Patent Publication Number: US-2022231497-A1

Title: Overcurrent protection device for protecting a consumer arranged in a dc grid

Description:
PRIORITY STATEMENT 
     This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/EP2020/063571 which has an International filing date of May 15, 2020, which designated the United States of America 2020 and which claims priority to European patent application No. EP19175083 filed May 17, 2019, the entire contents of each of which are hereby incorporated herein by reference. 
    
    
     FIELD 
     The present application generally relates to an overcurrent protection device for protecting a consumer arranged in a DC grid, to a DC grid and to methods for operating an overcurrent protection device and a DC grid. 
     BACKGROUND 
     Load assemblies that are supplied with power from a DC grid are used, in particular, in the industrial sphere. The supply of power to load assemblies from DC grids affords the advantage of being able to react to fluctuating grid quality and energy supplies in a flexible and robust manner by way of intelligent grid control and integrated stores. In particular, regenerative energy generators, such as battery stores and/or photovoltaics installations, for example, can easily be integrated into a DC grid. Conversion losses from AC to DC voltage can be prevented in this case. The option of being able to buffer-store braking energy, for example of drives operated by way of a generator, results in energy savings. 
     The distribution of the energy in a DC grid takes place as in the previously used AC grids. In tree-like DC grids, starting from the energy source or a supply rail, the current intensity and also the required cable cross-section decreases in steps from the infeed to the consumers. With each change in the line cross-section, that is to say after each branching, controllable overcurrent protection devices are usually provided, which rapidly switch off in the event of an overcurrent detected in the subsequent line branch. Overcurrents in a line branch can arise not only in the case of faults in the line branch but also in the case of greatly different consumers in different line branches, when, for example, one of the consumers passes to generator operation and temporarily feeds current into the other line branch. 
     SUMMARY 
     At least one embodiment of the invention specifies an overcurrent protection device and/or a method for operation in a DC grid that are improved in terms of function and/or structure with respect to the protective function thereof. At least one embodiment of the invention further specifies a DC grid having such an overcurrent protection device and/or a method for the operation thereof that are improved in terms of function and/or structure. 
     Embodiments are directed to an overcurrent protection device; a DC grid; a method for operating the overcurrent protection device; a computer program product; a method for operating the DC grid; and a computer program product. Advantageous configurations result from the claims. 
     According to a first embodiment of the present invention, an overcurrent protection device for protecting a consumer arranged in a DC grid is proposed. The consumer is, in particular, one or more capacitive consumers. Such capacitive consumers are inverters, for example, which generate a three-phase or at least an AC voltage for a load, for example a motor, from the voltage provided by the DC grid. In addition to a number of switching elements, such inverters generally have one or more capacitances for the operation thereof. 
     According to a second embodiment, a DC grid is proposed, which comprises a supply rail, which can be connected or is connected to a supply potential of the DC grid, and a load assembly comprising at least one consumer. Each of the consumers is coupled to the supply rail via an associated controllable overcurrent protection device. A current-dependent trigger characteristic curve is associated with each of the consumers. In an embodiment, the overcurrent protection device is designed according to an embodiment described herein. 
     According to a third embodiment of the present invention, a method for operating an overcurrent protection device for protecting a consumer arranged in a DC grid is proposed. In the DC grid, the consumer is coupled via the overcurrent protection device to a supply rail, which can be connected or is connected to a supply potential of the DC grid. In the method, a present trigger value is ascertained based upon a detection value of a current flowing through the overcurrent protection device and based upon a current-dependent trigger characteristic curve associated with the consumer, wherein the current is taken into consideration together with a first or a second factor in the trigger characteristic curve, depending on the current direction. Furthermore, in the method, the present trigger value is compared with a previously stipulated threshold value. Finally, the overcurrent protection device is triggered or not triggered depending on the result of the comparison. 
     According to a fourth embodiment, the invention proposes a computer program product, which can be loaded directly into the internal memory of a digital control unit of an overcurrent protection device and comprises software code sections, using which the steps of the method described herein are executed when the product is run on the control unit. The computer program product can be embodied in the form of a storage medium, such as a USB memory stick, a DVD, a CD-ROM or a memory card, for example. The computer program product can also be present in the form of a signal that can be loaded via a wireless or wired communication link. 
     According to a fifth embodiment of the present invention, a method for operating a DC grid is proposed, which comprises a supply rail, which can be connected or is connected to a supply potential of the DC grid, and a load assembly comprising at least one consumer, wherein each of the consumers is coupled to the supply rail via an associated controllable overcurrent protection device and wherein a current-dependent trigger characteristic curve is associated with each of the consumers. In the method, for each of the at least one consumer, the following steps are carried out independently of one another: a present trigger value is ascertained based upon a detection value of a current flowing through the overcurrent protection device associated with the consumer and based upon a current-dependent trigger characteristic curve associated with the respective consumer, wherein the current is taken into consideration together with a first or a second factor in the trigger characteristic curve, depending on the current direction. The present trigger value is compared with a threshold value previously stipulated for the respective consumer. The overcurrent protection device associated with a respective consumer is triggered or not triggered depending on the result of the comparison. 
     According to a sixth embodiment, the invention proposes a computer program product, which can be loaded directly into the internal memory of a digital control unit and comprises software code sections, using which the previously described steps are executed when the product is run on the control unit. The computer program product can be embodied in the form of a storage medium, such as a USB memory stick, a DVD, a CD-ROM or a memory card, for example. The computer program product can also be present in the form of a signal that can be loaded via a wireless or wired communication link. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in more detail below with reference to example embodiments in the drawing. In the figures: 
         FIG. 1  shows a schematic illustration of an example overcurrent protection device for protecting a consumer arranged in a DC grid; 
         FIG. 2  shows a schematic illustration of an example DC grid with a plurality of consumers that are protected by respective overcurrent protection devices; 
         FIG. 3  shows a graph in which example current-dependent trigger characteristic curves for determining a trigger criterion are represented; and 
         FIG. 4  shows a flowchart illustrating the steps of the method according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS 
     According to a first embodiment of the present invention, an overcurrent protection device for protecting a consumer arranged in a DC grid is proposed. The consumer is, in particular, one or more capacitive consumers. Such capacitive consumers are inverters, for example, which generate a three-phase or at least an AC voltage for a load, for example a motor, from the voltage provided by the DC grid. In addition to a number of switching elements, such inverters generally have one or more capacitances for the operation thereof. 
     In the DC grid of an embodiment, the consumer is coupled via the overcurrent protection device to a supply rail, which can be connected or is connected to a supply potential of the DC grid. The supply rail can therefore be connected to the supply potential directly, that is to say without further electronic components being interconnected. As an alternative, the supply rail can be connected to the supply potential via further electronic components, in particular a controllable switching element. The provision of a controllable switching element between the supply rail and the supply potential makes it possible to disconnect the supply rail from the supply potential. 
     The overcurrent protection device of an embodiment is a controllable overcurrent protection device, which makes it possible to disconnect the consumer from the supply rail in the event of an overcurrent arising. For this purpose, the overcurrent protection device can comprise a controllable switching element, in particular a power electronics component. In order to detect an overcurrent, the overcurrent protection device preferably has aspects that make it possible to detect a current value. 
     The overcurrent protection device of an embodiment is designed to ascertain a present trigger value based upon a detection value of a current flowing through the overcurrent protection device and based upon a current-dependent trigger characteristic curve associated with the consumer. The present trigger value is a computational value, which is ascertained from the detection value, which represents the current presently flowing through the overcurrent protection device, and the current-dependent trigger characteristic curve. The present trigger value therefore constitutes a measure for the thermal loading of the system in relation to the current flowing through the overcurrent protection device and thus the consumer that is to be protected. 
     The present trigger value of an embodiment is compared with a previously stipulated threshold value. The previously stipulated threshold value constitutes a trigger discriminant. The overcurrent protection device then triggers or does not trigger depending on the result of the comparison. If, for example, the computationally ascertained present trigger value increases as the current flowing through the overcurrent protection device increases, the overcurrent protection device triggers when the previously stipulated threshold value is exceeded, as a result of which the consumer is electrically isolated from the supply rail. As long as the present trigger value does not exceed the previously stipulated threshold value, the overcurrent protection device does not trigger. The previously stipulated threshold value can be stipulated, for example, by tests or by numerical determination. To this end, the previously stipulated threshold value can be stored permanently in a memory of the overcurrent protection device. By way of example, the previously stipulated threshold value is selected in such a way that it is a prescribed percentage value above a trigger value that is produced at the rated current. 
     In this case, the current is taken into consideration, that is to say processed, together with a first or with a second factor in the trigger characteristic curve, depending on the current direction. Taking the current into consideration in a manner dependent on direction makes weighting possible via the first and second factor and as a result better mapping of the thermal processes in the overcurrent protection device. This results in a higher availability at the same protection level in comparison to the previously used safety fuses. 
     As a result of the fact that the current is taken into consideration together with a first or a second factor in the trigger characteristic curve, depending on the current direction, a different present trigger value is produced depending on the current direction. This makes it possible, for example, to reliably take into consideration a cooling effect in the consumer brought about by the current direction. The first factor and the second factor are determined, for example, by tests or simulations. The first and the second factor are generally different. 
     According to an expedient configuration of an embodiment, the overcurrent protection device comprises a controllable switching element and a current measurement device interconnected in series therewith. The current measurement device detects the level of the current flowing through the controllable switching element during a switch-on phase of the controllable switching element and provides the level as detection value. According to this configuration, the overcurrent protection device itself comprises the current measurement device that determines and provides the detection value required to ascertain the present trigger value. In another configuration, the current value and the detection value can also be provided by a current measurement device outside of the overcurrent protection device. In order to be able to correctly detect the current direction flowing through the consumer, the current measurement device can comprise a sensor based on the Hall principle. 
     Another expedient configuration of an embodiment makes provision for the first and/or the second factor to be able to be parameterized or to be parameterized depending on the consumer that is to be protected. The first and/or the second factor can be determined for the current-dependent trigger characteristic curve associated with the consumer depending on the kind and/or the type and/or the power class of the consumer. The first and the second factor will generally have different values. In some circumstances, however, the first and second factor can also have the same value, as a result of which there is then no difference in the present trigger value, however, irrespective of the direction in which the current flows through the consumer. 
     Another expedient configuration of an embodiment makes provision for the first and/or second factor to be able to be parameterized or to be parameterized depending on the profile of the trigger characteristic curve. The trigger characteristic curve that is stipulated individually for the respective consumer can be selected, for example, depending on the kind and/or the type and/or the rated power. By way of example, trigger characteristic curves may be dependent on a linear or quadratic consideration of the current flowing through the consumer. While some consumers, for example, have trigger characteristic curves with a quadratic dependency on the current flowing through them, other consumers have a trigger characteristic curve that takes into consideration a linear dependency on the current. 
     It is furthermore expedient, in an embodiment, when the previously stipulated threshold value can be parameterized or is parameterized depending on the consumer that is to be protected. As described above, the previously stipulated threshold value can be used to stipulate the conditions under which the overcurrent protection device triggers or does not trigger, the conditions generally being dependent on temperature. 
     When the present description discusses a parameterization of different parameters or an ability of different parameters to be parameterized, this should be understood as meaning that the corresponding parameters for each consumer or each overcurrent protection device are stored in a memory of the computation unit that executes the method. This can occur once either upon delivery or initial start-up of the overcurrent protection device. As an alternative, provision can also be made for the parameterization to be changed during operation. 
     In particular, the trigger characteristic curve represents a modeling of the heating of the consumer that is to be protected. 
     According to a second embodiment, a DC grid is proposed, which comprises a supply rail, which can be connected or is connected to a supply potential of the DC grid, and a load assembly comprising at least one consumer. Each of the consumers is coupled to the supply rail via an associated controllable overcurrent protection device. A current-dependent trigger characteristic curve is associated with each of the consumers. In an embodiment, the overcurrent protection device is designed according to an embodiment described herein. 
     A DC grid of this kind has the same advantages as have been described above in connection with an overcurrent protection device according to an embodiment of the invention. 
     According to an expedient configuration of the DC grid of an embodiment, the supply rail can be connected or is connected to a supply potential of the DC grid via an overcurrent protection device of the kind described herein, wherein the overcurrent protection device is designed to process a current-dependent trigger characteristic curve associated with the load assembly. According to this configuration, the overcurrent protection device is associated not with a single consumer but with an entire load assembly that has a multiplicity of consumers. The overcurrent protection device described here is thus located in a superordinate line branch, which supplies a number of consumers of the load assembly with current. 
     Another expedient configuration of an embodiment makes provision, in the case of a plurality of consumers, for a respective current-dependent trigger characteristic curve to be associated with each consumer, the trigger characteristic curves being able to be the same or different in pairs. As an alternative or in addition, in the case of a plurality of consumers, a respective previously stipulated threshold value can be associated with each consumer, the threshold values being able to be the same or different in pairs. In other words, identical or different current-dependent trigger characteristic curves can be associated with the consumers. Likewise, identical or different respectively previously stipulated threshold values for carrying out the method described above can be associated with the consumers. This is significant, in particular, when consumers with greatly different rated powers are provided in the DC grid. In this case, the operating state of a consumer with a high rated power can have repercussions on the line branch of the consumer with a low rated power, for example during generator operation. These different operating situations can be taken into consideration by the parameterization in the described manner, such that it is possible to avoid disconnecting or tripping the overcurrent protection device unnecessarily and/or too early. 
     According to a third embodiment of the present invention, a method for operating an overcurrent protection device for protecting a consumer arranged in a DC grid is proposed. In the DC grid, the consumer is coupled via the overcurrent protection device to a supply rail, which can be connected or is connected to a supply potential of the DC grid. In the method, a present trigger value is ascertained based upon a detection value of a current flowing through the overcurrent protection device and based upon a current-dependent trigger characteristic curve associated with the consumer, wherein the current is taken into consideration together with a first or a second factor in the trigger characteristic curve, depending on the current direction. Furthermore, in the method, the present trigger value is compared with a previously stipulated threshold value. Finally, the overcurrent protection device is triggered or not triggered depending on the result of the comparison. 
     The method has the same advantages as have been described above in connection with the overcurrent protection device according to an embodiment of the invention. 
     According to a fourth embodiment, the invention proposes a computer program product, which can be loaded directly into the internal memory of a digital control unit of an overcurrent protection device and comprises software code sections, using which the steps of the method described herein are executed when the product is run on the control unit. The computer program product can be embodied in the form of a storage medium, such as a USB memory stick, a DVD, a CD-ROM or a memory card, for example. The computer program product can also be present in the form of a signal that can be loaded via a wireless or wired communication link. 
     According to a fifth embodiment of the present invention, a method for operating a DC grid is proposed, which comprises a supply rail, which can be connected or is connected to a supply potential of the DC grid, and a load assembly comprising at least one consumer, wherein each of the consumers is coupled to the supply rail via an associated controllable overcurrent protection device and wherein a current-dependent trigger characteristic curve is associated with each of the consumers. In the method, for each of the at least one consumer, the following steps are carried out independently of one another: a present trigger value is ascertained based upon a detection value of a current flowing through the overcurrent protection device associated with the consumer and based upon a current-dependent trigger characteristic curve associated with the respective consumer, wherein the current is taken into consideration together with a first or a second factor in the trigger characteristic curve, depending on the current direction. The present trigger value is compared with a threshold value previously stipulated for the respective consumer. The overcurrent protection device associated with a respective consumer is triggered or not triggered depending on the result of the comparison. 
     The method has the same advantages as have been described above. 
     In an expedient configuration, the method is carried out by a central control unit of the DC grid or by respective computation units of the overcurrent protection devices. A distribution of the tasks is also conceivable. 
     According to a sixth embodiment, the invention proposes a computer program product, which can be loaded directly into the internal memory of a digital control unit and comprises software code sections, using which the previously described steps are executed when the product is run on the control unit. The computer program product can be embodied in the form of a storage medium, such as a USB memory stick, a DVD, a CD-ROM or a memory card, for example. The computer program product can also be present in the form of a signal that can be loaded via a wireless or wired communication link. 
       FIG. 1  shows a schematic illustration of an overcurrent protection device  11 S for protecting a consumer arranged in a DC grid. The DC grid  1  provides a DC voltage at a supply rail  10 V. In the schematic illustration, the DC voltage is provided by way of example by a battery  5 . It is understood that the battery  5  is purely representative of an arbitrary energy source or a combination of a plurality of energy sources, at terminals of which a DC voltage is provided. Energy sources may be, for example, a photovoltaics installation and/or a battery store, but also a rectifier, which generates the DC voltage by rectifying an AC voltage generated by an AC voltage source. 
     In the present example embodiment, the consumer is represented by an inverter  11 , to which a three-phase motor  12  is connected. The inverter  11  in a known manner converts the DC voltage provided by the DC grid to a three-phase or AC voltage that is required by the motor  12 . For this purpose, the inverter  11  has a number of controllable switching elements (not illustrated) and at least one capacitor (not illustrated) and therefore constitutes a capacitive consumer. 
     It is understood that the consumer shown here is purely example and other consumers, such as resistors and/or inductive loads, for example, could also be used instead. 
     The overcurrent protection device  11 S comprises a controllable switching element  15  and a current measurement device  16  interconnected in series therewith. The controllable switching element  15  can be turned on or off by a control unit (either the overcurrent protection device  11 S itself or a superordinate control unit), which is not illustrated here. If the controllable switching element is turned on, the consumer  11 ,  12  (that is to say the associated unit composed of the inverter  11  and the motor  12  connected thereto) is connected to the supply rail  10 V, such that a current I 11  flows via the controllable switching element  15  and the current measurement device  16  into the consumer  11 ,  12 . In the event of an overcurrent, the controllable switching element  15  is turned off by the control unit so that the flow of current into the consumer  11 ,  12  is stopped. 
     The controllable switching element  15  is a power electronics component, for example a MOSFET (metal-oxide-silicon field-effect transistor), IGBT (insulated-gate bipolar transistor), and so on. The power electronics component may be of n-channel or p-channel type or npn or pnp type. The semiconductor material may be based on silicon (Si) or gallium nitride (GaN) or similar. The controllable switching element can comprise one or more power electronics components of the mentioned kind, in particular connected in anti-series or in parallel. 
     A current-dependent trigger characteristic curve is associated with the consumer  11 ,  12 . The current-dependent trigger characteristic curve represents a modeling of the heating of the consumer that is to be protected. Current-dependent trigger characteristic curves are shown by way of example in  FIG. 3 , wherein the graph shows the present trigger values MM of two different current-dependent trigger characteristic curves MM 1 , MM 2  as a function of time. The upper characteristic curve denoted by MM 1  represents a current-dependent characteristic curve that has a linear dependency on the current that flows through the consumer. The lower characteristic curve denoted by MM 2  represents a characteristic curve that has a quadratic dependency on the current flowing through the consumer. The characteristic curves are selected purely by way of example and serve for the purpose of illustration. The actual profile of the characteristic curves that represents a heating as a function of time and the current flowing through the consumer may also appear differently in practice. 
     The overcurrent protection device  11 S illustrated in  FIG. 1  is designed to ascertain a present trigger value based upon a detection value of the current I 11  flowing through the overcurrent protection device  11 S and thus the consumer  11 ,  12  and based upon the current-dependent trigger characteristic curve (MM 1  or MM 2 ) associated with the consumer  11 ,  12 . The present trigger value is determined computationally by the control unit, which has already been mentioned but is not illustrated, based on the actual current and, for example, the computation rule of the current-dependent trigger characteristic curve that is stored in a memory (step S 1  of the flowchart in  FIG. 4 ). In a next step (step S 2  of the flowchart in  FIG. 4 ), the presently ascertained trigger value is compared with a previously stipulated threshold value. The previously stipulated threshold value is referred to as a trigger discriminant and is stored in a memory of the control unit. The threshold value can be prescribed for the consumer under consideration in advance by tests or by the manufacturer. In a step S 3 , the present trigger value is compared with the previously stipulated threshold value (step S 3  in  FIG. 4 ). The overcurrent protection device is then triggered depending on the result of the comparison, wherein triggering is understood to mean turning off the controllable switching element  15  (step S 4  in  FIG. 4 ). 
     The current Ill, which is presently ascertained as the actual current by the current measurement device, is taken into consideration together with a first or a second factor, different from the first, in the trigger characteristic curve, depending on the current direction. Taking the current direction into consideration permits cooling effects, for example. As a result, there is no static triggering of the overcurrent protection device, as is the case, for example, in conventional safety fuses, but instead there is an adapted overcurrent triggering depending on the operating situation. 
     The advantage of the described procedure resides in a multiplicity of parameters being able to be adapted initially upon start-up of the overcurrent protection device and/or the consumer in the DC grid  1  and/or also at runtime. For example, the first and/or the second factor may be able to be parameterized or may be parameterized depending on the consumer that is to be protected. As an alternative or in addition, the first or the second factor may be able to be parameterized or may be parameterized depending on the profile of the trigger characteristic curve (MM 1  or MM 2 ). As an alternative or in addition, the previously stipulated threshold value may be able to be parameterized or may be parameterized depending on the consumer that is to be protected. This enables the overcurrent protection device to be matched precisely to the consumer  11 ,  12  associated therewith. Through the different evaluation of the current direction, it is not only possible to save on device variance, but it is also possible to realize a selectivity desired by the customer. This means that only the protection apparatus situated closest to the fault is triggered and disconnects the fault. 
     In order to be able to perform the weighting of the current in a manner dependent on the current direction when ascertaining the present trigger value, the current measurement device  16  has to be set up to detect the sign, that is to say the direction, of the current flowing through the device. This can be brought about, for example, by way of a current measurement device that comprises a sensor based on the Hall principle. A highly integrated Hall sensor of this type is described in EP 2 619 595 B1, the entire contents of which are hereby incorporated herein by reference, for example. 
     The controllable switching element  15  and the current measurement device  16  are preferably designed as a modular unit, as is illustrated in the drawings. However, this is not compulsory. 
       FIG. 2  shows a schematic illustration of an example DC grid  1 , to which a load assembly having by way of example two different consumers  11 ,  12  and  13 ,  14 , respectively is connected. The full ensemble composed of consumers  11 ,  12  and  13 ,  14 , respectively, and the overcurrent protection devices  11 S and  13 S, respectively, associated with the consumers is referred to in the present case as load assembly  10 . As can readily be seen in the diagrammatic illustration, the consumers  13 ,  14  are an inverter  13  and a motor  14  supplied thereby. The motors  12 ,  14  may be motors with greatly different rated powers, for example. 
     Each of the consumers  11 ,  12  and  13 ,  14 , respectively, is connected to the busbar  10 V via the respectively associated overcurrent protection device  11 S,  13 S. A further overcurrent protection device  10 S is also provided, which connects the busbar  10 V to the battery  5 . The construction of all of the overcurrent protection devices  10 S,  11 S and  13 S corresponds to the construction as has been described in connection with  FIG. 1 . Another explanation is therefore omitted. 
     In contrast to the preceding example embodiment, the detection values SI 11 , SI 12  and SI 10  provided by the respective current measurement devices  16 ,  18 ,  26  of the respective overcurrent protection devices  11 S,  13 S,  10 S are transmitted to a central computation unit  20  of the DC grid for the purpose of processing. In this example embodiment, the control unit  20  evaluates all of the detection values and carries out the method described in connection with  FIG. 1  for each consumer  11 ,  12  and  13 ,  14 , respectively, and for the load assembly  10  as a whole, wherein, for each of the consumers  11 ,  12  and  13 ,  14 , respectively, and the load assembly  10 , the respectively associated (identical or different) current-dependent trigger characteristic curve and respective previously stipulated (identical or different) threshold values and (identical or different) first and second factors are processed. 
     In the event of an overcurrent being determined in one of the branches, the relevant controllable switching element  15  and  16 , respectively, or  25  can then be turned off by the control unit  20 . For reasons of clarity, only one control signal STS for driving the controllable switching element  25  of the overcurrent protection device  10 S is illustrated. 
     The respective detection values SI 11 , SI 12  and SI 10  are provided at inputs  21 ,  23 ,  24  of the control unit  20 . The control signal STS for the controllable switching element  25  of the overcurrent protection device  10 S is provided to an output  22  of the control unit  20 . It is understood that corresponding outputs at which corresponding control signals are provided are also provided at the control unit  20  for the respective controllable switching elements  15 ,  17  of the overcurrent protection devices  11 S,  13 S. 
     Central processing as illustrated in  FIG. 2  for carrying out the method according to the invention is purely example. The method described in connection with  FIG. 1  could likewise also be carried out in a respective computation unit of each overcurrent protection device  11 S,  13 S,  10 S. A combination of different task distributions is also conceivable. 
     The provision of a central control unit facilitates the parameterization of a multiplicity of different overcurrent protection devices and consumers.