Low-voltage AC cable grounding fault judgment method and device based on armor layer

Abstract

The present application provides a method and device for judging the grounding fault of a low-voltage AC cable based on an armored layer, which relates to the field of power equipment fault detection, and includes: determining the background current mean value of the armored layer according to the background current values of the armored layer of the low-voltage AC cable at different moments under normal working conditions; determining the leakage current of the armored layer according to the capacitive reactance of the obtained armored layer, the voltage between the cable core layer and the armored layer, and the voltage between the armored layer and the ground; judging the grounding fault of the low-voltage AC cable according to a pre-determined fault threshold and the leakage current; wherein, the fault threshold is determined according to the background current mean value. The present application can judge whether there is a grounding fault in the low-voltage AC cable based on the background current value of the armored layer of the low-voltage AC cable.

Description

Technical Field

[0001] The present application relates to the field of power equipment fault detection, and specifically to a method and device for judging the grounding fault of low-voltage AC cables based on the armor layer. Background Art

[0002] Currently, the main problem existing in the AC system of substations is the lack of effective means for monitoring the insulation state of cables. When an insulation fault occurs in the line cable and a metallic short-circuit discharge occurs, it cannot be detected in time. Those skilled in the art know that a metallic short-circuit discharge may cause the AC cable to catch fire. Once an AC cable fire occurs, it may threaten the safety of the DC cables laid in the same trench. Due to the inconsistent design requirements for grounding methods, switch types, etc. in each substation, there is no mature technology in the field of substation cable fire monitoring. Summary of the Invention

[0003] In view of the problems in the prior art, the present application provides a method and device for judging the grounding fault of low-voltage AC cables based on the armor layer, which can judge whether there is a grounding fault in the low-voltage AC cable based on the background current value of the armor layer of the low-voltage AC cable.

[0004] To solve the above technical problems, the present application provides the following technical solutions:

[0005] In a first aspect, the present application provides a method for judging the grounding fault of a low-voltage AC cable based on the armor layer, including:

[0006] Determining the background current mean value of the armor layer according to the background current values of the armor layer of the low-voltage AC cable at different moments under normal working conditions;

[0007] Determining the leakage current of the armor layer according to the capacitive reactance of the obtained armor layer, the voltage between the cable core layer and the armor layer, and the voltage between the armor layer and the ground;

[0008] Judging the grounding fault of the low-voltage AC cable according to a pre-determined fault threshold and the leakage current; wherein, the fault threshold is determined according to the background current mean value.

[0009] Further, the determining the background current mean value of the armor layer according to the background current values of the armor layer of the low-voltage AC cable at different moments under normal working conditions includes:

[0010] Using a mutual inductor characteristic tester to determine the background current value;

[0011] Determining the background current mean value according to the moment, the background current value, and the sampling quantity.

[0012] Further, the capacitive reactance of the armored layer includes: a first capacitive reactance between the cable core layer and the armored layer; the steps of obtaining the capacitive reactance of the armored layer include:

[0013] Determine the first capacitance per unit length of the armored layer according to the surface radius of the cable core layer, the surface radius of the armored layer, and the first dielectric constant;

[0014] Determine the first capacitive reactance according to the angular frequency of the low-voltage AC power grid and the first capacitance per unit length.

[0015] Further, the capacitive reactance of the armored layer includes: a second capacitive reactance between the armored layer and the ground; the steps of obtaining the capacitive reactance of the armored layer include:

[0016] Determine the second capacitance per unit length of the armored layer according to the surface radius of the insulating sheath of the low-voltage AC cable, the surface radius of the armored layer, and the second dielectric constant;

[0017] Determine the second capacitive reactance according to the angular frequency of the low-voltage AC power grid and the second capacitance per unit length.

[0018] Further, the leakage current includes: the cable core layer leakage current and the armored layer leakage current; the steps of determining the leakage current of the armored layer according to the obtained capacitive reactance of the armored layer, the voltage between the cable core layer and the armored layer, and the voltage between the armored layer and the ground include:

[0019] Determine the cable core layer leakage current according to the capacitive reactance of the armored layer and the voltage between the cable core layer and the armored layer;

[0020] Determine the armored layer leakage current according to the capacitive reactance of the armored layer and the voltage between the armored layer and the ground.

[0021] Further, the fault threshold includes: a warning threshold and an alarm threshold; the steps of determining the fault threshold include:

[0022] Determine the warning threshold according to the simulated fault current value, the mean background current, the cable core layer leakage current, the armored layer leakage current, and the safety warning requirement coefficient;

[0023] Determine the alarm threshold according to the simulated fault current value, the mean background current, the cable core layer leakage current, the armored layer leakage current, and the safety alarm requirement coefficient.

[0024] Further, the step of judging the grounding fault of the low-voltage AC cable according to the pre-determined fault threshold and the leakage current includes:

[0025] When the leakage current is less than the warning threshold, it is judged that there is no grounding fault in the low-voltage AC cable;

[0026] When the leakage current is between the warning threshold and the alarm threshold, it is determined that there is a grounding fault in the low-voltage AC cable, and a warning is issued;

[0027] When the leakage current is greater than the alarm threshold, it is determined that there is a grounding fault in the low-voltage AC cable, and an alarm is given.

[0028] In a second aspect, the present application provides a device for judging the grounding fault of a low-voltage AC cable based on an armor layer, including:

[0029] A background current determination unit for determining the average background current of the armor layer according to the background current values of the armor layer of the low-voltage AC cable at different moments under normal working conditions;

[0030] A leakage current determination unit for determining the leakage current of the armor layer according to the capacitive reactance of the obtained armor layer, the voltage between the cable core layer and the armor layer, and the voltage between the armor layer and the ground;

[0031] A grounding fault judgment unit for judging the grounding fault of the low-voltage AC cable according to a pre-determined fault threshold and the leakage current; wherein, the fault threshold is determined according to the average background current.

[0032] Further, the background current determination unit includes:

[0033] A moment current determination module for determining the background current value by using a mutual inductor characteristic tester;

[0034] An average current determination module for determining the average background current according to the moment, the background current value, and the sampling quantity.

[0035] Further, the capacitive reactance of the armor layer includes: a first capacitive reactance between the cable core layer and the armor layer, and further includes:

[0036] A unit capacitive reactance determination unit for determining the first unit length capacitance of the armor layer according to the surface radius of the cable core layer, the surface radius of the armor layer, and the first dielectric constant;

[0037] An overall capacitive reactance determination unit for determining the first capacitive reactance according to the angular frequency of the low-voltage AC power grid and the first unit length capacitance.

[0038] Further, the capacitive reactance of the armor layer includes: a second capacitive reactance between the armor layer and the ground, and further includes:

[0039] The unit capacitive reactance determination unit is configured to determine the second capacitance per unit length of the armor layer according to the surface radius of the insulating sheath of the low-voltage AC cable, the surface radius of the armor layer, and the second dielectric constant;

[0040] The overall capacitive reactance determination unit is configured to determine the second capacitive reactance according to the angular frequency of the low-voltage AC power grid and the second capacitance per unit length.

[0041] Further, the leakage current includes: the core layer leakage current and the armor layer leakage current; the leakage current determination unit includes:

[0042] The core leakage current determination module is configured to determine the core layer leakage current according to the capacitive reactance of the armor layer and the voltage between the core layer and the armor layer;

[0043] The armor leakage current determination module is configured to determine the armor layer leakage current according to the capacitive reactance of the armor layer and the voltage between the armor layer and the ground.

[0044] Further, the fault threshold includes: a warning threshold and an alarm threshold; the device further includes:

[0045] The warning threshold determination unit is configured to determine the warning threshold according to the simulated fault current value, the background current mean value, the core layer leakage current, the armor layer leakage current, and the safety warning requirement coefficient;

[0046] The alarm threshold determination unit is configured to determine the alarm threshold according to the simulated fault current value, the background current mean value, the core layer leakage current, the armor layer leakage current, and the safety alarm requirement coefficient.

[0047] Further, the ground fault judgment unit includes:

[0048] The fault exclusion module is configured to determine that there is no ground fault in the low-voltage AC cable when the leakage current is less than the warning threshold;

[0049] The warning module is configured to determine that there is a ground fault in the low-voltage AC cable when the leakage current is between the warning threshold and the alarm threshold, and issue a warning;

[0050] The alarm module is configured to determine that there is a ground fault in the low-voltage AC cable when the leakage current is greater than the alarm threshold, and give an alarm.

[0051] In a third aspect, the present application provides an electronic device including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the steps of the method for judging the ground fault of a low-voltage AC cable based on the armor layer are implemented.

[0052] In a fourth aspect, the present application provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method for judging the grounding fault of a low-voltage AC cable based on the armor layer are implemented.

[0053] In a fifth aspect, the present application provides a computer program product, including a computer program / instructions. When the computer program / instructions are executed by a processor, the steps of the method for judging the grounding fault of a low-voltage AC cable based on the armor layer are implemented.

[0054] Regarding the problems in the prior art, the method and device for judging the grounding fault of a low-voltage AC cable based on the armor layer provided by the present application consider the operating characteristics that when the insulation of a low-voltage AC armored cable is damaged during actual operation, the armor layer first conducts the fault current. Under the condition of excluding the interference of the background current of the armor layer, the grounding fault of the cable is judged according to the leakage current, ensuring the accuracy of the monitoring data. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0056] Figure 1 It is a flowchart of the method for judging the grounding fault of a low-voltage AC cable based on the armor layer in an embodiment of the present application;

[0057] Figure 2 It is a flowchart of determining the average value of the background current of the armor layer in an embodiment of the present application;

[0058] Figure 3 It is a flowchart of obtaining the capacitive reactance of the armor layer in an embodiment of the present application;

[0059] Figure 4 It is a flowchart of determining the leakage current of the armor layer in an embodiment of the present application;

[0060] Figure 5 It is a flowchart of determining the fault threshold in an embodiment of the present application;

[0061] Figure 6 It is a flowchart of judging the grounding fault of the low-voltage AC cable in an embodiment of the present application;

[0062] Figure 7 It is one of the structural diagrams of the device for judging the grounding fault of a low-voltage AC cable based on the armor layer in an embodiment of the present application;

[0063] Figure 8 Structural diagram of the background current determination unit in the embodiment of the present application;

[0064] Figure 9 Structural diagram II of the low-voltage AC cable grounding fault judgment device based on the armor layer in the embodiment of the present application;

[0065] Figure 10 Structural diagram of the leakage current determination unit in the embodiment of the present application;

[0066] Figure 11 Structural diagram III of the low-voltage AC cable grounding fault judgment device based on the armor layer in the embodiment of the present application;

[0067] Figure 12 Structural diagram of the grounding fault judgment unit in the embodiment of the present application;

[0068] Figure 13 Structural schematic diagram of the electronic device in the embodiment of the present application;

[0069] Figure 14 Schematic diagram of the armor layer test wiring in the embodiment of the present application;

[0070] Figure 15 Schematic diagram of the structure of a conventional armored cable in the embodiment of the present application;

[0071] Figure 16 Schematic diagram of the equivalent model at the actual operation time in the embodiment of the present application;

[0072] Figure 17 Schematic diagram of the wiring circuit of the residual current generator in the embodiment of the present application;

[0073] Figure 18 Schematic diagram of the wiring of the AC system device for a certain substation in the embodiment of the present application. Detailed implementation manners

[0074] Next, the technical solutions in the embodiments of the present application will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0075] In one embodiment, referring to Figure 1 , in order to be able to judge whether there is a grounding fault in a low-voltage AC cable based on the background current value of the armor layer of the low-voltage AC cable, the present application provides a method for judging the grounding fault of a low-voltage AC cable based on the armor layer, including:

[0076] S101: Determine the average background current of the armor layer based on the background current values of the armor layer of the low-voltage AC cable at different times under normal working conditions;

[0077] It can be understood that in terms of cable insulation monitoring, the main problem existing in the current low-voltage AC system is the lack of effective cable insulation monitoring means. For this reason, the present application provides a method for monitoring the cable insulation status by monitoring the residual current of the armor layers at both ends of a long cable. In actual working conditions, referring to Figure 14 , if the insulation of the armored cable is damaged, the armor layer will pass the fault current first. The method provided by the present application is based on the above characteristics of the armored cable, and takes into account the leakage current error of the cable to the armor layer and the leakage current error of the armored cable to the ground existing in actual operation, eliminates the interference of the background current of the armor layer, ensures that the current flowing through the armor layer is zero under normal operating conditions, and thus ensures the accuracy of the monitoring data.

[0078] In one embodiment, referring to Figure 2 , the determining the average background current of the armor layer based on the background current values of the armor layer of the low-voltage AC cable at different times under normal working conditions includes: determining the background current value using a transformer characteristic tester (S201); determining the average background current according to the time, the background current value, and the number of samples (S202).

[0079] Referring to Figure 1 shown, the following method can be adopted when determining the average background current of the armor layer:

[0080] The armor layer of the low-voltage AC cable is mainly designed to protect the service life of the cable. Under normal working conditions, there will be background current in the armor layer. Before judging the grounding fault of the low-voltage AC cable, the influence of the background current should be eliminated first. For this reason, a transformer characteristic tester (abbreviated as CT measuring device) can be installed at one end of the armor layer to detect the background current value I k of the armor layer under normal working conditions. Samples are taken for the data at regular intervals, so that the background currents I1, I2, I3... at different load times t1, t2, t3... within a unit time (for example, within a day) can be obtained. Among them, different load times refer to different times such as load peaks and load valleys during a day.

[0081] According to the discrete variable average value calculation formula in formula (1), the average value of the background current I aa of the armor layer can be calculated; this average value is also called the average background current, which represents the average value of the background current at different load times within a unit time; n is a total of n load times, and i is different load times.

[0082]

[0083] S102: Determine the leakage current of the armored layer based on the capacitive reactance of the obtained armored layer, the voltage between the cable core layer and the armored layer, and the voltage between the armored layer and the ground;

[0084] It can be understood that the method provided in this application can monitor and judge the insulation state of the cable by calculating the leakage current of the armored layer. The leakage current mainly includes the leakage current from the cable core to the armored layer and the leakage current from the armored layer to the ground. Considering the problem that the armored layer and the insulating jacket (also called insulating sheath) have a certain thickness, it is necessary to exclude the interference of the sheath separately. Among them, the sheath refers to the main insulating sheath between the armored layer and the core wire.

[0085] Figure 15 In the figure, 1 is the core wire, and the material is copper; 2 is the main insulation, and the material is polyvinyl chloride; 3 is the armored sheath layer, and the material is polyvinyl chloride; 4 is the armored layer, and the material is steel; 5 is the sheath, and the material is polyvinyl chloride. For the structure of a conventional armored cable, see Figure 15 as shown:

[0086] Since the distances between the cable core, the metal sheath, and the armor in the cable line are very close, the cable capacitance is relatively large. Therefore, there is often a large capacitive current in the cable line. The capacitance per unit length is:

[0087] C = ε / 18ln(r2 / r1)×10 -9 (2)

[0088] Among them, r1 and r2 are the radii of the inner and outer surfaces of the cylinder, with the unit of m; ε is the dielectric constant of the insulating layer dielectric (if it is the armored layer, it refers to the dielectric constant of the armored layer, and the same applies to the rest). The expression for the capacitive reactance per unit length is:

[0089] Y c = wC (3)

[0090] Among them, Y c is the capacitive reactance per unit length, and w is the angular frequency of the low-voltage AC power grid.

[0091] For example, if it is the capacitance of the armored layer, it refers to the inner diameter and outer diameter of the armored layer. The capacitance can be considered as the capacitance per unit length of the armored layer (from the inner to the outer diameter), or it can also be considered as the capacitance per unit length between the outer layer of the armored layer sheath and the inner layer of the outer sheath.

[0092] In one embodiment, the capacitive reactance of the armored layer includes: the first capacitive reactance between the cable core layer and the armored layer; the capacitive reactance of the armored layer includes: the second capacitive reactance between the armored layer and the ground; see Figure 3 , according to the above principle, the steps of obtaining the capacitive reactance of the armored layer include:

[0093] S301: Determine the first capacitance per unit length of the armor layer based on the surface radius of the cable core layer, the surface radius of the armor layer, and the first dielectric constant. Considering that each layer and the insulating sheath have a certain thickness, the surface radius in steps S301 to S304 refers to the outer surface radius. The first dielectric constant refers to the dielectric constant between the cable core layer and the armor layer.

[0094] S302: Determine the first capacitive reactance Y based on the angular frequency of the low-voltage AC power grid and the first capacitance per unit length. ea 。

[0095] S303: Determine the second capacitance per unit length of the armor layer based on the surface radius of the insulating sheath of the low-voltage AC cable, the surface radius of the armor layer, and the second dielectric constant. Here, the surface radius refers to the outer surface radius of this layer. The second dielectric constant refers to the dielectric constant between the armor layer and the insulating sheath.

[0096] S304: Determine the second capacitive reactance Y based on the angular frequency of the low-voltage AC power grid and the second capacitance per unit length. ag 。

[0097] According to Figure 15 the cable structure diagram shown, an equivalent model at the actual operating moment can be obtained. See Figure 16 as shown:

[0098] Figure 16 In the following, the subscript e represents the cable core layer, the subscript y represents the sheath layer, the subscript a represents the armor layer, and the subscript g represents the ground. Figure 16 Y / 2 in ee is the capacitance value between the cable core layer and the armor layer. Among them, I aa represents the cable core layer current, I ea represents the background current of the armor layer, I ag represents the leakage current of the cable core layer through the cable sheath and the armor sheath, and I ea represents the leakage current of the armor layer flowing through the ground. During operation, U ag and U ea are the voltages between the cable core layer and the armor layer and between the armor layer and the ground respectively. U ag can be obtained through on-site measurement (such as using a multimeter to measure). The leakage current can be obtained as:

[0099]

[0100]

[0101] In an embodiment, see Figure 4, the leakage current includes: the leakage current of the cable core layer and the leakage current of the armor layer; determining the leakage current of the armor layer according to the capacitive reactance of the armor layer, the voltage between the cable core layer and the armor layer, and the voltage between the armor layer and the ground includes: determining the leakage current I of the cable core layer according to the capacitive reactance of the armor layer and the voltage between the cable core layer and the armor layer ea (S401); determining the leakage current I of the armor layer according to the capacitive reactance of the armor layer and the voltage between the armor layer and the ground ag (S402).

[0102] S103: Determine whether there is a grounding fault in the low-voltage AC cable according to a pre-determined fault threshold and the leakage current; wherein, the fault threshold is determined according to the background current mean value.

[0103] In one embodiment, see Figure 5 , the fault threshold includes: a warning threshold and an alarm threshold; the steps of determining the fault threshold include:

[0104] S501: Determine the warning threshold according to the simulated fault current value, the background current mean value, the leakage current of the cable core layer, the leakage current of the armor layer, and the safety warning demand coefficient;

[0105] S502: Determine the alarm threshold according to the simulated fault current value, the background current mean value, the leakage current of the cable core layer, the leakage current of the armor layer, and the safety alarm demand coefficient.

[0106] It can be understood that during normal monitoring, numerical settings need to be combined with the on-site situation, and the warning value and the alarm value are calculated according to the requirements of the operation personnel. By means of a fault simulation experiment on the corresponding line, on the premise of ensuring safety, a simulated fault capacitor is added to the end of the normally operating line to simulate the cable insulation fault, a measuring device is installed on the armor layer and the fault current value I at this time is obtained m . According to the safety demand coefficients α and β provided by the on-site personnel, the warning value and the alarm value are calculated.

[0107] The influence of the background current I of the armor layer aa and the leakage current I ea 、I ag on the residual current monitoring should be excluded. When there is no insulation damage, the measurement result is on the high side, and the corresponding value should be subtracted in the calculation; in specific implementation, for what is "the result is on the high side", a threshold value can be set, but this application does not make a numerical limitation on the specific threshold value. I ea is the leakage current of the cable core to the armor layer. During normal operation, current is injected into the armor layer, making the measurement result on the high side, and the corresponding value should be subtracted in the calculation; I agLet \(I_{armor - earth}\) be the current from the armored layer to the ground during normal operation, which makes the measurement result on the low side. The corresponding value should be added in the calculation. Therefore, the warning value is \(I_{warn}\) α =\(\alpha\times(|I_{armor - earth}|\) m \(|-|I_{normal}\) aa \(|-|I_{background}\) ea \(| + |I_{noise}|\)), and the alarm value is \(I_{alarm}\) ag =\(\beta\times(|I_{armor - earth}|\) β \(|-|I_{normal}\) m \(|-|I_{background}\) aa \(|-|I_{noise}|\)). ea | + |I_{noise}|\)). ag ).

[0108] As can be seen from the above description, the method for judging the grounding fault of the low - voltage AC cable based on the armored layer provided by this application can determine the fault threshold.

[0109] In one embodiment, referring to Figure 6 , judging the grounding fault of the low - voltage AC cable according to the pre - determined fault threshold and the leakage current includes:

[0110] Comparing the leakage current with the warning threshold:

[0111] S601: If the leakage current is less than the warning threshold, it is judged that the low - voltage AC cable has no grounding fault;

[0112] S602: If the leakage current is between the warning threshold and the alarm threshold, it is judged that the low - voltage AC cable has a grounding fault and a warning is issued;

[0113] S603: If the leakage current is greater than the alarm threshold, it is judged that the low - voltage AC cable has a grounding fault and an alarm is made.

[0114] It can be understood that, referring to Figure 17 , adjust the current value through the residual current generator so that the reading of ammeter A is 105% of the alarm set value of the specimen, and keep it for 60 s, record the alarm time T of the specimen k , and it should be set according to the relevant time during the actual monitoring process. The installation situation of the device is as Figure 17 shown. Figure 17 This is the wiring circuit of the residual current generator. Wherein:

[0115] GR-----Residual current generator;

[0116] A-----Ammeter;

[0117] WR-----Residual current wire;

[0118] TR-----Residual current monitoring detector;

[0119] TS1, TS2 ----- Signal input terminals;

[0120] CA ----- Residual current monitoring host.

[0121] Install residual current measuring devices at the head and end of the armored layer respectively to detect the residual current situation of the armored layer, and the displayed values are For the monitoring values of the armored layer in different situations I 1n , I 2n Compare them and simultaneously send out corresponding monitoring signals. The specific corresponding relationships are as follows:

[0122] When there is and , the monitoring platform sends out a warning signal.

[0123] When there is and , the monitoring platform sends out an alarm signal.

[0124] When there is only or , the monitoring platform sends out a warning signal and simultaneously sends out a device failure signal.

[0125] When there is only or , the monitoring platform sends out an alarm signal and simultaneously sends out a device failure signal.

[0126] When there is and or and , the monitoring platform sends out a warning signal.

[0127] From the above description, it can be seen that the method for judging the grounding fault of a low-voltage AC cable based on the armored layer provided in this application can judge the grounding fault of the low-voltage AC cable according to the pre-determined fault threshold and the leakage current.

[0128] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings. Figure 18 It is a wiring diagram of the AC system device for a certain substation. The method provided in this application can be used to monitor the installation of a monitoring device on the armored layer of a certain AC line.

[0129] After measurement, the background current values of the cable at peak and low peak times are 0.006A and 0.003A respectively. After calculation, the average value of the induced current

[0130] (1) Calculate the leakage current

[0131] Conduct on-site measurement in advance, and measure the voltage U between the cable core layer and the armored layer respectivelyea 1. The voltage U between the armored layer and the ground ag is measured. Combining the radii r1 and r2 of the inner and outer surfaces of the cable and the dielectric constant ε of the insulating layer dielectric, the leakage current I is obtained ea and I ag are 0.4 A and 0.6 A respectively.

[0132] (2) Calculate the expected alarm value and warning value

[0133] On-site personnel determine the safety requirement coefficients α and β according to the actual situation, where the warning coefficient α = 0.3 and the alarm coefficient β = 0.8. Through on-site simulated fault experiments, the measured I m = 300 mA warning value I α = 0.074 A, alarm value I β = 0.224 A.

[0134] (3) Set the alarm time

[0135] Install a residual current generator, adjust the current value to make the reading of ammeter A 105% of the warning and alarm set values of the specimen, and maintain it for 60 s. After statistics, the warning time and alarm time of the specimen are 50 s and 30 s respectively, then set the corresponding time. The monitoring platform determines the monitoring situation of the armored layer

[0136] (4) The monitoring platform determines the situation of the armored layer theater

[0137] Install residual current measuring devices at the head and end of the armored layer respectively, and judge the displayed values I 1n and I 2n .

[0138] This method improves the level of cable insulation monitoring in the low-voltage AC system in the substation, eliminates the dead zone existing in the professional management technical regulations of low-voltage AC cables, solves the problem that faults such as metal grounding and high-resistance grounding cannot be detected in time, improves the identification ability of major hazards such as substation full shutdown, and improves the application efficiency of the overall AC-DC system; through real-time monitoring of AC cables, it can judge whether there is insulation damage in low-voltage AC cables, and improves the insulation monitoring ability of the substation AC power supply system.

[0139] As can be seen from the above description, the low-voltage AC cable grounding fault judgment method provided by this application can take into account the operating characteristics that when the insulation of a low-voltage AC armored cable is damaged during actual operation, the armored layer first passes through the fault current. Under the condition of excluding the interference of the background current of the armored layer, the grounding fault of the cable is judged according to the leakage current, ensuring the accuracy of the monitoring data.

[0140] Based on the same inventive concept, an embodiment of the present application further provides a low-voltage AC cable grounding fault judgment device based on an armored layer, which can be used to implement the method described in the above embodiment, as described in the following embodiment. Since the principle of the low-voltage AC cable grounding fault judgment device based on the armored layer to solve the problem is similar to that of the low-voltage AC cable grounding fault judgment method based on the armored layer, the implementation of the low-voltage AC cable grounding fault judgment device based on the armored layer can refer to the implementation of the method for determining the software performance benchmark, and the repeated parts will not be described again. As used hereinafter, the term "unit" or "module" can be a combination of software and / or hardware that can achieve a predetermined function. Although the systems described in the following embodiments are preferably implemented in software, implementation in hardware, or a combination of software and hardware is also possible and contemplated.

[0141] In one embodiment, referring to Figure 7 , in order to be able to judge whether a low-voltage AC cable has a grounding fault based on the background current value of the armored layer of the low-voltage AC cable, the present application provides a low-voltage AC cable grounding fault judgment device based on the armored layer, including: a background current determination unit 701, a leakage current determination unit 702, and a grounding fault judgment unit 703.

[0142] The background current determination unit 701 is configured to determine the background current mean value of the armored layer according to the background current values of the armored layer of the low-voltage AC cable at different moments under normal working conditions;

[0143] The leakage current determination unit 702 is configured to determine the leakage current of the armored layer according to the capacitive reactance of the obtained armored layer, the voltage between the cable core layer and the armored layer, and the voltage between the armored layer and the ground;

[0144] The grounding fault judgment unit 703 is configured to judge the grounding fault of the low-voltage AC cable according to a predetermined fault threshold and the leakage current; wherein, the fault threshold is determined according to the background current mean value.

[0145] In one embodiment, referring to Figure 8 , the background current determination unit 701 includes: a moment current determination module 801 and an average current determination module 802.

[0146] The moment current determination module 801 is configured to determine the background current value by using a mutual inductor characteristic tester;

[0147] The average current determination module 802 is configured to determine the background current mean value according to the moment, the background current value, and the sampling quantity.

[0148] In one embodiment, referring to Figure 9, the capacitive reactance of the armored layer includes: a first capacitive reactance between the cable core layer and the armored layer, and further includes: a unit capacitive reactance determination unit 901 and an overall capacitive reactance determination unit 902.

[0149] The unit capacitive reactance determination unit 901 is configured to determine a first capacitance per unit length of the armored layer according to the surface radius of the cable core layer, the surface radius of the armored layer, and a first dielectric constant;

[0150] The overall capacitive reactance determination unit 902 is configured to determine the first capacitive reactance according to the angular frequency of the low-voltage AC power grid and the first capacitance per unit length.

[0151] In one embodiment, referring to Figure 9 , the capacitive reactance of the armored layer includes: a second capacitive reactance between the armored layer and the ground, and further includes: a unit capacitive reactance determination unit 901 and an overall capacitive reactance determination unit 902.

[0152] The unit capacitive reactance determination unit 901 is configured to determine a second capacitance per unit length of the armored layer according to the surface radius of the insulating sheath of the low-voltage AC cable, the surface radius of the armored layer, and a second dielectric constant;

[0153] The overall capacitive reactance determination unit 902 is configured to determine the second capacitive reactance according to the angular frequency of the low-voltage AC power grid and the second capacitance per unit length.

[0154] In one embodiment, referring to Figure 10 , the leakage current includes: a cable core layer leakage current and an armored layer leakage current; the leakage current determination unit 702 includes:

[0155] The cable core leakage current determination module 1001 is configured to determine the cable core layer leakage current according to the capacitive reactance of the armored layer and the voltage between the cable core layer and the armored layer;

[0156] The armored layer leakage current determination module 1002 is configured to determine the armored layer leakage current according to the capacitive reactance of the armored layer and the voltage between the armored layer and the ground.

[0157] In one embodiment, referring to Figure 11 , the fault threshold includes: a warning threshold and an alarm threshold; the device further includes:

[0158] The warning threshold determination unit 1101 is configured to determine the warning threshold according to the simulated fault current value, the background current mean value, the cable core layer leakage current, the armored layer leakage current, and a safety warning requirement coefficient;

[0159] An alarm threshold determination unit 1102 is configured to determine the alarm threshold according to the simulated fault current value, the background current mean value, the leakage current of the cable core layer, the leakage current of the armor layer, and the safety alarm requirement coefficient.

[0160] In one embodiment, referring to Figure 12 , the ground fault judgment unit 703 includes: a fault elimination module 1201, a warning module 1202, and an alarm module 1203.

[0161] The fault elimination module 1201 is configured to determine that there is no ground fault in the low-voltage AC cable when the leakage current is less than the warning threshold;

[0162] The warning module 1202 is configured to determine that there is a ground fault in the low-voltage AC cable and issue a warning when the leakage current is between the warning threshold and the alarm threshold;

[0163] The alarm module 1203 is configured to determine that there is a ground fault in the low-voltage AC cable and give an alarm when the leakage current is greater than the alarm threshold.

[0164] From a hardware level, in order to be able to judge whether there is a ground fault in a low-voltage AC cable based on the background current value of the armor layer of the low-voltage AC cable, this application provides an embodiment of an electronic device for implementing all or part of the content in the method for judging the ground fault of the low-voltage AC cable based on the armor layer. The electronic device specifically includes the following content:

[0165] A processor, a memory, a communication interface, and a bus; wherein, the processor, the memory, and the communication interface complete communication with each other through the bus; the communication interface is used to realize information transmission between the device for judging the ground fault of the low-voltage AC cable based on the armor layer and related devices such as the core business system, the user terminal, and the relevant database. The logic controller can be a desktop computer, a tablet computer, a mobile terminal, etc., and this embodiment is not limited thereto. In this embodiment, the logic controller can be implemented with reference to the embodiments of the method for judging the ground fault of the low-voltage AC cable based on the armor layer and the embodiments of the device for judging the ground fault of the low-voltage AC cable based on the armor layer, and the content is incorporated herein, and the repeated parts will not be described again.

[0166] It can be understood that the user terminal may include a smart phone, a tablet electronic device, a network set-top box, a portable computer, a desktop computer, a personal digital assistant (PDA), a vehicle-mounted device, a smart wearable device, etc. Among them, the smart wearable device may include smart glasses, smart watches, smart bracelets, etc.

[0167] In practical applications, part of the method for judging the grounding fault of a low-voltage AC cable based on the armor layer can be executed on the side of the electronic device as described above, or all operations can be completed in the client device. Specifically, it can be selected according to the processing capacity of the client device and the limitations of the user usage scenario, etc. This application does not make any limitations in this regard. If all operations are completed in the client device, the client device may further include a processor.

[0168] The above-mentioned client device may have a communication module (i.e., a communication unit), and can be communicatively connected to a remote server to achieve data transmission with the server. The server may include a server on the side of the task scheduling center, and in other implementation scenarios, it may also include a server of an intermediate platform, such as a server of a third-party server platform communicatively linked to the task scheduling center server. The server may include a single computer device, or may include a server cluster composed of multiple servers, or a server structure of a distributed device.

[0169] Figure 13 It is a schematic block diagram of the system composition of the electronic device 9600 according to an embodiment of the present application. As Figure 13 shown, the electronic device 9600 may include a central processing unit 9100 and a memory 9140; the memory 9140 is coupled to the central processing unit 9100. It should be noted that this Figure 13 is exemplary; other types of structures can also be used to supplement or replace this structure to achieve telecommunication functions or other functions.

[0170] In one embodiment, the function of the method for judging the grounding fault of a low-voltage AC cable based on the armor layer can be integrated into the central processing unit 9100. Among them, the central processing unit 9100 can be configured to perform the following controls:

[0171] S101: Determine the background current mean value of the armor layer according to the background current values of the armor layer of the low-voltage AC cable at different moments under normal working conditions;

[0172] S102: Determine the leakage current of the armor layer according to the capacitive reactance of the obtained armor layer, the voltage between the cable core layer and the armor layer, and the voltage between the armor layer and the ground;

[0173] S103: Judge the grounding fault of the low-voltage AC cable according to a pre-determined fault threshold and the leakage current; wherein, the fault threshold is determined according to the background current mean value.

[0174] As can be seen from the above description, the method for judging the grounding fault of a low-voltage AC cable based on the armor layer provided by the present application takes into account the operating characteristics that when the insulation of a low-voltage AC armored cable is damaged during actual operation, the armor layer first passes the fault current. Under the condition of eliminating the interference of the background current of the armor layer, the grounding fault of the cable is judged according to the leakage current, ensuring the accuracy of the monitoring data.

[0175] In another embodiment, the device for judging the grounding fault of a low-voltage AC cable based on the armor layer can be separately configured from the central processor 9100. For example, the device for judging the grounding fault of a low-voltage AC cable based on the data composite transmission device can be configured as a chip connected to the central processor 9100, and the functions of the method for judging the grounding fault of a low-voltage AC cable based on the armor layer are realized through the control of the central processor.

[0176] As Figure 13 shown, the electronic device 9600 may further include: a communication module 9110, an input unit 9120, an audio processor 9130, a display 9160, and a power supply 9170. It should be noted that the electronic device 9600 does not necessarily have to include Figure 13 all the components shown in Figure 13 ; in addition, the electronic device 9600 may further include

[0177] components not shown in Figure 13 ; reference may be made to the prior art.

[0177] As Figure 13 shown, the central processor 9100 is sometimes also referred to as a controller or an operation control, and may include a microprocessor or other processor devices and / or logic devices. The central processor 9100 receives inputs and controls the operations of the various components of the electronic device 9600.

[0178] Among them, the memory 9140 may be, for example, one or more of a buffer, a flash memory, a hard drive, a removable medium, a volatile memory, a non-volatile memory, or other suitable devices. The above information related to failures can be stored, and in addition, programs for executing relevant information can also be stored. And the central processor 9100 can execute the program stored in the memory 9140 to implement information storage or processing, etc.

[0179] The input unit 9120 provides inputs to the central processor 9100. The input unit 9120 is, for example, a key or a touch input device. The power supply 9170 is used to supply power to the electronic device 9600. The display 9160 is used to display display objects such as images and texts. The display may be, for example, an LCD display, but is not limited thereto.

[0180] The memory 9140 can be a solid-state memory, for example, a read-only memory (ROM), a random access memory (RAM), a SIM card, etc. It can also be a memory that stores information even when power is off, can be selectively erased and has more data. Examples of such a memory are sometimes referred to as EPROMs, etc. The memory 9140 can also be some other type of device. The memory 9140 includes a buffer memory 9141 (sometimes referred to as a buffer). The memory 9140 can include an application / function storage unit 9142, which is used to store application programs and function programs or the processes for operating the electronic device 9600 by the central processing unit 9100.

[0181] The memory 9140 can also include a data storage unit 9143, which is used to store data, such as contacts, digital data, pictures, sounds, and / or any other data used by the electronic device. The driver storage unit 9144 of the memory 9140 can include various drivers of the electronic device for communication functions and / or for performing other functions of the electronic device (such as a messaging application, an address book application, etc.).

[0182] The communication module 9110 is a transmitter / receiver 9110 that transmits and receives signals via the antenna 9111. The communication module (transmitter / receiver) 9110 is coupled to the central processing unit 9100 to provide input signals and receive output signals, which can be the same as in the case of a conventional mobile communication terminal.

[0183] Based on different communication technologies, multiple communication modules 9110 can be provided in the same electronic device, such as a cellular network module, a Bluetooth module, and / or a wireless local area network module, etc. The communication module (transmitter / receiver) 9110 is also coupled to the speaker 9131 and the microphone 9132 via the audio processor 9130 to provide an audio output via the speaker 9131 and receive an audio input from the microphone 9132, so as to implement normal telecommunication functions. The audio processor 9130 can include any suitable buffer, decoder, amplifier, etc. In addition, the audio processor 9130 is also coupled to the central processing unit 9100, so that recording can be performed on the local machine through the microphone 9132, and the sound stored on the local machine can be played through the speaker 9131.

[0184] An embodiment of the present application also provides a computer-readable storage medium capable of implementing all steps of the method for judging the grounding fault of a low-voltage AC cable based on an armored layer, where the execution subject in the above embodiment is a server or a client. A computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, all steps of the method for judging the grounding fault of a low-voltage AC cable based on an armored layer, where the execution subject in the above embodiment is a server or a client, are implemented. For example, when the processor executes the computer program, the following steps are implemented:

[0185] S101: Determine the background current mean value of the armored layer according to the background current values of the armored layer of the low-voltage AC cable at different moments under normal working conditions;

[0186] S102: Determine the leakage current of the armored layer according to the capacitive reactance of the obtained armored layer, the voltage between the cable core layer and the armored layer, and the voltage between the armored layer and the ground;

[0187] S103: Judge the grounding fault of the low-voltage AC cable according to a pre-determined fault threshold and the leakage current; wherein, the fault threshold is determined according to the background current mean value.

[0188] As can be seen from the above description, the method for judging the grounding fault of a low-voltage AC cable based on an armored layer provided by the present application takes into account the operating characteristics that when the insulation of a low-voltage AC armored cable is damaged during actual operation, the armored layer first passes through the fault current. Under the condition of excluding the interference of the background current of the armored layer, the grounding fault of the cable is judged according to the leakage current, ensuring the accuracy of the monitoring data.

[0189] Those skilled in the art should understand that the embodiments of the present invention can be provided as methods, devices, or computer program products. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0190] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (apparatus), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable data processing devices to generate a machine, so that the instructions executed by the processors of the computer or other programmable data processing devices generate for implementation in the process Figure 1One or more processes and / or blocks Figure 1 means for the functions specified in one or more blocks.

[0191] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce a manufacture including an instruction means that implements the functions in the process Figure 1 One or more processes and / or blocks Figure 1 specified in one or more blocks.

[0192] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus, such that a series of operational steps are performed on the computer or other programmable apparatus to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable apparatus provide steps for implementing the functions specified in the process Figure 1 One or more processes and / or blocks Figure 1 specified in one or more blocks.

[0193] Specific embodiments are used in the present invention to illustrate the principles and implementation manners of the present invention. The description of the above embodiments is only for helping to understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for judging the grounding fault of a low-voltage AC cable based on an armored layer, characterized in that, Including: Determining the average background current of the armor layer according to the background current values of the armor layer of the low-voltage AC cable at different moments under normal working conditions; The leakage current of the armor layer is determined according to the obtained capacitive reactance of the armor layer, the voltage between the cable core layer and the armor layer, and the voltage between the armor layer and the earth; wherein, sampling is performed once every certain period of time to obtain the leakage current of the armor layer at different load moments t per unit time. i Background current I i ; According to the formula for calculating the average value of discrete variables Calculate the armor layer background current I aa Average value; this average value is also called background current mean, which represents the average value of background current at different load moments within a unit time; n is the total n load moments, and i is the different load moments; Determine whether there is a ground fault in the low-voltage AC cable according to a pre-determined fault threshold and the leakage current; wherein, the fault threshold includes: a warning threshold and an alarm threshold; the fault threshold is determined according to the mean value of the background current; wherein, by means of a fault simulation experiment on the line, a cable insulation fault is simulated at the end of the normally operating line to obtain the fault current value I at this time m ; Calculate the warning threshold and the alarm threshold according to the safety requirement coefficients α and β provided by on-site personnel; I ea is the leakage current from the cable core to the armor layer; I ag is the current from the armor layer to the ground; the warning threshold is I α = α × (|I m | - |I aa | - |I ea | + |I ag |), and the alarm threshold is I β = β × (|I m | - |I aa | - |I ea | + |I ag |).

2. The method for judging the grounding fault of a low-voltage AC cable based on an armored layer according to claim 1, wherein The step of determining the average background current of the armor layer according to the background current values of the armor layer of the low-voltage AC cable at different moments under normal working conditions includes: Using a mutual inductor characteristic tester to determine the background current value.

3. The method for judging the grounding fault of a low-voltage AC cable based on the armored layer according to claim 1, wherein The capacitive reactance of the armor layer includes: the first capacitive reactance between the cable core layer and the armor layer; the step of obtaining the capacitive reactance of the armor layer includes: Determining the first capacitance per unit length of the armor layer according to the surface radius of the cable core layer, the surface radius of the armor layer, and the first dielectric constant; Determining the first capacitive reactance according to the angular frequency of the low-voltage AC power grid and the first capacitance per unit length.

4. The method for judging the grounding fault of a low-voltage AC cable based on the armored layer according to claim 3, wherein, The capacitive reactance of the armor layer includes: the second capacitive reactance between the armor layer and the ground; the step of obtaining the capacitive reactance of the armor layer includes: Determining the second capacitance per unit length of the armor layer according to the surface radius of the insulation sheath of the low-voltage AC cable, the surface radius of the armor layer, and the second dielectric constant; Determining the second capacitive reactance according to the angular frequency of the low-voltage AC power grid and the second capacitance per unit length.

5. The method for judging the grounding fault of a low-voltage AC cable based on the armor layer according to claim 4, characterized in that, The leakage current includes: the cable core layer leakage current and the armor layer leakage current; the step of determining the leakage current of the armor layer according to the obtained capacitive reactance of the armor layer, the voltage between the cable core layer and the armor layer, and the voltage between the armor layer and the ground includes: Determining the cable core layer leakage current according to the first capacitive reactance and the voltage between the cable core layer and the armor layer; Determining the armor layer leakage current according to the second capacitive reactance and the voltage between the armor layer and the ground.

6. The method for judging the grounding fault of a low-voltage AC cable based on the armored layer according to claim 5, wherein, The step of judging the grounding fault of the low-voltage AC cable according to the pre-determined fault threshold and the leakage current includes: Comparing the leakage current with the warning threshold. If the leakage current is between the warning threshold and the alarm threshold, the low-voltage AC cable has a grounding fault and a warning is issued; Comparing the leakage current with the warning threshold. If the leakage current is greater than the alarm threshold, the low-voltage AC cable has a grounding fault and an alarm is made.

7. A low-voltage AC cable grounding fault judgment device based on an armored layer, characterized in that, Including: A background current determination unit for determining the average background current of the armor layer according to the background current values of the armor layer of the low-voltage AC cable at different moments under normal working conditions; A leakage current determination unit is configured to determine the leakage current of the armor layer based on the capacitive reactance of the armor layer, the voltage between the cable core layer and the armor layer, and the voltage between the armor layer and the ground obtained; wherein, sampling is performed at regular intervals to obtain the background current I i at different load times t i within a unit time; according to the discrete variable average value calculation formula the average value of the background current I of the armor layer is calculated aa ; this average value is also called the background current average value, which represents the average value of the background current at different load times within a unit time; n is the total number of n load times, and i is different load times; The ground fault judgment unit is used to determine whether there is a ground fault in the low-voltage AC cable according to a pre-determined fault threshold and the leakage current; wherein, the fault threshold includes: a warning threshold and an alarm threshold; the fault threshold is determined according to the average value of the background current; wherein, by means of a fault simulation experiment on the line, a cable insulation fault is simulated at the end of the normally operating line, and the fault current value I at this time is obtained. m ; Calculate the warning threshold and the alarm threshold according to the safety requirement coefficients α and β provided by the on-site personnel; I ea is the leakage current from the cable core to the armor layer; I ag is the current from the armor layer to the ground; the warning threshold is I α = α × (|I m | - |I aa | - |I ea | + |I ag |), and the alarm threshold is I β = β × (|I m | - |I aa | - |I ea | + |I ag |).

8. The low-voltage AC cable grounding fault judgment device based on the armor layer according to claim 7, characterized in that The background current determination unit includes: A moment current determination module for using a mutual inductor characteristic tester to determine the background current value.

9. The low-voltage AC cable grounding fault judgment device based on an armored layer according to claim 7, characterized in that, The capacitive reactance of the armor layer includes: the first capacitive reactance between the cable core layer and the armor layer, and further includes: A unit capacitive reactance determination unit for determining the first capacitance per unit length of the armor layer according to the surface radius of the cable core layer, the surface radius of the armor layer, and the first dielectric constant; An overall capacitive reactance determination unit for determining the first capacitive reactance according to the angular frequency of the low-voltage AC power grid and the first capacitance per unit length.

10. The low-voltage AC cable grounding fault judgment device based on the armor layer according to claim 9, characterized in that, The capacitive reactance of the armor layer includes: the second capacitive reactance between the armor layer and the ground, and further includes: The unit capacitive reactance determining unit is configured to determine the second capacitance per unit length of the armor layer according to the surface radius of the insulating sheath of the low-voltage AC cable, the surface radius of the armor layer, and the second dielectric constant; The overall capacitive reactance determining unit is configured to determine the second capacitive reactance according to the angular frequency of the low-voltage AC power grid and the second capacitance per unit length; 11. The low-voltage AC cable grounding fault judgment device based on an armored layer according to claim 10, characterized in that, The leakage current includes: the core layer leakage current and the armor layer leakage current; the leakage current determining unit includes: The core leakage current determining module is configured to determine the core layer leakage current according to the capacitive reactance of the armor layer and the voltage between the core layer and the armor layer; The armor leakage current determining module is configured to determine the armor layer leakage current according to the capacitive reactance of the armor layer and the voltage between the armor layer and the ground; 12. The low-voltage AC cable grounding fault judgment device based on an armored layer according to claim 11, wherein The ground fault judging unit includes: The warning module is configured to compare the leakage current with the warning threshold. If the leakage current is between the warning threshold and the alarm threshold, there is a ground fault in the low-voltage AC cable, and a warning is issued; The alarm module is configured to compare the leakage current with the warning threshold. If the leakage current is greater than the alarm threshold, there is a ground fault in the low-voltage AC cable, and an alarm is made; 13. An electronic device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the program, the steps of the method for judging the ground fault of the low-voltage AC cable based on the armor layer according to any one of claims 1 to 6 are implemented; 14. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, the steps of the method for judging the ground fault of the low-voltage AC cable based on the armor layer according to any one of claims 1 to 6 are implemented; 15. A computer program product, comprising a computer program / instructions, characterized in that, When the computer program / instructions are executed by the processor, the steps of the method for judging the ground fault of the low-voltage AC cable based on the armor layer according to any one of claims 1 to 6 are implemented;

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