A nonlinear metal oxide resistor and a method for preparing the same

Abstract

The embodiment of the present invention discloses a nonlinear metal oxide resistor and a preparation method, wherein the nonlinear metal oxide resistor comprises a resistor body and an internal gap arranged inside the resistor body, and an aluminum electrode is sprayed on the periphery of the resistor body. Due to the combination of the internal plate-to-plate gap and the residual voltage reduction gap, the plate-to-plate gap of the resistor is not conductive under a DC 1mA reference voltage, thereby ensuring the high resistance of the resistor in the small current area. Under the residual voltage of lightning impulse / operation impulse, the plate-to-plate gap breaks down and discharges, thereby forming a conductive discharge of the entire internal gap. The resistor is short-circuited due to the internal gap, thereby reducing the residual voltage value of the resistor. After the impact residual voltage is completed, the gap returns to the open circuit state, restoring the high resistance state of the resistor in the small current area, thereby ensuring the charge rate of the resistor. In addition, the present invention adopts built-in gap discharge and arc extinguishing to control the space charge within the built-in space, thereby reducing the influence of the space charge on the overall insulation performance of the arrester.

Description

Technical Field

[0001] The present invention relates to the technical field of manufacturing nonlinear metal oxide gap resistors (varistor) for high voltage arresters, and in particular to a nonlinear metal oxide resistor. The present invention also relates to a method for preparing the nonlinear metal oxide resistor. Background Art

[0002] Metal oxide arresters are important protective devices used to protect various power transmission and transformation equipment in power systems from damage caused by lightning overvoltage, operating overvoltage, and power frequency transient overvoltage. Nonlinear metal oxide resistors (such as nonlinear zinc oxide resistors) are the core components of metal oxide arresters and are therefore the key components that determine the performance of arresters.

[0003] The core function of the arrester is to protect against lightning / operating overvoltage. Having a high DC reference voltage and a low residual voltage protection level is a requirement for future development. Currently, resistors cannot meet the needs of UHV and high-altitude arresters.

[0004] Therefore, how to develop a resistor that meets the needs of ultra-high voltage and high-altitude lightning arresters is a technical problem that technical personnel in this field currently need to solve. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a nonlinear metal oxide resistor to meet the needs of ultra-high voltage and high altitude lightning arresters;

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned nonlinear metal oxide resistor.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A nonlinear metal oxide resistor comprises a resistor body and an internal gap arranged inside the resistor body, wherein an aluminum electrode is sprayed on the outer periphery of the resistor body.

[0009] Optionally, in the above-mentioned nonlinear metal oxide resistor, the internal gap includes a residual voltage reduction gap, an annular area and a plate-to-plate gap, wherein the plate-to-plate gap is located between the residual voltage reduction gap and the annular area, and is smoothly transitioned to the residual voltage reduction gap and the annular area, and the thickness of the plate-to-plate gap is smaller than the thickness of the residual voltage reduction gap and the thickness of the annular area.

[0010] Optionally, in the above nonlinear metal oxide resistor, the diameter of the internal gap is not greater than 1 / 2 of the diameter of the nonlinear metal oxide resistor.

[0011] A method for preparing a nonlinear metal oxide resistor, wherein the nonlinear metal oxide resistor is any of the resistors described above, and the preparation method comprises the following steps:

[0012] S1: Prefabricate the resistor core through the model;

[0013] S2: Wrapping the resistor chip core in a full-enclosed molding method to obtain a resistor chip blank semi-finished product;

[0014] S3: performing binder removal and firing on the resistor chip blank semi-finished product to form a resistor chip body with an internal gap;

[0015] S4: spraying aluminum electrodes on the resistor body to obtain a resistor.

[0016] Optionally, in the method for preparing the nonlinear metal oxide resistor, the material of the resistor core prefabricated in step S1 is an ablative material.

[0017] Optionally, in the method for preparing the nonlinear metal oxide resistor, the ablatable material includes paraffin.

[0018] Optionally, in the above-mentioned method for preparing the nonlinear metal oxide resistor, after step S3, the maximum thickness area of ​​the resistor core forms a residual voltage reduction gap, and the minimum thickness area of ​​the resistor gap semi-finished product forms a circle of plate-to-plate gap.

[0019] Optionally, in the above-mentioned method for preparing the nonlinear metal oxide resistor, the step S2 comprises: placing the resistor core in a forming mold, and wrapping the resistor blank around the outer periphery of the resistor core to obtain the resistor blank semi-finished product.

[0020] Optionally, in the method for preparing the nonlinear metal oxide resistor, in step S2, the center line of the resistor core coincides with the center line of the molding die.

[0021] Optionally, in the above-mentioned method for preparing the nonlinear metal oxide resistor, the equipment for firing the resistor blank semi-finished product in step S3 is a high-temperature debinding furnace.

[0022] Optionally, in the method for preparing the nonlinear metal oxide resistor, before step S4, the method further includes coating an insulating coating on the peripheral surface of the resistor body and grinding both end surfaces of the semi-finished resistor.

[0023] Optionally, in the method for preparing the nonlinear metal oxide resistor, the insulating coating is an organic polymer or an inorganic glass.

[0024] In the preparation method of the nonlinear metal oxide gap resistor provided by the present invention, in step S1, the resistor core is prefabricated with an ablative material, and then in step S2, the resistor core is molded in a fully enclosed manner to obtain a resistor blank semi-finished product, and after molding, the resistor blank semi-finished product is debonded and fired in step S3, and the resistor core is ejected from the resistor blank semi-finished product, and finally the resistor semi-finished product formed after debonding is sprayed with aluminum, and finally a resistor with an internal gap is obtained. The two ends of the internal gap are arc-shaped, and the internal transition is maintained smoothly, which can effectively reduce the damage caused by stress concentration in the production process.

[0025] The minimum thickness area of ​​the resistor core forms a circle of plate-to-plate gaps. The thickness of the plate-to-plate gaps must ensure that the internal gap does not break down under the continuous operating voltage after the gap is formed, and gap discharge is formed under the impact current. The maximum thickness area forms a residual voltage reduction gap, and the maximum thickness of the resistor core must meet the requirement of residual voltage reduction. In this way, by adjusting the size of the internal gap, the internal gap starting discharge voltage can be adjusted, which not only ensures that the charge rate of the resistor is not reduced, but also plays a role in reducing the residual voltage value of the resistor.

[0026] The nonlinear metal oxide gap resistor provided by the present invention can realize that the plate gap of the resistor is not conductive under a DC 1mA reference voltage due to the combination of the internal plate gap and the residual voltage reduction gap, thereby ensuring the high resistance of the resistor in the small current area. Under the residual voltage of lightning impulse / operation impulse, the plate gap breaks down and discharges, thereby forming a conductive discharge of the entire internal gap. The resistor is short-circuited due to the internal gap, thereby reducing the residual voltage value of the resistor. After the impact residual voltage is completed, the gap returns to the open circuit state, restoring the high resistance state of the resistor in the small current area, and ensuring the charge rate of the resistor. In addition, the present invention adopts built-in gap discharge and arc extinguishing to control the space charge within the built-in space, thereby reducing the influence of the space charge on the overall insulation performance of the arrester. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 A schematic cross-sectional view of a nonlinear metal oxide resistor disclosed in an embodiment of the present invention;

[0029] Figure 2 A schematic diagram of electric field simulation of a nonlinear metal oxide resistor disclosed in an embodiment of the present invention;

[0030] Figure 3 A schematic diagram of electric field simulation of another nonlinear metal oxide resistor disclosed in an embodiment of the present invention;

[0031] Figure 4 A schematic diagram of a preparation process of a nonlinear metal oxide resistor disclosed in an embodiment of the present invention;

[0032] Figure 5 A schematic flow chart of a method for preparing a nonlinear metal oxide resistor disclosed in an embodiment of the present invention;

[0033] Wherein: 100 is a resistor; 101a is a resistor blank; 101 is the resistor body, and 102 is the internal gap;

[0034] 1021 is the residual pressure reduction gap, 1022 is the plate-plate gap, and 1023 is the annular area;

[0035] 200 is the inner core of the resistor. DETAILED DESCRIPTION

[0036] As can be seen from the background technology description, at present, resistors cannot meet the needs of UHV and high-altitude arresters. In order to meet the needs of UHV and high-altitude arresters, the industry has begun to try to solve the problem by increasing the charge rate of the arrester and the gap between the arrester and the outside. In order to solve the above problem, the inventor provides a new idea, in which an internal gap is set inside the nonlinear metal oxide resistor. According to the electric field simulation, the minimum thickness of the internal gap can make the internal gap non-conductive in the normal operating state, and the internal gap conductive under the lightning / operation impulse current. The maximum thickness of the internal gap can meet the demand for residual pressure reduction.

[0037] The core of the present invention is to provide a nonlinear metal oxide resistor to meet the needs of ultra-high voltage and high-altitude lightning arresters; another core of the present invention is to provide a method for preparing the above-mentioned nonlinear metal oxide resistor.

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] like Figure 1As shown, the embodiment of the present invention discloses a nonlinear metal oxide resistor 100, including a resistor body 101 and an internal gap 102 arranged inside the resistor body 101, and an aluminum electrode is sprayed on the periphery of the resistor body 101. Compared with the existing resistor without a gap inside the resistor body 101, the nonlinear metal oxide resistor 100 disclosed in the embodiment of the present invention can adjust the size of the internal gap 102 and adjust the gap starting discharge voltage, which can not only ensure that the charge rate of the resistor 100 does not change, but also play a role in reducing the residual voltage value of the resistor 100. At the same time, due to the use of built-in gap discharge arc extinguishing, the space charge is controlled in the built-in space, reducing the influence of the space charge on the overall insulation performance of the arrester.

[0040] In a specific embodiment of the present invention, the internal gap 102 includes a residual pressure reduction gap 1021, an annular area 1023 and a plate-to-plate gap 1022. The plate-to-plate gap 1022 is located between the residual pressure reduction gap 1021 and the annular area 1023, and the thickness of the plate-to-plate gap 1022 is less than the thickness of the residual pressure reduction gap 1021 and the thickness of the annular area 1023, that is, the plate-to-plate gap 1022 corresponds to the minimum thickness area of ​​the internal gap 102. At the same time, in order to effectively reduce the damage caused by stress concentration during the production process, the plate-to-plate gap 1022 is smoothly transitioned to the residual pressure reduction gap 1021 and the annular area 1023, and the annular area 1023 is set to be an arc shape.

[0041] In this embodiment, it should be noted that the plate-to-plate gap 1022 rather than the sharp-cornered gap is used as the minimum thickness area of ​​the internal gap 102 in order to reduce the damage to the gap caused by the number of discharges, thereby ensuring the uniformity of discharge, electrical corrosion resistance and reliability.

[0042] When the diameter of the internal gap 102 of the resistor 100 is greater than 1 / 2, the overall mechanical properties of the resistor will be reduced, and defective products may appear in the subsequent sintering process. Therefore, in a specific embodiment of the present invention, the diameter of the internal gap 102 is set to be no greater than 1 / 2 of the diameter of the nonlinear metal oxide resistor 100.

[0043] Regarding the specific thickness of the internal gap 102, the thickness of the residual pressure reduction gap 1021 needs to meet the requirement of residual pressure reduction, and the thickness of the plate-to-plate gap 1022 is based on the electric field simulation, which can meet the requirements that the internal gap 102 is non-conductive under normal operating conditions and is conductive under lightning / operational impulse current.

[0044] A specific embodiment of the present invention provides an electric field simulation method of the plate-plate gap 1022, such as Figure 3As shown in FIG. 1 , when the applied voltage is 6 kV, through simulation calculation, the minimum thickness of the internal gap 102, i.e., the thickness of the plate-to-plate gap 1022, satisfies the requirement that the plate-to-plate gap 1022 is non-conductive under a DC 1 mA reference voltage, and that the plate-to-plate gap 1022 breaks down and discharges under a residual voltage of a lightning impulse / operating impulse, thereby forming a conductive discharge of the entire internal gap 102. Figure 2 As shown in FIG. 1 , when the applied voltage is 5 kV, the plate gap 1022 is not broken down, indicating that the thickness of the plate gap is not appropriate and needs to be re-adjusted. It should be noted that the voltage applied to the resistor 100 is not unique. Figure 2 and Figure 3 For simulation purposes only.

[0045] See also Figure 4 and Figure 5 As shown, the embodiment of the present invention also discloses a method for preparing the above-mentioned nonlinear metal oxide resistor 100, comprising the following steps:

[0046] S1: prefabricate the resistor chip inner core 200 through a model;

[0047] S2: Wrapping the resistor chip core 200 with the resistor chip blank in a full-enclosed molding manner to obtain a resistor chip blank body 101a;

[0048] S3: performing debinding and firing on the resistor chip green body 101a to form a resistor chip body 101 having an internal gap 102;

[0049] S4: The resistor element 100 is obtained by spraying aluminum electrodes on the resistor element body 101 .

[0050] In the above preparation steps, the resistor core 200 is prefabricated, the blank is wrapped and formed, and the binder is removed and fired to obtain the resistor body 101 with the internal gap 102. The resistor 100 is obtained by spraying the resistor body 101 with aluminum electrodes.

[0051] Since the resistor core 200 in the resistor chip blank 101a needs to be discharged from the resistor chip blank 101a by debonding and firing in step S3, the material of the resistor chip core 200 prefabricated in step S1 should meet the requirement of undergoing physical or chemical changes such as decomposition, melting, evaporation, sublimation, corrosion, etc. under the action of heat so as to be discharged from the resistor chip blank 101a.

[0052] In step S1 of a specific embodiment of the present invention, an ablative material is used to prefabricate the resistor chip inner core 200. It should be noted that carbon materials such as paraffin wax can be used as ablative materials. Paraffin wax decomposes into gas at high temperature and is discharged through the pores of the resistor chip blank 101a. Fusible ablative materials such as quartz and glass can also be used to prefabricate the resistor chip inner core 200. The main components of quartz and glass are silicon dioxide, which can be discharged through the pores of the resistor chip blank 101a after absorbing heat, melting and evaporating.

[0053] Step S3: The process of debinding and firing the resistor sheet blank 101a can be performed in a high-temperature debinding furnace. After debinding and firing, in a specific embodiment of the present invention, the maximum thickness area of ​​the resistor sheet inner core 100 forms a residual voltage reduction gap 102, and the minimum thickness area of ​​the resistor sheet inner core 200 forms a circle of plate-to-plate gap 1021. The maximum thickness of the resistor sheet inner core 200 needs to meet the requirement of residual voltage reduction, and the maximum thickness accounts for about 10% to 20% of the thickness of the resistor sheet. The minimum thickness of the resistor sheet inner core 100 needs to meet the requirement that the internal gap 102 is not conductive in normal operation and is conductive under lightning / operation impulse current according to electric field simulation.

[0054] In a specific embodiment of the present invention, step S2 includes: placing the resistor core 200 in a molding die, and wrapping the resistor blank around the outer periphery of the resistor core 200 to obtain the resistor blank body 101a. Further, after molding, it should be ensured that the resistor core 200 is located at the center of the resistor blank body 101a. When placing the resistor core 200 in the molding die, the center line of the resistor core 200 and the center line of the molding die can be overlapped to ensure that the resistor core 100 is located at the center of the resistor blank body 101a.

[0055] In a specific embodiment of the present invention, before step S4, the process further includes coating the circumference of the resistor body 101 with an insulating coating, and grinding the two end faces of the semi-finished resistor. After grinding, the accuracy and surface finish of the resistor can be improved. The material of the insulating coating can be selected from organic polymers or inorganic glass. Coating the circumference of the resistor body 101 with an insulating coating can insulate the resistor 100, isolate the corrosion of the resistor 100 by water and moisture, and greatly extend the service life of the resistor 100.

[0056] The diameter of the internal gap 300 is about 1 / 2 of the diameter of the resistor 100, and the thickness is about 10% to 20%. The present invention does not exclude the possibility of a larger gap size, but further mechanical performance verification and preparation process verification are required. The combination of the plate-to-plate gap 1022 and the residual voltage reduction gap 1021 can achieve that the plate-to-plate gap 1022 of the resistor 100 is not conductive under a DC 1mA reference voltage, ensuring the high resistance of the resistor 100 in the low current area. Under the residual voltage of lightning impulse / operation impulse, the plate-to-plate gap 1022 breaks down and discharges, thereby forming a conductive discharge of the entire internal gap 102. The resistor 100 is short-circuited due to the internal gap, thereby reducing the residual voltage value of the resistor 100. After the impact residual voltage is completed, the gap returns to the open circuit state, restoring the high resistance state of the resistor 100 in the low current area.

[0057] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0058] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "a kind" and / or "the" do not refer to the singular, but also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of clearly identified steps and elements, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements. The elements defined by the sentence "includes a..." do not exclude the existence of other identical elements in the process, method, commodity or device that includes the elements.

[0059] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0060] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A nonlinear metal oxide resistor, characterized in that: It comprises a resistor body (101) and an internal gap (102) arranged inside the resistor body (101), wherein the outer periphery of the resistor body (101) is sprayed with an aluminum electrode; The internal gap (102) comprises a residual pressure reduction gap (1021), an annular area (1023) and a plate-plate gap (1022), wherein the plate-plate gap (1022) is located between the residual pressure reduction gap (1021) and the annular area (1023), and is smoothly transitionally connected to the residual pressure reduction gap (1021) and the annular area (1023), and the thickness of the plate-plate gap (1022) is smaller than the thickness of the residual pressure reduction gap (1021) and the thickness of the annular area (1023).

2. The nonlinear metal oxide resistor according to claim 1, characterized in that: The diameter of the internal gap (102) is no greater than 1 / 2 of the diameter of the nonlinear metal oxide resistor (100).

3. A method for preparing a nonlinear metal oxide resistor, characterized in that: The nonlinear metal oxide resistor is the resistor (100) according to claim 1 or 2, and the preparation method comprises the following steps: S1: prefabricate the resistor chip inner core (200) through a model; S2: wrapping the resistor chip inner core (200) with the resistor chip blank in a full-enclosed molding manner to obtain a resistor chip blank body (101a); S3: performing debinding and firing on the resistor chip blank (101a) to form a resistor chip body (101) having an internal gap (102); S4: spraying aluminum electrodes on the resistor body (101) to obtain a resistor (100).

4. The method for preparing a nonlinear metal oxide resistor according to claim 3, characterized in that: The material of the resistor chip inner core (200) prefabricated in step S1 is a burnable material.

5. The method for preparing a nonlinear metal oxide resistor according to claim 4, characterized in that: The ablatable material includes paraffin wax.

6. The method for preparing a nonlinear metal oxide resistor according to claim 3, characterized in that: After step S3, the maximum thickness area of ​​the resistor core (200) forms a residual voltage reduction gap (1021), and the minimum thickness area of ​​the resistor core (200) forms a circle of plate-to-plate gap (1022).

7. The method for preparing a nonlinear metal oxide resistor according to claim 3, characterized in that: The step S2 comprises: placing the resistor chip inner core (200) in a forming mould, and wrapping the resistor chip blank around the outer circumference of the resistor chip inner core (200) to obtain the resistor chip blank (101a).

8. The method for preparing a nonlinear metal oxide resistor according to claim 7, characterized in that: In the step S2, the center line of the resistor core (200) coincides with the center line of the forming mold.

9. The method for preparing a nonlinear metal oxide resistor according to claim 3, characterized in that: The equipment for firing the resistor chip green body (101a) in the step S3 is a high-temperature binder removal furnace.

10. The method for preparing a nonlinear metal oxide resistor according to claim 3, characterized in that: Before step S4, the method further includes coating the peripheral surface of the resistor body (101) with an insulating coating and grinding the two end surfaces of the resistor semi-finished product.

11. The method for preparing a nonlinear metal oxide resistor according to claim 10, characterized in that: The insulating coating is organic polymer or inorganic glass.

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