Circuit breaker and method

Abstract

The invention relates to a circuit breaker (SG) for protecting an electric low-voltage circuit, wherein: • - grid-side and load-side connections (LG, NG, LL, NL) are provided for conductors of the low-voltage circuit, • - a mechanical break contact unit (MK) is provided which has a closed state of the contacts for a current flow in the low-voltage circuit or an open state of the contacts for a galvanic isolation in the low-voltage circuit so as to prevent a current flow, • - an electronic interruption unit (EU) is provided which, on the current-circuit side, is connected to the mechanical break contact unit (MK) in series and which, as a result of semiconductor-based switch elements, has a high-ohmic state of the switch elements in order to prevent a current flow or a low-ohmic state of the switch elements for a current flow in the low-voltage circuit, and • - the level of a differential current of the conductors of the low-voltage circuit is ascertained, and if first differential current thresholds or first differential current time thresholds are exceeded, a process for preventing a current flow (VS) in the low-voltage circuit is initiated in that the switch elements of the electronic interruption unit are in a high-ohmic state (EUh) and a closed state (MKg) of the break contacts, and • - in that once current flow has been prevented as a result of the high-ohmic state of the switch elements of the electronic interruption unit and the closed state of the contacts, a test is performed to ascertain whether second differential current thresholds or second differential current time thresholds are exceeded.

Description

[0001] Description

[0002] Protective switching device and procedure

[0003] The invention relates to the technical field of a protective switching device for a low-voltage circuit with an electronic interruption unit according to the preamble of patent claim 1 and a method for a protective switching device for a low-voltage circuit with an electronic interruption unit.

[0004] Low voltage refers to voltages of up to 1000 volts AC or up to 1500 volts DC. Low voltage refers in particular to voltages greater than extra-low voltage, with values ​​of 50 volts AC or 120 volts DC.

[0005] The term low-voltage circuit, network or system refers to circuits with nominal or rated currents of up to 125 amperes, more specifically up to 63 amperes. The term low-voltage circuit particularly refers to circuits with nominal or rated currents of up to 50 amperes, 40 amperes, 32 amperes, 25 amperes, 16 amperes or 10 amperes. The current values ​​mentioned refer in particular to nominal, rated and / or breaking currents, i.e. the maximum current that is normally carried through the circuit or at which the electrical circuit is usually interrupted, for example by a protective device such as a protective switching device, circuit breaker or circuit breaker. The rated currents can be further staggered, from 0.5 A to 1 A, 2 A, 3 A, 4 A, 5 A, 6 A, 7 A, 8 A, 9 A, 10 A, etc. up to 16 A.

[0006] Circuit breakers are long-established overcurrent protection devices used in low-voltage electrical circuits. They protect cables from damage caused by overheating due to excessive current and / or short circuits. A circuit breaker can automatically disconnect the circuit in the event of an overload and / or short circuit. A circuit breaker is a non-self-resetting fuse element.

[0007] Unlike miniature circuit breakers, circuit breakers are designed for currents greater than 125 A, and in some cases even as low as 63 A. Miniature circuit breakers are therefore simpler and more delicate in design. Miniature circuit breakers typically have a mounting option for mounting on a so-called top-hat rail (support rail, DIN rail, TH35).

[0008] State-of-the-art circuit breakers are electromechanically constructed. They have a housing containing a mechanical switching contact or shunt release 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 devices for arc quenching are provided. There are also connection elements for conductors of the electrical circuit to be protected.

[0009] Residual current circuit breakers for electrical circuits, particularly for low-voltage circuits or systems, are well known. Residual current circuit breakers are also known as residual current devices, or RCDs for short. Residual current circuit breakers determine the total current in an electrical circuit, which is normally zero, and interrupt the electrical circuit when a differential current value is exceeded, i.e. a total current that is not equal to zero and exceeds a certain (differential) current value or residual current value. Almost all previous residual current circuit breakers have a summation current transformer, the primary winding of which is formed by the conductors of the circuit and the secondary winding outputs the total current that is used directly or indirectly to interrupt the electrical circuit.

[0010] For this purpose, two or more conductors, usually the forward and return conductors or the line and neutral conductors in a single-phase alternating current system, all three line conductors or all three line conductors and the neutral conductor in a three-phase alternating current system, are passed through a current transformer, usually with a ring-shaped core made of ferromagnetic material. Only the differential current, i.e. a current that differs from the forward and return current, from the conductors is converted. The total current in an electrical circuit is usually zero. This allows fault currents to be detected.

[0011] If, for example, a current flows to earth on the energy sink or consumer side, this is referred to in this context as a fault current. A fault occurs, for example, when there is an electrical connection from a phase conductor of the electrical circuit to earth. For example, if a person touches the phase conductor. In this case, part of the electrical current does not flow back via the neutral conductor as usual, but via the person and the earth. This fault current can now be detected with the help of the summation current transformer, since the recorded sum of the incoming and returning current is not equal to zero. The circuit, e.g. at least one, some or all of the lines, is interrupted via a relay or a holding magnet release, for example with associated mechanics.Residual current circuit breakers for detecting alternating fault currents are generally known from the publication DE 44 32 643 A1.

[0012] The main function of residual current circuit breakers is to protect people from electrical currents (electric shock), as well as systems, machines or buildings from fire caused by electrical insulation faults.

[0013] If the residual current circuit breaker or its summation current transformer is designed in such a way that the secondary energy of the summation current transformer is sufficient to actuate a tripping unit or an interruption unit or a release, then such residual current circuit breakers are said to be mains voltage independent.

[0014] If auxiliary power is required or used for the tripping circuit, which is usually generated by a power supply provided in the residual current device, such residual current devices are called line-voltage-dependent. This means that line-voltage-dependent residual current devices contain a power supply to supply power to a residual current detector (line-voltage-independent devices do not). These power supplies are required, for example, to detect residual currents in DC voltage systems and mixed DC / AC systems, or in high-frequency circuits.

[0015] Protective switching devices with an electronic interruption unit are relatively new developments. They have a semiconductor-based electronic interruption unit. This means that the electrical current flow in the low-voltage circuit is conducted via semiconductor components or semiconductor switches, which interrupt the electrical current flow or can be made conductive. Protective switching devices with an electronic interruption unit also often have a mechanical isolating contact system, in particular with isolating properties in accordance with the relevant standards for low-voltage circuits. The contacts of the mechanical isolating contact system are connected in series to the electronic interruption unit, i.e. the current in the low-voltage circuit to be protected is conducted via both the mechanical isolating contact system and the electronic interruption unit.The present invention relates in particular to low-voltage alternating current circuits with an alternating voltage, typically with a time-dependent sinusoidal alternating voltage with frequency f. The time dependence of the instantaneous voltage value u(t) of the alternating voltage is described by the equation: u(t) = U * sin (2n * f * t). Where: u(t) = instantaneous voltage value at time t.

[0016] U = amplitude of the voltage

[0017] A harmonic alternating voltage can be represented by the rotation of a pointer whose length corresponds to the amplitude (U) of the voltage. The instantaneous deflection is the projection of the pointer onto a coordinate system. One oscillation period corresponds to one full rotation of the pointer, and its full angle is 2n (2Pi) or 360°. The angular frequency is the rate of change of the phase angle of this rotating pointer. The angular frequency of a harmonic oscillation is always 2n times its frequency, i.e.: w = 2n*f = 2n / T = angular frequency of the alternating voltage (T = period of the oscillation)

[0018] Often, the specification of the angular frequency (w) is preferred over the frequency (f), since many formulas of oscillation theory can be represented more compactly using the angular frequency due to the occurrence of trigonometric functions whose period is by definition 2n: u ( t ) = U * sin (wt)

[0019] In the case of circular frequencies that are not constant over time, the term instantaneous circular frequency is also used. For a sinusoidal, in particular temporally constant, alternating voltage, the time-dependent value from the angular velocity w and the time t corresponds to the time-dependent angle cp ( t ) , which is also referred to as the phase angle cp ( t ). This means that the phase angle cp ( t ) periodically passes through the range O...2n or 0°...360°. This means that the phase angle periodically assumes a value between 0 and 2n or 0° and 360° (cp = n* (0...2n) or cp = n* ( 0 °...360 ° ) , due to periodicity; in short: cp = O...2n or cp = 0°...360° ).

[0020] The instantaneous voltage value u(t) 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 cp (cp = 0...2n or cp = 0°...360°, of the respective period).

[0021] The object of the present invention is to improve a protective switching device of the type mentioned above, in particular to ensure protection against (fault) currents caused by persons while simultaneously ensuring the reliability of supply and availability of electrical systems, i.e., to achieve immunity against technically induced (fault) currents that would lead to false tripping of the protective switching device. This means, on the one hand, ensuring personal protection and, on the other hand, improving the reliability of supply of a low-voltage circuit. Alternatively, to create a novel concept for such a protective switching device.

[0022] This object is achieved by a protective switching device having the features of patent claim 1, as well as by a method according to patent claim 12.

[0023] According to the invention, a protective switching device for protecting an electrical low-voltage circuit, in particular a low-voltage alternating current circuit, is provided, comprising:

[0024] - a housing with mains-side and load-side connections for conductors of the low-voltage circuit,

[0025] - a differential current sensor unit for determining the level of a differential current of the conductors of the low-voltage circuit,

[0026] - a mechanical isolating contact unit which has a closed state of the contacts for a current flow in the low-voltage circuit or an open state of the contacts for a galvanic isolation in the low-voltage circuit that prevents the flow of current, the mechanical isolating contact unit can be operated and switched in particular by a mechanical handle, so that an opening of contacts to prevent a current flow or a closing of the contacts for a current flow in the low-voltage circuit can be switched (by the handle), thus (in particular) a galvanic isolation in the low-voltage circuit can be switched; in the case of a mechanical isolating contact unit, an opening of contacts is also referred to as being switched off and a closing of contacts is referred to as being switched on;

[0027] - an electronic interruption unit which is connected in series with the mechanical isolating contact unit on the circuit side and which, by means of semiconductor-based switching elements, has a high-resistance (in particular non-conductive) state of the switching elements to prevent a current flow or a low-resistance state of the switching elements to allow current to flow in the low-voltage circuit; in the case of an electronic interruption unit, a high-resistance (in particular non-conductive) state of the switching elements (to prevent a current flow) is also referred to as the switched-off state (process: switching off) and a low-resistance (conductive) state of the switching elements (to allow current to flow) is referred to as the switched-on state (process: switching on);

[0028] - a control unit which is connected to the differential current sensor unit, the mechanical isolating contact unit and the electronic interruption unit. According to the invention, the protective switching device, in particular the control unit, is designed such that when first differential current limit values ​​or first differential current time limit values ​​are exceeded, avoidance of a current flow in the low-voltage circuit is initiated by a high-impedance state of the switching elements of the electronic interruption unit with the isolating contacts closed. After avoidance of a current flow by a high-impedance state of the switching elements of the electronic interruption unit and the contacts closed, a check is carried out to determine whether second differential current limit values ​​or second differential current time limit values ​​have been exceeded.

[0029] This has the particular advantage that after a faulty differential current event, for example caused by a person touching a (phase) conductor (critical event) or by a technically caused leakage current (not critical for people, i.e. non-critical event) (for example by switched capacitances), an immediate avoidance of a current flow in the low-voltage circuit is initiated by a high-resistance state of the switching elements of the electronic interruption unit.

[0030] Immediate prevention of current flow means, in particular, that the electronic interruption unit becomes highly resistive within 10 ms, especially 5 ms or 1 ms. (Today's residual current circuit breakers typically trip after at least / more than 20 ms.)

[0031] After avoiding the flow of current by a high-resistance state of the switching elements of the electronic interruption unit and the closed state of the contacts, a test is carried out to determine whether second differential current limit values ​​or second differential current time limit values ​​have been exceeded in order to further check for the presence of faulty differential current events and, if necessary, to differentiate between critical events and non-critical events in order to ensure the protection of persons on the one hand and the availability of systems on the other.

[0032] Thus, the status at the load-side terminals can be further monitored for the presence of differential current limits or differential current time limits. If the status changes, a further action can advantageously be taken, for example, according to the advantageous embodiments of the invention.

[0033] On the other hand, a completely new operating concept of a protective switching device is presented in which, in contrast to previous residual current circuit breakers, for example, a check is carried out even after an event that prevents the flow of current.

[0034] Advantageous embodiments of the invention are specified in the subclaims and in the exemplary embodiment.

[0035] The mechanical handle is particularly advantageous because only the mechanical isolating contact unit can be operated. Switching the device on and off using the electronic interruption unit cannot be operated (directly) on the device.

[0036] In an advantageous embodiment of the invention, if the second differential current limit values ​​or second differential current time limit values ​​are not exceeded for a first time range (10ms ... 20ms ... 30ms ... 50ms ... 100ms ... 200ms ... 1 s (any value depending on the application is possible)), the electronic interruption unit changes to the low-resistance state.

[0037] The first time range is, for example, a value from the range 10 ms to 100 ms to 200 ms to 1 s. This means that if, for example, after exceeding the first differential current limit values ​​or first differential current time limit values ​​for 10 ms (15 ms) or 20 ms (25 ms, 30 ms, ..., 95 ms, 100 ms, ... 1 s), the second differential current limit values ​​or second differential current time limit values ​​are not exceeded, the electronic interruption unit switches to the low-resistance state.

[0038] The first time range can be dependent in particular on the level of the determined differential current (in particular its effective value), ie with higher differential currents the first time range becomes smaller.

[0039] This has the particular advantage that automatic reconnection occurs when non-critical residual current limits or residual current time limits are present. This ensures high availability.

[0040] In an advantageous embodiment of the invention, if the second differential current limit values ​​or second differential current time limit values ​​are exceeded, the isolating contacts are opened for a first period of time.

[0041] The first time period, for example, is in the range of 10 ms to 100 ms to 10 s. The first time period can, in particular, be less than 300 ms, 200 ms, 150 ms, 100 ms, 50 ms, 40 ms, 30 ms, 20 ms, or 10 ms.

[0042] This has the particular advantage of achieving a switching-off behavior similar to that of classic residual current circuit breakers, where galvanic isolation is implemented for personal protection.

[0043] In an advantageous embodiment of the invention, the electronic interruption unit changes to the low-resistance state (after the expiration of a / the first time period and) if the second differential current limit values ​​or second differential current time limit values ​​are not exceeded for a second time range.

[0044] The second time range can be a value from 20 ms to 100 ms to 1 s to 10 s. The length of the second time range can be the same as or longer than the length of the first time range.

[0045] This has the particular advantage that the system is automatically switched back on, thus ensuring high energy supply availability.

[0046] In an advantageous embodiment of the invention, a communication unit, in particular an input unit, is provided. If the second differential current limit values ​​or second differential current time limit values ​​for a second time range are not exceeded, the electronic interruption unit only switches to the low-impedance state when an acknowledgment is received via the communication unit, in particular an input unit. The second time range can be a value from the range 20 ms to 100 ms to 1 s. The length of the second time range can correspond to the length of the first time range or be longer.

[0047] This has the particular advantage that the device can be switched on again after confirmation (acknowledgement) by a user, thus achieving a high level of security.

[0048] In an advantageous embodiment of the invention, the mechanical isolating contact unit (MK) is assigned to the load-side connections.

[0049] This has the particular advantage that an architecture supporting the inventive behavior of the protective switching device is provided, since on the one hand the current flow is interrupted in the case of a high-impedance interruption unit, by the

[0050] (load-side) closed contacts but a test according to the invention can still be carried out (by means of the load-side connections).

[0051] In an advantageous embodiment of the invention, the test for the existence of the exceedance of second differential current limit values ​​or second differential current time limit values ​​at the load-side connections is carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit becoming low-resistance, in particular for a first duty cycle.

[0052] This has the particular advantage that it provides a simple way of testing whether second differential current limit values ​​or second differential current time limit values ​​(of the load-side connections) have been exceeded, since the existing electronic interruption unit only needs to be switched (briefly) to the low-impedance state in order to briefly generate a measuring current or a measuring voltage in order to carry out the test for the existence of differential current limit values ​​or differential current time limit values ​​and their level.

[0053] The first duty cycle can be so short that there is no danger to persons. In an advantageous embodiment of the invention, the test for the existence of the exceedance of second differential current limit values ​​or second differential current time limit values ​​(of the load-side connections) is carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit becoming low-impedance at an instantaneous voltage value that is less than a first voltage threshold.

[0054] The first voltage threshold is preferably less than 50 volts or a (protective) extra-low voltage value. The first voltage threshold is advantageously adjustable.

[0055] This has the particular advantage that the test is carried out at a voltage that is harmless to humans, so that the safety of both the protective switching device and the low-voltage circuit is ensured.

[0056] Advantageously, a voltage sensor unit is also provided for this purpose, which determines the voltage in the low-voltage circuit, in particular the level of the voltage applied to the mains-side connections.

[0057] In an advantageous embodiment of the invention, the switching elements become high-resistance again when the instantaneous value of the voltage is greater than a second voltage threshold value.

[0058] This, in turn, has the particular advantage that the test is carried out at a voltage that is harmless to humans, thus ensuring the safety of both the protective switching device and the low-voltage circuit. The level of the second voltage threshold can correspond to the level of the first voltage threshold.

[0059] In an advantageous embodiment of the invention, the test for the presence of a violation of second differential current limits or second differential current time limits (at the load-side terminals) is carried out by applying an auxiliary voltage that is lower than a first voltage limit. This, in turn, has the particular advantage that the test is carried out using a different solution at a voltage that is safe for humans, thus ensuring the safety of both the protective switching device and the low-voltage circuit.

[0060] The level of the first voltage limit can correspond to the level of the first (or second) voltage threshold.

[0061] In an advantageous embodiment of the invention, the test is carried out when the second differential current limit values ​​or second differential current time limit values ​​are exceeded with a first time interval, which is in particular 1, 3, 5, 10, 15, 30 seconds or 1, 5, 10 or 15 minutes, wherein the test is carried out with the first time interval in particular after the expiry of a (the) first time period.

[0062] This has the particular advantage that a cyclical test is carried out over a longer period of time without having to carry out permanent test functions or test routines.

[0063] In an advantageous embodiment of the invention, if the second differential current limit values ​​or second differential current time limit values ​​are (continued) exceeded after a first time limit has elapsed, the mechanical isolating contact unit changes to an open state of the isolating contacts. In particular, the first time limit is 15 min, 30 min, 1 h, 8 h, 24 h, 36 h or 48 h. Any intermediate value is possible. The first time interval depends on the first time limit. I.e. the first time interval is shorter than the first time limit.

[0064] This has the particular advantage that after the first time limit has elapsed, a permanent or significant defect in the low-voltage circuit can be concluded and a safe state in the low-voltage circuit is initiated by galvanic isolation.

[0065] According to the invention, a corresponding method for a

[0066] Protective switching device for a low-voltage circuit with electronic (semiconductor-based) switching elements with the same and further advantages is claimed.

[0067] The method for a protective switching device for protecting a low-voltage electrical circuit, in which:

[0068] - mains-side and load-side connections are provided for conductors of the low-voltage circuit,

[0069] - a mechanical isolating contact unit with a closed state of the contacts for a current flow in the low-voltage circuit or an open state of the contacts for a current-preventing galvanic separation in the low-voltage circuit is provided,

[0070] - an electronic interruption unit is provided which is connected in series with the mechanical isolating contact unit on the circuit side and which, by means of semiconductor-based switching elements, has a high-resistance 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,

[0071] - that the level of a differential current of the conductors of the low-voltage circuit is determined and, if the first differential current limit values ​​or first differential current time limit values ​​are exceeded, the prevention of a current flow in the low-voltage circuit is initiated by a high-resistance state of the switching elements of the electronic interruption unit when the isolating contacts are closed,

[0072] - that after a current flow has been avoided by a high-resistance state of the switching elements of the electronic interruption unit and the closed state of the contacts, a test is carried out to determine whether second differential current limit values ​​or second differential current time limit values ​​have been exceeded.

[0073] In advantageous embodiments of the method: -if the second differential current limit values ​​or second differential current time limit values ​​are not exceeded for a first time range (e.g. 20...100 ms, 1 s), the electronic interruption unit switches to the low-impedance state. -if the second differential current limit values ​​or second differential current time limit values ​​are exceeded for a first time period, which is in particular less than 300 ms, 200 ms, 150 ms, 100 ms, 50 ms, 40 ms, 30 ms, 20 ms or 10 ms, the isolating contacts are opened.

[0074] -if the second differential current limit values ​​or second differential current time limit values ​​for a second time range (e.g. 20...100ms.. ,1s) are not exceeded, the electronic interruption unit only switches to the low-resistance state when an acknowledgment is given.

[0075] - the test for whether second differential current limit values ​​or second differential current time limit values ​​(of the load-side connections) have been exceeded by at least one switching element, in particular two or all switching elements, of the electronic interruption unit becoming low-impedance, in particular for a first duty cycle, - the test for whether second differential current limit values ​​or second differential current time limit values ​​(of the load-side connections) have been exceeded by at least one switching element, in particular two or all switching elements, of the electronic interruption unit becoming low-impedance, is carried out at an instantaneous voltage value that is less than a first voltage threshold.

[0076] According to the invention, a corresponding computer program product for a protective switching device is claimed. The computer program product comprises commands which, when the program is executed by a microcontroller, cause the microcontroller to perform a check for the presence of an exceedance of second differential current limits or second differential current time limits according to one of claims 1 to 17 after a current flow has been avoided by a high-resistance state of the switching elements of the electronic interruption unit and the contacts are closed.

[0077] The microcontroller is part of the protective switching device, in particular the control unit. According to the invention, a corresponding computer-readable storage medium on which the computer program product is stored is claimed.

[0078] According to the invention, a corresponding data carrier signal which transmits the computer program product is claimed.

[0079] All embodiments, both in dependent form referring back to patent claim 1 or 12, and referring back only to individual features or combinations of features of patent claims, in particular also a reference of the pending arrangement claims to the independent method claim, bring about an improvement in a protective switching device, in particular an improvement in the safety for persons as well as the security of supply in low-voltage circuits and provide a new safe concept for a protective switching device.

[0080] The described properties, features and advantages of this invention as well as the manner in which these are achieved will become clearer and more clearly understandable in connection with the following description of the embodiments, which are explained in more detail in connection with the drawing.

[0081] The drawing shows:

[0082] Figure 1 shows a first schematic diagram of a protective switching device,

[0083] Figure 2 shows a second schematic diagram of a protective switching device

[0084] Figures 3 to 8 show time sequences to explain the invention.

[0085] Figure 1 shows a representation of a protective switching device SG for protecting an electrical low-voltage circuit, in particular a low-voltage alternating current circuit, with a housing GEH, comprising:

[0086] - mains-side connections, which usually include a mains-side neutral conductor connection NG and a mains-side phase conductor connection LG,

[0087] - load-side connections, which usually include a load-side neutral conductor connection NL and a load-side phase conductor connection LL,

[0088] - the terminals are intended for the low-voltage circuit;

[0089] - an energy source is usually connected to the grid-side connections / the grid side GRID,

[0090] - a consumer is usually connected to the load-side connections / the load side LOAD;

[0091] - a (two-pole) mechanical isolating contact unit MK with load-side connection points APLL, APNL and line-side connection points APLG, APNG, whereby a load-side connection point APNL is provided for the neutral conductor, a load-side connection point APLL for the phase conductor, a line-side connection point APNG for the neutral conductor, and a line-side connection point APLG for the phase conductor. The load-side connection points APNL, APLL are connected to the load-side neutral and phase conductor connections NL, LL, so that the opening of contacts KKN, KKL to prevent current flow or the closing of contacts KKN, KKL to allow current flow in the low-voltage circuit can be switched.

[0092] - an electronic interruption unit EU, in particular a single-pole one (which in the case of a single-pole version is arranged in particular in the phase conductor), with a mains-side connection point EUG, which is electrically connected to the mains-side phase conductor connection LG, and a load-side connection point EUL, which is electrically connected or connected to the mains-side connection point APLG of the mechanical isolating contact unit MK, wherein the electronic interruption unit EU has or can be switched between a high-resistance state of the switching elements to prevent a current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit by means of semiconductor-based switching elements (not shown),

[0093] - a differential current sensor unit ZCT, for determining the level of a differential current in the conductors of the low-voltage circuit, the differential current sensor unit ZCT is arranged in the example between the electronic interruption unit EU and the mechanical isolating contact unit MK, it can alternatively be provided (arranged) between the mechanical isolating contact unit MK and the load-side neutral and phase conductor connections NL, LL, or alternatively be provided (arranged) between the electronic interruption unit EU and the mains-side connections NG, LG. The differential current sensor unit ZCT determines the level of the differential current in the conductors of the low-voltage circuit that are led through the protective switching device (and are to be protected). In the example for a single-phase alternating current circuit, this is the neutral conductor and the phase conductor.

[0094] The ZCT differential current sensor unit can be a conventional summation current transformer. The primary side of the summation current transformer is formed by the conductors of the low-voltage circuit (in the example, the phase conductor and neutral conductor). The secondary side of the summation current transformer is connected to the control unit SE.

[0095] - a current sensor unit SI for determining the level of the current in the low-voltage circuit, which is arranged in particular in the current path of the phase conductor or phase conductor current path,

[0096] - a control unit SE, which is connected to the differential current sensor unit ZCT, to the current sensor unit SI, to the mechanical isolating contact unit MK and to the electronic interruption unit EU, whereby if current and / or current time limit values ​​are exceeded, the avoidance of a current flow in the low-voltage circuit is initiated. In the example, the mechanical isolating contact unit MK is arranged on the load side, while the electronic interruption unit EU is arranged on the mains side according to the invention.

[0097] The grid side (GRID), containing the energy source, is normally energized. An electrical consumer is usually connected to the load side (LOAD).

[0098] This has the advantage that there are no other (especially live) parts or components between the contacts of the mechanical isolating contact unit / load-side connection points (APLL, APNL) of the mechanical isolating contact unit and the two load-side connections (LL, NL). This architecture and design ensures that, when the contacts KKL, KKN are open, there is never any voltage present at the load-side connections LL, NL. This increases the safety of the protective device.

[0099] In contrast, in other architectures where the mechanical isolating contact unit is located on the mains side, there are often (non-galvanically isolated) electronic units in front of the load-side connection.

[0100] According to the invention, the protective switching device can be designed such that the voltage level across the electronic interruption unit can also 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.

[0101] For this purpose, in the example according to Figure 1, a first voltage sensor unit SUI is provided which is connected to the control unit SE and which determines the level of the voltage between the network-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU.

[0102] When measuring the voltage by the first voltage sensor unit SUI, the voltage across the series circuit of the electronic interruption unit EU and the current sensor SI can alternatively be determined, as shown in Figure 1. The current sensor unit SI has a very low internal resistance, so that the determination of the voltage level is not affected or is negligibly affected.

[0103] 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.

[0104] The first voltage sensor unit can also be replaced by using two voltage measurements (before the electronic interruption unit and after the electronic interruption unit). The voltage across the electronic interruption unit is determined by forming a difference.

[0105] For example, a second voltage sensor unit SU2 can be provided which is connected to the control unit SE and determines the level of a second voltage between the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG. Furthermore, a third voltage sensor unit SU3 (not shown) can be provided which is connected to the control unit and determines the level of a third voltage between the mains-side neutral conductor connection NG and the load-side connection point EUL of the electronic interruption unit EU. The protective switching device is designed in such a way that the level of a first voltage between the mains-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU is determined from the difference between the second and third voltage.

[0106] 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 connection or parallel connection of a resistor and / or capacitor and / or inductance. In the example according to Figure 1, the electronic interruption unit EU is single-pole, in the example in the phase conductor. The mains-side connection point APNG for the neutral conductor of the mechanical isolating contact unit MK is connected to the mains-side neutral conductor connection NG of the housing GEH. This connection is made according to Figure 1 through the residual current sensor unit ZCT, for example its summation current transformer.

[0107] The protective switching device SG is advantageously designed in such a way that the contacts of the mechanical isolating contact unit MK can be opened but not closed by the control unit SE, which is indicated by an arrow from the control unit SE to the mechanical isolating contact unit MK.

[0108] The mechanical isolating contact unit MK can be operated using a mechanical handle HH on the protective switching device SG in order to manually open or close the contacts KKL, KKN. The mechanical handle HH indicates the switching state (open or closed) of the contacts of the mechanical isolating contact unit MK 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, such as a position sensor. The contact position or the switching state can be transmitted to the control unit SE. The position sensor can be part of the mechanical isolating contact unit MK. Alternatively, the position sensor can be a component in the electronic first part (EPART, Figure 2). E.g.A Hall sensor can be provided in the electronic first part (EPART), which detects and transmits the position of the contacts and / or the handle without contact.

[0109] The mechanical isolating contact unit MK is advantageously designed in such a way 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 is present (from the control unit). Without the enable or release signal, the handle HH can be operated, but the contacts cannot be closed ("permanent slipping").

[0110] The protective switching device SG has a power supply or power supply NT, for example, a switched-mode power supply. In particular, the power supply / power supply NT is provided for the control unit SE, which is indicated by a connection between the power supply / power supply NT and the control unit SE in Figure 1. The power supply / power supply NT is (on the other hand) connected to the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG. A fuse SS, in particular a safety fuse, or a switch SCH (Figure 2) can advantageously be provided in the connection to the mains-side neutral conductor connection NG (and / or phase conductor connection LG).

[0111] According to the invention, the NT power supply is normally continuously supplied with power, specifically from the mains-side connections. It is protected by the SS fuse if necessary or can be switched off using the SCH switch.

[0112] Advantageously, the SCH / Sch switch can be designed so that it can only be opened when the contacts are open. This increases the safety of the device, as the electronics (especially the control unit) cannot be switched off when the contacts are closed.

[0113] The purpose of the fuse SS is not only to protect the power supply via the power supply unit NT, but is also to protect the "electronic" first part EPART or its entire units (such as the control unit, electronic interruption unit, voltage sensor(s), current sensor, if applicable, measuring impedance, etc.), particularly in the case of a two-part structure (see Figure 2).

[0114] Alternatively, the measuring impedance ZM can be connected to the mains-side neutral conductor connection NG via the fuse SS. This advantageously allows a three-pole electronic unit or an electronic first part EPART (Figure 2) to be implemented, for example as a module which has three connections to the low-voltage circuit, a neutral conductor connection and two phase conductor connections. The electronic first part EPART can have further connections, in particular for control or measuring information, such as an enable signal Enable / enable, opening signal OEF, position information (from the positioning unit POS) and / or differential current signal (level of the differential current) from the differential current sensor unit ZCT.

[0115] The electronic unit or electronic first part EPART (Figure 2) comprises, for example, the electronic interruption unit EU, the control unit SE, the power supply NT (in particular including fuse SS), the current sensor unit ST, optionally the first voltage sensor unit SUI and / or optionally the second voltage sensor unit SU2.

[0116] The advantage of the three connections to the low-voltage circuit of the electronic first part EPART is that only two phase conductor connections need to have a high current-carrying capacity (several amperes to carry the load current) and the neutral conductor connection only needs to have a (comparatively) low current-carrying capacity (e.g. less than 1 A, a few mA - depending on the power requirement of the control unit). This simplifies the design and increases the safety of the device because, in the event of a fault in the electronic first part EPART, no large short-circuit current can flow via this connection. The low-voltage circuit can be a three-phase alternating current circuit with one neutral conductor and three phase conductors. The protective switching device can be designed as a three-phase variant for this and, for example, have additional mains-side and load-side phase conductor connections.Electronic interruption units and contacts of the mechanical isolating contact unit according to the invention are provided in a similar manner between the other mains-side and load-side phase conductor connections. The respective conductors (three phase conductors LI, L2, L3, neutral conductor N) are routed through the differential current unit ZCT.

[0117] Likewise, current sensor units and voltage detection (e.g. by first voltage sensor units) can be provided.

[0118] 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.

[0119] Low-resistance refers to a condition in which the current value specified on the protective device could flow. Specifically, low-resistance refers to resistance values ​​that are less than 10 ohms, preferably less than 1 ohm, 100 milliohms, 10 milliohms, 1 milliohm, or less.

[0120] Figure 2 shows a representation similar to Figure 1, with the difference that the protective switching device is constructed in two parts. It contains an electronic first part (EPART), for example, on a printed circuit board.

[0121] The first part EPART can comprise the control unit SE, the first voltage sensor unit SUI, the second voltage sensor unit SU2, the current sensor unit SI, the electronic interruption unit EU, and the power supply NT. Furthermore, the first part can comprise the fuse SS, a switch SCH, the measuring impedance ZM, a temperature sensor TEM (particularly for the electronic interruption unit EU), a communication unit COM, a display unit AE, and, as a variant, a position sensor unit POS.

[0122] The electronic first part EPART has only three connections to the low-voltage circuit:

[0123] - the mains-side phase conductor connection LG as the first connection,

[0124] - a (second) connection for or to the mains-side phase conductor connection point APLG of the mechanical isolating contact unit MK,

[0125] - a third terminal EN for a connection to the mains-side neutral conductor terminal NG .

[0126] The two connections: to the mains-side phase conductor connection LG and for the mains-side phase conductor connection point APLG have a high current-carrying capacity, e.g. several amperes, greater than 10A / 16 A - depending on the nominal current or rated current of the low-voltage circuit, in particular in order to carry the load current even in the event of a short circuit or overload.

[0127] The third connection EN for the connection to the mains-side neutral conductor connection NG has a (comparatively) low current carrying capacity, e.g. less than 1A, a few mA - depending on the energy requirements of the units supplied, especially in the first electronic part EPART. The third connection EN is designed with a low current carrying capacity in order to supply the power supply unit with power and to measure the voltage between the phase conductor and neutral conductor of the low-voltage circuit. In particular, this third connection EN is protected by a fuse SS. This can be implemented using a melting fuse or a cost-effective conductor track fuse (thin conductor track with the appropriate length and thickness on the circuit board). This has the particular advantage that the lower current carrying capacity in this cable or at this third connection EN ensures safety against a short circuit within the first electronic part (EPART) (or(electronic) units), e.g., on the power supply or control unit side. This means that if an electronic component of a unit within the first electronic part EPART fails or malfunctions, no dangerous short-circuit current can occur (fed from the mains-side connections LG, NG), which could lead to a fire in the device.

[0128] This short-circuit current is fed from the mains via the mains-side connections. An upstream circuit breaker often has a much higher tripping current and feeds parallel low-voltage circuits. If a fault occurs in the circuit breaker (the circuit breaker of the protected low-voltage circuit) and the upstream circuit breaker trips, fault-free parallel circuits would also be switched off, which is thus avoided.

[0129] The communication unit COM can, in particular, be a wireless communication unit. The communication unit COM can have a (manual) input unit on the protective switching device for (manual) acknowledgment of states on the protective switching device SG. Acknowledgment can also be performed (wired and / or wirelessly) via the communication unit COM.

[0130] Furthermore, the communication unit COM can have a display function. A separate display unit can also be provided.

[0131] The protective switching device contains a second part MPART , in particular a mechanical one. The second part MPART can have the mechanical isolating contact unit MK, the handle HH, and a release unit EG . Furthermore, the second part can have a positioning unit POS , for reporting the position of the contacts of the mechanical isolating contact unit MK to the control unit, as well as the (neutral conductor) connection(s). The second part MPART has the differential current sensor unit ZCT , such as a summation current transformer, as is known, for example, from classic residual current circuit breakers.

[0132] Additional units, not further specified, may be provided. The two-part design advantageously allows the implementation of a compact protective switching device according to the invention with a simplified construction.

[0133] The release unit / release function FG enables the actuation of the contacts of the mechanical isolating contact unit by the handle HH when an enable release signal is present. This means that the contacts KKL, KKN can only be closed by the handle when the enable release signal (from the SE control unit) is present. Otherwise, closing is not possible (continuous slipping of the HH handle). The contacts remain in the open position / switching state. Furthermore, the release unit FG can cause the contacts to open (second function of the release unit FG) when an opening signal OEF (from the SE control unit) is present. The release unit / release function FG then acts as a tripping unit to open the contacts of the mechanical isolating contact unit MK.

[0134] The protective switching device SG, in particular the control unit SE, is further configured such that, when current limits or current-time limits are exceeded (i.e., when a current limit is exceeded for a specific period of time), the prevention of current flow in the low-voltage circuit is initiated, in particular to prevent a short-circuit current. This is achieved, in particular, by the electronic interruption unit EU switching from the low-resistance state to the high-resistance state.

[0135] The initiation of the prevention of a current flow in the low-voltage circuit is carried out, for example, by a first interruption signal that is sent from the control unit SE to the electronic interruption unit EU.

[0136] The mechanical isolating contact unit MK can be controlled alternatively or additionally by the control unit SE to initiate the prevention of current flow in the low-voltage circuit when current limits or current-time limits are exceeded. Specifically, galvanic isolation is achieved if necessary. The initiation of the prevention of current flow or, if necessary, a galvanic interruption of the low-voltage circuit is initiated, for example, by a second interruption signal sent from the control unit SE to the mechanical isolating contact system MK.

[0137] The electronic interruption unit EU can comprise semiconductor components such as bipolar transistors, field-effect transistors (FETs), isolated-gate bipolar transistors (IGBTs), metal-oxide-layer field-effect transistors (MOSFETs), or other (self-commutated) power semiconductors. IGBTs and MOSFETs, in particular, are particularly well-suited for the protective switching device according to the invention due to their low forward resistance, high junction resistance, and good switching behavior.

[0138] The mechanical isolating contact unit MK specifically refers to a (standard-compliant) isolating function, implemented by the isolating contact unit MK. The isolating function includes the following points: -Minimum air gap according to the standard (voltage-dependent) (minimum distance between contacts), -Contact position indicator of the contacts of the mechanical isolating contact system, -Opening of the mechanical isolating contact system is always possible (no blocking of the isolating contact system - especially by the handle, trip-free mechanism).

[0139] For the purposes of the invention, the DIN EN 60947 and IEC 60947 series of standards are relevant for the isolating function and its properties, to which reference is made here.

[0140] The protective switching device can be designed as a DIN rail-mountable protective switching device SG with a width of, for example, 1 TE, 1.5 TE or 2 TE with two-pole connections (L, N). In electrical installation and switchgear cabinet construction, the width of built-in devices such as protective switching devices, miniature circuit breakers, residual current circuit breakers, etc. is specified in modular units, or TE for short. The width of a modular unit is approximately 18 mm. According to DIN 43880: 1988-12, the installation width of the devices should be between 17.5 and 18.0 mm, or be calculated by multiplying this dimension by 0.5 or an integer multiple thereof, i.e.: k x 0.5 x 18 mm or k x 0.5 x 17.5 mm (with k = 1, 2, 3, ...). For example, a single-pole circuit breaker according to the state of the art has a width of 1 module. The components of electrical distribution boards are matched to the module sizes according to DIN 43871 "Small distribution boards for built-in devices up to 63 A," e.g.the width of mounting rails / top-hat rails.

[0141] According to the invention, the protective switching device SG, in particular the control unit SE, is designed such that, when first differential current limit values ​​or first differential current time limit values ​​are exceeded, a current flow in the low-voltage circuit is prevented by a high-impedance state of the switching elements of the electronic interruption unit when the isolating contacts are closed. The first differential current limit values ​​or first differential current time limit values ​​can be limit values ​​according to relevant standards, such as DIN EN 61008-1. For example, 30 mA for personal protection in Europe in a 230 volt low-voltage circuit, 6 mA for personal protection in North America, and 300 mA for fire protection (230 volt effective value).After avoiding a current flow by a high-resistance state of the switching elements of the electronic interruption unit and the closed state of the contacts, a test is carried out to determine whether second differential current limit values ​​or second differential current time limit values ​​have been exceeded.

[0142] The magnitude of the second differential current limit values ​​or second differential current time limit values ​​can correspond to the magnitude of the first differential current limit values ​​or first differential current time limit values. However, according to the invention, the magnitude of the second differential current limit values ​​or second differential current time limit values ​​is advantageously smaller than the magnitude of the first differential current limit values ​​or first differential current time limit values.

[0143] The level of the second differential current limits or second differential current time limits advantageously corresponds to the standard values, but with a lower level which results from the test. If the test is carried out with a low, particularly protective extra-low voltage, for example, the differential currents also result in lower levels. This means that the level of the second differential current limits or second differential current time limits is determined by the voltage level during the test. The higher the voltage, the higher the level of the second differential current limits or second differential current time limits. If the mains voltage of the low-voltage circuit, e.g. 230 volts, is used for the test (briefly), the level of the second differential current limits or second differential current time limits corresponds to that of the first differential current limits or first differential current time limits.

[0144] According to the invention, the test for the existence of the exceedance of second differential current limit values ​​or second differential current time limit values ​​(of the load-side connections) can be carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit (EU) becoming low-impedance, in particular for a first duty cycle.

[0145] The first duty cycle can be set such that the effective value of the voltage at the load terminals (determined over one mains period) does not exceed 50 V. This means that the instantaneous value of the voltage can be greater than 50 V for a short time, but the effective value of the voltage determined over one mains period is less than 50 volts. The first duty cycle is therefore always less than 20 ms, more specifically less than 10 ms, in particular less than 1 ms. The test for whether second differential current limit values ​​or second differential current time limit values ​​(of the load-side terminals) have been exceeded can be carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit (EU) becoming low-resistance at an absolute instantaneous value of the voltage that is less than a first voltage threshold value (with respect to an alternating voltage).The electronic interrupt unit can be switched on briefly, i.e., the semiconductor-based switching element is switched to a low-impedance state for a short time. "Shorty" refers to a specific initial duty cycle (EDI) during which the instantaneous voltage value u(t) of the alternating voltage does not exceed a certain value, for example, 50 volts. For example, at the zero crossing of the alternating voltage (0°), the alternating voltage can be switched on for approximately 444 ps / up to 8° (electronic interrupt unit EU with low impedance), i.e., until the instantaneous voltage value of a maximum of 50 volts is reached.

[0146] Alternatively, the device can be switched on at approximately -8° (relative to the zero crossing of the AC voltage), passed through the zero crossing, and then switched off again at +8°, ​​i.e., for approximately 888 ps. This means that the switch-on time is less than 1 ms, in particular less than 0.9 ms, and more specifically, approximately 0.8 ms (or half of this, depending on the switch-on time).

[0147] By briefly switching on the electronic interruption unit, a reduced (test) voltage is applied to the load-side terminals. The effective value of this test voltage depends on the existing mains voltage and the initial duty cycle (EDI) and is always lower than the existing mains voltage. The initial duty cycle or the initial voltage threshold are selected so that the effective value of the test voltage (applied to the mains-side terminals) is less than 50V.

[0148] This allows for reliable testing to be carried out to determine whether second differential current limits or second differential current time limits have been exceeded. In the example, the second differential current limits or second differential current time limits are adjusted to a voltage of up to 50 volts. The reduction in the second differential current limit compared to the first differential current limit corresponds to the same ratio as the reduction in the test voltage compared to the nominal mains voltage. This means that for a test voltage of, for example, 50V rms and a nominal mains voltage of 230V, the second differential current limit is reduced by 50 / 230. For example, 30mA (as the first differential current limit) then becomes 30mA * 50 / 230 = 6.5mA (as the second differential current limit).

[0149] This means that the second differential current limit is smaller than the first differential current limit.

[0150] Alternatively or additionally, the switching elements can become high-impedance again when the instantaneous voltage value is greater than a second voltage threshold (such as 50 volts).

[0151] Alternatively, the test for at least one electrical parameter at the load-side terminals can be performed by applying an auxiliary voltage, in particular a pulsed DC voltage, that is less than a first voltage limit. The level of the first voltage limit can be a (limit) value of the safety extra-low voltage or correspond to the voltage threshold. According to the invention, no dangerous voltage is present at the load-side terminals in this case either.

[0152] The first voltage limit can be 50 volts, for example.

[0153] If the second differential current limit values ​​or second differential current time limit values ​​for a first time range ZB1 are not exceeded, the electronic interruption unit EU can switch to the low-resistance state.

[0154] (Alternatively, the test can be carried out until the second differential current limit values ​​or second differential current time limit values ​​are exceeded. The electronic interruption unit then switches to the low-resistance state.)

[0155] In contrast, if the second residual current limit values ​​or second residual current time limit values ​​are exceeded, the isolating contacts can be opened for a first time period ZS1 (galvanic isolation, as with a classic residual current circuit breaker).

[0156] The value of the first time period can correspond to the value of the first time range, i.e. after the first time period (= the first time range) has elapsed, the contacts of the mechanical isolating contact unit can open. The first time period can also have a different value. For example, the first time period can correspond to a time period in accordance with the standard for classic residual current protection / for classic residual current circuit breakers. Reference is made here to the standard DIN EN 61008-1, Residual current / differential current operated circuit breakers without integral overcurrent protection (RCCBs) for household installations and similar applications, in particular Part 1: General requirements, which is incorporated here by reference. For example, this standard states that a 30 mA residual current device (RCD) must trip within 300 ms at the rated residual current (30 mA). And within 150 ms at twice the rated residual current (60 mA).At 5 times or greater within 40ms.

[0157] For example, the first time period can be less than 300 ms, 150 ms, 100 ms, 40 ms, 30 ms, 20 ms, or 10 ms. This allows for behavior that complies with the standard or even better, where, for example, an interruption need only occur after 300 ms. According to the invention, further checks can be performed beforehand to determine whether residual current limits or residual current time limits have been exceeded, without, for example, violating the standard. This allows for greater supply reliability, especially in the case of non-critical faults.

[0158] For example, depending on the application, the first time period ZS1 can have a value from the range 10 ms to 10 s, more specifically 10 ms to 40 ms or 40 ms to 150 ms or 150 ms to 300 ms or 1 s to 10 s. The protective switching device SG can have a communication unit COM, in particular an input unit. If the second residual current limit values ​​or second residual current time limit values ​​for a second time range are not exceeded, for example a value from the range 20 ms ... 100 ms ... 1 s ... 10 s ... 100 s, the electronic interruption unit EU only changes to the low-impedance state when an acknowledgment Ql (e.g. by an operator, user) is made using the communication unit COM, in particular the input unit. The communication unit (input unit) can have input elements on the housing of the protective switching device. The communication unit can also or additionally have a wired (e.g. electrical, optical) or wireless (e.g.(radio, optical) input capability. The communication unit (input unit) can also have a display function.

[0159] Alternatively or additionally, after the first time period ZS1 has elapsed, the electronic interruption unit EU can only return to the low-resistance state (EUn) if it has been determined that the second residual current limit or second residual current time limit has not been exceeded for the duration of a (first (or) second) time period. Furthermore, after the first time period ZS1 has elapsed, an acknowledgment (Ql) of fault freedom can be made (or may be required) before the electronic interruption unit EU returns to the low-resistance state (EUn).

[0160] The protective switching device SG, in particular the control unit SE, can have a microcontroller (= microprocessor) running a computer program product, comprising instructions that, when the program is executed by the microcontroller, cause it to perform a test (as described above and below) for a protective switching device. The computer program product can advantageously be stored on a computer-readable storage medium; such as a USB stick, CD-ROM, etc.; to enable, for example, an upgrade to an extended version.

[0161] Alternatively, the computer program product can also advantageously be transmitted by a data carrier signal.

[0162] The SE control unit can:

[0163] * be implemented with a digital circuit, e.g. with a (further) microprocessor; the (further) microprocessor may also contain an analog part;

[0164] * be implemented with a digital circuit with analog circuit parts.

[0165] Figures 3 to 8 show some of the time sequences mentioned above by way of example. Figures 3 to 8 each show a time bar t on which certain, aforementioned, points in time are entered, as well as entries relating to the evaluations of the first differential current limit values ​​or first differential current time limit values ​​DSG1 or second differential current limit values ​​or second differential current time limit values ​​DSG2, and also states of the mechanical isolating contact unit MK and the electronic interruption unit EU.

[0166] Figure 3 shows the point in time at which a current flow VS is avoided, caused by the first differential current limit values ​​or the first differential current time limit values ​​DSG1 being exceeded. Before the point in time at which the current flow VS is avoided, the mechanical isolating contact unit MK is in a closed state MKg of the contacts and the electronic interruption unit EU is in a low-resistance state EUn of the switching elements for a current flow in the low-voltage circuit. After the current flow VS is avoided, the mechanical isolating contact unit MK continues to be in a closed state MKg of the contacts (for a potentially recurring current flow / in order to quickly enable current flow again) and the electronic interruption unit EU is in a high-resistance state EUh of the switching elements to avoid the current flow.After the current flow VS has been avoided, a check is carried out to determine whether the second residual current limit values ​​or the second residual current time limit values ​​DSG2 (at the load-side connection) have been exceeded.

[0167] Figure 4 shows a representation according to Figure 3, with the following differences.

[0168] After the avoidance of a current flow VS and subsequent (at any subsequent point in time) failure to exceed SB the second differential current limit values ​​or second differential current time limit values ​​DSG2 (i.e. if the second differential current limit values ​​or second differential current time limit values ​​DSG2 are in the target range), the electronic interruption unit EU changes to the low-resistance state EUn, in particular if the failure to exceed SB the second differential current limit values ​​or second differential current time limit values ​​DSG2 has occurred for a first time range ZB1, as shown in Figure 4. The first time range ZB1 can be very short (i.e. a quasi-immediate reclosure can take place), it can also be time-adjustable for safety-related reasons.

[0169] The test for the presence of an exceedance of the second residual current limit values ​​or the second residual current time limit values ​​DSG2 is carried out until the exceedance no longer occurs (SB). It can be continued until the electronic interruption unit EU switches to the low-resistance state EUn (ZB1). Subsequently, a test is carried out again with regard to the first residual current limit values ​​or the first residual current time limit values ​​DSG1.

[0170] In this case, the mechanical isolating contact unit MK has a closed state of the (isolating) contacts MKg over the entire period. Figure 5 shows a representation according to Figure 3, with the difference that after a current flow VS has been avoided and if the second differential current limit values ​​US or second differential current time limit values ​​DSG2 have been exceeded for a first time period ZS1, which is in particular less than 300 ms, 150 ms, 40 ms, 30 ms, 20 ms or 10 ms, the contacts of the mechanical isolating contact unit are opened (MKo). In the example, the electronic interruption unit EU remains in the high-impedance state EUh (since the current flow was avoided VS).

[0171] Figure 6 shows a representation similar to Figure 5, with the difference that the exceedance US of the second differential current limit values ​​or second differential current time limit values ​​DSG2 does not occur immediately after a current flow VS has been avoided, but rather at a later point in time, however still before (the expiration of) the first time period ZB1 (i.e. before the electronic interruption unit EU becomes low-resistance). If the exceedance US of the second differential current limit values ​​or second differential current time limit values ​​DSG2 for the first time period ZS1 occurs (after the first time period ZS1), the contacts MKo of the mechanical isolating contact unit MK open.

[0172] This means that there could be a change in the exceedance (US) / lack of exceedance (SB) of the second residual current limit values ​​or the second residual current time limit values ​​DSG2. If the second residual current limit values ​​or the second residual current time limit values ​​DSG2 are exceeded for the first time period ZS1, the contacts MKo of the mechanical isolating contact unit MK open.

[0173] Figure 7 shows a representation according to Figure 4, with the difference that after the avoidance of a current flow VS and subsequent lack of exceedance SB of the second differential current limit values ​​or second differential current time limit values ​​DSG2 (i.e. when the second differential current limit values ​​or second differential current time limit values ​​DSG2 are in the target range, whereby this should occur in particular before the end of the first time period ZS1, i.e. before the contacts are opened), the electronic interruption unit EU then changes to the low-resistance state EUn if the lack of exceedance SB of the second differential current limit values ​​or second differential current time limit values ​​DSG2 has occurred for a second time range ZB2 (this can correspond to the first time range ZB1) and an acknowledgment (Ql) has taken place (by means of the communication unit COM, in particular input unit).

[0174] The test for the presence of a violation of the second residual current limit values ​​or the second residual current time limit values ​​DSG2 is performed until the violation no longer exists (SB) and / or the second time period has expired and / or the acknowledgement has occurred. This means that the test for the presence of a violation of the second residual current limit values ​​or the second residual current time limit values ​​DSG2 can be continued until the electronic interruption unit EU changes to the low-resistance state EUn (in the example, Q1). Subsequently, a test is performed again with regard to the first residual current limit values ​​or the first residual current time limit values ​​DSG1.

[0175] In this case, the mechanical isolating contact unit MK has a closed state of the (isolating) contacts MKg over the entire period.

[0176] Figure 8 shows a representation according to Figure 5 or 6, with the difference that if the second differential current limit values ​​or second differential current time limit values ​​DSG2 are exceeded US and the first time period ZS1 has elapsed, the contacts of the mechanical isolating contact unit are not opened, i.e. they remain closed. Furthermore, after the first time period ZS1 has elapsed, the check for the existence of the second differential current limit values ​​or second differential current time limit values ​​(DSG2) being exceeded US is carried out with a first time interval ZA1 (i.e. not always). Furthermore, if the second differential current limit values ​​or second differential current time limit values ​​DSG2 continue to be exceeded US (at least if there is no lack of exceedance for the first or second time range ZB1, ZB2) after the first time limit ZG1 has elapsed, the mechanical isolating contact unit MK changes to an open state of the contacts MKo.

[0177] This means that after the first time period ZS1 has elapsed, the test is performed with the first time interval ZA1 until the first time limit ZG1 is reached. After the first time limit ZG1 has elapsed, the mechanical isolating contact unit MK changes to an open state MKo, provided the second residual current limit value US or the second residual current time limit value DSG2 is still exceeded. The electronic interruption unit EU remains in the high-resistance state EUh (since the current flow prevention VS).

[0178] In an analogous manner, other behaviors or procedures can be combined by the expert.

[0179] The test for the existence of the exceedance of second differential current limit values ​​or second differential current time limit values ​​DSG2 is advantageously carried out according to the invention by at least one switching element, in particular two or all switching elements, of the electronic interruption unit EU becoming low-resistance for a first duty cycle EDI.

[0180] This means that the high-impedance state EUh of the electronic interruption unit EU, as shown in the figures, does not mean a permanent high-impedance state, but rather a brief (for the initial duty cycle EDI) low-impedance state of the electronic interruption unit EU. The initial duty cycle EDI, for example, is very short (relative to the other times), so this does not conflict with the representation shown in the figures and the basic functionality.

[0181] Although the invention has been illustrated and described in detail by the embodiment, the invention is not limited by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the scope of the invention.

Claims

Patent claims 1 . Protective switching device (SG) for protecting a low-voltage electrical circuit comprising: - a housing with mains-side and load-side connections (LG, NG, LL, NL) for conductors of the low-voltage circuit, - a differential current sensor unit (ZCT) for determining the level of a differential current of the conductors of the low-voltage circuit, - a mechanical isolating contact unit (MK) which has a closed state of the contacts (MKg) for a current flow in the low-voltage circuit or an open state of the contacts (MKo) for a current flow-preventing galvanic separation in the low-voltage circuit, - an electronic interruption unit (EU) which is connected in series with the mechanical isolating contact unit (MK) on the circuit side and which, by means of semiconductor-based switching elements, has a high-resistance state (EUh) of the switching elements to prevent a current flow or a low-resistance state (EUn) of the switching elements to allow current flow in the low-voltage circuit, - a control unit (SE) which is connected to the differential current sensor unit (ZCT), the mechanical isolating contact unit (MK) and the electronic interruption unit (EU), characterized in that the protective switching device (SG), in particular the control unit (SE), is designed in such a way that when first differential current limit values ​​or first differential current time limit values ​​(DSG1) are exceeded, avoidance of a current flow (VS) in the low-voltage circuit is initiated by a high-resistance state (EUh) of the switching elements of the electronic interruption unit with the isolating contacts in the closed state (MKg), that after avoidance of a current flow (VS) by a high-resistance state of the switching elements of the electronic interruption unit and the contacts in the closed state, a check is carried out to determine whether second residual current limits or second residual current time limits (DSG2).

2. Protective switching device (SG) according to claim 1, characterized in that if the second differential current limit values ​​or second differential current time limit values ​​(DSG2) are not exceeded (SB) for a first time range (ZB1), which is in particular less than 200 ms, 100 ms, 50 ms, 30 ms, 20 ms, or 10 ms, the electronic interruption unit (EU) changes to the low-resistance state.

3. Protective switching device (SG) according to claim 1 or 2, characterized in that when the second differential current limit values ​​or second differential current time limit values ​​(DSG2) are exceeded (US) for a first time period (ZS1), which is in particular less than 300 ms, 150 ms, 40 ms, 30 ms, 20 ms or 10 ms, the contacts are opened (MKo).

4. Protective switching device (SG) according to claim 1, 2 or 3, characterized in that a communication unit COM, in particular input unit, is provided so that if the second differential current limit values ​​or second differential current time limit values ​​(DSG2) are not exceeded (SB) for a second time range (ZB2), which is in particular less than 5s, 3s, 1s, 500ms, 250ms, 100ms, the electronic interruption unit (EU) only changes to the low-impedance state when an acknowledgment (Ql) is made by means of the communication unit (COM), in particular input unit.

5. Protective switching device (SG) according to one of the preceding claims, characterized in that the mechanical isolating contact unit (MK) is assigned to the load-side terminals (LL, NL).

6. Protective switching device (SG) according to one of the preceding claims, characterized in that the test for the existence of the exceedance of second differential current limit values ​​or second differential current time limit values ​​(DSG2) is carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit (EU) becoming low-impedance, in particular for a first duty cycle (EDI), which is in particular less than 20 ms, more specifically less than 15 ms, 10 ms, 5 ms or 1 ms.

7. Protective switching device (SG) according to one of the preceding claims, characterized in that the test for the existence of the exceedance of second differential current limit values ​​or second differential current time limit values ​​(DSG2) is carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit (EU) becoming low-impedance at an instantaneous value of the voltage which is smaller than a first voltage threshold value.

8. Protective switching device (SG) according to claim 6 or 7, characterized in that the switching elements become high-resistance again at an instantaneous voltage value which is greater than a second voltage threshold value.

9. Protective switching device (SG) according to one of the preceding claims 1 to 5, characterized in that the test for the existence of the exceedance of second differential current limit values ​​or second differential current time limit values ​​(DSG2) is carried out by applying an auxiliary voltage which is lower than a first voltage limit.

10. Protective switching device (SG) according to one of the preceding claims, characterized in that the test is carried out when the second differential current limit values ​​or second differential current time limit values ​​(DSG2) are exceeded (US) with a first time interval (ZA1), which is in particular 1, 3, 5, 10, 15, 30 seconds or 1, 5, 10 or 15 minutes, wherein the test is carried out with the first time interval (ZA1) in particular after the expiry of a first time period (ZS1).

11. Protective switching device (SG) according to claim 10, characterized in that if the second differential current limit values ​​or second differential current time limit values ​​(DSG2) are (continued) exceeded after expiry of a first time limit (ZG1), the mechanical isolating contact unit (MK) changes to an open state of the contacts (MKo), in particular that the first time limit is 15 min, 30 min, 1h, 8h, 24h, 36h or 48h.

12. Method for a protective switching device (SG) for protecting a low-voltage electrical circuit, in which - mains-side and load-side connections (LG, NG, LL, NL) are provided for conductors of the low-voltage circuit, - a mechanical isolating contact unit (MK) with a closed state (MKg) of the contacts for a current flow in the low-voltage circuit or an open state (MKo) of the contacts for a current-preventing galvanic isolation in the low-voltage circuit is provided, - an electronic interruption unit (EU) is provided which is connected in series with the mechanical isolating contact unit (MK) on the circuit side and which, by means of semiconductor-based switching elements, has a high-resistance state (EUh) of the switching elements to prevent current flow or a low-resistance state (EUn) of the switching elements to allow current flow in the low-voltage circuit, - that the level of a differential current of the conductors of the low-voltage circuit is determined and, if the first differential current limit values ​​or first differential current time limit values ​​(DSG1) are exceeded, the prevention of a current flow in the low-voltage circuit is initiated by a high-resistance state (EUh) of the switching elements of the electronic interruption unit with the contacts (MKg) closed, - that after avoiding a current flow by a high-resistance state (EUh) of the switching elements of the electronic interruption unit (EU) and closed state (MKg) of the contacts, a test is carried out to determine whether second differential current limit values ​​or second differential current time limit values ​​(DSG2) have been exceeded.

13. Method according to claim 12, characterized in that if the second differential current limit values ​​or second differential current time limit values ​​(DSG2) are not exceeded for a first time range (ZB1), the electronic interruption unit (EU) changes to the low-resistance state (EUn).

14. Method according to claim 12 or 13, characterized in that if the second differential current limit values ​​or second differential current time limit values ​​(DSG2) are exceeded for a first time period (ZS1), which is in particular less than 300 ms, 150 ms, 40 ms, 30 ms, 20 ms or 10 ms, the contacts are opened (MKo).

15. Method according to claim 12, 13 or 14, characterized in that if the second differential current limit values ​​or second differential current time limit values ​​(DSG2) are not exceeded for a second time range (ZB2), the electronic interruption unit (EU) only changes to the low-resistance state when an acknowledgment (Ql) is made.

16. Method according to claim 12, 13, 14 or 15, characterized in that the test for the existence of the exceedance of second differential current limit values ​​or second differential current time limit values ​​(DSG2) is carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit (EU) becoming low-impedance, in particular for a first duty cycle (EDI) which is in particular less than 20 ms, more specifically less than 15 ms, 10 ms, 5 ms or 1 ms.

17. Method according to claim 12, 13, 14, 15 or 16, characterized in that the test for the existence of the exceedance of second differential current limit values ​​or second differential current time limit values ​​(DSG2) is carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit (EU) becoming low-resistance at an instantaneous value of the voltage which is smaller than a first voltage threshold value.

18. A computer program product comprising instructions which, when the program is executed by a microcontroller, cause the microcontroller to carry out a check for the existence of an exceedance of second differential current limit values ​​or second differential current time limit values ​​according to one of claims 1 to 17 after a current flow has been avoided by a high-resistance state of the switching elements of the electronic interruption unit and a closed state of the contacts.

19. A computer-readable storage medium on which the computer program product according to claim 18 is stored.

20. A data carrier signal that transmits the computer program product according to claim 18.

Images