Power cable fault detection early warning method and system based on high-frequency signal identification

Abstract

The invention relates to a power cable fault detection early warning method and system based on high-frequency signal identification. The method comprises the following steps: acquiring a high-frequency signal generated when a power cable has a fault; judging the discharge type and the discharge position of the power cable based on the high-frequency signal, wherein the discharge type comprises corona partial discharge, surface partial discharge and air gap partial discharge; and obtaining an alarm mode corresponding to the discharge type based on the discharge type, and giving an alarm according to the discharge type and the discharge position according to the alarm mode. Through the obtained partial discharge signal data, the defects of the power cable can be found as early as possible, the defect types and the defect positions can be obtained in time, maintainers are helped to rapidly remove fault hidden dangers, and important support can be provided for state maintenance of equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of power cable fault detection and early warning, and in particular to a power cable fault detection and early warning method and system based on high frequency signal recognition. Background Art

[0002] When a cable line fails or is disturbed, high-frequency signals may appear on the line in addition to the power frequency signal. There are many types of high-frequency signals that may appear on the cable line, and the reasons for the generation of the signals are different.

[0003] For example: the length of transmission cables in urban power grids is getting longer and longer, and there are more and more short-circuit faults in cable lines, and most of the faults are single-phase short-circuit faults. When a short-circuit fault occurs in a cable line, a high-frequency fault signal can be detected on the line. When the insulation of the cable line ages or deteriorates, it may cause partial discharge in the cable insulation. At this time, a partial discharge signal will appear on the line. Cable lines are generally laid underground and are not directly affected by lightning signals. However, when the cable line is connected to the overhead line, the lightning signal may be transmitted to the cable line through the overhead line and affect the cable insulation. At this time, a high-frequency lightning signal can be detected on the cable line. The circuit breaker of the closed line will also generate a high-frequency transient signal on the line.

[0004] Different high-frequency signals cause different disasters and have different corresponding solutions. Therefore, there is an urgent need to provide a cable line high-frequency signal recognition method to identify high-frequency signals and realize early warning of power cable fault detection. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a power cable fault detection and early warning method and system based on high-frequency signal recognition.

[0006] To solve the above problems, the technical solution adopted by the present invention is: A power cable fault detection and early warning method based on high-frequency signal recognition, the method comprising: Obtain high-frequency signals generated when power cables fail; Determining the discharge type and discharge position of the power cable based on the high-frequency signal, wherein the discharge type includes: corona partial discharge, surface partial discharge and air gap partial discharge; An alarm method corresponding to the discharge type is acquired based on the discharge type, and an alarm is issued according to the alarm method for the discharge type and the discharge position.

[0007] As an implementation mode of the invention, the high-frequency signal is obtained by a collection module. After the collection module obtains the high-frequency signal through a signal collector, the signal is envelope-detected and frequency-reduced by an envelope detection circuit and then transmitted along a coaxial cable.

[0008] As an embodiment of the invention, the coaxial cable comprises: a plurality of coaxially arranged cables and connectors; Each of the cables is used to transmit the signal to be transmitted along a fixed channel, enhance its anti-interference ability, ensure that the signal has a certain accuracy, and achieve low-loss and high-quality transmission; The connector is used to connect two or more coaxial cables to extend the length of the coaxial cables.

[0009] As an embodiment of the invention, the method of determining the discharge type of the power cable based on the high-frequency signal includes: Determining the power cable position where the high-frequency signal is located according to the amplitude value of the high-frequency signal; When it is determined that the electric field strength corresponding to the high-frequency signal is much smaller than the breakdown electric field strength of the insulating medium, it is judged to be a corona partial discharge; When it is determined that the high-frequency signal corresponds to a signal with small and dense amplitude values, it is judged to be a surface partial discharge; When it is determined that the capacitance of the other undamaged portions of the insulating medium inside the insulating medium corresponding to the high-frequency signal is much smaller than the capacitance formed when an air gap is formed inside due to structural damage, it is determined to be air gap partial discharge.

[0010] As an embodiment of the invention, the method for determining the discharge position of the power cable based on the high-frequency signal includes: a threshold method, an energy accumulation method and a correlation analysis method.

[0011] In a second aspect, a power cable fault detection and early warning system based on high-frequency signal recognition is provided, the system comprising: A high-frequency signal acquisition module, which is used to acquire the high-frequency signal generated when a power cable fails; A judgment module, which is used to judge the discharge type and discharge position of the power cable based on the high-frequency signal, wherein the discharge type includes: corona partial discharge, surface partial discharge and air gap partial discharge; An alarm module is used to obtain an alarm method corresponding to the discharge type based on the discharge type, and alarm the discharge type and the discharge position according to the alarm method.

[0012] As an embodiment of the invention, it also includes: The collection module is used to obtain the high-frequency signal through the signal collector, and then transmit it along the coaxial cable after performing envelope detection and frequency reduction processing on the signal through the envelope detection circuit.

[0013] As an embodiment of the invention, the coaxial cable comprises: a plurality of coaxially arranged cables and connectors; Each of the cables is used to transmit the signal to be transmitted along a fixed channel, enhance its anti-interference ability, ensure that the signal has a certain accuracy, and achieve low-loss and high-quality transmission; The connector is used to connect two or more coaxial cables to extend the length of the coaxial cables.

[0014] As an implementation mode of the invention, the judgment module includes: a first judgment unit, which is used to: Determining the power cable position where the high-frequency signal is located according to the amplitude value of the high-frequency signal; When it is determined that the electric field strength corresponding to the high-frequency signal is much smaller than the breakdown electric field strength of the insulating medium, it is judged to be a corona partial discharge; When it is determined that the high-frequency signal corresponds to a signal with small and dense amplitude values, it is judged to be a surface partial discharge; When it is determined that the capacitance of the other undamaged portions of the insulating medium inside the insulating medium corresponding to the high-frequency signal is much smaller than the capacitance formed when an air gap is formed inside due to structural damage, it is determined to be air gap partial discharge.

[0015] As an implementation mode of the invention, the judgment module includes: a second judgment unit, which is used to judge the discharge position of the power cable by using a threshold method, an energy accumulation method and a correlation analysis method.

[0016] The beneficial effects of adopting the above technical solution are: The power cable fault detection and early warning method and system based on high-frequency signal recognition provided by the present invention obtains the high-frequency signal generated when the power cable fails; based on the high-frequency signal, the discharge type and discharge position of the power cable are judged, and the discharge type includes: corona partial discharge, surface partial discharge and air gap partial discharge; based on the discharge type, an alarm method corresponding to the discharge type is obtained, and the discharge type and the discharge position are alarmed according to the alarm method. Through the acquired partial discharge signal data, the defects of the power cable can be discovered early, and the defect type and defect location can be obtained in time, which helps maintenance personnel to quickly eliminate the hidden dangers of the fault, and can also provide important support for the status maintenance of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of a corona discharge model provided by an embodiment of the present invention.

[0018] Figure 2 It is a schematic diagram of the principle of surface partial discharge provided by an embodiment of the present invention.

[0019] Figure 3 It is a schematic diagram of the principle of an insulating medium with an air gap provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is clearly and completely described below in conjunction with specific embodiments.

[0021] Example 1 An embodiment of the present invention provides a power cable fault detection and early warning method based on high-frequency signal recognition, the method comprising: Step S101, obtaining a high-frequency signal generated when a power cable fails; The high-frequency signal is obtained by a collection module. After the collection module obtains the high-frequency signal through a signal collector, the signal is envelope-detected and frequency-reduced by an envelope detection circuit and then transmitted along a coaxial cable.

[0022] Wherein, the coaxial cable comprises: a plurality of coaxially arranged cables and connectors; Each of the cables is used to transmit the signal to be transmitted along a fixed channel, enhance its anti-interference ability, ensure that the signal has a certain accuracy, and achieve low-loss and high-quality transmission; The connector is used to connect two or more coaxial cables to extend the length of the coaxial cables.

[0023] At present, the most commonly used are baseband coaxial cables and broadband coaxial cables. These two types of coaxial cables differ in the structure and material of the shielding layer and the characteristic impedance. In terms of characteristic impedance, the baseband coaxial cable is 50Ω, while the broadband coaxial cable is 75Ω. Broadband coaxial cable is generally used for cable TV signal transmission. Its advantage is that multiple TV signals can be transmitted in one broadband coaxial cable.

[0024] Step S102: judging the discharge type and discharge position of the power cable based on the high-frequency signal, wherein the discharge type includes: corona partial discharge, surface partial discharge and air gap partial discharge; The following describes the above three types respectively.

[0025] (1) Corona partial discharge Corona discharge (i.e. tip discharge) is caused by electric field distortion. When the electric field is unevenly distributed, ionization will occur, and a discharge channel will be formed. Discharge will occur in the channel, eventually leading to the breakdown of the insulating medium. In power cables, corona discharge will occur when the electric field is distorted. In the electrode structure, the radius of curvature of the structure is proportional to the discharge voltage. Among them, corona discharge has several obvious characteristics: the discharge electrode is generally a conductor; the discharge medium is generally a gas; there is a very small tip or needle tip during discharge; the schematic diagram of the corona discharge model is as follows: Figure 1 shown.

[0026] (2) Surface partial discharge The process of surface partial discharge is similar to that of internal partial discharge. When the electric field is distorted, a rectangular coordinate system is established based on the surface of the insulating medium, and the electric field is decomposed into two components in the vertical and horizontal directions. When the horizontal electric field strength is distorted to a certain extent, the electric field strength reaches the discharge strength and the discharge is called surface discharge. Figure 2 shown.

[0027] Figure 2 Middle C c Represents the capacitance formed between the high voltage conductor and the medium, C b It represents the capacitance connected in series with the part where partial discharge occurs, C a It represents the capacitance of other dielectrics that do not have partial discharge. Generally speaking, surface partial discharge is easy to occur between conductors and dielectrics. During discharge, the charge is transferred from the conductor to the dielectric, where it is stored and accumulated. When the voltage drops, it is not easy to discharge. Therefore, when the voltage on the conductor is in the positive half cycle, the generated partial discharge signal has a large amplitude, but the discharge frequency is low.

[0028] When the voltage on the conductor is in the negative half cycle, the electrons are more active and discharge is more likely to occur. Therefore, although the amplitude is smaller in the negative half cycle, the discharge is more frequent. At this time, the local discharge is characterized by being small and dense.

[0029] (3) Air gap partial discharge The insulating medium will be damaged to a certain extent during transportation or long-term use, resulting in internal defects (for example, internal cracks and bubbles). At this time, when the insulating medium is in an electric field, it will cause local field strength distortion in these places. When the electric field strength reaches a certain intensity, a discharge phenomenon will occur, which is called air gap discharge. Air gap discharge is a type of internal discharge. Air gap discharge does not immediately form a penetrating channel, but if discharge continues to occur, it will cause damage to the structure and performance of the insulating medium, causing more serious insulation degradation and eventually breaking down the entire insulating medium. The structural diagram of the insulating medium with an air gap is shown below. Figure 3 shown.

[0030] Among them, since the distance between insulation is generally very small, when it is determined that the capacitance of the other undamaged parts of the insulating medium inside the insulating medium corresponding to the high-frequency signal is much smaller than the capacitance formed when an air gap is formed inside due to structural damage, it is judged as air gap partial discharge.

[0031] Step S103: acquiring an alarm mode corresponding to the discharge type based on the discharge type, and alarming the discharge type and the discharge position according to the alarm mode.

[0032] The power cable fault detection and early warning method based on high-frequency signal recognition provided by the present invention obtains the high-frequency signal generated when the power cable fails; based on the high-frequency signal, the discharge type and discharge position of the power cable are judged, and the discharge type includes: corona partial discharge, surface partial discharge and air gap partial discharge; based on the discharge type, an alarm method corresponding to the discharge type is obtained, and the discharge type and the discharge position are alarmed according to the alarm method. Through the acquired partial discharge signal data, the defects of the power cable can be discovered early, and the defect type and defect position can be obtained in time, which helps maintenance personnel to quickly eliminate the hidden dangers of the fault, and can also provide important support for the status maintenance of the equipment.

[0033] Example 2 A power cable fault detection and early warning system based on high-frequency signal recognition, the system comprising: A high-frequency signal acquisition module, which is used to acquire the high-frequency signal generated when a power cable fails; A judgment module, which is used to judge the discharge type and discharge position of the power cable based on the high-frequency signal, wherein the discharge type includes: corona partial discharge, surface partial discharge and air gap partial discharge; An alarm module is used to obtain an alarm method corresponding to the discharge type based on the discharge type, and alarm the discharge type and the discharge position according to the alarm method.

[0034] Furthermore, it also includes: The collection module is used to obtain the high-frequency signal through the signal collector, and then transmit it along the coaxial cable after performing envelope detection and frequency reduction processing on the signal through the envelope detection circuit.

[0035] Further, the coaxial cable comprises: a plurality of coaxially arranged cables and connectors; Each of the cables is used to transmit the signal to be transmitted along a fixed channel, enhance its anti-interference ability, ensure that the signal has a certain accuracy, and achieve low-loss and high-quality transmission; The connector is used to connect two or more coaxial cables to extend the length of the coaxial cables.

[0036] Furthermore, the judgment module includes: a first judgment unit, which is used to: Determining the power cable position where the high-frequency signal is located according to the amplitude value of the high-frequency signal; When it is determined that the electric field strength corresponding to the high-frequency signal is much smaller than the breakdown electric field strength of the insulating medium, it is judged to be a corona partial discharge; When it is determined that the high-frequency signal corresponds to a signal with small and dense amplitude values, it is judged to be a surface partial discharge; When it is determined that the capacitance of the other undamaged portions of the insulating medium inside the insulating medium corresponding to the high-frequency signal is much smaller than the capacitance formed when an air gap is formed inside due to structural damage, it is determined to be air gap partial discharge.

[0037] Furthermore, the judgment module includes: a second judgment unit, which is used to judge the discharge position of the power cable by adopting a threshold method, an energy accumulation method and a correlation analysis method.

[0038] The power cable fault detection and early warning system based on high-frequency signal recognition provided by the present invention obtains the high-frequency signal generated when the power cable fails; based on the high-frequency signal, the discharge type and discharge position of the power cable are judged, and the discharge type includes: corona partial discharge, surface partial discharge and air gap partial discharge; based on the discharge type, an alarm method corresponding to the discharge type is obtained, and the discharge type and the discharge position are alarmed according to the alarm method. Through the acquired partial discharge signal data, the defects of the power cable can be discovered early, and the defect type and defect position can be obtained in time, which helps maintenance personnel to quickly eliminate the hidden dangers of the fault, and can also provide important support for the status maintenance of the equipment.

Claims

1. A power cable fault detection and early warning method based on high-frequency signal recognition, characterized in that: The method comprises: Obtain high-frequency signals generated when power cables fail; Determining the discharge type and discharge position of the power cable based on the high-frequency signal, wherein the discharge type includes: corona partial discharge, surface partial discharge and air gap partial discharge; An alarm method corresponding to the discharge type is acquired based on the discharge type, and an alarm is issued according to the alarm method for the discharge type and the discharge position.

2. The method for detecting and warning power cable faults based on high-frequency signal recognition according to claim 1 is characterized in that: The high-frequency signal is obtained by a collection module. After the collection module obtains the high-frequency signal through a signal collector, the signal is envelope-detected and frequency-reduced by an envelope detection circuit and then transmitted along a coaxial cable.

3. The method for detecting and warning power cable faults based on high-frequency signal recognition according to claim 2 is characterized in that: The coaxial cable comprises: a plurality of coaxially arranged cables and a connector; Each of the cables is used to transmit the signal to be transmitted along a fixed channel, enhance its anti-interference ability, ensure that the signal has a certain accuracy, and achieve low-loss and high-quality transmission; The connector is used to connect two or more coaxial cables to extend the length of the coaxial cables.

4. The method for detecting and warning power cable faults based on high-frequency signal recognition according to claim 1 is characterized in that: The determining the discharge type of the power cable based on the high-frequency signal includes: Determining the power cable position where the high-frequency signal is located according to the amplitude value of the high-frequency signal; When it is determined that the electric field strength corresponding to the high-frequency signal is much smaller than the breakdown electric field strength of the insulating medium, it is judged to be a corona partial discharge; When it is determined that the high-frequency signal corresponds to a signal with small and dense amplitude values, it is judged to be a surface partial discharge; When it is determined that the capacitance of the other undamaged portion of the insulating medium inside the insulating medium corresponding to the high-frequency signal is much smaller than the capacitance formed when an air gap is formed inside due to structural damage, it is determined to be air gap partial discharge.

5. The method for detecting and warning power cable faults based on high-frequency signal recognition according to claim 1 is characterized in that: The method for determining the discharge position of the power cable based on the high-frequency signal includes: a threshold method, an energy accumulation method and a correlation analysis method.

6. A power cable fault detection and early warning system based on high-frequency signal recognition, characterized in that: The system comprises: A high-frequency signal acquisition module, which is used to acquire the high-frequency signal generated when a power cable fails; A judgment module, which is used to judge the discharge type and discharge position of the power cable based on the high-frequency signal, wherein the discharge type includes: corona partial discharge, surface partial discharge and air gap partial discharge; An alarm module is used to obtain an alarm method corresponding to the discharge type based on the discharge type, and alarm the discharge type and the discharge position according to the alarm method.

7. The power cable fault detection and early warning system based on high-frequency signal recognition according to claim 1 is characterized in that: It also includes: The collection module is used to obtain the high-frequency signal through the signal collector, and then transmit it along the coaxial cable after performing envelope detection and frequency reduction processing on the signal through the envelope detection circuit.

8. The power cable fault detection and early warning system based on high-frequency signal recognition according to claim 7 is characterized in that: The coaxial cable comprises: a plurality of coaxially arranged cables and a connector; Each of the cables is used to transmit the signal to be transmitted along a fixed channel, enhance its anti-interference ability, ensure that the signal has a certain accuracy, and achieve low-loss and high-quality transmission; The connector is used to connect two or more coaxial cables to extend the length of the coaxial cables.

9. The power cable fault detection and early warning system based on high-frequency signal recognition according to claim 6 is characterized in that: The judgment module includes: a first judgment unit, which is used to: Determining the power cable position where the high-frequency signal is located according to the amplitude value of the high-frequency signal; When it is determined that the electric field strength corresponding to the high-frequency signal is much smaller than the breakdown electric field strength of the insulating medium, it is judged to be a corona partial discharge; When it is determined that the high-frequency signal corresponds to a signal with small and dense amplitude values, it is judged to be a surface partial discharge; When it is determined that the capacitance of the other undamaged portion of the insulating medium inside the insulating medium corresponding to the high-frequency signal is much smaller than the capacitance formed when an air gap is formed inside due to structural damage, it is determined to be air gap partial discharge.

10. The power cable fault detection and early warning system based on high-frequency signal recognition according to claim 6, characterized in that: The judgment module includes: a second judgment unit, which is used to judge the discharge position of the power cable by using a threshold method, an energy accumulation method and a correlation analysis method.

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