Adjustable sphere gap switch for transformer neutral point protection debugging and its application

Abstract

The present invention relates to an adjustable sphere gap switch for transformer neutral point protection debugging and its application. The electrodes of the sphere gap switch include an upper hemisphere electrode, a lower hemisphere electrode disposed opposite to the upper hemisphere electrode, a through hole provided at the spherical center of the lower hemisphere electrode, and a trigger electrode detachably disposed in the inner cavity of the lower hemisphere electrode; the trigger electrode includes an insulating sleeve with its top end disposed in the through hole and a trigger pin provided in the insulating sleeve through a threaded structure, and the trigger pin can move up and down relative to the insulating sleeve, thereby changing the height of the top end of the trigger pin relative to the lower hemisphere electrode. The technical solution provided by the present invention provides a test sphere gap switch that can flexibly adjust the trigger gap, the diameter of the trigger pin, and the position of the trigger pin relative to the surface of the lower hemisphere electrode. Using this sphere gap switch can be used to obtain a large number of tests, and finally enable the production of a sphere gap switch with a deeper trigger depth, a larger working range, and better compatibility with more lightning arresters according to the test results.

Description

Technical Field

[0001] The present invention belongs to the field of high-voltage switches, and in particular relates to an experimental spherical gap switch for transformer neutral point protection and its application, which can be used for breaking high voltage and high current. Background Art

[0002] Emerging power electronic switches are increasingly used due to their advantages such as fast breaking speed, small on-state voltage drop, and no switching noise. However, due to the limitations of breaking voltage and on-state current, they cannot be used in high voltage and high current fields. Therefore, traditional ball gap switches are still used as the main electrical switches of the entire test circuit in high voltage and high current fields.

[0003] As a transformer neutral point protection gap device, a spherical gap switch typically works in conjunction with a lightning arrester to protect the transformer's neutral point. The basic operating principle of a spherical gap switch is that gas will be ionized into a conductor (the switch is turned on) under the action of an electric field of a certain intensity. When certain external conditions remain unchanged, the electric field strength remains essentially constant. When the field strength drops to a certain value, the ions and free electrons generated by ionization recombine into gas molecules, restoring the insulation strength and disconnecting the switch. Because air discharge has a certain degree of dispersion, in order to ensure the reliability of the spherical gap switch when the transformer is subjected to overvoltage shocks and to better protect the transformer's neutral point from damage, a three-electrode controllable spherical gap switch with a trigger electrode has been developed based on the traditional two-electrode spherical gap switch. The three-electrode controllable spherical gap switch includes a high-voltage spherical electrode, a triggering spherical electrode, and a triggering needle electrode, with the triggering needle electrode installed inside the triggering spherical electrode.

[0004] During transformer protection, three-electrode controlled spherical gap switches (CGSs) interacting with lightning arresters present two challenges: First, when a power frequency overvoltage exceeds the continuous operating voltage of the arrester, the CGSs often fail to operate, often resulting in "rejection." Second, when a lightning overvoltage occurs, the CGSs may operate under the residual voltage of the arrester, often resulting in "false operation." Therefore, to minimize these "rejection" and "false operation" issues, it's necessary to accurately determine the trigger voltage for a specific arrester.

[0005] The operating voltage range of a ball-gap switch must match that of the arrester. Currently, this is achieved by selecting the diameter of the two balls and the main gap. However, even for the same model of arrester, the actual operating voltage range varies. Therefore, even a ball-gap switch designed based on the operating range of the ball-gap switch can still experience "refusal to operate" or "malfunction" in actual operation. Since the diameter of the two balls cannot be changed, overcoming this problem by adjusting the main gap would be very complicated.

[0006] In addition, when the transformer is subjected to overvoltage impact, the insulation level of its neutral point is the lowest and is damaged first. The current three-electrode controllable sphere gap switch cooperating with the lightning arrester adopts 100% triggering for protection, that is, once the overvoltage triggers the trigger electrode of the sphere gap switch, the main gap will also be broken down and discharge. However, in fact, the insulation of the transformer neutral point itself can withstand the power frequency overvoltage for a short time. If this characteristic is utilized, we can reduce the triggering probability of the trigger electrode. In other words, it is not required that the main gap be broken down when the trigger electrode is broken down for the first time. Instead, if the main gap is broken down after the trigger electrode is broken down and discharged multiple times, then the lower limit of the working voltage of the main gap can be further reduced, so that it can be adapted to more lightning arresters. However, this adjustment needs to be achieved by changing the position, size and trigger gap of the trigger needle in the trigger electrode, etc. And these several adjustment factors have no known linear relationship with the breakdown and discharge of the main gap after multiple triggers, and the optimal solution can only be obtained through actual tests with various permutations and combinations. At present, the current three-electrode sphere gap switch is not adjustable for these several methods, resulting in the fact that the test scheme of this permutation and combination is difficult to operate due to high cost and cannot be actually applied. Summary of the Invention

[0007] The present invention provides an adjustable sphere gap switch and application for debugging the protection of the transformer neutral point, so as to solve the problem that the current sphere gap switch cannot adapt to the trigger test to reduce the lower limit of the working voltage.

[0008] To solve the above technical problems, the technical solution of the present invention is: the adjustable sphere gap switch for debugging the protection of the transformer neutral point, the electrodes of the sphere gap switch include an upper hemisphere electrode, an upper high-voltage lead wire electrically connected to the upper hemisphere electrode, a lower hemisphere electrode oppositely arranged to the upper hemisphere electrode, a ground wire electrically connected to the lower hemisphere electrode, a through hole arranged at the spherical center of the lower hemisphere electrode, a trigger electrode detachably arranged in the inner cavity of the lower hemisphere electrode, and a lower high-voltage lead wire electrically connected to the trigger electrode; the trigger electrode includes an insulating sleeve with a top end arranged in the through hole and a trigger needle arranged in the insulating sleeve through a threaded structure, and the trigger needle can move up and down relative to the insulating sleeve, so as to change the height of the top end of the trigger needle relative to the lower hemisphere electrode.

[0009] Since the trigger needle and the insulating sleeve are in threaded connection, the trigger needle can move up and down and be fixed. By changing the position of the top end of the trigger needle relative to the lower hemisphere electrode, such as being higher than the surface of the lower hemisphere electrode, flush with the surface of the lower hemisphere electrode or lower than the surface of the lower hemisphere electrode, the trigger voltage can be finely adjusted.

[0010] In addition, the trigger electrode and the lower hemisphere electrode are detachably fixed, so that by changing the diameter of the trigger needle in the trigger electrode, the trigger gap can be changed, which is also a way to adjust the trigger voltage.

[0011] Optionally, when the top of the trigger pin is flush with the surface of the lower hemisphere electrode at zero point, the movement amplitude of the top of the trigger pin is -3 mm to +3 mm.

[0012] Optionally, the upper hemisphere electrode includes an upper hemispherical surface, an upper hemisphere seat provided on the bottom surface of the upper hemispherical surface, and a lead screw with a fixed top end provided at the center of the upper hemisphere seat. The upper hemisphere seat is provided with a lower convex edge that is snapped into the bottom of the upper hemispherical surface. The upper hemisphere seat is fixedly connected to the upper hemispherical surface through a plurality of corresponding threaded holes evenly distributed around the upper hemispherical surface and the lower convex edge.

[0013] With the position of the lower hemisphere electrode unchanged, the main gap between the upper hemisphere electrode and the lower hemisphere electrode can be adjusted by the movement of the lead screw relative to the upper hemispherical surface.

[0014] Optionally, the lower hemisphere electrode includes a lower hemispherical surface, a lower hemisphere seat provided on the bottom surface of the lower hemispherical surface, and a lead-out hole provided on the lower hemisphere seat for the bottom end of the insulating sleeve to pass through. The lower hemisphere seat is provided with an upper convex edge that is snapped into the bottom of the lower hemispherical surface. The lower hemisphere seat is fixedly connected to the lower hemispherical surface through a plurality of corresponding threaded holes evenly distributed around the lower hemispherical surface and the upper convex edge.

[0015] Optionally, it further includes a bracket for supporting the electrodes. The bracket includes an upper insulating cardboard for fixing the upper hemisphere electrode, a lower insulating cardboard for fixing the lower hemisphere electrode, and a plurality of insulating support columns provided between the upper insulating cardboard and the lower insulating cardboard.

[0016] Optionally, the top end of the lead screw is fixed on the upper insulating cardboard through a nut and a clip. A limit hole matching the lower end of the insulating sleeve is provided at the center of the lower insulating cardboard. The lower insulating cardboard is fixedly connected to the lower hemisphere seat through a fastener.

[0017] Optionally, the trigger pin includes an external thread section threadedly connected to the insulating sleeve, a needle head provided above the external thread section, and a screw head provided below the external thread section.

[0018] Optionally, the diameter of the needle head is smaller than the diameter of the external thread section, and the screw head is flat.

[0019] Optionally, the insulating sleeve includes an isolation section with an outer diameter matching the through hole, a guiding section extending downward from the isolation section, an internal thread section extending downward from the guiding section and provided with an internal thread, and a shoulder section extending downward from the internal thread section and having a smaller outer diameter to form a shoulder. The top end of the isolation section is flush with the surface of the lower hemisphere electrode. The insulating sleeve is fixed in the inner cavity of the lower hemisphere electrode through the shoulder.

[0020] Optionally, the inner diameter of the isolation section and the diameter of the needle head are in transition fit, and the outer diameter of the isolation section and the diameter of the through hole are in interference fit.

[0021] Optionally, the insulating sleeve is made of polytetrafluoroethylene, and the trigger pin is made of steel.

[0022] The present invention also provides a method for obtaining a ball gap switch adapted to a lightning arrester through transformer neutral point protection testing by using the above adjustable ball gap switch:

[0023] 1) According to the model of the lightning arrester to be matched, calculate the optimal diameter of the ball gap switch and the main interval distance through experiments, and give the working voltage range of the initial main gap;

[0024] 2) Prepare the upper hemisphere electrode and the lower hemisphere electrode according to step 1). Design various diameters of the through holes on the surface of the lower hemisphere electrode from small to large, and process a plurality of insulating sleeves with corresponding outer diameters according to these diameters. Design various diameters of the top of the trigger pin from small to large, and process the inner diameter of the insulating sleeve according to the diameter of the trigger pin;

[0025] 4) Assemble the ball gap switch. Send the trigger pulse voltage signal generated by the pulse circuit to the trigger pin electrode. An arc is emitted from the upper end of the trigger pin electrode to generate initial charged particles. Adjust the trigger pulse voltage. When the arc is generated at the trigger pin electrode 3 - 5 times, air breakdown will be induced, and the main gap will discharge. Record the effective voltage when the ball gap switch is turned on;

[0026] 5) Process the through hole diameter from small to large, process the inner diameter of the insulating sleeve with different outer diameters from small to large to match the trigger pin with the corresponding diameter, and perform multi - parameter permutations and combinations. Conduct the experiment in step 4) for each combination. During the experiment, change the position of the top of the trigger pin relative to the lower hemisphere electrode. The position of the trigger pin corresponding to the lowest value among the effective voltage values at each position is the optimal position and the lowest voltage for the corresponding combination size;

[0027] 6) Compare the lowest voltages of all combinations, and process the ball gap switch with the through hole diameter, the inner and outer diameters of the insulating sleeve, the diameter of the trigger pin, and the position of the top of the trigger pin relative to the lower hemisphere electrode corresponding to the minimum value. The lower limit of the working voltage of the ball gap switch used is the smallest.

[0028] The technical solution provided by the present invention provides a test ball gap switch that can flexibly adjust the trigger gap, the diameter of the trigger pin, and the position of the trigger pin relative to the surface of the lower hemisphere electrode. Using this ball gap switch can be used to obtain a large number of tests, and finally enable the production of a ball gap switch with a deeper trigger depth, a larger working range, and better adaptation to more lightning arresters according to the test results. Description of the Drawings

[0029] Figure 1 is a schematic structural diagram of a specific embodiment of the adjustable ball gap switch for transformer neutral point protection debugging described in the present invention;

[0030] Figure 2It is a schematic structural diagram of a specific embodiment of the lower hemisphere base described in the present invention;

[0031] Figure 3 is Figure 2 the top view of;

[0032] Figure 4 It is a schematic structural diagram of a specific embodiment of the insulating bushing described in the present invention

[0033] Figure 5 It is a schematic structural diagram of a specific embodiment of the trigger pin described in the present invention.

[0034] As shown in the figure:

[0035] 10 - upper hemisphere electrode, 11 - upper hemispherical surface, 12 - upper hemisphere base, 13 - lead screw, 14 - lower convex edge, 20 - lower hemisphere electrode, 21 - lower hemispherical surface, 22 - lower hemisphere base, 23 - lead-out hole, 24 - upper convex edge, 25 - threaded hole, 30 - trigger electrode, 31 - insulating bushing, 311 - isolation section, 312 - guiding section, 313 - internal threaded section, 314 - shoulder section, 32 - trigger pin, 321 - external threaded section, 322 - needle head, 323 - screw head, 40 - upper insulating cardboard, 50 - lower insulating cardboard, 51 - fastener, 60 - insulating support column. Specific embodiment

[0036] For the convenience of understanding, the adjustable sphere gap switch for transformer neutral point protection debugging is described below in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0037] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation and positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0038] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0039] As shown Figure 1 in the figure, the adjustable sphere gap switch for transformer neutral point protection debugging includes an electrode and a bracket for supporting the electrode. The electrode includes an upper hemisphere electrode 10, an upper high-voltage lead (not shown in the figure) electrically connected to the upper hemisphere electrode 10, a lower hemisphere electrode 20 disposed opposite to the upper hemisphere electrode 10, a ground wire (not shown in the figure) electrically connected to the lower hemisphere electrode 20, a through hole provided at the spherical center of the lower hemisphere electrode 20, a trigger electrode 30 detachably disposed in the inner cavity of the lower hemisphere electrode 20, and a lower high-voltage lead (not shown in the figure) electrically connected to the trigger electrode 30. The bracket includes an upper insulating cardboard 40 for fixing the upper hemisphere electrode 10, a lower insulating cardboard 50 for fixing the lower hemisphere electrode 20, and four insulating support columns 60 disposed between the upper insulating cardboard 40 and the lower insulating cardboard 50.

[0040] Continue to refer to Figure 1 , the upper hemisphere electrode 10 includes a copper upper hemisphere surface 11, an aluminum upper hemisphere seat 12 provided at the bottom of the upper hemisphere surface 11, and a lead screw 13 fixedly provided at the top position of the center of the upper hemisphere seat 12. The upper hemisphere seat 12 is provided with a lower convex edge 14 that snaps into the bottom of the upper hemisphere surface 11. The upper hemisphere seat 12 is fixedly connected to the upper hemisphere surface 11 through a plurality of corresponding threaded holes evenly distributed around the upper hemisphere surface 11 and the lower convex edge 14. The top of the lead screw 13 is fixed to the upper insulating cardboard 40 through a nut and a clip (not shown in the figure).

[0041] Continue as Figure 1 , 2 and as shown in FIG. 3, the lower hemisphere electrode 20 includes a copper lower hemisphere surface 21, an aluminum lower hemisphere seat 22 provided at the bottom of the lower hemisphere surface 21, and a lead-out hole 23 provided on the lower hemisphere seat 22. The lower hemisphere seat 22 is provided with an upper convex edge 24 that snaps into the bottom of the lower hemisphere surface 21. The lower hemisphere seat 22 is fixedly connected to the lower hemisphere surface 21 through four corresponding threaded holes 25 evenly distributed around the lower hemisphere surface 21 and the upper convex edge 24.

[0042] Continue as Figure 1 shown, the trigger electrode 30 includes an insulating sleeve 31 with its top disposed in the through hole at the spherical center of the lower hemisphere electrode 20, and a trigger pin 32 disposed in the insulating sleeve 31 through a threaded structure. The center of the lower insulating cardboard 50 is provided with a limit hole that mates with the lower end of the insulating sleeve 31. The lower insulating cardboard 50 is fixedly connected to the lower hemisphere seat 22 through a fastener 51.

[0043] As Figure 4As shown, the insulating sleeve 31 includes an isolation section 311 with an outer diameter matching the through hole, a guiding section 312 extending downward from the isolation section 311, an internal thread section 313 extending downward from the guiding section 312 and provided with internal threads, and a shoulder section 314 extending downward from the internal thread section 313 and having a reduced outer diameter to form a shoulder. The top end of the isolation section 311 is flush with the surface of the lower hemisphere electrode 20, and the insulating sleeve 31 is fixed in the inner cavity of the lower hemisphere electrode 20 through the shoulder. The insulating sleeve 31 is made of polytetrafluoroethylene.

[0044] As Figure 5 shown, the trigger pin 32 includes an external thread section 321 threadedly connected to the insulating sleeve 31, a needle head section 322 provided above the external thread section 321, and a screw head 323 provided below the external thread section 321. The diameter of the needle head section 322 is smaller than that of the external thread section 321, and the screw head 323 is a flat head. The trigger pin 32 is made of steel.

[0045] The inner diameters of the isolation section 311 and the guiding section 312 and the diameter of the needle head section 322 are in a transition fit, and the outer diameter of the isolation section and the diameter of the through hole are in an interference fit.

[0046] The length of the needle head section 322 is 3 mm longer than the total length of the isolation section 311 and the guiding section 312, and the length of the internal thread section 313 is much greater than 3 mm. Therefore, the top end of the needle head section 322 can be higher than, flush with, or lower than the lower hemisphere surface 21.

[0047] The method for obtaining a ball gap switch adapted to a lightning arrester through the transformer neutral point protection test by using the above adjustable ball gap switch:

[0048] 1) According to the model of the lightning arrester to be matched, calculate the optimal diameter of the ball gap switch and the main spacing distance through experiments; for the specific method, reference can be made to another patent CN114646285A of the inventor.

[0049] 2) Prepare the upper hemisphere electrode and the lower hemisphere electrode according to step 1), design various diameters of the through holes on the surface of the lower hemisphere electrode from small to large, and process a plurality of insulating sleeves with corresponding outer diameters according to these diameters; design various diameters of the top ends of the trigger pins from small to large, and process the inner diameters of the insulating sleeves according to the diameters of the trigger pins.

[0050] 3) Assemble the ball gap switch: specifically, install the steel trigger pin 3 in the polytetrafluoroethylene insulating sleeve 31, place the insulating sleeve 31 with the trigger pin 32 installed in the accommodation cavity of the lower hemisphere electrode 20, where the upper end of the insulating sleeve 31 is aligned with the through hole at the center of the lower hemisphere electrode 20, and the lower end of the insulating sleeve 31 is aligned with the outlet hole 23 at the center of the lower hemisphere seat of aluminum material to achieve the functions of fixation and sealing. Fix the lower hemisphere surface 21 and the lower hemisphere seat 22 with 4 screws.

[0051] The upper hemisphere electrode 10 is assembled in a similar manner. The assembled upper and lower hemisphere electrodes are placed in two insulating cardboard sheets with four insulating support columns 60. The upper hemisphere base 12 is fixed by a lead screw 13. The lead screw 13 passes through the upper insulating cardboard sheet 40 and is fixed by a nut. The length of the lead screw 13 can be adjusted to enable the main gap between the upper and lower hemisphere electrodes to be adjustable within the range of 0 - 2 times the diameter distance of the spherical electrode. The shoulder section 314 extending from the lower hemisphere base 22 is aligned with the central limit hole of the lower insulating cardboard sheet 50 to fix the spherical electrode. The lower insulating cardboard sheet 50 is fixedly connected to the lower hemisphere base 22 with screws, which serves to prevent the lower spherical electrode from rotating and to lead the grounding wire. After the three - electrode controllable sphere gap switch system is assembled, the upper high - voltage lead is connected to the upper hemisphere electrode 10 through the nut and clip at the upper end of the lead screw 13. The lower high - voltage lead enters from the bottom of the insulating bushing 31 and is connected to the trigger pin 32. The ground wire is connected to the screw fixing the lower hemisphere base 22 and the lower insulating cardboard sheet 50.

[0052] The trigger pulse voltage signal generated by the pulse circuit is sent to the trigger pin electrode. An arc is emitted from the upper end of the trigger pin electrode to generate initial charged particles. The trigger pulse voltage is adjusted. When the trigger pin electrode generates 5 arcs, it induces air breakdown, and the main gap discharges, and the sphere gap switch is turned on. The pulse voltage at this time is regarded as the effective voltage and recorded. More specifically, when the number of arcs generated by the trigger pin is less than 5 and the main gap discharges, the pulse voltage is lowered. When the number of arcs generated by the trigger pin is greater than 5 and the main gap still does not discharge, the pulse voltage is raised. When the trigger pin cannot generate an arc, that is, when the trigger electrode cannot discharge, the pulse voltage is naturally also raised.

[0053] 4) The diameter of the through - hole is processed from small to large, and the inner diameter of the insulating bushing with different outer diameters is processed from small to large to match the trigger pin with the corresponding diameter. Multiple parameter permutations and combinations are carried out. For each combination, the experiment in step 3) is carried out. During the experiment, the position of the top of the trigger pin relative to the lower hemisphere electrode is changed. The position of the trigger pin corresponding to the lowest value among the effective voltage values at each position is the optimal position and the lowest voltage for the corresponding combination size.

[0054] 5) Compare the lowest voltages of all combinations, and process the sphere gap switch with the diameter of the through - hole, the inner and outer diameters of the insulating bushing, the diameter of the trigger pin, and the position of the top of the trigger pin relative to the lower hemisphere electrode corresponding to the minimum value. The lower limit of the operating voltage of the sphere gap switch using this is the smallest.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An adjustable sphere gap switch for transformer neutral point protection debugging, characterized in that, A bracket including an electrode and a support for the electrode, the electrode including an upper hemispherical electrode, an upper high-voltage lead electrically connected to the upper hemispherical electrode, a lower hemispherical electrode disposed opposite to the upper hemispherical electrode, a ground wire electrically connected to the lower hemispherical electrode, a through hole provided at the spherical center of the lower hemispherical electrode, a trigger electrode detachably disposed in the inner cavity of the lower hemispherical electrode, and a lower high-voltage lead electrically connected to the trigger electrode; the trigger electrode includes an insulating sleeve with a top end disposed in the through hole and a trigger pin provided in the insulating sleeve through a threaded structure, and the trigger pin can move up and down relative to the insulating sleeve, thereby changing the height of the top end of the trigger pin relative to the lower hemispherical electrode; A method for obtaining a ball gap switch adapted to a lightning arrester through a transformer neutral point protection test by using the adjustable ball gap switch, comprising the following steps: 1) According to the model of the lightning arrester to be matched, calculate the diameter of the optimal ball gap switch and the main interval distance through experiments, and give the working voltage range of the initial main gap; 2) Prepare the upper hemispherical electrode and the lower hemispherical electrode according to step 1), design various diameters of the through holes on the surface of the lower hemispherical electrode from small to large, and process a plurality of insulating sleeves with corresponding outer diameters according to these diameters; design various diameters of the top ends of the trigger pins from small to large, and process the inner diameters of the insulating sleeves according to the diameters of the trigger pins; 3) Assemble the ball gap switch, generate a trigger pulse voltage signal by a pulse circuit and send it to the trigger pin electrode, and regard the pulse voltage when the main gap discharges after the trigger pin electrode discharges 3 - 5 times as the effective voltage and record it; 4) Process the through hole diameters from small to large, process the inner diameters of the insulating sleeves with different outer diameters from small to large to match the trigger pins with corresponding diameters, perform multi-parameter permutations and combinations, perform the experiment in step 3) for each combination, change the position of the top end of the trigger pin relative to the lower hemispherical electrode during the experiment, and the position of the trigger pin corresponding to the lowest value among the effective voltage values at each position is the optimal position and the lowest voltage for the corresponding combination size; optimal position and the lowest voltage; 5) Compare the lowest voltages of all combinations, and process a ball gap switch with the diameters of the through holes, the inner and outer diameters of the insulating sleeves, the diameter of the trigger pin, and the position of the top end of the trigger pin relative to the lower hemispherical electrode corresponding to the minimum value, and the lower limit of the working voltage of this ball gap switch is the smallest.

2. The adjustable sphere gap switch for debugging the neutral point protection of a transformer according to claim 1, wherein When the top end of the trigger pin is flush with the surface of the lower hemispherical electrode as the zero point, the movement range of the top end of the trigger pin is -3 mm to +3 mm.

3. The adjustable sphere gap switch for transformer neutral point protection debugging according to claim 1, characterized in that The lower hemispherical electrode includes a lower hemispherical surface, a lower hemispherical seat provided at the bottom surface of the lower hemispherical surface, and a lead-out hole provided on the lower hemispherical seat for the bottom end of the insulating sleeve to pass through. An upper convex edge that snaps into the bottom of the lower hemispherical surface is provided on the lower hemispherical seat, and the lower hemispherical seat is fixedly connected to the lower hemispherical surface through a plurality of corresponding threaded holes evenly distributed around the lower hemispherical surface and the upper convex edge.

4. The adjustable sphere gap switch for transformer neutral point protection debugging according to claim 3, characterized in that, The upper hemispherical electrode includes an upper hemispherical surface, an upper hemispherical seat provided at the bottom surface of the upper hemispherical surface, and a lead screw fixedly provided at the top position in the center of the upper hemispherical seat. A lower convex edge that snaps into the bottom of the upper hemispherical surface is provided on the upper hemispherical seat, and the upper hemispherical seat is fixedly connected to the upper hemispherical surface through a plurality of corresponding threaded holes evenly distributed around the upper hemispherical surface and the lower convex edge.

5. The adjustable sphere gap switch for transformer neutral point protection commissioning according to claim 4, characterized in that, The bracket includes an upper insulating cardboard for fixing the upper hemispherical electrode, a lower insulating cardboard for fixing the lower hemispherical electrode, and a plurality of insulating support columns arranged between the upper insulating cardboard and the lower insulating cardboard.

6. The adjustable sphere gap switch for transformer neutral point protection debugging according to claim 5, characterized in that, The top of the lead screw is fixed on the upper insulating cardboard through a nut and a clip. A limit hole matching the lower end of the insulating sleeve is provided at the center of the lower insulating cardboard. The lower insulating cardboard and the lower hemispherical seat are fixedly connected through a fastener.

7. The adjustable sphere gap switch for transformer neutral point protection debugging according to claim 1, characterized in that The trigger pin includes an external thread section threadedly connected to the insulating sleeve, a needle head portion provided above the external thread section, and a screw head provided below the external thread section.

8. The adjustable sphere gap switch for transformer neutral point protection debugging according to claim 1, characterized in that, The insulating sleeve includes an isolation section with an outer diameter matching the through hole, a guiding section extending downward from the isolation section, an internal thread section extending downward from the guiding section and provided with an internal thread, and a shoulder section extending downward from the internal thread section and having a reduced outer diameter to form a shoulder. The top of the isolation section is flush with the surface of the lower hemispherical electrode. The insulating sleeve is fixed in the inner cavity of the lower hemispherical electrode through the shoulder.

9. The adjustable sphere gap switch for transformer neutral point protection debugging according to claim 1, characterized in that, The material of the insulating sleeve is polytetrafluoroethylene, and the material of the trigger pin is steel.

10. A method for obtaining a sphere gap switch adapted to a lightning arrester through a transformer neutral point protection test by using the adjustable sphere gap switch according to any one of claims 1-9, characterized in that, It includes the following steps: 1) According to the model of the cooperating lightning arrester, calculate the optimal diameter of the sphere gap switch and the main spacing distance through experiments, and give the working voltage range of the initial main gap; 2) Prepare the upper hemispherical electrode and the lower hemispherical electrode according to step 1). Design various diameters of the through holes on the surface of the lower hemispherical electrode from small to large, and process a plurality of insulating sleeves with corresponding outer diameters according to these diameters. Design various diameters of the top of the trigger pin from small to large, and process the inner diameter of the insulating sleeve according to the diameter of the trigger pin; 3) Assemble the sphere gap switch. Send the trigger pulse voltage signal generated by the pulse circuit to the trigger pin electrode. When the trigger pin electrode discharges 3 - 5 times and the main gap generates a discharge, regard the pulse voltage as the effective voltage and record it; 4) Process the through hole diameter from small to large, process the inner diameter of the insulating sleeve with different outer diameters from small to large to match the trigger pin with the corresponding diameter, and perform multi-parameter permutations and combinations. For each combination, perform the experiment in step 3). During the experiment, change the position of the top of the trigger pin relative to the lower hemispherical electrode. The position of the trigger pin corresponding to the lowest value among the effective voltage values at each position is the optimal position and the lowest voltage for the corresponding combination size; [[ID= ​

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