CN113253049A - Power distribution network local fault section positioning and active distance measuring device and method - Google Patents
Power distribution network local fault section positioning and active distance measuring device and method Download PDFInfo
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- G—PHYSICS
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- 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
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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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
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/54—Testing for continuity
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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
- G01R31/58—Testing of lines, cables or conductors
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- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
Abstract
The invention relates to a device and a method for positioning local fault sections of a power distribution network and actively measuring distance, and belongs to the technical field of power distribution network fault positioning of a power system. The technical scheme is as follows: the sensor electricity-taking and sampling device (1) is connected with the power transmission line and a measuring port of the SSTDDR distance measuring device (2); in the SSDR ranging device, an FPGA processing module (21) is respectively connected with a fault diagnosis module (22), a wireless communication module (23) and an alarm display module (24); the coupler is connected with the SSTDDR distance measuring device and is clamped on a cable to be measured. According to the invention, the judgment of the disconnection, short circuit and ground faults is carried out by an external high-frequency signal application method, the fault discrimination and accurate distance measurement are carried out on the spot by a non-invasive high-frequency signal coupling mode by using carrier communication, a spread spectrum time domain reflection technology and a radar signal cross-correlation algorithm, the spot section positioning and distance measurement of the cable fault can be realized, a synchronous acquisition unit is not needed, the distance measurement is accurate, and the cost is low.
Description
Technical Field
The invention relates to a device and a method for positioning local fault sections of a power distribution network and actively measuring distance, and belongs to the technical field of power distribution network fault positioning of a power system.
Background
With the development of economy and the proposal of intelligent power grids, the reliability of people on daily life power utilization is continuously improved. The power distribution network is used as a bridge for connecting the power system and the terminal users, the operation environment is complex, the maintenance is difficult, and higher requirements are provided for the safety and the reliability of the power system. The method has the advantages that the faults of the power distribution network are frequent, the fault type of the power distribution network can be rapidly and accurately identified, fault location is carried out, and the method has important practical engineering significance for improving power supply reliability and building a strong intelligent power distribution network.
The existing fault indicator mostly collects the current of each phase on a transmission line, judges whether a short-circuit fault occurs by using a current mutation principle, and judges whether a ground fault occurs by using a transient zero-mode current polarity method. For single-phase earth faults under different conditions, fault line selection and fault location are often performed by using an external signal application method and a Phase Asymmetry (PAM) method. But the three-phase fault indicator is required to be used for synchronous acquisition, and each phase of electric capacity information is sent, collected and called by using a wireless communication technology to perform fault judgment and section positioning. In order to correctly acquire the transient information of the power distribution network with the characteristic frequency band of 200-3000Hz, the sampling rate of the fault indicator at least reaches 6kHz, and the time synchronization precision of synchronous acquisition is within 100 mu s. Obviously, the method puts high requirements on synchronous measurement acquisition, wave recording and communication technologies. In addition, when single-phase high-resistance grounding occurs, zero-sequence current is small, voltage mutation is not obvious, and how to accurately judge the high-resistance grounding fault is still a problem of the fault indicator. In a word, the fault indicator is difficult to simultaneously realize accurate judgment and accurate positioning of the single-phase earth fault, and the conventional realization method is complex, high in cost and difficult to popularize.
Disclosure of Invention
The invention aims to provide a device and a method for positioning and actively ranging local fault sections of a power distribution network, which are used for judging line breakage, short circuit and ground faults by an externally applied high-frequency signal method, and carrying out fault judgment and accurate ranging in a non-invasive high-frequency signal coupling mode on site by using carrier communication, Spread Spectrum Time-Domain Reflectometry (SSTDDR) technology and a radar signal cross-correlation algorithm for reference, so that the local section positioning and ranging of cable faults can be realized, a synchronous acquisition unit is not needed, the ranging is accurate, the cost is low, and the problems in the background art are effectively solved.
The technical scheme of the invention is as follows: a power distribution network local fault section positioning and active distance measuring device comprises a sensor power-taking and sampling device, an SSDR distance measuring device and a coupler, wherein the sensor power-taking and sampling device is connected with a power transmission line and a measuring port of the SSDR distance measuring device; the SSTDR ranging device comprises an FPGA processing module, a fault diagnosis module, a wireless communication module and an alarm display module, wherein the FPGA processing module is respectively connected with the fault diagnosis module, the wireless communication module and the alarm display module; the coupler is connected with the SSTDDR distance measuring device and is clamped on a cable to be measured.
The sensor electricity-taking and sampling device comprises a current transformer, an electric field sensor and a battery which are connected in sequence.
The fault diagnosis module comprises a DA (digital-to-analog) conversion module, a radio frequency amplification module, a coupler module, a conditioning circuit and a compression sampling module which are sequentially connected.
The coupler is a non-invasive coupler, the attenuation range in the wide frequency band frequency of 5 MHz-30 MHz is 5-8.5 dB, and the attenuation of the coupler is about 5dB under the frequency of 10 MHz.
The device also comprises a wave trap which is clamped at the non-measured end of the cable to be measured.
A method for positioning and actively measuring distance of local fault sections of a power distribution network comprises the following steps:
(1) data acquisition: the sensor electricity-taking and sampling device acquires electricity and current sampling through a current transformer, an electric field sensor acquires an electric field of each phase, voltage change acquired by the electric field sensor is used as a starting criterion, an integral current protection criterion is used for reference, a voltage starting criterion based on a fault component delta uk mean value is provided, the fault component is subjected to integral summation and then the mean value is used as an action quantity Ed, a corresponding action threshold Eo is set, and when a relational expression is met
When the SSTDR ranging device is started, the SSTDR ranging device is started;
(2) and (3) fault type judgment: after the SSTDR ranging device is started, firstly, judging which fault is the current sampling value, and when the current is close to a zero value, indicating that a disconnection fault occurs; when the current break amount is larger than a certain threshold value, the short-circuit fault is generated; otherwise, the result is the grounding fault; the fault of the broken line and the short circuit is directly turned over and alarmed;
(3) fault location: when the SSTDR ranging device is started, a radio frequency amplification module in the fault diagnosis module is started, a coupler is started through a coupler module to couple signals into a cable to be tested, and then echo signals are received to perform cross-correlation operation so as to perform fault judgment and fault ranging.
In the step (1), in order to avoid the situation that the SSTDR distance measuring device is started by mistake due to other interference, the SSTDR distance measuring device can judge the fault type and measure the fault distance only when the sampling value of the voltage continuously collected by the sensor electricity-taking and sampling device for three times meets the criterion formula.
In the step (3), after the 10MHz sinusoidal signal is BPSK (binary phase shift keying) modulated by the pseudorandom sequence, a detection signal with a wide bandwidth is formed to improve the signal-to-noise ratio; the generated detection signal is sent to a DA conversion module for digital-to-analog conversion, the radio frequency power amplification module is used for amplifying the detection signal to a higher power and voltage level, and the generated analog detection signal is coupled to the cable to be detected through a non-invasive coupler module; when a detection signal meets an impedance mismatching point caused by a fault point in a cable, a reflection echo signal is generated and coupled to a high-frequency signal acquisition module under the action of a coupler, the signal amplitude is adjusted through a conditioning circuit, the reflection signal is acquired by a compression sampling module, and an output digital signal is sent to an FPGA processing module; the FPGA processing module firstly performs FIFO (first in first out) data caching pretreatment on the detection signal and the reflection signal, then converts the detection signal and the reflection signal into a frequency domain to perform correlation operation to obtain a distance measurement result, and transmits the distance measurement result to an upper computer through the wireless communication module to display fault distance information so as to complete fault distance measurement.
The invention has the beneficial effects that: the method has the advantages that the disconnection, short circuit and ground faults are judged by an external high-frequency signal application method, the fault discrimination and accurate distance measurement are carried out on the spot by a non-invasive high-frequency signal coupling mode by using carrier communication, a spread spectrum time domain reflection technology and a radar signal cross-correlation algorithm for reference, the spot section positioning and distance measurement of the cable faults can be realized, a synchronous acquisition unit is not needed, the distance measurement is accurate, and the cost is low.
Drawings
FIG. 1 is a schematic view of the installation of the present invention;
FIG. 2 is an overall design principle architecture diagram of the present invention;
FIG. 3 is a flow chart of the fault determination of the present invention;
FIG. 4 is a schematic view of SSTDR cable fault location;
FIG. 5 is a COMSOL finite element simulation diagram of a coupler;
FIG. 6 is a graph of coupler coupling attenuation characteristics at different frequencies;
FIG. 7 is a graph of the detection signal and the reflected echo signal of superimposed noise in a 10kV cable;
FIG. 8 is a graph of the results of a cross-correlation operation;
in the figure: the sensor electricity-taking and sampling device 1, the SSTDR distance measuring device 2, the coupler 3, the wave trap 4, the power supply 5, the load 6, the wire core 71, the inner insulating layer 72, the shielding layer 73, the outer insulating layer 74, the current transformer 11, the electric field sensor 12, the battery 13, the FPGA processing module 21, the fault diagnosis module 22, the wireless communication module 23, the alarm display module 24, the DA conversion module 221, the radio frequency amplification module 222, the coupler module 223, the conditioning circuit 224, the compression sampling module 225, the current sampling 111, the energy-taking 112, the radio frequency identification 231, the wireless relay 232, the terminal 233, the upper computer 234, the tile-turning alarm 241 and the drive 242.
Detailed Description
The technical solution of the present invention will be further described in detail with reference to the accompanying drawings and embodiments, which are preferred embodiments of the present invention. It is to be understood that the described embodiments are merely a subset of the embodiments of the invention, and not all embodiments; it should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A power distribution network local fault section positioning and active distance measuring device is characterized in that a sensor power sampling device 1 is connected with a power transmission line and a measuring port of an SSTDDR distance measuring device 2; the SSTDR ranging device 2 comprises an FPGA processing module 21, a fault diagnosis module 22, a wireless communication module 23 and an alarm display module 24, wherein the FPGA processing module 21 is respectively connected with the fault diagnosis module 22, the wireless communication module 23 and the alarm display module 24; the coupler 3 is connected with the SSTDDR distance measuring device 2 and is clamped on a cable to be measured.
The sensor electricity-taking and sampling device 1 comprises a current transformer 11, an electric field sensor 12 and a battery 13 which are connected in sequence.
The fault diagnosis module 22 includes a DA conversion module 221, a radio frequency amplification module 222, a coupler module 223, a conditioning circuit 224, and a compression sampling module 225, which are connected in sequence.
The coupler 3 is a non-invasive coupler, the attenuation range in the wide frequency band frequency of 5 MHz-30 MHz is 5-8.5 dB, and the attenuation of the coupler 3 is about 5dB under the frequency of 10 MHz.
The device also comprises a wave trap 4, and the wave trap 4 is clamped at the non-tested end of the cable to be tested.
A method for positioning and actively measuring distance of local fault sections of a power distribution network comprises the following steps:
(1) data acquisition: the sensor electricity-taking and sampling device acquires electricity and current sampling through a current transformer, an electric field sensor acquires an electric field of each phase, voltage change acquired by the electric field sensor is used as a starting criterion, an integral current protection criterion is used for reference, a voltage starting criterion based on a fault component delta uk mean value is provided, the fault component is subjected to integral summation and then the mean value is used as an action quantity Ed, a corresponding action threshold Eo is set, and when a relational expression is met
When the SSTDR ranging device is started, the SSTDR ranging device is started;
(2) and (3) fault type judgment: after the SSTDR ranging device is started, firstly, judging which fault is the current sampling value, and when the current is close to a zero value, indicating that a disconnection fault occurs; when the current break amount is larger than a certain threshold value, the short-circuit fault is generated; otherwise, the result is the grounding fault; the fault of the broken line and the short circuit is directly turned over and alarmed;
(3) fault location: when the SSTDR ranging device is started, a radio frequency amplification module in the fault diagnosis module is started, a coupler is started through a coupler module to couple signals into a cable to be tested, and then echo signals are received to perform cross-correlation operation so as to perform fault judgment and fault ranging.
In the step (1), in order to avoid the situation that the SSTDR distance measuring device is started by mistake due to other interference, the SSTDR distance measuring device can judge the fault type and measure the fault distance only when the sampling value of the voltage continuously collected by the sensor electricity-taking and sampling device for three times meets the criterion formula.
In the step (3), after the 10MHz sinusoidal signal is BPSK modulated by the pseudorandom sequence, a detection signal with a wide bandwidth is formed to improve the signal-to-noise ratio; the generated detection signal is sent to a DA conversion module for digital-to-analog conversion, the radio frequency power amplification module is used for amplifying the detection signal to a higher power and voltage level, and the generated analog detection signal is coupled to a cable to be detected through a coupler module; when a detection signal meets an impedance mismatching point caused by a fault point in a cable, a reflection echo signal is generated and coupled to a high-frequency signal acquisition module under the action of a coupler, the signal amplitude is adjusted through a conditioning circuit, the reflection signal is acquired by a compression sampling module, and an output digital signal is sent to an FPGA processing module; the FPGA processing module firstly carries out FIFO data caching pretreatment on the detection signal and the reflection signal, then converts the detection signal and the reflection signal into a frequency domain to carry out correlation operation, obtains a distance measurement result, and transmits the distance measurement result to an upper computer through the wireless communication module to display fault distance information, so that fault distance measurement is completed.
In practical application, as shown in fig. 1, the sensor electricity-taking and sampling device is used for connecting a power transmission line and a fault indicator measurement port, and the FPGA processing module is respectively connected with the fault diagnosis module, the wireless communication module and the alarm display module. The coupler is connected with the FPGA processing module through the coupler module and clamped on a cable to be tested, so that the coupling of the high-frequency spread spectrum modulation signal is realized. The wave trap is clamped on the cable to be tested to realize the directional transmission of signals.
As shown in fig. 2, the whole hardware circuit mainly includes the following parts:
(1) the sensor gets electric sampling device: the power supply comprises a current transformer and an electric field sensor, and is used for completing current and voltage acquisition and power taking functions. Wherein the battery is used for back-up power supply.
(2) An FPGA processing module: and the method is used for judging and processing the collected electrical quantity information. When the electric field drop fault component exceeds a threshold value, starting a fault criterion, and when the current is close to a zero value, indicating that a disconnection fault occurs; when the current break amount is larger than a certain threshold value, the short-circuit fault is indicated; otherwise, indicating that the ground fault occurs; after the fault indicator starts the criterion, the FPGA transmits a high-frequency detection signal, receives an echo signal and performs correlation operation, and further determines the fault type and the fault distance according to the correlation peak value.
(3) A fault diagnosis module: the device comprises a DA conversion module, a radio frequency amplification module, a coupler module, a conditioning circuit and a compression sampling module. The high-frequency detection signal processing method mainly achieves the functions of performing digital-to-analog conversion, power amplification and coupling injection on the high-frequency detection signal to the cable to be detected, and performing signal conditioning and compression sampling on the echo signal.
(4) A wireless communication module: when a line fault is detected, the local upper computer comprehensively realizes fault judgment and distance measurement. The fault information, the fault type of the fault diagnosis module and the ranging result can also be sent to a nearby wireless repeater through the wireless radio frequency module, and the fault information is sent to the terminal through the GPRS communication mode.
(5) The alarm display module: and the failure indicator is used for carrying out card turning alarm on the processing result of the failure indicator.
(6) A coupler: the method is used for non-invasive injection and reception of the high-frequency spread spectrum modulation signal.
(7) A wave trap: for detecting the directional transmission of the signal.
The failure determination flow of the present invention will be explained below.
As shown in fig. 3, the fault determination process is as follows: the sensor electricity-taking and sampling device takes electricity and samples current through a current transformer, an electric field sensor is used for collecting an electric field of each phase, and each phase of current and electric field information collected by the two elements are used as starting criteria of open circuit, short circuit and ground fault. For the invention, whether the single-phase earth fault can be found in time is closely related to the performance of the starting criterion, the invention uses the voltage change collected by the electric field sensor as the starting criterion, and the integral current protection criterion is used for reference, and the fault component delta u based on the fault component is providedkMean value voltage starting criterion, integral summation of fault components and mean value as action quantity EdSet up the correspondingAction threshold value E ofoWhen the following relation is satisfied, the SSTDDR ranging device is started.
In order to avoid the situation that the SSTDR distance measuring device is started by mistake due to other interference, the SSTDR distance measuring device can judge the fault type and measure the fault distance only when the sensor power-taking sampling device continuously collects three voltage sampling values to meet a criterion formula.
After the SSTDR ranging device is started, firstly, the fault is judged according to the current sampling value. When the current is close to zero, the disconnection fault is indicated; when the current break amount is larger than a certain threshold value, the short-circuit fault is generated; otherwise, it is indicated as a ground fault. The fault of broken line and short circuit is directly turned over to alarm. When the SSTDR ranging device is started, the radio frequency amplification module is started, signals are coupled into a cable to be tested through the coupler module, and then echo signals are received to perform cross-correlation operation so as to perform fault judgment and fault ranging.
In addition, when a high-resistance ground fault occurs, the conventional fault indicator has a limited judgment because the sudden change amount of voltage is small. The invention applies high frequency signal externally, when the fault point generates echo signal due to impedance change, the fault is judged by cross-correlation operation with the detection signal, therefore, the influence of the grounding resistance is small, and the invention can carry out the turnover indication of the grounding fault after being comprehensively judged with SSTDDR distance measuring device.
Referring to fig. 4, in the SSTDR cable fault location, a 10MHz sinusoidal signal is BPSK modulated by a pseudo-random sequence to form a wide bandwidth detection signal to improve the signal-to-noise ratio. The generated digital signal is sent to a DA conversion module for digital-to-analog conversion. The 10kV power distribution network contains more background noise and impulse noise, and the quality of electric energy is poor; in addition, the coupling and transmission links of the detection signal are attenuated, so that the amplitude of the detection signal is increased as much as possible, the detection signal is amplified to a higher power and voltage level by using the radio frequency amplification module, and the finally generated analog detection signal is coupled into the cable to be detected through the coupler. When a detection signal meets an impedance mismatching point caused by a fault point in a cable, a reflection echo signal is generated and coupled to the high-frequency signal acquisition module under the action of the coupler, the signal amplitude value is adjusted through the conditioning circuit, the reflection signal is acquired by utilizing compression sampling, and an output digital signal is sent into the FPGA processing module. The FPGA processing module firstly carries out FIFO data caching pretreatment on the detection signal and the reflection signal, then converts the detection signal and the reflection signal into a frequency domain to carry out correlation operation, obtains a distance measurement result, and carries out serial port communication through the wireless communication module and transmits the distance measurement result to an upper computer to display fault distance information, so that fault distance measurement is completed.
As shown in fig. 5, the coupling principle of the coupler is the law of electromagnetic induction. In the simulation, the cable to be tested is a ZR-YJV-1 multiplied by 95 single-core cable as an example, the outer diameter of the cable is 33mm, the coupler is a magnetic ring, and the outer diameter is 80 mm.
TABLE 1 coupler design parameters
Fig. 6 is a frequency response curve of coupling effect under different frequency detection signals with a peak value of 30V applied to a magnetic ring. Compared with the experimental result, the attenuation range of the broadband optical fiber is 5-8.5 dB. The coupled signal experiences an attenuation of about 5dB at a frequency of 10 MHz. Noise distribution of a 10kV power distribution network is comprehensively considered, namely obvious narrow-band interference exists at positions of 12MHz, 13.5MH, 15MHz and the like, so that a detection signal frequency of 10MHz is adopted.
As shown in fig. 7, it can be seen that the signal is distorted in waveform and distortion under the noise interference. Even under the condition of high noise interference, the peak value of the correlation function can still be extracted by utilizing the good autocorrelation and cross-correlation characteristics of SSTDDR, and then the fault criterion is carried out.
As shown in fig. 8, when the SSTDR ranging apparatus is started, the FPGA processing module transmits a spread spectrum modulation signal with a frequency of 10MHz and a time of Δ t to the coupler, and the signal is amplified to have an amplitude of 10MHz through the DA conversion and rf amplification moduleThe amplitude of a 30V analog signal coupled into the cable to be tested is about 15V after being attenuated by the coupler, and then the FPGA processing module receives a reflected echo signal and obtains time delay delta t through correlation operation1Knowing the propagation velocity v of the signal in the cable, the distance d of the fault point from the fault indicator can be calculated according to the following formula:
the abscissa has been converted into the fault distance by the above equation. The peak point of the correlation waveform can be obtained by peak detection. The value is-7.629, corresponding to an abscissa fault distance of 2.007 km. Approximately equal to the set fault distance of 2km, and proving the accuracy of ranging.
The current transformer, the electric field sensor, the DA conversion module, the radio frequency amplification module, the conditioning circuit, the coupler, the FPGA processing module and the like which are related to the invention are the technical contents which are known and used in the field, and can be purchased or assembled by a person with ordinary skill in the field on the market according to the requirement.
Claims (8)
1. The utility model provides a distribution network fault section location in situ and initiative range unit which characterized in that: the device comprises a sensor electricity-taking and sampling device (1), an SSTDR (solid State digital radiography) distance measuring device (2) and a coupler (3), wherein the sensor electricity-taking and sampling device (1) is connected with a power transmission line and a measuring port of the SSTDR distance measuring device (2); the SSTDR ranging device (2) comprises an FPGA processing module (21), a fault diagnosis module (22), a wireless communication module (23) and an alarm display module (24), wherein the FPGA processing module (21) is respectively connected with the fault diagnosis module (22), the wireless communication module (23) and the alarm display module (24); the coupler (3) is connected with the SSTDDR distance measuring device (2) and is clamped on a cable to be measured.
2. The power distribution network in-situ fault zone location and active ranging device of claim 1, wherein: the sensor electricity-taking and sampling device (1) comprises a current transformer (11), an electric field sensor (12) and a battery (13), which are connected in sequence.
3. The power distribution network in-situ fault zone location and active ranging device of claim 1, wherein: the fault diagnosis module (22) comprises a DA conversion module (221), a radio frequency amplification module (222), a coupler module (223), a conditioning circuit (224) and a compression sampling module (225), which are connected in sequence.
4. The power distribution network in-situ fault zone location and active ranging device of claim 1, wherein: the coupler (3) is a non-invasive coupler, the attenuation range in the wide frequency band frequency of 5 MHz-30 MHz is 5-8.5 dB, and the attenuation of the coupler (3) is about 5dB under the frequency of 10 MHz.
5. The power distribution network in-situ fault zone location and active ranging device of claim 1, wherein: the cable testing device further comprises a wave trap (4), and the wave trap (4) is clamped at the non-tested end of the cable to be tested.
6. A method for positioning and actively measuring distance of local fault sections of a power distribution network is characterized by comprising the following steps:
(1) data acquisition: the sensor electricity-taking and sampling device acquires electricity and current sampling through a current transformer, an electric field sensor acquires an electric field of each phase, voltage change acquired by the electric field sensor is used as a starting criterion, an integral current protection criterion is used for reference, a voltage starting criterion based on a fault component delta uk mean value is provided, the fault component is subjected to integral summation and then the mean value is used as an action quantity Ed, a corresponding action threshold Eo is set, and when a relational expression is met
When the SSTDR ranging device is started, the SSTDR ranging device is started;
(2) and (3) fault type judgment: after the SSTDR ranging device is started, firstly, judging which fault is the current sampling value, and when the current is close to a zero value, indicating that a disconnection fault occurs; when the current break amount is larger than a certain threshold value, the short-circuit fault is generated; otherwise, the result is the grounding fault; the fault of the broken line and the short circuit is directly turned over and alarmed;
(3) fault location: when the SSTDR ranging device is started, a radio frequency amplification module in the fault diagnosis module is started, a coupler is started through a coupler module to couple signals into a cable to be tested, and then echo signals are received to perform cross-correlation operation so as to perform fault judgment and fault ranging.
7. The method of claim 6, wherein the method comprises the steps of: in the step (1), in order to avoid the situation that the SSTDR distance measuring device is started by mistake due to other interference, the SSTDR distance measuring device can judge the fault type and measure the fault distance only when the sampling value of the voltage continuously collected by the sensor electricity-taking and sampling device for three times meets the criterion formula.
8. The method of claim 6, wherein the method comprises the steps of: in the step (3), after the 10MHz sinusoidal signal is BPSK modulated by the pseudorandom sequence, a detection signal with a wide bandwidth is formed to improve the signal-to-noise ratio; the generated detection signal is sent to a DA conversion module for digital-to-analog conversion, the radio frequency power amplification module is used for amplifying the detection signal to a higher power and voltage level, and the generated analog detection signal is coupled to a cable to be detected through a coupler module; when a detection signal meets an impedance mismatching point caused by a fault point in a cable, a reflection echo signal is generated and coupled to a high-frequency signal acquisition module under the action of a coupler, the signal amplitude is adjusted through a conditioning circuit, the reflection signal is acquired by a compression sampling module, and an output digital signal is sent to an FPGA processing module; the FPGA processing module firstly carries out FIFO data caching pretreatment on the detection signal and the reflection signal, then converts the detection signal and the reflection signal into a frequency domain to carry out correlation operation, obtains a distance measurement result, and transmits the distance measurement result to an upper computer through the wireless communication module to display fault distance information, so that fault distance measurement is completed.
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