Protective circuit breaker and method

Abstract

The invention relates to a protective circuit breaker for protection of an electrical low-voltage circuit, comprising: - a housing with at least one grid-side connection and at least one load-side connection, and - a mechanical separating contact unit which is connected to an electronic interrupter unit in series, wherein - the serial connection is connected to the at least one grid-side connection and to the at least one load-side connection, - the mechanical separating contact unit can be switched by opening contacts in order to prevent a current flow or by closing the contacts for a current flow in the low-voltage circuit, - owing to the semiconductor-based switch elements, the electronic interrupter unit can be switched to a high-ohmic state of the switch elements in order to prevent a current flow or to a low-ohmic state of the switch elements for a current flow in the low-voltage circuit, - the level of the current in the low-voltage circuit, in particular between the grid-side phase conductor connection and the load-side phase conductor connection, is ascertained, - a process for preventing a current flow in the low-voltage circuit is initiated if current thresholds and / or current / time thresholds are exceeded, and - while the contacts of the mechanical separating contact unit are closed and the electronic interrupter unit is switched to a low-ohmic state, the electronic interrupter unit is switched to a high-ohmic state if the current of the low-voltage circuit reaches a level that falls below a first current threshold for a first duration of time.

Description

[0001] Description

[0002] Protective switching device and procedure

[0003] The invention relates to the technical field of a protective switching device for a low-voltage circuit with an electronic interruption unit and a method for a protective switching device for a low-voltage circuit with an electronic interruption unit.

[0004] Low voltage refers to voltages of up to 1000 volts AC or up to 1500 volts DC. Low voltage refers in particular to voltages greater than extra-low voltage, with values ​​of 50 volts AC or 120 volts DC.

[0005] The term low-voltage circuit, network or system refers to circuits with nominal or rated currents of up to 125 amperes, more specifically up to 63 amperes. The term low-voltage circuit particularly refers to circuits with nominal or rated currents of up to 50 amperes, 40 amperes, 32 amperes, 25 amperes, 16 amperes or 10 amperes. The current values ​​mentioned refer in particular to nominal, rated and / or breaking currents, i.e. the maximum current that is normally carried through the circuit or at which the electrical circuit is usually interrupted, for example by a protective device such as a protective switching device, circuit breaker or circuit breaker. The rated currents can be further staggered, from 0.5 A to 1 A, 2 A, 3 A, 4 A, 5 A, 6 A, 7 A, 8 A, 9 A, 10 A, etc. up to 16 A.

[0006] Circuit breakers are long-established overcurrent protection devices used in low-voltage electrical circuits. They protect cables from damage caused by overheating due to excessive current and / or a short circuit. A circuit breaker can automatically disconnect the circuit in the event of an overload and / or short circuit. A circuit breaker is a non-self-resetting fuse element.

[0007] Unlike miniature circuit breakers, circuit breakers are designed for currents greater than 125 A, and in some cases even as low as 63 A. Miniature circuit breakers are therefore simpler and more delicate in design. Miniature circuit breakers typically have a mounting option for mounting on a so-called top-hat rail (support rail, DIN rail, TH35).

[0008] Miniature circuit breakers are electromechanical in design. They contain a mechanical switching contact or shunt release in a housing to interrupt (trip) the electrical current. A bimetallic protective element or bimetallic element is usually used to trip (interrupt) the circuit in the event of a prolonged overcurrent (overcurrent protection) or thermal overload (overload protection). An electromagnetic release with a coil is used for brief 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 devices for arc quenching are provided. There are also connection elements for conductors of the electrical circuit to be protected.

[0009] Protective switching devices with an electronic interruption unit are relatively new developments. These have a semiconductor-based electronic interruption unit. This means that the electrical current flow in the low-voltage circuit is conducted via semiconductor components or semiconductor switches, which interrupt the electrical current flow or can be made conductive. Protective switching devices with an electronic interruption unit also often have a mechanical isolating contact unit, in particular with isolating properties in accordance with the relevant standards for low-voltage circuits. The contacts of the mechanical isolating contact unit are connected in series to the electronic interruption unit, i.e. the current in the low-voltage circuit to be protected is conducted via both the mechanical isolating contact unit and the electronic interruption unit.

[0010] The present invention relates in particular to low-voltage alternating current circuits with an alternating voltage, usually with a time-dependent sinusoidal alternating voltage with the frequency f. The time dependence of the instantaneous voltage value u(t) of the alternating voltage is described by the equation: u(t) = U * sin (2n * f * t). Where: u(t) = instantaneous voltage value at time t

[0011] U = amplitude of the voltage

[0012] A harmonic alternating voltage can be represented by the rotation of a pointer whose length corresponds to the amplitude (U) of the voltage. The instantaneous deflection is the projection of the pointer onto a coordinate system. One oscillation period corresponds to one full rotation of the pointer, and its full angle is 2n (2Pi) or 360°. The angular frequency is the rate of change of the phase angle of this rotating pointer. The angular frequency of a harmonic oscillation is always 2n times its frequency, i.e.: w = 2n*f = 2n / T = angular frequency of the alternating voltage (T = period of the oscillation)

[0013] Often, the specification of the angular frequency (w) is preferred over the frequency (f), since many formulas of oscillation theory can be represented more compactly using the angular frequency due to the occurrence of trigonometric functions whose period is by definition 2n: u (t) U * sin(wt)

[0014] In the case of angular frequencies that are not constant over time, the term instantaneous angular frequency is also used.

[0015] In the case of a sinusoidal, in particular temporally 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 referred to as the phase angle cp ( t ). This means that the phase angle cp ( t ) periodically passes through the range O...2n or 0°...360°. This means that the phase angle periodically assumes a value between 0 and 2n or 0° and 360° (cp = n* (0...2n) or cp = n* ( 0 °...360 ° ) , due to periodicity; in short: cp = O...2n or cp = 0°...360° ).

[0016] The instantaneous voltage value u(t) is therefore the instantaneous value of the voltage at time t, ie in the case of a sinusoidal (periodic) alternating voltage, the value of the voltage at the phase angle cp (cp = 0...2n or cp = 0°...360°, of the respective period).

[0017] The object of the present invention is to improve a protective switching device of the type mentioned above, in particular to achieve greater safety in the electrical low-voltage circuit to be protected by the protective switching device.

[0018] This object is achieved by a protective switching device having the features of patent claim 1, as well as by a method according to patent claim 13.

[0019] According to the invention, a protective switching device for protecting an electrical low-voltage circuit, in particular a low-voltage alternating current circuit, is proposed, comprising:

[0020] - a housing with at least one mains-side connection and at least one load-side connection, both for the low-voltage circuit,

[0021] - a mechanical isolating contact unit connected in series with an electronic interruption unit, the series circuit being connected on the one hand to the at least one mains-side connection and on the other hand to the at least one load-side connection,

[0022] - that the mechanical isolating contact unit can be switched by opening contacts to prevent current flow or closing the contacts to allow current flow in the low-voltage circuit,

[0023] - that the electronic interruption unit can be switched by semiconductor-based switching elements into a high-resistance state of the switching elements to prevent a current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit,

[0024] - a current sensor unit for determining the current level of the low-voltage circuit,

[0025] - a control unit which is connected to the current sensor unit, the mechanical isolating contact unit and the electronic interruption unit, wherein when current and / or current time limit values ​​are exceeded, avoidance of a current flow in the low-voltage circuit is initiated, in particular by a high-resistance state of the switching elements of the electronic interruption unit.

[0026] The protective switching device is designed according to the invention in such a way that the protective switching device is designed in such a way that when the contacts of the mechanical isolating contact unit are closed and the electronic interruption unit is switched to a low-resistance state, the electronic interruption unit is switched to the high-resistance state when the current in the low-voltage circuit falls below a first current threshold, specifically an effective value of the current as the first current threshold, for a first period of time.

[0027] This has the advantage that, when loads are not connected or switched on, an electrical line / cable in the low-voltage circuit is de-energized, thus avoiding an (unnecessary) electric field at the load-side connection. The first current threshold (e.g., effective value) can be less than 10 mA, 5 mA, or 1 mA; any intermediate value is possible and disclosed. Values ​​of up to 1 mA are possible for a voltage-free / field-free condition.

[0028] If standby power consumption is also to be minimized, the current threshold could advantageously be set at higher values, such as 5 mA or 10 mA. This would allow consumers to be switched off at the load-side connections during standby mode to reduce power consumption.

[0029] The first time period can be in the range of minutes. It can be one minute or more than one minute. In particular, it can be more than 2 minutes, 3 minutes, 5 minutes, 10 minutes, 15 minutes, or 30 minutes; any intermediate value is possible and disclosed.

[0030] According to the invention, on the one hand, a voltage-free / field-free state is achieved and the power consumption in the low-voltage circuit is reduced, whereby the safety in the low-voltage circuit is increased.

[0031] Further advantageous embodiments of the invention are specified in the subclaims and in the exemplary embodiment.

[0032] In an advantageous embodiment of the invention, after switching (off) the electronic interruption unit into the high-impedance state, a check is carried out to determine whether a current which is greater than a second current threshold (wherein the second current threshold is in particular an instantaneous value of the current level, which is in particular dependent on the level of the instantaneous value of the voltage at the network-side terminals) could flow.

[0033] If the test is positive, the electronic interruption unit is switched to the low-resistance state.

[0034] This means, for example, that (at least) two mains-side connections can be provided. Furthermore, a voltage sensor unit can be provided to determine the voltage level (in particular instantaneous voltage values) of the low-voltage circuit at the mains-side connections of the protective switching device. The voltage sensor unit can be connected to the control unit.

[0035] By "could flow" (a current that is greater than a second current threshold could flow) is meant, for example, a further current (= third current or third current threshold) which, for example, flows temporarily (phase angle wise / in a phase angle range of the voltage (at the network-side connections) or the current) and whose level allows a conclusion to be drawn about the current flow capability for the second current threshold (in particular an effective value), i.e. whether the second current threshold (effective value) could be exceeded.

[0036] The second current threshold (in particular an effective value, as an alternative to the instantaneous value) is in particular greater than the first current threshold. In particular, it is greater than 10%, 20%, or 30% of the first current threshold, with any intermediate value being possible and disclosed. More specifically, the second current threshold is greater than or equal to 1 mA.

[0037] This has the particular advantage that a restart is carried out in order to detect and supply energy to a (re)connected consumer or a (re)connected consumer.

[0038] In an advantageous embodiment of the invention, the test is performed by periodically switching the electronic interruption unit to the low-resistance state for a second period of time at a first time interval. During the second period of the low-resistance state, a determination is made as to whether a current exceeding the second current threshold could flow (see above: "further / third current"). If the determination is positive, the electronic interruption unit switches to the low-resistance state; otherwise, the periodic switching (to the low-resistance state) continues.

[0039] This means that the load output / at least one load-side connection is tested by briefly switching on / making the electronic interruption unit low-resistance.

[0040] The first time interval is, for example, in the range 500 ms to 1 second or . to 2 seconds, whereby any intermediate value is possible and disclosed .

[0041] The second time period is, for example, less than or equal to 20 ms, in particular less than 10 ms, more particularly less than 3 ms, 2 ms, 1 ms, 800 ps, ​​700 ps or 500 ps, ​​wherein any intermediate value is possible and disclosed.

[0042] This has the particular advantage that a simple testing option is provided, in which the electronic interruption unit is used and is only specifically controlled for the test.

[0043] In an advantageous embodiment of the invention, a voltage sensor unit is provided which is connected to the control unit and which determines the voltage level, in particular instantaneous values ​​of the voltage level, of the low-voltage circuit, in particular at the mains-side connections, specifically between the mains-side neutral conductor connection and the mains-side phase conductor connection. The periodic switching of the electronic interruption unit EU to the low-impedance state occurs when the absolute value of the instantaneous value of the voltage level falls below a first voltage limit, which is in particular less than or equal to 50 volts.

[0044] This has the particular advantage that increased operational safety is achieved, since the test is carried out at a voltage level that is in the range of (protective) extra-low voltage, which is harmless to humans.

[0045] In an advantageous embodiment of the invention, the test is carried out by using an auxiliary voltage, in particular auxiliary alternating voltage, which falls below a first voltage limit, which is in particular less than or equal to 50 volts.

[0046] This has the particular advantage of providing another simple way of testing the reclosure.

[0047] In an advantageous embodiment of the invention, the mechanical isolating contact unit is assigned to the load-side connection(s) and the electronic interruption unit is assigned to the mains-side connection(s).

[0048] This has the particular advantage of providing a structure for a protective switching device in which the protective switching device can function even when the contacts of the mechanical isolating contact unit are open.

[0049] In an advantageous embodiment of the invention, the mechanical isolating contact unit can be operated by a mechanical handle in order to switch the opening or closing of contacts.

[0050] This has the particular advantage that the functionality of a classic circuit breaker is provided.

[0051] In an advantageous embodiment of the invention, the protective switching device is designed in such a way that the contacts of the mechanical isolating contact unit can be opened but not closed by the control unit.

[0052] This has the particular advantage of achieving increased operational reliability, since the contacts cannot be accidentally closed by the control unit.

[0053] In an advantageous embodiment of the invention, the control unit comprises a microcontroller.

[0054] This has the particular advantage that the functions according to the invention for increasing the safety of the low-voltage electrical circuit to be protected can be implemented by an (adaptable) computer program product. Furthermore, modifications and improvements to the function can thereby be individually loaded onto a protective switching device. According to the invention, a corresponding method for a protective switching device for a low-voltage circuit with electronic (semiconductor-based) switching elements with the same and further advantages is claimed.

[0055] The method for a protective switching device for protecting a low-voltage electrical circuit with:

[0056] - a housing with at least one mains-side connection and at least one load-side connection,

[0057] - a mechanical isolating contact unit connected in series with an electronic interruption unit, the series circuit being connected on the one hand to the at least one mains-side connection and on the other hand to the at least one load-side connection,

[0058] - that the mechanical isolating contact unit can be switched by opening contacts to prevent current flow or closing the contacts to allow current flow in the low-voltage circuit,

[0059] - that the electronic interruption unit can be switched by semiconductor-based switching elements into a high-resistance state of the switching elements to prevent a current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit,

[0060] - that the level of the current in the low-voltage circuit, in particular between a mains-side phase conductor connection and a load-side phase conductor connection, is determined,

[0061] - that if current and / or current time limit values ​​are exceeded, an avoidance of current flow in the low-voltage circuit is initiated, in particular by a high-resistance state of the electronic interruption unit,

[0062] - that with the contacts of the mechanical isolating contact unit closed and the electronic interruption unit switched to low resistance, and a current in the low-voltage circuit that falls below a first current threshold for a first period of time, the electronic interruption unit is switched to the high resistance state. Advantageously, after the electronic interruption unit is switched to the high resistance state, a check is carried out to determine whether a current greater than a second current threshold could flow. If the test is positive, the electronic interruption unit is switched to the low resistance state.

[0063] Advantageously, the test is carried out by periodically switching the electronic interruption unit to the low-resistance state for a second period of time at a first time interval. During the second period of the low-resistance state, a determination is made as to whether a current exceeding the second current threshold could flow. If the determination is positive, the electronic interruption unit switches to the low-resistance state; otherwise, the periodic switching to the low-resistance state is continued for the purpose of testing.

[0064] According to the invention, a corresponding computer program product is claimed. The computer program product comprises instructions which, when the program is executed by a microcontroller, cause the microcontroller to support the behavior and the test, in particular to carry out the test in order to achieve greater safety in the low-voltage electrical circuit to be protected by the protective switching device.

[0065] The microcontroller is part of the protective switching device, in particular the control unit.

[0066] According to the invention, a corresponding computer-readable storage medium on which the computer program product is stored is claimed.

[0067] According to the invention, a corresponding data carrier signal which transmits the computer program product is claimed.

[0068] In an advantageous embodiment of the invention, with closed contacts of the mechanical isolating contact unit and low-resistance interruption unit and

[0069] - when a current is detected which exceeds a first current value, in particular when the first current value is exceeded for a first time limit, the electronic interruption unit becomes high-resistance and the mechanical isolating contact unit remains closed,

[0070] - when a current is detected which exceeds a (higher) second current value, in particular for a second time limit, the electronic interruption unit becomes high-resistance and the mechanical isolating contact unit is opened,

[0071] - when the detected current exceeds a (even higher) third current value, the electronic interruption unit becomes high-resistance and the mechanical isolating contact unit is opened.

[0072] This has the particular advantage that a graduated shutdown concept is available for a protective switching device according to the invention at increased currents.

[0073] All embodiments, both in dependent form referring back to patent claim 1 or 13, and referring back only to individual features or combinations of features of patent claims, in particular also a reference of the dependent arrangement claims to the independent method claim, bring about an improvement in a protective switching device, in particular an improvement in the safety of the electrical circuit, and provide a new concept for a protective switching device.

[0074] The described properties, features and advantages of this invention as well as the manner in which these are achieved will become clearer and more clearly understandable in connection with the following description of the embodiments, which are explained in more detail in connection with the drawing.

[0075] The drawing shows: Figure 1 a first representation of a protective switching device,

[0076] Figure 2 shows a second representation of a protective switching device, Figure 3 shows a third representation of a protective switching device, Figure 4 shows a representation with time courses of technical quantities.

[0077] Figure 1 shows a representation of a protective switching device SG for protecting an electrical low-voltage circuit, in particular a low-voltage alternating current circuit, with a housing GEH, comprising:

[0078] - a grid-side neutral conductor connection NG, a grid-side phase conductor connection LG, a load-side neutral conductor connection NL, a load-side phase conductor connection LL of the low-voltage circuit; an energy source is usually connected to the grid side Grid, and a consumer is usually connected to the load side Load;

[0079] - a (two-pole) mechanical isolating contact unit MK with load-side connection points APLL, APNL and line-side connection points APLG, APNG, whereby a load-side connection point APNL is provided for the neutral conductor, a load-side connection point APLL for the phase conductor, a line-side connection point APNG for the neutral conductor, and a line-side connection point APLG for the phase conductor. The load-side connection points APNL, APLL are connected to the load-side neutral and phase conductor connections NL, LL, so that the opening of contacts KKN, KKL to prevent current flow or the closing of the contacts to allow current flow in the low-voltage circuit can be switched.

[0080] - an electronic interruption unit EU, in particular a single-pole one (which in the case of a single-pole version is arranged in particular in the phase conductor), with a mains-side connection point EUG, which is electrically connected to the mains-side phase conductor connection LG, and a load-side connection point EUL, which is electrically connected to the mains-side connection point APLG of the mechanical isolating contact unit MK, wherein the electronic interruption unit has a high-resistance state of the switching elements to prevent a current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit by means of semiconductor-based switching elements,

[0081] - a current sensor unit SI for determining the level of the current in the low-voltage circuit, which is arranged in particular in the phase conductor,

[0082] - a control unit SE which is connected to the current sensor unit SI, the mechanical isolating contact unit MK and the electronic interruption unit EU, whereby if current and / or current time limit values ​​are exceeded, the avoidance of a current flow in the low-voltage circuit is initiated.

[0083] According to the invention, the protective switching device is designed in such a way that, when the contacts of the mechanical isolating contact unit MK are closed and the electronic interruption unit EU is switched to a low-resistance state, the electronic interruption unit EU is switched to a high-resistance state when the current in the low-voltage circuit falls below a first current threshold for a first period of time.

[0084] After switching the electronic interruption unit EU to the high-impedance state, a test is preferably performed to determine whether a current greater than a second current threshold could flow. If the test is positive, the electronic interruption unit EU is switched to the low-impedance state.

[0085] The test can be performed by periodically switching the electronic interruption unit EU to the low-resistance state for a second period of time, at a first time interval. During the second period of the low-resistance state, a determination is made as to whether a current exceeding the second current threshold could flow. If the determination is positive, the electronic interruption unit EU switches to the low-resistance state. Otherwise, the periodic switching (to the low-resistance state) continues.

[0086] Furthermore, a (first) voltage sensor unit SUA can be provided which is connected to the control unit SE and which determines the voltage level, in particular instantaneous values ​​of the voltage level, of the low-voltage circuit, in particular at the mains-side connections LG, NG, specifically between the mains-side neutral conductor connection NG and the mains-side phase conductor connection LG. The periodic switching of the electronic interruption unit EU to the low-impedance state advantageously occurs when the absolute value of the instantaneous value of the voltage level falls below a first voltage limit, which is in particular less than or equal to 50 volts.

[0087] Alternatively, the test can be carried out by using an auxiliary voltage, in particular auxiliary AC voltage, which falls below a first voltage limit, which is in particular less than or equal to 50 volts.

[0088] In general, the mechanical isolating contact unit MK and the electronic interruption unit EU form a series circuit. The series circuit is connected on the one hand to at least one mains-side connection and on the other hand to at least one load-side connection. The mechanical isolating contact unit MK can advantageously be assigned to the load-side connection and the electronic interruption unit EU to the mains-side connection, as shown in Figure 1. The mechanical isolating contact unit MK can be operated by a mechanical handle HH in order to open or close contacts, as with a classic circuit breaker or miniature circuit breaker (MCB).

[0089] The first current threshold can be less than 10 mA or less than 5 mA or less than 1 mA.

[0090] The second current threshold can be greater than the first current threshold. It can be greater than 10%, 20%, or 30% of the first current threshold.

[0091] The first time period can be equal to or greater than one minute. It can be greater than 2 minutes, 3 minutes, 5 minutes, 10 minutes, 15 minutes, or 30 minutes.

[0092] The first time interval can be between 500 ms or 2 seconds (any value possible).

[0093] The second time period may be less than or equal to 20 ms, in particular less than 10 ms, more particularly less than 3 ms, 2 ms, 1 ms, 700 ps or 500 ps.

[0094] The control unit SE can have a microcontroller MP.

[0095] Furthermore, a second voltage sensor unit SUB connected to the control unit SE can be provided, which determines the level of the voltage between the network-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU.

[0096] A measuring impedance ZM can be connected between the mains-side connection points APLG, APNG of the mechanical isolating contact unit MK. The measuring impedance ZM can, for example, be an electrical resistor and / or capacitor. The measuring impedance can also be an inductance. In particular, the measuring impedance can be a series connection or parallel connection of a resistor and / or capacitor and / or inductance. In the example according to Figure 1, the electronic interruption unit EU is single-pole, in the example in the phase conductor. The mains-side connection point APNG for the neutral conductor of the mechanical isolating contact unit MK is connected to the mains-side neutral conductor connection NG of the housing GEH.

[0097] The protective switching device SG is advantageously designed in such a way that the contacts of the mechanical isolating contact unit MK can be opened but not closed by the control unit SE, which is indicated by an arrow from the control unit SE to the mechanical isolating contact unit MK.

[0098] The mechanical isolating contact unit MK can be operated by a mechanical handle HH on the protective switching device SG to manually open or close the contacts KKL, KKN. The mechanical handle HH indicates (specifically through a mechanical connection between the contacts and the handle) the switching state (open or closed) of the contacts of the mechanical isolating contact unit MK on the protective switching device.

[0099] Furthermore, the contact position (or the position of the handle, closed or open) can be transmitted to the control unit SE. The contact position (or the position of the handle) can be determined, for example, using a sensor (POS).

[0100] The mechanical isolating contact unit MK is advantageously designed in such a way that a (manual) closing of the contacts by the mechanical handle is only possible after an enable, in particular an enable signal.

[0101] This is also indicated by the arrow pointing from the control unit SE to the mechanical isolating contact unit MK. This means that the contacts KKL, KKN of the mechanical isolating contact unit MK can only be closed by the handle HH when the release or the release signal is present (from the control unit). Without the release or the release signal, the handle HH can be operated, but the contacts cannot be closed ("permanent slipping").

[0102] The protective switching device SG has a power supply NT, for example a power supply unit. In particular, the power supply NT is provided for the control unit SE, which is 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 connection NG and the mains-side phase conductor connection LG. A fuse SS, in particular a melting fuse, and / or a switch can advantageously be provided in the connection to the mains-side neutral conductor connection NG (and / or phase conductor connection LG).

[0103] Alternatively, the measuring impedance ZM can be connected to the mains-side neutral conductor connection NG via the fuse SS. This advantageously allows a three-pole electronic unit EPART to be implemented, for example as a module, which has three connection points: one neutral conductor connection point and two phase conductor connection points. The electronic unit EPART has, for example, the electronic interruption unit EU, the control unit SE, the power supply NT (in particular including the fuse SS), the current sensor unit SI, the first voltage sensor unit SUA, and optionally the second voltage sensor unit SUB.

[0104] The low-voltage circuit can be a three-phase alternating current circuit, with a neutral conductor and three phase conductors. The protective switching device can be designed as a three-phase variant for this and, for example, have further mains-side and load-side phase conductor connections. Electronic interruption units and current sensor units (if necessary, further first voltage sensor units) according to the invention are provided in a similar manner between the further mains-side and load-side phase conductor connections. The same applies to contacts of the mechanical isolating contact unit. High-resistance means a state in which only a current of negligible magnitude flows. In particular, high-resistance means resistance values ​​greater than 1 kiloohm, preferably greater than 10 kiloohms, 100 kiloohms, 1 megaohm, 10 megaohms, 100 megaohms, 1 gigaohm or greater.

[0105] Low-resistance refers to a condition in which the current value specified on the protective device could flow. Specifically, low-resistance refers to resistance values ​​that are less than 10 ohms, preferably less than 1 ohm, 100 milliohms, 10 milliohms, 1 milliohm, or less.

[0106] In a first variant, the mechanical isolating contact unit MK can provide single-pole interruption. This means that only one conductor (of the two / several conductors), in particular the active conductor or phase conductor, is interrupted, i.e., it has a mechanical contact. The neutral conductor is then contact-free, i.e., the neutral conductor is directly connected.

[0107] If additional active conductors / phase conductors are provided, in a second variant, the phase conductors have mechanical contacts of the mechanical isolating contact unit. The neutral conductor is directly connected in this second variant. For example, in a three-phase AC circuit.

[0108] In a third variant of the mechanical isolating contact unit MK, the neutral conductor also has mechanical contacts, as shown in Figure 1.

[0109] The term mechanical isolating contact unit MK refers in particular to a (standard-compliant) isolating function implemented by the isolating contact unit MK. The isolating function includes the following points: - minimum air gap according to the standard (minimum distance between the contacts), - contact position indicator of the contacts of the mechanical isolating contact unit, - trip-free operation, i.e. actuation to interrupt the contacts of the mechanical isolating contact unit by the handle or control unit is always possible, so that no (permanent) blocking of the contacts in the closed state by the handle is possible.

[0110] The minimum clearance between the contacts of the isolating contact unit is essentially voltage-dependent. Other parameters include the degree of contamination, the type of field (homogeneous, inhomogeneous), and the air pressure or altitude above sea level.

[0111] There are corresponding regulations and standards for these minimum clearances and creepage distances. These regulations specify, for example, the minimum clearance for an inhomogeneous and a homogeneous (ideal) electric field in air for impulse voltage resistance, depending on the degree of pollution. The impulse voltage resistance is the resistance when a corresponding impulse voltage is applied. Only if this minimum length (minimum distance) is present does the isolating contact unit or protective switching device have an isolating function (isolating property).

[0112] For the purposes of the invention, the DIN EN 60947 and IEC 60947 series of standards are relevant for the isolating function and its properties, to which reference is made here.

[0113] The isolating contact unit is advantageously characterized by a minimum clearance between the open isolating contacts in the open position (open position, open contacts) depending on the rated impulse withstand voltage and the degree of pollution. The minimum clearance is in particular between (at least) 0.01 mm and 14 mm. In particular, the minimum clearance is advantageously between 0.01 mm at 0.33 kV and 14 mm at 12 kV, in particular for pollution degree 1 and in particular for inhomogeneous fields.

[0114] Advantageously, the minimum air gap can have the following values: E DIN EN 60947-1 (VDE 0660-100): 2018-06

[0115] Table 13 - Minimum clearances

[0116] The pollution levels and field types correspond to those defined in the standards. This advantageously allows for a standard-compliant protective switching device dimensioned according to the rated impulse withstand voltage.

[0117] In particular, the term mechanical isolating contact unit does not refer to a relay contact.

[0118] Figure 2 shows a diagram according to Figure 1 , with the difference that on the grid side an energy source EQ with a nominal voltage U N of the low-voltage circuit. Furthermore, a consumer or energy sink ES is connected to the load side Load.

[0119] Furthermore, an enable signal is shown for the connection between the control unit SE and the mechanical isolating contact unit MK. The mechanical isolating contact unit MK is shown in the OFF state, i.e., with the KKN and KKL contacts open to prevent current flow.

[0120] The protective switching device SG, for example, operates in principle in such a way that when the contacts of the mechanical isolating contact unit and the low-resistance interruption unit are closed and

[0121] - when a current is detected which exceeds a first current value, in particular when the first current value is exceeded for a first time limit, the electronic interruption unit EU becomes high-resistance and the mechanical isolating contact unit MK remains closed,

[0122] - (or / and) when a current is detected which exceeds a higher second current value, in particular for a second time limit, the electronic interruption unit EU becomes high-resistance and the mechanical isolating contact unit MK is opened,

[0123] - if the current detected exceeds an even higher third current value, the electronic interruption unit becomes high-resistance and the mechanical isolating contact unit MK is opened.

[0124] Figure 3 shows a representation similar to Figure 1 or 2, with the difference that the protective switching device SG is constructed in two parts. It contains an electronic first part EPART, for example on a printed circuit board / printed circuit

[0125] Board .

[0126] The first part EPART can comprise the control unit SE, the first voltage sensor unit SUA, the second voltage sensor unit SUB, the current sensor unit ST, the electronic interruption unit EU, and the power supply NT. Furthermore, the first part can comprise a fuse SS, a switch SCH, the measuring impedance ZM, a temperature sensor TEM (particularly for the electronic interruption unit EU), a communication unit COM, and a display unit DISP. The first part EPART has only three connections:

[0127] - the mains-side phase conductor connection LG,

[0128] - a connection for or to the mains-side phase conductor connection point APLG of the mechanical isolating contact unit MK,

[0129] - a terminal for a connection to the mains-side neutral conductor terminal NG .

[0130] The protective switching device contains a second part MPART, in particular a mechanical one. The second part MPART can have the mechanical isolating contact unit MK, the handle HH, and a release unit EG. Furthermore, the second part can have a positioning unit POS for reporting the position of the contacts of the mechanical isolating contact unit MK to the control unit, as well as the (neutral conductor) connection(s). Further, unspecified units can be provided.

[0131] By dividing the device into two parts, a compact protective switching device according to the invention can be advantageously realized.

[0132] The release unit EG enables the actuation of the contacts of the mechanical isolating contact unit by the handle HH when an enable signal is present. Furthermore, the release unit FG can cause the contacts to open when an opening signal OEF is present. The release unit then acts as a tripping unit.

[0133] Live electrical lines create an electric field. This is the case even when no load is connected or switched on. The protective switching device advantageously ensures that the electrical line and load / energy sink ES on the load side of the protective switching device are de-energized when no (or very little) current is flowing on the load side (no connected load needs to be supplied).

[0134] Advantageously, an electronic protection and switching device is extended for this purpose, for example by an extension in a firmware of a microcontroller MP of the control unit SE, for example by means of a corresponding computer program product.

[0135] Advantageously, the load current of the connected consumers is detected by the (electronic) protective switching device / the current sensor unit / current measurement contained therein. The protective switching device can be parameterized or programmed in such a way that the electronic interruption unit EU is switched to the high-impedance state as soon as the current on the load side Load or Load current 1 L OAD falls below a first current threshold. The connected line on the load side (Load) is then voltage-free and field-free.

[0136] The device then advantageously performs a test or verification function to check whether a current (greater than a second current threshold) could flow again on the load side. This test is performed, for example, by briefly switching the electronic interruption unit EU to the low-impedance state.

[0137] Figure 4 shows an example of such a test pulse. Figure 4 shows representations of various electrical quantities in connection with the above-mentioned designs over time t. In the first upper representation, the nominal voltage U N a sinusoidal alternating voltage is shown over time t. In the second diagram, a test pulse is shown synchronously over time t. The vertical Y-axis of the diagram is labeled SWITCH. Here, for a half-wave of the alternating voltage U N the electronic interruption unit EU is switched on / switched to the low-resistance state.

[0138] The activation can also be shorter (or longer), such as 5 ms, 1 ms, 800 ps, ​​700 ps (20 ms). For example, the electronic interruption unit EU can be activated / switched to the low-impedance state when the instantaneous value of the AC voltage falls below a first voltage limit, such as 50 volts. This ensures that a test pulse is only emitted when the instantaneous value of the mains voltage is below 50 V. This would have the additional advantage of electrical safety.

[0139] The resulting test pulse is shown in the third diagram of the load voltage U L OAD on the load side Load of the protective switching device SG shown over time t as a half-wave of the voltage.

[0140] Furthermore, this test pulse is carried out repeatedly, e.g. once per second. This means that after a consumer ES or load is connected or switched on, the consumer ES is supplied with voltage / energy again within one second. This delay time (or reaction time) can also be changed via the firmware. For example, a customer can choose between a faster reaction of 0.5 seconds or a slower reaction of 2 seconds. Furthermore, it is also possible to vary the reaction time depending on the time of day, e.g. 0.5 seconds during the day and 1 or 2 seconds at night. This means that the reaction time could be fast during the day and slower at night.

[0141] In the fourth illustration "case I" and fifth illustration "case II" the level of the load current 1 LOAD on the load side of the protective switching device SG is shown over time for a first and a second case. In the first case of the representation "case I", the determined load current is 1 L OAD less than the second current threshold i L im- Or it is determined that a (load) current that is greater than the second current threshold i L in is, could not flow.

[0142] The electronic interruption unit EU remains in the high-impedance state and carries out this test again later (the latter not shown in time).

[0143] In the second case of the representation "case II" the determined load current 1 L OAD greater than the second current threshold i L im- Or it is determined that a (load) current that is greater than the second current threshold i L in is , could flow .

[0144] The electronic interruption unit EU is switched to the low-resistance state. This is shown in the second illustration SWITCH with the dashed line and the state "Automatic on" , analogously in the fifth illustration "case II" with the dashed line that the load current 1 L OAD flows again.

[0145] The function according to the invention can be designed to be activatable (on / off).

[0146] A computer program product or algorithm, for example, evaluates (in the background) the level of the determined current in the low-voltage circuit on the load side of the protective switching device. If a first current threshold is undershot for an initial period of time, the electronic interruption unit EU is switched to the high-impedance state. After the electronic interruption unit EU has been switched to the high-impedance state, a test is carried out, for example using test pulses, to determine whether a current greater than the second current threshold could flow. If the test is positive, the electronic interruption unit EU is switched to the low-impedance state.

[0147] The control unit SE can (for this purpose) have a microcontroller. The computer program product can be executed on the microcontroller. The computer program product comprises commands which, when the program is executed by the microcontroller, cause the microcontroller to control the protective switching device, in particular to support, in particular to carry out, the method according to the invention.

[0148] The computer program product may be stored on a computer-readable storage medium, such as a CD-ROM, a USB stick or similar.

[0149] Furthermore, a data carrier signal that transmits the computer program product may exist. Although the invention has been illustrated and described in detail by the exemplary embodiment, the invention is not limited to the disclosed examples, and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims

Patent claims 1 . Protective switching device (SG) for protecting a low-voltage electrical circuit comprising: - a housing (GEH) with at least one mains-side connection and at least one load-side connection, - a mechanical isolating contact unit (MK) connected in series with an electronic interruption unit (EU), the series circuit being connected on the one hand to the at least one mains-side connection and on the other hand to the at least one load-side connection, - that the mechanical isolating contact unit (MK) can be switched by opening contacts to prevent a current flow or closing the contacts to allow a current flow in the low-voltage circuit, - 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 a current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit, - a current sensor unit ( ST ) for determining the current level of the low-voltage circuit, - a control unit (SE) connected to the current sensor unit (ST), the mechanical isolating contact unit (MK) and the electronic interruption unit (EU), whereby if current and / or current time limit values ​​are exceeded, the prevention of current flow in the low-voltage circuit is initiated, - that the protective switching device is designed in such a way that when the contacts of the mechanical isolating contact unit (MK) and the low-impedance switched electronic interruption unit (EU) are closed, the electronic interruption unit (EU) is switched to the high-impedance state when the current in the low-voltage circuit falls below a first current threshold for a first period of time.

2. Protective switching device (SG) according to claim 1, characterized in that after switching the electronic interruption unit (EU) into the high-impedance state, a test is carried out to determine whether a current greater than a second current threshold could flow, and if the test is positive, the electronic interruption unit (EU) is switched into the low-impedance state.

3. Protective switching device (SG) according to claim 2, characterized in that the test is carried out in such a way that the electronic interruption unit (EU) is periodically switched to the low-resistance state for a second time period at a first time interval, for the second time period of the low-resistance state a determination is made as to whether a current which exceeds the second current threshold could flow, if the determination is positive the electronic interruption unit (EU) switches to the low-resistance state, otherwise the periodic switching (to the low-resistance state) is continued.

4. Protective switching device (SG) according to claim 3, characterized in that a voltage sensor unit (SU) connected to the control unit (SE) is provided, which determines the level of the voltage, in particular instantaneous values ​​of the level of the voltage, of the low-voltage circuit, in particular at the mains-side connections, specifically between the mains-side neutral conductor connection (NG) and the mains-side phase conductor connection (LG), that the periodic switching of the electronic interruption unit (EU) into the low-resistance state takes place when the amount of the instantaneous value of the level of the voltage falls below a first voltage limit, which is in particular less than or equal to 50 volts.

5. Protective switching device (SG) according to claim 2, characterized in that the test is carried out by using an auxiliary voltage, in particular auxiliary alternating voltage, which falls below a first voltage limit, which is in particular less than or equal to 50 volts.

6. Protective switching device (SG) according to one of the preceding claims, characterized in that the mechanical isolating contact unit (MK) is assigned to the load-side connection and the electronic interruption unit (EU) is assigned to the mains-side connection, in particular that the mechanical isolating contact unit (MK) can be operated by a mechanical handle in order to switch an opening of contacts or a closing of the contacts.

7. Protective switching device (SG) according to one of the preceding claims, characterized in that the first current threshold is less than 10 mA or less than 5 mA or less than 1 mA.

8. Protective switching device (SG) according to claim 2 or claims related to claim 2, characterized in that the second current threshold is greater than the first current threshold, in particular greater than 10% or 20% or 30% of the first current threshold.

9. Protective switching device (SG) according to one of the preceding claims, characterized in that the first time period is equal to or greater than one minute, in particular greater than 2 minutes, 3 minutes, 5 minutes, 10 minutes, 15 minutes or 30 minutes. 10 . Protective switching device (SG) according to claim 3 or claims related to claim 3, characterized in that the first time interval is 500 ms or 1 second or 2 seconds.

11. Protective switching device (SG) according to claim 3 or claims related to claim 3, characterized in that the second time period is less than or equal to 20 ms, in particular less than 10 ms, more specifically less than 3 ms, 2 ms, 1 ms, 700 ps or 500 ps.

12. Protective switching device (SG) according to one of the preceding claims, characterized in that the control unit (SE) has a microcontroller. 13 . Method for a protective switching device (SG) for protecting a low-voltage electrical circuit with : - a housing (GEH) with at least one mains-side connection and at least one load-side connection, - a mechanical isolating contact unit (MK) connected in series with an electronic interruption unit (EU), the series circuit being connected on the one hand to the at least one mains-side connection and on the other hand to the at least one load-side connection, - that the mechanical isolating contact unit (MK) can be switched by opening contacts to prevent a current flow or closing the contacts to allow a current flow in the low-voltage circuit, - 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 a current flow or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit, - that the level of the current in the low-voltage circuit, in particular between a mains-side phase conductor connection and a load-side phase conductor connection, is determined, - that if current and / or current time limit values ​​are exceeded, an avoidance of current flow in the low-voltage circuit is initiated, - that when the contacts of the mechanical isolating contact unit (MK) are closed and the electronic interruption unit (EU) is switched to a low-resistance state, the electronic interruption unit (EU) is switched to a high-resistance state when the current in the low-voltage circuit falls below a first current threshold for a first period of time.

14. Method according to claim 13, characterized in that after switching the electronic interruption unit (EU) into the high-impedance state, a test is carried out to determine whether a current greater than a second current threshold could flow, and if the test is positive, the electronic interruption unit (EU) is switched into the low-impedance state. 15 . Method according to claim 14, characterized in that the test is carried out in such a way that the electronic interruption unit (EU) is periodically switched to the low-resistance state for a second time period at a first time interval, for the second time period of the low-resistance state a determination is carried out as to whether a current which exceeds the second current threshold could flow, if the determination is positive the electronic interruption unit (EU) changes to the low-resistance state, otherwise the periodic switching to the low-resistance state is continued for the test.

16. Computer program product comprising instructions which, when the program is executed by a microcontroller, cause the microcontroller to support, in particular to carry out, the behavior and the test according to one of claims 1 to 15 with a protective switching device. 17 . Computer-readable storage medium on which the computer program product according to claim 16 is stored . 18 . Data carrier signal which the computer program product according to Patent claim 16 transfers .

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