DE102024203215A1 - Circuit breaker - Google Patents

Abstract

The invention relates to a circuit breaker and a method for protecting a power supply formed by three phase conductors (L1, L2, L3) and a neutral conductor (N). The circuit breaker is designed to determine the current values of the three phase conductors (L1, L2, L3), to determine the voltages present between the phase conductors (L1, L2, L3) and the neutral conductor (N), and to evaluate certain current and voltage values. Virtual circuits are defined between the individual phase conductors (SKL1L2, SKL1L3, SKL2L3) for the evaluation. The circuit breaker is designed to determine circuit-specific voltages, currents, and impedances for the virtual circuits using the determined current and voltage values. The voltage of a virtual circuit (SKL1L2, SKL1L3, SKL2L3) between two phase conductors corresponds to the difference in the voltages between the respective phase conductors and the neutral conductor, the current of a virtual circuit (SKL1L2, SKL1L3, SKL2L3) between two phase conductors corresponds to the weighted difference in the currents of the respective phase conductors, and the impedance (ZL1L2, ZL1L3, ZL2L3) of a virtual circuit between two phase conductors corresponds to the quotient of the voltage and current of the virtual circuit between the two phase conductors. The values determined for the virtual circuits are used for diagnosing overcurrent events.

Description

The invention relates to a circuit breaker and a method for supporting the diagnosis of overcurrent events in a power supply formed by three phase conductors and one neutral conductor.

Loads with capacitive or inductive components (inrush loads) cause high inrush currents when connected to an AC network. For example, a load consisting of one or more single- or multi-phase rectifiers or switching power supplies can generate brief, high current peaks (inrush currents) when connected, the maximum values of which can reach several times their steady-state current amplitude. High-efficiency electrical machines also have inrush currents and starting currents that are significantly higher than their rated currents, e.g., up to a factor of 12 for machines in efficiency class IE4.

• • die Lastimpedanz
• • der Zeitpunkt, zu dem dieser Stromkreis zu der stromtreibenden Spannung zugeschaltet wird
• • der Zustand der Last unmittelbar vor dem Zuschaltzeitpunkt (z.B. bei kapazitiven Lasten die Ladung der Kapazität und bei elektrischen Maschinen die Amplitude und Phasenlage der induzierten Spannung)

One consequence of the inrush current can be the tripping of the miniature circuit breaker (MCB) when an inrush load is switched on or connected. For two-pole inrush loads, the amplitude of the inrush current and thus the probability of tripping due to an inrush current is determined by various factors. The most important of these are:

• • the load impedance
• • the time at which this circuit is connected to the current-driving voltage
• • the state of the load immediately before the switching on time (e.g. for capacitive loads the charge of the capacitance and for electrical machines the amplitude and phase position of the induced voltage)

For a capacitive load or a rectifier with a capacitive intermediate circuit, the tripping probability is lowest when the load is connected near the zero crossing of the relevant voltage. This is because, at such a selected switch-on time, the current rise rate is generally the lowest compared to other switch-on times. Furthermore, the time in the switched-on state until the current limit is reached is the longest (in case excessive current values are reached during an in-rush current). This allows a greater amount of energy or charge to be transferred to the load than with a very short and steep current pulse. Furthermore, more time is available for analyzing the load in the switched-on state.

With conventional electromechanical circuit breakers with manual contact actuation, there is no way to specifically implement an optimal switch-on time. In contrast, with switching devices with an electronic switching unit (Semiconductor Circuit Breaker (SCCB)) consisting of one or more power semiconductors, one or more energy absorbers (EA), a measuring unit, and a control unit, targeted switching at a selected time with a tolerance of a few microseconds is possible.

From the disclosure document DE 10 2020 216 405 A1 A method for controlling the power semiconductor in a two-pole SCCB is known, according to which the inrush current is switched off when a certain current limit is reached and then repeatedly switched on within a mains voltage period near the next voltage zero crossing. During the first switch-on, the capacitance of the inrush load may be partially charged, and the amplitude of the inrush current decreases with each subsequent switch-on attempt, so that the current limit of the SCCB may not be reached again during one of the subsequent switch-on attempts. After that, the load is continuously supplied.

In three-phase four-wire networks, the problem of inrush currents is more complex due to the higher number of conductors and requires different solutions than the method mentioned above.

The invention aims to support the diagnosis of overcurrent events in a power supply consisting of three phase conductors and one neutral conductor.

The object is achieved by a circuit breaker according to claim 1 and a method according to claim 10. Advantageous embodiments are specified in the subclaims.

The circuit breaker according to the invention is designed for a power supply comprising three phase conductors and one neutral conductor. It is configured to determine the current values of the three phase conductors and the voltage values between the phase conductors and the neutral conductor. This determination is typically performed by measurement, for which purpose it can be configured with current and voltage sensors. However, it is also conceivable that these values are calculated from other measured values. Solutions are also conceivable in which the measuring sensors are not part of the circuit breaker, but are measured externally and transmitted to the circuit breaker. In this case, the term "determine" is to be understood as receiving or querying an external entity.

The circuit breaker according to the invention is further designed to evaluate specific current and voltage values. This evaluation can be carried out with a view to fulfilling conditions for switching operations involving the interruption of the phase conductors and the restoration of broken connections. It can be equipped with one or more processing units, e.g., an MCU or CPU, for this evaluation.

In addition, the circuit breaker according to the invention can be configured to output control signals in accordance with switching actions to be performed based on the evaluation results, and to interrupt the phase conductors and restore broken connections triggered by the control signals. A "switching action" generally comprises at least one condition and one action, e.g., an overcurrent on a phase conductor and an interruption of the phase conductor. It is also possible that several conditions must be met for the action to occur.

For example, the circuit breaker can be equipped with switching transistors (e.g., MOSFETs or IGBTs) to interrupt the phase conductors. Additionally, galvanic isolation can be provided. A switch operating with switching transistors with a phase conductor and a neutral conductor is, for example, DE 102022201960 A1 The term "circuit breaker" is to be understood as meaning that the switch has protective functions (e.g., overcurrent protection). The switch can also perform other functions unrelated to protection, such as normal switching.

According to the invention, virtual circuits are defined between the individual phase conductors for the evaluation, and the circuit breaker is designed to determine circuit-specific voltages, currents, and impedances for the virtual circuits using the determined current and voltage values. The voltage of a virtual circuit between two phase conductors corresponds to the difference between the voltages between the respective phase conductors and the neutral conductor, the current of a virtual circuit between two phase conductors corresponds to the weighted difference between the currents of the respective phase conductors, and the impedance of a virtual circuit between two phase conductors corresponds to the quotient of voltage and current of the virtual circuit between the two phase conductors. The circuit breaker is designed to use values determined for the virtual circuits for the diagnosis of overcurrent events.

According to one embodiment of the circuit breaker according to the invention, virtual circuits are defined between individual phase conductors and the neutral conductor for the evaluation, and the circuit breaker is designed to determine circuit-specific voltages, currents, and impedances for the virtual circuits using the determined current and voltage values. The voltage of a virtual circuit between a phase conductor and the neutral conductor corresponds to the voltage present between the phase conductor and the neutral conductor, the current of a virtual circuit between a phase conductor and the neutral conductor corresponds to the current of the phase conductor, and the impedance of a virtual circuit between a phase conductor and the neutral conductor corresponds to the quotient of voltage and current of the virtual circuit. The circuit breaker is then designed to use values determined for the virtual circuits for the diagnosis of overcurrent events.

To improve the diagnosis of overcurrent events, the concept of a "virtual circuit" is introduced. The term "virtual circuit" is to be understood as simulating that the two affected conductors (two phase conductors or a phase conductor and a neutral conductor) form a circuit. On this basis, values are determined for this virtual circuit, which can then be checked, for example, for compliance with limit values. With three phase conductors and one neutral conductor, a total of six virtual circuits can be defined (three between phase conductors and three between a phase conductor and the neutral conductor).

This enables advanced and flexible diagnostics of overcurrent events. Overcurrent events can be assigned to virtual circuits, for example. If necessary, phase conductors can then be selectively interrupted or connected based on this information.

1. a) wenigstens ein Teil der Schalthandlungen virtuellen Stromkreisen zugeordnet ist,
2. b) bei der Auswertung für diese Schalthandlungen überprüft wird, ob ein Überstromereignis als Kriterium für einen möglichen Überstrom bei Durchführung der Schalthandlung erfasst ist und
3. c) die Schalthandlung nur durchgeführt wird, wenn kein Überstromereignis für die Schalthandlung erfasst ist.

According to one embodiment, the circuit breaker is configured to detect overcurrent events on virtual circuits. This can be done, for example, using threshold values for the magnitude of the current in the virtual circuits.
Detected overcurrent events can then be recorded or applied as a criterion for possible overcurrent in future switching operations affecting the respective virtual circuit. For this purpose, certain current and voltage values can be evaluated with regard to the fulfillment of conditions for interrupting the phase conductors and restoring interrupted connections in switching operations, whereby

1. a) at least some of the switching operations are assigned to virtual circuits,
2. b) during the evaluation of these switching operations, it is checked whether an overcurrent event is recorded as a criterion for a possible overcurrent when carrying out the switching operation and
3. c) the switching operation is only carried out if no overcurrent event is detected for the switching operation.

According to a further development, detected overcurrent events are deleted as a criterion for switching operations if a condition for freedom from overcurrent is met on the respective virtual circuit. This condition can either consist of the circuit breaker conducting current without overcurrent when the phase conductor encompassed by the virtual circuit is switched on or the phase conductors encompassed by the virtual circuit are switched on, or it can consist of the circuit breaker conducting current without overcurrent when all phase conductors encompassed by the virtual circuit are switched on. The term "conducting overcurrent-free" is to be understood in the sense of stable operation of phase conductors. A condition can be defined for this, e.g., by means of a time threshold for conducting the phase conductors of the virtual circuit without interruption after an overcurrent event. For example, a timer is started after a phase conductor connection is restored. If the timer reaches the threshold without the phase conductor being interrupted again, a stable state is reached by definition ("overcurrent-free") and a set criterion for overcurrent is deleted again.

According to one embodiment of the circuit breaker according to the invention, it is designed to assign switching operations of different types to virtual circuits, to count these switching operations related to virtual circuits, and to permanently switch itself off when a threshold value for the number of switching operations of one type related to a virtual circuit or a threshold value for the aggregate number of switching operations of several types of switching operations each related to a virtual circuit is reached. The term "permanently switching off" is to be understood as follows: In this embodiment, switching operations are provided by which, after the interruption of a phase conductor, the interrupted connection is restored. The circuit breaker performs these switching operations autonomously, i.e., without an external control instruction. Typically, such a switching operation is performed shortly after the interruption of the phase conductor, e.g., near the next zero crossing of a voltage relevant for the switching operation. "Permanently switching off" implies that the circuit breaker can only be switched on again by an external action or an external control command. In a preferred embodiment of the circuit breaker with an additional galvanic isolation, the state of “permanent switching off” can also include the opening of the galvanic isolation.

According to one embodiment of the circuit breaker according to the invention, it is designed to assign switching operations of different types to virtual circuits, to count the switching operations related to these virtual circuits, and to no longer perform switching operations of a type related to a virtual circuit when a threshold value for the number of switching operations of this type is reached. Depending on the connected loads, it may be appropriate to no longer permit certain switching operations if they occur disproportionately frequently. Reaching a threshold value for the number of switching operations can be a criterion for this.

The invention also relates to a method for supporting the diagnosis of overcurrent events in a power supply formed with three phase conductors and one neutral conductor, which method is preferably carried out by means of a circuit breaker according to the invention.

• 1: eine schematische Darstellung des generellen Problems mit einem abstrakten Schutzschaltgerät,
• 2: Spannungen im symmetrischen Vierleitersystem,
• 3: einen SCCB für ein Vierleiter-Drehstromsystem,
• 4: ein Einschalten ohne Überstromereignisse beginnend mit Schalthandlung SH1 (Szenario 1),
• 5: ein Einschalten ohne Überstromereignisse beginnend mit Schalthandlung SH2 (Szenario 2),
• 6: ein Einschalten mit einem Kurzschluss in Phase 3 beginnend mit Schalthandlung SH1 (Szenario 3),
• 7: ein Einschalten mit einem Kurzschluss in Phase 2 (Szenario 4),
• 8: ein Einschalten mit einem Kurzschluss zwischen den Phasen 2 und 3 (Szenario 5),
• 9: eine Ausführung von Schalthandlung SH 5 (Szenario 6),
• 10: ein Einschalten mit zwei einphasigen Kurzschlüssen in den Phasen 3 und 1 mit dem Grundschaltverfahren (Szenario 7),
• 11: ein Einschalten mit zwei einphasigen Kurzschlüssen in den Phasen 3 und 1 mit dem Grundschaltverfahren und Zusatzbedingungen ZB1 und ZB2 (Szenario 8),
• 12: ein Einschalten mit einem einphasigen Kurzschluss in Phase 3 mit dem Grundschaltverfahren und Zusatzbedingungen ZB1 und ZB2 (Szenario 9),
• 13: ein Einschalten mit einem einphasigen Kurzschluss in Phase 3 mit dem Grundschaltverfahren und Zusatzbedingungen ZB1, ZB2 und ZB3 (Szenario 10),
• 14: ein Einschalten mit einem zweiphasigen Kurzschluss zwischen den Phasen 2 und 3 mit dem Grundschaltverfahren und Zusatzbedingungen ZB1, ZB2und ZB3 (Szenario 11),
• 15: ein Einschalten mit einem zweiphasigen Kurzschluss zwischen den Phasen 2 und 3 mit dem Grundschaltverfahren und Zusatzbedingungen ZB1, ZB2und ZB3 und der Schalthandlung SH7 (Szenario 12),
• 16: ein Einschalten mit einem zweiphasigen Kurzschluss zwischen den Phasen 2 und 3 mit dem Grundschaltverfahren und Zusatzbedingungen ZB1, ZB2und ZB3 sowie Schalthandlungen SH7 und SH8,
• 17: ein Einschalten mit einem zweiphasigen Kurzschluss zwischen den Phasen 2 und 3 mit dem Grundschaltverfahren und Zusatzbedingungen ZB1, ZB2 und ZB3 sowie Schalthandlungen SH7, SH8 und SH9 (Szenario 14),
• 18: ein Einschalten mit einem zweiphasigen Kurzschluss zwischen den Phasen 2 und 3 mit dem Grundschaltverfahren und Zusatzbedingungen ZB1, ZB2 und ZB3 sowie Schalthandlungen SH7, SH8 und SH9 (Szenario 15),
• 19: ein Einschalten mit dem Grundschaltverfahren mit Zusatzbedingungen ZB1 bis ZB3 und Schalthandlungen SH7 und SH8 (Szenario 16),
• 20: ein Ablaufdiagramm zu einem ersten Verfahren zur Überprüfung bzgl. einer Selbstabschaltung eines erfindungsgemäßen Schalters (dauerhaftes Ausschalten),
• 21: ein Ablaufdiagramm zu einem zweiten Verfahren zur Überprüfung bzgl. einer Selbstabschaltung eines erfindungsgemäßen Schalters (dauerhaftes Ausschalten) und
• 22: ein Ablaufdiagramm bzgl. eines Resets von Bedingungen einer Selbstabschaltung entsprechend 20 oder 21.

The invention is described in more detail below using exemplary embodiments.

• 1 : a schematic representation of the general problem with an abstract protective switching device,
• 2 : Voltages in a symmetrical four-wire system,
• 3 : an SCCB for a four-wire three-phase system,
• 4 : a switch-on without overcurrent events starting with switching operation SH1 (scenario 1),
• 5 : a switch-on without overcurrent events starting with switching operation SH2 (scenario 2),
• 6 : a switch-on with a short circuit in phase 3 starting with switching operation SH1 (scenario 3),
• 7 : a switch-on with a short circuit in phase 2 (scenario 4),
• 8 : a switch-on with a short circuit between phases 2 and 3 (scenario 5),
• 9 : an execution of switching operation SH 5 (scenario 6),
• 10 : a switch-on with two single-phase short-circuits in phases 3 and 1 using the basic switching procedure (scenario 7),
• 11 : a switch-on with two single-phase short-circuits in phases 3 and 1 with the basic switching procedure and additional conditions ZB1 and ZB2 (scenario 8),
• 12 : a switch-on with a single-phase short-circuit in phase 3 with the basic switching procedure and additional conditions ZB1 and ZB2 (scenario 9),
• 13 : a switch-on with a single-phase short-circuit in phase 3 with the basic switching procedure and additional conditions ZB1, ZB2 and ZB3 (scenario 10),
• 14 : a switch-on with a two-phase short circuit between phases 2 and 3 with the basic switching procedure and additional conditions ZB1, ZB2 and ZB3 (scenario 11),
• 15 : a switch-on with a two-phase short-circuit between phases 2 and 3 with the basic switching procedure and additional conditions ZB1, ZB2 and ZB3 and the switching operation SH7 (scenario 12),
• 16 : a switch-on with a two-phase short-circuit between phases 2 and 3 with the basic switching procedure and additional conditions ZB1, ZB2 and ZB3 as well as switching operations SH7 and SH8,
• 17 : a switch-on with a two-phase short-circuit between phases 2 and 3 with the basic switching procedure and additional conditions ZB1, ZB2 and ZB3 as well as switching operations SH7, SH8 and SH9 (scenario 14),
• 18 : a switch-on with a two-phase short-circuit between phases 2 and 3 with the basic switching procedure and additional conditions ZB1, ZB2 and ZB3 as well as switching operations SH7, SH8 and SH9 (scenario 15),
• 19 : switching on with the basic switching procedure with additional conditions ZB1 to ZB3 and switching operations SH7 and SH8 (scenario 16),
• 20 : a flowchart for a first method for checking a self-switching off of a switch according to the invention (permanent switching off),
• 21 : a flow chart for a second method for checking a self-switching off of a switch according to the invention (permanent switching off) and
• 22 : a flow chart regarding a reset of conditions of a self-shutdown according to 20 or 21 .

Any loads and load combinations can be connected to a four-wire network with three phase conductors and one neutral conductor. This is 1 shown.

Between each of the phase conductors L1, L2, L3 and the neutral conductor N, a circuit with the impedances ZL1N, ZL2N, ZL3N can be formed, in which the currents iL1N, iL2N, iL3N are influenced by the phase voltages (voltages between the phase conductors and the neutral conductor) uL1N, uL2N, uL3N. These circuits are also referred to below as SKL1N, SKL2N, and SKL3N. In addition, three independent circuits with the impedances ZL1L2, ZL2L3, ZL3L1 can be present between the phase conductors, in which the line-to-line voltages (voltages between two phase conductors) uL1L2, uL2L3, uL3L1 are decisive for the gradient and amplitude of the currents iL1L2, iL2L3, iL3L1. These circuits are also referred to below as SKL1L2, SKL2L3, and SKL3L1. This results in a total of six circuits, each of which can contain any load, possibly including inrush loads or short circuits. 63 (2**6-1) combinations are possible, in which at least one conducting two-terminal circuit is present in one to six circuits.

Depending on the charge level of the intermediate circuit capacitance, single-phase and/or three-phase rectifiers may or may not be recognizable as loads at different times. Due to its mode of operation, a three-phase rectifier can conduct one or two phase-to-phase currents at different times and thus be recognizable as one or two line-to-line loads. The phase and amplitude of the currents iL1N, iL2N, iL3N as well as iL1L2, iL2L3, iL3L1 through the impedances ZL1N, ZL2N, ZL3N as well as ZL1L2, ZL2L3, ZL3L1 are determined accordingly by the voltages uL1N, uL2N, uL3N as well as uL1L2, uL2L3, uL3L1. In a symmetrical three-phase voltage system, the zero crossings of the three phase voltages uL1N, uL2N, uL3N are offset from each other by one sixth of the mains period or by 60 degrees (cf. 2 ). The phase positions of the phase-to-phase voltages uL1L2, uL2L3, uL3L1 are also offset by 60 degrees. In addition, each zero crossing of a phase-to-phase voltage is offset by one-twelfth of the grid period or by 30 degrees from a zero crossing of a phase voltage.

Classic multi-pole circuit breakers only allow the simultaneous switching on and off of all phase switches SL1, SL2, SL3, if necessary also SN (cf. 1 Due to the voltage phase positions described above in a four-wire system, several of the voltages uL1N, uL2N, uL3N, uL1L2, uL2L3, and uL3L1 typically have values at any given time that can cause very high inrush currents. The probability of unwanted MCB tripping due to an inrush current when connecting the inrush load in one of the impedances ZL1N, ZL2N, ZL3N, ZL1L2, ZL2L3, and ZL3L1 is not insignificant.

If the time-current characteristic of a circuit breaker is exceeded in one phase of a conventional MCB, this will trigger and permanently disconnect all protected conductors from the grid. The load can only be reconnected to the grid by manually reconnecting it.

An SCCB for a four-wire network is in 3 shown. An SCCB with self-commutated power semiconductors, energy absorbers, a measuring and control unit, and isolating contacts triggered by the control unit has the ability to actively switch the phase semiconductors on and off at any time.

The duration and maximum value of the inrush current play a major role in the dimensioning of the power semiconductors and energy absorbers of an SCCB. The duration of an unlimitated inrush current can range from a few milliseconds to several grid voltage periods. Sizing the power semiconductor to carry the inrush current over such time intervals increases the cost and volume of these components. Limiting the inrush currents in a multi-pole SCCB is therefore of great importance when designing the switching and operating strategy.

Furthermore, the objective is to reduce and, if possible, minimize the probability of tripping due to inrush current when operating as many load combinations as possible on the multi-pole SCCB. A four-wire system must transition to steady-state as quickly as possible when the SCCB is switched on. When connecting a new inrush load, e.g., by closing one of the switches SL1N, SL2N, SL3N, SL1L2, SL2L3, SL3L1 in 1 The effect of the disturbance caused by the inrush current on other loads must be minimal. In both cases, the inrush currents must be limited to a certain maximum value.

It is operated by an SSCB after 3 Based on this, operating procedures specifically developed for such SSCBs are described below. Based on the detected overcurrent events, current switching states of the power semiconductors, and the measured voltage and current values, decisions are made to switch the power semiconductors of the individual phases on and off. In addition, continuous monitoring of the load side is carried out in order to identify the probable causes of the overcurrent after an overcurrent event and, if necessary, to improve the quality of the switching decisions based on this. For the sake of simplicity, the power semiconductor of one phase is referred to below, although in reality the shutdown can be realized using several electronic components or switching elements (in 3 antiparallel transistors, each with a parallel protection diode). This scenario is intended to be included with reference to a switched power semiconductor; specifically, the term "power semiconductor," when referring to a phase, also includes all switching devices formed with power switches.

First, the basic switching method is described, which also defines the hardware requirements. The instantaneous values of the phase voltages uL1N, uL2N, and uL3N are recorded by the control unit. By measuring the three phase voltages, the voltage information from the four-wire system is fully captured—in contrast to the measurement of the phase-to-phase voltages, which omits the voltage to the neutral conductor. This is an important feature of the SCCB arrangement, which allows the basic switching method to be implemented.

• ◯ uL1L2 = uL1N - uL2N
• ◯ uL2L3 = uL2N - uL3N
• ◯ uL3L1 = uL3N - uL 1 N

The instantaneous values of the phase currents i1, i2, and i3 are recorded by the control unit. The phase-to-phase voltages uL1, uL2, uL2, and uL3 are calculated from the measured phase voltages uL1N, uL2N, and uL3N, thus eliminating the need for additional voltage measuring elements. The calculation rule for the phase-to-phase voltages is:

• ◯ uL1L2 = uL1N - uL2N
• ◯ uL2L3 = uL2N - uL3N
• ◯ uL3L1 = uL3N - uL 1 N

Another characteristic of the SSCB is phase-by-phase switching, meaning that the power semiconductor of each individual phase can be switched on or off by the control unit at any time, independently of the power semiconductors of the other phases. If a freely selectable current limit iMAX is exceeded in a phase (overcurrent event), the power semiconductor of that phase is switched off immediately. This current limit is not necessarily the same for all phases. The time from exceeding the current limit until the overcurrent is switched off is so short that the power semiconductor is not damaged by the short-term overcurrent. An overcurrent event in one phase does not trigger automatic shutdown of the power semiconductors in the other phases.

The mechanical isolating contacts are controlled by the control unit independently of the power semiconductors and are not automatically triggered in the event of an overcurrent event. The switching states of the power semiconductors and the overcurrent events that occur are recorded by the control unit.

• Sobald und solange mindestens ein Leistungshalbleiter eingeschaltet ist:
  • • Schalthandlung SH0: beim Überschreiten einer Strombetragsgrenze iMAX in einem Phasenleiter mit eingeschaltetem Leistungshalbleiter den Leistungshalbleiter dieser Phase ausschalten.
• Schalthandlungen, wenn Leistungshalbleiter aller Phasen ausgeschaltet sind (Schaltzustand SZ0):
  • • Schalthandlung SH1: wenn der Betrag der Phasenspannung zwischen einem Phasenleiter und dem Neutralleiter kleiner als ein bestimmter Wert uMAXLN(on) ist, den Leistungshalbleiter dieser Phase einschalten.
  • • Schalthandlung SH2: wenn der Betrag der verketteten Spannung zwischen zwei Phasenleitern kleiner als ein bestimmter Wert uMAXLL(on) ist, die Leistungshalbleiter dieser beiden Phasen einschalten.
• Schalthandlungen, wenn nur der Leistungshalbleiter einer Phase eingeschaltet ist (Schaltzustand SZ1):
  • • Schalthandlung SH3: wenn der Betrag der Spannung zwischen einem Phasenleiter mit ausgeschaltetem Leistungshalbleiter und dem Neutralleiter kleiner als ein bestimmter Wert uMAXLN(on) ist, den Leistungshalbleiter dieser Phase einschalten.
  • • Schalthandlung SH4: wenn der Betrag der verketteten Spannung zwischen einem Phasenleiter mit ausgeschaltetem Leistungshalbleiter und dem Phasenleiter mit eingeschaltetem Leistungshalbleiter kleiner als ein bestimmter Wert uMAXLL(on) ist, den Leistungshalbleiter dieser ausgeschalteten Phase einschalten.
• Schalthandlungen, wenn Leistungshalbleiter in nur zwei Phasen eingeschaltet sind (Schaltzustand SZ2):
  • • Schalthandlung SH5: wenn der Betrag der Spannung zwischen dem Phasenleiter mit ausgeschaltetem Leistungshalbleiter und dem Neutralleiter kleiner als ein bestimmter Wert uMAXLN(on) ist, den Leistungshalbleiter dieser Phase einschalten.
  • • Schalthandlung SH6: wenn der Betrag der verketteten Spannung zwischen dem Phasenleiter mit ausgeschaltetem Leistungshalbleiter und einem Phasenleiter mit eingeschaltetem Leistungshalbleiter kleiner als ein bestimmter Wert uMAXLL(on) ist, den Leistungshalbleiter der ausgeschalteten Phase einschalten.

The following switching operations are provided or defined:

• As soon as and as long as at least one power semiconductor is switched on:
  • • Switching operation SH0: when a current limit iMAX is exceeded in a phase conductor with a switched-on power semiconductor, switch off the power semiconductor of this phase.
• Switching operations when power semiconductors of all phases are switched off (switching state SZ0):
  • • Switching operation SH1: if the magnitude of the phase voltage between a phase conductor and the neutral conductor is less than a certain value uMAXLN(on), switch on the power semiconductor of this phase.
  • • Switching operation SH2: if the magnitude of the line-to-line voltage between two phase conductors is less than a certain value uMAXLL(on), switch on the power semiconductors of these two phases.
• Switching operations when only the power semiconductor of one phase is switched on (switching state SZ1):
  • • Switching operation SH3: if the magnitude of the voltage between a phase conductor with the power semiconductor switched off and the neutral conductor is less than a certain value uMAXLN(on), switch on the power semiconductor of this phase.
  • • Switching operation SH4: if the magnitude of the line-to-line voltage between a phase conductor with the power semiconductor switched off and the phase conductor with the power semiconductor switched on is less than a certain value uMAXLL(on), switch on the power semiconductor of this switched off phase.
• Switching operations when power semiconductors are switched on in only two phases (switching state SZ2):
  • • Switching operation SH5: if the voltage between the phase conductor with the power semiconductor switched off and the neutral conductor is less than a certain value uMAXLN(on), switch on the power semiconductor of this phase.
  • • Switching operation SH6: if the magnitude of the line-to-line voltage between the phase conductor with the power semiconductor switched off and a phase conductor with the power semiconductor switched on is less than a certain value uMAXLL(on), switch on the power semiconductor of the switched-off phase.

If power semiconductors are switched on in all three phase conductors (switching state SZ3), no switching operations are performed with the exception of switching operation SH0.

The values uMAXLN(on), uMAXLL(on) should be set close to zero or in the range of 0...20 percent of the phase voltage amplitude.

Switching operations SH0, SH1, SH2, and SH4 are the basic switching operations. The others are derived from them and simply describe a different initial situation. Nevertheless, they are defined separately in order to describe and explain the process in detail within this application.

Switching operations SH3 and SH5 are generally identical to SH1. If at least one power semiconductor is off, it will be switched on when the phase voltage between its phase and neutral conductors is close to zero crossing. The only difference between switching operations SH1, SH3, and SH5 is the number of switched-on power semiconductors before the switching operation.

Switching operation SH6 is generally identical to switching operation SH4. If at least one power semiconductor is off, it will be switched on when the phase-to-phase voltage between its phase and another phase is close to zero. The only difference between switching operations SH4 and SH6 is the number of switched-on power semiconductors before the switching operation.

• • „normal“, wenn beim Zuschalten des jeweiligen Stromkreises an das Netz die Wahrscheinlichkeit eines Überstromereignisses als gering eingeschätzt wird.
• • „Überstrom“, wenn beim Zuschalten des jeweiligen Stromkreises an das Netz die Wahrscheinlichkeit eines Überstromereignisses als hoch eingeschätzt wird.

Based on the expected overcurrent events, the switching operations can be improved. For the following description, two circuit states are defined: each of the circuits SKL1N, SKL2N, SKL3N, SKL1L2, SKL2L3, SKL3L1 has the state

• • “normal” if the probability of an overcurrent event is assessed as low when the respective circuit is connected to the grid.
• • “Overcurrent” if the probability of an overcurrent event is assessed as high when the respective circuit is connected to the grid.

• • Zusatzbedingung ZB1 für die Schalthandlung SH2: Schalthandlung SH2 nur dann ausführen, wenn die Zustände der Stromkreise zwischen jedem der zwei gemäß Schaltzahlung SH2 einzuschaltendem Phasenleiter und dem Neutralleiter „normal“ sind.
• • Zusatzbedingung ZB2 für die Schalthandlung SH4: Schalthandlung SH4 nur dann ausführen, wenn der Zustand des Stromkreises zwischen dem gemäß Schalthandlung SH4 einzuschaltenden

The following additional conditions for the execution of switching operations are defined:

• • Additional condition ZB1 for the switching operation SH2: Only carry out the switching operation SH2 if the states of the circuits between each of the two phase conductors to be switched on according to the switching operation SH2 and the neutral conductor are “normal”.
• • Additional condition ZB2 for switching operation SH4: Only carry out switching operation SH4 if the state of the circuit between the device to be switched on according to switching operation SH4

• • Zusatzbedingung ZB3 für die Schalthandlung SH6: Schalthandlung SH6 nur dann ausführen, wenn der Zustand des Stromkreises zwischen dem gemäß Schalthandlung SH6 einzuschaltenden Phasenleiter und dem Neutralleiter „normal“ ist.

phase conductor and the neutral conductor is “normal”.

• • Additional condition ZB3 for switching operation SH6: Only carry out switching operation SH6 if the state of the circuit between the phase conductor to be switched on according to switching operation SH6 and the neutral conductor is “normal”.

• • Schalthandlung SH7:
  1. a. wenn Leistungshalbleiter in nur einer Phase eingeschaltet ist (Schaltzustand SZ1), und
  2. b. der Betrag der Phasenspannung zwischen einem Phasenleiter mit ausgeschaltetem Leistungshalbleiter und dem Neutralleiter kleiner als ein bestimmter Wert uMAXLN(off) ist, und
  3. c. der Zustand des (verketteten) Stromkreises zwischen diesem Phasenleiter und dem bereits eingeschalteten Phasenleiter „Überstrom“ ist, den Leistungshalbleiter der eingeschalteten Phase ausschalten, wobei der Wert uMAXLN(off) größer ist als uMAXLN(on). (Danach folgt automatisches Einschalten des unter b) genannten Phasenleiters per Schalthandlung SH1)
• • Schalthandlung SH8:
  1. a. wenn Leistungshalbleiter in nur zwei Phasen eingeschaltet sind (Schaltzustand SZ2), und
  2. b. der Betrag der Phasenspannung zwischen dem Phasenleiter mit ausgeschaltetem Leistungshalbleiter und dem Neutralleiter kleiner als ein bestimmter Wert uMAXLN(off) ist, und
  3. c. der Zustand des verketteten Stromkreises zwischen diesem Phasenleiter und dem bereits eingeschalteten Phasenleiter „Überstrom“ ist, den Leistungshalbleiter dieser eingeschalteten Phase ausschalten, wobei der Wert uMAXLN(off) größer ist als uMAXLN(on).
• • Schalthandlung SH9:
  1. a. wenn Leistungshalbleiter in zwei Phasen eingeschaltet sind (Schaltzustand SZ2), und
  2. b. der Betrag der verketteten Spannung zwischen dem Phasenleiter LX mit ausgeschaltetem Leistungshalbleiter und einem zweiten Phasenleiter LY mit eingeschaltetem Leistungshalbleiter kleiner als ein bestimmter Wert uMAXLL(off) ist, und
  3. c. der Zustand des verketteten Stromkreises zwischen dem Phasenleiter mit ausgeschaltetem Leistungshalbleiter und dem dritten Phasenleiter LZ mit eingeschaltetem Leistungshalbleiter „Überstrom“ ist, den Leistungshalbleiter in dem Phasenleiter LZ ausschalten, wobei der Wert uMAXLL(off) größer ist als uMAXLL(on).

Additional switching-off actions are defined as:

• • Switching operation SH7:
  1. a. when power semiconductor is switched on in only one phase (switching state SZ1), and
  2. b. the magnitude of the phase voltage between a phase conductor with the power semiconductor switched off and the neutral conductor is less than a certain value uMAXLN(off), and
  3. c. If the condition of the (linked) circuit between this phase conductor and the already switched-on phase conductor is "overcurrent," switch off the power semiconductor of the switched-on phase, with the value uMAXLN(off) being greater than uMAXLN(on). (This is followed by automatic switching on of the phase conductor mentioned under b) via switching operation SH1.)
• • Switching operation SH8:
  1. a. when power semiconductors are switched on in only two phases (switching state SZ2), and
  2. b. the magnitude of the phase voltage between the phase conductor with the power semiconductor switched off and the neutral conductor is less than a certain value uMAXLN(off), and
  3. c. the state of the interlinked circuit between this phase conductor and the already switched-on phase conductor is "overcurrent", switch off the power semiconductor of this switched-on phase, whereby the value uMAXLN(off) is greater than uMAXLN(on).
• • Switching operation SH9:
  1. a. when power semiconductors are switched on in two phases (switching state SZ2), and
  2. b. the magnitude of the phase-to-phase voltage between the phase conductor LX with the power semiconductor switched off and a second phase conductor LY with the power semiconductor switched on is less than a certain value uMAXLL(off), and
  3. c. the state of the interlinked circuit between the phase conductor with the power semiconductor switched off and the third phase conductor LZ with the power semiconductor switched on is "overcurrent", switch off the power semiconductor in the phase conductor LZ, whereby the value uMAXLL(off) is greater than uMAXLL(on).

The useful range of values for the values uMAXLN(off) and uMAXLL(off) is similar to that for the values uMAXLN(on) and uMAXLL(on). By setting uMAXLN(off) greater than uMAXLN(on) and uMAXLL(off) greater than
uMAXLL(on) ensures that one phase is switched off first and then another phase is switched on after a certain time interval.

• ◯ SKL1N zwischen dem Phasenleiter L1 und dem Neutalleiter N
• ◯ SKL2N zwischen dem Phasenleiter L2 und dem Neutalleiter N
• ◯ SKL3N zwischen dem Phasenleiter L3 und dem Neutalleiter N
• ◯ SKL1L2 zwischen dem Phasenleiter L1 und dem Phasenleiter L2
• ◯ SKL2L3 zwischen dem Phasenleiter L2 und dem Phasenleiter L3
• ◯ SKL3L1 zwischen dem Phasenleiter L3 und dem Phasenleiter L1

The cause of the overcurrent can be determined using the current values before the overcurrent event. For this purpose, it is useful to define virtual circuits (VCs) as follows:

• ◯ SKL1N between the phase conductor L1 and the neutral conductor N
• ◯ SKL2N between the phase conductor L2 and the neutral conductor N
• ◯ SKL3N between the phase conductor L3 and the neutral conductor N
• ◯ SKL1L2 between the phase conductor L1 and the phase conductor L2
• ◯ SKL2L3 between the phase conductor L2 and the phase conductor L3
• ◯ SKL3L1 between the phase conductor L3 and the phase conductor L1

• ◯ „normal“, wenn beim Zuschalten des jeweiligen Stromkreises an das Netz die Wahrscheinlichkeit eines Überstromereignisses als gering eingeschätzt wird.
• ◯ „Überstrom“, wenn beim Zuschalten des jeweiligen Stromkreises an das Netz die Wahrscheinlichkeit eines Überstromereignisses als hoch eingeschätzt wird.

In addition, two circuit states are defined: each of the circuits SKL1N, SKL2N, SKL3N, SKL1L2, SKL2L3, SKL3L1 has the state

• ◯ “normal” if the probability of an overcurrent event is assessed as low when the respective circuit is connected to the grid.
• ◯ “Overcurrent” if the probability of an overcurrent event is assessed as high when the respective circuit is connected to the grid.

• • Die Phasenleiterströme i1, i2, i3 werden kontinuierlich gemessen bzw. abgetastet.
• • Neben der Messung der Phasenströme werden ihre Werte aus einem oder mehreren Punkten in der Vergangenheit so gespeichert, dass nach einem Überstromereignis in einem Phasenleiter Stromwerte aus allen drei Phasen für die Analyse verfügbar sind, die unmittelbar vor diesem Überstromereignis gemessen wurden, d.h. bevor der Strom in dem betroffenen Phasenleiter durch das Ausschalten des Leistungshalbleiters unterbrochen wurde.
• • Rechenvorschrift zur Berechnung der virtuellen verketteten Ströme durch die Stromkreise SKL1L2, SKL2L3, SKL3L1:
  • ◯ Der virtuelle verkettete Strom iSKL1L2 in dem Stromkreis SKL1L2:iSKL1L2 = ½*(i1 - i2)
  • ◯ Der virtuelle verkettete Strom iSKL2L3 in dem Stromkreis SKL2L3: iSKL2L3 = ½*(i2 - i3)
  • ◯ Der virtuelle verkettete Strom iSKL3L1 in dem Stromkreis SKL3L1: iSKL3L1 = ½*(i3 - i1)
• • Rechenvorschrift zur kontinuierlichen Berechnung des virtuellen Neutralleiterstromes iN:
  • ◯ iN =k*(i1 + i2 + i3) mit k als Gewichtungsfaktor, k = 1...2.

The following measurements and calculations can then be carried out:

• • The phase conductor currents i1, i2, i3 are continuously measured or sampled.
• • In addition to measuring the phase currents, their values from one or more points in the past are stored in such a way that after an overcurrent event in one phase conductor, current values from all three phases are available for analysis, which were measured immediately before this overcurrent event, ie before the current in the affected phase conductor was interrupted by switching off the power semiconductor.
• • Calculation rule for calculating the virtual interlinked currents through the circuits SKL1L2, SKL2L3, SKL3L1:
  • ◯ The virtual phase-to-phase current iSKL1L2 in the circuit SKL1L2:iSKL1L2 = ½*(i1 - i2)
  • ◯ The virtual phase-to-phase current iSKL2L3 in the circuit SKL2L3: iSKL2L3 = ½*(i2 - i3)
  • ◯ The virtual phase-to-phase current iSKL3L1 in the circuit SKL3L1: iSKL3L1 = ½*(i3 - i1)
• • Calculation rule for the continuous calculation of the virtual neutral conductor current iN:
  • ◯ iN =k*(i1 + i2 + i3) with k as weighting factor, k = 1...2.

• • Für jeden der Stromkreise SKL1N, SKL2N, SKL3N wird der Stromkreiszustand auf „normal“ gesetzt, sobald in der jeweiligen Phase der Leistungshalbleiter eingeschaltet ist und kein Überstromereignis stattfindet.
• • Für jeden der Stromkreise SKL1L2, SKL2L3, SKL3L1 wird der Stromkreiszustand auf „normal“ gesetzt, sobald in den beiden mit dem Stromkreis zusammenhängenden Phasen die Leistungshalbleiter eingeschaltet sind und in keiner der angeschlossenen Phasen ein Überstromereignis stattfindet.

Setting the circuit states to “normal”:

• • For each of the circuits SKL1N, SKL2N, SKL3N, the circuit state is set to “normal” as soon as the power semiconductor is switched on in the respective phase and no overcurrent event occurs.
• • For each of the circuits SKL1L2, SKL2L3, SKL3L1, the circuit state is set to “normal” as soon as the power semiconductors are switched on in the two phases connected to the circuit and no overcurrent event occurs in any of the connected phases.

• • Bei einem Überstromereignis in einem Phasenleiter LX wird der Zustand von dem Stromkreis LXN zwischen dem Phasenleiter LX und dem Neutralleiter N auf „Überstrom“ gesetzt, wenn unmittelbar vor diesem Überstromereignis der Betrag des virtuellen Neutralleiterstromes iN größer war als
  • ◯ der Betrag des virtuellen verketteten Stromes iLXLY in dem Stromkreis zwischen diesem Phasenleiter LX und einem zweiten Phasenleiter LY,
  • ◯ der Betrag des virtuellen verketteten Stromes iLZLX in dem Stromkreis zwischen diesem Phasenleiter LX und dem dritten Phasenleiter LZ.
• • Bei einem Überstromereignis in einem Phasenleiter LX wird der Zustand von dem Stromkreis zwischen dem Phasenleiter LX und einem zweiten Phasenleiter LY auf „Überstrom“ gesetzt, wenn unmittelbar vor diesem Überstromereignis der Betrag des virtuellen verketteten Stromes iLXLY in dem Stromkreis SKLXLY größer war als
  • ◯ der Betrag des virtuellen Neutralleiterstromes iN und
  • ◯ der Betrag des virtuellen verketteten Stromes iLZLX zwischen diesem Phasenleiter LX und dem dritten Phasenleiter LZ
• • Die Indizes X, Y, Z stehen dabei für 1, 2, 3 bzw. 2, 3, 1 bzw. 3, 2, 1.

Setting the circuit states to “overcurrent”:

• • In the event of an overcurrent event in a phase conductor LX, the state of the circuit LXN between the phase conductor LX and the neutral conductor N is set to “overcurrent” if, immediately before this overcurrent event, the magnitude of the virtual neutral conductor current iN was greater than
  • ◯ the magnitude of the virtual phase-to-phase current iLXLY in the circuit between this phase conductor LX and a second phase conductor LY,
  • ◯ the magnitude of the virtual phase-to-phase current iLZLX in the circuit between this phase conductor LX and the third phase conductor LZ.
• • In the event of an overcurrent event in a phase conductor LX, the state of the circuit between the phase conductor LX and a second phase conductor LY is set to “overcurrent” if, immediately before this overcurrent event, the magnitude of the virtual phase-to-phase current iLXLY in the circuit SKLXLY was greater than
  • ◯ the magnitude of the virtual neutral conductor current iN and
  • ◯ the magnitude of the virtual phase-to-phase current iLZLX between this phase conductor LX and the third phase conductor LZ
• • The indices X, Y, Z stand for 1, 2, 3 or 2, 3, 1 or 3, 2, 1.

• • Die virtuellen Stromkreise SKL1N, SKL2N, SKL3N, SKL1L2, SKL2L3, SKL3L1 und die virtuellen Ströme durch diese Stromkreise sowie der virtuelle Neutralleiterstrom dienen ausschließlich als Abstraktion für die Einschätzung der Stromflüsse in der Last und werden immer berechnet, unabhängig von den tatsächlich angeschlossenen Lasten. Das Ziel dieser Abstraktion ist, alle potenziellen Stromflüsse in der Lastüberwachung zu berücksichtigen.
• • Eine genaue Einschätzung der Stromflüsse in der Last, d.h. eine genaue Bestimmung der Ströme in den virtuellen Stromkreisen ist nicht bei allen Lastkonfigurationen möglich und wird nicht erzielt.
• • Kurz vor einem Überstromereignis ist der Inrush- bzw. Fehlerstrom um ein Vielfaches größer als der normale Betriebsstrom. Das Strombild in dem Vierleitersystem wird von dem Inrush- bzw. Fehlerstrom dominiert, wobei der Inrush- bzw. Fehlerstrom nahezu immer nur durch einen der sechs Stromkreise fließt.
• • Das macht diese Betrachtungsweise für den Zweck der Ermittlung der Überstromursache wertvoll, obwohl sie für die Analyse in einem normalen Betriebszustand nur bedingt geeignet ist.

The following should be noted:

• • The virtual circuits SKL1N, SKL2N, SKL3N, SKL1L2, SKL2L3, SKL3L1 and the virtual currents through these circuits, as well as the virtual neutral current, serve solely as an abstraction for estimating current flows in the load and are always calculated, regardless of the actual connected loads. The goal of this abstraction is to consider all potential current flows in load monitoring.
• • An accurate assessment of the current flows in the load, ie an accurate determination of the currents in the virtual circuits, is not possible and is not achieved for all load configurations.
• • Shortly before an overcurrent event, the inrush or fault current is many times greater than the normal operating current. The current pattern in the four-wire system is dominated by the inrush or fault current, with the inrush or fault current almost always flowing through only one of the six circuits.
• • This makes this approach valuable for the purpose of determining the cause of overcurrent, although it is only partially suitable for analysis in a normal operating condition.

• • Die Phasenströme i1, i2, i3 werden von dem SCCB kontinuierlich gemessen bzw. abgetastet.
• • Die Phasenspannungen u1, u2, u3 werden von dem SCCB kontinuierlich gemessen bzw. abgetastet.
• • Neben der Messung der Phasenströme und der Phasenspannungen werden ihre Werte aus einem oder mehreren Punkten in der Vergangenheit so gespeichert, dass nach einem Überstromereignis in einem Phasenleiter Strom- und Spannungswerte aus allen drei Phasen für eine Analyse verfügbar sind, die unmittelbar vor diesem Überstromereignis gemessen wurden, d.h. bevor der Strom in dem betroffenen Phasenleiter durch das Ausschalten des Halbleiters unterbrochen wurde.
• • Rechenvorschrift zur kontinuierlichen Berechnung der Impedanzen zL1N, zL2N, zL3N der virtuellen Stromkreise SKL1N, SKL2N, SKL3N:
  • ◯ Impedanz von dem Stromkreis L1N: zL1N = uL1N/i1
  • ◯ Impedanz von dem Stromkreis L2N: zL2N = uL2N/ i2
  • ◯ Impedanz von dem Stromkreis L3N: zL3N = uL3N/ i3
• • Rechenvorschrift zur kontinuierlichen Berechnung der Impedanzen zL1L2, zL2L3, zL3L1 der virtuellen Stromkreise SKL1L2, SKL2L3, SKL3L1:
  • ◯ Impedanz von dem Stromkreis SKL1L2: zL1L2 = (uL1N - uL2N)/(1/2*(i1 - i2))
  • ◯ Impedanz von dem Stromkreis SKL2L3: zL2L3 = (uL2N - uL3N)/(1/2*(i2 - i3))
  • ◯ Impedanz von dem Stromkreis SKL3L1: zL3L1 = = (uL3N - uL1N)/(1/2*(i3 - i1))

With these considerations, the cause of the overcurrent can be determined using the impedance values before the overcurrent event. The following continuous measurements and calculations are performed:

• • The phase currents i1, i2, i3 are continuously measured or sampled by the SCCB.
• • The phase voltages u1, u2, u3 are continuously measured or sampled by the SCCB.
• • In addition to measuring the phase currents and phase voltages, their values from one or more points in the past are stored in such a way that, following an overcurrent event in one phase conductor, current and voltage values from all three phases are available for analysis, which were measured immediately before this overcurrent event, ie before the current in the affected phase conductor was interrupted by switching off the semiconductor.
• • Calculation rule for the continuous calculation of the impedances zL1N, zL2N, zL3N of the virtual circuits SKL1N, SKL2N, SKL3N:
  • ◯ Impedance of the circuit L1N: zL1N = uL1N/i1
  • ◯ Impedance of the circuit L2N: zL2N = uL2N/ i2
  • ◯ Impedance of the circuit L3N: zL3N = uL3N/ i3
• • Calculation rule for the continuous calculation of the impedances zL1L2, zL2L3, zL3L1 of the virtual circuits SKL1L2, SKL2L3, SKL3L1:
  • ◯ Impedance of the circuit SKL1L2: zL1L2 = (uL1N - uL2N)/(1/2*(i1 - i2))
  • ◯ Impedance of the circuit SKL2L3: zL2L3 = (uL2N - uL3N)/(1/2*(i2 - i3))
  • ◯ Impedance of the circuit SKL3L1: zL3L1 = = (uL3N - uL1N)/(1/2*(i3 - i1))

• • Für jeden der Stromkreise SKL1N, SKL2N, SKL3N wird der Stromkreiszustand auf „normal“ gesetzt, sobald in der jeweiligen Phase der Halbleiter leitend ist und kein Überstromereignis stattfindet.
• • Für jeden der Stromkreise SKL1L2, SKL2L3, SKL3L1 wird der Stromkreiszustand auf „normal“ gesetzt, sobald in den beiden mit dem Stromkreis zusammenhängenden Phasen die Halbleiter leitend sind und in keiner der angeschlossenen Phasen ein Überstromereignis stattfindet.

Setting the circuit states to “normal”:

• • For each of the circuits SKL1N, SKL2N, SKL3N, the circuit state is set to “normal” as soon as the semiconductor is conductive in the respective phase and no overcurrent event occurs.
• • For each of the circuits SKL1L2, SKL2L3, SKL3L1, the circuit state is set to “normal” as soon as the semiconductors in the two phases connected to the circuit are conductive and no overcurrent event occurs in any of the connected phases.

• • Bei einem Überstromereignis in einem Phasenleiter LX wird der Zustand von dem Stromkreis LXN zwischen diesem Phasenleiter LX und dem Neutralleiter N auf „Überstrom“ gesetzt, wenn unmittelbar vor diesem Überstromereignis folgende Bedingungen gleichzeitig erfüllt wurden:
  • oder Leistungshalbleiter der Phase LX war eingeschaltet
  • ◯ die Impedanz zLXN war positiv
  • ◯ falls Leistungshalbleiter einer zweiten Phase LY eingeschaltet war: die Impedanz zLXLY war positiv und größer als Impedanz zLXN
  • ◯ falls Leistungshalbleiter einer dritten Phase LZ eingeschaltet war: die Impedanz zLZLX war positiv und größer als Impedanz zLXN
• • Bei einem Überstromereignis in einem Phasenleiter LX wird der Zustand von dem Stromkreis zwischen diesem Phasenleiter LX und einem zweiten Phasenleiter LY auf „Überstrom“ gesetzt, wenn unmittelbar vor diesem Überstromereignis folgende Bedingungen gleichzeitig erfüllt wurden:
  • o die Leistungshalbleiter der Phasen LX und LY waren eingeschaltet
  • o die Impedanz zLXLY war positiv
  • o die Impedanz zLXN war positiv und größer als die Impedanz zLXLY
  • o falls Leistungshalbleiter der dritten Phase LZ eingeschaltet war: die Impedanz zLZLX war positiv und größer als Impedanz zLXLY
• • Die Indizes X, Y, Z stehen dabei für 1, 2, 3 bzw. 2, 3, 1 bzw. 3, 2, 1.

Setting the circuit states to “overcurrent”:

• • In the event of an overcurrent event in a phase conductor LX, the state of the circuit LXN between this phase conductor LX and the neutral conductor N is set to “overcurrent” if the following conditions were met simultaneously immediately before this overcurrent event:
  • or power semiconductor of phase LX was switched on
  • ◯ the impedance zLXN was positive
  • ◯ if power semiconductor of a second phase LY was switched on: the impedance zLXLY was positive and greater than impedance zLXN
  • ◯ if power semiconductor of a third phase LZ was switched on: the impedance zLZLX was positive and greater than impedance zLXN
• • In the event of an overcurrent event in a phase conductor LX, the state of the circuit between this phase conductor LX and a second phase conductor LY is set to “overcurrent” if the following conditions were met simultaneously immediately before this overcurrent event:
  • o the power semiconductors of phases LX and LY were switched on
  • o the impedance zLXLY was positive
  • o the impedance zLXN was positive and greater than the impedance zLXLY
  • o if the third phase power semiconductor LZ was switched on: the impedance zLZLX was positive and greater than the impedance zLXLY
• • The indices X, Y, Z stand for 1, 2, 3 or 2, 3, 1 or 3, 2, 1.

• • Die virtuellen Stromkreise SKL1N, SKL2N, SKL3N, SKL1L2, SKL2L3, SKL3L1 und die Stromkreiszustände sind wie oben definiert.
• • Analog zur Betrachtung der virtuellen Ströme sind die berechneten virtuellen Impedanzen zL1N, zL2N, zL3N, zL1L2, zL2L3, zL3L1 eine Abstraktion für die Einschätzung des Lastzustandes und sind vor allem kurz vor einem Überstromereignis besonders wertvoll.
• • Die Analyse der Impedanzen kann im Vergleich zu der Analyse der Stromwerte dann Vorteile bringen, wenn hohe Ströme gleichzeitig zwischen einem Phasenleiter und dem Neutralleiter und zwischen demselben Phasenleiter und einem zweiten Phasenleiter auftreten.
• • Bei der Ermittlung der wahrscheinlichen Überstromursache anhand von Impedanzen wird die Wahrscheinlichkeit einer richtigen Überstromermittlung erhöht. Damit können bessere Schaltentscheidungen getroffen werden.

The following should be noted:

• • The virtual circuits SKL1N, SKL2N, SKL3N, SKL1L2, SKL2L3, SKL3L1 and the circuit states are defined as above.
• • Analogous to the consideration of the virtual currents, the calculated virtual impedances zL1N, zL2N, zL3N, zL1L2, zL2L3, zL3L1 are an abstraction for the assessment of the load status and are particularly valuable shortly before an overcurrent event.
• • Impedance analysis can be advantageous over current analysis when high currents occur simultaneously between a phase conductor and the neutral conductor and between the same phase conductor and a second phase conductor.
• • Determining the probable cause of an overcurrent based on impedances increases the probability of correctly determining the overcurrent. This allows for better switching decisions.

• Bedingungen für das Ausschalten basierend auf der maximalen Anzahl der Einschaltversuche für einen Stromkreis Bedingungen für die Dimensionierung der Energy Absorber Bedingungen für das Einhalten einer Norm oder Vorschrift zur Dauer der ultrakurzen Spannungsunterbrechung (engl. ultra short voltage interruption).

The following describes the conditions for permanent shutdown. To complete the operating procedure, conditions for terminating the reclosing attempts must be determined. Three options for such conditions are described below, each of which may be advantageous from different perspectives:

• Conditions for switching off based on the maximum number of switch-on attempts for a circuit Conditions for dimensioning the energy absorbers Conditions for compliance with a standard or regulation regarding the duration of the ultra-short voltage interruption.

i) Permanent shutdown after a number of switch-on attempts with overcurrent events

1. 1. For each of the circuits SKL1N, SKL2N, SKL3N, SKL1 L2, SKL2L3, SKL3L1, an overcurrent event counter is initialized to zero.
2. 2. Initially, the SCCB is in the “stationary” state. This applies
   1. a. The state in which all three power semiconductors are switched on and the loads are continuously supplied without overcurrent events occurring.
   2. b. The state in which all power semiconductors are switched off before an external switch-on request to the SCCB is received.
3. 3. In the event of an overcurrent event, the most probable overcurrent cause is assigned to one of the circuits SKL1N, SKL2N, SKL3N, SKL1L2, SKL2L3, or SKL3L1, according to the procedure described above. The overcurrent event counter of the circuit to which the overcurrent cause was assigned is incremented.
4. 4. If one of the overcurrent event counters reaches a certain limit, the SCCB is permanently switched off. It is advantageous to
   1. a. To set different limit values for the group of meters for the SKL1N, SKL2N, SKL3N circuits than for the group of meters for the SKL1L2, SKL2L3, SKL3L1 circuits.
   2. b. To set a limit value for the sum of the counters SKL1L2, SKL2L3, SKL3L1.
5. 5. After all three power semiconductors have been switched on, the counting of the time TSTAT begins.
6. 6. After the TSTAT time exceeds a certain value TSTAT.MAX, the SCCB returns to the "stationary" state. The overcurrent event counters are reset.

ii) Permanent switching off after a number of overcurrent events in a phase

1. 1. For each phase power semiconductor, an overcurrent event counter is initialized to zero.
2. 2. Initially, the SCCB is in the “stationary” state. This applies
   1. a. The state in which all three power semiconductors are switched on and the loads are continuously supplied without overcurrent events occurring.
   2. b. The state in which all power semiconductors are switched off and a switch-on request to the SCCB comes from outside.
3. 3. After an overcurrent event occurs in a phase, the overcurrent counter of that phase is incremented.
4. 4. After all three power semiconductors have been switched on, the counting of the time TSTAT begins.
5. 5. After the TSTAT time exceeds a certain value TSTAT.MAX, the SCCB returns to the "stationary" state. The overcurrent event counters are reset.

iii) Permanent switch-off after a time interval

1. 1. Initially, the SCCB is in the “stationary” state. This applies
   1. a. The state in which all three power semiconductors are switched on and the loads are continuously supplied without overcurrent events occurring.
   2. b. The state in which all power semiconductors are switched off before an external switch-on request to the SCCB is received.
2. 2. After an overcurrent event occurs, the procedure is executed for a specified time (TMAX). If, after TMAX has elapsed, all power semiconductors in all three phases are not switched on, the SCCB is permanently switched off and enters the "Fault" state.
3. 3. As long as overcurrent events occur during the time TMAX, the SCCB is in the “Transient” state.
4. 4. As soon as all three power semiconductors are switched on, the counting of the time TSTAT begins.
5. 5. If an overcurrent event occurs within the time TMAX, the counter for TSTAT is reset to zero and incremented again the next time the state with all three switches switched on is reached.
6. 6. If an overcurrent event occurs outside the TMAX time and within the TSTAT time, the SCCB is permanently switched off.
7. 7. After the time TSTAT exceeds a certain value TSTAT.MAX, the SCCB is back in the “stationary” state.

The inventive approach is explained in detail below using operating scenarios. All figures described below are created in a simulation and serve to illustrate the behavior of the SCCB in the described operating procedures. Noise and peaks in the voltage time profiles are caused by the simulation parameters.

Scenarios 1 to 14 demonstrate the current and voltage waveforms of an SCCB with three single-phase resistive loads. Short circuits are connected in parallel if necessary.

The first scenarios concern basic switching procedures.

The first scenario refers to switching on without overcurrent events starting with switching operation SH1 and is in 4 It shows how, with all three switches switched off (switching state SZ0), the power semiconductor of phase 3 is first switched on by the switching operation SH1. After that, a current flows only between the switched-on phase 3 and the neutral conductor. In this case, the current in the virtual circuit SKL3N corresponds exactly to the current in phase conductor 3.

As long as no overcurrent event occurs, the device is in switching state SZ1, and the next switching action is the switching on of the power semiconductor of a second phase if the magnitude of the phase-to-phase voltage between the switched-on phase and the other phase is small enough. In scenario 1, the switching on of the power semiconductor of phase 2 occurs with the switching action SH4. After switching on phase 2, currents flow in phases 2 and 3. Currents can flow in the virtual circuits SKL2N, SKL3N, and SKL2L3, if the circuits exist.

Subsequently, switching operation SH6 is executed from switching state SZ2, in which the power semiconductor of the still switched-off phase 1 is switched on at a zero crossing of the voltage between phase conductors 1 and 2. The device is in switching state SZ3, and all possible loads are continuously supplied.

The second scenario concerns a switch-on without overcurrent events starting with switching operation SH2.

Depending on the time at which the switch-on request comes in the switching state SZ0, the switching action SH1 or SH2 can be carried out first in the switching state SZ0. 5 shows an example in which switching operation SH2 is executed first. If no overcurrent event occurs, the device is in the same state after this switching operation as it was after switching operation SH4 in Scenario 1 described above. The subsequent sequence is similar to Scenario 1.

The third scenario concerns a switch-on with a short circuit in phase 3.

If there is a short circuit in the SKL3N circuit, an overcurrent event will occur after switching on the power semiconductor in phase 3. Scenario 3 in 6 shows such a case. Similar to scenario 1, the power semiconductor in phase 3 is switched on (switching operation SH1), but shortly afterwards the excessive current is interrupted with the subsequent switching operation SH0. After the switching operation SH0, the switching operation SH2 is carried out near the zero crossing of the voltage between phase conductors 2 and 3. Since the power semiconductor in phase 3 is not switched on at the zero crossing of the voltage uL3N during the switching operation SH2, the steepness of the short-circuit current is higher than in the earlier switch-on attempt, and an overcurrent event and a switching operation SH0 occur more quickly.

The fourth scenario concerns switching on with a short circuit in phase 2.

4 shows how, in the event of a short circuit in the SKL2N circuit, overcurrent events occur in phase conductor 2 after the switching operation SH4. From the switching operation SH1 to the switching operation SH4, the course of the currents and voltages is similar to that in scenario 3. After the switching operation SH4, the overcurrent in phase 2 is interrupted by the switching operation SH0 and the device is in the switching state SZ1 with phase 3 switched on. From this state, the switching operation SH3 is carried out in order to switch on phase 2 when the voltage uL3N crosses zero.

The fifth scenario concerns switching on with a short circuit between phases 2 and 3.

A short circuit in the circuit between two phases causes power semiconductors in one or both affected phases to be switched off. Scenario 5 in 8 shows such a case (short circuit between phases 2 and 3, i.e. in the SKL2L3 circuit). First, the power semiconductor in phase 3 is switched on by switching operation SH1. After switching operation SH4, an overcurrent occurs in phase 2 and the power semiconductor in phase 2 is switched off by switching operation SH0. Then, when the phase voltage uL2N passes through zero, the power semiconductor in phase 2 is switched on again by switching operation SH3. After this switching operation, the current in phases 2 and 3 rises at a faster rate of rise because the voltage uL2L3 between the two phase conductors is significantly higher than after switching operation SH4. However, during this overcurrent event, the power semiconductor in phase 3 is switched off because, due to the different voltage conditions, the current in this phase reaches the current limit more quickly. Thus, between switching operations SH1 and SH4, a current flows through phase conductor L1; from switching operation SH3 until switching operation SH4 at the earliest, a current flows through phase conductor L2. If single-phase rectifiers are connected to phases 2 and 3, the intermediate circuit capacitances of the two rectifiers can be partially charged during these time intervals. And if the overcurrent between phases 2 and 3 is not caused by a short circuit but by a three-phase rectifier, then the intermediate circuit capacitance of this rectifier will also be partially charged.

The sixth scenario concerns the execution of switching operation SH 5.

Scenario 6 is an example of the execution of the switching operation SH5 ( 9 ). During operation in switching state SZ3 (the power semiconductors of all three phases are switched on), an overcurrent occurs in phase 1, e.g. due to the switching on of an inrush or short-circuit load with an overcurrent between the phase conductor L1 and the neutral conductor N. The time of switching on is before a zero crossing of the phase voltage uL1N and after a zero crossing of one of the line-to-line voltages uL1L2 or uL3L1. After the short-circuit is switched on, the power semiconductor of phase 1 is switched off due to the overcurrent with the switching operation SH0. It is then switched on at the zero crossing of the phase voltage uL1N by the switching operation SH5 and shortly afterwards switched off again by the switching operation SH0. This is followed by switching on at the zero crossing of the voltage uL3L1 and repeated switching off by the switching operation SH0.

Scenarios 1 to 6 are briefly summarized below. The scenarios described above demonstrate how the basic switching procedure systematically attempts to utilize every zero voltage crossing for the individual switching on and off of the power semiconductors. If inrush loads are connected to the phases instead of the short circuits shown, this switching tactic transfers energy to these loads in the "gentlest" way possible. The procedure is optimal for switching single- or three-phase loads on and off as quickly as possible.

In some load cases, switching on a power semiconductor at the zero crossing of a phase voltage is not always optimal for a linked inrush or short-circuit load, and vice versa. The most complex load case occurs when single-phase and two- or three-phase loads are connected simultaneously. For this reason, the execution of the switching operations can be improved to avoid some switch-on commands if, based on previous tests, an overcurrent event is expected to occur subsequently. Additionally, in some cases, briefly switching off a power semiconductor can be advantageous.

The following scenarios illustrate additional conditions for switching on when single-phase overcurrents are detected.

The seventh scenario concerns switching on with two single-phase short circuits in phases 3 and 1 using the basic switching procedure.

The switching operation SH2 in scenario 3 ( 6 ) can be omitted if a previous switch-on attempt has shown that switching on this phase would cause an overcurrent between this phase and the neutral conductor. To demonstrate the advantages of such a tactic are in 10 and 11 Scenarios 7 and 8 are shown.

In scenario 7 acc. 10 A low-resistance short circuit exists between phase conductors 1 and 3 and the neutral conductor. The short circuit in phase 1 is simulated only to bring the SCCB into a state where the switching operations SH3 and SH4 in phase 3 can be demonstrated immediately after SH1 and SH2. The switching operations in phase 1 are not considered and are therefore shown in gray.

After phase 3 is switched on by SH1 at a time shortly before 0.148 [s], an overcurrent shutdown occurs with SH0. This is followed by the switching of phases 2 and 3 by the switching operation SH2. A short time later, phase 3 is switched off again due to an overcurrent by SH0. The second switching of phase 3 by SH2 at an even higher phase voltage than during the first switching attempt (SH1) was not advisable. If SH2 is omitted for phase 3, unnecessary loading of the energy absorber when switching off the overcurrent can be avoided. Omitting the switching operation SH4 after the time 0.158 [s] is advantageous for the same reasons. The process can be improved by additional conditions.

The eighth scenario shows switching on with two single-phase short circuits in phases 3 and 1 using the basic switching procedure and additional conditions ZB1 and ZB2.

Scenario 8 of 11 shows how, by introducing the additional conditions ZB1 and ZB2 for the switching operations SH2 and SH4, the unnecessary switching operations are avoided in contrast to scenario 7. Thus, with the power semiconductor in phase 3, only two instead of four overcurrent events had to be switched off in the shown period between 0.148 and 0.158 [s] (half the grid period) compared to scenario 7. This is a clear advantage for the dimensioning of the energy absorber of an SCCB.

The ninth scenario concerns switching on with a single-phase short-circuit in phase 3 using the basic switching procedure and additional conditions SZ1 and SZ2.

Scenarios 9 and 10 in 12 and 13 serve to demonstrate the effect of the additional condition ZB3.

In scenario 9 of 12 only phase conductor 3 is short-circuited to the neutral conductor. Thus, after time 0.156 [s], power semiconductors are switched on in two phases, and SH6 occurs in phase 3 (in contrast to SH4 in Scenario 7). This is followed by an overcurrent shutdown with SH0. Switching operation SH6 is superfluous for the same reasons as switching operations SH2 and SH4 in Scenario 7.

Scenario ten concerns switching on with a single-phase short-circuit in phase 3 using the basic switching procedure and additional conditions SZ1, SZ2 and SZ3.

Scenario 10 of 13 shows the omission of the switching operation SH6 when introducing the additional condition ZB3 compared to scenario 9.

In summary, the following can be said about scenarios 7 to 10. With the avoidable switch-on operations SH2, SH4, and SH6, the circuits SKL1N, SKL2N, and SKL3N are switched on at times when the voltage across the respective circuit is equal to half the phase voltage amplitude. The benefit of switching on these circuits at such times is very minimal. If the overcurrents are caused by a capacitance, these times are not optimal for switching on and charging this capacitance. Instead, the times near the phase voltage zero crossings should be used (switching operations SH1, SH3, SH5). These times are also more suitable as switch-on times for analyzing and distinguishing a short circuit from an inrush load.

On the other hand, the additional conditions ZB1, ZB2, and ZB3 prevent up to two shutdowns per half grid period in each phase. This reduces the amount of energy absorbed by the energy absorber by fifty percent.

The following scenarios concern proactive shutdown when two-phase overcurrents are detected.

The eleventh scenario concerns switching on with a two-phase short circuit between phases 2 and 3 using the basic switching procedure and additional conditions SZ1, SZ2 and SZ3.

If an overcurrent load is present between two phases (circuits SKL1L2, SKL2L3, SKL3L1), overcurrent events may occur after switching operations SH3 and SH5. Scenario 11 of 14 shows an example of this. First, switching operations SH1 and SH2 are carried out; shortly after SH2, an overcurrent occurs between phases 2 and 3, and phase 2 is switched off via SH0. Then, phase 2 is switched on via switching operation SH3, which again causes an overcurrent current between phases 2 and 3. Using the SH2 switching operation and the subsequent SH0 switching operation, it can be determined that the circuit between phases 2 and 3 is highly likely to generate overcurrent events. With this information, it is already known before the SH3 switching operation that it would lead to an overcurrent, because the voltage between phases 2 and 3 is significantly higher shortly before the SH3 switching operation than during the earlier attempt to switch on these two phases simultaneously (SH2).

1. 1. Einschalten des Leistungshalbleiters in Phase 2 durch SH3 und anschließend Abschaltung der Phase 2 ausgelöst durch den Überstrom, wie es in 14 dargestellt ist. In diesem Fall wird Phase 3 weiter bestromt. Zum Zeitpunkt kurz vor 0,155 [s] wird Phase 1 per SH3 eingeschaltet und kann auch bestromt werden. Dann wird zum Zeitpunkt 0,16 [s] SH6 ausgeführt und der Stromkreis zwischen den Phasen 2 und 3 wieder eingeschaltet.
2. 2. Einschalten des Leistungshalbleiters in Phase 2 durch SH3 und anschließend Abschaltung der Phase 3 ausgelöst durch den Überstrom (nicht in 14 gezeigt). In diesem Fall könnten einphasige Lasten in den Stromkreisen SKL2N, SKL1L2 und SKL3N in den relevanten Spannungsnulldurchgängen so schnell wie möglich „sanft“ nacheinander einschalten. (Ob bei dem zweiphasigen Überstrom Phase 2 oder 3 abschaltet, liegt an den Lastverhältnissen und an den Strommesstoleranzen und Offsets.)
3. 3. Einschalten des Leistungshalbleiters in Phase 2 durch SH3 und anschließend Abschaltung der beiden Phasen 2 und 3 aufgrund des Überstroms (nicht in 14 gezeigt). In diesem Fall würde der Algorithmus je nach rechentechnischer Umsetzung entweder
   1. a. den Leistungshalbleiter der Phase 2 sofort wieder einschalten, dann gilt der Ablauf nach dem Fall 2, oder
   2. b. bis zum Nulldurchgang der Phasenspannung uL1N warten, um dort Phase 1 einzuschalten. Damit werden um ca. ein Sechstel der Netzperiode keine Lasten versorgt und keine Versuche durchgeführt, neue Stromkreise einzuschalten.
4. 4. Proaktives Ausschalten der Phase 3 und anschließend Einschalten der Phase 2 per Schalthandlung SH1 (nicht 14 gezeigt). In diesem Fall werden gleiche Lasten versorgt, wie in dem Fall 2. Der Unterschied ist, dass der Leistungshalbleiter der Phase 3 beim proaktiven Ausschalten nicht einen Überstrom ausschaltet, sondern einen kleineren Betriebsstrom.

From the point in time immediately before the switching operation SH3, four cases are basically possible:

1. 1. Switching on the power semiconductor in phase 2 by SH3 and then switching off phase 2 triggered by the overcurrent, as shown in 14 as shown. In this case, phase 3 continues to be energized. At a time just before 0.155 [s], phase 1 is switched on via SH3 and can also be energized. Then, at a time 0.16 [s], SH6 is executed and the circuit between phases 2 and 3 is switched on again.
2. 2. Switching on the power semiconductor in phase 2 by SH3 and then switching off phase 3 triggered by the overcurrent (not in 14 (shown). In this case, single-phase loads in circuits SKL2N, SKL1L2, and SKL3N could switch on "softly" one after the other as quickly as possible at the relevant voltage zero crossings. (Whether phase 2 or 3 switches off during the two-phase overcurrent depends on the load conditions and the current measurement tolerances and offsets.)
3. 3. Switching on the power semiconductor in phase 2 by SH3 and then switching off both phases 2 and 3 due to the overcurrent (not in 14 In this case, depending on the computational implementation, the algorithm would either
   1. a. immediately switch on the power semiconductor of phase 2 again, then the procedure according to case 2 applies, or
   2. b. Wait until the phase voltage uL1N crosses zero to switch on phase 1. This means that for approximately one-sixth of the grid period, no loads are supplied and no attempts are made to switch on new circuits.
4. 4. Proactively switch off phase 3 and then switch on phase 2 by switching operation SH1 (not 14 shown). In this case, the same loads are supplied as in case 2. The difference is that the power semiconductor of phase 3 does not switch off an overcurrent during proactive switch-off, but a smaller operating current.

In cases 2, 3.a and 4, the energy can be “portioned” among the circuits: all available voltage zero crossings are optimally used for switching on the circuits.

In the other cases, the loads are supplied with energy asymmetrically or even all three phases are switched off for about 3.33 [ms].

Symmetrical precharging of the loads in circuits SKL1N, SKL2N, and SKL3N (phase-to-neutral) is a prerequisite for the smooth start-up of the other circuits (phase-to-phase) and must therefore be given higher priority. From this perspective, case 4 is the most attractive. Furthermore, it is the most favorable for the load on the energy absorbers.

The twelfth scenario concerns a demonstration of the switching operation SH7.

Scenario 12 of 15 shows the proactive switching off of phase 3 with the switching action SH7, as described in case 4 above.

The thirteenth scenario concerns a demonstration of the switching operation SH8.

In scenario 12, the switching operation SH7 is performed in the switching state SZ1. It is also advantageous to proactively switch off a phase in the switching state SZ2 when two-phase overcurrent loads are detected. Scenario 13 of 16 shows such a case. The switching operations before time 0.16 [s] are the same as in Scenario 12. The difference is that after 0.16 [s], switching operation SH8 is performed instead of SH5. This switches off a smaller current than the overcurrent after SH5 in Scenario 12. Furthermore, in Scenario 13, the later switching operations SH6 and SH0 do not occur, unlike in Scenario 12.

In contrast to scenario 12, executing SH8 results in phase 2 being energized in the time period after 0.16 [s].

The switching operations SH7 and SH8 ensure that the circuits are alternately energized in switching states SZ1 and SZ2.

The fourteenth scenario concerns a demonstration of the switching operation SH9.

• • Phase 3 eingeschaltet ist
• • bekannt ist, dass zwischen den Phasen 2 und 3 bei einem früheren Einschaltversuch in der Nähe des relevanten Nulldurchgangs ein Überstrom stattgefunden hat
• • Die Spannung zwischen den Phasen 2 und 3 kurz vor der erwähnten Schalthandlung SH6 betragsmäßig ca. 3/2 der Phasenspannungsamplitude beträgt.

In scenarios 12 and 13, after the switching operation SH6, an overcurrent event occurs shortly after the time 0.155 [s], after which phase 2 is switched off. With the switching operation SH6, phase 2 is switched on, whereby

• • Phase 3 is switched on
• • it is known that an overcurrent occurred between phases 2 and 3 during a previous switch-on attempt near the relevant zero crossing
• • The voltage between phases 2 and 3 shortly before the switching operation SH6 mentioned is approximately 3/2 of the phase voltage amplitude.

1. 1. Ausführung von SH6 und Ausschalten von Phase 2 wegen Überstrom, wie es in den Szenarien 12 und 13 gezeigt ist. So können nach der Schalthandlung SH0 in dem Zeitabschnitt 0,155-0,16 [s] die Stromkreise SKL1N, SKL3N, SKL3L1 bestromt werden. Die Nulldurchgänge der Spannungen uL3L1, uL3N können bei weiteren Überströmereignissen für das Wiedereinschalten optimal genutzt werden.
2. 2. Ausführung von SH6 und Ausschalten von Phase 3 wegen Überstrom. So wird in dem Zeitabschnitt nach der Schalthandlung SH0 in dem Zeitabschnitt 0,155-0,16 [s] der Stromkreise SKL2N bestromt.
3. 3. Proaktives Ausschalten der Phase 2 per Schalthandlung SH9, wie es in 17 dargestellt ist. In diesem Fall sind die Stromverläufe nach dem anschließenden Einschalten der Phase 3 analog zu dem Fall 1. Der Unterschied liegt daran, dass von Phase 2 ein kleinerer Strom ausgeschaltet wird. Die Fälle 1 und 3 sind für gleichmäßiges Beströmen der potenziellen Inrush-

It is therefore to be expected that after switching on phase 2 by SH6, an overcurrent will occur between phases 2 and 3. From the time before SH6, the following cases are possible:

1. 1. Execution of SH6 and deactivation of phase 2 due to overcurrent, as shown in scenarios 12 and 13. This allows the SKL1N, SKL3N, and SKL3L1 circuits to be energized after the SH0 switching operation in the time interval 0.155-0.16 [s]. The zero crossings of the voltages uL3L1 and uL3N can be optimally utilized for reclosing in the event of further overcurrent events.
2. 2. Execution of SH6 and deactivation of phase 3 due to overcurrent. Thus, in the time period following the SH0 switching operation, the SKL2N circuit is energized in the time period 0.155-0.16 [s].
3. 3. Proactively switch off phase 2 by switching operation SH9, as described in 17 In this case, the current waveforms after the subsequent switching on of phase 3 are analogous to case 1. The difference is that a smaller current is switched off from phase 2. Cases 1 and 3 are for uniform current flow to the potential inrush

Loads are advantageous. Only case 3 can be deliberately induced. If phase 2 is not proactively switched off, it is unknown whether case 1 or 2 will occur subsequently. If the previous overcurrent between phases 2 and 3 was an inrush current from a three-phase rectifier, it will most likely no longer have a high amplitude when phase 3 is switched on by SH6 (scenario 13), because the intermediate circuit has been precharged by the previously switched-on phases 1 and 2.

Carrying out the switching operation SH6 as in scenarios 12 and 13 is advantageous for switching on all phases as quickly as possible in the case where the overcurrent between phases 2 and 3 is not caused by a two-phase short circuit but by a three-phase rectifier.

Performing the SH9 switching operation instead of SH6 slows down the entire closing process, but offers the possibility of avoiding an overcurrent between phases 2 and 3 if it is caused by a short circuit. Furthermore, in this case, the circuit between phases 3 and 1 can be closed and analyzed.

A control circuit breaker without the SH9 switching action is characterized by a somewhat faster switch-on behavior. A control circuit breaker with SH9 is slower and more "prudent" and can offer advantages from a load detection perspective.

In summary, the following can be stated for scenarios 11 to 14. Switching operations SH7 and SH8 achieve a symmetrical distribution of energy between single-phase loads during transient conditions. This is an advantage and a prerequisite for connecting two- and three-phase loads. Switching operation SH9 is optional and only relevant under special circumstances, for example, when extended switching and re-switching is permitted and detection of the load generating the overcurrent is desired.

In the following, options for designing the control system are discussed.

The basic switching procedure consists of the switching operations SH0 to SH6 and aims to utilize the zero crossing of each of the six voltages for switching the respective circuit on or off. The minimum equipment of a control device must include the basic switching procedure and a criterion for permanent switching off.

The additional conditions ZB1 to ZB3 and switching operations SH7 to SH9 are advantageous additions to the basic switching procedure. Their implementation requires monitoring of the circuit states.

Two methods for monitoring circuit conditions and determining the cause of the overcurrent are described above. It cannot be ruled out that variations of these methods or other methods could be implemented for this purpose. Regardless of the monitoring implementation, it is important that after an overcurrent event, the cause of the overcurrent is assigned to one of the six virtual circuits. After this, it is expected that the next time one or two switches are switched on, with a very high probability whether an overcurrent event occurs in a particular circuit.

The additional conditions ZB1 to ZB3 improve the basic switching procedure by omitting switching-on operations that would most likely only lead to an overcurrent shutdown of the power semiconductor to be switched on.

The switching operations SH7 and SH8 proactively ensure that the energy is distributed as evenly as possible among the loads during the switch-on and switch-back processes. This may result in the fully switched-on state SZ3 being reached more quickly.

The switching operation SH9 is optional.

Individually and together, the additional conditions ZB1 to ZB3 switching operations SH7 to SH9 offer an opportunity to positively influence the dimensioning of the energy absorbers.

The benefits of these additions are only visible in certain operating conditions. In simple operating cases, they are hardly noticeable, e.g., with simple resistive loads without overcurrent.

Examples of a switch-on process with a rectifier load are described below.

The fifteenth scenario of 18 shows the switching on of an SCCB using the basic switching method. The loads are three single-phase rectifiers with 400 µF DC link capacitance each and one three-phase rectifier with 200 µF on the DC link.

The sixteenth scenario of 19 demonstrates the switching on of an SCCB using the basic switching procedure supplemented by the additional conditions ZB1 to ZB3 and switching operations SH7 and SH8 with the same loads. The transient process takes a few [ms] longer in scenario 16 than in scenario 15. In both scenarios, all three phases are permanently switched on after less than one grid period from the first switching operation.

In 20 A first basic procedure is shown, which provides for the permanent switching off of a circuit breaker according to the invention if stable operation is not achieved. This first procedure is based on the counting of switching events using a counter. In step S11, the method is started, e.g., as part of a switch-on routine of a circuit breaker according to the invention. The counter is set to zero (step S12) and the registration of overcurrent events is started (step S13). During operation, stable operation can occur, which triggers a reset of the counter (step S14). The procedure for a reset is described in 22 shown in more detail. In the event of an overcurrent event S15, the counter is incremented. If a threshold value for the counter reading is reached, this leads to permanent shutdown (step S18). Otherwise, the process continues. The reset S14 ensures that a permanent shutdown does not simply occur due to the accumulation of overcurrent events, but only in the event of unstable operation.

In 21 A second basic procedure is shown, which provides for the permanent switching off of a circuit breaker according to the invention if stable operation is not achieved. This method operates with a timer or timer. During the initialization of the switch (step S21), the detection of overcurrent events is provided (step S22). If an overcurrent event occurs (step S23), a timer is started (step S24). While this timer is running, a reset can occur (step S25). The reset is described below using 22 explained in more detail. The reset terminates the timer (step S26). A new timer can be started if an overcurrent event occurs again. If the timer reaches a limit value Tmax (step S27), this results in a permanent shutdown (step S28).

The 20 and 21 The methods shown can also be used in parallel or in combination.

In 22 A reset procedure is shown, which is suitable for both counter-based ( 20 ) and timer-based ( 21 ) permanent shutdown can be used. If an overcurrent event S32 and the interruption of a phase line occurs after the switch has been started (step S31), it is then switched on again using one of the switching operations described above (step S33). If all phases have been switched on by switching operations (query S34), a timer Tstat is started (step S35). This timer is deleted (step S37) if one of the three phases is interrupted again (due to an overcurrent event) (step S36). A corresponding timer would then be initiated again when the three phases are connected again. If the timer reaches a limit value Tstat,max (step S38) without any of the phases having been interrupted, the criterion for stable operation is met and a reset is initiated in the process of 20 or 21 triggered (step S39).

The above describes a novel approach for operating a 3+N SCCB with inrush current control by controlling the power semiconductors. This approach is less complex and more efficient than conventional approaches known from other switch types. The exemplary embodiments are merely illustrative. Numerous modifications that fall within the scope of the claims will be readily apparent to those skilled in the art.

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This 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 10 2020 216 405 A1 [0006]
• DE 102022201960 A1 [0013]

Claims (18)

A circuit breaker for protecting a power supply comprising three phase conductors (L1, L2, L3) and one neutral conductor (N), wherein the circuit breaker is designed to: - determine the current values of the three phase conductors (L1, L2, L3), - determine the voltage values between the phase conductors (L1, L2, L3) and the neutral conductor (N), and - evaluate specific current and voltage values, wherein: - virtual circuits between the individual phase conductors (SKL1L2, SKL1L3, SKL2L3) are defined for the evaluation, - the circuit breaker is designed to determine circuit-specific voltages, currents, and impedances for the virtual circuits using the specific current and voltage values, wherein: - the voltage of a virtual circuit (SKL1L2, SKL1L3, SKL2L3) between two phase conductors is the difference between the voltages between the respective phase conductors and the neutral conductor, - the current of a virtual circuit (SKL1L2, SKL1L3, SKL2L3) between two phase conductors corresponds to the weighted difference between the currents of the respective phase conductors, and -- the impedance (ZL1L2, ZL1L3, ZL2L3) of a virtual circuit between two phase conductors corresponds to the quotient of voltage and current of the virtual circuit between the two phase conductors, and - the circuit breaker is designed to use quantities determined for the virtual circuits for the diagnosis of overcurrent events. Circuit breaker according to Claim 1 , characterized in that - for the evaluation, virtual circuits (SKL1N, SKL2N, SKL2N) are each defined between individual phase conductors and the neutral conductor (N), - the circuit breaker is designed to determine circuit-specific voltages, currents and impedances for the virtual circuits with the aid of the determined current and voltage values, wherein -- the voltage of a virtual circuit (SKL1N, SKL2N, SKL2N) between a phase conductor and the neutral conductor corresponds to the voltage applied between the phase conductor and the neutral conductor, -- the current of a virtual circuit (SKL1N, SKL2N, SKL2N) between a phase conductor and the neutral conductor corresponds to the current of the phase conductor, and -- the impedance of a virtual circuit (SKL1N, SKL2N, SKL2N) between a phase conductor and the neutral conductor corresponds to the quotient of voltage and current of the virtual circuit, and - the circuit breaker is designed to determine, for the virtual Circuits (SKL1N, SKL2N, SKL2N) are to be used to diagnose overcurrent events. Circuit breaker according to Claim 1 or 2 , characterized in that the circuit breaker is designed to detect overcurrent events on virtual circuits. Circuit breaker according to Claim 3 , characterized in that the circuit breaker is designed to record detected overcurrent events as a criterion for possible overcurrent in future switching operations relating to the respective virtual circuit. Circuit breaker according to Claim 4 , characterized in that the circuit breaker is designed to - evaluate certain current and voltage values with regard to the fulfillment of conditions for the interruption of the phase conductors (L1, L2, L3) and the restoration of interrupted connections relating to switching operations, wherein -- at least some of the switching operations are assigned to virtual circuits, -- during the evaluation for these switching operations it is checked whether an overcurrent event is detected as a criterion for a possible overcurrent when carrying out the switching operation, and -- the switching operation is only carried out if no overcurrent event is detected for the switching operation. Circuit breaker according to Claim 5 , characterized in that the circuit breaker is designed to delete detected overcurrent events as a criterion for switching actions if a condition for freedom from overcurrent is met on the respective virtual circuit. Circuit breaker according to Claim 6 , characterized in that this condition consists either in the circuit breaker conducting current without excess current when the phase conductor encompassed by the virtual circuit is switched on or the phase conductors encompassed by the virtual circuit are switched on, or in the circuit breaker conducting current without excess current when all the phase conductors encompassed by the virtual circuit are switched on. Circuit breaker according to one of the preceding claims, characterized in that the circuit breaker is designed to - switch operations of different types of virtual to assign circuits, - to count the switching operations related to these virtual circuits, and - to switch off permanently when a threshold value for a number of switching operations of a type related to a virtual circuit or a threshold value for the aggregated number of switching operations of several types of switching operations each related to a virtual circuit is reached. Circuit breaker according to one of the preceding claims, characterized in that the circuit breaker is designed to - assign switching operations of different types to virtual circuits, - carry out a count of these switching operations related to virtual circuits, and - no longer carry out switching operations of a type related to a virtual circuit when a threshold value for a number of switching operations of this type is reached. Method for supporting the diagnosis of overcurrent events in a power supply comprising three phase conductors (L1, L2, L3) and one neutral conductor (N), comprising: - determining the current values of the three phase conductors (L1, L2, L3), - determining the voltage values between the phase conductors (L1, L2, L3) and the neutral conductor (N), and - evaluating specific current and voltage values, whereby: - virtual circuits between the individual phase conductors (SKL1L2, SKL1L3, SKL2L3) are defined for the evaluation, - using the specific current and voltage values, circuit-specific voltages, currents, and impedances are determined for the virtual circuits, whereby: - the voltage of a virtual circuit (SKL1L2, SKL1L3, SKL2L3) between two phase conductors is the difference between the voltages between the respective phase conductors and the neutral conductor, - the current of a virtual circuit (SKL1L2, SKL1L3, SKL2L3) between two phase conductors is the weighted difference between the currents of the respective phase conductors, and -- the impedance (ZL1L2, ZL1L3, ZL2L3) of a virtual circuit between two phase conductors is the quotient of voltage and current of the virtual circuit between the two phase conductors, and - quantities determined for the virtual circuits are used for the diagnosis of overcurrent events. Procedure according to Claim 10 , characterized in that - for the evaluation, virtual circuits (SKL1N, SKL2N, SKL2N) are each defined between individual phase conductors and the neutral conductor (N), - for the virtual circuits, circuit-specific voltages, currents and impedances are determined with the aid of the determined current and voltage values, whereby -- the voltage of a virtual circuit (SKL1N, SKL2N, SKL2N) between a phase conductor and the neutral conductor corresponds to the voltage applied between the phase conductor and the neutral conductor, -- the current of a virtual circuit (SKL1N, SKL2N, SKL2N) between a phase conductor and the neutral conductor corresponds to the current of the phase conductor, and -- the impedance of a virtual circuit (SKL1N, SKL2N, SKL2N) between a phase conductor and the neutral conductor corresponds to the quotient of voltage and current of the virtual circuit, and - for the virtual circuits (SKL1N, SKL2N, SKL2N) determined quantities are to be used for the diagnosis of overcurrent events. Procedure according to Claim 10 or 11 , characterized in that overcurrent events are detected on virtual circuits. Procedure according to Claim 12 , characterized in that detected overcurrent events are recorded as a criterion for possible overcurrent in future switching operations concerning the respective virtual circuit. Procedure according to Claim 13 , characterized in that - certain current and voltage values are evaluated with regard to the fulfillment of conditions for the interruption of the phase conductors (L1, L2, L3) and the restoration of interrupted connections relating to switching operations, wherein -- at least some of the switching operations are assigned to virtual circuits, -- during the evaluation for these switching operations it is checked whether an overcurrent event is detected as a criterion for a possible overcurrent when carrying out the switching operation, and -- the switching operation is only carried out if no overcurrent event is detected for the switching operation. Procedure according to Claim 14 , characterized in that detected overcurrent events are deleted as a criterion for switching operations if a condition for freedom from overcurrent is fulfilled on the respective virtual circuit. Procedure according to Claim 15 , characterized in that this condition consists either in the circuit breaker conducting current without excess current when the phase conductor encompassed by the virtual circuit is switched on or the phase conductors encompassed by the virtual circuit are switched on, or in the circuit breaker conducting current without excess current when all the phase conductors encompassed by the virtual circuit are switched on. Method according to one of the preceding claims, characterized in that - switching operations of different types are assigned to virtual circuits, - a counting of these switching operations related to virtual circuits is carried out, and - the three phase conductors (L1, L2, L3) are permanently interrupted when a threshold value for a number of switching operations of a type related to a virtual circuit or a threshold value for the aggregated number of switching operations of several types of switching operations each related to a virtual circuit is reached. Method according to one of the preceding claims, characterized in that - switching operations of different types are assigned to virtual circuits, - a count of these switching operations related to virtual circuits is carried out, and - switching operations of a type related to a virtual circuit are no longer carried out when a threshold value for a number of switching operations of this type is reached.