Fault current monitoring device and method

Abstract

The invention relates to the process of monitoring fault currents in an electric low-voltage current circuit for alternating currents. The level of a differential current (IΔ) of two conductors (L, N) of the low-voltage current circuit is ascertained, and the level of the voltage (ULN) of the two conductors of the low-voltage current circuit is ascertained. A differential active current (IΔ,WIRK) or a differential reactive current (IΔ,BLIND) is ascertained from the level of the voltage and the level of the differential current, and the level of the differential active current or the differential reactive current is displayed.

Description

[0001]202307374 1 Description Residual current monitoring device and method Regardless of the grammatical gender of a particular term, persons with male, female, or other gender identity are included. The invention relates to the technical field of a residual current monitoring device for monitoring the level of residual currents in an electrical low-voltage AC circuit, and to a method for residual current monitoring of an electrical low-voltage AC circuit. The term residual current monitoring device refers to low-voltage residual current monitoring devices. These are also referred to as residual current monitoring devices (RCM devices). With this residual current monitoring device (RCM device), in particular operational,Residual currents are measured and displayed (monitored). This is used to monitor (earth) fault currents in a low-voltage AC circuit or, in general, in an electrical system. Residual current monitoring devices display the measured residual currents in various ways. Low voltage refers to voltages up to 1000 volts AC or 1500 volts DC. Low voltage refers specifically to voltages greater than extra-low voltage, with values ​​of 50 volts AC or 120 volts DC. Low-voltage circuits refer to circuits for currents up to 6300 amperes, more specifically for currents up to 1600 amperes, 1200 amperes, 630 amperes, 125 amperes, 63 amperes, 40 amperes, 32 amperes, 16 amperes, 10 amperes, or 6 amperes. The current values ​​mentioned refer in particular to rated currents (formerly nominal and / or breaking currents).i.e., currents that the circuit or a residual current monitoring device can carry continuously, i.e., without damage, under standardized conditions (such as 202307374 2 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). This means, colloquially, the maximum current that is normally carried through the circuit or at which the electrical circuit is usually interrupted, such as a miniature circuit breaker or a circuit breaker. Residual current monitoring devices are used in particular for rated current ranges of or up to 16, 25, 32, 40, 63, 80, or 125 amperes. Residual current monitoring devices for electrical low-voltage AC circuits or systems,are generally known. Residual current monitoring devices 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. The magnitude of the current sum / differential current is displayed in order to monitor it. Almost all previous residual current monitoring devices have a summation current transformer, the primary windings of which are formed by the conductors of the circuit and the secondary winding of which 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 display the magnitude. For this purpose, two or more conductors, usually forward and return conductors or phase conductors (= outer conductors) and neutral conductors in a single-phase alternating current network,All three phase conductors (= outer conductors) or all three phase conductors (= outer conductors) and the neutral conductor in a three-phase alternating current network are routed through a current transformer, usually with a ring-shaped core made of ferromagnetic material 202307374 3. Only the differential current, i.e., a current that differs from the forward and return current, from the conductors is converted (or transferred to the secondary winding). The sum of the currents in an electrical circuit is usually zero. This allows the magnitude of a fault current to be determined. 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 (or leakage current to earth). 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. 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 via the person and the earth. This fault current can now be detected using the summation current transformer.because the recorded sum of incoming and returning current is not equal to zero. The main function of residual current monitoring devices is to monitor electrical systems with regard to their residual current behavior. This allows for the early detection and elimination of fault currents, ensuring high system availability through early detection and planned elimination. 202307374 4 In general, operational (technically caused) leakage currents and fault currents (caused, for example, by people or insulation faults) cannot be distinguished. The response of a residual current monitoring device is the same for both (operational, technically caused leakage currents or fault currents caused by people). When using electronic equipment,which often use capacitors connected to the protective conductor for interference suppression (EMC interference suppression) (this EMC measure is also referred to in the specialist literature as a Y capacitor), unwanted (technically caused) fault currents (leakage currents) can occur. The object of the present invention is to improve a residual current monitoring device. More specifically, to enable a distinction between fault currents caused, in particular, by people or insulation faults and technically caused fault currents (leakage currents). This object is achieved by a residual current monitoring device having the features of patent claim 1 and a method having the features of patent claim 15. According to the invention, a residual current monitoring device for monitoring fault currents in an electrical low-voltage AC circuit is proposed, comprising: - a differential current sensor unit,for determining the magnitude of a differential current between two conductors of the low-voltage circuit (in particular, a phase conductor and a neutral conductor of the low-voltage circuit, i.e., the differential current between the phase conductor and the neutral conductor, (alternatively, for two phase conductors of the low-voltage circuit, i.e., the differential current from phase conductor to phase conductor)), - an internal or external display unit suitable for displaying the magnitude of the differential current. According to the invention, the residual current monitoring device is expanded such that a voltage sensor unit is provided for determining the magnitude of a voltage between the two (alternatively: both) conductors of the low-voltage circuit (i.e., in particular, the voltage between the phase conductor and the neutral conductor (alternatively, the voltage between two phase conductors)), that a control unit is provided which is connected to the differential current sensor unit, the voltage sensor unit, and the display unit,that the residual current monitoring device, in particular the control unit, is designed such that a determination of a differential active current or differential reactive current is carried out from the voltage level and the differential current level, and that the level of the differential active current or differential reactive current is displayed on the display unit. This means that the differential active current or differential reactive current is displayed, for example, on an internal display unit or (or / and) reported to an external display unit and displayed there. 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 residual current monitoring device can have a housing with at least two mains-side connections for the two conductors of the low-voltage circuit. The two mains-side connections are connected to the voltage sensor unit. The residual current monitoring device can further have at least two load-side connections for the two conductors of the low-voltage circuit. The at least two mains-side connections are connected to the at least two load-side connections. This means that the first mains-side connection, for example for a phase conductor, is connected to the first 202307374 6 load-side connection and the second mains-side connection, for example for a neutral conductor,is connected to the second load-side connection. These connections between the mains-side connections and the load-side connections are connected to the differential current sensor unit or passed through it, depending on its design. 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, results in active electrical power. Active power is the electrical power that is available for conversion into other power (e.g., mechanical, thermal, or chemical). It must be distinguished from reactive power, which cannot be used for this conversion. Furthermore, terms such as active power,Reactive power or apparent power is commonly known. An ohmic resistance as a load or consumer converts its absorbed power completely into heat. This is called real power. This power is specified in watts (W). If a consumer has inductive and capacitive components in addition to the ohmic resistance, a temporal shift, also known as a phase shift, occurs between the temporal (especially sinusoidal) curve of current and voltage. Therefore, in addition to the real power, there is also reactive power (volt-amperes reactive (VAr)) that 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 referred to as oscillation 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 (unused "blind" power). 202307374 7 If the power consumption of a load / consumer includes reactive power in addition to active power, 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) are intended to express that the power contains reactive power in addition to active power. AC and AC voltage consumers are usually referred to as apparent power. 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. The current relating to apparent power is the total current,In this example, the total current is the differential current. The differential current is composed 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 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 refers to quantities in stationary processes. The effective value of the variable (in the example, voltage or current) is as large as the value of a constant quantity that 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 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 pointer whose length corresponds to the amplitude (Ua) of the voltage. The instantaneous deflection is 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,ie: ω = 2π*f = 2π / T = angular frequency of the alternating voltage (T = period of the oscillation) 202307374 9 The angular frequency (ω) is often preferred to the frequency (f), since many formulas in oscillation theory can be represented more compactly using the angular frequency due to the occurrence of trigonometric functions whose period is by definition 2π: u(t) = 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 temporally constant, alternating voltage, the time-dependent value of the angular velocity ω and the time t corresponds to the time-dependent angle φ(t), which is also referred to as the phase angle φ(t). This means that the phase angle φ(t) periodically passes through the range 0…2π or 0°…360°. This means that the phase angle periodically takes a value between 0 and 2π or 0° and 360° (φ = n*(0…2π) or φ = n*(0°…360°),due to periodicity; abbreviated: φ = 0…2π or φ = 0°…360°). The instantaneous voltage value u(t) or instantaneous current value or instantaneous differential current value i(t) therefore means the instantaneous value of the voltage / current / differential current at time t, i.e. in the case of a sinusoidal (periodic) alternating voltage, the value of the voltage / current / differential current at the phase angle φ (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 indicated with lowercase letters (u, i,…) 202307374 10 and effective values ​​(e.g., effective value of voltage U, effective value of differential current I, …) are designated with capital letters (U, I, …). State-of-the-art residual current monitoring devices use the differential current, more precisely the effective value of the differential current I, for display or signaling. 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 monitoring device "rigidly" (or "stupidly") displays or reports the effective value of the residual current. This applies in particular to the 50 Hz component in the residual current or the residual current flowing at the mains frequency of the voltage. According to the invention, it is now advantageous (in particular for the 50 Hz part of the residual current) not to use the (effective value of the) residual current, but only the differential active current, i.e., the active power component of the residual current, or (alternatively) the differential reactive current, i.e., the reactive power component of the residual current. This advantageously distinguishes between ohmic-induced fault currents caused by defective insulation or persons, since persons usually resemble an ohmic resistance (or always contain an ohmic component). The IEC 60479-1 standard describes the effect of electric current on the human body.and, on the other hand, capacitive or inductive induced fault currents (leakage currents), i.e., technically induced fault currents or leakage currents (which are not critical for personal protection). 202307374 11 This allows for faster searches for the causes and more specific maintenance, thereby saving costs. A voltage sensor unit is advantageously provided in the residual current monitoring device to determine the voltage level, as well as a control unit,to determine the differential active current or (alternatively) the differential reactive current from the determined voltage level and the determined differential current level. In this context, the effective value of the differential active current or the effective value of the differential reactive current is advantageously used. Specifically, the differential active current refers to the active current component in the differential current at the (mains) voltage frequency in the low-voltage circuit. This means, for example, that at an alternating voltage frequency of 50 Hz (as is common in Europe), the differential active current relative to 50 Hz,i.e., the fundamental component. In alternating current technology, harmonic oscillations are assumed 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 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 quantities (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 202307374 13 (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). -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 (fundamental oscillation) of the (grid) voltage). More generally, higher (relative to the fundamental frequency) frequency components of the current that are not equal to the fundamental frequency of the alternating voltage ((grid) voltage). For the purposes of the present invention, reactive power does not mean, in particular, distortion reactive power. 202307374 14 For the general case, especially for sampled, time-varying quantities (instantaneous value curves): - the distortion reactive current component is the component in the current that transmits reactive power with the (grid) voltage, - the distortion reactive current component has a higher frequency compared to the (grid) 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 magnitude of the differential current is (additionally) displayed. This has the particular advantage that, in addition to the display or signaling of the differential active current or differential reactive current, the differential current is also displayed or signaled. This has the particular advantage that it can be implemented analogously to conventional residual current monitoring devices. In an advantageous embodiment of the invention, the external display unit receives the magnitude of the differential active current or differential reactive current via wired or wireless communication. In particular, the external display unit receives the magnitude of the differential current. This has the particular advantagethat by transmitting the values, they can be displayed and / or stored in a central device. In an advantageous embodiment of the invention, a communication unit connected to the control unit is provided for wired or wireless communication to report the level of the differential active current or differential reactive current, in particular also the level of the differential current, for example, to enable display on an external display unit (or a central monitoring or management system). 202307374 15 This has the particular advantage that the data evaluation, monitoring, and data storage of the occurring differential currents can be carried out in a central management system. In an advantageous embodiment of the invention, the residual current monitoring device is designed such that the differential current sensor unit determines instantaneous differential current values ​​of the differential current level,that the voltage sensor unit determines instantaneous voltage values ​​of the voltage level, that an effective value of the voltage is determined from the instantaneous voltage values ​​(in particular over half, one or more periods of the alternating voltage - generally over a multiple of half the period of the alternating voltage), that an instantaneous differential power is determined from the instantaneous differential power, in particular 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 a differential active power 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 by the effective value of the voltage (determined 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), an (effective value of the) differential active current is determined, that the (effective value of the) differential active current is displayed or reported, in particular that a report is issued when the level of an active current limit is exceeded. 202307374 16 This has the particular advantage of demonstrating a simple possibility for determining the differential active current. In an advantageous embodiment of the invention, the instantaneous voltage values ​​u(t) (alternatively also: 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 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 - 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 ∆) can be calculated by dividing by the effective value of the voltage U (alternatively: ^^ ^ே,^^^ ) the effective value of the differential current I (alternatively: ^^ ௱,௪^^^ ) can be determined. 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.202307374 17 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 magnitude of the voltage, 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), that a differential apparent power is determined from the effective value of the voltage and the effective value of the differential current (in particular by multiplication).This has the particular advantage that the differential apparent power can be determined 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 that it shows 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 used to calculate the differential reactive power. ௱ ) and the square of the difference active power Pd (alternatively ^^ ௱ ) the difference reactive power ^^ ௱ determined. From the difference in reactive power ^^ ௱(over half, 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: ^^ ^ே,^^^ ) (over the same half, one or more periods 202307374 18 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 ^^ ௱,^^^^ௗ is displayed or (alternatively and) reported; in particular, if the level of a reactive current limit is exceeded (reactive current limit refers to a differential reactive current limit). Reactive current limit refers in particular to a differential reactive current limit of the fundamental frequency (e.g., 50 Hz). S = U * I (alternativ auch: SΔ = ULN , rms ⋅ I Δ , rms ) ^^ ^^௱ ௱,^^^^ௗ = ^^^ே,^^^This has the particular advantage of providing a specific way of determining the (effective value of) the differential reactive current, which can be implemented in particular by a control unit with a microprocessor. In an advantageous embodiment of the invention, the differential active current or (alternatively) the differential reactive current is determined continuously (periodically). This has the particular advantage of providing continuous periodic monitoring of the low-voltage circuit.In an advantageous embodiment of the invention, a mechanical isolating contact unit is provided, which has a closed state of the contacts for a current flow of the conductors of the 202307374 19 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, or (alternatively and) an electronic interruption unit, which 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 through semiconductor-based switching elements. If the differential active current exceeds a current limit value or current-time limit value (ieIf the current limit is exceeded for an initial period of time, the contacts are open to provide galvanic isolation to prevent current flow, or the switching elements are in a high-resistance state to prevent current flow. This has the particular advantage that, in addition to monitoring the fault current, the low-voltage circuit is interrupted in the event of fault currents (differential active currents) that are hazardous to persons, so that in addition to monitoring, a protective effect is also achieved (analogous to conventional residual current circuit breakers, but not with the differential current, but with the differential active current). According to the invention, a corresponding method for residual current monitoring in an electrical low-voltage circuit for alternating current, specifically for a residual current monitoring device, with the same and other advantages is claimed.The inventive method for monitoring fault currents in a low-voltage electrical circuit for alternating voltage: determines the magnitude of a differential current between two conductors of the low-voltage circuit, determines the voltage of the two conductors of the low-voltage circuit, from the voltage and the magnitude of the differential current, a differential active current or 202307374 20 differential reactive current is determined, the magnitude of the differential active current or differential reactive current is displayed (in particular, reported in order to be displayed at the location receiving the message, in particular, if the magnitude of an active current limit value or reactive current limit value is exceeded, a message is issued in order to be displayed at the location receiving the message). In particular, the magnitude of the differential current is additionally displayed (in particular, reported in order to be displayed at the location receiving the message).According to the invention, a corresponding computer program product for a residual current monitoring device is claimed. The computer program product comprises instructions which, when the program is executed by a microprocessor, cause the microprocessor to carry out or support the inventive embodiments or methods of the residual current monitoring device. In particular, the differential active current or (alternatively) differential reactive current is used for the display or message. The microprocessor is part of the residual current monitoring device, in particular the control unit. According to the invention, a corresponding computer-readable storage medium on which the computer program product is stored is claimed. According to the invention, a corresponding data carrier signal which the computer program product transmits is claimed. All embodiments, both in dependent form and referring back to patent claim 1 or15, as well as referring back 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 residual current monitoring device. 202307374 21 In general, a new concept for a residual current monitoring device 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 clearly understandable in connection with the following description of the exemplary embodiments, which are explained in more detail in connection with the drawings.The drawing shows: Figure 1 a first representation with a residual current monitoring device, Figure 2 a second representation with a residual current monitoring device, Figure 3 a third representation with a residual current monitoring device, Figure 4 a fourth representation with a residual current monitoring device, Figure 5 a first block diagram for a calculation unit, Figure 6 a representation of a display, Figure 7 a first test setup with a residual current monitoring device, Figure 8 a second test setup with a residual current monitoring device.Figure 1 shows a representation of a residual current monitoring device SG for monitoring an electrical low-voltage circuit for alternating voltage, comprising: 202307374 22 - a housing 103 with two mains-side 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 grid side 101 (Grid), and a consumer ES is usually connected to the load side 102 (Load); - 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 residual current monitoring 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 residual current monitoring device) the level of the neutral conductor current i N (in the residual current monitoring device), ie the level of the residual current i ∆ = i L – i Nis normally equal to zero. This arrangement would essentially correspond to a conventional residual current monitoring device. According to the invention, the residual current monitoring device SG according to Figure 1 is extended such that a voltage sensor unit SUA is used to determine the (in particular instantaneous) level of the voltage u LN , which is provided for two conductors L, N of the low-voltage circuit (connected to the 202307374 23 residual current monitoring device), ie the level of voltage u LN between the neutral conductor connection and the phase conductor connection. 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 monitoring device according to the prior 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 and the voltage sensor unit SUA. The residual current monitoring 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 is carried out. Alternatively (or additionally), a determination of an (effective value of the) differential reactive current ^^ ௱,^^^^ௗcarried out. In the example according to Figure 1, the control unit is connected to an internal display unit DISP for displaying information on the residual current monitoring device, in particular the level of the differential active current or differential reactive current. In addition, the level of the differential current can be displayed. In one embodiment, the level of the differential active current and the level of the differential reactive current (and, if applicable, also the level of the differential current) can be displayed. The control unit is connected to a communication unit COM for external display or reporting of the level of the differential active current or differential reactive current. In addition, the level of the differential current can be reported. 202307374 24 In one embodiment, the level of the differential active current and the level of the differential reactive current (and, if applicable, also the level of the differential current) can be reported.Alternatively or additionally, the message can only be sent when an active current limit or reactive current limit is exceeded. The active current limit can be, for example, 5 mA, 6 mA, 10 mA, 20 mA, 30 mA, 50 mA, 100 mA, or 300 mA. The reactive current limit is typically higher (e.g., 2, 3, 5, or 10 times) or equal to the active current limit. The COM communication unit can provide wired or wireless communication to report the level of the residual active current or residual reactive current, in particular also the level of the residual current, particularly for an external display. A message or transmission is provided. The level of the respective current can be transmitted (reported) to an external display unit. The external display unit can be part of a higher-level monitoring or management system or it can be reported to other units, in particular for display purposes.The (effective value of) the differential active current I. ∆,wirk or (alternatively and) differential reactive current is displayed on an internal or external display unit (e.g. by means of a message). Alternatively or additionally, a display (message) can be issued if the active current limit value (or (alternatively and) reactive current limit value) is exceeded. In one embodiment, signaling contacts can be provided on the residual current monitoring device SG. The signaling contacts can be controlled, for example, by the control unit SE. If a certain active current limit value (or (alternatively and) reactive current limit value) or (alternatively and) current limit value of the residual current is exceeded, the exceedance of a critical value can be reported or signaled by closing (alternatively opening) the contacts. This message via the signaling contacts can also be used to switch external switching devices (contactors, relays).The residual current monitoring device can be used to alert a user that there is a fault in the low-voltage circuit (in a system) before the shutdown threshold of a protective switching device is reached. This means that if values ​​​​are slowly deteriorating, for example due to aging insulation, measures can be taken before the system is switched off. The (effective value) of the residual active current is determined in relation 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 residual active current is determined in relation to 50 Hz. Further details of the energy source EQ and the energy sink ES according to Figure 1 are described in relation to Figure 2. Figure 2 shows a representation according to Figure 1, with the following differences and explanations.In Figure 2, the residual current monitoring device SG has a (two-pole) mechanical isolating contact unit MK, which has a closed state of the contacts for a current flow in 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, i.e. with one contact, wherein the contact is preferably arranged in the phase conductor, i.e. between the mains-side phase conductor connection LG and the load-side phase conductor connection LL. Alternatively, an electronic interruption unit can be provided which, by means of semiconductor-based switching elements, has a high-resistance state of the switching elements to prevent a current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit.The residual current monitoring device can be designed in such a way that if the differential active current exceeds a current limit or current-time limit (i.e. if the current limit is exceeded for an initial period of time), the contacts are open to provide (galvanic) isolation to prevent current flow, or the switching elements are in a high-impedance state to prevent current flow (depending on the design). In particular, if differential reactive currents are present, the contacts are not open or the switching elements are not in a high-impedance state (i.e. current continues to flow). 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 power source side, which is represented by an earth symbol. This grounding has an earth impedance Z. PEThe earth-side neutral conductor connection is provided as a protective earth connection PE (Protective Earth) according to Figure 2. The energy source EQ is connected to the two mains-side connections 101, according to Figures 1 and 2 to the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG. Figure 2 also shows a schematic diagram 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 Figures 1 and 2 to the load-side neutral conductor connection NL and the load-side phase conductor connection LL. 202307374 27 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 2. 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 3 shows a diagram according to Figure 2, with the difference that a first fault case FF1 is shown. In the example according to Figure 3, there is an electrical connection from the phase conductor to the protective conductor SL at the load-side output 102 of the residual current monitoring device SG, ie between the load-side output 102 of the residual current monitoring 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 an electrical fault current i RE1flow (to the energy source EQ), so that in the residual current monitoring device the current in the phase conductor i L and the current in the neutral conductor i N is 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 fault case FF is shown separately in Figure 3 (for explanation). The fault case FF can also occur in an analogous manner in the load ES or otherwise. 202307374 28 In the example according to Figure 3, 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). Figure 4 shows a representation according to Figure 2 or 3, with the difference that a second fault case FF2 is shown. In the example according to Figure 4, there is an electrical connection from the phase conductor to earth at the load-side output 102 of the residual current monitoring device SG, ie between the load-side output 102 of the residual current monitoring 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 residual current monitoring device the current in the phase conductor i L and the current in the neutral conductor i N is no longer identical, since a fault current i RE2to 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. The second fault case FF2 is shown separately in Figure 4 (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 4, the resulting fault current i RE2 the differential current i determined in the differential current sensor unit ZCT ∆ (i RE2 = i ∆ ). Figure 5 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 202307374 29 - 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 are fed, for example, to a calculation unit BE (which is part of the control unit SE). From the (instantaneous) voltage level u LN and the (instantaneous) level of the differential current i ∆ (i ∆ = i L – i N ) a determination of a differential active current I ∆,wirk (RMS value) or (and) differential reactive current I ∆,blind (effective value). The level of the differential active current I ∆,wirk (RMS value) or (and) differential reactive current I ∆,blind (RMS value) is used for display on an internal or external display unit. (The level of the differential active current I ∆,wirk(effective value) can be used to prevent current flow in the monitored circuit.) In the example according to Figure 5, the determination of the (effective value of the) differential active current I ∆,wirk The magnitude of the (instantaneous) differential current i ∆ , specifically according to Figure 5, the instantaneous level of the differential current (instantaneous differential current values), and the level of the voltage u LN , specifically according to Figure 5 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 ) an 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 5 the instantaneous level of voltage u LN (= u(t)), is fed to a 202307374 30 effective value unit, which according to Figure 5 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 5 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 the same half, one, one and a half, ... or several 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. 202307374 31 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 ∆,wirkcan be displayed by the internal display unit DISP or (and) reported by the communication unit COM for (storage and / or) display on an external display unit. The effective value of the differential active current I ∆,wirk can only be reported (displayed) when an active current limit is exceeded. The same applies to the residual reactive current. An external display unit can be, for example, a web browser. Technically speaking, there can be some kind of data storage / database from which the collected data is loaded and displayed. This process, as well as the subsequent processes, 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. 202307374 32 The instantaneous power p determined from the instantaneous voltage values ​​and the instantaneous residual 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.The differential reactive power (over a multiple of half the period of the alternating voltage) is divided by the effective value of the voltage (over the same multiple of half the period of the alternating voltage) to obtain an effective value of the differential reactive current ^^. ௱,^^^^ௗ The effective value of the differential reactive current I ∆,blind can be displayed by the internal display unit DISP or reported by the communication unit COM for (storage and / or) display on an external display unit. The effective value of the differential reactive current I ∆,blind can only be reported (displayed) when a reactive current limit value is exceeded.SΔ = ULN , rms ⋅ I Δ , rms 202307374 33 Q = S 2 2 Δ Δ − P Δ ^^ = ^^௱௱,^^^^ௗ ^^^ே,^^^The differential reactive current determined from the instantaneous voltage values ​​and the instantaneous differential current values ​​can alternatively be determined by other means. The determination of the differential active current, in particular the differential reactive current, is advantageously carried out continuously (periodically), for example, with microprocessor support. The residual current monitoring device can further be designed or expanded such that, in addition to the differential active or reactive current, the level of the differential current (effective value) is displayed by the internal display unit DISP or reported by the communication unit COM for (storage and / or) display on an external display unit. The effective value of the differential current can only be reported (displayed) when a limit value is exceeded. The level of the current limit values ​​or current time limit values ​​can be fully or partially adjustable, e.g.by means of an input unit or communication unit on the residual current monitoring device. This means that the residual current monitoring device according to the invention behaves, for example, as shown below. Figure 6 shows how the level of the differential active current or differential reactive current can be displayed on the (internal) display unit DISP (a corresponding display can also be made on an external display unit). In the example according to Figure 6, the differential current I is also displayed. ∆ Figure 6 shows a digital display on the left side, where the differential current I ∆ is displayed, 202307374 34 in the example according to Figure 6 a differential current I ∆ of 227 mA, in the lower range the differential active current I ∆,wirk displayed, represented as active differential current I ∆,active , in the example according to Figure 6 a (differential active current I ∆,wirk =) active differential current I ∆,activeof 4 mA. Figure 6 shows a corresponding display in the right part as a bar chart, where the type of current, ie differential current I ∆ or (differential active current I ∆,wirk =) active differential current I ∆,active, and the current level (logarithmic) in milliamperes (mA) is plotted on the vertical Y-axis. Figure 7 shows a test setup (measurement setup) with a residual current monitoring device SG. The residual current monitoring 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 connection LL is connected to the mains-side neutral conductor connection NG via an adjustable resistor R, a second switch S2 and a current measuring device AM. The load-side neutral conductor connection NL is not connected in the example. A voltmeter VM is (optionally) connected between the two mains-side connections NG, LG of the residual current monitoring device SG.A conventional residual current monitoring device as well as a residual current monitoring device according to the invention behaves in such a way that when the first and second switches S1, S2 are closed and a residual current I is set with the adjustable resistor R. ∆,R (= differential current in the test setup via the residual current monitoring device), which in this case flows through the ammeter AM, of, for example, 30 mA, both residual current monitoring devices display this value. The residual current monitoring device according to the invention would display this current (30 mA) as the differential active current I ∆,wirk (active differential current I ∆,active ) display. 202307374 35 In an embodiment of the residual current monitoring device according to the invention, in which the residual current I ∆ is displayed, this value (30 mA) would also be displayed. The residual current monitoring device according to the invention would, when displaying the residual reactive current I ∆,blinddo not display this value (ideally ~ 0 mA). Ohmic test fault currents I ∆,R Different levels can be set using the adjustable resistor R, and the residual current monitoring device SG can thus be tested with regard to its display behavior. 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 specific capacitance (advantageously variably adjustable). If the capacitance of the capacitor C is dimensioned such that a (capacitive) residual current of I ∆,C of 30 mA in the example (effective value, note tolerance ranges), a conventional residual current monitoring device (according to the state of the art) will display this current value. A residual current monitoring device SG according to the invention will display the differential active current I ∆,wirk(active differential current I ∆,active ) do not display this value (ideally ~ 0 mA). In an embodiment of the residual current monitoring device according to the invention, in which the residual current I ∆ is displayed, this value (30 mA) would also be displayed. The residual current monitoring device according to the invention would, when displaying the residual reactive current I ∆,blind display this value (30 mA). Using the test setup mentioned, 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. The curve of an instantaneous differential power is determined from the instantaneous values ​​of the measured differential current and the instantaneous values ​​of the measured voltage. This instantaneous value curve can be converted into an active power (by averaging) and then a differential active current can be determined from this (by dividing by the (50 Hz) effective value of the voltage). This determined differential active current is an effective value that relates to 50 Hz (or the fundamental frequency of the mains voltage). In addition to the active current calculation, the 50 Hz reactive current can be calculated using the same principle. The information can be displayed to the user via an (internal or external) display unit or transmitted via a communication unit (interface), in particular for an external display.Today, it is not possible to split the 50 Hz differential current into active and reactive components because only a current measurement is available and it is physically impossible to separate the 50 Hz component into active and reactive components from the exclusive analysis of the current curve. The method presented here 202307374 37 thus enables new information and new device functions. Active and reactive components can be detected and analyzed. For example, the active and reactive current values ​​can be used to determine the ohmic and capacitive impedance components in an electrical system. The solution according to the invention requires a voltage determination (measurement), which can be implemented cost-effectively. Only a small amount of calculation is required, since only multiplication and averaging 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 a person skilled in the art without departing from the scope of the invention.

Claims

202307374 38 claims 1. Residual current monitoring device (SG) for monitoring residual currents in an electrical low-voltage circuit for alternating voltage, comprising: - a differential current sensor unit (ZCT) for determining the level of a differential current of two conductors of the low-voltage circuit, - an internal or external display unit, suitable for displaying the level of a differential current, characterized in that a voltage sensor unit (SUA) is provided for determining the level of a voltage of the two conductors of the low-voltage circuit, that a control unit (SE) is provided which is connected to the differential current sensor unit (ZCT), the voltage sensor unit (SUA) and the display unit, that the residual current monitoring device (SG), in particular the control unit (SE), is designed in such a way,that a differential active current or differential reactive current is determined from the voltage level and the differential current level, that the differential active current or differential reactive current level is displayed on the display unit.

2. Residual current monitoring device (SG) according to claim 1, characterized in that the differential reactive current is the differential reactive current component with the fundamental frequency of the voltage in the low-voltage circuit.

3. Residual current monitoring device (SG) according to one of the preceding claims, characterized in that the differential current sensor unit (ZCT) has, in particular, a summation current transformer, that the two conductors of the low-voltage circuit are passed through the differential current sensor unit (ZCT). 202307374 39 4. Residual current monitoring device (SG) according to one of the preceding claims, characterized in that the residual current monitoring device has a housing with at least two mains-side connections (LG, NG) for the two conductors of the low-voltage circuit, wherein the two mains-side connections (LG, NG) are connected to the voltage sensor unit.

5. Residual current monitoring device (SG) according to claim 4, characterized in that the residual current monitoring device has at least two load-side connections (LG, NG) for the two conductors of the low-voltage circuit, that the at least two mains-side connections are connected to the at least two load-side connections, that the connections between the mains-side connections and the load-side connections are connected to the residual current sensor unit or are passed through it. 6.Residual current monitoring device (SG) according to one of the preceding claims, characterized in that the level of the differential current is displayed.

7. Residual current monitoring device (SG) according to one of the preceding claims, characterized in that the external display unit receives the level of the differential active current or differential reactive current, in particular also receives the level of the differential current, by means of wired or wireless communication.

8. Residual current monitoring device (SG) according to claim 7, characterized in that a communication unit connected to the control unit is provided, for which wired or wireless communication is possible. 202307374 40 wireless communication to report the level of the differential active current or differential reactive current, in particular also the level of the differential current.

9. Residual current monitoring device (SG) according to one of the preceding claims, characterized in that the differential current sensor unit (ZCT) determines instantaneous differential current values ​​of the level of the differential current, that the voltage sensor unit (SUA) determines instantaneous voltage values ​​of the level 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 displayed on the display unit. 10.Residual current monitoring device (SG) according to claim 9, characterized in that the differential effective 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.

11. Residual current monitoring device (SG) according to one of the preceding claims, characterized in that the differential current sensor unit (ZCT) determines instantaneous differential current values ​​of the magnitude of the differential current, that an effective value of the differential current is determined from the instantaneous differential current values, that the voltage sensor unit (SUA) determines instantaneous voltage values ​​of the magnitude of the voltage. 202307374 41 that an effective value of the voltage is determined from the instantaneous voltage values, that a differential apparent power is determined from the instantaneous voltage values ​​and the instantaneous differential current values, that a differential active power is determined from the differential apparent power and the differential active power, that the differential reactive current is determined from the differential reactive power, that the differential reactive current is displayed on the display unit. 12.Residual current monitoring device (SG) according to claim 11, 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 displayed on the display unit. 13.Residual current monitoring device (SG) according to one of the preceding claims, characterized in that a mechanical isolating contact unit (MK) connected to the control unit (SE), 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 flow-preventing galvanic isolation of the conductors of the low-voltage circuit, is provided that when the differential active current exceeds a current limit value or current time limit value, an open state. 202307374 42 state of the contacts for a current-preventing galvanic isolation is initiated.

14. Residual current monitoring device (SG) according to one of the preceding claims 1 to 12, characterized in that an electronic interruption unit connected to the control unit (SE), which 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 through semiconductor-based switching elements, is provided so that when the differential active current exceeds a current limit value or current-time limit value, an open state of the contacts for a current-preventing galvanic isolation or a high-resistance state of the switching elements to prevent a current flow is initiated. 15.Method for monitoring fault currents in a low-voltage electrical circuit for alternating current, in that the magnitude of a differential current between two conductors of the low-voltage circuit is determined, characterized in that the magnitude of a voltage between the two conductors of the low-voltage circuit is determined, that a differential active current or differential reactive current is determined from the magnitude of the voltage and the magnitude of the differential current, and that the magnitude of the differential active current or differential reactive current is displayed.

16. Method according to claim 15, characterized in that the magnitude of the differential current is displayed.

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