Circuit breaker

Abstract

The invention relates to a circuit breaker for protecting an electric low-voltage circuit, having: - a housing with grid-side connections and load-side connections for conductors of the low-voltage circuit; - a series circuit consisting of a mechanical separating contact unit and an electronic interruption unit, wherein - the separating contact unit is paired with the grid-side connections, and the interruption unit is paired with the load-side connections, and - the mechanical separating contact unit has a handle for closing and opening contacts; and - a current sensor unit, which is arranged in a conductor between the separating contact unit and the interruption unit, for ascertaining the level of the current of the low-voltage circuit. The circuit breaker is designed such that when current thresholds and / or current / time thresholds are exceeded, a process for preventing a current flow in the low-voltage circuit is initiated, and a power supply unit for supplying energy to the circuit breaker is provided, said power supply unit being connected to conductors of the low-voltage circuit between the grid-side connection and the separating contact unit.

Description

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

[0002] Low voltage refers to voltages up to 1000 volts AC or up to 1500 volts DC. In particular, low voltage refers to voltages higher than extra-low voltage, defined as 50 volts AC or 60 volts DC.

[0003] Low-voltage circuits, networks, or installations refer to circuits with rated currents of up to 125 amperes, or more specifically, up to 63 amperes. Low-voltage circuits also include circuits with rated currents of up to 50 amperes, 40 amperes, 32 amperes, 25 amperes, 16 amperes, or 10 amperes. These current values ​​refer specifically to rated, rated, and / or tripping currents, i.e., the maximum current that normally flows through the circuit or at which the electrical circuit is typically interrupted, for example, by a protective device such as a circuit breaker, miniature circuit breaker, or miniature circuit breaker. The rated currents can be further staggered, from 0.5 A through 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 (MCBs) are long-established overcurrent protection devices used in low-voltage electrical installations. They protect conductors from damage caused by overheating due to excessive current and / or short circuits. A MCB can automatically disconnect the circuit in case of overload and / or short circuit. A MCB is a non-resetting safety device. Circuit breakers, unlike MCBs, are designed for currents greater than 125 A, and sometimes even as low as 63 A. Therefore, MCBs are simpler and more delicate in design. MCBs typically have a mounting option for installation on a DIN rail (also known as a top-mounted rail or TH35).

[0005] Miniature circuit breakers (MCBs) are electromechanical devices. They contain a mechanical switching contact or shunt trip within a housing to interrupt (trigger) the electrical current. Typically, a bimetallic element is used for tripping (interruption) in the event of a prolonged overcurrent (overcurrent protection) or thermal overload (overload protection). An electromagnetic trip with a coil is used for momentary tripping when an overcurrent limit is exceeded or in the event of a short circuit (short-circuit protection). One or more arc-quenching chambers or devices are provided. Furthermore, they include connection elements for conductors of the electrical circuit to be protected.

[0006] Protective switching devices with an electronic interruption unit are relatively new developments. These devices feature a semiconductor-based electronic interruption unit. This means that the electrical current flow of the low-voltage circuit is routed through semiconductor components or semiconductor switches that can interrupt the electrical current flow or be switched to conductivity. Protective switching devices with an electronic interruption unit also frequently feature a mechanical isolating contact system, particularly with isolating characteristics according to 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 of the low-voltage circuit to be protected is routed through both the mechanical isolating contact system and the electronic interruption unit.

[0007] German patent application DE 10 2019 213 604 A1 discloses a protective switching device, protective switching system, and method. The invention relates to a protective switching device or protective switching system for a low-voltage circuit, configured with a series connection of a semiconductor switch and a isolating contact system, in which the current level is determined. This involves: During a switch-on process, the isolating contact system is closed first, and then the semiconductor switch becomes low-resistance. During a manual first switch-off process, the semiconductor switch becomes high-resistance, and the isolating contact system remains closed. If a detected current exceeds a first current threshold for a first time period, the semiconductor switch becomes high-resistance, and the isolating contact system remains closed, according to the first switch-off process. If a detected current exceeds a second current threshold for a second time period, the semiconductor switch becomes high-resistance for a second switch-off process, and then the isolating contact system opens. If a detected current exceeds a third current threshold, the semiconductor switch becomes high-resistance, and then the isolating contact system opens, according to the second switch-off process.

[0008] European patent application EP 2 234 136 A1 describes a DC circuit breaker. The DC circuit breaker comprises a housing (2) provided with a power terminal (2a) that can be connected to a power source during use, and a load terminal (2b) that can be connected to a load during use. A contact unit (1) is arranged between the power terminal (2a) and the load terminal (2b). The contact unit (1) has mechanical contacts (10) and a semiconductor switch (11) connected in series with the mechanical contacts (10). The DC circuit breaker further comprises a switching mechanism unit (3) with an operating handle (30) used for manual operation and movably attached to the housing (2), a position detection unit (4) configured to detect an operating position of the operating handle (30), and a control unit (7).The switching mechanism unit (3) is configured to open and close the mechanical contacts (10) in response to manual operation of the operating handle (30). The control unit (7) is configured to turn on the semiconductor switch (11) when, based on the operating position detected by the position detection unit (4), it determines that the operating handle (30) has been moved from an open position to a closed position.

[0009] US patent application US 2020 / 0366078 A1 describes an intelligent circuit breaker. The circuit breaker comprises 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 switched to either a closed or 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 generates a current measurement signal. The voltage sensor is configured to detect a voltage at any point along the path between the line input terminal and the load output terminal and generates a voltage measurement signal.The processor is configured to receive and process the current and voltage measurement signals to determine the operating status information of the circuit breaker and to determine the power consumption information of a load connected to the load output terminal.

[0010] US patent application US 2021 / 0066013 A1 describes a semiconductor self-contained circuit breaker (SSCB) with self-diagnostic, self-maintenance, and self-protection capabilities. The SSCB comprises: a power semiconductor device; an air gap isolating unit connected in series with the power semiconductor device; a sensor and actuator circuit that shuts down the power semiconductor device when a short circuit or an overload of unacceptably long duration is detected; and a microcontroller unit (MCU) that triggers the air gap isolating unit to create an air gap and galvanically isolate a connected load after the sensor and actuator circuit has shut down the power semiconductor device.The MCU is also configured to monitor the functionality of the air gap separator, power semiconductor device and other critical components of the SSCB, and to take corrective action as necessary to prevent damage or destruction of the SSCB and the connected load, and / or to protect people and the environment from hazardous electrical conditions.

[0011] The object of the present invention is to improve a protective switching device of the type mentioned above, in particular to specify a new, improved architecture for such a protective switching device or to specify a concept with increased safety for a protective switching device or the low-voltage circuit to be protected.

[0012] This problem is solved by a protective switching device with the features of claim 1.

[0013] According to the invention, a protective switching device for the protection of a low-voltage electrical circuit, in particular a low-voltage alternating current circuit, is proposed, comprising: a housing with mains-side and load-side connections for conductors of the low-voltage alternating current circuit, in particular a mains-side phase conductor connection, a mains-side neutral conductor connection, a load-side phase conductor connection, a load-side neutral conductor connection, a mechanical disconnect contact unit (MK) connected to the mains-side connections, which on the other hand is connected to an electronic interruption unit (EU), which on the other hand is connected to the load-side connections (L2, N2), so that, through closed contacts of the isolating contact unit and a low-resistance state of semiconductor-based switching elements of the electronic interruption unit, current flow in the low-voltage circuit is enabled, or through open contacts of the isolating contact unit, galvanic isolation is enabled while preventing current flow in the low-voltage circuit, and / or through a high-resistance state of the switching elements, preventing current flow in the low-voltage circuit, i.e., a series connection of a mechanical isolating contact unit and an electronic interruption unit, wherein the mechanical isolating contact unit is arranged on the network side and the electronic interruption unit on the load side, that the mechanical isolating contact unit has a handle for manually closing and opening the contacts, and a current sensor unit arranged in a conductor between the isolating contact unit and the interruption unit.for determining the magnitude of the current in the low-voltage circuit, a control unit connected to the current sensor unit, the electronic interruption unit, and the mechanical disconnect contact unit, wherein the protective switching device is designed such that, if current and / or current-time limits are exceeded, a current flow in the low-voltage circuit is prevented, a power supply unit for supplying energy to the protective switching device, in particular the control unit, wherein the power supply unit is connected to conductors of the low-voltage circuit between the mains-side (L1, N1) terminals and the mechanical disconnect contact unit (MK), i.e., is arranged on the mains side.

[0014] According to the invention, a protective switching device is proposed, wherein the electronic interruption unit is assigned to the load-side connections (consumer, energy sink) and the mechanical disconnect contact unit is assigned to the mains-side connections (energy source). The power supply unit is electrically connected to the mains-side connections of the low-voltage circuit conductors, upstream of the mechanical disconnect contact unit. This means that the power supply unit is normally constantly supplied with energy (voltage) from the low-voltage circuit, regardless of the switching position of the contacts of the mechanical disconnect contact unit or the high or low resistance state of the electronic interruption unit (it is assumed that the low-voltage circuit / energy source normally supplies energy / voltage). Thus, the protective switching device, in particular the control unit, can provide protection or...Perform monitoring functions even when the contacts of the mechanical disconnect contact unit are open or the electronic interrupt unit is in a high-resistance state to prevent current flow.

[0015] The protective switching device is designed such that, during initial commissioning, when the low-voltage circuit is de-energized (iB de-energized), the switching elements of the electronic interruption unit are in a high-resistance state and the mechanical disconnect contact unit is locked. When power is supplied to the low-voltage circuit, the protective switching device is energized by the power supply unit. The protective switching device, specifically the control unit, performs an initial self-test. If this test is successful, the mechanical disconnect contact unit is unlocked, allowing the contacts to be closed manually. This provides the significant advantage of a highly reliable protective switching device.Only if the initial verification functions, which include a self-test, are successfully completed, ensuring that the protective switching device is functioning correctly and can monitor the circuit, is it possible to supply energy to the circuit or the load-side lines, thus ensuring that a load or consumer, or the load-side circuit or the load-side lines, is safely protected.

[0016] Advantageous embodiments of the invention are specified in the dependent claims and in the exemplary embodiment.

[0017] In an advantageous embodiment of the invention, a voltage sensor unit connected to the control unit is provided. The voltage sensor unit is designed to determine the voltage level between the conductors of the low-voltage circuit, and in particular, the voltage sensor unit is connected to the conductors between the isolating contact unit and the interruption unit.

[0018] This has the particular advantage that the voltage of the low-voltage circuit can be monitored and, if necessary, the circuit can be disconnected in the event of over- or undervoltages. Thus, the architecture according to the invention supports increased operational reliability of the protective switching device and / or in the circuit.

[0019] In an advantageous embodiment of the invention, the mechanical disconnect contact unit includes a position indicator unit. The position indicator unit shows the position of the contacts, i.e., the contact state (open, closed) is signaled. The position indicator unit is, for example, a mechanical position indicator unit.

[0020] This has the particular advantage of providing information about the contact position (open, closed). Furthermore, with a mechanical position indicator unit, this information can also be displayed when the device is de-energized.

[0021] In an advantageous embodiment of the invention, the protective switching device has a display unit connected to the control unit.

[0022] This has the particular advantage that (status) information from the protective switching device can be displayed, e.g. about switching and / or fault states.

[0023] In an advantageous embodiment of the invention, the protective switching device has a communication unit connected to the control unit, which in particular enables wireless communication.

[0024] This has the particular advantage that (status) information, such as switching and fault states, can be transmitted to another protective switching device or monitoring or management system.

[0025] In an advantageous embodiment of the invention, a differential current detection unit connected to the control unit is provided for determining the differential current of the conductors of the low-voltage circuit. This has the particular advantage that the protective switching device also features residual current monitoring (differential current monitoring) and thus has an additional functionality.

[0026] In an advantageous embodiment of the invention, the protective switching device is designed such that, when the mechanical disconnect contact unit is actuated by the handle before the contacts open, a signal is sent to the control unit, so that the latter puts the semiconductor-based switching elements of the electronic interruption unit into a high-resistance state.

[0027] This has the particular advantage of supporting currentless (powerless) switching of the mechanical disconnect contact unit, in particular avoiding arcing or contact erosion.

[0028] In an advantageous embodiment of the invention, the mechanical disconnect contact unit is designed such that the contacts can be opened by the control unit but not closed. Specifically, the contacts can be opened even if the handle is blocked.

[0029] This has the particular advantage of increased operational reliability, as the contact(s) cannot be accidentally closed by the control unit. Because the contacts open even when the handle is blocked, a so-called free trip / free trip is achieved, meaning that the low-voltage circuit is reliably protected even if the handle is blocked.

[0030] In an advantageous embodiment of the invention, the protective switching device, in particular the mechanical isolating contact unit, is designed such that the mechanical isolating contact unit can be placed in a blocked state, thus preventing the contacts from being closed by the handle. In particular, the control unit can place the mechanical isolating contact unit in a blocked state.

[0031] In an advantageous embodiment of the invention, the protective switching device, in particular the mechanical isolating contact unit, is designed such that the mechanical isolating contact unit can be moved into an unlocked state, whereby the contacts, in particular by the control unit, are not closed. In the unlocked state, the contacts can be closed (again) by the handle. In particular, the control unit can move the mechanical isolating contact unit into an unlocked state.

[0032] The unblocked state is resumed particularly after a blocked state.

[0033] In an advantageous embodiment of the invention, the protective switching device, in particular the mechanical isolating contact unit, is designed such that a bistable blocking state is provided, so that the blocked state or the unblocked state of the mechanical isolating contact unit is maintained even in the event of a power failure in the low-voltage circuit.

[0034] This has the particular advantage that, for example, after a blocking signal is received, especially from the control unit, the contacts are prevented from closing by the handle.

[0035] For example, after a release signal has been received, especially from the control unit, it is possible to close the contacts again using the handle.

[0036] This means that the mechanical disconnect contact unit has a blocking function or a blocking state that can be reset, and is designed to be bistable.

[0037] This has the particular advantage that, before the completion of testing functions or after a fault, especially in the control unit of the protective switching device, which specifically jeopardizes the functionality of the protective switching device, the power supply to the low-voltage circuit to be protected is interrupted (by preventing current flow and the contacts from closing). Thus, the safety of the low-voltage circuit is increased, since the contacts cannot be closed and consequently an unprotected load is not supplied with power.

[0038] In an advantageous embodiment of the invention, a protective element, in particular a fuse, and / or a switch is connected upstream of the power supply unit.

[0039] This has the particular advantage that the power supply unit or the control unit can be switched off, e.g., for insulation measurements. Furthermore, the power supply unit or the control unit can be protected to increase the safety of the protective switching device against further faults.

[0040] In an advantageous embodiment of the invention, the power supply unit features galvanic isolation. In particular, a transformer is provided. Furthermore, the power supply unit can have reinforced insulation, such as double insulation.

[0041] This has the particular advantage that the power supply unit exhibits isolating characteristics corresponding to those for open contacts, in order to achieve standard-compliant isolation between the mains side and the load side. Thus, a standard-compliant protective switching device is provided, whose control unit, in particular, is normally always active (switched on).

[0042] In an advantageous embodiment of the invention, after a positive result of the first verification function and an unlocked mechanical disconnect contact unit, the mechanical disconnect contact unit is also unlocked after a power failure. This has the particular advantage that the protective switching device can be switched on immediately after a power failure.

[0043] In an advantageous embodiment of the invention, after a positive first verification function and unblocking the mechanical disconnect contact unit, the switching elements of the electronic interruption unit are in a high-resistance state after the contacts of the mechanical disconnect contact unit have been closed by means of the handle.

[0044] A second test function is performed. If the second test function is successful, the switching elements of the electronic interruption unit are set to a low-resistance state.

[0045] This step completes the power-on process.

[0046] This has the particular advantage of providing a very reliable protective switching device and circuit. Only after successful completion of secondary verification functions, which may include a self-test of the electronic interruption unit as well as specific load-side and / or network-side parameters, ensuring that the protective switching device is functioning correctly and that the circuit to be protected is tested with regard to its selected parameters—in particular, that the protective switching device is suitable for the circuit to be protected and that the circuit is functioning correctly with regard to its tested parameters—will power be supplied to the load-side lines, thus ensuring the reliable protection of the load or consumer, the load-side circuit, or the load-side lines.

[0047] In an advantageous embodiment of the invention, the first (or second) verification function includes a self-test of the functionality of the protective switching device. During the self-test of the functionality of the protective switching device: At least one component, in particular several components, of a unit, in particular several units, of the protective switching device is checked. If the at least one component, in particular several components, of a unit, in particular several units, is functioning correctly, the first (or second) check function is completed with a positive result.

[0048] This has the particular advantage that only one protective switching device with functioning units is switched on or monitors the circuit, thus ensuring safety in the low-voltage circuit.

[0049] In an advantageous embodiment of the invention, if the first verification function yields a negative result, the contacts of the mechanical disconnect contact unit remain in a blocked state, so that they cannot be closed by the handle.

[0050] If the second test function fails, the contacts of the mechanical disconnect contact unit may be opened and locked, depending on the fault. Alternatively, depending on the fault, only the electronic interrupt unit may remain high-resistance.

[0051] This has the particular advantage that a defective protective switching device, which cannot perform its monitoring functions, does not allow an (accidental) power supply to a load or the load-side lines, thus avoiding unprotected circuits and massively increasing safety.

[0052] In an advantageous embodiment of the invention, the verification functions include a verification of at least one electrical parameter of the load-side or grid-side connection. In particular, the verification function performs a verification of at least one, and in particular several or all, of the following parameters: Checking for exceeding a first overvoltage value, in particular on the grid side, and / or a second overvoltage value, and / or a third overvoltage value; checking for falling below a first undervoltage value, in particular on the grid side; checking for exceeding a first temperature limit, and / or a second temperature limit, and / or a third temperature limit; checking parameters of the load-side connection, in particular for falling below a first and / or a second resistance value or a first and / or a second impedance value on the load side.

[0053] Overvoltage, or overvoltage value, refers to exceeding the valid operating voltage. This does not include voltage dips, such as those experienced during bursts or surges, which typically reach 4 kV or 8 kV (in a 230-volt or 400-volt network, respectively), or so-called network overvoltages (i.e., for example, ten times the nominal voltage of the low-voltage circuit).

[0054] In particular, the first overvoltage value can be a certain percentage higher than the normative voltage value.

[0055] For example, with a standard voltage value of 230 volts, the voltage could be 10% higher, i.e., 230V + 10%.

[0056] In particular, the second overvoltage value can be a certain higher percentage higher than the nominal voltage value. For example, with a nominal voltage value of 230 volts, it could be 20% higher: 230V + 20%.

[0057] In particular, the third overvoltage value can be a certain even higher percentage than the nominal voltage value. For example, with a nominal voltage value of 230 volts, it could be 30% higher: 230V + 30%.

[0058] This has the particular advantage that, for example, a protective switching device is not switched on when connected to a network with a different standard voltage (operating voltage) or to a load with faulty parameters. Thus, for example, a lack of protection due to an incorrect connection of, say, a 230-volt protective switching device to, say, two phases with a voltage of 400 volts can be detected and avoided, as can the incorrect supply of a load with excessively high voltage. Likewise, the associated potential damage to the protective switching device can be avoided. Similarly, switching on in the event of a short circuit before the full supply voltage is applied can be detected and prevented. Likewise, problems and a lack of protection can be avoided in the case of excessively low voltages (e.g., a 230-volt device in a 115-volt network). This results in increased operational reliability in the low-voltage circuit.Furthermore, this has the distinct advantage that not only the protective switching device itself is checked, but also the circuit / lines connected to it, i.e., specifically the power source or the power sink / load. This represents a new functionality for a protective switching device. Faults on the mains side, such as connecting the protective switching device to the wrong conductors (400 volts instead of 230 volts), can thus be detected and prevented. Likewise, potential faults on the load side, such as clean short circuits, can be detected in time, preventing the device from switching on in the event of a short circuit.

[0059] In an advantageous embodiment of the invention, depending on the parameters checked: If the first overvoltage value is exceeded, an overvoltage warning is issued; if the second overvoltage value is exceeded, the electronic interrupt unit is prevented from becoming low-impedance; if the third overvoltage value is exceeded, the contacts open; if the first undervoltage value is not reached, an undervoltage warning is issued and / or the electronic interrupt unit remains high-impedance, especially if the voltage level is greater than a second undervoltage value; if the first temperature limit is exceeded, temperature information is issued; if the second temperature limit is exceeded, the electronic interrupt unit remains high-impedance; if the third temperature limit is exceeded, the contacts open; if the first load-side resistance value or first load-side impedance value is not reached, impedance information is issued.If the second resistance value or impedance value on the load side falls below the specified threshold, the electronic interruption unit remains in high resistance mode.

[0060] This has the particular advantage that graduated, defined measures – warning, maintaining high resistance, galvanic isolation – are implemented depending on whether certain defined parameters are exceeded or fallen below. This achieves a graduated protection concept and increased operational reliability in the low-voltage circuit.

[0061] In an advantageous embodiment of the invention, the protective switching device is configured such that, when the handle is actuated to open the contacts, a signal is sent to the control unit before the contacts actually open, thus setting the switching elements of the electronic interruption unit into a high-resistance state. Furthermore, the control unit stores at least one current value or current-time value of the current flow in the low-voltage circuit in a mains-voltage-independent memory. This has the particular advantage of supporting currentless (powerless) switching of the mechanical disconnect contact unit, in particular preventing arcing or contact erosion. Moreover, the current level before, for example, the initiated opening is detected and can be read out subsequently. This facilitates the determination of the cause of a fault.

[0062] In an advantageous embodiment of the invention, the protective switching device is configured such that, if a current and / or current-time limit is exceeded, the switching elements of the electronic interruption unit are put into a high-resistance state to prevent current flow in the low-voltage circuit. Depending on the adjustable configuration of the protective switching device, the following also occurs: The contacts of the mechanical isolating contact unit are opened, or the switching elements remain in a high-resistance state, and this state is indicated. In particular, a low-resistance state of the switching elements can be initiated by an input. Alternatively, a low-resistance state of the switching elements can occur after an initial period of time or after a test of the load-side connection, specifically a test of at least one electrical parameter of the load-side connection, or more precisely, after a threshold value of the electrical parameter has been reached or exceeded.

[0063] This has the distinct advantage that the behavior of the protective switching device is configurable. In particular, various measures can be configured to prevent current flow, depending on the application. Furthermore, the re-energizing of the circuit can be configured. This increases the range of applications and the functionality of the protective switching device.

[0064] In an advantageous embodiment of the invention, the protective switching device is designed such that, upon detection of a fault in a unit of the protective switching device, the switching elements of the electronic interruption unit are put into a high-resistance state to prevent current flow in the low-voltage circuit. that furthermore the contacts of the mechanical isolating contact unit are opened and the mechanical isolating contact unit is placed in a blocked state, so that closing of the contacts by the handle is prevented, and that the detection of the fault is communicated by the communication unit.

[0065] This has the particular advantage that a protective switching device detects faults itself and, in the event of a detected fault, independently establishes a safe state in the low-voltage circuit, also prevents a restart and communicates the fault, the latter being made possible or supported in particular by the power supply unit which is constantly supplied with energy due to the inventive architecture of the protective switching device.

[0066] In an advantageous embodiment of the invention, the protective switching device is designed such that in the event of a power failure of the low-voltage electrical circuit, the mechanical isolating contact unit remains in its switching state, so that if the contacts are closed and a subsequent power failure occurs, the contacts remain closed after the power supply is restored.

[0067] This has the particular advantage that after a power failure, the protective switching device does not need to be switched on again (manually), thus ensuring a renewed power supply.

[0068] In an advantageous embodiment of the invention, the control unit comprises a microcontroller.

[0069] 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 by a (customizable) computer program. Furthermore, changes and improvements to the function can be individually loaded onto a protective switching device, for example, also via the communication unit.

[0070] According to the invention, a corresponding method for a protective switching device for a low-voltage circuit with electronic (semiconductor-based) switching elements is claimed, offering the same and further advantages.

[0071] A method for operating a protective switching device according to one of the patent claims is claimed, in particular according to patent claims 14 to 23.

[0072] The method is directed, for example, to the operation of a protective switching device with a series connection of a mechanical isolating contact unit and an electronic interruption unit, wherein the mechanical isolating contact unit is located on the network side and the electronic interruption unit is located on the load side (in the protective switching device). The mechanical isolating contact unit has a handle for closing and opening contacts. A current flow in the low-voltage circuit can be enabled by closed contacts of the isolating contact unit and a low-resistance state of semiconductor-based switching elements of the electronic interruption unit; OR a galvanic isolation is enabled by open contacts of the isolating contact unit, preventing a current flow in the low-voltage circuit; and / or a high-resistance state of the switching elements prevents a current flow in the low-voltage circuit.The current level of the low-voltage circuit is determined (in the protective switching device) and, if current and / or current time limits are exceeded, a current flow prevention measure is initiated in the low-voltage circuit (by means of the mechanical isolating contact unit and / or the electronic interruption unit).

[0073] A power supply unit for the protective switching device is provided, which is connected to conductors of the low-voltage circuit in the housing on the mains side, i.e. in the area from the mains connections to the isolating contact unit (in the protective switching device).

[0074] During initial commissioning of the protective switching device with the low-voltage circuit de-energized, the switching elements of the electronic interruption unit are in a high-resistance state and the mechanical disconnect contact unit is locked. When power is supplied to the low-voltage circuit, the protective switching device is energized by the power supply unit. An initial test function of the protective switching device is then performed. If the initial test function is successful, the mechanical disconnect contact unit is unlocked, allowing the contacts of the mechanical disconnect contact unit to be closed manually.

[0075] Further method configurations can be derived from the present configurations, patent claims and the exemplary embodiment.

[0076] All embodiments, whether dependent on claim 1 or 25 or relating only to individual features or combinations of features of claims, result in an improvement of a protective switching device, in particular a new architecture and improvement of the safety of a protective switching device or of the electrical circuit, and provide a new concept for a protective switching device.

[0077] The described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more easily understood in connection with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the drawing.

[0078] The drawing shows: Figure 1 A block diagram of a protective switching device.

[0079] Figure 1shows a representation of a protective switching device SG for the protection of a low-voltage electrical circuit, in particular a low-voltage alternating current circuit: A housing GEH with mains-side L1, N1 and load-side L2, N2 connections for conductors of the low-voltage AC circuit; the mains-side connections comprise a mains-side neutral conductor connection N1 and a mains-side phase conductor connection L1; the load-side connections comprise a load-side neutral conductor connection N2 and a load-side phase conductor connection L2; a power source is connected to the mains-side connections or the mains side Grid; (at least) a consumer or load is connected to the load-side connections or the load side Load; a mechanical disconnect contact unit MK connected to the mains-side L1, N1 connections, which is in turn connected to an electronic interruption unit EU, which in turn is connected to the load-side connections L2, N2, i.e., a series connection of a mechanical disconnect contact unit MK and an electronic interruption unit EU.wherein the mechanical isolating contact unit MK is assigned to the grid-side terminals L1, N1 and the grid side, and the electronic interruption unit EU is assigned to the load-side terminals L2, N2 and the load side, such that closed contacts KL, KN of the isolating contact unit MK and a low-resistance state of semiconductor-based switching elements T1, T2 of the electronic interruption unit EU allow current flow in the low-voltage circuit, or open contacts KL, KN of the isolating contact unit MK provide galvanic isolation while preventing current flow in the low-voltage circuit, and / or a high-resistance state of the switching elements T1, T2 of the electronic interruption unit EU prevents current flow in the low-voltage circuit. The mechanical isolating contact unit MK has a handle for closing and opening the contacts KL, KN, which is accessible on the outside of the housing.so that it can be manually operated by an operator, a current sensor unit SI, which is arranged in a conductor between the isolating contact unit MK and the interruption unit EU, for determining the magnitude of the current in the low-voltage circuit, in the example the current sensor unit SI is arranged in the phase conductor, a control unit SE, which is connected to the current sensor unit SI, the electronic interruption unit EU and the mechanical isolating contact unit MK, wherein the protective switching device SG is designed such that if current and / or current time limits are exceeded, a current flow in the low-voltage circuit is prevented, this can be achieved by the switching elements T1, T2 of the electronic interruption unit EU becoming high-impedance and / or by opening the contacts KL, KN of the mechanical isolating contact unit MK, a power supply unit NT for supplying energy to the protective switching device SG,In particular, the control unit SE, which is connected to conductors of the low-voltage circuit between the mains-side (L1, N1) terminals and the mechanical isolating contact unit (MK). This includes a connection that provides a direct connection to the mains-side (L1, N1) terminals or the mechanical isolating contact unit (MK). Electrically, the power supply unit NT is connected upstream of the mechanical isolating contact unit (MK), so that it is supplied with energy from the mains-side terminals regardless of the switching state of the contacts of the mechanical isolating contact unit (MK) (provided the mains-side terminals supply energy / voltage).

[0080] This ensures that the power supply unit (power adapter) is normally constantly supplied with energy (provided the mains supply or energy source is delivering power). Therefore, protection and monitoring functions can be performed (virtually) continuously by the protective switching device or the control unit.

[0081] The power supply unit can be equipped with a protective element, in particular a fuse (as in Figure 1 (shown), or / and a switch may be installed upstream.

[0082] In the example, the protective switching device SG also has a voltage sensor unit SU connected to the control unit SE, for determining the voltage level between the conductors of the low-voltage circuit between the isolating contact unit MK and the interruption unit EU.

[0083] In the example, the protective switching device SG has a differential current detection unit ZCT connected to the control unit, which is arranged on the conductors of the low-voltage circuit between the isolating contact unit MK and the interruption unit EU, to determine a differential current of the conductors of the low-voltage circuit.

[0084] In the example, the protective switching device SG has a display unit AE connected to the control unit SE, for displaying status information of the protective switching device, in particular the control unit SE.

[0085] In this example, the protective switching device SG has a communication unit COM connected to the control unit SE. This can enable wired or wireless communication, or both.

[0086] The control unit (SE) includes a microcontroller (MCU) for controlling the protective switching device. The microcontroller (MCU), or the control unit (SE), may contain a computer program product (CPP). The computer program product (CPP) comprises instructions that, when executed by the microcontroller (MCU), cause it to perform the specified functions for the protective switching device.

[0087] A computer-readable storage medium on which the computer program product CPP is stored may be provided. Likewise, a data carrier signal that transmits the computer program product CPP may be provided. In this way, the computer program product CPP, or a new computer program product CPP, can reach the protective switching device via the communication unit COM.

[0088] For example, according to Figure 1 The control unit SE comprises the microcontroller MCU along with the computer program product CPP, the display unit AE, the communication unit CPP, the current sensor unit SI, the voltage sensor unit SU, and the differential current detection unit ZCT. This is just one example; the units can also be separate or grouped differently.

[0089] The electronic interruption unit EU, in the example, shows according to Figure 1 two semiconductor-based switching elements T1, T2, such as transistors, field-effect transistors, IGBTs, etc.

[0090] The semiconductor-based switching elements T1 and T2 can be controlled by a driver unit Drv. In this example, the driver unit Drv is in turn controlled by the control unit SE. The electronic interrupt unit EU can include an energy absorber EA to prevent destructive voltage spikes or the absorption of switching energies.

[0091] The electronic interruption unit EU is designed as a single-pole device (for one conductor of the low-voltage circuit) in this example. In this example, the electronic interruption unit EU is located in the phase conductor.

[0092] The mechanical isolating contact unit MK is designed as a two-pole unit in this example (in both conductors of the single-phase AC circuit). A reliable galvanic isolation is possible with a two-pole design, provided the mechanical isolating contact unit MK conforms to the standard and has the necessary isolating properties (distances, minimum clearances, etc.).

[0093] The mechanical disconnect contact unit MK features a position indicator unit POSA, which displays the (switching) position of the contacts of the mechanical disconnect contact unit MK. The position indicator unit is mechanically designed so that the contact position can be displayed even when de-energized (no power from the grid).

[0094] The protective switching device or mechanical disconnect contact unit MK is designed such that, when the mechanical disconnect contact unit MK is actuated by the handle HH, an (actuation) signal AS is sent to the control unit SE before the contacts KL, KN open. The protective switching device SG or the control unit SE is designed such that the semiconductor-based switching elements T1, T2 of the electronic interrupt unit EU are then set to a high-resistance state, thus enabling power-free switching with the mechanical disconnect contact unit MK.

[0095] The protective switching device or mechanical isolating contact unit MK is designed such that the contacts KL and KN can be opened by the control unit SE, for example by an OPEN signal, but cannot be closed. Specifically, the contacts can be opened even if the handle is blocked (for example, if the "On" / closing position of the contacts is permanently engaged contrary to normal use).

[0096] The protective switching device or the mechanical isolating contact unit MK is designed in such a way that, in particular, the control unit SE can put the mechanical isolating contact unit MK into a blocked state, so that closing of the contacts by the handle is prevented.

[0097] Furthermore, the control unit SE, in particular, can put the mechanical isolating contact unit MK into an unblocked state, whereby the contacts, especially those of the control unit, are not closed, but can be closed by the handle. Furthermore, the protective switching device, specifically the mechanical isolating contact unit MK, is designed such that a bistable blocking state is provided, so that the blocked or unblocked state of the mechanical isolating contact unit MK is maintained even in the event of a power failure in the low-voltage circuit.

[0098] Additional units may be provided, such as a switching lock unit SS or a combined opening / blocking unit O / B.

[0099] The new protective switching device SG according to the invention is designed such that, during initial commissioning of the protective switching device in the de-energized (iB voltage-free) state of the low-voltage circuit, the switching elements of the electronic interruption unit are in a high-resistance state and the mechanical disconnect contact unit is in a blocked state. When energy (iB voltage supply) is applied to the low-voltage circuit, the protective switching device is supplied with energy by the power supply unit. The protective switching device, in particular the control unit, performs a first test function. If the first test function is successful, the mechanical disconnect contact unit is unlocked, so that the contacts of the mechanical disconnect contact unit can be closed by the handle.

[0100] After a positive initial test function and unblocked mechanical disconnect contact unit, after (now possible) closing of the contacts of the mechanical disconnect contact unit by means of the handle, the switching elements of the electronic interruption unit (as before) are in a high-resistance state.

[0101] A second test function is performed. If the second test function is successful, the switching elements of the electronic interruption unit are set to a low-resistance state.

[0102] This step completes the power-on process.

[0103] The first and second verification functions, for example, include a self-test of the protective switching device's functionality. During the self-test of the protective switching device's functionality: At least one component, in particular several components, of a unit, in particular several units, of the protective switching device is checked. If the at least one component, in particular several components, of a unit, in particular several units, is functioning correctly, the first (or second) check function is completed with a positive result.

[0104] The first verification function, for example, is specifically aimed at a self-test of the SE control unit, since it is supplied with power.

[0105] The second verification function can, for example, be specifically aimed at a self-test of the electronic interruption unit EU, since it is now supplied with energy / voltage is applied.

[0106] If the first verification function fails, the contacts of the mechanical disconnect contact unit remain in a blocked state, so they cannot be closed by the handle.

[0107] If the second test function fails, the contacts of the mechanical disconnect unit may be opened and locked, depending on the fault. Alternatively, depending on the fault, only the electronic interrupt unit may remain high-resistance.

[0108] The verification functions include a check of at least one electrical parameter of the load-side or grid-side connection. In particular, the verification function performs a check of at least one, and especially several or all, of the following parameters: Checking for exceeding a first overvoltage value, in particular on the grid side, and / or a second overvoltage value, and / or a third overvoltage value; checking for falling below a first undervoltage value, in particular on the grid side; checking for exceeding a first temperature limit, and / or a second temperature limit, and / or a third temperature limit; checking parameters of the load-side connection, in particular for falling below a first and / or a second resistance value or a first and / or a second impedance value on the load side.

[0109] The first verification function can include checking for exceedance of a first, second, or third overvoltage value on the grid side. It can also include checking for falling below a first undervoltage value on the grid side. The second verification function can include checking parameters of the load-side connection, in particular for falling below a first or second resistance value or a first or second impedance value on the load side. This prevents switching on during a short circuit.

[0110] Furthermore, depending on the parameters checked: If the first overvoltage value is exceeded, an overvoltage warning is issued; if the second overvoltage value is exceeded, the electronic interrupt unit is prevented from becoming low-impedance; if the third overvoltage value is exceeded, the contacts open; if the first undervoltage value is not reached, an undervoltage warning is issued and / or the electronic interrupt unit remains high-impedance, especially if the voltage level is greater than a second undervoltage value; if the first temperature limit is exceeded, temperature information is issued; if the second temperature limit is exceeded, the electronic interrupt unit remains high-impedance; if the third temperature limit is exceeded, the contacts open; if the first load-side resistance value or first load-side impedance value is not reached, impedance information is issued.If the second resistance value or impedance value on the load side falls below the specified threshold, the electronic interruption unit remains in high resistance mode.

[0111] When the handle is activated to open the contacts, a signal is sent to the control unit before the contacts actually open, thus setting the switching elements of the electronic interruption unit into a high-resistance state. Furthermore, the control unit stores at least one current value or current-time value of the current flow in the low-voltage circuit in a mains-voltage-independent memory.

[0112] If a current and / or current-time limit is exceeded, the switching elements of the electronic interruption unit are put into a high-resistance state to prevent current flow in the low-voltage circuit. Depending on the adjustable configuration of the protective switching device, the following may also occur: The contacts of the mechanical isolating contact unit are opened, or the switching elements remain in a high-resistance state, and this state is indicated. In particular, a low-resistance state of the switching elements can be initiated by an input. Alternatively, a low-resistance state of the switching elements can occur after an initial period of time or after a test of the load-side connection, specifically a test of at least one electrical parameter of the load-side connection, or more precisely, after a threshold value of the electrical parameter has been reached or exceeded.

[0113] Upon detection of a fault in a component of the protective switching device, the switching elements of the electronic interruption unit are set to a high-resistance state to prevent current flow in the low-voltage circuit. Furthermore, the contacts of the mechanical disconnect contact unit are opened, and the mechanical disconnect contact unit is placed in a blocked state, preventing the contacts from being closed by the handle. The fault detection is also communicated by the communication unit.

[0114] The first / second verification function can be implemented by the control unit, specifically the microcontroller MCU, in conjunction with the computer program product CPP.

[0115] If the mechanical isolating contact unit malfunctions, its contacts can be opened. If it fails to function after a subsequent (or a certain number of further, e.g., 0 to 3) switching-on attempt, the mechanical isolating contact unit can be locked, preventing the contacts from closing again.

[0116] The protective switching device can be designed in such a way that, in the event of a power failure of the low-voltage electrical circuit, the mechanical isolating contact unit remains in its switching state, so that if the contacts are closed and a subsequent power failure occurs, the contacts remain closed after the power supply is restored.

[0117] High resistance refers to a state in which only a negligible current flows. Specifically, high resistance values ​​greater than 1 kilohm, preferably greater than 10 kilohms, 100 kilohms, 1 megahms, 10 megahms, 100 megahms, 1 gigahms, or higher.

[0118] Low resistance refers to a condition in which the current value specified on the protective switching device could flow. Specifically, low resistance means resistance values ​​less than 10 ohms, preferably less than 1 ohm, 100 milliohms, 10 milliohms, 1 milliohm, or less.

[0119] The invention will now be described or summarized again in other words.

[0120] In electronic protective switching devices according to the invention, mechanical switching contacts in combination with an electronic switch perform the switching functions. 1.) New concept:

[0121] Mechanical disconnect contacts in both poles. One pole (especially phase conductor L) is protected by an electronic interruption unit with semiconductor-based switching elements, e.g., power semiconductors. A load-suppression network (energy absorber) is located across the switching elements. A mechanical handle is designed so that a signal is sent to the control unit before the contacts open, causing the interruption unit to become high-impedance. The mechanical disconnect contact unit can be opened by the control unit, but not closed. Closing the mechanical disconnect contact unit is only possible manually using the handle. Measurement technology: • Voltage measurement between L and N • Current measurement in the protected pole (L) • Total current measurement across L and N. The power supply (= power supply unit) for the control unit taps the voltage at L and N before the contacts of the mechanical disconnect contact unit.

[0122] The power supply unit has galvanic isolation (e.g., via a transformer-based voltage converter) to maintain the isolation function of the mechanical contacts within the overall design. The galvanic isolation must meet standard-compliant requirements, such as double insulation.

[0123] The power supply (= power supply unit) has a protected connection to L (e.g. fuse) The control unit can lock the mechanical disconnect contact unit into a blocked state. Closing the contacts using the handle is then no longer possible. The control unit can also unlock the mechanical disconnect contact unit. The device has a communication interface (preferably wireless). The contact position of the (mechanical) contacts is indicated mechanically (e.g., green: off, red: on). The device has a display unit that shows the device status, e.g., with light-emitting diodes / LEDs, as follows: Red: on state; Green: off state, unlocked; Yellow: control state, high resistance. 2.) Behavior when switching on:

[0124] The device is switched on via the handle when it is turned on. a) The device is connected to mains voltage. b) The power supply unit begins to supply the device, specifically the control unit, with power. c) The device, specifically the control unit, performs an initial check function / self-test (specifically of the electronic components). d) Upon successful completion, the mechanical disconnect contact unit, e.g., the switch lock, is switched from the blocked to the unblocked state (manual mechanical switching on by handling the main current path is now possible). Preferably bistable states: It remains in the respective state even when de-energized; switching is actively controlled by the control unit. e) The contacts are closed by handling. f) Contacts close. g) The load-side output is still de-energized because the interrupt unit is high-impedance / in the blocked state. h) Second check function, e.g., the load is checked for...Short circuit i) Upon a positive test, the interrupting unit becomes low-resistance (without further (manual) actuation). j) Load side receives energy, load / consumer is supplied. 3.) Behavior when switching off:

[0125] When switching off, the device is switched off via the handle (manual operation). a) The handle is switched to the off position (contacts open). b) The actuation signal is sent to the control unit before the contacts open. c) The interrupt unit immediately becomes high-impedance (or intelligently at the zero crossing). d) The contacts open. e) The power supply for the electronics remains active even in the disconnected (unlocked) state. i. The control unit is supplied with a suitable extra-low voltage from the power supply unit, e.g., 3 V or 5 V. ii. The power supply provides safe galvanic isolation from the mains voltage (e.g., through double or extra-reinforced insulation in the transformer-based voltage converter). iii. The power supply could be disconnected from the mains via a small switch. 4.) Behavior in case of a fault in the load: short circuit or overload:

[0126] If a device experiences, for example, a short circuit in the load, the device reacts as follows. a) The relevant units detect when a current limit is exceeded. b) The interrupting unit switches to a high-resistance state, so the load / consumer is no longer supplied with energy / voltage. c) Depending on the configuration, the device can then decide (based on the type of fault and / or fault current) which of the following (two) states occurs: 1) The device automatically opens the mechanical contacts and the load is completely disconnected. 2) The device remains in a high-resistance state (the contacts of the disconnecting contact unit remain closed – the device does not disconnect). Automatic reconnection is possible from this state. 5.) Behavior in case of (internal) device failure:

[0127] If a fault occurs in the protective switching device, particularly the control unit, the device enters a safe state from which it cannot be switched back on. This requires the protective switching device to detect the fault. a) The fault in the protective switching device is detected. b) The device switches the interrupt unit to high resistance. c) The device opens the contacts of the isolating contact unit and thereby blocks the isolating contact unit (e.g., the switch lock) to such an extent that closing the contacts by hand is no longer possible. d) The fault is reported via the communication unit. 6.) Behavior in case of network failure / power failure:

[0128] In the event of a power outage, the protective switching device is no longer supplied with energy. The contacts remain closed / in their previous position. Therefore, when power is restored, the device can return to its previous switching state without manual intervention.

[0129] Although the invention has been illustrated and described in detail by the exemplary embodiment, the invention is not limited by the disclosed examples and other variations can be derived by the person skilled in the art within the scope of protection defined by the claims.

Claims

1. Circuit breaker (SG) for protecting an electrical low-voltage AC circuit, comprising: - a housing (GEH) with grid-side (L1, N1) and load-side (L2, N2) terminals for conductors of the low-voltage AC circuit, - a mechanical isolating contact unit (MK) connected to the grid-side (L1, N1) terminals and secondly connected to an electronic interruption unit (EU) that is secondly connected to the load-side terminals (L2, N2), so that closed contacts of the isolating contact unit and a low-resistance state of semiconductor-based switching elements of the electronic interruption unit permit a flow of current in the low-voltage AC circuit, or open contacts of the isolating contact unit permit electrical isolation preventing a flow of current in the low-voltage AC circuit and / or a high-resistance state of the switching elements permits a flow of current in the low-voltage AC circuit to be prevented, - the mechanical isolating contact unit having a handle for closing and opening the contacts, - a current sensor unit (SI) for determining the level of the current in the low-voltage AC circuit, - a control unit (SE) connected to the current sensor unit (SI), the electronic interruption unit (EU) and the mechanical isolating contact unit (MK), the circuit breaker (SG) being designed such that current limit values and / or current-time limit values being exceeded results in prevention of a flow of current in the low-voltage AC circuit being initiated, characterized in that - the current sensor unit is arranged in a conductor between the isolating contact unit and the interruption unit, with - a power supply unit (NT) for supplying power to the circuit breaker (SG), which is connected to conductors of the low-voltage AC circuit between the grid-side (L1, N1) terminals and the mechanical isolating contact unit (MK), in that the circuit breaker (SG) is designed such that when the circuit breaker is first started up in the de-energized state of the low-voltage AC circuit the switching elements of the electronic interruption unit (EU) are in the high-resistance state and the mechanical isolating contact unit (MK) is in a blocked state in which the contacts of the mechanical isolating contact unit are prevented from being closed by way of the handle, in that when power is supplied in the low-voltage AC circuit the circuit breaker is supplied with power by the power supply unit (NT), the control unit (SE) performs a first checking function of the circuit breaker, a successful outcome of the checking function resulting in the mechanical isolating contact unit being unblocked, so that it is possible for the contacts of the mechanical isolating contact unit to be closed by way of the handle.

2. Circuit breaker (SG) according to Claim 1, characterized in that there is provision for a voltage sensor unit (SU), connected to the control unit (SE), for determining the level of the voltage between the conductors of the low-voltage AC circuit between the isolating contact unit and the interruption unit.

3. Circuit breaker (SG) according to Claim 1 or 2, characterized in that the mechanical isolating contact unit has a position indicator unit for the position of the contacts, in particular a mechanical position indicator unit.

4. Circuit breaker device (SG) according to Claim 1, 2 or 3, characterized in that the circuit breaker has an indicator unit (AE), connected to the control unit (SE), in particular for indicating the high-resistance or low-resistance state of the electronic interruption unit.

5. Circuit breaker (SG) according to one of the preceding claims, characterized in that the circuit breaker has a communication unit (COM), connected to the control unit (SE), that permits in particular a wireless communication capability.

6. Circuit breaker (SG) according to one of the preceding claims, characterized in that there is provision for a differential current determination unit (ZCT), connected to the control unit (SE), for determining a differential current in the conductors of the low-voltage AC circuit.

7. Circuit breaker (SG) according to one of the preceding claims, characterized in that the circuit breaker is designed such that operation of the mechanical isolating contact unit by way of the handle results in a signal being sent to the control unit (SE) before the contacts open, so that the control unit puts the semiconductor-based switching elements of the electronic interruption unit (EU) into a high-resistance state.

8. Circuit breaker (SG) according to one of the preceding claims, characterized in that the mechanical isolating contact unit (MK) is designed such that the contacts can be opened by the control unit (SE) but not closed, in particular that the contacts can be opened even if the handle is blocked.

9. Circuit breaker (SG) according to one of the preceding claims, characterized in that the circuit breaker is designed such that in particular the control unit (SE) can put the mechanical isolating contact unit (MK) into a blocked state, so that the contacts are prevented from being closed by way of the handle.

10. Circuit breaker (SG) according to Claim 9, characterized in that in particular the control unit (SE) can put the mechanical isolating contact unit (MK) into an unblocked state, the contacts not being closed, in particular by the control unit, but the contacts being able to be closed by way of the handle.

11. Circuit breaker (SG) according to Claim 9 or 10, characterized in that the mechanical isolating contact unit (MK) is designed such that there is provision for a bistable blocking state, so that the blocked state or the unblocked state of the mechanical isolating contact unit (MK) is maintained even in the event of a power failure in the low-voltage AC circuit.

12. Circuit breaker (SG) according to one of the preceding claims, characterized in that the power supply unit (NT) has a protective element (SICH), in particular a fuse, or switch connected upstream of it.

13. Circuit breaker (SG) according to one of the preceding claims, characterized in that the power supply unit (NT) has electrical isolation, in particular a transformer.

14. Circuit breaker (SG) according to one of the preceding claims, characterized in that after the first checking function has had a successful outcome and the mechanical isolating contact unit (MK) has been unblocked the mechanical isolating contact unit (MK) is unblocked even after a power failure.

15. Circuit breaker (SG) according to one of the preceding claims, characterized in that after the first checking function has been successful and the mechanical isolating contact unit has been unblocked the switching elements of the electronic interruption unit are in a high-resistance state after the contacts of the mechanical isolating contact unit have been closed by means of the handle, in that a second checking function is performed, in that after the second checking function has had a successful outcome the switching elements of the electronic interruption unit are put into a low-resistance state.

16. Circuit breaker (SG) according to one of the preceding claims, characterized in that the first checking function comprises a self-test of the functionality of the circuit breaker, which involves at least one component, in particular multiple components, of a unit, in particular of multiple units, of the circuit breaker being checked, and if the at least one component, in particular multiple components, of a unit, in particular of multiple units, is / are functional then the first checking function is terminated with a successful outcome.

17. Circuit breaker (SG) according to one of the preceding claims, characterized in that the first checking function encompasses a check on at least one electrical parameter of the grid-side terminal, in particular the level of the voltage of the grid-side terminal, in particular in that an overvoltage value being exceeded results in the first checking function being terminated unsuccessfully.

18. Circuit breaker (SG) according to one of the preceding claims, characterized in that the second checking function comprises a self-test of the functionality of the circuit breaker in accordance with the first checking function and / or encompasses a check on at least one electrical parameter of the load-side terminal.

19. Circuit breaker (SG) according to one of the preceding claims, characterized in that the circuit breaker is designed such that initiated opening of the contacts by means of the handle results in a signal being sent to the control unit before the contacts open, so that the switching elements of the electronic interruption unit are put into a high-resistance state, and in particular in that the control unit stores at least one current value or current-time value of the flow of current in the low-voltage AC circuit in a grid-voltage-independent memory.

20. Circuit breaker (SG) according to one of the preceding claims, characterized in that the circuit breaker is designed such that a current limit value and / or current-time limit value being exceeded results in the switching elements of the electronic interruption unit (EU) being put into a high-resistance state to prevent a flow of current in the low-voltage AC circuit, in that, depending on the adjustable configuration of the circuit breaker, further: - the contacts of the mechanical isolating contact unit are opened or - the switching elements remain in a high-resistance state and this state is indicated, in particular that the changing of the switching elements to a low-resistance state can be initiated by way of an input, or - in that the switching elements change to a low-resistance state after a first period of time or after a check on the load-side terminal, in particular a check on at least one electrical parameter of the load-side terminal, more specifically on a threshold value of the electrical parameter being underrun or exceeded.

21. Circuit breaker (SG) according to one of the preceding claims, characterized in that the circuit breaker is designed such that detection of a fault in a unit of the circuit breaker results in the switching elements of the electronic interruption unit being put into a high-resistance state to prevent a flow of current in the low-voltage AC circuit, in that, further, the contacts of the mechanical isolating contact unit are opened and the mechanical isolating contact unit is put into a blocked state, so that the contacts are prevented from being closed by way of the handle, in that the detection of the fault is communicated by way of the communication unit.

22. Circuit breaker (SG) according to one of the preceding claims, characterized in that the circuit breaker is designed such that a power failure in the electrical low-voltage AC circuit results in the mechanical isolating contact unit remaining in its switching state, so that closed contacts and a subsequent power failure result in the contacts still being closed after the power supply has been restored.

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

24. Method for operating a circuit breaker (SG) according to one of the preceding claims.

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