A cable fault detection method and system
By combining cable surface temperature and stress signals, the cable fault point can be initially located. By combining the spread spectrum time-domain reflectometry and electromagnetic field changes, the types of internal and surface faults of the cable can be identified. This solves the problem of false detection and missed detection in complex electromagnetic environments by traditional methods, and improves the accuracy and reliability of detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA UNIV OF MINING & TECH
- Filing Date
- 2025-05-29
- Publication Date
- 2026-05-26
AI Technical Summary
Existing cable fault detection methods are prone to false detections or missed detections in complex electromagnetic environments. Traditional spread spectrum time-domain reflectometry requires long-term signal transmission, resulting in low accuracy of detection results.
By acquiring temperature and stress signals from the cable surface, the abnormal location of the fault is initially located. The spread spectrum time-domain reflectometry method is used for internal cable inspection. Combined with changes in the electromagnetic field, the cable fault type is identified, including the type of fault at the cable fault point, the location of the cable fault point, the type of surface and internal faults of the cable, and the location of the cable fault point.
It improves the accuracy and reliability of cable fault detection, reduces false detections or missed detections caused by changes in reflected signal characteristics, and lowers system costs and computing resource requirements.
Smart Images
Figure CN120490692B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of cable testing technology, and in particular to a cable fault detection method and system. Background Technology
[0002] With the rapid development of power and communication systems, cable fault detection has become particularly important.
[0003] Traditional cable fault detection methods, such as manual inspection, time-domain reflectionometry (TDR), and impedance measurement, have limitations in fault type identification. While traveling wave methods offer high accuracy, they are costly and complex. Among traveling wave methods, spread-spectrum time-domain reflectionometry (SS-TDR) is widely used, estimating the distance to the fault point by measuring the transmission time of the reflected pulse signal.
[0004] Existing spread spectrum time-domain reflectometry requires long-term signal transmission during cable testing. However, in complex electromagnetic environments, the spread spectrum signal emitted by the equipment can interfere with other signals, causing changes in the characteristics of the reflected signal, resulting in false detections or missed detections, and affecting the accuracy of the test results. Summary of the Invention
[0005] Therefore, it is necessary to provide a cable fault detection method and system to address the aforementioned technical problems.
[0006] This invention provides a cable fault detection method, comprising:
[0007] Acquire temperature and stress signals from the surface of the cable under test;
[0008] When either the temperature signal or the stress signal exceeds a set threshold, the abnormal point of the cable under test is initially located to obtain the first fault point location; based on the change of electromagnetic field around the first fault point location on the surface of the cable under test, the fault type at the first fault point location is identified to obtain the second fault type.
[0009] The spread spectrum time-domain reflectometry method is used to detect faults inside the cable under test and obtain the location of the second fault point. The phase of the reflected signal corresponding to the location of the second fault point obtained by the spread spectrum time-domain reflectometry method is compared with the phase of the incident signal to identify the fault type inside the cable under test at the location of the second fault point and obtain the first fault type.
[0010] Based on the change in electromagnetic field around the first fault point on the surface of the cable under test, the fault type at the first fault point is identified, and the second fault type is obtained; based on the change in electromagnetic field around the second fault point on the surface of the cable under test, the fault type at the second fault point is identified, and the third fault type is obtained.
[0011] Based on the judgment results of whether the first fault location and the second fault location belong to the same fault location, and whether the first fault type, the second fault type and the third fault type belong to the same fault type, the fault detection result of the cable under test is obtained.
[0012] Optionally, based on the judgment results of whether the first fault location and the second fault location belong to the same fault location and whether the first fault type, the second fault type, and the third fault type belong to the same fault type, the fault detection result of the cable under test is obtained, specifically including:
[0013] When the locations of the first and second fault points are the same, the second and third fault types are merged, and it is determined whether the second and first fault types are the same. If they are the same, the second fault type is taken as the fault detection result of the cable under test; otherwise, the first and second fault types are taken as the fault detection results of the cable under test.
[0014] When the locations of the first and second fault points are different, determine whether the first and third fault types are the same. If they are the same, use the first and second fault types as the fault detection results of the cable under test; otherwise, use the first, second, and third fault types as the fault detection results of the cable under test.
[0015] Optionally, during the use of the spread spectrum time-domain reflectometry method, the phase of the reflected signal at the second fault location is compared with the phase of the incident signal to identify the fault type inside the cable under test at the second fault location.
[0016] If the phase of the reflected signal at the second fault point is out of phase with the phase of the incident signal, then a short circuit fault occurs inside the cable under test at the second fault point.
[0017] If the phase of the reflected signal at the second fault location is the same as the phase of the incident signal, then an open circuit occurs inside the cable under test at the second fault location.
[0018] Optionally, based on the electromagnetic field changes around the first fault location on the surface of the cable under test, the fault type at the first fault location is identified, specifically including:
[0019] If a high-frequency electromagnetic pulse appears on the surface of the cable under test around the location of the first fault point, then a short circuit fault occurs on the surface of the cable under test at the location of the first fault point.
[0020] If a low-frequency steady-state magnetic field and electric field signal appear on the surface of the cable under test around the location of the first fault point, a grounding fault occurs on the surface of the cable under test at the location of the first fault point.
[0021] If a high-frequency oscillating electromagnetic signal appears on the surface of the cable under test around the location of the first fault point, a partial discharge will occur on the surface of the cable under test at the location of the first fault point.
[0022] Optionally, the fault type at the second fault location can be identified based on the electromagnetic field changes around the surface of the cable under test at the second fault location, specifically including:
[0023] If a high-frequency electromagnetic pulse appears on the surface of the cable under test around the location of the second fault point, then a short circuit fault occurs on the surface of the cable under test at the location of the second fault point.
[0024] If a low-frequency steady-state magnetic field and electric field signal appear on the surface of the cable under test around the location of the second fault point, a grounding fault has occurred on the surface of the cable under test at the location of the second fault point.
[0025] If a high-frequency oscillating electromagnetic signal appears on the surface of the cable under test around the location of the second fault point, a partial discharge will occur on the surface of the cable under test at the location of the second fault point.
[0026] Optionally, the spread spectrum time-domain reflectometry method is used to detect faults inside the cable under test and obtain the location of the second fault point, specifically including:
[0027] Based on the time difference between signal transmission and reflected signal reception time, and the traveling wave propagation speed, the distance between the fault location and the signal transmitter is determined using the following formula:
[0028] ;
[0029] Where t is the time difference between the signal transmission time and the reflected signal reception time, v is the traveling wave propagation speed, and x is the distance between the fault location and the signal transmitting end;
[0030] Based on the distance between the fault location and the signal transmitting end, the cable fault location is located twice to obtain the second fault location.
[0031] This invention also provides a cable fault detection system, comprising:
[0032] The FODS module is used to acquire temperature and stress signals from the surface of the cable under test.
[0033] The anomaly analysis and location module is used to initially locate the anomaly point of the cable under test and obtain the location of the first fault point when either the temperature signal or the stress signal exceeds a set threshold.
[0034] The SS-TDR module is used to detect faults inside the cable under test using the spread spectrum time-domain reflectometry method to obtain the location of the second fault point. The phase of the reflected signal corresponding to the location of the second fault point obtained by the spread spectrum time-domain reflectometry method is compared with the phase of the incident signal to identify the fault type inside the cable under test at the location of the second fault point and obtain the first fault type.
[0035] The EMM module is used to identify the fault type at the first fault point location of the cable under test based on the electromagnetic field changes around the first fault point location, and obtain the second fault type; and to identify the fault type at the second fault point location based on the electromagnetic field changes around the second fault point location of the cable under test, and obtain the third fault type.
[0036] The fault comparison module is used to obtain the fault detection results of the cable under test based on the judgment results of whether the first fault point location and the second fault point location belong to the same fault point location and whether the first fault type, the second fault type and the third fault type belong to the same fault type.
[0037] The cable fault detection method and system provided in this invention have the following advantages compared with the prior art:
[0038] This invention can quickly identify anomalies and preliminarily determine the location of the fault point, i.e., the first fault point, by acquiring the temperature and stress signals on the cable surface. Subsequently, the spread spectrum time domain reflection method is used to conduct in-depth inspection of the inside of the cable to determine the location of the second fault point. In this process, the temperature and stress signals on the cable surface are used as prerequisites, and then the spread spectrum time domain reflection method is used to detect the inside of the cable, which effectively solves the problem that the traditional spread spectrum time domain reflection method requires a long time to transmit signals in cable detection.
[0039] Based on this, the present invention will also determine whether the first fault location and the second fault location belong to the same fault location, and determine whether the first fault type, the second fault type and the third fault type belong to the same fault type; by comparing and analyzing the detection results under the prerequisite conditions with the detection results inside the cable, it can reduce the false detection or missed detection caused by changes in the characteristics of the reflected signal, thereby improving the accuracy and reliability of the cable fault detection results. Attached Figure Description
[0040] Figure 1 This is a flowchart illustrating a cable fault detection method provided in one embodiment;
[0041] Figure 2 This is a flowchart illustrating a cable fault detection method provided in one embodiment;
[0042] Figure 3 This is a schematic diagram of the structure of a cable fault detection system provided in one embodiment;
[0043] Figure 4 This is a structural diagram of a cable fault detection system provided in one embodiment. Detailed Implementation
[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0045] like Figure 1 As shown, the present invention includes: First, performing cable fault early warning. Next, performing first fault location and second fault location. Fault type determination is performed on the two fault point locations, including first, second, and third fault type determinations (wherein, the second determination is for the first fault point location, and the first and third determinations are for the second fault point location). The two fault point locations are compared, and the three fault types are compared. Based on the comparison results, the fault detection result is output.
[0046] In one embodiment, a cable fault detection method is provided, such as... Figure 2 As shown, the method specifically includes:
[0047] Acquire the temperature and stress signals on the surface of the cable under test.
[0048] When either the temperature signal or the stress signal exceeds a set threshold, the abnormal point of the cable under test is initially located, and the location of the first fault point is obtained.
[0049] The spread spectrum time-domain reflectometry method is used to detect faults inside the cable under test and obtain the location of the second fault point. By comparing the phase of the reflected signal corresponding to the second fault point location obtained by the spread spectrum time-domain reflectometry method with the phase of the incident signal, the fault type inside the cable under test at the second fault point location is identified, and the first fault type is obtained.
[0050] Based on the changes in the electromagnetic field around the first fault point on the surface of the cable under test, the fault type at the first fault point is identified, resulting in a second fault type. Based on the changes in the electromagnetic field around the second fault point on the surface of the cable under test, the fault type at the second fault point is identified, resulting in a third fault type.
[0051] Based on the judgment results of whether the first fault location and the second fault location belong to the same fault location, and whether the first fault type, the second fault type and the third fault type belong to the same fault type, the fault detection result of the cable under test is obtained.
[0052] It is important to note that if two or more second fault locations are obtained after using the spread spectrum time-domain reflectometry, the second fault location closest to the first fault location and that first fault location should be used as the judgment objects. For other second fault locations that are not judgment objects, it is determined whether the first fault type and the third fault type of the cable under test are the same at the other second fault locations. If they are the same, the first fault type of the cable under test at the other second fault locations should be used as the fault detection result of the cable under test at those other second fault locations; otherwise, both the first fault type and the third fault type of the cable under test at those other second fault locations should be used as the fault detection result of the cable under test at those other second fault locations.
[0053] Furthermore, based on the electromagnetic field changes around the first fault location on the surface of the cable under test, the fault type at the first fault location is identified, specifically including:
[0054] If a high-frequency electromagnetic pulse appears on the surface of the cable under test around the location of the first fault point, then a short circuit fault has occurred on the surface of the cable under test at the location of the first fault point.
[0055] If a low-frequency steady-state magnetic field and electric field signal appear on the surface of the cable under test around the location of the first fault point, a grounding fault has occurred on the surface of the cable under test at the location of the first fault point.
[0056] If a high-frequency oscillating electromagnetic signal appears on the surface of the cable under test around the location of the first fault point, a partial discharge will occur on the surface of the cable under test at the location of the first fault point.
[0057] Furthermore, using the spread spectrum time-domain reflectometry method, fault detection is performed inside the cable under test to obtain the location of the second fault point, specifically including:
[0058] Based on the time difference between signal transmission and reflected signal reception time, and the traveling wave propagation speed, the distance between the fault location and the signal transmitter is determined using the following formula:
[0059] ;
[0060] Where t is the time difference between the signal transmission time and the reflected signal reception time, v is the traveling wave propagation speed, and x is the distance between the fault location and the signal transmitting end;
[0061] Based on the distance between the fault location and the signal transmitting end, the cable fault location is located twice to obtain the second fault location.
[0062] Furthermore, in the process of using the spread spectrum time-domain reflectometry method, the phase of the reflected signal at the second fault location is compared with the phase of the incident signal to identify the fault type inside the cable under test at the second fault location, specifically including:
[0063] If the phase of the reflected signal at the second fault location is out of phase with the phase of the incident signal, then a short circuit fault has occurred inside the cable under test at the second fault location.
[0064] If the phase of the reflected signal at the second fault location is the same as the phase of the incident signal, then an open circuit occurs inside the cable under test at the second fault location.
[0065] Furthermore, based on the electromagnetic field changes around the second fault location on the surface of the cable under test, the fault type at the second fault location is identified, specifically including:
[0066] If a high-frequency electromagnetic pulse appears on the surface of the cable under test around the location of the second fault point, then a short circuit fault occurs on the surface of the cable under test at the location of the second fault point.
[0067] If a low-frequency steady-state magnetic field and electric field signal appear on the surface of the cable under test around the location of the second fault point, a grounding fault has occurred on the surface of the cable under test at the location of the second fault point.
[0068] If a high-frequency oscillating electromagnetic signal appears on the surface of the cable under test around the location of the second fault point, a partial discharge will occur on the surface of the cable under test at the location of the second fault point.
[0069] Furthermore, based on the judgment results regarding whether the first fault location and the second fault location belong to the same fault location, and whether the first fault type, the second fault type, and the third fault type belong to the same fault type, the fault detection results of the cable under test are obtained, specifically including:
[0070] When the location of the first fault point is the same as the location of the second fault point, the second fault type and the third fault type are merged, and it is determined whether the second fault type and the first fault type are the same. If they are the same, the second fault type is taken as the fault detection result of the cable under test; otherwise, the first fault type and the second fault type are taken as the fault detection result of the cable under test.
[0071] When the locations of the first and second fault points are different, determine whether the first and third fault types are the same. If they are the same, use the first and second fault types as the fault detection results of the cable under test; otherwise, use the first, second, and third fault types as the fault detection results of the cable under test.
[0072] This invention provides a specific embodiment, including:
[0073] First, a preliminary diagnosis of the cable's operating condition is made based on temperature and stress signals:
[0074] Temperature and stress signals from the cable surface are acquired using distributed fiber optic sensors. These signals are compared to set thresholds. If either parameter exceeds the threshold, a fault is identified, and the location of the fault detected by the sensors is output, providing an initial location of the abnormal point in the cable under test, thus determining the first fault location. Then, spread spectrum time-domain reflectometry is used to detect faults inside the cable under test, determining the second fault location. If neither parameter exceeds a reference value, temperature and stress signal acquisition continues.
[0075] The phase of the reflected signal corresponding to the second fault location obtained by the spread spectrum time-domain reflection method is compared with the phase of the incident signal. If the reflected signal is out of phase with the incident wave, the cable is short-circuited. If the two are in phase, the fault is open-circuited. The first fault type judgment is output. If the maximum permissible error is not exceeded, the excitation signal is retransmitted.
[0076] Based on the changes in the electromagnetic field around the first fault point on the surface of the cable under test, the fault type at the first fault point is identified, resulting in a second fault type. Similarly, based on the changes in the electromagnetic field around the second fault point on the surface of the cable under test, the fault type at the second fault point is identified, resulting in a third fault type. The presence of high-frequency electromagnetic pulses indicates a short-circuit fault; the presence of low-frequency steady-state magnetic and electric field signals indicates a grounding fault; and the generation of high-frequency oscillating electromagnetic signals indicates partial discharge.
[0077] Based on the judgment results of whether the first fault location and the second fault location belong to the same fault location, and whether the first fault type, the second fault type and the third fault type belong to the same fault type, the fault detection result of the cable under test is obtained.
[0078] The specific steps are as follows:
[0079] S1 uses a distributed optical fiber sensing module to collect cable surface temperature and strain signals;
[0080] S2 determines whether either the temperature signal or the stress signal exceeds the reference value. If it does, proceed to S3; otherwise, return to S1.
[0081] S3 outputs a distributed fiber optic sensor to monitor abnormal locations, initially locate cable faults, and obtain the location of the first fault point.
[0082] S4 uses the spread spectrum time-domain reflectometry method to detect faults inside the cable under test and obtain the location of the second fault point.
[0083] S5 calculates the time difference between the reception time and the transmission time;
[0084] S6 calculates the distance between the fault point and the signal receiver based on the traveling wave propagation speed and time difference;
[0085] S7 outputs the location of the second fault point, and distinguishes it from the output signal of S3;
[0086] S8 compares the phase of the reflected signal corresponding to the second fault point location obtained by the spread spectrum time-domain reflection method with the phase of the incident signal to identify the fault type inside the cable under test at the second fault point location and obtain the first fault type.
[0087] S9. Based on the change in electromagnetic field around the first fault point on the surface of the cable under test, identify the fault type at the first fault point and obtain the second fault type. Based on the change in electromagnetic field around the second fault point on the surface of the cable under test, identify the fault type at the second fault point and obtain the third fault type.
[0088] S10 Based on the judgment results of whether the first fault location and the second fault location belong to the same fault location and whether the first fault type, the second fault type and the third fault type belong to the same fault type, the fault detection result of the cable under test is obtained.
[0089] S11 transmits the fault detection results to the monitoring equipment.
[0090] Based on the same inventive concept, the present invention also provides a cable fault detection system, such as... Figure 3 As shown, the system includes:
[0091] The FODS (Fiber Optic Distributed Sensing) module is used to acquire temperature and stress signals from the surface of the cable under test.
[0092] The anomaly analysis and location module is used to initially locate the anomaly point of the cable under test when either the temperature signal or the stress signal exceeds a set threshold, thus obtaining the location of the first fault point. Based on the electromagnetic field changes around the first fault point location on the surface of the cable under test, the fault type at the first fault point location is identified, thus obtaining the second fault type.
[0093] The SS-TDR module is used to detect internal faults in the cable under test using the spread spectrum time-domain reflectometry method, obtaining the location of a second fault point. By comparing the phase of the reflected signal corresponding to the second fault point location obtained by the spread spectrum time-domain reflectometry method with the phase of the incident signal, the fault type inside the cable under test at the second fault point location is identified, thus obtaining the first fault type.
[0094] The EMM (Electromagnetic Method) module is used to identify the fault type at the second fault location of the cable surface based on the electromagnetic field changes around the second fault location, and thus obtain the third fault type.
[0095] The fault comparison module is used to obtain the fault detection results of the cable under test based on the judgment results of whether the first fault point location and the second fault point location belong to the same fault point location and whether the first fault type, the second fault type and the third fault type belong to the same fault type.
[0096] like Figure 4 As shown, the fault comparison module includes a fault location comparison module and a fault type comparison module. The fault location comparison module is used to determine whether the first fault location and the second fault location belong to the same fault location, and the fault type comparison module is used to determine whether the first fault type, the second fault type, and the third fault type belong to the same fault type.
[0097] In addition, it also includes a communication module for transmitting fault detection results to monitoring equipment.
[0098] The beneficial effects that this invention can achieve include at least the following:
[0099] (1) The spread spectrum time-domain reflection method is started only after the distributed optical fiber sensor transmits the fault warning signal. There is no need to generate pseudo-random codes at all times, which reduces the required computing resources and hardware usage time, and lowers the system cost.
[0100] (2) The spread spectrum time domain reflection method can still be used under low signal-to-noise ratio conditions, has strong anti-interference ability, and improves the accuracy of fault location and fault type judgment.
[0101] (3) There are at least one technical aid for fault location and fault type identification. The SS-TDR module combined with the FODS module can accurately locate the fault location. The EMM module combined with the SS-TDR module can accurately identify the fault type, enhance the robustness of the system, have a certain tolerance for equipment failure or measurement error, and improve the accuracy and reliability of the system output results.
[0102] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.
Claims
1. A cable fault detection method, characterized in that, Including: Obtain the temperature signal and stress signal on the surface of the cable to be measured; When any one of the temperature signal and stress signal exceeds the set threshold, preliminarily locate the abnormal point of the cable to be measured to obtain the position of the first fault point; Use the extended spectrum time domain reflectometry to detect faults inside the cable to be measured to obtain the position of the second fault point; compare the phase of the reflected signal corresponding to the position of the second fault point obtained by the extended spectrum time domain reflectometry with the phase of the incident signal to identify the fault type at the position of the second fault point inside the cable to be measured, and obtain the first fault type; Identify the fault type at the position of the first fault point on the surface of the cable to be measured according to the electromagnetic field change around the position of the first fault point on the surface of the cable to be measured, and obtain the second fault type; Identify the fault type at the position of the second fault point on the surface of the cable to be measured according to the electromagnetic field change around the position of the second fault point on the surface of the cable to be measured, and obtain the third fault type; Obtain the fault detection result of the cable to be measured according to the judgment result of whether the position of the first fault point and the position of the second fault point belong to the same fault point position and whether the first fault type, the second fault type and the third fault type belong to the same fault type.
2. The cable fault detection method according to claim 1, wherein, The step of obtaining the fault detection result of the cable to be measured according to the judgment result of whether the position of the first fault point and the position of the second fault point belong to the same fault point position and whether the first fault type, the second fault type and the third fault type belong to the same fault type specifically includes: When the position of the first fault point and the position of the second fault point are the same, merge the second fault type and the third fault type, and judge whether the second fault type and the first fault type are the same. If so, use the second fault type as the fault detection result of the cable to be measured; if not, use the first fault type and the second fault type as the fault detection result of the cable to be measured; When the position of the first fault point and the position of the second fault point are different, judge whether the first fault type and the third fault type are the same. If so, use the first fault type and the second fault type as the fault detection result of the cable to be measured; if not, use the first fault type, the second fault type and the third fault type as the fault detection result of the cable to be measured.
3. A cable fault detection method according to claim 1, characterized in that, In the process of using the extended spectrum time domain reflectometry, compare the phase of the reflected signal at the position of the second fault point with the phase of the incident signal to identify the fault type at the position of the second fault point inside the cable to be measured, which specifically includes: If the phase of the reflected signal at the position of the second fault point is opposite to the phase of the incident signal, a short circuit fault occurs at the position of the second fault point inside the cable to be measured; If the phase of the reflected signal at the position of the second fault point is the same as the phase of the incident signal, an open circuit fault occurs at the position of the second fault point inside the cable to be measured.
4. The cable fault detection method according to claim 1, characterized in that, The step of identifying the fault type at the position of the first fault point on the surface of the cable to be measured according to the electromagnetic field change around the position of the first fault point on the surface of the cable to be measured specifically includes: If a high-frequency electromagnetic pulse appears around the position of the first fault point on the surface of the cable to be measured, a short circuit fault occurs at the position of the first fault point on the surface of the cable to be measured; If a low-frequency steady magnetic field and electric field signal appear around the first fault point on the surface of the cable to be measured, a grounding fault occurs at the first fault point on the surface of the cable to be measured; If an electromagnetic signal generating high-frequency oscillation appears around the first fault point on the surface of the cable to be measured, partial discharge occurs at the first fault point on the surface of the cable to be measured.
5. The cable fault detection method according to claim 1, wherein Identifying the fault type at the second fault point on the surface of the cable to be measured according to the electromagnetic field change around the second fault point on the surface of the cable to be measured specifically includes: If a high-frequency electromagnetic pulse appears around the second fault point on the surface of the cable to be measured, a short-circuit fault occurs at the second fault point on the surface of the cable to be measured; If a low-frequency steady magnetic field and electric field signal appear around the second fault point on the surface of the cable to be measured, a grounding fault occurs at the second fault point on the surface of the cable to be measured; If an electromagnetic signal generating high-frequency oscillation appears around the second fault point on the surface of the cable to be measured, partial discharge occurs at the second fault point on the surface of the cable to be measured.
6. The cable fault detection method according to claim 1, wherein Using the extended spectrum time domain reflectometry to detect faults inside the cable to be measured to obtain the second fault point position specifically includes: Determining the distance between the fault point position and the signal transmitting end according to the time difference between the signal emission time and the reflected signal reception time and the traveling wave propagation speed. The calculation formula is: ； Where t is the time difference between the signal emission time and the reflected signal reception time, v is the traveling wave propagation speed, and x is the distance between the fault point position and the signal transmitting end; Performing secondary positioning of the cable fault position according to the distance between the fault point position and the signal transmitting end to obtain the second fault point position.
7. A cable fault detection system based on the cable fault detection method according to any one of claims 1-6, characterized in that, Including: The FODS module is used to obtain the temperature signal and stress signal on the surface of the cable to be measured; The abnormal analysis and positioning module is used to preliminarily locate the abnormal point of the cable to be measured to obtain the first fault point position when any one of the temperature signal and stress signal exceeds the set threshold; The SS-TDR module is used to detect faults inside the cable to be measured using the extended spectrum time domain reflectometry to obtain the second fault point position; comparing the phase of the reflected signal corresponding to the second fault point position obtained by the extended spectrum time domain reflectometry with the phase of the incident signal to identify the fault type at the second fault point position inside the cable to be measured to obtain the first fault type; The EMM module is used to identify the fault type at the first fault point position on the surface of the cable to be measured according to the electromagnetic field change around the first fault point position on the surface of the cable to be measured to obtain the second fault type; identifying the fault type at the second fault point position on the surface of the cable to be measured according to the electromagnetic field change around the second fault point position on the surface of the cable to be measured to obtain the third fault type; The fault comparison module is used to obtain the fault detection result of the cable to be measured according to the judgment result of whether the first fault point position and the second fault point position belong to the same fault point position and whether the first fault type, the second fault type and the third fault type belong to the same fault type.