Current transformer and multi-core alternating current cable fault monitoring device and method

Abstract

The invention relates to the technical field of cable operation monitoring, and provides a current transformer and a multi-core alternating current cable fault monitoring device and method.The current transformer comprises a first coil assembly, a second coil assembly and a third coil assembly, one end of the first coil forms a first electrode, the other end of the first coil forms a second electrode, one end of the second coil forms a third electrode, the other end of the second coil forms a fourth electrode, the first electrode and the third electrode are electrically connected with a first load respectively, and the second electrode is connected with the fourth electrode; if the first coil and the second coil are arranged in the same induced magnetic field, the first electrode and the third electrode have the same polarity. According to the technical scheme, signal interference of the conductive shielding layer can be inhibited, and fault monitoring of the multi-core AC cable is improved.

Description

Technical Field

[0001] The present application relates to the technical field of cable operation monitoring, and in particular to a current transformer, a multi-core AC cable fault monitoring device and a method. Background Art

[0002] The sampling device and power extraction device of the three-core cable are two common devices in the power system. Among them, the sampling device is mainly used to detect and collect current signals in the cable. Analysis of the current signal can be used for fault detection and positioning. The power extraction device is mainly used to extract electricity from the cable to power the monitoring equipment.

[0003] In the sampling device and the power-drawing device, the current transformer is used for sampling and power-drawing of fault monitoring of a multi-core AC cable. The multi-core AC cable includes a conductive shielding layer and a first phase core and a second phase core located in the conductive shielding layer. In the related art, there are some sampling and power-drawing devices based on current transformers that integrate sampling devices and power-drawing devices. However, in actual use, there are many problems with the existing current transformer sampling, power-drawing and subsequent fault judgment: on the one hand, since the distribution cable usually uses a three-core cable, and since the cable is a three-core-in-one cable, the magnetic fields generated by the three-phase conductors will cancel each other out, thereby affecting the current transformer from obtaining power and sampling, which is not conducive to fault analysis and judgment; on the other hand, due to the interference of the conductive shielding layer, when there is a short-circuit current in the conductive shielding layer, its associated magnetic field will further affect the fault signal sampling of the current transformer, thereby making it impossible to effectively and more accurately monitor its fault online. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a current transformer, a multi-core AC cable fault monitoring device and method, in order to suppress signal interference of the conductive shielding layer and improve multi-core AC cable fault monitoring.

[0005] In a first aspect, an embodiment of the present application provides a current transformer for fault monitoring of a multi-core AC cable, wherein the multi-core AC cable comprises a conductive shielding layer and a first phase core and a second phase core located in the conductive shielding layer, and the current transformer comprises: a first coil group, wherein the first coil group comprises a first coil for monitoring the first phase core and a second coil for monitoring the second phase core, wherein one end of the first coil forms a first electrode and the other end forms a second electrode, one end of the second coil forms a third electrode and the other end forms a fourth electrode, the first electrode and the third electrode are respectively used to be electrically connected to a first load, the second electrode is connected to the fourth electrode, and the first coil and the second coil satisfy the condition: if the first coil and the second coil are placed in the same induced magnetic field, the first electrode and the third electrode exhibit the same polarity, and the second electrode and the fourth electrode exhibit the same polarity.

[0006] In the above scheme, if a cable fails, the current in the faulty core increases abnormally, and an induced current is induced in the first coil group, thereby monitoring whether the cable has a fault. When a changing current is generated in the conductive shielding layer, the two coils will synchronously generate an induced current and an induced electromotive force in the same direction. Since the two poles of the same polarity in the first coil and the second coil are connected together, the influence of the induced magnetic field generated by the current in the conductive shielding layer on the first coil and the second coil can be weakened or even eliminated, thereby improving the accuracy of current transformer sampling. In addition, after the interference of the conductive shielding layer is weakened, the current transformer can be used for sampling and monitoring faults as well as for drawing power.

[0007] As an optional manner, the multi-core AC cable is a three-phase cable that also includes a third phase core located in the conductive shielding layer, and the current transformer also includes: a second coil group, the second coil group includes a third coil for monitoring one of the first phase core and the second phase core and a fourth coil for monitoring the third phase core, one end of the third coil forms a fifth electrode, and the other end forms a sixth electrode, one end of the fourth coil forms a seventh electrode, and the other end forms an eighth electrode; the fifth electrode and the seventh electrode are connected, the sixth electrode and the eighth electrode are respectively used to be electrically connected to a second load, and the third coil and the fourth coil meet the condition: if the third coil and the fourth coil are placed in the same induced magnetic field, the fifth electrode and the seventh electrode exhibit the same polarity, and the sixth electrode and the eighth electrode exhibit the same polarity.

[0008] In the above scheme, the first coil group correspondingly arranged on the first phase core and the second phase core can only monitor the faults of the first phase core and the second phase core. For a three-core cable, adding a second coil group can also monitor the faults of the third phase core, thereby realizing all-round online fault monitoring of multi-core AC cables. In addition, it can also increase the energy obtained from electricity.

[0009] As an optional manner, the first coil and the second coil have the same number of coil turns; and / or, the first coil and the second coil have the same coil area, and the coil area is the area of ​​a plane figure enclosed by a single turn of the coil in the coil; and / or, the first coil and the second coil have the same internal resistance; and / or, the third coil and the fourth coil have the same number of coil turns; and / or, the third coil and the fourth coil have the same coil area, and the coil area is the area of ​​a plane figure enclosed by a single turn of the coil in the coil; and / or, the third coil and the fourth coil have the same internal resistance.

[0010] In the above scheme, when the configuration of the first coil and the second coil is the same, the conductive shielding layer will generate equal and same-direction induced currents and induced electromotive forces in the first coil and the second coil as much as possible, and then offset the influence of the magnetic field excited by the current in the conductive shielding layer by reverse connection. At this time, the weakening effect of the interference generated by the conductive shielding layer is most obvious, thereby improving the accuracy of current transformer sampling. The third coil and the fourth coil are the same.

[0011] In a second aspect, an embodiment of the present application provides a multi-core AC cable fault monitoring device, comprising: a current transformer as described in the first aspect; a first load, electrically connected to the first electrode and the third electrode, the first load being at least used to perform fault monitoring on the multi-core AC cable through the collected first induced current.

[0012] In the above solution, the induced current sampled by the first coil group can be sent to the first load connected in series with the first coil group for analysis to further determine the fault type, thereby achieving more detailed fault monitoring.

[0013] As an optional manner, the method further includes: a second load electrically connected to the sixth electrode and the eighth electrode, wherein the second load is at least used to perform fault monitoring on the multi-core AC cable through the collected second induced current.

[0014] In the above scheme, the first coil group correspondingly arranged on the first phase core and the second phase core can only monitor the faults of the first phase core and the second phase core. For a three-core cable, adding a second coil group can also monitor the faults of the third phase core, thereby realizing all-round online fault monitoring of multi-core AC cables. In addition, it can also increase the energy obtained from electricity.

[0015] As an optional method, the first load includes a first duplex switching circuit, a first polarity detection circuit, a first power supply module and a first processor; the first duplex switching circuit is electrically connected to the second electrode and the fourth electrode, and is used to receive the first induced current and separate the first induced current into two electrical signals, one is the industrial frequency current, and the other is the fault high-frequency signal; the first polarity detection circuit is connected to the first duplex switching circuit, and is used to receive the fault high-frequency signal and transmit the fault high-frequency signal to the processor; the first power supply module is connected to the first duplex switching circuit, and is used to receive the industrial frequency current and convert the industrial frequency current into electrical energy that can be used by the first processor; the first processor is respectively connected to the first polarity detection circuit and the first power supply module, and is used to receive the fault high-frequency signal to perform multi-core AC cable fault monitoring.

[0016] In the above scheme, the first duplex switching circuit receives the first induced current and separates the first induced current into two electrical signals, one is the industrial frequency current, and the other is the fault high-frequency signal; the first polarity detection circuit receives the fault high-frequency signal and transmits the processed fault high-frequency signal to the processor to facilitate the analysis of the fault type. The first power supply module, as a power supply device, can provide electrical energy for the circuit part involved in sampling and fault analysis.

[0017] As an optional manner, the first duplex switching circuit is a duplex filter circuit or an antenna switch; and / or, the first polarity detection circuit includes a first positive polarity detection circuit and a first negative polarity detection circuit, wherein the first positive and negative polarity detection circuits both include a capacitance adjustable RC integration circuit and a Schmitt trigger circuit; and / or, the first power supply module also includes an energy storage battery, which is used to store the electric energy converted by the first power supply module; and / or, the second load has the same structure as the first load.

[0018] In the above solution, the second load has the same structure as the first load, and the second load and the first load also play the same role, which is to process the induced current in the corresponding coil group and analyze the fault type.

[0019] In a third aspect, an embodiment of the present application provides a multi-core AC cable fault monitoring method, the method comprising: obtaining a first induced current, the first induced current coming from at least one multi-core AC cable fault monitoring device according to the second aspect; wherein, when there are multiple multi-core AC cable fault monitoring devices, the multiple multi-core AC cable fault monitoring devices are arranged side by side and spaced apart along the multi-core AC cable, and the multi-core AC cable fault monitoring device is configured such that, when in use, a first coil and a second coil are spaced apart in a circumferential direction around an axis of the multi-core AC cable, a distance from the first coil to the axis is equal to a distance from the second coil to the axis, the first coil is configured to be close to one side of a first phase core, and the second coil is configured to be close to one side of a second phase core; and fault monitoring of the multi-core AC cable is performed based on the fault high-frequency signal separated by the first induced current.

[0020] In the above scheme, when one current transformer is arranged along the multi-core AC cable, it can play a role in monitoring faults. When multiple current transformers are arranged along the multi-core AC cable, they can play a role in locating the fault section and determining the fault type.

[0021] As an optional manner, the fault high-frequency signal separated from the first induced current is used to perform fault monitoring on the multi-core AC cable, including: if there are two adjacent current transformers, the fault high-frequency signal cannot be obtained based on the first induced current of one of the current transformers, and the fault high-frequency signal is obtained based on the first induced current of the other current transformer, then it is determined that the fault point is located between the two adjacent current transformers, and the fault type is a phase-to-phase short circuit; and / or, if there are two adjacent current transformers, the fault high-frequency signal is obtained based on the first induced current of one of the current transformers and the polarity is a first polarity, and the fault high-frequency signal is obtained based on the first induced current of the other current transformer and the polarity is a second polarity opposite to the first polarity, then it is determined that the fault point is located between the two adjacent current transformers, and the fault type is a phase-to-ground short circuit.

[0022] In the above scheme, the cable fault is judged according to the first induced current in the current transformer. The cable fault includes phase-to-phase short circuit and phase-to-ground short circuit. When the phase-to-phase short circuit and the phase-to-ground short circuit occur, the polarity and magnitude of the induced current induced in the current transformer have their own characteristics, and the fault type can be determined according to the characteristics. In addition, the induced currents induced by the current transformers between the distribution power supply and the fault point and between the fault point and the electrical appliance are also different. Therefore, the fault interval can be located by arranging multiple current transformers along the multi-core AC cable.

[0023] In a fourth aspect, an embodiment of the present application further provides a multi-core AC cable fault monitoring method, the method comprising: obtaining a first induced current and a second induced current, the first induced current and the second induced current coming from the multi-core AC cable fault monitoring device described in the second aspect, wherein the multi-core AC cable fault monitoring device is configured such that, when in use, a first coil and a second coil are spaced apart in a circumferential direction around the axis of the multi-core AC cable, a distance from the first coil to the axis is equal to a distance from the second coil to the axis, the first coil is configured to be close to one side of a first phase core, and the second coil is configured to be close to one side of a second phase core; a third coil and a fourth coil are spaced apart in a circumferential direction around the axis of the multi-core AC cable, a distance from the third coil to the axis is equal to a distance from the fourth coil to the axis, the third coil is configured to be close to one side of the first phase core or the second phase core, and the fourth coil is configured to be close to one side of the third phase core; according to the first induced current and the second induced current The induction parameters of the separated fault high-frequency signal are used to perform fault monitoring on the multi-core AC cable, wherein the fault monitoring includes: if the fault high-frequency signal cannot be obtained by filtering based on the first induced current, and the fault high-frequency signal is obtained based on the second induced current, it is determined that the third phase core has a phase-to-ground short circuit, or the first phase core and the second phase core are short-circuited between phases, or the first phase core and the second phase core are short-circuited between phases; and / or, the fault high-frequency signal is obtained based on the first induced current, and the fault high-frequency signal cannot be obtained based on the second induced current. If the third coil is configured to be close to one side of the first phase core, it is determined that the second phase core has a phase-to-ground short circuit, or the first phase core and the third phase core are short-circuited between phases, or the first phase core and the third phase core are short-circuited between phases; if the third coil is configured to be close to one side of the second phase core, it is determined that the first phase core has a phase-to-ground short circuit, or the second phase core and the third phase core are short-circuited between phases, or the second phase core and the third phase core are short-circuited between phases.

[0024] In the above scheme, the cable fault is determined based on the first induced current and the second induced current in a current transformer. The cable fault includes phase-to-phase short circuit and phase-to-ground short circuit. When the phase-to-phase short circuit and the phase-to-ground short circuit occur, the polarity and magnitude of the induced current induced in the current transformer have their own characteristics, and the fault type can be determined based on the characteristics.

[0025] In a fifth aspect, an embodiment of the present application further provides a multi-core AC cable fault monitoring method, the method comprising: obtaining a first induced current and a second induced current, wherein the first induced current and the second induced current are respectively from a plurality of current transformers described in the third embodiment of the first aspect, and each of the current transformers is arranged side by side and spaced apart along the multi-core AC cable; if there are two adjacent current transformers that respectively meet the following conditions, it is determined that the fault point is located between the two adjacent current transformers, wherein the first induced currents of the two current transformers are different and / or the second induced currents are different, and the difference includes at least one of the magnitude and polarity. One, the following situations include: based on the first induced current and the second induced current of the two current transformers, the first fault high-frequency signal is obtained, and the polarity of the first fault high-frequency signal of one current transformer is opposite, and the polarity of the first fault high-frequency signal of the other current transformer is also opposite, then it is determined that the fault type is that the common phase line core of the first coil group and the second coil group has a phase-to-ground short circuit, or the non-common phase line cores in the phase line cores corresponding to the first coil group and the second coil group have a phase-to-ground short circuit respectively; and / or, based on the first induced current and the second induced current of the two current transformers, the first fault high-frequency signal is obtained, and there is only one current transformer. If the polarity of the first fault high-frequency signal of the two current transformers is the same, it is determined that the fault type is a phase-to-phase short circuit between two non-common phase cores in the phase cores corresponding to the first coil group and the second coil group; and / or, if the fault high-frequency signal cannot be obtained based on the first induced currents of the two current transformers, and the first fault high-frequency signal is obtained based on the second induced currents of the two current transformers, then the fault type is determined to be a phase-to-ground short circuit in the third phase core, or a phase-to-ground short circuit in the first phase core and the second phase core; and / or, if the first fault high-frequency signal is obtained based on the first induced currents of the two current transformers, and the first fault high-frequency signal is obtained based on the second induced currents of the two current transformers. If no fault high-frequency signal can be obtained, the fault type is determined to be a phase-to-ground short circuit in the first phase core, or a phase-to-ground short circuit in both the second phase core and the third phase core; and / or, based on the first induced current of one of the current transformers, a second fault high-frequency signal is obtained, then the fault type is determined to be a phase-to-phase short circuit in the first phase core and the second phase core, wherein the second fault high-frequency signal is a fault high-frequency signal that is greater than the first fault high-frequency signal by a preset threshold value; and / or, based on the second induced current of one of the current transformers, the second fault high-frequency signal is obtained, then the fault type is determined to be a phase-to-phase short circuit in the two-phase cores where the second coil group is provided.

[0026] In the above scheme, the cable fault is judged according to the first induced current and the second induced current in multiple current transformers. The cable fault includes phase-to-phase short circuit and phase-to-ground short circuit. When the phase-to-phase short circuit and the phase-to-ground short circuit occur, the polarity and magnitude of the induced current induced in the current transformer have their own characteristics, and the fault type can be determined according to the characteristics. In addition, the induced currents induced by the current transformers located between the distribution power supply and the fault point and between the fault point and the electrical appliance are also different, so the fault interval can be located.

[0027] In a sixth aspect, an embodiment of the present application further provides a multi-core AC cable fault monitoring method, the method comprising:

[0028] Obtaining a first induced current and a second induced current, wherein the first induced current and the second induced current are respectively from a plurality of multi-core AC cable fault monitoring devices provided in the second aspect, and each of the multi-core AC cable fault monitoring devices is arranged side by side and spaced apart along the multi-core AC cable;

[0029] If there are two adjacent current transformers that respectively meet the following conditions, it is determined that the fault point is located between the two adjacent current transformers, wherein the first induced currents of the two current transformers are different and / or the second induced currents are different, and the difference includes at least one of magnitude and polarity, and the following conditions include:

[0030] When a first monitoring result is obtained based on one of the current transformers and a second monitoring result is obtained based on the other current transformer, it is determined that there is a phase-to-ground short circuit between the two current transformers; wherein the first monitoring result includes that a fault high-frequency signal cannot be obtained based on the first induced current and a first fault high-frequency signal of a first polarity is obtained based on the second induced current, or, a first fault high-frequency signal of a second polarity is obtained based on the first induced current and a fault high-frequency signal cannot be obtained based on the second induced current, or, a first fault high-frequency signal of a first polarity is obtained based on the first induced current and a first fault high-frequency signal of a second polarity is obtained based on the second induced current; the second monitoring result includes that a first fault high-frequency signal of a first polarity is obtained based on the first induced current and a fault high-frequency signal cannot be obtained based on the second induced current, or, a first fault high-frequency signal of a second polarity is obtained based on the first induced current and a first fault high-frequency signal of a first polarity is obtained based on the second induced current, or, a first fault high-frequency signal of a second polarity is obtained based on the first induced current and a first fault high-frequency signal of a first polarity is obtained based on the second induced current, or, a fault high-frequency signal cannot be obtained based on the first induced current and a first fault high-frequency signal of a second polarity is obtained based on the second induced current; and / or,

[0031] When a third monitoring result is obtained based on one of the current transformers and a second monitoring result is obtained based on the other current transformer, it is determined that there is a phase-to-phase short circuit between the two current transformers; wherein the second monitoring result includes obtaining a first fault high-frequency signal of a first polarity based on the first induced current and failing to obtain a fault high-frequency signal based on the second induced current, or obtaining a first fault high-frequency signal of a second polarity based on the first induced current and obtaining a first fault high-frequency signal of a first polarity based on the second induced current, or failing to obtain a fault high-frequency signal based on the first induced current and obtaining a first fault high-frequency signal of a second polarity based on the second induced current; the third monitoring result includes obtaining a first fault high-frequency signal based on one of the first induced current and the second induced current and obtaining a second fault high-frequency signal based on the other of the first induced current and the second induced current, or obtaining first fault high-frequency signals of the same polarity based on the first induced current and the second induced current, respectively.

[0032] Other features and advantages of the embodiments of the present application will be described in the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the implementation methods of the present application, the drawings required for use in the implementation methods of the present application will be briefly introduced below. It should be understood that the following drawings only show certain implementation methods of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A schematic diagram of the assembly of a first current transformer provided in an embodiment of the present application;

[0035] Figure 2 A schematic diagram of the assembly of a second current transformer provided in an embodiment of the present application;

[0036] Figure 3 A three-dimensional schematic diagram of a current transformer and a cable during installation provided in an embodiment of the present application;

[0037] Figure 4 A schematic structural diagram of a first multi-core AC cable fault monitoring device provided in an embodiment of the present application;

[0038] Figure 5 A schematic diagram of electrical connections of a first multi-core AC cable fault monitoring device provided in an embodiment of the present application;

[0039] Figure 6 A schematic diagram of electrical connections of a second multi-core AC cable fault monitoring device provided in an embodiment of the present application;

[0040] Figure 7 A schematic diagram of electrical connections of a third multi-core AC cable fault monitoring device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0041] The following detailed description of the implementation of the technical solution of the present application is provided in conjunction with the accompanying drawings. The following implementation is only used to more clearly illustrate the technical solution of the present application, and is therefore only used as an example, and cannot be used to limit the scope of protection of the present application.

[0042] It should be noted that all technical and scientific terms used in this document have the same meanings as those commonly understood by technicians in the technical field of this application; the terms used in this document are only for the purpose of describing specific implementation methods and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0043] In the description of the implementation methods of this application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the implementation methods of this application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0044] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0045] Reference Figure 1 and Figure 4 , Figure 1 The assembly diagram of the first current transformer provided in the embodiment of the present application. The current transformer is used for fault monitoring of a multi-core AC cable, the multi-core AC cable includes a conductive shielding layer and a first phase core and a second phase core located in the conductive shielding layer, the current transformer includes: a first coil group, used to monitor the fault of the first phase core and the second phase core, the first coil group includes a first coil and a second coil, one end of the first coil forms a first electrode 01, and the other end forms a second electrode 02, one end of the second coil forms a third electrode 03, and the other end forms a fourth electrode 04, the first electrode 01 and the third electrode 03 are respectively used to be electrically connected to the first load 20, the second electrode 02 is connected to the fourth electrode 04, and the first coil and the second coil meet the condition: if the first coil and the second coil are placed in the same induced magnetic field, the first electrode 01 and the third electrode 03 exhibit the same polarity, and the second electrode 02 and the fourth electrode 04 exhibit the same polarity.

[0046] The conductive shielding layer of a multi-core AC cable is an important structural component used to reduce electromagnetic interference, evenly distribute the electric field, provide grounding protection, and improve mechanical strength. The conductive shielding layer is usually made of materials such as metal foil, metal wire mesh, or conductive paint. The conductive shielding layer surrounds a hollow space in which each phase core is passed.

[0047] The first coil group is used to monitor the faults of the first phase core and the second phase core. Figure 1 In the example, the A phase core is the first phase core and the B phase core is the second phase core. The first coil is denoted as A1 and the second coil is denoted as B1. When the same magnetic flux passes through the first coil and the second coil at the same time, the first electrode 01 of the first coil and the third electrode 03 of the second coil show the same polarity, specifically, they show positive polarity (first polarity) at the same time, or they show negative polarity (second polarity) at the same time. It can be understood that in the same induced magnetic field, the induced electromotive force of the first electrode 01 and the third electrode 03 is also the same. After connecting the first electrode 01 and the third electrode 03, the interference of the induced magnetic field generated by the changing current in the conductive shielding layer on the two coils can be offset or partially offset. The first coil and the second coil are arranged at intervals along the circumference of the multi-core AC cable and are located on the same cross section of the multi-core AC cable.

[0048] As an implementation mode, the first coil is arranged at a certain magnetic field extreme point of the first phase line core, and the second coil is arranged at a certain magnetic field extreme point of the second phase line core. The magnetic field extreme point where the first coil is located and the magnetic field extreme point where the second coil is located are located on the same cross-section of the multi-core AC cable.

[0049] For the first coil group, define Figure 1 and Figure 2 The induced current of the first coil group flows from the first electrode 01 through the first load to the third electrode 03 in the first polarity (positive polarity) direction; the induced current of the first coil group flows from the third electrode 03 through the first load to the first electrode 01 in the second polarity (negative polarity) direction.

[0050] Furthermore, if Figure 1 and Figure 4 As shown, coils A1 and B1 are close to the two-phase cores A and B, so coils A1 and B1 mainly sense the induced current of the two-phase cores A and B. Since the first electrode 01 and the third electrode 03 of the same polarity of coils A1 and B1 are connected through the first load 20, and when the cable fails, the current will increase sharply. The following takes the first coil group located between the power distribution power supply and the fault point as an example to explain how to perform fault analysis and define polarity based on the induced current induced by the first coil group in principle:

[0051] If a phase-to-ground short circuit occurs in the A-phase core, the current in the A-phase core increases sharply. Since the distance between coil A1 and the A-phase core is smaller than the distance between coil B1 and the A-phase core, the induced current generated by coil A1 is greater than the induced current generated by coil B1. The induced current of the first coil group flows from the first electrode 01 to the third electrode 03 through the first load 20. In summary, the polarity of the induced current generated by the first coil group is positive, that is, the first polarity.

[0052] If the B phase core is short-circuited to the ground, the current in the B phase core increases sharply. Since the distance between coil B1 and the B phase core is smaller than the distance between coil A1 and the B phase core, the induced current generated by coil B1 is greater than the induced current generated by coil A1. In summary, the polarity of the induced current generated by the first coil group is negative, that is, the second polarity. At this time, the induced current of the first coil group flows from the third electrode 03 through the first load 20 to the first electrode 01 in the second polarity (negative polarity) direction, and the magnitude is I B1 -I A1 .

[0053] If a short circuit occurs between the two-phase cores AB, the two-phase cores AB form a loop, and the current therein increases sharply and is equal in magnitude. The current direction can be divided into A→B or B→A. When the current direction is A→B, that is, the induced current of the first coil group flows from the first electrode 01 through the first load 20 to the third electrode 03, the polarity of the induced current generated by the first coil group is positive polarity, and the magnitude is 2A1. When the current direction is B→A, that is, the induced current of the first coil group flows from the third electrode 03 through the first load 20 to the first electrode 01, the polarity of the induced current generated by the first coil group is negative polarity, and the magnitude is -2A1.

[0054] Similarly, definition Figure 2 The induced current of the second coil group flows from the sixth electrode 06 through the second load 30 to the eighth electrode 08 in the first polarity (positive polarity) direction; the induced current of the second coil group flows from the eighth electrode 08 through the second load 30 to the sixth electrode 06 in the second polarity (negative polarity) direction;

[0055] Among them, when the second coil group is located between the power distribution source and the fault point, when the current direction is B current, that is, the induced current of the second coil group flows from the sixth electrode 06 through the second load to the eighth electrode 08, the polarity of the induced current generated by the second coil group is the first polarity (positive polarity) flow direction; when the current direction is C current, that is, the induced current of the second coil group flows from the eighth electrode 08 through the second load to the sixth electrode 06, the polarity of the induced current generated by the second coil group is the second polarity (negative polarity) flow direction. Specifically, the definition of the polarity of the induced current of the second coil group is the same as the definition principle of the first coil group, and the details are not repeated.

[0056] In the above scheme, if a cable fails, the current in the faulty core increases abnormally, and an induced current is induced in the first coil group, thereby monitoring whether the cable has a fault. When a changing current is generated in the conductive shielding layer, the two coils will synchronously generate an induced current and an induced electromotive force in the same direction. Since the two poles of the same polarity in the first coil and the second coil are connected together, the influence of the induced magnetic field generated by the current in the conductive shielding layer on the first coil and the second coil can be weakened or even eliminated, thereby improving the accuracy of current transformer sampling. In addition, after the interference of the conductive shielding layer is weakened, the current transformer can be used for sampling and monitoring faults as well as for drawing power.

[0057] In some embodiments, reference Figure 2 , Figure 2 The assembly diagram of the second current transformer provided in the embodiment of the present application. The multi-core AC cable is a three-phase cable further including a third phase core located in the conductive shielding layer, and the current transformer further includes: a second coil group for monitoring the fault of one of the first phase core and the second phase core and the third phase core, the second coil group includes a third coil and a fourth coil, one end of the third coil forms a fifth electrode 05, and the other end forms a sixth electrode 06, one end of the fourth coil forms a seventh electrode 07, and the other end forms an eighth electrode 08; the fifth electrode 05 is connected to the seventh electrode 07, the sixth electrode 06 and the eighth electrode 08 are respectively used to be electrically connected to the second load, and the third coil and the fourth coil meet the condition: if the third coil and the fourth coil are placed in the same induced magnetic field, the fifth electrode 05 and the seventh electrode 07 show the same polarity, and the sixth electrode 06 and the eighth electrode 08 show the same polarity.

[0058] When the multi-core AC cable is a three-core cable, including three-phase cores, if there is only the first coil group, such as A1B1, only the fault of the AB phase core can be monitored. When the C phase core is short-circuited to the ground, the C phase core is at the same distance from coil A1 and coil B1, and the induced current generated by the first coil group is 0, which is easily confused with the normal alternating induced current. In order to monitor the fault of the third phase core, a second coil group is required on the basis of the first coil group, and one of the two coils of the second coil group is configured to be close to one side of the third phase core. The design concept and connection method of the second coil group and the first coil group are the same.

[0059] If another coil of the second coil group is configured to be close to one side of the first phase core, the second coil group is used to monitor faults of the first phase core and the third phase core; if another coil of the second coil group is configured to be close to one side of the second phase core, the second coil group is used to monitor faults of the second phase core and the third phase core.

[0060] Reference Figure 3 , Figure 3A three-dimensional schematic diagram of a current transformer and a cable installed in an embodiment of the present application. Explanatory, Figure 1-2 The middle coil is wound around all phase wire cores and is a conductive shield. Take a current transformer with two coil sets as an example. Figure 1-3 , the current transformer in each scheme of the present application also includes a coil bracket 100, the first coil group and the second coil group are fixed on the coil bracket 100, the coil bracket 100 is configured to be set on a multi-core AC cable, and the first coil group and the second coil group are evenly arranged in a circular array around the multi-core AC cable. In some embodiments, the current transformer also includes a clamping frame 200, the clamping frame 200 is connected to the coil bracket 100, and the clamping frame 200 is configured to be clamped with the multi-core AC cable, so that the first coil group and the second coil group are evenly arranged in a circular array around the multi-core AC cable. The coil bracket 100 and the clamping frame 200 can adopt the existing structure, and the details are not repeated. The first coil group and the second coil group are fixed on the coil bracket 100, and are arranged in a circular array around the multi-phase AC cable. The first coil and the second coil of the first coil group, the third coil and the fourth coil of the second coil group refer to Figure 2 The arrangement forms a spatial correspondence with the corresponding phase core. The first coil may correspond to the first phase core; the second coil may correspond to the second phase core; the third coil may correspond to the second phase core or the first phase core; and the fourth coil may correspond to the three-phase core for fault monitoring.

[0061] In the above scheme, the first coil group arranged at the corresponding side position of the first phase core and the second phase core can only monitor the faults of the first phase core and the second phase core. For a three-core cable, adding a second coil group can also monitor the faults of the third phase core, thereby realizing all-round online fault monitoring of multi-core AC cables.

[0062] In some embodiments, the first coil and the second coil have the same number of coil turns; and / or, the first coil and the second coil have the same coil area, which is the area of ​​a plane figure enclosed by a single turn of the coil in the coil; and / or, the first coil and the second coil have the same internal resistance; and / or, the first coil group and the second coil group have the same structure; and / or, the third coil and the fourth coil have the same number of coil turns; and / or, the third coil and the fourth coil have the same coil area, which is the area of ​​a plane figure enclosed by a single turn of the coil in the coil; and / or, the third coil and the fourth coil have the same internal resistance.

[0063] In the above scheme, when the configuration of the first coil and the second coil is the same, the conductive shielding layer will generate equal and same-direction induced currents and induced electromotive forces in the first coil and the second coil as much as possible, and then offset the influence of the magnetic field excited by the current in the conductive shielding layer by reverse connection. At this time, the weakening effect of the interference generated by the conductive shielding layer is most obvious, thereby improving the accuracy of current transformer sampling. The third coil and the fourth coil are the same.

[0064] In some embodiments, the current transformer further includes an iron core, and at least one iron core is inserted through the first coil group and the second coil group.

[0065] Reference Figure 4 , Figure 4 A structural schematic diagram of a first multi-core AC cable fault monitoring device provided in an embodiment of the present application, the multi-core AC cable fault monitoring device comprises: a current transformer 10 in any of the aforementioned embodiments; a first load 20, electrically connected to the first electrode 01 and the third electrode 03, the first load 20 being at least used to perform fault monitoring on the multi-core AC cable through the collected first induced current.

[0066] In the above solution, the induced current sampled by the first coil group can be sent to the first load 20 connected in series with the first coil group for analysis to determine the fault type, thereby achieving more detailed fault monitoring.

[0067] In some embodiments, the multi-core AC cable fault monitoring device further includes a second load 30. The second load 30 is electrically connected to the sixth electrode 06 and the eighth electrode 08, and the second load 30 is at least used to perform fault monitoring on the multi-core AC cable through the collected second induced current.

[0068] In the above scheme, the first load 20 connected to the first coil group can only monitor the faults of the first phase core and the second phase core. For a three-core cable, adding a second coil group can also monitor the faults of the third phase core, thereby realizing all-round online fault monitoring of multi-core AC cables and increasing the energy obtained from electricity.

[0069] In some embodiments, reference Figure 5 , Figure 5The electrical connection diagram of the first multi-core AC cable fault monitoring device provided in the embodiment of the present application. The first load 20 includes a first duplex switching circuit 201, a first polarity detection circuit 202, a first power extraction module 203 and a first processor 204; the first duplex switching circuit 201 is electrically connected to the second electrode 02 and the fourth electrode 04, and is used to receive the first induced current and separate the first induced current into two electrical signals, one of which is the power frequency current and the other is the fault high frequency signal; the first polarity detection circuit 202 is connected to the first duplex switching circuit 201, and is used to receive the fault high frequency signal and transmit the fault high frequency signal to the processor; the first power extraction module 203 is connected to the first duplex switching circuit 201, and is used to receive the power frequency current and convert the power frequency current into electrical energy that can be used by the first processor 204; the first processor 204 is respectively connected to the first polarity detection circuit 202 and the first power extraction module 203, and is used to receive the fault high frequency signal to perform multi-core AC cable fault monitoring.

[0070] When the multi-core AC cable operates normally, the alternating current inside the cable will generate power frequency current in the first coil group. The power frequency current flows to the first power extraction module 203 through the first duplex switching circuit 201 and can be used to supply energy to the first processor 204.

[0071] When a grounding or short circuit fault occurs in the multi-core AC cable, the induced current induced in the current transformer 10 will be separated into a fault high-frequency signal by the first duplex switching circuit 201, and then the first processor 204 will be awakened through the first polarity detection circuit 202. The first duplex switching circuit 201 is equivalent to the filtering principle of a filter, which realizes the separation of the power frequency signal and the fault high-frequency signal.

[0072] In the above scheme, the first duplex switching circuit 201 receives the first induced current and separates the first induced current into two electrical signals, one is the industrial frequency current, and the other is the fault high-frequency signal; the first polarity detection circuit 202 receives the fault high-frequency signal and transmits the processed fault high-frequency signal to the processor 204, so as to facilitate the analysis of the fault type. The first power supply module 203 can provide power for the circuit part involved in sampling and fault analysis.

[0073] In some embodiments, reference Figure 6 , Figure 6The electrical connection diagram of the second multi-core AC cable fault monitoring device provided in the embodiment of the present application. The first duplex switching circuit 201 is a duplex filter circuit or an antenna switch; and / or, the first polarity detection circuit 202 includes a first positive polarity detection circuit 2021 and a first negative polarity detection circuit 2022, wherein the first positive and negative polarity detection circuits 2021 and 2022 both include an adjustable capacitance RC integration circuit and a Schmitt trigger circuit; and / or, the first power extraction module 203 also includes an energy storage battery, which is used to store the electric energy converted by the first power extraction module 203; and / or, the second load 30 has the same structure as the first load 20.

[0074] If the first duplex switching circuit 201 is a duplex filtering circuit, the duplex filtering circuit includes a capacitor high-pass coupling part and an inductor low-pass coupling part, wherein the induced current in the current transformer 10 can separate the fault high-frequency signal through the capacitor high-pass coupling part, and separate the industrial frequency current for energy supply through the inductor low-pass coupling part.

[0075] Reference Figure 7 , Figure 7 The electrical connection diagram of the third multi-core AC cable fault monitoring device provided in the embodiment of the present application is as follows. The first load 20 and the second load 30 have the same structure, and both can be set as independent load circuits or as Figure 7 The power taking module and processor are shared, but each has a separate duplex switching circuit and polarity detection circuit.

[0076] In the above solution, the second load 30 has the same structure as the first load 20 , and the second load 30 and the first load 20 also play the same role, which is to process the induced current in the corresponding coil group and analyze the fault type.

[0077] Based on the above multi-core AC cable fault monitoring device, the embodiments of the present application also provide a variety of multi-core AC cable fault monitoring methods, and the various multi-core AC cable fault monitoring methods are described in detail below.

[0078] First, a first multi-core AC cable fault monitoring method provided by an embodiment of the present application is introduced, the method comprising:

[0079] Step S10: Obtain a first induced current, the first induced current comes from at least one multi-core AC cable fault monitoring device described in an embodiment of the present application; wherein, when there are multiple multi-core AC cable fault monitoring devices, the multiple multi-core AC cable fault monitoring devices are arranged side by side and spaced apart along the multi-core AC cable, and the multi-core AC cable fault monitoring device is configured such that when in use, the first coil and the second coil are spaced apart in the circumferential direction around the axis of the multi-core AC cable, the distance from the first coil to the axis is equal to the distance from the second coil to the axis, the first coil is configured to be close to one side of the first phase core, and the second coil is configured to be close to one side of the second phase core.

[0080] Step S20: performing fault monitoring on the multi-core AC cable according to the fault high-frequency signal separated from the first induced current.

[0081] The first induced current is the induced current in the first coil group in the multi-core AC cable fault monitoring device.

[0082] In the above scheme, when one current transformer is arranged along the multi-core AC cable, it can play a role in monitoring faults. When multiple current transformers are arranged along the multi-core AC cable, they can play a role in locating the fault section and determining the fault type.

[0083] In some embodiments, step S20 includes:

[0084] If there are two adjacent current transformers, and a fault high-frequency signal cannot be obtained based on the first induced current of one of the current transformers, but a fault high-frequency signal is obtained based on the first induced current of the other current transformer, then it is determined that the fault point is between the two adjacent current transformers, and the fault type is a phase-to-phase short circuit. And / or,

[0085] If there are two adjacent current transformers, a fault high-frequency signal is obtained based on the first induced current of one of the current transformers and the polarity is a first polarity, and a fault high-frequency signal is obtained based on the first induced current of the other current transformer and the polarity is a second polarity opposite to the first polarity, then it is determined that the fault point is located between the two adjacent current transformers, and the fault type is a phase-to-ground short circuit.

[0086] The present application does not specifically limit the direction of the first polarity, and those skilled in the art may adjust it according to actual conditions. For example, the induced current in the first coil group flowing from the first electrode 01 through the first load 20 to the third electrode 03 may be defined as the first polarity, and correspondingly, the second polarity is the current flowing from the third electrode 03 through the first load 20 to the first electrode 01.

[0087] The polarity of the first induced current induced by the current transformer is affected by the flow direction of the current in the corresponding phase line core. In the case of different faults such as phase-to-ground short circuit and phase-to-phase short circuit, the corresponding current flow direction in the line core is different. Specifically, there will be significant differences in the current direction in the corresponding phase line core between the fault point and the substation and between the fault point and the electrical appliance, so the polarity of the corresponding first induced current will also be different. Based on this, the cause of the fault and the fault interval can be located according to the above characteristics, and the judgment basis is as follows:

[0088] One end of the multi-core AC cable is connected to the substation, and the other end is connected to the electricity user; the fault point is located in the multi-core AC cable between the substation and the electricity user.

[0089] When a phase-to-ground short circuit occurs, the direction of the large current generated by the faulty core of the multi-core AC cable between the substation and the fault point is from the substation to the fault point, and finally flows from the faulty core to the ground at the fault point; the direction of the large current generated by the faulty core between the substation and the fault point is from the substation to the fault point, and finally flows from the faulty core to the ground at the fault point; the direction of the large current generated by the faulty core between the substation and the fault point is opposite to that between the fault point and the power user.

[0090] When a phase-to-phase short circuit occurs, the situation between the substation and the fault point is that the direction of the current generated by the fault in the multi-core AC cable is from one phase core to another phase core, and the current directions of the two are opposite. The situation between the fault point and the electricity user is that the directions of the fault currents generated by the fault in the fault cores are the same, both flowing to the fault point.

[0091] Based on the analysis of the above phenomenon, when the current transformer is installed on a multi-core AC cable, the current transformer can generate an induced current. At the same time, for different types of faults and the location differences of the current transformer relative to the fault point and the substation, the fault high-frequency signal corresponding to the induced current captured will be different in terms of presence, size and polarity. Therefore, if multiple current transformers are deployed in a cable line, the specific fault interval and fault type of the multi-core AC cable can be deduced from the presence, size and polarity of the fault high-frequency signal.

[0092] In the above scheme, the cable fault is judged according to the first induced current in the current transformer. The cable fault includes phase-to-phase short circuit and phase-to-ground short circuit. When the phase-to-phase short circuit and the phase-to-ground short circuit occur, the polarity and magnitude of the induced current induced in the current transformer have their own characteristics, and the fault type can be determined according to the characteristics. In addition, the induced currents induced by the current transformers between the distribution power supply and the fault point and between the fault point and the electrical appliance are also different. Therefore, the fault interval can be located by arranging multiple current transformers along the multi-core AC cable.

[0093] Next, a second multi-core AC cable fault monitoring method provided by the embodiment of the present application is introduced, and the method includes:

[0094] A first induced current and a second induced current are obtained, wherein the first induced current and the second induced current are from the multi-core AC cable fault monitoring device described in the embodiment of the present application, wherein the multi-core AC cable fault monitoring device is configured such that, when in use, the first coil and the second coil are spaced apart in the circumferential direction around the axis of the multi-core AC cable, the distance from the first coil to the axis is equal to the distance from the second coil to the axis, the first coil is configured to be close to one side of the first phase core, and the second coil is configured to be close to one side of the second phase core; the third coil and the fourth coil are spaced apart in the circumferential direction around the axis of the multi-core AC cable, the distance from the third coil to the axis is equal to the distance from the fourth coil to the axis, the third coil is configured to be close to one side of the first phase core or the second phase core, and the fourth coil is configured to be close to one side of the third phase core;

[0095] According to the induction parameters of the fault high-frequency signal separated from the first induction current and the second induction current, fault monitoring is performed on the multi-core AC cable, wherein the fault monitoring includes:

[0096] If no fault high-frequency signal can be obtained by filtering based on the first induced current, and a fault high-frequency signal is obtained based on the second induced current, it is determined that a phase-to-ground short circuit occurs in the third phase core, or a phase-to-phase short circuit occurs between the first phase core and the second phase core, or both phases of the first phase core and the second phase core are short-circuited to the ground.

[0097] and / or,

[0098] If a fault high-frequency signal is obtained based on the first induced current, and a fault high-frequency signal cannot be obtained based on the second induced current, and if the third coil is configured to be close to one side of the first phase core, it is determined that a phase-to-ground short circuit occurs in the second phase core, or a phase-to-phase short circuit occurs between the first phase core and the third phase core, or both phases of the first phase core and the third phase core are short-circuited to the ground; if the third coil is configured to be close to one side of the second phase core, it is determined that a phase-to-ground short circuit occurs in the first phase core, or a phase-to-phase short circuit occurs between the second phase core and the third phase core, or both phases of the second phase core and the third phase core are short-circuited to the ground.

[0099] In the above scheme, the cable fault is determined based on the first induced current and the second induced current in a current transformer. The cable fault includes phase-to-phase short circuit and phase-to-ground short circuit. When the phase-to-phase short circuit and the phase-to-ground short circuit occur, the polarity and magnitude of the induced current induced in the current transformer have their own characteristics, and the fault type can be determined based on the characteristics.

[0100] Next, a third multi-core AC cable fault monitoring method provided by the embodiment of the present application is introduced, the method comprising:

[0101] A first induced current and a second induced current are obtained, wherein the first induced current and the second induced current are respectively obtained from a plurality of multi-core AC cable fault monitoring devices described in the embodiments of the present application, wherein each multi-core AC cable fault monitoring device is arranged side by side and spaced apart along the multi-core AC cable, wherein the multi-core AC cable fault monitoring device is configured such that, when in use, the first coil and the second coil are spaced apart in a circumferential direction around the axis of the multi-core AC cable, the distance from the first coil to the axis is equal to the distance from the second coil to the axis, the first coil is configured to be close to one side of the first phase core, the second coil is configured to be close to one side of the second phase core, the third coil and the fourth coil are spaced apart in a circumferential direction around the axis of the multi-core AC cable, the distance from the third coil to the axis is equal to the distance from the fourth coil to the axis, the third coil is configured to be close to one side of the first phase core or the second phase core, and the fourth coil is configured to be close to one side of the third phase core.

[0102] If there are two adjacent current transformers that respectively meet the following conditions, it is determined that the fault point is located between the two adjacent current transformers, wherein the first induced currents of the two current transformers are different and / or the second induced currents are different, and the difference includes at least one of magnitude and polarity, and the following conditions include:

[0103] Based on the first induced current and the second induced current of the two current transformers, a first fault high-frequency signal is obtained, and the polarity of the first fault high-frequency signal of one of the current transformers is opposite, and the polarity of the first fault high-frequency signal of the other current transformer is also opposite, then the fault type is determined to be that a phase-to-ground short circuit occurs in the common phase core of the first coil group and the second coil group, or that a phase-to-ground short circuit occurs in the non-common phase cores in the phase cores corresponding to the first coil group and the second coil group, respectively.

[0104] and / or,

[0105] Based on the first induced current and the second induced current of the two current transformers, the first fault high-frequency signal is obtained, and the polarity of the first fault high-frequency signal of only one current transformer is the same, then the fault type is determined to be a phase-to-phase short circuit between two non-common phase cores in the phase cores corresponding to the first coil group and the second coil group.

[0106] and / or,

[0107] If no fault high-frequency signal can be obtained based on the first induced currents of the two current transformers, and first fault high-frequency signals are obtained based on the second induced currents of the two current transformers, then the fault type is determined to be a phase-to-ground short circuit in the third phase core, or a phase-to-ground short circuit in both the first phase core and the second phase core.

[0108] and / or,

[0109] If a first fault high-frequency signal is obtained based on the first induced currents of the two current transformers, and no fault high-frequency signal can be obtained based on the second induced currents of the two current transformers, then the fault type is determined to be a phase-to-ground short circuit in the first phase core, or a phase-to-ground short circuit in both the second phase core and the third phase core.

[0110] and / or,

[0111] A second fault high-frequency signal is obtained based on the first induced current of one of the current transformers, and the fault type is determined to be a phase-to-phase short circuit between the first phase core and the second phase core, wherein the second fault high-frequency signal is a fault high-frequency signal that is greater than the first fault high-frequency signal by a preset threshold.

[0112] and / or,

[0113] A second fault high-frequency signal is obtained based on a second induced current of one of the current transformers, and the fault type is determined to be a phase-to-phase short circuit of a two-phase core provided with a second coil group.

[0114] As an implementation mode, an example is given in which a first coil group is arranged on the AB phase core of a three-phase cable and a second coil group is arranged on the BC phase core. The first polarity is denoted as a positive polarity. In the first coil group, the direction of the first polarity is that the induced current of the first coil group flows from the first electrode 01 through the first load 20 to the third electrode 03. In the second coil group, the direction of the first polarity is that the induced current of the second coil group flows from the sixth electrode 06 through the second load 30 to the eighth electrode 08. Table 1 below shows the correspondence between the fault occurring in the cable and the fault high-frequency signal when the current transformer is located at different positions. The different positions include two situations: being located between the fault point and the power supply and being located outside the fault point and the power supply. Among them, 0 represents a fault-free high-frequency signal, + represents the first polarity, i.e., the positive polarity, - represents the second polarity, i.e., the negative polarity, 1 represents the first fault high-frequency signal, and 2 represents the second fault high-frequency signal. AB and BC in the first column represent the first coil group and the second coil group respectively. A, B, C, AB, BC, and AC belonging to the phase-to-ground short circuit list respectively represent phase-to-ground short circuit faults occurring in phase A, phase B, phase C, AB at the same time, BC at the same time, and AC at the same time. AB belonging to the phase-to-phase short circuit list represents a phase-to-phase short circuit occurring in phase AB and the current flows from A to B. BA represents a phase-to-phase short circuit occurring in phase AB and the current flows from B to A. The same is true for BC, CB, AC, and CA, which will not be repeated here.

[0115]

[0116]

[0117] Table 1 Correspondence between cable faults and fault high frequency signals

[0118] It should be noted that 1 and 2 only represent the magnitude relationship between the first and second fault high-frequency signals, which may represent that the integrated energy value of the second fault high-frequency signal is greater than the integrated energy value of the first fault high-frequency signal, rather than an absolute two-fold relationship. Since the current directly forms a loop between the two-phase cores when a phase-to-phase short circuit occurs, the magnitude of the current in the phase-to-phase short circuit is greater than the phase-to-ground short circuit in which the current directly flows from the core to the ground, and thus the induced current corresponding to the phase-to-phase short circuit is also greater than the phase-to-ground short circuit. Therefore, the preset threshold value can be adjusted according to the actual situation, and the magnitude of the preset threshold value is sufficient to distinguish between the two different fault types.

[0119] Optionally, in the above implementation, the fault high frequency signals of the first and second coil groups may be combined for comprehensive judgment, and Table 2 below is obtained by sorting Table 1. Table 2 also shows the corresponding relationship between the faults of the cable and the fault high frequency signals:

[0120]

[0121] Table 2 Correspondence between cable faults and fault high frequency signals

[0122] In Table 2, AB occurs indicating that the fault high frequency signals of the first coil group and the second coil group are merged together. For example, the first number -1 in -10 represents the fault high frequency signal of the first coil group, and the second number 0 represents that the second coil group does not obtain the fault high frequency signal.

[0123] Encode the two combined numbers in Table 2 above according to the following rules:

[0124] 10==0,-11==1,0-1==2,01==3,-10==4,1-1==5,2-1==6,-21==7,-12==8,1-2==9,11==10,-1-1==11.

[0125] After coding, the following Table 3 is obtained, which shows the corresponding relationship between the cable faults and the codes:

[0126]

[0127] Table 3 Correspondence between cable faults and codes

[0128] After sorting out Table 3 above, we get Table 4 below, which also shows the corresponding relationship between cable faults and codes:

[0129] Located between the fault point and the power supply Located outside the fault point and power source Single-phase phase-to-ground short circuit 0、1、2 3、4、5 Two-phase phase-to-ground short circuit 3、4、5 0、1、2 Phase short circuit 6、7、8、9、10、11 0、1、2

[0130] Table 4 Correspondence between cable faults and codes

[0131] It can be seen from Table 4 that when {3, 4, 5} appears, it can be judged that a phase-to-ground short circuit occurs, and the phase-to-ground short circuit fault interval is between {0, 1, 2} and {3, 4, 5}; when {6, 7, 8, 9, 10, 11} appears, it can be judged that a phase-to-phase short circuit occurs, and the fault interval is between {6, 7, 8, 9, 10, 11} and {0, 1, 2}.

[0132] In the above scheme, the cable fault is judged according to the first induced current and the second induced current in multiple current transformers. The cable fault includes phase-to-phase short circuit and phase-to-ground short circuit. When the phase-to-phase short circuit and the phase-to-ground short circuit occur, the polarity and magnitude of the induced current induced in the current transformer have their own characteristics, and the fault type can be determined according to the characteristics. In addition, the induced currents induced by the current transformers located between the distribution power supply and the fault point and between the fault point and the electrical appliance are also different, so the fault interval can be located.

[0133] Furthermore, by summarizing and analyzing the above Table 4, the following new implementation method for fault judgment can be obtained.

[0134] The embodiment of the present application further provides a multi-core AC cable fault monitoring method, the method comprising:

[0135] Obtaining a first induced current and a second induced current, wherein the first induced current and the second induced current are respectively from a plurality of multi-core AC cable fault monitoring devices provided in the above-mentioned embodiments, and each of the multi-core AC cable fault monitoring devices is arranged side by side and spaced apart along the multi-core AC cable;

[0136] If there are two adjacent current transformers that respectively meet the following conditions, it is determined that the fault point is located between the two adjacent current transformers, wherein the first induced currents of the two current transformers are different and / or the second induced currents are different, and the difference includes at least one of magnitude and polarity, and the following conditions include:

[0137] When a first monitoring result is obtained based on one of the current transformers and a second monitoring result is obtained based on the other current transformer, it is determined that there is a phase-to-ground short circuit between the two current transformers; wherein the first monitoring result includes that a fault high-frequency signal cannot be obtained based on the first induced current and a first fault high-frequency signal of a first polarity is obtained based on the second induced current, or, a first fault high-frequency signal of a second polarity is obtained based on the first induced current and a fault high-frequency signal cannot be obtained based on the second induced current, or, a first fault high-frequency signal of a first polarity is obtained based on the first induced current and a first fault high-frequency signal of a second polarity is obtained based on the second induced current; the second monitoring result includes that a first fault high-frequency signal of a first polarity is obtained based on the first induced current and a fault high-frequency signal cannot be obtained based on the second induced current, or, a first fault high-frequency signal of a second polarity is obtained based on the first induced current and a first fault high-frequency signal of a first polarity is obtained based on the second induced current, or, a first fault high-frequency signal of a second polarity is obtained based on the first induced current and a first fault high-frequency signal of a first polarity is obtained based on the second induced current, or, a fault high-frequency signal cannot be obtained based on the first induced current and a first fault high-frequency signal of a second polarity is obtained based on the second induced current; and / or,

[0138] When a third monitoring result is obtained based on one of the current transformers and a second monitoring result is obtained based on the other current transformer, it is determined that there is a phase-to-phase short circuit between the two current transformers; wherein the second monitoring result includes obtaining a first fault high-frequency signal of a first polarity based on the first induced current and failing to obtain a fault high-frequency signal based on the second induced current, or obtaining a first fault high-frequency signal of a second polarity based on the first induced current and obtaining a first fault high-frequency signal of a first polarity based on the second induced current, or failing to obtain a fault high-frequency signal based on the first induced current and obtaining a first fault high-frequency signal of a second polarity based on the second induced current; the third monitoring result includes obtaining a first fault high-frequency signal based on one of the first induced current and the second induced current and obtaining a second fault high-frequency signal based on the other of the first induced current and the second induced current, or obtaining first fault high-frequency signals of the same polarity based on the first induced current and the second induced current, respectively.

[0139] The advantage of the above scheme is that when multiple current transformers are used for fault monitoring, it is not necessary to strictly correspond the first coil group and the second coil group of each current transformer to each phase core of the three-phase cable, that is, the first coils of the first coil groups of different current transformers can correspond to different phase cores, and do not have to correspond to the same phase core, which can greatly reduce the difficulty of installing each current transformer and greatly reduce the installation workload. In addition, the above-mentioned logical judgment method can be used to locate the fault interval and determine the fault type of phase-to-phase short circuit or phase-to-ground short circuit.

[0140] It should be understood that the multi-core AC cable fault monitoring device corresponds to the above-mentioned multi-core AC cable fault monitoring method implementation method, and can perform the various steps involved in the above-mentioned method implementation method. The specific functions of the device can be found in the description above. To avoid repetition, the detailed description is appropriately omitted here. The device includes at least one software function module that can be stored in a memory in the form of software or firmware or solidified in the operating system (OS) of the device.

[0141] The present application provides a computer program product, including computer program instructions. When the computer program instructions are read and executed by a processor, the methods provided by the above-mentioned method implementation modes are executed.

[0142] The present application provides a computer-readable storage medium, including: the computer-readable storage medium stores computer instructions, and the computer instructions enable a computer to execute the methods provided by the above-mentioned method implementation methods.

[0143] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device implementation described above is only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of devices or units can be electrical, mechanical or other forms.

[0144] In addition, the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0145] Furthermore, the functional modules in each embodiment of the present application may be integrated together to form an independent part, or each module may exist independently, or two or more modules may be integrated to form an independent part.

[0146] The above is only an implementation method of the present application and is not intended to limit the scope of protection of the present application. For those skilled in the art, the present application may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. A current transformer for fault monitoring of a multi-core AC cable, wherein the multi-core AC cable comprises a conductive shielding layer and a first phase core and a second phase core located in the conductive shielding layer, characterized in that: The current transformer comprises: A first coil group, the first coil group includes a first coil for monitoring a first phase core and a second coil for monitoring a second phase core, one end of the first coil forms a first electrode, and the other end forms a second electrode, one end of the second coil forms a third electrode, and the other end forms a fourth electrode, the first electrode and the third electrode are respectively used to be electrically connected to a first load, the second electrode is connected to the fourth electrode, and the first coil and the second coil meet the condition: if the first coil and the second coil are placed in the same induced magnetic field, the first electrode and the third electrode exhibit the same polarity, and the second electrode and the fourth electrode exhibit the same polarity.

2. The current transformer according to claim 1, characterized in that: The multi-core AC cable is a three-phase cable further including a third phase core located in the conductive shielding layer, and the current transformer further includes: a second coil group, the second coil group comprising a third coil for monitoring one of the first phase core and the second phase core and a fourth coil for monitoring the third phase core, one end of the third coil forming a fifth electrode and the other end forming a sixth electrode, one end of the fourth coil forming a seventh electrode and the other end forming an eighth electrode; The fifth electrode is connected to the seventh electrode, the sixth electrode and the eighth electrode are respectively used to be electrically connected to a second load, and the third coil and the fourth coil satisfy the condition: if the third coil and the fourth coil are placed in the same induced magnetic field, the fifth electrode and the seventh electrode exhibit the same polarity, and the sixth electrode and the eighth electrode exhibit the same polarity.

3. A multi-core AC cable fault monitoring device, characterized in that: include: The current transformer according to any one of claims 1 or 2; The first load is electrically connected to the first electrode and the third electrode, and the first load is at least used to perform fault monitoring on the multi-core AC cable through the collected first induced current.

4. The device according to claim 3, characterized in that Also includes: The second load is electrically connected to the sixth electrode and the eighth electrode, and the second load is at least used to perform fault monitoring on the multi-core AC cable through the collected second induced current.

5. The device according to claim 4, characterized in that The first load includes a first duplex switching circuit, a first polarity detection circuit, a first power extraction module and a first processor; The first duplex switching circuit is electrically connected to the second electrode and the fourth electrode, and is used to receive the first induced current and separate the first induced current into two electrical signals, one of which is a power frequency current and the other is a fault high frequency signal; The first polarity detection circuit is connected to the first duplex switching circuit and is used to receive the fault high-frequency signal and transmit the fault high-frequency signal to the processor; The first power taking module is connected to the first duplex switching circuit and is used to receive the power frequency current and convert the power frequency current into electric energy that can be used by the first processor; The first processor is connected to the first polarity detection circuit and the first power extraction module respectively, and is used to receive the fault high-frequency signal to perform multi-core AC cable fault monitoring.

6. A multi-core AC cable fault monitoring method, characterized in that: The method comprises: Obtaining a first induced current, the first induced current coming from at least one multi-core AC cable fault monitoring device according to any one of claims 3 to 5; wherein, when there are multiple multi-core AC cable fault monitoring devices, the multiple multi-core AC cable fault monitoring devices are arranged side by side and spaced apart along the multi-core AC cable, and the multi-core AC cable fault monitoring device is configured such that, when in use, a first coil and a second coil are spaced apart in a circumferential direction around an axis of the multi-core AC cable, a distance from the first coil to the axis is equal to a distance from the second coil to the axis, the first coil is configured to be close to one side of a first phase core, and the second coil is configured to be close to one side of a second phase core; Fault monitoring is performed on the multi-core AC cable according to the fault high-frequency signal separated from the first induced current.

7. The method according to claim 6, characterized in that The method of performing fault monitoring on the multi-core AC cable according to the fault high-frequency signal separated from the first induced current includes: If there are two adjacent current transformers, the fault high-frequency signal cannot be obtained based on the first induced current of one of the current transformers, and the fault high-frequency signal is obtained based on the first induced current of the other current transformer, then it is determined that the fault point is located between the two adjacent current transformers, and the fault type is phase-to-phase short circuit; and / or, If there are two adjacent current transformers, the fault high-frequency signal is obtained based on the first induced current of one of the current transformers and the polarity is a first polarity, and the fault high-frequency signal is obtained based on the first induced current of the other current transformer and the polarity is a second polarity opposite to the first polarity, then it is determined that the fault point is located between the two adjacent current transformers, and the fault type is a phase-to-ground short circuit.

8. A multi-core AC cable fault monitoring method, characterized in that: The method comprises: Obtaining a first induced current and a second induced current, wherein the first induced current and the second induced current are from the multi-core AC cable fault monitoring device according to any one of claims 4 or 5, wherein the multi-core AC cable fault monitoring device is configured such that, when in use, the first coil and the second coil are spaced apart in a circumferential direction around the axis of the multi-core AC cable, the distance from the first coil to the axis is equal to the distance from the second coil to the axis, the first coil is configured to be close to one side of the first phase core, and the second coil is configured to be close to one side of the second phase core; the third coil and the fourth coil are spaced apart in a circumferential direction around the axis of the multi-core AC cable, the distance from the third coil to the axis is equal to the distance from the fourth coil to the axis, the third coil is configured to be close to one side of the first phase core or the second phase core, and the fourth coil is configured to be close to one side of the third phase core; According to the induction parameters of the fault high-frequency signal separated from the first induction current and the second induction current, fault monitoring is performed on the multi-core AC cable, wherein the fault monitoring includes: If the fault high-frequency signal cannot be obtained by filtering based on the first induced current, and the fault high-frequency signal is obtained based on the second induced current, it is determined that a phase-to-ground short circuit occurs in the third phase core, or a phase-to-phase short circuit occurs between the first phase core and the second phase core, or both phases of the first phase core and the second phase core are short-circuited to the ground; and / or, If the fault high-frequency signal is obtained based on the first induced current, and the fault high-frequency signal cannot be obtained based on the second induced current, if the third coil is configured to be close to one side of the first phase line core, it is determined that a phase-to-ground short circuit occurs in the second phase line core, or the first phase line core and the third phase line core are short-circuited between phases, or both the first phase line core and the third phase line core are short-circuited between phases; if the third coil is configured to be close to one side of the second phase line core, it is determined that a phase-to-ground short circuit occurs in the first phase line core, or the second phase line core and the third phase line core are short-circuited between phases, or both the second phase line core and the third phase line core are short-circuited between phases.

9. A multi-core AC cable fault monitoring method, characterized in that: The method comprises: Obtaining a first induced current and a second induced current, wherein the first induced current and the second induced current are respectively from a plurality of multi-core AC cable fault monitoring devices according to any one of claims 4 or 5, wherein each of the multi-core AC cable fault monitoring devices is arranged side by side and spaced apart along the multi-core AC cable, wherein the multi-core AC cable fault monitoring device is configured such that, when in use, a first coil and a second coil are spaced apart in a circumferential direction around an axis of the multi-core AC cable, a distance from the first coil to the axis is equal to a distance from the second coil to the axis, the first coil is configured to be close to one side of a first phase core, the second coil is configured to be close to one side of a second phase core, a third coil and a fourth coil are spaced apart in a circumferential direction around an axis of the multi-core AC cable, a distance from the third coil to the axis is equal to a distance from the fourth coil to the axis, the third coil is configured to be close to one side of the first phase core or the second phase core, and the fourth coil is configured to be close to one side of the third phase core; If there are two adjacent current transformers that respectively meet the following conditions, it is determined that the fault point is located between the two adjacent current transformers, wherein the first induced currents of the two current transformers are different and / or the second induced currents are different, and the difference includes at least one of magnitude and polarity, and the following conditions include: A first fault high-frequency signal is obtained based on the first induced current and the second induced current of the two current transformers, and the first fault high-frequency signal of one current transformer has opposite polarity, and the first fault high-frequency signal of the other current transformer also has opposite polarity, then the fault type is determined to be a phase-to-ground short circuit in the common phase core of the first coil group and the second coil group, or a phase-to-ground short circuit occurs in the non-common phase cores of the phase cores corresponding to the first coil group and the second coil group respectively; and / or, The first fault high-frequency signal is obtained based on the first induced current and the second induced current of the two current transformers, and the polarity of the first fault high-frequency signal of only one current transformer is the same, then the fault type is determined to be a phase-to-phase short circuit between two non-common phase cores in the phase cores corresponding to the first coil group and the second coil group; and / or, If no fault high-frequency signal can be obtained based on the first induced currents of the two current transformers, and the first fault high-frequency signal is obtained based on the second induced currents of the two current transformers, then the fault type is determined to be a phase-to-ground short circuit in the third phase core, or a phase-to-ground short circuit in both the first phase core and the second phase core; and / or, The first fault high-frequency signal is obtained based on the first induced currents of the two current transformers, and the fault high-frequency signal cannot be obtained based on the second induced currents of the two current transformers, then the fault type is determined to be a phase-to-ground short circuit in the first phase core, or a phase-to-ground short circuit in both the second phase core and the third phase core; and / or, A second fault high-frequency signal is obtained based on the first induced current of one of the current transformers, and the fault type is determined to be a phase-to-phase short circuit between the first phase core and the second phase core, wherein the second fault high-frequency signal is a fault high-frequency signal that is greater than the first fault high-frequency signal by a preset threshold; and / or, The second fault high-frequency signal is obtained based on the second induced current of one of the current transformers, and the fault type is determined to be a phase-to-phase short circuit between the two-phase cores where the second coil group is arranged.

10. A multi-core AC cable fault monitoring method, characterized in that: The method comprises: Obtaining a first induced current and a second induced current, wherein the first induced current and the second induced current are respectively from a plurality of multi-core AC cable fault monitoring devices according to any one of claims 4 or 5, wherein the multi-core AC cable fault monitoring devices are arranged side by side and spaced apart along the multi-core AC cable; If there are two adjacent current transformers that respectively meet the following conditions, it is determined that the fault point is located between the two adjacent current transformers, wherein the first induced currents of the two current transformers are different and / or the second induced currents are different, and the difference includes at least one of magnitude and polarity, and the following conditions include: When a first monitoring result is obtained based on one of the current transformers and a second monitoring result is obtained based on the other current transformer, it is determined that there is a phase-to-ground short circuit between the two current transformers; wherein the first monitoring result includes that a fault high-frequency signal cannot be obtained based on the first induced current and a first fault high-frequency signal of a first polarity is obtained based on the second induced current, or, a first fault high-frequency signal of a second polarity is obtained based on the first induced current and a fault high-frequency signal cannot be obtained based on the second induced current, or, a first fault high-frequency signal of a first polarity is obtained based on the first induced current and a first fault high-frequency signal of a second polarity is obtained based on the second induced current; the second monitoring result includes that a first fault high-frequency signal of a first polarity is obtained based on the first induced current and a fault high-frequency signal cannot be obtained based on the second induced current, or, a first fault high-frequency signal of a second polarity is obtained based on the first induced current and a first fault high-frequency signal of a first polarity is obtained based on the second induced current, or, a first fault high-frequency signal of a second polarity is obtained based on the first induced current and a first fault high-frequency signal of a first polarity is obtained based on the second induced current, or, a fault high-frequency signal cannot be obtained based on the first induced current and a first fault high-frequency signal of a second polarity is obtained based on the second induced current; and / or, When a third monitoring result is obtained based on one of the current transformers and a second monitoring result is obtained based on the other current transformer, it is determined that there is a phase-to-phase short circuit between the two current transformers; wherein the second monitoring result includes obtaining a first fault high-frequency signal of a first polarity based on the first induced current and failing to obtain a fault high-frequency signal based on the second induced current, or obtaining a first fault high-frequency signal of a second polarity based on the first induced current and obtaining a first fault high-frequency signal of a first polarity based on the second induced current, or failing to obtain a fault high-frequency signal based on the first induced current and obtaining a first fault high-frequency signal of a second polarity based on the second induced current; the third monitoring result includes obtaining a first fault high-frequency signal based on one of the first induced current and the second induced current and obtaining a second fault high-frequency signal based on the other of the first induced current and the second induced current, or obtaining first fault high-frequency signals of the same polarity based on the first induced current and the second induced current, respectively.

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