Power supply system with coupling device

Abstract

A local power supply system (1) has a power supply network transmission point (4) for connecting to a power supply network (5), the local power supply system having: a first transmission line (2) for transmitting electric energy from the power supply network transmission point (4) to a first connection terminal (16) for connecting to an electric device (6); and a second transmission line (3) for transmitting electric energy from the power supply network transmission point (4) to a second connection terminal (18) for connecting to an energy storage device (8). A first separation point (7) is arranged in the first transmission line (2) between the power supply network transmission point (4) and the first connection terminal (16), and a second separation point (9) is arranged in the second transmission line (3) between the power supply network transmission point (4) and the second connection terminal (18). A coupling device (10) for electrically connecting a first connection (16) to a second connection (18) comprises a first switch (11) and a second switch (13) connected in series with the first switch (11), wherein a coupling element (12) is arranged between the two series-connected switches (11, 13) and comprises a grounding device, a phase connection device, a neutral conductor connection device, a connection device to a diesel generator and / or a device for generating a neutral conductor potential. A method for operating such a system is also described.

Description

[0001] The invention relates to a local power supply system for selectively supplying power to electrical consumers from a connected power supply grid or an energy storage device.

[0002] Furthermore, the invention relates to a method for operating a local power supply system.

[0003] In particular, the invention relates to so-called emergency power supply systems, backup power supplies or backup systems, which protect the grid-connected power supply system in the event of a grid failure, i.e. are able to continue to supply at least some of the connected loads with power, for example according to a predetermined priority. To this end, a series of switching operations must be carried out, for example disconnecting the grid, starting the grid former (Netzbildner), connecting it to the power supply line. In addition, the state of the grid must be monitored in order, for example, to start the synchronization of local generators when the grid is restored and to be able to reconnect the system to the grid. These requirements and many others must be met, and their fulfillment is documented in various guidelines, specifications and standards in different countries.

[0004] In particular, meeting the requirements for central grid and system protection in connection with such emergency power supply systems is complex and costly. Thus, for example, some countries require all-pole disconnection of the supply line before switching to emergency operation, while other countries absolutely prohibit disconnection of the neutral conductor. For suppliers of emergency power supply systems, this results in a large number of variants and the associated costs. It would be desirable to achieve standardization or at least modular interchangeability of components depending on the country and requirements.

[0005] In the prior art, common network disconnection points for electrical loads and backup systems are mainly described, EP 2 668 705 81 B1 in Figure 1 , a disconnection device is shown, by which a transmission line can be divided into two parts electrically insulated from each other, namely a supply part and a discharge part. A grid former is provided in the discharge part for establishing a local supply grid in order to supply power to the electrical consumers after disconnection from the grid by the disconnection device. The disadvantage here is that the grid former (including batteries and inverters) and the electrical consumers are located in the same discharge part, so that the size of the disconnection device must be significantly increased, because the disconnection device must be designed for the entire maximum possible power.

[0006] DE 10 2012 113 016 B4 Figure 1A photovoltaic generator is shown, whose energy can be fed into the upper power supply grid via a PV inverter and a grid disconnect device. In the event of a grid failure, the local energy distribution grid is disconnected from the upper power supply grid, and the grid backup system establishes a local grid, and the PV inverter can continue to feed power to the local grid. Here, the electrical appliances, generators and backup systems are also arranged on the same power supply line. Since in many countries the limits of the feeders in terms of permitted grid parameters (voltage, frequency) are narrower than those of the electrical appliances, even if the grid status still allows the operation of the electrical appliances, it may have to be disconnected from the grid. This is very disadvantageous.

[0007] The task of the present invention is to overcome the above disadvantages and further simplify the realization of the above requirements, thereby proposing a local power supply system that can more easily adapt to corresponding local regulations and environment, making it possible to produce a backup system at a lower cost.

[0008] This task is achieved by a local power supply system, which is connected to the power supply grid via a grid transmission point and has: a first transmission line, which is used to transmit electrical energy to an electrical device; and a second transmission line, which is used to transmit electrical energy back and forth between an energy storage device and the power supply grid. Here, the first transmission line is arranged between the grid transmission point and a first connection end, to which the electrical device can be connected. The first separation point is located in the first transmission line between the grid transmission point and the first connection end. The second transmission line is arranged between the grid transmission point and the second connection end, to which the energy storage device can be connected. The second separation point is located in the second transmission line between the grid transmission point and the second connection end. In addition, the local power supply system also has a coupling device, which is electrically connected to the first connection end and the second connection end. The coupling device has a first switch and a second switch connected in series therewith.

[0009] A coupling element is connected between the two switches connected in series, and the coupling element has at least one element from a group of devices. The group of devices includes a grounding device, a phase connection device, a neutral conductor connection device, a connection device to a diesel generator, and a device for generating a neutral conductor potential. In the present invention, the central separation point commonly seen in the prior art is divided into a separation point for the energy storage device and a separation point for the load. This can be achieved by separating the common transmission line into transmission lines to the two devices respectively. This is advantageous because, as mentioned above, the requirements for the separation point applicable to the energy storage device are usually different from the requirements for the separation point applicable to the load. Nevertheless, in normal operation, the electrical appliance can be supplied with power from the power grid, and local power supply can be achieved from the energy storage device, that is, local power supply can be achieved through two transmission lines.

[0010] In principle, the local power supply system according to the invention is suitable for connection to any power supply system. Examples of this are single-phase or three-phase power grids, with or without a neutral conductor, and so-called split-phase power grids. In order to detect power grid disturbances or power grid faults, the power supply grid can be monitored at points other than the separation point (e.g., power grid transmission points) by means of sensors. The values ​​determined by the power grid monitoring can be sent to a central control unit, which can be located in the local power supply system. However, the central control unit can also be designed as part of a converter / inverter belonging to the energy storage device. If a power grid disturbance / power grid fault is detected, the first transmission line and the second transmission line are disconnected by means of a first separation point and a second separation point, which means that the electrical device and the energy storage device are disconnected from the power supply grid. The individual switches can also be controlled by the central control unit. The prerequisite for disconnecting from the power supply grid is that the energy storage device can establish a local independent power grid. To this end, the first switch and the second switch of the coupling device are closed, thereby forming a local power grid, and the energy storage device supplies power to the electrical device through the coupling device. In order to be able to establish a local power grid, for example, the battery inverter can be configured as a grid former, that is, the grid former can independently establish an isolated power grid, which is also referred to as standby operation here.

[0011] In principle, the energy storage device can consist of one or more energy storage devices, and similarly the consumer device can consist of one or more consumers.

[0012] In an advantageous embodiment of the invention, the coupling device has a grounding device between the two switches. In most power supply networks, a grounded neutral conductor is specified (star point grounding). Depending on the location of the neutral conductor grounding in normal operation, the grounding connection may be lost in standby operation due to disconnection from the grid. The grounding of the neutral conductor must then be achieved in standby operation. In a preferred embodiment, this grounding of the neutral conductor is provided by a coupling element, that is, the coupling element may comprise a fixed connection from the neutral conductor to ground (PE).

[0013] In an advantageous embodiment of the invention, the local power supply system comprises an energy storage device. It is particularly advantageous if the energy storage device also has a central control unit or if a central control unit present in the local power supply system also controls the functions of the energy storage device.

[0014] In another advantageous embodiment of the invention, the energy storage device comprises further energy generators, which can particularly preferably be supplied by renewable energy sources. Here, for example, photovoltaic power plants, wind power plants or biogas plants may be possible. Advantageously, in normal operation (connected to the power supply grid) and in standby operation (for example, in the event of a grid failure), the electrical consumers can also be supplied with energy from locally generated energy. In the event of a grid failure lasting a long time, the electrical consumers can be supplied with energy for a long time, and in the event of excess energy, the battery can also be charged from the local energy generation system.

[0015] In another advantageous embodiment of the invention, a first switch of the coupling device is connected between the first connection end and the coupling element, and a second switch of the coupling device is connected between the second connection end and the coupling element. If the first transmission line has a first number (e.g. 3) of external conductors, the first switch can have a corresponding first number of switch contacts and a switch contact for the neutral conductor, whereby in the example the first switch has four contacts. In some countries, such all-pole disconnection is specified.

[0016] In another advantageous embodiment of the invention, the first transmission line has a first number of external conductors and the first switch has a corresponding first number of switch contacts, but the neutral conductor is not switched by the first switch. Since in some North American countries the disconnection of the neutral conductor is prohibited by standard, here, for example in a conventional "split-phase" network, the first switch can be handled with two switch contacts, and the neutral conductor can be always switched on.

[0017] In a further advantageous embodiment of the invention, the second transmission line has a second number of outer conductors and the second switch has a corresponding second number of switch contacts and a switch contact for the neutral conductor.

[0018] If the first number is greater than the second number, the coupling element can have a phase connection device, which connects a plurality of outer conductors of the first transmission line to an outer conductor of the second transmission line. In this way, a single-phase load connected to a first transmission line, for example three-phase, can still be supplied by an energy storage device, for example single-phase: three outer conductors of the first transmission line are connected to an outer conductor of the second transmission line via the coupling element.

[0019] In another advantageous embodiment of the invention, the coupling element has a grounding device which establishes a connection between the neutral conductor N and ground. In standby operation, due to the disconnection from the grid at two separation points, the ground reference of the neutral conductor may be lost. In this case, it is usually desirable or provided to restore the connection of the neutral conductor to ground so that protective measures like RCD (FI switch) can take effect, in particular protective measures present in grid operation can be used in standby situations.

[0020] In a further advantageous embodiment of the invention, the first transmission line is designed as a single-phase three-conductor network ("split-phase") and the coupling element has a device for generating a neutral conductor potential in the form of an autotransformer as an inductive voltage divider. In this way, an energy storage device with two-phase external conductor connections and no neutral conductor can be coupled to the "split-phase" transmission line in order to supply single-phase loads.

[0021] In another advantageous embodiment of the invention, the coupling element has a connection device for a diesel generator. This allows the diesel generator to be integrated into the power supply of the electrical load in the standby situation. The connection device can contain further switches for coupling the generator as required. The term diesel generator is to be understood here as a typical generator which can generate alternating current via a rotor driven by an internal combustion engine.

[0022] When large amounts of energy are required in standby situations, diesel generators are often integrated into emergency power or backup systems, especially in preparation for grid failures lasting longer, for example when it is not always sufficient to ensure the supply of renewable energy sources. The generator is then started when needed (usually depending on the charge state of the batteries of the battery inverter), synchronized and connected to the system. When the batteries have a sufficient charge state again, the generator can be stopped and disconnected again.

[0023] Advantageously, this embodiment enables that in the event of a grid failure and a battery system cut-off or failure and / or a failure of the entire operational control of the power supply system, if the generator has been manually started, for example, the generator voltage applied to the coupling element is directly supplied to the load by controlling the first switch. The grounding of the central neutral conductor can also be successfully implemented in emergency operation, and safety measures for the electrical safety of electrical appliances (for example, the use of a fault current protection switch) are still effective.

[0024] This embodiment further enables, for example, the electrical load to be supplied with power from the generator, while the energy store is charged by the renewable generator integrated into the energy store arrangement by opening the second switch and closing the first switch.

[0025] Due to the modular construction of the coupling device with the first switch and the second switch and the coupling element, the local power supply system according to the invention can be easily adapted to regional conditions and regulations by adjusting the coupling element.

[0026] In an advantageous embodiment of the invention, the first disconnection point, the second disconnection point, the first switch and the second switch each have auxiliary contacts, via which an electromechanical interlock is established, so that even if a central control unit fails, the required safety function is ensured. In principle, it should be noted that the grid disconnection point and the connection via the coupling device are interlocked with each other, that is, the grid disconnection point must be open when the electrical load is connected to the energy storage device via the coupling device. This can be achieved in a fundamentally known manner, namely by controlling the relays via the auxiliary contacts of the respective "matching" relays required for the interlock.

[0027] The first switch and the first disconnection point are interlocked with each other, and the second switch and the second disconnection point are interlocked with each other. This can be designed so that, for example, the disconnection point is connected to the mains voltage via the respective control contacts and the respective auxiliary contacts (signal contacts) of the relevant switches. These auxiliary contacts are designed so that the disconnection point can only be closed when the mains voltage is present, the coupling switch is open, and the auxiliary contacts are therefore closed. Vice versa: here, when the relevant disconnection points are simultaneously open, the auxiliary contacts are therefore closed, and of course the control signal is activated, the coupling switch is controlled with the isolated mains voltage (standby situation). This ensures that only the disconnection point or the coupling switch is closed, but not both at the same time. This also makes it possible to switch the mains to the electrical consumer via the first disconnection point when the standby system has been disconnected and the mains voltage is present.

[0028] In another embodiment of the invention, the coupling element has a connection for the generator. In this way, the generator is only incorporated in the standby operation. This is particularly advantageous in connection with the above-mentioned electromechanical interlock. Thus, when the standby system is cut off and there is no power supply grid, for example, the generator can be started manually and then connected to the electrical consumer via corresponding wiring. However, it must now be ensured that when the power supply grid is present, the switch to the generator does not automatically disconnect again, because otherwise a phase jump (asynchronous switching) may occur on the electrical consumer, which may damage or destroy the electrical consumer. The electromechanical interlock can ensure that the generator must first be stopped and only then the power supply grid is reconnected to the electrical consumer.

[0029] In another advantageous embodiment of the invention with a single-phase load connection and a single-phase connection of the energy storage device, i.e. the load is connected to an external conductor and a neutral conductor, the coupling device and the switch of the two disconnection points can be designed as two switch components, for example as two protective devices (Schutz) each with four contacts (2 normally closed contacts and 2 normally open contacts). Thus, the first disconnection point and the first switch of the coupling device can be designed together in such a protective device, and the second disconnection point can also be designed together with the second switch of the coupling device.

[0030] In order to solve the above-mentioned task, the present invention also proposes a method for operating a local power supply system. Here, the local power supply system has: a first transmission line, which is used to transmit electric energy from a power grid transmission point to a first connection end, and an electrical device can be connected to the first connection end; and a second transmission line, which is used to transmit electric energy between the power grid transmission point and the second connection end, and an energy storage arrangement can be connected to the second connection end. In the first transmission line, the first separation point is located between the power grid transmission point and the first connection end. In the second transmission line, the second separation point is located between the power grid transmission point and the second connection end. The local power supply system also has a coupling device, which is electrically connected to the first connection end and the second connection end, wherein the coupling device has a first switch and a second switch connected in series therewith, and a coupling element is arranged between the two switches connected in series. The local power supply system also has a central control unit. The method includes the following steps: for normal operation, the first separation point and the second separation point are closed by the central control unit, and the two switches of the coupling device are opened, and for standby operation, the first separation point and the second separation point are opened by the central control unit, and the two switches of the coupling device are closed, thereby activating the coupling element. The activation of the coupling element solves the technical problem of the requirements of different standards between normal operation and standby operation as detailed above.

[0031] In an advantageous embodiment of the method, the first disconnection point and the second disconnection point and the two switches connected in series are switched simultaneously, thereby enabling uninterrupted power supply to the electrical load.

[0032] In an advantageous embodiment of the method, grid parameters of the power supply grid are measured at the grid transfer point and transmitted to a central control unit which controls the opening and closing of the first and second disconnecting points and the two switches of the coupling device as a function of the measured grid parameters.

[0033] The present invention will be described below based on embodiments and with reference to the accompanying drawings. Other features, properties and advantages of the present invention will be apparent from the accompanying drawings in combination with the features of the claims. In the accompanying drawings:

[0034] Figure 1A schematic diagram showing a local power supply system with a unit connected thereto according to the present invention is shown;

[0035] Figure 2 An exemplary implementation of a power supply system according to the present invention is shown;

[0036] Figure 3 An exemplary embodiment of a coupling element according to the invention is shown;

[0037] Figure 4 A further exemplary embodiment of the coupling element according to the invention is shown.

[0038] Figure 1 A local power supply system 1 is schematically shown, which is connected to a power supply grid 5 via a grid transmission point 4. A first transmission line 2 for transmitting electrical energy leads from the grid transmission point 4 to a first connection 16. An electrical device 6 can be connected to the first connection 16. A first separation point 7 is located in the first transmission line 2 between the grid transmission point 4 and the first connection 16. A second transmission line 3 extends between the grid transmission point 4 and the second connection 18. An energy storage device 8 can be connected to the connection 18. Energy can be exchanged bidirectionally between the power supply grid 5 and the energy storage device 8 via the second transmission line 3. A second separation point 9 is located in the second transmission line 3 between the grid transmission point 4 and the second connection 18. A coupling device 10 is electrically connected to the first connection 16 and the second connection 18. The coupling device 10 has a first switch 11 and a second switch 13 connected in series with the first switch 11. A coupling element 12 is arranged between the two switches 11, 13 connected in series. The coupling device 10 is connected to the first transmission line 2 between the first disconnection point 7 and the first connection 16 and is connected to the second transmission line 3 between the second disconnection point 9 and the second connection 18 .

[0039] Figure 2 A local power supply system 1 according to a preferred embodiment is shown. Here, the power supply grid 5 is designed as a three-phase grid having outer conductors L1, L2, L3 and a neutral conductor N. In normal operation, the separation points 7 and 9 are closed, the switches 11 and 13 are open, and the coupling element 12 is ineffective in this operating state. The electrical device 6 is powered by the power supply grid 5. The energy storage device 8 can be charged by the power supply grid 5, or feed power to the power supply grid 5, for example to provide grid services. In an embodiment of the present invention, the energy storage device 8 includes a battery 20 and a generator 21. Preferably, the generator 21 can include renewable energy. The generator 21 and the battery 20 can each have an independent converter 25, or can be operated with a common converter 25. With combined heat and power A combined heat and power plant (Blockheizkraftwerk), which is operated, for example, with biogas, can also be integrated into the energy storage device 8 as a generator 21, which makes it possible to eliminate the need for a converter.

[0040] If the power supply grid 5 is disturbed, for example the grid frequency exceeds the permissible limit of the generator and the battery, the disconnection point 9 is opened to disconnect the energy storage device 8 from the power supply grid 5. The electrical device 6 can usually continue to operate on the power supply grid 5. Therefore, the disconnection point 7 can remain closed. Despite being disconnected from the power supply grid 5, the battery 20 can be charged by the generator 21 in the energy storage device 8.

[0041] If a fault occurs in the power supply grid 5, for example if the grid voltage drops below the permissible limit, in addition to the disconnection point 9, the disconnection point 7 can also be disconnected in order to start the backup operation. After disconnecting the disconnection point 7, the second switch 13 of the coupling device 10 can be closed first, so that the coupling element 12 (designed as a grounding device 22 in the present embodiment) is connected to the energy storage device 8. In this way, a star point grounding can be established for the energy storage device 8, which allows the use of a protective device for the electrical device 6 after the first switch 11 is closed. This can be a regional regulation. After the first switch 11 is closed, energy can be supplied to the electrical device 6 from the energy storage device 8. The energy storage device 8 includes at least one grid former (not shown), for example, this function can be taken over by the converter 25 of the battery 20. This means that the converter 25 can independently establish an isolated grid.

[0042] The grid status is detected by sensors at the grid transmission point 4 and transmitted to a central controller (not shown). The controller may be located in the grid former or may also be part of the local power supply system 1 .

[0043] If the power supply network 5 returns to a state that allows the electrical device 6 to be supplied with power, the return to normal state can be started. For this purpose, the grid former is synchronized with the frequency, phase and voltage of the grid 5. The transmitted values ​​of the sensors can be used for this purpose. Now, the disconnection point 7 can be closed, and at the same time or before that, the first switch 11 can be opened in order to supply power to the electrical device 6 from the power supply network 5.

[0044] If the operating conditions of the energy storage device 8 are also met, the second switch 13 can also be opened and the disconnection point 9 can be closed after or at the same time. These conditions can include limits on the grid voltage and frequency that must be observed within a specified time period. Alternatively, for uninterrupted switching, all of the above switches can also be switched simultaneously in the manner described.

[0045] Local power supply systems known so far are usually designed with a switch in the connection between the neutral conductor N and the ground. This must be monitored in a complex manner or implemented in a complex manner. This is simplified by the use of the coupling element 12, because the connection between the neutral conductor N and the ground is permanently installed and automatically correctly connected during the connection procedure of the standby operation. The solution of connecting the electrical device 6 to the power supply network 5 and supplying it with electricity from the power supply network also brings additional benefits, even if the connection conditions of the storage device 8 are not met or have not yet been met.

[0046] Figure 3 The embodiment of the coupling device 10 according to the invention is shown. Here, the first transmission line 2 is equipped with three external conductors L1, L2, L3 and a neutral conductor N. The second transmission line 3 and the connection 18 are also designed as single-phase (here connected to L3 as an example), and the energy storage device 8 is fed into the local power supply system through the connection 18. In this embodiment, the coupling element 12 has a phase connection device 23. In the event of a fault in the power grid, the electrical consumers distributed on the external conductors L1, L2, L3 can be powered by the single-phase energy storage device 8 when connected via the first switch 11 and the second switch 13 and the phase connection device 23.

[0047] Figure 4 Another embodiment of the coupling device 10 according to the invention is shown. In this embodiment, the coupling element 12 has a device 24 for generating a neutral conductor potential in the form of an autotransformer. The first transmission line 2 is designed with two outer conductors L1, L2 and a neutral conductor N for a single-phase three-wire network. The second transmission line 3 and the connection 18 are designed here as two-phase, without a neutral conductor N, via which the energy storage device 8 can feed the local power supply system 1. Therefore, in standby operation, a neutral conductor potential must be generated by the device 24. This is necessary for connecting a single-phase electrical consumer between one phase and the neutral conductor N. In addition, in this example, it is also assumed that switching the neutral conductor N is prohibited by regulations, so that the first switch 11 is only equipped with two switching contacts for the two outer conductors L1, L2.

[0048] Reference Mark List

[0049] 1 Power supply system

[0050] 2,3 Transmission Lines

[0051] 4 Grid transmission points

[0052] 5 Power supply grid

[0053] 6 Electrical devices

[0054] 7, 9 separation point

[0055] 8 Energy storage device

[0056] 10 Coupling equipment

[0057] 11, 13 Switch

[0058] 12 Coupling elements

[0059] 20 Batteries

[0060] 21 Generator

[0061] 22 Grounding device

[0062] 23 Phase connection device

[0063] 24 Device for producing neutral conductor potential

[0064] 25 Converters.

Claims

1. A local power supply system (1) having a power grid transmission point (4) for connecting to a power supply grid (5), the local power supply system having: a first transmission line (2) for transmitting electric energy from the grid transmission point (4) to a first connection end (16) for connecting an electric device (6), wherein a first separation point (7) is located in the first transmission line (2) between the grid transmission point (4) and the first connection end (16); a second transmission line (3) for transmitting electrical energy from the grid transmission point (4) to a second connection (18) for connecting an energy storage device (8), wherein a second disconnection point (9) is located in the second transmission line (3) between the grid transmission point (4) and the second connection (18); a coupling device (10) which electrically connects the first connection end (16) and the second connection end (18), It is characterized in that The coupling device (10) comprises a first switch (11) and a second switch (13) connected in series with the first switch (11), and a coupling element (12) is arranged between the first switch (11) and the second switch (13), the coupling element (12) comprising at least one element from the following group: a grounding device, by means of which the connection between the neutral conductor N and the ground is permanently installed and is automatically correctly connected during the connection procedure of the standby operation, Connecting device, Neutral conductor connection device, Connections to diesel generators, and Device for producing neutral conductor potential.

2. The local power supply system (1) according to claim 1, characterized in that: The energy storage device (8) is a component of the power supply system (1).

3. The local power supply system (1) according to claim 1, characterized in that: The energy storage device (8) comprises a further energy generator.

4. The local power supply system (1) according to claim 2, characterized in that: The energy storage device (8) comprises a further energy generator.

5. The local power supply system (1) according to any one of claims 1 to 4, characterized in that: The first switch (11) is connected between the first connection end (16) and the coupling element (12), and the second switch (13) is connected between the second connection end (18) and the coupling element (12).

6. The local power supply system (1) according to claim 5, characterized in that: The first transmission line (2) has a first number of external conductors and the first switch (11) has a corresponding first number of switch contacts and a switch contact for a neutral conductor (N).

7. The local power supply system (1) according to claim 5, characterized in that: The first transmission line (2) has a first number of outer conductors, and the first switch (11) has a corresponding first number of switch contacts, and the neutral conductor (N) is not switched by the first switch (11).

8. The local power supply system (1) according to any one of claims 1 to 4, characterized in that: The second transmission line (3) has a second number of external conductors, and the second switch (13) has a corresponding second number of switch contacts and a switch contact for a neutral conductor (N).

9. The local power supply system (1) according to claim 6 or 7, characterized in that: The second transmission line (3) has a second number of external conductors, and the second switch (13) has a corresponding second number of switch contacts and a switch contact for a neutral conductor (N).

10. The local power supply system (1) according to claim 5, characterized in that: The second transmission line (3) has a second number of external conductors, and the second switch (13) has a corresponding second number of switch contacts and a switch contact for a neutral conductor (N).

11. The local power supply system (1) according to claim 9, characterized in that: The first number is greater than the second number, and the coupling element (12) has a phase connection device (23) which connects a plurality of outer conductors of the first transmission line (2) to outer conductors of the second transmission line (3).

12. The local power supply system (1) according to any one of claims 1-4, 6-7 and 10-11, characterized in that: The first transmission line (2) is designed for a single-phase three-wire network, and the coupling element (12) has means (24) for generating a neutral conductor potential in the form of an autotransformer.

13. The local power supply system (1) according to claim 5, characterized in that: The first transmission line (2) is designed for a single-phase three-wire network, and the coupling element (12) has means (24) for generating a neutral conductor potential in the form of an autotransformer.

14. The local power supply system (1) according to claim 8, characterized in that: The first transmission line (2) is designed for a single-phase three-wire network, and the coupling element (12) has means (24) for generating a neutral conductor potential in the form of an autotransformer.

15. The local power supply system (1) according to claim 9, characterized in that: The first transmission line (2) is designed for a single-phase three-wire network, and the coupling element (12) has means (24) for generating a neutral conductor potential in the form of an autotransformer.

16. The local power supply system (1) according to any one of claims 1-4, 6-7, 10-11 and 13-15, characterized in that: The first separation point (7), the second separation point (9), the first switch (11) and the second switch (13) respectively have auxiliary contacts, through which an electromechanical interlock is established, so that even if a central control unit fails, it is possible to switch to a backup operation.

17. The local power supply system (1) according to claim 5, characterized in that: The first separation point (7), the second separation point (9), the first switch (11) and the second switch (13) respectively have auxiliary contacts, through which an electromechanical interlock is established, so that even if a central control unit fails, it is possible to switch to a backup operation.

18. The local power supply system (1) according to claim 8, characterized in that: The first separation point (7), the second separation point (9), the first switch (11) and the second switch (13) respectively have auxiliary contacts, through which an electromechanical interlock is established, so that even if a central control unit fails, it is possible to switch to a backup operation.

19. The local power supply system (1) according to claim 9, characterized in that: The first separation point (7), the second separation point (9), the first switch (11) and the second switch (13) respectively have auxiliary contacts, through which an electromechanical interlock is established, so that even if a central control unit fails, it is possible to switch to a backup operation.

20. The local power supply system (1) according to claim 12, characterized in that: The first separation point (7), the second separation point (9), the first switch (11) and the second switch (13) respectively have auxiliary contacts, through which an electromechanical interlock is established, so that even if a central control unit fails, it is possible to switch to a backup operation.

21. The local power supply system (1) according to claim 16, characterized in that: The coupling element (12) has a connection for a generator.

22. The local power supply system (1) according to any one of claims 17 to 20, characterized in that: The coupling element (12) has a connection for a generator.

23. The local power supply system (1) according to claim 3 or 4, characterized in that: The further energy generator is an energy generator supplied by renewable energy.

24. A method for operating a local power supply system (1), the local power supply system having: A first transmission line (2) for transmitting electric energy from a grid transmission point (4) to a first connection end (16) for connecting an electrical device (6), wherein a first separation point (7) is located in the first transmission line (2) between the grid transmission point (4) and the first connection end (16); a second transmission line (3) for transmitting electrical energy from the grid transmission point (4) to a second connection (18) for connecting an energy storage device (8), wherein a second disconnection point (9) is located in the second transmission line (3) between the grid transmission point (4) and the second connection (18), A coupling device (10) electrically connects the first connection end (16) and the second connection end (18), wherein: The coupling device (10) has a first switch (11) and a second switch (13) connected in series with the first switch (11), and a coupling element (12) is arranged between the first switch (11) and the second switch (13), the coupling element (12) having a grounding device (22), wherein the connection between the neutral conductor N and the ground is permanently installed via the grounding device and is automatically correctly connected during a connection procedure of a standby operation, and Central control unit, Wherein, the method comprises the following steps: In normal operation, the first disconnection point (7) and the second disconnection point (9) are closed by the central control unit and the first switch (11) and the second switch (13) of the coupling device (10) are opened, In the standby operation, the first disconnection point (7) and the second disconnection point (7, 9) are opened by the central control unit and the first switch (11) and the second switch (13) of the coupling device (10) are closed, thereby activating the coupling element (12).

25. The method for operating a local power supply system (1) according to claim 24, wherein the first separation point (7), the second separation point (9), the first switch (11) and the second switch (13) are switched simultaneously.

26. A method for operating a local power supply system (1) according to claim 24 or 25, wherein: measuring grid parameters of the power supply grid (5) at the grid transmission point (4) and transmitting the grid parameters to the central control unit, and The central control unit controls the opening and closing of the first separation point (7) and the second separation point (9) and the first switch (11) and the second switch (13) of the coupling device (10).

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