DE102022209018A1 - Circuit breaker and method - Google Patents

Abstract

The invention relates to a protective switching device for protecting an electrical low-voltage circuit, in which - network-side and load-side connections for conductors of the low-voltage circuit are provided, - a mechanical isolating contact unit with a closed state of the contacts for a current flow in the low-voltage circuit or an open state of the contacts for a galvanic current flow-avoiding Isolation in the low-voltage circuit is provided, - an electronic interruption unit is provided, which is connected in series on the circuit side to the mechanical isolating contact unit and which has a high-resistance state of the switching elements to avoid current flow or a low-resistance state of the switching elements to prevent current flow in the low-voltage circuit due to semiconductor-based switching elements, - that the level of a differential current of the conductors of the low-voltage circuit is determined and if first differential current limit values or first differential current time limit values are exceeded, an avoidance of a current flow in the low-voltage circuit is initiated by a high-resistance state of the switching elements of the electronic interruption unit when the isolating contacts are closed, - that after avoiding one Current flow is carried out due to a high-resistance state of the switching elements of the electronic interruption unit and the closed state of the contacts for the existence of exceedance of second differential current limit values or second differential current time limit values.

Description

The invention relates to the technical field of a protective switching device for a low-voltage circuit with an electronic interruption unit according to the preamble of claim 1 and a method for a protective switching device for a low-voltage circuit with an electronic interruption unit.

Low voltage refers to voltages of up to 1000 volts AC or up to 1500 volts DC. Low voltage refers in particular to voltages that are greater than low voltage, with values of 50 volts alternating voltage or 120 volts direct voltage.

Low-voltage circuits or networks or systems mean circuits with nominal currents or rated currents of up to 125 amperes, more specifically up to 63 amperes. Low-voltage circuits particularly refer to circuits with rated currents or rated currents of up to 50 amps, 40 amps, 32 amps, 25 amps, 16 amps or 10 amps. The current values mentioned in particular mean nominal, rated and/or switching off currents, i.e. the maximum current that is normally carried across the circuit or in 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 vary further, 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.

Circuit breakers have long been known overcurrent protection devices that are used in electrical installation technology in low-voltage circuits. These protect cables from damage caused by heating due to excessive current and/or short circuits. A circuit breaker can automatically switch off the circuit in the event of an overload and/or short circuit. A circuit breaker is a safety element that does not reset automatically.

In contrast to circuit breakers, circuit breakers are intended for currents greater than 125 A, sometimes even from 63 amps. Circuit breakers are therefore simpler and more delicate in design. Circuit breakers usually have a mounting option for mounting on a so-called top-hat rail (mounting rail, DIN rail, TH35).

Circuit breakers according to the state of the art are constructed electromechanically. In a housing they have a mechanical switching contact or shunt release to interrupt (trigger) the electrical current. A bimetal protective element or bimetal element is usually used to trigger (interrupt) in the event of a long-lasting overcurrent (overcurrent protection) or in the event of thermal overload (overload protection). An electromagnetic release with a coil is used for short-term tripping when an overcurrent limit is exceeded or in the event of a short circuit (short circuit protection). One or more arc extinguishing chamber(s) or devices for arc extinguishing are provided. Furthermore, connection elements for conductors of the electrical circuit to be protected.

Residual current circuit breakers for electrical circuits, especially for low-voltage circuits or systems, are well known. Residual current circuit breakers are also known as residual current devices, or RCD for short. Residual current circuit breakers determine the current sum in an electrical circuit, which is normally zero, and interrupt the electrical circuit when a differential current value is exceeded, i.e. a current sum of non-zero that exceeds a certain (differential) current value or residual current value.

Almost all previous residual current circuit breakers have a summation current transformer, the primary winding of which is formed by the conductors of the circuit and the secondary winding of which emits the sum of the current, which is used directly or indirectly to interrupt the electrical circuit.

For this purpose, two or more conductors, usually forward and return conductors or external and neutral conductors in a single-phase alternating current network, all three external conductors or all three external conductors and the neutral conductor in a three-phase alternating current network, are replaced by one, usually having an annular core made of ferromagnetic material, Current transformer led. Only the differential current, i.e. a current that deviates from the forward and reverse current, is converted from the conductors. Typically, the sum of current in an electrical circuit is zero. In this way, fault currents can be detected.

For example, if a current flows towards earth on the energy sink side or consumer side, this is referred to as a fault current. A fault occurs, for example, if there is an electrical connection from a phase conductor of the electrical circuit to ground. For example, if a person touches the phase conductor. Then part of the electrical current does not flow through the neut as usual ral conductor or neutral conductor, but via the person and the earth. This fault current can now be detected using the summation current transformer, since the sum of the inflowing and returning current recorded in terms of amount is not equal to zero. An interruption of the circuit, for example at least one, a part or all of the lines, is effected via a relay or a holding magnet release, for example with connected mechanics. Residual current circuit breakers for detecting alternating residual currents are generally from the literature DE 44 32 643 A1 known.

The main function of residual current circuit breakers is to protect people from electrical currents (electric shock), as well as systems, machines or buildings from fire caused by electrical insulation faults.

If the residual current circuit breaker or its summation current transformer is designed in such a way that the secondary-side energy of the summation current transformer is sufficient to actuate a trip unit or an interruption unit or a trigger, then such residual current circuit breakers are called mains voltage independent.
If auxiliary energy is required or used for the tripping circuit, which is usually generated by a power supply provided in the residual current circuit breaker, such residual current circuit breakers are called mains voltage dependent. This means that mains voltage-dependent residual current circuit breakers contain a power supply to supply energy for residual current detection (mains voltage independent ones do not). These power supplies are required, for example, to detect residual currents in DC voltage networks as well as mixed DC/AC networks or in circuits with high frequencies.

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 of the low-voltage circuit is conducted via semiconductor components or semiconductor switches, which interrupt the electrical current flow or can be switched to conduction. Protective switching devices with an electronic interruption unit also often have a mechanical isolating contact system, in particular with isolating properties in accordance with relevant standards for low-voltage circuits, whereby the contacts of the mechanical isolating contact system are connected in series to the electronic interruption unit, i.e. the current of the low-voltage circuit to be protected is transmitted both via the mechanical isolating contact system and also carried out via the electronic interruption unit.

beschrieben. Wobei:

u(t)

momentaner Spannungswert zu der Zeit t

U

Amplitude der Spannung

The present invention relates in particular to low-voltage alternating current circuits, with an alternating voltage, usually with a time-dependent sinusoidal alternating voltage with the frequency f. The time dependence of the instantaneous voltage value u(t) of the alternating voltage is given by the equation: $$\text{u}\left(\text{t}\right)=\text{U}*\text{sin}\left(2\mathrm{\pi }*\text{f}*\text{t}\right)$$

described. Where:

u(t)

instantaneous voltage value at time t

U

Amplitude of voltage

(T = Periodendauer der Schwingung)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 period of oscillation corresponds to one full revolution of the pointer and its full angle is 2π (2Pi) or 360°. The angular frequency is the rate of change of the phase angle of this rotating pointer. The angular frequency of a harmonic oscillation is always 2π times its frequency, i.e.: $$\mathrm{\omega }=2\mathrm{\pi }*\text{f}=2\mathrm{\pi }/\text{T}=\text{Circular frequency of the alternating voltage}$$

(T = period of the oscillation)

The specification of the angular frequency (ω) is often preferred over the frequency (f), since many formulas in vibration theory can be represented more compactly using the angular frequency due to the occurrence of trigonometric functions, the period of which is by definition 2n: $$\text{u}\left(\text{t}\right)=\text{U}*\text{sin}\left(\mathrm{\omega }\text{t}\right)$$

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

In the case of a sinusoidal, in particular time-constant, alternating voltage, the time-dependent value from the angular velocity ω and the time t corresponds to the time-dependent angle φ(t), which is also referred to as the phase angle φ(t). This means that the phase angle φ(t) periodically passes through the range 0...2π or 0°...360°. This means that the phase angle periodically assumes a value between 0 and 2n or 0° and 360° (φ = n* (0...2π) or φ = n* (0°...360°), due to periodicity; shortened: φ = 0...2π or φ = 0°...360°).

With the instantaneous voltage value u(t), the instantaneous value of the voltage at time t is therefore the case with a sinusoidal (periodic schen) alternating voltage means the value of the voltage at the phase angle φ (φ = 0...2π or φ = 0°...360°, of the respective period).

The object of the present invention is to improve a protective switching device of the type mentioned at the beginning, in particular to ensure protection against (fault) currents caused by people while at the same time ensuring security of supply or availability of electrical systems, i.e. immunity to technically caused (fault) currents which would lead to a false tripping of the protective switching device. This means, on the one hand, to ensure personal protection and, on the other hand, to improve the security of supply of a low-voltage circuit. Alternatively, to create a novel concept for such a protective switching device.

This object is achieved by a protective switching device with the features of patent claim 1, and by a method according to patent claim 12.

• - ein Gehäuse mit netzseitigen und lastseitigen Anschlüssen für Leiter des Niederspannungsstromkreises,
• - eine Differenzstromsensoreinheit, zur Ermittlung der Höhe eines Differenzstromes der Leiter des Niederspannungsstromkreises,

• - eine mechanische Trennkontakteinheit, die einen geschlossenen Zustand der Kontakte für einen Stromfluss im Niederspannungsstromkreis oder einen geöffneten Zustand der Kontakte für eine stromflussvermeidende galvanische Trennung im Niederspannungsstromkreis aufweist, die mechanische Trennkontakteinheit ist insbesondere durch eine mechanische Handhabe bedienbar und schaltbar, so dass ein Öffnen von Kontakten zur Vermeidung eines Stromflusses oder ein Schließen der Kontakte für einen Stromfluss im Niederspannungsstromkreis (durch die Handhabe) schaltbar ist, damit ist (insbesondere) eine galvanische Trennung im Niederspannungsstromkreis schaltbar; bei einer mechanischen Trennkontakteinheit wird ein Öffnen von Kontakten auch als Freischalten und ein Schließen von Kontakten als Zuschalten bezeichnet;
• - eine elektronische Unterbrechungseinheit, die stromkreisseitig in Serie zur mechanischen Trennkontakteinheit geschaltet ist und die durch halbleiterbasierte Schaltelemente einen hochohmigen (insbesondere nichtleitenden) Zustand der Schaltelemente zur Vermeidung eines Stromflusses oder einen niederohmigen Zustand der Schaltelemente zum Stromfluss im Niederspannungsstromkreis aufweist; bei einer elektronische Unterbrechungseinheit wird ein hochohmiger (insbesondere nichtleitender) Zustand der Schaltelemente (zur Vermeidung eines Stromflusses) auch als ausgeschalteter Zustand (Vorgang: Ausschalten) und ein niederohmiger (leitender) Zustand der Schaltelemente (zum Stromfluss) als eingeschalter Zustand (Vorgang: Einschalten) bezeichnet;
• - einer Steuerungseinheit, die mit der Differenzstromsensoreinheit, der mechanischen Trennkontakteinheit und der elektronischen Unterbrechungseinheit verbunden ist. Erfindungsgemäß ist das Schutzschaltgerät, insbesondere die Steuerungseinheit, derart ausgestaltet, dass bei Überschreitung von ersten Differenzstromgrenzwerten oder ersten Differenzstrom-Zeitgrenzwerten eine Vermeidung eines Stromflusses im Niederspannungsstromkreis durch einen hochohmigen Zustand der Schaltelemente der elektronischen Unterbrechungseinheit bei geschlossenem Zustand der Trennkontakte initiiert wird. Nach einer Vermeidung eines Stromflusses durch einen hochohmigen Zustand der Schaltelemente der elektronischen Unterbrechungseinheit und geschlossenem Zustand der Kontakte wird eine Prüfung auf Vorliegen der Überschreitung von zweiten Differenzstromgrenzwerten oder zweiten Differenzstrom-Zeitgrenzwerten durchgeführt.

According to the invention, a protective switching device is provided for protecting an electrical low-voltage circuit, in particular a low-voltage alternating circuit, comprising:

• - a housing with network-side and load-side connections for conductors of the low-voltage circuit,
• - a differential current sensor unit for determining the level of a differential current in the conductors of the low-voltage circuit,

• - a mechanical isolating contact unit, which has a closed state of the contacts for a current flow in the low-voltage circuit or an open state of the contacts for a current flow-avoiding galvanic isolation in the low-voltage circuit, the mechanical isolating contact unit can be operated and switched in particular by a mechanical handle, so that contacts can be opened to avoid a current flow or a closing of the contacts for a current flow in the low-voltage circuit can be switched (through the handle), so (in particular) a galvanic isolation in the low-voltage circuit can be switched; In the case of a mechanical isolating contact unit, opening contacts is also referred to as disconnecting and closing contacts is referred to as switching on;
• - an electronic interruption unit, which is connected in series on the circuit side to the mechanical isolating contact unit and which, through semiconductor-based switching elements, has a high-resistance (in particular non-conducting) state of the switching elements to prevent current flow or a low-resistance state of the switching elements to prevent current flow in the low-voltage circuit; In an electronic interruption unit, a high-resistance (in particular non-conducting) state of the switching elements (to avoid current flow) is also called a switched-off state (process: switching off) and a low-resistance (conducting) state of the switching elements (for current flow) is also called a switched-on state (process: switching on). designated;
• - a control unit which is connected to the differential current sensor unit, the mechanical isolating contact unit and the electronic interruption unit. According to the invention, the protective switching device, in particular the control unit, is designed in such a way that when first differential current limit values or first differential current time limit values are exceeded, avoidance of a current flow in the low-voltage circuit is initiated by a high-resistance state of the switching elements of the electronic interruption unit when the isolating contacts are closed. After avoiding a current flow due to a high-resistance state of the switching elements of the electronic interruption unit and the closed state of the contacts, a test is carried out to determine whether second differential current limit values or second differential current time limit values have been exceeded.

This has the particular advantage that after a faulty differential current event, for example caused by a person touching a (phase) conductor (critical event) or by a technically caused leakage current (not critical for people, ie non-critical event) (for example due to switched capacitances). ) an immediate avoidance of current flow in the low-voltage circuit is initiated by a high-resistance state of the switching elements of the electronic interruption unit. Immediate avoidance of a current flow means in particular that the electronic interruption unit becomes high impedance within 10 ms, in particular 5 ms or 1 ms. (Today's residual current circuit breakers typically trip after at least / greater than 20 ms.)
After avoiding the current flow due to a high-resistance state of the switching elements of the electronic interruption unit and the closed state of the contacts, a check is carried out for the existence of exceedance of second differential current limit values or second differential current time limit values in order to further check for the presence of faulty differential current events and, if necessary, critical ones To distinguish events from non-critical events in order to ensure personal protection on the one hand and the availability of systems on the other.
In this way, the condition at the load-side connections can be further monitored with regard to the presence of differential current limit values or differential current time limit values. If the state changes, a further action can advantageously take place, for example according to the advantageous embodiments of the invention.
On the other hand, a completely new operating concept for a protective switching device is presented in which, in contrast to previous residual current circuit breakers, for example, a check is also carried out after an event that prevents the flow of current.

Advantageous embodiments of the invention are specified in the subclaims and in the exemplary embodiment.

Advantageously, only the mechanical isolating contact unit can be operated by the mechanical handle. Switching on and off using the electronic interruption unit cannot be operated (directly) on the device.

In an advantageous embodiment of the invention, if the second differential current limit values or second differential current time limit values are not exceeded, the system changes for a first time range (10ms...20ms...30ms...50ms...100ms...200ms...1 s ( any value depending on the application is possible)) the electronic interruption unit into the low-resistance state.
The first time range is, for example, a value from the range 10ms to 100ms to 200ms to 1s. Ie if, for example, after exceeding the first differential current limit values or first differential current time limit values for 10 ms (15 ms) or 20 ms (25 ms, 30 ms, ..., 95 ms, 100 ms, ... 1 s) the second differential current limit values or second differential current time limit values are not exceeded, the electronic interruption unit switches to the low-resistance state.
The first time range can in particular be dependent on the level of the determined differential current (in particular its effective value), that is, with higher differential currents, the first time range becomes smaller.
This has the particular advantage that an automatic restart occurs when non-critical differential current limit values or differential current time limit values are present. This ensures high availability.

In an advantageous embodiment of the invention, if the second differential current limit values or second differential current time limit values are exceeded, the isolating contacts are opened for a first period of time.
The first time period is, for example, in the range 10ms to 100ms to 10s. The first time period can in particular be smaller than 300 ms, 200 ms, 150 ms, 100 ms, 50 ms, 40 ms, 30 ms, 20 ms or 10 ms.
This has the particular advantage that a switch-off behavior is achieved like that of classic residual current circuit breakers, in which galvanic isolation is carried out to protect people.

In an advantageous embodiment of the invention, the electronic interruption unit switches to the low-resistance state (after the expiration of a/the first time period and) if the second differential current limit values or second differential current time limit values are not exceeded for a second time range.
The second time range can be a value from the range 20ms to 100ms to 1s to 10s. The length of the second time range can correspond to the length of the first time range or be longer.
This has the particular advantage that it switches on again automatically, thereby achieving a high level of availability of the energy supply.

In an advantageous embodiment of the invention, a communication unit, in particular an input unit, is provided. If the second differential current limit values or second differential current time limit values for a (the) second time range are not exceeded, the electronic interruption unit only switches to the low-resistance state when an acknowledgment occurs by means of the communication unit, in particular the input unit.
The second time range can be a value from the range 20ms to 100ms to 1s. The length of the second time range can correspond to the length of the first time range or be longer.
This has the particular advantage that it can be switched on again after confirmation (acknowledgment) by a user, thus achieving a high level of security.

In an advantageous embodiment of the invention, the mechanical isolating contact unit (MK) is assigned to the load-side connections.
This has the particular advantage that there is an architecture that supports the behavior of the protective switching device according to the invention, since on the one hand the current flow is interrupted with a high-resistance interruption unit, but a test according to the invention can still be carried out (by means of the load-side connections) through the (load-side) closed contacts.

In an advantageous embodiment of the invention, the check is made for the presence of the excess Increase in second differential current limit values or second differential current time limit values at the load-side connections due to at least one switching element, in particular two or all switching elements, of the electronic interruption unit becoming low-resistance, in particular for a first duty cycle.
This has the particular advantage that there is a simple possibility of checking whether second differential current limit values or second differential current time limit values (of the load-side connections) have been exceeded, since only the existing electronic interruption unit needs to be switched (briefly) to the low-resistance state, to briefly generate a measuring current or a measuring voltage in order to test for the presence of differential current limit values or differential current time limit values and their level.
The first switch-on time can be so short that there is no danger to people.

In an advantageous embodiment of the invention, the check for whether second differential current limit values or second differential current time limit values (of the load-side connections) have been exceeded is carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit becoming low-resistance at an instantaneous value of the voltage, which is smaller than a first voltage threshold.
The first voltage threshold is in particular less than 50 volts or a value of the (protective) low voltage. The first voltage threshold value is advantageously adjustable.
This has the particular advantage that the test is carried out at a voltage that is harmless to humans, so that the safety of both the protective switching device and the low-voltage circuit is ensured.
A voltage sensor unit is also advantageously provided, which determines the voltage in the low-voltage circuit, in particular the level of the voltage present at the network-side connections.

In an advantageous embodiment of the invention, the switching elements become high-resistance again at an instantaneous value of the voltage that is greater than a second voltage threshold value.
This in turn has the particular advantage that the test is carried out at a voltage that is harmless to humans, so that the safety of both the protective switching device and the low-voltage circuit is ensured. The height of the second voltage threshold value can correspond to the height of the first voltage threshold value.

In an advantageous embodiment of the invention, the check for whether second differential current limit values or second differential current time limit values (at the load-side connections) have been exceeded is carried out by applying an auxiliary voltage that is smaller than a first voltage limit.
This in turn has the particular advantage that the test is carried out using a different solution at a voltage that is safe for people, so that the safety of both the protective switching device and the low-voltage circuit is ensured.
The height of the first voltage limit can correspond to the height of the first (or second) voltage threshold value.

In an advantageous embodiment of the invention, the test is carried out when the second differential current limit values or second differential current time limit values are exceeded with a first time interval, which is in particular 1, 3, 5, 10, 15, 30 seconds or 1, 5, 10 or 15 minutes is, the test being carried out at the first time interval, in particular after one (of) the first period of time has elapsed.
This has the particular advantage that a cyclic test is carried out over a longer period of time without permanently carrying out test functions or test routines.

In an advantageous embodiment of the invention, if the second differential current limit values or second differential current time limit values are (further) exceeded, the mechanical isolating contact unit switches to an open state of the isolating contacts after a first time limit has elapsed. In particular, the first time limit is 15 min, 30 min, 1h, 8h, 24h, 36h or 48h. Any intermediate value is possible. The first time interval depends on the first time limit. Ie the first time interval is smaller than the first time limit.
This has the particular advantage that after the first time limit has expired, a permanent or significant defect in the low-voltage circuit can be concluded and a safe state in the low-voltage circuit is initiated by galvanic isolation.

According to the invention, a corresponding method for a protective switching device for a low-voltage circuit with electronic (semiconductor-based) switching elements is claimed with the same and further advantages.

• - netzseitige und lastseitige Anschlüssen für Leiter des Niederspannungsstromkreises vorgesehen sind,
• - eine mechanische Trennkontakteinheit mit einem geschlossenen Zustand der Kontakte für einen Stromfluss im Niederspannungsstromkreis oder einen geöffneten Zustand der Kontakte für eine stromflussvermeidende galvanische Trennung im Niederspannungsstromkreis vorgesehen ist,
• - eine elektronische Unterbrechungseinheit vorgesehen ist, die stromkreisseitig in Serie zur mechanischen Trennkontakteinheit geschaltet ist und die durch halbleiterbasierte Schaltelemente einen hochohmigen Zustand der Schaltelemente zur Vermeidung eines Stromflusses oder einen niederohmigen Zustand der Schaltelemente zum Stromfluss im Niederspannungsstromkreis aufweist,
• - dass die Höhe eines Differenzstromes der Leiter des Niederspannungsstromkreises ermittelt wird und bei Überschreitung von ersten Differenzstromgrenzwerten oder ersten Differenzstrom-Zeitgrenzwerten eine Vermeidung eines Stromflusses im Niederspannungsstromkreis durch einen hochohmigen Zustand der Schaltelemente der elektronischen Unterbrechungseinheit bei geschlossenem Zustand der Trennkontakte initiiert wird,
• - dass nach einer Vermeidung eines Stromflusses durch einen hochohmigen Zustand der Schaltelemente der elektronischen Unterbrechungseinheit und geschlossenem Zustand der Kontakte eine Prüfung auf Vorliegen der Überschreitung von zweiten Differenzstromgrenzwerten oder zweiten Differenzstrom-Zeitgrenzwerten durchgeführt wird.

The procedure for a protective switching device to protect a low voltage electrical circuit in which:

• - network-side and load-side connections are provided for conductors of the low-voltage circuit,
• - a mechanical isolating contact unit is provided with a closed state of the contacts for a current flow in the low-voltage circuit or an open state of the contacts for a galvanic isolation that prevents current flow in the low-voltage circuit,
• - an electronic interruption unit is provided, which is connected in series on the circuit side to the mechanical isolating contact unit and which has a high-resistance state of the switching elements to avoid a current flow or a low-resistance state of the switching elements to prevent current flow in the low-voltage circuit due to semiconductor-based switching elements,
• - that the level of a differential current of the conductors of the low-voltage circuit is determined and, if first differential current limit values or first differential current time limit values are exceeded, an avoidance of a current flow in the low-voltage circuit is initiated by a high-resistance state of the switching elements of the electronic interruption unit when the isolating contacts are closed,
• - that after avoiding a current flow due to a high-resistance state of the switching elements of the electronic interruption unit and the closed state of the contacts, a test is carried out to determine whether second differential current limit values or second differential current time limit values have been exceeded.

• -bei fehlender Überschreitung der zweiten Differenzstromgrenzwerte oder zweiten Differenzstrom-Zeitgrenzwerte für einen ersten Zeitbereich (z.B. 20...100ms...1s) die elektronische Unterbrechungseinheit in den niederohmigen Zustand wechselt.
• -bei Vorliegen der Überschreitung der zweiten Differenzstromgrenzwerte oder zweiten Differenzstrom-Zeitgrenzwerte für eine erste Zeitspanne, die insbesondere kleiner als 300 ms, 200 ms, 150 ms, 100 ms, 50 ms, 40ms, 30ms, 20 ms oder 10 ms ist, die Trennkontakte geöffnet werden.
• -bei fehlender Überschreitung der zweiten Differenzstromgrenzwerte oder zweiten Differenzstrom-Zeitgrenzwerte für einen zweiten Zeitbereich (z.B. 20...100ms...1s) die elektronische Unterbrechungseinheit erst dann in den niederohmigen Zustand wechseln, wenn eine Quittierung erfolgt.
• -die Prüfung auf Vorliegen der Überschreitung von zweiten Differenzstromgrenzwerten oder zweiten Differenzstrom-Zeitgrenzwerten (der lastseitigen Anschlüsse) durch niederohmig werden mindestes eines Schaltelementes, insbesondere zweier oder aller Schaltelemente, der elektronischen Unterbrechungseinheit erfolgen, insbesondere für eine erste Einschaltdauer.
• -die Prüfung auf Vorliegen der Überschreitung von zweiten Differenzstromgrenzwerten oder zweiten Differenzstrom-Zeitgrenzwerten (der lastseitigen Anschlüsse) durch niederohmig werden mindestes eines Schaltelementes, insbesondere zweier oder aller Schaltelemente, der elektronischen Unterbrechungseinheit bei einem betragsmäßigen Momentanwert der Spannung erfolgen, der kleiner als ein erster Spannungsschwellwert ist.

In advantageous embodiments of the method:

• -if the second differential current limit values or second differential current time limit values are not exceeded for a first time range (e.g. 20...100ms...1s), the electronic interruption unit switches to the low-resistance state.
• -If the second differential current limit values or second differential current time limit values are exceeded for a first period of time, which is in particular less than 300 ms, 200 ms, 150 ms, 100 ms, 50 ms, 40 ms, 30 ms, 20 ms or 10 ms, the isolating contacts be opened.
• -If the second differential current limit values or second differential current time limit values are not exceeded for a second time range (e.g. 20...100ms...1s), the electronic interruption unit only switches to the low-resistance state when an acknowledgment occurs.
• -the test for whether second differential current limit values or second differential current time limit values (of the load-side connections) have been exceeded is carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit becoming low-resistance, in particular for a first duty cycle.
• -the test for whether second differential current limit values or second differential current time limit values (of the load-side connections) have been exceeded is carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit becoming low-resistance at an instantaneous value of the voltage that is smaller than a first voltage threshold value is.

According to the invention, a corresponding computer program product for a protective switching device is claimed. The computer program product includes commands which, when the program is executed by a microcontroller, cause the microcontroller to carry out a check for whether second differential current limit values or second differential current time limit values have been exceeded after avoiding a current flow due to a high-resistance state of the switching elements of the electronic interruption unit and the closed state of the contacts to carry out one of claims 1 to 17.
The microcontroller is part of the protective switching device, especially the control unit.

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

According to the invention, a corresponding data carrier signal that transmits the computer program product is claimed.

All refinements, both in a dependent form based on patent claim 1 or 12, as well as based only on individual features or combinations of features of patent claims, in particular also a reference of the pending arrangement claims to the independent method claim, bring about an improvement in a protective switching device, in particular an improvement in the Safety for people as well as security of supply in Lower Spain voltage circuits and provide a new, safe concept for a protective switching device.

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 understood in connection with the following description of the exemplary embodiments, which are explained in more detail in connection with the drawing.

• 1 eine erste Prinzipdarstellung eines Schutzschaltgerätes,
• 2 eine zweite Prinzipdarstellung eines Schutzschaltgerätes
• 3 bis 8 zeitliche Abläufe zur Erläuterung der Erfindung.

The drawing shows:

• 1 a first schematic diagram of a protective switching device,
• 2 a second schematic diagram of a protective switching device
• 3 to 8 temporal sequences to explain the invention.

• - netzseitige Anschlüsse, die i.B. einen netzseitigen Neutralleiteranschluss NG und einen netzseitigen Phasenleiteranschluss LG umfassen,
• - lastseitige Anschlüsse, die i.B. einen lastseitigen Neutralleiteranschluss NL und einen lastseitigen Phasenleiteranschluss LL umfassen,
• - die Anschlüsse sind für den Niederspannungsstromkreis vorgesehen;
• - an den netzseitige Anschlüssen / der Netzseite GRID ist üblicherweise eine Energiequelle angeschlossen,
• - an den lastseitige Anschlüssen / der Lastseite LOAD ist üblicherweise ein Verbraucher angeschlossen;
• - eine (zweipolige) mechanische Trennkontakteinheit MK mit lastseitigen Anschlusspunkten APLL, APNL und netzseitigen Anschlusspunkten APLG, APNG, wobei für den Neutralleiter ein lastseitiger Anschlusspunkt APNL, für den Phasenleiter ein lastseitiger Anschlusspunkt APLL, für den Neutralleiter ein netzseitiger Anschlusspunkt APNG, für den Phasenleiter ein netzseitiger Anschlusspunkt APLG vorgesehen ist. Die lastseitigen Anschlusspunkte APNL, APLL sind mit den lastseitigen Neutral- und Phasenleiteranschlüssen NL, LL verbunden, so dass ein Öffnen von Kontakten KKN, KKL zur Vermeidung eines Stromflusses oder ein Schließen der Kontakte KKN, KKL für einen Stromfluss im Niederspannungsstromkreis schaltbar ist,
• - eine, insbesondere einpolige, elektronische Unterbrechungseinheit EU, (die bei einpoliger Ausführung insbesondere im Phasenleiter angeordnet ist,) mit einem netzseitigen Verbindungspunkt EUG, der mit dem netzseitigen Phasenleiteranschluss LG in elektrischer Verbindung steht, und einem lastseitigen Verbindungspunkt EUL, der mit dem netzseitigen Anschlusspunkt APLG der mechanischen Trennkontakteinheit MK in elektrischer Verbindung steht bzw. verbunden ist, wobei die elektronische Unterbrechungseinheit EU durch (nicht dargestellte) halbleiterbasierte Schaltelemente einen hochohmigen Zustand der Schaltelemente zur Vermeidung eines Stromflusses oder einen niederohmigen Zustand der Schaltelemente zum Stromfluss im Niederspannungsstromkreis aufweist bzw. schaltbar ist,
• - eine Differenzstromsensoreinheit ZCT, zur Ermittlung der Höhe eines Differenzstromes der Leiter des Niederspannungsstromkreises, die Differenzstromsensoreinheit ZCT ist im Beispiel zwischen elektronischer Unterbrechungseinheit EU und mechanischer Trennkontakteinheit MK angeordnet, sie kann alternativ zwischen mechanischer Trennkontakteinheit MK und den lastseitigen Neutral- und Phasenleiteranschlüssen NL, LL vorgesehen (angeordnet) sein, ebenso alternativ zwischen elektronischer Unterbrechungseinheit EU und den netzseitige Anschlüssen NG, LG vorgesehen (angeordnet) sein. Die Differenzstromsensoreinheit ZCT ermittelt die Höhe des Differenzstromes der durch das Schutzschaltgerät geführten (zu schützenden) Leiter des Niederspannungsstromkreises. Im Beispiel bei einem Einphasenwechselstromkreis von Neutralleiter und Phasenleiter.

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

• - network-side connections, which iB include a network-side neutral conductor connection NG and a network-side phase conductor connection LG,
• - load-side connections, which iB include a load-side neutral conductor connection NL and a load-side phase conductor connection LL,
• - the connections are intended for the low voltage circuit;
• - an energy source is usually connected to the network-side connections / the GRID network side,
• - A consumer is usually connected to the load side connections / the load side LOAD;
• - a (two-pole) mechanical isolating contact unit MK with load-side connection points APLL, APNL and network-side connection points APLG, APNG, with a load-side connection point APNL for the neutral conductor, a load-side connection point APLL for the phase conductor, a network-side connection point APNG for the neutral conductor, and a network-side connection point APNG for the phase conductor Grid-side connection point APLG is provided. The load-side connection points APNL, APLL are connected to the load-side neutral and phase conductor connections NL, LL, so that an opening of contacts KKN, KKL to avoid a current flow or a closing of the contacts KKN, KKL to prevent a current flow in the low-voltage circuit can be switched,
• - a, in particular single-pole, electronic interruption unit EU (which in the case of a single-pole version is arranged in particular in the phase conductor) with a network-side connection point EUG, which is in electrical connection with the network-side phase conductor connection LG, and a load-side connection point EUL, which is connected to the network-side connection point APLG of the mechanical isolating contact unit MK is in electrical connection or is connected, the electronic interruption unit EU having or being switchable by means of (not shown) semiconductor-based switching elements a high-resistance state of the switching elements to avoid a current flow or a low-resistance state of the switching elements for current flow in the low-voltage circuit ,
• - a differential current sensor unit ZCT, for determining the level of a differential current of the conductors of the low-voltage circuit, the differential current sensor unit ZCT is arranged in the example between the electronic interruption unit EU and the mechanical isolating contact unit MK, it can alternatively be provided between the mechanical isolating contact unit MK and the load-side neutral and phase conductor connections NL, LL (arranged), also alternatively be provided (arranged) between the electronic interruption unit EU and the network-side connections NG, LG. The differential current sensor unit ZCT determines the magnitude of the differential current of the conductors of the low-voltage circuit (to be protected) that are routed through the protective switching device. In the example of a single-phase AC circuit with neutral conductor and phase conductor.

• - eine Stromsensoreinheit SI, zur Ermittlung der Höhe des Stromes des Niederspannungsstromkreises, die insbesondere im Strompfad des Phasenleiter bzw. Phasenleiterstrompfad angeordnet ist,
• - einer Steuerungseinheit SE, die mit der Differenzstromsensoreinheit ZCT, mit der Stromsensoreinheit SI, mit der mechanischen Trennkontakteinheit MK und der elektronischen Unterbrechungseinheit EU verbunden ist, wobei bei Überschreitung von Strom- oder/und Strom-Zeitgrenzwerten eine Vermeidung eines Stromflusses des Niederspannungsstromkreises initiiert wird.

The differential current sensor unit ZCT can be a classic summation current transformer. The primary side of the summation current transformer is formed by the conductors of the low-voltage circuit (in the example phase conductor and neutral conductor). The secondary side of the summation current transformer is connected to the control unit SE.

• - a current sensor unit SI, for determining the level of the current of the low-voltage circuit, which is arranged in particular in the current path of the phase conductor or phase conductor current path,
• - a control unit SE, which is connected to the differential current sensor unit ZCT, to the current sensor unit SI, to the mechanical isolating contact unit MK and the electronic interruption unit EU, whereby if current and/or current time limit values are exceeded, avoidance of a Current flow of the low-voltage circuit is initiated.

In the example, the mechanical isolating contact unit MK is arranged on the load side, the electronic interruption unit EU is arranged on the network side according to the invention.
The GRID network side with the energy source is normally under electrical voltage. An electrical consumer is usually connected to the load side LOAD.
This has the advantage that there are no further (particularly live) parts or components between the contacts of the mechanical isolating contact unit / load-side connection points (APLL, APNL) of the mechanical isolating contact unit and the two load-side connections (LL, NL). Due to this architecture or construction, it can be ensured that when the contacts KKL, KKN are open, there is never any voltage present at the load-side connections LL, NL. This increases the safety of the protective device.
In contrast, in other architectures in which the mechanical isolating contact unit is arranged on the network side, there are often (not galvanically isolated) electronic units in front of the load-side connection.

According to the invention, the protective switching device can be designed in such a way that the level of the voltage across the electronic interruption unit can also be determined. This means that the level of a first voltage between the network-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU can be determined or is determined.

This is shown in the example 1 a first voltage sensor unit SU1 connected to the control unit SE is provided, which determines the level of the voltage between the network-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU.
When measuring the voltage by the first voltage sensor unit SU1, the voltage across the series connection of the electronic interruption unit EU and current sensor SI can alternatively also be determined, as in 1 shown. The current sensor unit SI has a very low internal resistance, so that the determination of the level of the voltage is not or negligibly affected.

A second voltage sensor unit SU2 can advantageously be provided, which determines the level of the voltage between the network-side neutral conductor connection NG and the network-side phase conductor connection LG.

The first voltage sensor unit can also be replaced by using two voltage measurements (before the electronic interruption unit and after the electronic interruption unit). The voltage across the electronic interruption unit is determined by forming a difference.
A second voltage sensor unit SU2 connected to the control unit SE can thus be provided, which determines the level of a second voltage between the network-side neutral conductor connection NG and the network-side phase conductor connection LG. Furthermore, a third voltage sensor unit SU3 (not shown) connected to the control unit can be provided, which determines the level of a third voltage between the network-side neutral conductor connection NG and the load-side connection point EUL of the electronic interruption unit EU. The protective switching device is designed in such a way that the level of a/the first voltage between the network-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU is determined from the difference between the second and third voltage.

A measuring impedance ZM can be connected between the network-side connection points APLG, APNG of the mechanical isolating contact unit MK. The measurement impedance ZM can be, for example, an electrical resistor and/or capacitor. The measurement impedance can also be an inductance. In particular, the measurement impedance can be a series connection or parallel connection of a resistor and/or capacitor and/or inductance.

According to the example 1 The electronic interruption unit EU is single-pole, in the example in the phase conductor. Here, the network-side connection point APNG for the neutral conductor of the mechanical isolating contact unit MK is connected to the network-side neutral conductor connection NG of the GEH housing. This connection is made according to 1 through the differential current sensor unit ZCT, for example its summation current transformer.

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 by the control unit SE, but cannot be closed, which is indicated by an arrow from the control unit SE to the mechanical isolating contact unit MK.

The mechanical isolating contact unit MK can be operated by a mechanical handle HH on the protective switching device SG in order to switch the contacts KKL, KKN to manual (manual) opening or closing. The mechanical handle HH shows the switching status (open or closed) the contacts of the mechanical isolating contact unit MK on the protective switching device. Furthermore, the contact position (or the position of the handle, closed or opened) can be transmitted to the control unit SE. The contact position (or the position of the handle) can be determined, for example, using a sensor, such as a position sensor. The contact position or the switching state can be transmitted to the control unit SE. The position sensor can be part of the mechanical isolating contact unit MK. Alternatively, the position sensor can be a component in the electronic first part (EPART, 2 ) be. For example, a Hall sensor can be provided in the electronic first part (EPART), which detects and transmits the position of the contacts and/or the handle without contact.

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

The protective switching device SG has a power supply or power supply NT, for example a switching power supply. In particular, the energy supply/power supply NT is provided for the control unit SE, which is achieved by a connection between the energy supply/power supply NT and the control unit SE 1 is indicated. The power supply/power pack NT is (on the other hand) connected to the network-side neutral conductor connection NG and the network-side phase conductor connection LG. A fuse SS, in particular a fuse, or a switch SCH ( 2 ) be provided.
According to the invention, the power supply unit NT is normally constantly supplied with energy, especially from the network-side connections. If necessary, it is protected by the SS fuse or can be switched off using the SCH switch. Advantageously, the switch SCH/Sch can be designed in such a way that the switch can only be opened when the contacts are in the open state. This increases the safety of the device because the electronics (especially the control unit) cannot be switched off when the contacts are closed.

The fuse SS not only has the purpose of securing the energy supply via the power supply unit NT, but is also intended to be used, especially in the case of a two-part structure (see 2 ) protect the “electronic” first part EPART or its entire units (such as specifically the control unit, electronic interruption unit, voltage sensor(s), current sensor, if necessary measurement impedance, etc.).

Alternatively, the measuring impedance ZM can be connected to the network-side neutral conductor connection NG via the fuse SS. This means that a three-pole electronic unit or an electronic first part EPART ( 2 ) can be realized, for example as a module that has three connections with regard to the low-voltage circuit, a neutral conductor connection and two phase conductor connections. The electronic first part EPART can have further connections, in particular for control or measurement information, such as a release signal Enable/enable, opening signal OEF, position information (from the position unit POS) and/or differential current signal (level of the differential current) from the differential current sensor unit ZCT.

The electronic unit or electronic first part EPART ( 2 ) has, for example, the electronic interruption unit EU, the control unit SE, the energy supply NT (in particular including fuse SS), the current sensor unit SI, optionally the first voltage sensor unit SU1 and/or optionally the second voltage sensor unit SU2.

With regard to the three connections with regard to the low-voltage circuit of the electronic first part EPART, there is the advantage that only two phase conductor connections have to have a high current-carrying capacity (several amperes in order to carry the load current) and the neutral conductor connection only has to have a (in comparison) low current-carrying capacity (for example smaller than 1 A, a few mA - depending on the energy requirement of the control unit). This simplifies the design and increases the safety of the device, since in the event of a fault in the electronic first part EPART, no large short-circuit current can flow through this connection.

The low voltage circuit may be a three-phase AC circuit, with a neutral conductor and three phase conductors. For this purpose, the protective switching device can be designed as a three-phase variant and, for example, have additional line-side and load-side phase conductor connections. Between Electronic interruption units according to the invention and contacts of the mechanical isolating contact unit are provided in an analogous manner for the other mains-side and load-side phase conductor connections. The respective conductors (three phase conductors L1, L2, L3, neutral conductor N) are routed through the differential current unit ZCT.
Likewise, current sensor units and voltage determinations (eg by first voltage sensor units) can be provided.

High-resistance means a condition in which only a negligible current flows. In particular, high-resistance means resistance values of greater than 1 kiloohm, better greater than 10 kiloohm, 100 kiloohm, 1 megaohm, 10 megaohm, 100 megaohm, 1 gigaohm or greater.

Low-resistance means a condition in which the current value specified on the protective switching device could flow. In particular, low-resistance means resistance values that are smaller than 10 ohms, preferably smaller than 1 ohm, 100 milliohms, 10 milliohms, 1 milliohms or smaller.

• - den netzseitigen Phasenleiter Anschluss LG als ersten Anschluss,
• - einen (zweiten) Anschluss für den bzw. zum netzseitigen Phasenleiteranschlusspunkt APLG der mechanischen Trennkontakteinheit MK,
• - einen dritten Anschluss EN für eine Verbindung zum netzseitigen Neutralleiteranschluss NG.

Die beiden Anschlüsse: zum netzseitigen Phasenleiter Anschluss LG und für den bzw. zum netzseitigen Phasenleiteranschlusspunkt APLG weisen eine hohe Stromtragfähigkeit auf, z.B. mehrere Ampere, größer als 10A / 16 A - anhängig von Nennstrom bzw. Bemessungsstrom des Niederspannungsstromkreises, insbesondere um den Laststrom auch im Kurzschluss oder Überlastfall zu tragen.
Der dritte Anschluss EN für die Verbindung zum netzseitigen Neutralleiteranschluss NG weist eine (im Vergleich) geringe Stromtragfähigkeit auf, z.B. kleiner als 1A, wenige mA - in Abhängigkeit vom Energiebedarf der versorgten Einheiten, speziell im elektronischen ersten Teil EPART. Der dritte Anschluss EN ist mit einer geringen Stromtragfähigkeit ausgeführt, um das Netzteil mit Strom zu versorgen und um eine Spannungsmessung zwischen dem Phasenleiter und Neutralleiter des Niederspannungsstromkreises. Insbesondere ist dieser dritte Anschluss EN über eine Sicherung SS abgesichert. Dies kann durch eine Schmelzsicherung oder eine kostengünstige Leiterbahn-Sicherung (dünne Leiterbahn mit entsprechender Länge und Dicke auf der Leiterplatte) realisiert werden.
Dies hat den besonderen Vorteil, dass durch die geringere Stromtragfähigkeit in dieser Leitung bzw. an diesem dritten Anschluss EN die Sicherheit gegen einen innerhalb des elektronischen ersten Teils (EPART) (bzw. (elektronischen) Einheiten) auftretenden Kurzschluss, z.B. auf Seiten des Netzteils bzw. der Steuerungseinheit, verbessert wird.
Das heißt, beim Ausfall oder Versagen einer elektronischen Komponente einer Einheit innerhalb des elektronischen ersten Teils EPART kann kein gefährlicher Kurzschlussstrom entstehen (gespeist von den netzseitigen Anschlüssen LG, NG), der zu einem Brand im Gerät führen könnte.
Dieser Kurzschlussstrom wird vom Netz über die netzseitigen Anschlüsse gespeist. Ein vorgelagerter Schutzschalter weist häufig einen viel höheren Auslösestrom auf und speist parallel vorgesehene Niederspannungsstromkreise. Bei einem Fehler im Schutzschaltgerät (das Schutzschaltgerät des geschützten Niederspannungsstromkreis) und auslösen des vorgelagerten Schutzschalters würden somit auch fehlerfreie parallele Stromkreise abgeschaltet werden, was somit vermieden wird. 2 shows a representation according to 1 , with the difference that the protective switching device is constructed in two parts. It contains an electronic first part EPART, for example on a printed circuit board.
The first part EPART can have the control unit SE, the first voltage sensor unit SU1, the second voltage sensor unit SU2, the current sensor unit SI, the electronic interruption unit EU, the power supply NT. Furthermore, the first part can have the fuse SS, a switch SCH, the measuring impedance ZM, a temperature sensor TEM (in particular for the electronic interruption unit EU), a communication unit COM, a display unit AE, and, as a variant, a position sensor unit POS.
The electronic first part EPART has only three connections to the low-voltage circuit:

• - the mains-side phase conductor connection LG as the first connection,
• - a (second) connection for or to the mains-side phase conductor connection point APLG of the mechanical isolating contact unit MK,
• - a third connection EN for a connection to the network-side neutral conductor connection NG.

The two connections: to the mains-side phase conductor connection LG and for or to the mains-side phase conductor connection point APLG have a high current-carrying capacity, e.g. several amps, greater than 10A / 16 A - depending on the nominal current or rated current of the low-voltage circuit, in particular around the load current Short circuit or overload.
The third connection EN for the connection to the network-side neutral conductor connection NG has a (in comparison) low current carrying capacity, e.g. less than 1A, a few mA - depending on the energy requirements of the units supplied, especially in the electronic first part EPART. The third connection EN is designed with a low current carrying capacity to supply power to the power supply and to measure voltage between the phase conductor and neutral conductor of the low-voltage circuit. In particular, this third connection EN is protected by a fuse SS. This can be achieved using a fuse or a cost-effective conductor track fuse (thin conductor track of the appropriate length and thickness on the circuit board).
This has the particular advantage that the lower current-carrying capacity in this line or at this third connection EN ensures security against a short circuit occurring within the electronic first part (EPART) (or (electronic) units), for example on the power supply side or . the control unit is improved.
This means that in the event of failure or failure of an electronic component of a unit within the electronic first part EPART, no dangerous short-circuit current can arise (supplied by the mains-side connections LG, NG), which could lead to a fire in the device.
This short-circuit current is fed from the network via the network-side connections. An upstream circuit breaker often has a much higher tripping current and feeds low-voltage circuits provided in parallel. If there is a fault in the protective switching device (the protective switching device of the protected low-voltage circuit) and the upstream circuit breaker is triggered, error-free parallel circuits would also be switched off, which is therefore avoided.

The communication unit COM can in particular be a wireless communication unit. The communication unit COM can have a (manual) input unit on the protective switching device for (manual) acknowledgment of states on the protective switching device SG. The acknowledgment can also take place (wired and/or wirelessly) via the communication unit COM.
Furthermore, the communication unit COM can have a display function. A separate display unit can also be provided.

The protective switching device contains a second part MPART, in particular a mechanical one. The second part MPART can have the mechanical isolating contact unit MK, the handle HH, a release have FG. Furthermore, the second part can have a position unit POS, for reporting the position of the contacts of the mechanical isolating contacts unit MK to the control unit, as well as the (neutral conductor) connection(s). The second part MPART has the differential current sensor unit ZCT, like a summation current transformer, as is known, for example, from classic residual current circuit breakers.
Additional, unspecified units may be provided.

The division into two parts makes it possible to advantageously realize a compact protective switching device according to the invention with a simplified construction.

The release unit/release function FG enables the actuation of the contacts of the mechanical isolating contact unit to be released by the handle HH when a release signal enable is present. This means that the contacts KKL, KKN can only be closed by the handle when the release signal enable (from the control unit SE) is present. Otherwise closing is not possible (continuous slide of the HH handle). The contacts remain in the open position/switching state. Furthermore, the release unit FG can cause the contacts to open (second function of the release unit FG) if an opening signal OEF (from the control unit SE) is present. The release unit/release function FG then acts as a trigger unit for opening the contacts of the mechanical isolating contact unit MK.

The protective switching device SG, in particular the control unit SE, is further designed in such a way that if current limit values or current time limit values are exceeded (i.e. if a current limit value is exceeded for a certain period of time), avoidance of a current flow in the low-voltage circuit is initiated, in particular in order to avoid a short-circuit current . This is achieved in particular by the electronic interruption unit EU changing from the low-resistance state to the high-resistance state. The avoidance of a current flow in the low-voltage circuit is initiated, for example, by a first interruption signal that is sent from the control unit SE to the electronic interruption unit EU.

The mechanical isolating contact unit MK can alternatively or additionally be controlled by the control unit SE in order to initiate an avoidance of current flow in the low-voltage circuit when current limit values or current time limit values are exceeded. In particular, a galvanic isolation may be achieved here. The initiation of the avoidance of a current flow or a possible galvanic interruption of the low-voltage circuit is carried out, for example, by a second interruption signal that is sent from the control unit SE to the mechanical isolating contact system MK.

The electronic interruption unit EU can have semiconductor components such as bipolar transistors, field effect transistors (FET), isolated gate bipolar transistors (IGBT), metal oxide layer field effect transistors (MOSFET) or other (self-conducted) power semiconductors. In particular, IGBTs and MOSFETs are particularly suitable for the protective switching device according to the invention due to low flow resistances, high junction resistances and good switching behavior.

• -Mindestluftstrecke nach Norm (spannungsabhängig) (Mindestabstand der Kontakte),
• -Kontaktstellungsanzeige der Kontakte des mechanischen Trennkontaktsystem,
• -Öffnen des mechanischen Trennkontaktsystem ist immer möglich (keine Blockierung des Trennkontaktsystems - insbesondere durch die Handhabe, Freiauslösung),

gemeint.By mechanical isolating contact unit MK is meant in particular a (standard) isolating function, implemented by the isolating contact unit MK. With separator function the points are:

• -Minimum clearance according to standard (voltage-dependent) (minimum contact distance),
• -Contact position display of the contacts of the mechanical isolating contact system,
• -Opening the mechanical isolating contact system is always possible (no blocking of the isolating contact system - especially by the handle, free release),

meant.

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

The protective switching device can be designed as a DIN rail-mountable protective switching device SG with a width of, for example, 1 TE, 1.5 TE or 2 TE with two-pole connections (L, N). In electrical installation and control cabinet construction, the width of built-in devices such as protective switching devices, circuit breakers, residual current circuit breakers, etc. is specified in division units, or TE for short. The width of a division unit is -18 mm. The installation width of the devices should comply with the standard DIN 43880: 1988-12 between 17.5 and 18.0 mm, or can be calculated by multiplying this dimension by 0.5 or an integer multiple thereof, i.e.: k × 0.5 × 18 mm or k × 0.5 × 17.5 mm (with k = 1, 2, 3, ...). For example, a single-pole circuit breaker according to the prior art has a width of 1 HP. The installations of electrical installation distributors are according to DIN 43871 “Small installation distributor for built-in devices up to 63 A” matched to the division units, e.g. B. the width of mounting rails/top-hat rails.

According to the invention, the protective switching device SG, in particular the control unit SE, is designed in such a way that when first differential current limit values or first differential current time limit values are exceeded, avoidance of a current flow in the low-voltage circuit is initiated by a high-resistance state of the switching elements of the electronic interruption unit when the isolating contacts are closed. The first differential current limit values or first differential current time limit values can be limit values according to relevant standards, such as DIN EN 61008-1 , be. For example, 30 mA for personal protection in Europe on a 230 volt low voltage circuit, 6 mA for personal protection in North America, 300 mA for fire protection (230 volts RMS). After avoiding a current flow due to a high-resistance state of the switching elements of the electronic interruption unit and the closed state of the contacts, a test is carried out to determine whether second differential current limit values or second differential current time limit values have been exceeded.
The level of the second differential current limit values or second differential current time limit values can correspond to the level of the first differential current limit values or first differential current time limit values. According to the invention, the height of the second differential current limit values or second differential current time limit values is advantageously smaller than the height of the first differential current limit values or first differential current time limit values.
The height of the second differential current limit values or second differential current time limit values advantageously correspond to the standard values, but with a lower height, which results from the test. For example, if the test is carried out with a small voltage, especially a safety extra-low voltage, the residual currents will also be lower. Ie the level of the second differential current limit values or second differential current time limit values is determined by the level of the voltage during the test. The higher the voltage, the higher the level of the second differential current limit values or second differential current time limit values. If the mains voltage of the low-voltage circuit, for example 230 volts, is used for the test (for a short time), the height of the second differential current limit values or second differential current time limit values corresponds to those of the first differential current limit values or first differential current time limit values.

According to the invention, the check for whether second differential current limit values or second differential current time limit values (of the load-side connections) have been exceeded can be carried out by making at least one switching element, in particular two or all switching elements, of the electronic interruption unit (EU) low-resistance, in particular for a first duty cycle.
The first duty cycle can be set in such a way that the effective value of the voltage present at the load connections (determined over one mains period) does not exceed 50 V. This means that the instantaneous value of the voltage can be briefly greater than 50 V, but the effective value of the voltage determined over a network period is less than 50 volts. The first duty cycle is therefore always less than 20 ms, more specifically less than 10 ms, in particular less than 1 ms.

The test for whether second differential current limit values or second differential current time limit values (of the load-side connections) have been exceeded can be carried out by making at least one switching element, in particular two or all switching elements, of the electronic interruption unit (EU) low-resistance at an instantaneous value of the voltage that is less than is a first voltage threshold (relative to an alternating voltage). The electronic interruption unit can be switched on briefly, i.e. the semiconductor-based switching element is briefly switched to low resistance. What is meant by short-term is a specific first duty cycle ED1, at which the instantaneous voltage value u(t) of the alternating voltage does not exceed a specific value, for example 50 volts. For example, when the alternating voltage passes zero (0°), the alternating voltage can be switched on for approx. 444 ps / up to 8° (electronic interruption unit EU with low resistance), i.e. until the current voltage value reaches a maximum of 50 volts.

Alternatively, it can be switched on at approx. -8° (based on the zero crossing of the alternating voltage), passed through the zero crossing and switched off again at +8°, i.e. for approx. 888 ps. Ie the switch-on time period is less than 1 ms, in particular less than 0.9 ms, more specifically about 0.8 ms (or half, depending on the switch-on time).
By briefly switching on the electronic interruption unit, a reduced (test) voltage is applied to the load-side connections (load connections). The effective value of this test voltage depends on the existing mains voltage and the first duty cycle ED1 and is always smaller than the existing mains voltage. The first switch-on period or the first voltage threshold are selected so that the effective value of the test voltage (applied to the network-side connections) is less than 50V.
This allows a reliable check for the existence of the Second differential current limit values or second differential current time limit values are exceeded.

In the example, the second differential current limit values or second differential current time limit values are adapted to a voltage of up to 50 volts. The reduction of the second differential current limit compared to the first differential current limit corresponds to the same ratio as the reduction of the test voltage in relation to the nominal mains voltage. This means that with a test voltage of, for example, 50V effective value and a nominal mains voltage of 230V, the second differential current limit value is reduced by 50/230. For example, 30mA (as the first differential current limit) then becomes 30mA * 50/230 = 6.5mA (as the second differential current limit).

This means that the second differential current limit is smaller than the first differential current limit.

Alternatively or additionally, the switching elements can become high-resistance again at an instantaneous value of the voltage that is greater than a second voltage threshold (such as 50 volts).

Alternatively, the test for at least one electrical parameter on the load-side connections can be carried out by applying an auxiliary voltage, in particular pulsed direct voltage, which is smaller than a first voltage limit. The height of the first voltage limit can be a (limit) value of the protective extra-low voltage or correspond to the voltage threshold value. According to the invention, there is no dangerous voltage at the load-side connections.
The first voltage limit can be, for example, 50 volts.

If the second differential current limit values or second differential current time limit values for a first time range ZB1 are not exceeded, the electronic interruption unit EU can switch to the low-resistance state.
(Alternatively, the test can be carried out until the second residual current limit values or second differential current time limit values are exceeded. The electronic interruption unit then switches to the low-resistance state.)
In contrast, if the second differential current limit values or second differential current time limit values are exceeded for a first period of time ZS1, the isolating contacts can be opened (galvanic isolation, as with a classic residual current circuit breaker).
The value of the first time period can correspond to the value of the first time range, ie after the first time period (=the first time range) has elapsed, the contacts of the mechanical isolating contact unit can open. The first time period can also have a different value. For example, the first time period can have a time period in accordance with the standard for classic residual current protection/for classic residual current circuit breakers. Reference is made here to the standard DIN EN 61008-1, residual current/residual current circuit breakers without built-in overcurrent protection (RCCBs) for domestic installations and similar applications, in particular Part 1: General Requirements, which is incorporated herein by reference. For example, this standard states that a 30mA residual current circuit breaker (RCD) must trip within 300ms at the rated residual current (30mA). At 2 times the nominal fault current (60mA) within 150ms. At 5 times, or greater within 40ms.
For example, the first time period can be less than 300 ms, 150 ms, 100 ms, 40 ms, 30 ms, 20 ms or 10 ms. In this way, behavior according to the standard or better can be provided, in which, for example, an interruption only has to occur after, for example, 300 ms. According to the invention, it is possible beforehand to check whether differential current limit values or differential current time limit values have been exceeded, without, for example, violating the standard. In this way, greater security of supply can be achieved, especially in the event of non-critical errors.
For example, depending on the application, the first time period ZS1 can have a value in the range 10 ms to 10 s, more specifically 10 ms to 40 ms or 40 ms to 150 ms or 150 ms to 300 ms or 1 s to 10 s.

The protective switching device SG can have a communication unit COM, in particular an input unit. If the second differential current limit values or second differential current time limit values for a second time range are not exceeded, for example a value from the range 20ms...100ms...1s...10s...100s, the electronic interruption unit EU only then changes to the low-resistance one State when an acknowledgment Q1 (e.g. by an operator, user) takes place by means of the communication unit COM, in particular an input unit. The communication unit (input unit) can have input elements on the housing of the protective switching device. The communication unit can also or additionally have a wired (e.g. electrical, optical) or wireless (e.g. radio, optical) input option. The communication unit (input unit) can also have a display function.

Alternatively or additionally, after the first time period ZS1 has expired, the electronic sub The refraction unit EU only switches back to the low-resistance state (EUn) when it has been determined that the second differential current limit value or second differential current time limit value has not been exceeded for the duration of a (first (or) second) time range. Furthermore, after the first time period ZS1 has elapsed, an acknowledgment (Q1) of the absence of errors can take place (be necessary) before the electronic interruption unit EU changes back to the low-resistance state (EUn).

The protective switching device SG, in particular the control unit SE, can have a microcontroller (= microprocessor) on which a computer program product runs, comprising commands which, when the program is executed by the microcontroller, cause it to carry out a test (as described above and below) for a protective switching device to carry out.

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

Alternatively, the computer program product can also advantageously be transmitted using a data carrier signal.

• * mit einer digitalen Schaltung, z.B. mit einem (weiteren) Mikroprozessor, realisiert sein; der (weitere) Mikroprozessor kann auch einen Analog-Teil enthalten;
• * mit einer digitalen Schaltung mit analogen Schaltungsteilen realisiert sein.

The SE control unit can:

• * be implemented with a digital circuit, for example with a (further) microprocessor; the (further) microprocessor can also contain an analogue part;
• * be implemented with a digital circuit with analog circuit parts.

In the 3 to 8 A part of the above-mentioned time sequences is shown as an example. The 3 to 8 each show a timeline t on which certain points in time mentioned above are entered, further entries regarding the evaluations of the first differential current limit values or first differential current time limit values DSG1 or second differential current limit values or second differential current time limit values DSG2, as well as states of the mechanical isolating contact unit MK and the electronic Interruption unit EU.

3 shows the time of avoiding a current flow VS, caused by exceeding first differential current limit values or first differential current time limit values DSG1. Before the current flow VS is avoided, the mechanical isolating contact unit MK is in a closed state MKg of the contacts and the electronic interruption unit EU is in a low-resistance state EUn of the switching elements for a current flow in the low-voltage circuit. After avoiding the current flow VS, the mechanical isolating contact unit MK continues to be in a closed state MKg of the contacts (for a potentially recurring current flow / to quickly enable current flow again) and the electronic interruption unit EU is in a high-resistance state EUh of the switching elements to avoid the current flow . After the current flow VS has been avoided, a check is carried out to determine whether second differential current limit values or second differential current time limit values DSG2 (at the load-side connection) have been exceeded.

4 shows a representation according to 3 , with the following differences.
After the avoidance of a current flow VS and subsequent (at any subsequent time) the second differential current limit values or second differential current time limit values DSG2 are not exceeded (ie if the second differential current limit values or second differential current time limit values DSG2 are in the target range), the electronic interruption unit EU changes in the low-resistance state EUn, in particular if the second differential current limit values SB or second differential current time limit values DSG2 have not been exceeded for a first time range ZB1, as in 4 drawn.
The first time range ZB1 can be very short (ie a quasi-immediate reconnection can take place), it can also be adjustable in terms of safety.

The check for whether second differential current limit values or second differential current time limit values DSG2 have been exceeded is carried out until the excess is no longer present (SB). It can be continued until the electronic interruption unit EU changes to the low-resistance state EUn (ZB1). A check is then carried out again with regard to the first differential current limit values or first differential current time limit values DSG1.

In this case, the mechanical isolating contact unit MK has a closed state of the (isolating) contacts MKg over the entire period.

5 shows a representation according to 3 , with the difference that after avoiding a current flow VS and if the second differential current limit values or second differential current time limit values DSG2 are exceeded US for a first period of time ZS1, which is in particular small ner than 300ms, 150ms, 40ms, 30ms, 20 ms or 10 ms, the contacts of the mechanical isolating contact unit are opened (MKo). In the example, the electronic interruption unit EU remains in the high-resistance state EUh (since the current flow avoidance VS).

6 shows a representation according to 5 , with the difference that the existence of the exceedance US of the second differential current limit values or second differential current time limit values DSG2 does not occur immediately after the avoidance of a current flow VS, but at a later point in time, but before the (expiry of) the first time range ZB1 (ie before the electronic interruption unit EU becomes low impedance). If the second differential current limit values US or second differential current time limit values DSG2 are exceeded for the first time period ZS1, the contacts MKo of the mechanical isolating contact unit MK are opened (after the first time period ZS1).

This means that there could be a change in the exceedance (US) / lack of exceedance SB of the second differential current limit values or second differential current time limit values DSG2. If the second differential current limit values or second differential current time limit values DSG2 are exceeded for the first time period ZS1, the contacts MKo of the mechanical isolating contact unit MK are opened.

7 shows a representation according to 4 , with the difference that after the avoidance of a current flow VS and subsequent failure to exceed SB of the second differential current limit values or second differential current time limit values DSG2 (ie if the second differential current limit values or second differential current time limit values DSG2 are in the target range, this in particular before the expiry of the first Time period ZS1 should take place, ie before the contacts are opened), the electronic interruption unit EU then switches to the low-resistance state EUn if the second differential current limit values SB or second differential current time limit values DSG2 have not been exceeded for a second time range ZB2 (this can be the correspond to the first time range ZB1) and an acknowledgment (Q1) took place (by means of the communication unit COM, in particular input unit).

The check for whether second differential current limit values or second differential current time limit values DSG2 have been exceeded is carried out until the excess is no longer present (SB) and/or the second time range has expired and/or the acknowledgment has taken place. This means that the check for whether second differential current limit values or second differential current time limit values DSG2 have been exceeded can be continued until the electronic interruption unit EU changes to the low-resistance state EUn (Q1 in the example). A check is then carried out again with regard to the first differential current limit values or first differential current time limit values DSG1.

In this case, the mechanical isolating contact unit MK has a closed state of the (isolating) contacts MKg over the entire period.

8th shows a representation according to 5 and 6 respectively , with the difference that if the second differential current limit values or second differential current time limit values DSG2 are exceeded and the first time period ZS1 has expired, the contacts of the mechanical isolating contact unit are not opened, ie remain closed. Furthermore, after the first time period ZS1 has elapsed, the check for whether the second differential current limit values or second differential current time limit values (DSG2) have been exceeded is carried out with a first time interval ZA1 (ie not always).

Furthermore, if the second differential current limit values or second differential current time limit values DSG2 are exceeded US (at least if there is no missing excess for the first or second time range ZB1, ZB2), the mechanical isolating contact unit MK is in an open state after a first time limit ZG1 has expired the contacts MKo changes. I.e. after the first time period ZS1 has expired, the test is carried out with the first time interval ZA1 until the first time limit ZG1 is reached. After the first time limit ZG1 has expired, the mechanical isolating contact unit MK changes to an open state MKo, provided that the second differential current limit values or second differential current time limit values DSG2 are still exceeded. The electronic interruption unit EU remains in the high-resistance state EUh (since current flow avoidance VS).

In an analogous manner, other behaviors or procedures can be combined by the person skilled in the art.

According to the invention, the test for whether second differential current limit values or second differential current time limit values DSG2 have been exceeded is advantageously carried out by making at least one switching element, in particular two or all switching elements, of the electronic interruption unit EU low-resistance for a first duty cycle ED1. Ie with high impedance State EUh of the electronic interruption unit EU, as shown in the figures, does not mean a permanent high-resistance state, but rather a short-term (for the first duty cycle ED1) the electronic interruption unit EU becomes low-resistance. The first duty cycle ED1 is, for example, very short (in relation to the other times), so that this does not conflict with the representation according to the figures and the basic functionality.

Although the invention has been illustrated and described in detail by the exemplary embodiment, the invention is not limited by the examples disclosed and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4432643 A1 [0010]

Non-patent literature cited

• DIN 43880: 1988-12 [0076]
• DIN 43871 [0076]
• DIN EN 61008-1 [0077]

Claims (20)

Protective switching device (SG) for protecting an electrical low-voltage circuit, comprising: - a housing with network-side and load-side connections (LG, NG, LL, NL) for conductors of the low-voltage circuit, - a differential current sensor unit (ZCT), for determining the level of a differential current of the conductors of the low-voltage circuit , - a mechanical isolating contact unit (MK), which has a closed state of the contacts (MKg) for a current flow in the low-voltage circuit or an open state of the contacts (MKo) for a galvanic isolation that prevents current flow in the low-voltage circuit, - an electronic interruption unit (EU), which is connected in series on the circuit side to the mechanical isolating contact unit (MK) and which has a high-resistance state (EUh) of the switching elements to avoid current flow or a low-resistance state (EUn) of the switching elements for current flow in the low-voltage circuit due to semiconductor-based switching elements, - a control unit (SE), which is connected to the differential current sensor unit (ZCT), the mechanical isolating contact unit (MK) and the electronic interruption unit (EU), characterized in that the protective switching device (SG), in particular the control unit (SE), is designed such that when the first Differential current limit values or first differential current time limit values (DSG1) an avoidance of a current flow (VS) in the low-voltage circuit is initiated by a high-resistance state (EUh) of the switching elements of the electronic interruption unit when the isolating contacts are closed (MKg), that after avoiding a current flow (VS) A test is carried out to determine whether second differential current limit values or second differential current time limit values (DSG2) have been exceeded due to a high-resistance state of the switching elements of the electronic interruption unit and the closed state of the contacts. Protective switching device (SG). Patent claim 1 , characterized in that if the second differential current limit values or second differential current time limit values (DSG2) are not exceeded (SB) for a first time range (ZB1), which is in particular smaller than 200ms, 100ms, 50ms, 30ms, 20ms, or 10ms, the electronic Interrupting unit (EU) switches to the low-resistance state. Protective switching device (SG). Patent claim 1 or 2 , characterized in that if the second differential current limit values or second differential current time limit values (DSG2) are exceeded (US) for a first period of time (ZS1), which is in particular smaller than 300ms, 150ms, 40ms, 30ms, 20ms or 10ms, the contacts are opened (MKo). Protective switching device (SG). Patent claim 1 , 2 or 3 , characterized in that a communication unit COM, in particular an input unit, is provided so that if the second differential current limit values (SB) or second differential current time limit values (DSG2) are not exceeded for a second time range (ZB2), which is in particular smaller than 5s, 3s, 1s, 500ms, 250ms, 100ms, the electronic interruption unit (EU) only changes to the low-resistance state when an acknowledgment (Q1) occurs by means of the communication unit (COM), in particular the input unit. Protective switching device (SG) according to one of the preceding claims, characterized in that the mechanical isolating contact unit (MK) is assigned to the load-side connections (LL, NL). Protective switching device (SG) according to one of the preceding patent claims, characterized in that the test for whether second differential current limit values or second differential current time limit values (DSG2) have been exceeded is carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit (EU) becoming low-resistance. takes place, in particular for a first duty cycle (ED1), which is in particular smaller than 20 ms, more specifically smaller than 15 ms, 10 ms, 5 ms or 1 ms. Protective switching device (SG) according to one of the preceding patent claims, characterized in that the test for whether second differential current limit values or second differential current time limit values (DSG2) have been exceeded is carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit (EU) becoming low-resistance. takes place at an instantaneous value of the voltage that is smaller than a first voltage threshold value. Protective switching device (SG). Patent claim 6 or 7 , characterized in that the switching elements become high-resistance again at an instantaneous value of the voltage that is greater than a second voltage threshold value. Protective switching device (SG) according to one of the preceding Patent claims 1 until 5 , characterized in that the check for whether second differential current limit values or second differential current time limit values (DSG2) have been exceeded is carried out by applying an auxiliary voltage that is smaller than a first voltage limit. Protective switching device (SG) according to one of the preceding patent claims, characterized in that the test is carried out when the second differential current limit values or second differential current time limit values (DSG2) are exceeded (US) with a first time interval (ZA1), which is in particular 1, 3, 5, 10, 15, 30 seconds or 1, 5, 10 or 15 minutes, the test being carried out at the first time interval (ZA1), in particular after a first time period (ZS1). Protective switching device (SG). Patent claim 10 , characterized in that if the second differential current limit values or second differential current time limit values (DSG2) are (further) exceeded after a first time limit (ZG1) has elapsed, the mechanical isolating contact unit (MK) switches to an open state of the contacts (MKo) , in particular that the first time limit is 15 min, 30 min, 1h, 8h, 24h, 36h or 48h. Method for a protective switching device (SG) for protecting a low-voltage electrical circuit, in which - network-side and load-side connections (LG, NG, LL, NL) are provided for conductors of the low-voltage circuit, - a mechanical isolating contact unit (MK) is provided with a closed state (MKg) of the contacts for a current flow in the low-voltage circuit or an open state (MKo) of the contacts for a galvanic isolation that prevents current flow in the low-voltage circuit, - an electronic interruption unit (EU) is provided, which is connected in series on the circuit side to the mechanical isolating contact unit (MK) and which uses semiconductor-based switching elements to ensure a high-resistance state (EUh) of the switching elements to prevent current flow or a low-resistance state (EUn) of the switching elements to prevent current flow in the low voltage circuit, - that the level of a differential current of the conductors of the low-voltage circuit is determined and, if the first differential current limit values or first differential current time limit values (DSG1) are exceeded, a current flow in the low-voltage circuit is avoided by a high-resistance state (EUh) of the switching elements of the electronic interruption unit when the contacts are closed ( MKg) is initiated, - that after avoiding a current flow due to a high-resistance state (EUh) of the switching elements of the electronic interruption unit (EU) and the closed state (MKg) of the contacts, a test is carried out to determine whether second differential current limit values or second differential current time limit values (DSG2) have been exceeded. Procedure according to Patent claim 12 , characterized in that if the second differential current limit values (SB) or second differential current time limit values (DSG2) are not exceeded for a first time range (ZB1), the electronic interruption unit (EU) changes to the low-resistance state (EUn). Procedure according to Patent claim 12 or 13 , characterized in that if the second differential current limit values or second differential current time limit values (DSG2) are exceeded for a first period of time (ZS1), which is in particular smaller than 300 ms, 150 ms, 40 ms, 30 ms, 20 ms or 10 ms, the contacts are opened (MKo). Procedure according to Patent claim 12 , 13 or 14 , characterized in that if the second differential current limit values or second differential current time limit values (DSG2) are not exceeded for a second time range (ZB2), the electronic interruption unit (EU) only switches to the low-resistance state when an acknowledgment (Q1) occurs. Procedure according to Patent claim 12 , 13 , 14 or 15 , characterized in that the check for whether second differential current limit values or second differential current time limit values (DSG2) have been exceeded is carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit (EU), in particular for a first duty cycle (ED1 ), which is in particular less than 20 ms, more specifically less than 15 ms, 10 ms, 5 ms or 1 ms. Procedure according to Patent claim 12 , 13 , 14 , 15 or 16 , characterized in that the test for whether second differential current limit values or second differential current time limit values (DSG2) have been exceeded is carried out by at least one switching element, in particular two or all switching elements, of the electronic interruption unit (EU). an instantaneous value of the voltage that is smaller than a first voltage threshold value. Computer program product comprising commands which, when the program is executed by a microcontroller, cause the microcontroller to carry out a check for the existence of exceedance of second differential current limit values or second differential current time limit values after avoiding a current flow due to a high-resistance state of the switching elements of the electronic interruption unit and the closed state of the contacts the Patent claims 1 until 17 to carry out. Computer-readable storage medium on which the computer program product is stored Patent claim 18 is stored. Disk signal that the computer program product after Patent claim 18 transmits.

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