Circuit breaker device and method

Abstract

The invention relates to a circuit breaker device (SG) for fault current protection for low-voltage AC circuits having at least two conductors (LI, NI), the circuit breaker device comprising: a mechanical separating contact unit (MK) which is connected in series with an electronic interruption unit (EU); a differential current sensor unit which determines the level of a fault current of the at least two conductors of the low-voltage AC circuit, wherein the level of the fault current is compared with a fault current limit value or fault current time limit value and, if the fault current limit value or fault current time limit value is exceeded, a prevention of current flow is initiated. A test circuit (S2, Ztest) is provided which bypasses the differential current sensor unit (ZCT). The test circuit has a switch (S2) which can be controlled by the control unit and which can close or open the test circuit. In order to test the fault current detection, the test circuit is closed by means of the controllable switch so that the test circuit causes a test current of a specific level to bypass the differential current sensor unit, such that a fault current is caused and detected in the differential current sensor unit. The circuit breaker device detects the level of a first fault current prior to the closing of the test circuit and the level of a second fault current with the test circuit closed. A difference of the level of the test current flowing through the test circuit from the level of the fault current component, caused by the closed test circuit, in the second fault current is determined. The magnitude of the difference determined in this way is compared with a first threshold value and, if the first threshold value is exceeded: • a) information is signaled, or • b) a prevention of current flow is initiated.

Description

[0001] 202420316

[0002] 1

[0003] Description

[0004] Protective switching device and procedure

[0005] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

[0006] The invention relates to the technical field of a protective switching device for a low-voltage alternating current circuit according to the preamble of claim 1 and a method for a protective switching device for a low-voltage alternating current circuit according to the preamble of claim 15.

[0007] Low voltage refers to voltages up to 1000 volts AC or up to 1500 volts DC. In particular, low voltage refers to voltages higher than extra-low voltage, defined as 50 volts AC or 120 volts DC.

[0008] Low-voltage AC circuits, networks, or installations refer to circuits with rated currents of up to 125 amperes, or more specifically, up to 63 amperes. Low-voltage AC circuits specifically include circuits with rated currents of up to 50 amperes, 40 amperes, 32 amperes, 25 amperes, 16 amperes, or 10 amperes (amperes, abbreviated A). These current values ​​refer specifically to rated, rated, and / or tripping currents, i.e., the maximum current that normally flows through the circuit or at which the electrical circuit is typically interrupted, for example, by a protective device such as a circuit breaker, miniature circuit breaker, or miniature circuit breaker. The rated currents can be further staggered, from 0.5 A via 1 A, 2 A, 3 A, 4 A, 5 A, 6 A, 7 A, 8 A, 9 A, 10 A, etc. up to 16 A / up to 25 A / up to 32 A (amperes, abbreviated: A).

[0009] Miniature circuit breakers (MCBs) are long-established overcurrent protection devices used in low-voltage electrical installations. They protect cables from damage caused by overheating due to excessive current and / or short circuits. A MCB can automatically disconnect the circuit in case of overload and / or short circuit. A MCB is a non-resetting safety device.

[0010] 2

[0011] Unlike miniature circuit breakers (MCBs), power circuit breakers are designed for currents greater than 125 A, and sometimes even as low as 63 A. MCBs are therefore simpler and more delicate in design. MCBs typically have a mounting option for installation on a DIN rail (also known as a top-mounted rail or TH 35 rail).

[0012] State-of-the-art miniature circuit breakers (MCBs) are electromechanical in design. They contain a mechanical switching contact or shunt trip within a housing to interrupt (trigger) the electrical current. Typically, a bimetallic protective element is used for tripping (interruption) in the event of a prolonged overcurrent (overcurrent protection) or thermal overload (overload protection). An electromagnetic trip with a coil is used for momentary tripping when an overcurrent limit is exceeded or in the event of a short circuit (short-circuit protection). One or more arc-quenching chambers or arc-quenching devices are provided. Furthermore, connection elements for conductors of the electrical circuit to be protected are included.

[0013] Residual current devices (RCDs) for electrical circuits, especially low-voltage circuits and installations, are widely known. RCDs are also known as residual current circuit breakers. They measure the total current (or differential current between the live (positive) and neutral (negative) conductors) in an electrical circuit, which is normally zero. If this differential current exceeds a certain value (i.e., a non-zero total current exceeding a specific differential current value or residual current value), they interrupt the circuit.

[0014] Almost all previous residual current circuit breakers feature a summation current transformer, whose primary winding is formed by the conductors of the circuit and whose secondary winding outputs the sum of the currents (or a representation of the differential current), which is used directly or indirectly to interrupt the electrical circuit.

[0015] For this purpose, two or more conductors, usually the outgoing and return conductors or phase conductors and neutral conductor in a single-phase AC network, or all three phase conductors or all three phase conductors and the neutral conductor in a three-phase AC network, are passed through a current transformer, which usually has a ring-shaped core made of ferromagnetic material. Only the differential current is converted, i.e., a current that differs from the outgoing and return currents.

[0016] 3

[0017] Current flows from the conductors. Normally, the total current in an electrical circuit is zero. This allows fault currents to be detected.

[0018] If, for example, current flows to earth on the energy sink or consumer side, this is referred to as a fault current or leakage current. A fault occurs, for instance, when an electrical connection exists between a phase conductor of the electrical circuit and earth. This can happen, for example, if a person touches the phase conductor. In this case, part of the electric current does not flow back via the neutral conductor as usual, but instead flows through the person and earth. This fault current can then be detected using a summation current transformer, since the sum of the incoming and outgoing currents (the difference in magnitude) is not zero. A relay or a holding magnet release, for example, with an associated mechanism, interrupts the circuit, e.g., at least one, part, or all of the conductors.Residual current circuit breakers for detecting alternating residual currents are generally known from the publication DE 4432643 A1.

[0019] The main function of residual current circuit breakers is to protect people from electric currents (electric shock) and to protect equipment, machines or buildings from fire caused by electrical insulation faults.

[0020] If the residual current circuit breaker or its summation current transformer is designed in such a way that the secondary-side energy of the summation current transformer is sufficient to actuate a tripping unit or an interrupting unit or a trip, then such residual current circuit breakers are called mains voltage independent.

[0021] If auxiliary energy is required or used for the tripping circuit, which is usually generated by a power supply unit provided in the residual current device, such residual current devices are called mains voltage dependent.

[0022] Mains voltage-dependent residual current circuit breakers (RCCBs) contain a power supply unit to power the residual current detection mechanism (mains voltage-independent RCCBs do not). These power supplies are necessary, for example, to detect residual currents in DC networks, mixed DC / AC networks, or in circuits with high frequencies.

[0023] Protective switching devices with an electronic interruption unit are relatively new developments. These feature a semiconductor-based electronic interruption unit. This means that the electrical current flow in the low-voltage circuit is interrupted via semiconductor components.

[0024] 4

[0025] respectively semiconductor switches that interrupt the electrical current flow or can be switched to conductivity. Protective switching devices with an electronic interruption unit also frequently have a mechanical disconnect contact system, in particular with disconnect characteristics according to relevant standards for low-voltage circuits, wherein the contacts of the mechanical disconnect contact system are connected in series with the electronic interruption unit, i.e., the current of the low-voltage circuit to be protected is carried through both the mechanical disconnect contact system and the electronic interruption unit.

[0026] The present invention relates in particular to low-voltage alternating current circuits with an alternating voltage, usually a time-dependent sinusoidal alternating voltage with frequency f. The time dependence of the instantaneous voltage value u(t) of the alternating voltage is given by the equation:

[0027] u(t) = U * sin (2TT * f * t)

[0028] described. Whereby:

[0029] u(t) = instantaneous voltage value at time t

[0030] U = Amplitude of the voltage

[0031] A harmonic alternating voltage can be represented by the rotation of a phasor whose length corresponds to the amplitude (U) of the voltage. The instantaneous displacement is the projection of the phasor onto a coordinate system. One oscillation period corresponds to one full rotation of the phasor, and its full angle is 2πt (2t) or 360°. The angular frequency is the rate of change of the phase angle of this rotating phasor. The angular frequency of a harmonic oscillation is always 2πt times its frequency, i.e.,

[0032] w = 2TT*f = 2TT / T = angular frequency of the alternating voltage

[0033] (T = period of the oscillation)

[0034] The angular frequency (w) is often preferred over 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 2TT:

[0035] u(t) = II * sin(wt)202420316

[0036] 5

[0037] In the case of angular frequencies that are not constant over time, the term instantaneous angular frequency is also used.

[0038] In the case of a sinusoidal, especially time-constant, alternating voltage, the time-dependent value of the angular velocity w and the time t corresponds to the time-dependent angle cp(t), which is also called the phase angle cp(t).

[0039] This means the phase angle cp(t) periodically traverses the range O...2TT or 0°...360°. This means the phase angle periodically assumes a value between 0 and 2TT or 0° and 360° (cp = n*(0...2TT) or cp = n*(0°...360°), due to periodicity; simplified: (p = O...2TT or (p = 0°...360°).

[0040] The instantaneous voltage value u(t) is therefore the instantaneous value of the voltage at time t; that is, in the case of a sinusoidal (periodic) alternating voltage, the value of the voltage at the phase angle cp (cp = 0...2TT or cp = 0°...360°, of the respective period). In contrast to the instantaneous voltage value or instantaneous current value, there is the RMS value of the voltage or RMS value of the current. In electrical engineering, the RMS value is understood to be the root mean square (RMS) value of a time-varying physical quantity. The term is preferably applied to alternating quantities.

[0041] The effective value of a variable quantity is equal to the value of an equivalent quantity that would dissipate the same electrical energy in a resistive load over a representative period of time. An equivalent statement can be made for electrical power. The effective value depends on both the peak value and the waveform. In English, the effective value is denoted by RMS (abbreviation for Root Mean Square).

[0042] Modern residual current circuit breakers (RCCBs) feature a test circuit with a test button that can be pressed to check the functionality of the residual current detection. The test circuit is typically implemented by connecting a resistor to the test button, which is typically wired between, for example, the phase and neutral conductors and bypasses (but does not pass through) the residual current transformer. This generates a test current, equivalent to a simulated residual current, which is then detected by the residual current transformer. However, this test cannot accurately determine whether the residual current transformer is faulty, as the test button always generates residual currents that are higher than the residual current limits.

[0043] 6

[0044] Furthermore, the conversion principle of the summation current transformer is susceptible to direct currents (DC currents), which can disrupt the transformer's operation (transmission behavior). This is also referred to as "blinding." Causes can include DC currents within the load current, small DC leakage currents, or other effects.

[0045] Manually pressing the test button only tests whether a trigger works in general, but not whether it still triggers correctly in case of a fault.

[0046] The object of the present invention is to improve a protective switching device of the type mentioned above, in particular to ensure or guarantee the correct detection of fault currents in a protective switching device with a summation current transformer, and to ensure safety in the circuit for personal protection.

[0047] This problem is solved by a protective switching device with the features of claim 1, and by a method according to claim 15.

[0048] According to the invention, a protective switching device for residual current protection for low-voltage alternating current circuits is provided, comprising:

[0049] - a housing with at least two mains-side connections and at least two load-side connections, for connecting at least two conductors of the low-voltage alternating current circuit, in particular for connecting a neutral conductor and a phase conductor of the low-voltage alternating current circuit,

[0050] - a mechanical isolating contact unit which can be switched by a closed state of the contacts to allow current flow in the conductors of the low-voltage alternating current circuit or by an open state of the contacts to prevent current flow by means of galvanic isolation of the conductors of the low-voltage alternating current circuit,

[0051] - that the mechanical disconnect contact unit is connected in series with an electronic interruption unit,

[0052] - that the electronic interruption unit can be switched by semiconductor-based switching elements into a high-resistance state of the switching elements to prevent current flow in at least one conductor or a low-resistance state of the switching elements to allow current flow in the low-voltage alternating current circuit, in particular that the electronic interruption unit is arranged in the phase conductor,

[0053] - a differential current sensor unit for determining the magnitude of a fault current (differential current) of the at least two conductors of the low-voltage alternating current circuit connected to the protective switching device, 202420316

[0054] 7

[0055] - a test circuit which is realized by an electrical connection between the at least two conductors of the low-voltage alternating current connected to the protective switching device within the protective switching device, wherein this electrical connection is routed past the differential current sensor unit,

[0056] - a control unit connected to the mechanical disconnect contact unit, the electronic interrupt unit and the differential current sensor unit,

[0057] and is designed such that if the magnitude of the fault current exceeds fault current limits or fault current time limits (i.e., if a fault current of a certain magnitude is present for a certain duration), current flow is prevented. According to the invention, the protective switching device is designed such that the test circuit has a switch that can be controlled (exclusively) by the control unit (i.e., the controllable switch can only be closed electronically by the control unit), with which the test circuit can be closed or opened by the control unit.Furthermore, the protective switching device is designed such that, for testing the fault current detection, the control unit closes the test circuit by means of the controllable switch, so that a test current of a certain magnitude (and frequency) is passed through the test circuit by the differential current sensor unit, so that (additionally) a fault current of the same magnitude is induced and detected in the differential current sensor unit.

[0058] The protective switching device uses the differential current sensor unit to detect the magnitude of a first fault current before the test circuit is closed and the magnitude of a second fault current when the test circuit is closed.

[0059] According to the invention, a deviation of the magnitude of the test current flowing through the test circuit from the magnitude of the fault current component in the second fault current caused by the closed test circuit is determined. The magnitude of the deviation thus determined is compared with a first threshold value, and if this threshold is exceeded:

[0060] a) information is signaled, or( / and)

[0061] b) an avoidance of current flow is initiated.

[0062] The currents and current levels mentioned refer specifically to RMS values. This has the advantage that changes in the detection or transmission behavior can be identified. For example, a "blinding" of the differential current sensor unit, particularly the summation current transformer, can be detected. This "blinding" can be caused, for example, by DC components in the low-voltage AC circuit or by saturation effects in the (magnetic material of the) summation current transformer. This allows for the advantageous signaling of an incorrect fault current detection.

[0063] 8

[0064] Advantageous embodiments of the invention are specified in the dependent claims and in the exemplary embodiment.

[0065] In an advantageous embodiment of the invention, the deviation is determined by subtracting the magnitude of the first fault current from the magnitude of the second fault current. The first difference thus determined (magnitude of the second fault current minus magnitude of the first fault current equals first difference) is subtracted from the magnitude of the test current flowing through the test circuit.

[0066] The magnitude of the second difference determined in this way (the magnitude of the test current flowing through the test current circuit minus the first difference equals the second difference) is compared as a deviation with the first threshold value, and if it is exceeded:

[0067] a) information is signaled, or( / and)

[0068] b) an avoidance of current flow is initiated.

[0069] This has the particular advantage that a simple initial calculation method for determining the deviation is provided.

[0070] In an advantageous embodiment of the invention, the deviation is determined by subtracting the magnitude of the test current flowing through the test circuit from the magnitude of the second fault current. The third difference thus determined (magnitude of the second fault current minus the magnitude of the test current flowing through the test circuit equals the third difference) is subtracted from the magnitude of the first fault current. The magnitude of the second difference thus determined (magnitude of the first fault current minus the third difference equals the second difference) is compared as the deviation with the first threshold value, and if this threshold is exceeded: a) information is signaled, or ( / and)

[0071] b) an avoidance of current flow is initiated.

[0072] This has the particular advantage that a simple alternative or second calculation method for determining the deviation is provided.

[0073] In an advantageous embodiment of the invention, the current flow is prevented by a high-resistance state of the switching elements of the electronic interruption unit.

[0074] This has the particular advantage of quickly interrupting the current flow, since very fast switching operations can be achieved with an electronic interruption unit. 202420316

[0075] 9

[0076] In an advantageous embodiment of the invention, the current flow is avoided by an open state of the contacts of the mechanical isolating contact unit.

[0077] This has the particular advantage of creating galvanic isolation, thus ensuring a safe condition in the low-voltage alternating current circuit for personal protection.

[0078] In an advantageous embodiment of the invention, the protective switching device is designed such that the method of preventing current flow is configurable.

[0079] This has the particular advantage that a user can set whether the protective switching device, after automatically detecting a deviation (fault), signals information (warning) (e.g., displays or transmits) or initiates the prevention of current flow, e.g., through a high-resistance state (standby state) or open contacts (galvanic isolation).

[0080] In an advantageous embodiment of the invention, an optical display unit is provided which is connected to the control unit, such that the signaling of the information is carried out by the optical display unit.

[0081] This has the particular advantage that it can be easily implemented on the protective switching device by, for example, a light emitter diode or light-emitting diode (LED) as (part of the) optical display unit, thus enabling direct display.

[0082] In an advantageous embodiment of the invention, a communication unit is provided which is connected to the control unit, such that the signaling of the information takes place via wireless (or conductorless) communication.

[0083] This has the particular advantage that, for example, a central monitoring or management system can be provided, in which the information is displayed, so that a replacement of a faulty protective switching device can be initiated.

[0084] In an advantageous embodiment of the invention, an input unit is provided, wherein the protective switching device is designed such that, after the current flow has been prevented by a high-resistance state of the switching elements of the electronic interruption unit, a low-resistance state of the switching elements of the electronic interruption unit is achieved by an acknowledgement.

[0085] This has the particular advantage that, if maximum system availability is desired, the energy supply can be provided even if the protective switching device is faulty.

[0086] 10

[0087] This can be enabled if desired and confirmed (emergency operation). This means that operation is permitted in which the protective switching device only trips in the event of fault currents exceeding, for example, 30 mA.

[0088] In an advantageous embodiment of the invention, the test is carried out periodically using the test circuit which can be closed by the control unit.

[0089] This has the particular advantage that automatic, continuous monitoring of the protective switching device is possible, especially without manually pressing a test button. With conventional residual current circuit breakers, regular testing by qualified personnel is required, particularly according to DGIIV regulations. This requirement is eliminated by the invention, thus saving time and effort.

[0090] For example, the recurring check can be performed once a day, once an hour, every 13 hours (deliberate shift throughout the day), once a week, etc., with all intermediate values ​​being possible and disclosed.

[0091] In an advantageous embodiment of the invention, the test is carried out by means of the test circuit which can be closed by the control unit by means of a specific pulse pattern with which the controllable switch is switched on or off.

[0092] This has the particular advantage that the fault current component caused by the closed test circuit could be separated from the load current component in the second fault current.

[0093] In an advantageous embodiment of the invention, the test is carried out for a limited time using the test circuit that can be closed by the control unit. In particular, the test can, for example, have a maximum duration of 30 ms, 20 ms or 10 ms.

[0094] In particular, the magnitude of the test current flowing through the test circuit should be greater than the resolution of the fault current measurement; for example, with a resolution of 1...2 mA, the minimum magnitude of the test current flowing through the test circuit should be a multiple thereof, for example, 2...3...4...5...10 mA.

[0095] In particular, the maximum magnitude of the test current flowing through the test current circuit should be determined by the magnitude of the rated residual current (residual current limit), for example 30 mA, of the low-voltage AC circuit / protective switching device to be protected.

[0096] The differential current sensor unit is designed in particular to be able to detect a multiple (e.g., 3, 4, 5, or 6 times) of the nominal residual current (residual current limit), e.g., 150 mA for 30 mA.

[0097] 11

[0098] This has the particular advantage that it is possible to remain within the tripping limits defined by standards (current-time limits), so that even if the test current flowing through the test circuit is present (and possible addition with permanently present (smaller) fault currents or technically caused leakage currents) a current flow is not prevented (no tripping).

[0099] In an advantageous embodiment of the invention, the mechanical disconnect contact unit is assigned to the load-side connection.

[0100] This has the particular advantage that an architecture of the protective switching device supporting the invention is provided, since the control unit and the electronic interruption unit continue to be supplied with energy, regardless of whether the contacts are closed or open.

[0101] In an advantageous embodiment of the invention, the contacts of the mechanical isolating contact unit can be opened, but not closed, by the control unit. This has the particular advantage of providing a particularly reliable protective switching device. Thus, the contacts cannot be accidentally closed due to a fault, such as a software error.

[0102] The mechanical disconnect contact unit is advantageously operable via a mechanical handle. Switching on and off using the electronic interruption unit is not (directly) possible at the protective switching device.

[0103] In an advantageous embodiment of the invention, the contacts of the mechanical disconnect contact unit have a release functionality such that the contacts are opened by the control unit even if the mechanical handle is blocked.

[0104] This has the particular advantage that a high level of safety of the protective switching device is ensured, since the contacts could not be closed manually in the event of an excessively high fault current.

[0105] In an advantageous embodiment of the invention, the protective switching device is designed such that, with the test circuit closed, the determination of whether the magnitude of the fault current exceeds the fault current limits or fault current time limits is possible.

[0106] The magnitude of the fault current determined by the differential current sensor unit is reduced by the magnitude of the fault current component in the second fault current caused by the closed test circuit, so that a current flow is avoided by the magnitude of the 202420316

[0107] 12

[0108] The fault current component caused by the closed test current circuit is avoided in the second fault current.

[0109] This means that the determination of whether the magnitude of the fault current exceeds the fault current limits or fault current time limits when the test circuit is closed is carried out by reducing the magnitude of the second fault current determined by the differential current sensor unit by the magnitude of the fault current component in the second fault current caused by the closed test circuit.

[0110] This has the particular advantage that current flow is prevented by the magnitude of the fault current component caused by the closed test circuit in the second fault current. This means that a test of the residual current detection of the protective switching device can be carried out without interrupting the low-voltage AC circuit. If the detection error becomes too large, current flow can be prevented to protect personnel.

[0111] In an advantageous embodiment of the invention, the test circuit comprises a test impedance, in particular a (test) resistance, a (test) capacitance, a (test) inductance, or a combination thereof. A combination refers in particular to a series or parallel connection of a resistor, capacitance, or inductance. This has the particular advantage that the test current flowing through the test circuit can be individually adapted (dimensioned and controlled) for different test cases by means of the test resistance, the test capacitance, the test inductance, or a combination thereof.

[0112] According to the invention, a corresponding method for a protective switching device for residual current protection for low-voltage alternating current circuits with at least two conductors is claimed, with

[0113] - a mechanical isolating contact unit which can be switched by a closed state of the contacts to allow current flow in the conductors of the low-voltage alternating current circuit or by an open state of the contacts to prevent current flow by means of galvanic isolation of the conductors of the low-voltage alternating current circuit,

[0114] - that the mechanical disconnect contact unit is connected in series with an electronic interruption unit,

[0115] - that the electronic interruption unit can be switched by semiconductor-based switching elements into a high-resistance state of the switching elements to prevent current flow in at least one conductor or a low-resistance state of the switching elements to allow current flow in the low-voltage alternating current circuit,202420316

[0116] 13

[0117] - a differential current sensor unit that determines the magnitude of a fault current (RMS values) of at least two conductors of the low-voltage alternating current circuit,

[0118] - that the magnitude of the fault current is compared with a fault current limit or fault current time limit,

[0119] that if the fault current limit or fault current time limit is exceeded, a current flow prevention is initiated,

[0120] - that a test circuit is provided which is realized by an electrical connection between the at least two conductors of the low-voltage alternating current connected to the protective switching device within the protective switching device, wherein this electrical connection is routed past the differential current sensor unit.

[0121] According to the invention, to test the fault current detection, the test circuit is closed by the protective switching device, so that a test current of a specific magnitude, and in particular also of a specific frequency, is passed by the differential current sensor unit through the test circuit, so that an (additional) fault current of the same magnitude is induced and detected in the differential current sensor unit. The protective switching device detects the magnitude of a first fault current before the test circuit is closed and the magnitude of a second fault current when the test circuit is closed. A deviation of the magnitude of the test current flowing through the test circuit from the magnitude of the fault current component induced by the closed test circuit in the second fault current is determined. The magnitude of the deviation thus determined is compared with a first threshold value, and if this threshold is exceeded:

[0122] a) information is signaled, or ( / and)

[0123] b) an avoidance of current flow is initiated.

[0124] The corresponding procedure offers the same advantages.

[0125] In an advantageous embodiment of the procedure, the deviation is determined as described above or below.

[0126] In an advantageous embodiment of the method, the current flow is prevented by a high-resistance state of the switching elements of the electronic interruption unit.

[0127] In an advantageous embodiment of the method, the current flow is prevented by an open state of the contacts of the mechanical isolating contact unit. 202420316

[0128] 14

[0129] In an advantageous embodiment of the method, the way in which the current flow is avoided can be configured.

[0130] In an advantageous embodiment of the method, the information is signaled visually.

[0131] In an advantageous embodiment of the method, the information is signaled wirelessly.

[0132] In an advantageous embodiment of the method, the test is carried out repeatedly using the test circuit that can be closed by the control unit.

[0133] In an advantageous embodiment of the method, the test is carried out using a specific pulse pattern via the test circuit which can be closed by the control unit.

[0134] In an advantageous embodiment of the method, the test of the test circuit closed by the control unit is time-limited. Specifically, by a test with a maximum duration of 10 ms, or a maximum of 20 ms, or a maximum of 30 ms; any intermediate value is possible and disclosed.

[0135] In an advantageous embodiment of the method, when the test circuit is closed, the magnitude of the fault current determined by the differential current sensor unit is reduced by the magnitude of the fault current component in the second fault current caused by the closed test circuit in order to determine whether the magnitude of the fault current has exceeded the fault current limits or fault current time limits.

[0136] This advantageously avoids the flow of current due to the magnitude of the fault current component caused by the closed test circuit in the second fault current.

[0137] According to the invention, a corresponding computer program product for a protective switching device is claimed. The computer program product comprises commands which, when the program is executed by a microcontroller (for example, in the control unit), cause it to support or carry out the aforementioned method (or the aforementioned embodiments), in particular to close the test circuit for checking the fault current detection using the control unit, and to determine the magnitude of a first fault current.

[0138] 15

[0139] to detect the closing of the test circuit and the magnitude of a second fault current when the test circuit is closed, to determine a deviation between the magnitude of the test current flowing through the test circuit and the magnitude of the fault current component in the second fault current caused by the closed test circuit, to compare the magnitude of the deviation thus determined with a first threshold value and, if this threshold is exceeded: a) to signal information or (and)

[0140] b) to initiate the prevention of a current flow.

[0141] According to the invention, a corresponding computer-readable storage medium on which the computer program product is stored is claimed.

[0142] According to the invention, a corresponding data carrier signal, which transmits the computer program product, is claimed.

[0143] All embodiments, both in dependent form relating back to patent claim 1 or

[0144] 15, as well as referring back only to individual features or combinations of features of patent claims, in particular also a reference of the pending arrangement claims to the independent method claim, effect an improvement of a protective switching device, in particular to ensure or guarantee the correct detection of fault currents in a protective switching device with a summation current transformer, and to ensure an improvement in the safety of persons in low-voltage alternating current circuits.

[0145] The described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more easily understood in connection with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the drawing.

[0146] The drawing shows:

[0147] Figure 1 shows a first schematic representation of a protective switching device,

[0148] Figure 2 shows a second schematic representation of a protective switching device,

[0149] Figure 3 shows a third schematic representation of a protective switching device,

[0150] Figure 4 shows an electrical distribution system with a protective switching device, 202420316

[0151] 16

[0152] Figure 5 shows a first current-time diagram of the magnitude of a measured fault current,

[0153] Figure 6 shows a second current-time diagram of the magnitude of a measured fault current.

[0154] Figure 7 shows a third current-time diagram of the magnitude of a measured fault current.

[0155] Figure 1 shows a representation of a protective switching device SG for the protection of a low-voltage alternating current electrical circuit with a housing GEH, comprising:

[0156] - an enclosure (GEH) with at least two mains-side connections and at least two load-side connections, for connecting at least two conductors of the low-voltage alternating current circuit,

[0157] The at least two network-side connections have, for example:

[0158] - (at least) one mains-side phase conductor connection LG,

[0159] - a mains-side neutral conductor connection NG,

[0160] The at least two load-side connections have, for example:

[0161] - (at least) one load-side phase conductor connection LL,

[0162] - a load-side neutral conductor connection NL.

[0163] The phase conductor connections LG, LL are intended for a phase conductor L of the low-voltage alternating current circuit; the neutral conductor connections NG, NL are intended for a neutral conductor N of the low-voltage alternating current circuit.

[0164] A power source is typically connected to the grid-side connections LG, NG / the grid side. A load is typically connected to the load-side connections LL, NL / the load side.

[0165] The housing GEH contains a (two-pole) mechanical disconnect contact unit MK with load-side connection points APLL, APNL and network-side connection points APLG, APNG, wherein a load-side connection point APNL is provided for the neutral conductor N, a load-side connection point APLL for the phase conductor L, a network-side connection point APNG for the neutral conductor N, and a network-side connection point APLG for the phase conductor L.

[0166] The load-side connection points APNL, APLL are connected to the load-side neutral and phase conductor connections NL, LL, wherein the (two-pole) mechanical isolating contact unit MK has a closed state of one neutral conductor contact KKN (for the neutral conductor NI) and (at least) one phase conductor contact KKL (for the phase conductor LI) for current flow in the low-voltage AC circuit or an open state of neutral conductor contact KKN and phase conductor contact KKL for current-flow-preventing galvanic isolation in the low-voltage AC circuit, 202420316

[0167] 17

[0168] so that the opening of contacts KKN, KKL to prevent current flow or the closing of contacts KKN, KKL to allow current flow in the low-voltage alternating current circuit can be switched,

[0169] - a (single-pole) electronic interrupting unit EU,

[0170] which is connected in series with the mechanical isolating contact unit MK in the phase conductor LI, with a mains-side connection point EUG, which is electrically connected to the mains-side phase conductor connection LG, and

[0171] a load-side connection point EUL which is electrically connected to the network-side connection point APLG of the mechanical disconnect contact unit MK, wherein the electronic interruption unit EU has a high-resistance state of the switching elements to prevent current flow or a low-resistance state of the switching elements to allow current flow in the phase conductor LI by means of (not shown) semiconductor-based switching elements,

[0172] - a differential current sensor unit ZCT, for determining the magnitude of a fault current (or differential current) of the neutral conductor and phase conductor of the low-voltage alternating current circuit (caused by leakage currents (of the phase conductor LI or (and) neutral conductor NI to earth or the protective conductor PE)),

[0173] In the example shown in Figure 1, the differential current sensor unit ZCT is arranged between the electronic interruption unit EU and the mechanical disconnect contact unit MK. Alternatively, it can be arranged between the mechanical disconnect contact unit MK and the load-side neutral and phase conductor connections NL, LL, or alternatively between the electronic interruption unit EU and the network-side connections NG, LG. The differential current sensor unit ZCT determines the magnitude of the fault current (fault current refers to the differential current; in the case of residual current circuit breakers according to the prior art, fault current refers to the differential current; fault current does not refer to an overcurrent or short-circuit current (between phase conductor and neutral conductor) in the low-voltage AC circuit) of the conductors of the low-voltage AC circuit that pass through the protective switching device (and are to be protected).In the example of a single-phase alternating current circuit with neutral conductor NI and phase conductor LI.

[0174] The differential current sensor unit ZCT can be a classic summation current transformer. The primary side of the summation current transformer is formed by the conductors of the low-voltage AC circuit (in the example, phase conductor LI and neutral conductor NI) (primary winding = first winding). The secondary side (secondary winding = second winding) of the summation current transformer is connected to a control unit SE.

[0175] 18

[0176] - a test circuit PS, which in the example of a single-phase alternating current circuit, as shown in Figure 1, is realized by an electrical connection between the phase conductor LI and the neutral conductor NI, wherein the electrical connection is routed past the differential current sensor unit ZCT.

[0177] The test circuit PS is connected on the one hand (in the example according to Figure 1) between the electronic interruption unit EU and the differential current sensor unit ZCT with the phase conductor LI and on the other hand between the mechanical disconnect contact unit MK and the differential current sensor unit ZCT with the neutral conductor NI.

[0178] Alternatively, the test circuit PS can be connected to the phase conductor LI or the neutral conductor NI at other positions.

[0179] According to the invention, the test circuit PS has a switch S2 connected to a control unit SE and controllable (exclusively) by it.

[0180] Additionally, a current sensor unit Sl can be provided to determine the magnitude of the current in the low-voltage alternating current circuit, which is arranged in particular in the phase conductor (current path of the phase conductor or phase conductor current path).

[0181] The control unit SE is connected to the differential current sensor unit ZCT, the (optional) current sensor unit Sl, the mechanical isolating contact unit MK, the electronic interruption unit EU and the test circuit PS, specifically to the controllable switch S2 of the test circuit.

[0182] The protective switching device SG is designed in such a way that if the magnitude of the fault current is exceeded above fault current limits or fault current time limits, a current flow prevention is initiated.

[0183] According to the invention, the protective switching device is designed such that, in order to test the fault current detection of the protective switching device, the control unit SE closes the test circuit PS by means of the controllable switch S2, so that a test current of a certain magnitude is passed through the test circuit PS by the differential current sensor unit ZCT and thus an (additional) fault current of a (normally the same) magnitude is caused and detected in the differential current sensor unit ZCT.

[0184] According to the invention, the protective switching device SG detects the magnitude of a first fault current before the test circuit PS is closed and the magnitude of a second fault current when the test circuit PS is closed. A deviation of the magnitude of the test current flowing through the test circuit PS from the magnitude of the current flowing through the closed test circuit PS is detected.

[0185] 19

[0186] The fault current component caused by the PS circuit in the second fault current is determined. The magnitude of the deviation thus determined is compared with a first threshold value, and if this threshold is exceeded:

[0187] a) information is signaled, or

[0188] b) an avoidance of current flow is initiated.

[0189] This test determines the deviation of the test current flowing through test circuit PS from the magnitude of the fault current component in the second fault current caused by the closed test circuit PS. If the test current flowing through test circuit PS does not correspond to the fault current component detected in the second fault current, and this deviation is too large (i.e., exceeds the first threshold), this leads to the aforementioned reaction (signaling of the information or (and) prevention of current flow).

[0190] Ideally, the deviation is zero, meaning the magnitude of the fault current component in the second fault current caused by the closed test circuit PS corresponds exactly to the magnitude of the test current flowing through the test circuit PS. Normally, the deviation is zero, close to zero, or very small, i.e., within the limits of measurement accuracy.

[0191] The threshold value can depend on the level of the residual current limit or residual current time limit. For example, with a limit of 30 mA for personal protection, the threshold value could be 10% of the limit value. From 10% onwards, this includes all higher values, e.g., 11%, 12%, ..., 15%, ..., 20%, ..., 25%, ..., 30%, ...

[0192] That means at 30 mA and 10% the threshold would be 3 mA. That means the threshold can be, for example, 3 ... (7) ... 10 mA.

[0193] This allows changes in the detection behavior or transmission behavior to be identified.

[0194] The currents and current levels mentioned refer specifically to effective values.

[0195] The deviation can be determined by subtracting the magnitude of the first fault current from the magnitude of the second fault current, and then subtracting the resulting first difference (magnitude of the second fault current minus magnitude of the first fault current equals the first difference) from the magnitude of the test current flowing through the test circuit. Alternatively, the deviation can be determined by subtracting the magnitude of the test current flowing through the test circuit from the magnitude of the second fault current, and then subtracting the resulting third difference (magnitude of the second fault current minus magnitude of the test current flowing through the test circuit equals the third difference) from the magnitude of the first fault current.

[0196] 20

[0197] Additionally, the protective switching device SG can be designed such that, if current limits and / or current time limits are exceeded (i.e., if a current of a certain magnitude is present in the circuit for a certain period of time), the current flow in the low-voltage AC circuit is interrupted for one of the current levels determined by the current sensor unit Sl. Exceeding current limits and / or current time limits refers to overcurrents or short-circuit current (in the phase conductor / neutral conductor) in the low-voltage AC circuit (line protection). The interruption of current flow can be achieved by a high-resistance state of the electronic interruption unit EU and / or an open state of the contacts of the mechanical disconnect contact unit MK.

[0198] In this example, the mechanical disconnect contact unit MK is located on the load side, while the electronic interruption unit EU is located on the network side.

[0199] The grid side, containing the energy source, is normally live. An electrical load is typically connected to the load side.

[0200] This has the advantage that no other parts or components (especially live ones) are located between the contacts of the mechanical disconnect contact unit MK / load-side connection points APLL, APNL of the mechanical disconnect contact unit MK and the two load-side terminals LL, NL. This architecture and design ensures that, when contacts KKL, KKN are open, there is never any voltage present at the load-side terminals LL, NL. This increases the safety of the protective switching device in the low-voltage AC circuit.

[0201] In contrast, other architectures where the mechanical isolation contact unit MK is located on the network side often have (non-galvanically isolated) electronic units in front of the load-side connection.

[0202] The protective switching device can be designed such that the voltage across the electronic interruption unit EU can be determined. This means that the magnitude of the first voltage between the network-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU can be determined or is determined.

[0203] In the example shown in Figure 1, a first voltage sensor unit SU1 is provided, connected to the control unit SE, which determines the voltage level between the grid-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU.

[0204] 21

[0205] When measuring the voltage using the first voltage sensor unit SU1, the voltage across the series connection of the electronic interruption unit EU and the current sensor Sl can alternatively be determined, as shown in Figure 1. The current sensor unit Sl has a very low internal resistance, so that the determination of the voltage level is not affected or only negligibly affected.

[0206] Advantageously, a second voltage sensor unit SU2 can be provided, which determines the level of voltage between the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG.

[0207] The electronic interruption unit EU is arranged in the phase conductor LI (Figure 1). The mains-side connection point APNG for the neutral conductor of the mechanical disconnect contact unit MK is connected to the mains-side neutral conductor connection NG of the housing GEH. This connection is routed through the differential current sensor unit ZCT, for example, its summation current transformer, as shown in Figure 1.

[0208] The protective switching device SG is advantageously designed such that the contacts KKL, KKN of the mechanical isolating contact unit MK can be opened but not closed by the control unit SE, which is indicated by an arrow OEF from the control unit SE to the mechanical isolating contact unit MK.

[0209] The mechanical isolating contact unit MK can be operated via a mechanical handle HH on the protective switching device SG to manually open or close contacts KKL and KKN. Both contacts can be switched simultaneously, for example. The mechanical handle HH indicates the switching state (open or closed) of the contacts of the mechanical isolating contact unit MK on the protective switching device SG.

[0210] The mechanical disconnect contact unit MK is advantageously designed such that (manual) closing of the contacts by the mechanical handle HH is only possible after an enable signal. This is also indicated by the arrow from the control unit SE to the mechanical disconnect contact unit MK. That is, the contacts KKL and KKN of the mechanical disconnect contact unit MK can only be closed by the handle HH when the enable signal (from the control unit SE) is present. Without the enable signal, the handle HH can be actuated, but the contacts cannot be closed ("permanent slip").

[0211] 22

[0212] The protective switching device SG has a power supply NT, for example, a switched-mode power supply. In particular, the power supply NT is intended for the control unit SE, as indicated by a connection between the power supply NT and the control unit SE in Figure 1. The power supply NT is (on the other hand) connected to the mains-side neutral conductor terminal NG and the mains-side phase conductor terminal LG. A fuse SS, in particular a cartridge fuse, or (and) a switch can advantageously be provided in the connection to the mains-side neutral conductor terminal NG (and / or phase conductor terminal LG).

[0213] According to the invention, the power supply unit (NT) is normally continuously supplied with energy, specifically from the mains-side connections. It is optionally protected by the fuse (SS) or can be switched off by the switch.

[0214] The low-voltage AC circuit can be a three-phase AC circuit with a neutral conductor and three phase conductors. The protective switching device SG can be configured as a three-phase variant and, for example, have additional line-side and load-side phase conductor connections. Electronic interruption units EU and contacts of the mechanical disconnect contact unit MK, according to the invention, are provided between these additional line-side and load-side phase conductor connections. The respective conductors (three phase conductors L1, L2, L3, neutral conductor N) are routed through the differential current sensor unit ZCT.

[0215] Similarly, current sensor units and voltage measurements (e.g., by means of initial voltage sensor units) may be provided.

[0216] A mechanical disconnect contact unit (MK) is a standard-compliant disconnect contact unit, conforming to relevant DIN and VDE standards (e.g., DIN EN 60947-3). The contacts must maintain certain (standard-compliant) minimum distances. Furthermore, the mechanical disconnect contact unit (MK) features a (standard-compliant) release function, meaning the contacts cannot be closed again by the handle (HH) if they are opened by the control unit (SE). Conversely, the contacts can be opened by the control unit (SE) even if the handle (HH) is blocked (for the closed position).

[0217] High resistance refers to a state in which only a negligible current flows. Specifically, high resistance values ​​greater than 1 kilohm, preferably greater than 10 kilohms, 100 kilohms, 1 megahm, 10 megahms, 100 megahms, 1 gigahms, or higher.

[0218] 23

[0219] Low resistance refers to a state in which the current value specified on the protective switching device SG could flow.

[0220] In particular, low resistance values ​​are meant to be less than 10 ohms, preferably less than 1 ohm, 100 milliohms, 10 milliohms, 1 milliohm or less.

[0221] The test of the fault current detection using the test circuit PS, which can be closed by the control unit SE and which can lead to the prevention of current flow (if the deviation is too large, i.e., if the first threshold is exceeded), can, for example, be designed such that the prevention of current flow is achieved by a high-resistance state of the switching elements of the electronic interrupt unit EU. Alternatively or additionally, the prevention of current flow can be achieved by an open state of the contacts of the mechanical disconnect contact unit MK.

[0222] Alternatively or additionally, the protective switching device (SG) can be designed such that the method of current flow prevention is configurable. This means that the protective switching device (SG) can be configured to determine whether current flow prevention is achieved through a high-resistance state of the switching elements of the electronic interruption unit (EU) or through an open state of the contacts of the mechanical disconnecting contact unit (MK). Alternatively, this configurability or the specific configuration can be predefined by the firmware. Alternatively, the method of current flow prevention can be configured / set via a wireless or wired connection, for example, using a mobile computer or a higher-level management system.

[0223] The protective switching device SG or the control unit SE can have an optical display unit AE. The optical display unit AE can be part of the control unit SE or connected to the control unit SE, so that the information is signaled by the optical display unit. The optical display unit AE can have a (manual) first input unit on the protective switching device SG for (manual) acknowledgment of states on the protective switching device SG.

[0224] The protective switching device SG or the control unit SE can have a communication unit COM. The communication unit COM can be part of the control unit SE or connected to the control unit SE, so that the information signaling is carried out by the communication unit COM.

[0225] The communication unit COM can in particular be a wireless communication unit, so that the signaling of information takes place via wireless communication.

[0226] 24

[0227] The COM communication unit can have a (manual) second input unit on the protective switching device SG for (manual) acknowledgment of states on the protective switching device SG. Acknowledgment can also be performed (wired and / or wirelessly) via the COM communication unit. Furthermore, the COM communication unit can have a display function.

[0228] With the communication unit COM or the first or second input unit, after preventing current flow due to a high-resistance state of the switching elements of the electronic interruption unit EU, especially if the deviation is too large, i.e., if the first threshold is exceeded, a low-resistance state of the switching elements of the electronic interruption unit EU can be initiated by an acknowledgment.

[0229] The residual current detection test of the protective switching device using the test circuit PS, which can be closed by the control unit SE, can be performed repeatedly, e.g., periodically. The test using the test circuit PS, which can be closed by the control unit SE, can also be performed for a limited time, as already described.

[0230] In one embodiment of the protective switching device SG, the controllable switch S2 can be switched on or off with a specific pulse pattern.

[0231] The electronic interruption unit EU can comprise semiconductor devices such as bipolar transistors, field-effect transistors (FETs), insulated-gate bipolar transistors (IGBTs), metal-oxide-layer field-effect transistors (MOSFETs), or other (self-commutated) power semiconductors. In particular, IGBTs and MOSFETs are especially well-suited for the protective switching device SG according to the invention due to their low forward resistance, high junction resistance, and good switching characteristics.

[0232] The term "mechanical disconnect contact unit MK" refers specifically to a (standard-compliant) disconnect function, implemented by the disconnect contact unit MK. The following points are included with the disconnect function:

[0233] - Minimum air gap according to standard (voltage-dependent) (minimum contact spacing), - Contact position indicator of the contacts of the mechanical disconnect contact unit MK or the mechanical disconnect contact system,

[0234] -Opening the mechanical disconnect contact system MK is always possible (no blockage of the disconnect contact system - especially by the handle HH, free release),

[0235] meant. 202420316

[0236] 25

[0237] For the purposes of the invention, the standards DIN EN 60947 and IEC 60947 are relevant, for example, for the separator function and its properties, and are hereby referenced.

[0238] The protective switching device (SG) can be designed as a DIN rail-mountable device with a width of, for example, 2 TE (module units) with two-pole connections (phase conductor L, neutral conductor N). In electrical installations and control cabinet construction, the width of built-in devices such as protective switching devices, miniature circuit breakers (MCBs), residual current devices (RCDs), etc., is specified in module units, abbreviated TE. The width of one module unit is approximately 18 mm. According to the standard DIN 43880: 1988-12, the installation width of the devices should be between 17.5 and 18.0 mm, or be calculated by multiplying this dimension by 0.5 or an integer multiple thereof, i.e.:

[0239] kx 0.5 x 18 mm or kx 0.5 x 17.5 mm (with k = 1, 2, 3, ...). For example, a single-pole circuit breaker, according to current technology, has a width of 1 module. The components of electrical distribution boards are designed according to DIN 43871 "Small distribution boards for built-in devices up to 63 A" to match the modular units, e.g., the width of DIN rails.

[0240] According to the invention, the protective switching device SG, in particular the control unit SE, is designed such that if the magnitude of the fault current exceeds the fault current limits or fault current time limits, current flow is prevented, in particular by a high-resistance state of the switching elements of the electronic interruption unit EU when the isolating contacts are closed. The fault current limits or fault current time limits can be limits according to relevant standards, such as DIN EN 61008-1. For example, 30 mA for personal protection in Europe in a 230-volt low-voltage AC circuit, 6 mA for personal protection in North America, 300 mA for fire protection (230 volts RMS).

[0241] The standard DIN EN 61008-1, Residual current circuit breakers without built-in overcurrent protection (RCCBs) for domestic and similar applications, in particular Part 1: General requirements, is included here by reference. For example, this standard specifies that a 30 mA residual current circuit breaker (RCD) must trip within 300 ms at the rated residual current (30 mA). At twice the rated residual current (60 mA), it must trip within 150 ms. At five times the rated residual current, or greater, it must trip within 40 ms.

[0242] In one embodiment of the invention, the protective switching device is designed such that, with the test circuit closed, the level of the fault current is used to determine whether the fault current exceeds the fault current limit values ​​or fault current time limit values.202420316

[0243] 26

[0244] The magnitude of the fault current determined by the differential current sensor unit is reduced by the magnitude of the fault current component in the second fault current caused by the closed test circuit, thus preventing current flow due to the magnitude of the fault current component in the second fault current. In one embodiment of the invention, this enables uninterrupted testing of the low-voltage AC circuit by the protective switching device.

[0245] The protective switching device SG or the test circuit PS can have a test impedance Z. tesexhibiting t, which in the example according to Figure 1 is connected in series with the controllable switch S2. In particular, the test impedance Ztest can be a (test) resistance, a (test) capacitance, a (test) inductance, or a combination thereof. A combination specifically refers to a series or (and) parallel connection of resistance, capacitance, or inductance.

[0246] This allows the test current flowing through the test circuit to be individually adapted (dimensioned and controlled) for different test cases by means of the test resistor, the test capacitance, the test inductance or a combination of these.

[0247] The protective switching device (SG), in particular the control unit (SE), may include a microcontroller (microprocessor) running a computer program. This program contains instructions that, when executed, cause the microcontroller to perform a specific action or test on the protective switching device. The control unit (SE) with microprocessor may have memory. A tripping curve with specific fault current limits or fault current time limits may be stored in the control unit (SE), particularly in its memory. The tripping curve can be retrieved from memory. The values ​​of the tripping curve are compared with the determined fault current magnitude in the control unit (SE) (e.g., using the microprocessor). If the limit is exceeded, a corresponding current-preventing trip is initiated.

[0248] The computer program product can be advantageously stored on a computer-readable storage medium, such as a USB stick, CD-ROM, etc., to allow, for example, an upgrade to an extended version.

[0249] The computer program product can alternatively also be advantageously transmitted via a data carrier signal. 202420316

[0250] 27

[0251] Figure 2 shows a representation according to Figure 1, with the difference that the optical display unit AE is part of the control unit SE. Furthermore, the communication unit COM is part of the control unit SE. Additionally, the test circuit PS is connected on one side between the mechanical isolating contact unit MK and the differential current sensor unit ZCT to the phase conductor LI, and on the other side between the mains-side neutral conductor connection NG and the differential current sensor unit ZCT to the neutral conductor NI.

[0252] In one embodiment of the invention, a test button PT is further provided, which is connected to the control unit SE, as shown in Figure 2. The test button PT is part of the protective switching device SG and can be actuated on the protective switching device SG. This test button PT can correspond to a conventional test button of a residual current circuit breaker. A test of the differential current sensor unit ZCT according to the invention can be manually initiated by means of the test button PT.

[0253] Figure 3 shows a representation according to Figure 1 or Figure 2, with the difference that the optical display unit AE is connected to the control unit SE. Furthermore, the communication unit COM is connected to the control unit SE. Additionally, the test circuit PS is connected on the one hand between the current sensor unit Sl and the electronic interrupt unit EU to the phase conductor LI, and on the other hand between the mechanical disconnect contact unit MK and the differential current sensor unit ZCT to the neutral conductor NI.

[0254] In the illustrated embodiment shown in Figure 3, the electronic interruption unit EU can be switched to a high-resistance state for the duration of the test procedure to prevent current flow, so that no first fault current (load current) flows during the test. Due to the high-resistance state of the electronic interruption unit EU during the test, the second fault current does not contain a load current component. With correctly functioning fault current detection, the test current flowing through the test circuit PS should, in this case, correspond to the second fault current generated by the closed test circuit PS in the differential current sensor unit ZCT.For this embodiment of the invention, the advantage is that the high-resistance state of the electronic interruption unit EU during the test process calibrates the combination of differential current sensor unit ZCT, control unit SE and test circuit PS, and allows a defect or offset error in the fault current detection to be detected. Furthermore, the test can be simplified because the determination of the deviation can be simplified, since the202420316.

[0255] 28

[0256] The first fault current does not need to be determined (no difference needs to be calculated between the first and second fault current).

[0257] Figure 4 shows a schematic representation of an electrical power distribution system with a protective switching device SG according to the invention. On the grid side, a grid-side feed-in phase conductor L1.E, a grid-side feed-in neutral conductor NE, and a protective conductor PE are provided. The grid side of the protective switching device SG is connected to the grid-side feed-in phase conductor L1.E and the grid-side feed-in neutral conductor NE. Between these, a (pre-connected) fuse F1 and a (pre-connected) first circuit breaker F2 are provided in the phase conductor, as shown in Figure 4.

[0258] A load-side sub-distribution phase conductor L1.S and a load-side sub-distribution neutral conductor NS are connected to the load side of the protective switching device SG. Furthermore, the protective conductor PE of the supply side is connected to the load side, as shown in Figure 4.

[0259] In this example, a socket outlet SDV with an electrical load VBR is connected to the load-side phase conductor L1.S and the load-side neutral conductor NS of the sub-distribution board. A second circuit breaker F4 is installed in the phase conductor of this connection. The socket outlet SDV is also connected to the protective earth conductor PE. The socket outlet SDV may have an electrical connection (electrical bridge) between the neutral conductor and the protective earth conductor PE.

[0260] The terms grid-side feed-in phase conductor L1.E, grid-side feed-in neutral conductor NE, load-side sub-distribution phase conductor L1.S, and load-side sub-distribution neutral conductor NS are sometimes used synonymously with phase conductor and neutral conductor, or abbreviated as such. A qualified electrician knows what each term means and how it is understood.

[0261] A current iioad flows through the consumer VBR via phase conductors and neutral conductors. This current is protected by fuse F1, the first circuit breaker F2, and the second circuit breaker F4 – and advantageously also by the protective switching device SG, with current sensor unit Sl. This could potentially eliminate the need for the first circuit breaker F2 and / or the second circuit breaker F4.

[0262] The diagram shows a person (HUM) touching the phase conductor between socket (SDV) and load (VBR). A phase-side leakage current (if.i_) flows through person HUM to earth (earth symbol). 202420316

[0263] 29

[0264] In the event of a potential difference between the neutral conductor N and the protective conductor PE, a neutral-side leakage current / neutral-side fault current if.N would flow, as indicated in Figure 4.

[0265] The protective switching device SG has a summation current transformer that detects the magnitude of the fault current between the two conductors (LI and NI) of the low-voltage network.

[0266] A test of the fault current detection according to the invention can be carried out as described above and below.

[0267] Figure 5 shows a current-time diagram where the magnitude of a (measured) fault current L.meas is in mA (l A Figure 5 shows the current kmeas.vT on the vertical y-axis / ordinate as a function of a time t in ms (t [ms]) on the abscissa. According to Figure 5, a first fault current kmeas.vT of 0 mA is measured from the origin to the first time t0. At the first time t0, the control unit SE closes the test circuit PS by means of the controllable switch S2, so that a test current l flows through the test circuit PS. AA test current of 10 mA is passed by the differential current sensor unit ZCT for a duration of 20 ms, i.e., until the second time point to +2 0 ms. This means that for a duration of 20 ms, i.e., from the first time point to to the second time point to +2 0 ms, a second fault current l is measured. A , me as@test (with the test circuit PS closed) is generated or measured at (normally) the same level of 10 mA in the differential current sensor unit ZCT. After the second time point, i.e., after the test current flowing through the test circuit PS has reached l A , tes If t is no longer present, the first fault current l will again be A , m eas,vT (with test circuit PS open) measured at 0 mA.

[0268] That is, from the first time point to to the second time point to + 20 ms, i.e., for the duration of the test (20 ms in the example), the determined second fault current l is, in the example according to Figure 5, where no fault current flows (magnitude of the first fault current 0 mA). A , me as@test (with closed test circuit PS) equals the magnitude of the test current flowing in the test circuit l A , tes t, in this example 10 mA.

[0269] Figure 6 shows a diagram according to Figure 5, with the difference that the case where there is already a (non-critical) fault current I A The diagram shows a first fault current of 5 mA flowing in the low-voltage AC circuit to be protected. This means that a first fault current flows in the low-voltage AC circuit to be protected, the magnitude of which is less than the fault current limit or fault current time limit.

[0270] In Figure 6, the first fault current l flows A , meas,vT at a level of 5 mA (corresponds to I A as t at an altitude of 5 mA) from the origin of the coordinate system to the first time point to and is also recorded at this altitude 202420316

[0271] 30

[0272] or measured. At the first time t0, the control unit SE closes the test circuit PS by means of the controllable switch S2, so that a test current l flows through the test circuit PS. A A test current of 10 mA is passed by the differential current sensor unit ZCT for a duration of 20 ms, i.e., until the second time point to +2 0 ms. That is, for a duration of 20 ms, i.e., from the first time point to to the second time point to +2 0 ms, assuming the fault current detection is functioning correctly (and the differential current sensor unit ZCT is functioning correctly), the sum of the first fault current lA.meas.vT (5 mA) and the test current l flowing through the test circuit PS is measured. Ä , test (10 mA) is detected, i.e. the determined second fault current lA,meas@test (with closed test circuit PS) has a level of 15 mA (5 mA + 10 mA), as shown in Figure 6.

[0273] After the second point in time, i.e., after the test current I A.test flowing through the test circuit PS is no longer present, the first fault current lA,meas,vT (with the test circuit PS open) is again equal to the amount of the flowing fault current I. A ,iast is detected or measured at 5 mA.

[0274] In Figures 5 and 6, a case is shown in which the fault current detection works correctly / the differential current sensor unit ZCT or combination of differential current sensor unit ZCT and control unit SE works correctly.

[0275] Figure 7 shows a diagram corresponding to Figure 6, with the difference that a detection error is present. According to Figure 7, a (non-critical) fault current I flows. AThe fault current in the low-voltage AC circuit to be protected is again 5 mA. A A current of 5 mA flows continuously, analogous to Figure 6.

[0276] However, according to Figure 7, the first fault current lA,meas,vT is only recorded or measured at a level of 2 mA (instead of 5 mA) from the origin of the coordinate system to the first time to.

[0277] This means the magnitude of the fault current is being measured incorrectly.

[0278] At the first point in time, the control unit SE closes the test circuit PS by means of the controllable switch S2, so that a test current l flows through the test circuit PS. A ,test at a level of 10 mA for a duration of 20 ms is passed by the differential current sensor unit ZCT, i.e. until the second time point to +2Oms.

[0279] With correctly functioning fault current detection, a second fault current lA,meas@test of 2 mA + 10 mA = 12 mA should be detected in this case (taking into account the offset error of 3 mA), or more accurately, 5 mA + 10 mA = 15 mA. However, according to Figure 7, the differential current sensor unit ZCT only detects a second fault current lA,meas@test (with the test circuit PS closed) of 6 mA.

[0280] 31

[0281] This suggests a faulty fault current detection, i.e., the differential current sensor unit ZCT or combination of differential current sensor unit ZCT (possibly with measurement processing) and control unit SE is not working properly (faultily).

[0282] After the second point in time, i.e., after the test current I flowing through the test circuit PS Ä If the test is no longer available, the first fault current will again be l A,meas,vT (with test circuit PS open) at the level of the flowing fault current of (faulty) 2 mA detected or measured.

[0283] Figures 5 and 6 show fault current waveforms when the fault current detection system is functioning correctly. Figure 7 shows a fault current waveform when the fault current detection system is malfunctioning.

[0284] According to the invention, as indicated in Figures 5 to 7, the differential current sensor unit ZCT detects the magnitude of the first fault current lA.meas.vT before the test current is applied and the magnitude of the second fault current lA,meas@test when the test current is applied. The magnitude of the first fault current lA,meas,vT is subtracted from the magnitude of the second fault current lA,meas@test. The first difference l thus determined D ifri is determined by the magnitude of the test current flowing through the test circuit PS l A The test result was subtracted. The amount of the second difference thus determined is lD iff2 is compared as a deviation with a first threshold value SW1. This is represented mathematically below, where the reference symbols are also used as formula symbols.

[0285] lA,meas@test " lA,meas,vT — loiffl

[0286] iDiffl - lA.test = I Diff2

[0287] | I DifT2 | > SW1

[0288] This calculation can also be rearranged mathematically (equivalently) so that:

[0289] lA,meas@test " lA.test — I Diff3

[0290] lDiff3 - lA,meas,vT - Ioiff2

[0291] | l Di fT2 | > SW1202420316

[0292] 32

[0293] That is, it can also be equivalent to the magnitude of the test current I flowing through the test circuit PS. Ä The third difference determined in this way is subtracted from the magnitude of the second fault current l. Diff3 is subtracted from the magnitude of the first fault current L.meas.vT. The second difference l is calculated analogously. D iff2 determined. The amount of the determined second difference l D iff2 is then compared as a deviation with the first threshold SW1.

[0294] It is essential to determine the deviation between the magnitude of the test current flowing through test circuit PS and the magnitude of the fault current component in the second fault current caused by the closed test circuit PS. If the test current flowing through test circuit PS does not correspond to the fault current component detected in the second fault current, which is caused by the closed test circuit PS, and this deviation is too large, i.e., the second difference l D If iff2 exceeds the first threshold SW1, this triggers a reaction.

[0295] If the first threshold SW1 is exceeded,

[0296] a) information is signaled, for example by the optical display unit AE or (and) by the communication unit COM

[0297] or

[0298] b) an avoidance of current flow is initiated, for example by a high-resistance state of the switching elements of the electronic interruption unit EU (alternatively by an open state of the contacts of the mechanical isolating contact unit MK).

[0299] The second difference l D iff2 is the deviation, which ideally is zero. This means that the magnitude of the fault current component in the second fault current caused by the closed test current circuit PS corresponds exactly to the magnitude of the test current flowing through the test current circuit PS. Normally, the deviation is zero, close to zero, or very small, i.e., within the limits of measurement accuracy.

[0300] The first threshold SW1 can be a value in the range of 1 ... 3 ... 5 ... 7 ... 9 to 10 mA, depending on the design, tolerance threshold, and application (any intermediate value is possible and disclosed). (see also above) In the example shown in Figure 7, a first threshold SW1 of 3 to 5 mA would be practical.

[0301] This allows changes in the detection or transmission behavior to be identified. The currents and current levels mentioned in the example refer specifically to RMS values. 202420316

[0302] 33

[0303] The invention is described further below, albeit in slightly different terms. Currently, the detection of the magnitude of a fault current by a differential current sensor unit (ZCT), i.e., differential current detection, is typically implemented for residual current protection using a so-called summation current transformer (also referred to as a differential current transformer). The conductors to be protected in the low-voltage AC circuit are routed through this summation current transformer in the form of a primary winding; that is, usually in a two-pole protective switching device (SG), the phase conductor (internally LI) and the neutral conductor (internally NI), or several or all conductors in multi-pole devices. The magnitude of the fault current is determined via magnetic coupling by means of the summation current transformer, which is made of ferromagnetic material, using the secondary winding, so that the control unit (SE) receives the magnitude of the fault current, i.e., differential current information.This may initiate the prevention of a current flow, i.e., a triggering.

[0304] The summation current transformer physically works with alternating currents, i.e., with current changes over time.

[0305] This current transformer principle, using a summation current transformer, is susceptible to direct currents (DC currents). DC currents interfere with the operation of the summation current transformer and the differential current sensor unit (ZCT), affecting its transmission behavior. This can cause the summation current transformer to become "blind," consequently impairing the determination of the magnitude of a fault current by the differential current sensor unit (ZCT). Causes of DC currents can include (unwanted or randomly occurring) DC currents in the low-voltage AC circuit, or DC leakage currents resulting from various effects.

[0306] If a magnetic transformer (summation current transformer with ferromagnetic material) is used to detect (differential) fault currents, it exhibits known problems, such as saturation effects due to DC currents, susceptibility to interference from stray fields, or asymmetries in its construction. Many factors can disrupt the accurate detection of the magnitude of a fault current (differential current). Almost all of these factors result in the fault current not being correctly detected in the event of a fault, and consequently, the device failing to trigger a fault alarm. Such a situation reduces safety and should therefore be avoided.

[0307] According to the invention, the protective switching device SG has a control unit SE and a test circuit PS, consisting of a controllable 202420316 connected to the control unit SE.

[0308] 34

[0309] Switch S2 and a test impedance Z tesThe control unit SE, or rather its integrated microprocessor (pC), can actuate the controllable switch S2 and thus open or close the test circuit PS. The test current flowing through the test circuit PS depends on the test impedance Ztest and the measured mains voltage and can also be adjusted by a pulse pattern controlled by the microprocessor at the controllable switch S2. Since the test circuit PS is implemented within the protective switch SG via an electrical connection between at least two conductors of the low-voltage alternating current connected to the protective switch SG, and also passes by the differential current sensor unit ZCT, an (additional) fault current of (normally the same) magnitude as the test current flowing in the test circuit PS is generated and detected in the differential current sensor unit ZCT.

[0310] The fault current l measured with the PS test circuit closed A ,meas can be sent to the SE control unit for evaluation.

[0311] Test algorithms in the SE control unit can detect early on whether the residual current monitoring, in particular the differential current sensor unit ZCT, is functioning correctly or whether the transmission behavior is faulty. In the event of faulty residual current monitoring, a dangerous situation can be prevented.

[0312] The test current is, for example, introduced in such a way that the control unit SE (or the microcontroller contained therein) can separate it from an already flowing (non-critical) fault current kiast in the low-voltage AC circuit, e.g. by repeatedly switching the test circuit PS on and off (pulse pattern). According to the present invention, this fault current is factored out.

[0313] The SE control unit can determine the transmission behavior of the residual current detection. If the residual current detection (or its transmission behavior) is incorrect or faulty, a deviation from the undisturbed (known) detection behavior (or transmission behavior) can also be determined.

[0314] If a fault is detected in the residual current detection (in the transmission behavior), the protective device (SG) can automatically signal (report) this via a corresponding indicator (AE) or a communication unit (COM). This allows the operator to be warned early of a potential fault in the tripping behavior of the protective device (SG) or the residual current detection. This increases safety in the low-voltage AC circuit (of the protected electrical lines).

[0315] 35

[0316] Depending on the configuration, the protective switching device SG can, after detecting the fault, only display or report it, or additionally switch to a standby (high impedance) or off state (open contacts) to further increase safety.

[0317] After acknowledgment, it would be possible to go from standby (high impedance) back to an ON state (low impedance).

[0318] The test can be performed automatically according to a recurring time sequence or due to an event (e.g. switching on, switching off, overvoltage event, change in operating temperature, test button pressed).

[0319] A purely electromechanical residual current device (RCD, e.g., type A) can only verify whether the residual current detection is functioning at all. It cannot, however, detect whether the integrated summation current transformer is faulty (since the test button generates residual currents that are always greater than 30 mA). This only tests whether tripping is generally possible, but not whether it will actually trip correctly in the event of a fault.

[0320] The present invention describes an electronic protective switching device SG which detects the "blinding" and warns the user accordingly, or switches off (high resistance) or disconnects (open contacts).

[0321] A completely new test concept for a protective switching device SG is presented.

[0322] Although the invention has been illustrated and described in detail by the exemplary embodiment, the invention is not limited by the disclosed examples and other variations can be derived from them by the person skilled in the art without leaving the scope of protection of the invention.

Claims

202420316 36 Patent claims 1. Protective switching device (SG) for residual current protection for low-voltage alternating current circuits, comprising: - an enclosure (GEH) with at least two mains-side connections and at least two load-side connections, for connecting at least two conductors of the low-voltage alternating current circuit, - a mechanical isolating contact unit (MK) which can be switched by a closed state of the contacts to allow current flow in the conductors of the low-voltage alternating current circuit or by an open state of the contacts to prevent current flow by means of galvanic isolation of the conductors of the low-voltage alternating current circuit, - that the mechanical disconnect contact unit (MK) is connected in series with an electronic interruption unit (EU), - that the electronic interruption unit (EU) can be switched by semiconductor-based switching elements into a high-resistance state of the switching elements to prevent current flow in at least one conductor or a low-resistance state of the switching elements to allow current flow in the low-voltage alternating current circuit, - a differential current sensor unit (ZOT) for determining the magnitude of a fault current of the at least two conductors of the low-voltage alternating current circuit connected to the protective switching device (SG), - a test circuit (PS) which is realized by an electrical connection between the at least two conductors of the low-voltage alternating current connected to the protective switching device (SG) within the protective switching device, wherein this electrical connection is routed past the differential current sensor unit (ZCT), - a control unit (SE) connected to the mechanical disconnect contact unit (MK), the electronic interruption unit (EU) and the differential current sensor unit (ZCT), designed in such a way that, if the magnitude of the fault current is exceeded above fault current limits or fault current time limits, a current flow prevention is initiated, characterized by that the test circuit (PS) has a switch (S2) controllable by the control unit (SE) with which the test circuit (PS) can be closed or opened by the control unit (SE), that the protective switching device (SG) is designed in such a way, 202420316 37 that, to test the fault current detection, the control unit (SE) closes the test circuit (PS) by means of the controllable switch (S2), so that a test current of a certain magnitude is passed through the test circuit (PS) at the differential current sensor unit (ZCT), so that a fault current of a certain magnitude is induced and detected in the differential current sensor unit (ZCT), that the protective switching device (SG) detects the magnitude of a first fault current before the test circuit (PS) is closed and the magnitude of a second fault current when the test circuit (PS) is closed, that a deviation of the magnitude of the test current flowing through the test circuit (PS) from the magnitude of the fault current component caused by the closed test circuit (PS) in the second fault current is determined, that the amount of the deviation thus determined is compared with a first threshold value and if it is exceeded: a) information is signaled, or b) an avoidance of current flow is initiated.

2. Protective switching device (SG) according to claim 1, characterized by that the prevention of current flow is achieved through a high-resistance state of the switching elements of the electronic interruption unit (EU).

3. Protective switching device (SG) according to claim 1 , characterized by that the prevention of current flow is achieved by an open state of the contacts of the mechanical isolating contact unit (MK).

4. Protective switching device (SG) according to claim 1, 2 or 3, characterized by that the protective switching device (SG) is designed in such a way that the method of preventing current flow is configurable.

5. Protective switching device (SG) according to claim 1, 2, 3 or 4, characterized by that an optical display unit (AE) is provided which is connected to the control unit (SE) such that the signaling of the information is carried out by the optical display unit (AE). 202420316 38 6. Protective switching device (SG) according to one of the preceding patent claims, characterized by that a communication unit (COM) is provided which is connected to the control unit (SE) such that the signaling of the information is carried out by wireless communication.

7. Protective switching device (SG) according to one of the preceding patent claims, characterized by that the test is carried out repeatedly using the test circuit (PS) that can be closed by the control unit (SE).

8. Protective switching device (SG) according to one of the preceding patent claims, characterized by that the controllable switch (S2) is switched on or off with a specific pulse pattern.

9. Protective switching device (SG) according to one of the preceding patent claims, characterized by that the mechanical disconnect contact unit (MK) is assigned to the load-side connection.

10. Protective switching device (SG) according to one of the preceding patent claims, characterized by that the contacts of the mechanical isolating contact unit (MK) can be opened by the control unit (SE), but not closed.

11. Protective switching device (SG) according to one of the preceding patent claims, characterized by that, when the test circuit (PS) is closed, the magnitude of the fault current determined by the differential current sensor unit (ZCT) is reduced by the magnitude of the fault current component in the second fault current caused by the closed test circuit (PS) when determining whether the fault current exceeds the fault current limits or fault current time limits, thus preventing current flow by reducing the magnitude of the fault current component in the second fault current. 202420316 39 12. Protective switching device (SG) according to one of the preceding patent claims, characterized by that the test circuit (PS) has a test impedance (Z) tes t) exhibits, in particular that the test impedance (Ztest) is a test resistance, a test capacitance, a test inductance or a combination thereof.

13. Protective switching device (SG) according to one of the preceding patent claims, characterized by that the deviation is determined in such a way, - that the magnitude of the first fault current is subtracted from the magnitude of the second fault current, - the first difference determined in this way is subtracted from the magnitude of the test current flowing through the test circuit (PS), - the amount of the second difference determined in this way is compared as a deviation with the first threshold.

14. Protective switching device (SG) according to one of the preceding claims 1 to 13, characterized in that, that the deviation is determined in such a way, - that the magnitude of the test current flowing through the test current circuit (PS) is subtracted from the magnitude of the second fault current, - the third difference determined in this way is subtracted from the magnitude of the first fault current, - the amount of the second difference determined in this way is compared as a deviation with the first threshold value.

15. Method for a protective switching device (SG) for residual current protection for low-voltage alternating current circuits with at least two conductors, with - a mechanical isolating contact unit (MK) which can be switched by a closed state of the contacts to allow current flow in the conductors of the low-voltage AC circuit or by an open state of the contacts to prevent current flow by means of galvanic isolation of the conductors of the low-voltage AC circuit, - that the mechanical isolating contact unit (MK) is connected in series with an electronic interrupting unit (EU),202420316 40 - that the electronic interruption unit (EU) can be switched by semiconductor-based switching elements into a high-resistance state of the switching elements to prevent current flow in at least one conductor or a low-resistance state of the switching elements to allow current flow in the low-voltage alternating current circuit, - a differential current sensor unit (ZCT) that determines the magnitude of a fault current in at least two conductors of the low-voltage alternating current circuit, - that the magnitude of the fault current is compared with a fault current limit or fault current time limit, that if the fault current limit or fault current time limit is exceeded, a current flow prevention is initiated, - that a test circuit (PS) is provided, which is realized by an electrical connection between the at least two conductors of the low-voltage alternating current connected to the protective switching device (SG) within the protective switching device, wherein this electrical connection is routed past the differential current sensor unit (ZCT), characterized by that, to test the fault current detection, the test circuit (PS) is closed by the protective switching device, so that a test current of a certain magnitude is passed through the test circuit (PS) by the differential current sensor unit (ZCT), so that a fault current of a certain magnitude is induced and detected in the differential current sensor unit (ZCT), that the magnitude of a first fault current before the test circuit (PS) is closed and the magnitude of a second fault current with the test circuit (PS) closed is detected, that a deviation of the magnitude of the test current flowing through the test circuit (PS) from the magnitude of the fault current component caused by the closed test circuit (PS) in the second fault current is determined, that the amount of the deviation thus determined is compared with a first threshold value and if it is exceeded: a) information is signaled, or b) an avoidance of current flow is initiated.

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