CN114755603A - A method and device for grounding loop current testing and fault diagnosis of portable cables - Google Patents

Abstract

The present application relates to a portable cable ground loop test and fault diagnosis method and device. The device includes an acquisition host and a background diagnosis system; the acquisition host includes a synchronous acquisition module, an analysis and processing module, a communication module, a power supply module and a display screen. The synchronous acquisition module includes two acquisition channels, which are respectively connected to a cable body composite current acquisition sensor and a ground loop current acquisition sensor. The analysis and processing module processes the acquired signals to obtain accurate cable load currents; the communication module The processed cable load current and ground loop current are transmitted to the background diagnosis system, and threshold analysis and cluster analysis are performed on the information detected at multiple points. The invention can test the ground loop current of the cable and analyze and diagnose the ground fault. , improve the reliability of grounding circulation detection, and accurately diagnose the grounding of cable lines.

Description

A method and device for grounding loop current testing and fault diagnosis of portable cables

technical field

The present application relates to the field of on-line monitoring of power system cables, and in particular, to a portable cable ground loop test and fault diagnosis method and device.

Background technique

The single-core power cable has the particularity of the structure. When the AC current flows through the core, the metal sheath of the cable generates induced electromotive force due to mutual inductance in the alternating magnetic field generated by the core current. The greater the current flowing through the core, the longer the cable, and when the cable is laid in an equilateral triangle, the induced electromotive force of the metal sheath will be higher. In order to ensure the safety of personnel and the normal operation of the cable, 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 methods of the metal sheath of the single-core power cable of the AC system mainly include single-end grounding, two-end grounding, and cross-connection grounding. One end of a single-ended grounded cable is directly grounded, and the other end is grounded through a sheath protector. For underwater cables and cables with small transmission capacity, when the single-end direct grounding method of the metal sheath cannot meet the limit of the induced voltage within the range specified in GB 50217-2007 Design Specifications for Power Engineering Cables, the metal sheath at both ends of the line will be used. The protective layer is directly grounded, and its applicable conditions are very harsh, so this method is rarely used in general. When the line is very long, the cross-connected grounding method is adopted, the line is divided into several units, and the cable is divided into 3 sections at equal distances in each unit. A set of insulating joints is installed between each section, and the metal sheath at the insulating joint is led to the cross-connected grounding box with coaxial cable for transposition, and then grounded through the cable sheath protector, and the two units are directly connected to each other. Grounded so that within each unit, the induced voltages on the metal sheaths of equidistant cables cancel each other out by being 120° out of phase with each other.

Due to the aging of the outer sheath of the cable, the scratching of the outer sheath when the cable is laid, the fault of the sheath protector, and the transposition wiring error in the cross-connection, the abnormal grounding circulation of the cable will occur, which is easy to cause the cable line after long-term operation. breakdown faults, so periodic testing of ground loops makes sense and is necessary. At present, the current test of cable grounding circulation is usually carried out with a clamp meter to test the grounding current, reading the grounding current value, basically ignoring the influence caused by the cable load and grounding method, and not paying attention to the correlation of grounding circulation current at different grounding points, resulting in grounding The current test is inaccurate and misses a lot of hidden troubles. The ground loop current can reflect the operating state of the cable line to a certain extent, and it can be easily obtained without affecting the power supply of the system, and has become an important indicator for evaluating the reliability of high-voltage cables. According to Q-GDW11223-2014 "Technical Specifications for Condition Detection of High Voltage Cables", the diagnostic basis for grounding circulating current of high-voltage cable lines includes: 1) the absolute value of grounding circulating current <50A; 2) the ratio of grounding circulating current and load <20%; 3) single-phase grounding Circulation maximum/minimum value <3. Before that, the grounding current detection and diagnosis of high-voltage cable lines was only judged based on the absolute value of the grounding circulating current. This standard provides the basic diagnostic basis for the ground current detection of high-voltage cable lines, and shows that the ground loop current is related to the cable load. The method of judging system failure is meaningful. 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 power transmission cable body, and the current value includes the cable load current and the grounding circulating current, which is likely to cause very large errors in the cable grounding fault diagnosis through the grounding current.

Due to the above problems, in the field of cable grounding circulation, there is an urgent need for a method and device that can collect the real load of the cable on-site, accurately judge the grounding state of the cable, and have a fault diagnosis function.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the present invention proposes a method and device for portable ground loop current testing and fault diagnosis of cables. Perform vector calculation on the composite current of the cable body and the grounding circulating current, and accurately calculate the load current of the transmission cable. Detect the grounding loop current and the load current of the cable body at each point in a grounding system, and realize the identification and location of cable grounding defects through the characteristic value threshold and cluster analysis.

To achieve the above purpose, the application provides the following technical solutions:

In a first aspect, an embodiment of the present application provides a portable cable ground loop test and fault diagnosis device, including a collection host and a background diagnosis system;

Wherein, the acquisition host includes a synchronous acquisition module, an analysis and processing module, a communication module, a power supply module and a display screen,

The synchronous acquisition module includes two acquisition channels, which are respectively connected to a composite current acquisition sensor of the cable body and a grounding circulating current acquisition sensor for synchronously collecting the composite current and the grounding circulating current of the power transmission cable body,

The analysis and processing module processes the collected signal, calculates the phase difference between the collected composite current of the power transmission cable body and the grounding loop current of the cable, and performs a vector difference operation on the collected signal to obtain an accurate cable load current;

The communication module transmits the processed cable load current and ground loop current to the background diagnosis system, and performs threshold analysis and cluster analysis on the information detected by multiple points,

The power supply module supplies power to the acquisition host,

The display screen is used to realize the function of data collection and display.

The composite current through the cable body includes the load current flowing through the conductor core of the high-voltage cable and the time-domain superimposed current of the grounding circulating current flowing through the metal sheath of the cable. The real load current of the cable is the current through the cable body and the circulating current through the cable sheath. vector difference.

In a second aspect, an embodiment of the present application provides a portable grounding loop current testing and fault diagnosis method for a portable cable. The specific steps include: at a detection point, installing a cable body composite current acquisition sensor on the power transmission cable body, and installing the grounding loop current acquisition sensor on the power transmission cable body. Installed on the corresponding grounding wire of the same-phase cable, synchronously collect the composite current and grounding circulation current of the cable body, and transmit the collected signal to the analysis and processing module of the acquisition host through the data synchronization acquisition module, and process the composite current and grounding circulation current of the cable body to obtain the accurate detection point. At the next detection point, repeat the above steps to complete the detection of the grounding point of the cable, and the detection data is transmitted to the background diagnosis system through the communication network. With minimum ratio, circulating current and load ratio, ratio mode identification, establish self-learning mode for fault interval location and fault type diagnosis.

By measuring the grounding circulating current of the three-phase cable at the same detection point, and calculating the total grounding circulating current by vector calculation, it is determined whether the grounding system is abnormal.

Determine whether the grounding system is abnormal by measuring the maximum, minimum, maximum and minimum ratios of the grounding current. The single-phase grounding circulating current value is greater than 50A, the grounding circulating current and the transmission cable load ratio are greater than 50%, and the three-phase grounding circulating current maximum and minimum If the ratio of values is greater than 3, the grounding system is abnormal.

Determine whether the grounding system is abnormal by calculating the proportional relationship between the grounding circulating current and the cable load current.

For cross-connection and grounding, the line is divided into several units, and the cable is divided into 3 sections at equal distances in each unit. A set of insulating joints is installed between each section, and the metal sheath at the insulating joint is used The coaxial cable is led to the cross-connection grounding box for transposition, and then grounded through the cable sheath protector, and the two units are directly grounded. After normalization, cluster analysis is performed on the normalized values to distinguish the normal and abnormal points of the grounding circulation and load ratio, and determine the ground fault interval and fault type according to the points.

By drawing a complete grounding system and comprehensively analyzing the transmission cable load current and grounding circulation current at multiple detection points, typical single fault types can be distinguished:

If both ends of the grounding system are directly grounded, the structure does not meet the design and use requirements of the cable line, and the abnormality is the wrong grounding method;

If the protective grounding system is abnormal, it is determined that the abnormality is the abnormality of the sheath protector;

If the cross-connection system is abnormal, according to the cluster analysis of the load circulation ratio, it can be judged whether the abnormality is the cross-connection transposition wiring error of the three equally divided sections of the cross-connection section or the first or third section of the cross-connection section. ground fault.

Compared with the prior art, the beneficial effects of the present invention are: (1) The cable load current measured by the present invention is based on the principle of the composite current collection sensor and the composition analysis of the composite current of the power transmission cable body, and the composite current of the cable body is collected synchronously. It can analyze the components of the composite current of the cable body, eliminate the mixed grounding circulating current, and obtain the real cable load current. Therefore, the load circulating current ratio, a key characteristic parameter for judging grounding system faults, is more accurate and effective.

(2) The present invention studies the load circulation ratio and grounding defects based on the circuit topology by measuring the precise load and grounding circulation of the transmission cables at multiple detection points in the complete grounding system, especially the cross-connected grounding system. The relationship between the maximum and minimum values of grounding circulation current, the maximum and minimum ratios, the load circulation ratio and other characteristic state quantities are analyzed by threshold value and cluster analysis, and the fault type and defect interval are determined by clustering outliers.

(3) The present invention measures the transmission cable load current and grounding circulation at multiple detection points in a complete grounding system, and the background diagnosis system can observe the line conditions from the overall system structure, such as grounding system design errors, cross-connection transposition errors, etc. It is necessary to analyze the overall circulation data of the line to avoid blindness.

Description of drawings

In order to explain the technical solutions of the embodiments of the present application more clearly, the following briefly introduces the accompanying drawings that need to be used in the embodiments of the present application. It should be understood that the following drawings only show some embodiments of the present application, therefore It should not be regarded as a limitation of the scope. For those of ordinary skill in the art, other related drawings can also be obtained from these drawings without any creative effort.

FIG. 1 is a schematic structural diagram of a portable cable grounding circulating current collection device according to the present invention.

Figure 2 is a schematic diagram of a cross-connected grounding system.

FIG. 3 is a schematic diagram of a method for grounding loop current testing and fault diagnosis of a portable cable according to the present invention.

Detailed ways

The technical solutions in the embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application. It should be noted that like numerals and letters refer to like items in the following figures, so once an item is defined in one figure, it does not require further definition and explanation in subsequent figures.

The terms "comprising", "comprising" or any other variation thereof are intended to encompass non-exclusive inclusion such that a process, method, article or device comprising a list of elements includes not only those elements, but also other not expressly listed elements, or also include elements inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in a process, method, article or apparatus that includes the element.

As shown in FIG. 1, the present invention provides a portable cable grounding loop test and fault diagnosis device. As shown in FIG. 1, the device includes a collection host and a background diagnosis system. The collection host includes a display screen 1, a casing 2, and a body composite current Collection sensor 3 , grounding circulation collection sensor 4 , synchronous collection module 5 , analysis and processing module 6 , communication module 7 , and power supply module 8 .

The synchronous acquisition module 5 includes two acquisition channels, which are respectively connected to a cable body composite current acquisition sensor 3 and a ground circulation current acquisition sensor 4 for synchronously collecting the power transmission cable body composite current and ground circulation current.

The analysis and processing module 6 processes the collected signal, calculates the phase difference between the collected composite current of the power transmission cable body and the grounding loop current of the cable, and performs a vector difference operation on the collected signal to obtain an accurate cable load current;

The communication module 7 transmits the processed cable load current and ground loop current to the background diagnosis system, and performs threshold analysis and cluster analysis on the information detected by multiple points,

The power supply module 8 supplies power to the acquisition host,

The display screen 1 is used to realize the function of data collection and display.

The composite current through the cable body includes the load current flowing through the conductor core of the high-voltage cable and the time-domain superimposed current of the grounding circulating current flowing through the metal sheath of the cable. The real load current of the cable is the current through the cable body and the circulating current through the cable sheath. vector difference.

As shown in FIG. 2 , the present invention can perform ground fault determination on a cross-connected cable grounding system including FIG. 2 . C2 and C3 have a total of 12 detection points. For a cross-connected cable grounding system, the portable cable grounding circulation collecting device should be used to detect the grounding circulation and the composite current of the cable body at the points shown in Figure 2.

As shown in Figure 3, the schematic diagram of the data acquisition, analysis and diagnosis of the present invention, the grounding loop current of the three-phase cable and the composite current of the corresponding phase transmission cable body are collected respectively. Through vector calculation, threshold analysis, normalization processing, and cluster analysis, fault interval determination and fault type diagnosis are realized.

At a detection point, install the composite current acquisition sensor of the cable body on the transmission cable body, install the ground loop current acquisition sensor on the corresponding ground wire of the same-phase cable, synchronously collect the composite current of the cable body and the ground loop current, and collect the signal through the data synchronously collected The module is transmitted to the analysis and processing module of the acquisition host, and the composite current of the cable body and the grounding circulating current are processed to obtain the accurate cable load current of the detection point; at the next detection point, repeat the above steps to complete the detection of the grounding point of the cable once. The detection data is transmitted to the background diagnosis system through the communication network. The background diagnosis system establishes a self-learning mode to locate the fault interval and diagnose the fault type by identifying the maximum, minimum, maximum and minimum ratios of the grounding circulating current, the ratio of the circulating current and the load, and the ratio. .

By measuring the grounding circulating current of the three-phase cable at the same detection point, and calculating the total grounding circulating current by vector calculation, it is determined whether the grounding system is abnormal.

Determine whether the grounding system is abnormal by measuring the maximum value, minimum value, and the ratio of the maximum and minimum grounding current. For protective grounding, if the single-phase grounding circulating current value is greater than 0.7A, the grounding system is abnormal. Variety;

For direct grounding, if the single-phase grounding circulating current value is greater than 50A, the grounding circulating current and the transmission cable load ratio is greater than 50%, and the ratio of the three-phase grounding circulating current maximum value to the minimum value is greater than 3, the grounding system is abnormal.

Determine whether the grounding system is abnormal by calculating the proportional relationship between the grounding circulating current and the cable load current.

For cross-connection and grounding, the line is divided into several units, and the cable is divided into 3 sections at equal distances in each unit. A set of insulating joints is installed between each section, and the metal sheath at the insulating joint is used The coaxial cable is led to the cross-connection grounding box for transposition, and then grounded through the cable sheath protector, and the two units are directly grounded. After normalization, cluster analysis is performed on the normalized values to distinguish the normal and abnormal points of the grounding circulation and load ratio, and determine the ground fault interval and fault type according to the points.

By drawing a complete grounding system and comprehensively analyzing the transmission cable load current and grounding circulation current at multiple detection points, typical single fault types can be distinguished:

If both ends of the grounding system are directly grounded, the structure does not meet the design and use requirements of the cable line, and the abnormality is the wrong grounding method;

If the protective grounding system is abnormal, it is determined that the abnormality is the abnormality of the sheath protector;

If the cross-connection system is abnormal, according to the cluster analysis of the load circulation ratio, it can be judged whether the abnormality is the cross-connection transposition wiring error of the three equally divided sections of the cross-connection section or the first or third section of the cross-connection section. ground fault.

The acquisition host includes two acquisition channels, which are used to synchronously collect the composite current of the cable body and the grounding loop current of the cable, and obtain the accurate cable load current after analysis and processing by the host; , upload the data to the background diagnosis system, analyze the abnormal parameter indicators of the grounding cable, and determine the fault interval and fault type of the cable sheath. The invention can test the grounding circulating current of the cable and analyze and diagnose the grounding fault, improve the reliability of the grounding circulating current detection, and accurately diagnose the grounding condition of the cable line.

The above descriptions are merely examples of the present application, and are not intended to limit the protection scope of the present application. For those skilled in the art, various modifications and changes may be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this 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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