Device and method for accurately positioning defect position of cable grounding system through characteristic voltage method

Abstract

The invention provides a device for accurately positioning a defect position of a cable grounding system by a characteristic voltage method. The device comprises a characteristic voltage signal generator, a characteristic voltage signal receiver and a non-contact voltage signal coupler, the characteristic voltage signal generator is connected with a grounding lead in the defective cable section cross interconnection box and injects coupling characteristic voltage signals, and the characteristic voltage signal receiver is connected with the non-contact voltage signal coupler and receives and processes detection signals of the non-contact voltage signal coupler. The non-contact voltage signal coupler is an inductive voltage coupler. Voltage values are measured on the two sides of each part of the grounding system defect cable section respectively, obvious voltage drop positions are found, and the specific position of the grounding system defect is determined and marked. By detecting the amplitude of the characteristic voltage signal, the specific position of the grounding system defect of the cable can be accurately judged, so that the power failure time required for defect elimination is effectively reduced, and the power supply reliability is improved.

Description

Technical Field

[0001] The present invention relates to the field of high-voltage cable grounding system defect determination, and in particular to a device and method for accurately locating the position of a cable grounding system defect using a characteristic voltage method. Background Art

[0002] In recent years, high-voltage cable grounding system failures and defects have occurred frequently, which has put forward higher requirements for the production preparation and acceptance, operation and maintenance of high-voltage cables. Common high-voltage cable grounding system defects such as loose and oxidized sealing lead and loose grounding bolts mainly occur in the grounding box or accessories, which are sealed by other strips or equipment and are difficult to detect with the naked eye or traditional detection methods such as infrared temperature measurement. After such defects occur, the grounding system loop resistance increases, and the insulation deteriorates after the grounding current is blocked, eventually leading to cable insulation breakdown. In addition, the grounding loop resistance of the high-voltage cable is very low under normal conditions. When a defect occurs, the absolute value of the grounding loop resistance changes little. Therefore, higher technical requirements are put forward for the precise positioning and investigation of defects in the high-voltage cable grounding system. At present, there are mainly the following methods for locating defects in the high-voltage cable grounding system: Kelvin method: This method involves applying a voltage between two points on a metal conductor and calculating the resistance by measuring the voltage and current between them. A micro-resistance tester employs this method, but conventional micro-resistance testers cannot measure resistance between two points on a conductor while energized. Equipment specialized for measuring the loop resistance of high-voltage cable grounding systems can perform live testing. This method is primarily used to measure the ground loop resistance of single-ended grounding systems, either live or in a power-off state, to determine if the tested cable section has grounding system defects.

[0003] Coupling method: This method couples a voltage signal into the ground loop via a voltage transformer, measures the current in the ground loop via a current transformer, and calculates the loop resistance. Currently, most ground resistance testers on the market use the coupling method, which means there's no voltage in the measured loop. However, during operation, high-voltage cable ground loops can induce significant voltage. Therefore, measuring the ground loop resistance of high-voltage cables with cross-connected grounding requires a specialized high-voltage cable ground loop resistance tester. However, these instruments can only measure the loop resistance of a single branch consisting of three cable segments. While they can determine if there are any defects such as poor contact within the entire branch, they cannot determine the cable segment or its precise location.

[0004] DC direction method: This method is to add a DC source to the transposition valve plate in the cross-connection box, and use an active Hall sensor to measure the DC current in the cables on both sides of the connector. According to Ohm's law, the current is larger on the side with lower resistance. Through this method, it can be determined in which direction of the cable grounding loop on both sides of the DC power access point there is a poor contact defect. However, under normal operating conditions, the internal circulating current of the cable grounding wire has a strong interference with the DC signal acquisition. Therefore, this method can only detect the defect direction during a power outage and cannot be detected with power on. In actual engineering applications, after the cable is powered off, the Kelvin method is generally used to measure the grounding resistance of each cable section to determine whether there is a poor grounding defect. The DC direction method is often used to determine the defective cable section, and then destructively open the window of the cable outer insulation sheath to determine which end of the lead seal has a poor grounding defect.

[0005] In summary, these methods can only determine whether a branch has a poor grounding defect based on the resistance of the three-segment grounding loop within that branch. To pinpoint the exact cable segment and location of the defect, it is necessary to remove the transposition valve plate within the cross-connection box after a power outage and perform destructive window inspections on multiple cable segments for further testing. Therefore, even if a live-powered grounding system defect is detected on a cable branch, a lengthy power outage and subsequent location-by-location inspection are required to locate and eliminate the defect. Therefore, the ability to quickly and accurately locate grounding system defects under non-destructive conditions is crucial for reducing outage duration and improving power supply reliability. Summary of the Invention

[0006] The purpose of the present invention is to provide a device and method for accurately locating the position of defects in a cable grounding system by using the characteristic voltage method. By detecting the amplitude of the characteristic voltage signal, the specific location of the grounding system defect in the cable section can be accurately determined, thereby effectively reducing the power outage time required to eliminate the defect and improving power supply reliability.

[0007] In order to achieve the above-mentioned purpose, the present invention is implemented through the following technical solutions.

[0008] A device for accurately locating a defect position in a cable grounding system using a characteristic voltage method, comprising: a characteristic voltage signal generator, a characteristic voltage signal receiver, and a non-contact voltage signal coupler; The characteristic voltage signal generator is connected to the grounding lead in the cross-connection (protection) box of the defective cable section and is used to inject the coupled characteristic voltage signal.

[0009] The characteristic voltage signal receiver is connected to the non-contact voltage signal coupler and is used for receiving and processing the detection signal of the non-contact voltage signal coupler.

[0010] The non-contact voltage signal coupler is an inductive voltage coupler, which is connected to the characteristic voltage signal receiver signal and is used to measure the voltage generated after the characteristic voltage signal generator applies the coupled characteristic voltage signal.

[0011] Furthermore, the characteristic voltage signal generator includes a control unit, a driving circuit, a filtering circuit, a voltage regulating circuit, and a coupling transmission circuit. The power input end is connected to the mains or a rechargeable battery, and the signal output end emits a non-industrial frequency voltage excitation signal.

[0012] Furthermore, the characteristic voltage signal receiver includes an input protection unit, an amplification processing unit, a microcomputer processing unit, a signal tracking and zeroing unit, and a display screen.

[0013] The present invention also discloses a method for accurately locating a defect position in a cable grounding system using a characteristic voltage method. The device for accurately locating a defect position in a cable grounding system using the characteristic voltage method includes the following steps: S1. Identify cross-connected subsections or single-ended grounding subsections with defects in the high-voltage cable grounding system S2. Check the specific location of the grounding system defects during power outage and add an excitation voltage signal to the non-directly grounded side of the high-voltage cable grounding system. S3. Measure the voltage values ​​on both sides of each part of the defective cable section in the grounding system, find the location of obvious voltage drop, determine the specific location of the grounding system defect and mark it.

[0014] Furthermore, before finding the specific location of the defect in the high-voltage cable grounding system, the power supply to the line should be shut down; After the power outage, open the grounding box to eliminate the defects in the grounding system, and then modify the grounding boxes on both sides so that the high-voltage cable section to be tested forms a grounding form with one end directly grounded and the other end suspended.

[0015] Furthermore, the test location is the single-core connecting lead in the cross-interconnection box of the high-voltage cable cross-interconnection sub-section, or the grounding lead in the protective grounding box of the single-ended grounding sub-section. The characteristic voltage signal generator is directly connected with a wire clamp to the single-core connecting lead in the cross-interconnection grounding box or the grounding lead in the protective grounding box after the transposition valve plate is removed. The signal input to the cable line of the characteristic voltage signal generator is an AC signal.

[0016] Furthermore, the equivalent circuit of the test site is the resistance R at the test point in the high-voltage cable ground loop, with one end grounded and the other connected to a characteristic voltage signal generator. U1 is the voltage on the side of resistance R close to the power supply, and U2 is the voltage on the side of resistance R close to ground. Under normal circumstances, the cable ground loop is conductive, R is extremely small, and the values ​​of U1 and U2 are essentially equal.

[0017] Furthermore, the method for determining the defect location in step S3 is: The characteristic voltage U is input into the line through the power supply, and the voltage values ​​U1 and U2 on both sides of the seal are measured using a non-contact voltage signal coupler. If U1>>U2, when the resistance of the test point in the ground loop increases due to poor grounding, the voltage drop will be larger according to the voltage division, and it can be determined that the defect occurs at the test point.

[0018] The advantages of the present invention are: This device and method can quickly identify faulty sections and locate high-voltage cable grounding defects without interfering with the normal operation of the equipment under non-destructive conditions. The specific cross-connected sub-sections and defect locations can be determined within 5 minutes. This effectively improves the efficiency of finding defects in concealed grounding systems, reduces power outages and their impact on grid operation, and avoids irreparable damage to the insulation performance of the cable itself caused by multiple window inspections. The present invention can effectively detect and accurately locate grounding system defects such as rusted and warped edges of high-voltage cable lead seals, loose grounding bolts, and rusted inner surfaces of grounding copper bars. The device is compact, offers high measurement accuracy and reliability, and is suitable for outdoor operations and confined spaces in cable tunnels. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is an equivalent circuit diagram of the test part of the present invention; Figure 2 This is a schematic diagram of the structure of a device for accurately locating a defect position in a cable grounding system using the characteristic voltage method according to Example 1 of the present invention; Figure 3 This is a schematic diagram of the structure of a device for accurately locating the defect position of a cable grounding system using the characteristic voltage method according to Example 2 of the present invention; Figure 4 This is a schematic diagram of the connection between the characteristic voltage signal generator and the test part in Example 1 of the present invention; Figure 5 Schematic diagram of the connection relationship between the characteristic voltage signal receiver and the contactless voltage signal coupler according to embodiment 2 of the present invention. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0021] Example 1 This embodiment discloses a device for accurately locating a defect position in a cable grounding system using a characteristic voltage method, comprising: a characteristic voltage signal generator, a characteristic voltage signal receiver, and a non-contact voltage signal coupler.

[0022] Please refer to Figure 2 ,The characteristic voltage signal generator is connected to the grounding lead in the cross-interconnection (protection) box of the defective cable section to inject the coupled characteristic voltage signal.

[0023] The characteristic voltage signal receiver is connected to the non-contact voltage signal coupler and is used for receiving and processing the detection signal of the non-contact voltage signal coupler.

[0024] The non-contact voltage signal coupler is an inductive voltage coupler, which is connected to the characteristic voltage signal receiver signal and is used to measure the voltage generated after the characteristic voltage signal generator applies the coupled characteristic voltage signal.

[0025] The characteristic voltage signal generator includes a control unit, a drive circuit, a filtering circuit, a voltage regulation circuit, and a coupling transmission circuit. The power input end is connected to the mains or a rechargeable battery, and the signal output end emits a non-industrial frequency voltage excitation signal, including but not limited to DC signals, sine waves, cosine waves, square waves, triangle waves, special-shaped waves, etc., which can be detected by a non-contact voltage signal coupler.

[0026] The characteristic voltage signal receiver comprises an input protection unit, an amplification processing unit, a microcomputer processing unit, a signal tracking and zeroing unit and a display screen.

[0027] The non-contact voltage signal coupler is an inductive voltage coupler. It is placed close to the cable under test to measure the voltage generated by the characteristic voltage signal generator after applying the coupled characteristic voltage signal. The measured signal is then transmitted to the characteristic voltage signal receiver for further processing and analysis to determine the specific location of the grounding system defect within the cable section.

[0028] Example 2 This embodiment discloses a method for accurately locating a defect position in a cable grounding system using a characteristic voltage method. The device for accurately locating a defect position in a cable grounding system based on the characteristic voltage method includes the following steps: S1. Identify the cross-connected subsections or single-ended grounding subsections with defects in the high-voltage cable grounding system; S2. Check the specific location of the grounding system defects during power outage and add an excitation voltage signal to the non-directly grounded side of the high-voltage cable grounding system. S3. Measure the voltage values ​​on both sides of each part of the defective cable section in the grounding system, find the location of obvious voltage drop, determine the specific location of the grounding system defect and mark it.

[0029] The test cable segment determined in step S1 is a cross-connected sub-segment or a single-ended grounded sub-segment determined to have a high-voltage cable grounding system defect according to the method described in step S3.

[0030] The equivalent circuit of the test site is as follows Figure 1 As shown in the figure, R represents the resistance of the high-voltage cable ground loop at the point to be measured, and U1 and U2 are the voltages across the point to be measured. Under normal circumstances, the cable ground loop is a conductor, R is extremely small, and the values ​​of U1 and U2 are basically equal.

[0031] The characteristic voltage U is input into the circuit through the power supply. When the resistance of the grounding loop test point increases due to poor grounding, a large voltage drop will occur according to the voltage division. Here, U1 will be significantly greater than U2, which can be used to determine that the defect occurs at the test point.

[0032] Example 3 This embodiment discloses a specific testing method in engineering construction.

[0033] S1. Before finding the specific location of the high-voltage cable grounding system defect, first shut down the power supply to the line.

[0034] S2. After a power outage, open the grounding box and eliminate obvious grounding system defects such as loose bolts and broken grounding wires.

[0035] S3. Modify the grounding boxes on both sides. By removing the transposition valve plate in the cross-connection box and short-circuiting the protector in the cross-connection box, the high-voltage cable section to be tested is grounded in a way that one end is directly grounded and the other end is suspended.

[0036] S4. The test location is the single-core connecting lead in the cross-connection box of the high-voltage cable cross-connection sub-section, or the grounding lead in the protective grounding box of the single-ended grounding sub-section. Connect the characteristic voltage signal generator directly with a wire clamp to the single-core connecting lead or the grounding lead in the protective grounding box after the transposition valve plate is removed. The signal input to the characteristic voltage signal generator is an AC signal.

[0037] S5. Use a non-contact voltage signal coupler to measure the voltage values ​​U1 and U2 on both sides of the lead seal. If the characteristic voltage signal receiver shows a sudden change in voltage value, it indicates that there is a grounding system defect at that location, and the location is complete.

[0038] Example 4 The method for determining the defect location is: The characteristic voltage U is input into the line through the power supply, and the voltage values ​​U1 and U2 on both sides of the seal are measured using a non-contact voltage signal coupler. If U1>>U2, when the resistance of the test point in the ground loop increases due to poor grounding, the voltage drop will be larger according to the voltage division, and it can be determined that the defect occurs at the test point.

[0039] Example 5 Please refer to Figure 2 This embodiment provides a precise positioning solution for detecting the specific location of a defect in the grounding system of the cross-connection sub-segment A1 according to the present invention. The specific steps are as follows: When a line is outage, the first step is to open the grounding box and check for obvious grounding system defects, such as loose bolts and broken grounding wires. The No. 2 cross-connection grounding box is then modified, and the transposition valve plate inside the No. 2 cross-connection box is disassembled.

[0040] Connect the characteristic voltage signal generator directly to the ground lead inside the #2 cross-connect box with a wire clamp and input the excitation voltage signal. The characteristic voltage signal receiver measures the characteristic voltage amplitudes U1 and U2 on both sides of the lead seal and other locations using a non-contact voltage signal coupler.

[0041] The equivalent circuit of the test site is as follows Figure 1 As shown in the figure, R represents the resistance of the high-voltage cable ground loop at the point to be measured, and U1 and U2 are the voltages across the point to be measured. Under normal circumstances, the cable ground loop is a conductor, R is extremely small, and the values ​​of U1 and U2 are basically equal.

[0042] The characteristic voltage U is input into the circuit through the power supply. When the resistance of the grounding loop test point increases due to poor grounding, a large voltage drop will occur according to the voltage division. Here, U1 will be significantly greater than U2, which can be used to determine that the defect occurs at the test point.

[0043] If the characteristic voltage amplitudes U1 and U2 on both sides differ greatly, it means that there is a defect in the internal grounding system. If the characteristic voltage amplitudes U1≈U2 on both sides, it means that there is no defect in the internal grounding system.

[0044] exist Figure 2 In the figure, the characteristic voltage amplitudes U1 and U2 on both sides of the right lead seal are quite different, indicating that there is a grounding system defect inside the right lead seal.

[0045] Example 6 Please refer to Figure 3 This embodiment provides a precise positioning solution for detecting the specific location of a defect in the grounding system of the cross-connected intermediate sub-segment B2 according to the present invention. The specific steps are as follows: When a line is outage, the first step is to open the grounding box and check for obvious grounding system defects, such as loose bolts and broken ground wires. The grounding boxes on both sides are then modified, with the transposition valve plate in the #3 cross-connection box removed and the sheath protector in the #2 cross-connection box directly grounded.

[0046] Connect the characteristic voltage signal generator directly to the ground lead inside the 3# cross-connect box with a wire clamp and input the excitation voltage signal. The characteristic voltage signal receiver measures the characteristic voltage amplitudes U1 and U2 on both sides of the lead seal and other locations using a non-contact voltage signal coupler.

[0047] The equivalent circuit of the test site is as follows Figure 1 As shown in the figure, R represents the resistance of the high-voltage cable ground loop at the point to be measured, and U1 and U2 are the voltages across the point to be measured. Under normal circumstances, the cable ground loop is a conductor, R is extremely small, and the values ​​of U1 and U2 are basically equal.

[0048] The characteristic voltage U is input into the circuit through the power supply. When the resistance of the grounding loop test point increases due to poor grounding, a large voltage drop will occur according to the voltage division. Here, U1 will be significantly greater than U2, which can be used to determine that the defect occurs at the test point.

[0049] If the characteristic voltage amplitudes U1 and U2 on both sides differ greatly, it means that there is a defect in the internal grounding system. If the characteristic voltage amplitudes U1 and U2 on both sides are basically equal, it means that there is no defect in the internal grounding system.

[0050] exist Figure 3 In the figure, the characteristic voltage amplitudes U1 and U2 on both sides of the right lead seal are quite different, indicating that there is a grounding system defect inside the right lead seal.

[0051] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A device for accurately locating the position of defects in a cable grounding system using a characteristic voltage method, characterized in that: include: Characteristic voltage signal generator, characteristic voltage signal receiver and contactless voltage signal coupler; The characteristic voltage signal generator is connected to the grounding lead in the defective cable segment cross-connection box and is used to inject a coupled characteristic voltage signal. The characteristic voltage signal receiver is connected to the non-contact voltage signal coupler and is used for receiving and processing the detection signal of the non-contact voltage signal coupler. The non-contact voltage signal coupler is an inductive voltage coupler, which is connected to the characteristic voltage signal receiver signal and is used to measure the voltage generated after the characteristic voltage signal generator applies the coupled characteristic voltage signal.

2. The device for accurately locating the defect position of the cable grounding system using the characteristic voltage method according to claim 1 is characterized in that: The characteristic voltage signal generator includes a control unit, a driving circuit, a filtering circuit, a voltage regulating circuit, and a coupling transmission circuit. The power input end is connected to the mains or a rechargeable battery, and the signal output end sends a non-power frequency voltage excitation signal.

3. The device for accurately locating the defect position of the cable grounding system using the characteristic voltage method according to claim 1 is characterized in that: The characteristic voltage signal receiver comprises an input protection unit, an amplification processing unit, a microcomputer processing unit, a signal tracking and zeroing unit and a display screen.

4. A method for accurately locating the position of a defect in a cable grounding system using a characteristic voltage method, and a device for accurately locating the position of a defect in a cable grounding system using a characteristic voltage method according to any one of claims 1 to 3, characterized in that: Including steps: S1. Identify the cross-connected subsections or single-ended grounding subsections with defects in the high-voltage cable grounding system; S2. Check the specific location of the grounding system defects during power outage and add an excitation voltage signal to the non-directly grounded side of the high-voltage cable grounding system. S3. Measure the voltage values ​​on both sides of each part of the defective cable section in the grounding system, find the location of obvious voltage drop, determine the specific location of the grounding system defect and mark it.

5. The method for accurately locating the defect position of the cable grounding system using the characteristic voltage method according to claim 4 is characterized in that: Before finding the specific location of the high-voltage cable grounding system defect, first shut down the line; After the power outage, open the grounding box to eliminate the defects in the grounding system, and then modify the grounding boxes on both sides so that the high-voltage cable section to be tested forms a grounding form with one end directly grounded and the other end suspended.

6. The method for accurately locating the defect position of the cable grounding system using the characteristic voltage method according to claim 4 is characterized in that: The test location is the single-core connecting lead in the cross-interconnection box of the high-voltage cable cross-interconnection sub-section, or the grounding lead in the protective grounding box of the single-ended grounding sub-section. The characteristic voltage signal generator is directly connected with a wire clamp to the single-core connecting lead in the cross-interconnection grounding box or the grounding lead in the protective grounding box after the transposition valve plate is removed. The signal input to the cable line of the characteristic voltage signal generator is an AC signal.

7. The method for accurately locating the defect position of the cable grounding system using the characteristic voltage method according to claim 4 is characterized in that: The equivalent circuit of the test site is the resistance R at the test point of the high-voltage cable grounding loop with one end grounded and the other end connected to the characteristic voltage signal generator. U1 is the voltage on the side of the resistance R near the power supply, and U2 is the voltage on the side of the resistance R near the ground.

8. The method for accurately locating the defect position of the cable grounding system using the characteristic voltage method according to claim 7 is characterized in that: The method for determining the defect location in step S3 is: The characteristic voltage U is input into the line through the power supply, and the voltage values ​​U1 and U2 on both sides of the seal are measured using a non-contact voltage signal coupler. If U1>>U2, it can be determined that the defect occurs at the measured point.

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