A large-current self-help current limiting method

Abstract

The application discloses a large-current self-help current limiting method, which comprises the following steps: installing a current limiting reactor and a self-help switch for automatically disconnecting when the current size exceeds a short-circuit current critical value in series on a target line; when a large current exceeding the short-circuit current critical value flows through the target line, the self-help switch is directly driven to automatically open a circuit by the large current, the current is transferred to the current limiting reactor to limit the short-circuit current amplitude, and the self-help switch is automatically closed under the action of internal closing force after automatic disconnection to release the current limiting effect. The self-help switch is directly driven to automatically open a circuit by the large current when the large current exceeding the short-circuit current critical value flows through the target line, the current is transferred to the current limiting reactor to limit the short-circuit current amplitude, no additional large-current detection or large-current current limiting control structure is needed, the structure is simple, the reliability is high, and the response time is fast.

Description

Technical Field

[0001] This invention relates to the field of power engineering, specifically to a high-current self-regulating current limiting method. Background Technology

[0002] As power grids grow larger, the short-circuit currents following short-circuit faults also increase. Large short-circuit currents pose a greater threat to power grid equipment. In order to limit short-circuit currents, some high-current limiting devices have emerged in recent years. However, current high-current limiting devices achieve high current limiting through controller detection and control, which are complex in structure and have poor reliability. There is a need to develop current limiting devices with simple structure and high reliability. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a high-current self-operated current limiting method in view of the above-mentioned problems of the prior art. When a high current exceeding the short-circuit current threshold flows through the target line, the present invention directly drives the self-operated switch to open the circuit automatically through the high current, and the current is transferred to the current limiting reactor to limit the short-circuit current amplitude. Since no additional high current detection or high current limiting control structure is required, the structure is simple, the reliability is high, and the response time is fast.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A high-current self-operated current limiting method includes a current-limiting reactor connected in series and in parallel on the target line, and a self-operated switch for automatically disconnecting when the current exceeds the short-circuit current threshold. When a large current exceeding the short-circuit current threshold flows through the target line, the large current directly drives the self-operated switch to automatically open the circuit, and the current is transferred to the current-limiting reactor to limit the short-circuit current amplitude. After the self-operated switch is automatically opened, it automatically closes under the action of internal closing force to release the current limiting effect.

[0006] Optionally, the self-operated switch includes a first conductive rod, a second conductive rod, and a third conductive rod. The first and third conductive rods are fixedly arranged, and the second conductive rod is rotatably mounted between the first and third conductive rods. An insulating spring connects the second conductive rod to the first conductive rod. An insulating spring also connects the second conductive rod to the third conductive rod. When the current flowing through the target line does not exceed the short-circuit current threshold, the second conductive rod is electrically connected to the first and third conductive rods respectively by the pushing force of the insulating springs at both ends. When the current flowing through the target line exceeds the short-circuit current threshold, the second conductive rod is electrically connected to the first and third conductive rods respectively by the pushing force of the insulating springs at both ends. When the current reaches the critical value of a large current, an electrical repulsion force is generated between the second conductive rod and the first conductive rod, and between the second conductive rod and the third conductive rod. This causes the second conductive rod to overcome the pushing force of the insulating spring and disconnect from the first and third conductive rods respectively, thereby realizing the automatic opening of the self-operated switch to limit the short-circuit current amplitude. After the self-operated switch automatically opens, the electrical repulsion force disappears. Under the combined action of the potential energy and elastic force of the electrical repulsion force, the insulating spring reaches its maximum compression and returns, causing the two ends of the second conductive rod to be electrically connected to the first and third conductive rods respectively, thereby realizing the automatic closing of the self-operated switch and releasing the current limiting effect.

[0007] Optionally, the second conductive rod is inclinedly arranged between the first conductive rod and the third conductive rod, so that the first conductive rod, the second conductive rod and the third conductive rod form a Z-shaped structure.

[0008] Optionally, a first set of electromagnetic coils with opposite magnetic properties may be provided between the second conductive rod and the first conductive rod, and a second set of electromagnetic coils with opposite magnetic properties may be provided between the second conductive rod and the third conductive rod. The electromagnetic coils with opposite magnetic properties refer to two electromagnetic coils with opposite winding directions to form magnetic fields with opposite magnetic properties.

[0009] Optionally, the self-operated switch is placed in a separate enclosed space, and the enclosed space contains air, vacuum, insulating oil, or insulating gas.

[0010] Optionally, the critical short-circuit current value of the self-operated switch is ykA, the rated current of the self-operated switch is xkA, and x is much smaller than the value y.

[0011] Optionally, the target line is a short line in the primary circuit of the substation.

[0012] Compared with existing technologies, the present invention has the following main advantages: The high-current self-operated current limiting method of the present invention includes a current-limiting reactor connected in series and in parallel on the target line and a self-operated switch for automatically disconnecting when the current exceeds the short-circuit current threshold. When a large current exceeding the short-circuit current threshold flows through the target line, the large current directly drives the self-operated switch to automatically open the circuit, and the current is transferred to the current-limiting reactor to limit the short-circuit current amplitude. After the self-operated switch is automatically opened, it automatically closes under the action of internal closing force to release the current limiting effect. The present invention directly drives the self-operated switch to automatically open the circuit and transfers the current to the current-limiting reactor to limit the short-circuit current amplitude when a large current exceeding the short-circuit current threshold flows through the target line. It does not require additional high-current detection or high-current limiting control structure, and has the advantages of simple structure, high reliability and fast response time. Attached Figure Description

[0013] Figure 1 This is a schematic diagram illustrating the basic principle of the method in an embodiment of the present invention.

[0014] Figure 2 This is a schematic diagram of the parallel structure of the current-limiting reactor 1 and the self-operated switch 2 in an embodiment of the present invention.

[0015] Figure 3 This is a schematic diagram illustrating the main structure and force analysis of the self-operated switch under conditions where the high current is not disconnected, as described in an embodiment of the present invention.

[0016] Figure 4 This is a schematic diagram showing the main structure and force analysis of the self-operated switch in the automatic disconnection state in an embodiment of the present invention.

[0017] Legend: 1. Current-limiting reactor; 2. Self-operated switch; 21. First conductive rod; 22. Second conductive rod; 23. Third conductive rod; 24. Insulating spring. Detailed Implementation

[0018] like Figure 1 As shown, this embodiment provides a high-current self-regulating current limiting method, including: a current-limiting reactor 1 connected in series and in parallel on the target line, and a self-regulating switch 2 for automatically disconnecting when the current exceeds the short-circuit current threshold, such as... Figure 2As shown, when a large current exceeding the short-circuit current threshold flows through the target line, this large current directly drives the self-operated switch 2 to automatically open the circuit. The current is transferred to the current-limiting reactor 1 to limit the short-circuit current amplitude. After the self-operated switch 2 is automatically opened, it automatically closes under the action of internal closing force to release the current-limiting effect. Since the power grid does not need to limit the current (when the current flowing through the target line does not exceed the short-circuit current threshold), the load current passes through the self-operated switch 2 of the current-limiting device. The large current after the power grid experiences a short-circuit fault directly drives the self-operated switch 2 to operate and limit the short-circuit current amplitude. That is, when a short-circuit current occurs in the power grid, the self-operated switch 2 is opened due to the electrodynamic force of the large current, and the short-circuit current is transferred to the reactor to produce a current-limiting effect. No additional large current detection or large current-limiting control structure is required. It has the advantages of simple structure, high reliability, and fast response time.

[0019] like Figure 3 As shown, the self-operated switch 2 includes a first conductive rod 21, a second conductive rod 22, and a third conductive rod 23. The first conductive rod 21 and the third conductive rod 23 are fixedly arranged, while the second conductive rod 22 is rotatably installed between the first conductive rod 21 and the third conductive rod 23. An insulating spring 24 connects the second conductive rod 22 to the first conductive rod 21. An insulating spring 24 also connects the second conductive rod 22 to the third conductive rod 23. When the current flowing through the target line does not exceed the short-circuit current threshold, the second conductive rod 22 is electrically connected to the first conductive rod 21 and the third conductive rod 23 by the pushing force of the insulating springs 24 at both ends. When a large current exceeding the short-circuit current threshold flows through the target line, an electrical repulsion force is generated (in this embodiment, the electrical repulsion force between the second conductive rod 22 and the first conductive rod 21 is as follows). Figure 3 As shown in F1, the electrical repulsion between the third conductive rod 23 and the first conductive rod 21 is as follows: Figure 3 As shown in F2, the second conductive rod 22 overcomes the pushing force of the insulating spring 24 (i.e., the internal closing force mentioned above) and disconnects from the first conductive rod 21 and the third conductive rod 23 respectively, thereby realizing the automatic opening of the self-operated switch 2 to limit the short-circuit current amplitude. After the self-operated switch 2 is automatically opened, the electric repulsion forces F1 and F2 disappear. Under the combined action of the potential energy and elastic force of the electric repulsion forces F1 and F2, the insulating spring 24 reaches its maximum compression and returns, causing the two ends of the second conductive rod 22 to be electrically connected to the first conductive rod 21 and the third conductive rod 23 respectively, thereby realizing the automatic closing of the self-operated switch 2 and releasing the current limiting effect. In this embodiment, the insulating spring 24 includes a spring and insulating pads disposed at both ends of the spring. The insulating pads are used to achieve insulation isolation between the first conductive rod 21 and the third conductive rod 23 or between the second conductive rod 22 and the first conductive rod 21.

[0020] In this embodiment, the two electric repulsive forces F1 and F2 act together to cause the second conductive rod 22 to rotate clockwise. In this embodiment, the electric repulsive force between the second conductive rod 22 and the first conductive rod 21 is as Figure 3 shown by F1, and the electric repulsive force between the third conductive rod 23 and the first conductive rod 21 is as Figure 3 shown by F2. The directions of the electric repulsive forces F1 and F2 are perpendicular to the second conductive rod 22, so that the second conductive rod 22 can be more reliably pushed to rotate relative to the hinge point, ensuring reliable and rapid rotation during movement.

[0021] As Figure 3 shown, as a preferred embodiment, in this embodiment, the second conductive rod 22 is arranged obliquely between the first conductive rod 21 and the third conductive rod 23, so that the first conductive rod 21, the second conductive rod 22 and the third conductive rod 23 form a Z-shaped structure. In this embodiment, the second conductive rod 22 is limited to rotate clockwise within a range of 15 to 45 degrees, so as to improve the response speed and the reliability of opening and closing.

[0022] In this embodiment, a first set of electromagnetic coils with opposite magnetism may be provided between the second conductive rod 22 and the first conductive rod 21, and a second set of electromagnetic coils with opposite magnetism may be provided between the second conductive rod 22 and the third conductive rod 23. The electromagnetic coils with opposite magnetism refer to two electromagnetic coils whose winding directions are opposite to form magnetic fields with opposite magnetism, which are used to generate electric repulsive force to disconnect the electrical connection with the first conductive rod 21 and the third conductive rod 23 respectively when a large current exceeding the critical value of short-circuit current flows through the target line.

[0023] The critical value of the short-circuit current of the self-operated switch 2 is y kA, the rated current of the self-operated switch 2 is x kA, and x is much smaller than the value y. According to Figure 2 the current limiting device formed by integrating both the current limiting reactor 1 and the self-operated switch 2 is connected in series into the circuit. When the power grid does not need current limiting, the load current (generally less than x kA) flows through the self-operated switch of the current limiting device. When a short-circuit current (greater than y kA) occurs in the power grid, the self-operated switch is actuated to disconnect due to the electric force of the large current, and the short-circuit current is transferred to the reactor to achieve the current limiting effect. Let the current flowing through the target line be i, as Figure 3 shown, in the state where the current does not reach the state requiring current limiting (the current flowing through the target line does not exceed the critical value of the short-circuit current), that is, when i<x, the electric repulsive forces F1 and F2 are very small, less than the spring force F, the second conductive rod 22 will not move, the contact a at the end of the second conductive rod 22 is in contact with the first conductive rod 21 and maintains electrical connection, and the contact c at the end of the second conductive rod 22 is in contact with the third conductive rod 23 and maintains electrical connection; as Figure 4 shown, when a large current i>y flows through, the electric repulsive forces F1 and F2 are very large, greater than the spring force F so that the spring force F can be overcome, causing the second conductive rod 22 to move around the central position (asFigure 4 As shown in b), when the second conductive rod 22 rotates, the contact a at the end of the second conductive rod 22 separates from the first conductive rod 21, and the contact c at the end of the second conductive rod 22 separates from the third conductive rod 23, thereby disconnecting the self-operated switch 2.

[0024] To improve the reliability of the self-operated switch 2, in this embodiment the self-operated switch 2 is placed in a separate enclosed space, and the enclosed space is filled with air, vacuum, insulating oil or insulating gas, such as SF6.

[0025] In this embodiment, the target line is a short circuit in the primary circuit of a substation. Since the high-current self-operated current limiting method in this embodiment directly drives the current limiting device to operate and limit the short-circuit current amplitude by using the large current after a short-circuit fault occurs in the power grid, and the voltage of the primary circuit of the substation is high and can generate a large short-circuit current, the high-current self-operated current limiting method in this embodiment is particularly suitable for the primary circuit of a substation.

[0026] In summary, the self-operated high-current limiting method of this embodiment directly drives the current limiting device to operate and limit the short-circuit current amplitude by utilizing the large current after a short-circuit fault in the power grid. The current limiting device consists of a self-operated switch and a reactor connected in parallel, and the current limiting device is connected in series in the circuit. When the grid current does not reach the required current limiting level, the load current passes through the self-operated switch of the current limiting device. When a short-circuit current occurs in the power grid, the self-operated switch operates and disconnects due to the electrodynamic force of the large current, and the short-circuit current is transferred to the reactor, thus producing a current limiting effect. The self-operated high-current limiting method of this embodiment does not require additional high-current detection or high-current limiting control structure, and therefore has the advantages of simple structure, high reliability, and fast response time.

[0027] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A high-current self-regulating current limiting method, characterized in that, include: A current-limiting reactor and a self-operated switch are connected in series and in parallel on the target line to automatically disconnect when the current exceeds the short-circuit current threshold. When a large current exceeding the short-circuit current threshold flows through the target line, this large current directly drives the self-operated switch to automatically open the circuit, and the current is transferred to the current-limiting reactor to limit the short-circuit current amplitude. After automatically opening, the self-operated switch automatically closes under the action of internal closing force to release the current-limiting effect. The self-operated switch includes a first conductive rod, a second conductive rod, and a third conductive rod. The first and third conductive rods are fixedly arranged, and the second conductive rod is rotatably installed between the first and third conductive rods. An insulating spring connects the second conductive rod to the first conductive rod. An insulating spring connects the second conductive rod to the third conductive rod. When the current in the target line does not exceed the short-circuit current threshold, the second conductive rod is electrically connected to the first and third conductive rods respectively by the pushing force of the insulating springs at both ends. When a large current exceeding the short-circuit current threshold flows through the target line... Under high current, an electric repulsion force is generated between the second conductive rod and the first conductive rod, and between the second conductive rod and the third conductive rod. This causes the second conductive rod to overcome the pushing force of the insulating spring and disconnect from the first and third conductive rods respectively, thereby realizing the automatic opening of the self-operated switch to limit the short-circuit current amplitude. After the self-operated switch automatically opens, the electric repulsion force disappears, and the insulating spring reaches its maximum compression under the combined action of the potential energy and elastic force of the electric repulsion force and returns, so that the two ends of the second conductive rod are electrically connected to the first and third conductive rods respectively, thereby realizing the automatic closing of the self-operated switch and releasing the current limiting effect. The second conductive rod is inclined between the first and third conductive rods, so that the first, second, and third conductive rods form a Z-shaped structure. A first set of electromagnetic coils with opposite magnetic properties is also provided between the second and first conductive rods, and a second set of electromagnetic coils with opposite magnetic properties is also provided between the second and third conductive rods. The electromagnetic coils with opposite magnetic properties refer to two electromagnetic coils with opposite winding directions to form magnetic fields with opposite magnetic properties.

2. The high-current self-regulating current limiting method according to claim 1, characterized in that, The self-operated switch is placed in a separate enclosed space, and the enclosed space is filled with vacuum, insulating oil, or insulating gas.

3. The high-current self-regulating current limiting method according to claim 2, characterized in that, The critical short-circuit current value of the self-operated switch is ykA, and the rated current of the self-operated switch is xkA, where x is much smaller than the value y.

4. The high-current self-regulating current limiting method according to claim 3, characterized in that, The target line is a short line in the primary circuit of the substation.

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