Reliable Fault Identification and Fault Location in the Load Area of a DC Power Grid

Abstract

The present invention relates to a load area (1) having an electronic switch (2), a DC bus (3), an interface (30) for supplying electrical energy to the load area (1), and at least two electrical devices (4), wherein the electronic switch (2) is arranged between the interface (30) and the DC bus (3), and wherein the electrical devices (4) are each electrically connected in parallel with the DC bus (3). In order to improve fault recognition and fault location in the load area (1), it is proposed that a fuse device (5) be arranged between the DC bus (3) and the corresponding electrical device (4), and a voltage sensor (7) is arranged to detect the voltage (u Sx ) applied to the fuse device (5). The present invention also relates to a DC power grid (10) having such a load area (1) and at least one power source (6), wherein the power source (6) is connected to the interface (30) of the load area (1). The present invention also relates to a method for operating such a load area (1) or such a DC power grid (10), wherein a faulty device of the electrical device (4) is determined based on the voltage (u Sx ) applied to the fuse device (5), that is, the voltage (u Sx ) on the fuse device (5) exceeds a preset boundary value.

Description

Field of the Invention

[0001] The present invention relates to a load area having an electronic switch, a DC bus, and at least two electrical devices, wherein the electronic switch is arranged to disconnect the DC bus from a power supply connectable to the load area, and wherein the electrical devices are each electrically connected to the DC bus. The present invention also relates to a DC power grid connected to such a load area and a power supply, wherein the power supply is connected to the load area such that electrical devices can be supplied with electrical energy from the power supply. The present invention also relates to a method for operating such a load area or such a DC power grid. Background Art

[0002] Today, the power grid is no longer constructed solely as an AC voltage grid. The power grid is generally always implemented as a DC voltage grid, also referred to as a DC power grid. Here, different electrical devices are arranged in parallel at the DC bus. The DC bus is at least two electrical conductors between which a DC voltage is present. Subsequently, the DC voltage supplies electrical energy to the electrical devices arranged in parallel. The electrical devices can be electrical appliances or energy storage devices. Here, the electrical appliance can also be a feedback electrical appliance that can feed electrical energy into the DC bus. The stored energy can be a charged capacitor or a coil through which current flows. The feedback of the kinetic energy or rotational energy of a drive system is also possible. Such a drive system can also be described as an electrical device.

[0003] Here, generally, multiple electrical devices are combined into a so-called load area. The electronic switch is located at the input of one such load area. The load area can be disconnected from one or more power supplies, especially voltage sources, that supply electrical energy to the load area by means of these electronic switches. This disconnection can occur, for example, in the event of a fault, such as a short circuit, in order to protect the electrical appliances in the load area or other components of the DC power grid outside the load area. Thereby, the reaction of the fault is reliably prevented on exactly the other load areas of the DC power grid. In particular, the electronic switch can quickly and reliably identify a short circuit in the load area by means of its control or logic circuit, and the load area can be separated from the power supply to protect the DC power grid. Here, the electronic switch interrupts the current, the so-called network current, which flows from the power supply into the load area. Subsequently, only the sum of the currents from adjacent, parallel electrical devices flows into the fault location.

[0004] By applying an electronic switch, a quick separation from the power supply without arcing can be achieved. This enables reliable operation, even in low-inductance situations with a high current rise rate, such as in the event of a short circuit. Since electronic switches are relatively expensive, they are not used at each electrical device for protection, but only upstream of the parallel circuit of the multiple devices forming the load area.

[0005] The influence of a fault on the corresponding load area can be limited by means of an electronic switch. Summary of the Invention

[0006] The object underlying the present invention is to improve the fault identification and fault location, for example in the load area of a DC grid in the event of a short circuit.

[0007] This object is achieved by a load area having an electronic switch, a DC bus, and at least two electrical devices, wherein the electronic switch is arranged such that the DC bus can be separated from the power supply connected to the load area, wherein the electrical devices are each electrically connected to the DC bus, wherein a fuse device is arranged between the DC bus and the respective electrical device, and wherein a voltage sensor is arranged to be able to detect the voltage across the fuse device. This object is particularly achieved by a load area having an electronic switch, a DC bus, an interface for supplying electrical energy to the load area, and at least two electrical devices, wherein the electronic switch is arranged between the interface and the DC bus, wherein the electrical devices are each electrically connected in parallel to the DC bus, wherein a fuse device is arranged between the DC bus and the respective electrical device, and wherein a voltage sensor is arranged to be able to detect the voltage applied across the fuse device. This object is also achieved by a DC grid having such a load area and at least one power supply, wherein the power supply is connected to the interface of the load area, in particular connected to the load area such that electrical devices can be supplied with electrical energy from the power supply and the electrical connection between the power supply and the DC grid can be disconnected by means of the electronic switch. This object is also achieved by a method for operating such a load area or such a DC grid, wherein a faulty device of the electrical devices is derived based on the voltage across the fuse device by the voltage across the fuse device exceeding a preset threshold value.

[0008] Other advantageous embodiments of the present invention are given in the individual embodiments.

[0009] The present invention is based on the knowledge that a faulty device in the electrical devices can be identified and / or derived therefrom, namely by measuring the respective voltage across the fuse device of the load area with the aid of a corresponding voltage sensor. Electrical devices are also commonly referred to as electrical appliances or loads. The electrical appliance or load can also be a feed-in one. The identification of a faulty device within the load area is also referred to as fault location.

[0010] The load area is referred to as an arrangement having a plurality, namely at least two, electrical devices, which are supplied with electrical energy via a DC bus and an electronic switch. Here, the DC bus and the electronic switch are part of the respective load area. The electrical devices of the load area can be separated from an electronic switch of one power supply or multiple power supplies together.

[0011] As soon as the safety device is triggered, i.e., the connection conducting between the interfaces of the safety device is disconnected, a faulty device can be identified in a simple manner, because the faulty device is an electrical device connected to the DC bus via the triggered safety device. However, a problem arises in that when a short circuit occurs in the electrical device, the safety device of the electrical device may not trigger quickly enough, but the electronic switch in the load area quickly interrupts the connection to the power supply, especially to the voltage source, so that the energy required to trigger the safety device is no longer available. In this case, it is not possible to identify which electrical device in the load area has a fault based on the state of the safety device.

[0012] Therefore, it can be regarded as an advantage that a fault can also be quickly identified before the safety device is triggered, so that it is no longer necessary to trigger the safety device, but other protection measures such as opening the electronic switch can be used. Since the safety device is not triggered, it is difficult to determine the faulty device. However, by applying the method according to the present invention, the faulty device can also be reliably identified in this case.

[0013] However, according to the present invention, the faulty device can be determined based on the voltage measured by the voltage sensor on the safety device. If there is a fault in the electrical device and the electronic switch disconnects the power supply connection, only the energy exchange can still take place between the electrical devices in the load area. Here, considering the positive potential of the DC bus, the current flows from the faultless device to the faulty device. The direction of the current flow can also be identified by the polarity of the voltage according to the voltage measured on the safety device through the safety device. Therefore, the faulty device is subsequently identified, because the faulty device causes the voltage on the safety device, which is generated according to the current flowing through the resistance of the safety device. It can be assumed therefrom that these electrical devices generating energy are defect-free.

[0014] The safety device is mostly arranged in the connection between the electrical device and the positive potential of the DC bus. Similarly, alternatively or additionally, it is feasible that the safety device or other additional safety devices are arranged in the connection to the negative potential of the DC bus. In this case, the current flows out of the faulty device.

[0015] Therefore, in case of a fault, especially after the electronic switch has been opened due to the fault, the faulty device can be determined with the aid of a voltage sensor that measures the voltage on the safety device respectively. This can be achieved in a simple manner, for example, based on the knowledge of the polarity of the voltage and thus the direction of the current flow.

[0016] The resistance value of an individual fuse is subject to high variability. Therefore, it is also difficult to correlate the measured voltage with the current value. It has been shown, however, that the polarity of the voltage provides sufficient information about which electrical device has failed for this method. Therefore, the fault location can be reliably determined independent of the variability of the resistance value.

[0017] Alternatively or additionally, it is also feasible to consider the voltage value of the measured value of the corresponding voltage sensor for determining the faulty device. Here, it can be assumed that the current in the faulty device exhibits a high value due to the fault (e.g., a short circuit), in particular a high value that differs from the current occurring during operation by at least one order of magnitude and / or has a high voltage change. The correspondingly high current value and the corresponding high rate of change of the current can be reliably identified in the voltage at the corresponding fuse by means of the voltage sensor. The relatively inaccurate interconnection between the current intensity derived from the large variability of the resistance value of the fuse and the measured voltage does not interfere here because only the fault current has to be distinguished from the current occurring during operation. It has been shown that this can also be reliably achieved in the case of the corresponding variability of the resistance value of the fuse.

[0018] Particularly advantageously, the resistance of the fuse increases as the temperature rises. The fault current represents a particularly high current and quickly causes the fuse to heat up. Therefore, this also increases the voltage drop across the fuse in the event of a fault. The fault current is at least significantly greater than the current occurring during normal operation. Therefore, the fault current produces an unduly high voltage drop across the fuse due to the heating up of the fuse. Therefore, the fault current can be detected particularly reliably.

[0019] It is also particularly advantageous in this application that the use of a current transformer can be dispensed with. The fault can also be reliably located in one of the electrical devices without a current transformer.

[0020] Here, the preset boundary value can also be correlated with the sign according to the characteristics of the electrical device (i.e., for example, in the case of a regenerative electrical device). This means that the triggering of the switch has different boundary values in the case of the first voltage direction than in the case of the opposite polarity of the first voltage direction. Therefore, protective measures are taken by opening the switch according to the operating state of the electrical device.

[0021] In an advantageous design of the present invention, the connection between the DC bus and the corresponding electrical device is implemented without a converter. Without a converter means that no converter is provided in the connection between the DC bus and the corresponding electrical device. Since the converter can be dispensed with for fault identification or localization, the individual branches of the DC bus can be implemented particularly cost-effectively because the converter is no longer required, where the electrical devices are connected at the individual buses. In addition, no losses are generated by the converter either, such as those generated when using a measuring shunt. This converterless arrangement enables the load area to be particularly cost-effective and low-loss. Therefore, a particularly economical solution with high efficiency is proposed.

[0022] In another advantageous design of the present invention, the electrical device with the highest voltage measured by the voltage sensor is determined as the faulty device. In addition to considering the polarity of the voltage, it has proven advantageous to also consider the voltage value. It can be concluded that a faultless device does not supply or feedback energy to a faulty device. This is the case, for example, if the faultless device does not have an energy storage. Thus, for example, a purely ohmic electrical appliance (such as a heater) does not feed energy into a faulty electrical appliance. Similarly, an inductive electrical appliance also receives energy from the DC bus when another electrical device in the load area fails. Therefore, a large number of electrical appliances that do not supply energy to a faulty electrical appliance can be considered. This is illustrated, for example, in the example of inductive electrical devices, which can continue to receive energy from the remaining faultless electrical appliances. In this case, it is advantageous to evaluate not only the polarity of the measured voltage but also the voltage value. Here, it can be assumed that a fault exists in the electrical device if the highest voltage has been measured or is measured by the voltage sensor at the fuse or in the connection of the electrical device to the DC bus. Therefore, the electrical device with the highest voltage measured by the voltage sensor is the faulty device.

[0023] Here, the voltage of the voltage sensor is positive if the branch with the associated electrical device receives electrical energy. Correspondingly, the voltage at the voltage sensor is negative if the corresponding branch and its electrical appliance release energy to the DC bus.

[0024] In another advantageous design of the present invention, a faulty device is identified thereby, i.e., the voltage measured by the voltage sensor exceeds a preset boundary value. Regardless of this, whether the electronic switch is closed or the electronic switch has opened, for example, due to a fault in the load area, a fault can be identified and located in the electrical device in the load area, i.e., by comparing the voltage measured by the voltage sensor with the preset boundary value. If the voltage does not exceed the boundary value, it can be assumed thereby that a fault has occurred in the relevant electrical device. Particularly advantageously, the boundary value is at least one order of magnitude greater than the voltage, and the voltage is obtained by the fuse device when current occurs during operation regardless of the resistance of the fuse device. In the context, regardless of the resistance value means determining the boundary value within the worst-case range of the resistance of the fuse device. As long as the electronic switch is still closed, exceeding the boundary value can also be used as a criterion for opening the electronic switch.

[0025] Contrary to triggering the fuse device, it is only necessary for the measured voltage to briefly exceed the boundary value so that not only can the fault be reliably identified and located, but also a protection reaction, such as opening the electronic switch, can be triggered.

[0026] Also herein, if the branch line with the relevant electrical device absorbs energy, the voltage of the voltage sensor is positive. Correspondingly, if the corresponding branch line and its electrical appliance release energy to the DC bus, the voltage at the voltage sensor is negative, that is, if the electric energy flowing in the branch line causes a negative voltage on the fuse device, a faulty device is identified when the voltage measured by the voltage sensor does not exceed the preset negative boundary value.

[0027] In another advantageous design of the present invention, a faulty device is determined when or after a fault occurs in the load area, wherein the peak value of the voltage applied to the fuse device is respectively detected and stored as a data value and considered for determining the faulty device. Herein, in the corresponding load area, the peak value of the voltage applied to the fuse device can be respectively detected and stored as a data value particularly by means of a peak rectifier provided between the fuse device and the voltage sensor. For determining the faulty device, the peak value of the voltage that appears is decisive. It can be identified there that the corresponding peak value of the current must also exist in the corresponding electrical device. Therefore, instead of the measured value, the corresponding peak value can be considered for determining the corresponding faulty device. The corresponding highest peak value of all measured voltages can also be considered using this peak value to determine the faulty device. The data value can also be compared with the preset boundary value, and a fault in the load area is identified when the boundary value is exceeded. The fault exists in the electrical device when the voltage at the fuse device in the branch line of the electrical device exceeds the preset boundary value.

[0028] Storage can be accomplished, for example, by storing the voltage in data processing. Alternatively, it is feasible to store the voltage value by means of a peak rectifier having a capacitor at the output. Here, the capacitor holds the voltage of the peak that appears at its two interfaces. Particularly advantageously, in this design, it is also possible to identify a faulty device in a particularly simple manner after a fault occurs. This is because the peak is stored accordingly. As described above, this storage can be achieved in a similar manner by the voltage at the capacitor of the peak rectifier or within the data processing, where the corresponding voltage value is stored as a data value.

[0029] Advantageously, in this design, the method for operating the load area does not have to be continuously implemented, but only when a fault exists in the load area. This saves computing time and computing power in the control or regulation of the load area.

[0030] In another advantageous design of the present invention, the data value stored when the voltage applied to the fuse device is negative is decreased, especially reset. In the corresponding load area, the corresponding stored data value can be decreased, especially reset, when a negative voltage appears on the fuse device. Then, if the corresponding electrical appliance releases electrical energy, the negative voltage applied to the fuse device is decisive. Therefore, it is assumed that there is no fault at this electrical appliance. Thus, it has been proven advantageous to consider the state of the detected negative voltage, that is, the stored data value of the peak is decreased or even completely reset, that is, set to zero. This can be achieved by discharging the capacitor at the output of the peak rectifier or completely discharging it for reset. Alternatively, this can also be achieved by rewriting the stored data value with a new smaller value or a zero value in the data processing. The difference in the data value stored in the corresponding voltage sensor becomes larger in this way, because in the case of a fault (such as a short circuit), a negative voltage appears at the feedback, fault-free device. However, a positive voltage appears in the faulty device. This positive voltage can be identified particularly simply and reliably by this embodiment. Therefore, the reliability of fault location is further improved.

[0031] In another advantageous design of the present invention, the positive peak is detected and stored as a stored data value, wherein detecting and storing another data value corresponds to the negative peak of the voltage applied to the protection device. In this design, the corresponding reduction or reset of the data value can be dispensed with. Here, for each voltage sensor, the maximum positive value is detected and stored as the positive peak. In addition, the minimum negative value is detected and stored as another data value. This other data value is referred to as the negative peak. Thus, for each electrical appliance, it is possible to simply identify whether the electrical appliance absorbs electrical energy or feeds electrical energy into the DC bus at the time of a fault. It is possible to thereby identify which of the two peaks, the positive peak or the negative peak, is larger. If the positive peak is larger, it can be assumed therefrom that electrical energy from the DC bus is received. However, if the negative peak is larger, it can be assumed therefrom that electrical energy is released in the direction of the DC bus. Thus, in addition to the criterion for obtaining the maximum positive peak of the faulty device, another criterion is available. Here, an electrical device in which the positive peak (i.e., the stored data value) is greater than the negative peak (i.e., the other data value) is first considered to be an electrical device that may be faulty. Subsequently, it can be tested which of the possible electrical devices detected the highest positive peak. By means of this dual criterion, faulty devices can be identified particularly reliably.

[0032] In another advantageous design of the present invention, the time point at which the stored data value and / or the stored other data value appears is detected and stored, wherein the faulty device is identified based on the time point of the stored data. By knowing the time point at which the peak appears, the state of the electrical device in the load area at the time of the fault can be inferred in a simple manner. The time point at which the fault occurs is known by the maximum voltage value, which is measured by one of the voltage sensors and stored as a data value. The state of all electrical devices can only be determined based on the data values or other data values stored at the time of the fault or its immediate time environment, for example, in the order of magnitude of up to 10 ms before and after. Here, the time correlation between the positive peak and the negative peak is maintained in each evaluation unit, so that it is possible to identify which value appears first afterwards. By means of the additional information, in the case of a wobbling process in the DC section with a large power spectrum expansion at the electrical appliance, misunderstandings regarding fault analysis can be excluded. The reliability in obtaining the fault and the faulty device is thereby further improved.

[0033] In another advantageous design of the present invention, a method is started when a fault occurs in the load area. Only if a fault occurs in the load area, the configuration of the load area with an electronic switch and a plurality of, at least two existing electrical devices allows the method for operating the load area to be started. Here, the electronic switch with a corresponding evaluation device or regulation device or control device can be designed to identify a fault in the load area and react accordingly by opening the electronic switch. The determination of the faulty device among the electrical devices in the load area can subsequently be carried out by the method for operating the load area. As long as the measured value of the voltage sensor is not stored, the method should be started as soon as possible when a fault occurs in the load area so that the peak value is still available for the method. However, the voltage that appears after the electronic switch is opened can also be considered for determining the faulty device. As described above, the reliable determination of the faulty device can also be carried out using the voltage value and / or data value. In particular, by storing the corresponding measured values of the voltage sensor, the determination of the faulty device can be postponed to almost any time point after the fault occurs and after the electronic switch is opened. This is because the information required for determining the faulty device is continuously available, or at least available to the corresponding evaluation unit for a sufficient length of time. In this method, the evaluation is started only after or when a fault occurs in the load area. Advantageously, in this method, a large computing power is not required for normal operation. Only when a fault occurs, the corresponding computing power and processing power for the measured values of the voltage sensor are required. Continuous monitoring of voltage or current can be dispensed with in the load area. Therefore, the method for determining the faulty device in the electrical device is particularly simple and resource-saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Hereinafter, the present invention will be further described and explained based on the embodiments shown in the drawings, which show:

[0035] Figure 1 A DC power grid showing a load area; and

[0036] Figures 2 to 5 An embodiment of an advantageous peak rectifier is shown. DETAILED DESCRIPTION OF THE INVENTION

[0037] Figure 1 A DC power grid 10 with a load area 1 and a power supply 6 is shown. Here, the power supply 6 can be implemented, for example, as a voltage source. The power supply 6 is connected to the interface 30 of the load area 1 and feeds electrical energy to the electrical devices 4 in the load area 1. For this purpose, a DC bus 3 is provided in the load area 1, and the DC bus leads to the voltage at the electrical devices 4. Here, the electrical devices 4 are connected to the DC bus 3 via an electrical connection. In this electrical connection, a fuse device 5 is respectively provided for each electrical device 4 in the load area 1. The voltage u on the fuse device 5 SxIt is detected by the voltage sensor 7. The detected value of the voltage is transmitted from the voltage sensor 7 to the evaluation unit 9 via the corresponding fuse device 5. For this case, the number of electrical devices 4 existing in the load area is n, so the total number of fuse devices 5 is also n and thus the number of existing voltage sensors 7 is also n. The label u of the voltage Sx is the voltage at the x-th fuse device 5, where x thus takes values between 1 and n. In this embodiment, the electrical device 4 represents an inverter 12, and each inverter has an intermediate circuit capacitor 11. Alternatively, the electrical device can also be each type of electrical appliance and / or energy storage.

[0038] If a short circuit occurs in or at the electrical device 4, the intermediate circuit capacitors 11 of the remaining electrical devices 4 are also fed into this short circuit. In addition, additional energy from a single inverter 12 can also be fed into this short circuit. To separate the load area 1 from the power supply 6, the load area 1 has an electronic switch 2, which is arranged between the interface 30 of the load area and the DC bus 3. With this electronic switch 2, the energy supply from the power supply 6 to the electrical devices 4 in the load area 1 can be quickly interrupted.

[0039] If a fault occurs in the first electrical device 41, for example a short circuit, this causes the triggering of the fuse device 5 in the corresponding connection between the first electrical device 41 and the DC bus 3 due to the current from the power supply 6 and the other electrical devices 4. By the triggering of the corresponding fuse device 5, the fault location can be clearly located at the first electrical device 41.

[0040] However, if a protection device (not further described here) in the DC grid 10 or the load area 1 identifies a fault within this load area 1, the electronic switch 2 can be opened as a reaction, and this is already before the fuse device 5 is triggered. In this case, after the electronic switch 2 is opened, the electrical energy from the power supply 6 is no longer fed into the short circuit of the first electrical device 41. Only the remaining electrical devices 4 feed energy (for example from the intermediate circuit capacitor 11 and / or the inverter 12) into the short circuit of the first electrical device 41. Here, the corresponding current through the fuse device 5 can be small, such that the fuse device 5 is no longer triggered but remains conducting. In this case, the faulty first electrical device can no longer be identified based on the state of the fuse device 5. Now, in this case, a current sensor is usually arranged in series with the fuse device in order to be able to detect the current generated, for example, by the short circuit.

[0041] However, also in order to be able to achieve fault location without a current sensor (i.e., without current), the voltage u dropping across the fuse device 5 is measured for each individual fuse device 5 in the load area 1 SxHere, the polarity of the measurement is implemented by the voltage sensor 7 such that the electrical energy flowing in the electrical device 4 is detected as the anode voltage. Among them, the electrical device 4 with the highest measured voltage u Sx is identified as a faulty electrical device. It can be assumed therefrom that there is a fault, especially a short circuit, in the device. Since the fuse device 5 is required to be used as the type of measurement shunt of the current sensor in any case, no additional components are required in the power path. Contrary to the measurement shunt of the current sensor, the resistance value of the fuse device 5 is inaccurate and is affected by a considerable variability between different fuse devices. However, it is feasible that even when the resistance of the fuse device 5 still has these large variations / inaccuracies, the operating current can be distinguished from the fault current in the event of a fault. Generally, high requirements are imposed on the measurement shunt so that fault identification and fault location can be accurately implemented accordingly. It has been proven that it is not necessary to meet the general requirements for the resistance of the fuse device 5 in order to reliably distinguish the operating current from the fault current. Therefore, no additional losses are generated in the feeder line between the DC grid 3 and the electrical device 4. The evaluation unit 9 can determine which of the electrical devices 4 is faulty based on the values transmitted by the voltage sensor 7.

[0042] If a fault has been identified in the load area 1, for example, based on overcurrent, and the electronic switch 2 has been opened, then by comparing the voltages u Sx dropped across the corresponding fuse devices 5 with each other, the fault can be accurately located inside the load area 1. In the connection between the electrical device and the DC bus 3, the electrical device with the highest voltage u Sx dropped across the fuse device 5 is identified as a faulty device. Alternatively or additionally, it is feasible that the faulty device is identified thereby, that is, the voltage u Sx dropped across the fuse device 5 exceeds a preset boundary value. By exceeding the boundary value, it can be assumed that there is a fault in the device and thus the fault exists in the load area 1. The evaluation unit 9 also optionally uses the identification of the fault to open, as shown by the dashed line in Figure 1 .

[0043] In addition, it has been proven advantageous to detect and store the individual voltages u Sx dropped across the corresponding fuse devices 5. It has also been proven advantageous to alternatively or additionally detect and store the peak value of the voltage u Sx across the fuse device 5. Here, the peak value can be determined and stored, for example, by a peak rectifier 8 (not shown here) or within data processing (such as the evaluation unit 9). In the case of the peak rectifier 8, the storage can be achieved by continuously applying the peak value across the capacitor 15. This will be described in the following Figures 2 to 5is further described and explained below. Since the peak value is known, if there is no short-circuit current or only a relatively small short-circuit current flows, the fault can still be located by comparing the peak value of the voltage u Sx of the peak value.

[0044] Figure 2 shows an embodiment of the peak rectifier 8. With the peak rectifier, the voltage u applied to the fuse device 5 can be generated at the rectifier capacitor 15 Sx . Once the voltage u Sx on the fuse device 5 is greater than the voltage at the rectifier capacitor 15, the rectifier capacitor 15 is charged via the diode 16 until the voltage at the rectifier capacitor 15 also reaches the voltage u Sx on the fuse device 5. Sx If the voltage u Sx on the fuse device 5 drops again, the discharge current of the rectifier capacitor 15 is prevented by the diode 16 and the peak value of the voltage u Sx applied to the fuse device 5 is held at the rectifier capacitor 15. This corresponds to the storage of the peak value of the voltage u

[0045] applied to the fuse device 5. The voltage sensor 7 can then record the peak value stored in this way and transmit it to an evaluation unit 9 (not shown here). Subsequently, the faulty electrical device can be determined in the evaluation unit 9.

[0046] Figure 3 shows another embodiment of the peak rectifier 8. To avoid repetition, reference is made to the description in Figure 2 and the reference numerals introduced there. This embodiment also has a switch 17 controlled by the polarity detection device 20. If the voltage u Sx applied to the fuse device 5 is negative, the polarity detection device 20 recognizes this situation and closes the switch 17. Thus, the rectifier capacitor 15 is short-circuited and discharged. Here, the value of the voltage at the rectifier capacitor is zero. Therefore, the peak value applied and stored at the rectifier capacitor is reset. Alternatively, a resistor can be arranged in series with the switch 17. Subsequently, the capacitor discharges continuously with this arrangement and not suddenly. This corresponds to a decrease in the stored value.

[0047] Once the voltage u Sx applied to the fuse device 5 takes a positive value, the switch 15 is opened and the voltage u SxThe peak value is applied again at the rectifier capacitor, and this peak value is generated starting from the opening of switch 17.

[0048] Switch 17 can be part of a contactor, where switch 17 is the switching contact of the contactor and the coil of the contactor is part of the polarity detection device 20. The diode of the polarity detection device 20 ensures that once the voltage u applied to the protection device 5 Sx is negative, a voltage is applied at the coil of the contactor. This voltage causes the contactor to operate when switch 17 is closed.

[0049] Figure 4 Another embodiment of the peak rectifier 8 is shown. To avoid repetition, reference is made to the description in Figure 2 and Figure 3 and the reference numerals introduced therein. This embodiment also has a switch 17 and a polarity detection device 20. Here, switch 17 is arranged such that when the voltage u applied to the fuse device 5 Sx is negative, the voltage at the rectifier capacitor 15 decreases and does not discharge suddenly. Here, a resistor 19 is arranged in series with switch 17. Here, the magnitude of the resistance value of resistor 19 determines the rate at which the voltage at the rectifier capacitor 15 decreases. As the voltage at the rectifier capacitor 15 decreases, the stored data value of the peak decreases.

[0050] By resetting or reducing the stored data value of the peak, a faulty electrical device can be very easily identified. This is because a non-faulty electrical device often releases energy when a fault occurs in the load area, and thus a negative voltage is generated at the fuse device. Therefore, a faulty device that has a positive voltage applied at least at the moment of the fault occurrence can be more simply and reliably determined, because a normally operating electrical device has a negative voltage u Sx at least partially at its assigned fuse device 5, and thereby reduces the stored data value.

[0051] Figure 5 Another embodiment of the peak rectifier 8 is shown. To avoid repetition, reference is made to the description in Figures 2 to 4 and the reference numerals introduced therein. This embodiment no longer has a switch 17 and a polarity detection device 20. In this peak rectifier 8, by means of a diode 16, similar to Figures 2 to 4The embodiments in [description] determine and store the positive peak value. Additionally, the negative peak value is determined by means of another diode 18 and stored as a voltage at the second rectifier capacitor 15. The negative peak value is defined as the maximum value of the negative voltage numerically. The positive peak value and the negative peak value can be detected by the voltage detection device 7 respectively and fed to the evaluation unit 9. The knowledge of the positive peak value and the negative peak value can further improve the reliability when determining a faulty electrical device, because in addition to comparing the data values of different electrical devices, there are positive peak values and negative peak values for each electrical device. Here, the positive peak value and the negative peak value can be compared with each other as other criteria for determining a faulty electrical device.

[0052] In summary, the present invention relates to a load area having an electronic switch, a DC bus, and at least two electrical devices, wherein the electronic switch is arranged to disconnect the DC bus from a power supply that can be connected to the load area, and wherein the electrical devices are electrically connected to the DC bus respectively. To improve fault identification in the load area, it is proposed to provide a fuse device between the DC bus and the corresponding electrical device, and a voltage sensor is arranged to be able to detect the voltage applied to the fuse device. The present invention also relates to a DC power grid connected to such a load area and at least one power supply, wherein the power supply is connected to the load area such that electrical devices can be supplied with electrical energy from the power supply, and wherein the electrical connection between the power supply and the DC bus can be interrupted by means of the electronic switch. The present invention also relates to a method for operating such a load area or such a DC power grid, wherein the faulty device of the electrical device is determined according to the voltage applied to the fuse device.

[0053] In other words, in summary, the present invention relates to a load area having an electronic switch, a DC bus, an interface for supplying electrical energy to the load area, and at least two electrical devices, wherein the electronic switch is arranged between the interface and the DC bus, and wherein the electrical devices are electrically connected in parallel to the DC bus respectively. To improve fault identification and fault location in the load area, it is proposed to provide a fuse device between the DC bus and the corresponding electrical device, and a voltage sensor is provided to detect the voltage applied to the fuse device. The present invention also relates to a DC power grid having such a load area and at least one power supply, wherein the power supply is connected to the interface of the load area. The present invention also relates to a method for operating such a load area or such a DC power grid, wherein the faulty device of the electrical device is obtained by determining that the voltage applied to the fuse device exceeds a preset boundary value according to the voltage applied to the fuse device.

Claims

1. A load area (1), having: - An electronic switch (2), - A DC bus (3), - An interface (30) for supplying electrical energy to the load area (1), - At least two electrical devices (4), - A protection device (5), - A voltage sensor (7), and - An evaluation unit (9), wherein, The electronic switch (2) is arranged between the interface (30) and the DC bus (3), wherein the electrical devices (4) are each electrically connected in parallel with the DC bus (3), and wherein the fuse device (5) is provided between the DC bus (3) and the corresponding electrical device (4), and wherein the voltage sensor (7) is arranged to detect the voltage (u Sx ) applied across the fuse device (5), and wherein the evaluation unit (9) is arranged to determine the faulty device based on the polarity of the voltage applied across the fuse device (5) measured by the voltage sensor (7).

2. The load area (1) according to claim 1, wherein, The connection between the DC bus (3) and the respective electrical device (4) is not equipped with an inverter.

3. The load area (1) according to claim 1 or 2, wherein, By means of a peak rectifier (8) provided between the fuse device (5) and the voltage sensor (7), the peak value of the voltage (u Sx ) applied to the fuse device (5) can be detected and stored as a stored data value, wherein when a negative value of the voltage (u Sx ) applied to the fuse device (5) appears, the stored data value can be reduced.

4. The load area (1) according to claim 1 or 2, wherein, By means of a peak rectifier (8) provided between the fuse device (5) and the voltage sensor (7), the peak value of the voltage (u Sx ) applied to the fuse device (5) can be detected and stored as a stored data value, wherein when a negative value of the voltage (u Sx ) applied to the fuse device (5) appears, the stored data value can be reset.

5. The load area (1) according to claim 3, wherein, It is capable of detecting and storing additional data values, wherein the stored data values are determined for detecting and storing positive peaks and the additional data values are determined for detecting and storing negative peaks.

6. A DC power grid (10), having the load area (1) according to any one of claims 1 to 5 and at least one power source (6), wherein, The power source (6) is connected to the interface (30) of the load area (1), and the power source is also connected to the load area (1) to be able to supply electrical energy from the power source (6) to the electrical device (4), and the electrical connection between the power source (6) and the DC bus (3) can be disconnected by means of the electronic switch (2).

7. A method for fault location in the load area (1) according to any one of claims 1 to 5 or in the DC power grid (10) according to claim 6, wherein, The corresponding voltage (u applied to the fuse device (5) is measured by means of the corresponding voltage sensor (7). Sx ), wherein a faulty device in the electrical equipment (4) is determined based on the polarity of the voltage (u Sx ) applied to the fuse device (5).

8. The method according to claim 7, wherein, A faulty device is identified by the voltage applied to the protection device (5) exceeding a preset boundary value.

9. The method according to claim 7, wherein, The voltages (u Sx ) dropping at the respective said protection device (5) are compared with each other, wherein the electrical device with the highest voltage connected to the DC bus, which is measured or has been measured at the protection device (5) by the voltage sensor (7), is determined as the faulty device.

10. The method according to claim 7, wherein, By separately detecting and storing the peak value of the voltage (u Sx ) applied to the fuse device (5) as a stored data value and determining a faulty device based on the stored data value, a faulty device is determined during or after a fault occurs in the load area (1).

11. The method according to claim 10, wherein, The highest peak value of all measured voltages is used to determine the faulty device, and the electrical device with the highest peak value connected to the DC bus measured or already measured by the voltage sensor (7) at the protection device (5) is determined as the faulty device.

12. The method according to claim 10, wherein, When the voltage (u Sx ) applied to the protection device (5) is negative, the stored data value is decreased.

13. The method according to claim 10, wherein, When the voltage (u Sx ) applied to the protection device (5) is negative, the stored data value is reset.

14. The method according to claim 10, wherein, Detect and store the positive peak as a stored data value, wherein additional data values are detected and stored, the additional data values corresponding respectively to the negative peaks of the voltage (u Sx ) applied to the fuse device (5).

15. The method according to claim 14, wherein, The time points when the stored data values and / or additional data values appear are detected and stored, and the faulty device is identified according to the time points of the stored data values and the additional data values.

16. The method according to claim 7, wherein, The method is started when there is a fault in the load area (1).

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