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 of two conductors of the low-voltage current circuit is ascertained, and the level of the voltage of the two conductors of the low-voltage current circuit is ascertained. A differential active current or a differential reactive current 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]202312101 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 202312101 2 connection cross-sections of the copper conductors and their length) at a defined ambient temperature (such as 40°C). Such conditions 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 power breaker. Residual current monitoring devices are used primarily 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 passed through a current transformer, usually having a ring-shaped core made of ferromagnetic material. Only the differential current, i.e., a current that differs from the forward and return current, from the conductors is converted (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. 202312101 4 In general, operational (technically caused) leakage currents (especially at the mains frequency (fundamental frequency) (e.g., 50 Hz in Europe)) and fault currents (e.g., caused by people) 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 with the features of patent claim 1 and a method with the features of patent claim 15. According to the invention, a residual current monitoring device for monitoring fault currents in an electrical low-voltage circuit for alternating current is proposed,comprising: - a housing with at least two 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), - that the two connections (inside the housing, i.e. internally) are connected to a voltage sensor unit for determining the voltage level of the two conductors of the low-voltage circuit, - at least one first input for connecting a 202312101 5 (external, i.e. outside the housing) first differential current sensor unit for determining the level of a first differential current of the two conductors 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)), - an internal or external display unit (particularly suitable for displaying the level of the differential current), - a control unit,which is connected to the first input for the first 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 first differential active current or first differential reactive current is carried out from the level of the voltage and the level of the first differential current, that the level of the first differential active current or first 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. Differential active current means the active current component in the differential current, i.e. the ohmic current component (real component) in the differential current, i.e. the current component,which, together with the voltage, results in active electrical power. Active power is the electrical power 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 are generally known from the fundamentals of AC voltage 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 the unit watt (W). If a consumer has inductive and capacitive components in addition to the ohmic resistance, a time shift occurs between the temporal (especially sinusoidal) course of current and voltage.also called phase shift. 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 referred to 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 (unused "blind" power). If the power consumption of a load / consumer includes reactive power in addition to the active power, the total power is referred to as apparent power. According to DIN 40110-1, the apparent power is specified in volt-amperes (VA). Volt-amperes (VA) are intended to expressthat in addition to the active power, reactive power is also included in the power. In the case of AC and AC voltage consumers, we usually speak of apparent power. Apparent power is generally greater than the active power. The current component relating to the 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 the 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: resistive component, active power) and the differential reactive current (imaginary part: capacitive or inductive component,Reactive power). 202312101 7 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 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 202312101 8 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 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 202312101 9 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 / 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, …). State-of-the-art residual current monitoring devices use the residual current, more precisely the effective value of the residual current I,for display or message. 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. Especially for residual currents with the fundamental frequency (the mains voltage), no distinction is possible today. 202312101 10 According to the invention, it is now advantageous (especially for the 50 Hz part of the residual current) to use not 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 allows a distinction to be made 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). 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. 202312101 11 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 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). 202312101 12 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 (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). -The reactive current component (displacement reactive current) has a (+ / -) 90° phase shift (or phase position) to the (mains) voltage. 202312101 13 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 magnitude of the first differential current is (additionally) displayed. This has the particular advantage that, in addition to the display or signaling of the (first) differential active current or (first) differential reactive current, the (first) differential current is also displayed or signaled. This has the particular advantage that an implementation analogous to conventional residual current monitoring devices is provided. 202312101 14 In an advantageous embodiment of the invention, the external display unit receives the magnitude of the (first) differential active current or (first) differential reactive current via wired or wireless communication. In particular, the external display unit receives the magnitude of the (first) 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 in order to report the level of the (first) differential active current or (first) differential reactive current, in particular also the level of the (first) differential current, in order to enable, for example, a display on an external display unit (or a central monitoring or management system). 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 thatthat the (first) differential current sensor unit determines instantaneous (first) differential current values ​​of the magnitude of the (first) 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 a period, 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 (first) differential power is determined from the instantaneous voltage values ​​and the instantaneous 202312101 15 (first) differential current values; that a (first) differential effective power is determined from the instantaneous (first) differential power, in particular by averaging (in particular over half a period, 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) (first) differential active current is determined from the (first) 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 division with 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), that the (effective value of the) (first) differential active current is displayed or reported, in particular that a report is issued when the level of a (first) active current limit value is exceeded. 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 (first) differential current values ​​i(t) (alternatively: i ∆ ) by averaging the product of the instantaneous voltage values ​​u(t) and the instantaneous (first) 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 (first) differential active power Pd (alternatively also: P ∆ ) is determined. This means that the current (first) difference power pd(t) (alternatively: p ∆ ) is determined by (in particular arithmetic) averaging (ie by integrating the instantaneous 202312101 16 (first) 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 (first) differential active power Pd is determined. From the (first) differential active power Pd (= P ∆ ) can be calculated by dividing by the effective value of the voltage U (alternatively: ^^ ^ே,^^^ ) the effective value of the (first) differential current I (alternatively: ^^ ௱,௪^^^ ) can be determined. This has the particular advantage that specific possibilities for determining the (first) differential active power (the (effective value of the) (first) 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 (first) differential current sensor unit determines instantaneous (first) differential current values ​​of the level of the (first) differential current, an effective value of the (first) differential current (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 determined from the instantaneous (first) differential current values, the voltage sensor unit determines instantaneous voltage values ​​of the level of the voltage, an effective value of the voltage (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 determined from the instantaneous voltage values, 202312101 17 that a (first) differential apparent power is determined from the effective value of the voltage and the effective value of the (first) differential current.This has the particular advantage that a determination of the (first) difference apparent power is provided for further embodiments of the invention. In an advantageous embodiment of the invention, a (first) difference reactive power is determined from the (first) difference apparent power and the (first) difference active power. The (first) difference reactive current is determined from the (first) difference reactive power. This has the particular advantage that a possibility for determining the (first) difference reactive current is demonstrated. In an advantageous embodiment of the invention, the square root of the difference from the square of the (first) difference apparent power S (alternatively also ^^. ௱ ) and the square of the (first) difference active power Pd (alternatively ^^ ௱ ) the (first) difference reactive power ^^ ௱ determined. From the (first) differential 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 determined by dividing by the effective value of the voltage U (alternatively: ^^ ^ே,^^^ ) (over the same half, 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 (first) differential reactive current ^^ ௱,^^^^ௗ The effective value of the (first) differential reactive current ^^ ௱,^^^^ௗ is displayed or (alternatively and) reported; in particular, a message is issued when the level of a (first) (differential) reactive current limit is exceeded. Reactive current limit refers in particular to a differential reactive current limit of the fundamental frequency (e.g., 50 Hz). S = U * I 202312101 18 (alternatively also: S ^ ^U LN , rms ^ I ^ , rms ) This has the particular advantage that a specific possibility of determining the (effective value of the) (first) 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, a second input is provided for connecting an (external) second differential current sensor unit for determining the level of a second differential current of two (other, second) conductors of the low-voltage circuit (the voltage of the two conductors corresponds to the voltage level determined by the voltage sensor unit, i.e. the two (other, second) conductors are connected to the conductors from which the voltage level is determined, the two (other, second) conductors of the second differential current sensor unit form, for example, a second circuit with respect to the two (first) conductors of the first differential current sensor unit).The control unit is connected to the second input for the second differential current sensor unit. The residual current monitoring device, in particular the control unit, is designed such that a second differential active current or second differential reactive current is determined from the voltage level and the level of the second differential current. The level of the second differential active current or second differential reactive current is displayed on the display unit. 202312101 19 This has the particular advantage that two circuits (of the same voltage source / energy source) can be monitored. In an advantageous embodiment of the invention, the level of the second differential current is displayed.In an advantageous embodiment of the invention, the receipt, reporting, display, or (and) determination of the second differential active current or second differential reactive current is carried out in a manner analogous to the aforementioned embodiments. (Therefore, first / first is often placed in parentheses.) This has the particular advantage of providing a simple parallel evaluation for two circuits. In an advantageous embodiment of the invention, a third input is provided for the connection of an (external) third differential current sensor unit for determining the magnitude of a third differential current of two (other, third) conductors of the low-voltage circuit (the voltage of the third conductor corresponds to the voltage level determined by the voltage sensor unit, ieThe two (other, third) conductors are connected to the conductors from which the voltage level is determined. The two (other, third) conductors of the third differential current sensor unit form, for example, a third circuit with respect to the two (first and second) conductors of the first (and second) differential current sensor unit. The control unit is connected to the third input for the third differential current sensor unit. The residual current monitoring device, in particular the control unit, is designed such that a determination of a third differential active current or third differential reactive current is carried out from the voltage level and the level of the third differential current. The level of the third differential active current or third differential reactive current is displayed on the display unit. 202312101 20 In an analogous manner, a fourth, fifth, etc. input can be provided for a fourth, fifth, etc.A differential current sensor unit may be provided. This has the particular advantage that multiple circuits (of the same voltage source / energy source) can be monitored. In an advantageous embodiment of the invention, the level of the third differential current is displayed. In an advantageous embodiment of the invention, the receipt, reporting, display, or (and) determination of the third differential active current or third differential reactive current is carried out in a similar manner to the aforementioned embodiments. (This is why first / first is often placed in parentheses.) The same applies to fourth, fifth, etc. differential active currents or differential reactive currents or differential currents. This has the particular advantage that a simple parallel evaluation is provided for multiple circuits (of the same voltage source / energy source).In an advantageous embodiment of the invention, the (first) differential active current or (alternatively) the (first) 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, an external mechanical isolating contact unit is provided, 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, or (alternatively and) an external electronic interruption unit, which, through semiconductor-based switching elements, has a high-resistance state of the switching elements to prevent 202312101 21 a current flow or a low-resistance state of the switching elements for current flow in the low-voltage circuit. If the first 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-impedance 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 life, 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 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 202312101 22 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. In general, a new concept for a residual current monitoring device is provided. 202312101 23 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: - a housing 103 with two (mains-side) connections 101 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, 202312101 24 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), - a voltage sensor unit SUA, for determining the (in particular instantaneous) level of the voltage u. LN, the two conductors L, N (connected to the residual current monitoring device) of the low-voltage circuit, ie the level of the voltage u LN between the neutral conductor connection and the phase conductor connection; (A residual current monitoring device according to the state of the art does not have a voltage sensor unit (voltage detection).) - (at least) a first input E1 for the connection of an (external) first differential current sensor unit ZCT1, for determining the level of a first differential current i ∆1 of the two conductors L, N of the low-voltage circuit or of a first branch A1 (partial circuit) of the conductors L, N, as shown in Figure 1, ie a, in particular instantaneous, first differential current i ∆1 = i L1 – i N1 , where i L1 is the magnitude of the phase conductor current in the first branch A1 (in the phase conductor L1), and i N1is the magnitude of the neutral conductor current in the first branch A1 (in the neutral conductor N1). A first load Load1 with a first impedance or resistance RL1 is connected to the first branch A1. The first phase conductor L1 is connected on one side to the phase conductor L and on the other side to the first load Load1. The first neutral conductor N1 is connected on the one side to the neutral conductor N and on the other side to the first load Load1, as shown in Figure 1. The first differential current sensor unit ZCT1 is arranged between the phase conductor L and neutral conductor N1 on the one side and the load Load1 on the other side. 202312101 25 In a circuit, the magnitude of the phase conductor current i L1 (in the first differential current sensor unit ZCT1) the level of the neutral conductor current i N1 (in the first differential current sensor unit ZCT1), ie the level of the differential current i ∆1 = i L1 – i N1is normally equal to or approximately zero. In an analogous manner, a second input E2, second branch A2 (partial circuit) with a second phase conductor L2, a second neutral conductor N2, a second differential current sensor unit ZCT2, a second consumer Load2, a second impedance or resistance RL2 is provided. An internal or external display unit DISP is provided. In the example according to Figure 1, an internal display unit DISP. A control unit SE is provided, which is connected to the first input E1 (the second input E2) of the voltage sensor unit SUA and the internal display unit DISP in the example. 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) first differential current i ∆1 (i ∆1 = i L1 – i N1) a determination of an (effective value of the) first differential active current I ∆,wirk Alternatively (or additionally), a determination of an (effective value of the) first differential reactive current 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 first differential active current or first differential reactive current. In addition, the level of the first differential current can be displayed. In one embodiment, the level of the first differential active current and the level of the first differential reactive current 202312101 26 (and, if applicable, also the level of the first differential current) can be displayed. The control unit can be connected to a communication unit COM for external display or reporting of the level of the first differential active current or first differential reactive current. In addition, the level of the differential current can be reported. In these cases, for example, the internal display unit DISP can be omitted.In one embodiment, the level of the differential active current and the level of the differential reactive current (and, if necessary, also the level of the differential current) can be reported. In these cases, the internal display unit DISP can also be omitted, for example. Alternatively or additionally, the report can only be issued when an active current limit or reactive current limit is exceeded. The level of 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 level of the reactive current limit is typically greater (e.g., 2, 3, 5, or 10 times) or equal to the level of the active current limit. The communication unit COM can provide wired or wireless communication to report the level of the first differential active current or first differential reactive current, in particular also the level of the first differential current, particularly for an external display. A message orTransmission 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, particularly for display. The (effective value of the) first differential active current I. ∆,wirkor (alternatively and) the first differential reactive current is displayed on 202312101 27 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) the 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 first active current limit value (or (alternatively and) the first reactive current limit value) or (alternatively and) the first current limit value of the differential 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 give a user a message that there is a fault in the low-voltage circuit (in a system) ((partial circuit, branch A1)) 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 first differential 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 first differential active current is determined in relation to 50 Hz. The same applies to the second input E2 / of the second differential current sensor unit ZCT2 and the associated second differential active current or second differential reactive current or second differential current.The (external) differential current sensor unit has, in particular, a (classic) summation current transformer. 202312101 28 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. This means that the (external) differential current sensor unit has, for example, no connections for the conductors of the low-voltage circuit (because these are passed through an opening (in the core of the summation current transformer). Figure 2 shows a representation according to Figure 1, with the following differences and explanations. The energy source EQ essentially has a voltage source SQ, which supplies an alternating voltage u. Gprovides, 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 earthed on the power source side, which is indicated by an earth symbol. This earthing 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. In Figure 2, the first consumer Load1 with the first impedance or resistance RL1 has a metal housing. In the example, the metal housing of the first consumer Load1 is connected via a protective conductor SL to the protective conductor 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. 202312101 29 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 first phase conductor L1 to the protective conductor SL, whereby this connection is connected on one side between the first differential current sensor unit ZCT1 and the first consumer Load1 to the first phase conductor L1. This would be the case, for example, if a person touches the phase conductor and, on the other hand, simultaneously has contact with the protective conductor (e.g., via a metal housing). This means that an electrical fault current i RE1 flow (to the energy source EQ), so that in the first differential current sensor unit ZCT1 the current in the first phase conductor i L1 and the current in the first neutral conductor i N1 is no longer identical, since a fault current iRE1 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 first fault case FF1 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 3 (for explanation). The first fault case FF1 can also occur in an analogous manner in the first consumer Load1 or otherwise. In the example according to Figure 3, the resulting fault current i RE1 the differential current i determined in the first differential current sensor unit ZCT1 ∆1 (i RE1 = i PE = i ∆1 ) (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). 202312101 30 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 first phase conductor L1 to earth, whereby this connection is connected on one side between the first residual current sensor unit ZCT1 and the first consumer Load1 with the first phase conductor L1. This is the case, for example, when 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 first differential current sensor unit ZCT1 the current in the first phase conductor i L1 and the current in the first neutral conductor i N1 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 / in the first consumer Load1 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 ∆1 (i RE2 = i ∆1 ). 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 (first) differential current (i ∆1 ) = 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). 202312101 31 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 (first) 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 same applies to the second differential current; therefore, the corresponding terminology and formulas have been simplified, in particular the first or the index 1 have been omitted or placed in parentheses for clarity. The magnitude of the (first) differential active current I ∆,wirk (RMS value) or (and) (first) 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 ) a momentary 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. 202312101 32 The magnitude of the voltage u LN , specifically according to Figure 5 the instantaneous level of voltage u LN(= u(t)), is fed to an 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. 202312101 33 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. 202312101 34 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. 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 (differential) reactive current limit is exceeded. S ^ ^U LN , rms ^ I ^ , rms 202312101 35 Q ^ 2 2 ^S ^ ^P ^ ^^ ^^௱ ௱ ,^^^^ௗ ൌ ^^^ே,^^^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 also 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 display (storage and / or) 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. With the invention, differential active currents or differential reactive currents (or also differential currents) of several consumers connected to a power source / voltage source can be separately recorded and displayed by appropriately assigned differential current sensor units (partial circuits). This means that the residual current monitoring device according to the invention behaves, for example, as shown below. 202312101 36 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. ∆ Figure 6 shows a digital display on the left side, where the differential current I ∆is displayed, 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 ∆,active of 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. The first residual current sensor unit ZCT1 is connected in parallel to the residual current monitoring device SG, also on the mains side, via the two-pole first switch S1 to the energy source EQ. On the first residual current sensor unit ZCT1, the load-side phase conductor connection L1 is connected to the mains-side neutral conductor connection NG / neutral conductor N via an adjustable resistor R, a second switch S2 and an ammeter AM. The load-side neutral conductor connection N1 is not connected in the example.A voltage measuring device VM is (optionally) connected between the two mains-side terminals NG, LG of the residual current monitoring device SG. 202312101 37 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 first differential current sensor unit ZCT1), 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 ). In one embodiment of the residual current monitoring device according to the invention, in which the differential 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 do 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 ∆,Cof 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). 202312101 38 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 ∆,blinddisplay 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 division by the (50 Hz) effective value of the voltage). This determined differential active current is an effective value that refers 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 202312101 39 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 an analysis of the current curve alone. The method presented here therefore 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 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

202312101 40 Patent Claims 1. Residual current monitoring device (SG) for monitoring residual currents in an electrical low-voltage circuit for alternating voltage, comprising: - a housing with at least two terminals () for at least two conductors of the low-voltage circuit, in particular a phase conductor and a neutral conductor of the low-voltage circuit, - the two terminals are connected to a voltage sensor unit (SUA) for determining the voltage level of the two conductors of the low-voltage circuit, - at least one first input for connecting a first differential current sensor unit (ZCT1) for determining the level of a first differential current of the two conductors of the low-voltage circuit, - an internal or external display unit, - a control unit (SE) connected to the first input for the first differential current sensor unit (ZCT1), the voltage sensor unit (SUA) and the display unit,- that the residual current monitoring device (SG), in particular the control unit (SE), is designed such that a determination of a first differential active current or first differential reactive current is carried out from the voltage level and the level of the first differential current, and that the level of the first differential active current or first differential reactive current is displayed on the display unit.

2. Residual current monitoring device (SG) according to claim 1, characterized in that the first 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 first differential current sensor unit (ZCT1), 202312101 41, in particular, has a summation current transformer, such that the two conductors of the low-voltage circuit are passed through the differential current sensor unit (ZCT).

4. Residual current monitoring device (SG) according to one of the preceding claims, characterized in that the magnitude of the first differential current is displayed.

5. Residual current monitoring device (SG) according to one of the preceding claims, characterized in that the external display unit receives the magnitude of the first differential active current or first differential reactive current, in particular also receives the magnitude of the first differential current, by means of wired or wireless communication. 6.Residual current monitoring device (SG) according to claim 3, characterized in that a communication unit connected to the control unit is provided for wired or wireless communication in order to report the level of the first differential active current or first differential reactive current, in particular also the level of the first differential current.

7. Residual current monitoring device (SG) according to one of the preceding claims, characterized in that the first differential current sensor unit (ZCT1) determines instantaneous first differential current values of the level of the first 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 an effective value of the voltage is determined from the instantaneous voltage values and the instantaneous. 202312101 42 first differential current values, a first differential active power is determined; that an effective value of the first differential active current is determined from the first differential active power by dividing it by the effective value of the voltage, that the effective value of the first differential active current is displayed on the display unit.

8. Residual current monitoring device (SG) according to claim 7, characterized in that the first differential active power is determined from the instantaneous voltage values and the instantaneous first differential current values by averaging the product of the instantaneous voltage values and the instantaneous first differential current values.

9. Residual current monitoring device (SG) according to one of the preceding claims, characterized in that the first differential current sensor unit (ZCT1) determines instantaneous first differential current values of the magnitude of the first differential current,that an effective value of the first differential current is determined from the instantaneous first differential current values, that the voltage sensor unit (SUA) determines instantaneous voltage values of the voltage level, that an effective value of the voltage is determined from the instantaneous voltage values, that a first differential apparent power is determined from the effective value of the voltage and the effective value of the first differential current, that a first differential active power is determined from the instantaneous voltage values and the instantaneous first differential current values, that a first differential reactive power is determined from the first differential apparent power and the first differential active power, that the first differential reactive power is determined from the first differential reactive power, 202312101 43 Differential reactive current is determined, that the first differential reactive current is displayed on the display unit.

10. Residual current monitoring device (SG) according to claim 9, characterized in that the first differential reactive power is determined from the square root of the difference between the square of the first differential apparent power and the square of the first differential active power, that an effective value of the first differential reactive current is determined from the first differential reactive power by dividing it by the effective value of the voltage, that the effective value of the first differential reactive current is displayed on the display unit. 11.Residual current monitoring device (SG) according to one of the preceding claims, characterized in that a second input is provided for connecting a second differential current sensor unit (ZCT2) for determining the level of a second differential current of two conductors of the low-voltage circuit, that the control unit (SE) is connected to the second input for the second differential current sensor unit (ZCT2), that the residual current monitoring device (SG), in particular the control unit (SE), is designed such that a determination of a second differential active current or second differential reactive current is carried out from the level of the voltage and the level of the second differential current, that the level of the second differential active current or second differential reactive current is displayed on the display unit. 12.Residual current monitoring device (SG) according to claim 11, characterized in that the level of the second differential current is displayed. 202312101 44 that the receipt, notification, display and / or determination of the second differential active current or second differential reactive current takes place in an analogous manner according to patent claims 3 to 8. 13.Residual current monitoring device (SG) according to one of the preceding claims, characterized in that a third input is provided for connecting a third differential current sensor unit (ZCT3) for determining the level of a third differential current of two conductors of the low-voltage circuit, that the control unit (SE) is connected to the third input for the third differential current sensor unit (ZCT3), that the residual current monitoring device (SG), in particular the control unit (SE), is designed such that a determination of a third differential active current or third differential reactive current is carried out from the level of the voltage and the level of the third differential current, that the level of the third differential active current or third differential reactive current is displayed on the display unit. 14.Residual current monitoring device (SG) according to claim 13, characterized in that the level of the third differential current is displayed, that the receipt, notification, display and / or determination of the third differential active current or third differential reactive current takes place in an analogous manner according to claims 3 to 8.

15. Method for monitoring residual currents in an electrical low-voltage circuit for alternating voltage, that the level of a differential current of two conductors of the low-voltage circuit is determined, characterized in that the level of a voltage of the two conductors of the low-voltage circuit is determined. 202312101 45 that a differential active current or differential reactive current is determined from the voltage level and the differential current level, and that the differential active current or differential reactive current level is displayed.

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

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