A cable partial discharge detection method and device

Abstract

The present invention relates to a cable partial discharge detection method and device. The device is installed on a high-voltage cable and includes a first high-frequency current transformer, a second high-frequency current transformer, a third high-frequency current transformer, and a processor. The first high-frequency current transformer is sheathed outside the cable core, the second high-frequency current transformer is sheathed outside the grounding cable, and the third high-frequency current transformer is sheathed outside the high-voltage cable. The processor is connected to the first high-frequency current transformer, the second high-frequency current transformer, and the third high-frequency current transformer, respectively. The processor includes an adding circuit and a subtracting circuit. The input end of the adding circuit is respectively connected to the first high-frequency current transformer and the second high-frequency current transformer, and the input end of the subtracting circuit is respectively connected to the output end of the adding circuit and the third high-frequency current transformer. Compared with the existing technology, the present invention can effectively detect partial discharge signals at high-voltage cable joints with high accuracy and can eliminate interference caused by cable circulating current.

Description

Technical Field

[0001] The present invention relates to the technical field of cable partial discharge detection, and in particular to a cable partial discharge detection method and device. Background Art

[0002] High-voltage cables are the lifeblood of cities, providing the energy they need for urban life. A cable failure can have an immeasurable impact on urban life. High-voltage circuit failures are primarily located at the high-voltage cable connectors. Proper inspection of high-voltage cable connectors is crucial for ensuring stable operation of high-voltage cables.

[0003] Localized discharge (PD) in high-voltage XLPE cables is a major factor in high-voltage cable accidents and has garnered widespread attention for years. This problem is primarily due to defects in the cable's insulation, which can cause localized micro-discharges. This discharge accelerates insulation degradation, ultimately leading to cable breakdown. Measuring early-stage PD in cables is crucial for preventing cable accidents. Furthermore, due to the concentrated electric field stress at the intermediate joints of power cables, these joints represent a weak link in the cable's insulation, making them more susceptible to insulation failure. Statistics show that the majority of cable insulation breakdowns occur at these joints.

[0004] Partial discharge (PD) in cable joints primarily occurs in the silicone rubber layer of high-voltage cables. If the specific location of the rubber insulation layer in cable joints could be located, data-driven analysis of faults related to the rubber layer could be conducted, identifying weak links within the rubber layer. This would facilitate the production of products with a higher yield rate. Traditional PD testing, whether using electromagnetic pulse or ultrasonic methods, cannot locate the rubber layer. Traditional capacitive PD testing can only test the entire cable joint and cannot provide location detection.

[0005] Cable partial discharge (PD) detection has long been an important indicator for diagnosing cable joint faults. Common methods for detecting PD at cable joints include HFCT and capacitor plate PD detection. HFCT PD detection has significant drawbacks. First, the HFCT's frequency response presents a technical bottleneck, making it incapable of detecting higher-frequency PD signals. Second, the HFCT is installed on both sides of the grounding joint. This results in interference from circulating currents in the grounding wire, which can mask PD signals within the interfering signal. Summary of the Invention

[0006] The purpose of the present invention is to provide a cable partial discharge detection method and device in order to overcome the defects of the above-mentioned prior art that the HFCT is installed on both sides of the grounding joint, is interfered by the circulating current on the grounding wire, and the partial discharge signal is easily buried in the interference signal.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A method for detecting partial discharge of a cable comprises the following steps:

[0009] Data collection steps: a first high-frequency current transformer is sheathed outside the cable core to collect the high-frequency signal of the high-voltage cable core; a second high-frequency current transformer is sheathed outside the grounding cable to collect the high-frequency signal of the grounding cable; a third high-frequency current transformer is sheathed outside the high-voltage cable to collect the high-frequency signal of the high-voltage cable;

[0010] Partial discharge current detection steps: Calculate the cable partial discharge signal based on the collected high-frequency signals of the high-voltage cable core wire, grounding cable, and high-voltage cable. The calculation expression of the cable partial discharge signal is:

[0011]

[0012] Where I is the cable partial discharge signal value, i1 is the high-frequency signal value of the high-voltage cable core wire, i2 is the high-frequency signal of the grounding cable, and i3 is the high-frequency signal value of the high-voltage cable.

[0013] The present invention also provides a cable partial discharge detection device, which is installed on a high-voltage cable. The cable partial discharge detection device includes a first high-frequency current transformer, a second high-frequency current transformer, a third high-frequency current transformer, and a processor. The first high-frequency current transformer is sheathed on the outside of the cable core, the second high-frequency current transformer is sheathed on the outside of the grounding cable, and the third high-frequency current transformer is sheathed on the outside of the high-voltage cable.

[0014] The processor is respectively connected to the first high-frequency current transformer, the second high-frequency current transformer and the third high-frequency current transformer. The processor includes an adding circuit and a subtracting circuit. The input end of the adding circuit is respectively connected to the first high-frequency current transformer and the second high-frequency current transformer, and the input end of the subtracting circuit is respectively connected to the output end of the adding circuit and the third high-frequency current transformer.

[0015] Furthermore, the current frequency range to which the first high-frequency current transformer, the second high-frequency current transformer and the third high-frequency current transformer respond is 1M to 200Mhz.

[0016] Furthermore, the magnetic core materials of the first high-frequency current transformer, the second high-frequency current transformer and the third high-frequency current transformer are all nickel-zinc ferrite.

[0017] Furthermore, the response operating frequency of the processor is within the range of 80-120Mhz.

[0018] Furthermore, the response operating frequency of the processor is 100Mhz.

[0019] Furthermore, the processor is also connected to an analog-to-digital conversion circuit and a communication circuit, and the analog-to-digital conversion circuit is respectively connected to the subtraction circuit and the communication circuit.

[0020] Furthermore, the cable partial discharge detection device also includes a server, which is communicatively connected to the communication circuit.

[0021] Furthermore, the adding circuit and the subtracting circuit both include operational amplifiers.

[0022] Furthermore, the processor further includes a dividing circuit connected to the output end of the subtraction circuit.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The present invention collects high-frequency current signals on the cable inner core, grounding cable and high-voltage cable respectively as signal 1, signal 2 and signal 3, and the present invention takes into account that when no partial discharge occurs, signal 3 is equal to signal 1 plus signal 2. When partial discharge occurs, the partial discharge signal is reflected in both the cable inner core and the grounding cable, while only a weak partial discharge signal exists on the high-voltage cable. Therefore, by performing addition and subtraction operations on each high-frequency current signal, the value of the partial discharge signal can be directly obtained. This method can effectively detect the partial discharge signal of the high-voltage cable joint with high accuracy and can eliminate the interference caused by the cable circulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of an installation state of a cable partial discharge detection device provided in an embodiment of the present invention;

[0026] Figure 2 A schematic structural diagram of a cable partial discharge detection device provided in an embodiment of the present invention;

[0027] In the figure, 1. first high-frequency current transformer, 2. second high-frequency current transformer, 3. third high-frequency current transformer, 4. processor, 401. addition circuit, 402. subtraction circuit, 403. division circuit, 404. analog-to-digital conversion circuit, 405. communication circuit, 5. cable inner core, 6. grounding cable, 7. high-voltage cable. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of 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. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0030] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0031] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limiting the present invention.

[0032] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0033] Example 1

[0034] This embodiment provides a method for detecting partial discharge in a cable, comprising the following steps:

[0035] Data collection steps: a first high-frequency current transformer 1 is sheathed outside the cable core 5 to collect the high-frequency signal of the high-voltage cable 7 core wire; a second high-frequency current transformer 2 is sheathed outside the grounding cable 6 to collect the high-frequency signal of the grounding cable 6; a third high-frequency current transformer 3 is sheathed outside the high-voltage cable 7 to collect the high-frequency signal of the high-voltage cable 7;

[0036] Partial discharge current detection steps: Calculate the cable partial discharge signal based on the collected high-frequency signals of the high-voltage cable 7 core wire, the grounding cable 6, and the high-voltage cable 7. The calculation expression of the cable partial discharge signal is:

[0037]

[0038] Where I is the cable partial discharge signal value, i1 is the high-frequency signal value of the core wire of the high-voltage cable 7, i2 is the high-frequency signal of the grounding cable 6, and i3 is the high-frequency signal value of the high-voltage cable 7.

[0039] like Figure 1 and Figure 2 As shown, this embodiment further provides a cable partial discharge detection device, which is installed on a high-voltage cable 7. The cable partial discharge detection device includes a first high-frequency current transformer 1, a second high-frequency current transformer 2, a third high-frequency current transformer 3, and a processor 4. The first high-frequency current transformer 1 is sleeved on the outside of the cable core 5, the second high-frequency current transformer 2 is sleeved on the outside of the grounding cable 6, and the third high-frequency current transformer 3 is sleeved on the outside of the high-voltage cable 7.

[0040] The processor 4 is respectively connected to the first high-frequency current transformer 1, the second high-frequency current transformer 2 and the third high-frequency current transformer 3. The processor 4 includes an adding circuit 401 and a subtracting circuit 402. The input end of the adding circuit 401 is respectively connected to the first high-frequency current transformer 1 and the second high-frequency current transformer 2, and the input end of the subtracting circuit 402 is respectively connected to the output end of the adding circuit 401 and the third high-frequency current transformer 3.

[0041] Working Principle: Traditional cable partial discharge detection only installs a high-frequency current transformer on the grounding cable. Affected by the cable's circulating current, the grounding cable not only has partial discharge signals, but also a lot of grounding loop current signals. To eliminate background interference, this solution specifically incorporates:

[0042] A built-in first high-frequency current transformer 1. The first high-frequency current transformer 1 is sleeved on the cable core 5 to collect the high-frequency current signal of the core wire of the high-voltage cable;

[0043] The second high-frequency current transformer 2 of the grounding cable is externally arranged on the grounding cable 6 to collect the high-frequency signal of the grounding cable 6 .

[0044] The external third high-frequency current transformer 3 is externally arranged on the high-voltage cable 7 to detect the high-frequency signal of the high-voltage cable 7 .

[0045] When no partial discharge occurs, the third high-frequency current transformer 3 collects the high-frequency signal of the entire cable as signal 3. The first high-frequency current transformer 1 collects the high-frequency signal of the core wire as signal 1, and the second high-frequency current transformer 2 collects the high-frequency current signal of the cable armor as signal 2. Therefore, signal 1 plus signal 2 equals signal 3. Signals 1 and 2 are added, and signal 3 is compared with the sum of the summing circuit and subtracted, resulting in a zero output.

[0046] When partial discharge occurs at a high-voltage cable joint, most of the partial discharge current flows through the cable core 5 to the grounding cable 6 of the cable armor. Only a small part of the partial discharge current is transmitted to both ends through the cable body.

[0047] Therefore, the first and second high-frequency current transformers 1 and 2 will detect partial discharge signals, and the signals are in the same direction. However, the third high-frequency current transformer 3 can only detect partial discharge signals generated by a small number of cable joints. Corresponding to the arithmetic circuit designed above, signals 1 and 2 are added, and signal 3 is compared with the sum of the addition circuit and subtracted, resulting in a doubled partial discharge signal output.

[0048] This method can effectively detect the partial discharge signal of high-voltage cable joints and eliminate the interference caused by cable circulation.

[0049] In this embodiment, the current frequency range to which the first high-frequency current transformer 1 , the second high-frequency current transformer 2 , and the third high-frequency current transformer 3 respond is 1 MHz to 200 MHz.

[0050] The magnetic core materials of the first high-frequency current transformer 1 , the second high-frequency current transformer 2 and the third high-frequency current transformer 3 are all nickel-zinc ferrite.

[0051] The response operating frequency of the processor 4 is within the range of 80-120 MHz, preferably 100 MHz.

[0052] Both the adding circuit 401 and the subtracting circuit 402 include operational amplifiers.

[0053] As a preferred embodiment, in order to transmit the acquired partial discharge signal, the processor 4 is further connected to an analog-to-digital conversion circuit 404 and a communication circuit 405 , and the analog-to-digital conversion circuit 404 is respectively connected to the subtraction circuit 402 and the communication circuit 405 .

[0054] Preferably, the cable partial discharge detection device further comprises a server, which is communicatively connected to the communication circuit 405, and performs unified data storage and processing through the server.

[0055] As a preferred embodiment, the processor 4 further includes a division circuit 403 , which is connected to the output end of the subtraction circuit 402 . The divisor parameter of the division circuit 403 is set to 2 to directly output the magnitude of the partial discharge signal.

[0056] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A cable partial discharge detection method, characterized in that: The cable partial discharge detection method is implemented based on a cable partial discharge detection device, the cable partial discharge detection device being installed on a high-voltage cable (7), the cable partial discharge detection device comprising a first high-frequency current transformer (1), a second high-frequency current transformer (2), a third high-frequency current transformer (3) and a processor (4), the first high-frequency current transformer (1) being sheathed on the outside of a cable core (5), the second high-frequency current transformer (2) being sheathed on the outside of a grounding cable (6), and the third high-frequency current transformer (3) being sheathed on the outside of the high-voltage cable (7); The processor (4) is respectively connected to the first high-frequency current transformer (1), the second high-frequency current transformer (2), and the third high-frequency current transformer (3); the processor (4) comprises an adding circuit (401) and a subtracting circuit (402); the input end of the adding circuit (401) is respectively connected to the first high-frequency current transformer (1) and the second high-frequency current transformer (2); the input end of the subtracting circuit (402) is respectively connected to the output end of the adding circuit (401) and the third high-frequency current transformer (3); The method comprises the following steps: Data collection steps: a first high-frequency current transformer (1) is sheathed outside the cable inner core (5) to collect the high-frequency signal of the core wire of the high-voltage cable (7); a second high-frequency current transformer (2) is sheathed outside the grounding cable (6) to collect the high-frequency signal of the grounding cable (6); a third high-frequency current transformer (3) is sheathed outside the high-voltage cable (7) to collect the high-frequency signal of the high-voltage cable (7); Partial discharge current detection step: Calculate the cable partial discharge signal based on the collected high-frequency signals of the high-voltage cable (7) core wire, the grounding cable (6) and the high-voltage cable (7). The calculation expression of the cable partial discharge signal is: I=(i1+i2-i3) / 2 Wherein, I is the cable partial discharge signal value, i1 is the high-frequency signal value of the core wire of the high-voltage cable (7), i2 is the high-frequency signal of the grounding cable (6), and i3 is the high-frequency signal value of the high-voltage cable (7).

2. A cable partial discharge detection method according to claim 1, characterized in that: The current frequency range to which the first high-frequency current transformer (1), the second high-frequency current transformer (2) and the third high-frequency current transformer (3) respond is 1M-200Mhz.

3. A cable partial discharge detection method according to claim 1, characterized in that: The magnetic core materials of the first high-frequency current transformer (1), the second high-frequency current transformer (2) and the third high-frequency current transformer (3) are all nickel-zinc ferrite.

4. A cable partial discharge detection method according to claim 1, characterized in that: The response operating frequency of the processor (4) is within the range of 80-120Mhz.

5. A cable partial discharge detection method according to claim 1, characterized in that: The response operating frequency of the processor (4) is 100Mhz.

6. A cable partial discharge detection method according to claim 1, characterized in that: The processor (4) is further connected to an analog-to-digital conversion circuit (404) and a communication circuit (405), and the analog-to-digital conversion circuit (404) is respectively connected to the subtraction circuit (402) and the communication circuit (405).

7. A cable partial discharge detection method according to claim 6, characterized in that: The cable partial discharge detection device further comprises a server, which is communicatively connected to the communication circuit (405).

8. A cable partial discharge detection method according to claim 1, characterized in that: The adding circuit (401) and the subtracting circuit (402) both include operational amplifiers.

9. A cable partial discharge detection method according to claim 1, characterized in that: The processor (4) further comprises a dividing circuit (403), wherein the dividing circuit (403) is connected to the output end of the subtracting circuit (402).

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