CN113805007A - High-voltage cable health state online monitoring system and monitoring method thereof - Google Patents
High-voltage cable health state online monitoring system and monitoring method thereof Download PDFInfo
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- CN113805007A CN113805007A CN202111205818.3A CN202111205818A CN113805007A CN 113805007 A CN113805007 A CN 113805007A CN 202111205818 A CN202111205818 A CN 202111205818A CN 113805007 A CN113805007 A CN 113805007A
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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
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
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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
- G01R31/083—Locating faults in cables, transmission lines, or networks according to type of conductors in cables, e.g. underground
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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
- G01R31/088—Aspects of digital computing
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Abstract
The invention discloses a high-voltage cable health state online monitoring system and a monitoring method thereof, aiming at the problem that the detection result of the existing cable monitoring technology is not accurate and comprehensive enough, the invention provides the following technical scheme that the high-voltage cable health state online monitoring system is deployed on a high-voltage cable transmission line to monitor the running load and the high-frequency current and the power frequency current flowing in a grounding line in real time; judging whether the cable is normally grounded or not according to the comparison of the cable operation load data and the circulating current data; if the grounding system is normal, extracting high-frequency current transient characteristic quantity including energy ratio P2And information entropy S2(ii) a Acquiring normal threshold values P of the energy ratio and the information entropy of the system according to the monitoring samples of the energy ratio and the information entropy1And S1(ii) a Analysis of P by thresholding1And P2、S1And S2And evaluating the health state of the cable. The invention can simultaneously monitor the running state of the cable grounding system and the condition of the cable body insulation structure, and realize multi-level and comprehensive evaluation of the cable health state.
Description
Technical Field
The invention relates to the field of cable monitoring, in particular to a high-voltage cable health state online monitoring system and a monitoring method thereof.
Background
In the process of building an urban power grid, the power cable is more and more widely applied due to the advantages of stable and reliable power transmission performance, difficult weather influence, small occupied area and the like. However, the high-voltage cable in operation has a circulating current flowing through the sheath, and the value of the circulating current can reach the same quantity level as the operation load under the abnormal condition, so that a large amount of energy loss can be generated, the temperature rise of the cable is too high, and the aging of the cable body is accelerated.
The size of the high-voltage cable sheath circulating current is closely related to the cable laying mode, the cable phase sequence arrangement mode, the quality of the sheath material and the running state of the protector. In addition, under the action of electricity, heat and machinery, the insulation material of the body can age to cause the reduction of insulation resistance, so that the increase of insulation leakage current is caused; further, the aging of the cable also accelerates the development of the inherent defects of the cable, and the discharge current of the defects also increases. The traditional cable grounding circulation monitoring system judges whether the insulation of the cable outer sheath and the cable grounding system have problems only by monitoring circulation (power frequency current effective value), the detection result is not accurate enough, the detection range is not comprehensive enough, and an excitation source needs to be applied externally when planning power failure of an operating cable, so that the cost is high, and the adverse effect is large.
The currently applied sheath grounding circulating current monitoring system and other types of online monitoring systems can not meet the requirement of operating cable health state evaluation, so that a novel high-voltage cable health state detection technology which is different from the traditional technology for monitoring the cable health state by using the effective value of the power frequency current, is more comprehensive and accurate in monitoring, low in cost and less in influence on users is needed.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide the high-voltage cable health state online monitoring system and the monitoring method thereof, and the system and the method have the advantages of more comprehensive and accurate monitoring, low cost and less influence on users.
In order to achieve the purpose, the invention provides the following technical scheme:
a high-voltage cable health state online monitoring system comprises a sensor group, a monitoring terminal and a monitoring center, wherein the sensor group is connected with the monitoring terminal through a signal shielding cable, and the monitoring terminal is in communication connection with the monitoring center; the sensor group comprises a plurality of broadband current sensors and load current sensors; the monitoring terminal includes:
the data conditioning unit is connected with the sensor group through a signal shielding cable and amplifies, filters and separates signals output by the sensor group;
the high-speed data acquisition module converts the analog voltage signal transmitted by the data conditioning unit into a digital signal;
the clock module is used for providing time for the high-speed data acquisition module and is used for time synchronization among different devices;
the main controller collects the digital signal data of the high-speed data acquisition module, calculates and judges the health state of the cable and locally stores the data;
the communication module is used for transmitting the data collected by the main controller and the judgment result of the cable health state back to the monitoring center;
and the power module provides power for the monitoring terminal.
Furthermore, the broadband current sensor is arranged on a grounding wire of a grounding box of the cable, the load current sensor is arranged on the cable body, and the monitoring terminal is arranged on the cable framework.
Further, the ground tank includes a direct ground tank, a cross-connect tank, and a protection ground tank.
Because the insulation leakage current and the defect discharge current of the cable body can flow through the grounding wire of the sheath, and the grounding circulating current of the sheath contains a large amount of information capable of representing the health state of the cable, the invention fully utilizes the grounding current data information of the sheath by adopting a broadband current sensor mode, and realizes the online evaluation of the health state of the high-voltage cable transmission line.
Furthermore, the power module adopts one or more of induction energy-taking power supply, solar power supply or commercial power supply.
Various power supply selection modes can provide all-weather power supply for the whole device, and the working stability of the equipment is ensured.
Further, the communication module adopts one of 3G, 4G or 5G optical fiber communication.
A monitoring method of a high-voltage cable health state online monitoring system comprises the following steps:
step one, system installation: the broadband current sensor is arranged on each grounding wire of the cable, the load current sensor is arranged on the cable body, and the monitoring terminal is arranged on the cable framework;
step two, cable grounding normal judgment: the system collects the cable running load and the power frequency current on the cable body; the data acquired by the sensor group are converted into digital signals through the data conditioning unit and the high-speed data acquisition module and transmitted to the main controller, and the main controller compares the data to judge whether the cable state is normal or not;
step three, extracting waveform transient characteristic quantity:
under the condition that the cable is determined to be normal, the main controller carries out FFT (fast Fourier transform) on high-frequency current waveform data and extracts transient characteristic quantity of the waveform, including energy ratio P2And information entropy S2The calculation method is as follows
Wherein the content of the first and second substances,i, j-in-band firsti，jA frequency component having a value of 1, 2, 3 … …;
A i -a first stepiThe amplitude corresponding to each frequency component;
wherein the content of the first and second substances,n-in-band firstnA frequency component of 1, 2, 3 … …m；
P n -a first stepnThe probability of occurrence of a frequency component in the acquired waveform;
step four, collecting sample values and comparing and judging: recording transient characteristic quantity P in time T2And S2And forming a data set, and taking the maximum value of the transient characteristic quantity in the time period T as the normal threshold value P of the energy ratio and the information entropy of the system1、S1Comparison of P2，P1Size and S of2、S1When P is the size of2>P1Or S2>S1In the meantime, the health state is judged to be poor.
Further, the specific indexes of the main controller for comparing and judging the digital signal in the first step are as follows:
a. each grounding current effective value is less than 100A;
b. the ratio of each grounding current effective value to the cable running load is less than 20 percent;
c. the ratio of the maximum value to the minimum value of the grounding currents of the phases at the same position is less than 1;
d. the current effective value of each grounding point should not have an abnormal growth trend, namely the ratio of the maximum value to the minimum value is less than 3;
and judging the cable state to be normal according to the standard that a, b, c and d all meet.
Furthermore, before performing FFT on the high-frequency current waveform data in the third step, a wavelet packet decomposition method is also required to perform noise reduction on the acquired high-frequency current waveform data to remove environmental noise, intermittent interference and white noise.
In conclusion, the invention has the following beneficial effects:
1. the invention provides a high-voltage cable health state on-line monitoring system and a monitoring method thereof.A broadband current sensor is used for monitoring the grounding current of a cable sheath, so that the running state of a cable grounding system can be monitored, and the conditions of an insulation structure, a grounding mode error and a connection point of a cable body can be judged by extracting high-frequency current transient characteristic quantity, thereby realizing multi-level and comprehensive evaluation of the health state of the cable;
2. compared with the prior art, the method does not need to plan power failure of the running cable, does not need to apply an external excitation source, only needs to monitor the grounding current of the cable sheath, and extracts the waveform transient quantity, so that the insulation aging state of the cable can be obtained, the health state of the cable can be evaluated on line, the monitoring cost is greatly reduced, the influence on users is slight, and the method has wide application prospect.
Drawings
FIG. 1 is a schematic installation diagram of an online health status monitoring system for a high-voltage cable according to an embodiment;
FIG. 2 is a functional block diagram of a monitor terminal according to an embodiment;
FIG. 3 is a graph of an energy ratio 30 day monitoring data set according to an embodiment;
FIG. 4 is a diagram of an example of an information entropy 30-day monitoring data set.
In the figure: 1. a load current sensor; 2. a broadband current sensor; 3. a signal shielded cable; 4. a cable body; 5. an intermediate joint; 6. a direct grounding box; 7. a cross-connect box; 8. a protective grounding box; 9. and (4) cable termination.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and examples.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.
Examples
The embodiment provides an online monitoring system for the health state of a high-voltage cable, as shown in fig. 1, the installed high-voltage cable is a three-phase single-core cable, cable terminals 9 are arranged on two sides of the high-voltage cable, a three-section type cross interconnection grounding mode is adopted, and a cross interconnection box 7 is connected with an intermediate connector 5 on the high-voltage cable; as shown in fig. 1, the broadband current sensor 2 is installed on each ground wire of the cable, and comprises a direct grounding box 6, a cross-connection box 7 and a protection grounding box 8, the load current sensor 1 is installed on the wire of the cable body 4, and the monitoring terminal is installed on the surrounding cable framework (not shown in the figure);
as shown in fig. 2, the monitoring terminal is provided with a plurality of functional modules, and as shown in fig. 2, the monitoring terminal specifically includes a data conditioning unit, a high-speed data acquisition module, a clock module, a communication module, a main controller and a power module; the system comprises a clock module, a power module, a data conditioning unit, a high-speed data acquisition module and a data processing unit, wherein the clock module is used for adjusting time synchronization among different devices, the power module provides power for a monitoring terminal, the data conditioning unit is connected with a load current sensor 1 and a broadband current sensor 2 through a signal shielding cable 3, the data conditioning unit amplifies, filters and separates output signals of a sensor group and transmits the signals to the high-speed data acquisition module, and the high-speed data acquisition module converts obtained analog voltage signals into digital signals; the clock module provides time for the high-speed data acquisition module and is used for time synchronization among different devices; the main controller collects digital signal data of the high-speed data acquisition module, calculates and judges the health state of the cable and locally stores the data through the storage; the communication module transmits the data collected by the main controller and the judgment result of the cable health state back to the monitoring center;
the specific operation process of this embodiment is as follows:
step one, as shown in fig. 1, installing a high-voltage cable health state online monitoring system on a running cable, and monitoring current flowing in a sheath and a cable running load in real time, wherein the circuit of the embodiment is a three-phase single-core cable and adopts a three-section type cross interconnection grounding mode;
and step two, comparing the obtained cable operation load data with the power frequency current data of the grounding wire in the transverse direction and the longitudinal direction to judge whether the grounding of the cable is normal, wherein if the judgment method does not meet one of the following standards, the abnormity of the cable grounding system is judged: a. each grounding current effective value is less than 100A; b. the ratio of each grounding current effective value to the cable running load is less than 20 percent; c. the ratio of the maximum value to the minimum value of the grounding currents of the phases at the same position is less than 1; d. the current effective value of each grounding point should not have an abnormal growth trend, namely the ratio of the maximum value to the minimum value is less than 3;
when the grounding system of the cable is judged to be abnormal, whether the cable has the conditions of outer sheath damage, grounding mode error, connection point looseness and the like or not is checked and repaired as soon as possible.
Thirdly, under the condition that the grounding state of the cable is determined to be normal, after the noise reduction and the removal of white noise, environmental noise and random interference are carried out on the waveform data of the high-frequency current (frequency band of 100 kHz-20 MHz) of the grounding wire obtained in the first step by utilizing a wavelet packet decomposition method, analyzing and extracting waveform transient characteristics including an energy ratio P2And information entropy S2The specific calculation method is as follows:
wherein, i, j is the second in-bandi，jA frequency component of 1, 2, 3 … …
A i -a first stepiAmplitude corresponding to frequency component, the firstiA frequency value of 1MHz or more, the firstjThe frequency value is less than 1MHz, and the frequency step is 10 kHz.
Wherein the content of the first and second substances,n-in-band firstnA frequency component of 1, 2, 3 … …m. The frequency step size is 10kHz, and then m takes the value 1991.
P n -a first stepnThe probability of occurrence of a frequency component in the acquired waveform; in this embodiment, the waveform duration of one-time high-frequency current sampling is 1s, the waveforms are separated according to 20ms intervals to perform FFT conversion, and the probability of each frequency appearing in 1s is counted asP n ；
Step four, as shown in fig. 3 and 4, forming data samples within 30 days by using the energy ratio and the information entropy obtained in the step three according to the acquisition interval of 1 hour, and obtaining the maximum value of the transient characteristic quantity within the period as the normal threshold value P of the energy ratio and the information entropy of the system1、S1In this embodimentP1Is 0.11, S13.2, continue to monitor the operation data according to step two and step three, when P2>P1Or S2>S1And judging that the health state of the operating cable is poor.
The invention relates to an on-line monitoring system and a monitoring method for the health state of a high-voltage cable, which can monitor the running state of a cable grounding system by adopting a load current sensor and a broadband current sensor to monitor the running of the cable, the current flowing in a sheath and the grounding current of the sheath of the load cable, can judge the insulation condition of a cable body by extracting transient characteristic quantity of high-frequency current so as to realize the comprehensive evaluation of the health state of the running cable.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.
Claims (8)
1. A high-voltage cable health state online monitoring system comprises a sensor group, a monitoring terminal and a monitoring center, wherein the sensor group is connected with the monitoring terminal through a signal shielding cable (3), and the monitoring terminal is in communication connection with the monitoring center; the sensor group comprises at least one of a plurality of broadband current sensors (2) and load current sensors (1); the monitoring terminal includes:
the data conditioning unit is connected with the sensor group through a signal shielding cable (3), and amplifies, filters and separates signals output by the sensor group;
the high-speed data acquisition module converts the analog voltage signal transmitted by the data conditioning unit into a digital signal;
the clock module is used for providing time for the high-speed data acquisition module and is used for time synchronization among different devices;
the main controller collects the digital signal data of the high-speed data acquisition module, calculates and judges the health state of the cable and locally stores the data;
the communication module is used for transmitting the data collected by the main controller and the judgment result of the cable health state back to the monitoring center;
and the power module provides power for the monitoring terminal.
2. The high-voltage cable health status on-line monitoring system according to claim 1, wherein: the broadband current sensor (2) is installed on a grounding wire of a grounding box of the cable, the load current sensor (1) is installed on the cable body (4), and the monitoring terminal is installed on a cable framework.
3. The high-voltage cable health status on-line monitoring system according to claim 1, wherein: the grounding box comprises a direct grounding box (6), a cross-connection box (7) and a protection grounding box (8).
4. The high-voltage cable health status on-line monitoring system according to claim 1, wherein: the power module adopts one or more of induction energy-taking power supply, solar power supply or commercial power supply.
5. The high-voltage cable health status on-line monitoring system according to claim 1, wherein: the communication module adopts one of 3G, 4G or 5G optical fiber communication.
6. A monitoring method of the on-line health status monitoring system for high-voltage cable according to claim 1, comprising the steps of:
step one, system installation: the broadband current sensor (2) is installed on each grounding wire of the cable, the load current sensor (1) is installed on the cable body (4), and the monitoring terminal is installed on a cable framework;
step two, cable grounding normal judgment: the system collects the cable running load and the power frequency current on the cable body (4); the data acquired by the sensor group are converted into digital signals through the data conditioning unit and the high-speed data acquisition module and transmitted to the main controller, and the main controller compares the data to judge whether the cable state is normal or not;
step three, extracting waveform transient characteristic quantity:
under the condition that the cable is determined to be normal, the main controller carries out FFT (fast Fourier transform) on high-frequency current waveform data and extracts transient characteristic quantity of the waveform, including energy ratio P2And information entropy S2The calculation method is as follows
Wherein the content of the first and second substances,i, jare respectively the first in the frequency bandi，jA frequency component having a value of 1, 2, 3 … …;
A i is as followsiThe amplitude corresponding to each frequency component;
wherein the content of the first and second substances,nis the first in the frequency bandnA frequency component of 1, 2, 3 … …m；
P n Is as followsnThe probability of occurrence of a frequency component in the acquired waveform;
step four, collecting sample values and carrying outAnd (4) line comparison judgment: recording transient characteristic quantity P in time T2And S2And forming a data set, and taking the maximum value of the transient characteristic quantity in the time period T as the normal threshold value P of the energy ratio and the information entropy of the system1、S1Comparison of P2，P1Size and S of2、S1When P is the size of2>P1Or S2>S1In the meantime, the health state is judged to be poor.
7. The monitoring method according to claim 6, wherein the specific indexes for the main controller to compare and judge the digital signal in the second step are as follows:
a. each grounding current effective value is less than 100A;
b. the ratio of each grounding current effective value to the cable running load is less than 20 percent;
c. the ratio of the maximum value to the minimum value of the grounding currents of the phases at the same position is less than 1;
d. the current effective value of each grounding point should not have an abnormal growth trend, namely the ratio of the maximum value to the minimum value is less than 3;
and judging the cable state to be normal according to the standard that a, b, c and d all meet.
8. The monitoring method according to claim 6, wherein before performing FFT on the high frequency current waveform data in the third step, a wavelet packet decomposition method is further used to perform noise reduction on the acquired high frequency current waveform data to remove environmental noise, intermittent interference and white noise.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114814461A (en) * | 2022-05-10 | 2022-07-29 | 苏州纬讯光电科技有限公司 | Method and system for evaluating insulation aging state of high-voltage operation cable |
| CN115656683A (en) * | 2022-11-03 | 2023-01-31 | 深圳市铭泽智能电力科技有限公司 | Cable operation monitoring method, system, terminal equipment and storage medium |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109346386A (en) * | 2018-10-12 | 2019-02-15 | 江苏佳源科技有限公司 | Intelligent low-pressure breaker of plastic casing |
| CN110031732A (en) * | 2019-04-15 | 2019-07-19 | 安徽康能电气有限公司 | A kind of comprehensive on-line monitoring system of cable sheath |
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2021
- 2021-10-15 CN CN202111205818.3A patent/CN113805007A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109346386A (en) * | 2018-10-12 | 2019-02-15 | 江苏佳源科技有限公司 | Intelligent low-pressure breaker of plastic casing |
| CN110031732A (en) * | 2019-04-15 | 2019-07-19 | 安徽康能电气有限公司 | A kind of comprehensive on-line monitoring system of cable sheath |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114814461A (en) * | 2022-05-10 | 2022-07-29 | 苏州纬讯光电科技有限公司 | Method and system for evaluating insulation aging state of high-voltage operation cable |
| CN115656683A (en) * | 2022-11-03 | 2023-01-31 | 深圳市铭泽智能电力科技有限公司 | Cable operation monitoring method, system, terminal equipment and storage medium |
| CN115656683B (en) * | 2022-11-03 | 2023-10-31 | 深圳市铭泽智能电力科技有限公司 | Cable operation monitoring method, system, terminal equipment and storage medium |
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