An armored shielding direct current cable grounding wire breakage fault early warning method and system

Abstract

This invention discloses a method and system for early warning of grounding wire breakage in armored shielded DC cables. The method includes: measuring the grounding current of the shielding layer and the grounding current of the armoring layer at both ends of the armored shielded DC cable; calculating the waveform similarity between the grounding current of the armoring layer and the grounding current of the shielding layer at each end; comprehensively judging whether a grounding wire breakage has occurred at each end based on the current amplitude, waveform similarity, cable operating status, and grounding grid health status; and issuing a corresponding breakage warning signal when a grounding wire breakage occurs. This invention can effectively improve the operation and maintenance level of substation secondary circuits.

Description

Technical Field

[0001] This invention belongs to the field of operation and maintenance technology of substation secondary systems, and relates to a method and system for early warning of grounding wire breakage faults in armored shielded DC cables. Background Technology

[0002] The secondary system of a substation is the "nervous system" of the substation system. Currently, a large number of DC cables, such as control cables, in substations use armored shielded cables. The shielding layer of these cables is generally copper foil or copper braid covering the conductor, which can shield the conductor from external electromagnetic interference and also shield the electromagnetic field generated by the conductor from external interference. The armor layer of these cables can significantly improve the mechanical properties of the cable, prevent the cable from being chewed by animals, and also play a positive role in preventing external damage.

[0003] Since the armor layer is also a metal covering the conductor, it can provide a certain degree of interference immunity. In many regions, both ends of the armor layer are grounded to enhance the interference immunity of DC cables. On the other hand, because both ends of the cable armor layer are grounded through grounding wires, if a loop is formed in the armor layer due to certain conditions such as ground potential difference or strong magnetic environment, current may flow through the armor layer for a long time. If the grounding process of the armor layer is poor, long-term harsh operating environment may cause the grounding wire of the armor layer to break. A broken wire may reduce the interference immunity of the DC cable and is not conducive to the safe and stable operation of the DC cable. However, since a broken grounding wire of the armor layer does not directly affect the signal transmission of the DC cable, it is difficult to detect through conventional methods.

[0004] Existing methods for analyzing broken armor and shielding grounding wires mainly include visual inspection and power outage inspection. Visual inspection involves observing the grounding wires during routine substation inspections to determine if a break has occurred. However, since cables are generally located in cable trenches, this method is very inefficient, only detecting a very small number of broken grounding wires. The break is only visible to the naked eye if the outer sheath is also damaged. Power outage inspection involves injecting a small current into the armor and shielding layers of the relevant cables during power outages for maintenance. The current reading is then used to determine if a broken grounding wire has occurred. This method is limited by the timing of the power outage, requires special current-carrying devices, and may be unusable if the circuit spans multiple bays. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method and system for early warning of grounding wire breakage in armored shielded DC cables, thereby improving the operation and maintenance level of DC cables and secondary circuits in substations.

[0006] The present invention adopts the following technical solution.

[0007] The first aspect of this invention proposes a method for early warning of grounding wire breakage faults in armored shielded DC cables, comprising: Measure the grounding current of the shielding layer and the grounding current of the armor layer at both ends of the armored shielded DC cable; For each end, calculate the waveform similarity between the armor layer grounding current and the shielding layer grounding current. For each end, a comprehensive judgment is made based on the current amplitude, waveform similarity, cable operating status, and grounding grid health status to determine whether a grounding wire breakage has occurred, and a corresponding breakage warning signal is issued when a grounding wire breakage occurs.

[0008] Preferably, the armored shielded DC cable is connected to a protective screen and a terminal box at both ends A and B, respectively.

[0009] Preferably, the measurement of the shielding layer grounding current and the armor layer grounding current at both ends of the armored shielded DC cable includes obtaining the following current signals: The effective value and instantaneous sampling value of the grounding wire current of the shielding layer at end A; the effective value and instantaneous sampling value of the grounding wire current of the armor layer at end A; the effective value and instantaneous sampling value of the grounding wire current of the shielding layer at end B; the effective value and instantaneous sampling value of the grounding wire current of the armor layer at end B.

[0010] Preferably, the step of calculating the waveform similarity between the armor layer grounding current and the shielding layer grounding current for each end includes:

[0011] in, The waveform similarity between the grounding current of the armor layer at end A of the cable and the grounding current of the shield layer; This is the instantaneous sampled value of the grounding current of the shield layer at end A of the cable; This is the t-th instantaneous sampled value of the grounding wire current of the armor layer at end A of the cable.

[0012] Preferably, This is the threshold value for low current control, ranging from 10mA to 100mA.

[0013] Preferably, the determination of whether a break in the armor layer grounding wire has occurred at each end is based on a comprehensive assessment of current amplitude, waveform similarity, cable operating status, and grounding grid health status. Specific criteria include:

[0014] in, This is the t-th instantaneous sampled value of the grounding wire current of the armor layer at end A of the cable in the overcurrent extreme value comparison data window; This represents the effective value of the grounding current of the shielding layer at end A of the cable. This is the extreme overcurrent alarm value for the armor layer at end A of the cable; This is the overcurrent range alarm value for the armor layer at end A of the cable; This is the overcurrent alarm value for the shielding layer at end A of the cable; , , The adjustment coefficient is determined based on the current ground network health status H; E represents the waveform similarity between the grounding current of the armor layer and the grounding current of the shield layer at end A of the cable; E=1 indicates that the cable is in operation. The waveform similarity threshold; The norm; Q is the total number of data points in the overcurrent extreme value comparison data window; M is the maximum value. j The total number of data points in sub-data window j within the range comparison data window; l This represents the number of sub-data windows in the range comparison data window; The first current of the armor layer grounding wire at cable end A in sub-data window j tj A number of instantaneous sampled values.

[0015] Preferably, The value range of A is [0.42, 1.41]. The value range of A is [0.57, 2.83]. The value range of A is [0.3, 1].

[0016] Preferably, the adjustment coefficient is determined as follows: When H=1 , , Take 1, 1, 1; When H=0 , , Use values ​​of 0.8, 0.8, and 1.2. Where H=1 indicates that the ground network is in normal health status, and H=0 indicates that the ground network is in abnormal health status.

[0017] A second aspect of this invention provides a fault early warning system for grounding wire breakage in armored shielded DC cables, comprising: The current measurement module is used to measure the grounding current of the shielding layer and the grounding current of the armor layer at both ends of the armored shielded DC cable, respectively. The similarity calculation module is used to calculate the waveform similarity between the armor layer grounding current and the shielding layer grounding current for each end. The grounding wire breakage warning module is used to comprehensively judge whether a grounding wire breakage has occurred at each end based on the current amplitude, waveform similarity, cable operating status, and grounding grid health status, and to issue a corresponding grounding wire breakage warning signal when a grounding wire breakage occurs.

[0018] A third aspect of the present invention provides a terminal, including a processor and a storage medium; the storage medium is used to store instructions; the processor is used to perform operations according to the instructions to execute the steps of the method.

[0019] A fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method.

[0020] Compared with the prior art, the beneficial effects of the present invention include at least the following: This invention proposes a criterion for judging grounding wire breakage based on a comprehensive analysis of current amplitude, waveform similarity, cable operating status, and grounding grid health status. This criterion enables real-time monitoring of DC cable grounding wire breakage faults, overcoming the shortcomings of relying on clamp meters to directly measure the current on the grounding wire to determine whether a breakage has occurred, which is difficult to monitor and determine in real time.

[0021] This invention takes into account both the accuracy of on-site measurements and the urgency of early warning for grounding wire breakage. It introduces a small current control threshold, which can improve the calculation accuracy of waveform similarity within the allowable error range. Furthermore, the calculation error range can be controlled by the value of the small current control threshold. Attached Figure Description

[0022] Figure 1 This refers to the cable grounding method on the field side. Figure 2 It is a double-ended grounding method for armored shielded DC cables; Figure 3 Logic diagram for determining the breakage of the grounding wire in the armor layer; Figure 4 This is a flowchart of the method of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0024] Embodiment 1 of this invention provides a method for early warning of grounding wire breakage faults in armored shielded DC cables. The overall idea of ​​this method is as follows: Utilizing the opening and closing of the local switch and disconnector (taking disconnector opening and closing as an example), monitor the current of the armored layer grounding wire in protection panel A and the armored layer grounding wire in box B on the protection room side to determine if a breakage has occurred. Due to the high coupling degree between the shielding layer and the armored layer, if the current of the shielding layer grounding wire on this side is large while the current current of the armored layer grounding wire is extremely small, it is very likely that the armored layer grounding point has been lost. Simultaneously, considering the significant impact of the grounding grid on the grounding wire current of the armored cable, if the grounding grid is abnormal, the alarm logic becomes more stringent. Specific judgment criteria are designed based on this idea. For example... Figure 4 As shown, the method specifically includes: Step 1: Measure the grounding current of the shielding layer and the grounding current of the armor layer at both ends of the armored shielded DC cable; More preferably, taking a field connection between box A (protective cabinet) and box B as an example, the grounding method is that both ends of the shielding layer are grounded, and both ends of the armor layer are grounded. That is, the shielding layer of the cable on the box A side is connected to the secondary ground busbar inside box A through the shielding layer grounding wire; the shielding layer of the cable on the box B side is connected to the secondary ground busbar inside box B through the shielding layer grounding wire. The armoring layer of the cable on the box A side is connected to the primary ground busbar inside box A through the armoring layer grounding wire; the armoring layer of the cable on the box B side is connected to the primary ground busbar inside box B through the armoring layer grounding wire. The grounding method of the cable on the field side is as follows: Figure 1 As shown, this method monitors the armor layer and shielding layer grounding wire current of the armored shielded cable, and records the shielding layer grounding wire current of the armored shielded cable in box A as... (RMS value), the grounding current of the armor layer in box A is recorded as... (RMS value). Similarly, the grounding current of the armored shielded cable in box B can be denoted as... (RMS value), the grounding wire current of the armor layer inside box B is recorded as... (RMS value). The double-end grounding method for armored shielded DC cables is as follows: Figure 2 As shown.

[0025] The specific measurement of cable connection current is as follows: Let's take the example of a measurement system with a sampling rate of M points per cycle. Without loss of generality, let the total number of measurement points be N points, which is a positive integer multiple of M points, i.e., a total of l cycles are collected, so N = lM. As defined before, let the effective value of the grounding current of the shielding layer of the armored shielded cable within the protective panel A be denoted as... The instantaneous sampled value is denoted as The effective value of the grounding current of the armor layer inside protective panel A is recorded as follows: The instantaneous sampled value is denoted as The effective value of the grounding current of the shielding layer of the armored shielded cable in terminal box B is recorded as: The instantaneous sampled value is denoted as The effective value of the grounding current of the armor layer inside terminal box B is recorded as follows: The instantaneous sampled value is denoted as .

[0026] Step 2: Calculate the waveform similarity between the armor layer grounding current and the shielding layer grounding current for each end; More preferably, the waveform similarity can be calculated using the cosine of the included angle formula:

[0027] In actual cases of wire breakage, the current may be small. When the current is extremely small, the relative error increases, which may lead to excessive waveform similarity error. When the denominator is close to zero, it may lead to an unreasonablely large value in waveform similarity.

[0028] To address this, this invention comprehensively considers both the accuracy of on-site measurements and the urgency of early warning for grounding wire breakage. It introduces a small current control threshold, which, under certain circumstances (below the small current control threshold), sacrifices some accuracy while resolving the aforementioned two problems within the allowable error range. Furthermore, the error range is controlled by the value of the small current control threshold. Specifically: Considering the coupling relationship between the shielding layer and the armor layer grounding wire, if the armor layer grounding wire is intact, the current is synchronized well with the shielding layer grounding wire. If the wire is broken, the current in the armor layer grounding wire on this side is smaller and the similarity between its waveform and the shielding layer grounding wire decreases. This invention proposes an improved cosine angle method to identify the similarity between the armor layer grounding wire waveform and the shielding layer waveform. This addresses the aforementioned M-dimensional... , Vectors, the algorithm for which is as follows:

[0029] in, To protect the waveform similarity between the grounding current of the armor layer of shield A and the grounding current of the shield layer; To protect the instantaneous sampling value of the grounding wire current of the armor layer within screen A; This is the instantaneous sampled value of the grounding current of the armored shielded cable within protective panel A; The threshold value is set for low current control. Considering that the current may be very small after the grounding wire of the armor layer is broken, which would cause the denominator of the cosine formula of the included angle to be too small, this value is set, with a range of 10mA-100mA and a typical value of 50mA.

[0030] It can be seen that the closer the improved cosine value D of the included angle is to 0, the lower the similarity.

[0031] Similarly, the waveform similarity calculation formula between the grounding current of the armor layer of terminal box B and the grounding current of the shield layer is as follows:

[0032] Step 3: For each end, comprehensively judge whether a grounding wire break has occurred based on the current amplitude, waveform similarity, cable operating status, and grounding grid health status. If a grounding wire break occurs, issue a corresponding break warning signal.

[0033] More preferably, such as Figure 3 As shown, the criteria for determining a broken ground wire in the armor layer of the protective screen are as follows:

[0034] in, The instantaneous sampled value of the armor layer grounding wire current in protection panel A within the overcurrent extreme value comparison data window; The effective value of the grounding current of the shielding layer inside protective panel A of the armored shielded cable.

[0035] for A certain norm of, here we take the 1-norm.

[0036] To protect the overcurrent extreme value alarm value of the armor layer on side A of the screen; To protect the overcurrent range alarm value of the armor layer on side A of the screen; To protect the overcurrent alarm value of the shielding layer on side A of the screen.

[0037] The value range can be set to [0.42, 1.41] (0.3A, 1A √2), and the empirical value is 0.71A (0.5A √2). The value range is [0.57, 2.83] The empirical value is taken as 1.13 A (because it is continuous). l Taking the maximum value from a data window is rather strict, therefore... l In each sub-data window, the current difference is considered as twice the effective value of 0.4A (√2 times 2, which is 1.13A), and the range is the difference between the maximum and minimum values. .

[0038] The value range can be set to [0.3, 1] (valid value), and the empirical value is 0.5A (valid value).

[0039] , , To adjust the coefficients to real numbers, the values ​​are determined based on the current health status H of the ground network. The first set of empirical values ​​is 1, 1, 1; the second set of empirical values ​​is 0.8, 0.8, 1.2.

[0040] H represents the current health status of the grounding network. When the grounding network is normal, H=1, and the adjustment coefficient is taken from the first set of empirical values. When the grounding network is abnormal, H=0, and the adjustment coefficient is taken from the second set of empirical values.

[0041] E represents the operating status of the cable. When the cable is in operation, E=1; when it is out of operation and not in testing state, E=2; when it is in testing state, E=3; when the cable's operating status is uncertain, E=0.

[0042] D represents the improved cosine value of the included angle. The waveform similarity between the grounding current of the armor layer at end A of the cable and the grounding current of the shield layer.

[0043] The waveform similarity threshold is set to 0.5-0.8, with a check value of 0.7.

[0044] Q represents the total number of data points in the overcurrent extreme value comparison data window; M represents the total number of data points in the overcurrent extreme value comparison data window. j The total number of data points in sub-data window j within the range comparison data window; l This represents the number of sub-data windows in the range comparison data window; The first current of the armor layer grounding wire at cable end A in sub-data window j tj A number of instantaneous sampled values.

[0045] In practice, t represents time, and the data points sampled within a certain data window are denoted as 1 for the first point and 2 for the second point. The extreme value comparison data window has two layers. At the time level, it's considered to be based on a greatest common divisor, such as 480, aligning the two ranges to 480 (one is counting to 480, and the other is...). Q represents the total number of data points in the overcurrent extreme value comparison data window. For example, if 48 points are sampled per cycle and 10 cycles need to be compared, then N is 480; M j M represents the total number of data points in the sub-data windows of the range comparison data window. For example, if 48 points are sampled per cycle and two cycles need to be compared, M represents the total number of data points in the sub-data windows. j That's 96; l This refers to the number of sub-data windows. For example, if you need to compare 5 data windows, l It's 5.

[0046] Once the criteria are met, a signal is sent: "The grounding wire of the armor layer of the XX cable in the XX protection panel is broken".

[0047] The criteria for determining a broken grounding wire in the armor layer on the terminal box side are as follows:

[0048] in, The instantaneous sampled value of the armored layer grounding wire current in terminal box B within the overcurrent extreme value comparison data window; The effective value of the grounding current of the shielding layer in terminal box B of the armored shielded cable.

[0049] for A certain norm of, here we take the 1-norm.

[0050] The alarm value for overcurrent extreme value of the armor layer on side B of the terminal box is 0.71 A, based on experience.

[0051] The overcurrent differential alarm value for the armor layer on the B side of the terminal box is taken as 1.13 A based on experience.

[0052] The overcurrent alarm value for the shielding layer on side B of the terminal box is taken as an empirical value of 0.5A.

[0053] , , To adjust the coefficients to real numbers, the first set of empirical values ​​is 1, 1, 1; the second set of empirical values ​​is 0.8, 0.8, 1.2.

[0054] H represents the current health status of the grounding network. When the grounding network is normal, H=1, and the adjustment coefficient is taken from the first set of empirical values. When the grounding network is abnormal, H=0, and the adjustment coefficient is taken from the second set of empirical values.

[0055] E represents the operating status of the cable. When the cable is in operation, E=1; when it is out of operation and not in testing state, E=2; when it is in testing state, E=3; when the cable's operating status is uncertain, E=0.

[0056] D represents the improved cosine value of the included angle. The waveform similarity between the grounding current of the armor layer at end B of the cable and the grounding current of the shield layer.

[0057] Once the criteria are met, a signal is sent: "The grounding wire of the armor layer of the XX cable in the XX terminal box is broken".

[0058] By replacing the armor layer parameters with shielding layer parameters and vice versa in the above criteria, the cable shielding layer grounding wire breakage detection can be achieved.

[0059] Embodiment 2 of the present invention provides a grounding wire breakage early warning system for armored shielded DC cables, comprising: The current measurement module is used to measure the grounding current of the shielding layer and the grounding current of the armor layer at both ends of the armored shielded DC cable, respectively. The similarity calculation module is used to calculate the waveform similarity between the armor layer grounding current and the shielding layer grounding current for each end. The grounding wire breakage warning module is used to comprehensively judge whether a grounding wire breakage has occurred at each end based on the current amplitude, waveform similarity, cable operating status, and grounding grid health status, and to issue a corresponding grounding wire breakage warning signal when a grounding wire breakage occurs.

[0060] Embodiment 3 of the present invention provides a terminal, including a processor and a storage medium; the storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method.

[0061] Embodiment 4 of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method.

[0062] Compared with the prior art, the beneficial effects of the present invention include at least the following: This invention proposes a criterion for judging grounding wire breakage based on a comprehensive analysis of current amplitude, waveform similarity, cable operating status, and grounding grid health status. This criterion enables real-time monitoring of DC cable grounding wire breakage faults, overcoming the shortcomings of relying on clamp meters to directly measure the current on the grounding wire to determine whether a breakage has occurred, which is difficult to monitor and determine in real time.

[0063] This invention takes into account both the accuracy of on-site measurements and the urgency of early warning for grounding wire breakage. It introduces a small current control threshold value. Under certain circumstances (when the current is less than the small current control threshold value), it can improve the calculation accuracy of waveform similarity within the allowable error range by sacrificing some accuracy. Furthermore, the calculation error range can be controlled by the value of the small current control threshold value.

[0064] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0065] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0066] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0067] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for early warning of grounding wire breakage fault in armored shielded DC cables, characterized in that, include: Measure the grounding current of the shielding layer and the grounding current of the armor layer at both ends of the armored shielded DC cable; For each end, calculate the waveform similarity between the armor layer grounding current and the shielding layer grounding current. For each end, a comprehensive judgment is made based on the current amplitude, waveform similarity, cable operating status, and grounding grid health status to determine whether a grounding wire breakage has occurred, and a corresponding breakage warning signal is issued when a grounding wire breakage occurs.

2. The method for early warning of grounding wire breakage fault in armored shielded DC cable according to claim 1, characterized in that: The armored shielded DC cable is connected to the protection panel and the terminal box at both ends A and B, respectively.

3. The method for early warning of grounding wire breakage fault in armored shielded DC cable according to claim 2, characterized in that: The measurement of the shielding layer grounding current and the armor layer grounding current at both ends of the armored shielded DC cable includes obtaining the following current signals: The effective value and instantaneous sampling value of the grounding wire current of the shielding layer at end A; the effective value and instantaneous sampling value of the grounding wire current of the armor layer at end A; the effective value and instantaneous sampling value of the grounding wire current of the shielding layer at end B; the effective value and instantaneous sampling value of the grounding wire current of the armor layer at end B.

4. The method for early warning of grounding wire breakage fault in armored shielded DC cable according to claim 1, characterized in that: The calculation of the waveform similarity between the armor layer grounding current and the shielding layer grounding current for each end includes: in, The waveform similarity between the grounding current of the armor layer at end A of the cable and the grounding current of the shield layer; This is the instantaneous sampled value of the grounding current of the shield layer at end A of the cable; t is the t-th instantaneous sampled value of the grounding wire current of the armor layer at end A of the cable, and M is the number of sampling points.

5. The method for early warning of grounding wire breakage fault in armored shielded DC cable according to claim 4, characterized in that: This is the threshold value for low current control, ranging from 10mA to 100mA.

6. The method for early warning of grounding wire breakage fault in armored shielded DC cable according to claim 1, characterized in that: The method for comprehensively judging whether a break in the armor layer grounding wire has occurred at each end is based on current amplitude, waveform similarity, cable operating status, and grounding grid health status. Specific criteria include: in, This is the t-th instantaneous sampled value of the grounding wire current of the armor layer at end A of the cable in the overcurrent extreme value comparison data window; This represents the effective value of the grounding current of the shielding layer at end A of the cable. This is the extreme overcurrent alarm value for the armor layer at end A of the cable; This is the overcurrent range alarm value for the armor layer at end A of the cable; This is the overcurrent alarm value for the shielding layer at end A of the cable; , , The adjustment coefficient is determined based on the current ground network health status H; E represents the waveform similarity between the grounding current of the armor layer and the grounding current of the shield layer at end A of the cable; E=1 indicates that the cable is in operation. The waveform similarity threshold; The norm; Q is the total number of data points in the overcurrent extreme value comparison data window; M is the maximum value. j The total number of data points in sub-data window j within the range comparison data window; l This represents the number of sub-data windows in the range comparison data window; The first current of the armor layer grounding wire at cable end A in sub-data window j tj A number of instantaneous sampled values.

7. The method for early warning of grounding wire breakage fault in armored shielded DC cable according to claim 6, characterized in that: The value range of A is [0.42, 1.41]. The value range of A is [0.57, 2.83]. The value range of A is [0.3, 1].

8. The method for early warning of grounding wire breakage fault in armored shielded DC cable according to claim 6, characterized in that: The adjustment coefficient is determined as follows: When H=1 , , Take 1, 1, 1; When H=0 , , Use values ​​of 0.8, 0.8, and 1.

2. Where H=1 indicates that the ground network is in normal health status, and H=0 indicates that the ground network is in abnormal health status.

9. A fault early warning system for grounding wire breakage of an armored shielded DC cable, comprising the method described in any one of claims 1-8, characterized in that, The system includes: The current measurement module is used to measure the grounding current of the shielding layer and the grounding current of the armor layer at both ends of the armored shielded DC cable, respectively. The similarity calculation module is used to calculate the waveform similarity between the armor layer grounding current and the shielding layer grounding current for each end. The grounding wire breakage warning module is used to comprehensively judge whether a grounding wire breakage has occurred at each end based on the current amplitude, waveform similarity, cable operating status, and grounding grid health status, and to issue a corresponding grounding wire breakage warning signal when a grounding wire breakage occurs.

10. A terminal, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 1-8.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program implements the steps of the method according to any one of claims 1-8.

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