Cable fault detection method and system

Abstract

The invention discloses a cable fault detection method and system, and relates to the technical field of cable detection. Comprising the steps of obtaining a temperature signal and a stress signal of the surface of a to-be-detected cable, and obtaining a first fault point position when any signal exceeds a set threshold value; detecting the interior of the cable by adopting a spread spectrum time domain reflection method, and determining the position of a second fault point; obtaining a first fault type by comparing phases of the reflected signal and the incident signal at the position of the second fault point; respectively determining a second fault type and a third fault type according to electromagnetic field changes around the first fault point and the second fault point on the surface of the cable; and obtaining a fault detection result of the to-be-detected cable according to a judgment result whether the first fault point position and the second fault point position belong to the same fault point position or not and whether the first fault type, the second fault type and the third fault type belong to the same fault type or not. According to the invention, the accuracy and reliability of cable fault detection results can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cable detection, and in particular to a cable fault detection method and system. Background Art

[0002] With the rapid development of power and communication systems, cable fault detection has become particularly important.

[0003] Traditional cable fault detection methods include manual inspections, time domain reflectometry (TDR), and impedance measurement. Impedance measurement has limited ability to identify fault types, while traveling wave methods, while highly accurate, are expensive and complex. Among traveling wave methods, spread spectrum time domain reflectometry (SS-TDR) is widely used. It estimates the distance to the fault point by using the transmission time of reflected pulse signals.

[0004] The existing spread spectrum time domain reflectometry method requires long-term signal transmission during cable detection. However, in complex electromagnetic environments, the spread spectrum signal transmitted by the equipment will interfere with other signals, causing the characteristics of the reflected signal to change, resulting in false detection or missed detection, and affecting the accuracy of the detection results. Summary of the Invention

[0005] Based on this, it is necessary to provide a cable fault detection method and system to address the above technical issues.

[0006] An embodiment of the present invention provides a cable fault detection method, comprising: Obtain temperature signals and stress signals on the surface of the cable to be tested; When either the temperature signal or the stress signal exceeds a set threshold, the abnormal point of the cable under test is preliminarily located to obtain the first fault point location; based on the electromagnetic field changes around the first fault point on the surface of the cable under test, the fault type at the first fault point on the surface of the cable under test is identified to obtain the second fault type; Performing fault detection inside the cable under test using spread spectrum time domain reflectometry to obtain a second fault point location; comparing the phase of a reflected signal corresponding to the second fault point location obtained using spread spectrum time domain reflectometry with the phase of an incident signal to identify the fault type inside the cable under test at the second fault point location, thereby obtaining a first fault type; Identify the fault type of the cable surface under test at the first fault point according to the change of the electromagnetic field around the first fault point on the surface of the cable under test, and obtain a second fault type; identify the fault type of the cable surface under test at the second fault point according to the change of the electromagnetic field around the second fault point on the surface of the cable under test, and obtain a third fault type; A fault detection result of the cable to be tested is obtained according to a judgment result 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.

[0007] Optionally, obtaining a fault detection result of the cable to be tested according to a judgment result 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 specifically includes: When the first fault point location and the second fault point location are the same, the second fault type and the third fault type are combined, and it is determined whether the second fault type is the same as the first fault type. If so, the second fault type is used as the fault detection result of the cable under test; if not, the first fault type and the second fault type are used as the fault detection results of the cable under test; When the first fault point location and the second fault point location are different, determine 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 results of the cable under test; if not, use the first fault type, the second fault type and the third fault type as the fault detection results of the cable under test.

[0008] Optionally, when using the spread spectrum time domain reflectometry method, the phase of the reflected signal at the second fault point is compared with the phase of the incident signal to identify the fault type at the second fault point inside the cable under test: If the phase of the reflected signal at the second fault point is inverse to the phase of the incident signal, a short circuit fault occurs inside the cable under test at the second fault point. If the phase of the reflected signal at the second fault point is the same as the phase of the incident signal, a circuit breaker occurs at the second fault point inside the cable under test.

[0009] Optionally, identifying the fault type on the surface of the cable to be tested at the first fault point location according to changes in the electromagnetic field around the first fault point location on the surface of the cable to be tested specifically includes: If a high-frequency electromagnetic pulse appears on the surface of the cable under test around the first fault point, a short circuit fault occurs on the surface of the cable under test at the first fault point. If low-frequency steady-state magnetic field and electric field signals appear on the surface of the cable under test around the first fault point, a ground fault occurs on the surface of the cable under test at the first fault point; If an electromagnetic signal generating high-frequency oscillation appears on the surface of the cable under test around the first fault point, local discharge occurs on the surface of the cable under test at the first fault point.

[0010] Optionally, identifying the fault type on the surface of the cable to be tested at the second fault point location according to changes in the electromagnetic field around the second fault point location on the surface of the cable to be tested specifically includes: If a high-frequency electromagnetic pulse appears on the surface of the cable under test around the second fault point, a short circuit fault occurs on the surface of the cable under test at the second fault point. If low-frequency steady-state magnetic field and electric field signals appear on the surface of the cable under test around the second fault point, a ground fault occurs on the surface of the cable under test at the second fault point. If an electromagnetic signal generating high-frequency oscillation appears on the surface of the cable under test around the second fault point, partial discharge occurs on the surface of the cable under test at the second fault point.

[0011] Optionally, using spread spectrum time domain reflectometry to perform fault detection inside the cable to be tested and obtain the second fault point location, specifically including: According to the time difference between the signal transmission time and the reflected signal reception time and the traveling wave propagation speed, the distance between the fault point and the signal transmission end is determined. The calculation formula is: ; 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 point and the signal transmission end; The cable fault location is located secondary according to the distance between the fault point and the signal transmitting end to obtain the second fault point location.

[0012] An embodiment of the present invention further provides a cable fault detection system, comprising: FODS module, used to obtain temperature and stress signals on the surface of the cable to be tested; The abnormality analysis and positioning module is used to initially locate the abnormal point of the cable under test and obtain the first fault point when either the temperature signal or the stress signal exceeds the set threshold; The SS-TDR module is configured to use spread spectrum time domain reflectometry to perform fault detection on the cable under test to obtain a second fault location; compare the phase of the reflected signal corresponding to the second fault location obtained by the spread spectrum time domain reflectometry with the phase of the incident signal to identify the fault type at the second fault location within the cable under test to obtain the first fault type; The EMM module is configured to identify the fault type of the surface of the cable under test at the first fault point according to changes in the electromagnetic field around the first fault point, thereby obtaining a second fault type; and to identify the fault type of the surface of the cable under test at the second fault point according to changes in the electromagnetic field around the second fault point, thereby obtaining a third fault type. The fault comparison module is used to obtain the fault detection result of the cable to be tested based on the judgment result 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.

[0013] The cable fault detection method and system provided by the embodiment of the present invention have the following beneficial effects compared with the prior art: By acquiring temperature and stress signals from the cable surface, the present invention can quickly identify anomalies and preliminarily locate the fault point, namely the first fault point. Subsequently, spread spectrum time-domain reflectometry is used to conduct in-depth testing inside the cable to locate the second fault point. In this process, the cable surface temperature and stress signals are used as prerequisites before using spread spectrum time-domain reflectometry to conduct internal cable testing. This effectively addresses the drawback of traditional spread spectrum time-domain reflectometry, which requires long signal transmission times for cable testing. On this basis, the present invention will also determine whether the first fault point location and the second fault point location belong to the same fault point 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 false detection or missed detection caused by changes in the reflected signal characteristics, thereby improving the accuracy and reliability of the cable fault detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic flow chart of a cable fault detection method provided in one embodiment; Figure 2 A specific flow chart of a cable fault detection method provided in one embodiment; Figure 3 A schematic structural diagram of a cable fault detection system provided in one embodiment; Figure 4 The figure is a specific structural diagram of a cable fault detection system provided in one embodiment. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present 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 only used to explain the present invention and are not intended to limit the present invention.

[0016] like Figure 1As shown, the present invention includes: first, performing a cable fault early warning. Next, performing a first fault location and a second fault location. Fault type determination is performed at the two fault locations, including a first, second, and third fault type determination (the second determination is for the first fault location, and the first and third determinations are for the second fault location). The two fault locations are compared, and the three fault types are compared. Based on the comparison results, a fault detection result is output.

[0017] In one embodiment, a cable fault detection method is provided, such as Figure 2 As shown, the method specifically includes: Obtain the temperature signal and stress signal of the cable surface to be tested.

[0018] When either the temperature signal or the stress signal exceeds a set threshold, the abnormal point of the cable to be tested is initially located to obtain the first fault point position.

[0019] Use spread spectrum time-domain reflectometry to detect faults within the cable under test and determine the location of the second fault point. Compare the phase of the reflected signal corresponding to the second fault point, as determined by spread spectrum time-domain reflectometry, with the phase of the incident signal to identify the fault type within the cable under test at the second fault point and determine the first fault type.

[0020] Based on the electromagnetic field changes around the first fault point on the surface of the cable under test, the fault type on the surface of the cable under test at the first fault point is identified, thereby obtaining a second fault type. Based on the electromagnetic field changes around the second fault point on the surface of the cable under test, the fault type on the surface of the cable under test at the second fault point is identified, thereby obtaining a third fault type.

[0021] A fault detection result of the cable to be tested is obtained according to a judgment result 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.

[0022] It should be noted that if two or more second fault locations are obtained using spread spectrum time domain reflectometry, the second fault location closest to the first fault location and the first fault location will be used as the judgment object. 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 at the other second fault location are the same. If so, the first fault type of the cable under test at the other second fault location will be used as the fault detection result of the cable under test at the other second fault location. If not, the first fault type and the third fault type of the cable under test at the other second fault location will be used as the fault detection result of the cable under test at the other second fault location.

[0023] Furthermore, according to the change of the electromagnetic field around the first fault point on the surface of the cable to be tested, the fault type on the surface of the cable to be tested at the first fault point is identified, which specifically includes: If a high-frequency electromagnetic pulse appears on the surface of the cable under test around the first fault point, a short circuit fault occurs on the surface of the cable under test at the first fault point.

[0024] If low-frequency steady-state magnetic field and electric field signals appear on the surface of the cable under test around the first fault point, a ground fault occurs on the surface of the cable under test at the first fault point.

[0025] If an electromagnetic signal generating high-frequency oscillation appears on the surface of the cable under test around the first fault point, local discharge occurs on the surface of the cable under test at the first fault point.

[0026] Furthermore, the spread spectrum time domain reflectometry method is used to perform fault detection inside the cable to obtain the second fault point location, specifically including: According to the time difference between the signal transmission time and the reflected signal reception time and the traveling wave propagation speed, the distance between the fault point and the signal transmission end is determined. The calculation formula is: ; 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 point and the signal transmission end; The cable fault location is located secondary according to the distance between the fault point and the signal transmitting end to obtain the second fault point location.

[0027] Furthermore, in the process of using the spread spectrum time domain reflectometry, the phase of the reflected signal at the second fault point is compared with the phase of the incident signal to identify the fault type at the second fault point inside the cable under test, specifically including: If the phase of the reflected signal at the second fault point is opposite to the phase of the incident signal, a short circuit fault occurs inside the cable under test at the second fault point.

[0028] If the phase of the reflected signal at the second fault point is the same as the phase of the incident signal, a circuit breaker occurs at the second fault point inside the cable under test.

[0029] Furthermore, according to the change of the electromagnetic field around the second fault point on the surface of the cable to be tested, the fault type on the surface of the cable to be tested at the second fault point is identified, which specifically includes: If a high-frequency electromagnetic pulse appears on the surface of the cable under test around the second fault point, a short circuit fault occurs on the surface of the cable under test at the second fault point. If low-frequency steady-state magnetic field and electric field signals appear on the surface of the cable under test around the second fault point, a ground fault occurs on the surface of the cable under test at the second fault point. If an electromagnetic signal generating high-frequency oscillation appears on the surface of the cable under test around the second fault point, partial discharge occurs on the surface of the cable under test at the second fault point.

[0030] Furthermore, according to the judgment result 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, a fault detection result of the cable to be tested is obtained, which specifically includes: When the first fault point location and the second fault point location are the same, 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 so, the second fault type is used as the fault detection result of the cable under test; if not, the first fault type and the second fault type are used as the fault detection results of the cable under test.

[0031] When the first fault point location and the second fault point location are different, determine 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 results of the cable under test; if not, use the first fault type, the second fault type and the third fault type as the fault detection results of the cable under test.

[0032] The present invention provides a specific embodiment, comprising: First, make a preliminary diagnosis of the cable operation status based on the temperature signal and stress signal: Distributed fiber optic sensors collect temperature and stress signals from the cable surface. These signals are compared with set thresholds. If either parameter exceeds the threshold, a fault is detected and the sensor outputs the fault location. This helps to initially locate the abnormal point in the cable under test, determining the location of the first fault. Spread spectrum time-domain reflectometry is then used to detect faults within the cable under test, determining the location of the second fault. If neither parameter exceeds the reference value, temperature and stress signal acquisition continues.

[0033] The phase of the reflected signal corresponding to the second fault point location obtained by the spread spectrum time domain reflectometry method is compared with the phase of the incident signal. If the reflected signal and the incident wave are in opposite phases, the cable has a short circuit fault. If the two have the same phase, the fault is an open circuit, and the first fault type judgment is output. If the maximum allowable error is not exceeded, the excitation signal is re-transmitted.

[0034] Based on the electromagnetic field changes 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 electromagnetic field changes 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, while the presence of low-frequency steady-state magnetic and electric field signals indicates a ground fault. The generation of high-frequency oscillating electromagnetic signals indicates partial discharge.

[0035] A fault detection result of the cable to be tested is obtained according to a judgment result 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.

[0036] The specific steps are: S1 uses distributed optical fiber sensing modules to collect cable surface temperature and strain signals; S2 determines whether any one of the temperature signal and the stress signal exceeds the reference value. If so, it enters S3; if not, it returns to S1; S3 outputs distributed optical fiber sensors to monitor abnormal locations, preliminarily locate cable faults, and obtain the first fault point location; S4 uses spread spectrum time domain reflectometry to detect faults inside the cable to obtain the location of the second fault point; S5 calculates the time difference between the receiving time and the transmitting time; S6 calculates the distance between the fault point and the signal receiving end based on the traveling wave propagation speed and time difference; S7 outputs the second fault point location and is distinguished from the S3 output signal; S8 compares the phase of the reflected signal corresponding to the second fault point position obtained by the spread 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 tested, and obtain the first fault type; S9: identifying the fault type of the cable surface under test at the first fault point based on the electromagnetic field changes around the first fault point on the cable surface under test, and obtaining a second fault type. identifying the fault type of the cable surface under test at the second fault point based on the electromagnetic field changes around the second fault point on the cable surface under test, and obtaining a third fault type.

[0037] S10 obtaining a fault detection result of the cable under test according to a determination result of whether the first fault point location and the second fault point location are the same fault point location and whether the first fault type, the second fault type, and the third fault type are the same fault type; S11 transmits the fault detection result to the monitoring device.

[0038] 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: The FODS (Fiber Optic Distributed Sensing) module is used to obtain temperature and stress signals on the surface of the cable under test.

[0039] The anomaly analysis and location module is used to initially locate the abnormal point on the cable under test when either the temperature signal or the stress signal exceeds a set threshold, determining the location of the first fault point. Based on the electromagnetic field changes around the first fault point on the surface of the cable under test, the module identifies the fault type at the first fault point and determines the second fault type.

[0040] The SS-TDR module uses spread spectrum time domain reflectometry to detect faults within the cable under test and determine the location of the second fault point. The phase of the reflected signal corresponding to the second fault point, determined by spread spectrum time domain reflectometry, is compared with the phase of the incident signal to identify the fault type within the cable under test at the second fault point and determine the first fault type.

[0041] The EMM (Electromagnetic Method) module is used to identify the fault type on the surface of the cable under test at the second fault point based on changes in the electromagnetic field around the second fault point on the surface of the cable under test, thereby obtaining a third fault type.

[0042] The fault comparison module is used to obtain the fault detection result of the cable to be tested based on the judgment result 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.

[0043] 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 are 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 are the same fault type.

[0044] In addition, it also includes: a communication module for transmitting fault detection results to the monitoring device.

[0045] The beneficial effects that can be achieved by the present invention include at least: (1) The spread spectrum time domain reflectometry method is only started after the distributed optical fiber sensor transmits the fault warning signal. There is no need to generate pseudo-random codes all the time, which reduces the required computing resources and hardware usage time, and reduces system costs.

[0046] (2) The spread spectrum time domain reflectometry method can still be used under low signal-to-noise ratio conditions, has strong anti-interference ability, and improves the accuracy of fault point location and fault type judgment.

[0047] (3) There are at least one technology to assist in 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 failures or measurement errors, and improve the accuracy and reliability of the system output results.

[0048] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A cable fault detection method, characterized in that: include: Obtain temperature signals and stress signals on the surface of the cable to be tested; When any one of the temperature signal and the stress signal exceeds the set threshold, the abnormal point of the cable under test is initially located to obtain the first fault point position; Performing fault detection inside the cable under test using spread spectrum time domain reflectometry to obtain a second fault point location; comparing the phase of a reflected signal corresponding to the second fault point location obtained using spread spectrum time domain reflectometry with the phase of an incident signal to identify the fault type inside the cable under test at the second fault point location, thereby obtaining a first fault type; Identifying the fault type of the surface of the cable under test at the first fault point according to the change of the electromagnetic field around the first fault point on the surface of the cable under test, and obtaining a second fault type; identifying the fault type of the surface of the cable under test at the second fault point according to the change of the electromagnetic field around the second fault point on the surface of the cable under test, and obtaining a third fault type; A fault detection result of the cable to be tested is obtained according to a judgment result 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.

2. A cable fault detection method according to claim 1, characterized in that: The method of obtaining a fault detection result of the cable to be tested according to a judgment result 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 specifically includes: When the first fault point location and the second fault point location are the same, the second fault type and the third fault type are combined, and it is determined whether the second fault type is the same as the first fault type. If so, the second fault type is used as the fault detection result of the cable under test; if not, the first fault type and the second fault type are used as the fault detection results of the cable under test; When the first fault point location and the second fault point location are different, determine 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 results of the cable under test; if not, use the first fault type, the second fault type and the third fault type as the fault detection results of the cable under test.

3. A cable fault detection method according to claim 1, characterized in that: In the process of using the spread spectrum time domain reflectometry, the phase of the reflected signal at the second fault point is compared with the phase of the incident signal to identify the fault type at the second fault point inside the cable to be tested, specifically including: If the phase of the reflected signal at the second fault point is inverse to the phase of the incident signal, a short circuit fault occurs inside the cable under test at the second fault point. If the phase of the reflected signal at the second fault point is the same as the phase of the incident signal, a circuit breaker occurs at the second fault point inside the cable under test.

4. A cable fault detection method according to claim 1, characterized in that: The method of identifying the fault type of the surface of the cable under test at the first fault point according to the change of the electromagnetic field around the first fault point on the surface of the cable under test specifically includes: If a high-frequency electromagnetic pulse appears on the surface of the cable under test around the first fault point, a short circuit fault occurs on the surface of the cable under test at the first fault point. If low-frequency steady-state magnetic field and electric field signals appear on the surface of the cable under test around the first fault point, a ground fault occurs on the surface of the cable under test at the first fault point; If an electromagnetic signal generating high-frequency oscillation appears on the surface of the cable under test around the first fault point, local discharge occurs on the surface of the cable under test at the first fault point.

5. A cable fault detection method according to claim 1, characterized in that: The method of identifying the fault type of the surface of the cable under test at the second fault point according to the change of the electromagnetic field around the second fault point on the surface of the cable under test specifically includes: If a high-frequency electromagnetic pulse appears on the surface of the cable under test around the second fault point, a short circuit fault occurs on the surface of the cable under test at the second fault point. If low-frequency steady-state magnetic field and electric field signals appear on the surface of the cable under test around the second fault point, a ground fault occurs on the surface of the cable under test at the second fault point. If an electromagnetic signal generating high-frequency oscillation appears on the surface of the cable under test around the second fault point, partial discharge occurs on the surface of the cable under test at the second fault point.

6. A cable fault detection method according to claim 1, characterized in that: The method of using spread spectrum time domain reflectometry to perform fault detection inside the cable to be tested and obtain the second fault point location specifically includes: According to the time difference between the signal transmission time and the reflected signal reception time and the traveling wave propagation speed, the distance between the fault point and the signal transmission end is determined. The calculation formula is: ； 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 point and the signal transmission end; The cable fault location is located secondary according to the distance between the fault point and the signal transmitting end to obtain the second fault point location.

7. A cable fault detection system based on a cable fault detection method according to any one of claims 1 to 6, characterized in that: include: FODS module, used to obtain temperature and stress signals on the surface of the cable to be tested; The abnormality analysis and positioning module is used to initially locate the abnormal point of the cable under test and obtain the first fault point when either the temperature signal or the stress signal exceeds the set threshold; The SS-TDR module is configured to use spread spectrum time domain reflectometry to perform fault detection on the cable under test to obtain a second fault location; compare the phase of the reflected signal corresponding to the second fault location obtained by the spread spectrum time domain reflectometry with the phase of the incident signal to identify the fault type at the second fault location within the cable under test to obtain the first fault type; The EMM module is configured to identify the fault type of the surface of the cable under test at the first fault point according to changes in the electromagnetic field around the first fault point, thereby obtaining a second fault type; and to identify the fault type of the surface of the cable under test at the second fault point according to changes in the electromagnetic field around the second fault point, thereby obtaining a third fault type. The fault comparison module is used to obtain the fault detection result of the cable to be tested based on the judgment result 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.

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