Live Wire Inspection Apparatus with Contact Pole of Bushing in Processing Switch

Abstract

The live-line inspection device for an overhead switch bushing equipped with a contact electrode according to the present invention may include: a leakage line forming a current path for measuring leakage occurring in an overhead switch; a sealing contact terminal located at one end of the leakage line and in contact with the bushing and mold cone joint of the overhead switch; a grounding terminal located at the other end of the leakage line and connected to a grounding frame of the overhead switch; a leakage detector that detects leakage occurring along the leakage line; and a calculation device that analyzes the measurement value detected by the leakage detector.

Description

Technology Field

[0001] The present invention relates to a live-line inspection device for an overhead switch bushing capable of detecting a failure occurring in the bushing due to a poor seal between the bushing insulator and the mold cone of a gas-insulated overhead switch. Background Technology

[0003] As of December 2023, there are approximately 140,000 overhead switchgear units in operation in Korea, of which epoxy insulation type accounts for about 90,000 units (65%) and SF6 gas insulation type accounts for about 50,000 units (33%).

[0004] FIG. 1 is a perspective view of an overhead switch showing its external appearance and name.

[0005] Figure 2 is a photograph of the site where the overhead switch is installed.

[0006] Figure 3 is a photograph of a fault condition between a fixed and a moving contact related to a processing switch, and Figure 4 is a photograph of a bushing fault condition.

[0007] In the last five years, 883 failures related to overhead switches occurred, with 483 cases identified as failures unrelated to switch defects such as foreign object contact and 400 cases identified as failures of the switch itself. Failures caused by switch defects were accounted for by gas insulation type with 276 cases (69%), epoxy insulation type with 101 cases (25%), and polymer insulation type with 23 cases (6%).

[0009] Figure 5 is a cross-sectional view of a bushing joint showing the structure and names of the bushing and mold cone joint.

[0010] Figure 6 is a photograph showing a case where the bonding condition between the insulator and the mold cone is poor, and Figure 7 is a photograph showing a case where the bonding condition between the insulator and the mold cone is normal.

[0011] Gas insulation type accounted for the largest share of overhead switch failures, and the major causes of failure in the gas insulation type were analyzed to be 68 cases of failure between main body contacts and 208 cases of bushing seal failure.

[0012] The Power Equipment Center analyzed that failures in overhead switch bushings are caused by moisture absorbed due to poor sealing between the bushing insulator and the mold cone, which freezes or expands during the winter, leading to bushing failure.

[0014] To prevent failures of overhead switchgear, inspections and diagnoses are being conducted using optical, thermal imaging, and ultrasonic visual inspections. In 2022, 6,498,000 extra-high voltage utility poles (3,710,000 thermal, 2,449,000 optical, and 301,000 ultrasonic) were diagnosed, resulting in a diagnosis rate of 144% for poles in operation, with service costs amounting to approximately 31.1 billion won. 800 overhead switchgear cases were identified through these diagnoses.

[0016] Fig. 8 is a photograph showing the optical diagnosis of the processing switch, Fig. 9 is a photograph showing the thermal image diagnosis, and Fig. 10 is a photograph showing the ultrasonic diagnosis.

[0017] Previously, overhead switchgear could be diagnosed using optical, thermal, and ultrasonic diagnostics performed on the ground to identify issues such as gas pressure failure, carbon coating defects, bushing cracks, and rescue wire erosion; however, there were no cases of defects identified due to poor airtightness at the bushing and mold cone joints. Optical diagnosis is a method that inspects the external appearance of equipment using a high-performance camera, enabling the identification of gas pressure failures and bushing cracks. Thermal imaging diagnosis measures heat generation caused by increased contact resistance due to incomplete connections at wire connection points, allowing for the identification of poor connections between wires and lead wires. Ultrasonic diagnosis can also detect local discharges caused by carbon coating defects. However, the three diagnostic methods described above cannot verify the airtightness of the bushing insulator and mold cone, which are major causes of failure in overhead switchgear. Prior art literature

[0019] Republic of Korea Registered Publication No. 10-1310280 The problem to be solved

[0020] The present invention aims to provide a live-line inspection device for overhead switch bushings that can safely and easily check the airtightness of the bushing insulator and mold cone, which are major causes of failure in overhead switchgear. means of solving the problem

[0022] A live-line inspection device for an overhead switch bushing according to one aspect of the present invention may include: a leakage line forming a current path for measuring leakage occurring in an overhead switch; a sealing contact terminal located at one end of the leakage line and in contact with the bushing and mold cone joint of the overhead switch; a grounding terminal located at the other end of the leakage line and connected to a grounding frame of the overhead switch; a leakage detector that detects leakage occurring along the leakage line; and a calculation device that analyzes the measurement value detected by the leakage detector.

[0023] Here, a safety stick may be further included that serves as a handle, which is grasped by the operator to bring the seal contact terminal into contact with the bushing and the mold cone joint.

[0024] Here, the above-mentioned sealing contact terminal may include a contact electrode having an internal contact surface formed of a conductive sponge material or mesh material so as to be in complete contact with the insulator of the bushing and the mold cone joint.

[0025] Here, the leakage line and the contact electrode can be electrically connected via a predetermined resistance material.

[0026] Here, the above-mentioned sealing contact terminal can be connected to one end of the leakage line via a predetermined high-resistance element.

[0027] Here, the leakage detector may be a CT that measures current in a non-contact manner using a magnetic field induced by the leakage current, in a ring shape that surrounds the leakage line.

[0028] Here, the leakage detector may be a voltage meter in the form of a voltage divider.

[0029] Here, the computing device may include an ADC that converts the output value of the leakage detector into a digital value; and a CPU that analyzes the magnitude and frequency of the leakage current from the converted digital value.

[0030] Here, the computing device may further include a display that displays the magnitude and frequency of the analyzed leakage current and a diagnostic result based on the analyzed leakage current.

[0031] Here, the computing device further includes a GPS module for verifying location information of a location and can display the location information verified by the GPS module on the display. Effects of the invention

[0033] By implementing the live-line inspection device for a processing switch bushing according to the concept of the present invention with the above-described configuration, there is an advantage of reducing the cost of disposing of normal products during individual inspections of processing switches.

[0034] The live-line inspection device for overhead switch bushings according to the concept of the present invention has the advantage of improving power supply reliability and customer satisfaction by preventing repeated failures of overhead switchgear.

[0035] In addition, other features and advantages of the present invention may be newly identified through the embodiments of the present invention. Brief explanation of the drawing

[0037] FIG. 1 is a perspective view of an overhead switch showing its external appearance and name. Figure 2 is a photograph of the site where the overhead switch is installed. Figure 3 is a photograph of a fault condition between a fixed and a moving contact related to a processing switch, and Figure 4 is a photograph of a bushing fault condition. Figure 5 is a cross-sectional view of a bushing joint showing the structure and names of the bushing and mold cone joint. Figure 6 is a photograph showing a case where the bonding condition between the insulator and the mold cone is poor, and Figure 7 is a photograph showing a case where the bonding condition between the insulator and the mold cone is normal. Fig. 8 is a photograph showing the optical diagnosis of the processing switch, Fig. 9 is a photograph showing the thermal image diagnosis, and Fig. 10 is a photograph showing the ultrasonic diagnosis. Fig. 11 is a photograph showing the direction of moisture penetration, and Fig. 12 is a photograph showing the direction of leakage current generated in the case of Fig. 11. Figure 13 is a photograph showing the measurement of leakage current in an experimental environment simulating a leak caused by moisture penetration. Figure 14 is a photograph of the grounding of the bushing joint for an experiment simulating a leak, and Figure 15 is a photograph showing the insulation breakdown caused by leakage current. FIG. 16 is a conceptual diagram of a leakage current measuring device as a live-line inspection device for a processing switch bushing according to the concept of the present invention. FIG. 17 is a detailed configuration diagram of the leakage current measuring device of FIG. 16. FIG. 18 is an example diagram of the configuration of a detector for current measurement. Figure 19 is an example of a voltage measurement method. FIG. 20 is a cross-sectional view showing the joint between the processing switch bushing tube and the mold cone as the contact portion of the contact electrode of the probe. FIG. 21 is a structural diagram illustrating an example of a contact electrode of a probe. Figure 22 is a conceptual diagram of the operation unit of the leakage current measuring device. FIG. 23 is a photograph illustrating the components for measuring a live-line inspection device for a processing switch bushing according to one embodiment of the present invention. FIG. 24 is a photograph of a test scene to determine the effect of the processing switch bushing leakage current measuring device according to the concept of the present invention. Figure 25 is a graph showing the test results of Figure 24. FIG. 26 is a conceptual diagram of the process of applying a pilot leakage current measuring device for an overhead switch to demonstrate the concept of the present invention. Specific details for implementing the invention

[0038] In describing the present invention, terms such as first, second, etc. may be used to describe various components, but the components may not be limited by the terms. The terms are intended solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component.

[0039] When it is mentioned that a component is connected to or coupled with another component, it can be understood that it may be directly connected to or coupled with that other component, or that there may be other components in between.

[0040] The terms used in this specification are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions may include plural expressions unless the context clearly indicates otherwise.

[0041] In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0042] In addition, the shapes and sizes of elements in the drawings may be exaggerated for clearer explanation.

[0044] Fig. 11 is a photograph showing the direction of moisture penetration, and Fig. 12 is a photograph showing the direction of leakage current generated in the case of Fig. 11.

[0045] Reflecting the phenomenon illustrated in FIGS. 11 and 12, the present invention determines that if moisture is absorbed due to poor airtightness between the processing switch bushing and the mold cone joint, leakage current may also flow along the same path, and proposes a preventive measure against this.

[0047] Figure 13 is a photograph showing the measurement of leakage current in an experimental environment simulating a leak caused by moisture penetration.

[0048] Figure 14 is a photograph of the grounding of the bushing joint for an experiment simulating a leak, and Figure 15 is a photograph showing the insulation breakdown caused by leakage current.

[0049] After grounding the joint between the overhead switch bushing and the mold cone with aluminum tape (Fig. 14), the change in leakage current for each bushing was measured while gradually increasing the voltage to 13.2 kV for each circuit. As a result, for bushings with good airtightness between the bushing tube and the mold cone, the magnitude of the leakage current was very small (less than 0.1 mA) and there was no change in the magnitude of the leakage current as the voltage increased, but for bushings with poor airtightness, the magnitude of the leakage current increased proportionally as the applied voltage increased, and it was found that when the voltage exceeded a certain level, the leakage current increased rapidly and even led to insulation breakdown (Fig. 15).

[0050] Therefore, it was confirmed that the airtightness of the joint can be verified if the leakage current between the bushing tube and the mold cone can be measured.

[0052] FIG. 16 is a conceptual diagram of a leakage current measuring device as a live-line inspection device for a processing switch bushing according to the concept of the present invention.

[0053] FIG. 17 is a detailed configuration diagram of the leakage current measuring device of FIG. 16.

[0054] A live-line inspection device for an overhead switch bushing may include: a leakage line (110) forming a current path for measuring leakage occurring in the overhead switch; a sealing contact terminal (120) located at one end of the leakage line and in contact with the bushing and mold cone joint of the overhead switch; a grounding terminal (140) located at the other end of the leakage line and connected to the grounding frame of the overhead switch; a leakage detector (160) detecting that leakage is occurring along the leakage line; and a calculation device (200) for analyzing the measurement value detected by the leakage detector (160).

[0056] FIG. 18 is an example diagram of the configuration of a detector for current measurement.

[0057] Figure 19 is an example of a voltage measurement method.

[0058] In order to measure the magnitude of the leakage current at the joint between the overhead switch bushing and the mold cone, a ground wire can be directly connected to the joint as shown in FIG. 16 and 17, and then measured using a Current Transformer (160-1). In this case, the leakage detector (160) is a CT (160-1) that has a ring shape surrounding the leakage line and measures the current in a non-contact manner using a magnetic field induced by the leakage current.

[0059] However, if the airtightness of the joint between the overhead switch bushing and the molded cone is poor, insulation breakdown may occur immediately upon connecting the grounding wire, which could progress to a ground fault, and there is a high risk of worker safety accidents caused by arcs, etc. Therefore, it is practically difficult to measure leakage current by directly connecting the grounding wire to the joint between the bushing and the molded cone. In other words, since the current measurement method (Fig. 18) that directly measures the leakage current of the overhead switch bushing and the molded cone joint carries a risk of ground faults and safety accidents, it is advantageous to use the voltage measurement method (Fig. 19) which applies a voltage measuring device (160-2) in the form of a voltage divider.

[0060] However, in the case of a current measurement method (Fig. 18) using a CT (160-1) which is widely used in the field and for which parts and analysis algorithms are easily obtained, the bushing tube and the mold cone joint and the ground can be connected directly, but can be performed by connecting them through a resistor element of a predetermined size.

[0061] The voltage measurement method utilizes a method in which two high-voltage resistors, one large and one small, are installed between the overhead switch bushing insulator and the molded cone joint and the ground, and when leakage current passes through the high-voltage resistors, the voltage across the two terminals of the high-voltage resistors is measured to calculate the magnitude of the leakage current. The high-voltage resistor with the large resistance value is intended to prevent ground faults, while the resistor with the small resistance value is intended to calculate the leakage current by measuring the voltage across the resistors through voltage division.

[0063] FIG. 20 is a cross-sectional view showing the joint between the processing switch bushing tube and the mold cone as the contact portion of the contact electrode of the probe.

[0064] FIG. 21 is a structural diagram illustrating an example of a contact electrode of a probe.

[0065] Figure 22 is a conceptual diagram of the operation unit of the leakage current measuring device.

[0066] FIG. 23 is a photograph illustrating the components for measuring a live-line inspection device for a processing switch bushing according to one embodiment of the present invention.

[0068] Leakage current at the joint between the overhead switch bushing insulator and the molded joint must be measured using an indirect contact probe to ensure the safety of the operator. Insulation must be maintained at the parts of the contact probe that come into direct contact with the human body by utilizing an indirect live-line tool hot stick (safety stick). The grounding electrode used to measure leakage current must be manufactured to primarily protect the human body from overvoltage and overcurrent by incorporating high resistance, and secondarily to prevent damage to various IC chips within the processing unit.

[0069] To this end, the live-line inspection device for a processing switch bushing illustrated in FIG. 23 further includes a safety stick (150) that serves as a handle for a worker to grasp and bring the seal contact terminal into contact with the bushing and the mold cone joint.

[0071] For accurate leakage current detection, the internal contact surface of the probe must be structured to be in complete contact with the bushing tube and the molded cone joint, and must be made of a conductive material (conductive sponge, copper brass mesh, etc.). The probe's contact surface should be manufactured in a clamp-like form to ensure complete contact with the molded cone joint, allowing the user to firmly adhere it with easy and comfortable movement. Depending on the implementation, a high-resistance element may be placed on the inner surface or between the connection point and the line conductor.

[0072] Specifically, the sealing contact terminal (120) illustrated in FIG. 21 may include a contact electrode (122) having an internal contact surface formed of a conductive sponge material or mesh material so as to be in complete contact with the bushing tube and the mold cone joint.

[0073] In addition, to prevent a ground fault caused by a sudden leakage current, it is advantageous for the leakage line and the contact electrode (122) of the sealing contact terminal to be electrically connected through a predetermined resistance material.

[0074] For example, in the structure of the sealing contact terminal (120) of FIG. 21, a separate high-resistance conductive pad may be attached between the inner surface of the upper end of the clamp-shaped probe and the contact electrode (122), or a predetermined high-resistance element may be connected between the lower end of the illustrated probe and one end of the leakage line (110) of FIG. 16 to provide a resistance component in the path of the leakage current.

[0076] The calculation device (200) for measuring leakage current exemplified in FIG. 22 consists of an amplifier (AMP), an AC-DC converter (ADC), and a CPU. The amplifier can amplify the voltage measured by the leakage detector (160) up to 10 times, the ADC (210) converts the output value of the CT into a digital value, and the CPU (220) can analyze the magnitude, frequency, etc. of the leakage current from the converted digital value.

[0077] Additionally, the above-mentioned computing device (200) according to FIG. 22 further includes a display (280) that displays the magnitude and frequency of the analyzed leakage current and the diagnostic result based on the analyzed leakage current.

[0078] For example, the display (280) for displaying the measured leakage current as exemplified in FIG. 22 (which may also function as a physical body depending on the implementation) is protected by a movable case, and a hook is attached to the movable case so that it can be hung on a bucket of a live-line inspection vehicle, etc., allowing the user to use it comfortably during measurement. The configuration of the display and operation functions that the display (280) can perform is as follows.

[0079] ○ Display using LCD (LCD size: 7 inches)

[0080] ○ Display of bushing leakage current value (0.1µA ~ 214µA, displayed in 0.1µA increments)

[0081] ○ Display of remaining battery level and charging status, display of main unit power ON / OFF

[0082] ○ Display diagnosis result (Normal, Poor, Caution)

[0083] ○ Display leakage current as a waveform graphic

[0084] ○ Power ON / OFF button

[0085] ○ Securing storage memory slot and external connection terminal (USB)

[0086] ○ Built-in GPS for verifying the location of the diagnosis site

[0087] For example, the above-mentioned computing device (200) with added GPS function may further include a GPS module for verifying location information of a location and may display the location information verified by the GPS module on the display (280).

[0089] FIG. 24 is a photograph of a test scene to determine the effect of the processing switch bushing leakage current measuring device according to the concept of the present invention.

[0090] Figure 25 is a graph showing the test results of Figure 24.

[0091] FIG. 26 is a conceptual diagram of the process of applying a pilot leakage current measuring device for an overhead switch to demonstrate the concept of the present invention.

[0092] To prove the practicality of the concept of the present invention, a prototype of a processing switch bushing leakage current measuring device was manufactured as shown in FIG. 24, and the change in leakage current according to the applied voltage was measured in a test room, and as a result, it was measured well as shown in FIG. 25.

[0093] As a result of applying a prototype of the overhead switch bushing leakage current measuring device to eight overhead switches currently in operation at the Gochang Power Testing Center, leakage current was measured in three bushings. The overhead switches in which leakage current was measured were removed and subjected to insulation performance testing, which revealed insulation breakdown. Upon disassembly and analysis, it was confirmed that the connection between the bushing insulator and the mold cone was defective.

[0095] Those skilled in the art to which the present invention pertains should understand that the present invention may be implemented in other specific forms without altering its technical concept or essential features, and therefore the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims set forth below rather than by the detailed description, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention. Explanation of the symbols

[0097] 110 : Leakage line 120 : Seal contact terminal 140 : Grounding terminal 160 : Leakage detector 160-1 : CT 160-2 : Voltage meter 200: Arithmetic Unit 280 : Display

Claims

Claim 1 A leakage line forming a current path for leakage current to measure leakage occurring in an overhead switch; a sealing contact terminal located at one end of the leakage line and in contact with the bushing and mold cone joint of the overhead switch; a grounding terminal located at the other end of the leakage line and connected to the grounding frame of the overhead switch; a leakage detector that detects leakage occurring along the leakage line; and a computing device that analyzes the measurement value detected by the leakage detector. A live-line inspection device for a processing switch bushing, comprising a safety stick that serves as a handle for a worker to grasp and contact the sealing contact terminal with the joint between the bushing and the mold cone, wherein the sealing contact terminal includes a contact electrode having an internal contact surface formed of a conductive sponge material or mesh material so as to be in complete contact with the joint between the bushing insulator and the mold cone to measure leakage current caused by a seal failure between the bushing insulator and the mold cone, and wherein the leakage line and the contact electrode are electrically connected through a predetermined resistance material. Claim 2 In claim 1, the above-described sealing contact terminal is a live-line inspection device for an overhead switch bushing having a contact electrode connected to one end of the leakage line via a predetermined high-resistance element. Claim 3 In claim 1, the leakage detector is a live-line inspection device for an overhead switch bushing equipped with a contact electrode that is a CT, which measures current in a non-contact manner using a magnetic field induced by the leakage current, in a ring shape that surrounds the leakage line. Claim 4 In claim 1, the leakage detector is a live-line inspection device for an overhead switch bushing equipped with a contact electrode that is a voltage measuring device in the form of a voltage divider. Claim 5 A live-line inspection device for a processing switch bushing having a contact electrode, wherein the computing device comprises: an ADC that converts the output value of the leakage detector into a digital value; and a CPU that analyzes the magnitude and frequency of the leakage current from the converted digital value. Claim 6 In claim 5, the above-mentioned calculation device is a live-line inspection device for a processing switch bushing equipped with a contact electrode, further comprising a display that displays the magnitude and frequency of the analyzed leakage current and a diagnostic result based on the analyzed leakage current. Claim 7 In claim 6, the above-mentioned computing device further includes a GPS module for verifying location information of a location and a contact pole for displaying the location information verified by the GPS module on the display, thereby forming a live-line inspection device for a processing switch bushing.

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