Circuit breaker device and method

Abstract

The invention relates to a fault current protection of an electric low-voltage alternating current circuit. The level of a differential current of two conductors of the low-voltage current circuit is ascertained, and the level of a voltage between the two conductors of the low-voltage current circuit is ascertained. A differential active current is ascertained from the level of the voltage and the level of the differential current. The differential active current is compared with a first current threshold or a first current time threshold. If the first current threshold or the first current time threshold is exceeded, a process of preventing a current flow in the low-voltage alternating current circuit is initiated.

Description

[0001] 202222458 1 Description Protective switching device and method Regardless of the grammatical gender of a particular term, persons with male, female or other gender identity are also included. The invention relates to the technical field of a protective switching device for protecting an electrical low-voltage alternating current circuit and to a method for residual current protection of an electrical low-voltage circuit. The term protective switching device refers to low-voltage protective switching devices, in particular residual current circuit breakers. Low voltage refers to voltages up to 1000 volts AC or 1500 volts DC. More specifically, low voltage refers to voltages that are greater than extra-low voltage with values ​​of 50 volts AC or 120 volts DC. Low voltage circuits are circuits for currents up to 6300 amperes, more specifically for currents up to 1600 amperes, 1200 amperes, 630 amperes, 125 amperes,63 amps, 40 amps, 32 amps, 16 amps, 10 amps, or 6 amps. The current values ​​mentioned refer in particular to rated currents (formerly nominal and / or breaking currents), i.e., currents that the circuit or a protective switching device can carry continuously, i.e., without damage, under standardized conditions (such as the connection cross-sections of the copper conductors and their length) at a defined ambient temperature (such as 40°C). Such points are specified in relevant product standards (e.g., DIN EN 60947-2 or 60898-1 for circuit breakers and miniature circuit breakers, DIN EN 61008-1 or 61009-1 for residual current devices). This means, colloquially, the maximum current that is normally carried through the circuit or where the electrical circuit is usually interrupted, for example by a protective switching device,such as a miniature circuit breaker or a circuit breaker. Residual current circuit breakers are used primarily for rated current ranges of or up to 6, 10, 16, 25, 32, 40, 63, 80, or 125 amperes. Residual current circuit breakers (differential current circuit breakers) determine the current sum (i.e. a total current or, depending on the current direction / power flow direction, a differential current) between two or more conductors in an electrical circuit, which is normally zero, and interrupt the electrical circuit when a differential current value is exceeded, i.e. a current sum not equal to zero that exceeds a certain differential current limit (differential current threshold value or response current value or residual current value or fault response current value), which is also referred to as tripping. Typical differential current thresholds are, for example, 30 mA for personal protection and 300 mA for fire protection (IEC World,230 volts / 400 volts nominal voltage network). For special requirements regarding personal protection, a differential current threshold of 10 mA or 6 mA is typical. Almost all existing residual current circuit breakers have a summation current transformer, whose primary windings are formed by the conductors of the circuit and whose secondary winding outputs the current sum or the differential current or an equivalent of the current sum / differential current, e.g., in the form of a voltage (or current), which is used directly or indirectly to interrupt the electrical circuit. For this purpose, two or more conductors, usually the forward and return conductors or the phase conductor (= outer conductor) and neutral conductor in a single-phase AC network, all three phase conductors (= outer conductor) and the neutral conductor in a three-phase AC network, are connected by a core, usually with a ring-shaped core made of ferromagnetic material.Current transformers are used. Only the differential current, i.e., a current that differs from the forward and return current, is converted (or transferred to the secondary winding). 202222458 3 from the conductors. Usually, the total current in an electrical circuit is zero. This allows fault currents to be detected. If, for example, a current flows to earth on the energy sink side or the consumer side, this is referred to as a fault current. This is the case, for example,when a person touches a live phase conductor. In this case, this current to earth is referred to as a fault current. In contrast, electrical equipment (such as power supplies or frequency converters) can also discharge a current to earth due to, for example, so-called Y capacitors (or parasitic capacitances of live parts / conductors to earth; e.g., shielded cables or equipment / loads with earthed metal housings). This current is typically referred to as a leakage current. A fault occurs, for example, when there is an electrically conductive connection from a phase conductor or outer conductor of the electrical circuit to earth. For example, when a person touches the phase conductor. In this case, part of the electrical current does not flow back via the neutral conductor or neutral conductor as usual.but rather through the person and the earth. This residual current can now be detected using the summation current transformer, since the measured sum of the incoming and returning current is not equal to zero. A holding magnet release (= self-holding magnet) or a relay or a trip coil, generally an interruption unit, for example with connected mechanics and contacts, interrupts the circuit, e.g., at least one, some, or all lines. The main function of residual current circuit breakers is to protect people from electrical currents (electric shock), 202222458 4 as well as systems, machines, or buildings from fire caused by electrical insulation faults. If the residual current circuit breaker or its summation current transformer is designed so that the secondary-side energy is sufficient to actuate a trip unit or an interruption unit or a release,then such residual current circuit breakers are called mains voltage-independent; otherwise, they are called mains voltage-dependent residual current circuit breakers. If a power supply unit is provided to supply power to a residual current detector, they are called mains voltage-dependent residual current circuit breakers. These are required, for example, to detect residual currents in DC voltage networks and mixed DC / AC networks, or in high-frequency circuits. Residual current circuit breakers are available in different versions, referred to as types, and are identified by letters or letter combinations, such as AC, A, F, G, K, S, B, B+. Each type detects a specific type of residual current. Currently, residual current circuit breakers are available in 2-pole (1+N) for phase and neutral conductors (L+N), 4-pole for three phase conductors and neutral conductors (L1, L2, L3,N). For example, type AC only detects purely sinusoidal residual currents. Type A detects both purely sinusoidal alternating currents and pulsating direct residual currents. Type F are mixed-frequency sensitive residual current devices. They detect all types of residual currents like type A, and are also suitable for detecting residual currents consisting of a mix of frequencies up to 1 kHz. Type S are selective residual current circuit breakers that can be graded in both the rated residual current and the tripping time. Type B residual current circuit breakers (= residual current protective devices) are used, in addition to detecting the residual current waveforms of type F,also for detecting smooth 202222458 5 DC residual currents. Furthermore, they are suitable for residual currents with frequencies up to 2 kHz. The same conditions apply to Type B+ residual current circuit breakers as to Type B residual current circuit breakers. Only the frequency range for detecting residual currents applies to an extended range up to 20 kHz. Type K residual current circuit breakers have the characteristics of Type A, but their tripping behavior is short-time delayed. Type K is also referred to as super-resistant. They are used because (generally with residual current circuit breakers) operational leakage currents and fault currents cannot be distinguished. The response of a residual current circuit breaker is the same for both (operational leakage currents or fault currents). In the case of a short-term high leakage current, disconnection of the load is neither necessary nor desired. When using electronic equipment,which frequently use capacitors connected to the protective conductor for interference suppression, unwanted tripping of the residual current device (RCD) can occur when switched on. To avoid these shutdowns, the use of super-resistant residual current devices (RCDs) is recommended. They have a short-time delay in their shutdown behavior (and are designated as Type K). The product standards DIN EN 61008-1 (RCDs) and DIN EN 61009-1 (RCDs / MCBs) describe the behavior of residual current devices, particularly the limit values ​​for the shutdown times. According to the standard, super-resistant residual current devices (RCDs) are instantaneous versions. The super-resistant Type K RCDs utilize the maximum permissible tripping range of the standard. They have a minimal time delay. This means,Short-term leakage currents and high surge currents are ignored during this period (so that unwanted tripping of the residual current device does not occur). Only when a fault current flows for longer than the delay time is shutdown initiated. The protective effect against electric shock is still achieved by this residual current device. The system is spared from unwanted shutdowns – system availability is significantly increased. For systems with frequency converters, system availability should be high. This means that false tripping, e.g., due to technically caused leakage currents,should be avoided. On the other hand, personal protection should be ensured. Protective switching devices with an electronic interruption unit or an electronic switch are relatively new developments. These have a semiconductor-based electronic interruption unit or a semiconductor-based electronic switch. This means that the electrical current flow in the low-voltage circuit is guided via semiconductor components or semiconductor switches, which interrupt the electrical current flow or can be switched to conduction. Protective switching devices with an electronic interruption unit also often have a mechanical isolating contact unit, in particular with isolating properties in accordance with relevant standards for low-voltage circuits, with the contacts of the mechanical isolating contact unit connected in series with the electronic interruption unit.i.e., the current of the low-voltage circuit to be protected is conducted via both the mechanical isolating contact unit and the electronic interruption unit. The object of the present invention is to improve a protective switching device. More specifically, on the one hand, to ensure personal protection, if possible even at low fault current levels, and on the other hand, to maintain high system availability, i.e., in particular, to avoid false tripping, e.g., due to technically induced leakage currents. This object is achieved by a protective switching device having the features of patent claim 1 and a method having the features of patent claim 15. 202222458 7 According to the invention, a protective switching device for protecting an electrical low-voltage circuit for alternating current is proposed,comprising: - a housing with at least two mains-side and at least two load-side connections for at least two conductors of the low-voltage circuit, in particular a phase conductor and a neutral conductor of the low-voltage circuit (alternatively for two phase conductors of the low-voltage circuit), - a differential current sensor unit for determining the magnitude of a differential current of the two / two conductors (connected to the protective switching device) of the low-voltage circuit (i.e. the differential current of the phase conductor and neutral conductor (alternatively the differential current of two phase conductors)), - a voltage sensor unit for determining the magnitude of a voltage of the two conductors (connected to the protective switching device) of the low-voltage circuit (i.e. the voltage between the phase conductor and the neutral conductor (alternatively the voltage between two phase conductors)), - a mechanical isolating contact unit,which has a closed state of the contacts for a current flow of the conductors of the low-voltage circuit or an open state of the contacts for a current-preventing galvanic isolation of the conductors of the low-voltage circuit, - an electronic interruption unit, which is connected in series with the mechanical isolating contact unit on the circuit side and which, through 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 for current flow in the low-voltage circuit, - a control unit, which is connected to the differential current sensor unit, the voltage 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 thatthat a differential active current 202222458 8 is determined from the voltage level and the differential current level, that the differential active current is compared with a first current limit or first current-time limit, that if the first current limit or first current-time limit is exceeded, the avoidance of a current flow in the low-voltage circuit is initiated. (The first current limit or first current-time limit is, for example, a differential current threshold according to the relevant standards.) Differential active current refers to the active current component in the differential current, i.e. the ohmic current component (real part) in the differential current, i.e. the current component that, together with the voltage (voltage connected to the protective switching device), causes an electrical active power. The active power is the electrical power that is required for conversion into other power (e.g. mechanical,thermal or chemical) is available. It must be distinguished from reactive power, which cannot be used for this conversion. Furthermore, the terms active power, reactive power, or apparent power are generally known from the fundamentals of AC technology. An ohmic resistor as a load or consumer converts its absorbed power completely into heat. This is called active power. This power is expressed in watts (W). If a consumer has inductive and capacitive components in addition to the ohmic resistance, a temporal shift, also called a phase shift, occurs between the temporal (especially sinusoidal) course of current and voltage. However, inductive and capacitive elements do not convert electrical energy into heat.but store it. In circuits with alternating current, this stored energy is typically periodically absorbed and released again. This creates what is known as oscillating power, also known as reactive power. In addition to the active power, there is therefore also reactive power (volt-amperes reactive (VAr)), which is not converted into heat. Instead, the reactive power is shifted back and forth at twice the frequency of the alternating voltage. This reactive power is also known as oscillating power or displacement reactive power. This type of reactive power should not be confused with the so-called distortion reactive power, which in turn is caused by different frequency components in current and voltage. The reactive power is not consumed (unconsumed "blind" power). If the power consumption of a load / consumer includes reactive power in addition to the active power,then the total power is referred to as apparent power. According to DIN 40110-1, apparent power is specified in volt-amperes (VA). Volt-amperes (VA) expresses that the power includes both active power and reactive power. Typically, the term apparent power refers to alternating current and alternating voltage consumers. Apparent power is generally greater than active power. The current component relating to reactive power is referred to as reactive current. In the differential current according to the present invention, this current component is referred to as differential reactive current. In particular, this refers to the reactive current that occurs at the fundamental frequency of the mains voltage (e.g., 50 Hz in European grids). The current relating to apparent power is the total current, in this example, the total current is the differential current. The differential current consists of the differential active current (real part: ohmic component,active power) and the differential reactive current (imaginary part: capacitive or inductive component, reactive power). The apparent power S is defined as the product of the effective value of the total current and the effective value of the voltage U. In the example related to the differential current, the apparent power is the product of the effective value of the 202222458 10 differential current and the effective value of the voltage U, i.e., a differential apparent power. The apparent power S is composed of the actually converted active power P and the additional reactive power Q. In electrical engineering, the effective value is understood to be the root mean square of a time-varying physical quantity. The term is preferably applied to alternating quantities, generally to quantities in stationary processes. The effective value of the variable quantity (in the example, voltage or current) is as large as the value of a constant quantity,which converts the same electrical power to a resistive load or converts the same electrical energy in a representative period of time as the time-varying quantity. The effective value depends on both the peak value and the curve shape. In English, the effective value is referred to as RMS (abbreviation for Root Mean Square). The present invention relates in particular to low-voltage 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: u(t) = Ua * sin (2π * f * t). Where: u(t) = instantaneous voltage value at time t Ua = amplitude of the voltage A harmonic alternating voltage can be represented by the rotation of a phasor,whose length corresponds to the amplitude (Ua) of the voltage. The instantaneous deflection is 202222458 11, the projection of the pointer onto an axis of the coordinate system (typically the abscissa). One oscillation period corresponds to one full revolution of the pointer, and its full angle is 2π (2Pi) or 360°. The angular frequency is the rate of change of the phase angle of this rotating pointer. The angular frequency of a harmonic oscillation is always 2π times its frequency, i.e.: ω = 2π*f = 2π / T = angular frequency of the alternating voltage (T = period of the oscillation). The angular frequency (ω) is often preferred over the frequency (f), since many formulas in oscillation theory differ due to the occurrence of trigonometric functions whose period is, by definition, 2π.can be represented more compactly using the angular frequency: u(t) = Ua * sin(ωt) In the case of angular frequencies that are not constant over time, the term instantaneous angular frequency is also used. For a sinusoidal, in particular time-constant, alternating 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 the phase angle φ(t). This means that the phase angle φ(t) periodically passes through the range 0…2π or 0°…360°. This means that the phase angle periodically assumes a value between 0 and 2π or 0° and 360° (φ = n*(0…2π) or φ = n*(0°…360°), due to periodicity; in short: φ = 0…2π or φ = 0°…360°). With instantaneous voltage value u(t) or instantaneous current value or instantaneous differential current value i(t) is therefore the instantaneous value of the voltage / current / differential current at time t,i.e. for a sinusoidal (periodic) alternating voltage, the value of the voltage / current / 202222458 12 of the differential current at the phase angle φ is meant (φ = 0…2π or φ = 0°…360°, of the respective period). An effective value of the voltage U can be calculated from instantaneous voltage values ​​u(t), and an effective value of the differential current I can be calculated from instantaneous differential current values ​​i(t). The calculation is usually carried out over at least one period of the voltage or differential current. In the patent application, instantaneous values ​​(e.g. instantaneous voltage value u(t), instantaneous differential current value i(t), instantaneous differential power p(t)) are designated with lower case letters (u, i, …) and effective values ​​(e.g. effective value of the voltage U, effective value of the differential current I, …) are designated with capital letters (U, I, …). Residual current circuit breakers according to the state of the art use the differential current, more precisely the effective value of the differential current I,to trip. This means that a residual current device with a differential current threshold of, for example, 30 mA will interrupt the low-voltage circuit at an effective value of the differential current greater than 30 mA. The effective value of the differential current can contain both active and reactive components (differential active current and differential reactive current components). For example, the effective value of the differential current can consist only of differential active current components; alternatively, the effective value of the differential current can consist only of differential reactive current components; alternatively, or generally, the effective value of the differential current can consist of differential active current components and differential reactive current components. This means that regardless of whether active or reactive current components are included in the differential current,According to the state of the art, a residual current device "rigidly" (or "stupidly") interrupts the circuit when its differential current threshold is exceeded. Thus, tripping occurs regardless of the type (active or reactive current) of the differential current. 202222458 13 Especially with differential currents at the fundamental frequency (the mains voltage), no distinction is possible today. According to the invention, the (effective value of the) differential current is now advantageously used, but only the differential active current, i.e., the active power component of the differential current. This advantageously provides, on the one hand, reliable personal protection, since people usually resemble an ohmic resistance (or always contain an ohmic component). The IEC 60479-1 standard describes the effect of electrical current on the human body. On the other hand, robustness against technically induced leakage currents (which are not critical for personal protection) is also achieved.which are usually capacitive in nature. This can prevent false tripping due to technically caused (capacitive) leakage currents. A voltage sensor unit is advantageously provided in the protective switching device to determine the voltage level, as well as a control unit to determine the differential active current from the determined voltage level and the determined differential current level. The level of the first current limit or first current-time limit is advantageously adjustable, e.g., adjustable on the protective switching device. Current-time limit means that the current must exceed the current limit for a specific time.before an interruption of the low-voltage electrical circuit occurs. In this context, the effective value of the differential active current is advantageously used with regard to the exceedance of the first current limit or first current-time limit. Specifically, the differential active current refers to the active current component in the differential current at the (mains) frequency of the voltage in the low-voltage circuit. This means, for example, at an alternating voltage frequency of 50 Hz (as is common in Europe, for example), the differential active current relative to 50 Hz,i.e., the fundamental component. In alternating current technology, harmonic oscillations are considered as a first approximation. This means that a voltage is considered a harmonic alternating voltage u(t) = Ua * sin(ωt) (see above), and a current in the same circuit is considered a harmonic alternating current i(t) = I * sin(ωt – phi), where phi is the phase shift between (alternating) voltage and (alternating) current (0° to 360° or -180° and +180°, etc.). The alternating current i(t) = I * sin(ωt – phi) can be decomposed (related to the phase angle phi) into two orthogonal components, according to the well-known alternating current theory: a first component in phase with the voltage (phase shift = phase difference 0°) and a second component with a 90° phase shift with the voltage. Bronstein,Pocket book of mathematics: sin(α – β) = cos(β) * sin(α) + sin(-β) * cos(α) i(t) = I * sin(ωt – phi) α = ωt β = phi i(t) = I * (cos(phi) * sin(ωt) + sin(-phi) * cos(ωt)) The component cos (phi) * sin (ωt) is the 202222458 15 alternating current component (decomposed alternating current component) that is in phase (phase shift 0°) with the (alternating) voltage (sin (ωt)) and is referred to as the active current component (active current component). The component sin (-phi) * cos (ωt) is the alternating current component (decomposed alternating current component) orthogonal (phase shift 90°) to the (alternating) voltage (sin (ωt)) and is referred to as the reactive current component, i.e., the reactive current component with the fundamental frequency (= fundamental oscillation) (e.g., 50 Hz). This applies, as already mentioned in the introduction, to a harmonic oscillation / harmonic alternating voltage / harmonic alternating current with a phase shift Phi between voltage and current (between 0° and 360°). For the general case,In particular for sampled, time-varying variables (instantaneous value curves): - the active current component is the component in the current that transmits active power with the (mains) voltage, - the active current component has the same frequency as the (mains) voltage, in particular the same fundamental frequency (fundamental oscillation) as the (mains) voltage (e.g. 50 Hz), - the active current component has the same phase (or phase position) as the (mains) voltage, in particular the phase shift between the active current component and the fundamental oscillation of the (mains) voltage is 0°. The reactive power is shifted back and forth at twice the frequency of the alternating voltage; this is referred to as oscillating power or displacement reactive power. For the general case, especially for sampled, time-varying quantities (instantaneous value curves), the following is: -the reactive current component is the component in the current that transmits reactive power with the (mains) voltage,-The reactive current component (also called displacement reactive current component) has the same frequency as the (mains) voltage, in particular the same fundamental frequency (fundamental oscillation) as the (mains) voltage (e.g. 50 Hz), 202222458 16 -The reactive current component (displacement reactive current) has a (+ / -) 90° phase shift (or phase position) to the (mains) voltage. The differential reactive current is the differential reactive current component with the fundamental frequency of the voltage in the low-voltage circuit. This reactive power should not be confused with the so-called distortion reactive power, which in turn is caused by different frequency components in the current, in particular higher frequency components (relative to the fundamental frequency (fundamental oscillation) of the (mains) voltage) in the current. More specifically, the third, fourth, fifth,... harmonic of the current (relative to the fundamental frequency of the (mains) voltage). More generally, higher (relative to the fundamental frequency) frequency components of the current that are different from the fundamental frequency of the alternating voltage ((mains) voltage). For the purposes of the present invention, reactive power does not mean distortion reactive power. For the general case, especially for sampled, time-varying quantities (instantaneous value curves), the following is: - the distortion reactive current component is the component in the current that transmits reactive power with the (mains) voltage, - the distortion reactive current component has a higher frequency compared to the (mains) voltage,in particular to the fundamental frequency (fundamental oscillation) of the (mains) voltage (e.g., 50 Hz). Advantageous embodiments of the invention are specified in the subclaims. In an advantageous embodiment of the invention, the avoidance of 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 contacts are closed. 202222458 17 This has the particular advantage of enabling, on the one hand, a rapid interruption and, on the other hand, a reconnection initiated by the protective switching device. The electronic interruption (high-resistance state of the switching elements of the electronic interruption unit) lasts only a few microseconds and not a few milliseconds, as is typical with today's mechanical contacts. This has the advantage that, in the event of a fault, less fault current is generated, particularly when there is a risk of personal injury.can flow. Furthermore, the reconnection allows for a more sensitive (i.e., faster) response to fault currents, as erroneous and unwanted tripping by reconnection (preferably during or shortly before the next mains voltage zero crossing) is avoided. Both of these factors together result in significantly less fault current being able to flow, thus increasing personal protection. In an advantageous embodiment of the invention, the prevention of current flow in the low-voltage circuit is initiated by an open state of the contacts. This has the particular advantage of establishing galvanic isolation. This state can ensurethat no further current flow can occur and reconnection (closing the contacts) is only possible by actuating the protective switching device. Thus, a typical, known, and expected operation can be implemented when needed. In an advantageous embodiment of the invention, the magnitude of the differential current (in particular, the effective value of the differential current) is compared with a second current limit or second current-time limit. If the second current limit or second current-time limit is exceeded, the prevention of current flow in the low-voltage circuit is initiated. This has the particular advantage thatthat in addition to the interruption when the differential active current is exceeded, an interruption also occurs when the differential current is exceeded. 202222458 18 In an advantageous embodiment of the invention, the second current limit or second current-time limit is greater than the first current limit or first current-time limit, in particular, this is up to 10 times or up to 20 times or up to 100 times the first current limit or first current-time limit. In particular, the factor is related to the current-limit component (current limit component) (current magnitude) (i.e., the factor is not related to the time limit component). This has the particular advantage thatthat safety is provided analogous to conventional residual current circuit breakers, and that the low-voltage circuit is interrupted even if the corresponding residual reactive currents are exceeded. The level of the second current limit or second current-time limit is advantageously adjustable, e.g., on the protective switching device. In this context, the effective value of the residual current is advantageously used with regard to the exceedance of the second current limit or second current-time limit. For example, the first current limit for the residual active current can be 30 mA, 10 mA, or 6 mA to ensure high personal protection, and the second current limit for the effective value of the residual current can be 300 mA.To ensure high robustness against false tripping due to operational leakage currents, a differential reactive current is determined from the voltage level and the differential current level. The differential reactive current is compared with a third current limit or third current-time limit. If the third current limit or third current-time limit is exceeded, the current flow in the low-voltage circuit is prevented. This has the particular advantage that, in addition to the interruption when the differential active current is exceeded, an interruption also occurs when the differential reactive current is exceeded. 202222458 19 In an advantageous embodiment of the invention, the third current limit or third current-time limit is greater than the first current limit or first current-time limit.In particular, this is up to 10 times, up to 20 times, or up to 100 times the first current limit or first current-time limit. In particular, the factor is related to the current-limit component (current limit component) (current magnitude) (i.e., the factor is not related to the time-limit component). This has the particular advantage of ensuring safety even in the event of excessively high differential reactive currents. If the corresponding differential reactive currents are exceeded, the low-voltage circuit is interrupted. The magnitude of the third current limit or third current-time limit is advantageously adjustable, e.g., adjustable on the protective switching device. In this context, the effective value of the differential reactive current is advantageously used with regard to the exceedance of the third current limit or third current-time limit. Specifically, differential reactive current refers to the reactive current componentwhich results from the total current after deducting the differential active current at the frequency of the alternating voltage in the low-voltage circuit. This means the differential reactive current which results after deducting the differential active current at an alternating voltage frequency of, for example, 50 Hz (as is common in Europe, for example). This means, in particular, the differential reactive current is the differential reactive current component with the fundamental frequency of the voltage in the low-voltage circuit. In an advantageous embodiment of the invention, the first current limit value or first current-time limit value is a residual current limit value for personal protection. In particular, on the current limit side (relative to the first current limit value or first current-time limit value), it has a level of 30 mA or less. Alternatively, it can also have a level of 6 mA or less. 202222458 20 This has the particular advantage that only with differential active currents,i.e., in the case of, for example, personal-related ohmic differential currents (fault currents), the low-voltage circuit is interrupted, in compliance with applicable personal protection regulations. In an advantageous embodiment of the invention, the mechanical isolating contact unit is assigned to the load-side connection. In this case, the electronic interruption unit is assigned to the mains-side connection. In particular, the mechanical isolating contact unit can be operated by a mechanical handle to switch the contacts open or close. In particular, the mechanical isolating contact unit can be opened by the control unit. In particular, the contacts cannot be closed by the control unit. This has the particular advantage of providing a structure for a protective switching device,in which the protective switching device functions even when the contacts of the mechanical isolating contact unit are open. Or that the electronic interruption unit is connected to the applied mains voltage, even when the isolating contacts are open. Furthermore, in certain embodiments, increased safety of the protective switching device is provided. In an advantageous embodiment of the invention, the protective switching device is designed such that the differential current sensor unit determines instantaneous differential current values ​​of the magnitude of the differential current, that the voltage sensor unit determines instantaneous voltage values ​​of the magnitude of the voltage, that an effective value of the voltage (in particular over half, one or more periods of the alternating voltage - generally over a multiple of half the period of the alternating voltage) is determined from the instantaneous voltage values,that an instantaneous differential power is determined from the instantaneous voltage values ​​and the instantaneous 202222458 21 differential current values; that a differential active power is determined from the instantaneous differential power by averaging (in particular over half, one or more (half) periods of the alternating voltage - generally over a multiple of half the period of the alternating voltage); that an (effective value of the) differential active current is determined from the differential active power, which was determined over half, one or more (half) periods of the alternating voltage - generally over a multiple of half the period of the alternating voltage), by dividing it by the effective value of the voltage (over the same half, one or more (half) periods of the alternating voltage - generally over the same multiple of half the period of the alternating voltage),that the (effective value of the) differential active current is compared with the first current limit or first current-time limit in order to initiate the prevention of current flow in the low-voltage circuit if the first current limit or first current-time limit is exceeded. This has the particular advantage of demonstrating a simple method for determining the differential active current. In an advantageous embodiment of the invention, the instantaneous voltage values ​​u(t) (alternatively: u, LN ) and the instantaneous differential current values ​​i(t) (alternatively: i ∆ ) by averaging the product of the instantaneous voltage values ​​u(t) and the instantaneous differential current values ​​i(t) (over half, one or more (half) periods of the alternating voltage – generally over a multiple of half the period of the alternating voltage) the differential active power Pd (alternatively also: P ∆) is determined. This means that from the instantaneous difference power pd(t) (alternatively: p ∆ ) is determined by (especially arithmetic) averaging (ie by integrating the instantaneous difference power pd(t) and dividing by the integration time (t b - 202222458 22 t a ); the integration period is half, one or more (half) periods of the alternating voltage – generally over a multiple of half the period of the alternating voltage) a differential active power Pd is determined. From the differential active power Pd (= P ∆ ) the effective value of the differential current I (alternatively: ^^^^^^^^ ^^^^, ^^^^ ^^^^ ^^^^) can be determined by dividing it by the effective value of the voltage U (alternatively: ^^^^^^^^ ^^^^, ^^^^ ^^^^ ^^^^) ^^^^ ^^^^ ^^^^^^^^, ^^^^ ^^^^ ^^^^ ^^^^= ^^^^ ^^^^ ^^^^, ^^^^ ^^^^ ^^^^This has the particular advantage that specific possibilities for determining the differential active power (the (effective value of the) differential active current) are provided, which can be implemented in particular by a control unit having a microprocessor.In an advantageous embodiment of the invention, the differential current sensor unit determines instantaneous differential current values ​​of the magnitude of the differential current. From the instantaneous differential current values, an effective value of the differential current is determined (over half a period, one or more periods of the alternating voltage - generally over a multiple of half the period of the alternating voltage). The voltage sensor unit determines instantaneous voltage values ​​of the voltage magnitude. From the instantaneous voltage values, an effective value of the voltage is determined (over half a period, one or more periods of the alternating voltage - generally over a multiple of half the period of the alternating voltage). A differential apparent power is determined from the effective value of the voltage and the effective value of the differential current. 202222458 23 This has the particular advantage that a determination of the differential apparent power is provided for further embodiments of the invention.In an advantageous embodiment of the invention, a differential reactive power is determined from the differential apparent power and the differential active power. The differential reactive current is determined from the differential reactive power. This has the particular advantage of demonstrating a possibility for determining the differential reactive current. In an advantageous embodiment of the invention, the square root of the difference from the square of the differential apparent power S (alternatively also ^^^^) is calculated. ^^^^ ) and the square of the difference active power Pd (alternatively ^^^^ ^^^^ ) the difference reactive power ^^^^ ^^^^ determined. From the difference in reactive power ^^^^ ^^^^(over half a period, one or more periods of the alternating voltage - generally over a multiple of half the period of the alternating voltage) is calculated by dividing by the effective value of the voltage U (alternatively also: ^^^^^^^^ ^^^^, ^^^^ ^^^^ ^^^^) (over the same half a period, one or more periods of the alternating voltage - generally over the same multiple of half the period of the alternating voltage) an effective value of the differential reactive current The effective value of the differential reactive current ^^^^^^^^, ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ is compared with the third current limit or third current-time limit in order to initiate the prevention of current flow in the low-voltage circuit if the third current limit or third current-time limit is exceeded. S = U * I (alternatively: S ∆ = U LN , rms ⋅ I ∆ , rms )^^^^ ^^^^ = � ^^^^ 2 ^^^^ − ^^^^ ^^^^ 2 202222458 24 ^^^^ ^^^^ ^^^^^^^^, ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ =^^^^ ^^^^ ^^^^, ^^^^ ^^^^ ^^^^This has the particular advantage that a specific possibility of determining the (effective value of the) differential reactive current is provided, which can be implemented in particular by a control unit having a microprocessor. In an advantageous embodiment of the invention, the determination of the differential active current, in particular the differential reactive current, is carried out continuously (periodically). This has the particular advantage that continuous periodic monitoring of the low-voltage circuit is provided. According to the invention, a corresponding method for residual current protection of an electrical low-voltage circuit for AC voltage, specifically for a residual current circuit breaker, with the same and further advantages is claimed.In the method according to the invention for residual current protection of an electrical low-voltage AC circuit: - the magnitude of a differential current of two conductors of the low-voltage circuit is determined, - the magnitude of a voltage between the two conductors of the low-voltage circuit is determined, - a differential active current is determined from the voltage level and the magnitude of the differential current, - the differential active current is compared with a first current limit value or first current-time limit value, - if the first current limit value or first current-time limit value is exceeded, avoidance of a current flow in the low-voltage AC circuit is initiated. 202222458 25 In an advantageous embodiment of the method, the magnitude of the differential current is compared with a second current limit value or second current-time limit value.If the second current limit or second current-time limit is exceeded, the avoidance of current flow in the low-voltage circuit is initiated. In an advantageous embodiment of the method, a differential reactive current is determined from the voltage level and the differential current level. The differential reactive current is compared with a third current limit or third current-time limit. If the third current limit or third current-time limit is exceeded, the avoidance of current flow in the low-voltage circuit is initiated. According to the invention, a corresponding computer program product for a protective switching device is claimed. The computer program product comprises instructions which, when the program is executed by a microprocessor, cause the microprocessor to implement or support the inventive embodiments or methods of the protective switching device.In particular, that the differential active current is used for comparison with current limit values ​​or current-time limit values. In particular, furthermore, that if these are exceeded, the avoidance of a current flow in the low-voltage circuit is initiated. The microprocessor is part of the protective switching 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 that the computer program product transmits is claimed. 202222458 26 All embodiments, both in dependent form with reference back to patent claim 1 or 15, and with reference back only to individual features or combinations of features of patent claims, in particular also a reference back of the dependent arrangement claims to the independent method claim, bring about an improvement in a protective switching device.Specifically, on the one hand, personal protection is ensured even at low fault current levels, and on the other hand, system availability is increased by preventing false tripping due to technically induced leakage currents. In general, a new concept for a protective switching device, specifically a residual current circuit breaker, is provided. The described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more easily understood in conjunction with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the drawings.The drawing shows: Figure 1 a first representation with a protective switching device, Figure 2 a second representation with a protective switching device, Figure 3 a third representation with a protective switching device, Figure 4 a first block diagram for a control unit, Figure 5 a second block diagram for a control unit, Figure 6 a first block diagram for a calculation unit, Figure 7 a first test setup with a protective switching device, 202222458 27 Figure 8 a second test setup with a protective switching device.Figure 1 shows a representation of a protective switching device SG for protecting an electrical low-voltage circuit for alternating voltage, comprising: - a housing 103 with two mains-side connections 101 and two load-side connections 102 for two conductors L, N of the low-voltage circuit, in particular a phase conductor L and a neutral conductor N of the low-voltage circuit, according to Figure 1, a mains-side neutral conductor connection NG, a mains-side phase conductor connection LG, a load-side neutral conductor connection NL and a load-side phase conductor connection LL for the two conductors L, N of the low-voltage circuit are provided on the housing 103; an energy source EQ is usually connected to the mains side 101, and a consumer ES is usually connected to the load side 102; - a differential current sensor unit ZCT, for determining the level of a differential current i. ∆of the two conductors L, N of the low-voltage circuit (connected to the protective device), ie a, in particular instantaneous, differential current i ∆ = i L – i N , where i L is the magnitude of the phase conductor current (in the phase conductor L), ie the magnitude of the current flowing between the mains-side phase conductor connection LG and the load-side phase conductor connection LL, and i N is the magnitude of the neutral conductor current, ie the magnitude of the current flowing between the mains-side neutral conductor terminal NG and the load-side neutral conductor terminal NL. In a circuit, the magnitude of the phase conductor current i L (in the protective switching device) the level of the neutral conductor current i N (in the protective switching device), ie the level of the differential current i ∆ = i L – i Nis normally equal to zero. - a (two-pole) mechanical isolating contact unit MK, which has a closed state of the contacts for a current flow 202222458 28 of the conductors of the low-voltage circuit or an open state of the contacts for a current flow-preventing galvanic isolation of the conductors of the low-voltage circuit; the mechanical isolating contact unit MK can also be designed as a single-pole mechanical isolating contact unit, ie with one contact, wherein the contact is preferably arranged in the phase conductor, ie between the mains-side phase conductor connection LG and the load-side phase conductor connection LL.(This previous arrangement essentially corresponds to a classic residual current circuit breaker, whereby the differential current sensor unit ZCT controls the mechanical isolating contact unit MK, usually in the case of mains voltage-independent residual current circuit breakers via a so-called holding magnet release, so that if the level of the differential current exceeds a current limit value or current-time limit value, the current flow in the low-voltage circuit is prevented by opening the contacts.) Furthermore, an (in particular single-pole) electronic interruption unit EU is provided, which is connected in series to the mechanical isolating contact unit MK (related to the low-voltage circuit, circuit side) and which, through semiconductor-based switching elements, has a high-resistance state of the switching elements to prevent current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit.In the single-pole version, the electronic interruption unit EU is arranged in particular in the phase conductor L, as shown in Figure 1. The mechanical isolating contact unit MK is assigned to the load-side 102 connections LL, NL as shown in Figure 1. The electronic interruption unit EU is assigned to the mains-side 101 connections LG, NG. A voltage sensor unit SUA is provided to determine the (particularly instantaneous) level of the voltage u. LN , the two conductors L, N of the low-voltage circuit (connected to the protective switching device), ie the level of the voltage u LN between the neutral conductor connection and the phase conductor connection 202222458 29. In the example according to Figure 1, the voltage sensor unit SUA is arranged at or in the area of ​​the mains-side connections 101, ie in this example the level of the voltage u LNbetween the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG. (A residual current device according to the state of the art does not have a voltage sensor unit (voltage detection).) Furthermore, a control unit SE is provided, which is connected to the residual current sensor unit ZCT, the voltage sensor unit SUA, the mechanical isolating contact unit MK, and the electronic interruption unit EU. The protective switching device SG, in particular the control unit SE, is designed such that the level of the (instantaneous) voltage u LN and the level of the (instantaneous) differential current i ∆ (i ∆ = i L – i N ) a determination of an (effective value of the) differential active current I ∆,wirk The (effective value of) the differential active current I ∆,wirk is set to a first current limit value I ∆,wirk*(effective value) or the first current time limit. If the first current limit I ∆,wirk*or first current-time limit value, the control unit SE initiates the avoidance of current flow in the low-voltage circuit. The avoidance of current flow in the low-voltage circuit can be initiated by a high-impedance state of the switching elements of the electronic interruption unit when the contacts (of the mechanical isolating contact unit MK) are closed. For example, by an off signal off, represented by an arrow from the control unit SE to the electronic interruption unit EU. The avoidance of current flow in the low-voltage circuit can alternatively or additionally be initiated by an open state of the contacts (of the mechanical isolating contact unit MK). For example, by a contact opening signal open, represented by an arrow from the control unit SE to the mechanical isolating contact unit MK.202222458 30 The (effective value) of the differential active current is determined relative to the frequency of the alternating voltage in the low-voltage circuit. This means that for an alternating voltage frequency of 50 Hz, for example, the differential active current is determined relative to 50 Hz. For example, the (effective value) of the differential active current is determined using the measured voltage (or the applied alternating voltage) in the low-voltage circuit. In the example according to Figure 1, the differential current sensor unit ZCT is (rather) assigned to the network-side 101 connections LG, NG. The differential current sensor unit has, in particular, a (classic) summation current transformer. The two conductors of the low-voltage circuit are, for example, passed through the differential current sensor unit, in particular the summation current transformer. This means that they form the primary winding of the summation current transformer, for example with a number of turns of 0.5 to 1.The protective switching device SG is advantageously designed such that the contacts of the mechanical isolating contact unit MK can be opened but not closed by the control unit SE, which is (likewise) indicated by an arrow or the contact opening signal open from the control unit SE to the mechanical isolating contact unit MK. The control unit SE can switch the electronic interruption unit EU to a high-impedance state with an off signal. The control unit SE can switch the electronic interruption unit EU to a low-impedance state with an on signal. The mechanical isolating contact unit MK can be operated, for example, by a mechanical handle (not shown) on the protective switching device SG in order to switch a manual opening or closing of the contacts.The 202222458 31 mechanical handle indicates (specifically through a mechanical connection between contacts and handle) the switching state (open or closed) of the contacts of the mechanical isolating contact unit MK on the protective switching device. The mechanical isolating contact unit MK is advantageously designed such that (manual) closing of the contacts by the mechanical handle is only possible after an enable, in particular an enable signal. This means that the contacts of the mechanical isolating contact unit MK can only be closed by the handle when the enable or release signal is present (from the control unit). Without the enable or release signal, for example, the handle HH can be operated, but the contacts cannot be closed (“permanent slipping”). The protective switching device SG has a power supply (not shown), for example a power supply unit.In particular, the power supply is provided for the control unit SE. The power supply is connected, for example, to the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG. A fuse, in particular a safety fuse, and / or a switch can advantageously be provided in the connection to the mains-side neutral conductor connection NG (and / or phase conductor connection LG). 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. Low-resistance refers to a state in which the current value specified on the protective switching device could flow. In particular, low-ohm resistance values ​​are meant that are less than 10 ohms, preferably less than 1 ohm, 100 milliohms, 10 milliohms, 1 milliohm or less.202222458 32 In a first variant, the mechanical isolating contact unit MK can interrupt single-pole. This means that only one conductor (of the two / several conductors), in particular the active conductor or phase conductor, is interrupted, i.e. it has a mechanical contact. The neutral conductor is then contact-free, i.e. the neutral conductor is directly connected. In a second variant of the mechanical isolating contact unit MK, the neutral conductor also has mechanical contacts, as shown in Figure 1. The term "mechanical isolating contact unit MK" refers in particular 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 (minimum distance between the contacts), -(mechanical) contact position indication of the contacts of the mechanical isolating contact unit, -Trip-free, i.e.This means that actuation to interrupt the contacts of the mechanical isolating contact unit by the handle or control unit is always possible, so that no (permanent) blocking of the contacts in the closed state by the handle is possible. Furthermore, the standard-compliant isolating function can include the ability to lock the isolating contact unit or the handle in the switched on or off state. The minimum air gap between the contacts of the isolating contact unit is essentially voltage-dependent. Other parameters include the degree of contamination, the type of field (homogeneous, inhomogeneous), and the air pressure or altitude above sea level. There are corresponding regulations and standards for these minimum air gaps and creepage distances.These regulations specify, for example, the minimum clearance for an inhomogeneous and a homogeneous (ideal) electric field in the case of air for impulse voltage withstand capacity, depending on the degree of pollution. The impulse voltage withstand capacity is the 202222458 33 strength when a corresponding impulse voltage is applied. Only if this minimum length (minimum distance) is present does the isolating contact unit or protective switching device exhibit an isolating function (isolating property). For the purposes of the invention, the DIN EN 60947 and IEC 60947 series of standards, to which reference is made here, are relevant for the isolating function and its properties. The isolating contact unit is advantageously characterized by a minimum clearance of the open isolating contacts in the OFF position (open position, open contacts) depending on the rated impulse voltage withstand capacity and the degree of pollution.The minimum clearance is, in particular, between (at least) 0.01 mm and 14 mm. In particular, the minimum clearance is advantageously between 0.01 mm at 0.33 kV and 14 mm at 12 kV, particularly for pollution degree 1 and particularly for inhomogeneous fields. The minimum clearance can advantageously have the following values:

[0002] 202222458 34 The pollution levels and field types correspond to those defined in the standards. This advantageously allows for a standard-compliant protective switching device dimensioned according to the rated impulse withstand voltage. A mechanical isolating contact unit does not, in particular, mean a relay contact. Figure 1 also shows the basic principles of individual units of the grid-side energy source EQ. The energy source EQ essentially comprises a voltage source SQ, which provides an alternating voltage, for example, in Europe 230 volts phase conductor to neutral conductor or 400 volts between two phase conductors (not shown), effective values ​​of the alternating voltage. The neutral conductor is grounded on the energy source side, which is represented by an earth symbol. This grounding has an earth impedance Z PEas shown in Figure 1. 202222458 35 The earth-side neutral conductor connection is provided as a protective earth connection PE (Protective Earth) according to Figure 1. The energy source EQ is connected to the two mains-side connections 101, according to Figure 1 to the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG. Figure 1 also shows the basic principle of the load-side consumer ES. It has a load, in the example a resistor RL. This is connected to the load-side connections 102, according to Figure 1 to the load-side neutral conductor connection NL and the load-side phase conductor connection LL. Typically, a protective earth connection is provided for consumers with a metal housing (or similar). The metal housing of the consumer ES, for example, is connected in the example via a protective conductor SL to the protective earth connection PE of the energy source EQ. Alternatively, the housing could also be grounded.The protective conductor SL has a protective conductor impedance Z. SL as indicated in Figure 1. Depending on the device type, a so-called operational current i flows on the protective conductor SL SL , such as a leakage current. This can be the case, for example, with a power supply unit containing Y capacitors. Figure 2 shows a diagram according to Figure 1, with the difference that a first fault case FF1 is shown. In the example according to Figure 2, there is an electrical connection from the phase conductor to the protective conductor SL at the load-side output 102 of the protective switching device SG, ie between the load-side output 102 of the protective switching device SG and the consumer ES. This would be the case, for example, if a person touches the phase conductor and, at the same time, has contact with the protective conductor (e.g., via a metal housing). This means that a 202222458 36 electrical fault current i RE1flow away (to the energy source EQ), so that in the protective switching device the current in the phase conductor i L and the current in the neutral conductor i N are no longer identical, since a fault current i RE1 via the protective conductor SL, here as protective conductor current i SL marked, can flow to the protective conductor terminal PE of the energy source EQ. The fault case has a resistance value RE1, which can consist of fault resistances (e.g., resistance of a person). The first fault case FF1 is shown separately in Figure 2 (for explanation). The first fault case FF1 can also occur in an analogous manner in the load ES or otherwise. In the example according to Figure 2, the resulting fault current i RE1 the differential current i determined in the differential current sensor unit ZCT ∆ (i RE1 = i PE = i ∆ ) (the impedance Z SLof the protective conductor SL is not taken into account in this example; it can be taken into account in an analogous manner; furthermore, the impedance Z SL typically comparatively small compared to the impedance at the fault location (e.g. RE1) so that this can be neglected). Figure 3 shows a representation according to Figure 1 or 2, with the difference that a second fault case FF2 is shown. In the example according to Figure 3, there is an electrical connection from the phase conductor to earth at the load-side output 102 of the protective switching device SG, ie between the load-side output 102 of the protective switching device SG and the consumer ES. This is the case, for example, if a person touches the phase conductor. This means that an electrical fault current i RE2 flow (to the energy source EQ), so that in the protective switching device the current in the phase conductor i L and the current in the neutral conductor i Nis no longer identical, since a fault current i RE2 to earth and via it to the energy source EQ or its earth. The second fault case FF2 has a resistance value RE2, which can consist of fault resistances and (if applicable) earth resistances. 202222458 37 The second fault case FF2 is shown separately in Figure 3 (for explanation). The second fault case FF2 can also occur in an analogous manner at the load ES or otherwise. In the example according to Figure 3, the resulting fault current i RE2 the differential current i determined in the differential current sensor unit ZCT ∆ (i RE2 = i ∆ ). Figure 4 shows a functional block diagram of functions executed in the control unit SE, which are represented as units. The control unit SE receives - from the differential current sensor unit ZCT the level of the differential current i ∆(= i(t)), in particular the instantaneous level of the differential current (instantaneous differential current values), and - from the voltage sensor unit SUA the level of the voltage u LN (= u(t)), in particular the instantaneous voltage level (instantaneous voltage values). Both can be fed into a calculation unit BE. From the (instantaneous) voltage level u LN and the (instantaneous) level of the differential current i ∆ (i ∆ = i L – i N ), for example in the calculation unit BE, a determination of a differential active current I ∆,wirk (effective value). The (effective value of the) differential active current I ∆,wirk is set to a first current limit value I ∆,wirk* (effective value) or the first current-time limit value (see also Fig. 5). For example, in a comparison unit VE. If the first current limit value I ∆,wirk*or the first current-time limit value, the control unit SE initiates the avoidance of current flow in the low-voltage circuit by means of an off signal (or (and) a contact opening signal) that is sent to the electronic interruption unit EU (or mechanical isolating contact unit MK). For example, the comparison unit VE can optionally be triggered when the first current limit value I is exceeded. ∆,wirk*or first current-time limit value, issue an exceedance signal trip, which is fed to another optional configuration unit CE 202222458 38, with which, for example, configuration, adaptation, or conversion can be carried out. For example, it can be configured whether an off signal or (and) a contact opening signal open is issued, ie whether the electronic interruption unit EU should become high-impedance or (and) the mechanical isolating contact unit MK should open the contacts (the contact in the single-pole version). Figure 5 shows a representation according to Figure 4, with the difference that the comparison unit VE has been replaced by a modified comparison unit VE*. The modified comparison unit VE* not only performs a comparison against a first current limit value I ∆,wirk*by, but alternatively or additionally against a first current-time limit value or a current-time limit value behavior, which is indicated by a current-time curve in a diagram in which the current limit value I ∆,wirk* as a function of time t (on the vertical Y-axis). Typically / for example, the current limit decreases with the duration of the flowing fault current. This means that for a very short time in which the residual fault current flows, the current limit is higher than for a longer duration (i.e., in the latter case, the current limit is lower). Figure 6 shows another functional block diagram of an example of functions performed in the calculation unit BE, which are represented or described as units. This is an example of a determination of the (effective value of the) residual active current I ∆,wirk . The magnitude of the (instantaneous) differential current i ∆, specifically according to Figure 6 the instantaneous level of the differential current (instantaneous differential current values), and the level of the voltage u LN , specifically according to Figure 6 the instantaneous voltage level (instantaneous voltage values), is fed to a multiplication unit ME, which is calculated by (in-phase) multiplication of the two supplied quantities (differential current i ∆ and tension u LN ) a 202222458 39 instantaneous difference power p ∆ (= pd) is determined or calculated. The instantaneous difference power p ∆ is fed to a first integration unit INT1 to determine the differential active power P ∆ , which is obtained by integrating or averaging the instantaneous difference power p ∆ over a multiple of half the period of the alternating voltage, e.g. over half, one, one and a half, ... or several periods of the alternating voltage, a differential active power P ∆determined or calculated. The level of voltage u LN , specifically according to Figure 6 the instantaneous level of voltage u LN (= u(t)), is fed to an effective value unit, which, according to Figure 6, is calculated from the instantaneous level of the voltage u LN an effective value of the voltage U LN,rms determined or calculated. The effective value unit according to Figure 6 consists of three series-connected units: a squaring unit QQ, a second integration unit INT2, and a square root unit QW. The squaring unit QQ squares the instantaneous voltage level u. LNThe squared instantaneous voltage level is fed to the second integration unit INT2, which calculates an average value by integrating or, in particular, averaging (the squared instantaneous voltage level) over a multiple of half the period of the alternating voltage, e.g., over half, one, one and a half, ... or more periods of the alternating voltage (integration unit INT2 alternatively also means or includes a unit for averaging). The square root unit QW takes the square root of the average value, so that the effective value of the voltage U LN,rmsdetermined or calculated (root mean square, the calculation of an effective value is usually known). It is important that the first integration unit INT1 (= mean value unit 1) and the second integration unit INT2 (mean value unit 2) (each) integrate over the same multiple of half the period of the alternating voltage, e.g., over 202222458 40 the same half, one, one and a half, ... or more periods of the alternating voltage. The differential active power P determined by the first integration unit INT1 ∆ and the effective value of the voltage U determined by the three series-connected units (squaring unit QQ, second integration unit INT2, square root unit QW) LN,rms is fed to a division unit DIV, which is calculated by dividing the difference active power P ∆ by the effective value of the voltage U LN,rms the effective value of the differential active current I ∆,wirkdetermined or calculated. This means that from the instantaneous voltage values ​​an effective value of the voltage U is calculated. LN,rms (over a multiple (1, 2, … n) of half the period of the alternating voltage). From the instantaneous voltage values ​​and the instantaneous differential current values, a differential active power P ∆ (over the same multiple of half the period of the alternating voltage). The differential active power P ∆ (over the multiple (1, 2, … n) of half the period of the alternating voltage) is determined by dividing by the effective value of the voltage U LN,rms (over the same multiple (1, 2, … n) of half the period of the alternating voltage) an effective value of the differential active current I ∆,wirk The effective value of the differential active current I ∆,wirk is set to the first current limit I ∆,wirk*or first current-time limit value is compared in order to initiate the prevention of current flow in the low-voltage circuit if the first current limit value or first current-time limit value is exceeded. 202222458 41 This sequence, as well as the other sequences, can be implemented by a method, algorithm, or computer program product that runs on a microprocessor in the control unit SE. This means that the units are, for example, functions that are executed. The instantaneous power p determined from the instantaneous voltage values ​​and the instantaneous differential current values ∆ , from which by integration (over a multiple (such as 1, 2, 3, 4, … n) of half the period of the alternating voltage) the differential active power P ∆is determined, can alternatively also be determined in another way. The control unit can, in an analogous manner, determine an effective value of the differential current (over a multiple of half the period of the alternating voltage) from the instantaneous differential current values. A differential apparent power is determined by multiplying the effective value of the voltage and the effective value of the differential current (equal times / (multiples of) the period durations are considered in each case). A differential reactive power is determined from the differential apparent power and the differential active power. The differential reactive current is determined from the differential reactive power. More specifically, the differential reactive power is determined from the square root of the difference between the square of the differential apparent power and the square of the differential active power.From the differential reactive power (over a multiple of half the period of the alternating voltage) an effective value of the differential reactive current ^^^^^^^^, ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ is determined by dividing it by the effective value of the voltage (over the same multiple of half the period of the alternating voltage). The effective value of the differential reactive current. is compared with a third current limit or third current time limit in order to initiate the avoidance of current flow in the low-voltage circuit if the third current limit or third current time limit is exceeded. The differential active current, in particular the differential reactive current, is advantageously determined continuously (periodically), for example, with microprocessor support. The protective switching device can further be designed or expanded such that, as an alternative to the differential reactive current or in addition to it, the magnitude of the differential current is compared with a second current limit or second current-time limit. If the second current limit or second current-time limit is exceeded, the prevention of current flow in the low-voltage circuit is initiated. The second or third current limit or second or third current-time limit can be greater than the first current limit or first current-time limit. In particular, it can be double, triple, quadruple, ... up to 10 times the first current limit.In other applications, it can be up to 20 times or up to 100 times the first current limit value or first current-time limit value (any intermediate value is possible). In particular, the factor is related to the current limit value component (current limit value component) (current level) (i.e., the factor is not related to the time limit value component). The effective value of the differential current (differential reactive current) can advantageously be used with regard to the exceedance of the second (third) current limit value or second (third) current-time limit value. 202222458 43 The level of the current limits or current-time limit values ​​can be fully or partially adjustable, e.g., by means of an input unit or communication unit on the protective switching device. The first current limit value or first current-time limit value is advantageously a residual current limit value from personal protection.In particular, on the current limit side (relative to the first current limit or first current-time limit), it has a level of 30 mA or less. Alternatively, it can also have a level of 10 mA or less. Alternatively, it can also have a level of 6 mA or less. The second or third current limit or (second or third) current-time limit (especially its current limit component) can be, for example, 150 mA or 300 mA. This means that the protective switching device according to the invention behaves, for example, as shown below. Figure 7 shows a test setup (measurement setup) with a protective switching device SG. The protective switching device SG is connected to the energy source EQ on the mains side via a two-pole first switch S1. On the load side, the load-side phase conductor terminal LL is connected to the mains-side neutral conductor terminal NG via an adjustable resistor R, a second switch S2, and an ammeter AM.The load-side neutral conductor terminal NL is not connected in the example. A voltmeter VM is (optionally) connected between the two mains-side terminals NG and LG of the protective switching device SG. A conventional residual current device, as well as a protective switching device SG according to the invention, behaves in such a way that when the first and second switches S1 and S2 are closed and the residual current I is set to 202222458 44 with the adjustable resistor R. ∆,R (= differential current in the test setup via the protective switching device), which in this case flows via the current measuring device AM, of, for example, 30 mA (classic value for residual current circuit breakers in personal protection, effective value). The residual current circuit breaker, as well as the protective switching device SG according to the invention, interrupts the electrical circuit, i.e., trips, when the current limit or current-time limit (in the example 30 mA) is exceeded. Ohmic test residual currents I ∆,RDifferent values ​​can be set using the adjustable resistor R, thus testing the residual current device / protective switching device SG with regard to its tripping behavior. This means that it can be tested whether the residual current device / protective switching device SG trips at its specified or set current limit or current-time limit (e.g., at a maximum of 30 mA). A conventional residual current device, as well as a protective switching device SG according to the invention, with a current limit or current-time limit of, for example, 30 mA, must be able to trip at an ohmic residual current (differential active current) I ∆,R of a maximum of 30 mA (effective value, observe device tolerance ranges, the residual current device has, for example, a tolerance of + / - 5 mA when measuring the residual current I ∆,R, then the protective switching device could be set so that it already trips at 22.5 mA, for example), set by the adjustable resistor. Figure 8 shows a structure / arrangement according to Figure 7, with the difference that instead of the adjustable resistor R, a particularly adjustable, capacitive or inductive component is provided, in the example a capacitor C with a certain capacitance (advantageously variably adjustable). If the capacitance of the capacitor C is dimensioned such that a (capacitive) fault current of I ∆,C of 30 mA in the example (effective value, note tolerance ranges), a 202222458 45 conventional residual current device (according to the state of the art) will interrupt the circuit, i.e., trip. A protective switching device SG according to the invention will interrupt the circuit at this capacitive residual current I ∆,C(differential reactive current, effective value) of 30 mA. If the protective switching device SG according to the invention is equipped with a second or third current limit value or current-time limit value, for example, of 300 mA, the protective switching device SG according to the invention would not interrupt the capacitive residual current I ∆,C (differential reactive current, effective value) of 300 mA. However, the protective switching device SG according to the invention would trigger at an ohmic fault current I ∆,R (differential active current, effective value) of 30 mA. Using the test setup described above, the effectiveness of the invention can be easily demonstrated. The capacitance of capacitor C would only need to be dimensioned for corresponding fault currents (depending on the frequency of the low-voltage AC circuit). U LN= 230 Volt, f=50 Hz The invention is briefly explained again below in other words. Electrical voltage and the resulting body current is dangerous for people and can quickly lead to injury or death if you come into contact with electrical voltage. The effects of current and voltage on the human body are now described in international standards, such as IEC 60479-1. The danger to the human body depends, among other things, on the current level and duration. In order to protect people from the danger of electrical current, residual current devices (RCDs) are used today. Pulsing voltage transformers are increasingly being used these days. These devices cause common-mode currents to flow via protective conductors or earth potential.These currents close their circuit via existing residual current circuit breakers and, in particular, disrupt the correct fault current detection and operation of the residual current circuit breaker. Filter capacitors (so-called Y capacitors) or parasitic capacitances to earth potential (e.g., in shielded cables) also lead to a current flow on the protective conductor and, as a result, to a disruption in the fault current detection. These currents are all detected as fault currents in the residual current transformer and can lead to the (incorrect) tripping of the residual current circuit breaker. The inventive solution and method for residual current evaluation can separate the (fault or differential) active current from the (fault or differential) reactive current and thus react separately to the active current (component) in the (fault or differential) current.This allows the sensitivity to a residual active current to be increased (to achieve increased personal safety) and, at the same time, the robustness against parasitic residual currents (reactive currents or so-called operational leakage currents) to be increased. This can improve the protective function of a residual current device. The new residual current detection method thus considers the cause (or effect) of the fault current. If, in the event of a fault, there is an ohmic connection between the phase conductor and earth (or the protective conductor), active energy is transported from the 202222458 47 network to the fault location. This current at the fault location is detected along with all other currents by the residual current measurement in the device and separated from parasitic residual currents (or operational leakage currents) using the new method.The source of this fault current is always the applied mains voltage, which is taken into account for further analysis. The analysis of the residual current is (thus) expanded to include a consideration of the residual current power. Here, the applied (instantaneous) (mains) voltage and LN (t) and the measured (instantaneous) differential current i(t) (= i ∆ = i diff (t)) a momentary difference power is determined (a difference power curve pd(t) (= p diff (t)). By means of integration or (in particular) averaging, an effective component P difffrom the instantaneous differential power / the differential power curve. The integration or averaging is conveniently carried out as a multiple of the period duration / fundamental oscillation period or as a multiple of half the period duration / fundamental oscillation period. If the determined differential active power is then divided by the effective value of the voltage (applied mains voltage), the (effective value of the) differential active current is obtained, which characterizes the active power transfer in the differential current. This makes it possible to separate the active current (and analogously reactive current) components in the recorded differential current, and operational fault currents (or leakage currents) due to common-mode currents or leakage currents can be separated from a fault current at an ohmic fault location.This separation enables more sensitive tripping of the residual current device / protective switching device with differential current detection, while simultaneously increasing robustness against operational fault currents. The invention offers the advantage of enabling more sensitive tripping due to ohmic fault currents. More sensitive tripping enables increased electrical safety in low-voltage circuits. With the new solution and method, it is possible (for example) to build a protective switching device with tripping characteristics in the AC-2 range (according to IEC 60479-1) and thus does not permit dangerous body currents (from the AC-3 or AC-4 range).A protective device with such a tripping characteristic offers a new type of electrical safety and can no longer be compared to a typical residual current device (RCD) today, since a typical residual current device does not ensure that higher body currents or even lower body currents cannot flow for an extended period of time. The invention offers increased robustness against false tripping due to operational residual currents or common mode currents. Increased robustness against false tripping increases customer satisfaction and reduces complaints due to false tripping. The new solution and method enables, for example, the use of residual current devices in networks with many (power supplies or) converter systems. In these systems, residual current devices can currently trip due to high-frequency common mode currents orDifferential fault currents and operational currents on the protective conductor cannot be used. The method according to the invention requires a voltage measurement, which can be implemented cost-effectively. The additional computational effort is minimal, since in one embodiment, only multiplication and averaging (and effective value calculations) are required. Although the invention has been illustrated and described in detail by the embodiment, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims

202222458 49 Patent Claims 1. A protective switching device (SG) for protecting an electrical low-voltage circuit for alternating voltage, comprising: - a housing with two mains-side and two load-side connections (LG, NG, LL, NL) for two conductors of the low-voltage circuit, in particular a phase conductor and a neutral conductor of the low-voltage circuit, - a differential current sensor unit (ZCT) for determining the magnitude of a differential current of the two conductors of the low-voltage circuit, - a voltage sensor unit (SUA) for determining the magnitude of a voltage between the two conductors of the low-voltage circuit, - a mechanical isolating contact unit (MK) having 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 isolation 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, through semiconductor-based switching elements, has a high-resistance state of the switching elements to prevent current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit, - a control unit (SE) which is connected to the differential current sensor unit (ZCT), the voltage sensor unit (SUA), 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 such that a differential active current is determined from the voltage level and the differential current level, and that the differential active current is compared with a first current limit value or first current-time limit value, 202222458 50 that when the first current limit value or first current-time limit value is exceeded, the prevention of a current flow in the low-voltage circuit is initiated.

2. Protective switching device (SG) according to claim 1, characterized in that 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 contacts are closed.

3. Protective switching device (SG) according to claim 1, characterized in that the prevention of a current flow in the low-voltage circuit is initiated by an open state of the contacts. 4.Protective switching device (SG) according to claim 1, 2 or 3, characterized in that the level of the differential current is compared with a second current limit value or second current-time limit value, and that if the second current limit value or second current-time limit value is exceeded, avoidance of a current flow in the low-voltage circuit is initiated, in particular by a high-impedance state of the switching elements of the electronic interruption unit when the contacts are closed.

5. Protective switching device (SG) according to claim 4, characterized in that the second current limit value or second current-time limit value is greater than the first current limit value or first current-time limit value, in particular up to 10 times, up to 20 times or up to 100 times the first current limit value or first current-time limit value.

6. Protective switching device (SG) according to claim 1, 2 or 3, characterized in that. 202222458 51 that a determination of a differential reactive current is carried out from the voltage level and the differential current level, in particular that the differential reactive current is the differential reactive current component with the fundamental frequency of the voltage in the low-voltage circuit, that the differential reactive current is compared with a third current limit value or third current-time limit value, that if the third current limit value or third current-time limit value is exceeded, avoidance of a current flow in the low-voltage circuit is initiated, in particular by a high-resistance state of the switching elements of the electronic interruption unit when the contacts are closed. 7.Protective switching device (SG) according to claim 6, characterized in that the third current limit value or third current-time limit value is greater than the first current limit value or first current-time limit value, in particular up to 10 times, up to 20 times or up to 100 times the first current limit value or first current-time limit value.

8. Protective switching device (SG) according to one of the preceding patent claims, characterized in that the first current limit value or first current-time limit value is a residual current limit value from personal protection, in particular is 30 mA or less on the current limit side.

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

10. Protective switching device (SG) according to one of the preceding patent claims, characterized in that. 202222458 52 that the differential current sensor unit (ZCT) determines instantaneous differential current values ​​of the magnitude of the differential current, that the voltage sensor unit (SUA) determines instantaneous voltage values ​​of the magnitude of the voltage, that an effective value of the voltage is determined from the instantaneous voltage values, that a differential active power is determined from the instantaneous voltage values ​​and the instantaneous differential current values; that an effective value of the differential active current is determined from the differential active power by dividing it by the effective value of the voltage, that the effective value of the differential active current is compared with the first current limit value or first current-time limit value in order to initiate the avoidance of current flow in the low-voltage circuit if the first current limit value or first current-time limit value is exceeded. 11.Protective switching device (SG) according to claim 10, characterized in that the differential active power is determined from the instantaneous voltage values ​​and the instantaneous differential current values ​​by averaging the product of the instantaneous voltage values ​​and the instantaneous differential current values.

12. Protective switching device (SG) according to claim 10 or 11, characterized in that an effective value of the differential current is determined from the instantaneous differential current values, and that a differential apparent power is determined from the effective value of the voltage and the effective value of the differential current.

13. Protective switching device (SG) according to claim 12, characterized in that a differential reactive power is determined from the differential apparent power and the differential active power. 202222458 53 that the differential reactive current is determined from the differential reactive power.

14. Protective switching device (SG) according to claim 13, characterized in that the differential reactive power is determined from the square root of the difference between the square of the differential apparent power and the square of the differential active power, that an effective value of the differential reactive current is determined from the differential reactive power by dividing it by the effective value of the voltage, that the effective value of the differential reactive current is compared with the third current limit value or third current-time limit value in order to initiate the avoidance of current flow in the low-voltage circuit if the third current limit value or third current-time limit value is exceeded. 15.Method for residual current protection of an electrical low-voltage alternating current circuit, in that the level of a differential current of two conductors of the low-voltage circuit is determined, in that the level of a voltage between the two conductors of the low-voltage circuit is determined, in that a differential active current is determined from the level of the voltage and the level of the differential current, in that the differential active current is compared with a first current limit value or first current-time limit value, in that if the first current limit value or first current-time limit value is exceeded, avoidance of a current flow in the low-voltage alternating current circuit is initiated.

16. Method according to patent claim 15, characterized in that the level of the differential current is compared with a second current limit value or second current-time limit value, in that if the second current limit value or. 202222458 54 second current-time limit value, avoidance of a current flow in the low-voltage circuit is initiated.

17. Method according to claim 15 or 16, characterized in that a determination of a differential reactive current is carried out from the level of the voltage and the level of the differential current, that the differential reactive current is compared with a third current limit value or third current-time limit value, that if the third current limit value or third current-time limit value is exceeded, avoidance of a current flow in the low-voltage circuit is initiated.

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