Protection switch device and method

Abstract

The invention relates to a protective switching device (SG) for protecting a low-voltage circuit, comprising:-a housing (GEH) having at least one network-side connection and at least one load-side connection,-a mechanical disconnecting contact unit (MK) which is connected in series to an electronic interrupting unit (EU), the series circuit being connected, on one hand, to the at least one network-side connection and, on the other hand, to the at least one load-side connection and the mechanical disconnecting contact unit (MK) being connected, on the other hand, to the at least one load-side connection. The mechanical separation contact unit (MK) can be switched by opening the contacts in order to avoid a current flow or closing the contacts for a current flow in the low-voltage circuit, the electronic interruption unit (EU) can be switched to a high-resistance state of the switching element by means of the semiconductor-based switching element in order to avoid a current flow or to a low-resistance state of the switching element for a current flow in the low-voltage circuit, determining a current magnitude of the low-voltage circuit, when a current limit value and / or a current-time limit value are / is exceeded, an avoidance of a current flow in the low-voltage circuit is initiated, and the electronic interruption unit (EU) can be switched to a high-resistance state or a low-resistance state by means of the control input (CI).

Description

Technical Field

[0001] The invention relates to the technical field of a protective switching device for a low-voltage circuit having an electronic interruption unit and a method for a protective switching device for a low-voltage circuit having an electronic interruption unit. Background Art

[0002] Low voltage refers to voltages up to 1000 V AC or 1500 V DC. Specifically, low voltage refers to voltages greater than minimum voltage, which is 50 V AC or 120 V DC.

[0003] A low-voltage circuit, low-voltage network, or low-voltage system is a circuit with a rated or nominal current of up to 125 amperes, more particularly up to 63 amperes. A low-voltage circuit is particularly a circuit with a rated or nominal current of up to 50 amperes, 40 amperes, 32 amperes, 25 amperes, 16 amperes, or 10 amperes. The current values ​​mentioned are particularly the rated current, the nominal current, and / or the cut-off current, i.e., the maximum current conducted through the circuit under normal circumstances, or the current normally interrupted by the circuit, for example, by a protective device such as a protective switchgear, a circuit breaker, or a circuit breaker. The rated current can be further graded, from 0.5 A through 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.

[0004] Circuit breakers are long-known overcurrent protection devices used in low-voltage circuits in electrical installation technology. They protect circuits from damage caused by overcurrent and / or short-circuit-induced heating. They automatically disconnect circuits in the event of an overload and / or short-circuit. They are non-self-resetting fuses.

[0005] Unlike circuit breakers, circuit breakers are rated for currents greater than 125 amperes, sometimes starting at 63 amperes. Consequently, circuit breakers are simpler and more compact. They typically have a mounting option for top-hat rails (supporting rails, DIN rails, TH35).

[0006] Circuit breakers are electromechanical. They contain mechanical switching contacts or operating current triggers within their housings for interrupting (triggering) the current. Typically, a bimetallic protective element or bimetallic element is used to trigger (interrupt) the circuit in the event of a prolonged overcurrent (overcurrent protection) or thermal overload (overload protection). An electromagnetic trigger with a coil is used for short-term triggering when the overcurrent limit is exceeded or a short circuit occurs (short-circuit protection). One or more arc extinguishing chambers or arc extinguishing devices are provided. Furthermore, connection elements for the conductors of the circuit to be protected are provided.

[0007] Protection switchgear with electronic interruption units are a relatively recent development. These devices feature semiconductor-based electronic interruption units. This means that the current in the low-voltage circuit is conducted through a semiconductor device or switch, which interrupts the current or switches it into conduction mode. Protection switchgear with electronic interruption units also typically have a mechanical disconnect contact unit, which has disconnection characteristics, particularly in accordance with the relevant standards for low-voltage circuits. The contacts of the mechanical disconnect contact unit are connected in series with the electronic interruption unit, meaning that the current in the low-voltage circuit to be protected is conducted through both the mechanical disconnect contact unit and the electronic interruption unit.

[0008] The present invention can be used both for low-voltage DC circuits and for low-voltage AC circuits. In particular, the invention relates to low-voltage AC circuits having an AC voltage, which is typically a time-dependent sinusoidal AC voltage with a frequency f. The time dependence of the instantaneous voltage value u(t) of the AC voltage is described by the following equation:

[0009] u(t)=U*sin(2π*f*t)

[0010] in:

[0011] u(t) = instantaneous voltage value at time t

[0012] U = voltage amplitude

[0013] A harmonic AC voltage can be represented by the rotation of a pointer, where the length of the pointer corresponds to the voltage amplitude (U). Here, the instantaneous deflection is the projection of the pointer onto the coordinate system. The oscillation period corresponds to a full rotation of the pointer, and its full angle is 2π (2Pi), or 360°. The angular frequency is the rate of change of the phase angle of this rotating pointer. The angular frequency of a harmonic oscillation is always 2π times its frequency, i.e.:

[0014] ω = 2π * f = 2π / T = angular frequency of the AC voltage (T = duration of the oscillation cycle)

[0015] The specification of angular frequency (ω) is often preferred to frequency (f) because many vibration theory formulas can be expressed more compactly in terms of angular frequency due to the presence of trigonometric functions, which, by definition, have a period of 2π:

[0016] u(t)=U*sin(ωt)

[0017] In the case of an angular frequency that is not constant over time, the term instantaneous angular frequency is also used.

[0018] In the case of a sinusoidal, in particular temporally constant, alternating voltage, the time-dependent value as a function of the angular velocity ω and the time t corresponds to a time-dependent angle φ(t), which is also called the phase angle φ(t).

[0019] That is, the phase angle φ(t) periodically passes through the range of 0...2π or 0°...360°. That is, the phase angle periodically assumes values ​​between 0 and 2π or 0° and 360° (φ=n*(0...2π) or φ=n*(0°...360°), abbreviated to: φ=0...2π or φ=0°...360° due to the periodicity).

[0020] The instantaneous voltage value u(t) therefore refers to the instantaneous value of the voltage at the time t, i.e. in the case of a sinusoidal (periodic) alternating voltage, to the value of the voltage about the phase angle φ (φ=0...2π or φ=0°...360° for the respective period). Summary of the Invention

[0021] The object of the present invention is to improve a circuit breaker device of the type mentioned at the outset, in particular to achieve greater flexibility and new features for the circuit breaker device.

[0022] The aforementioned object is achieved by a protective switching device having the features of patent claim 1 and by a method according to patent claim 15 .

[0023] According to the present invention, a protective switchgear for protecting a low-voltage circuit, in particular a low-voltage AC circuit, comprises:

[0024] a housing having at least one line-side connection and at least one load-side connection, both for a low-voltage circuit,

[0025] a mechanically isolating contact unit, which is connected in series with the electronic interruption unit, wherein 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,

[0026] - a mechanically separating contact unit can be switched by opening at least one contact to prevent current flow in the low-voltage circuit or closing at least one contact for current flow in the low-voltage circuit,

[0027] - the electronic interruption unit can switch the switching element, based on a semiconductor, into a high-resistance state of the switching element to prevent current flow or into a low-resistance state of the switching element for current flow in the low-voltage circuit,

[0028] -Current sensor unit, used to determine the current level of the low voltage circuit,

[0029] a control unit connected to the current sensor unit, the mechanically isolating contact unit and the electronic interruption unit, wherein when a current limit value and / or a current-time limit value is exceeded, prevention of a current flow in the low-voltage circuit is initiated, in particular by a high-resistance state of a switching element of the electronic interruption unit.

[0030] According to the present invention, a control input is provided on the protective switching device. The control input is in particular connected to the control unit. The protective switching device is designed such that the electronic interruption unit can be switched to a high-impedance state or a low-impedance state by means of the control input.

[0031] This has the advantage of providing a control input with which the electronic interruption unit can be switched unambiguously. Usually, mechanically disconnecting contact units can only be switched using a handle accessible on the protective switchgear. External (control input) switchability of the electronic interruption unit is usually not provided. The present invention makes this possible externally and offers the possibility of expanding the functionality of the device.

[0032] Further advantageous embodiments of the invention are specified in the dependent claims and exemplary embodiments.

[0033] In an advantageous embodiment of the present invention, the mechanical disconnecting contact unit is associated with the load-side connection, and the electronic disconnecting unit (EU) is associated with the grid-side connection. In particular, the mechanical disconnecting contact unit can be operated by a mechanical handle to open at least one contact or close at least one contact.

[0034] This has the particular advantage that a structure for a protective switching device is provided, wherein the protective switching device is also functional when the contacts of the mechanically isolating contact unit are open.

[0035] In an advantageous embodiment of the present invention, two grid-side connections and at least one load-side connection are provided, in particular, a grid-side phase conductor connection, a grid-side neutral conductor connection, and a load-side phase conductor connection.

[0036] This has the particular advantage that a structure for a protective switching device is provided, wherein, on the one hand, an energy supply to the protective switching device is provided and, on the other hand, a space-saving structure can be achieved with only one switching pole.

[0037] In an advantageous embodiment of the present invention, two grid-side connections and two load-side connections are provided, in particular, a grid-side neutral conductor connection, a grid-side phase conductor connection, a load-side neutral conductor connection, and a load-side phase conductor connection.

[0038] This has the particular advantage that a design for a two-pole circuit breaker device is provided, so that the phase conductor and the neutral conductor can be connected directly and, for example, an additional neutral conductor track can be omitted.

[0039] In an advantageous embodiment of the present invention, the control input has particularly safe galvanic isolation. In particular, there is safe galvanic isolation between the control input and the control unit. More particularly, there is safe galvanic isolation between the control input and the low-voltage circuit (the voltage of the low-voltage circuit in the device).

[0040] For example, safe galvanic isolation can be achieved by means of an optocoupler or a relay. Alternatively, safe galvanic isolation can be achieved by inductive or capacitive galvanic isolation.

[0041] This has the particular advantage that the control inputs can be used universally in a potential-free manner or provide safe galvanic isolation from the phase conductors (or from the control unit). Since the phase conductors (or control unit) are at mains voltage (e.g., 230 V (AC)) during operation, this galvanic isolation allows for safe use of the control inputs. This prevents electric shock or so-called residual voltage on the connected cables and devices connected thereto. In the event of residual voltage, potential is unintentionally transferred to the cables or other devices.

[0042] This has the particular advantage that the protective switching device can be used universally without electrical potential or provides a safe galvanic isolation with respect to the phase conductors (or with respect to the control unit).

[0043] In an advantageous embodiment of the present invention, the electronic interruption unit can be switched to the low-impedance state by means of the control input only when a release condition exists. In particular, if the electronic interruption unit is in a high-impedance state due to a protective function of the protective switching device, it cannot be switched to the low-impedance state by means of the control input (in particular, at least not within a first time period after the high-impedance state).

[0044] The first duration may be in the range of 10 seconds or longer.

[0045] This has the particular advantage that the basic protective function of the protective switching device is not influenced by the control input and that, for example, a defective protective switching device (without release conditions) cannot be forced to close by the control input, ie, supply energy to the low-voltage circuit without protection.

[0046] Furthermore, in particular, in the case of a high-resistance state of the electronic interruption unit caused by the protective function of the protective switching device (e.g., when / after a current limit value and / or a current-time limit value is exceeded), this high-resistance state cannot be changed by the control input, i.e., a low-resistance state cannot be forced (immediately) to be switched back on. Therefore, the protective device can only be switched back to low resistance or can be switched to low resistance after the fault has been acknowledged or after the fault no longer exists.

[0047] In an advantageous embodiment of the invention, the test function on the protection switching device side

[0048] a) switching the electronic interrupt unit from a high-resistance state to a low-resistance state for a first period of time, or (and)

[0049] b) switching the electronic interrupt unit from the low-resistance state to the high-resistance state for a second period of time,

[0050] Ability to be independent of control inputs (i.e., execution of the check function does not depend on (the state of) a control input).

[0051] This has the particular advantage that the test function of the protective switching device is not influenced by the control input, so that functional reliability is ensured in particular by the test function of the protective switching device (during operation).

[0052] The first time period is, for example, a short time period ranging from μs or ms to one second, such as 100 μs ... 200 μs ... 300 μs ... 600 μs ... 700 μs ... 800 μs ... 1 ms ... 10 ms ... 20 ms ... 40 ms ... 50 ms ... 100 ms ... 200 ms ... 500 ms ... 1s (any possible intermediate value).

[0053] The second time period is, for example, a short time period in the range of μs or ms to one second, such as 100 μs ... 200 μs ... 300 μs ... 600 μs ... 700 μs ... 800 μs ... 1 ms ... 10 ms ... 20 ms ... 40 ms ... 50 ms ... 100 ms ... 200 ms ... 500 ms ... 1 s (any possible intermediate value).

[0054] In an advantageous embodiment of the present invention, at least one contact of the mechanically isolating contact unit can be opened by means of a control input, in particular it can be configured whether

[0055] a) the electronic interrupt unit can be switched to a high-impedance state or a low-impedance state, or

[0056] b) At least one contact of the mechanically separate contact unit can be opened.

[0057] Alternatively or additionally, one or the other state can be initiated, for example, further by a (particularly configurable) switching sequence; this can be configurable in particular.

[0058] This has the particular advantage that it provides for further flexibility and functional expansion of the protective switching device.

[0059] In an advantageous embodiment of the invention, the control input is accessible on the housing side. In particular, the control input has a plurality of connection terminals, in particular two or three connection terminals, wherein these connection terminals are connected within the protective switching device to, in particular, at least one optocoupler or relay contact (typically to a potential isolation element, for example based on inductance or capacitance).

[0060] Furthermore, the control input provides a wired interface (particularly a two-wire or three-wire wired communication interface), so that quasi-delayless signaling (substantially no latency) is provided via the control input. Quasi-delayless refers to direct signaling, i.e., without overhead information processing, such as occurs in principle in a LAN / WLAN connection by using communication protocols such as MAC addresses, TCP / IP communication, or OSI communication.

[0061] This has the particular advantage of providing a simple possibility of connecting control inputs.

[0062] In an advantageous embodiment of the invention, a display unit connected to the control unit is provided, which has a display device visible on the protective switching device for displaying the high-resistance state or the low-resistance state of the electronic interruption unit.

[0063] This has the particular advantage that a visualization of the status of the electronic interruption unit is provided.

[0064] In an advantageous embodiment of the invention, the protection switching device is designed such that, when the high-impedance state of the electronic interruption unit is initiated by the control input, this high-impedance state of the electronic interruption unit is established at a current zero crossing.

[0065] Current zero crossing means directly at or near the current zero crossing, that is to say, for example at a momentary value of the current which is less than a first current limit, for example less than 5 Amperes...1 Ampere (any intermediate values ​​are possible; the first current limit depends on the nominal current of the low-voltage circuit or the protective switchgear, for example 20%...15%...10%...5%...1% or less of the nominal current).

[0066] This has the particular advantage of supporting quasi-powerless switching and thus reducing the load on the electronic interruption unit, in particular its semiconductor-based switching elements.

[0067] In an advantageous embodiment of the present invention, a (first) voltage sensor unit connected to the control unit is provided for determining the voltage level of the low-voltage circuit, in particular the instantaneous value of the voltage level. The protective switching device is designed such that, when a low-impedance state of the electronic interruption unit is activated by a control input, this low-impedance state of the electronic interruption unit is established at a voltage zero crossing. Alternatively or additionally, when a high-impedance state of the electronic interruption unit is activated by a control input, this high-impedance state of the electronic interruption unit is established at a voltage zero crossing.

[0068] This has the particular advantage of supporting further quasi-powerless switching and thus reducing the load on the electronic interruption unit, in particular its semiconductor-based switching elements.

[0069] Voltage zero crossing means directly at or near the voltage zero crossing, ie for example at a momentary value of the voltage that is less than a first voltage limit, eg less than 10 Volts, 25 Volts or 50 Volts (any intermediate or smaller values ​​are possible).

[0070] In an advantageous embodiment of the invention, the circuit breaker device is designed such that the control input:

[0071] a) initiates a high-impedance state upon application of a first voltage level, or initiates a low-impedance state upon application of a second voltage level, or

[0072] b) initiating a change of state of the electronic interrupt unit by applying a third voltage level for a first duration, or

[0073] c) changing to the low-resistance state by applying a third voltage level for a second duration and changing to the high-resistance state after a third, in particular adjustable, duration.

[0074] This has the particular advantage that there are different switching options which can be configured, for example, advantageously.

[0075] In an advantageous embodiment of the present invention, the protective switching device is designed so that a fault-induced high-resistance state of the electronic interruption unit is detected by means of a control input, in particular, the fault-induced high-resistance state is initiated by exceeding a current limit value and / or a current-time limit value in the low-voltage circuit, so that the electronic interruption unit can subsequently switch to a low-resistance state when there is no fault, or automatically switches to a low-resistance state. In particular, it can be configured whether the control input is used to detect the fault-induced high-resistance state.

[0076] a) the electronic interrupt unit can be switched to a high-impedance state or a low-impedance state, or

[0077] b) Confirm the high resistance state caused by the fault.

[0078] This has the particular advantage that an additional functionality of the protective switching device is provided.

[0079] According to the invention, a corresponding method is claimed for a protective switching device for a low-voltage circuit having electronic (semiconductor-based) switching elements, which has the same and other advantages.

[0080] A method for a protective switching device for protecting a low-voltage circuit, the protective switching device comprising:

[0081] - a housing having at least one line-side connection and at least one load-side connection,

[0082] a mechanically isolating contact unit, which is connected in series with the electronic interruption unit, wherein 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,

[0083] - a mechanically separating contact unit can be switched by opening at least one contact to prevent current flow in the low-voltage circuit or closing at least one contact for current flow in the low-voltage circuit,

[0084] - the electronic interruption unit can switch the switching element via a semiconductor-based switching element into a high-resistance state of the switching element to prevent a current flow in the low-voltage circuit or into a low-resistance state of the switching element for a current flow in the low-voltage circuit,

[0085] - determining the magnitude of the current of the low-voltage circuit and, if a current limit value and / or a current-time limit value is exceeded, initiating the prevention of the current flow in the low-voltage circuit,

[0086] The electronic interruption unit can be switched to a high-impedance state or a low-impedance state via a control input.

[0087] All designs, whether in dependent form by referring to patent claims 1 or 15 or by referring only to individual features or combinations of features of the claims, in particular by referring to independent method claims from dependent device claims (and vice versa), lead to improvements in the protective switchgear, in particular functional improvements, and provide new concepts for protective switchgear. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] The described characteristics, features, and advantages of the present invention and their implementation will become clearer and more easily understood in conjunction with the following description of the embodiments, which are described in detail in conjunction with the accompanying drawings.

[0089] Here, in the accompanying drawings:

[0090] Figure 1 A first diagram showing a protective switchgear,

[0091] Figure 2 A second diagram showing a protective switchgear,

[0092] Figure 3 A diagram showing the control inputs,

[0093] Figure 4 A diagram showing functional groupings,

[0094] Figure 5 shows a diagram of a first configuration,

[0095] Figure 6 shows a diagram of a second configuration,

[0096] Figure 7 shows a diagram of a third configuration,

[0097] Figure 8 A diagram showing a fourth configuration is shown. DETAILED DESCRIPTION

[0098] Figure 1 The diagram shows a circuit breaker device SG for protecting a low-voltage circuit, in particular a low-voltage AC circuit, having a housing GEH, which comprises:

[0099] -Grid-side neutral conductor connection NG, grid-side phase conductor connection LG, load-side neutral conductor connection NL, load-side phase conductor connection LL of the low-voltage circuit;

[0100] On the grid side, the grid is usually connected to an energy source.

[0101] On the load side, the load is usually connected to electrical consumers;

[0102] - a (two-pole) mechanically disconnecting contact unit MK with load-side connection points APLL, APNL and grid-side connection points APLG, APNG,

[0103] A load-side connection point APNL is provided for the neutral conductor, a load-side connection point APLL is provided for the phase conductor, a grid-side connection point APNG is provided for the neutral conductor, and a grid-side connection point APNG is provided for the phase conductor. The load-side connection points APNL and APLL are connected to the load-side neutral conductor connection NL and the phase conductor connection LL, so that the contacts KKN and KKL can be opened to prevent current flow in the low-voltage circuit or closed to allow current flow in the low-voltage circuit.

[0104] The mechanically disconnecting contact unit can also be designed as a single-pole mechanically disconnecting contact unit, ie with contacts, wherein the contact KKL is preferably arranged in the phase conductor L, without providing a neutral conductor N passing through the protective switching device SG.

[0105] an electronic interruption unit EU, in particular a single-pole unit (which in a single-pole embodiment is in particular arranged in the phase conductor L), which has 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 or is connected to the mains-side connection point APLG of the mechanical disconnecting contact unit MK, wherein the electronic interruption unit has, via a semiconductor-based switching element, a high-resistance state of the switching element to prevent a current flow or a low-resistance state of the switching element for a current flow in the low-voltage circuit,

[0106] a current sensor unit SI for determining the magnitude of the current in the low-voltage circuit, which is arranged in particular in the phase conductor L,

[0107] a control unit SE connected to the current sensor unit SI, the mechanical disconnecting contact unit MK and the electronic interruption unit EU, wherein the prevention of the current flow of the low-voltage circuit is initiated when a current limit value and / or a current-time limit value is exceeded.

[0108] According to the present invention, the protective switching device SG is designed such that a control input CI is provided on the protective switching device SG. The control input CI is connected, in particular, to the control unit SE. The protective switching device is designed such that the electronic interruption unit EU can be switched to a high-impedance state or a low-impedance state by means of the control input CI.

[0109] Furthermore, a first voltage sensor unit SUA connected to the control unit SE can be provided, which determines the voltage level of the low-voltage circuit, in particular the instantaneous value of the voltage level, in particular at the grid-side connections LG, NG, in particular between the grid-side neutral conductor connection NG and the grid-side phase conductor connection LG. Advantageously, the electronic interruption unit EU is switched to the low-resistance state, in particular via a control input, when the absolute value of the instantaneous value of the voltage level falls below a first voltage limit, in particular less than or equal to 50 V (or 25 V or 10 V).

[0110] For example, if the electronic interruption unit EU is to be switched to a low-impedance state (switched on) via the control input CI, the switch-on signal is sent from the control unit SE to the electronic interruption unit (EU) only when the instantaneous value of the voltage magnitude is below a first voltage limit, specifically less than or equal to 50 volts. This results in a time delay of up to approximately 10 ms (at a 50 Hz grid frequency) between the time of the external control signal ESS (switching-on signal) (at the control input CI) and the low-impedance state of the electronic interruption unit EU. The same applies to the switching of the electronic interruption unit EU to a high-impedance state initiated by the control input CI. Alternatively, a first current limit can be used instead of the first voltage limit when the electronic interruption unit EU is switched to a high-impedance state initiated by the control input.

[0111] Generally speaking, the mechanical disconnecting contact unit MK and the electronic interruption unit EU form a series circuit. The series circuit is connected to at least one mains-side connection on the one hand and to at least one load-side connection on the other hand. The mechanical disconnecting contact unit MK can advantageously be associated with the load-side connection, and the electronic interruption unit EU can be associated with the mains-side connection, such as Figure 1 shown.

[0112] The mechanically disconnecting contact unit MK can be operated by means of a mechanical handle HH in order to open the contacts or close the contacts, just like a conventional circuit breaker or a miniature circuit breaker (MCB).

[0113] The control unit SE may have a microcontroller MP (microcontroller unit) (eg Figure 2 shown).

[0114] A second voltage sensor unit SUB connected to the control unit SE can also be provided, which determines the voltage level between the grid-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU.

[0115] The measuring impedance ZM can be connected between the grid-side connection points APLG and APNG of the mechanically disconnecting contact unit MK. The measuring impedance ZM can be, for example, a resistor and / or a capacitor. The measuring impedance can also be an inductor. In particular, the measuring impedance can be a series or parallel connection of resistors and / or capacitors and / or inductors.

[0116] In accordance with Figure 1 In the example shown, the electronic interruption unit EU is designed as a single-pole, in this example, in the phase conductor. Here, the grid-side connection point APNG for the neutral conductor of the mechanically disconnecting contact unit MK is connected to the grid-side neutral conductor connection NG of the housing GEH. In the single-pole variant, this connection and the neutral conductor contact KKN of the mechanically disconnecting contact unit can be omitted.

[0117] The protective switching device SG is advantageously designed such that the contacts of the mechanical disconnecting contact unit MK can be opened by the control unit SE, but cannot be closed, as indicated by the arrow from the control unit SE to the mechanical disconnecting contact unit MK. This means, for example, that in one embodiment, the contacts of the mechanical disconnecting contact unit MK can be opened by means of the control input CI, but cannot be closed.

[0118] The mechanical disconnect contact unit MK can be operated by a mechanical handle HH on the protective switching device SG to manually (manually) open or close the contacts KKL and KKN. The mechanical handle HH indicates (particularly via a mechanical connection between the contacts and the handle) the switching state (open or closed) of the contacts of the mechanical disconnect contact unit MK on the protective switching device.

[0119] The mechanically disconnecting contact unit MK is advantageously designed such that the contacts can be closed (manually) by a mechanical handle only after a release (activation), in particular a release signal.

[0120] This is also indicated by the arrow from the control unit SE to the mechanical disconnect contact unit MK. This means that the contacts KKL, KKN of the mechanical disconnect contact unit MK can only be closed by the handle HH when a release or release signal (from the control unit) is present. Without a release or release signal, the handle HH can be operated, but the contacts cannot close ("continuous slip").

[0121] The protective switching device SG has an energy supply device NT, for example a power supply. In particular, an energy supply device NT is provided for the control unit SE, which is provided by Figure 1 The connection between the energy supply device NT and the control unit SE is indicated. The energy supply device NT is (on the other hand) connected to the grid-side neutral conductor connection NG and the grid-side phase conductor connection LG. A fuse SS, in particular a fuse and / or a switch, can advantageously be provided in the connection to the grid-side neutral conductor connection NG (and / or the phase conductor connection LG).

[0122] In the case of purely single-pole circuit breakers, the energy supply is provided via an external energy source / another connection.

[0123] High resistance refers to a state where only negligible current flows. In particular, high resistance refers to a resistance value greater than 1 kilo-ohm, preferably greater than 10 kilo-ohm, 100 kilo-ohm, 1 megohm, 10 megohm, 100 megohm, 1 gigaohm or greater.

[0124] Low resistance refers to a state in which a specified current value can flow through the protective switch device. In particular, low resistance refers to a resistance value of less than 10 ohms, preferably less than 1 ohm, 100 milliohms, 10 milliohms, 1 milliohm or less.

[0125] In a first variant, the mechanical disconnect contact unit MK can be interrupted in a single-pole manner. This means that only one of the two / multiple conductors, in particular the active conductor or the phase conductor, is interrupted, i.e., mechanically contacted. The neutral conductor is then contactless, i.e., directly connected.

[0126] In a second variant of the mechanically disconnecting contact unit MK, the neutral conductor also has a mechanical contact, such as Figure 1 shown.

[0127] Mechanical contacts or mechanical disconnecting contact units MK are particularly those which implement a disconnecting function (compliant with standards) via the disconnecting contact unit MK. The essential features of a disconnecting function are:

[0128] - According to the standard minimum air distance (minimum distance of contacts),

[0129] - (mechanical) contact position indication of the contacts of a mechanically separated contact unit,

[0130] - Free triggering, i.e. interruption of the mechanical separation of the contacts of the contact unit by operation via the handle or the control unit is always possible, so that (permanent) locking of the contacts in the closed state by the handle is not possible.

[0131] Furthermore, the standard disconnect function can include the ability to lock the disconnect contact unit or the handle in the switched-on or switched-off state.

[0132] Regarding the minimum air distance between the contacts of a separate contact unit, this minimum air distance depends essentially on the voltage. Other parameters are the degree of contamination, the type of field (homogeneous, non-homogeneous), and the air pressure or the height above the standard zero point.

[0133] There are corresponding regulations or standards for these minimum air or creepage distances. These regulations, for example, specify minimum air distances for surge voltage resistance in air, which apply to both inhomogeneous and uniform (ideal) electric fields, depending on the degree of pollution. Surge voltage resistance is the strength that can be withstood when a corresponding surge voltage is applied. Only when this minimum length (minimum distance) exists does the disconnecting contact unit or protective switching device have the disconnecting function (disconnector characteristic).

[0134] In this context, for the function of the separator and its characteristics, the standard series DIN EN 60947 or IEC 60947 is relevant within the meaning of the present invention and is hereby incorporated by reference.

[0135] The disconnect contact unit is advantageously characterized by a minimum air distance of the open disconnect contacts in the off position (open position, open contacts), depending on the rated impulse withstand voltage and the degree of contamination. The minimum air distance is preferably between (minimum) 0.01 mm and 14 mm. The minimum air distance is particularly advantageously between 0.01 mm at 0.33 kV and 14 mm at 12 kV, particularly for contamination degree 1 and particularly for inhomogeneous fields.

[0136] Advantageously, the minimum air distance may have the following values:

[0137] E DIN EN 60947-1 (VDE 0660-100): 2018-06

[0138] Table 13 - Minimum air distances

[0139]

[0140] The pollution degree and field type correspond to the pollution degree and field type defined in the standard. This advantageously makes it possible to achieve a standard-compliant circuit breaker device that is dimensioned according to the rated surge voltage resistance.

[0141] Mechanically isolating contact units do not, in particular, refer to relay contacts.

[0142] Figure 2 Shown according to Figure 1 , in which additional or different units are shown.

[0143] exist Figure 2 In the embodiment, the energy supply device NT is part of the control unit SE. Furthermore, a (particularly wireless) communication unit COM is provided, which is connected to the control unit SE or a part thereof.

[0144] Furthermore, a display unit AE is 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 part of it. The display unit has a display device visible on the protective switching device, in particular for indicating the high-resistance state or low-resistance state of the electronic interrupting unit EU.

[0145] according to Figure 2 , the electronic interruption unit EU is part of the control unit SE.

[0146] according to Figure 2 The control unit SE may have a microcontroller MP (microcontroller unit). The microcontroller may have different functions or routines / methods, such as a configuration function KF, a switching logic function SF, and a protection function PF.

[0147] For example, the protective switching device SG operates in principle in such a way that, with the contacts of the mechanically separating contact unit closed and the interruption unit low-resistance,

[0148] If the determined current exceeds a first current value, in particular within a first time limit, the electronic interruption unit EU becomes high-resistance and the mechanical separation contact unit MK remains closed, and / or

[0149] (and / or) if the determined current exceeds a second, higher current value, in particular within a second time limit, the electronic interruption unit EU becomes high-resistance and the mechanically separating contact unit MK opens, and / or

[0150] If the determined current exceeds an even higher third current value, the electronic interruption unit becomes high-resistance and the mechanically separating contact unit MK opens.

[0151] The invention is described in more detail below in partly differentiated terms.

[0152] In new electronic protective switchgear, contacts (mechanically disconnecting contact units) are used in conjunction with electronic switches / semiconductor-based switching elements (electronic interruption units). The ability to control these switching elements via (galvanically isolated) control inputs CI offers a new possibility for expanding the functionality of the protective switchgear. At the same time, the present invention ensures that the controllability of the switching elements / electronic interruption units does not impair the safety-related protective functions of the protective switchgear.

[0153] The control unit SE can switch the electronic interruption unit EU into a high-resistance state or a low-resistance state, ie, switch it on and off, and open the contact(s) of the mechanically separating contact unit.

[0154] Furthermore, there are handles (for opening and closing the separating contact units), current measurement, advantageously voltage measurement, and energy supply. Protective switching devices can perform different protective functions PF, such as short-circuit protection, overload protection, differential fault current protection, fire protection, overvoltage protection, undervoltage protection, overtemperature protection.

[0155] Overload protection, for example, involves exceeding a first current limit value and / or a current-time limit value. Short-circuit protection, for example, involves exceeding a second (higher) current limit value and / or a current-time limit value. Differential fault current protection, for example, involves exceeding a differential current limit value (e.g., 30 mA). Fire protection, for example, involves detecting a series arc fault in a low-voltage circuit. The same applies to overvoltage protection, undervoltage protection, and overtemperature protection.

[0156] According to the present invention, a control input CI, particularly one with galvanic isolation, is added. The switching state of the electronic interruption unit EU can be controlled via this control input CI. Since the electronic interruption unit EU must implement the protection function PF, the control unit SE transmits a signal for switching the electronic interruption unit EU to a low-impedance state via the control input CI to the electronic interruption unit EU only when the stored protection function PF detects no fault, i.e., when a release condition exists. In particular, for a defined fault, i.e., when the electronic interruption unit EU is in a high-impedance state, the control input cannot change this state (i.e., cannot switch to a low-impedance state).

[0157] This means that, by means of the control input CI, the electronic interruption unit EU can only be switched to the low-resistance state if a release condition exists.

[0158] In particular, in the case of a high-resistance state of the electronic interruption unit EU caused by the protection function PF of the protective switching device, the electronic interruption unit cannot be switched to a low-resistance state via the control input.

[0159] Faults detected in protective switchgear are typically device faults, such as defective current sensor units, defective interruption units, or overheating. These can also occur due to external faults, such as overvoltage or undervoltage (voltage levels below the effective value for a certain period of time). This can also involve the normal protection function PF, which makes it impossible or impossible to immediately "force control" to a low impedance state via the control input IC after exceeding the current limit value and / or current-time limit value, thereby preventing current flow in the low-voltage circuit.

[0160] The same applies to other internal device functions / test functions on the protective switchgear side, e.g. for device diagnostics or surge protection.

[0161] a) switching the electronic interruption unit EU from a high-resistance state to a low-resistance state for a first period of time, or (and)

[0162] b) switching the electronic interruption unit EU from the low-resistance state to the high-resistance state for a second period of time,

[0163] Not affected by control input.

[0164] These brief switching actions can be used, for example, to test electronic interruption units or to check the functionality of current sensor units.

[0165] These brief switching actions are prioritized by the control unit SE or the switching logic function SF, so that the (external) control signal ESS at the control input CI cannot prevent these brief switching actions.

[0166] Therefore, the electronic interruption unit EU (or its switching elements) can only be controlled via the control input CI when the protective switching device is in a fault-free state and / or no fault is detected at the load-side connection / connections (at the load output) (tripping conditions exist). This task is taken over by the switching logic function SF. Therefore, the control input CI cannot directly access the electronic interruption unit (or its switching elements) for control purposes; instead, it only sends a signal ESSI to the switching logic function SF to switch the electronic interruption unit on or off. The switching logic function SF ensures that the protection function PF always has primary control over the electronic interruption unit.

[0167] This applies not only to the protection function PF of the protective switching device, but also to a test function of the protective switching device, which in particular tests the switchability of the electronic interruption unit by, for example, switching it on or off within a (short) first or second time period.

[0168] Figure 3 The basic structure of a galvanically isolated control input CI connected to an external control unit ESE is shown.

[0169] Figure 3 The control input CI, accessible from the housing, is shown. It has multiple connection terminals, in this example two connection terminals AK1 and AK2, which are connected to at least one optocoupler OPK within the protective switchgear. In this example, the optocoupler OPK is connected on the one hand to a resistor R1, which is connected on the other hand to a voltage of 3.3 V (i.e., a positive terminal at an internal voltage of 3.3 volts). The connection between resistor R1 and optocoupler OPK is accessible {0 V; 3.3 V} {0.1}, and in this example, an internal control signal ESSI equivalent to (and galvanically isolated from) the external control signal ESS is provided for further processing in the protective switchgear. The other terminal of the optocoupler OPK is connected to another terminal at a voltage of 0 V (i.e., ground).

[0170] The two connection terminals AK1, AK2 are connected outside the housing to a two-wire line having a first conductor LT1 and a second conductor LT2. The two-wire line is also connected to an external control unit ESE. The external control unit ESE optionally provides a voltage signal 24V, which drives an optocoupler via a control input CI to set the electronic interruption unit to the (desired) high or low resistance.

[0171] This means that an optocoupler OPK with corresponding galvanic isolation is provided. The external (remote) control unit ESE sends the voltage to transmit the control signal ESS.

[0172] Instead of an optocoupler, a relay or other element may be provided or used for galvanic isolation, such as an element based on capacitive or inductive galvanic isolation.

[0173] Figure 4 Another embodiment of the present invention illustrates the functional grouping of a microcontroller MP. The microcontroller MP has a connection to a control input CI, to which a signal from a control input SCI is fed. This signal is fed to a control signal configuration unit CSC. Optionally, for example, it can be configured to disconnect the mechanical disconnect contact unit MK via a disconnect signal TRIP (opening one or more contacts) via a control input. The signal from the control input is further fed to a switching logic function SF. The switching logic function is also connected to a protection function PF, in this example to an internal protection function IPF for internally checking and reporting the absence of faults in the protective switching device, and an external protection function CPF, which monitors the low-voltage circuit and reports overcurrent events, short circuits, and other events in the low-voltage circuit.

[0174] If there are no internal faults in the protective switching device (reported by the internal protection function IPF) and no external faults in the low-voltage circuit to be protected (reported by the external protection function CPF), both messages are sent to the switching logic function SF, then the release condition exists and the electronic interruption unit can be switched to the low-impedance state or the high-impedance state via the control inputs (connection of the switching logic function SF to the electronic interruption unit EU (arrow pointing there)).

[0175] The switching logic function SF ensures in the protective switchgear that the protection functions PF, IPF, and CPF, which rely on the controllability of the electronic interruption unit EU, can always safely switch the electronic interruption unit when necessary. If the protection function is active, the electronic interruption unit cannot be controlled via the control input. If no protection state is active (release condition), the electronic interruption unit is released for control again via the control input.

[0176] The same principle applies to the internal device function / internal protection function IPF. This internal protection function IPF also accesses the electronic interruption unit. This can be done, for example, for brief switching operations, such as for device diagnostics. If this function is executed, control via the control inputs is not possible.

[0177] The control signal configuration unit CSC can be configured as to what is / should be done with the (digital) control signal.

[0178] For example, the electronic interruption unit EU, or the mechanical separation contact unit, or both can be controlled.

[0179] This can be done by different levels, time offsets or sequences of the external control signal ESS.

[0180] The following is an example of parameterization and configuration.

[0181] 1.) Simple on / off switching

[0182] When the applied external control signal ESS is 1, the electronic interrupt unit is in low resistance, and when the applied external control signal ESS is 0, the electronic interrupt unit is in high resistance.

[0183] 2.) Simple on / off switching (reverse)

[0184] When the external control signal ESS is 1, the electronic interrupt unit is in high resistance, and when the external control signal ESS is 0, the electronic interrupt unit is in low resistance.

[0185] [1 or 2 generally: when a first voltage level is applied, a high-impedance state is initiated, or when a second voltage level is applied, a low-impedance state is initiated, and the two voltage levels may be the same]

[0186] 3.) Current shock switching

[0187] The electronic interruption unit changes state when a rising (or falling) signal edge occurs at the control input. This means that the state change of the electronic interruption unit is initiated by applying the third voltage level for the first duration.

[0188] 4.) Current surge switching with timing / timer

[0189] The electronic interruption unit switches to the on state when a rising (or falling) signal edge occurs at the control input. The electronic interruption unit automatically switches to the high-impedance state after an (adjustable) time. In other words, the electronic interruption unit switches to the low-impedance state by applying a third voltage level for a second duration, and then switches to the high-impedance state after a third, in particular adjustable, duration.

[0190] 5.) Delayed connection

[0191] The electronic interruption unit switches like point 1 or point 2, but with an adjustable switch-on delay.

[0192] 6.) Delayed shutdown

[0193] The electronic interruption unit switches like point 1 or point 2, but with an adjustable switch-off delay.

[0194] Other parameterization options are:

[0195] 7.) Only the contacts of the mechanically separated contact unit are opened. For example, the separated contacts are opened at the edge change of the control signal (or signal sequence).

[0196] This is Figure 5 It is shown schematically in FIG. Figure 5 The figure shows that the external protection function can control the parameter configuration of 3 states.

[0197] A1 = Mechanically separated contact unit One or more contacts are open, electronic interruption unit is high resistance

[0198] S1 = Mechanically separated contact unit One or more contacts are closed, electronic interruption unit is high resistance

[0199] E1 = Mechanically separated contact unit One or more contacts are closed, electronic interruption unit is low resistance

[0200] The protective switching device is configured such that at least one contact of the mechanically disconnecting contact unit MK is opened by means of the control input CI. This means that the external / internal control signal ESS / ESSI leads to the state A1.

[0201] Figure 6 Shown according to Figure 5The difference is that the external / internal control signal ESS / ESSI causes a simple on / off state by means of the switching logic function SF, i.e. a low-resistance / high-resistance state of the electronic interruption unit, wherein the high-resistance state occurs when a "positive" logic-one control signal ESS / ESSI is applied. Figure 6 The low-resistance state should be activated when the control signal ESS / ESSI is not applied, i.e., logic zero. Figure 6 is marked by status 0.

[0202] Figure 7 Shown according to Figure 6 , differing in that it shows that the protective switchgear is designed or configured such that the electronic interruption unit EU is switched between a high-resistance / low-resistance state via the control signals ESS / ESSI, for example, via a logic zero or logic one state, alternatively via a first sequence, i.e., a sequence of zero / one states. On the other hand, one or more contacts of the mechanical disconnect contact unit can also be opened, for example, via a second sequence SEQB. In this example, the circuit of the mechanical disconnect contact unit is identified by the control signal configuration unit CSC. This means that the electronic interruption unit EU can be switched between a high-resistance / low-resistance state via the control input CI. Simultaneously, one or more contacts of the mechanical disconnect contact unit can be opened via a (switching) sequence stored in the protective switchgear.

[0203] Figure 8 Shown according to Figures 5 to 7 The difference is that it shows that the protective switching device is designed to confirm the fault state via the control signal ESS / ESSI.

[0204] This means that if the protective switching device is in state S1 due to exceeding the current limit value and / or the current-time limit value, this state can be acknowledged and reset via control input CI. Thus, the protective switching device can switch from state S1 to state E1 after a fault (when the fault has been eliminated again). This can be done remotely; the device does not have to be on site to switch to state E1.

[0205] This means that the protective switching device SG can be designed such that a fault-induced high-impedance state of the electronic interruption unit is detected by means of the control input CI, in particular the fault-induced high-impedance state is triggered by exceeding a current limit value and / or a current-time limit value in the low-voltage circuit.

[0206] The electronic interruption unit can then switch to a low-impedance state without a fault or automatically switch to a low-impedance state, in particular with or without the aid of a control input.

[0207] a) the electronic interrupt unit (EU) can be switched to a high-impedance state or a low-impedance state, or

[0208] b) Confirm the high resistance state caused by the fault.

[0209] Furthermore, the protective switching device can be designed such that the control input CI:

[0210] a) a high-impedance state is initiated when a first voltage level is applied, or a low-impedance state is initiated when a second voltage level is applied, or

[0211] b) changing the state by applying a third voltage level for a short time (e.g., less than 1 second). More specifically, changing to a low-resistance state by applying the third voltage level for a short time (e.g., less than 1 second), and changing back to a high-resistance state by applying a subsequent third voltage level.

[0212] The display unit has a display device visible on the protective switching device for displaying (illustrating) the high-resistance state or the low-resistance state of the electronic interruption unit EU, for example, by means of an LED display.

[0213] The contact position of the mechanically disconnecting contact unit is indicated by the handle; this indication by the handle does not indicate the switching state of the electronic interruption unit.

[0214] In particular, the switching state of the electronic interruption unit should be indicated when the switching state has been changed / switched on or off via the control input CI.

[0215] Although the present invention has been illustrated and described in detail through the embodiments, the present invention is not limited to the disclosed examples, and those skilled in the art may derive other variations therefrom without departing from the scope of protection of the present invention.

Claims

1. A protective switchgear (SG) for protecting a low voltage circuit, comprising: a housing (GEH) having at least one grid-side connection and at least one load-side connection, a mechanical disconnecting contact unit (MK) which is connected in series with the electronic interruption unit (EU), wherein 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 mechanically separating contact unit (MK) is switchable by opening at least one contact to prevent current flow in the low-voltage circuit or closing at least one contact for current flow in the low-voltage circuit, the electronic interruption unit (EU) can switch via a semiconductor-based switching element into a high-resistance state of the switching element to prevent a current flow or into a low-resistance state of the switching element for a current flow, - Current sensor unit (SI), used to determine the current level of the low voltage circuit, a control unit (SE) connected to the current sensor unit (SI), the mechanical disconnecting contact unit (MK) and the electronic interruption unit (EU), wherein: initiating the prevention of the current flow in the low-voltage circuit when a current limit value and / or a current-time limit value is exceeded, - A control input (CI) is provided on the protective switchgear (SG), The protective switchgear is designed to: The electronic interruption unit (EU) can be switched into a high-resistance state or a low-resistance state by means of the control input (CI).

2. The protective switchgear (SG) according to claim 1, It is characterized by: The mechanically disconnecting contact unit (MK) is associated with the load-side connection, and the electronic interruption unit (EU) is associated with the grid-side connection, In particular, the mechanically disconnecting contact unit (MK) can be operated by a mechanical handle in order to open the contacts or to close the contacts.

3. The protective switchgear (SG) according to claim 1 or 2, It is characterized by: Two grid-side connections and at least one load-side connection are provided.

4. The protective switchgear (SG) according to claim 1 or 2, It is characterized by: Two grid-side connections and two load-side connections are provided.

5. The protective switchgear (SG) according to any one of the preceding claims, It is characterized by: The control input (CI) has a particularly safe galvanic isolation.

6. The protective switchgear (SG) according to any one of the preceding claims, It is characterized by: Only when a release condition exists can the electronic interruption unit (EU) be switched to the low-resistance state by means of the control input. In particular, when the high-resistance state of the electronic interruption unit (EU) is caused by the protection function of the protective switching device, the electronic interruption unit cannot be switched to the low-resistance state via the control input.

7. The protective switchgear (SG) according to any one of the preceding claims, It is characterized by: Inspection function on the protection switchgear side, a) switching the electronic interrupt unit (EU) from a high-resistance state to a low-resistance state for a first period of time, or b) switching the electronic interruption unit (EU) which is in a low-resistance state to a high-resistance state for a second period of time, Not affected by the control input.

8. The protective switchgear (SG) according to any one of the preceding claims, It is characterized by: At least one contact of the mechanically disconnecting contact unit (MK) can be opened by means of the control input, In particular, it is possible to configure whether a) capable of switching the electronic interruption unit (EU) to a high-resistance state or a low-resistance state, or b) At least one contact of the mechanically disconnecting contact unit (MK) can be opened.

9. The protective switchgear (SG) according to any one of the preceding claims, It is characterized by: The control input is accessible on the housing side and in particular has a plurality of connection terminals, in particular two or three connection terminals, wherein the connection terminals are connected to at least one optocoupler within the protective switching device.

10. The protective switchgear (SG) according to any one of the preceding claims, It is characterized by: A display unit connected to the control unit (SE) is provided, which has a display device visible on the protective switching device for displaying a high-resistance state or a low-resistance state of the electronic interruption unit (EU).

11. The protective switchgear (SG) according to any one of the preceding claims, It is characterized by: The protective switching device is designed such that, in the case of a high-impedance state of the electronic interruption unit initiated via the control input (CI), the high-impedance state of the electronic interruption unit is established at a current zero crossing.

12. The protective switchgear (SG) according to any one of claims 1 to 10, It is characterized by: A first voltage sensor unit (SUA) connected to the control unit (SE) is provided for determining the voltage level of the low-voltage circuit, in particular the instantaneous value of the voltage level, The protective switching device is designed such that, in the case of a low-resistance state of the electronic interruption unit initiated via the control input (CI), the low-resistance state of the electronic interruption unit is established at a voltage zero crossing, and / or In the case of a high-impedance state of the electronic interruption unit initiated via the control input (CI), the high-impedance state of the electronic interruption unit is established at a voltage zero crossing.

13. The protective switchgear (SG) according to any one of the preceding claims, It is characterized by: The protective switching device is designed such that the control input (CI): a) a high-impedance state is initiated when a first voltage level is applied, or a low-impedance state is initiated when a second voltage level is applied, or b) the change of state of the electronic interruption unit is initiated by applying a third voltage level for a first period of time, or c) The change of the electronic interruption unit to the low-resistance state is initiated by applying a third voltage level for a second time period, and after a third, in particular adjustable, time period, the electronic interruption unit changes to the high-resistance state.

14. The protective switchgear (SG) according to any one of the preceding claims, It is characterized by: The protective switching device (SG) is designed such that a fault-induced high-impedance state of the electronic interruption unit is detected by means of the control input (CI), in particular such that the fault-induced high-impedance state is triggered by exceeding a current limit value and / or a current-time limit value in the low-voltage circuit. The electronic interruption unit can be switched to a low-resistance state or automatically switched to a low-resistance state when there is no fault, and can be configured to switch to a low-resistance state by means of the control input. a) switching the electronic interrupt unit (EU) to a high-resistance state or a low-resistance state, or b) Confirm the high resistance state caused by the fault.

15. A method for a protection switchgear (SG) for protecting a low-voltage circuit, the protection switchgear having: a housing (GEH) having at least one grid-side connection and at least one load-side connection, a mechanical disconnecting contact unit (MK) which is connected in series with the electronic interruption unit (EU), wherein 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, - a mechanically separated contact unit (MK) capable of switching by opening contacts to prevent current flow in a low-voltage circuit or closing contacts for current flow in a low-voltage circuit, the electronic interruption unit (EU) can be switched via a semiconductor-based switching element into a high-resistance state of the switching element to prevent a current flow in the low-voltage circuit or into a low-resistance state of the switching element for a current flow in the low-voltage circuit, - determining the magnitude of the current of the low-voltage circuit and, if a current limit value and / or a current-time limit value is exceeded, initiating the prevention of the current flow in the low-voltage circuit, The electronic interruption unit (EU) can be switched into a high-resistance state or a low-resistance state by means of a control input (CI).

16. The method for a protective switchgear (SG) according to claim 15, It is characterized in that Only when a release condition exists does the electronic interruption unit (EU) switch to the low-resistance state via the control input. In particular, when the high-resistance state of the electronic interruption unit (EU) is caused by the protection function of the protective switching device, the electronic interruption unit cannot be switched to the low-resistance state via the control input.

17. Protection switchgear (SG) according to claim 15 or 16, It is characterized in that Inspection function on the protection switchgear side, a) switching the electronic interrupt unit (EU) from a high-resistance state to a low-resistance state for a first period of time, or b) switching the electronic interruption unit (EU) which is in a low-resistance state to a high-resistance state for a second period of time, Not affected by the control input.

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