Protective switching device and procedure

Abstract

The invention relates to a protective switching device for protecting a low-voltage electrical circuit, in which - a mechanical isolating contact unit having a closed state of a neutral conductor contact and a phase conductor contact for current flow or an open state of neutral conductor contact and phase conductor contact for galvanic isolation preventing current flow, - an electronic interruption unit which is connected in series with the mechanical isolating contact unit in the phase conductor and which has a high-resistance state of the switching elements or a low-resistance state of the switching elements due to semiconductor-based switching elements, - the magnitude of a differential current between the neutral conductor and the phase conductor is determined. If the differential current exceeds the first differential current time limit, the current flow in the phase conductor is prevented by a high-impedance state of the switching elements when the neutral conductor contact and the phase conductor contact are closed. After the current flow in the phase conductor has been prevented, a test is carried out to determine whether the differential current has exceeded the higher second differential current time limit, and if the differential current exceeds the higher limit, the neutral conductor contact and the phase conductor contact are opened.

Description

The invention relates to the technical field of a circuit breaker for a low-voltage alternating current circuit according to the preamble of claim 1 and to a method for a circuit breaker for a low-voltage alternating current circuit according to the preamble of claim 6.By low voltage is meant voltages of up to 1000 volts AC or up to 1500 volts DC. Low voltage means in particular voltages which are greater than the low voltage, with values of 50 volt AC voltage and 120 volt DC voltage, respectively.By low voltage alternating current circuit or mains or installation is meant circuits with rated currents or rated currents of up to 125 amperes, more specifically up to 63 amperes. Low-voltage alternating current circuits are understood in particular to mean circuits with rated currents or rated currents of up to 50 amperes, 40 amperes, 32 amperes, 25 amperes, 16 amperes or 10 amperes. The current values mentioned mean in particular rated, rated or / and disconnection currents, i.e. the current which is normally conducted at maximum across the circuit or at which the electrical circuit is usually interrupted, for example by a protective device such as a circuit breaker, circuit breaker or circuit breaker. The rated currents can 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. to 16 A / to 25 A / to 32 A.Circuit breakers have long been known overcurrent protection devices which are used in electrical installation technology in low-voltage circuits. These protect lines from damage due to heating as a result of excessively high current and / or short circuit. A circuit breaker can automatically switch off the circuit in the event of overload and / or short circuit. A circuit breaker is a non-automatically resetting safety element.In contrast to circuit breakers, circuit breakers are provided for currents greater than 125 A, in some cases even starting from 63 amperes. Circuit breakers are therefore of simpler and more delicate construction. Circuit breakers usually have a fastening possibility for fastening on a so-called top hat rail (mounting rail, DIN rail, TH35).Circuit breakers according to the prior art are of electromechanical design. In a housing, they have a mechanical switching contact or operating current release for interrupting (releasing) the electrical current. A bimetallic protective element or bimetallic element is usually used for triggering (interruption) in the event of prolonged overcurrent (overcurrent protection) or thermal overload (overload protection). An electromagnetic trip with a coil is used for short-term trip when an overcurrent limit value is exceeded or in the case of a short circuit (short circuit protection). One or more arc extinguishing chamber(s) are provided. Furthermore, connection elements for conductors of the electrical circuit to be protected.Residual current circuit breakers for electrical circuits, in particular for low-voltage circuits or installations, are generally known. Residual current circuit breakers are also referred to as residual current devices, RCD for short. Residual current circuit breakers determine the current sum (or the differential current of forward (positive sign) and return (negative sign)) in an electrical circuit which is normally zero, and interrupt the electrical circuit when a differential current value, i.e. a current sum of not zero which exceeds a specific (differential) current value or residual current value, is exceeded.Almost all current fault interrupters known to the prior art have a sum current converter, the primary winding of which is formed by the conductors of the circuit and the secondary winding of which emits the sum of current (or a representation of the differential current), which is used directly or indirectly for interrupting the electrical circuit.For this purpose, two or more conductors, usually forward and return conductors or outer conductors (or phase conductors) and neutral conductors in a single-phase alternating current network, all three outer conductors or all three outer conductors and the neutral conductor in a three-phase alternating current network, are guided through a current transformer, usually having an annular core made of ferromagnetic material. Only the differential current, i.e. a current differing from forward and reverse current, is converted from the conductors. Usually, the current sum in an electric circuit is equal to zero. Fault currents can thus be detected.If, for example, a current flows to ground on the energy sink side or load side, a fault current or leakage current is referred to in this context. A fault case is present, for example, when an electrical connection exists from a phase conductor of the electrical circuit to ground. For example, when a person touches the phase conductor. Then, a part of the electric current does not flow back via the neutral conductor or neutral conductor as usual, but via the person and the earth. This residual current can now be detected with the aid of the sum current converter, since the sum of the incoming and return current detected (difference in magnitude) is not zero. Via a relay or a holding magnet release, for example with connected mechanism, an interruption of the circuit, for example at least one, a part or all lines, is effected. Residual current circuit breakers for detecting alternating residual currents are generally known from the publication DE 44 32 643 A1.The main function of earth leakage circuit breakers is to protect persons from electrical currents (electrical shock), and also installations, machines or buildings from fire as a result of electrical insulation faults.If the residual current circuit breaker or its sum current converter is designed such that the secondary-side energy of the sum current converter is sufficient for actuating a trip unit or an interruption unit or a trip, then such residual current circuit breakers are referred to independently of the mains voltage. If an auxiliary energy is required or used for the triggering circuit, which is generally generated by a power supply unit provided in the residual current circuit breaker, such residual current circuit breakers are called as a function of the mains voltage. That is to say, mains voltage-dependent residual current circuit breakers contain a power supply unit for supplying power to a residual current detection (mains voltage-independent circuit breakers not). These power supplies are required, for example, in order to detect fault currents in DC voltage networks and mixed DC / AC networks or in circuits with high frequencies.Circuit breakers with an electronic interrupting unit are relatively novel developments. These comprise a semiconductor-based electronic interruption unit. That is to say that the electrical current flow of the low-voltage current circuit is conducted via semiconductor components or semiconductor switches which interrupt the electrical current flow or can be switched to conductive. Circuit breakers with an electronic break unit also often have a mechanical break contact system, in particular with break properties according to relevant standards for low-voltage circuits, wherein the contacts of the mechanical break contact system are connected in series with the electronic break unit, i.e. the current of the low-voltage circuit to be protected is conducted both via the mechanical break contact system and via the electronic break unit.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 described by the equation:. Wherein:u(t)=current voltage value at time tU = Amplitude of voltageA 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 period of oscillation 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 hand. The angular frequency of a harmonic oscillation is always 2π times its frequency, i.e.Frequently, the indication of the angular frequency (ω) is preferred over the frequency (f), since many formulas of the vibration guide can be represented more compactly with the aid of the angular frequency because of the occurrence of trigonometric functions, the period of which is 2π by definition:In the case of circular frequencies which are not constant over time, the term instantaneous circular frequency is also used.In the case of a sinusoidal, in particular temporally constant, AC voltage, the time-dependent value from the angular velocity ω and the time t corresponds to the time-dependent angle φ(t), which is also referred to as phase angle φ(t). That is, the phase angle φ(t) periodically passes through the range 0...2π or 0°...360°. That is, the phase angle periodically assumes a value between 0 and 2π or 0° and 360° (φ=n* (0...2π) or φ=n* (0°...360°), because of periodicity; shortened: φ=0...2π or φ=0°...360°).The instantaneous voltage value u(t) consequently means the instantaneous value of the voltage at the time t, i.e. in the case of a sinusoidal (periodic) alternating voltage the value of the voltage at the phase angle φ (φ=0...2π or φ=0°...360°, of the respective period).It is an object of the present invention to improve a circuit breaker of the type mentioned at the beginning, in particular to ensure protection against (fault) currents by persons with simultaneous supply safety or availability of electrical installations, i.e. to achieve immunity against non-critical (fault) currents or leakage currents which would lead to a faulty triggering of the circuit breaker. This means, on the one hand, that personal protection is ensured and, on the other hand, that the supply safety of a low-voltage alternating current circuit is improved. Alternatively, a novel concept for such a circuit breaker can be provided.This object is achieved by a circuit breaker having the features of claim 1 and by a method according to claim 6.According to the invention, a protective switching device for protecting (residual current protection) an electrical low-voltage alternating current circuit is provided, having:a housing having (at least):• a network-side phase conductor connection,• a load-side phase conductor connection,for a phase conductor of the low-voltage alternating circuit;• a neutral conductor connection on the mains side,• a load-side neutral conductor connection,for a neutral conductor of the low-voltage alternating circuit;a differential current sensor unit for determining the magnitude of a differential current (caused by leakage currents (of the phase conductor or (and) neutral conductor to ground or the protective conductor) of the neutral conductor and phase conductor of the low-voltage alternating current circuit,a mechanical isolation contact unit which has a closed state of a neutral conductor contact and (at least) one phase conductor contact for a current flow in the low-voltage alternating current circuit or an open state of neutral conductor contact and phase conductor contact for a current-flow-avoiding galvanic isolation in the low-voltage alternating current circuit,an electronic interruption unit which is connected in the phase conductor in series with the mechanical break contact unit and which has a high-resistance state of the switching elements to avoid a current flow or a low-resistance state of the switching elements to the current flow in the phase conductor by semiconductor-based switching elements,a control unit connected to the differential current sensor unit, the mechanical disconnect contact unit and the electronic disconnect unit.The protective switching device, in particular the control unit, is designed in such a way that, if the differential current is exceeded above first differential current time limits, an avoidance of a current flow in the phase conductor is initiated by a high-resistance state of the switching elements of the electronic interruption unit when the neutral conductor contact and the phase conductor contact are closed, that after the avoidance of the current flow in the phase conductor (by the high-resistance state of the switching elements of the electronic interruption unit when the neutral conductor contact and the phase conductor contact are closed), a check is carried out for the presence of the exceeding of the differential current above, in particular larger, second differential current time limits, and are opened when the neutral conductor contact and the phase conductor contact are exceeded. This has the advantage that a different triggering behavior is made possible in the case of leakage currents of the phase conductor compared to leakage currents of the neutral conductor.Larger or higher second differential current time limit values are to be understood as meaning second differential current time limit values whose second differential current limit value (proportion) is greater in terms of absolute value than the first differential current limit value (proportion). Alternatively or additionally, the second time limit value (proportion) can be greater than the first time limit value (proportion). In general, a differential current time limit value means a limit value that a differential current (of a specific level) must be present for a certain time before the differential current time limit value is exceeded. That is to say that the differential current time limit value has a differential current limit value component and a time limit value component.Advantageous embodiments of the invention are specified in the dependent claims and in the exemplary embodiment.In an advantageous embodiment of the invention, a triggering behavior offset in time is made possible in the case of differential currents caused by a leakage current of the phase conductor in comparison with differential currents caused by a leakage current of the neutral conductor.This has the particular advantage that selectivity with respect to the triggering conditions can be achieved. Critical differential fault currents / leakage currents of the phase conductor are quickly switched off. More non-critical differential fault currents / leakage currents of the neutral conductor can (are) switched off more slowly (or with a time delay).In an advantageous embodiment of the invention, a presence of a leakage current on the phase conductor or the neutral conductor is (determined and) communicated. For this purpose, a communication unit, for example with an input unit, can advantageously be provided. This has the particular advantage that an overview is given, for example in a superordinate management system, of the type of the differential current / fault current / leakage current that is causing.Advantageously, the mechanical separating contact unit can be operated by a mechanical handle. The switching on and off by means of the electronic interruption unit cannot be operated (directly) on the device.In an advantageous embodiment of the invention, the mechanical isolation contact unit is assigned to the load-side connections.This has the particular advantage that an architecture supporting the behavior of the circuit breaker device according to the invention is provided, since on the one hand, in the case of a high-resistance interruption unit, the current flow is interrupted, but a test (by means of the load-side connections) can still be carried out through the (load-side) closed contacts. Furthermore, the control unit and the electronic interruption unit are further supplied with power, independently of the closed or open state of the neutral conductor contact and of the phase conductor contact.The check for the presence of the exceeding of the differential current above the second differential current time limit values takes place in the high-impedance state of the electronic interruption unit (in the phase conductor) (in the closed state of the neutral conductor contact and of the phase conductor contact).According to the invention, a corresponding method for a circuit breaker device for protecting an electrical low-voltage alternating current circuit having (at least) one phase conductor and one neutral conductor is claimed, in whicha mechanical isolation contact unit which is provided with a closed state of a neutral conductor contact (in the neutral conductor) and a phase conductor contact (in the phase conductor) for a current flow in the low-voltage alternating current circuit or an open state of neutral conductor contact and phase conductor contact for a current-flow-preventing galvanic isolation in the low-voltage alternating current circuit,an electronic interruption unit which is connected in the phase conductor of the low-voltage alternating current circuit in series with the mechanical disconnection contact unit and which is provided by semiconductor-based switching elements with a high-resistance state of the switching elements in order to avoid a current flow or with a low-resistance state of the switching elements in order to current flow in the phase conductor,the magnitude of a differential current (caused by leakage currents (of the phase conductor or / and neutral conductor) (to ground or the protective conductor) of the neutral conductor and phase conductor of the low-voltage alternating current circuit) is determined. The protective switching device is designed in such a way that, if the differential current exceeds (the magnitude and / or duration) first differential current time limit values, an avoidance of a current flow in the phase conductor is initiated by a high-impedance state of the switching elements of the electronic interruption unit when the neutral conductor contact and the phase conductor contact are in the closed state. After the current flow in the phase conductor has been avoided (due to the high-resistance state of the switching elements of the electronic interruption unit and the closed state of the neutral conductor contact and of the phase conductor contact), a check is carried out for the presence of the exceeding (of the magnitude and / or duration) of the differential current above, in particular larger, second differential current time limits and is opened when the neutral conductor contact and the phase conductor contact are exceeded, so that a different triggering behavior is made possible in the case of leakage currents of the phase conductor compared to leakage currents of the neutral conductor.In advantageous embodiments of the method, it is possible to provide:a triggering behavior offset over time in the case of differential currents caused by a leakage current of the phase conductor in comparison with differential currents caused by a leakage current of the neutral conductor are made possible, and / orthe presence of a leakage current on the phase conductor or the neutral conductor (determined and communicated).According to the invention, a corresponding computer program product for a circuit breaker is claimed. The computer program product comprises commands which, when the program is executed by a microcontroller (for example in the control unit), cause the latter to support or carry out the above method (or the above embodiments), in particular, when the differential current exceeds first differential current time limits, to initiate an avoidance of a current flow in the phase conductor by a high-impedance state of the switching elements of the electronic interruption unit when the neutral conductor contact and the phase conductor contact are closed, after the avoidance of the current flow in the phase conductor, to initiate a check for the presence of the exceeding of the differential current above second differential current time limits and, when it is exceeded, to initiate an opening of the neutral conductor contact and of the phase conductor contact, such that a different triggering behavior is made possible in the case of leakage currents of the phase conductor compared to leakage currents of the neutral conductor. The microcontroller is part of the circuit breaker device, in particular of the control unit.According to the invention, a corresponding computer-readable storage medium on which the computer program product is stored is claimed.According to the invention, a corresponding data carrier signal which transmits the computer program product is claimed.All embodiments, both in dependent form referred back to patent claim 1 or 6, and also referred 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 of a circuit breaker device, in particular an improvement of the safety for persons and of the supply safety in low-voltage alternating current circuits and provide a new safe concept for a circuit breaker device.The described properties, features and advantages of this invention and the manner in which these are achieved become clearer and more clearly comprehensible in conjunction with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the drawing.The drawing shows: FIG. 1 shows a first schematic illustration of a circuit breaker device, FIG. 2 shows a second schematic illustration of a circuit breaker device, FIG. 3 shows an illustration of an electrical distribution with a protective switching device, FIG. 4 shows a schematic illustration of a chain of action.FIG. 1 shows a representation of a protective switching device SG for protecting an electrical low-voltage alternating current circuit having a housing GEH, having:(at least) one network-side phase conductor connection LG,(at least) one load-side phase conductor connection LL for a phase conductor L of the low-voltage alternating current circuit;a neutral conductor connection NG on the mains side,a load-side neutral conductor connection NL,for a neutral conductor N of the low-voltage alternating current circuit;a power source is usually connected to the mains-side connections LG, NG / the mains side Grid,a load is usually connected to the load-side connections LL, NL / the load side Load;a (two-pole) mechanical isolation contact unit MK having load-side connection points APLL, APNL and grid-side connection points APLG, APNG,wherein a load-side connection point APNL is provided for the neutral conductor N, a load-side connection point APLL is provided for the phase conductor L, a grid-side connection point APLG is provided for the neutral conductor N, a grid-side connection point APLG is provided for the phase conductor L. The load-side connection points APNL, APLL are connected to the load-side neutral and phase conductor connections NL, LL, wherein the (two-pole) mechanical disconnection contact unit MK has a closed state of a neutral conductor contact KKN (for the neutral conductor) and (at least) one phase conductor contact KKL (for the phase conductor) for a current flow in the low-voltage alternating current circuit or an open state of neutral conductor contact KKN and phase conductor contact KKL for a current-flow-avoiding galvanic disconnection in the low-voltage alternating current circuit, so that an opening of the contacts KKN, KKL for avoiding a current flow or a closing of the contacts KKN, KKL for a current flow in the low-voltage alternating current circuit can be switched,a (single-pole) electronic interruption unit EU,which is connected in series in the phase conductor L to the mechanical break contact unit MK, having a network-side connection point EUG, which is in electrical connection with the network-side phase conductor connection LG, and a load-side connection point EUL, which is in electrical connection or is connected to the network-side connection point APLG of the mechanical break contact unit MK, wherein the electronic break unit EU has or can be switched by semiconductor-based switching elements (not shown) a high-resistance state of the switching elements in order to avoid a current flow or a low-resistance state of the switching elements in order to current flow in the phase conductor L,a differential current sensor unit ZCT for determining the magnitude of a differential current (caused by leakage currents (of the phase conductor L or (and) neutral conductor N to ground or the protective conductor PE)) of neutral conductor and phase conductor of the low-voltage alternating current circuit, the differential current sensor unit ZCT is arranged (arranged) in the example between the electronic interruption unit EU and the mechanical break contact unit MK, it can alternatively be provided (arranged) between the mechanical break contact unit MK and the load-side neutral and phase conductor connections NL, LL, and likewise alternatively provided (arranged) between the electronic interruption unit EU and the grid-side connections NG, LG. The differential current sensor unit ZCT determines the magnitude of the differential current of the conductors of the low-voltage alternating current circuit that are routed through the protective switching device (to be protected). In the example, in the case of a single-phase alternating current circuit of neutral conductor N and phase conductor L.The differential current sensor unit ZCT can be a classic sum current converter. The primary side of the sum current converter is formed by the conductors of the low-voltage alternating current circuit (in the example phase conductor L and neutral conductor N). The secondary side of the sum current converter is connected to the control unit SE.a current sensor unit SI for determining the magnitude of the current of the low-voltage alternating current circuit, which current sensor unit is provided in particular in the phase conductor L (current path of the phase conductor or phase conductor current path),a control unit SE which is connected to the differential current sensor unit ZCT, to the (optional) current sensor unit SI, to the mechanical isolation contact unit MK and to the electronic interruption unit EU.The protective switching device is designed in such a way that, if the differential current determined by the differential current sensor unit ZCT is exceeded above first differential current time limit values, an avoidance of a current flow in the phase conductor L is initiated by a high-impedance state of the switching elements of the electronic interruption unit EU when the neutral conductor contact KKN and the phase conductor contact KKL are in the closed state. After the current flow in the phase conductor L has been avoided (due to the high-resistance state of the switching elements of the electronic interruption unit EU when the neutral conductor contact KKN and the phase conductor contact KKL are closed), a check is carried out for the presence of the exceeding of the differential current above, in particular larger, second differential current time limit values. When it is exceeded, the neutral conductor contact KKN and the phase conductor contact KKL are opened. This has the advantage that a different triggering behavior is made possible in the case of leakage currents of the phase conductor compared to leakage currents of the neutral conductor.Larger or higher second differential current time limit values are to be understood as meaning second differential current time limit values whose second differential current limit value (proportion) is greater in terms of absolute value than the first differential current limit value (proportion). Alternatively or additionally, the second time limit value (proportion) can be greater than the first time limit value (proportion). In general, a differential current time limit value means a limit value that a differential current (of a specific magnitude-differential current limit value component) must be present for a certain time before the differential current time limit value is exceeded. That is to say that the differential current time limit value has a differential current limit value component and a time limit value component.In addition, the protective switching device can be designed in such a way that, if current or / and current time limit values are exceeded (i.e. if a current of a specific level is present in the circuit for a specific time), avoidance of a current flow of the low-voltage alternating circuit is initiated for one of the levels of the current of the low-voltage alternating circuit determined by the current sensor unit SI.The mechanical separating contacts unit MK is arranged on the load side in the example, and the electronic interruption unit EU is arranged on the grid side.The grid side Grid with the energy source is normally under electrical voltage. An electrical load is usually connected to the load side Load.This has the advantage that no further parts or components (in particular under voltage) are located between the contacts of the mechanical disconnect contact unit / load-side connection points APLL, APNL of the mechanical disconnect contact unit and the two load-side connections LL, NL. Thus, due to this architecture or construction, it can be ensured that, with the contacts KKL, KKN opened, a voltage is never present at the load-side terminals LL, NL. This increases the safety of the protective switching device / in the low-voltage alternating current circuit. In contrast, in other architectures in which the mechanical isolation contact unit is arranged on the network side, electronic units (not galvanically isolated) are frequently located before the load-side connection.The protective switching device can be designed in such a way that the level of the voltage across the electronic interruption unit EU can be determined. That is to say, the magnitude of a first voltage between grid-side connection point EUGand load-side connection point EULof the electronic interruption unit EU can be ascertained or is ascertained.For this purpose, in the example according to FIG. 1, a first voltage sensor unit SU 1 connected to the control unit SE is provided, which voltage sensor unit determines the level of the voltage between the grid-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU. During the voltage measurement by the first voltage sensor unit SU 1, alternatively, the voltage across the series circuit of electronic interruption unit EU and current sensor SI can also be determined, as illustrated in FIG. 1. The current sensor unit SI has a very low internal resistance, so that the determination of the magnitude of the voltage is not impaired or is impaired to a negligible extent.Advantageously, a second voltage sensor unit SU 2 can be provided, which determines the level of the voltage between the grid-side neutral conductor terminal NG and the grid-side phase conductor terminal LG.A measurement impedance ZM can be connected between the network-side connection points APLG, APNG of the mechanical isolation contact unit MK. The measurement impedance ZMmay be, for example, an electrical resistor and / or capacitor. The measurement impedance may further be an inductance. In particular, the measurement impedance can be a series circuit or parallel circuit of a resistor and / or capacitor and / or inductance.The electronic interruption unit EU is arranged in the phase conductor L (FIG. 1 ). The grid-side connection point APRG for the neutral conductor of the mechanical isolation contact unit MK is connected to the grid-side neutral conductor connection NG of the housing GEH. According to FIG. 1, this connection is passed through the differential current sensor unit ZCT, for example its sum current converter.The protective switching device SG is advantageously designed in such a way that the contacts KKL, KKN of the mechanical disconnect contact unit MK can be opened by the control unit SE but cannot be closed, which is indicated by an arrow OEF from the control unit SE to the mechanical disconnect contact unit MK.The mechanical disconnect contact unit MK can be operated by a mechanical handle HH on the circuit breaker device SG in order to switch a manual (manual) opening or closing of the contacts KKL, KKN. Both contacts are switched simultaneously, for example. The mechanical handle HH indicates the switching state (open or closed) of the contacts of the mechanical disconnect contact unit MK on the protective switching device. Furthermore, the contact position (or the position of the handle, closed or opened) can be transmitted to the control unit SE. The contact position (or the position of the handle) can be determined, for example, by means of 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 may be a part of the mechanical disconnect contact unit MK. Alternatively, the position sensor may be a component in the electronic first part (EPART, FIG. 2 ). For example, a Hall sensor can be provided in the electronic first part (EPART), which detects and transmits the position of the contacts and / or of the handle in a contactless manner.The mechanical disconnect contact unit MK is advantageously designed such that (manual) closing of the contacts by the mechanical handle is possible only after a release (enable), in particular a release signal enable. This is likewise indicated by the arrow from the control unit SE to the mechanical disconnect contacts unit MK. That is to say, the contacts KKL, KKN of the mechanical disconnect contact unit MK can be closed by the handle HH only when the enable or enable signal is present (by the control unit). Without the release or the release signal, the handle HH can be actuated, but the contacts cannot be closed ("permanent slide").The protective switching device SG has a power supply or power supply unit NT, for example a switched-mode power supply. In particular, the power supply / power supply unit NT is provided for the control unit SE, which is indicated by a connection between the power supply / power supply unit NT and the control unit SE in FIG. 1. The power supply / power supply NT is (on the other hand) connected to the grid-side neutral conductor terminal NG and the grid-side phase conductor terminal LG. In the connection to the mains-side neutral conductor connection NG (or / and phase conductor connection LG), a fuse SS, in particular a fuse, or (and) a switch Sch can advantageously be provided. According to the invention, the power supply unit NT is normally constantly supplied with energy, especially from the connections on the power supply unit side. It is optionally protected by the fuse SS or can be switched off by the switch Sch. Advantageously, the switch SCH / Sch can be designed such that the switch can only be opened when the contacts are in the open state. This increases the safety of the device, since the control unit (electronics) cannot be switched off when the contacts are closed.The purpose of the fuse SS is not only to protect the energy supply by means of the power supply unit NT, but is also to protect the "electronic" part or its in particular entire units (such as a special control unit, electronic interruption unit, sum current converter, if necessary, particularly in the case of a two-part construction, for example. Voltage sensor(s), optionally. Current sensor, optionally. Measurement impedance, etc.).The low voltage alternating current circuit may be a three phase alternating current circuit having a neutral conductor and three phase conductors. The protective switching device can be designed as a three-phase variant for this purpose and can have, for example, further line-side and load-side phase conductor connections. Between the further line-side and load-side phase conductor connections, electronic interruption units according to the invention and contacts of the mechanical isolation contact unit are provided in an analogous manner. The respective conductors (three phase conductors L 1, L 2, L 3, neutral conductors N) are routed through the differential current unit ZCT. Current sensor units, voltage determinations (e.g. by first voltage sensor units) can likewise be provided.By high-resistance is meant a state in which only a current of negligible magnitude still flows. In particular, high-resistance values of greater than 1 kiloohm, better greater than 10 kiloohm, 100 kiloohm, 1 megaohm, 10 megaohm, 100 megaohm, 1 gigaohm or greater are meant.By low-ohmic is meant a state in which the current value indicated on the circuit breaker could flow. In particular, low-resistance values are meant which are less than 10 ohms, better less than 1 ohm, 100 milliohms, 10 milliohms, 1 milliohm or less.FIG. 2 shows a representation according to FIG. 1, with the difference that the circuit breaker is constructed in two parts. It contains an electronic first part EPART, for example on a printed circuit board / board.The first part EPART may include the control unit SE, optionally the first voltage sensor unit SU 1, optionally the second voltage sensor unit SU 2, optionally the current sensor unit SI, the electronic interruption unit EU, the power supply NT. Furthermore, the first part can have the fuse SS, a switch SCH, the measuring impedance ZM, a temperature sensor TEM (in particular for the electronic interruption unit EU), a communication unit COM, a display unit AE, and as a variant a position sensor unit POS.The communication unit COM can be, in particular, a wireless communication unit. The communication unit COM can have a (manual) input unit on the circuit breaker device for (manual) acknowledgement of states on the circuit breaker device SG. The acknowledgement can also be effected (wired or / and wireless) via the communication unit COM.Further, the communication unit COM may have a display function. A separate display unit can likewise be provided.The circuit breaker device contains a second part MPART, in particular a mechanical part. The second part MPART can have the mechanical disconnect contact unit MK, the handle HH, a release unit FG. Furthermore, the second part can have a position unit POS for reporting the position of the contacts of the mechanical disconnect contacts unit MK to the control unit, and the (neutral conductor) connection(s). The second part MPART has the differential current sensor unit ZCT, such as a sum current converter, as is known, for example, from classical residual current circuit breakers.Further units, not designated in more detail, can be provided.The division into two parts advantageously allows a compact circuit breaker according to the invention to be realized with a simplified construction.The enable unit / enable function FG enables the actuation of the contacts of the mechanical disconnect contact unit by the handle HH if an enable signal is available. That is to say that closure of the contacts KKL, KKN by the handle is possible only when the enable signal is present (which is enabled by the control unit SE). Otherwise, closing is not possible ("permanent slide" of the handle HH).The contacts remain in the open position / switching state.Furthermore, the enabling unit FG can cause the contacts to open (second function of the enabling unit FG) if an opening signal OEF (from the control unit SE) is present. The release unit / release function FG then acts as a trip unit for opening the contacts of the mechanical disconnect contact unit MK.The protective switching device SG, in particular the control unit SE, is furthermore configured such that, when current limit values or current time limit values are exceeded (i.e. when a current limit value is exceeded for a specific period of time), avoidance of a current flow of the low-voltage alternating current circuit is initiated, in particular in order to avoid a short-circuit current. This is achieved in particular by the electronic interruption unit EU changing from the low-impedance state to the high-impedance state. The initiation of the avoidance of a current flow of the low-voltage alternating current circuit is effected, for example, by a first interrupt signal off which is sent from the control unit SE to the electronic interrupt unit EU. The electronic interrupt unit EU can be switched to the low-impedance state by a switch-on signal on.The mechanical break contact unit MK can alternatively or additionally be controlled by the control unit SE in order to initiate an avoidance of a current flow of the low-voltage alternating current circuit if current limit values or current time limit values are exceeded. Specifically, galvanic separation is optionally brought about here. The initiation of the avoidance of a current flow or a possibly galvanic interruption of the low-voltage alternating current circuit takes place, for example, by a second interruption signal (OEF) which is transmitted from the control unit SE to the mechanical break contact system MK.The electronic interruption unit EU may comprise semiconductor components such as bipolar transistors, field effect transistors (FETs), insulated gate bipolar transistors (IGBTs), metal oxide layer field effect transistors (MOSFETs) or other (self-commutated) power semiconductors. In particular, IGBTs and MOSFETs are particularly well suited for the protective switching device according to the invention because of low flow resistances, high junction resistances and good switching behavior.Mechanical disconnect contact unit MK means, in particular, a (norm-compliant) disconnect function realized by disconnect contact unit MK. With a separation function, the points are:minimum air path according to standard (voltage-dependent) (minimum distance of the contacts),indicating the position of the contacts of the mechanical disconnection contact system,Opening of the mechanical separating contact system is always possible (no blocking of the separating contact system-in particular by the handle, release of the load),By this means.In the sense of the invention, the series of standards DIN EN 60947 and IEC 60947, respectively, are relevant here, for example for the separator function and its properties, which are referred to here by reference.The circuit breaker can be designed as a top-hat rail-mountable circuit breaker SG having a width of, for example, 2 TE with two-pole connections (phase conductor L, neutral conductor N). In electrical installation and in switchgear cabinet construction, the width of built-in devices such as circuit breakers, line breakers, residual current circuit breakers, etc. is specified in dividing units, TE for short. The width of a division unit is ~18 mm. The installation width of the devices should be between 17.5 and 18.0 mm according to the standard DIN 43880: 1988-12, or be calculated from 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 (where k=1, 2, 3,... ). Thus, for example, a single-pole circuit breaker according to the prior art has a width of 1 TE. The installations of electrical installation distributors are matched to the dividing units in accordance with DIN 43871 "Installation small distributors for installation devices up to 63 A", for example the width of mounting rails / top-hat rails.According to the invention, the protective switching device SG, in particular the control unit SE, is designed in such a way that, if first differential current time limit values are exceeded, an avoidance of a current flow in the low-voltage alternating current circuit is initiated by a high-impedance state of the switching elements of the electronic interruption unit when the disconnection contacts are closed. The 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, 300 mA for fire protection (230 volt root mean square).The standard DIN EN 61008-1, residual current / differential current circuit breakers without built-in overcurrent protection (RCCBs) for domestic installations and for similar applications, in particular part 1: General requirements, are incorporated herein by reference. For example, this standard reveals that a 30 mA residual current circuit breaker (RCD) must trip within 300 ms at the rated residual current (30 mA). At 2 times rated leakage current (60 mA) within 150 ms. At 5 times, or greater within 40 ms.After a current flow through a high-impedance state of the switching elements of the electronic interruption unit and a closed state of the contacts has been avoided, a check is carried out for the presence of the exceeding of second differential current time limits.The magnitude of the second differential current time limits is greater than that of the first differential current time limits.The magnitude of the second differential current limit value (current component from the differential current time limit value) can be a multiple of the magnitude of the first differential current limit value: for example 1.5, 2, 3, 5, 10 or 20 times (intermediate values possible). The length of the second time limit value (time component from the differential current time limit value) can be a multiple of the length (or duration) of the first time limit value: e.g. 1.5, 2, 3, 5, 10, 20, 50, 100 or 1000 times.The first differential current time limit values can be values from known standards / product standards (in particular manufacturer-specific standards). For example, the first differential current time limits can be values from the standard residual current / differential current circuit breakers: DIN EN 61008-1 or (and) DIN EN 61009-1 (e.g. VDE 0664-10) or from other standards for residual current / differential current circuit breakers (with built-in overcurrent protection (RCBOs) for domestic installations and for similar applications).The circuit breaker device SG, in particular the control unit SE, can have a microcontroller (=processor) on which a computer program product runs, comprising commands which, when the program is executed by the microcontroller, cause the microcontroller to carry out a behavior or a test (as described above and below) for a circuit breaker device. The microprocessor-based control unit may have a memory. A trigger curve with concrete (first / second) differential current time limit values can then be stored in the control unit, in particular in the memory. The trigger curve can be removed from the memory. The values of the selected trigger curve are compared with the determined level of the fault current in the control unit (e.g. with the aid of the microprocessor). If it is exceeded, a corresponding current flow-avoiding triggering is initiated.The computer program product can advantageously be stored on a computer-readable storage medium; such as a USB stick, CD-ROM, etc.; in order to enable, for example, an upgrade to an extended version.Alternatively, the computer program product can also advantageously be transmitted by a data carrier signal.The invention is explained further below in other words and further figures.Present-day residual current (RCD) circuit breakers serve (inter alia) for personal protection (protection aim: protection against electrical shock) and, in the event of a differential current occurring (also referred to as differential residual current or residual current) which exceeds differential current time limit values, trip and disconnect the existing circuit on the phase conductor L (also referred to as L conductor) and neutral conductor N (also referred to as N conductor). The residual current protection switching devices (RCD protection devices) typically measure the differential current that occurs via a sum current converter (or else differential current converters). The protection devices do not thereby distinguish whether the fault current has occurred on the N or the L conductor.If, for example, a person touches the phase conductor L (L conductor or active conductor), the person must be protected from a dangerous electrical shock and the protective switching device disconnects the load output Load from the mains connection Grid within a determined (and standardized) current-time triggering limit (differential current-time limit values).In the normal case, a voltage of approximately zero volts is present on the neutral conductor N ("N conductor" or "zero conductor"), since the N conductor and the protective conductor (also referred to as PE conductor) are typically connected to one another in the electrical distribution (typically at the feed transformer). Nevertheless, small voltages (in the range of a few volts or even 10 to 20 volts) are possible between the neutral conductor N and the protective conductor (PE conductor). This is due, for example, to currents on the N conductor which lead to a voltage drop on the N conductor. Or the capacitive coupling between the N and L conductors, which can occur more frequently in particular in the case of EMC interference.This has the result that, for example, when an electrically conductive (or very low-ohmic) connection occurs between the N and PE conductors (for example, due to the contacting of the two conductors), a differential fault current can flow on the N conductor. If this (N-conductor) differential current exceeds the triggering limit, a current residual current circuit breaker (RCD circuit breaker) triggers.Because of its design (with the differential current converter present), residual current circuit breakers cannot distinguish whether the residual current (leakage current) flows on the N conductor or the L conductor and thus triggers (always the same).According to the invention, a solution is proposed how a protective switching device can trip in different ways (in relation to the current level and / or the trip time) when a differential fault current occurs on the L conductor or the N conductor. That is, the circuit breaker no longer triggers immediately at L and N fault currents (leakage currents).FIG. 3 shows a schematic illustration of an electrical energy distribution with a circuit breaker device SG according to the invention. On the grid side, a grid side feed phase conductor L 1E, a grid side feed neutral conductor NE and a protective conductor PE are provided. The mains side Grid of the protective switching device SG is connected to the mains side feed phase conductor L 1 and to the mains side feed neutral conductor NE. In between, a (upstream) fuse F 1 and a (upstream) first line protection switch F 2 are provided in the phase conductor, according to FIG. 3.A load-side sub distribution phase conductor L 1S and a load-side sub distribution neutral conductor NS are connected to the load side Load of the protective switching device SG.Furthermore, the feeder-side protective conductor PE is connected through to the load side, as shown in FIG. 3.In the example, a socket SDV with an electrical load VBR is connected to the load-side sub distribution phase conductor L 1S and load-side sub distribution neutral conductor NS. In the phase conductor of this connection, a further second line protection switch F4 is provided. The socket SDV is also connected to the protective conductor PE. The socket SDV can be an electrical connection (el. The bridge between the neutral conductor and the protective conductor PE can be provided.The terms grid-side feed phase conductor L 1E, grid-side feed neutral conductor NE, load-side sub-distribution phase conductor L 1S, load-side sub-distribution neutral conductor NS are used or abbreviated, in part, as synonyms with phase conductor and neutral conductor. One skilled in the art knows what and how it is meant.A current i load, which is protected by fuse F1, first line circuit breaker F2 and second line circuit breaker F4 and is advantageously also protected by circuit breaker device SG, with current sensor unit SI, flows through load VBR via phase conductors and neutral conductors. Thus, the first line circuit breaker F 2 and / or the second line circuit breaker F 4 could be omitted if necessary.A person HUM is shown schematically, which touches the phase conductor between the socket SDV and the load VBR. A phase conductor-side leakage current / phase conductor-side differential current i fL flows via the person HUM to ground (ground symbol).In the case of a potential difference between neutral conductor N and protective conductor PE, a leakage current on the neutral conductor side / differential current i on the neutral conductor side would flow off in fN as indicated in FIG. 3.The protective switching device SG typically has a sum current converter which detects the magnitude of the differential current between the two conductors (L and N) of the low-voltage power supply system. The device now has a different chain of action and switch-off limits (differential current time limit values) for the two different conductors of the low-voltage power supply system.When a fault current occurs on the phase conductor L, the fault current is detected by the differential current sensor unit ZCT (also referred to as a sum current converter as synonym) and is sent to the control unit (evaluation electronics, including μController). Here, it cannot be distinguished first whether this differential current flows on the L conductor or on the N conductor. After first differential current time limit values DSG 1 are exceeded (a first switch-off limit is exceeded), the device switches the electronic interruption unit EU (its electronic switch) into the high-impedance state and thus interrupts the current path in the L conductor and thus also the flowing differential current.If a differential current flows on the N conductor, the electronic interruption unit EU is likewise switched to the high-impedance state when the first differential current time limit values DSG 1 (first switch-off limit) are reached. However, the leakage current of the neutral conductor ("neutral conductor differential current") can continue to flow, since a current flow via the neutral conductor is still possible (no electronic interruption unit EU in the neutral conductor).The magnitude of the differential current is also monitored by means of the differential current sensor unit and the control unit. The second differential current time limit values are present for this purpose (second shutdown limit), which is greater than the first shutdown limit. The protective switching device remains in the high-impedance state of the electronic interruption unit EU as long as the second differential current time limit values (second switch-off limit) are not exceeded. If the second differential current time limits are exceeded, the contacts are opened and the differential current on the N conductor is interrupted (avoided).This is indicated in FIG. 4.The circuit breaker thus offers the possibility of implementing a different triggering behavior, depending on which conductor (L- or N-) a leakage current (differential current) flows on. If it is taken into account that the two conductors (L and N) present a different risk, in particular with regard to personal protection, a reasonable new device behavior results. The L-conductor is typically below a dangerous mains voltage of e.g. 230V. The neutral (N) conductor, on the other hand, typically does not have a dangerous voltage. A differential current (leakage current) on the L conductor is thus significantly more dangerous with respect to the protection of persons than a differential current (leakage current) on the N conductor. The cut-off limit with respect to the differential current level and the trip time can therefore be higher and longer for N conductors, respectively. This would lead to false triggerings being avoided by opening the contacts of the mechanical disconnect contact unit.Advantageously, a fast and sensitive current avoidance (triggering) in the case of differential currents (leakage currents) of the phase conductor (L conductor) and a slow and robust current avoidance in the case of differential currents (leakage currents) of the neutral conductor can thus take place. The behavior can be advantageously configured or activated.The first and second differential current time limit values can advantageously be configured or activated (yes after the field of use / application of the circuit breaker device).This has the particular advantage that, after an erroneous differential current event, for example caused by a person touching a (phase) conductor (critical event) or by a technically induced leakage current (non-critical for persons, i.e. non-critical event) (for example by switched capacitances), immediate avoidance of a current flow in the low-voltage alternating current circuit is initiated by a high-resistance state of the switching elements of the electronic interruption unit.Immediate avoidance of a current flow means in particular high impedance of the electronic interruption unit within 10 ms, in particular 5 ms or 1 ms. (Present day earth leakage circuit breakers typically trip after at least / greater than 20 ms.)After the current flow through a high-impedance state of the switching elements of the electronic interruption unit and the closed state of the contacts has been avoided, a check is carried out for the presence of the exceeding of second differential current limit values or second differential current time limit values in order to check further for the presence of faulty differential current events and, if appropriate, to distinguish critical events from non-critical events in order to thus ensure firstly protection against personnel and secondly the availability of installations.A completely new operating concept for a circuit breaker is presented.Although the invention has been illustrated and described in more detail by the exemplary embodiment, the invention is not restricted by the disclosed examples and other variations can be derived therefrom by the person skilled in the art without departing from the scope of protection of the invention.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 44 32 643 A1

[0010] Cited Non-Patent LiteratureDIN EN 61008-1

[0083] DIN EN 61009-1

[0083]

Claims

Protective switching device (SG) for protecting an electrical low-voltage alternating current circuit, having: - a housing having: a grid-side phase conductor connection (LG), a load-side phase conductor connection (LG), for a phase conductor (L) of the low-voltage alternating current circuit; a grid-side neutral conductor connection (NG), a load-side neutral conductor connection (NL), for a neutral conductor (N) of the low-voltage alternating current circuit; - a differential current sensor unit (ZCT) for determining the magnitude of a differential current of neutral conductor (N) and phase conductor (L) of the low-voltage alternating current circuit, - a mechanical isolation contact unit (MK), which has a closed state of a neutral conductor contact (KKN) and a phase conductor contact (KKL) for a current flow in the low-voltage alternating current circuit or an open state of neutral conductor contact (KKN) and phase conductor contact (KKL) for a current-flow-avoiding galvanic isolation in the low-voltage alternating current circuit, - an electronic interruption unit (EU) which is connected in the phase conductor (L) in series with the mechanical isolation contact unit (MK) and which has, by means of semiconductor-based switching elements, a high-resistance state (EUh) of the switching elements for avoiding a current flow or a low-resistance state (EUn) of the switching elements for current flow in the phase conductor (L), - a control unit (SE) which is connected to the differential current sensor unit (ZCT), the mechanical isolation contact unit (MK) and the electronic interruption unit (EU) are connected, characterized in that the protective switching device (SG) is designed in such a way that, if the differential current is exceeded above first differential current time limit values (DSG1), an avoidance of a current flow (VS) in the phase conductor (L) is initiated by a high-resistance state (EUh) of the switching elements of the electronic interruption unit when the neutral conductor contact (KKN) and the phase conductor contact (KKL) are closed, that after the current flow (VS) in the phase conductor (L) is avoided, a check is carried out for the presence of the exceeding of the differential current via second differential current time limit values (DSG2) and, when the neutral conductor contact (KKN) and the phase conductor contact (KKL) are exceeded, are opened, so that a different triggering behavior is made possible in the case of leakage currents of the phase conductor compared to leakage currents of the neutral conductor.Circuit breaker device (SG) according to Patent Claim 1, characterized in that the second differential current time limit values (DSG2) are greater than the first differential current time limit values (DSG1).Circuit breaker (SG) according to Patent Claim 1 or 2, characterized in that a triggering behavior which is offset over time is made possible in the case of differential currents caused by a leakage current of the phase conductor in comparison with differential currents caused by a leakage current of the neutral conductor.Circuit breaker (SG) according to Patent Claim 1, 2 or 3, characterized in that a leakage current is communicated on the phase conductor or the neutral conductor.Circuit breaker device (SG) according to one of the preceding patent claims, characterized in that the mechanical disconnection contact unit (MK) is assigned to the load-side connections (LL, NL).Method for a protective switching device (SG) for protecting an electrical low-voltage alternating current circuit, in which - a mechanical disconnection contact unit (MK) which comprises a closed state of a neutral conductor contact (KKN) and a phase conductor contact (KKL) for a current flow in the low-voltage alternating current circuit or an open state of neutral conductor contact (KKN) and phase conductor contact (KKL) for a current-flow-avoiding galvanic disconnection in the low-voltage alternating current circuit is provided, - an electronic interruption unit (EU), which is connected in series with the mechanical isolation contact unit (MK) in the phase conductor (L) of the low-voltage alternating circuit and which is provided by semiconductor-based switching elements a high-resistance state (EUh) of the switching elements in order to avoid a current flow or a low-resistance state (EUn) of the switching elements for the current flow in the phase conductor (L), - the magnitude of a differential current of neutral conductor (N) and phase conductor (L) of the low-voltage alternating circuit is determined, characterized in that, wherein, if the differential current is exceeded above first differential current time limits (DSG1), an avoidance of a current flow (VS) in the phase conductor (L) is initiated by a high-resistance state (EUh) of the switching elements of the electronic interruption unit when the neutral conductor contact (KKN) and the phase conductor contact (KKL) are closed, it is initiated that, after the avoidance of the current flow (VS) in the phase conductor (L), a check is carried out for the presence of the exceeding of the differential current above second differential current time limits (DSG2) and, if the neutral conductor contact (KKN) and the phase conductor contact (KKL) are exceeded, such that a different triggering behavior is made possible in the case of leakage currents of the phase conductor compared to leakage currents of the neutral conductor.Method according to claim 6, characterised in that the second differential current time limit values (DSG2) are greater than the first differential current time limit values (DSG1).Method according to claim 6 or 7, characterised in that a triggering behavior offset over time is made possible in the case of differential currents caused by a leakage current of the phase conductor in comparison with differential currents caused by a leakage current of the neutral conductor.Method according to claim 6, 7 or 8, characterised in that the presence of a leakage current is communicated on the phase conductor or the neutral conductor.Computer program product comprising instructions which, when the program is executed by a microcontroller, cause the latter to support or carry out the method according to one of Patent Claims 6 to 9, in particular, when the differential current exceeds first differential current time limit values (DSG1), to initiate avoidance of a current flow (VS) in the phase conductor (L) by a high-impedance state (EUh) of the switching elements of the electronic interruption unit when the neutral conductor contact (KKN) and the phase conductor contact (KKL) are in the closed state, after the avoidance of the current flow (VS) in the phase conductor (L), a check for the presence of the exceeding of the differential current above second differential current time limit values (DSG2) is initiated and, if it is exceeded, an opening of the neutral conductor contact (KKN) and of the phase conductor contact (KKL) is initiated, so that a different triggering behavior is made possible in the case of leakage currents of the phase conductor compared to leakage currents of the neutral conductor.A computer readable storage medium having stored thereon the computer program product of claim 10.A data carrier signal carrying the computer program product of claim 10.

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