State monitoring scheme of MOV series fuse

Abstract

According to the MOV series fuse state monitoring scheme, the MOV series fuse comprises an MOV, a mechanical firing pin and a fuse, the mechanical firing pin is arranged on a shell of the MOV, the fuse is arranged in the shell of the MOV, and therefore the size of the MOV in series connection with the fuse is effectively reduced. Besides, by arranging the mechanical firing pin structure and the fuse, maloperation or abnormal disconnection of the fuse in the operation process can be easily detected, and then a worker is reminded to take solution measures in time, so that the MOV can effectively protect the device capable of being turned off, and damage to the device capable of being turned off is avoided.

Description

Technical Field

[0001] This invention belongs to the field of circuit protection and monitoring technology, and in particular relates to a status monitoring scheme for MOV series fuses. Background Technology

[0002] High-voltage direct current (HVDC) transmission is an important component of the new power system. In traditional HVDC transmission, thyristor-based converters suffer from commutation failure due to grid voltage drops. Converters with turn-off devices in their bridge arms (hereinafter referred to as turn-off converters) can provide commutation voltage by actively turning off the bridge arm devices, which is an important means to solve the commutation failure problem.

[0003] In high-voltage converter stations, turn-off devices are often required to be connected in series in large numbers. Parallel discrete MOVs are an ideal solution for protecting devices. However, parallel MOVs may experience faults such as short circuits or device failure to turn on, causing them to carry large currents for a long time, which poses a significant risk to the safe and reliable operation of the converter.

[0004] To address this technical problem, the inventors of this invention have proposed a scheme that connects a fuse in series with an MOV (invention title: "An MOV Applicable to a Turn-Off Converter", publication number CN116488122A), so that the fuse blows and cuts off the MOV current when the MOV experiences abnormal current flow. However, this scheme has the problems of being too large in size, and the branch containing the MOV being open when the fuse malfunctions or abnormally disconnects during operation, making it impossible for the MOV to effectively protect the turn-off device. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a condition monitoring scheme for an MOV series fuse. The MOV series fuse includes an MOV, a mechanical striker, and a fuse. The mechanical striker is located on the outer casing of the MOV, and the fuse is located inside the outer casing of the MOV. This technical solution effectively reduces its size by integrating the fuse and the MOV valve plate into the same casing.

[0006] In some embodiments, a through hole is provided at the edge of the upper electrode of the MOV, and a mechanical striker is installed in the through hole. The through hole includes an upper hole, a middle hole, and a lower hole from top to bottom; the diameters of the upper hole and the lower hole are both smaller than the diameter of the middle hole.

[0007] In some embodiments, the aforementioned mechanical striking pin mainly includes a striking pin, a conductive movable component, a spring, and a copper wire. The conductive movable component is disposed within the aforementioned intermediate hole and can move freely up and down within the intermediate hole; one end of the spring is fixedly connected to the lower surface of the conductive movable component, and the other end of the spring is fixedly connected to the lower surface of the intermediate hole; one end of the striking pin is fixedly connected to the upper surface of the conductive movable component, and the other end of the striking pin can freely pass through the upper hole; both ends of the aforementioned copper wire are connected to the upper electrode of the MOV and the conductive movable component, respectively.

[0008] One end of the fuse wire is connected to the lower surface of the conductive moving part, and the other end passes through the lower end hole and is connected to the lower electrode of the fuse; when the fuse wire does not melt, the copper wire is set to have a slack and remain in a relaxed state.

[0009] When it is detected that the upper surface of the striker is higher than the upper surface of the MOV upper electrode, it indicates that it is prone to disconnection, and relevant personnel should be notified to take timely corrective measures.

[0010] In some embodiments, a monitoring device is provided to detect whether the striker is above the upper surface of the upper electrode of the MOV.

[0011] The condition monitoring scheme for MOV series fuses includes the following detection methods:

[0012] S1: Connect the MOV series fuse to the application circuit;

[0013] S2: Detect whether the upper surface of the impact pin is higher than the upper surface of the upper electrode of the MOV;

[0014] S3: If so, then determine that the fuse wire of the fuse is broken;

[0015] S4: If not, then it is determined that the fuse wire has not broken, and the test continues.

[0016] In step S2 above, the detection of whether the upper surface of the striker pin is higher than the upper surface of the upper electrode of the MOV is performed by maintenance personnel or by installing monitoring equipment.

[0017] Based on the above-mentioned condition monitoring scheme for MOV series fuses, this application also proposes a bridge arm of a switchable converter. The bridge arm includes a buffer and static voltage equalization circuit, a device branch, and the above-mentioned MOV series fuse, and the buffer and static voltage equalization circuit, the device branch, and the MOV series fuse are connected in parallel.

[0018] The aforementioned buffer and static voltage equalization circuit includes multiple buffer branches connected in series and multiple static voltage equalization branches connected in series. Each device branch includes multiple turn-off devices connected in series. Furthermore, the number of buffer branches, static voltage equalization branches, and turn-off devices are equal, and each static voltage equalization branch, buffer branch, and turn-off device is connected in parallel. Compared with the prior art, this disclosure has the following advantages:

[0019] This invention integrates the fuse and MOV valve into the same housing, which can effectively reduce its size. Furthermore, by setting a mechanical striker structure on the MOV housing, the on / off state of the fuse is reflected in the striker state. Maintenance personnel can know the status of the fuse in the MOV through the striker and then take corresponding actions, thereby enabling the MOV to effectively protect the turn-off device. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This illustrates the topology of a fuse-connected MOV in a converter in the prior art;

[0022] Figure 2 The overall structure of the fuse and valve plate in the MOV of the present invention is shown;

[0023] Figure 3 It shows Figure 2 Enlarged view of point A in the middle;

[0024] Figure 4 The diagram shows the structure when the fuse is not disconnected;

[0025] Figure 5 The diagram shows the structure when the fuse is disconnected;

[0026] Figure 6 A method for detecting MOV series fuses is shown.

[0027] Icons: MOV upper electrode 1; MOV lower electrode 2; through hole 3; upper hole 4; lower hole 5; middle hole 6; striking pin 7; conductive moving part 8; spring 9; copper wire 10; fuse 11; lower surface of middle hole 12; fuse upper electrode 13; fuse lower electrode 14; valve 15; MOV housing 16. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0029] This invention provides a condition monitoring scheme for an MOV (Metal Oxide Varistor) series fuse, comprising an MOV, a mechanical striker, and a fuse, wherein the mechanical striker is located on the housing of the MOV and the fuse is located inside the housing of the MOV.

[0030] In some embodiments, such as Figure 2 As shown, a through hole 3 is machined at the edge of electrode 1 on the MOV. The through hole 3 includes an upper hole 4, a middle hole 6, and a lower hole 5 from top to bottom. The diameters of the upper hole 4 and the lower hole 5 are both smaller than the diameter of the middle hole 6. The mechanical striker is installed in the through hole 3. This invention effectively reduces the overall volume of the fuse connected in series with the MOV by integrating the fuse and the MOV valve plate into a single housing.

[0031] like Figure 4-5 As shown, in some embodiments, the aforementioned mechanical striking pin mainly includes a striking pin 7, a conductive moving part 8, a spring 9, and a copper wire 10.

[0032] The conductive movable part 8 is located inside the intermediate hole 6 and can move freely up and down inside the intermediate hole 6; one end of the spring 9 is fixedly connected to the lower surface of the conductive movable part 8, and the other end is fixedly connected to the lower surface 12 of the intermediate hole. The surface formed by the upper electrode part of the MOV with the lower end hole 5 facing the intermediate hole 6 is the lower surface 12 of the intermediate hole.

[0033] One end of the firing pin 7 is fixedly connected to the upper surface of the conductive moving part 8, and the other end freely passes through the upper hole 4;

[0034] The two ends of the copper wire 10 are connected to the upper electrode 1 of the MOV and the conductive moving part 8, respectively.

[0035] In some embodiments, the spring 9 is fixedly connected to the conductive moving part 8 and the lower surface 12 of the intermediate hole by welding.

[0036] In some embodiments, one end of the fuse 11 is connected to the lower surface of the conductive moving part 8, and the other end passes through the lower end hole 5 and is connected to the lower electrode 14 of the fuse. The fuse 11 is connected to the lower surface of the conductive moving part 8 by welding. When the fuse 11 does not melt, the copper wire 10 has a slack and remains in a relaxed state.

[0037] In some embodiments, a monitoring device is provided on the upper electrode 1 of the MOV around the upper hole 4 to detect whether the striker 7 is higher than the upper surface of the upper electrode 1. The monitoring device includes a camera and can trigger an early warning system.

[0038] The working principle of this technical solution is as follows:

[0039] 1. For example Figure 4 As shown, when the fuse 11 has not melted, the fuse 11, which is fixed between the conductive moving part 8 and the lower electrode 14 of the fuse, is in a taut state, and the spring 9 is in a compressed state. At this time, the upper surface of the striker 7 is flush with the upper surface of the upper electrode 1 of the MOV. The copper wire 10 connecting the conductive moving part 8 and the upper electrode 1 of the MOV has a certain length and is kept in a slack state to prevent the copper wire 10 from hindering the operation of the striker 7 device due to its length and stress.

[0040] 2. For example Figure 5 As shown, when the fuse 11 is disconnected, the disconnected fuse 11 will cause the tension on the conductive moving part 8 to disappear, the energy of the spring 9 will be released, and the ejector pin 7 will be ejected, so that the upper surface of the ejector pin 7 is higher than the upper surface of the upper electrode 1 of the MOV.

[0041] When the upper surface of the striker 7 is found to be higher than the upper surface of the MOV upper electrode 1, it is very easy for maintenance personnel to notice. When maintenance personnel notice this phenomenon, they can determine that the fuse 11 has blown and take appropriate measures in time. If a monitoring device is installed on the upper surface of the MOV upper electrode 1 around the upper hole 4, the status of the fuse can be detected in real time. When the monitoring device detects that the upper surface of the striker 7 is higher than the upper surface of the MOV upper electrode 1, it triggers the early warning system, which then issues an early warning message that the fuse has blown so that the staff can take appropriate measures in time.

[0042] The condition monitoring scheme for MOV series fuses includes the following detection methods: Figure 6 As shown:

[0043] S1: Connect the above MOV series fuse into the application circuit.

[0044] S2: Detect whether the upper surface of the impact pin is higher than the upper surface of the upper electrode of the MOV;

[0045] S3: If so, then it is determined that the fuse wire of the fuse is broken;

[0046] S4: If not, it is determined that the fuse wire has not broken, and the test continues.

[0047] This detection method uses a mechanical striker set on the electrode of the MOV to reflect the on / off state of the fuse in the striker's position. This allows maintenance personnel or monitoring devices to know the status of the MOV fuse by observing the striker's position and then take appropriate actions.

[0048] In some embodiments, based on the above-described state monitoring scheme for the MOV series fuse, this application also proposes a bridge arm of a turn-off converter. This bridge arm includes a buffer and static voltage equalization circuit, a device branch, and the aforementioned MOV series fuse. The buffer and static voltage equalization circuit, the device branch, and the MOV series fuse are connected in parallel. The buffer and static voltage equalization circuit includes multiple series-connected buffer branches and multiple series-connected static voltage equalization branches. The device branch includes multiple series-connected turn-off devices. The number of buffer branches, static voltage equalization branches, and turn-off devices is the same; and each static voltage equalization branch, buffer branch, and turn-off device is connected in parallel.

[0049] The aforementioned buffer branch can be used to suppress the switching losses of the turn-off devices connected in parallel with it, reduce their turn-off overvoltage, and extract energy online. The static voltage equalization branch is connected in parallel with the buffer branch and can be used to achieve static voltage equalization of the corresponding turn-off devices.

[0050] In this technical solution, the fuse simultaneously provides over-energy protection for MOVs and over-voltage protection for turn-off devices.

[0051] In summary, the technical solution of this application can easily detect malfunctions or abnormal disconnections of fuses during operation, reminding staff to take timely corrective measures, thereby enabling the MOV to effectively protect the turn-off device and avoid damage to it.

[0052] It should be noted that the electrical connections between the various units mentioned above do not necessarily represent the connections between lines. Any indirect connection method can be applied to the embodiments of this disclosure as long as it achieves the purpose of this disclosure.

[0053] Although the present disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A MOV-in-series fuse status monitoring scheme, characterized by, The MOV series fuse includes an MOV, a mechanical striker on the shell of the MOV, and a fuse in the shell of the MOV.

2. The condition monitoring scheme according to claim 1, wherein, A through hole is arranged on the MOV upper electrode edge of the MOV, and the mechanical striker is arranged in the through hole.

3. The condition monitoring scheme of claim 2, wherein, The through hole includes an upper end hole, a middle hole, and a lower end hole from top to bottom, and the diameter of the lower end hole is smaller than that of the middle hole.

4. A condition monitoring scheme according to claim 3, characterised in that, The diameter of the upper end hole is smaller than that of the middle hole.

5. The condition monitoring scheme according to any one of claims 1-3, characterized in that, The mechanical striker includes a striker, a conductive movable piece, a spring, and a copper wire.

6. The condition monitoring scheme according to claim 5, wherein, The conductive movable piece is arranged in the middle hole and can freely move up and down in the middle hole; One end of the spring is fixedly connected with the lower surface of the conductive movable piece, and the other end is fixedly connected with the lower surface of the middle hole; One end of the striker is fixedly connected with the upper surface of the conductive movable piece, and the other end freely passes through the upper end hole; Two ends of the copper wire are respectively connected with the MOV upper electrode and the conductive movable piece.

7. The condition monitoring scheme of claim 5, wherein, One end of the fuse of the fuse is connected with the lower surface of the conductive movable piece, and the other end passes through the lower end hole and is connected with the lower electrode of the fuse; when the fuse is not broken, the copper wire has a surplus and remains in a relaxed state.

8. A condition monitoring scheme according to claim 6 or 7, characterised in that, A monitoring device is arranged on the MOV upper electrode around the upper end hole, and the monitoring device is used to detect whether the striker is higher than the upper surface of the MOV upper electrode.

9. The condition monitoring scheme of claim 8, wherein, The detection method includes the following steps: S1: connecting the MOV series fuse to an application circuit; S2: detecting whether the upper surface of the striker is higher than the upper surface of the MOV upper electrode; S3: if yes, determining that the fuse of the fuse is disconnected; S4: if no, determining that the fuse of the fuse is not disconnected, and continuing to detect it.

10. The condition monitoring scheme of claim 9, wherein, The detection in step S2 that whether the upper surface of the striker is higher than the upper surface of the MOV upper electrode is detected by a maintenance personnel or a monitoring device.

11. A bridge arm of a turn-off converter, characterized in that The bridge arm includes a buffer and static voltage equalization circuit, a device branch, and the MOV series fuse according to any one of claims 1-8, and the buffer and static voltage equalization circuit, the device branch, and the MOV series fuse are mutually connected in parallel.

12. The bridge arm of claim 11, wherein, The buffer and static voltage equalization circuit includes a plurality of mutually connected buffer branches and a plurality of mutually connected static voltage equalization branches; the device branch includes a plurality of mutually connected turn-off devices; the number of the buffer branches, the static voltage equalization branches, and the turn-off devices is the same, and each of the static voltage equalization branches, the buffer branches, and the turn-off devices is mutually connected in parallel.

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