Procedure and arrangement for residual current monitoring

Abstract

The invention relates to a method for fault current monitoring of at least one part of a power grid having a plurality of different consumers, in which a current monitoring device is functionally connected and operated with the part of the power grid on the supply line supplying the outer, neutral and protective conductors to part of the power grid for distribution in such a way that it retrieves at least one usable signal supplied via at least one input for the purpose of knowing a total current defined by the sum of the currents of the outer and neutral conductors, the retrieval is repeated at least temporarily, in particular periodically, on the basis of the signal, the total current is determined for each repetition and is compared with a preferably adjustable threshold value, in particular indicating a dangerous tendency of the detected total current, if the threshold value is exceeded by the current monitoring device, a process for troubleshooting,in particular, a signaling of the exceedance, is initiated, it interacts adaptively with the power grid such that at least at one point in time, in particular during at least a first time interval, at least a portion of the properties of the power grid, in particular a history of the portion of the properties updated in the first time interval, is used at least as a basis for the threshold decision. Furthermore, the invention relates to a corresponding arrangement.

Description

[0001] The invention relates to a method for fault current monitoring according to the preamble of claim 1 and to an arrangement for fault current monitoring according to the preamble of claim 12.

[0002] The use of so-called residual current devices (RCDs) in electrical circuits, especially in domestic installations, is well known. Due to advancing international harmonization, a so-called "residual current device" (RCD) is increasingly replacing the older, colloquial terms "FI circuit breaker" or "FI switch," where the terms refer to a device in which the "F" stands for fault and the "I" for the symbol for electrical current. If the terms FI and RCD are used alone in this disclosure, they are equivalent, i.e., synonymous, especially with the term "RCD / FI."

[0003] It is also known that in a typical domestic electrical installation, RCDs are usually combined with multiple fuse circuits, each of which usually consists of at least one electrically operated device assigned to the fuse circuit. This results in the disadvantage that if a fault current is detected and the RCD is thus triggered, all fuse circuits downstream of the RCD are de-energized, even if only one device in this combined circuit is experiencing a problem.

[0004] Such a problem can have very unpleasant and expensive consequences in a home's electrical system, especially if it happens while you're away or at night. This applies not only to private households, of course, but also to larger-scale installations, such as factories and computer centers.

[0005] In Germany, in particular, there is a regulation that ensures that the maximum current that an RCD / FI safety switch can handle must never be exceeded in all new electrical installations, especially in apartments and houses. If this regulation is applied, for example, a 4-pole RCD / FI safety switch with 40A can monitor a maximum of two fuses per phase, i.e., six in total.

[0006] This regulation only partially solves this disadvantage, as it only reduces the maximum number of circuits that are unnecessarily switched off, because there is still the possibility that a fault in the 6 circuits will also switch off the other 5.

[0007] In principle, it is also possible to largely protect devices whose unnecessary shutdown could have serious consequences, such as freezers or electric heaters, from unnecessary shutdown by cleverly wiring the home's electrical system in such a way that shutdown is avoided. However, this is only possible to a limited extent or at great expense with existing installations.

[0008] One solution to this disadvantage, albeit one that is limited or only possible with considerable effort, is to use a combined fuse (i.e., a miniature circuit breaker, also known as a "miniature circuit breaker" MCB) with an RCD / FI fuse switch. This combination of a miniature circuit breaker (MCB) with a residual current device (RCB), known as a "residual current operated circuit breaker with overcurrent protection" (RCBO) (also known as FI-LS in Germany), can only be used if the circuits are individually introduced into the distribution board. However, this is predominantly only the case for large consumers such as washing machines, dryers, etc., so that in around 90% of cases, this individual introduction is not available.

[0009] Outside of household use, residual current monitoring is known in computer / server rooms for early fault current detection. This makes fault currents visible in real time to specialist personnel assigned to monitoring / maintenance of the server rooms and enables these specialist personnel to carry out targeted maintenance measures, as this residual current monitoring is provided individually for each server room, server cabinet or each server.

[0010] The object underlying the invention is therefore to provide a technical solution for residual current monitoring which overcomes the disadvantages of the prior art.

[0011] This object is achieved by the method for residual current monitoring having the features according to the preamble of claim 1, by its features, and by the arrangement for residual current monitoring having the features of the preamble of claim 12, by its characterizing features.

[0012] In the method according to the invention for monitoring the residual current of at least one part of a power grid having a plurality of different consumers, a current monitoring device is functionally connected and operated with the part of the power grid on the supply line supplying the external, neutral and protective conductors to the part of the power grid for distribution in such a way that a) it retrieves at least one usable signal supplied via at least one input for the purpose of knowing a total current defined by the sum of the currents of the phase and neutral conductors, b) the retrieval is repeated at least temporarily, in particular periodically, c) on the basis of the signal, the total current per repetition is determined and compared with a preferably adjustable threshold value, which indicates in particular a dangerous tendency of the total current detected, d) if the threshold value is exceeded by the current monitoring device, a process for troubleshooting, in particular a signalling of the exceedance, is started, (e) it interacts adaptively with the power grid in such a way that at least at one point in time, in particular during at least a first time interval, at least some of the properties of the power grid, in particular a history of the part of the properties updated in the first time interval, is used at least as a basis for the threshold decision.

[0013] The method according to the invention enables fault current monitoring, because the total current defined by the sum of the phase and neutral conductors corresponds to the fault current that would be given, i.e. measurable by measuring instruments, whereby the fault current monitoring according to the invention offers the possibility of triggering a problem treatment in good time by recording the current fault currents and comparing the threshold values ​​and by adapting it, which avoids switching off at problematic times.

[0014] The invention takes into account, among other things, that electrical installations are tested after completion using various measurement methods. These methods include measurements of low-ohm, insulation resistance, loop impedance, and RCD measurements, insulation testing, resistance measurements, etc. of the system. These measurements are performed only once after installation and before commissioning (in commercial systems), and thereafter only rarely, or depending on requirements. For example, in safety-critical systems such as oil platforms, this usually happens regularly.

[0015] This results in characteristic values ​​for the installed devices that prevail during normal operation. This includes, for example, the actual leakage current of a device, which does contribute to the measurable fault current but is not due to a fault, but rather occurs during normal operation. The invention takes into account that a dangerous tendency of the measurable fault current of the device, i.e. one that indicates an actual fault current attributable to a real fault, generally occurs when the value of the measurable fault current of the device deviates from a value of the measurable fault current during normal operation. For example, a cause due to a fault and thus a dangerous tendency within the meaning of the invention can be assumed if the measurable fault current of the device is greater than the leakage current during normal operation of the device, as it would be at the time of installation when there is no fault.

[0016] The method according to the invention is able to detect precisely these deviations from the time of installation and thus generate a warning signal at an early stage.

[0017] Due to the fact that it determines the total current, which is defined by the sum of the phase conductors and the neutral conductor, the invention takes into account that such a power grid usually has several devices which, for example, already contribute to a measurable fault current in the power grid through a leakage current in normal operation, because this fault current is determined by forming the total current, which will already be non-zero in normal operation due to the actual, i.e. measurable, leakage currents in normal operation.

[0018] "Early" means well before safety devices such as an RCD are triggered. Such a warning signal can trigger troubleshooting routines. A simple routine would be, for example, for the user to check whether any changes have been made to the power grid recently, so that, for example, there is no fault at all, but rather the addition of a new device has caused an additional leakage current during normal operation to change the total current. If there are no such harmless reasons, further steps would have to be taken to search for the source of the error. If, on the other hand, such a harmless reason is the cause of the alarm, i.e. it was a false positive signal, the invention also detects this because it takes into account a history of adapting the threshold value that would trigger a signal.In the example mentioned, the user could provide feedback to the system as a further troubleshooting action, indicating whether or not the alarm was a false alarm. Such feedback could also be used, for example, in connection with automatic adaptation options based on machine learning algorithms.

[0019] For example, in a further development, the invention could implement automatic adaptation, then, after a learning period, adapt the threshold more precisely, even allowing it to vary according to a time schedule, in order to also take into account the measurable fault currents during normal operation that occur at different times. For example, kitchen appliances, hair dryers, or other devices are used at certain times, thus driving the total current during normal operation into a higher range. This can significantly reduce false positive alarms.

[0020] The invention is therefore not statically limited to a one-time adaptation, particularly in conjunction with a test, for example, during installation, at a given time. Rather, step e) can be performed at least once according to the invention. Thus, the step according to feature e) can also be repeated at regular intervals, particularly to determine time-related deviations.

[0021] It is particularly advantageous in applications, such as households, where regular monitoring is not planned, but can also be used advantageously in areas where monitoring is performed more frequently, helping to avoid unnecessary shutdowns. The approach with signaling and / or feedback is transparent and easy to understand, so that a specialist, i.e., an electrician, only needs to be called in when there is no indication of a false positive alarm and a visual inspection of the power grid does not reveal any obvious sources of error.

[0022] The process can also be implemented cost-effectively and with little effort, as existing hardware can be used, for example as an additional feature of a smart meter or in the form of an extended RCD, and any additional hardware requirements can be met at low cost.

[0023] The arrangement according to the invention enables the implementation of the method according to the invention and / or its further developments and thus mutatis mutandis also the realization of the advantages of the method and / or its further developments.

[0024] Advantageous embodiments and further developments of the invention are specified by the subclaims.

[0025] According to an advantageous development of the method according to the invention, the current monitoring device is operated in such a way that it operates an input for each phase and neutral conductor, which is connected to one of these conductors in such a way that it generates suitable signals for a threshold comparison from the currents present at the inputs. Using suitable values ​​of the analog currents measured at the inputs, for example, converted analog-to-digital, the fault current can be determined from the difference between the sum of the currents on the phase conductors and the neutral conductor and fed into the threshold comparison.

[0026] Alternatively or additionally, the method according to the invention can be further developed such that the current monitoring device is operated in such a way that it operates an input to which a total current formed from the outer and neutral conductors is present, this total current being generated by an induction sensor connected upstream of the current monitoring device, which is operated in such a way that it is connected to all outer and neutral conductors in such a way that they all generate a contribution to the induction current of the sensor in such a way that the value of the resulting induction current corresponds to the value of the sum of the currents of the outer and neutral conductors and is output via an output for forwarding to the input of the current monitoring device.

[0027] In this way, an analogue computer is realized in a certain way, since the current induced by the neutral conductor has a different sign, i.e. flow direction, than the currents induced by the outer conductors and the induced total current at the induction sensor represents an analogue value of the total current, which can be fed to the input of the current monitoring device for threshold value comparison, for example after an analogue-to-digital conversion.

[0028] The method according to the invention can advantageously also be further developed such that the signals for generating the total current are recorded over a predetermined period of time, in particular 200 ms. This makes it possible, for example, to largely exclude false signals caused by short, pulse-like disturbances. The period can be selected according to legal and / or technical parameters, for example, the circuit to be protected. A value of around 200 ms, for example, is generally sufficient in German households to realize the benefits of the further development.

[0029] Preferably, the method according to the invention is advantageously further developed such that the current monitoring device is operated in such a way that it is capable of signaling when the threshold value is exceeded. This provides the simplest form and, at the same time, the basis for troubleshooting, since users or operators of the current monitoring device are thereby informed of a problem, and thus either an autonomous human and / or at least partially automated procedure for rectification can be carried out. A simple autonomously performed action could be, for example, the visualization and / or metrological testing of the consumers of the monitored circuit. This can be dimensioned such that it occurs before a critical fault current occurs and thus the necessary shutdown is certainly required.A complete and / or partial shutdown can also be initiated semi-automatically or fully automatically with alternative or supplementary measures to eliminate the harmful consequences of a critical fault current.

[0030] In addition, the method according to the invention can be further developed such that at least one device, in particular a loudspeaker, light source, preferably at least one light-emitting diode, display, and / or similarly functioning human-machine interface, is operated for signaling, particularly in the near field of the current monitoring device and functionally connected to it, emitting auditory and / or visual signals. This further development provides at least one signaling system particularly suitable for informing or alerting human users. If the device is located in the near field, this can result in an immediate association with a fault in the circuit when using visual signaling devices. This is advantageous for very simple visual signaling devices, such as LEDs.Auditory signals located in the near field can be operated at a correspondingly quieter volume while still achieving the same association. Displays can be used as an alternative or in addition to the signaling, providing additional information to which the user can respond after the signaling, for example, using additional human-machine interfaces, particularly input devices such as a keyboard. However, the functional connection not only enables signaling in the near field. Alternatively or in addition, signaling devices according to advanced technology can also be placed away from the current monitoring device, for example, to additionally or alternatively improve the detectability of the signal by being closer to a user.

[0031] According to a further advantageous development of the method according to the invention, the current monitoring device is alternatively or additionally functionally connected to at least one communication interface and / or communication device that is operated in such a way that it can send a message containing at least an indication of the fault current via a wired and / or wireless communication connection via a data and / or communication network, such as the "Wide Area Network", WLAN or "Long Range Wide Area Network", LoRaWAN, and / or direct, in particular short-range radio communication, such as Bluetooth. This can, for example, provide an interaction with the current monitoring device and / or corresponding smart home devices or the user that is at least similar to smart home approaches.At the very least, however, this will enable the user to be informed even at greater distances from the monitored circuit.

[0032] Particularly for the latter, the method according to the invention can be further developed such that the power monitoring device is operated in such a way that it generates and sends the message according to a messaging protocol, such as SMS, MMS, the so-called "push notification," and / or email protocol. This primarily enables autonomous transmission of messages for signaling to remote users.

[0033] The method according to the invention can further advantageously be further developed by operating the current monitoring device in such a way that the adaptation takes place at at least one initialization time, for example during installation of the current monitoring device and / or at times when a change to parameters of the power grid, in particular of the connected devices, is carried out, in particular by manually entering the parameters of the power grid, in particular parameters of the devices, such as the associated leakage current and / or fault current. This ensures the adaptation of the current monitoring according to the invention, i.e. both the arrangement and the method, to the power grid to be monitored, thus supporting the accuracy of the signaling, because false signals can be avoided simply by taking characteristic or nominal values ​​into account, in particular during initialization.If a further adaptation is performed at a later time, the power monitoring can be updated based on changed parameters if necessary. This can be triggered by an event, for example, when the power grid changes due to the addition or removal of consumers or other manipulation of the circuit, and / or can be triggered without an event at regular, particularly adjustable, intervals.

[0034] Alternatively or additionally, the method according to the invention can be further developed such that the current monitoring device is operated such that the adaptation takes place such that the current monitoring device automatically adapts, as needed, one or more of the following variables in a second time interval based on the history formed from at least one of the properties of the power grid: measurement interval, threshold value, individual leakage current for each device supplied by the power grid. This development can take into account the fact that properties of devices can change over time and that actual, i.e. measurable, values ​​of the leakage currents during operation can deviate at least slightly from the underlying nominal values ​​even at the time of installation.If relevant parameters of the circuit are recorded over one and / or more time intervals, the current monitoring system according to the invention can adjust parameters entered during initialization accordingly, for example. The history of the recorded values ​​is used as a basis for this. The current monitoring device according to the invention and the method according to the invention can thus also train and / or implement machine learning algorithms.

[0035] This means that, for example, the current monitoring device according to the invention can, after a period of, for example, 2 weeks, be able to differentiate the fault currents that can be measured in the protected circuit in such a way that it can very accurately distinguish actual fault currents, i.e. those that are really caused by faults, in particular those that endanger life, from fault currents that can be measured during normal operation, usually by actual leakage currents.

[0036] One or more of the advantages mentioned also enable the power monitoring to dynamise these parameters, i.e. the monitoring is based on a (daily / usage) profile of the parameters.

[0037] Alternatively or additionally, the method according to the invention can also be further developed such that at least parts of the function of the current monitoring device are operated in a functionally integrated manner in at least one device of the power grid, in particular an electricity meter, preferably a smart meter, residual current device (RCD), and / or a miniature circuit breaker. This further development makes it possible to implement the current monitoring according to the invention as far as possible without installing additional hardware and, for example, to expand existing structural features in devices such as smart meters with inventive functions by implementing the method according to the invention in the device via a corresponding software update.However, the further development also allows the functions, for example the use of processors, to be transferred in whole or in part to individual devices located in the power grid, in particular at the distributor, so that the current detection device according to the invention requires only minor additional hardware changes.

[0038] Further advantages and details of the invention will be explained with reference to the Fig. 1 and in the Fig. 2 shown embodiments of the arrangement according to the invention and with reference to the Fig. 3 illustrated or indicated embodiment of the method according to the invention. Fig. 1 schematically shows a first embodiment of the arrangement according to the invention, showing an implementation in which individual currents are detected and digitally summed, Fig. 2 schematically shows a second embodiment of the arrangement according to the invention, showing an implementation in which the summation of the currents is provided as an analog value by an induction sensor, Fig. 3 schematically shows a flow diagram of the error monitoring according to the invention as an embodiment of the method according to the invention.

[0039] In the following in the Fig. The embodiments explained in Figures 1 to 3 are preferred embodiments and developments of the invention.

[0040] In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that are to be considered independently of one another, which also further develop the invention independently of one another and are therefore to be regarded as part of the invention individually or in a combination other than that shown.

[0041] Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0042] The same reference symbols, if they appear across figures, have the same meaning in the different figures.

[0043] In Fig. 1 shows a schematic representation of a first embodiment of the arrangement according to the invention, which represents one of the possible implementations of the method, so that explanations given for this purpose regarding procedures, in particular functional aspects, of the arrangement also at least partially reproduce embodiments of the method according to the invention or explain them in more detail.

[0044] What can be seen is a central power distribution SV, as it can be found in a household, i.e. an apartment or a residential building, leading from an electricity meter (not shown).

[0045] A power distribution board (SV) in a residential network typically includes at least phase conductors that carry power from the source to the consumers, neutral or zero conductors that go to the neutral point of the power grid and return power from the consumer there, and protective conductors via a supply line (ZL), for example, branched off from the main distribution board, to one or more fuse boxes. The power distribution board (SV) according to the example shown can be considered to be congruent with the fuse box, especially if it is a single such fuse box. If there are multiple fuse boxes, they can be considered sub-distribution boards that form subnetworks of the main or house / apartment network.

[0046] The example shows that three phase conductors L1...L3, a neutral conductor N, and a protective earth conductor (PE) are routed via the supply line ZL to a circuit representing the fuses in the fuse box. Also visible is the combined use of several miniature circuit breakers LS1...n and a residual current device (FI), although the use of miniature circuit breakers combined with residual current devices is also known. Thus, the application is not limited to what is shown.

[0047] It can also be seen how at an output of the residual current device FI, the neutral conductor NL or connection to the neutral point present at the input is connected through and from which the neutral conductor NL is passed on to a first busbar SS_N providing the connection to the neutral conductor NL.

[0048] Furthermore, it can be seen that the protective conductor PE, which is led into the distribution board via the supply line ZL, is led to a second busbar SS_PE and is also connected there, so that the protective conductors of consumers connected to the house network are connected to the protective conductor PE via this second busbar.

[0049] For the sake of simplicity, the schematic diagram only shows a defective consumer DV.

[0050] The fault is symbolically represented as a jagged connection between the load's outer conductor and the protective conductor (PE). It can also be seen that this causes a fault current (IF) to flow on the protective conductor.

[0051] One cause of such a defect could be, for example, a leak in the screw connection of the sensors, which are typically found in kettles. Such leaks can occur because the appliance was purchased defective or because they develop after a long period of use.

[0052] If water that has previously evaporated due to the heat accumulates on the “cooker”, this water vapor would, due to the accumulation, cause a time delay in the supply plug in state-of-the-art installations and trigger a fault current IF and a fault circuit breaker.

[0053] If the house's electrical system is older and all devices are monitored by a residual current device, this would result in the shutdown of all devices. Due to the delay, this might not happen until nighttime, for example, meaning that someone might find themselves in a situation where they have to move around the house in the dark, such as when using the toilet. Such situations therefore mean that a residual current device, although intended to protect lives, endangers the health of the residents of the apartment or house.

[0054] Furthermore, this can also lead to property damage of varying degrees. For example, appliances in such a house may also have refrigerators and / or freezers, whose shutdown would at least disrupt the cold chain, or electric or electrically controlled heaters, which could lead to heating failure if the fault circuit breaker is triggered in winter and, during an extended absence, cause significant property damage, for example, due to burst pipes caused by freezing water.

[0055] With new installations of domestic electrical systems, the described health hazards or property damage are less likely, at least in Germany, because in Germany in particular, only so many fuses (circuit breakers) are connected downstream of a residual current device that the maximum current of the sum of all fuses is always smaller than the maximum current for which the residual current device is rated. This way, the domestic electrical system is divided into several circuits protected by residual current devices with downstream fuses, and not every fault current that triggers immediately paralyzes the lighting system and / or the refrigerator circuit. However, the probability of this happening remains high.

[0056] This is where the Fig. 1 schematically illustrated installation of an adaptive residual current monitor SM_1 in the central power distribution SV and helps to avoid all these disadvantages by - as shown schematically in the figure at the output of the residual current monitor - sending an ALARM warning when a residual current is detected, for example via an Internet connection via e-mail, via a mobile phone connection via SMS and / or directly at the central power distribution by means of signaling devices such as an LED (arrangement) or via a display.

[0057] The current monitoring according to the invention, i.e. also the one according to the embodiment in Fig. The current monitoring device SM_1 shown in Figure 1 can be further developed such that it has the aforementioned communication options and / or display devices, i.e., it uses communication devices / interfaces and / or such devices / interfaces in the power grid. This can be realized by integrated, separate connections to these interfaces / devices. These connections can be wireless, i.e., realized, for example, by a near-field communication technology such as Bluetooth and / or longer-range radio communications, such as WLAN or LoRaWAN. A further development is also possible in which the residual current monitoring device according to the invention has a mobile radio connection, for example, using an eSIM.

[0058] It is also conceivable that further development could use the power lines for data transmission.

[0059] The invention can also be implemented in such a way that at least parts of the existing devices are implemented by implementing a method such that at least parts of the functions of the current monitoring SM according to the invention are realized by devices already arranged in the power grid that provide usable (sub)functions. For example, this can be achieved by controlling them to interact with other (sub)functions of the current monitoring SM according to the invention through implementation of the method, for example, through a software installation / software update, and thus the current monitoring SM is provided, so to speak, by distributed, orchestrated functions.

[0060] A significant advantage of the residual current monitoring SM according to the invention is also that the current monitoring SM according to the invention is also adapted at least once in such a way that it is set to at least one parameter of the current installation of the power grid, i.e. at least the currently connected devices.

[0061] By adapting the current monitoring SM according to the invention at least once, it is advantageously taken into account, among other things, that many devices very often have a minimal fault current. In the German industrial standard DIN, this is referred to as the so-called leakage current. According to the standard, this leakage current may amount to a maximum of 3.5 mA of current on the protective conductor PE per piece of equipment, i.e. device. The actual leakage current during operation, however, is usually much lower. Nevertheless, the actual leakage currents per device add up and lead to a measurable fault current during normal operation. This means that a fault current can also be measured during normal operation; however, this is not caused by a fault, but by the actual leakage currents.

[0062] Since, as can be seen in the illustration, the central residual current monitoring device SM_1 installed in the exemplary embodiment is supplied with a current flowing on the outer conductors L1... L3 as well as the neutral conductor N as input signals, the current monitoring device can sum these up internally to a total current and determine this measurable, i.e. currently given value, of the residual current.

[0063] During this summation, the invention takes into account at least the actual leakage current per device. Only when the value of the measurable fault current (total current) based on an internal threshold comparison exceeds a threshold set according to the invention is the ALARM warning sent.

[0064] This threshold is above the sum of the actual leakage currents of all connected devices in order to avoid false triggering.

[0065] As a result, a further advantageous effect of the invention is achieved that a user of the power grid is not informed of a possible shutdown of an electrical circuit with several devices due to an actually occurring fault current in only one device and the resulting negative effects (e.g. unnoticed failure of heating, refrigerator, etc.) already on the basis of existing leakage currents, but largely only when the value of the total current indicates that something is making a further contribution to the measurable fault current (total current) that goes beyond the sum of the actual leakage currents in normal operation.

[0066] However, the threshold is also set in such a way that it triggers the ALARM alarm in good time before a circuit breaker is triggered.

[0067] This allows the user to determine the cause of this excess. It could well be a false positive, for example, because a new device has been connected, especially temporarily, and its actual leakage current in a fault-free state increases the total current without a fault being the cause. The user can then take this into account and, for example, as a possible solution for the problem, have the current monitoring system according to the invention adapted to this new configuration of the power grid, so that the threshold value is adjusted.

[0068] To determine the fault current in the present embodiment of the fault current monitoring SM_1, currents are present on the outer conductors L1...L3 and the neutral conductor N as input signals, i.e. they are measured or detected by the fault current monitoring device according to the embodiment.

[0069] This measurement can be performed continuously and / or repeated at discrete intervals. A suitable interval might be 200 ms. However, this can also take any other value, for example, adapted to the current installation of the power grid, i.e., the type, number, and / or connections of the devices, or other parameters of the power grid.

[0070] The calculation of the measurable, i.e. currently present, fault current for the aforementioned threshold value comparison is then carried out after the recording / measurement at the stated time intervals by subtracting the current of the neutral conductor N from the sum of the currents of the outer conductors L1...L3 or, taking into account the fact that the current of the neutral conductor N has a current flow direction opposite to that of the outer conductors and thus an opposite sign, the sum of the currents of the outer conductors L1...L3 and the neutral conductor N is formed.

[0071] For signal processing, the current monitoring device SM_1 according to the illustrated embodiment has corresponding, in particular integrated, circuits in order to be able to carry out this calculation and comparison.

[0072] A reduction in the necessary signal processing and thus the necessary circuits is achieved by the Fig. 2 shown embodiment.

[0073] In the Fig. 2 it can be seen that this variant represents a real alternative, since it can easily be installed in the same power grid, which is characterized by the phase conductors L1...L3, the neutral conductor N, the protective conductor PE, the residual current device FI with the circuit breakers L1...N and the defective consumer DV, and also in the central power distribution SV.

[0074] The difference to the previous example essentially lies in the way the fault current is determined and an alternative embodiment of the fault current monitoring SM_2 adapted to this.

[0075] According to the Fig. In the embodiment shown in Figure 2, an induction sensor is installed to determine the actual fault current, through which all three outer conductors L1...L3 and the neutral conductor N are passed.

[0076] This results in the summation of the current contributions from the respective conductors L1...L3, N in the induction sensor IS. In this embodiment, the induction sensor IS is thus essentially an analog computer. Because the currents introduced by induction in the outer conductors L1...L3 are summed at exactly the same time and the current through the neutral conductor N is subtracted due to its opposing contribution, a total induction current SIL1...3,N is generated in the induction sensor, which has a value corresponding to the fault current present at the time.

[0077] Accordingly, the current monitoring according to this embodiment has an input for this induction total current SIL1...3,N.

[0078] The illustrated embodiment has the advantageous feature of eliminating the need for ICs, AD converters, and individual sensors through the use of the induction sensor. A further, albeit less significant, advantage is that it requires less computing power for the calculation.

[0079] In addition to the detection by the induction sensor IS, as already mentioned in the first embodiment, a threshold decision is carried out at intervals or continuously by the further current monitoring SM_2 and the ALARM warning is provided.

[0080] For both exemplary embodiments, the level of the actual leakage current per device and the measurable fault current not only realizes an initial adaptation by taking known, fixed parameters into account once, as mentioned in the first exemplary embodiment, but the adaptation can alternatively or additionally be made adaptive in such a way that the central fault current monitoring SM_1, SM_2 determines the actual leakage and fault currents after a period of time after installation, for example within approximately 2 weeks. This process can also be repeated at longer intervals, for example to take into account that the properties of the devices can change over time. For example, the actual leakage current during normal operation of a device can change due to the aging of the device.This allows the monitoring unit SM_1, SM_2 to independently adjust the threshold values ​​for the threshold decision, i.e., the warning levels, according to this inventive development. Changes to the installation in the power grid can also be taken into account in this way, and the threshold values ​​can be updated.

[0081] The threshold value according to the invention will therefore ideally adapt itself in a value range whose lower limit is predetermined by a measurable fault current of the power grid given during normal operation, in particular resulting from the sum of the actual leakage currents of the devices present in the power grid, and whose upper limit will be given below a tripping current of the RDC / FI safety switch, so that according to the invention the alarm can indicate faults before the safety switch is triggered.

[0082] It can also be provided that this upper limit value can lead to an adaptation of the threshold value according to the invention, for example to take into account the fact that the value of the actual tripping current of an RCD safety switch, i.e. the response value of the residual current safety switch, can deviate from the so-called rated residual current.

[0083] For a purely sinusoidal fault current, the tripping current must be between 50% and 100% of the rated residual current. The rated residual current (of the RCD) is defined such that, at the latest, when the residual current detected by the RCD exceeds this limit, the RCD must trip and de-energize the monitored circuit. Therefore, this is often the value specified as the nominal tripping current for an RCD, which is often 30 mA.

[0084] When implementing the range within which the threshold can vary, the person skilled in the art will therefore consider the values ​​provided by the specific devices. According to a further development, the invention can also adapt (semi-)automatically to changes in this upper limit, whether due to a change in the safety switch or due to age-related changes.

[0085] The power monitoring system according to the invention, particularly the two exemplary embodiments, provides a very cost-effective power monitoring function that is independent of any installation and can distribute important information promptly. Furthermore, it can be installed at any time, meaning it can be used both in existing power grids and in the planning and installation of new ones.

[0086] In contrast to current solutions, which always require installation in each monitored room or in individual server racks or devices, as is the case with devices from the PDU manufacturer Raritan, the solution according to the invention works centrally, but can also be provided for each floor or apartment, for example.

[0087] In contrast, the invention is also more suitable for home use, as it is not so expensive and can also be installed on devices where there is no direct access to their electrical circuits, such as built-in kitchen appliances.

[0088] Due to the adaptation possibility according to the invention, in particular the continuous, independent adaptation according to further developments, the solution according to the invention also generally makes it possible to dispense with manual reconfiguration when devices are added in order to take account of the changed leakage currents.

[0089] Furthermore, spontaneously occurring and / or developing changes, for example due to the aging of the devices, can also be detected in this way.

[0090] The invention is therefore fundamentally adaptable to the individual conditions of the respective environment.

[0091] This also creates the possibility of responding in an individually adaptable manner, for example with messages and warnings of different priorities on one or more channels, in order to detect and evaluate significant changes in advance, before the fault circuit breaker is forced to trigger, so that measures can be taken to remedy potentially dangerous situations, for example by replacing an outdated device.

[0092] In principle, both exemplary embodiments can achieve these advantages according to the invention. However, the first exemplary embodiment can generally also be implemented by a solution based purely on a software update in an existing system, which, for example, uses so-called smart meters. Here, the method according to the invention is thus implemented by utilizing existing functionalities. This means that the functions and problem areas addressed in the exemplary embodiments are already available / integrated in the power grid and, through implementation of the method according to the invention, effectively become an arrangement according to the invention.

[0093] A simple embodiment of the method according to the invention is shown schematically in a flow chart in the Fig. 3 shown.

[0094] It can be seen that, according to this simple embodiment, starting from a first state Z1 of the power grid in which it is in normal operation, the currents are detected in a first step S1.

[0095] This can be done in such a way that at the time of recording, this value is recorded at points where the current value can be determined.

[0096] Subsequently, in a second step S2, the currents measured in the first step S1 are summed. This results in the sum of the currents measured at points on the phase conductors L1...L3, minus the current measured at a point on the neutral conductor in the first step S1.

[0097] Since the currents are essentially always present at the detection points, detection can occur at any time. According to the exemplary embodiment, this occurs at discrete time intervals of 200 ms each. A value is thus taken every 200 ms. After this detection, a third step S3 performs a threshold comparison, which checks whether the summation results in a value that indicates a dangerous trend in the measurable fault current. According to the invention, a threshold value SW indicating this trend is therefore selected such that it has a value that is smaller than the tripping current but also greater than the sum of the leakage currents occurring during normal operation.

[0098] The value for the time intervals is not limited to the example. This parameter must be selected so that it is suitable for the specific installation, in particular so that a so-called True RMS measurement and / or the measurement of the desired frequencies is possible.

[0099] A value should be chosen for the time interval so that it is sufficient for measuring the frequencies occurring in the specific installation.

[0100] Depending on the expected frequencies, values ​​in the lower millisecond range, especially <10ms, or even values ​​in the microsecond range may be useful.

[0101] If this is not the case, the process goes into the first state Z1 or remains in this state, from which the first three steps S1... S3 are repeated again after 200ms until it is confirmed that the threshold value SW has been exceeded, i.e. the accumulated current is above this threshold and thus suggests the presence of a fault to be treated.

[0102] In this case, a fourth step involves issuing a warning as a message, as a visual and / or acoustic signal, so that the user and / or manager of the power grid is triggered and can inspect the power grid.

[0103] The method according to the embodiment is thus in a second state Z2, in which a process for handling the warning, i.e. finding and correcting the error and / or manually resetting to normal operation can take place and, after successful correction, can return to normal operation, i.e. the first state Z1, where the method is repeated again with the execution of the first three steps S1... S3 basically endlessly or until the current monitoring is switched off.

[0104] Alternatively or additionally, an automatic reset to normal operation is also conceivable, since the warning has already been issued and a renewed detection can provide added value; moreover, the error may be transient and the relevant device may already have been removed / disposed of.

[0105] The invention is so flexible that its implementation is not only possible as in the Fig. 1 and Fig.2, can be implemented as a dedicated device, but rather existing structures from the prior art can be utilized, and by imprinting the functional features according to the invention, the problem underlying the invention can be advantageously solved. In particular, it is so flexible that this imprinting can be achieved by installing software that adds the functions of the method according to the invention. For example, it is therefore possible to enable a smart meter to implement the invention and thus to realize the arrangement and method according to the invention through a software update.

[0106] The invention therefore enables cost-effective and low-effort implementation in existing devices. A further development of the method according to the invention provides for the generation of different reactions to detected events depending on their severity. This can be demonstrated by the use of different signal generators and / or signals or message contents, which can alternatively or additionally lead to the shutdown of the circuit.

[0107] Furthermore, it may also be provided to issue at least once, in particular at regular intervals and / or upon user request, a summary of information on “unusual events”, possibly with a reference to manual diagnosis by experts.

[0108] According to further training, the warning can be sent not only via SMS, email and / or signal output, but also via an app.

[0109] The illustrated embodiments show possible implementations for typical home networks and the network configurations encountered there. However, the invention is suitable for all network configurations, such as "Terre Terre" (TT), "Isole Terre" (IT), or "Terre Neutre" (TN). The current monitoring according to the invention, in particular the connections / measurement of the line currents, is then carried out according to the network configuration in order to determine the sum of the fault currents.

[0110] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

Claims

[1] Method for monitoring residual currents in at least one part of a power grid having a plurality of different consumers, characterized by that a current monitoring device is functionally connected and operated with the part of the power grid on the supply line supplying the external, neutral and protective conductors to the part of the power grid for distribution in such a way that a) it retrieves at least one usable signal supplied via at least one input for the purpose of knowing a total current defined by the sum of the currents of the phase and neutral conductors, b) the retrieval is repeated at least temporarily, in particular periodically, c) on the basis of the signal, the total current per repetition is determined and compared with a preferably adjustable threshold value, which indicates in particular a dangerous tendency of the total current detected, d) if the threshold value is exceeded by the current monitoring device, a process for troubleshooting, in particular a signalling of the exceedance, is started, (e) it interacts adaptively with the power grid in such a way that at least at one point in time, in particular during at least a first time interval, at least some of the properties of the power grid, in particular a history of the part of the properties updated in the first time interval, is used at least as a basis for the threshold decision. [2] Method according to claim 1, characterized by that the current monitoring device is operated in such a way that it operates an input for each phase and neutral conductor, which is connected to one of these conductors of the supply line in such a way that it generates signals suitable for a threshold value comparison from the currents applied to the inputs. [3] Method according to claim 1, characterized bythat the current monitoring device is operated in such a way that it operates an input to which a signal is present which is at least correlated with, in particular identical to, a total current formed from the outer and neutral conductors, wherein this total current, in particular also the correlating signal, is generated by an induction sensor connected upstream of the current monitoring device, which is operated in such a way that it is connected to all outer and neutral conductors in such a way that they all generate a contribution to the induction current of the sensor in such a way that the value of the resulting induction current corresponds to the value of the sum of the currents of the outer and neutral conductors and is output via an output for forwarding to the input of the current monitoring device. [4] Method according to one of the preceding claims, characterized bythat the signals for summation current formation are recorded over a determined period of time, in particular 200ms. [5] Method according to one of the preceding claims, characterized by that the current monitoring device is operated in such a way that it is capable of signalling when the threshold value is exceeded. [6] Method according to the preceding claim, characterized by that for the signalling, a device which emits audio and / or visual signals and is functionally connected to the current monitoring device, in particular a loudspeaker, a light source, preferably at least one light-emitting diode, a display and / or a similarly acting human-machine interface, is operated, in particular in the near field of the current monitoring device. [7] Method according to one of the two preceding claims, characterized bythat the current monitoring device is functionally connected to at least one communication interface and / or communication device which is operated in such a way that it can send a message containing at least an indication of the fault current via a wired and / or wireless communication connection via a data and / or communication network, such as the “Wide Area Network”, WLAN or “Long Range Wide Area Network”, LoRaWAN, and / or direct, in particular short-range radio, communication, such as Bluetooth. [8] Method according to the preceding claim, characterized by that the power monitoring device is operated in such a way that it generates and sends the message according to a messaging protocol, such as SMS, MMS, the so-called “push notification” and / or email protocol. [9] Method according to one of the preceding claims, characterized bythat the current monitoring device is operated in such a way that the adaptation is carried out in such a way that it is carried out at at least one initialization time, for example during installation of the current monitoring device and / or at times when a change in parameters of the power grid, in particular of the connected devices, is carried out, in particular by manual input of the parameters of the power grid, in particular parameters of the devices, such as the associated leakage current and / or fault current. [10] Method according to one of the preceding claims, characterized bythat the current monitoring device is operated in such a way that the adaptation takes place in such a way that the current monitoring device automatically adapts, as needed, one or more of the following variables in a second time interval, based on the measuring interval, threshold value, individual leakage current for each device supplied by the power grid, at least on the basis of the history which is formed from at least one of the properties of the power grid. [11] Method according to one of the preceding claims, characterized by that at least parts of the function of the power monitoring device are operated in a functionally integrated manner in at least one device of the power grid, in particular an electricity meter, preferably a smart meter, residual current device (FI) and / or circuit breaker. [12] Arrangement for carrying out the method according to one of the preceding claims.

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