A precise point method and system for cable fault

Abstract

The application provides a cable fault pinpointing method and system, comprising the following steps: acquiring electrical parameter data of a fault cable, judging the fault property of the fault cable; determining the distance range of a fault point from a measuring end according to a measured pulse value and the fault property of the fault cable; setting multiple measuring mark points according to a preset interval distance, measuring the potential and current change data on both sides of each measuring mark point; determining a fault positioning range according to the potential and current change data on both sides of the measuring mark point, and reducing the interval distance to measure the potential and current change data on both sides of the fault cable, and judging whether the fault cable has a fault at this position. The application measures the potential or current change condition along the cable path by keeping two metal electrodes at a fixed distance, and finally realizes accurate and efficient pinpointing of high-voltage and low-voltage cable faults.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of accurate pinpointing of cable faults, and particularly to an accurate pinpointing method and system for cable faults. BACKGROUND

[0002] Power cables gradually replace overhead lines in urban power grids and become the main mode of power transmission due to their safety, aesthetics, and high reliability of power supply. Power cables are generally laid underground and have a certain burial depth. Once a fault occurs, it is difficult to find the fault point as in the case of overhead line patrol, and there are certain requirements for the skills and theoretical level of the testers. Common voltage levels of power systems include 380V, 10kV, 35kV, 66kV, 110kV, and 220kV, among which 10kV and below are referred to as low-voltage levels, and also have a high fault rate.

[0003] The process of cable fault finding generally follows the classic four steps: judging the fault nature, pre-positioning the fault distance, path finding, and accurate pinpointing. The main methods for accurate pinpointing in the existing stage are acoustic-magnetic synchronization method and step voltage method, but both have certain limitations and cannot meet the requirements of pinpointing faults of various types of cables. For example, the efficiency of the acoustic-magnetic synchronization method is not high for low-resistance grounding faults and most low-voltage cable faults. When the cable is short-circuited to ground, the sound of the fault click-through gap discharge is light or even non-existent, so the acoustic-magnetic synchronization method cannot be used. Low-voltage cables do not have copper shielding or even steel armor, so it is not easy to form a test loop like 10kV cables. Therefore, a rough distance cannot be obtained, and only blind listening and digging along the cable can be performed, which is time-consuming and labor-intensive. Due to environmental factors and personal experience, the conventional acoustic-magnetic synchronization method often has an error of about 0.5 meters for direct-buried high and low voltage cables, which indirectly leads to an enlarged excavation area or even a wrong location of the cable. If the cable is laid in a pipe, it is more difficult to locate the discharge sound at the pipe opening. The traditional step voltage method has certain requirements for the use scene, and the instrument needle can only test open grounding faults of direct-buried cables and cannot be used for detecting non-open and other laying methods of cable faults. With the progress of the times, newly produced outdoor low-voltage cables are required to be laid in pipes, and the acoustic-magnetic synchronization method and step voltage method cannot be used for pinpointing the fault points of the cables laid in pipes. SUMMARY

[0004] The purpose of the present application is to provide an accurate pinpointing method and system for cable faults, which solves the technical problem of low efficiency of accurate pinpointing of fault points of power cable faults in direct-buried laying, metallic grounding faults, and top-pipe or pipe-laid cables.

[0005] In one aspect, an accurate pinpointing method for cable faults is provided, comprising:

[0006] Obtaining electrical parameter data of the fault cable, and judging a fault property of the fault cable according to the electrical parameter data of the fault cable; wherein the electrical parameter data at least includes voltage, current and resistance;

[0007] Emitting corresponding pulses from a measurement end of the fault cable by a preset cable fault locator, and determining a distance range of the fault point from the measurement end according to a measured pulse value and the fault property of the fault cable;

[0008] Obtaining a trend and a depth of the fault cable, setting multiple measurement marker points according to a preset interval distance, and outputting high-voltage pulses at the multiple measurement marker points by a preset cable fault locator, and measuring potential and current change data on both sides of each measurement marker point;

[0009] Determining a fault location range according to the potential and current change data on both sides of each measurement marker point, gradually reducing the interval distance in the fault location range to measure potential and current change data on both sides of the fault cable, and judging whether the fault cable at the place has a fault according to the potential and current change data on both sides of the fault cable.

[0010] Preferably, the judging of the fault property of the fault cable according to the electrical parameter data of the fault cable specifically includes:

[0011] When a measured ground insulation value is greater than a preset insulation value threshold, judging that the fault property of the fault cable is high-resistance fault;

[0012] When the measured ground insulation value is less than the preset insulation value threshold, judging that the fault property of the fault cable is low-resistance fault.

[0013] Preferably, the emitting of the corresponding pulses from the measurement end of the fault cable by the preset cable fault locator specifically includes:

[0014] When the fault property of the fault cable is high-resistance fault, emitting multiple high-voltage pulses from the measurement end of the fault cable by the preset cable fault locator;

[0015] When the fault property of the fault cable is low-resistance fault, emitting a low-voltage pulse from the measurement end of the fault cable by the preset cable fault locator.

[0016] Preferably, the method further includes:

[0017] When the fault cable is a low-voltage cable without steel armor, measuring corresponding pulse values by preset three fault location points, and determining a range in which the fault point is located between two fault location points according to the measured pulse values;

[0018] In the range between the two fault location points where the fault point is located, three fault location points are set again and the corresponding pulse values are measured to determine the range where the fault point is located, until the final fault point is determined.

[0019] Preferably, the potential and current variation data on both sides of each measurement marker point are measured, specifically including:

[0020] When the fault cable is located under the road surface or other hard surface, the two-pole measurement rods are respectively provided with preset conductive fittings and immersed in conductive liquid, and the measurement rods are inserted into both sides of the measurement marker points to measure the corresponding pulse values.

[0021] Preferably, the potential and current variation data on both sides of each measurement marker point are measured, specifically including:

[0022] When the fault cable is located in a pipe, corresponding pipe detection rods are arranged on the pipe-penetrating strip of the fault cable, and the pipe-penetrating strip and the pipe detection rods are inserted into both sides of the measurement marker points to detect the step voltage signal.

[0023] Preferably, the potential and current variation data on both sides of each measurement marker point are measured, specifically including:

[0024] When the potential difference rapidly increases, it is determined that the fault point is approached;

[0025] When the potential difference does not increase after reaching the maximum value, it is determined that the candidate fault point is located.

[0026] Preferably, the potential and current variation data on both sides of each measurement marker point are measured, specifically including:

[0027] The potential difference on both sides of the candidate fault point is tested by a preset test rod, and if the candidate fault point is in the middle of the test rod and the potential difference is zero, it is determined that the candidate fault point is the final fault point.

[0028] Preferably, the preset insulation value threshold is between 200Ω and 1000Ω.

[0029] In another aspect, a precise fault point system of a cable fault is also provided to implement the precise fault point method of the cable fault, which includes:

[0030] A fault property judgment module is configured to obtain electrical parameter data of the fault cable and determine the fault property of the fault cable according to the electrical parameter data of the fault cable, wherein the electrical parameter data at least includes voltage, current and resistance;

[0031] The distance judging module is used for transmitting corresponding pulses from the measuring end of the fault cable through a preset cable fault locator, and determining the distance range of the fault point from the measuring end according to the measured pulse value and the fault nature of the fault cable.

[0032] The change detecting module is used for acquiring the trend and depth of the fault cable, setting multiple measuring mark points according to a preset interval distance, and outputting high-voltage pulses at the multiple measuring mark points through a preset cable fault locator, and measuring the potential and current change data on both sides of each measuring mark point.

[0033] The fault judging module is used for determining the fault locating range according to the potential and current change data on both sides of the measuring mark point, gradually reducing the interval distance to measure the potential and current change data on both sides of the fault cable in the fault locating range, and judging whether the fault cable at the place exists fault according to the potential and current change data on both sides of the fault cable.

[0034] In summary, the embodiment of the present application has the following beneficial effects:

[0035] The cable fault accurate pinpointing method and system provided by the present application optimizes and integrates the classic cable fault finding operation steps on the basis of the traditional step voltage method, reselects a high-voltage emission source and adds auxiliary accessories, and finally realizes accurate and efficient pinpointing of high-voltage and low-voltage cable faults. The high-voltage unit of the tester can effectively break down the fault point due to its large energy. When the tester breaks down the cable fault point by adding pulse voltage, the current enters the ground through the cable fault point, generating a step voltage around the fault point. The potential or current change is measured along the cable path by two metal electrodes with a fixed distance. When approaching the fault point, the potential difference will rapidly increase and reach the maximum value before and after the fault point. When the fault point is exactly at the midpoint of the two test rods, the galvanometer indication is 0, so the polarity of the step voltage can be detected to accurately pinpoint the fault point. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to these drawings without creative labor.

[0037] Figure 1 It is a main flow diagram of a cable fault accurate pinpointing method in an embodiment of the present application.

[0038] Figure 2 It is a logic diagram of a cable fault accurate pinpointing method in an embodiment of the present application.

[0039] Figure 3 This is a schematic diagram showing the connection between the cable fault locator and the faulty cable in an embodiment of the present invention.

[0040] Figure 4 This is a schematic diagram of the positioning of a direct-buried cable in an embodiment of the present invention.

[0041] Figure 5 This is a schematic diagram of a precise location system for cable faults according to an embodiment of the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0043] like Figure 1 and Figure 2 The diagram shown is a schematic representation of an embodiment of a method for accurately locating cable faults provided by the present invention. In this embodiment, the method includes the following steps:

[0044] Obtain electrical parameter data of the faulty cable, and determine the nature of the fault based on the electrical parameter data of the faulty cable; wherein, the electrical parameter data includes at least voltage, current and resistance; that is, determine whether the fault is grounding, short circuit, open circuit or mixed fault; whether it is single-phase, two-phase or three-phase fault; whether it is high resistance, low resistance or leakage or flashover fault.

[0045] In this embodiment, when the measured insulation value to ground is greater than a preset insulation value threshold, the faulty cable is determined to be a high-resistance fault; when the measured insulation value to ground is less than the preset insulation value threshold, the faulty cable is determined to be a low-resistance fault. The preset insulation value threshold is between 200Ω and 1000Ω. An insulation megohmmeter and a multimeter are mainly used, and the boundaries between low-resistance and high-resistance faults are generally defined by an insulation value to ground of 200Ω to 1000Ω.

[0046] A preset cable fault locator emits a corresponding pulse from the measuring end of the faulty cable. Based on the measured pulse value and the nature of the fault in the cable, the distance range between the fault point and the measuring end is determined. In other words, based on the nature of the fault, the cable fault locator selects an appropriate testing method to measure the distance from the fault point to the testing end. The cable fault locator has a high-voltage unit.

[0047] In the embodiment, when the fault property of the fault cable is high resistance fault, the cable fault locator is preset to emit multiple high voltage pulses from the measuring end of the fault cable; when the fault property of the fault cable is low resistance fault, the cable fault locator is preset to emit low voltage pulses from the measuring end of the fault cable. The method is mainly applied to multiple pulse method and low voltage pulse method. The multiple pulse method is used for high resistance fault (insulation value greater than 1000Ω), and the low voltage pulse method is used for low resistance fault. The connection between the cable fault locator and the fault cable is shown in Figure 3

[0048] Specifically, when the fault cable is a low voltage cable without steel armor, the corresponding pulse values are measured by the preset three fault locating points, and the range of the fault point between the two fault locating points is determined according to the measured pulse values; three fault locating points are set in the range between the two fault locating points where the fault point is located, and the corresponding pulse values are measured, and the range of the fault point is determined in turn until the final fault point is determined. That is, the low voltage cable without steel armor is not easy to form a test loop, so a rough distance cannot be obtained, and therefore the bisection method is used to continuously reduce the range of the fault point.

[0049] The trend and depth of the fault cable are obtained, multiple measurement marker points are set at a preset interval distance, and the cable fault locator is preset to output high voltage pulses at the multiple measurement marker points to measure the potential and current change data on both sides of each measurement marker point. That is, for the direct buried and buried pipe laid cable, the cable trend and depth need to be measured by a path instrument, and the trend and depth are marked every 15 meters, and the direction and depth are marked at the turning nodes.

[0050] In the embodiment, when the fault cable is located below the road surface or other hard surface, the two poles of the measuring rod are respectively provided with a preset conductive fitting and immersed in conductive liquid, and the measuring rod is inserted into both sides of the measurement marker point to measure the corresponding pulse value. When the fault cable is located in the pipe, a corresponding pipe detection rod is arranged on the pipe penetrating strip of the fault cable, and the pipe detection rod is inserted into both sides of the measurement marker point together with the pipe penetrating strip to detect the step voltage signal. That is, if the fault point is located below the road surface or other hard surface, a sponge sleeve can be used. The sponge sleeve is immersed in conductive liquid, and two metal electrodes are inserted into the sponge sleeve. The detection can be performed in the normal manner. During detection, the sponge sleeve should be kept as wet as possible, but the two sponge sleeves should not be connected by water to cause signal short circuit. Alternatively, some water can be sprinkled on the two ground needles. If the fault point is located in the pipe, a special pipe detection rod is installed on the pipe penetrating strip, and the pipe detection rod is inserted into the fault point together with the pipe penetrating strip to detect the step voltage signal. The precondition for use is to inject an appropriate amount of water into the pipe to ensure that the leakage current of the fault point has a good propagation medium.

[0051] ​Specifically, a detection rod capable of being used in a pipe is provided for the cable fault of pipe laying, two metal electrodes are replaced by metal soft wires with insulating sheaths, and a small section of the two wires is exposed as a test pole of a galvanometer, the two poles are fixed on a glass fiber rod at a certain distance, and finally the detection rod is sleeved on the front end of the pipe laying strip to detect the step voltage signal near the fault point. The premise for use is to inject an appropriate amount of water into the pipe to ensure that the leakage current at the fault point has a good propagation medium; for the operating environment of hardened pavement with rapid signal attenuation, a matched sponge sleeve and conductive liquid are installed for detection of the hardened pavement. After the sponge sleeve is soaked in the conductive liquid, it is installed on the metal detection pole to absorb more signals.

[0052] According to the potential and current change data of both sides of the measurement mark point, the fault positioning range is determined, and the potential and current change data of both sides of the fault cable are measured by gradually reducing the interval distance in the fault positioning range. Whether the fault cable at this position exists a fault is judged according to the potential and current change data of both sides of the fault cable. That is, the approximate range of the fault point is measured by referring to the fault distance pre-positioning and the cable path, and the corresponding accurate pinpointing method (including acoustic method, acoustic-magnetic synchronous method, step voltage method, audio induction method, infrared temperature measurement method, electromagnetic positioning method, etc.) is used according to the operating environment and the fault nature. For the directly buried cable, the acoustic-magnetic synchronous method is used for detection first, the sound maximum point is found, and the range is reduced to within 0.5 meters. Then, the point position is verified by using the invented step voltage cable fault finding auxiliary positioning instrument, and the range is further accurately determined, and finally the range is accurately determined to within 0.1 meters.

[0053] In this embodiment, as shown in Figure 4 When the potential difference rapidly increases, it is determined that the fault point is approached; when the potential difference does not increase after reaching the maximum value, it is determined that the candidate fault point is at this position. The potential difference of both sides of the candidate fault point is tested by the preset test rod. If the candidate fault point is in the middle of the test rod and the potential difference is zero, it is determined that the candidate fault point is the final fault point.

[0054] As shown in Figure 5 The application also provides an accurate pinpointing system of a cable fault, which is used to realize the accurate pinpointing method of the cable fault, and comprises:

[0055] A fault nature judgment module is used to acquire the electrical parameter data of the fault cable, and to judge the fault nature of the fault cable according to the electrical parameter data of the fault cable; wherein the electrical parameter data at least includes voltage, current and resistance;

[0056] A distance judgment module is used to emit corresponding pulses from the measurement end of the fault cable by a preset cable fault positioning instrument, to determine the distance range of the fault point from the measurement end according to the measured pulse value and the fault nature of the fault cable.

[0057] The change detection module is used to obtain the route and depth of the fault cable, set multiple measurement marker points according to a preset interval distance, and output high-voltage pulses at the multiple measurement marker points through a preset cable fault locator, and measure the potential and current change data on both sides of each measurement marker point.

[0058] The fault judgment module is used to determine a fault positioning range according to the potential and current change data on both sides of the measurement marker point, gradually reduce the interval distance to measure the potential and current change data on both sides of the fault cable in the fault positioning range, and determine whether the fault cable at the position exists a fault according to the potential and current change data on both sides of the fault cable.

[0059] It should be noted that the system described in the above embodiment corresponds to the method described in the above embodiment, and therefore, the parts not described in detail in the system described in the above embodiment can be obtained by referring to the content of the method described in the above embodiment, which will not be described here.

[0060] In summary, the embodiments of the present application have the following beneficial effects:

[0061] The cable fault accurate positioning method and system provided by the present application optimizes and integrates the classic cable fault finding operation steps on the basis of the traditional step voltage method, reselects a high-voltage emission source and adds auxiliary accessories, and finally realizes accurate and efficient positioning of high-voltage and low-voltage cable faults. The high-voltage unit of the tester has a large energy, which can effectively break down the fault point. When the tester adds pulse voltage to break down the cable fault point, the current enters the ground through the cable fault point, generating a step voltage around the fault point. The potential or current change is measured along the cable path by two metal electrodes with a fixed distance. When approaching the fault point, the potential difference will rapidly increase and reach a maximum value before and after the fault point. When the fault point is exactly at the midpoint of the two test rods, the indicating meter of the current detector is 0, so the polarity of the step voltage can be detected to accurately position the fault point.

[0062] The above only discloses the preferred embodiments of the present application, and of course cannot limit the scope of the rights of the present application, so equivalent changes made according to the claims of the present application still fall within the scope of the present application.

Claims

1. A method of pinpointing a cable fault, characterized in that, The method comprises the following steps: acquiring electrical parameter data of a fault cable and determining the fault property of the fault cable according to the electrical parameter data of the fault cable; wherein the electrical parameter data at least includes voltage, current and resistance; emitting corresponding pulses from a measuring end of the fault cable by a preset cable fault locator, and determining the distance range of the fault point from the measuring end according to the measured pulse value and the fault property of the fault cable; acquiring the trend and depth of the fault cable, setting multiple measuring marker points according to a preset interval distance, and outputting high-voltage pulses at the multiple measuring marker points by a preset cable fault locator, and measuring the potential and current change data on both sides of each measuring marker point; determining the fault location range according to the potential and current change data on both sides of the measuring marker point, gradually reducing the interval distance in the fault location range to measure the potential and current change data on both sides of the fault cable, and determining whether there is a fault in the fault cable according to the potential and current change data on both sides of the fault cable; when the fault cable is a low-voltage cable without a steel armor, measuring corresponding pulse values by preset three fault location points, and determining the range of the fault point between the two fault location points according to the measured pulse values; setting three fault location points in the range between the two fault location points where the fault point is located and measuring corresponding pulse values, sequentially determining the range where the fault point is located, and determining the final fault point until the final fault point is determined; the method of determining the fault location range according to the potential and current change data on both sides of the measuring marker point, specifically comprising: when the potential difference rapidly increases, it is determined that the fault point is close; when the potential difference reaches the maximum value and does not increase, it is determined that the candidate fault point is located.

2. The method of claim 1, wherein, the method of determining the fault property of the fault cable according to the electrical parameter data of the fault cable, specifically comprising: when the measured insulation value to ground is greater than a preset insulation value threshold, it is determined that the fault property of the fault cable is high-resistance fault; when the measured insulation value to ground is less than a preset insulation value threshold, it is determined that the fault property of the fault cable is low-resistance fault.

3. The method of claim 2, wherein, the method of emitting corresponding pulses from the measuring end of the fault cable by a preset cable fault locator, specifically comprising: when the fault property of the fault cable is high-resistance fault, emitting multiple high-voltage pulses from the measuring end of the fault cable by a preset cable fault locator; when the fault property of the fault cable is low-resistance fault, emitting low-voltage pulses from the measuring end of the fault cable by a preset cable fault locator.

4. The method of claim 3, wherein, the method of measuring the potential and current change data on both sides of each measuring marker point, specifically comprising: when the fault cable is located below the road surface or other hard surface, the two-pole measuring rods are respectively provided with a preset conductive accessory and immersed in conductive liquid, the measuring rods are inserted into both sides of the measuring marker point, and the corresponding pulse values are measured.

5. The method of claim 4, wherein, the method of measuring the potential and current change data on both sides of each measuring marker point, further comprising: When the fault cable is located in the pipe, corresponding pipe detection rods are arranged on the pipe penetrating strips of the fault cable, and are inserted into both sides of the measurement mark point together with the pipe penetrating strips and detect the step voltage signal.

6. The method of claim 1, wherein, The fault positioning range determined according to the potential and current change data on both sides of the measurement mark point further comprises: The potential difference on both sides of the candidate fault point is tested by the preset test rod, and if the candidate fault point is in the middle of the test rod and the potential difference is zero, the candidate fault point is determined as the final fault point.

7. The method of claim 2, wherein, The preset insulation value threshold is between 200Ω and 1000Ω.

8. A system for accurate fault location of a cable for implementing the method according to claims 1-7, characterized in that, Comprise: The fault property judgment module is used to acquire the electrical parameter data of the fault cable, and determine the fault property of the fault cable according to the electrical parameter data of the fault cable; wherein the electrical parameter data at least includes voltage, current and resistance; The distance judgment module is used to emit corresponding pulses from the measurement end of the fault cable by the preset cable fault locator, and determine the distance range of the fault point from the measurement end according to the measured pulse value and the fault property of the fault cable; The change detection module is used to acquire the trend and depth of the fault cable, set multiple measurement mark points according to the preset interval distance, and output high-voltage pulses at multiple measurement mark points by the preset cable fault locator, and measure the potential and current change data on both sides of each measurement mark point; The fault judgment module is used to determine the fault positioning range according to the potential and current change data on both sides of the measurement mark point, and gradually reduce the interval distance to measure the potential and current change data on both sides of the fault cable in the fault positioning range, and determine whether there is a fault in the fault cable according to the potential and current change data on both sides of the fault cable; The distance judgment module is further used to: when the fault cable is a low-voltage cable without steel armor, measure the corresponding pulse value by the preset three fault positioning points, and determine the range between the two fault positioning points where the fault point is located according to the measured pulse value; set three fault positioning points in the range between the two fault positioning points where the fault point is located and measure the corresponding pulse value, and sequentially determine the range where the fault point is located until the final fault point is determined; The fault judgment module is further used to: when the potential difference rapidly increases, it is determined that the fault point is close; when the potential difference reaches the maximum value and does not increase, it is determined that this place is a candidate fault point.

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