Protective switching device and procedure

Abstract

Protective switching device (SG) for protecting a low-voltage electrical circuit comprising: - a housing (GEH) with at least one mains-side connection and one load-side connection, - a mechanical isolating contact unit (MK) connected in series with an electronic interruption unit (EU), whereby the mechanical isolating contact unit (MK) is assigned to the load-side connection and the electronic interruption unit (EU) is assigned to the mains-side connection, - that the mechanical isolating contact unit (MK) can be switched by opening contacts to prevent a current flow or closing the contacts to allow a current flow in the low-voltage circuit, - that the electronic interruption unit (EU) can be switched by semiconductor-based switching elements into a high-resistance state of the switching elements to prevent current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit, - a current sensor unit (SI) for determining the current level of the low-voltage circuit, - a control unit (SE) connected to the current sensor unit (SI), the mechanical isolating contact unit (MK) and the electronic interruption unit (EU), whereby, if current and / or current time limit values ​​are exceeded, the prevention of current flow in the low-voltage circuit is initiated, - that the protective switching device (SG) is designed in such a way that when the contacts of the mechanical isolating contact unit (MK) are closed and the electronic interruption unit (EU) is switched to a low-resistance state, the electronic interruption unit (EU) is switched to a high-resistance state for a first period of time for functional testing.

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] Low-voltage circuits, networks, or systems refer to circuits with nominal or rated currents of up to 125 amps, more specifically up to 63 amps. Low-voltage circuits specifically refer 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 specifically 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, miniature circuit breaker, or circuit breaker. The rated currents can be further staggered, from 0.5 A to 1 A, 2 A, 3 A, 4 A, 5 A, 6 A, 7 A, 8 A, 9 A, 10 A, etc. up to 16 A.

[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 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 also provided.

[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, particularly 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(2π*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=2π*f=2π / T=angular frequency of the alternating voltage (T = period of the oscillation)

[0010] Often, the specification of 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; abbreviated: φ = 0...2π or φ = 0°...360°).

[0013] The instantaneous voltage value u(t) is therefore the instantaneous value of the voltage at time t, ie 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] The American patent application US 2021 / 0 066 013 A1 discloses a semiconductor power switch with self-diagnostic, self-maintenance, and self-protection functions. A semiconductor power switch (SSCB) with self-diagnostic, self-maintenance, and self-protection functions comprises: a power semiconductor; an air gap separation unit connected in series with the power semiconductor; a measuring and control circuit that switches off the power semiconductor upon detection of a short circuit or an excessively long overload; and a microcontroller unit (MCU) that triggers the air gap separation unit to form an air gap and galvanically isolate a connected load after the measuring and control circuit has switched off the power semiconductor.The MCU is also configured to monitor the functionality of the air gap isolation unit, the power semiconductor, and other critical components of the SSCB and take corrective action as needed to prevent damage or destruction to the SSCB and the connected load and / or to protect people and the environment from hazardous electrical conditions.

[0015] German patent application DE 10 2018 213 354 A1 discloses a switching device and method. The application relates to a switching device for a multi-conductor low-voltage circuit, - with a housing, with connecting 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.

[0016] 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 which in turn is connected to the electronic unit, the auxiliary switch and the electronic unit are designed in such a way that when the mechanical unit is opened, the electronic unit becomes high-impedance.

[0017] The American patent application US 2020 / 0 366 078 A1 discloses an intelligent circuit breaker. A circuit breaker comprises an electromechanical switch, a current sensor, a voltage sensor, and a processor. The electromechanical switch is connected in series between a mains input and a load output of the circuit breaker and can be set to a closed or open state. The current sensor detects the current flow between the mains input and the load output and generates a current measurement signal. The voltage sensor detects the voltage flow at a point between the mains input and the load output and generates a voltage measurement signal. The processor receives and processes the current measurement signal and the voltage measurement signal to determine operating state information of the circuit breaker and the power consumption of a load connected to the load output.

[0018] 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.

[0019] This object is achieved by a protective switching device having the features of patent claim 1, as well as by a method according to patent claim 14.

[0020] 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, the mechanical isolating contact unit being assigned to the load-side connection and the electronic interruption unit being assigned to the mains-side connection, - that the mechanical isolating contact unit can be switched by opening contacts to prevent current flow or closing contacts to allow 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 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 current level of the low-voltage circuit, - a control unit connected to the current sensor unit, the mechanical isolating contact unit and the electronic interruption unit, whereby prevention of current flow in the low-voltage circuit is initiated when current and / or current time limit values ​​are exceeded.

[0021] According to the invention, the protective switching device is designed such that when the contacts of the mechanical isolating contact unit (MK) are closed and the electronic interruption unit (EU) is switched to a low-resistance state, the electronic interruption unit (EU) is switched to a high-resistance state for a first period of time for functional testing.

[0022] The first time period can preferably be in the range from 100 µs to 5 ms. The first time period can be in the range from 100 µs to 20 ms. For example, 100 µs, 200 µs, ..., 1 ms, 2 ms, ... 5 ms, ... 20 ms; any intermediate value is possible and disclosed. This has the particular advantage that the electronic interruption unit can be tested for its "switchability." Furthermore, this takes place during operation, without further restrictions. Due to the short times, the loads or consumers are advantageously not disconnected from the mains for as long. 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.

[0023] Advantageous embodiments of the invention are specified in the subclaims and in the exemplary embodiment.

[0024] 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.

[0025] This has the particular advantage that 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.

[0026] 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.

[0027] By determining the voltage level across the electronic interruption unit, the functional capability of the electronic interruption unit can be easily and advantageously supported. This results in increased operational reliability of a protective switching device. Furthermore, a new architecture or design for a protective switching device is proposed.

[0028] In an advantageous embodiment of the invention, the protective switching device is designed such that when the electronic interruption unit is switched to the high-impedance state for the first period of time, the voltage level across the electronic interruption unit is determined. This means that the voltage level is determined in the high-impedance state. If the voltage falls below a first voltage threshold, a first fault condition occurs, which initiates the electronic interruption unit becoming further high-impedance and / or the opening of the contacts.

[0029] This has the particular advantage that the electronic interruption unit is checked during operation and, if the electronic interruption unit is faulty, the avoidance of current flow in the low-voltage circuit is initiated, thus ensuring a safe condition.

[0030] The first voltage threshold could be an effective / average / 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.

[0031] The first voltage threshold can be, for example, 5-15% of the nominal voltage of the low-voltage circuit, for example 10%, which applies to the effective voltage values. The first voltage threshold can be, for example, 5-15% below the expected or determined instantaneous voltage level on the line side of the protective switching device, for example 10%.

[0032] The first voltage threshold can be dimensioned depending on the impedance or resistance of the load or the load current, in particular the one that flowed previously.

[0033] This has the particular advantage that it is easy to check the switching-off behavior or the ability to switch-off the electronic interruption unit during operation.

[0034] Furthermore, in the case of an energy absorber or surge protector within the electronic interrupter unit, its functionality can also be tested. If current has previously flowed in the low-voltage circuit, the freewheeling current through or the resulting voltage across the energy absorber can be tested after it has become high-impedance. If the electronic interrupter unit is opened while a current is flowing, the voltage rises (due to the inductance in the circuit) to the voltage of the surge protector. This allows the functionality of the energy absorber to be tested. Advantageously, the electronic interrupter unit can become high-impedance at the zero crossing of the current. This has the particular advantage that there is no current interruption. Furthermore, since the load is not supplied with current at this moment, the measurement has less impact on the load.Furthermore, a commutation process (reduction of current in the inductive circuit) does not occur and the electronic interruption unit (including energy absorber) can block immediately.

[0035] In an advantageous embodiment of the invention, the electronic interruption unit is switched to a high-impedance state when the instantaneous value of the voltage between the mains-side neutral conductor connection and the mains-side phase conductor connection exceeds a second voltage threshold, in particular when the instantaneous value of the voltage is at its maximum.

[0036] This has the particular advantage that the brief interruption of the power supply occurs at the maximum level of available energy. Furthermore, the electronic interruption unit is tested under maximum voltage, allowing any malfunction to be detected early.

[0037] The second voltage threshold can be greater than 160 V, 200 V, 240 V, or 300 V (any value in between is also possible). The instantaneous maximum voltage is 325 V (for a 230 V mains supply).

[0038] 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 closed and the electronic interruption unit is switched to low resistance, the voltage level across the electronic interruption unit is determined. If a third voltage threshold is exceeded, a second fault condition occurs, which initiates the electronic interruption unit becoming high-resistance and / or the opening of the contacts. This has the particular advantage that a (further) (switchless) check of the electronic interruption unit is carried out during operation, and if the electronic interruption unit is faulty, the current flow in the low-voltage circuit is prevented, thus ensuring a safe condition.

[0039] The third voltage threshold should be less than 1 V. Ideally, the voltage across the electronic interrupt unit in the low-impedance state is zero or close to zero volts (less than 1 volt).

[0040] 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 first voltage between a network-side connection point and a load-side connection point of the electronic interruption unit.

[0041] This has the particular advantage of providing a simple solution with only one voltage sensor unit.

[0042] In an advantageous embodiment of the invention, a second voltage sensor unit connected to the control unit is alternatively provided, which detects the magnitude 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 detects the magnitude of a third voltage between the mains-side neutral conductor connection and the load-side connection point of the electronic interruption unit. The protective switching device is designed such that the magnitude of a / the first voltage between the mains-side connection point and the load-side connection point of the electronic interruption unit is determined from the difference between the second and third voltages.

[0043] 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.

[0044] 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.

[0045] This has the particular advantage of providing a compact two-part device: 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.

[0046] In an advantageous embodiment of the invention, the low-voltage circuit is a three-phase alternating current circuit. The protective switching device has additional line-side and load-side phase conductor connections to protect the phases of the electrical circuit. An electronic interruption unit with a voltage detection device according to the invention, in particular first voltage sensor units, is provided between each of the line-side and load-side phase conductor connections. A contact of the mechanical isolating contact unit is also provided between each of the line-side and load-side phase conductor connections.

[0047] This has the particular advantage of enabling protection for three-phase alternating current circuits.

[0048] 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.

[0049] This has the particular advantage of achieving increased operational reliability, since the contacts cannot be accidentally closed by the control unit.

[0050] 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.

[0051] This has the particular advantage of providing the functionality of a classic circuit breaker.

[0052] 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 fuse, is provided in the connection to the mains-side neutral conductor connection.

[0053] This has the particular advantage of allowing for a compact electronic assembly. Furthermore, there is only one cross-connection between the phase conductor and the neutral conductor, making it easy to protect against a fault in the device that would cause a short circuit.

[0054] In an advantageous embodiment of the invention, with closed contacts of the mechanical isolating contact unit and low-resistance interruption unit and - if a current is detected which exceeds a first current value, in particular if 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, - if a detected current 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, - if the detected current exceeds a (even higher) third current value, the electronic interruption unit becomes high-resistance and the mechanical isolating contact unit is opened.

[0055] This has the particular advantage that a graduated shutdown concept is available for a protective switching device according to the invention at increased currents.

[0056] In an advantageous embodiment of the invention, the control unit comprises a microcontroller.

[0057] 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 a (customizable) computer program product. Furthermore, changes and improvements to the function can be individually loaded onto a protective switching device.

[0058] 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.

[0059] 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 connected in series with an electronic interruption unit, the mechanical isolating contact unit being assigned to the load-side connection and the electronic interruption unit being assigned to the mains-side connection, - that the mechanical isolating contact unit can be switched by opening contacts to prevent current flow or closing contacts to allow current flow in the low-voltage circuit, - that the electronic interruption unit (EU) can be switched by semiconductor-based switching elements into a high-resistance state of the switching elements to prevent current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit, - that the current level in the low-voltage circuit, in particular between the mains-side phase conductor connection and the load-side phase conductor connection, 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.

[0060] To test the function of the protective switching device with the contacts of the mechanical isolating contact unit closed and the electronic interruption unit switched to a low-resistance state, the electronic interruption unit is switched to a high-resistance state for an initial period of time.

[0061] When the electronic interrupt unit is switched to the high-impedance state for the first period of time, the voltage across the electronic interrupt unit is determined. This means that the voltage in the high-impedance state is determined. If the voltage falls below a first threshold, a first fault condition occurs, which initiates the electronic interrupt unit becoming high-impedance again and / or the opening of the contacts.

[0062] Advantageously, the electronic interruption unit is switched to a high-impedance state when the instantaneous value of the voltage between the mains-side neutral conductor connection and the mains-side phase conductor connection exceeds a second voltage threshold, in particular when the instantaneous value of the voltage is at its maximum.

[0063] Advantageously, the voltage level across the electronic interruption unit is determined when the mechanical isolating contact unit's contacts are closed and the electronic interruption unit is switched to low resistance. If a third voltage threshold is exceeded, a second fault condition occurs, which initiates the electronic interruption unit becoming high-resistance again and / or the opening of the contacts.

[0064] According to the invention, a corresponding computer program product is claimed. The computer program product comprises commands 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. The microcontroller is part of the protective switching device, in particular the control unit.

[0065] According to the invention, a corresponding computer-readable storage medium on which the computer program product is stored is claimed.

[0066] According to the invention, a corresponding data carrier signal which transmits the computer program product is claimed.

[0067] All embodiments, both in dependent form referring back to patent claim 1 or 14, and referring back only to individual features or combinations of features of patent claims, in particular also a reference back of the pending arrangement claims to the independent method claim, 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.

[0068] The described properties, features and advantages of this invention and the manner in which they are achieved will become clearer and more clearly understandable in connection with the following description of the embodiments, which are explained in more detail in connection with the drawings.

[0069] The drawing shows: Fig. 1 a first representation of a protective switching device, Fig. 2 a second representation of a protective switching device, Fig. 3 a third representation of a protective switching device, Fig. 4 a representation with first voltage curves, Fig. 5 a representation with second voltage curves, Fig. 6 a fourth representation of a protective switching device.

[0070] Fig. 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, and a load-side phase conductor connection LL of the low-voltage circuit; an energy source is usually connected to the grid side GRID, and 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 line-side connection points APLG, APNG, with a load-side connection point APNL for the neutral conductor, a load-side connection point APLL for the phase conductor, a line-side connection point APNG for the neutral conductor, and a line-side connection point APLG for the phase conductor. The load-side connection points APNL, APLL are connected to the load-side neutral and phase conductor terminals NL, LL, so that the opening of contacts KKN, KKL to prevent current flow or the closing of the contacts to allow current flow in the low-voltage circuit can be switched. - 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, wherein the electronic interruption unit has a high-resistance state of the switching elements to prevent a current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit by means of semiconductor-based switching elements, - a current sensor unit SI, for determining the level of the current of 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, whereby an avoidance of a current flow in the low-voltage circuit is initiated when current and / or current time limit values ​​are exceeded.

[0071] According to the invention, the protective switching device is designed such that the voltage level across the electronic interruption unit can advantageously 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.

[0072] For this purpose, in the example according to Fig. 1, a first voltage sensor unit SU1 is provided, which is connected to the control unit SE and determines the voltage level between the mains-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU. When measuring the voltage by the first voltage sensor unit SU1, the voltage across the series connection of the electronic interruption unit EU and the current sensor SI can also be determined, as shown in Fig. 1. The 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] A measuring impedance ZM can be connected between the mains-side connection points APLG, APNG of the mechanical isolating contact unit MK. The measuring impedance ZM can, for example, be an electrical resistor and / or capacitor. The measuring impedance can also be an inductance. In particular, the measuring impedance can be a series or parallel connection of a resistor and / or capacitor and / or inductance.

[0077] In the example according to Fig. 1, the 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.

[0078] 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.

[0079] 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 contacts KKL and KKN. The mechanical handle HH indicates the switching state (open or closed) of the contacts of the mechanical isolating contact unit MK on the protective switching device. Furthermore, the contact position (or the position of the handle, closed or open) can be transmitted to the control unit SE. The contact position (or the position of the handle) can be determined, for example, using a sensor.

[0080] The mechanical isolating contact unit MK is advantageously designed such that (manual) closing of the contacts by the mechanical handle is only possible after an enable, in particular an enable signal. This is also indicated by the arrow from the control unit SE to the mechanical isolating contact unit MK. This means that the contacts KKL, KKN of the mechanical isolating contact unit MK can only be closed by the handle HH when the enable or release signal (from the control unit) is present. Without the enable or release signal, the handle HH can be operated, but the contacts cannot be closed ("permanent slipping").

[0081] 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 Fig. 1. 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).

[0082] Alternatively, the measuring impedance ZM can be connected to the mains-side neutral conductor terminal NG via the fuse SS. This allows the advantageous use of a three-pole electronic unit EE ( Fig. 6), for example, as a module with three connection points: one neutral conductor connection point and two phase conductor connection points. The electronic unit EE includes, for example, the electronic interruption unit EU, the control unit SE, the power supply NT (especially including the fuse SS), the current sensor unit SI, the first voltage sensor unit SU1, and optionally the second voltage sensor unit SU2.

[0083] 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 contacts of the mechanical isolating contact unit.

[0084] High-resistance refers to a state in which only a negligible current flows. In particular, high-resistance refers to resistance values ​​greater than 1 kiloohm, preferably greater than 10 kiloohms, 100 kiloohms, 1 megaohm, 10 megaohms, 100 megaohms, 1 gigaohm, or greater.

[0085] 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.

[0086] Fig. 2 shows a figure according to Fig. 1, with the difference that on the grid side GRID an energy source EQ with a nominal voltage U N of the low-voltage circuit. Furthermore, a consumer or energy sink ES is connected to the load side LOAD. Furthermore, an enable signal is shown at the connection from the control unit SE to the mechanical isolating contact unit MK.

[0087] The mechanical isolating contact unit MK is shown in an open OFF state, ie with open contacts KKN, KKL to prevent current flow.

[0088] 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 - if a current is detected which exceeds a first current value, in particular if 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, - if a current is detected that 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, - if the current detected exceeds an even higher third current value, the electronic interruption unit becomes high-resistance and the mechanical isolating contact unit MK is opened.

[0089] Fig. 3 shows a representation according to Fig. 2, with various differences. The voltages on and in the protective switching device are shown in more detail: - the nominal voltage U N the energy source EQ of the low-voltage circuit, - the mains voltage U applied between the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG LN , - the second voltage U2 or U measured in the protective switching device by the second voltage sensor unit SU2 N,GND , - the first voltage U1 or U measured with the first voltage sensor unit SU1 across the electronic interruption unit EU SW ..

[0090] In this variant according to Fig. 3, the first voltage U1 (or U SW ) is measured directly across the electronic interruption unit (ie without the current sensor unit SI). The second voltage U2 (or U N,GND ) corresponds to the mains voltage U LNminus the (minimal) voltage drop across the current sensor unit SI and the ohmic losses.

[0091] 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 Fig. 3, two series-connected semiconductor-based switching elements T1, T2 are provided. Advantageously, a surge protection device (TVS) is provided above the series connection of the two semiconductor-based switching elements T1, T2.

[0092] In the design according to Fig. 3, two 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, wherein the unidirectional switching elements are 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.

[0093] The following situation is considered below: - Nominal voltage or mains voltage (e.g. 230 V AC) is applied to 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,

[0094] Fig. Figure 3 further shows the difference that the contacts of the mechanical isolating contact unit MK are closed and the electronic interruption unit is low-resistance. The protective switching device is designed such that when the contacts of the mechanical isolating contact unit MK are closed and the electronic interruption unit EU is switched to low-resistance, the voltage level across the electronic interruption unit is determined. If the third voltage threshold is exceeded, a second fault condition occurs, which initiates the electronic interruption unit becoming high-resistance and / or the opening of the contacts.

[0095] Furthermore, the protective switching device is designed such that when the contacts of the mechanical isolating contact unit MK are closed and the electronic interruption unit EU is switched to a low-impedance state, the electronic interruption unit EU is switched to a high-impedance state for the first period of time, and the voltage across the electronic interruption unit is determined. If the voltage falls below the first voltage threshold, a first fault condition occurs, which initiates the electronic interruption unit becoming high-impedance and / or the opening of the contacts.

[0096] This is in Fig. 5 is indicated by the fact that the connection between the control unit SE and the electronic interrupt unit EU has a square-wave signal that is in the on state and is briefly switched to the off state. This means that the electronic interrupt unit EU is briefly switched to a high-impedance state (first period of time). If necessary, the electronic interrupt unit can be switched to the high-impedance state several times to test its functionality, which is indicated, for example, by two consecutive off states of the square-wave signal.

[0097] If the first or second fault condition is present, an opening signal OEF is sent from the control unit SE to the mechanical isolating contact unit MK to initiate the opening of the contacts, as shown in Fig. 5. Furthermore, the control unit SE can send a signal (not shown) to the electronic interruption unit to increase resistance (or avoid a corresponding low resistance signal). The mechanical contacts are preferably opened shortly before the current crosses zero, so that the mechanical switching contacts can more easily interrupt the current flow, preventing contact erosion or an arc.

[0098] The electronic interruption unit is advantageously switched to a high-impedance state when the instantaneous value of the voltage between the mains-side neutral conductor connection and the mains-side phase conductor connection exceeds a second voltage threshold, in particular when the instantaneous value of the voltage is at its maximum.

[0099] In Fig. Figure 3 also shows a grid-side line inductance Lgrid with the associated voltage drop ULgrid and grid-side current igrid. Furthermore, the load-side current iload and the load-side voltage drop ULoad are plotted across the load or energy sink ES. The energy sink ES is shown with its inductive and resistive components.

[0100] Fig. 4 shows graphics with voltage and current curves during the test by briefly switching off the electronic interruption unit (for a functioning protective switching device).

[0101] The vertical y-axis represents the voltage in volts (V) or the current in amperes (A), and the horizontal x-axis represents the time in milliseconds (ms).

[0102] In the upper graphic of Fig. Figure 4 shows the load-side voltage ULoad and the load-side current iload. They show brief voltage and current dips at the time when the electronic interruption unit becomes high-impedance for an initial period. In the example, this occurs at the maximum voltage or current, i.e., when the instantaneous value of the voltage or current is at its maximum.

[0103] If the first voltage U1 across the electronic interruption unit / semiconductor-based switching element is positive, switching element T2, for example, can be checked. If the first voltage U1 across the electronic interruption unit / semiconductor-based switching element is negative, switching element T1, for example, can be checked.

[0104] Fig. 5 shows voltage and current curves according to Fig. 4. In the upper graphic of Fig. 5 shows a first turn-off pulse AI1 at time t= 16 ms and a second turn-off pulse AI2 of the semiconductor-based switching elements at time t= 25 ms.

[0105] The middle graph shows the load-side voltage curves ULoad and the load-side current curve iload. During the first switch-off pulse AI1, no load-side voltage or current dip is detectable. During the second switch-off pulse AI2, a brief load-side voltage or current dip occurs.

[0106] The graph below shows the curve of the first voltage U1. At the time of the second switch-off pulse AI2, a voltage peak of the first voltage U1 can be seen.

[0107] Fig. Figure 5 shows the voltage curves during a test by briefly switching off the switching elements in a defective protective switching device. It can be seen that no switching off occurs during the positive half-wave (no voltage spike of the first voltage U1). This fault pattern occurs, for example, in a defective switching element, so it can be concluded that a defective switching element, e.g., switching element T2, is present.

[0108] During the negative half-wave, the first voltage U1 is switched off (voltage peak). This means, for example, that the switching element T1 is (still) working properly.

[0109] If the first voltage U1 across the electronic switching element is positive, one switching element, T2, can be checked, for example. If the first voltage U1 across the electronic switching element is negative, the other switching element, T1, can be checked, for example (in the case of unidirectional switching elements).

[0110] Fig. 6 shows a representation according to Fig. 1-3, 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 include 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 include the fuse SS, a switch SCH, the measuring impedance ZM, a temperature sensor TEM (particularly for the electronic interruption unit EU), a communication unit COM, and a display unit DISP.

[0111] 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.

[0112] 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). Further, unspecified units can be provided.

[0113] The division into two parts makes it possible to advantageously realize a compact protective switching device according to the invention.

[0114] 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. Furthermore, the release unit FG can cause the contacts to open when an opening signal OEF is present. The release unit then acts as a tripping unit.

[0115] The invention will be summarized and explained in more detail below. An example of an electronic protection and switching device is proposed, comprising: - Housing with mains and load side connections - Voltage sensor unit for measuring the mains voltage - Current sensor unit for measuring the (load) current - mechanical isolating contact unit including handle (including contact position indicator, electronic trigger, isolating properties) - electronic interruption unit with semiconductor-based switching elements - Control unit - the functionality of the electronic interruption unit is checked, by briefly switching the electronic interruption unit off (<10ms, preferably <1ms) and then immediately switching it back on, and at the same time voltage measurement values ​​and / or current measurement values ​​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.

[0116] Furthermore, the functionality of the electronic interrupt unit is tested by continuously measuring the voltage across it. This can, for example, detect whether a semiconductor has burned out while the device is switched on.

[0117] 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 with the second voltage sensor unit. This third voltage sensor unit 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 to the phase conductor on the one hand and to the neutral conductor on the other. 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.

[0118] A computer program product or algorithm is proposed that 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.

[0119] 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, and in particular to carry out, the method according to the invention.

[0120] The computer program product may be stored on a computer-readable storage medium, such as a CD-ROM, a USB stick or similar.

[0121] Furthermore, a data carrier signal that transmits the computer program product may exist.

[0122] An automatic check of the electronic interruption unit can be performed cyclically during "normal" operation. (E.g., automatic check once per hour / every 45 / 30 / 15 minutes, etc.)

[0123] If the semiconductor-based switching elements are tested by briefly turning them off while the electronic interrupt unit is switched on, and then switched at a time when a current is flowing, this, together with the existing line inductance, can cause an overvoltage to develop at the electronic switch, which allows for a test of the existing energy absorber / surge protection (TVS). A functioning surge protection device limits the voltage to a specific range.

[0124] 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.

[0125] 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), - Voltage detection across the electronic interruption unit will be used to: detect a broken or burnt-out condition of a power semiconductor - Possibility of opening the mechanical isolating contact unit after detecting a fault in the electronic interruption unit.

[0126] Although the invention has been illustrated and described in detail by the embodiment, the invention is not limited by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the scope of the invention.

Claims

[1] Protective switching device (SG) for protecting a low-voltage electrical circuit comprising: - a housing (GEH) with at least one mains-side connection and one load-side connection, - a mechanical isolating contact unit (MK) connected in series with an electronic interruption unit (EU), whereby the mechanical isolating contact unit (MK) is assigned to the load-side connection and the electronic interruption unit (EU) is assigned to the mains-side connection, - that the mechanical isolating contact unit (MK) can be switched by opening contacts to prevent a current flow or closing the contacts to allow a current flow in the low-voltage circuit, - that the electronic interruption unit (EU) can be switched by semiconductor-based switching elements into a high-resistance state of the switching elements to prevent current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit, - a current sensor unit (SI) for determining the current level of the low-voltage circuit, - a control unit (SE) connected to the current sensor unit (SI), the mechanical isolating contact unit (MK) and the electronic interruption unit (EU), whereby, if current and / or current time limit values ​​are exceeded, the prevention of current flow in the low-voltage circuit is initiated, - that the protective switching device (SG) is designed in such a way that when the contacts of the mechanical isolating contact unit (MK) are closed and the electronic interruption unit (EU) is switched to a low-resistance state, the electronic interruption unit (EU) is switched to a high-resistance state for a first period of time for functional testing. [2] Protective switching device (SG) according to claim 1, characterized by that the protective switching device (SG) is designed in such a way that the level of the voltage across the electronic interruption unit (EU) can be determined for a conductor. [3] Protective switching device (SG) according to claim 2, characterized by , that when the electronic interruption unit (EU) is switched to the high-impedance state for the first period of time, the level of the voltage across the electronic interruption unit (EU) is determined, that if a first voltage threshold is undershot, a first fault condition exists, which initiates a further high-resistance switching of the electronic interruption unit (EU) and / or opening of the contacts initiated. [4] Protective switching device (SG) according to claim 3, characterized by that the electronic interruption unit (EU) is switched to a high-impedance state when the instantaneous value of the voltage between the mains-side neutral conductor connection (NG) and the mains-side phase conductor connection (LG) exceeds a second voltage threshold, in particular when the instantaneous value of the voltage is at its maximum. [5] Protective switching device (SG) according to one of the preceding claims 2 to 4, characterized by , that the protective switching device (SG) is designed in such a way that when the contacts of the mechanical isolating contact unit (MK) are closed and the electronic interruption unit (EU) is switched to low resistance, the level of the voltage across the electronic interruption unit (EU) is determined, that when a third voltage threshold is exceeded, a second fault condition occurs, which initiates a further high-resistance switching of the electronic interruption unit (EU) and / or opening of the contacts. [6] Protective switching device (SG) according to one of the preceding claims, characterized by that a first voltage sensor unit (SU1) connected to the control unit (SE) is provided, which determines the level of a first voltage between a network-side connection point (EUG) and a load-side connection point (EUL) of the electronic interruption unit (EU). [7] Protective switching device (SG) according to one of the preceding claims 1 to 5, characterized by , that a second voltage sensor unit (SU2) connected to the control unit (SE) is 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), that a third voltage sensor unit (SU3) connected to the control unit (SE) is 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), that the protective switching device (SG) is designed in such a way that the level of a first voltage between the network-side connection point (EUG) and the load-side connection point (EUL) of the electronic interruption unit (EU) is determined from the difference between the second and third voltage. [8] Protective switching device (SG) according to one of the preceding claims, characterized by that the current sensor unit (SI) is provided on the circuit side between the mains-side phase conductor connection (LG) and the load-side phase conductor connection (LL). [9] Protective switching device (SG) according to one of the preceding claims, characterized by , that the low-voltage circuit is a three-phase alternating current circuit and the protective switching device (SG) has a plurality of mains-side and load-side phase conductor connections, between each of which a contact of the mechanical isolating contact unit (MK) and electronic interruption units (EU) are provided, and, in particular, first voltage sensor units (SU) are provided, with which the level of the voltage across the respective electronic interruption unit (EU) can be determined. [10] Protective switching device (SG) according to one of the preceding claims, characterized bythat the protective switching device (SG) is designed in such a way that the contacts of the mechanical isolating contact unit (MK) can be opened but not closed by the control unit (SE). [11] Protective switching device (SG) according to one of the preceding claims, characterized by that the mechanical isolating contact unit (MK) can be operated by a mechanical handle (HH) in order to switch the opening or closing of contacts. [12] Protective switching device (SG) according to one of the preceding claims, characterized by that when the contacts of the mechanical isolating contact unit (MK) and low-resistance interruption unit (EU) are closed and - if a current is detected which exceeds a first current value, in particular if 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 detected which exceeds a 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 the detected current exceeds a third current value, the electronic interruption unit (EU) becomes high-resistance and the mechanical isolating contact unit (MK) is opened. [13] Protective switching device (SG) according to one of the preceding claims, characterized by that the control unit (SE) has a microcontroller. [14] Method for a protective switching device (SG) for protecting a low-voltage electrical circuit with: - a housing (GEH) with at least one mains-side connection and one load-side connection, - a mechanical isolating contact unit (MK) connected in series with an electronic interruption unit (EU), whereby the mechanical isolating contact unit (MK) is assigned to the load-side connection and the electronic interruption unit (EU) is assigned to the mains-side connection, - that the mechanical isolating contact unit (MK) can be switched by opening contacts to prevent a current flow or closing the contacts to allow a current flow in the low-voltage circuit, - that the electronic interruption unit (EU) can be switched by semiconductor-based switching elements into a high-resistance state of the switching elements to prevent current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit, - that the current level in the low-voltage circuit, in particular between the mains-side phase conductor connection (LG) and the load-side phase conductor connection (LL), is determined, - that if current and / or current time limit values ​​are exceeded, the prevention of current flow in the low-voltage circuit is initiated, - that in order to test the function of the protective switching device (SG) with the contacts of the mechanical isolating contact unit (MK) closed and the electronic interruption unit (EU) switched to a low-resistance state, the electronic interruption unit (EU) is switched to a high-resistance state for an initial period of time. [15] Method according to claim 14, characterized by , that when the electronic interruption unit (EU) is switched to the high-impedance state for the first period of time, the level of the voltage across the electronic interruption unit (EU) is determined, that when a first voltage threshold is undershot, a first fault condition occurs which initiates a further high-resistance switching of the electronic interruption unit (EU) and / or opening of the contacts. [16] Method according to claim 14 or 15, characterized in that the electronic interruption unit (EU) is switched to a high-impedance state when the instantaneous value of the voltage between the mains-side neutral conductor connection (NG) and the mains-side phase conductor connection (LG) exceeds a second voltage threshold value, in particular when the instantaneous value of the voltage is at its maximum. [17] Method according to claim 14, 15 or 16, characterized bythat when the contacts of the mechanical isolating contact unit (MK) are closed and the electronic interruption unit (EU) is switched to low resistance, the level of the voltage across the electronic interruption unit (EU) is determined, that when a third voltage threshold is exceeded, a second fault condition exists which initiates the electronic interruption unit (EU) becoming further high-resistance and / or opening of the contacts. [18] Computer program product comprising instructions which, when the program is executed by a microcontroller, cause the microcontroller to support, in particular to carry out, the method according to one of claims 14 to 17 with a protective switching device (SG) according to one of claims 1 to 13. [19] Computer-readable storage medium on which the computer program product according to claim 18 is stored. [20] Data carrier signal transmitting the computer program product according to claim 18.

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