Circuit breaker device and method

Abstract

The invention relates to a circuit breaker device for protecting a low-voltage electrical circuit, said circuit breaker device comprising: - a mechanical separating contact unit which is connected in series with an electronic interruption unit, the series connection being connected to at least one grid-side terminal and to at least one load-side terminal, - wherein the magnitude of the current in the low-voltage circuit is ascertained, - wherein a process for preventing a current flow in the low-voltage circuit is initiated if current thresholds and / or current-time thresholds are exceeded, - wherein the temperature in the circuit breaker device, in particular the temperature of the electronic interruption unit, in particular the temperature of at least one of the semiconductor-based switching elements, is ascertained - wherein, if a first temperature threshold is exceeded, the electronic interruption unit is switched to a high-resistance state of the switching elements so as to prevent a current flow in order to prevent overheating of the circuit breaker device.

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 short circuits. 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 can be used for both low-voltage direct current circuits and low-voltage alternating current circuits. The invention particularly relates to low-voltage alternating current circuits with an alternating voltage, typically a time-dependent sinusoidal alternating voltage with frequency f. The time dependence of the instantaneous voltage value u(t) of the alternating voltage is described by the equation: u(t) = 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 revolution 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). Often, the angular frequency (w) is 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, 2n: u ( t ) = U * sin (wt )

[0013] In the case of angular frequencies that are not constant over time, the term instantaneous angular frequency is also used.

[0014] 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° ).

[0015] 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).

[0016] The object of the present invention is to improve a protective switching device of the type mentioned above, in particular to avoid destruction, damage or an inadmissible operating state (in particular an inadmissible operating temperature) of a protective switching device.

[0017] 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 16. 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:

[0018] - a housing with at least one mains-side connection and at least one load-side connection, both for the low-voltage circuit,

[0019] - 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,

[0020] - that the mechanical isolating contact unit can be switched by opening at least one contact to prevent a current flow or closing the at least one contact for a current flow in the low-voltage circuit,

[0021] - 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,

[0022] - a current sensor unit for determining the current level of the low-voltage circuit,

[0023] - 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 (i.e. when a current level is present for a certain time), 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.

[0024] According to the invention, a temperature sensor connected to the control unit is provided in the protective switching device. In particular, the temperature sensor is provided or arranged at (i.e. on, in or in the region of) the electronic interruption unit. In particular, the temperature sensor is provided or arranged at (i.e. on, in or in the region of) the semiconductor-based switching elements. According to the invention, the protective switching device is designed such that when a first temperature threshold value is exceeded, the electronic interruption unit is switched to a high-impedance state of the switching elements to avoid a current flow in order to avoid overheating of the protective switching device, in particular the electronic interruption unit. Avoiding overheating means that the protective switching device, in particular the electronic interruption unit, remains within its permissible thermal limits orpermissible device temperatures remain.

[0025] This has the advantage of preventing overheating of the protective switching device, especially the electronic interruption unit. This can prevent thermal overload or thermal destruction. By preventing the flow of current, heating of the protective switching device is avoided, and a safe condition is ensured.

[0026] Further advantageous embodiments of the invention are specified in the subclaims and in the exemplary embodiment.

[0027] In an advantageous embodiment of the invention, the mechanical isolating contact unit is assigned to the load-side connection and the electronic interruption unit (EU) is assigned to the mains-side connection. In particular, the mechanical isolating contact unit can be operated by a mechanical handle in order to switch an opening of the at least one contact or a closing of the at least one contact. This has the particular advantage of providing a structure for a protective switching device in which the protective switching device functions even when the contacts of the mechanical isolating contact unit are open.

[0028] In an advantageous embodiment of the invention, two mains-side connections and at least one load-side connection are provided. In particular, a mains-side phase conductor connection, a mains-side neutral conductor connection, and a load-side phase conductor connection are provided.

[0029] This has the particular advantage that a structure for a protective switching device is provided which, on the one hand, provides an energy supply for the protective switching device and, on the other hand, enables a space-saving design by only having one switched pole.

[0030] In an advantageous embodiment of the invention, two mains-side connections and two load-side connections are provided. In particular, a mains-side neutral conductor connection, a mains-side phase conductor connection, a load-side neutral conductor connection, and a load-side phase conductor connection are provided.

[0031] This has the particular advantage that a structure for a two-pole protective switching device is provided, so that phase and neutral conductors can be connected directly and, for example, additional neutral conductor rails can be omitted.

[0032] In an advantageous embodiment of the invention, when the switching elements are in an initiated high-resistance state to avoid overheating and when a higher second temperature threshold is exceeded (i.e. the second temperature threshold is higher than the first temperature threshold), at least one contact of the mechanical isolating contact unit is opened.

[0033] This has the particular advantage of providing additional safety in the protective switch device. If increasing heating occurs despite the high-impedance electronic interruption unit being initiated, this could be due to the fact that the electronic interruption unit is not high-impedance or not high enough, and a (faulty) current flow leads to further heating of the protective switch device. In this case, at least one contact of the mechanical isolating contact unit is opened in order to achieve galvanic isolation and thus prevent any current flow completely. This additional safety measure prevents the protective switch device from being destroyed.

[0034] In an advantageous embodiment of the invention, when the switching elements are in a high-impedance state, the electronic interruption unit is switched to a low-impedance state (for current flow in the low-voltage circuit) to prevent overheating and a third temperature threshold from being undershot. The third temperature threshold is lower than the first temperature threshold. This has the particular advantage that, once the protective switching device, in particular the electronic interruption unit, has cooled down, current flow is permitted again. The protective switching device is thus always in a safe operating state.

[0035] In an advantageous embodiment of the invention, the electronic interruption unit can alternatively be switched to the low-resistance state (for a current flow in the low-voltage circuit) when the switching elements are in a high-resistance state to prevent overheating and after a first period of time has elapsed since the switching elements entered the high-resistance state (to prevent overheating). The first period of time can, for example, be in the order of 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes.

[0036] This has the particular advantage of implementing a fixed cooling time (first period). After the protective switching device, particularly the electronic interruption unit, has cooled down, current flow is enabled again.

[0037] In an advantageous embodiment of the invention, if a change to the high-impedance state exceeds a first number to avoid overheating (and back to the low-impedance state) within a first time frame, at least one contact of the mechanical isolating contact unit is opened. The first time frame can be, for example, one hour, several hours, such as 3 hours, 5 hours, 6 hours, 10 hours, 12 hours, 18 hours, 24 hours (one day), several days, or one week. The number of changes can be, for example, from 2, 3, 4, ..., 10, .... 20 changes.

[0038] This has the particular advantage that, in the event of frequent temperature-related changes to the high-resistance state (from the low-resistance to the high-resistance state), additional safety is implemented. At least one contact of the mechanical isolating contact unit is opened to provide galvanic isolation and completely prevent a heating current flow. This prevents further changes to the high-resistance state (from the high-resistance state and back to the low-resistance state) of the electronic interruption unit, and safety is ensured in the low-voltage circuit.

[0039] In an advantageous embodiment of the invention, a communication unit connected to the control unit is provided. If a fourth temperature threshold is exceeded, a warning is issued via the communication unit. The fourth temperature threshold is lower than the first temperature threshold.

[0040] The fourth temperature threshold can, for example, be 10 , ..., 20 , ..., 30 , ..., 40 Kelvin lower than the first temperature threshold.

[0041] This has the particular advantage that when a temperature threshold is reached, an indication is communicated so that, for example, a cause can be determined advantageously before a shutdown due to overtemperature occurs.

[0042] Alternatively or additionally, the temperature level (or an equivalent) of the temperature sensor can be transmitted (communicated) via the communication unit.

[0043] This has the particular advantage that (central) temperature monitoring of one or more protective switching devices can be carried out, so that appropriate measures can be taken if temperatures rise. In an advantageous embodiment of the invention, a display unit is provided which is connected to the control unit and has display means visible on the protective switching device for displaying the exceeding of temperature limit values ​​(first and / or second and / or third and / or fourth) or (and) the temperature level. Alternatively or additionally, a high-resistance or low-resistance state of the electronic interruption unit.

[0044] This has the particular advantage that a visualization of the temperature state is provided.

[0045] In an advantageous embodiment of the invention, the at least one contact of the mechanical isolating contact unit can be opened by the control unit, but cannot be closed.

[0046] This has the particular advantage that a high level of safety is ensured for the protective switching device, since the contact cannot be closed incorrectly within the protective switching device.

[0047] In an advantageous embodiment of the invention, the at least one contact of the mechanical isolating contact unit has an enabling function. This can be an enabling function provided for in accordance with the relevant standards. In particular, such that the at least one contact can be opened by the control unit even if the mechanical handle is blocked, i.e., for example, if the handle is / is blocked for the closed contact state.

[0048] This has the particular advantage of providing a high level of safety and, in particular, a protection device that complies with standards for low-voltage circuits. The current flow can be galvanically interrupted at any time by opening at least one contact.

[0049] 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. The method for a protective switching device for protecting an electrical low-voltage circuit with:

[0050] - a housing with at least one mains-side connection and at least one load-side connection,

[0051] - 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,

[0052] - that the mechanical isolating contact unit can be switched by opening at least one contact to prevent a current flow or closing at least one contact to allow a current flow in the low-voltage circuit,

[0053] - 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 or a low-resistance state of the switching elements to allow current flow in the low-voltage circuit,

[0054] - that the current level of the low-voltage circuit is determined and, if current and / or current-time limit values ​​are exceeded, the prevention of current flow in the low-voltage circuit is initiated,

[0055] - that the temperature in the protective switching device is determined, in particular the temperature of the electronic interruption unit, in particular the temperature of at least one of the semiconductor-based switching elements,

[0056] - that when a first temperature threshold is exceeded, the electronic interruption unit is switched to a high-resistance state of the switching elements to prevent a current flow in order to prevent overheating of the protective switching device.

[0057] All embodiments, both in dependent form referring back to patent claim 1 or 16, 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 (and vice versa), increase the safety of a protective switching device and provide a new concept for a protective switching device.

[0058] 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.

[0059] The drawing shows:

[0060] Figure 1 shows a first representation of a protective switching device,

[0061] Figure 2 shows a first representation of a diagram,

[0062] Figure 3 shows a second representation of a diagram,

[0063] Figure 4 shows a third representation of a diagram,

[0064] Figure 5 is a fourth representation of a diagram,

[0065] Figure 6 shows a fifth representation of a diagram.

[0066] 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:

[0067] - a mains-side neutral conductor connection NG, a mains-side phase conductor connection LG, a load-side

[0068] 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 (an energy sink) is usually connected to the load side Load;

[0069] - a (two-pole) mechanical isolating contact unit MK with load-side connection points APLL, APNL and mains-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 mains-side connection point APNG for the neutral conductor and a mains-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 contacts KKN, KKL can be opened to prevent current flow or the contacts can be closed to allow current flow in the low-voltage circuit. The mechanical isolating contact unit can also be designed as a single-pole mechanical isolating contact unit, i.e.with one contact, whereby the contact KKL is preferably arranged in the phase conductor L, a neutral conductor N passing through the protective switching device SG is then not provided.

[0070] - 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 L), 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 or 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,

[0071] - 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 L,

[0072] - 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.

[0073] According to the invention, the protective switching device SG is designed such that a temperature sensor TS connected to the control unit SE is provided in the protective switching device SG. In particular, the temperature sensor TS is provided or arranged at the electronic interruption unit EU, as indicated in Figure 1. In particular, the temperature sensor TS is provided or arranged at the semiconductor-based switching elements (at least one semiconductor-based switching element). In order to determine the level of the temperature of the protective switching device SG, in particular of the electronic interruption unit EU, in particular of the semiconductor-based switching elements (at least one semiconductor-based switching element).

[0074] According to the invention, the protective switching device SG is designed in such a way that when a first temperature threshold is exceeded, the electronic interruption unit is switched to a high-resistance state of the switching elements to prevent a current flow in order to avoid overheating of the protective switching device.

[0075] 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 electronic interruption unit EU is advantageously switched to the low-impedance state 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 (or 25 volts or 10 volts).

[0076] 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.

[0077] The mechanical isolating contact unit MK can be operated by a mechanical handle HH in order to switch the contacts open or close, as with a classic circuit breaker or miniature circuit breaker (MCB).

[0078] The control unit SE can have a microcontroller (microcontroller unit).

[0079] In the example shown in 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. In a single-pole version of the protective switching device SG, this connection can be omitted, as can the neutral conductor contact KKN of the mechanical isolating contact unit.

[0080] 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.

[0081] The mechanical isolating contact unit MK can be operated using a mechanical handle HH on the protective switch device SG in order to switch the contacts KKL, KKN manually open or close. The mechanical handle HH indicates (in the non-blocked state) (specifically through a mechanical connection between contacts and handle) the switching state (open or closed) of the contacts of the mechanical isolating contact unit MK on the protective switch device. The mechanical isolating contact unit MK is advantageously designed in such a way that (manual) closing of the contacts by the mechanical handle is only possible after an enable, in particular an enable signal. This means that the contacts KKL, KKN of the mechanical isolating contact unit MK can only be closed by the handle HH when the enable or the enable signal is present (from the control unit SE). Without the enable orThe release signal can operate the handle HH, but the contacts cannot be closed ("permanent slip").

[0082] The protective switching device SG has a power supply NT (not shown), for example a power pack. In particular, the power supply NT is provided for the control unit SE. The power supply NT is connected, for example, 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).

[0083] In the case of a purely single-pole protective switching device, the power supply is provided by an external power source / additional connections.

[0084] High-resistance refers to a state in which only a negligible current flows. In particular, high-resistance refers to resistance values ​​greater than 1 kiloohm, preferably greater than 10 kiloohms, 100 kiloohms, 1 megaohm, 10 megaohms, 100 megaohms, 1 gigaohm, or greater.

[0085] Low-resistance means a state in which the current value specified on the protective switching device could flow. In particular, low-resistance means resistance values ​​that are less than 10 ohms, preferably less than 1 ohm, 100 milliohms, 10 milliohms, 1 milliohm or less. In a first variant, the mechanical isolating contact unit MK can interrupt in a single pole. This means that only one conductor (of the two / several conductors), in particular the active conductor or phase conductor, is interrupted, i.e. it has a mechanical contact. The neutral conductor is then contact-free, i.e. the neutral conductor is directly connected.

[0086] In a second variant of the mechanical isolating contact unit MK, the neutral conductor also has mechanical contacts (two-pole interruption), as shown in Figure 1.

[0087] 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 contacts), - (mechanical) contact position indicator of the contacts of the mechanical isolating contact unit, - release function or release functionality, 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.

[0088] In particular, release functionality means that at least one contact can be opened by the control unit, even if the mechanical handle is blocked (e.g. in the on state).

[0089] Furthermore, the standard-compliant isolating function can include the ability to lock the isolating contact unit or the handle in the switched on or off state.

[0090] The minimum clearance between the contacts of the isolating contact unit is essentially voltage-dependent. Other parameters are the degree of pollution, the type of field (homogeneous, inhomogeneous), and the air pressure or altitude above sea level. There are corresponding regulations and standards for these minimum clearances or creepage distances. For example, for air, these regulations specify the minimum clearance for an inhomogeneous and a homogeneous (ideal) electrical field for a surge voltage withstand capacity depending on the degree of pollution. The surge voltage withstand capacity is the withstand capacity when a corresponding surge voltage is applied. The isolating contact unit or protective switching device only has an isolating function (isolating property) if this minimum length (minimum distance) is present.

[0091] For the purposes of the invention, the DIN EN 60947 and IEC 60947 series of standards are particularly relevant for the isolating function and its properties, to which reference is made here.

[0092] 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 0.01 mm and 14 mm (at least). In particular, the minimum clearance is advantageously between 0.01 mm at 0.33 kV and 14 mm at 12 kV, especially for pollution degree 1 and especially for inhomogeneous fields.

[0093] Advantageously, the minimum air gap can have the following values: E DIN EN 60947-1 (VDE 0660-100): 2018-06

[0094] Table 13 - Minimum clearances

[0095] 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.

[0096] In particular, the term mechanical isolating contact unit does not refer to a relay contact.

[0097] The protective switching device can have a (particularly wireless) communication unit COM which is connected to the control unit SE or is a part of it. If a fourth temperature threshold value is exceeded, a warning can be issued by means of the communication unit COM. Alternatively or additionally, the temperature level can be issued (communicated) by means of the communication unit COM. Furthermore, a display unit AE can be provided. The display unit AE can be designed as a combined display and input unit. The display unit AE (display and input unit) is connected to the control unit SE or is a part of it. The display unit has visible display means on the protective switching device, in particular for displaying the high-resistance or low-resistance state of the electronic interruption unit EU. Alternatively or additionally,in addition to the indication of exceeding of temperature limits ( first or / and second or / and third or / and fourth ) or (and) the level of temperature .

[0098] 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 electronic interruption unit are closed and

[0099] - 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, or / and

[0100] - (or / and) in the case of a determined current 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, or / and

[0101] - 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.

[0102] Figure 2 shows a representation of a first diagram or coordinate system, in which the level of the current I of the low-voltage circuit is plotted on the horizontal axis (abscissa) and the level of the temperature T on the vertical axis (ordinate). S of the temperature sensor TS is plotted. The course of the temperature T S of the temperature sensor TS as a function of the current I of the low-voltage circuit.

[0103] It is assumed that the heating in the protective switching device, more specifically in the electronic interruption unit EU, more specifically in the semiconductor-based switching elements of the electronic interruption unit EU, depends on the current I of the low-voltage circuit through the protective switching device (the protective switching device is intended to protect the low-voltage circuit). As the current I increases, the temperature of the protective switching device, more specifically in the electronic interruption unit EU, more specifically in its semiconductor-based switching elements, increases. Thus, the temperature T determined by the temperature sensor TS increases. S of the protective switching device. The temperature increases monotonically with the current level. (In addition to the current level, the ambient temperature also influences the heating in the protective switching device. For simplicity, this is not shown in Figure 2.)

[0104] According to Figure 2, various temperature thresholds are shown. A first temperature threshold 1 . SW, in the example 100 ° C, a second temperature threshold 2 . SW, in the example 110 ° C, and a third temperature threshold 3 . SW, in the example 80 ° C.

[0105] Figure 3 shows a representation according to Figure 2 , with the difference that three correlated diagrams are shown, with time t being plotted on the horizontal axis (abscissa).

[0106] In the upper part of Figure 3 the height of the temperature T S of the temperature sensor TS as a function of time t. The first temperature threshold value l . SW and the third temperature threshold value 3 . SW are shown.

[0107] In the middle section of Figure 3, the magnitude of the current I is plotted as a function of time t. In the lower section of Figure 3, the switching state of the electronic interruption unit EU is plotted as a function of time t. A low-resistance state of the electronic interruption unit EU is marked with on. A high-resistance state of the electronic interruption unit EU is marked with off.

[0108] For example, a ( constant ) current I or a current I with a constant effective value of a first magnitude flows for a certain time ( Figure 3 middle ) . A corresponding heating occurs in the protective switching device SG . The temperature in the protective switching device / the determined magnitude of the temperature T S of the temperature sensor TS increases until the first temperature threshold value 1 . SW is reached at the first time tl (Figure 3 above).

[0109] When the first temperature threshold l SW is reached or exceeded, in the example 100 °C, the electronic interruption unit EU is switched to a high-resistance state of f (of the switching elements) to prevent current flow, first time tl (Figure 3 below). This prevents further heating and overheating (and associated damage) of the protective switching device.

[0110] The protective switching device is allowed to cool down. At a second time t2, the third temperature threshold value 3 . SW, in the example 80 ° C, is reached or undershot. When the third temperature threshold value 3 . SW is reached or undershot, the electronic interruption unit is (again) (at the second time t2) switched to a low-resistance state on (for a current flow in the low-voltage circuit) (Figure 3 bottom). The current I can flow again (from the second time t2) (Figure 3 middle). If necessary, the temperature can rise again (Figure 3 top).

[0111] The third temperature threshold is smaller than the first temperature threshold.

[0112] Alternatively or additionally, instead of the third temperature threshold value 3 . SW, the expiration of a first time period since the high-resistance state of the switching elements occurs can be waited for. After the expiration of a first time period since the high-resistance state of the electronic interruption unit occurs, the electronic interruption unit is switched to the low-resistance state (not shown).

[0113] If the switch between the high-resistance state to prevent overheating and back to the low-resistance state occurs too frequently, at least one contact of the mechanical isolating contact unit MK will open. This means that if the switch (toggling) between the high-resistance state to prevent overheating and back to the low-resistance state exceeds a first number of times within a first time frame, at least one contact of the mechanical isolating contact unit MK will open.

[0114] Figure 4 shows a representation according to Figure 3 , with the difference that a fourth diagram is shown which is correlated with the three upper diagrams.

[0115] The fourth diagram, in the bottom section of Figure 4, shows the switching state of the mechanical isolating contact unit MK as a function of time t. A closed state of at least one contact of the mechanical isolating contact unit MK is marked with "closed". An open state of at least one contact of the mechanical isolating contact unit MK is marked with "open".

[0116] Furthermore, the first temperature threshold value 1 . SW and the second temperature threshold value 2 . SW are shown in the upper area of ​​Figure 4.

[0117] For example, a ( constant ) current I of a first magnitude flows for a certain time ( Figure 4 middle ) . A corresponding heating occurs in the protective switching device SG . The temperature in the protective switching device / the determined magnitude of the temperature T S of the temperature sensor TS increases until the first temperature threshold value 1. SW is reached at the first time tl (Figure 4 above).

[0118] When the first temperature threshold l.SW is reached or exceeded, in the example 100 °C, the electronic interruption unit EU is switched to a high-resistance state off (of the switching elements) to prevent a current flow, first time tl (Figure 4 below).

[0119] The current is reduced (Figure 4 middle).

[0120] If the temperature continues to rise despite the electronic interruption unit EU being switched to high impedance, for example because the electronic interruption unit EU is defective (i.e. the high impedance state is initiated but not or not fully effective, for example) and a (lower) current flows, then when the second temperature threshold value 2. SW is reached or exceeded, in the example 110 °C, at least one contact of the mechanical isolating contact unit MK is opened (Figure 4 bottom), third time t3. The second temperature threshold value 2. SW is higher than the first temperature threshold value l.SW.

[0121] Figure 5 shows a representation according to Figure 3, with the difference that in the middle area of ​​Figure 5 the issuing of a warning Warn is shown as a function of time t.

[0122] Furthermore, the first temperature threshold 1.SW and the fourth temperature threshold 4.SW are shown in the upper section of Figure 5. If the fourth temperature threshold is exceeded at the fourth time t4, a warning (Warn) (wireless / wired) is issued via the communication unit COM, for example, to a higher-level management system. Alternatively or additionally, this can be displayed, for example, with the display unit AE. The fourth temperature threshold is lower than the first temperature threshold.

[0123] The electronic interruption unit EU remains on in the low-resistance state. Alternatively or additionally, the temperature level can be transmitted (wireless / wired) via the communication unit COM. For example, to a higher-level management system. Alternatively or additionally, the temperature level can be displayed, for example, with the display unit AE.

[0124] Figure 6 shows a representation according to Figure 5 , with the difference that the warning Warn , with a time offset (time delay) t v is issued. This means that if the fourth temperature threshold value 4 SW is exceeded at the fourth time t4, no warning Warn is issued, but the warning Warn is only issued at a fifth time t5, as shown in Figure 6. This way, for example, warnings can be avoided which are based on brief heating due to briefly increased starting or switching currents. If before the fifth time t5 is reached, the temperature T S If the temperature falls below the fourth threshold value 4 , SW, no warning Warn is issued.

[0125] The time offset (time delay) t v is in the range from one second, ..., 5 seconds, ... 10 seconds, ... 1 minute.

[0126] In the following the invention is explained again in other words.

[0127] An electrical (sub-) distribution board contains a large number of different protective and switching devices which are connected to one another via corresponding cables. When designing such a sub-distribution board, thermal considerations and calculations must also be carried out, since ohmic losses on the cables and electrical equipment cause losses in the sub-distribution board. This causes the sub-distribution board to heat up. Thermal overload is now prevented by appropriate (over-) dimensioning (in accordance with standards, guidelines or regulations). New types of electronic protective and switching devices use electronic switching elements (power semiconductors) in the main current path, which also cause increased ohmic losses in the sub-distribution board. This exacerbates the problem of thermal design of a sub-distribution board.

[0128] The existing load current (through the device) significantly influences the temperature of the protective switching device and thus also the temperature increase. If a critical temperature is reached, a high-impedance state is initiated. This prevents current from flowing through the protective switching device, allowing the device (and the sub-distribution board) to cool down.

[0129] Furthermore, a corresponding warning message can be issued.

[0130] Since no more current flows through the device, it cools down again. Once the temperature drops below a certain level, the device can automatically return to the low-resistance state for current flow (hysteresis).

[0131] Depending on the device configuration, opening of the contacts of the mechanical isolating contact unit can also be initiated instead of the low-resistance state. Automatic reactivation after cooling is then not possible. Manual reclosing of the contacts is required.

[0132] The present invention describes a solution that simplifies thermal design, avoids oversizing and prevents a dangerous condition in the sub-distribution due to overheating.

[0133] Although the invention has been illustrated and described in detail by the embodiment, the invention is not limited by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the scope of the invention.

Claims

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 at least one contact to prevent a current flow or closing at least one contact for 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 a temperature sensor (TS) connected to the control unit is provided in the protective switching device (SG), in particular in the electronic interruption unit (EU), in particular in the semiconductor-based switching elements, - that the protective switching device is designed in such a way that when a first temperature threshold value (l . SW) is exceeded, the electronic interruption unit (EU) is switched to a high-resistance state of the switching elements to avoid a current flow in order to prevent overheating of the protective switching device to avoid.

2. Protective switching device (SG) according to claim 1, 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.

3. Protective switching device (SG) according to claim 1 or 2, characterized in that two mains-side connections and at least one load-side connection are provided.

4. Protective switching device (SG) according to claim 1 or 2, characterized in that two mains-side connections and two load-side connections are provided.

5. Protective switching device (SG) according to one of the preceding claims, characterized in that when an initiated high-impedance state of the switching elements of the electronic interruption unit (EU) is initiated to avoid overheating and when a higher second temperature threshold value (2. SW) is exceeded, at least one contact of the mechanical isolating contact unit (MK) is opened.

6. Protective switching device (SG) according to one of the preceding claims, characterized in that when the switching elements of the electronic interruption unit (EU) are in a high-impedance state, the electronic interruption unit (EU) is switched to a low-impedance state to avoid overheating and falling below a third temperature threshold value (3. SW).

7. Protective switching device (SG) according to one of the preceding claims, characterized in that the third temperature threshold value is smaller than the first temperature threshold value.

8. Protective switching device (SG) according to one of the preceding claims 1 to 5, characterized in that when the switching elements are in a high-resistance state to avoid overheating and a first time period has elapsed since the high-resistance state of the switching elements occurs, the electronic interruption unit is switched to the low-resistance state to avoid overheating.

9. Protective switching device (SG) according to one of the preceding claims, characterized in that when a change to the high-resistance state exceeds a first number, at least one contact of the mechanical isolating contact unit (MK) is opened within a first time frame to avoid overheating.

10. Protective switching device (SG) according to one of the preceding claims, characterized in that a communication unit (COM) connected to the control unit (SE) is provided.

11. Protective switching device (SG) according to claim 10, characterized in that when a fourth temperature threshold value (4th SW) is exceeded, a warning is issued by means of the communication unit (COM).

12. Protective switching device (SG) according to claim 10 or 11, characterized in that by means of the communication unit (COM) the height of the Temperature (T S ) of the temperature sensor (TS) or an equivalent.

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

14. Protective switching device (SG) according to one of the preceding claims, characterized in that the mechanical isolating contact unit (MK) can be operated by a mechanical handle (HH) in order to switch an opening of the at least one contact or a closing of the at least one contact.

15. Protective switching device (SG) according to claim 14, characterized in that the at least one contact of the mechanical isolating contact unit (MK) has an isolating functionality such that the at least one contact is opened by the control unit (SE), even if the mechanical handle (HH) is blocked.

16. Method for a 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 connection 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) is opened by at least one contact to prevent a current flow or by closing at least one contact for 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 current level ( I ) of the low-voltage circuit is determined, - that if current and / or current time limit values ​​are exceeded, the prevention of current flow in the low-voltage circuit is initiated, - that the temperature ( T S ) in the protective switching device (SG), in particular the temperature of the electronic interruption unit (EU), in particular the temperature of at least one of the semiconductor-based switching elements, - that when a first temperature threshold (l . SW) is exceeded, the electronic interruption unit (EU) is switched to a high-resistance state of the switching elements to prevent a current flow in order to avoid overheating of the protective switching device.

17. Method according to claim 16, characterized in that when an initiated high-resistance state of the switching elements is initiated to avoid overheating and when a higher second temperature threshold value (2. SW) is exceeded, at least one contact of the mechanical isolating contact unit (MK) is opened. 18 . Method according to claim 16 or 17, characterized in that in a high-resistance state of the switching elements, in order to avoid overheating and falling below a third temperature threshold value ( 3 . SW), the electronic interruption unit (EU) is switched to a low-resistance state (for a current flow in the low-voltage circuit), in particular that the third temperature threshold (3. SW) is smaller than the first temperature threshold (1. SW) 19. Method according to claim 16 or 17, characterized in that when the switching elements are in a high-resistance state to avoid overheating and a first time period has elapsed since the high-resistance state of the switching elements has occurred to avoid overheating, the electronic interruption unit is switched to the low-resistance state (for a current flow in the low-voltage circuit).

20. Method according to claim 16, 17, 18 or 19, characterized in that when a change to the high-resistance state exceeds a first number, at least one contact of the mechanical isolating contact unit (MK) is opened within a first time frame to avoid overheating.

21. Method according to claim 16, 17, 18, 19 or 20, characterized in that if a fourth temperature threshold value (4. SW) is exceeded, a warning (Warn.) is issued.

22. Method according to claim 16, 17, 18, 19, 20 or 21, characterized in that the level of the temperature (T S ) or an equivalent is given.

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