circuit of a resistor and / or capacitor and / or inductance.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] The protective switching device SG is advantageously designed such 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.

[0090] 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.

[0091] 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.

[0092] The mechanical isolating contact unit MK is advantageously designed in such a way that a (manual) closing of the contacts by the mechanical handle is only possible after an enable, in particular an enable signal.

[0093] This is also indicated by the arrow pointing from the control unit SE to the mechanical isolating contact unit MK. 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").

[0094] 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 1is 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).

[0095] Alternatively, the measuring impedance ZM can be connected to the mains-side neutral conductor connection NG via the fuse SS. This allows the advantageous use of a three-pole electronic unit EE ( Figure 5), for example, as a module with three connection points: one neutral conductor connection point and two phase conductor connection points. The electronics unit EE includes, for example, the electronic interruption unit EU, the control unit SE, the power supply NT (including the fuse SS), the current sensor unit SI, the first voltage sensor unit SU1, and optionally the second voltage sensor unit SU2.

[0096] 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 voltage detection devices (e.g., by means of first voltage sensor units) are provided in a similar manner between the additional mains-side and load-side phase conductor connections. The same applies to the contacts of the mechanical isolating contact unit.

[0097] The measuring impedance ZM should have a very high value (resistance or impedance value) to keep losses low. For example, a resistance value of 1 MOhm would result in losses of approximately 50 mW in a 230 V low-voltage circuit.

[0098] The measuring impedance should preferably be greater than 100 KOhm.

[0099] 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.

[0100] 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.

[0101] Figure 2 shows an illustration according to Figure 1 , with the difference that an energy source EQ with a nominal voltage UN of the low-voltage circuit is connected to the grid side GRID. Furthermore, a consumer or energy sink ES is connected to the load side LOAD.

[0102] Furthermore, an enable signal is shown for the connection from the control unit SE to the mechanical isolating contact unit MK.

[0103] The mechanical isolating contact unit MK is shown in an open OFF state, ie with open contacts KKN, KKL to prevent current flow.

[0104] 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.

[0105] Figure 3 shows a representation according to Figure 2 , with various differences. The voltages on and in the protective switching device are shown in more detail: the nominal voltage UN of the energy source EQ of the low-voltage circuit, the mains voltage U LN applied between the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG, the second voltage U2 or UN,GND measured in the protective switching device by the second voltage sensor unit SU2, the first voltage U1 or U SW measured with the first voltage sensor unit SU1 across the electronic interruption unit EU.

[0106] In this variant according to Figure 3 The first voltage U1 (or U SW ) is measured directly across the electronic interruption unit (i.e., without the current sensor unit SI). The second voltage U2 (or UN,GND ) corresponds to the mains voltage U LN minus the (minimal) voltage drop across the current sensor unit SI and the ohmic losses.

[0107] Furthermore, a detail of the electronic interruption unit EU is shown, whereby the (single-pole) electronic interruption unit EU has semiconductor-based switching elements T1, T2. In the example according to Figure 3 Two semiconductor-based switching elements T1, T2 are provided in series. Advantageously, an overvoltage protection device (TVS) is provided above the series connection of the two semiconductor-based switching elements T1, T2.

[0108] In the design according to Figure 3Two unidirectional electronic switching elements are connected in series (anti-serial). The first unidirectional switching element is arranged to be switchable in a first current direction, and the second unidirectional switching element is arranged to be switchable in the opposite current direction, with the unidirectional switching elements being conductive opposite to their current switching direction (directly or indirectly, e.g., through internally or externally connected diodes in parallel). In particular, the protective switching device is designed such that the first and second switching elements can be switched independently of one another.

[0109] The following situation is considered below: Nominal voltage or mains voltage (e.g. 230 V AC) is present at the mains-side connection LG, NG or mains side GRID or mains connection of the protective switching device, A consumer or energy sink ES or load is connected to the load side LOAD of the protective switching device,

[0110] The first step is to consider the test in the OFF state of the electronic protective device.

[0111] This includes: The mechanical isolating contact unit is open (contacts open) The electronic interruption unit is switched off (semiconductor-based switching elements high resistance) The control unit (incl. controller unit) is active

[0112] The electrical potential between the electronic interruption unit and the mechanical isolating contact unit is defined by the measuring impedance ZM and the impedance of the electronic interruption unit in the switched-off state (voltage divider).

[0113] The control unit can now switch on the semiconductor-based switching elements (which of the two semiconductors is active?) at any time (and thus at a specific voltage distribution (depending on the instantaneous value of the voltage, half-wave of the voltage). Taking into account the polarity of the alternating voltage or AC voltage, the switching elements of the electronic interruption unit EU can be tested.

[0114] The electronic interruption unit EU (or the electronic switch) is thus switched on for a very short time (in the millisecond range). If the electronic interruption unit is functional, this can be determined by (simultaneous) voltage measurement (e.g., first voltage sensor unit, second voltage sensor unit) and (subsequent) evaluation. For example, in the case of a defective semiconductor-based switching element, it can be determined whether it always remains switched on (fault pattern: "alloyed") or always remains switched off (fault pattern: "burned").

[0115] This covers two typical and common fault patterns. If the test is error-free, a (first) enable condition for switching on the protective switching device, specifically the electronic interruption unit or the mechanical isolating contact unit, may be present.

[0116] If the check is not error-free, the protective switching device will not be enabled to switch on; an error condition exists, meaning that the outgoing device or consumer / load cannot be switched on, thus preventing a dangerous condition.

[0117] The protective switching device is designed such that when the contacts of the mechanical isolating contact unit MK are open and the electronic interruption unit EU is switched to high impedance, the voltage level across the electronic interruption unit, i.e., the first voltage U1, is determined. If a first voltage threshold is undershot, a first fault condition exists, so that the electronic interruption unit is prevented from becoming low impedance and / or closing the contacts. With regard to the mechanical isolating contact unit MK, for example, an enable signal is not sent from the control unit SE to the mechanical isolating contact unit MK.

[0118] On the right side of the Figure 3 Three corresponding voltage curves are shown over time. The voltage level in volts is plotted on the vertical y-axis, and the time in milliseconds (ms) is plotted on the horizontal x-axis. The curves of the first voltage U1 and the second voltage U2 over time are shown.

[0119] The first upper graphic, NORM, shows the voltage curves for a fault-free state of the electronic interruption unit EU. In this case, the difference in amplitude between the first voltage U1 and the second voltage U2 is determined by the voltage drop across the measuring impedance ZM. The first voltage threshold should be based on the magnitude of the measuring impedance. For example, the first voltage threshold should be slightly smaller than the nominal voltage minus the voltage drop across the measuring impedance. If the first voltage U1 is greater than the first voltage threshold, the electronic interruption unit EU is fault-free. The evaluation can be based on the instantaneous voltage values ​​or the effective voltage values.If the first voltage U1 is greater than the first voltage threshold, a first enable condition is met, allowing the electronic interruption unit to become low-resistance and / or the closing of the contacts of the mechanical isolating contact unit. This is shown in . Figure 3represented by an arrow, labeled enable, from the control unit SE to the mechanical isolating contact unit MK, for enabling the closing of the contacts of the mechanical isolating contact unit MK by the handle HH. The connection or arrow from the control unit SE to the electronic interruption unit EU shows a representation of a curve of the switching state of the electronic interruption unit over time, in which a switched off / high-impedance state is labeled off and a switched on / low-impedance state of the electronic interruption unit EU is labeled on. In the example, the electronic interruption unit EU is in the switched off state off, which is represented by a straight line next to 'off'.

[0120] The second middle graphic, "T1 is "shortened," shows the voltage curve for a defective electronic interruption unit EU, in which a semiconductor-based switching element, in this example switching element T1, is constantly conductive (short-circuited). As a result, a current flows through the electronic interruption unit in one half-wave of the electrical voltage, even though it is (should be) highly resistive. The conductivity in the current direction affected by the affected semiconductor-based switching element prevents the buildup of a voltage across the affected semiconductor-based switching element. This means that the level of the first voltage U1 cannot exceed the first voltage threshold, which can be determined using the first voltage sensor unit SU1 in conjunction with the control unit SE. This is Figure 3 indicated by the abbreviation DT.

[0121] The third lower graph, "T2 is "shortened," shows the voltage curve for a defective electronic interruption unit EU, in which the other semiconductor-based switching element, in this example, switching element T2, is constantly conductive (short-circuited). The same applies to the middle graph.

[0122] The second and third graphics show a fault condition of the electronic interruption unit EU, which, according to the invention, can be detected before the contacts of the mechanical isolating contact unit are closed when the contacts of the mechanical isolating contact unit and the low-resistance interruption unit are closed, and which prevents manual closing of the contacts of the mechanical isolating contact unit.

[0123] This will be explained again in other words. Figure 3shows an overview of the circuit diagram and voltage curves in the event that a switching element in the electronic interruption unit is defective, in this case broken down / short-circuited. Since unidirectional blocking power semiconductors are typically used, the semiconductor-based switching element T1 or T2 can be tested for functionality depending on the applied voltage polarity. If an alternating voltage is applied to the terminals of a functioning protective switching device, a voltage U1 or Uw is generated across the electronic interruption unit, which can be determined using a corresponding first voltage sensor unit SU1. This is shown in the upper graphic NORM. If one of the two switching elements is broken down, the voltage can no longer be absorbed by the electronic interruption unit. The measured voltage is zero for a certain period of time (approx. 5 ms).This is illustrated by the two curves "T1 is shortened" and "T2 is shortened." This allows for the measurement or detection of a defective switching element. If both switching elements are shorted, the first voltage U1 or U2 is always zero (not shown).

[0124] Figure 4 shows a representation according to Figure 3 with the difference that the electronic interrupt unit EU is briefly switched on and off. This is indicated by a square wave signal relating to the off and on states at the connection between the control unit SE and the electronic interrupt unit EU.

[0125] On the right side of the Figure 4 There are again three graphics according to Figure 3Shown are voltage waveforms for the case where a switching element in the electronic interrupt unit is defective, in this case, burned out / open. Since unidirectional blocking power semiconductors are typically used, switching element T1 or T2 can be tested for functionality depending on the applied voltage polarity.

[0126] If an AC voltage is applied to the functioning protective switching device on the mains side, a voltage U1 or Uw is generated across the electronic interruption unit, which can be measured using a corresponding voltage measurement (first voltage sensor unit SU1). This is shown in the upper "Health" curves.

[0127] To check whether one of the two semiconductor-based switching elements is burned out, a short switch-on pulse is applied (first time period). If one of the two switching elements is burned out, the switching element can no longer be switched on by the electronic interruption unit. Even when switched on, the measured voltage always remains the same as in the off state. This is shown in the middle graphic, "T1 is "open"," and the lower graphic, "T2 is "open." This allows the measurement or detection of a defective switching element.

[0128] This means that the protective switching device is designed in such a way that when the contacts of the mechanical isolating contact unit MK are open and the electronic interruption unit EU is switched to a high-resistance state, the electronic interruption unit EU is switched to a low-resistance state for a first period of time and the level of the voltage across the electronic interruption unit is determined.

[0129] If a second voltage threshold is exceeded, a second fault condition occurs, so that the electronic interruption unit does not become low-resistance and / or the contacts do not close.

[0130] The protective switching device is advantageously designed such that, in the event of a fault condition, the contacts of the mechanical isolating contact unit MK are prevented from closing. In particular, no enable signal is sent to the mechanical isolating contact unit MK.

[0131] Figure 5shows a representation according to Figures 1 to 4 , 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. The first part EPART can have the control unit SE, the first voltage sensor unit SU1, the second voltage sensor unit SU2, the current sensor unit SI, the electronic interruption unit EU, and the power supply NT. Furthermore, the first part can have the fuse SS, a switch SCH, the measuring impedance ZM, a temperature sensor TEM (in particular for the electronic interruption unit EU), a communication unit COM, and a display unit DISP.

[0132] 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.

[0133] The protective switching device contains a second part, MPART, which is particularly mechanical. The second part, MPART, can include the mechanical isolating contact unit MK, the handle HH, and a release unit FG. Furthermore, the second part can include 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). Additional, unspecified units can be provided.

[0134] The division into two parts makes it possible to advantageously realize a compact protective switching device according to the invention.

[0135] The release unit FG enables the actuation of the contacts of the mechanical isolating contact unit by the handle HH when an enable signal is present.

[0136] In the following, the invention will be summarized again and explained in more detail.

[0137] An example of an electronic protection and switching device is proposed with: Housing with mains and load-side connections Voltage sensor unit Current sensor unit for measuring the (load) current Mechanical isolating contact unit including handle (including display of contact position, release by the electronics, isolating properties) Electronic interruption unit with semiconductor-based switching elements Control unit The functionality of the electronic interruption unit is checked by continuously measuring the voltage across the electronic interruption unit. This can be used to determine, for example, whether a semiconductor component has burned out when the unit is switched on. By briefly switching the electronic interruption unit on (<10 ms, preferably <1 ms, generally: <20 ms, 50 ms, 100 ms, 200 ms, 500 ms or 1 s) with the contacts open and then immediately switching it off again. and at the same time voltage measurements and / or current measurements are recorded and analyzed in such a way that a defective or blown electronic interruption unit is detected or defective or blown switching elements are detected.

[0138] It is advantageous to measure first, then switch and measure.

[0139] A first voltage sensor unit / voltage measuring unit is proposed above the electronic interruption unit in order to determine the voltage across the electronic interruption unit. Alternatively, a third voltage sensor unit can be provided in parallel to the second voltage sensor unit, which is provided at the load-side connection of the electronic interruption unit, i.e. between the electronic interruption unit and the mechanical isolating contact unit, wherein the third voltage sensor unit is connected on the one hand to the phase conductor and on the other hand to the neutral conductor. The first voltage can be determined from the difference between the voltages between the second and third voltage sensor units. In this case, the first voltage sensor unit can be omitted.

[0140] An additional measuring impedance is proposed, which is installed between the two conductors / current paths (phase conductor L and neutral conductor N) to define the electrical potential between the electronic interruption unit EU and the mechanical isolating contact unit for measuring purposes (no "floating" potential).

[0141] A computer program product or algorithm is proposed which switches the electronic interruption unit or the semiconductor-based switching elements 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.

[0142] 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.

[0143] The computer program product may be stored on a computer-readable storage medium, such as a CD-ROM, a USB stick or similar.

[0144] Furthermore, a data carrier signal that transmits the computer program product may exist.

[0145] A mechanical isolating contact unit is proposed which cannot be switched on as long as the control unit does not send an enable signal.

[0146] The timing for switching the semiconductor-based switching elements (for testing) depends on the polarity of the currently applied mains voltage, allowing for targeted testing of individual switching elements. Furthermore, the instantaneous voltage value can be taken into account when selecting the timing.

[0147] In particular: the first time period: very short to short, 10 µs to 1 s, the first voltage threshold: 5-10% of the effective value / RMS value of the nominal voltage or applied AC voltage or the instantaneous value of the AC voltage; e.g. 10-20 V, the second voltage threshold: less than 1 volt,

[0148] In summary: Voltage measurement across the electronic interruption unit or determination of the voltage drop across the electronic interruption unit EU (e.g. via a simple voltage divider), high-ohmic measuring impedance (preferably R and / or C) to determine the electrical potential between the electronic interruption unit and the mechanical isolating contact unit. Voltage determination across the electronic interruption unit will be used to: detect a broken or burnt-out condition of a power semiconductor, enable the possibility of switching on the mechanical isolating contact unit after error-free testing of the electronic interruption unit.

[0149] 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 those skilled in the art without departing from the scope of the invention, which is defined by the appended claims.

Claims

1. Circuit breaker (SG) for protecting an electrical low-voltage circuit, having: - a housing (GEH) having at least one grid-side terminal and one load-side terminal, - a mechanical break contact unit (MK) which is connected in series with an electronic interrupt unit (EU), wherein the mechanical break contact unit is assigned to the load-side terminal and the electronic interrupt unit (EU) is assigned to the grid-side terminal, - wherein the mechanical break contact unit (MK) can be switched by opening contacts for avoiding a current flow or closing the contacts for a current flow in the low-voltage circuit, - wherein the electronic interrupt unit (EU) can be switched by semiconductor-based switching elements into a high-resistance state of the switching elements for avoiding a current flow or a low-resistance state of the switching elements for current flow in the low-voltage circuit, - a current sensor unit (SI) for determining the level of the current of the low-voltage circuit, - a control unit (SE) which is connected to the current sensor unit (SI), the mechanical break contact unit (MK) and the electronic interrupt unit (EU), wherein avoidance of a current flow of the low-voltage circuit is initiated if current or / and current / time limit values are exceeded, characterized - in that a measuring impedance is provided between two wires of the low-voltage circuit, wherein on one side, the measuring impedance is connected to the connection between mechanical break contact unit (MK) and electronic interrupt unit (EU), - in that the circuit breaker is designed in such a manner that, to function test the circuit breaker when contacts of the mechanical break contact unit (MK) are open and the electronic interrupt unit (EU) is switched to high-resistance, the electronic interrupt unit (EU) is switched to a low-resistance state for a first time period.

2. Circuit breaker (SG) according to Patent Claim 1, characterized in that the circuit breaker is designed in such a manner that, for one wire, the level of the voltage can be determined across the electronic interrupt unit.

3. Circuit breaker (SG) according to Patent Claim 2, characterized in that the circuit breaker is designed in such a manner that, when contacts of the mechanical break contact unit (MK) are open, the level of the voltage across the electronic interrupt unit is determined when the electronic interrupt unit (EU) is switched to high-resistance, in that if a value falls below a first voltage threshold value, a first fault condition exists, so the electronic interrupt unit becoming low-resistance is avoided or / and closing of the contacts is avoided.

4. Circuit breaker (SG) according to Patent Claim 2 or 3, characterized in that during the switching of the electronic interrupt unit (EU) to the low-resistance state for the first time period, the level of the voltage is determined across the electronic interrupt unit, in that if a second voltage threshold value is exceeded, a second fault condition exists, so the electronic interrupt unit becoming low-resistance a further time is avoided or / and closing of the contacts is avoided.

5. Circuit breaker (SG) according to Patent Claims 3 and 4, characterized in that when a fault condition exists, closing of the contacts of the mechanical break contact unit (MK) is avoided, in particular, no approval signal (enable) is output to the mechanical break contact unit (MK).

6. Circuit breaker (SG) according to one of the preceding patent claims, characterized in that a first voltage sensor unit (SU1) is provided, which is connected to the control unit (SE) and which determines the level of a first voltage between a grid-side connecting point (EUG) and a load-side connecting point (EUL) of the electronic interrupt unit (EU).

7. Circuit breaker (SG) according to one of the preceding Patent Claims 1 to 5, characterized in that a second voltage sensor unit (SU2) is provided, which is connected to the control unit (SE) and which determines the level of a second voltage between grid-side neutral wire terminal (NG) and grid-side phase wire terminal (LG), in that a third voltage sensor unit (SU3) is provided, which is connected to the control unit and which determines the level of a third voltage between grid-side neutral wire terminal (NG) and load-side connecting point (EUL) of the electronic interrupt unit (EU), in that the circuit breaker is designed in such a manner that the level of a first voltage between grid-side connecting point (EUG) and load-side connecting point (EUL) of the electronic interrupt unit (EU) is determined from the difference between second and third voltage.

8. Circuit breaker (SG) according to one of the preceding patent claims, characterized in that the current sensor unit (SI) is provided at the circuit between grid-side phase wire terminal and load-side phase wire terminal.

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

10. Circuit breaker (SG) according to one of the preceding patent claims, characterized in that the low-voltage circuit is a three-phase AC circuit and the circuit breaker has a plurality of grid-side and load-side phase wire terminals, between which in each case one contact of the mechanical break contact unit and electronic interrupt units are provided, and, in particular first, voltage sensor units are provided, using which the level of the voltage across the respective electronic interrupt unit can be determined.

11. Circuit breaker (SG) according to one of the preceding patent claims, characterized in that the circuit breaker (SG) is designed in such a manner that the contacts of the mechanical break contact unit (MK) can be opened, but not closed by the control unit (SE).

12. Circuit breaker (SG) according to one of the preceding patent claims, characterized in that the mechanical break contact unit (MK) can be operated by a mechanical handle, in order to engage an opening of contacts or a closing of the contacts.

13. Circuit breaker (SG) according to Patent Claim 12, characterized in that the mechanical break contact unit (MK) is designed in such a manner that a closing of the contacts by the mechanical handle is only possible after an approval (enable), particularly an approval signal.

14. Circuit breaker (SG) according to one of the preceding patent claims, characterized in that when contacts of the mechanical break contact unit are closed and the interrupt unit is low-resistance, and - when a current is determined, which exceeds a first current value, in particular in that the first current value is exceeded for a first time limit, the electronic interrupt unit becomes high-resistance and the mechanical break contact unit (MK) stays closed, - when a current is determined, which exceeds a second current value, in particular for a second time limit, the electronic interrupt unit becomes high-resistance and the mechanical break contact unit (MK) is opened, - when a current is determined, which exceeds a third current value, the electronic interrupt unit becomes high-resistance and the mechanical break contact unit (MK) is opened.

15. Circuit breaker (SG) according to one of the preceding patent claims, characterized in that the control unit (SE) has a microcontroller.

16. Method for a circuit breaker (SG) for protecting an electrical low-voltage circuit, having: - a housing (GEH) having at least one grid-side terminal and one load-side terminal, - a mechanical break contact unit (MK) which is connected in series with an electronic interrupt unit (EU), wherein the mechanical break contact unit is assigned to the load-side terminal and the electronic interrupt unit (EU) is assigned to the grid-side terminal, - wherein the mechanical break contact unit (MK) can be switched by opening contacts for avoiding a current flow or closing the contacts for a current flow in the low-voltage circuit, - wherein the electronic interrupt unit can be switched by semiconductor-based switching elements into a high-resistance state of the switching elements for avoiding a current flow or a low-resistance state of the switching elements for current flow in the low-voltage circuit, - wherein the level of the current in the low-voltage circuit particularly between grid-side phase wire terminal and load-side phase wire terminal, is determined, wherein avoidance of a current flow of the low-voltage circuit is initiated when current or / and current / time limit values are exceeded, - wherein a measuring impedance is provided between two wires of the low-voltage circuit, wherein on one side, the measuring impedance is connected to the connection between mechanical break contact unit (MK) and electronic interrupt unit (EU), - wherein, to function test the circuit breaker when contacts of the mechanical break contact unit (MK) are open and the electronic interrupt unit (EU) is switched to high resistance, the electronic interrupt unit (EU) is switched to a low-resistance state for a first time period.

17. Method according to Patent Claim 16, characterized in that when contacts of the mechanical break contact unit (MK) are open and the electronic interrupt unit (EU) is switched to high-resistance, the level of the voltage across the electronic interrupt unit is determined, in that if a value falls below a first voltage threshold value, a first fault condition exists, so the electronic interrupt unit becoming low-resistance is avoided or / and closing of the contacts is avoided.

18. Method according to Patent Claim 16 or 17, characterized in that during the switching of the electronic interrupt unit (EU) to the low-resistance state for the first time period, the level of the voltage is determined across the electronic interrupt unit, in that if a second voltage threshold value is exceeded, a second fault condition exists, so the electronic interrupt unit becoming low-resistance a further time is avoided or / and closing of the contacts is avoided.

19. Method according to Patent Claims 17 and 18, characterized in that when a fault condition exists, manual closing of the contacts by a handle of the mechanical break contact unit (MK) is avoided.

20. Computer program product comprising commands which, during the execution of the program by a microcontroller, cause the microcontroller to support, in particular to carry out the method according to one of Patent Claims 16 to 19 using a circuit breaker according to one of Patent Claims 1 to 15.

21. Computer-readable storage medium, on which the computer program product according to Patent Claim 20 is stored.

22. Data carrier signal which transmits the computer program product according to Patent Claim 20.