Inductive current transformer, smart meter and method for measuring electrical quantities in an electrical conductor

Abstract

The invention relates to an inductive current transformer (10) for a smart meter (7), comprising a measuring coil (23) for inductively measuring the actual current (IIST) in an electrical conductor (13). According to the invention, the inductive current transformer (10) has at least one means (24, 25, 21, 22, 23) for a capacitive coupling process and, in addition to inductively measuring the actual current (IIST), is designed to capacitively measure the actual voltage (UIST) in the electrical conductor (13) via said means (24, 25, 21, 22, 23) for the capacitive coupling process.

Description

[0001] Inductive current transformer, smart meter and

[0002] Method for measuring electrical quantities in an electrical conductor

[0003] This application claims priority from German patent application No. 10 2024 107 596.1, the contents of which are incorporated herein by reference.

[0004] The invention relates to an inductive current transformer for a smart meter, in particular for power control of power storage devices, for inductive measurement of an actual current in an electrical conductor, according to the preamble of claim 1.

[0005] The invention further relates to a smart meter comprising the inductive current transformer, as well as to an electrical supply network, in particular a household power network, comprising the smart meter and the electrical conductor.

[0006] The invention also relates to a method for measuring electrical quantities in an electrical conductor, in particular for power control of power storage devices.

[0007] The control procedures for electricity storage systems, such as battery storage, are defined by regulations and standards in many countries. In Germany, VDE-AR-N 4100, VDE-AR-N 4105, VDE-AR-N 4110, and VDE FNN are relevant. According to these regulations, the use of electricity storage systems should not lead to an additional load on the supply grid. This means that the storage system neither draws power from the supply grid nor feeds power into it. Such power control, also known as

[0008] This system, also known as "zero-energy storage," is particularly advantageous for consumers with solar systems, wind turbines, combined heat and power plants, or fuel cells. This is because the remuneration for energy feed-in is generally significantly lower than the cost of purchasing energy.

[0009] In practice, a so-called “smart meter” (also known as an “intelligent measuring system” or “intelligent counter”) is used to implement the control procedure at the grid connection point. This records the power exchange between the

[0010] Customer network and the supply grid. Based on these power measurements, the power storage system regulates its output so that the power exchange between the supply and consumer grids is reduced to zero.

[0011] To carry out the power measurements, the voltage and current values ​​at the grid connection point must be measured.

[0012] Inductive current transformers are typically used for current measurements. This allows for non-contact inductive measurement of the current flow in the current-carrying conductor, usually without having to shut down the electrical system for installation. According to the magnetic flux and induction law, a measuring current I is generated in a measuring coil short-circuited across a measuring resistor R. M = induced, with the actual current I IST to be measured and the number of turns N of the measuring coil, which finally produces an evaluable measuring voltage U M = R ■ at the measuring resistor R. The current measurement is therefore comparatively easy to install and can also be carried out reliably.

[0013] In contrast, three-phase alternating voltages (e.g., 230 volts) are measured directly on the live conductors in practice. These measurements require physical contact and, due to the high voltages involved, must be performed by qualified electricians. Another challenge in setting up the measurements is the correct assignment of the voltage and current measurements in terms of phases and current flow directions. These difficulties make self-installation of the smart meter by the end customer virtually impossible.

[0014] Especially nowadays, for example with balcony solar power plants, the possibility of simple and safe self-assembly of the individual components of the system is increasingly desirable.

[0015] In view of the known state of the art, the object of the present invention is to provide an inductive current transformer and a smart meter which are particularly (but not exclusively) suitable for power control of power storage devices, preferably for use with renewable energy sources, and which can be installed easily and safely for power measurement.

[0016] The present invention is also based on the object of providing an electrical supply network, in particular a household electricity network, with a smart meter which is particularly (but not exclusively) suitable for power control of electricity storage devices, preferably for use with renewable energy sources, and which can be installed easily and safely for power measurement.

[0017] Finally, it is also an object of the invention to provide a method for measuring electrical quantities in an electrical conductor, which is particularly (but not exclusively) suitable for power measurement for controlling power storage devices, preferably for use with renewable energy sources, and which can be carried out simply and safely.

[0018] The problem is solved for the inductive current transformer with the features listed in claim 1. With regard to the smart meter, the problem is solved by the features of claim 11 and with regard to the method by the features of claim 15.

[0019] The dependent claims and the features described below relate to advantageous embodiments and variants of the invention. The invention relates to an inductive current transformer for a smart meter, comprising a measuring coil for inductively measuring an actual current in an electrical conductor or in an electrical line (which may include the electrical conductor).

[0020] The two ends of the measuring coil are preferably short-circuited via a measuring resistor (hereinafter: “R”).

[0021] The electrical conductor and the electrical line or cable containing the electrical conductor are not to be understood as components of the inductive current transformer or the smart meter. Rather, the electrical conductor or electrical line is the test object, whose electrical quantities (in this case, in particular, the actual current and the actual voltage mentioned below) are to be measured, preferably without damaging the electrical line or cable and without direct mechanical or physical contact with the electrical conductor, which is usually enclosed by an electrically insulating insulator, in particular a cable sheath.

[0022] The electrical line or cable can, in particular, have a current- and voltage-carrying electrical conductor. It is preferably a power cable of a household power grid, which, for example, carries an alternating current with an effective value of the alternating voltage or a mains voltage of 230 V or 120 volts. However, the invention or the use of the inductive current transformer or the smart meter is not to be understood as being limited to a specific application or a specific electrical line or conductor. It should be noted at this point that the invention can, in principle, also be suitable for use with an electrical conductor that is not part of an electrical line or cable—such as a busbar or a bare wire.

[0023] In particular, the suitability of the inductive current transformer or smart meter for power control of power storage systems should not be understood as a limiting application. Another—purely exemplary—use could also include power recording for cost accounting during the operation of a power generation plant.

[0024] According to the invention, the inductive current transformer has at least one means for capacitive coupling and is configured to carry out, in addition to the inductive measurement of the actual current, a capacitive measurement of an actual voltage in the electrical conductor via said means for capacitive coupling (preferably simultaneously with the measurement of the actual current).

[0025] The said means for capacitive voltage measurement can therefore basically represent a capacitive voltage sensor or a capacitive probe.

[0026] The main application of the invention can relate to an inductive current transformer for a smart meter, which measures the voltages and currents of an electrical supply network without contact and, based on these measured values, determines the level of power exchange between the consumer network and the supply network for the control of decentralized energy supply facilities, such as solar systems or battery storage systems.

[0027] The proposed inductive current transformer and the proposed smart meter can be easily installed and, if necessary, even by an untrained user, since the electrical conductor to be measured does not need to be physically contacted and can therefore remain in its protective sheath or in a cable sheath.

[0028] It should be noted here that the means for capacitive coupling does not necessarily have to be located at the same axial position or at the same position along the length of the electrical conductor as the measuring coil. For example, it can also be provided that the measuring coil and the capacitive means perform their respective non-contact measurements at offset positions along the length of the electrical conductor to avoid mutual interference.

[0029] It should be noted that the smart meter may also have more than one inductive current transformer in accordance with the above and following definitions and optional features, particularly if multiple supply lines within the supply network are to be measured (e.g., three phases in a three-phase supply network). Thus, for example, two, three, or even more inductive current transformers may be provided.

[0030] In an advantageous development of the invention, it can be provided that the current transformer has a line receptacle for the electrical line or cable having the electrical conductor.

[0031] The cable receptacle can be designed to position the electrical cable in sufficient proximity to the measuring coil and the means for capacitive coupling for contactless measurement. Guiding, fixing, or limiting the movement of the electrical cable in the receptacle can be advantageous but is not absolutely necessary.

[0032] In principle, the cable receptacle can already be realized by a flat support surface, but preferably at least one convex support surface is provided, particularly preferably an at least partially annular feedthrough for the electrical cable, very particularly preferably a completely annular feedthrough.

[0033] It can be provided that the cable receptacle is designed to guide the electrical cable in a defined and tight manner, so that, for example, a relative positioning of the electrical cable to the means for capacitive coupling, which will be defined in more detail below, can be assumed to be at least approximately known. For example, the electrical cable can be in direct contact with an inner surface of the cable receptacle.

[0034] According to a further development of the invention, it can be provided that the current transformer has a first half-shell and a second half-shell that can be mechanically connected to the first half-shell.

[0035] The two half-shells can preferably be movable relative to one another between an open state in which the electrical line or the electrical conductor can be inserted into the two half-shells and a closed state in which the electrical line or the electrical conductor is captively received in the two half-shells.

[0036] The installation of the inductive current transformer and the smart meter can be particularly easy if the current transformer has an open state to accommodate the line and a closed state to secure the line.

[0037] The two half-shells can together form the above-mentioned cable receptacle (when the half-shells are closed, this is then preferably completely closed in a ring shape around the cable accommodated therein).

[0038] The two half shells can be connected to each other in one piece or in several parts.

[0039] According to a further development of the invention, it can be provided that the half-shells are movable relative to one another via a common hinge connection (e.g. a film hinge or a multi-part hinge which is divided between the two half-shells) and / or a common linear guide.

[0040] In particular, a hinged connection between the two half-shells has proven particularly suitable for opening and closing the half-shells. A pivoting or rotating movement can be provided for this purpose.

[0041] A current transformer with two half-shells connected to each other by a hinge connection is sometimes also known as a “split-type current transformer”.

[0042] It should be noted at this point that guiding the relative movement of the two half-shells is not absolutely necessary. If necessary, it can also be provided that the two half-shells can be moved completely independently of each other. Thus, the two half-shells can be separated as desired in the open state and, for example, only latched / locked together in the closed state. In a further development of the invention, it can be provided that the inductive current transformer has a magnetic assembly that can be arranged at least partially around the electrical line or electrical conductor.

[0043] Preferably, it can be provided that at least one winding of the measuring coil is arranged at least partially circumferentially around the magnetic assembly.

[0044] The core of the current transformer can thus be formed predominantly from a ring-shaped magnet around which the measuring coil with N turns is wound at least in sections.

[0045] Magnetic in the sense of the "magnetic assembly," the "magnet," and the "magnetic bodies" referred to below preferably means that the said components comprise a material with high magnetic permeability (e.g., ferrite or iron powder), so that electromagnetic coupling can be increased, comparable to an (iron) core of a conventional transformer. Preferably, the magnetic assembly, the magnet, and / or the magnetic bodies are not permanent magnets.

[0046] In a further development of the invention, it can be provided that the magnetic assembly has a first partially annular magnetic body and a second partially annular magnetic body.

[0047] In particular, it can be provided that the at least one winding of the measuring coil is arranged circumferentially around a ring segment of at least one of the magnetic bodies.

[0048] Preferably, the first partially annular magnetic body is connected to the first half-shell and the second magnetic body is connected to the second half-shell.

[0049] A ring magnet can therefore be provided which is divided into two magnetic half rings, whereby one of these half rings can be designed to be rotatable or pivotable.

[0050] In an advantageous development of the invention, it can be provided that the means for capacitive coupling has at least one partially annular electrically conductive measuring body (in particular made of a metal) which can be arranged at least in sections around the electrical line or around the electrical conductor.

[0051] Preferably, at least two measuring bodies are provided, wherein in this case a first measuring body can be attached to the first half-shell and a second measuring body can be attached to the second half-shell.

[0052] In particular, each half-shell can be provided with a magnetic body in which a respective measuring element is arranged. The actual voltage is usually measured relative to a (pre-existing) reference potential, such as ground potential. Therefore, a single voltage tap may be sufficient, regardless of the variant of the capacitive coupling means implemented.

[0053] In a further development of the invention, it can be provided in particular that the at least one partially annular electrically conductive measuring body is designed as a metal sheet, metal foil or metallic coating of a lateral surface of the inductive current transformer.

[0054] The outer surface can, for example, be an inner surface of the inductive current transformer, preferably an inner surface of a magnetic body or a corresponding (e.g. insulating) cover of the magnetic body.

[0055] In an alternative or additional development of the invention, it can be provided that a measuring line is connected to the magnetic assembly in order to use the magnetic assembly as a means for capacitive coupling.

[0056] In an alternative or additional development of the invention, it can also be provided that a measuring line is connected to the measuring coil in order to use the measuring coil as a means for capacitive coupling.

[0057] The measuring line can preferably be connected to one end of the measuring coil (e.g. at a node point to which the electrical resistance on the measuring coil is also connected).

[0058] This variant of the invention may be particularly preferred since in this case an inductive current transformer, such as a split-core current transformer, may be used without structural changes within the meaning of the invention to carry out the proposed contactless voltage measurement.

[0059] The invention also relates to a smart meter, in particular for power control of energy storage devices, comprising an inductive current transformer according to the above and following explanations. The features of the inductive current transformer can also be understood as features of the smart meter—and vice versa—and the applicant explicitly reserves the right to claim said smart meter separately from the inductive current transformer of claim 1.

[0060] In a further development of the invention, it can be provided that the smart meter has a computing unit which is designed and configured to determine an effective current value, an effective voltage value, a reactive power, an active power and / or a phase shift and / or a phase angle on the basis of the detected actual current and the detected actual voltage.

[0061] In particular, the computing unit can also be one of several software or hardware modules of a control device of the smart meter. The computing unit and / or control device can be designed as a microprocessor. Instead of a microprocessor, any other device can be provided for implementing the computing unit and / or control device, for example, one or more arrangements of discrete electrical components on a circuit board, a programmable logic controller (PLC), an application-specific integrated circuit (ASIC), or another programmable circuit, for example, a field-programmable gate array (FPGA), a programmable logic array (PLA), and / or a commercially available computer.

[0062] In one embodiment of the invention, it can also be provided that the smart meter has an output interface electrically connected to the computing unit, wherein the computing unit can be configured to output measured values ​​via the output interface (in particular the above-mentioned effective current value, the effective voltage value, the reactive power, the active power and / or the phase angle).

[0063] The output interface can be a wired interface, such as a data bus, optionally with a plug-in interface for connecting to an electrical data cable. However, the output interface can also be a wireless interface for wirelessly transmitting the measured values ​​to a separate module.

[0064] The output interface can therefore be connected electrically (wirelessly or wired) and, if necessary, mechanically, in particular to a separate module, such as the power storage unit, in order to transmit the recorded measured values ​​to the module for further use in the separate module.

[0065] However, it can also be provided that the recorded measured values ​​are not transmitted to a separate module, but are used by the smart meter itself for a corresponding application.

[0066] In an advantageous development of the invention, it can be provided that the smart meter and / or the electrical assembly or the power storage device has a calibration unit which is configured to correct measurement errors in the amplitude and / or phase of the detected actual voltage and / or the detected actual current on the basis of at least one reference value.

[0067] The correction of measurement errors in amplitude and / or phase of the

[0068] Voltage and / or current can be advantageous for increasing measurement accuracy. Corresponding errors can result from an undefined position of the live conductor in the inductive current transformer and thus from an undefined coupling capacitance. An alternative or supplement to correcting measurement errors can be to use mechanical means to ensure that the position of the electrical line or conductor within the inductive current transformer is clearly defined, for example, by defining and firmly clamping the electrical line in the cable receptacle of the inductive current transformer.

[0069] The calibration unit can be part of the computing unit and / or control device, but can also be designed as a separate component of the smart meter and, for example, be connected to the computing unit for communication purposes in order to transmit the calibration data.

[0070] It may also be provided that the calibration unit transmits correction values ​​for the amplitude and / or phase of the detected actual voltage and / or the detected actual current to a separate module, in particular to the power storage device. For this purpose, the output interface mentioned above can be used, for example.

[0071] In a further development of the invention, it can be provided that the smart meter has a calibration input for electrical connection to a separate module (e.g. with the power storage device) for detecting the at least one reference value from the separate module, preferably for detecting the at least one reference value from the power storage device.

[0072] The calibration input can be a wired interface, such as a data bus, optionally with a plug-in interface for connecting to an electrical data cable. However, the calibration input can also be a wireless interface for wirelessly receiving the reference values ​​from the separate module.

[0073] The invention also relates to an electrical supply network, in particular a consumer power network, such as a household power network, comprising an inductive current transformer and / or a smart meter according to the above and following embodiments and the electrical conductor.

[0074] Optionally, within the scope of the invention, it can be provided that the electrical supply network also includes the power storage device.

[0075] In an advantageous manner, an electrical supply network can thus be provided which has an innovative inductive current transformer or an innovative smart meter with the ability to measure both currents and voltages in a contactless manner.

[0076] The invention also relates to a method for measuring electrical quantities in an electrical conductor, in particular for power control of power storage devices, comprising at least the following method steps:

[0077] Providing an inductive current transformer and inductively measuring an actual current in the electrical conductor using a measuring coil of the inductive current transformer; and capacitively measuring an actual voltage in the electrical conductor using at least one means for capacitively coupling the inductive current transformer. The current measurement is thus preferably based on the principle of an inductive current transformer, while the voltage measurement can advantageously be carried out by capacitive voltage coupling.

[0078] The capacitive voltage measurements can preferably be performed by detecting the voltages at the measuring coil of the current transformer, compared to a reference voltage, which is usually a ground potential. As already mentioned, the voltage can also be measured by incorporating an additional measuring element (e.g., a metallic ring) into the inductive current transformer, whereby the capacitively coupled measuring voltage at the measuring element can in turn be measured against the aforementioned reference voltage. Alternatively, the voltage can also be measured using the magnetic core (i.e., the "magnetic assembly") of the inductive current transformer against the reference voltage.

[0079] Errors in the measured amplitude and / or phase of the voltage measurements can be corrected in the smart meter or the connected component (e.g., the power storage unit or a decentralized power supply device), as already explained. Preferably, voltages measured at the connection points of the decentralized power supply devices or the power storage unit can serve as reference values ​​for the corrections.

[0080] Calibration parameters can be defined to correct the measured values. This can be done once, for example, during the initial installation of the smart meter or the electrical grid. The correction parameters can be stored in a data memory within the smart meter, for example, in a lookup table. The correction parameters can be manually or automatically redefined or adjusted at regular intervals if necessary. Permanent or continuous recording of the calibration parameters can also be provided.

[0081] An advantageous use of the invention may relate to a balcony solar power plant, in particular one with a power storage device that requires power control.

[0082] Features described in connection with one of the subject matters of the invention, namely the inductive current transformer according to the invention, the smart meter according to the invention, the electrical supply network according to the invention, and the method according to the invention, can also be advantageously implemented for the other subject matters of the invention. Likewise, advantages mentioned in connection with one of the subject matters of the invention can also be understood to relate to the other subject matters of the invention.

[0083] It should also be noted that terms such as "comprising," "having," or "with" do not exclude other features or steps. Furthermore, terms such as "a" or "the," which indicate a singular number of steps or features, do not exclude a plurality of features or steps—and vice versa.

[0084] In a purist embodiment of the invention, however, it may also be provided that the features introduced in the invention with the terms "comprising," "having," or "with" are listed exhaustively. Accordingly, one or more lists of features may be considered complete within the scope of the invention, for example, for each claim. The invention may, for example, consist exclusively of the features mentioned in claim 1.

[0085] It should be noted that terms such as "first" or "second" etc. are used primarily for reasons of distinguishing between respective device or process features and are not necessarily intended to indicate that features are mutually dependent or related to one another.

[0086] Furthermore, it should be emphasized that the values ​​and parameters described herein include deviations or fluctuations of ±10% or less, preferably ±5% or less, more preferably ±1% or less, and most preferably ±0.1% or less of the respective specified value or parameter, provided that these deviations are not excluded in the practical implementation of the invention. The specification of ranges by initial and final values ​​also includes all those values ​​and fractions enclosed by the respective specified range, in particular the initial and final values ​​and a respective mean value.

[0087] In the following, embodiments of the invention are described in more detail with reference to the drawings.

[0088] The figures each show preferred embodiments in which individual features of the present invention are illustrated in combination with one another. Features of one embodiment can also be implemented independently of the other features of the same embodiment and can therefore be readily combined by a person skilled in the art to form further useful combinations and subcombinations with features of other embodiments.

[0089] In the figures, functionally identical elements are provided with the same reference numerals.

[0090] They show schematically:

[0091] Figure 1 shows an electrical supply network with a smart meter, according to an embodiment of the invention;

[0092] Figure 2 shows an inductive current transformer, comprising two half-shells, according to an embodiment of the invention, in a perspective view; Figure 3 shows an inductive current transformer, comprising two half-shells, two magnetic bodies, and two measuring bodies, according to an embodiment of the invention, in an open state for receiving the electrical line;

[0093] Figure 4 shows the current transformer according to Figure 3 in a closed state;

[0094] Figure 5 shows an inductive current transformer comprising two half-shells and two magnetic bodies, wherein the magnetic bodies are used as means for capacitive coupling, according to an embodiment of the invention, in a closed state;

[0095] Figure 6 shows an inductive current transformer comprising two half-shells and two magnetic bodies, wherein the measuring coil is used as a means for capacitive coupling, according to an embodiment of the invention, in a closed state;

[0096] Figure 7 shows the use of a calibration unit in the electricity storage unit to correct the measured values ​​recorded by the smart meter in the electricity storage unit;

[0097] Figure 8 shows the use of a calibration unit in the smart meter to use reference values ​​recorded by the power storage device via a calibration input to correct the recorded measured values;

[0098] Figure 9 shows a schematic circuit diagram of an electrical supply network according to an embodiment of the invention;

[0099] Figure 10 shows a flow chart for calculating measured values ​​according to an embodiment of the invention;

[0100] Figure 11 shows a method for measuring electrical quantities in the electrical conductor according to an embodiment of the invention; and

[0101] Figure 12 shows a schematic circuit diagram of an electrical supply network according to a further embodiment of the invention.

[0102] Figure 1 schematically shows an electrical supply network 1 , which is exemplarily divided into a network operator or supplier side (see left side of the dashed line) and a household or consumer side connected to it (see right side of the dashed line).

[0103] For example, a photovoltaic system 2 or a solar power system, as well as several connection points 3 for electrical consumers, are connected to the supply grid 1. Furthermore, a power storage unit 4 or a battery storage unit is provided, which can store the electrical energy generated by the photovoltaic system 2.

[0104] The exemplary supply network 1 is implemented as a three-phase alternating current network, whereby the individual circuits can be protected by overcurrent protection devices 5 in a known manner. Further details of the supply network 1 will not be discussed further below, since corresponding supply networks 1 are sufficiently known and the present invention can, in principle, be advantageously suitable for any variants of supply networks 1.

[0105] In the supply network 1, the electrical energy is distributed by means of several electrical lines 6 - in the present example, one electrical line 6 is provided for each of the three phases, starting from the connection point.

[0106] The supply network 1 according to the invention comprises a smart meter 7, with which contactless voltage and current measurements can be performed, for example, for implementing a power control process of the power storage unit 4 and / or the photovoltaic system 2 and / or for recording a feed-in tariff. A wired data connection 8 (e.g., a bus connection, such as according to the RS485 standard, among others) to the power storage unit 4 is indicated by way of example, and a wireless interface 9 is indicated as an alternative.

[0107] The smart meter 7 has an inductive current transformer 10 for each of the three phases or electrical lines 6. An exemplary inductive current transformer 10 is indicated in Figure 2 and is described in more detail below using various exemplary embodiments in Figures 3 to 6.

[0108] The current transformer 10 can have a cable receptacle 11 for the electrical cable 6, preferably an at least partially annular feedthrough for the electrical cable 6. The electrical cable 6 can be inserted into the cable receptacle 11 and optionally held therein in a captive manner. In particular, it can also be provided that the electrical cable 6 is tightly fastened within the cable receptacle 11, so that the electrical cable 6 assumes a defined position (not shown in the exemplary embodiments), which can be advantageous for the subsequent calculations and measurements, but is not absolutely necessary (a defined position of the cable 6 can be particularly advantageous for capacitive voltage measurement - for inductive current measurement, however, a defined position of the cable 6 generally does not lead to any further improvement).

[0109] The electrical line 6 can in principle be designed in any way desired, but generally has at least one cable sheath 12 and at least one current-carrying electrical conductor 13 or cable core running within the cable sheath 12. In the exemplary embodiments, the electrical line 6 is shown in simplified form as a single-core cable with a current-carrying inner conductor 13 and a cable sheath 12, but this is not intended to be restrictive. The current transformer 10 preferably has a first half-shell 14 and a second half-shell 15 which is mechanically connectable or connected to the first half-shell 14 (cf. Figures 2 to 6). The two half-shells 14, 15 can be switched between an open state, in which the electrical line 6 orThe two half-shells 14, 15 are movable relative to one another in a closed state in which the electrical cable 6 is at least captively received in the two half-shells 14, 15. Figures 2 and 3 show, by way of example, an open state of the half-shells 14, 15, whereas Figures 4 to 6 each illustrate a closed state.

[0110] In the illustrated embodiments, the two half-shells 14, 15 are connected to each other via a common hinge 16 and can thus pivot relative to each other. Alternatively, a common linear guide can be provided—or no guide at all.

[0111] Optionally, the two half-shells 14, 15 can be provided to engage or lock with each other in the closed state. For this purpose, the first half-shell 14 can, for example, have a locking means 17, and the second half-shell 15 can have a corresponding counter-locking means 18 (see Figure 2). However, a screw connection or other fastening means can also be provided.

[0112] The respective current transformers 10 can be electrically connected to the smart meter 7 via a data cable 19.

[0113] The current transformer 10 shown in Figure 2 and Figures 3 to 6 can also be referred to as a “split current transformer”.

[0114] In the exemplary embodiments, the inductive current transformer 10 has a magnetic assembly 20 that can be arranged in a ring around the electrical line 6. The magnetic assembly 20 has, for example, a partially ring-shaped first magnetic body 21 and a partially ring-shaped second magnetic body 22, wherein the first magnetic body 21 is connected to the first half-shell 14 and the second magnetic body 22 is connected to the second half-shell 15. The two magnetic bodies 21, 22 can be pivotally connected to one another via the hinge connection 16 already mentioned. Optionally, the magnetic bodies 21, 22 are arranged within an insulating or protective housing and are therefore not visible in Figure 2. In Figures 3 to 6, the current transformer 10 is shown without a housing and, moreover, only highly schematically in order to clarify the functional principle.

[0115] The current transformer 10 has a measuring coil 23 for inductively measuring an actual current IIST in the electrical conductor 13. The measuring coil 23 has N windings, which are arranged in sections around a ring segment of one of the magnetic bodies 21, 22. In this way, the measuring current I M - which can be detected, for example, by means of a voltage measurement of the measuring voltage UM falling across the resistor R, which short-circuits the two ends or terminals of the measuring coil 23.

[0116] As already mentioned, in addition to the contactless current measurement, a contactless voltage measurement is provided within the scope of the invention, which is preferably carried out simultaneously with the current measurement. For this purpose, the inductive current transformer 10 has at least one means 24, 25, 21, 22, 23 for capacitive coupling and is configured to carry out a capacitive measurement of an actual voltage UIST in the electrical conductor 13 via said means 24, 25, 21, 22, 23 for capacitive coupling. Various variants can be provided for implementing the means 24, 25, 21, 22, 23 for capacitive coupling (individually or in combination with one another), three particular embodiments of which are presented below by way of example with reference to Figures 3 to 6.

[0117] To detect the actual voltage UIST in the electrical conductor 13 without contact, a probe with a defined coupling capacitance CK to the respective conductor 13 can be provided. This capacitive probe can be implemented, for example, by installing an electrically conductive ring around the electrical line 6. The shape of the ring can be variable, but a ring-shaped and at least approximately round shape is preferred. This variant is illustrated in Figures 3 and 4.

[0118] In Figures 3 and 4, the means 24, 25, 21, 22, 23 for capacitive coupling thus comprises an electrically conductive first measuring body 24 attached to the first half-shell 14 and an electrically conductive second measuring body 25 attached to the second half-shell 15. The at least one partially annular, electrically conductive measuring body 24, 25 can be formed, for example, as a metal sheet, metal foil, or metallic coating (e.g., the inner surface 26 of the magnetic bodies or their housing) (see Figure 2).

[0119] In order to increase the capacitive coupling, i.e., the coupling capacitance CK, between the measuring elements 24, 25 or the ring and the electrical conductor 13, it may be advantageous to make the surface of the measuring elements 24, 25 as large as possible. However, a single half-ring or semi-ring-shaped measuring element may also be sufficient, although a complete ring is preferred. Because the metallic ring in the exemplary embodiment is divided into two halves (the two aforementioned "measuring elements 24, 25"), the electrical line 6 can be particularly easily inserted into the current transformer 10 without having to shut down the electrical system during installation (see Figure 3).

[0120] Optionally, it can be provided that the two measuring bodies 24, 25 are electronically connected to one another, for example via the illustrated separate electrical connection 27 and / or a hinge connection 16.

[0121] It should be noted that the thickness of the ring or measuring body 24, 25 generally plays no role in the voltage measurements, which is why the aforementioned thin-walled measuring bodies 24, 25 (e.g., foil or electroplated layer on an inner surface 26) may be sufficient. At least one of the two measuring bodies 24, 25 is contacted by means of a measuring line 28, whereby the capacitively coupled measuring voltage UKM is measured relative to a reference potential GND (in this case, ground potential), and from this, the actual voltage UIST in the electrical conductor 13 is calculated, as described below.

[0122] To avoid the expense of an additional metallic ring or measuring bodies 24, 25 for capacitive coupling with the live conductor 13, the already existing coupling capacitance CK of the ring magnet or the magnetic assembly 20 can also be utilized for voltage measurement. The magnetic assembly 20 can be contacted using a measuring line 28, and the capacitively coupled measuring voltage UKM of the electrical conductor 13 can in turn be measured relative to the reference potential GND or the ground potential. To achieve a high coupling capacitance and thus a high capacitively coupled measuring voltage UKM ZU, the two halves or magnetic bodies 21, 22 of the magnetic ring can be connected by an electrical connection 27 or the hinge connection 16 (optional).

[0123] In order to preferably use a commercially available split-core current transformer or other commercially available current transformer 10 for contactless voltage measurement without significant structural changes, a further advantageous variant utilizes the capacitive coupling of the measuring coil 23. In this case, the capacitively coupled measuring voltage UK can be detected relative to the reference potential GND at one of the two ends or terminals of the measuring coil 23. Although the values ​​that can be measured in this way may be an order of magnitude smaller than in the previous examples, they can still be sufficient for a meaningful and sufficiently precise determination of the actual voltage UIST of the electrical conductor 13.

[0124] The amplitude and phase of the capacitively coupled measurement voltage UKM are primarily influenced by the coupling capacitance CK, which in turn depends on other factors such as areas, distances, shapes, etc., with respect to the means 24, 25, 21, 22, 23 for capacitive measurement or the "probe," and therefore cannot always be readily determined. It may therefore be advantageous to correct any resulting deviation in the capacitively detected measurement voltage UKM.

[0125] Preferably, voltages that can be measured or read out, for example, at the connection point of the power storage device 4, for example a battery storage device, can serve as reference values ​​for the corrections.

[0126] The corrections can be carried out either in the separate module 4, which is supplied with the measured values ​​from the smart meter 7, e.g. in the power storage unit 4, or in the smart meter 7 itself. These two exemplary variants are shown in Figures 7 and 8. When correcting the measured values ​​in the power storage unit 4 or in the separate module, which is indicated in Figure 7, the measured values, such as the effective voltage value Ueff, angle of rotation y, active power P and reactive power Q, are transmitted from the smart meter 7 to the power storage unit 4 (e.g. via an output interface 29 of the smart meter 7). The measured values ​​Ueff and y are required to determine the time profile of the actual voltage UIST in the electrical conductor 13, according to u(t) = V2 ■ U eff ■ cos (y). However, these measured values ​​may be inaccurate and should preferably be corrected.

[0127] For correction, the effective value U*eff and the angle of rotation y* of the grid voltage can be measured in power storage unit 4 with no or very small errors, which then serve as reference values. Finally, the correction of the active and reactive power can be performed using the following formulas: and y)), where P* and Q* are the corrected active and reactive power, respectively, and Ay = y* - y. A calibration unit 30 can be provided for the correction—in the embodiment of Figure 7, in the power storage unit 4.

[0128] In the case of a correction or calibration in the smart meter 7, as shown in Figure 8, the calibration unit 30 can be configured accordingly in the smart meter 7, for example as a software or hardware module of a control device 31. In this case, the reference values ​​U*eff and y* can be recorded or read in via a calibration input 32, which is connected to the separate module or the power storage unit 4. Using these reference values, the correction can finally be carried out by the calibration unit 30 within the smart meter 7, as already explained above. The active and reactive power P* and Q* thus corrected can then be transmitted from the smart meter 7 to the power storage unit 4.

[0129] At this point, it should be mentioned that all procedures described here, in particular the procedure for calibrating / correcting the measured values, can be used for a single-phase, three-phase or other version of the supply network 1, whereby the measurements and corrections can be carried out separately for each phase if necessary.

[0130] With reference to Figure 9, an implementation of a measuring circuit 33 according to the invention for detecting the actual voltage UIST and the actual current IIST of the electrical conductor 13 will be described, which implementation can be implemented at least partially on the control device 31 of the smart meter 7. Figure 9 shows, by way of example, the capacitive coupling by means of the at least one capacitive measuring body (e.g., metallic ring) or by means of the magnetic assembly 20 (e.g.,

[0131] B. ring magnet). Alternatively, for example, capacitive coupling can also be provided by means of the measuring coil 23, as already mentioned. In this case, the coupling capacitance CK and the capacitance CM would be connected to the measuring coil 23 (see also Figure 6), as shown in Figure 12 (otherwise, Figure 12 does not differ from the embodiment of Figure 9).

[0132] The actual voltage UIST is introduced into the smart meter 7 as the capacitively coupled measurement voltage UKM by means of capacitive coupling via the coupling capacitance CK. The level of the capacitively coupled measurement voltage UKM depends not only on the coupling capacitance CK, but also on the displayed capacitance CM, which is mainly determined by the parasitic capacitance of the measuring circuit and can be influenced by an additional capacitance in the circuit for adjusting the capacitively coupled measurement voltage UKM.

[0133] A voltage divider and / or an amplifier and / or a signal filter 34 can be provided to adapt or process the capacitively coupled measuring voltage UK.

[0134] The measuring coil 23 of the current transformer 10 is short-circuited via the resistor R. Thus, the measuring current IM flowing through the measuring coil 23 is converted into a measuring voltage U M = R ■ implemented. A differential amplifier 35 can be used to adjust the voltage level.

[0135] The measured voltages UKM and UM can then be read into a computing unit 36, such as a microcontroller, via an analog-to-digital converter. The computing unit 36 ​​can, for example, perform the calculations and corrections of all measured values, as already explained. The resulting and, if necessary, corrected measured values ​​can then be transmitted via the wireless or wired output interface 29 to the separate module, for example, to the power storage unit 4. The output interface 29 or the communication can be implemented, for example, via a Modbus (RS485) with two bus lines, an RS422 bus with four bus lines, or a CAN bus with two bus lines.

[0136] A power supply 37 for the electronic components in the smart meter 7 can optionally be provided via the power storage unit 4. This can, for example, be a DC supply voltage of 12 volts, as indicated in Figures 9 and 12.

[0137] For measuring the voltage UKM (or any other voltage), the ground potential can be used as the reference potential GND, which can preferably also be obtained from the power storage device 4. It should be noted at this point that the reference potential GND and the negative supply signal of the power supply 37 can also be routed in a single, common supply line. However, the separation into separate supply lines has the advantage that the voltage drop caused by the supply current does not negatively influence the voltage measurement.

[0138] To implement wireless data transmission between the smart meter 7 and the power storage unit 4, a converter 38 can be provided that converts the wired communication into wireless communication (indicated by dashed lines in Figures 9 and 12). In this case, the converter 38 can optionally also assume the power supply functions and, for example, also supply the reference potential GND (not shown in Figures 9 and 12). The ground potential or reference potential GND can be taken, for example, from a PE connection of a standard household socket 3.

[0139] The described measuring circuit 33 can, in principle, be well suited for all described variants of the invention, i.e., in particular for capacitive coupling by means of a metallic ring (measuring body 24, 25) or the ring magnet (magnetic body 21, 22), but also for capacitive coupling by means of the measuring coil 23. It should be noted in this regard that, in the case of a circuit for measuring the actual voltage UIST by means of capacitive coupling, the differential amplifier 35 may require a high impedance at one end of the measuring coil 23, e.g., several hundred kΩ (relative to ground potential GND), so that the capacitively coupled measuring voltage UKM is not excessively attenuated. For the same reason, the capacitance CM is preferably very low.

[0140] Insofar as the measuring circuit 33 shown in Figures 9 and 12 is to be used for a three-phase design, the dashed-line component, which is essentially intended to represent the inductive current transformer 10, can be duplicated three times accordingly, as indicated in Figure 1.

[0141] A flow chart for calculating the measured values ​​will now be described using Figure 10. The calculations of the measured values ​​of active and reactive power, as well as the angle of rotation and the effective voltage value, are known. The calculations can be performed in the previously mentioned control device 31 or computing unit 36. First, the angle of rotation y and the frequency f of the measured voltage U can be calculated using a first phase-locked loop 39 (PLL). The angle of rotation yi of the current can be determined using a second phase-locked loop 40. The active and reactive power P and Q, as well as the effective voltage value Ueff, can be calculated using the following equations in the control device 31 or computing unit 36: with cp = y — yi and T = 1 / f.

[0142] The calculation described here can also be used for a three-phase configuration, whereby the calculations can be duplicated three times. Finally, a method according to the invention for measuring the electrical quantities in the electrical conductor 13 will be described schematically with reference to Figure 11. The method is particularly suitable for power control of power storage devices 4 and can comprise at least the following method steps:

[0143] Providing the inductive current transformer 10 and inductively measuring the actual current IIST in the electrical conductor 13 using the measuring coil 23 of the inductive current transformer 10 (cf. method step “V1”); and

[0144] Capacitive measurement of the actual voltage UIST in the electrical conductor 13 using the at least one means 24, 25, 21, 22, 23 for capacitive coupling of the inductive current transformer 10 (cf. method step “V2”).

[0145] In addition, further process steps can of course be provided, including signal processing and error correction, some of which are mentioned below only as examples:

[0146] It can be provided that the capacitively coupled measuring voltage UKM is stabilized and amplified, or that other signal processing measures are carried out for the capacitively coupled measuring voltage UKM, as indicated in process step “V3”.

[0147] Calibration, conversion, and / or error correction of the coupled measurement voltage UKM can be performed as described above and indicated in process step "V4." The reference values ​​mentioned above can be used for this purpose.

[0148] Active and reactive power can be calculated from the recorded current and voltage values, as indicated in process step “V5”.

[0149] As already mentioned above, all embodiments and variants of the invention mentioned in the drawings and in the present description can be combined with one another as desired, unless this is technically impossible.

Claims

Patent claims 1. Inductive current transformer (10) for a smart meter (7), with a measuring coil (23) for the inductive measurement of an actual current (I IST) in an electrical conductor (13), characterized in that the inductive current transformer (10) has at least one means (24, 25, 21, 22, 23) for capacitive coupling and is set up, in addition to the inductive measurement of the actual current (I IST), to carry out a capacitive measurement of an actual voltage (UIST) in the electrical conductor (13) via said means (24, 25, 21, 22, 23) for capacitive coupling.

2. Inductive current transformer (10) according to claim 1, characterized by a line receptacle (11) for an electrical line (6) having the electrical conductor (13), preferably an at least partially annular feedthrough for the electrical line (6).

3. Inductive current transformer (10) according to claim 1 or 2, characterized by a first half-shell (14) and a second half-shell (15) which can be mechanically connected to the first half-shell (14) and which can be moved relative to one another between an open state and a closed state.

4. Inductive current transformer (10) according to claim 3, characterized in that the half-shells (14, 15) are movable relative to one another via a common hinge connection (16) and / or a common linear guide.

5. Inductive current transformer (10) according to one of claims 1 to 4, characterized by a magnetic assembly (20) which can be arranged at least in sections around the electrical conductor (13) and around which at least in sections at least one winding (N) of the measuring coil (23) is arranged so as to encircle.

6. Inductive current transformer (10) according to claim 3 or 4 and 5, characterized in that the magnetic assembly (20) has a first partially annular magnetic body (21) and a second partially annular magnetic body (22), wherein the first magnetic body (21) is connected to the first half-shell (14) and the second magnetic body (22) is connected to the second half-shell (15).

7. Inductive current transformer (10) according to one of claims 1 to 6, characterized in that the means for capacitive coupling comprises at least one partially annular electrically conductive measuring body (24, 25) which can be arranged at least in sections around the electrical conductor (13), preferably a first measuring body (24) fastened to the first half-shell (14) and a second measuring body (25) fastened to the second half-shell (15).

8. Inductive current transformer (10) according to claim 7, characterized in that the at least one partially annular electrically conductive measuring body (24, 25) is designed as a metal sheet, metal foil or metallic coating of a lateral surface (26) of the inductive current transformer (10).

9. Inductive current transformer (10) according to one of claims 5 to 8, characterized in that a measuring line (28) is connected to the magnetic assembly (20) in order to use the magnetic assembly (20) as a means for capacitive coupling.

10. Inductive current transformer (10) according to one of claims 1 to 9, characterized in that a measuring line (28) is connected to the measuring coil (23), preferably to one end of the measuring coil (23), in order to use the measuring coil (23) as a means for capacitive coupling.

11. Smart meter (7), in particular for power control of power storage devices (4), comprising an inductive current transformer (10) according to one of claims 1 to 10.

12. Smart meter (7) according to claim 11, characterized by a computing unit (36) and an output interface (29) electrically connected to the computing unit (36), wherein the computing unit (36) is configured to determine an effective current value (letr), an effective voltage value (Ueff), a reactive power (Q), an active power (P) and / or a phase angle (y) on the basis of the detected actual current (IIST) and the detected actual voltage (UIST) and to output it via the output interface (29).

13. Smart meter (7) according to claim 11 or 12, characterized by a calibration unit (30) which is set up to correct measurement errors in amplitude and / or phase of the detected actual voltage (UIST) on the basis of at least one reference value (U* eff, y*) to be corrected.

14. Smart meter (7) according to claim 13, characterized by a calibration input (32) for electrical connection to a separate module for detecting the at least one reference value (U*eff, y*) from the separate module, preferably for detecting the at least one reference value (U* e ff, y*) from the power storage device (4).

15. Method for measuring electrical quantities in an electrical conductor (13), in particular for Power control of power storage devices (4), comprising at least the following method steps: Providing an inductive current transformer (10) and inductively measuring an actual current (IIST) in the electrical conductor (13) using a measuring coil (23) of the inductive current transformer (10); and Capacitive measurement of an actual voltage (UIST) in the electrical conductor (13) using at least one means (24, 25, 21, 22, 23) for capacitive coupling of the inductive current transformer (10).

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