Direct current network

Abstract

The invention relates to a direct current network (100; 200) which has a main line (102; 202) and at least one stub (106; 204) which is electrically connected to the main line (102; 202). The direct current network (100; 200) is characterised in that a first end of the stub (106; 204) is connected to the main line (102; 202) by means of an exothermic welding method. The invention also relates to a direct current conductor connection unit (108) and to a direct current network manufacturing method (300).

Description

[0001] DESIGNATION

[0002] DC network

[0003] TECHNICAL AREA

[0004] The present invention relates to a direct current network, a direct current conductor connection and a direct current network manufacturing method.

[0005] STATE OF THE ART

[0006] Direct current (DC) networks have been known since the early days of electrical power supply. However, transmission losses and voltage drops across long DC networks initially led research to focus on alternating current (AC). The invention of the three-phase AC motor finally brought about the breakthrough for AC networks. AC networks are still standard in households worldwide today.

[0007] As part of the trend towards renewable energy, energy sources are increasingly converting to direct current (DC) sources, such as photovoltaic systems and batteries, and energy consumers are also becoming DC consumers, such as charging stations and electric vehicle batteries. DC grids are currently experiencing a renaissance, as they reduce conversion losses for modern DC sources and consumers, thus increasing overall efficiency.

[0008] From DE 102022211752 A1, a system for supplying power to an electrical consumer is known. This known system comprises a high-voltage electrical energy generation system, a low-voltage battery system, and a microgrid controller coupled to the electrical energy generation system at its input. The microgrid controller is coupled to a DC bus at its output, which is configured for charging and discharging the battery system. The DC bus performs the discharge at a medium voltage. The system is characterized by the fact that the battery system is designed for charging at a medium voltage and for discharging at a low voltage.

[0009] US Patent 8970176 B2 discloses a system and method for creating and operating a DC microgrid. Such a known DC microgrid can include power generators, energy storage devices, and loads connected to a common DC bus. Power electronic devices can connect the power generators, energy storage devices, and loads to the common DC bus and provide power transmission.

[0010] WO 2024052083 A1 describes a power distribution system for a data center. This system includes, among other things, several medium-voltage DC busbar sections and several low-voltage DC busbar sections. The medium-voltage DC busbar sections can form a ring bus.

[0011] US Patent 2023318435 A1 discloses a power grid comprising a conversion stage with multiple DC-to-DC converters. At least one of the DC-to-DC converters is a single-stage isolated DC-to-DC converter with voltage control configured to control a voltage of the respective DC-to-DC converter. The DC-to-DC converters are connected in series, and at least one of the multiple converters in the conversion stage is configured to deliver a predetermined output voltage to a load.

[0012] From CN 107322157 A, a heat-releasing welding process for an underground cable in the Amazon rainforest is known.

[0013] TASK OF INVENTION

[0014] Therefore, the object of the invention is to provide an easy-to-manufacture, cost-efficient, highly conductive, mechanically stable and safe electrical connection for direct current networks.

[0015] REVELATION OF THE INVENTION

[0016] According to the invention, a direct current network according to claim 1 is provided. The direct current network according to the invention comprises in particular a main line and at least one branch line which is electrically connected to the main line, wherein a first end of the branch line can be connected to the main line by means of an exothermic welding process.

[0017] A direct current (DC) network is generally a system with one or more electrical conductors in which a current flows constantly in one direction. The DC network according to the invention is characterized by the fact that the direction of current flow can be changed by adjusting the voltage levels. This adjustment of the voltage levels can be achieved by DC-DC converters or by inverters, transformers, and rectifiers. Changing the direction of flow is advantageous, for example, to minimize losses, improve network stability, provide protection against overload in the DC network, or generally create greater flexibility for changing loads or conditions.

[0018] Preferably, the DC network comprises a low-voltage DC network from 0 to 1500 V or a medium-voltage DC network from 1500 to 20000 V. Low voltage in DC networks particularly includes a voltage range up to 1500 V. A main line particularly includes a busbar. The main line may comprise an insulated copper conductor. Furthermore, the main line may have a nominal cross-section of 120 mm². 2 , 300 mm 2 , 500 mm 2 or even more preferably, 1000 mm 2 They must be capable of safely conducting and transmitting direct currents of 550 A, 930 A, 1200 A, or even 1800 A. The main conductor can be made of the following materials: copper, aluminum, copper-aluminum alloy, copper-nickel alloy, and / or silver.

[0019] The main line and the branch line are preferably electrical conductors or wires. The main line and the branch line preferably each comprise a forward conductor and a return conductor; in other words, the main line and the branch line are generally designed to form a closed circuit.

[0020] The exothermic welding process preferably comprises an aluminothermic welding process, in particular thermite welding. The aluminothermic welding process is essentially a special welding process used to produce metallic joints, especially for rails and other solid metal parts. It is generally based on an exothermic chemical reaction between aluminum and iron(III) oxide, which generates a very high temperature. In this process, a mixture of aluminum powder and iron(III) oxide (Fe₂O₃) is typically ignited in a special container, the so-called thermite furnace. The reaction between aluminum and iron(III) oxide leads, in particular, to a very high temperature of about 2500°C to 3000°C, at which the iron(III) oxide is reduced to iron and the aluminum is oxidized to aluminum oxide.This reaction can generate a large amount of heat, which can be used to melt the metal parts.

[0021] In the present invention, aluminum powder is preferably used and copper as the welding metal. The exothermic welding process can connect the main conductor and the branch line in a simple, cost-effective, highly conductive, mechanically stable and electrically safe manner.

[0022] Conventional connections, such as connectors, are usually expensive, unwieldy, mechanically unstable in the long term, and have a higher ohmic resistance than a welded connection produced by the exothermic welding process, especially at high DC voltages of about 1500 V and higher and high DC currents of about 2000 A and higher.

[0023] According to a further embodiment, the main conductor can comprise a first metal, in particular copper, and the branch conductor can comprise a second metal, in particular aluminum, wherein the first and second metals are preferably different materials. In particular, the second metal has a lower conductivity than the first metal. Advantages of branch conductors designed in this way can include lower material costs and / or easier handling due to a lower specific weight compared to a copper main conductor. Joining two different metals is generally a particular challenge. The exothermic welding process can be particularly suitable for joining the two metals in a simple, cost-effective, highly conductive, mechanically stable, and electrically safe manner.

[0024] In a further configuration, the branch line can include a short-circuit-proof conductor. Faults or short circuits can occur in DC networks, such as overcurrent faults, transverse faults, or longitudinal faults. To prevent damage to people, systems, or equipment in conjunction with the DC network, means for rapid and reliable current disconnection are particularly important. The short-circuit-proof conductor can also be referred to as a short-circuit-proof cable or intrinsically safe cable. The short-circuit-proof conductor is essentially characterized by insulation to reduce or prevent the risk of a cable fire. Furthermore, the short-circuit-proof conductor can have a specific cross-section that carries a rated current but melts under a short-circuit current, thus disconnecting the conductor or causing a current break.The DC network according to the invention preferably comprises the exothermically welded branch line, wherein the branch line includes a short-circuit-proof conductor. In this way, a simple-to-manufacture, cost-effective, highly conductive, mechanically stable and at the same time safe electrical connection can be provided in the DC network.

[0025] According to a further embodiment, the branch line has a smaller cross-sectional area than the main line. A difference in cross-sectional area between the branch line and the main line can cause different behavior in the event of a short circuit. Preferably, in the event of a short circuit, the branch line melts, but not the main line.

[0026] The branch line can, in particular, act as a safety device. If a fault or short circuit occurs in a DC power supply unit connected to the branch line, the branch line can safely interrupt the short-circuit current without damaging or affecting the main line or other DC power supply units.

[0027] The DC network can comprise at least two or more branch lines. A branch line, in particular, electrically connects a DC network unit to the main line. A DC network unit, in particular, comprises a power source or power sink and one or more voltage transformers. A power source essentially comprises a DC power source, for example, a battery, a capacitor, a wind turbine, and / or a photovoltaic system, or an AC power source, for example, a transformer. The power sink essentially comprises a DC power sink, for example, a DC machine, a robot with DC power requirements, a three-phase motor, a passive load, a power supply unit, a sensor, a PLC controller, and / or a charging station, or an AC power sink, for example, a household socket.A voltage converter preferably comprises a buck converter, boost converter, DC / DC converter, inverter or rectifier.

[0028] Preferably, the DC network comprises at least a first spur line and a second spur line, wherein the first spur line electrically connects a DC network unit comprising a power source to the main line, and wherein the second spur line electrically connects a DC network unit comprising a power sink to the main line. According to a further embodiment, the DC network can comprise at least one DC voltage source or DC voltage power source and at least one DC voltage sink or DC voltage power sink.

[0029] According to a further embodiment, the DC network according to the invention can include a DC-DC converter, which is electrically coupled to the branch line, particularly at a second end of the branch line. In other words, the branch line can be electrically connected to a DC network unit, wherein the DC network unit comprises one or more cascaded DC-DC converters. A DC-DC converter can adapt a DC voltage of the main line to a voltage range of an energy consumer or to adapt a voltage supplied by a power source to a voltage range of the main line.

[0030] Furthermore, a DC conductor connection according to claim 10 is proposed. The DC conductor connection can comprise a copper conductor section, an aluminum conductor section, a copper weld metal section, or an aluminum weld metal section and aluminum oxide residues.

[0031] The copper pipe section can form a main line. The aluminum pipe section can form a branch line. The copper or aluminum welded metal section is formed primarily by a thermite welding process. During thermite welding, an aluminum oxide residue may form on the welded section.

[0032] Furthermore, a direct current network manufacturing method is proposed in claim 11, which essentially comprises the following steps:

[0033] Arranging a spur line end relative to a main conductor section so that a weld gap is created,

[0034] Arranging a mold that surrounds the branch line end, the main line section, and the weld gap,

[0035] Arranging a crucible filled with welding metal and aluminum powder,

[0036] Starting a thermite reaction in the crucible,

[0037] Filling the weld gap with liquid welding metal.

[0038] The mold can be two-part, e.g., half-shells, or three-part. The welding metal can comprise copper, iron, and / or aluminum. The mold and the crucible can be integrated or a single unit. The mold is preferably reusable. Furthermore, the DC network manufacturing process can include placing a spark arrestor and / or a chimney on the crucible. The DC network manufacturing process can also include a step for arranging a branch splice, wherein the branch splice insulates the branch end, the main conductor section, and a weld point. The mold can have several openings, in particular a through-hole for receiving the main conductor section and a blind hole arranged at right angles to it for receiving the branch end.In a further embodiment, the mold can have additional blind holes to accommodate two or more branch line ends. The DC network manufacturing process can be used to simultaneously weld several branch lines to the main line. The DC network manufacturing process can be used to establish the DC conductor connection.

[0039] BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Exemplary embodiments of the invention are explained in more detail with reference to the drawings and the following description. The drawings show:

[0041] Figure 1 shows an embodiment of a DC power network according to the invention.

[0042] Figure 2 shows a further embodiment of a DC power network according to the invention, and

[0043] Figure 3 shows an embodiment of a direct current network manufacturing method according to the invention.

[0044] FORMS OF EXECUTION OF THE INVENTION

[0045] Figure 1 shows a direct current network 100 comprising a copper main line 102. The copper main line 102 has a cross-sectional area of ​​500 mm². 2 and carries up to 1800 A direct current. A weld 104, formed by thermite welding, or a copper weld metal section, is arranged on a section of the copper main line 102. The direct current network 100 also includes an aluminum branch line 106, which is mechanically and electrically connected to the copper main line 102 via the weld 104. The aluminum branch line 106 has a cross-sectional area of ​​70 mm². 2and conducts a direct current of up to 400 A. The aluminum branch line 106 has plastic insulation and provides a high degree of intrinsic safety. If a short circuit occurs in the DC network 100, the aluminum branch line 106 can melt without causing a fire, thus acting as a fuse. The weld 104, produced by thermite welding, forms a simple, cost-effective, highly conductive, mechanically stable, and safe electrical connection for the DC network 100. The area shown with dashed lines in Fig. 1 forms a DC conductor connection 108 with a copper conductor section, an aluminum branch line section, a copper weld metal section, and aluminum oxide residue.

[0046] Figure 2 shows a direct current (DC) network 200. The DC network 200 comprises a copper main line 202, several aluminum branch lines 204, and several DC network units 206. The branch lines 204 electrically connect the DC network units 206 to the main line 202. To ensure a simple, cost-effective, highly conductive, mechanically stable, and safe connection, the branch lines 204 are welded to the main line using a thermite welding process. Each DC network unit 206 comprises at least one DC source or DC sink and one or more voltage converters. A DC fast-charging station 208 is electrically connected directly to the main line 202. The main line 202 carries a voltage of 1000 to 1500 V and a direct current of approximately 2000 A flows through it. If a fault occurs in one of the DC network units 206, the associated branch line 204 can melt and act as a fuse.

[0047] Figure 3 shows a manufacturing process for DC networks 300. It comprises the steps of arranging a branch line end relative to a main conductor section 302 so that a weld gap is formed, arranging a mold that surrounds the branch line end, the main conductor section and the weld gap 304, arranging a crucible filled with a welding metal and with aluminum powder 306, starting a thermite reaction in the crucible 308 and filling the weld gap with liquid welding metal 310. The manufacturing process 300 can be used to produce the DC network 100, 200 or the DC conductor connection 108. REFERENCE SYMBOL LIST

[0048] 100 DC network

[0049] 102 copper main line

[0050] 104 Welding point

[0051] 106 Aluminum branch line

[0052] 108 DC conductor connection

[0053] 200 DC network

[0054] 202 Main line

[0055] 204 branch lines

[0056] 206 DC network units

[0057] 208 DC fast charging station

[0058] 300 manufacturing processes for direct current networks

[0059] 302 310 procedural steps

Claims

REQUIREMENTS 1. DC network (100; 200) with a main line (102; 202) and at least one branch line (106; 204) which is electrically connected to the main line (102; 202) characterized by the fact that a first end of the branch line (106; 204) is connected to the main line (102; 202) by means of an exothermic welding process.

2. DC network (100; 200) according to claim 1 characterized by the fact that The exothermic welding process includes an aluminothermic welding process, in particular thermite welding.

3. DC network (100; 200) according to claim 1 or 2 characterized by the fact that the main line (102; 202) comprises a first metal, in particular copper, and the branch line (106; 204) comprises a second metal, in particular aluminium, wherein the first metal and the second metal are different materials, in particular the second metal has a lower conductivity than the first metal.

4. Direct current network (100; 200) according to one of the preceding claims characterized in that the branch line (106; 204) includes a short-circuit-proof line (106; 204).

5. Direct current network (100; 200) according to one of the preceding claims characterized in that the branch line (106; 204) has a smaller cross-sectional area than the main line (102; 202).

6. Direct current network (100; 200) according to one of the preceding claims characterized in that the branch line (106; 204) forms a safety device.

7. Direct current network (100; 200) according to one of the preceding claims characterized in that the direct current network includes at least two branch lines (106; 204).

8. Direct current network (100; 200) according to one of the preceding claims characterized in that the direct current network (100; 200) includes a direct current converter, which is electrically coupled to the spur line (106; 204) in particular at a second end of the spur line (106; 204).

9. Direct current network (100; 200) according to one of the preceding claims characterized in that the DC network (100; 200) includes at least one DC voltage source and at least one DC voltage sink.

10. DC conductor connection (108) comprising: a copper conductor section (102; 202), an aluminium pipe section (106; 204), a copper welding metal section (104) or an aluminium welding metal section (104) and Aluminum oxide residues.

11. Direct current network manufacturing process (300) comprising the steps: Arranging a spur line end with respect to a main conductor section (302) so that a weld gap is created, Arranging a mold that surrounds the branch end, the main section and the weld gap (304), Arranging a crucible filled with welding metal and with aluminium powder (306), Starting a thermite reaction in the crucible (308) and Filling the weld gap with liquid welding metal (310).

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