CN114755603A - Portable cable grounding circulation testing and fault diagnosis method and device - Google Patents
Portable cable grounding circulation testing and fault diagnosis method and device Download PDFInfo
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- CN114755603A CN114755603A CN202210255678.9A CN202210255678A CN114755603A CN 114755603 A CN114755603 A CN 114755603A CN 202210255678 A CN202210255678 A CN 202210255678A CN 114755603 A CN114755603 A CN 114755603A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
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Abstract
The application relates to a portable cable grounding circulation testing and fault diagnosis method and a portable cable grounding circulation testing and fault diagnosis device, wherein the device comprises an acquisition host and a background diagnosis system; the acquisition host comprises a synchronous acquisition module, an analysis processing module, a communication module, a power supply module and a display screen, wherein the synchronous acquisition module comprises two acquisition channels which are respectively connected with 1 cable body composite current acquisition sensor and 1 grounding circulation acquisition sensor, and the analysis processing module processes acquired signals to obtain accurate cable load current; the communication module transmits the processed cable load current and the grounding circulation to the background diagnosis system, and performs threshold analysis and cluster analysis on information detected by a plurality of point positions.
Description
Technical Field
The application relates to the field of online monitoring of cables of power systems, in particular to a portable cable grounding circulation testing and fault diagnosis method and device.
Background
The single-core power cable has structural particularity, and when alternating current flows through a wire core, the cable metal protective layer generates induced electromotive force in an alternating magnetic field generated by the wire core current due to mutual inductance. The larger the current flowing through the wire core is, the longer the cable is, and when the cable is laid on a non-equilateral triangle, the higher the induced electromotive force of the metal protective layer is. In order to ensure the safety of personnel and the normal operation of the cable, the electrical safety regulations stipulate that the metal sheath of the cable must take corresponding grounding measures to eliminate or release the excessive induced voltage during operation. The grounding mode of the metal sheath of the single-core power cable of the alternating current system mainly comprises single-end grounding, two-end grounding, cross interconnection grounding and the like. One end of the single-end grounded cable line is directly grounded, and the other end of the single-end grounded cable line is grounded through the sheath protector. For underwater cables and cables with smaller transmission capacity, when the single-end direct grounding mode of the metal sheath cannot meet the requirement of limiting the induction voltage within the range specified by the design specifications of GB 50217-2007 power engineering cables, the direct grounding mode of the metal sheaths at the two ends of the circuit is adopted, the application conditions are very strict, and the mode is rarely adopted under the common conditions. When the line is long, a cross interconnection grounding mode is adopted to divide the line into a plurality of units, and the cable is divided into 3 sections with equal distance in each unit. A group of insulating joints are arranged among each section, the metal sheath at the insulating joints is led to a cross interconnection grounding box for transposition by a coaxial cable, then the metal sheath is grounded by a cable sheath protector, and every two units are directly grounded, so that induced voltages on the metal sheaths of the cables with equal distances in each unit are mutually offset due to the phase difference of 120 degrees.
Due to the aging of the outer protection layer of the cable, the scratch of the outer protection layer during the laying of the cable, the fault of a protection layer protector, the transposition wiring error in cross interconnection and other reasons, the abnormity of the grounding circulation of the cable can occur, and the breakdown fault of a cable line can be easily caused after long-time operation, so that the periodical test on the grounding circulation is very necessary. At present, a cable grounding circulation test is usually carried out by carrying a clamp meter to test grounding current, the value of the grounding current is read, the influence caused by cable load and a grounding mode is basically ignored, the relevance of grounding circulation of different grounding points is not concerned, the grounding current test is inaccurate, and a lot of fault hidden dangers are omitted. The grounding circulation can reflect the running state of a cable line to a certain extent, and can be conveniently obtained under the condition of not influencing the power supply of a system, so that the grounding circulation becomes an important index for evaluating the reliability of the high-voltage cable. According to Q-GDW11223-2014 technical Specification for detecting high-voltage cable states, the basis for detecting and diagnosing the grounding circulation of the high-voltage cable line comprises the following steps: 1) the absolute value of the grounding circulation is less than 50A; 2) the ratio of the grounding circulation to the load is less than 20 percent; 3) the maximum/minimum value of the single-phase grounding circulation is less than 3. Before that, the detection and diagnosis of the grounding current of the high-voltage cable line are judged according to the absolute value of the grounding circulation current. The standard provides a basic diagnosis basis for detecting the ground current of the high-voltage cable line, shows that the ground circulation is related to the size of the cable load, and is meaningful to form a judgment method for the fault of the cable grounding system by researching the relation between the state characteristic quantity of the load circulation ratio and the positions of grounding defects and defects. Therefore, obtaining the true value of the cable load affects the accuracy of the grounding system fault.
According to the prior art, the equipment for testing the cable load current actually obtains the composite current of the transmission cable body, and the current value comprises the cable load current and the grounding circulation current, which easily causes great errors for carrying out cable grounding fault diagnosis through the grounding current.
Due to the problems, in the field of cable grounding circulation, a method and a device which can collect the real load of a cable on site, accurately judge the grounding state of the cable and have a fault diagnosis function are urgently needed.
Disclosure of Invention
In order to solve the technical problems, the invention provides a portable method and a device for testing the grounding circulation of the cable and diagnosing the fault. And detecting the grounding circulation current of each point in a grounding system and the load current of the cable body, and realizing the identification and the positioning of the grounding defects of the cable through a characteristic value threshold value and cluster analysis.
In order to achieve the above purpose, the present application provides the following technical solutions:
In a first aspect, an embodiment of the present application provides a portable cable grounding loop current testing and fault diagnosing apparatus, which includes an acquisition host and a background diagnosing system;
wherein the acquisition host comprises a synchronous acquisition module, an analysis processing module, a communication module, a power supply module and a display screen,
the synchronous acquisition module comprises two acquisition channels which are respectively connected with 1 cable body composite current acquisition sensor and 1 grounding circulation acquisition sensor and used for synchronously acquiring the composite current and the grounding circulation of the transmission cable body,
the analysis processing module processes the acquired signals, calculates the phase difference between the acquired composite current of the transmission cable body and the cable grounding circulation, and performs vector difference operation on the acquired signals to obtain accurate cable load current;
the communication module transmits the processed cable load current and the ground circulation to the background diagnosis system, performs threshold analysis and cluster analysis on the information detected by the plurality of point locations,
the power supply module supplies power to the acquisition host,
the display screen is used for realizing the data acquisition and display functions.
The composite current passing through the cable body comprises a load current flowing through a conductor core of the high-voltage cable and a time domain superposed current flowing through a grounding circular current of a metal sheath of the cable, and the real load current of the cable is a vector difference between the current passing through the cable body and the circular current of the cable sheath.
In a second aspect, an embodiment of the present application provides a portable cable ground loop current testing and fault diagnosis method, which includes: at a detection point, a cable body composite current acquisition sensor is installed on a transmission cable body, a grounding circulation acquisition sensor is installed on a corresponding grounding wire of an in-phase cable, the composite current and the grounding circulation of the cable body are synchronously acquired, an acquired signal is transmitted to an acquisition host analysis processing module through a data synchronous acquisition module, the composite current and the grounding circulation of the cable body are processed, and the accurate cable load current of the detection point is obtained; and at the next detection point, repeating the steps to complete the detection of the cable return earth point, transmitting detection data to a background diagnosis system through a communication network, and establishing a self-learning mode by the background diagnosis system through identifying the maximum value, the minimum value, the maximum and minimum ratio of the grounding circulation, the circulation-load ratio and the ratio mode to perform fault interval positioning and fault type diagnosis.
And (3) calculating the total grounding circulation by measuring the grounding circulation of the three-phase cables at the same detection point, and judging whether the grounding system is abnormal or not.
And (3) judging whether the grounding system is abnormal or not by measuring the maximum value, the minimum value and the ratio of the maximum value to the minimum value of the grounding current, wherein the single-phase grounding circulation value is greater than 50A, the ratio of the grounding circulation to the load of the transmission cable is greater than 50%, and the ratio of the maximum value to the minimum value of the three-phase grounding circulation is greater than 3, so that the grounding system is abnormal.
And judging whether the grounding system is abnormal or not by calculating the proportional relation between the grounding circulation and the cable load current.
Aiming at cross interconnection grounding, a line is divided into a plurality of units, a cable is divided into 3 sections at equal intervals in each unit, a group of insulating joints are arranged between each section, a metal sheath at the insulating joints is led to a cross interconnection grounding box by a coaxial cable for transposition, then the cable sheath protector is grounded, every two units are directly grounded, the grounding circulation current and the load ratio of a plurality of detection points of a cross interconnection section are normalized, then the numerical values after normalization are subjected to cluster analysis, the points with normal grounding circulation current and load ratio and abnormal points are distinguished, and the grounding fault section and the fault type are judged according to the points.
By drawing a complete grounding system and comprehensively analyzing the load current and the grounding circulation current of the power transmission cable with a plurality of detection points, the typical single fault type can be distinguished:
if the two ends of the grounding system are directly grounded, the structural design and use requirements of the cable line are not met, and the abnormity is a grounding mode error;
if the protection grounding system is abnormal, judging the abnormality as the abnormality of the protective layer protector;
If the cross interconnection system is abnormal, whether the abnormal condition is a three-small-section cross interconnection transposition wiring error in the cross interconnection section or a ground fault of a first small section or a third small section in the cross interconnection section can be judged according to the cluster analysis of the load circulation ratio.
Compared with the prior art, the invention has the beneficial effects that: (1) the cable load current measured by the invention is established on the basis of the principle of a composite current collecting sensor of a power transmission cable body and the analysis of composite current composition, the composite current and the grounding circulation of the cable body are synchronously collected, the composite current of the cable body is subjected to component analysis, the mixed grounding circulation is eliminated, and the real cable load current is obtained, so that the method is more accurate and effective in judging the load circulation ratio of key characteristic parameters of the grounding system fault.
(2) The invention researches the relation between the state characteristic quantity of the load circulation ratio and the grounding defect and the defect position by measuring the accurate load and the grounding circulation of the power transmission cables of a plurality of detection points in a complete grounding system, particularly a cross-connection grounding system, on the basis of circuit topology, carries out threshold analysis and cluster analysis on the characteristic state quantity of the maximum value, the minimum value, the maximum-minimum ratio, the load circulation ratio and the like of the grounding circulation, and determines the fault type and the defect interval by clustering abnormal values.
(3) The invention measures the load current and the grounding circulation of the transmission cable at a plurality of detection points in the complete grounding system, and the background diagnosis system can observe the line condition from the whole system structure, such as the design error of the grounding system, the cross interconnection transposition error and the like, which need to analyze the whole circulation data of the line, thereby avoiding a single-leaf fault.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments of the present application will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and that those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.
Fig. 1 is a schematic structural diagram of a portable cable grounding circulation current collecting device according to the present invention.
Fig. 2 is a schematic diagram of a cross-interconnect grounding system.
Fig. 3 is a schematic diagram of a portable cable ground loop current testing and fault diagnosis method according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
As shown in fig. 1, the invention provides a portable cable grounding circulation testing and fault diagnosis device, as shown in fig. 1, the device comprises a collection host and a background diagnosis system, wherein the collection host comprises a display screen 1, a shell 2, a body composite current collection sensor 3, a grounding circulation collection sensor 4, a synchronous collection module 5, an analysis processing module 6, a communication module 7 and a power supply module 8.
The synchronous acquisition module 5 comprises two acquisition channels which are respectively connected with 1 cable body composite current acquisition sensor 3 and 1 grounding circulation acquisition sensor 4 and are used for synchronously acquiring the composite current and the grounding circulation of the transmission cable body,
The analysis processing module 6 is used for processing the acquired signals, calculating the phase difference between the acquired composite current of the transmission cable body and the cable grounding circulating current, and performing vector difference operation on the acquired signals to obtain accurate cable load current;
the communication module 7 transmits the processed cable load current and the ground circulation current to the background diagnosis system, performs threshold analysis and cluster analysis on information detected by a plurality of point locations,
the power module 8 supplies power to the acquisition host,
the display screen 1 is used for realizing the data acquisition and display functions.
The composite current passing through the cable body comprises a load current flowing through a conductor core of the high-voltage cable and a time domain superposed current flowing through a grounding circular current of a metal sheath of the cable, and the real load current of the cable is a vector difference between the current passing through the cable body and the circular current of the cable sheath.
As shown in fig. 2, the present invention can determine the ground fault of a cross-connected cable grounding system including the cross-connected cable grounding system shown in fig. 2, wherein 12 detection points are a0, a1, a2, A3, B0, B1, B2, B3, C0, C1, C2 and C3, and the portable cable grounding circulation current collecting device should be used for detecting the grounding circulation current and the cable body composite current of the points shown in fig. 2 for a cross-connected cable grounding system.
As shown in fig. 3, the schematic diagrams of data acquisition, analysis and diagnosis of the present invention respectively acquire the grounding loop current of a three-phase cable and the composite current of a corresponding-phase transmission cable body, and implement fault interval determination and fault type diagnosis by vector calculation, threshold analysis, normalization processing and cluster analysis for three grounding modes, namely, direct grounding, protection grounding and cross interconnection grounding.
At a detection point, a cable body composite current acquisition sensor is installed on a transmission cable body, a grounding circulation acquisition sensor is installed on a corresponding grounding wire of an in-phase cable, the composite current and the grounding circulation of the cable body are synchronously acquired, an acquired signal is transmitted to an acquisition host analysis processing module through a data synchronous acquisition module, the composite current and the grounding circulation of the cable body are processed, and the accurate cable load current of the detection point is obtained; and repeating the steps at the next detection point, completing the detection of the cable-return ground point, transmitting detection data to a background diagnosis system through a communication network, and establishing a self-learning mode by the background diagnosis system through identifying the modes of the maximum value, the minimum value, the maximum and minimum ratio of the grounding circulation, the circulation-load ratio and the ratio, so as to perform fault interval positioning and fault type diagnosis.
And (3) calculating the total grounding circulation by measuring the grounding circulation of the three-phase cable at the same detection point position and carrying out vector calculation, and judging whether the grounding system is abnormal or not.
Whether the grounding system is abnormal or not is judged by measuring the maximum value, the minimum value and the ratio of the maximum value to the minimum value of the grounding current, and if the single-phase grounding circulating current value is greater than 0.7A aiming at protection grounding, the grounding system is abnormal, the threshold value is adjustable, and the threshold value can be changed according to different application environments;
for direct grounding, the single-phase grounding circulation value is larger than 50A, the ratio of the grounding circulation to the load of the power transmission cable is larger than 50%, and the ratio of the maximum value to the minimum value of the three-phase grounding circulation is larger than 3, the grounding system is abnormal.
And judging whether the grounding system is abnormal or not by calculating the proportional relation between the grounding circulation current and the cable load current.
Aiming at cross interconnection grounding, a line is divided into a plurality of units, a cable is divided into 3 sections at equal intervals in each unit, a group of insulating joints are arranged between each section, a metal sheath at the insulating joints is led to a cross interconnection grounding box by a coaxial cable for transposition, then the cable sheath protector is grounded, every two units are directly grounded, the grounding circulation current and the load ratio of a plurality of detection points of a cross interconnection section are normalized, then the numerical values after normalization are subjected to cluster analysis, the points with normal grounding circulation current and load ratio and abnormal points are distinguished, and the grounding fault section and the fault type are judged according to the points.
By drawing a complete grounding system and comprehensively analyzing the load current and grounding circulation of the power transmission cable at a plurality of detection points, the typical single fault type can be distinguished:
if the two ends of the grounding system are directly grounded, the structural design and use requirements of the cable line are not met, and the abnormity is a grounding mode error;
if the protection grounding system is abnormal, judging the abnormality as the abnormality of the protective layer protector;
if the cross-connection system is abnormal, judging whether the abnormality is a wiring error of three equally-divided small cross-connection transposition sections in the cross-connection section or a ground fault of a first small section or a third small section in the cross-connection section according to cluster analysis of the load circulation ratio.
The collection host comprises two collection channels for synchronously collecting the composite current of the cable body and the cable grounding circulation current, and obtaining accurate cable load current after the analysis and the processing of the host; the data are uploaded to a background diagnosis system by acquiring grounding circulation currents of all grounding positions in a cable return line and load currents of the same-phase cable, abnormal parameter indexes of the grounding cable are analyzed, and a fault interval and a fault type of a cable sheath are determined. The invention can test the cable grounding circulation and analyze and diagnose the grounding fault, thereby improving the reliability of the grounding circulation detection and accurately diagnosing the grounding condition of the cable line.
The above description is only an example of the present application and is not intended to limit the scope of the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (8)
1. A portable cable grounding circulation testing and fault diagnosis device is characterized by comprising a collection host and a background diagnosis system;
wherein the acquisition host comprises a synchronous acquisition module, an analysis processing module, a communication module, a power supply module and a display screen,
the synchronous acquisition module comprises two acquisition channels which are respectively connected with 1 cable body composite current acquisition sensor and 1 grounding circulation acquisition sensor and used for synchronously acquiring composite current and grounding circulation of the transmission cable body,
the analysis processing module processes the acquired signals, calculates the phase difference between the acquired composite current of the transmission cable body and the cable grounding circulation, and performs vector difference operation on the acquired signals to obtain accurate cable load current;
the communication module transmits the processed cable load current and the ground circulation to the background diagnosis system, performs threshold analysis and cluster analysis on the information detected by the plurality of point locations,
The power supply module supplies power to the acquisition host,
the display screen is used for realizing the data acquisition and display functions.
2. The portable cable ground loop testing and fault diagnosis device of claim 1, wherein the composite current passing through the cable body comprises a time domain superimposed current of a load current flowing through the conductor core of the high voltage cable and a ground loop current flowing through the metal sheath of the cable, and a real load current of the cable is a vector difference between a current passing through the cable body and a loop current of the cable sheath.
3. A portable cable grounding circulation testing and fault diagnosis method is characterized by comprising the following specific steps: at a detection point, a cable body composite current acquisition sensor is installed on a transmission cable body, a grounding circulation acquisition sensor is installed on a corresponding grounding wire of an in-phase cable, the composite current and the grounding circulation of the cable body are synchronously acquired, an acquired signal is transmitted to an acquisition host analysis processing module through a data synchronous acquisition module, the composite current and the grounding circulation of the cable body are processed, and the cable load current with accurate detection point is obtained; and repeating the steps at the next detection point, completing the detection of the cable-return ground point, transmitting detection data to a background diagnosis system through a communication network, and establishing a self-learning mode by the background diagnosis system through identifying the modes of the maximum value, the minimum value, the maximum and minimum ratio of the grounding circulation, the circulation-load ratio and the ratio, so as to perform fault interval positioning and fault type diagnosis.
4. The portable cable grounding circulation testing and fault diagnosis method as claimed in claim 3, wherein the grounding circulation of the three-phase cable at the same detection point is measured, the total grounding circulation is calculated vectorially, and whether the grounding system is abnormal or not is determined.
5. The portable cable ground circulation test and fault diagnosis method according to claim 3, wherein the maximum value, the minimum value, and the maximum-to-minimum ratio of the ground current are measured to determine whether the ground system is abnormal, wherein the single-phase ground circulation value is greater than 50A, the ratio of the ground circulation to the transmission cable load is greater than 50%, and the ratio of the maximum value to the minimum value of the three-phase ground circulation is greater than 3, and the ground system is abnormal.
6. The portable cable grounding circulation testing and fault diagnosis method as claimed in claim 3, wherein whether the grounding system is abnormal is determined by calculating a proportional relationship between grounding circulation and cable load current.
7. A portable cable ground circulation test and fault diagnosis method as claimed in claim 3,
aiming at cross interconnection grounding, a line is divided into a plurality of units, a cable is divided into 3 sections at equal intervals in each unit, a group of insulating joints are arranged between each section, a metal sheath at the insulating joints is led to a cross interconnection grounding box by a coaxial cable for transposition, then the cable sheath protector is grounded, every two units are directly grounded, the grounding circulation current and the load ratio of a plurality of detection points of a cross interconnection section are normalized, then the numerical values after normalization are subjected to cluster analysis, the points with normal grounding circulation current and load ratio and abnormal points are distinguished, and the grounding fault section and the fault type are judged according to the points.
8. The portable cable grounding loop current testing and fault diagnosis method according to claim 7,
by drawing a complete grounding system and comprehensively analyzing the load current and the grounding circulation current of the power transmission cable with a plurality of detection points, the typical single fault type can be distinguished:
if the two ends of the grounding system are directly grounded, the structural design and use requirements of the cable line are not met, and the abnormity is a grounding mode error;
if the protection grounding system is abnormal, judging the abnormality as the abnormality of the protective layer protector;
if the cross-connection system is abnormal, judging whether the abnormality is a wiring error of three equally-divided small cross-connection transposition sections in the cross-connection section or a ground fault of a first small section or a third small section in the cross-connection section according to cluster analysis of the load circulation ratio.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115856708A (en) * | 2023-02-28 | 2023-03-28 | 江苏省电力试验研究院有限公司 | Cross interconnection grounding test method and system using coaxial cable |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115856708A (en) * | 2023-02-28 | 2023-03-28 | 江苏省电力试验研究院有限公司 | Cross interconnection grounding test method and system using coaxial cable |
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