CN103926510B - A method for on-line monitoring and fault diagnosis and positioning of cable sheath current and ampacity - Google Patents

Abstract

The invention relates to a method for on-line monitoring and fault diagnosis and positioning of current and current-carrying capacity of a cable sheath, and belongs to the technical field of on-line monitoring, fault diagnosis and positioning of power cables. The technical scheme is as follows: the sheath current and current-carrying capacity sensors synchronously acquire current data and upload the current data to the data management platform through a communication network; the data management platform collects, automatically processes and temporarily or permanently stores state monitoring data at regular time, displays all state data on a screen of a monitoring center in real time, and provides various data report functions; the fault diagnosis system extracts real-time sheath current data in a database management platform and compares the real-time sheath current data with an expected value; once the fault in the cable is found, early warning information is provided for the cable operation and maintenance personnel through the warning unit. The invention can monitor the operation condition of the power cable in real time, automatically carry out fault diagnosis and positioning and early warning prompt when abnormal monitoring information occurs, can accurately diagnose and position the selected cable fault type, and saves manpower and financial resources.

Description

A method for on-line monitoring and fault diagnosis and positioning of cable sheath current and ampacity

technical field

The invention relates to a method for on-line monitoring of cable sheath current and ampacity and fault diagnosis and location, in particular to a method for diagnosing and locating cable faults through the ratio relationship between the real-time measured value and the expected value of the cross-connected cable sheath current, belonging to Power cable online monitoring and fault diagnosis and positioning technology field.

Background technique

With the development of the city, the number of single-core high-voltage power cables of 110kV and above has increased sharply, and the cable load has increased day by day. The problem of grounding current of the cable metal sheath caused by the operation of a large number of single-core cables has attracted more and more attention. . Under normal circumstances, the metal sheath of 110kV and above high-voltage single-core cables generally adopts the operation mode of cross-connected double-ended grounding or single-ended direct grounding. According to GB-50217 "Code for Design of Electric Power Engineering Cables", the maximum value of the normal induced potential at any point on the metal layer of the AC single-core power cable that is not directly grounded should meet the following requirements: Safety measures that can effectively prevent personnel from arbitrarily touching the metal layer are not adopted. Measures, shall not be greater than 50V; in addition to the above circumstances, shall not be greater than 300V. Since the high-voltage cable adopts a single-core structure, according to the principle of electromagnetism, this will inevitably cause an induced voltage to appear on the metal sheath. In order to reduce the induced voltage on the cable sheath so that it will not be too large, the cable metal sheath should be grounded in sections to limit the magnitude of the induced voltage. Under normal circumstances, the induced voltage in the sheath is low and meets the design standards. However, when the cross-interconnection grounding point of the intermediate joint or the metal sheath of the cable body fails, it will cause the breakdown of the outer sheath or the burnout of the sheath protector, and more seriously, the breakdown of the main insulation of the cable. In this case The metal sheath may be grounded at multiple points, forming a high sheath current, which not only reduces the current carrying capacity of the cable, but also wastes electric energy and causes loss, and accelerates the aging of the cable insulation. Therefore, it is necessary to periodically check the metal sheath of the above cable. Ground current detection to prevent unplanned power outages caused by cable faults.

The detection methods of the background technology mainly include: (1) regular or irregular manual inspections, in order to find abnormalities and hidden dangers of high-voltage cables and their ancillary facilities and deal with them in time; (2) regularly inspect important cables such as high-voltage cable terminals and intermediate joints (3) Regularly measure the current of the metal sheath of the high-voltage cable manually; (4) Conduct a preventive test on important high-voltage cable lines every year. The main items include testing the main insulation resistance, sheath insulation resistance and AC voltage withstand test for main insulation. In actual work, due to the gradual increase in the total length of the laying of high-voltage cable lines, it is difficult to carry out manual daily operation, maintenance and repair work in strict accordance with the regulations due to its high labor costs. In particular, high-voltage cable joints or terminals are usually installed in special electric wells or on high-voltage cable towers. Manually measuring state parameters such as the metal sheath current or surface temperature of these cables requires a lot of manpower, material resources, and financial resources; During the inspection of the line, the real-time operation status of the high-voltage cable is usually not known during the interval between two inspections, so that the operation and maintenance personnel cannot obtain the necessary early warning information in time before the high-voltage cable fault occurs, resulting in some unnecessary economic losses. Therefore, it is necessary to develop a set of sheath current online monitoring technology that can be used for cable fault diagnosis and location.

Contents of the invention

The purpose of the present invention is to provide an on-line monitoring of cable sheath current and ampacity and a method for fault diagnosis and location, which can realize the diagnosis and location of faults in cables through on-line monitoring of sheath current, and solve the problems existing in the background technology.

Technical scheme of the present invention is:

A method for on-line monitoring of cable sheath current and ampacity and fault diagnosis and location, comprising the following steps:

① Through the data acquisition module, communication network, data management platform and fault diagnosis module, the online monitoring of cable sheath current and carrying capacity and fault diagnosis and positioning are realized;

②The data acquisition module is composed of multiple sheath current sensors and an ampacity sensor; the clamp current sensor is installed at the inlet of the cross-connected grounding box under the condition of live cable operation to collect the sheath current signal and pass it on the cable body. The clamp current sensor on the cable collects the current carrying capacity data of the cable; the current signal is collected synchronously through the data acquisition card; the collected sheath current signal and current carrying capacity data are uploaded to the data management platform for theoretical calculation and the cable information is stored in the database;

③The sheath current and ampacity sensor in the data acquisition module samples the sheath current signal and ampacity data of the high-voltage cable, and then uploads them to the data management platform located in the monitoring center through the communication network; the data management platform regularly collects, automatically processes and temporarily Or store status monitoring data permanently, and display all status data on the monitoring center screen in real time, and provide various data reporting functions; the database of the data management platform is used to store various temporary or permanent storage status monitoring data; temporarily stored data It consists of real-time monitoring data; the permanently stored data includes various parameter values of the target cable: segment length, phase-to-phase distance, cable design parameters, and the sheath at each measurement point under non-fault conditions calculated according to these parameter values The expected value of the current under different load conditions and the ratio relationship between the measured values of the sheath current at the two joints;

④The fault diagnosis module evaluates the health status of the cable by comparing the real-time monitoring data with the expected value stored in the cable state database; when the deviation between the real-time data of the cable and the expected value of the non-fault state is greater than the set Status information to diagnose and locate typical faults in cables.

The present invention is also equipped with an alarm unit, including a large-screen display interface and an early warning mode that jumps out of the alarm window; when the early warning information appears, the monitoring host can promptly and effectively notify the high-voltage cable operation and maintenance personnel, realizing the comprehensive online monitoring and early warning of the high-voltage cable state The purpose is to facilitate the operation and maintenance personnel of high-voltage cables to grasp the status of the cables and their operating environment at any time, find defects in time, and avoid electrical accidents.

The beneficial effects of the present invention are: (1) Real-time monitoring of the operation of power cables, transmission of monitoring information to the data management platform of the system for record and analysis, and automatic fault diagnosis and positioning and early warning prompts when abnormal monitoring information occurs; (2) For A set of sheath current amplitude standards that can be used for cable fault diagnosis and location is proposed for cross-connected three-phase cables with equal cable segment lengths and return lines; The simple judgment standard of current change can accurately diagnose and locate the selected cable fault type; abandon the traditional method of finding the fault point by inspecting the line after an abnormal situation is found, saving manpower and financial resources.

Description of drawings

Fig. 1 is the structural diagram of the fault diagnosis and positioning system of the sheath current online monitoring level; 1 is the monitoring center, 2 is the data acquisition module, including multiple current sensors, 3 is the fault diagnosis and positioning module, 4 is the alarm unit, and 5 is the database system , 6 is the communication system;

Figure 2 is a schematic diagram of three-phase cable cross interconnection wiring and sensor installation.

detailed description

The present invention will be further described below in conjunction with accompanying drawing.

As shown in Figure 1, the main purpose of the present invention is to realize the on-line monitoring function of the sheath current in the metal sheath of the high-voltage cable, to realize the real-time monitoring of the high-voltage cable line, and to detect cable fault defects and send an alarm in time. The sheath current and ampacity sensors collect current data synchronously and upload them to the data management platform through the communication network. The data management platform regularly collects, automatically processes, and temporarily or permanently stores status monitoring data, and displays all status data on the monitoring center screen in real time, while providing various data reporting functions. The fault diagnosis system extracts the real-time sheath current data from the database management platform and compares it with the expected value. Once a fault in the cable is found, it will automatically diagnose its type and locate the joint or circuit, and provide early warning information to the cable operation and maintenance personnel through the alarm unit.

As shown in Figure 2, for the cross-connected grounding box JX1, the currents measured by the current transformers at the three measurement points are , , , for the cross-connected grounding box JX2, the currents measured by the current transformers at the three measurement points are , , , the three-phase balanced load current measured by the ampacity sensor is . Then the ratio of the current through the sheath to the carrying capacity and the sheath current , , The three ratios between the following types of faults can be diagnosed and located to the joint or sheath circuit, as shown in Table 1.

use Indicates the expected value of the sheath current (the expected value varies with the load), using express express When the expected value of the three-phase cable segment is equal and the system is equipped with a return line, the fault diagnosis and location can be based on the following standards:

If "the real-time measurement value at a certain sensor is 0";

FaultType = "Sensor fault here"

If "the real-time measured values are all 0";

FaultType = "Line Empty"

If "for any , can make the inequality established and for any , can make the inequality established";

The line is running normally

If "exists , so that the inequality established and for any , can make the inequality Established", then enter this section of the judgment process:

If "for any , can make the inequality established and for any , can make the inequality established";

failure_type = "1"

If "for any , can make the inequality established and for any , can make the inequality established";

failure_type = "2"

If "for any , can make the inequality established and for any , can make the inequality established";

failure_type = "3"

If "for any , can make the inequality established";

FaultType = "6"

Else FaultType = "Unknown Type"

If "exists makes the inequality established and exists , so that the inequality Established", then enter this section of the judgment process:

If "for any , can make the inequality established";

failure_type = "4"

If "for any , can make the inequality established";

FaultType = "5"

like" and exists , so that the inequality established";

failure_type = "7"

like" and for any , can make the inequality established";

failure_type = "10"

like" and exists , so that the inequality established";

failure_type="8"

like" and for any , can make the inequality established";

FaultType = "11"

like" and exists , so that the inequality established";

failure_type = "9"

like" and for any , can make the inequality established";

failure_type = "12"

Else FaultType = "Unknown Type"

When the real-time monitored sheath current value reaches the expected fault current value, the fault diagnosis and location system automatically judges the type and location of the fault based on the measured data, and displays the early warning information on the large screen of the monitoring center, so that the cable operation and maintenance personnel can quickly Dealing with faults provides important support for ensuring the stability of the power system.

Claims (2)

1. cable sheath electric current and a current-carrying capacity on-line monitoring and fault diagonosing localization method, is characterized in that, comprise following steps:

1. cable sheath electric current and current-carrying capacity on-line monitoring and fault diagonosing location is realized by data acquisition module, communication network, data management platform and fault diagnosis module;

2. data acquisition module is made up of multiple circulating current sensor and a current-carrying capacity sensor; Cross connection grounding case incoming line place under the charged ruuning situation of cable is set with pincerlike current sensor to gather circulating current signal and by being sleeved on the pincerlike current sensor on cable body, to gather current-carrying capacity of cable data; By data collecting card synchronous acquisition current signal; Upload the circulating current signal that collects and current-carrying capacity data to data management platform carries out theory calculate and stored in a database by cable information;

The circulating current signal of the circulating current 3. in data acquisition module and current-carrying capacity sensor sample high-tension cable and current-carrying capacity data, be then uploaded to the data management platform being positioned at Surveillance center by communication network; Data management platform timed collection, automatically process and interim or permanent storage Condition Monitoring Data, and all status datas are shown in real time on Surveillance center's screen, various data sheet function is provided simultaneously; The database of data management platform is used for depositing the Condition Monitoring Data of various interim or permanent storage; The data of temporary reservoir are made up of Real-time Monitoring Data; The data of permanent storage comprise the parameters value of object cable: section length, phase spacing, cable design parameter, and the circulating current desired value under different load conditions of each measurement point in the non-faulting situation gone out according to these parameter value calculation and the ratio relation of two joint circulating current measured values;

4. fault diagnosis module is by comparing the expected value stored in the data of Real-Time Monitoring and cable status database, the health status of assessment cable; When the deviation of cable real time data and non-faulting state desired value is greater than setting value, according to the status information in database, the typical fault in cable is diagnosed and locates.

2. a kind of cable sheath electric current according to claim 1 and current-carrying capacity on-line monitoring and fault diagonosing localization method, is characterized in that being provided with alarm unit, comprises large screen display interface and the alarm mode jumping out warning window; When there is early warning information, monitoring main frame can notify high-tension cable operation maintenance personnel timely and effectively, achieve the object of the comprehensive on-line monitoring of high-tension cable state, early warning, be convenient to the state that high-tension cable operation maintenance personnel grasp cable and running environment thereof at any time, Timeliness coverage defect, avoids electric power accident occurs.