A method, medium, and system for selecting fuses in a fusible DC surge arrester group.

Abstract

This invention discloses a method, medium, and system for selecting fuses in a fusible DC surge arrester group. The method includes: selecting fuses that meet a first preset requirement, wherein the specifications include: aperture width, thickness, fuse width, and aperture spacing; and selecting fuses that meet a second preset requirement from the fuses that meet the first preset requirement through an arc-starting test. This invention can select suitable fuses so that during energy absorption by the energy-absorbing device, the arcing current of the fuse is limited to the zero-crossing current of the energy-absorbing branch, ensuring the safety of the fusible DC surge arrester group.

Description

Technical Field

[0001] This invention relates to the technical field of fuse-type DC surge arrester assemblies, and more particularly to a fuse selection method, medium, and system for fuse-type DC surge arrester assemblies. Background Technology

[0002] Based on their specific application, fuses can be divided into two main categories: circuit-breaking fuses without parallel resistive energy-absorbing bypasses and energy-displacement fuses with parallel resistive energy-absorbing bypasses. Circuit-breaking fuses need to completely absorb the short-circuit energy within the system, which places high demands on the fuse's energy capacity and structural strength. In contrast, energy-displacement fuses, because they have bypass energy-absorbing devices to absorb short-circuit energy, only need to generate sufficient arc voltage to transfer the short-circuit current to the energy-absorbing branch, thus absorbing less energy.

[0003] Under the influence of the anticipated fault current, the fuse undergoes two phase transitions due to the Joule integral: the molten metal changes from a solid to a liquid state, and then from a liquid to a gaseous state. Particularly during the second phase, the arc-initiating process from liquid to gas, the fault current is carried by gaseous metallic plasma. Combined with the blocking and cooling effect of the silica sand, this is reflected in the waveform as a rapid increase in the voltage across the fuse from an extremely low point until it conducts the parallel zinc oxide energy-absorbing branch. Essentially, this is a result of the fuse's arc impedance rapidly increasing. At this point, the fuse current drops rapidly, while the zinc oxide current rises rapidly; the sum of these two currents constitutes the fault current. During this process, a series of characteristics are exhibited: (1) No interruption overvoltage. Due to the existence of the bypass energy absorption device, the fault current has a path condition. When the fuse blows, the fault current will not be cut off, thus objectively losing the conditions for generating overvoltage; (2) The circuit breaking process is transformed into an energy transfer process. The conducting zinc oxide energy absorption branch will exhibit an impedance, which will be shunt with the arc impedance of the fuse. The shunt relationship depends on the changing trend of the arc impedance of the fuse under this shunt.

[0004] A monotonically increasing arc resistance of a fuse indicates smooth development of the fuse's insulation medium, allowing the shunt current to quickly decay below the arc-extinguishing current, thus extinguishing the arc – this is the desired outcome. However, if the arc resistance reaches its peak, meaning the insulation medium stops developing and remains above the arc-extinguishing current, a fuse current tail or residual current will appear within the fuse. This current will be accompanied by residual voltage from zinc oxide, objectively increasing the amount of fuel burned, disrupting the fuse's insulation recovery conditions, and even causing the arc resistance to decrease due to excessive burning, increasing shunt current and creating a vicious cycle. This will lead to the failure of the energy transfer function and ultimately, the fuse explosion. Summary of the Invention

[0005] This invention provides a method, medium, and system for selecting fuses in a fusible DC surge arrester assembly, in order to solve the problem that the prior art cannot effectively select fuses, leading to fuse explosions.

[0006] Firstly, a method for selecting fuses in a fusible DC surge arrester assembly is provided, including:

[0007] Select the specifications of the fuse that meet the first preset requirements, wherein the specifications include: neck width, thickness, fuse width and neck spacing;

[0008] For fuses that meet the first preset requirement, an arc ignition test is conducted to select fuses that meet the second preset requirement.

[0009] In a second aspect, a computer-readable storage medium is provided, wherein computer program instructions are stored on the computer-readable storage medium; when the computer program instructions are executed by a processor, they implement the fuse selection method for a fuse-type DC surge arrester group as described in the first aspect embodiment above.

[0010] Thirdly, a fuse selection system for a fusible DC surge arrester group is provided, comprising: a computer-readable storage medium as described in the second aspect embodiment above.

[0011] Thus, in this embodiment of the invention, a suitable fuse can be selected so that during the energy absorption period of the energy absorption device, the arcing current of the fuse can be limited to the zero crossing of the energy absorption branch current, thereby ensuring the safety of the fuse-type DC surge arrester group. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a flowchart of the fuse selection method for a fusible DC surge arrester group according to an embodiment of the present invention;

[0014] Figure 2 This is a schematic diagram of a narrow neck with equal width;

[0015] Figure 3 This is a schematic diagram of a crescent-shaped narrow neck. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] This invention discloses a method for selecting fuses in a fusible DC surge arrester assembly. For example... Figure 1 As shown, the method of this embodiment of the invention includes the following steps:

[0018] Step S101: Select the specifications of the fuse that meet the first preset requirements.

[0019] Specifically, the specifications include: neck width, thickness, fuse width, and neck spacing. Figure 2 and Figure 3 In a Indicates the width of the narrow neck. c Indicates the fuse width. b This indicates the neck spacing. Thickness refers to the thickness after multiple fuses are crimped together.

[0020] Specifically, in this step, we will analyze two types of fuses.

[0021] First, we have the following known parameters:

[0022] Zinc oxide residual pressure: U =50kV.

[0023] Zinc oxide current: I =1250A.

[0024] Zinc oxide pathway: n 1=38, n 2 = 19.

[0025] Zinc oxide absorbs energy: W =1MJ.

[0026] Single group of zinc oxide current: ;

[0027] .

[0028] Zinc oxide reaction time: .

[0029] Single set of zinc oxide current equations: ;

[0030] .

[0031] (1) First type of fuse specification: 0.41×0.05×2.54×3.4 (neck width×thickness×fuse width×neck spacing)

[0032] S1 = 0.41 × 0.05 = 2.05 × 10 -2 mm 2

[0033] S12 C=49.253

[0034] Where C represents the energy absorption parameter of the surge arrester.

[0035] (2) Second type of fuse specification: 0.41×0.08×1.27×1.7 (neck width×thickness×fuse width×neck spacing)

[0036] S² = 0.41 × 0.08 = 3.28 × 10⁻⁶ -2 mm 2

[0037] S2 2 C=126.088

[0038] In this step, the first preset requirement includes: the non-melting time of the fuse is greater than the melting time of the fuse when a short circuit fault occurs in one of the zinc oxide surge arresters.

[0039] When the first type of fuse is selected (0.41×0.05×2.54×3.4):

[0040] Non-fusing time: T1

[0041] Therefore, T1 = 44.5 ms.

[0042] When a short circuit occurs in one zinc oxide circuit:

[0043] Circuit breaker time: T2

[0044] Therefore, T2 = 31.5 μs.

[0045] When the second type of fuse is selected (0.41×0.08×1.27×1.7):

[0046] Non-fusing time: T3

[0047] Therefore, T3 = 70.3 ms.

[0048] When a short circuit occurs in one zinc oxide circuit:

[0049] Circuit breaker time: T4

[0050] Therefore, T4 = 70.3 μs.

[0051] Therefore, both of the above-mentioned fuse specifications meet the first preset requirement.

[0052] Step S102: For fuses that meet the first preset requirements, select fuses that meet the second preset requirements by conducting an arc ignition test on the fuses.

[0053] Specifically, in this step, the second preset requirement includes: under the preset voltage, the initial arc resistance after the fuse arc is ignited is greater than the preset threshold, and a temperature gradient is formed in the neck region before the fuse arc is ignited.

[0054] Necks can come in different shapes. For example... Figure 2 As shown, the fuse neck shape is a rectangle of equal width, with a neck width of 0.41 mm and a length of 0.91 mm for the equal-width portion. The transition radius from the equal-width portion to the wide portion of the neck is the natural diameter of the die-cutting wire. Figure 3 As shown, the fuse neck uses an R4.4mm arc-shaped cut, which widens to a wide neck at an angle of 15° at a chord length of approximately 0.92mm. The transition arc between the narrow neck and the wide neck is the natural diameter of the die-cutting wire.

[0055] An arc-starting test was conducted on the fuse. For example, the crescent-shaped fracture surface had a fracture spacing of 12.59 mm, a narrow neck cut of 8.75 mm in diameter, and a gradually widening narrow neck of 0.51 mm. The arc-starting test showed that the remaining thickness was 11.54 mm, and 1.05 mm was burned. The total burning length of the narrow neck was 300 * 1.05 = 315 mm.

[0056] An arc-starting test was conducted on the fuse. For example, a copper triangular fracture with a fracture spacing of 3.4 mm, a narrow neck spacing of 0.41 mm, a neck length of 0.27 mm, and a 60° fan-shaped widening was tested. The result was that the remaining length was 2.9 mm, and 0.5 mm was burned. The total burning length of the narrow neck was 600 * 0.5 = 300 mm.

[0057] For example, the failure of the 300 copper triangular fracture to transfer energy during combustion resulted in a residual thickness of 2.47 mm, with 0.93 mm burned. The total burning length of the narrow neck was 279 mm, and there was a current tailing effect.

[0058] Successful energy transfer examples illustrate that within a short time (<100µs) after arc ignition, the fuse current can be smoothly cut off, indicating that the fuse arc resistance shows a monotonically increasing trend and quickly reduces the fuse shunt current below the arc extinguishing current. The more breaks there are, the shorter the arcing time, indicating that each break will have arc resistance. With more breaks, the arc resistance naturally increases. It can be approximated that there is a certain proportional relationship between the total arc length of the narrow neck and the development of arc resistance. When the total arc length is insufficient, the development of arc resistance is hindered, that is, the fuse shunt current stops decreasing, and the shunt current is maintained, resulting in a tailing phenomenon, which leads to energy transfer failure.

[0059] The initial arc column of the triangular fracture neck is relatively short (0.27 mm), and the number of quartz sand particles (quartz sand particle size between 0.15 and 0.35 mm) is relatively small. The cooling effect of quartz sand on the arc is not ideal. Therefore, the arc column needs to be extended by continuous combustion of the narrow neck to incorporate more quartz sand for cooling, so as to achieve the effect of continuously increasing arc resistance. However, continuous combustion also increases the heat generation. Once the quartz sand near the arc column is heated, the cooling effect weakens, and the development of arc resistance will slow down. The game between the heat capacity of quartz sand and the heat generation of the arc determines the development trend of arc resistance. This is the inherent physical phenomenon of arc resistance development. The 0.05 filament is easier to extinguish the arc than the 0.08 filament because the current cut-off value is lower, so that the arc energy after arc initiation starts to accumulate from a lower starting point, which indirectly improves the cooling effect of quartz sand on the arc.

[0060] From the perspective of rapidly reducing fuse shunting, a higher initial arc resistance after fuse arc ignition is better. Therefore, a preset threshold can be set empirically to ensure that the initial arc resistance after fuse arc ignition is greater than this preset threshold. Based on this, the neck section should be lengthened to increase the distance between the two electrodes of the fracture arc, and more quartz sand should be incorporated to cool the fracture arc. Moreover, its shape should preferably be a rectangle of equal width, and the length of the equal width section should be between 0.5 and 1 mm. This can increase the number of initial arc ignition points by 1.85 to 3.7 times, and the arc resistance will naturally increase accordingly.

[0061] Through repeated experiments, it was found that a crescent-shaped neck shape satisfies this requirement. Before arc initiation, the crescent-shaped neck creates a temperature gradient in the neck region, establishing a unique point of highest temperature within the fracture surface—the arc initiation point. As time increases after arc initiation, the arc initiation point gradually increases, resulting in a gradual increase in arc voltage at a certain slope, thus reducing the dV / dt of the fuse arc initiation process. Furthermore, considering the effect of the di / dt of the distributed inductance between the fuse and zinc oxide, which would create a very high overvoltage across the fuse, a crescent-shaped neck design is preferred to avoid excessively high peak values ​​at the arc initiation time, even if the peak value occurs within 1µs.

[0062] Preferably, the method in this embodiment of the invention further includes:

[0063] Based on the preset ratio of residual pressure to the number of fractures, determine the minimum number of fractures of the fuse under the required residual pressure.

[0064] For example, if the preset ratio is 10.5kV residual voltage / 600 breaks, then 3428 breaks are needed at a required residual voltage of 60kV, which is the minimum number of breaks. Therefore, the number of selectable breaks is no less than 3428. Using the fuse die design, fuses with a narrow neck spacing of 1.7mm can be produced. The fuse skeleton length is designed to be 300mm (due to single-cylinder processing limitations), allowing for 44 turns, each approximately 150mm long. The fuse wire length can reach 6600mm, resulting in 3882 breaks, which is achievable in terms of the number of breaks.

[0065] The calculated energy absorption of the fuse is 60 / 10.5×113J=656J. Since it is less than 1KJ, the heat capacity of the fuse should be able to withstand it based on experience.

[0066] Preferably, the method in this embodiment of the invention further includes:

[0067] (1) Determine the peak voltage at the second arc initiation moment corresponding to the minimum number of breaks based on the ratio of the number of breaks to the peak voltage at the first arc initiation moment.

[0068] For example, it has been experimentally determined that the peak voltage at the first moment of arc initiation corresponding to 600 breaks is 22.6kV. Then, through proportional calculation, the peak voltage at the second moment of arc initiation corresponding to the minimum number of breaks of 3882 is 146.2kV.

[0069] (2) Determine the height of the second fuse frame corresponding to the peak voltage at the moment of the first arc initiation based on the height of the first fuse frame corresponding to the peak voltage at the moment of the second arc initiation.

[0070] For example, if the peak voltage of 22.6kV at the first moment of arc initiation corresponds to a first fuse frame height of 115mm, then through proportional calculation, the peak voltage of 146.2kV at the second moment of arc initiation corresponds to a second fuse frame height of 742mm.

[0071] The first and second arc initiation moments are the moments when the fuse melts, creating a gap, and the voltage in the gap breaks down the air, triggering an electric arc.

[0072] (3) If the height of the second fuse frame is less than the height limited by the processing conditions of the single cylinder, then the height of the fuse frame is determined to be the height of the second fuse frame.

[0073] (4) If the height of the second fuse frame is not less than the height limited by the single cylinder processing conditions, then the height of the fuse frame is determined to be the height limited by the single cylinder processing conditions.

[0074] The processing conditions for a single column cylinder limit the height to 300mm. Since 742mm is greater than 300mm, the height of the fuse skeleton is determined to be 300mm.

[0075] For example, in a specific embodiment of the present invention, a fuse wire with dimensions of 0.41*0.08*1.27*1.7 (neck width*thickness*fuse wire width*neck spacing) is selected. The fuse wire length is required to be 5 meters. One end of the fuse wire is soldered to the electrode at the lower part of the fuse frame using a soldering machine, and then wound clockwise around the fuse frame. The other end is soldered to the upper electrode of the frame, and a copper sheet is soldered to the lower electrode. A lead wire with a length of 200 mm is soldered to one end of the fuse, and the copper sheet at the other end is screwed onto the center stopcock. The wound fuse assembly is placed in an epoxy tube, and the position is initially restricted by the center stopcock. 703 silicone sealant is applied around the assembly to facilitate sand filling. Each set of dried resistor elements is removed and placed into the epoxy tube, connected to the center stopcock of the resistor element. A spring electrode and spring are placed at the other end, and then the stopcock is tightened. During tightening, 703 silicone sealant is applied to facilitate sealing. Fill the epoxy tube with quartz sand from the fused wire side and vibrate it until it completely covers the fused wire.

[0076] To meet the protection function of fuses, the selected fuse characteristics must satisfy two requirements: 1. Under the normal operating current of the surge arrester, the fuse should reliably withstand the current, and should not deform, soften, or melt during multiple surge arrester operations; 2. When a fault current flows through a resistor element or single-pole surge arrester, the fuse should quickly and reliably melt, isolating the faulty branch and preventing operational failure or system blockage. Therefore, experiments can be designed to analyze and verify the feasibility of fuse-based failure protection, specifically including: verifying the selected fuse through energy withstand experiments and simulated fault branch isolation experiments.

[0077] This invention also discloses a computer-readable storage medium storing computer program instructions; when the computer program instructions are executed by a processor, they implement the fuse selection method for a fuse-type DC surge arrester group as described in the above embodiments.

[0078] This invention also discloses a fuse selection system for a fusible DC surge arrester group, comprising: a computer-readable storage medium as described in the above embodiments.

[0079] In summary, the embodiments of the present invention allow for the selection of a suitable fuse so that during the energy absorption period of the energy absorption device, the arcing current of the fuse is limited to the zero-crossing current of the energy absorption branch, thereby ensuring the safety of the fuse-type DC surge arrester group.

[0080] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for selecting fuses in a fusible DC surge arrester assembly, characterized in that, include: Select the specifications of the fuse that meet the first preset requirements, wherein the specifications include: neck width, thickness, fuse width and neck spacing; For fuses that meet the first preset requirement, an arc ignition test is conducted to select fuses that meet the second preset requirement. The first preset requirement includes: the non-melting time of the fuse is greater than the melting time of the fuse when a short circuit fault occurs in one of the zinc oxide surge arresters; The second preset requirement includes: under a preset voltage, the initial arc resistance after the fuse arc is ignited is greater than a preset threshold, and the shape of the narrow neck is crescent-shaped, and a temperature gradient is formed in the narrow neck area before the fuse arc is ignited.

2. The fuse selection method for a fusible DC surge arrester group according to claim 1, characterized in that, Also includes: Based on the preset ratio of residual pressure to the number of fractures, determine the minimum number of fractures of the fuse under the required residual pressure.

3. The fuse selection method for a fusible DC surge arrester group according to claim 2, characterized in that, Also includes: The peak voltage at the second moment of arc initiation corresponding to the minimum number of breaks is determined based on the ratio of the number of breaks to the peak voltage at the first moment of arc initiation. Based on the height of the first fuse frame corresponding to the peak voltage at the first arc initiation moment, the height of the second fuse frame corresponding to the peak voltage at the second arc initiation moment is determined. The first arc initiation moment and the second arc initiation moment are the moments when the fuse melts, creating a gap, and the voltage in the gap breaks down the air, triggering an electric arc. If the height of the second fuse frame is less than the height limited by the single-cylinder processing conditions, then the height of the fuse frame is determined to be the height of the second fuse frame. If the height of the second fuse frame is not less than the height limited by the single-cylinder processing conditions, then the height of the fuse frame is determined to be the height limited by the single-cylinder processing conditions.

4. The fuse selection method for a fusible DC surge arrester group according to claim 1, characterized in that, Also includes: The selected fuse was verified through energy tolerance tests and simulated fault branch isolation tests.

5. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer program instructions; when the computer program instructions are executed by a processor, they implement the fuse selection method for a fusible DC surge arrester group as described in any one of claims 1 to 4.

6. A fuse selection system for a fusible DC surge arrester group, characterized in that, include: The computer-readable storage medium as described in claim 5.

Images