A high-voltage thermocouple probe with built-in grounding protection

Abstract

This utility model discloses a high-voltage thermocouple probe with built-in grounding protection. The metal cylinder of the thermocouple probe is connected to the equipment grounding grid via a grounding bracket. An insulating cylinder is coaxially fitted onto the metal cylinder, and an outer sleeve is coaxially fitted onto the insulating cylinder. The metal cylinder is a cylindrical heat-resistant metal tube with one open end and a hemispherical metal blind head at the other end. The grounding bracket is welded to the open end of the metal cylinder and grounded to the equipment grounding grid. The metal cylinder with expansion joints and the hemispherical metal blind head is inserted into the insulating cylinder and elastically and tightly contacts the inner wall of the hemispherical insulating blind head. The insulating cylinder is a cylindrical cylinder with one open end and a skirt, and the other end has a hemispherical insulating blind head. The outer sleeve is made of cylindrical quartz glass with one open end and a hemispherical blind head at the other end. The outer sleeve is embedded in the solid heat storage body, and its outer wall is in close contact with the solid heat storage body. The creepage distance of the skirt of the insulating cylinder meets the creepage distance requirements for insulation protection of the high-voltage heating wire in the solid heat storage body.

Description

Technical Field

[0001] This utility model relates to the field of control and detection technology for high-voltage solid-state electric thermal storage furnaces, specifically to an insertion-type thermocouple probe that can withstand a working voltage of 150kV when the solid thermal storage body is at a temperature above 800℃. Background Technology

[0002] Currently, high-voltage solid-state electric thermal storage furnaces used for heating generally have outlet water temperatures below 100℃, and the thermal storage temperature of the solid thermal storage body does not need to exceed 550℃. Therefore, the furnace temperature control system of these devices uses an indirect temperature measurement method, with thermocouples mounted on an infrared radiation receiving metal plate 1.5m away from the solid thermal storage body. This method is affected by various conditions, and the accuracy error can sometimes exceed 200℃. However, this method has its advantages: the 1.5m distance between the thermocouples and the solid thermal storage body isolates the system from the 66kV to 150kV high voltage, ensuring that the temperature control system will not be damaged by high voltage, causing personal injury and equipment safety accidents. Therefore, it is practical for devices with lower solid thermal storage temperatures. However, for some users who need to output high-temperature steam above 200℃, the thermal storage temperature of the equipment far exceeds the 550℃ required for hot water boilers, sometimes even reaching above 800℃ for efficient operation. For these types of devices, the thermocouples need to be precisely measured, making long-distance measurement unsuitable.

[0003] Currently, the temperature detection methods used for high-temperature and high-voltage solid-state electric thermal storage furnaces with operating voltages of 66kV to 150kV are all indirect temperature detection methods, such as infrared and thermal radiation, which are conducted at a distance of 1.5m from the furnace. Direct temperature detection methods have not yet been adopted. Summary of the Invention

[0004] Purpose of the invention: In view of the above technical requirements, the purpose of this utility model is to provide a high-temperature and high-pressure thermocouple sheath probe with built-in grounding protection, which aims to solve the problem of ensuring the direct contact temperature measurement device of 66kV~150kV high-voltage solid thermal storage body when the thermal storage temperature of solid electric thermal storage boiler is above 800℃.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A built-in high-temperature and high-pressure thermocouple probe with a grounding protection sleeve is characterized in that: a metal cylinder is provided on the outer periphery of the thermocouple, the metal cylinder is connected to the equipment grounding grid via a grounding bracket; an expansion joint is provided on the metal cylinder, an insulating cylinder is coaxially fitted on the metal cylinder, and an outer sleeve is coaxially fitted outside the insulating cylinder; the thermocouple is placed in the heat storage brick of a solid heat storage body.

[0006] Furthermore, the metal cylinder is composed of a cylindrical heat-resistant metal tube with one end open and the other end being a hemispherical metal blind head. A grounding bracket is welded at the open end of the metal cylinder, and the tube is grounded through the equipment grounding grid. The expansion joint on the metal cylinder is 1mm wide at 1000℃.

[0007] Furthermore, the insulating cylinder is a cylindrical structure with one end open and the other end having a hemispherical insulating blind head. The cylinder wall is provided with a skirt. It is a cylindrical cylinder formed by injection molding with aluminum oxide slurry with a purity of 99.3% or higher and sintered at high temperature.

[0008] Furthermore, the outer wall of the metal cylinder with the expansion joint comes into elastic and tight contact with the inner wall of the insulating cylinder.

[0009] Furthermore, the outer sleeve is made of cylindrical quartz glass with one end open and the other end having a hemispherical blind head. The outer sleeve is embedded in the solid heat storage body, and the outer wall is in close contact with the solid heat storage body.

[0010] Furthermore, the length of the umbrella skirt installed on the insulating cylinder should meet the creepage distance requirements for insulation protection of the high-voltage electric furnace wire in the heat storage brick of the solid heat storage body.

[0011] Furthermore, the distance between the solid heat storage body and the grounding support is 650mm to 1300mm.

[0012] The technical solution adopted in this utility model has the following advantages: This technical solution adopts direct contact temperature measurement, which improves the measurement accuracy compared with the existing radiation temperature measurement technology. It solves the insulation problem of 66kV to 150kV voltage by vacuum injection molding of alumina paste with a purity of 99.3% or higher and high temperature sintering. This technical solution enables thermocouples to perform high-precision contact measurements while adding a metal cylinder inside the insulating cylinder, achieving two functions: First, during high-voltage temperature measurement, the skirts on the insulating cylinder must be exposed outside the solid heat storage body to achieve insulation. The higher the voltage, the more skirts are required, and the longer and heavier the insulating cylinder exposed outside the solid heat storage body becomes. For example, the length of the insulating cylinder with skirts for a 110kV operating voltage temperature measurement is generally greater than 850mm. A metal cylinder needs to be tightly inserted inside the insulating cylinder to provide stable and fixed support. Second, it reliably grounds the metal cylinder, preventing the thermocouple from being broken down by 66kV to 150kV high voltage due to insulation failure of the insulating cylinder. This would allow high-voltage power to enter the weak current control system, causing serious equipment damage or even electric shock accidents. The expansion joint left on the metal cylinder in this technical solution eliminates the problem of tight fit between the metal cylinder and the insulating cylinder, which are two materials with different expansion coefficients, at the same ambient temperature. Attached Figure Description

[0013] The above and other objects, features, and advantages of the present invention will become readily understood by reading the following detailed description of exemplary embodiments with reference to the accompanying drawings. In the drawings, several embodiments of the present invention are shown by way of example and not limitation, with the same or corresponding reference numerals denoteing the same or corresponding parts, wherein: Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is a partially enlarged schematic diagram of position A of this utility model; Figure 3 This is a schematic diagram of the metal cylinder structure of this utility model; Figure 4 This is a cross-sectional view of the metal cylinder of this utility model from direction A; Figure 5 This is a cross-sectional view of the metal cylinder of this utility model from direction B.

[0014] Explanation of icon numbers: 1. Thermocouple; 2. Metal cylinder; 3. Insulating cylinder; 4. Outer sleeve; 5. Grounding bracket; 6. Grounding grid; 7. Expansion joint; 8. High-voltage heating wire; 9. Insulating support for heat storage body; 10. Umbrella skirt; 11. Metal blind head; 12. Insulating blind head; 13. Solid heat storage body. Detailed Implementation

[0015] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Unless otherwise specified, the techniques used in the embodiments are conventional means well known to those skilled in the art.

[0016] In this embodiment, a high-voltage thermocouple probe with built-in grounding protection is described as "built-in," which differs from existing technologies. The thermocouple is embedded within the heat storage brick of the solid heat storage body 13, and this embedded location is connected to the interior of the solid heat storage body 13. Combined with... Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 A metal cylinder 2 is installed outside the thermocouple 1. The metal cylinder 2 is a hollow cylindrical structure with one end closed and the other end open. The thermocouple 1 is inserted into the metal cylinder 2. The metal cylinder 2 is made of metal material that is resistant to high temperature and high pressure. The metal cylinder 2 on which the thermocouple 1 is installed is connected to the equipment grounding grid 6 via a grounding bracket 5. The distance between the grounding bracket 5 and the solid heat storage body 13 must be greater than the required safe clearance between the energized part of the working voltage and the ground part.

[0017] The metal cylinder 2 is simply an outer layer of the thermocouple 1, a conductive metal layer protecting the thermocouple 1 from voltage breakdown. The metal cylinder 2 also supports the stability of the thermocouple probe structure via a welded grounding bracket 5. The insulation function, which isolates the high-temperature, high-voltage heating wire 8 in the solid heat storage body 13, is achieved by the insulating cylinder 3 coaxially mounted on the metal cylinder 2. To improve measurement accuracy, the metal cylinder 2 and the insulating cylinder 3 must be in close contact to reduce thermal resistance. If the metal cylinder 2 and the insulating cylinder 3 were completely integrated, their thermal expansion and contraction would differ under the same ambient temperature due to their different materials. To prevent the insulating cylinder 3 from cracking due to the larger linear expansion coefficient of the metal cylinder 2 inside the insulating cylinder 3 caused by temperature rise, thus compromising its insulation function, the design requires the metal cylinder 2 and the insulating cylinder 3 to have elastic and tight contact. The simplest solution is to have an expansion joint 7 on the metal cylinder 2, allowing the outer wall of the metal cylinder 2 to elastically contact the inner wall of the insulating cylinder 3.

[0018] The metal cylinder 2 is a cylindrical heat-resistant metal tube with one end open and the other end having a hemispherical metal blind head 11. The open end of the metal cylinder 2 is welded with a grounding bracket 5 and grounded through the equipment grounding grid 6.

[0019] The insulating cylinder 3 is a cylindrical structure with one end open and the other end equipped with a hemispherical insulating blind head 12. The internal cavity is equipped with a metal cylinder 2, and the outer wall of the insulating cylinder 3 is equipped with a skirt 10.

[0020] The insulating cylinder 3 is a cylindrical tube formed by injection molding of aluminum oxide slurry with a purity of 99.3% or higher and then sintered at high temperature. The manufacturing process of the aluminum oxide insulating cylinder 3 is the key to the voltage insulation performance of this technical solution.

[0021] Design calculation length: Generally, the length should be determined based on the safe clearance between the live parts of the equipment's operating voltage and the grounding part. The safe clearance between the live parts of the equipment and the grounding support 5 is between 650mm and 1300mm for operating voltages of 66kV to 150kV. The length of the insulating cylinder 3 consists of two parts: the part inserted into the solid heat storage body 13 for temperature acquisition is about 200mm; the part exposed outside the solid heat storage body 13 with the umbrella skirt 10 is 550mm to 1200mm long. The umbrella skirt 10 is composed of multiple pieces. The diameter and spacing of the multiple umbrella skirts 10 are adjusted so that the part of the insulating cylinder 3 with the umbrella skirt 10 meets the creepage distance required by the operating voltage of the high-voltage heating wire 8. The length of the insulating cylinder 3 exposed outside the solid heat storage body 13 is about 100mm shorter than the metal cylinder 2. This section of the metal cylinder 2 exposed outside the insulating cylinder 3 is used to weld and connect the grounding support 5 to complete the reliable grounding of the thermocouple probe and the metal cylinder 2.

[0022] Design calculation of inner diameter and wall thickness: Generally, the inner diameter of the metal cylinder 2 should be 1mm to 3mm larger than the diameter of the thermocouple 1 with ceramic sleeve, so as to facilitate insertion and removal and not affect the temperature measurement accuracy. The inner diameter of the insulating cylinder 3 is equal to the outer diameter of the metal cylinder 2 when it is compressed by hand with slight pressure. The wall thickness of the insulating cylinder 3 is approximately equal to the voltage value required for the type test of the solid electric thermal storage equipment ÷ 20kV / mm × 1.2 (safety factor). For example, if the working voltage of the equipment is 110kV and the voltage value required for the type test of the equipment is 200kV, then the wall thickness of the insulating cylinder 3 is approximately 200kV ÷ 20kV / mm × 1.2 ≈ 12mm. The manufacturing process of insulating cylinder 3: (i) Make a model using hard materials such as metal and plastic according to the design dimensions of insulating cylinder 3, plus the sum of the alumina slurry blank and the shrinkage ratio after sintering, to ensure a smooth surface and accurate dimensions; (ii) Using models to create plaster casting bodies; (III) Prepare an aluminum oxide slurry with a purity of 99.3% or higher, and after ensuring that the slurry is stirred evenly in a vacuum device without air bubbles, inject it into the gypsum substrate; (iv) Insulating cylinder 3 is demolded and sintered; (v) After the insulation cylinder 3 passes the withstand voltage test, it shall be put into use.

[0023] During installation and use, the portion of the metal cylinder 2 with expansion joint 7 and hemispherical metal blind head 11 is inserted into the inner cavity of the insulating cylinder 3 with hemispherical insulating blind head 12 to achieve elastic and tight contact.

[0024] An outer sleeve 4 is installed outside the insulating cylinder 3. The outer sleeve 4 is made of cylindrical quartz glass with one end open and the other end having a hemispherical blind end. The outer sleeve 4 is embedded in the heat storage brick of the solid heat storage body 13. The outer wall of the outer sleeve 4 is in close contact with the heat storage brick of the solid heat storage body 13, and can completely conduct the temperature from the inside of the solid heat storage body 13. Quartz material is transparent and strong, and the thermal conductivity and expansion coefficient of quartz material are also close to those of the insulating cylinder 3.

[0025] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model 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 this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the protection scope of the claims.

Claims

1. A high-voltage thermocouple probe with built-in grounding protection, characterized in that: The thermocouple is provided with a metal cylinder (2) on its outer periphery. The metal cylinder (2) is connected to the equipment grounding grid (6) via a grounding bracket (5). An expansion joint (7) is provided on the metal cylinder (2). An insulating cylinder (3) is coaxially fitted on the metal cylinder (2). An outer sleeve (4) is also coaxially fitted on the outside of the insulating cylinder (3). The thermocouple probe is placed in the heat storage brick of the solid heat storage body (13).

2. A high-voltage thermocouple probe with built-in grounding protection according to claim 1, characterized in that: The metal cylinder (2) is a cylindrical heat-resistant metal tube with one end open and the other end being a hemispherical metal blind head (11). A grounding bracket (5) is welded at the open end of the metal cylinder (2) and grounded through the equipment grounding grid (6). The expansion joint (7) on the metal cylinder (2) is 1 mm wide at 1000℃.

3. A high-voltage thermocouple probe with built-in grounding protection according to claim 1, characterized in that: The insulating cylinder (3) is a cylindrical structure with one end open and the other end equipped with a hemispherical insulating blind head (12). The insulating cylinder (3) has a skirt (10) on its wall. It is a cylindrical cylinder formed by injection molding with aluminum oxide slurry with a purity of 99.3% or higher and sintered at high temperature.

4. A high-voltage thermocouple probe with built-in grounding protection according to claim 1, characterized in that: The outer wall of the metal cylinder (2) with the expansion joint (7) is in elastic and tight contact with the inner wall of the insulating cylinder (3).

5. A high-voltage thermocouple probe with built-in grounding protection according to claim 1, characterized in that: The outer sleeve (4) is made of cylindrical quartz glass with one end open and the other end having a hemispherical blind head. The outer sleeve (4) is embedded in the solid heat storage body (13), and the outer wall is in close contact with the solid heat storage body (13).

6. A high-voltage thermocouple probe with built-in grounding protection according to claim 3, characterized in that: The umbrella skirt (10) installed on the insulating cylinder (3) shall have a length that meets the creepage distance requirements of the working voltage insulation protection of the high-voltage electric furnace wire (8) in the solid heat storage body (13).

7. A high-voltage thermocouple probe with built-in grounding protection according to claim 1, characterized in that: The distance between the solid heat storage body (13) and the grounding bracket (5) is 650mm to 1300mm.

Images