DE102017215820A1 - Circuit breakers and procedures - Google Patents

Abstract

The invention relates to a circuit breaker for interrupting a multi-conductor low-voltage circuit, - with an interruption unit, for interrupting at least one conductor of the low-voltage circuit, - with a power supply, which is connected to at least two conductors of the low-voltage circuit, wherein from a voltage difference of at least two conductors Supply voltage for the circuit breaker is generated, with a sensor unit for determining the magnitude of the electric current of at least one conductor of the low-voltage circuit, with a control unit connected to the interruption unit, the sensor unit and the power unit, which is designed such that when current is exceeded or Strom-Zeitspannen-Grenzwerte an interruption of at least one conductor of the low-voltage circuit by the interruption unit takes place, - that the power switch is designed such that in the de-energized State of the low-voltage circuit always at least one conductor of the low-voltage circuit is interrupted and a current flow of the low-voltage circuit is provided by the power switch only in the presence of a low voltage in the low-voltage circuit.

Description

The invention relates to a circuit breaker for interrupting and closing a multi-conductor low-voltage circuit and a corresponding method.

Circuit breakers are protective devices that function in a similar way to a fuse. Circuit breakers monitor the current flowing through them through a conductor and interrupt the electrical current to an energy sink, referred to as a break, when protection parameters such as current limits or current-time-out limits, i. if a current value exists for a certain period of time, be exceeded. The set current limit values or current-time limit limits are corresponding tripping reasons. The interruption occurs, for example, through contacts of the circuit breaker, which are opened.

In particular for low-voltage circuits or networks there are different types of circuit breakers depending on the level of the intended electrical current in the electric circuit. With circuit breaker according to the invention in particular switches are meant, as used in low-voltage systems for currents of 63 to 6300 amps. More specifically, closed circuit breakers are used for currents of 63 to 1600 amps, in particular from 125 to 630 or 1200 amps. Open circuit breakers are used in particular for currents from 630 to 6300 amps, more specifically from 1200 to 6300 amps. Open Circuit Breakers are also referred to as Air Circuit Breaker, ACB for short, and Molded Case Circuit Breaker or Molded Case Circuit Breaker, MCCB for short circuit breakers.

By low voltage is meant in particular voltages up to 1000 volts AC or 1500 volts DC. Specifically, low voltage means voltages that are greater than the low voltage, with values of 25 volts or 50 volts AC, and 60 volts or 120 volts DC.

With circuit breaker in the context of the invention, in particular circuit breaker with a serving as a control unit electronic trip unit, also referred to as Electronic Trip Unit, short ETU meant.

If the current flow is too high, circuit breakers interrupt the circuit according to their protection parameters or response values. The protection parameters or response values are essentially the magnitude of the current and the time after which an interruption of the circuit should take place with a constantly high current flow. In contrast to a fuse these protection parameters or response values are adjustable in a circuit breaker, for example by means of the control unit / electronic trip unit. This is usually attached accessible via the front of the circuit breaker. The protection parameters can be set or parameterized here.

Previous circuit breakers in electrical systems are generally switched on. After switching on, they monitor the electrical current in the circuit. In the event of a power failure or when a higher-level circuit breaker triggers, these circuit breakers remain in the switched-on state. If there is another electrical voltage, it is immediately available to the consumers.

Only when a short circuit or overcurrent event occurs, i. If current or current timeout limits are exceeded, the circuit breaker trips and remains off - until the fault is cleared and the circuit breaker is turned back on.

That Circuit breakers, as well as fuses, are permanently switched on as long as there is no overload or short-circuit situation. This results from the i.d.R. purely mechanical design principle, in which overcurrent events are detected by thermal or magnetic forces and these forces to trigger the circuit breaker, i. Break in the electrical circuit, lead. Also all power switches with electronic current monitoring, for example by a control unit, e.g. In the form of an electronic trip unit, this principle of the permanently closed circuit, e.g. closed contacts, on.

Object of the present invention is to improve a circuit breaker of the type mentioned, in particular to provide increased functional safety means of a circuit breaker.

This object is achieved by a circuit breaker having the features of patent claim 1 or a method having the features of patent claim 17.

According to the invention, a circuit breaker for interrupting a multi-conductor low-voltage circuit is provided, which interrupts the low-voltage circuit in the absence of voltage in the low-voltage circuit, ie triggered, and only when applying a voltage in the low-voltage circuit allows switching on. This circuit breaker is inventively supplied by a power supply that is connected to at least two conductors of the low-voltage circuit, so that a power supply of the circuit breaker is made from the voltage applied to the low-voltage circuit.

• - mit einen Netzteil, das mit mindestens zwei Leitern, insbesondere mit den Phasenleitern bzw. allen Leitern, des Niederspannungsstromkreises verbunden ist, wobei aus einer Spannungsdifferenz der mindestens zwei Leiter eine Versorgungsspannung für den Leistungsschalter erzeugt wird,
• - mit einer Sensoreinheit zur Ermittlung der Höhe des elektrischen Stromes mindestens eines Leiters des Niederspannungsstromkreises, insbesondere der Höhe jedes Phasenleiters bzw. jedes Leiters des Niederspannungsstromkreises,
• - mit einer mit der Unterbrechungseinheit, der Sensoreinheit und dem Netzteil verbundenen Steuerungseinheit, die derart ausgestaltet ist, dass bei Überschreitung von Strom- oder Strom-Zeitspannen-Grenzwerten ein Signal an die Unterbrechungseinheit zur Unterbrechung mindestens eines Leiters, insbesondere aller Phasenleiter oder aller Leiter, des Niederspannungsstromkreises gesendet wird,
• - dass der Leistungsschalter derart ausgestaltet ist, dass im spannungslosen Zustand des Niederspannungsstromkreises immer mindestens ein Leiter, insbesondere alle Phasenleiter oder alle Leiter, des Niederspannungsstromkreises unterbrochen ist und ein Stromfluss des Niederspannungsstromkreises durch den Leistungsschalter nur bei Vorliegen einer Niederspannung im Niederspannungsstromkreises vorgesehen ist.

Anvil is a circuit breaker for interrupting a multi-conductor low-voltage circuit, - with an interrupt unit, for interrupting at least one conductor of the low-voltage circuit, more specifically all phase conductors or all conductors of the low-voltage circuit,

• with a power supply which is connected to at least two conductors, in particular to the phase conductors or all conductors, of the low-voltage circuit, a supply voltage for the circuit breaker being generated from a voltage difference of the at least two conductors,
• with a sensor unit for determining the magnitude of the electric current of at least one conductor of the low-voltage circuit, in particular the height of each phase conductor or each conductor of the low-voltage circuit,
• with a control unit connected to the interruption unit, the sensor unit and the power supply, which is designed such that when current or current-time threshold limits are exceeded, a signal is sent to the interrupt unit for interrupting at least one conductor, in particular all phase conductors or all conductors, the low-voltage circuit is sent,
• - That the circuit breaker is designed such that in the de-energized state of the low-voltage circuit always at least one conductor, in particular all phase conductors or all conductors, the low-voltage circuit is interrupted and a current flow of the low-voltage circuit is provided by the circuit breaker only in the presence of a low voltage in the low-voltage circuit.

This has the particular advantage that the circuit breaker has a functionally safer state. That in the case of safety-related faults or faults, the circuit breaker falls back to a state in which no energy or voltage is made available on the energetic side. In particular, after a power failure consumers are not automatically supplied with a voltage again. Thus, a hazard to persons and equipment is avoided by faulty devices.

Advantageous embodiments of the invention are specified in the subclaims.

In an advantageous embodiment of the invention, the interruption unit has contacts, in particular mechanical contacts, with which at least one conductor, in particular the phase conductors or all conductors, are electrically opened or closed. In the case of DC voltage circuits or DC voltage in particular the ungrounded conductor, such as the conductor with positive potential (at grounded conductor with a negative potential), is opened or closed. This has the particular advantage that a galvanic isolation of the circuit is achieved in the open state.

In an advantageous embodiment of the invention, the power supply has a transformer, the first terminal of the primary winding is connected to a conductor and the second terminal of the primary winding is connected to another conductor. This has the particular advantage that a power supply is effected by the voltage of the low-voltage circuit. Previously conventional energy converters in circuit breakers whose primary side is formed by a conductor of the low-voltage circuit can be omitted. These only work if there is a current flow with a conductor. With no or little current flow, these energy converters do not provide any electrical energy.

In an advantageous embodiment of the invention, the power supply is a switching power supply. This has the particular advantage that switching power supplies on the one hand have a high energy efficiency and on the other hand can be designed for very large input voltage ranges. Thus, a power supply can be provided both at low and at high voltages in the low-voltage circuit or a circuit breaker can be provided for different voltages. In particular, switched-mode power supplies are also advantageous for DC voltage networks, since no transformer is possible here.

In an advantageous embodiment of the invention, the sensor unit has a current sensor per phase conductor, in particular for each conductor. In particular, the current sensor is designed as a Rogowski coil, Hall sensor, AMR sensor or resistor. This has the particular advantage that a particularly simple and accurate current measurement in each phase conductor / conductor can be made. Especially in DC networks are Hall sensors, AMR sensors or resistors for the current measurement of advantage.

In an advantageous embodiment of the invention, only one electrical power switch is provided on the circuit breaker for closing the low-voltage circuit. This can be designed in particular as a push button. This has the particular advantage that switching can be done only when there is an electrical voltage. A mechanical switching in the de-energized state is thus prevented, whereby functional safety is ensured.

In an advantageous embodiment of the invention, a mechanical emergency stop switch is provided for opening the low-voltage circuit. This has the particular advantage that the circuit can be mechanically interrupted for emergencies.

In an advantageous embodiment of the invention, a motor drive is provided for closing the low-voltage circuit. This has the particular advantage that switching on the low-voltage circuit is possible only in the live case and thus switching on in the de-energized case is prevented, whereby functional safety is ensured.

In an advantageous embodiment of the invention, at least for one phase conductor, in particular for all phase conductors or all conductors, in addition to the energy source side an energiesenkenseitiger voltage sensor is provided, which is / is connected to the control unit / are. This has the particular advantage that a voltage drop across the interrupt unit can be determined, which allows a conclusion about the state of the interrupt unit, so that any information for replacement of the interrupt unit, especially in those with mechanical contacts, present. Furthermore, it can be checked whether, after triggering the circuit breaker, the power side of the power grid side is de-energized. Thus, a reconnection to a voltage can be prevented or a synchronized switching on done.

In an advantageous embodiment of the invention, temperature sensors for determining the temperature of the interruption unit and the circuit breaker are provided. This has the particular advantage that a monitoring of the circuit breaker can be done and at elevated temperatures tripping of the circuit breaker / can be done to prevent damage.

In an advantageous embodiment of the invention, a communication unit (COM) connected to the control unit (ETU) is provided. This has the particular advantage that information of the circuit breaker can be forwarded to a higher-level management or information system.

• - ein vorangegangener Auslösegrund ermittelt wird,
• - die Spannung des Niederspannungsstromkreises ermittelt wird,
• - die ermittelte Spannung mit einem Minimalspannungsgrenzwert verglichen wird,
• - bei dessen Überschreitung und wenn der vorangegangene Auslösegrund eine Spannungsunterschreitung im Niederspannungsstromkreis war, ein Stromfluss im elektrischen Niederspannungsstromkreis ermöglicht wird.

Dies hat den besonderen Vorteil, dass ein Leistungsschalter mit funktionaler Sicherheit zur Verfügung gestellt wird, der nach einer Kurzschluss- oder Überstromauslösung, verbunden mit einem folgenden Spannungsausfall, nicht automatisch den Leistungsschalter wiedereinschaltet. Nur bei „normalen“ Spannungsausfällen wird wiedereingeschaltet.According to the invention, a corresponding method for a circuit breaker for interrupting and closing a multi-conductor having low-voltage circuit is further claimed. This is characterized in that, in particular in the presence of a voltage, in particular after the resumption of a voltage of the low-voltage circuit:

• - a previous triggering reason is determined,
• - the voltage of the low-voltage circuit is determined,
• the determined voltage is compared with a minimum voltage limit value,
• - When exceeded and if the previous triggering reason was a voltage drop in the low-voltage circuit, a current flow in the low-voltage electrical circuit is enabled.

This has the particular advantage of providing a circuit breaker with functional safety that does not automatically reconnect the circuit breaker after a short circuit or overcurrent trip, combined with a subsequent power failure. Only in case of "normal" power failures will be switched back on.

In an advantageous embodiment of the invention, in the presence of a voltage of the low-voltage circuit, in particular resubmissions, a self-test of the circuit breaker is performed first. This has the particular advantage that a defective circuit breaker does not provide an unsecured power supply. Thus, the aspect of functional safety continues to be taken into account.

• - der Strom im Niederspannungsstromkreis ermittelt wird,
• - dieser mit Strom- oder Strom-Zeitspannen-Grenzwerten verglichen wird,
• - die Spannung im Niederspannungsstromkreis ermittelt wird,
• - diese mit einen Unterspannungsgrenzwert verglichen wird,
• - bei Überschreiten der Strom- oder Strom-ZeitspannenGrenzwerte oder Unterschreiten des Unterspannungsgrenzwertes eine Unterbrechung des Niederstromkreises sowie eine Speicherung des Auslösegrundes erfolgt, insbesondere in einem nichtflüchtigen Speicher, wie einem EEPROM.

In an advantageous embodiment of the invention is periodically:

• - the current in the low-voltage circuit is determined,
• - This is compared with current or current-time limit limits,
• - the voltage in the low-voltage circuit is determined,
• - this is compared with an undervoltage limit,
• - If the current or current time span limits are exceeded or the undervoltage limit value is exceeded, a Interruption of the low circuit and storage of the cause of the trip takes place, especially in a non-volatile memory, such as an EEPROM.

This has the particular advantage that, on the one hand, a permanent monitoring of the circuit takes place and, on the other hand, there is the cause of the tripping in the circuit breaker.

All embodiments, both in dependent form based on the claim 1 and 17, as well as referred back only to individual features or combinations of features of claims, cause an improvement of a circuit breaker to increase the functional safety.

The described characteristics, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the embodiments, which will be explained in connection with the drawing.

• 1 eine erste Darstellung eines erfindungsgemäßen Leistungsschalters,
• 2 eine zweite Darstellung eines erfindungsgemäßen Leistungsschalters,
• 3 eine Prinzipdarstellung zur Erläuterung der Erfindung,
• 4 eine Detaildarstellung,
• 5 ein erstes Ablaufdiagramm,
• 6 ein zweites Ablaufdiagramm.

The drawing shows:

• 1 a first representation of a circuit breaker according to the invention,
• 2 a second representation of a circuit breaker according to the invention,
• 3 a schematic diagram for explaining the invention,
• 4 a detailed description,
• 5 a first flowchart,
• 6 a second flowchart.

1 shows a schematic diagram of a circuit breaker LS according to the invention. This has a first to fourth conductor L1 . L2 . L3 , N on, with the first to third conductors L1 . L2 . L3 Phase conductors of an electrical circuit, in particular low-voltage circuit, are, for example, a three-phase AC circuit. The fourth conductor N is, for example, a neutral conductor of the circuit. The four conductors pass through the power switch, wherein they are connected on the input side to a power source, not shown, ie have a power source side terminal EQ. On the output side, the conductors are connected to a load, not shown, or a load, ie, have an energiesenkenseitigen connection load. The first to third leaders L1 . L2 . L3 go through an interruption unit UE, for example, the mechanical and / or electronic contacts K1 . K2 . K3 each having a contact associated with a conductor. In the example according to 1 are three mechanical double break contacts K2 . K2 . K3 provided that interrupt or close the current flow of the conductors through the circuit breaker, for example by a rotary motion.

The four-wire N can also be interrupted or closed by contacts.

The interrupt unit UE is driven, for example, by a motor unit M, the motor M being used exclusively for closing the interrupt unit / closing the contacts, i. closing the circuit is used.

The interruption unit UE may further comprise a mechanism such that the closed contacts are biased and activated by a small mechanical movement, for example by a relay switch OS connected to the interruption unit UE, e.g. in the form of an OFF solenoid, can be opened so that the current flow of the conductors is interrupted by the circuit breaker.

Furthermore, an unillustrated mechanical emergency stop switch can be provided, with which the contacts can be opened or the current flow can be interrupted.

Furthermore, the interrupt unit UE may comprise position sensors POS with which the position of the contacts or a broken or closed state of the interrupt unit can be determined.

The interruption unit UE or its control elements, i. the motor unit M for closing the breaker unit / contacts and the relay switch OS for opening the breaker unit / contacts are connected to a control unit ETU, for example an electronic trip unit, e.g. having a microprocessor. In this case, the connection between control unit ETU and interruption unit UE respectively motor unit M and relay switch OS driver units DM, DOS have, for amplifying the control signal or control of the units.

The interruption unit can also be designed as an electronic interruption unit, for example with semiconductor switches. This eliminates mechanical motor drives to close and relay switch to open. The control of an electronic interruption unit UE can be carried out fully electronically by means of closing and opening signals by the control unit ETU.

The four leaders L1 . L2 . L3 , N, but at least the phase conductors L1 . L2 . L3 , respectively a current sensor I1 . I2 . I3 . I0 on, which form a sensor unit SE, which is connected to the control unit ETU. That is, the height of the currents, the conductor having a current sensor, is transmitted to the control unit ETU. For example, the current sensors can be Rogowski coils, allowing for easy and accurate current measurement.

The three phase conductors L1 . L2 . L3 or four conductors L1 . L2 . L3 , N are further connected to a power source side voltage sensor US, which determines the voltage of the phase conductors with each other and / or the phase conductor to neutral. This voltage sensor US is connected to the control unit ETU, so that the control unit receives the magnitude of the voltages.

Furthermore, at least two conductors, in particular the phase conductors or all conductors are connected to a power supply VDD. This generates from the voltage difference between two conductors a supply voltage for the control unit ETU. Optional for possibly provided driver units DOS, DM or / and motor unit M or relay switch OS or interrupt unit UE.

The supply voltage of the power supply VDD can be supported by an energy storage buffer, for example in the form of a rechargeable battery, a battery or a supercapacitor in case of power failure.

The position sensors POS are also connected directly or via a driver unit DPOS to the control unit ETU.

The control unit ETU is connected to an electrical ON switch ON, for example in the form of a pushbutton.

On the control unit ETU an input for (external) under-voltage protection UVR, and (external) tripping function SHT can be provided. At these connections, emergency stop switches placed in the course of the installation of the interruption unit UE can be connected in functionally safe form.

Furthermore, the control unit ETU can be connected to a communication unit COM, for the transmission of data or information to another circuit breaker, computer or monitoring or management system and for remote control by a computer or a (management) system.

The circuit breaker may further comprise temperature sensors, in particular a temperature sensor in the interruption unit, more particularly another in the device. The current temperature or temperature difference can be used to detect problems with the interrupt unit or circuit breaker.

The control unit ETU may also have at least one output Out, for example to display information or to control units.

In the case of a DC voltage circuit or DC voltage network usually two conductors are provided, usually a positive conductor and a negative conductor. That the circuit breaker leads in this case in particular only two conductors or the current of two conductors. For a person skilled in the resulting change in the circuit breaker is clear.

In principle, for the present invention AC applications are in the foreground, which are also supported in DC applications.

2 shows a schematic diagram according to 1 , with the difference that three phase conductors L1 . L2 . L3 or four conductors L1 . L2 . L3 , N are further connected to an energy-side voltage sensor LUS, which determines the voltage of the phase conductors with each other and / or the phase conductor to neutral. This voltage sensor LUS is connected to the control unit ETU, so that the control unit receives the level of the voltages on the load side LOAD.

From the voltage difference between the power source side and the power side voltage, it is possible to infer the characteristics of the breaker, more specifically the contacts. If the voltage difference is too large, i. if it exceeds a threshold value, a warning signal may be given, e.g. to exchange the interruption unit or contacts.

Furthermore, a synchronized connection to a network can take place if further energy sources are provided on the consumer side.

3 shows on the right and left side each a representation with three circuit breakers LS1 . LS2 . LS3 , a power source U and a load load. Between power source U and load load is in principle the series connection of the first and second power switch LS1 . LS2 shown. Between the first and second circuit breaker is the third circuit breaker on one side LS3 connected to the example, more consumers can be connected. The first circuit breaker LS1 is thus the parent circuit breaker to the second and third power switch LS2 . LS3 , On the left figure in 3 the de-energized state is shown in the low voltage circuit. This means that all circuit breakers are open, ie interrupt the electrical circuit. On the right figure in 3 the live state is shown in the low voltage circuit. This means that the circuit breakers are closed, ie the electrical circuit is closed.

4 shows a detailed representation according to 1 , namely the connection of two-phase power supply VDD1 to two conductors of the low voltage circuit. It is essential that the power supply is from the voltage of the conductors, not from the consumer-generated current flow of the conductors (as before). Therefore, in the example according to 4 a transformer TR connected to the two conductors. In the example, the first primary-side connection of the transformer TR with the third conductor L3 , the second primary-side terminal of the transformer TR to the second conductor L2 ,

Analogously, a power supply VDD be constructed that is connected to all conductors or a ladder subset. For example, a three-phase power supply.

5 shows a first flowchart for a circuit breaker according to the invention. 5 shows an example of the initial program flow, such as a firmware of the microprocessor / microcontroller of the control unit ETU. This will be run once once the supply voltage / power supply through the power supply VDD , For example, switching power supply, is ensured from the primary voltage of the low-voltage circuit.

After initializing the microcontroller and all memory and registers and loading the configuration in step 100 , eg InitHW (), becomes a self-test in step 110 go through the electromechanical and / or electronic components. Kicking the self-test 110 Error on "false", will an error message in step 200 issued. Will the self-test 110 without error "true" completed, so the last cause of action can be read from the memory, especially non-volatile memory, such as EEPROM. This is done in the step 120 , eg loadLastTripEvent (). Now in the step 130 the input voltage is measured at the conductors / primary conductors of the low voltage circuit (fU = measU ()). This tension is in the step 140 compared with a minimum voltage limit. This can be a minimum voltage configured based on the application. If this voltage becomes smaller "false" will be in one step 300 a main loop according to later shown and described 6 run through. If this voltage is greater "true" than the minimum voltage limit, it can also be checked whether an undervoltage signal is present. Has the last shutdown due to a voltage drop in the low voltage circuit or Primärspannungseinbruchs (evLowVolt) occurred, which in step 150 is checked, so in the positive case "yes" in the step 160 the circuit are closed, for example, the contact system in the circuit breaker, eg by means of the motor unit M, closed. Is the circuit / contact system in step 160 closed, it continues with the main loop 300 , Optionally, there is still a biasing of the contact system via an intermediate step 170 necessary. In the negative case of step 150 "No" the contact system or the circuit remains open and it continues with the main loop 300 , Subsequently, the main loop of the firmware is run continuously.

6 shows a second flow diagram for a circuit breaker according to the invention. 6 shows an example of the program flow of the continuously swept main loop, for example in the firmware. The main loop begins after the completion of the initialization routine, ie after at least one of the example steps according to FIG 5 , and constantly monitors the operating state in the circuit breaker and the load conditions on the primary conductors.

In one step 210 the currents of the conductors or primary currents are measured (fI = measI ()) and in one step 220 compared with the current or current-time limit limits, eg function calcLSI (), ie with the configured tripping characteristics. If an overload or short-circuit situation results in "trip", ie if current-time-period limits or current limit values are exceeded, this is done in step 230 ff an interruption of the circuit, eg the firmware solves the interruption unit UE or contacts K1 . K2 . K3 by deactivating (or activating) the relay switch OS, eg (setTRIP ()). In step 240 the triggering event is stored in memory, in particular non-volatile memory, eg in the control unit ETU (storeLastTripEvent ()). The memory may be, for example, an EEPROM.

If there is no overload or short circuit situation takes place in step 250 a monitoring of external trigger signals, as they may be present for example at the inputs UVR and SHT of the control unit. If such signals are "true", takes place in the step 230 a described interruption. Otherwise, in step 260 a measurement of the electrical voltage, in particular energy source side. The determined voltage is in the step 270 compared with the minimum voltage limit. If this value is undershot, an interruption occurs with the described step (s) 230 ff.

Alternatively, it is additionally possible to test for falling below a second, even lower basic voltage limit. This is in the step 310 located. Here, the voltage is compared with the base voltage limit. This base voltage limit is defined by the base voltage for safe operation of the internal power supply VDD, eg switching power supply. If the voltage at the conductors falls below this threshold, the operation of the power switch, in particular of the control unit ETU, can no longer be ensured. If this limit is reached, steps are taken 230a . 240a taking the steps 230 and 240 and 320 trigger and reset (step 320 ) of the circuit breaker to prevent malfunction.

Once the voltage / primary voltage returns to the safe startup of power supply VDD and control unit ETU allows, the above-described initialization routine is run through again and possibly the contact system closed again.

From an application point of view, the described behavior is neutral, since with massive undervoltage no load can be operated.

Optionally conceivable is a delay of the spontaneous undervoltage release, i. Below the minimum voltage limit value. However, this requires an additional buffer memory buffer, which must also apply the energy for the temporal bridging of the permanently energized relay coil OS.

If, with the test implemented, the basic voltage limit is not undershot, this is done in step 330 a self-test function, eg (permanent) monitoring of important electromechanical / electronic components. The failure of safety-relevant components "false" leads again to the steps 230a . 240a . 320 , ie reset the circuit breaker as this should result in a tripping of the circuit breaker.

If the self-test is successful, ON can be turned on in one step with respect to turning it ON 340 being checked. If you press the power button, it will be in steps 350 , optional 360 , and 370 the circuit is closed, ie, for example, the contacts closed. The step 360 may include biasing the contact system. The steps 350 or 370 an activation of the motor unit M for closing the circuit. Is the circuit / contact system in step 370 closed, the main loop starts in step 210 from the beginning.

In the negative case of step 340 "False" leaves the contact system or circuit open and the main loop starts from the beginning 210 ,

It goes without saying that changes of the initialization and the main loop are possible without departing from the scope of the invention.

In the following, the invention will be described again in other words.

Functional safety is today demanded in almost all areas of everyday life in a wide variety of forms (IEC 61508 and application-specific standards). The area of application has some time ago been from the classic area of highest safety, such as in nuclear power plants and aerospace (SIL 4 ), developed into other areas. Today, the ideas of IEC 61508 come up with somewhat weaker requirements in automotive (ASIL) and railway (SIL 3 ) in front. They are used in the manufacturing industry as well as in the processing industry (eg in the form of the Machinery Directive).

One of the main pillars of functional safety is the requirement that all systems must have a functionally safe state, in which the system automatically drops back in the event of safety-relevant faults or faults. The underlying idea is to avoid any further endangerment of persons and the environment due to faulty devices. The requirement of functional safety is justified today also for energy distribution systems, because of uncontrolled feed-in with achievements in the MVA range a very high endangerment potential emanates. All electrical installations have a main switch, e.g. in the form of circuit-breakers, load switches or load-break switches, with which the system can be disconnected from the mains. This can be done for maintenance purposes or in the form of an emergency shutdown. In electrical drives with electronic control technology, today the switch-disconnector is automatically actuated depending on the operating status of the system and critical system failures. In addition, this main switch is often equipped with a system-independent protection function for short-circuit detection. Corresponding switches are referred to as circuit breakers, since they are able to separate a multiple of the rated current.

Regardless of the system protection described above, the historically grown approach is usual until now that overcurrent protection elements, eg in the form of fuses, are permanently switched on as long as no overload or short-circuit situation is detected. This approach results from the generally purely mechanical design principle that overcurrent events are detected by thermal or magnetic forces and these forces are used to trigger the protective function. All too Circuit-breakers with electronic current monitoring and trip unit (ETU) apply the principle of permanently closed contact path.

In low-voltage circuit-breakers, the ETU control unit is often supplied by magnetically coupled primary current transformers. The control unit ETU can therefore only work under current flow, which results in a problem with the safe configuration of the switch. More serious than the configuration problem weighs the fact that a potential malfunction of essential parts of the control unit ETU can not be determined independently of the load current. In the extreme case of switching on the mains voltage to a short circuit present behind the circuit breaker, tripping can not be ensured. The protection function can fail and must be absorbed by the redundant function in a superordinate network level. As a result, the local short circuit results in the shutdown of a much larger network area.

The core of the invention is to couple the function of the contact system to the external mains voltage. An electrical energy flow (current flow) to the consumers without mains voltage is not possible and not desirable, since it must be a fault or leakage current in any current flow. Therefore, the invention provides to keep the contact system in the open position without applied mains voltage, see 1 . 2 respectively. 3 - left side. From an application point of view, this change makes no difference, but rather improves the situation by interrupting faulty paths. By a voltage applied to the input side, the control unit / electronic trip unit ETU is activated. The control unit ETU carries out a self-test during the initialization and then checks the existing situation, eg regarding the mains voltage level, external control signals, etc. A positive verification of the current situation as well as the evaluation of the last state before the mains voltage failure enables the firmware of the control unit ETU to close the contact system and thus allow the electrical energy flow to consumers, see 3 - right side. Thus, from today's standard state of closed contacts is achieved from an application perspective.

Subsequent arranged circuit breakers of the inventive type behave the same way. They wake up with the mains voltage activated via the higher-level switch. They carry out the same evaluations and also independently close their contact system.

1 provides an overview of the proposed system design. 1 exemplifies mechanical, electromechanical and electronic components in a schematic block diagram. Depending on the network topology, the circuit breaker LS has n or (n-1) contact points for n conductors L1 . L2 . L3 , N installed. These contact points are always in the inactive state, for example by a spring force, open. Per conductor are on the input side, ie eg energy source side, the circuit breaker each a potential tap for voltage measurement and a current sensor available. The n potential taps are connected to n voltage sensors. Parallel to the voltage sensors US, the self-power supply of the control unit ETU is generated from the primary voltage, eg with a switched-mode power supply VDD. This power supply VDD should be designed for a wide voltage range, eg 20% to 150% of the voltage or nominal voltage of the low-voltage circuit. The internal voltage distribution from the power supply feeds all electronic and electromechanical components in the circuit breaker. A buffer memory for the internal voltage can be optionally provided to bridge short-term voltage dips.

The control unit ETU has electronic signal processing elements, such as one or more microcontrollers, which evaluate and set the signals by means of firmware. The microcontroller (s) are provided with volatile memory elements (RAM) for program execution. Configuration data and current state data of the firmware are permanently stored in a nonvolatile memory element such as an EEPROM or the like. The measuring signals of the current and voltage sensors are fed to the control unit ETU / processing electronics. The control unit ETU also processes external inputs for shunt-trip SHT, undervoltage release UVR and switch-on signal ON and provides status message outputs Out.

The connection to a network, such as fieldbus or Ethernet, eg by a communication module COM, opens up further digital control and signaling paths. All incoming signals are processed eg in firmware by the microcontroller or the control unit ETU. The firmware also controls the motor unit M / the motor drive to close the contacts or biasing of the contact system. The motor drive M is electronically controlled and supplied from the switching power supply to the primary conductors. Furthermore, the firmware controls a relay switch OS, such as an electromechanical coil drive via an electronic coil driver, which is also powered from the power supply VDD. This relay switch closes the contact system or keeps the contact system closed as long as the relay switch is energized, eg, energized by current flow. Interrupts the Current flow to the relay switch, the contact system / the interruption unit opens automatically, for example by spring force and interrupts at least one, a part or all conductors, so that the current flow in the low-voltage circuit is interrupted.

The location of significant moving parts in the breaker unit / contact system and in the motor or spring drive can be determined by position sensors POS and transmitted to the control unit, as well as there, e.g. in firmware, to be processed. Position-dependent states as well as error cases can be so, e.g. via firmware, recognized and treated.

The circuit breaker does not have a mechanically acting on-off switch. A power switch, such as a push button or pushbutton on the circuit breaker works only as an electrical closing contact for the electronic ON input.

A mechanically acting switch is provided because it has a redundant (emergency) switch-off function.

At the same time, the switch can also be designed as a make contact for the electronic SHT signal, as a break contact for the electronic UVR signal or otherwise as a signaling contact to the ETU control unit.

The described electromechanical design represents the e.g. Firmware, which can be processed on the microcontroller of the control unit ETU, at the center of the entire functional chain. Apart from the mechanical (emergency) shutdown, there is no control system for the contact system that is not controlled and controlled by the control unit or firmware. Only the control unit / firmware controls all activities and is therefore safety-relevant to implement. This approach offers the possibility of using the control unit / firmware "independent" action options. Thus, the firmware can not only open / trigger the contact system - as is usual today - but also close it if the operating situation allows it.

According to the invention, a circuit breaker with the property that this monitors the state of the mains voltage on the feed side and in case of power failure (= falling below a minimum voltage limit or minimum voltage threshold) triggers the contact system, and automatically closes again when reaching the operating voltage, in particular if the previous opening the contact system was caused by power failure and in particular no other states prevent this.

The mains voltage is monitored by voltage sensors in the electronic trip unit. The control unit ETU is supplied from the mains voltage via a long-range (switching) power supply. A buffer memory buffer is optionally implemented in the electronic trip unit, to bridge short-term voltage dips. In the ETU control unit, the cause of the trip is stored permanently. The reason for the trip is loaded when (re) starting the control unit ETU. The electronic decision to independently close the contact system is made on the basis of the evaluation of the current mains voltage, the states of external control and communication channels as well as the last triggering reason. The self-closing of the contact system is / can be delayed adjustable in time. An emergency stop switch operates redundantly with the electronic trip unit and blocks the closing of the contact system.

The advantage of the invention lies in the introduction of the principle of "functional safety" in low-voltage circuit breakers. Particular emphasis is placed on the functionally safe ground state. Only the state with the contact system open can be considered functionally safe, as a malfunction of safety-relevant components in the circuit-breaker could otherwise prevent tripping. If an application in the field requires that the safe state enforces a closed contact system, then this means for the system design that this is only possible with redundant circuit breakers, since the failure of a critical component "circuit breaker" has to be absorbed by the parallel-operated component.

• Nur noch eine elektromechanische Komponente zur Steuerung → Relaisschalter, z.B. als Bereitschaftspule.
• Die Eliminierung redundanter Schaltelemente bietet folgende Vorteile:
  • Vereinfachung des mechanischen Designs (→ Kosteneinsparung in Entwicklung und Produktion).
  • Kosteneinsparung: Entfall separater SHT, UVR und ON Solenoide, da deren Funktion durch die Steuerungseinheit ETU übernommen wird.

The electromechanical overall design has been simplified so far that only the control unit ETU or its firmware controls and controls all safety-relevant conditions. Parallel switching options are consistently eliminated. The ETU and its firmware must therefore be implemented in a safety-relevant manner:

• Only one electromechanical component to control → relay switch, eg as standby coil.
• The elimination of redundant switching elements offers the following advantages:
  • Simplification of mechanical design (→ cost savings in development and production).
  • Cost savings: no separate SHT, UVR and ON solenoids as their function is taken over by the ETU control unit.

• Entfall der komplizierten, höchst ineffizienten und teuren Stromwandler für die Eigenversorgung.
• Betriebsbereitschaft der Steuerungseinheit ETU für alle Spannungen oberhalb einer Minimalspannung unabhängig vom Lastzustand, d.h. insbesondere auch bei geöffnetem Kontaktsystem. Damit ist die Steuerungseinheit ETU i.d.R. kommunikationsfähig, ohne eine externe Versorgung über 24V Hilfsspannung o.ä. zur Verfügung zu stellen.
• Energiemonitoring basierend auf dieser Eigenversorgung benötigt keine Hilfsspannung mehr.
• Ohne ausreichende Primärspannung kann das Kontaktsystem nicht geschlossen werden. Damit sind die Geräte auf der Lastseite vor Unterspannung geschützt.

The self-supply from the input-side mains voltage offers the following advantages:

• The elimination of the complicated, highly inefficient and expensive current transformer for self-supply.
• Operational readiness of the control unit ETU for all voltages above a minimum voltage, regardless of the load condition, ie especially when the contact system is open. Thus, the control unit ETU is usually communication capable, without an external supply via 24V auxiliary voltage or similar. to provide.
• Energy monitoring based on this self-supply no longer requires auxiliary voltage.
• Without sufficient primary voltage, the contact system can not be closed. This protects the devices on the load side from undervoltage.

• Bei Ausfall der Primärspannung oder unterschreiten einer Unterspannungsschwelle auf einer oder mehreren Phasen öffnet sich das Kontaktsystem und schützt die Last vor Phasenausfall.
• Das Einschalten der Netzspannung auf ein geschütztes Teilnetz mit Kurzschluss ist prinzipiell nicht möglich → Entfall aller Risiken und Schutzmaßnahmen zur Behandlung dieses kritischen Testfalls.
• Ein elektrischer Fehler im Relaisschalter, z.B. Bereitschaftsspule, löst den Leistungsschalter aus, d.h. der sichere Zustand wird selbstständig erreicht. (Heute führt ein elektrischer Fehler im Auslösemagnet zum Versagen der Schutzfunktion.)
• Durch die automatische Abschaltung des Leistungsschalters / Öffnen des Kontaktsystems bei (Primär-)Spannungsausfall ergibt sich für die Anwendung bzw. für den Netzbetreiber der Vorteil, dass das Netz im lastfreien Zustand angefahren werden kann.
• Die Last wird vor den Einschaltschwingungen des Umspanntransformators geschützt.
• Eine Stromversorgung aus Verbrennungsmotor und Generator wird vor der sofortigen Überlastung im Motor- bzw. Generatoranlauf geschützt. Der heute zum Generatoranlauf notwendige Trennschalter entspricht dem hier vorgestellten Konzept und inkludiert die unabhängige Kurzschlussüberwachung.

Together with the changed electromechanical design, the following advantages result:

• If the primary voltage fails or falls below an undervoltage threshold on one or more phases, the contact system opens and protects the load from phase failure.
• Switching the mains voltage on a protected subnetwork with a short circuit is not possible in principle → elimination of all risks and protective measures for the treatment of this critical test case.
• An electrical fault in the relay switch, eg standby coil, triggers the circuit breaker, ie the safe state is reached automatically. (Today an electrical fault in the trip solenoid leads to failure of the protection function.)
• The automatic disconnection of the circuit breaker / opening of the contact system during (primary) power failure has the advantage for the application or for the network operator that the network can be started up in the no-load state.
• The load is protected from the switch-on vibrations of the transformer transformer.
• A power supply from the combustion engine and generator is protected against immediate overload in the motor or generator startup. The disconnector required today for the generator start-up corresponds to the concept presented here and includes the independent short-circuit monitoring.

This invention discloses a new approach to the system design of low voltage circuit breakers. It combines the switching function with the protective function and emphasizes the aspects of functional safety.

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

Claims (19)

Circuit breaker (LS) for interrupting a low-voltage circuit comprising a plurality of conductors (L1, L2, L3, N), - with an interruption unit (UE), to interrupt at least one conductor of the low-voltage circuit, - With a power supply (VDD), which is connected to at least two conductors of the low-voltage circuit, wherein from a voltage difference of at least two conductors, a supply voltage for the circuit breaker is generated, with a sensor unit (SE) for determining the magnitude of the electric current of at least one conductor of the low-voltage circuit, with a control unit (ETU) connected to the interruption unit (UE), the sensor unit (SE) and the power supply unit (VDD), which is designed in such a way that an interruption of at least one conductor of the at least one conductor is prevented if the current or current time span limits are exceeded Low-voltage circuit through the interruption unit, - That the circuit breaker is designed such that in the de-energized state of the low-voltage circuit always at least one conductor of the low-voltage circuit is interrupted and a current flow of the low-voltage circuit is provided by the circuit breaker only in the presence of a low voltage in the low-voltage circuit. Circuit breaker (LS) after Claim 1 , characterized in that the low-voltage circuit is a three-phase AC circuit or DC circuit. Circuit breaker (LS) after Claim 1 or 2 , characterized in that the interruption unit (UE) contacts (Kl, K2, K3), with the at least one conductor, in particular the phase conductors or all conductors, can be electrically opened or closed. Circuit breaker (LS) after Claim 3 , characterized in that the contacts (Kl, K2, K3) are opened in the de-energized state. Circuit breaker (LS) after Claim 1 . 2 . 3 or 4 , characterized in that the power supply (VDD, VDD1) comprises a transformer (TR) whose first terminal of the primary winding is connected to a conductor and whose second terminal of the primary winding is connected to another conductor. Circuit breaker (LS) according to one of the preceding claims, characterized in that the power supply (VDD) is a switching power supply. Circuit breaker (LS) according to one of the preceding claims, characterized in that the sensor unit (SE) has a current sensor (I1, I2, I3, I0) per phase conductor, in particular the current sensor is designed as Rogowski coil, Hall sensor, AMR sensor or resistor. Circuit breaker (LS) according to one of the preceding claims, characterized in that only one electrical power switch (ON) is provided on the circuit breaker for closing the low-voltage circuit. Circuit breaker (LS) after Claim 8 , characterized in that the electrical power switch (ON) is designed as a push-button. Circuit breaker (LS) according to one of the preceding claims, characterized in that a mechanical emergency stop switch is provided for opening the low-voltage circuit. Circuit breaker (LS) according to one of the preceding claims, characterized in that a motor unit (M) is provided for closing the low-voltage circuit. Circuit breaker (LS) according to one of the preceding claims, characterized in that at least one phase conductor, in particular for all phase conductors, in each case a power-source-side voltage sensor (US) is provided which is / is connected to the control unit / are. Circuit breaker (LS) after Claim 12 , characterized in that at least for one phase conductor, in particular for all phase conductors, in each case an energiesenkenseitiger voltage sensor (LUS) is provided, which is / is connected to the control unit / are. Circuit breaker (LS) according to one of the preceding claims, characterized in that position sensors (POS) are provided for determining the state of the interruption unit (UE). Circuit breaker (LS) according to one of the preceding claims, characterized in that temperature sensors are provided for determining the temperature of the interruption unit and of the circuit breaker. Circuit breaker (LS) according to one of the preceding claims, characterized in that a communication unit (COM) connected to the control unit (ETU) is provided. Method for a circuit-breaker (LS) for interrupting and closing a low-voltage circuit comprising a plurality of conductors (L1, L2, L3, N), which in the presence of a voltage of the low-voltage circuit: - a previous triggering reason is determined, - the voltage of the low-voltage circuit is determined, the determined voltage is compared with a minimum voltage limit value, - When exceeded and if the previous triggering reason was a voltage drop in the low-voltage circuit, a current flow in the low-voltage electrical circuit is enabled. Method according to Claim 17 , characterized in that in the presence of a voltage of the low-voltage circuit, a self-test of the circuit breaker is performed first. Method according to Claim 17 or 18 , characterized in that periodically: - the current in the low-voltage circuit is determined, - this is compared with current or current-time limit limits, - the voltage in the low-voltage circuit is determined, - this is compared with an undervoltage limit, - when the current is exceeded - or current-time periods limit values or undershooting of the undervoltage limit value, an interruption of the low-voltage circuit as well as a storage of the reason for the action takes place.

Images