A power cable fault section locating method, device and system

Abstract

The application discloses a power transmission cable fault interval positioning method, device and system. The method comprises the following steps: detecting the electrical characteristic signals of the core wires and the sheaths of each phase cable at the two ends of the cross-connection large section; determining the fault phase and the fault sheath according to the electrical characteristic signals of the core wires and the sheaths of each phase cable, so as to determine the cross-connection sub-section where the fault is located. When the cross-connection large section has a fault, the core wire phase and the cross-connection sub-section where the fault is located can be accurately determined through the electrical characteristic signals of the core wires and the sheaths, the fault interval can be accurately positioned, and the positioning of the fault interval is not affected by the environment.

Description

Technical Field

[0001] This application relates to the field of power transmission cable fault location technology, and in particular to a method, device and system for locating fault sections in power transmission cables. Background Technology

[0002] Currently, after a fault occurs in a power transmission cable, online fault location technology can be used to pinpoint the fault location. Online fault location technology mainly includes two types: precise fault location and fault range location.

[0003] Generally, online fault location outputs a distance value, indicating the distance between the fault and the monitoring device. However, the fault location result cannot be directly correlated to the cable location. Furthermore, online fault location is based on traveling wave technology, requiring accurate time synchronization between devices. Since cables are located underground, GPS synchronization signals are difficult to obtain. Fiber optic synchronization significantly increases construction difficulty and cost, and is not applicable in buried pipe or direct burial environments.

[0004] Existing online fault location technology, if it is required to pinpoint the fault range to the cross-interconnection segment, requires the installation of monitoring equipment at each insulation joint of the cross-interconnection segment. Furthermore, it is necessary to determine whether the fault is located between or outside the two monitoring devices based on the polarity of the core current collected by each monitoring device. Since the grounding wire at the cross-interconnection is the combined amount of the left and right sheaths, it is impossible to measure the core current or the sheath current of a single phase by installing monitoring equipment at the cross-interconnection segment. Therefore, this technology is not applicable to fault ranges within the cross-interconnection segment of the cable.

[0005] Therefore, accurately locating the fault section within the cross-connection section of power transmission cables is a technical problem that needs to be solved. Summary of the Invention

[0006] The main objective of this application is to provide a method, device, and system for locating fault sections in power transmission cables, aiming to solve the technical problem that related technologies cannot accurately locate fault sections when faults occur in large interconnected sections.

[0007] Firstly, this application provides a method for locating fault sections in power transmission cables, which is applied to large cross-connected sections of power transmission cables. The cross-connected section includes three-phase cable cores and a sheath disposed on the outside of each phase cable core. The cross-connected section is divided into multiple cross-connected sub-segments by the sheath. The method includes the following steps:

[0008] The electrical characteristic signals of each phase cable core and sheath are detected at both ends of the cross-interconnection section;

[0009] The faulty phase and faulty sheath are determined by the electrical characteristic signals of each phase cable core and sheath, so as to determine the cross-connection sub-segment where the fault is located.

[0010] In some embodiments, waveforms of core currents of each phase cable core and waveforms of sheath currents of each phase sheath are detected at both ends of the crossbonding section;

[0011] Polarities of the core currents of each phase at both ends of the crossbonding section are determined according to the waveforms of the core currents, and polarities of the sheath currents of each phase at both ends of the crossbonding section are determined according to the waveforms of the sheath currents;

[0012] Whether a fault exists in the crossbonding section is determined according to the polarities of the core currents at both ends of the crossbonding section;

[0013] After determining that a fault exists, a fault phase is determined according to the core currents of each phase, and a fault sheath is determined according to the sheath currents of each phase.

[0014] In some embodiments, the method further comprises:

[0015] If the fault phase is three-phase, a crossbonding subsection where the fault is located is determined according to the polarities of the core currents of three phases and the polarities of the sheath currents of three phases at both ends of the crossbonding section;

[0016] Or, if the fault phase is single-phase or two-phase, a crossbonding subsection where the fault is located is determined according to the fault phase and the fault sheath.

[0017] In some embodiments, determining whether a fault exists in the crossbonding section according to the polarities of the core currents at both ends of the crossbonding section comprises the following steps:

[0018] It is determined whether the polarities of the core currents at both ends of the crossbonding section are opposite;

[0019] If the polarities of the core currents of any phase at both ends of the crossbonding section are opposite, it is determined that a fault exists in the crossbonding section.

[0020] In some embodiments, determining a fault phase according to the core currents of each phase comprises the following steps:

[0021] A cable core phase with a core current greater than a set core current threshold value is determined as the fault phase.

[0022] In some embodiments, determining a fault sheath according to the sheath currents of each phase comprises the following steps:

[0023] A sheath with a sheath current greater than a set sheath current threshold value is determined as the fault sheath.

[0024] In some embodiments, determining a fault phase according to the core currents of each phase comprises the following steps:

[0025] The core current is one of a power frequency current, a traveling wave current and a transient current.

[0026] The sheath current is one of a power frequency current, a traveling wave current and a transient current.

[0027] In some embodiments, the method further comprises the steps of:

[0028] If the power transmission cable comprises a plurality of the cross-linked large sections, determining whether a corresponding cross-linked large section has a fault according to the electrical characteristic signals of all the sheaths;

[0029] After determining that the corresponding cross-linked large section has a fault, determining a fault phase according to the electrical characteristic signals of the cable cores of each phase at both ends of the power transmission cable;

[0030] Determining a fault sheath according to the electrical characteristic signals of the sheaths of each phase at both ends of the corresponding cross-linked large section;

[0031] According to the determined fault phase and fault sheath, determining a cross-linked sub-section where the fault is located.

[0032] In a second aspect, the present application also provides a power transmission cable fault interval positioning device, which comprises:

[0033] A detection device configured to detect electrical characteristic signals of cable cores of each phase and sheaths at both ends of the cross-linked large section;

[0034] A processing device configured to determine a fault phase and a fault sheath according to the electrical characteristic signals of the cable cores of each phase and the sheaths, so as to determine a cross-linked sub-section where the fault is located.

[0035] In a third aspect, the present application also provides a power transmission cable fault interval positioning system, which comprises:

[0036] A power transmission cable comprising at least one cross-linked large section;

[0037] A detection device installed at both ends of the cross-linked large section and configured to detect electrical characteristic signals of cable cores of each phase and sheaths at both ends of the cross-linked large section;

[0038] A processing device connected with the detection device and configured to determine a fault phase and a fault sheath according to the electrical characteristic signals of the cable cores of each phase and the sheaths, so as to determine a cross-linked sub-section where the fault is located.

[0039] The application provides a power cable fault interval positioning method, device and system, which detects the electrical characteristic signals of each phase cable core and the sheath at two ends of the cross-connection large section; determines the fault phase and the fault sheath according to the electrical characteristic signals of each phase cable core and the sheath, so as to determine the cross-connection sub-section where the fault is located. When the cross-connection large section has a fault, the electrical characteristic signals of the core and the sheath are used to accurately determine the cable core phase and the cross-connection sub-section where the fault is located, the fault interval is accurately positioned, and the method is simple and is not affected by the environment. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0041] Figure 1 It is a schematic diagram of the cross-connection large section of the power cable.

[0042] Figure 2 It is a schematic diagram of the installation position of the power cable fault interval positioning device.

[0043] Figure 3 It is a first cross-connection mode of the cross-connection large section.

[0044] Figure 4 It is a second cross-connection mode of the cross-connection large section.

[0045] Figure 5 It is a flowchart of a power cable fault interval positioning method provided by the embodiment of the application.

[0046] Figure 6 It is a schematic block diagram of a power cable fault interval positioning device provided by the embodiment of the application.

[0047] The implementation, functional features and advantages of the application will be further described with reference to the embodiments and the drawings. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the application will be described clearly and completely with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are some embodiments of the application, not all embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0049] The flowchart shown in the drawings is only an example and does not necessarily include all the contents and operations / steps, nor does it have to be executed in the order described. For example, some operations / steps can be further divided, combined or partially merged, so the actual execution order can be changed according to the actual situation.

[0050] Embodiments of the present application provide a power cable fault interval positioning method, device and system.

[0051] Some embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the case of no conflict, the following embodiments and features in the embodiments can be combined with each other.

[0052] The power cable fault interval positioning method of the present application is applied to a cross-interlinked large section of a power cable, as shown in Figure 1 and Figure 2 . As shown in Figure 3 and Figure 4 , each cross-interlinked large section includes three-phase cable cores, and each phase cable core is provided with a sheath on the outside. Each phase cable core is provided with 3 sub-sheaths on the outside, so that the three-phase cable cores are provided with 9 sub-sheaths on the outside. The sub-sheaths can be cross-linked in the manner shown in Figure 3 or Figure 4 . The cross-interlinked large section is divided into a plurality of cross-interlinked sub-sections according to the sub-sheaths, and the interval corresponding to the sub-sheath is the cross-interlinked sub-section.

[0053] Please refer to Figure 5 , Figure 5 for a flowchart of a power cable fault interval positioning method provided by an embodiment of the present application.

[0054] As shown in Figure 1 , the method includes steps S1 to S2.

[0055] Step S1, detecting the electrical characteristic signals of each phase cable core and sheath at both ends of the cross-interlinked large section.

[0056] Step S2, determining the fault phase and fault sheath according to the electrical characteristic signals of each phase cable core and sheath, to determine the cross-interlinked sub-section where the fault is located.

[0057] Specifically, waveforms of core currents of each phase cable core and waveforms of sheath currents of each phase sheath are detected at two ends of the cross-connection large section; polarities of the core currents of each phase at two ends of the cross-connection large section are determined according to the waveforms of the core currents, and polarities of the sheath currents of each phase at two ends of the cross-connection large section are determined according to the waveforms of the sheath currents; whether the cross-connection large section has a fault is determined according to the polarities of the core currents at two ends of the cross-connection large section; after it is determined that there is a fault, a fault phase is determined according to the core currents of each phase, and a fault sheath is determined according to the sheath currents of each phase.

[0058] As shown in the figures, Figure 2 In the embodiment of the present application, a power cable fault interval positioning device is arranged at each end of the cross-connection large section, and the power cable interval positioning device is installed at a direct grounding box or a protective grounding box at each end of the cross-connection large section. As shown in the figures, Figure 3 and Figure 4 Each device detects a waveform of a core current of each phase of three-phase power cores at the end where the device is located, and detects a waveform of a sheath current of three-phase sheaths. The waveform of the current contains characteristic information of the current, and after the waveform of the core current is detected, the polarity and size of the core current can be determined, and after the waveform of the sheath current is detected, the polarity and size of the sheath current can be determined.

[0059] It is worth noting that the core current can be one of a power frequency current, a traveling wave current and a transient current, and the sheath current can also be one of a power frequency current, a traveling wave current and a transient current.

[0060] Further, whether the cross-connection large section has a fault is determined according to the polarities of the core currents at two ends of the cross-connection large section, including the following steps:

[0061] It is determined whether the polarities of the core currents at two ends of the cross-connection large section are opposite; if the polarities of the core currents of any phase at two ends of the cross-connection large section are opposite, it is determined that the cross-connection large section has a fault.

[0062] It can be understood that if the polarities of the core currents of any phase cable core at two ends are opposite, it is determined that the cross-connection large section has a fault, and if the polarities of the core currents of each phase of three-phase cable cores at two ends are the same, the cross-connection large section does not have a fault. That is, as long as the polarities of the core currents of any single phase, any two phases or three phases of cable cores at two ends of the cross-connection large section are opposite, it is determined that the cross-connection large section has a fault. The polarity of the core current is the positive and negative polarity of the current.

[0063] Further, the fault phase is determined according to the core currents of each phase, including the following steps:

[0064] A cable phase with a core current exceeding a set core current threshold is identified as a faulty phase. This set core current threshold can be the core current of a fault-free cable phase. Because when a single-phase cable core experiences a fault, the core current of that phase will abnormally increase, a phase is identified as faulty when its core current exceeds that of a fault-free phase.

[0065] Furthermore, determining the faulty sheath based on the sheath current of each phase specifically includes the following steps:

[0066] A sheath with a sheath current exceeding a set sheath current threshold is designated as a faulty sheath. This set sheath current threshold can be the sheath current of the corresponding sheath of a fault-free cable core. This is because when a cable fault occurs, current flows through the corresponding sheath, resulting in a higher sheath current for that sheath compared to others.

[0067] In a preferred embodiment, after determining the faulty phase and the faulty sheath, the cross-connection sub-segment where the fault is located is determined based on the polarity of the core current of each phase cable core and the polarity of the sheath current.

[0068] Specifically, if the faulty phase is single-phase or two-phase, the cross-connection segment where the fault is located is determined based on each faulty phase and each faulty sheath, without needing to use the polarity of the core wire current and the sheath current. If the faulty phase is three-phase, the cross-connection segment where the fault is located is determined based on the polarity of the three-phase core wire current and the polarity of the three-phase sheath current at both ends of the cross-connection segment. When determining the cross-connection segment where the fault is located, it is also necessary to consider the cross-connection method.

[0069] If the cross-connection method for a large segment is as follows: Figure 3 The first cross-interconnection method is shown. The sheaths for the first phase are A1, A2, and A3; the sheaths for the second phase are B1, B2, and B3; and the sheaths for the third phase are C1, C2, and C3. The sheaths correspond to the cross-interconnection sub-segments. Within a large cross-interconnection segment, the first cross-interconnection method for the sheaths is A1-B2-C3 connection, B1-C2-A3 connection, and C1-A2-B3 connection. When detecting the sheath current, the sheath current is detected at points A (left), B (left), C (left), A (right), B (right), and C (right) of the sheath.

[0070] Exemplary, in such Figure 3When the fault phase is one phase in the first cross-connection mode shown, if the fault phase is A phase and the fault shield is A1-B2-C3, the currents of the left A shield and the right C shield will obviously increase. Through analysis, it can be concluded that the cross-connection sub-section 1 generates a fault, and the final fault interval is the A phase sub-section 1. The principle is that when the cable core of the A phase sub-section 1 generates a fault, the fault current will flow through the A1 of the corresponding shield, and because the A1-B2-C3 connects the entire shield current, the currents of the left A shield and the right C shield will increase. Therefore, based on the above principle, the fault cross-connection sub-section can be determined according to the fault phase and the fault shield.

[0071] As a preferred embodiment, the fault sub-section judgment table of the first single-phase fault can be pre-set in the power cable fault interval positioning device according to the first cross-connection mode of the cross-connection large section. The fault sub-section judgment table of the first single-phase fault is shown in Table 1. After the fault phase and the fault shield are determined, the fault cross-connection sub-section can be determined by table lookup, so that the fault interval can be quickly and accurately determined.

[0072] Table 1 Fault sub-section judgment table of the first single-phase fault

[0073]

[0074]

[0075] Further, when the fault phase is two phases, the fault cross-connection sub-section can also be determined according to the principle when the fault is single-phase. Similarly, the fault sub-section judgment table of the first two-phase fault shown in Table 2 can be pre-set in the power cable fault interval positioning device according to the first cross-connection mode of the cross-connection large section, and the fault cross-connection sub-section can be determined by table lookup, so that the fault interval can be accurately determined.

[0076] Table 2 Fault sub-section judgment table of the first two-phase fault

[0077]

[0078] It is worth noting that when the fault phase is three phases, in addition to combining the fault phase and the fault shield, the polarity of the core current and the polarity of the shield current also need to be combined to determine the fault cross-connection sub-section. When the fault phase is three phases, the method of determining the fault cross-connection sub-section can be determined according to the polarity of the core current at the head end of the three-phase cable and the polarity of the shield current at both ends. Specifically, the fault sub-section judgment table of the first three-phase fault shown in Table 3 can be referred to.

[0079] Table 3 Fault sub-section judgment table of the first three-phase fault

[0080]

[0081]

[0082] If the cross-connection method for a large segment is as follows: Figure 4 The second cross-interconnection method is shown. The sheaths for the first phase are A1, A2, and A3; the sheaths for the second phase are B1, B2, and B3; and the sheaths for the third phase are C1, C2, and C3. The sheaths correspond to the cross-interconnection sub-segments. Within a large cross-interconnection segment, the cross-interconnection method for the sheaths is A1-C3-B3 connection, B1-A2-C3 connection, and C1-B2-A3 connection. When the faulty phase is one phase, the faulty sub-segment can be determined according to the faulty sub-segment judgment table for the second type of single-phase fault in Table 4. When the faulty phase is two phases, the faulty sub-segment can be determined according to the faulty sub-segment judgment table for the second type of two-phase fault in Table 5. When the faulty phase is three phases, the faulty sub-segment can be determined according to the faulty sub-segment judgment table for the second type of three-phase fault in Table 6.

[0083] Table 4. Fault Segment Judgment Comparison Table for the Second Type of Single-Phase Fault

[0084]

[0085] Table 5. Fault Segment Judgment Comparison Table for the Second Type of Two-Phase Fault

[0086]

[0087]

[0088] Table 6. Fault Segment Judgment Comparison Table for the Second Type of Three-Phase Fault

[0089]

[0090] In some embodiments, if the power transmission cable includes multiple cross-interconnected segments, only the fault location devices at both ends of the power transmission cable need to simultaneously detect the core current and sheath current, while other devices only need to detect the sheath current. After detecting the core current and sheath current, the presence of a fault in the corresponding cross-interconnected segment is determined based on the electrical characteristic signals of all the sheaths. After determining that a fault exists in the corresponding cross-interconnected segment, the faulty phase is determined based on the electrical characteristic signals of the core wires of each phase at both ends of the power transmission cable. The faulty sheath is determined based on the electrical characteristic signals of the sheaths of each phase at both ends of the corresponding cross-interconnected segment. Based on the determined faulty phase and faulty sheath, the cross-interconnected sub-segment where the fault is located is determined.

[0091] Because the cable cores in the interlinked large section on the power transmission cable are continuous, only the core currents at both ends of the interlinked large section need to be detected to determine which phase of the power transmission core is faulty. When a power transmission core in a cross interlinked large section is faulty, the sheath current of the sheath in the cross interlinked large section increases, so whether the cross interlinked large section where the fault is located and the faulty sheath in the cross interlinked large section can be determined according to whether the sheath current exceeds a set sheath current threshold. After the cross interlinked large section, the faulty phase, and the faulty sheath in the cross interlinked large section are determined, the fault interval can be determined according to the core current and its polarity and the sheath current and its polarity according to the method for determining the cross interlinked sub-section where the fault is located.

[0092] The application provides a power transmission cable fault interval positioning method, device, and system. The electrical characteristic signals of each phase cable core and sheath are detected at both ends of the cross interlinked large section. The fault phase and the faulty sheath are determined according to the electrical characteristic signals of each phase cable core and sheath to determine the cross interlinked sub-section where the fault is located. When the cross interlinked large section is faulty, the cable core phase and the cross interlinked sub-section where the fault is located can be accurately determined according to the core current and its polarity and the sheath current and its polarity, the fault interval can be accurately positioned, the method is simple to implement, and the positioning of the fault interval is not affected by the environment.

[0093] As shown in Figure 6 The application also provides a power transmission cable fault interval positioning device. The device comprises:

[0094] A detection device configured to detect the electrical characteristic signals of each phase cable core and sheath at both ends of the cross interlinked large section;

[0095] A processing device configured to determine the fault phase and the faulty sheath according to the electrical characteristic signals of each phase cable core and sheath to determine the cross interlinked sub-section where the fault is located.

[0096] The detection device is further configured to detect the waveforms of the core currents of each phase cable core and the waveforms of the sheath currents of each phase sheath at both ends of the cross interlinked large section;

[0097] The polarities of the core currents of each phase at both ends of the cross interlinked large section are determined according to the waveforms of the core currents, and the polarities of the sheath currents of each phase at both ends of the cross interlinked large section are determined according to the waveforms of the sheath currents;

[0098] The processing device is further configured to determine whether the cross interlinked large section is faulty according to the polarities of the core currents at both ends of the cross interlinked large section;

[0099] After it is determined that there is a fault, the fault phase is determined according to the core currents of each phase, and the faulty sheath is determined according to the sheath currents of each phase.

[0100] wherein the core current is one of a power frequency current, a traveling wave current and a transient current;

[0101] the sheath current is one of a power frequency current, a traveling wave current and a transient current.

[0102] wherein the processing device is further configured to determine the cross-linking sub-section where the fault is located according to the polarity of the three-phase core current and the polarity of the three-phase sheath current at both ends of the cross-linking large section if the fault phase is three-phase.

[0103] Alternatively, if the fault phase is single-phase or two-phase, the cross-linking sub-section where the fault is located is determined according to each fault phase and each fault sheath.

[0104] wherein the processing device is further configured to determine whether the polarity of the core current at both ends of the cross-linking large section is opposite;

[0105] if the polarity of the core current of any phase at both ends of the cross-linking large section is opposite, it is determined that the cross-linking large section has a fault.

[0106] wherein the processing device is further configured to determine the cable core phase with a core current greater than a set core current threshold as a fault phase;

[0107] wherein the processing device is further configured to determine the sheath with a sheath current greater than a set sheath current threshold as a fault sheath.

[0108] wherein the processing device is further configured to determine whether the corresponding cross-linking large section has a fault according to the electrical characteristic signals of all the sheaths if the power transmission cable includes a plurality of cross-linking large sections;

[0109] after determining that the corresponding cross-linking large section has a fault, the fault phase is determined according to the electrical characteristic signals of each phase cable core at both ends of the power transmission cable;

[0110] the fault sheath is determined according to the electrical characteristic signals of each phase sheath at both ends of the corresponding cross-linking large section;

[0111] the cross-linking sub-section where the fault is located is determined according to the determined fault phase and fault sheath.

[0112] The embodiments of the present application also provide a power transmission cable fault interval positioning system, which comprises:

[0113] a power transmission cable comprising at least one cross-linking large section;

[0114] a detection device installed at both ends of the cross-linking large section and configured to detect electrical characteristic signals of each phase cable core and sheath at both ends of the cross-linking large section;

[0115] A processing device is connected with the detecting device, and is configured to determine the fault phase and the fault sheath according to the electrical characteristic signals of the phase cable core and the sheath, so as to determine the cross-interlinked sub-section where the fault is located.

[0116] It should be noted that, for the convenience and brevity of description, the specific working processes of the above-described devices, modules and units can refer to the corresponding processes in the foregoing embodiments, and will not be described here.

[0117] It should be noted that, in this document, the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusion, so that processes, methods, articles or systems that include a series of elements not only include those elements, but also include other elements not explicitly listed, or further include elements inherent in such processes, methods, articles or systems. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of other identical elements in the process, method, article or system that includes the element.

[0118] The above-mentioned sequence number of the embodiments of the present application is only for description, and does not represent the advantages and disadvantages of the embodiments. The above description is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for fault section location of a power cable, which is applied to a cross-linked large section of a power cable, the cross-linked large section comprising three-phase cable cores and a sheath provided outside each phase cable core, and the cross-linked large section is divided into a plurality of cross-linked sub-sections by the sheath, characterized in that, comprising the steps of: detecting electrical signatures of each phase cable core and shield at both ends of the cross-bonded section; determining the faulted phase and faulted shield according to the electrical signatures of each phase cable core and shield to determine the cross-bonded subsection where the fault is located; wherein waveforms of core current of each phase cable core and waveforms of shield current of each phase shield are detected at both ends of the cross-bonded section; polarities of core current of each phase at both ends of the cross-bonded section are determined according to the waveforms of core current, and polarities of shield current of each phase at both ends of the cross-bonded section are determined according to the waveforms of shield current; whether there is a fault in the cross-bonded section is determined according to the polarities of core current at both ends of the cross-bonded section; after determining that there is a fault, the faulted phase is determined according to the core current of each phase, and the faulted shield is determined according to the shield current of each phase; if the faulted phase is three-phase, the cross-bonded subsection where the fault is located is determined according to the polarities of three-phase core current and the polarities of three-phase shield current at both ends of the cross-bonded section.

2. The method of claim 1, wherein: if the faulted phase is single-phase or two-phase, the cross-bonded subsection where the fault is located is determined according to the faulted phase and the faulted shield.

3. The method of claim 1, wherein, whether there is a fault in the cross-bonded section according to the polarities of core current at both ends of the cross-bonded section comprises the steps of: determining whether the polarities of core current at both ends of the cross-bonded section are opposite; if the polarities of core current of any phase at both ends of the cross-bonded section are opposite, it is determined that there is a fault in the cross-bonded section.

4. The method of claim 1, wherein, determining the faulted phase according to the core current of each phase specifically comprises the steps of: determining the cable core phase whose core current is greater than a set core current threshold as the faulted phase.

5. The method of claim 1, wherein, determining the faulted shield according to the shield current of each phase specifically comprises the steps of: determining the shield whose shield current is greater than a set shield current threshold as the faulted shield.

6. The method of claim 1, wherein: the core current is one of power frequency current, traveling wave current and transient current; the shield current is one of power frequency current, traveling wave current and transient current.

7. The method of claim 1, wherein, further comprising the steps of: if the power transmission cable comprises a plurality of cross-bonded sections, whether there is a fault in the corresponding cross-bonded section is determined according to the electrical signatures of all the shields; after determining that there is a fault in the corresponding cross-bonded section, the faulted phase is determined according to the electrical signatures of each phase cable core at both ends of the power transmission cable; the faulted shield is determined according to the electrical signatures of each phase shield at both ends of the corresponding cross-bonded section; the cross-bonded subsection where the fault is located is determined according to the determined faulted phase and faulted shield.

8. A power cable fault location apparatus, characterized by comprising: a detection device configured to detect electrical signatures of each phase cable core and shield at both ends of the cross-bonded section; a processing device configured to determine the faulted phase and faulted shield according to the electrical signatures of each phase cable core and shield to determine the cross-bonded subsection where the fault is located; The detection device is further configured to detect the waveform of the core current of each phase cable core and the waveform of the sheath current of each phase sheath at both ends of the cross-interlinked large section. The polarity of the core current of each phase at both ends of the cross-interlinked large section is determined according to the waveform of the core current, and the polarity of the sheath current of each phase at both ends of the cross-interlinked large section is determined according to the waveform of the sheath current. The processing device is further configured to determine whether there is a fault in the cross-interlinked large section according to the polarity of the core current at both ends of the cross-interlinked large section. After determining that there is a fault, the fault phase is determined according to the core current of each phase, and the fault sheath is determined according to the sheath current of each phase. The processing device is further configured to determine the cross-interlinked sub-section where the fault is located according to the polarity of the core current of three phases and the polarity of the sheath current of three phases at both ends of the cross-interlinked large section if the fault phase is three phases.

9. A power cable fault location system, characterized by The power transmission cable comprises at least one cross-interlinked large section. A detection device is installed at both ends of the cross-interlinked large section and is configured to detect the electrical characteristic signals of each phase cable core and sheath at both ends of the cross-interlinked large section. A processing device is connected with the detection device and is configured to determine the fault phase and the fault sheath according to the electrical characteristic signals of each phase cable core and sheath, so as to determine the cross-interlinked sub-section where the fault is located. The detection device is further configured to detect the waveform of the core current of each phase cable core and the waveform of the sheath current of each phase sheath at both ends of the cross-interlinked large section. The polarity of the core current of each phase at both ends of the cross-interlinked large section is determined according to the waveform of the core current, and the polarity of the sheath current of each phase at both ends of the cross-interlinked large section is determined according to the waveform of the sheath current. The processing device is further configured to determine whether there is a fault in the cross-interlinked large section according to the polarity of the core current at both ends of the cross-interlinked large section. After determining that there is a fault, the fault phase is determined according to the core current of each phase, and the fault sheath is determined according to the sheath current of each phase. The processing device is further configured to determine the cross-interlinked sub-section where the fault is located according to the polarity of the core current of three phases and the polarity of the sheath current of three phases at both ends of the cross-interlinked large section if the fault phase is three phases. ​

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