CN110907343A - Method for detecting corrosion rate of grounding grid - Google Patents
Method for detecting corrosion rate of grounding grid Download PDFInfo
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Abstract
The application relates to a method for detecting corrosion rate of a grounding grid, which comprises the steps of providing a frequency sweep voltage signal for the grounding grid, detecting a frequency sweep current signal flowing out of the grounding grid, and calculating according to the frequency sweep voltage signal and the frequency sweep current signal to obtain a frequency sweep impedance spectrum. And carrying out impedance spectrum simulation on the grounding grid according to the structure of the grounding grid and the soil resistivity to obtain a standard impedance spectrum. And calculating the corrosion degree and the corrosion position of the conductor in the grounding grid according to the sweep frequency impedance spectrum and the standard impedance spectrum, and further calculating the corrosion rate of the grounding grid according to the corrosion degree and the detection time corresponding to the corrosion degree. The grounding grid corrosion rate detection method provided by the application can avoid digging the grounding grid, so that the detection of the grounding grid corrosion rate can be realized while the grounding grid is prevented from being damaged, the time of field maintenance personnel can be greatly reduced, the detection efficiency is improved, and therefore latent faults and even substation accidents can be avoided in time.
Description
Technical Field
The application relates to the technical field of grounding grid corrosion detection, in particular to a method for detecting the corrosion rate of a grounding grid.
Background
The grounding grid is an important guarantee for the safe operation of the transformer substation, and the grounding performance of the grounding grid is always valued by design and production operation departments. In China, accidents of a power system caused by the defects of corrosion, breakage and the like of a grounding grid occur occasionally, and each accident causes great economic loss.
In the prior art, defects such as corrosion and breakage of a grounding grid are generally detected by adopting a pilot frequency current injection method. However, although the conventional pilot frequency current injection method can reflect the corrosion degree of the grounding grid to a certain extent, the volume and the current of the pilot frequency current source equipment used by the conventional pilot frequency current injection method are large, and the measurement result is easily influenced by power frequency and harmonic waves, so that the measurement result is inaccurate. In addition, the different frequency current injection method cannot measure the corrosion rate of the grounding grid.
Disclosure of Invention
Therefore, it is necessary to provide a method for detecting the corrosion rate of the ground grid in order to solve the problems that the prior art cannot measure the corrosion rate of the ground grid and the measurement result is inaccurate.
The application provides a method for detecting corrosion rate of a grounding grid, which comprises the following steps:
providing a frequency sweep voltage signal for a grounding grid, and detecting a frequency sweep current signal flowing out of the grounding grid;
calculating to obtain a frequency sweep impedance spectrum according to the frequency sweep voltage signal and the frequency sweep current signal;
recording the soil resistivity of the position of the grounding grid, and performing impedance spectrum simulation on the grounding grid according to the structure of the grounding grid and the soil resistivity to obtain a standard impedance spectrum;
calculating the corrosion degree and the corrosion position of the conductor in the grounding grid according to the sweep frequency impedance spectrum and the standard impedance spectrum;
and calculating the corrosion rate of the grounding grid according to the corrosion degree and the detection time corresponding to the corrosion degree.
In one embodiment, the method for detecting the corrosion rate of the grounding grid further comprises the following steps:
before providing the sweep frequency voltage signal for the grounding grid, selecting the grid with the minimum unit length from the grids of the grounding grid, and taking two ends of the grid with the minimum unit length as an input port of the grounding grid and an output port of the grounding grid respectively.
In one embodiment, the calculating the corrosion degree and the corrosion position of the conductor in the grounding grid according to the swept impedance spectrum and the standard impedance spectrum includes:
carrying out Fourier inversion processing on the sweep frequency impedance spectrum to obtain an actual time domain impedance signal, and carrying out Fourier inversion processing on the standard impedance spectrum to obtain a standard time domain impedance signal;
and calculating the corrosion degree and the corrosion position of the conductor in the grounding grid according to the actual time domain impedance signal and the standard time domain impedance signal.
In one embodiment, the calculating the corrosion degree and the corrosion position of the conductor in the grounding grid according to the actual time-domain impedance signal and the standard time-domain impedance signal includes:
calculating the positions of all conductors in the grounding grid according to the actual time domain impedance signals;
respectively calculating the ratio of the actual time domain impedance signal to the standard time domain impedance signal according to the conductor position;
judging whether the ratio is larger than a preset threshold value or not;
if the ratio is larger than or equal to the preset threshold value, the conductor corresponding to the standard impedance spectrum is not corroded;
and if the ratio is smaller than the preset threshold value, the corrosion position of the conductor corresponding to the standard impedance spectrum is the corrosion position.
In one embodiment, the calculating, according to the conductor position, a ratio of the actual time-domain impedance signal to the standard time-domain impedance signal corresponding to each conductor segment includes:
respectively calculating the standard time domain impedance signal when each section of conductor in the grounding grid is corroded according to the conductor position;
and respectively calculating the ratio of the actual time domain impedance signal to the standard time domain impedance signal when each section of conductor is corroded.
In one embodiment, the actual time-domain impedance signal is a real part of a complex value obtained by performing inverse fourier transform processing on the swept impedance spectrum.
In one embodiment, the standard time-domain impedance signal is a real part of a complex value obtained by performing inverse fourier transform processing on the standard impedance spectrum.
In one embodiment, the standard time-domain impedance signal is:
wherein rho is the resistivity of the soil, S is the total area of the grid of the grounding grid, epsilon∞And the high-frequency dielectric constant is D, the electric flux in the grid of the grounding grid is D, r is the conductor resistivity of the grounding grid, and l is the total length of the grounding grid.
In one embodiment, the corrosion rate is FMIN/h,FMINIs the degree of corrosion, and h is the degree of corrosion FMINThe time of (a), wherein,
ZMis the actual time domain impedance signal, ZM(m，n)The standard time domain impedance signal when the corrosion conductor position is (m, n).
In one embodiment, the frequency range of the sweep voltage signal is 20Hz to 30 MHz.
In one embodiment, the swept impedance spectrum includes an impedance magnitude-frequency characteristic and an impedance phase-frequency characteristic.
The method for detecting the corrosion rate of the grounding grid can provide a frequency sweep voltage signal for the grounding grid, detect a frequency sweep current signal flowing out of the grounding grid, and calculate and obtain a frequency sweep impedance spectrum according to the frequency sweep voltage signal and the frequency sweep current signal. In addition, the impedance spectrum of the grounding grid can be simulated by recording the soil resistivity of the position of the grounding grid and according to the structure of the grounding grid and the soil resistivity, so that a standard impedance spectrum is obtained. According to the sweep frequency impedance spectrum and the standard impedance spectrum, the corrosion degree and the corrosion position of the conductor in the grounding grid can be calculated, and further according to the corrosion degree and the detection time corresponding to the corrosion degree, the corrosion rate of the grounding grid can be calculated. The grounding grid corrosion rate detection method provided by the application can avoid digging the grounding grid, so that the grounding grid can be prevented from being damaged, meanwhile, the detection of the grounding grid corrosion rate is realized, the working time of field maintainers can be greatly reduced, the detection efficiency is improved, and therefore latent faults and even substation accidents can be timely avoided.
Drawings
Fig. 1 is a flowchart of a method for detecting corrosion rate of a ground grid according to an embodiment of the present disclosure;
fig. 2 is a schematic connection structure diagram of a system for detecting corrosion rate of a ground grid according to an embodiment of the present disclosure;
FIG. 3 shows a graph of F under different corrosion degrees at a section of a conductor of a grounding grid according to an embodiment of the present inventionMINThe variation curve of (d);
fig. 4 is a schematic diagram illustrating a connection structure of a main control device in a system for detecting corrosion rate of a ground grid according to an embodiment of the present disclosure;
fig. 5 is a schematic diagram of a connection structure of a frequency sweeping power source in a system for detecting corrosion rate of a ground grid according to an embodiment of the present disclosure;
fig. 6 is a final output circuit of a power amplifier circuit in a system for detecting a corrosion rate of a ground grid according to an embodiment of the present application.
Description of the reference numerals
100 grounding grid corrosion rate detection system
10 ground net
110 input port
120 outlet
20 frequency sweep power supply
210 signal generating circuit
211 signal generating branch
212 control branch
213 signal filtering branch
220 power amplifying circuit
221 input stage branch
222 push stage bypass
223 output stage branch
224 protection stage branch
230 impedance transformer
240 power supply
30 current sensor
40 Master control device
410 data acquisition unit
420 impedance spectrum calculating unit
430 ground net simulation unit
440 corrosion rate calculation unit
50 resistivity measuring device
Detailed Description
In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying the present application are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is capable of embodiments in many different forms than those described herein and those skilled in the art will be able to make similar modifications without departing from the spirit of the application and it is therefore not intended to be limited to the embodiments disclosed below.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
In the grounding grid monitoring method in the prior art, the grounding grid 10 needs to be excavated for detection, a large amount of manpower and material resources are wasted, and the detection efficiency is low. In addition, the inter-frequency current injection method requires injecting a large current into the ground grid 10, and then indirectly estimates the corrosion degree of the ground grid 10 by detecting the electromagnetic intensity of the ground surface. The method has the defects of large test current, long measurement time, large influence of a power frequency electromagnetic field and the like, and easily causes the change of the detection precision, thereby causing the measurement deviation. In addition, a test instrument required by the pilot frequency current injection method is large in size, the corrosion rate of the grounding grid cannot be monitored on line, and the change trend of latent faults cannot be effectively reflected.
Referring to fig. 1, the present application provides a method for detecting corrosion rate of a ground grid, including:
step S100, providing a frequency sweep voltage signal for a grounding grid, and detecting a frequency sweep current signal flowing out of the grounding grid;
step S200, calculating according to the sweep frequency voltage signal and the sweep frequency current signal to obtain a sweep frequency impedance spectrum;
step S300, recording the soil resistivity of the position of the grounding grid, and carrying out impedance spectrum simulation on the grounding grid according to the structure of the grounding grid and the soil resistivity to obtain a standard impedance spectrum;
step S400, calculating the corrosion degree and the corrosion position of a conductor in the grounding grid according to the sweep frequency impedance spectrum and the standard impedance spectrum;
and S500, calculating the corrosion rate of the grounding grid according to the corrosion degree and the detection time corresponding to the corrosion degree.
Referring to fig. 2, the present application also provides a system 100 for detecting corrosion rate of a ground grid. The system 100 for detecting the corrosion rate of the grounding grid comprises the grounding grid 10, a swept-frequency power supply 20, a current sensor 30 and a master control device 40. The sweep power supply 20 is electrically connected to the ground grid 10 and is configured to provide a sweep voltage signal to the ground grid 10. The current sensor 30 is connected in series on the loop between the swept frequency power source 20 and the grounding grid 10, and is used for detecting the swept frequency current signal of the grounding grid 10. The main control device 40 is electrically connected to the frequency sweep power supply 20 and the current sensor 30, and is configured to receive the frequency sweep voltage signal and the frequency sweep current signal, calculate a frequency sweep impedance spectrum of the ground grid 10 according to the frequency sweep voltage signal and the frequency sweep current signal, calculate a corrosion degree and a corrosion position of the ground grid 10 according to the frequency sweep impedance spectrum, and calculate a corrosion rate of the ground grid 10 according to the corrosion degree of the ground grid 10 and detection time corresponding to the corrosion degree. In one embodiment, the grounding grid 10 has an input port 110 and an output port 120, wherein the input port 110 and the output port 120 are two ends of a grid with the smallest unit length in the grounding grid 10. In one embodiment, the grid erosion rate detection system 100 further includes a resistivity measurement device 50. The resistivity measuring device 50 is electrically connected to the main control device 40, and is configured to measure the soil resistivity of the position of the grounding grid 10, and send the soil resistivity to the main control device 40.
It can be understood that the sweep power source 20 can inject a unit sine wave with a sweep frequency range of 20Hz to 30MHz from the input port 110 of the ground grid 10, i.e., provide a sweep voltage signal for the ground grid 10. And the current sensor 30 can measure the response current of the grounded screen 10 flowing out of the output port 120, i.e. the swept current signal. The frequency sweep impedance spectrum of the ground grid 10 can be calculated according to the frequency sweep voltage signal and the frequency sweep current signal. The swept frequency impedance spectrum includes impedance amplitude-frequency characteristics and impedance phase-frequency characteristics, and can be expressed as:
wherein Z isx(omega) is the swept impedance spectrum of the two ports of the grounding grid 10, ΓLThe reflection coefficient of the far end of the grounding grid 10, i.e. the two ports farthest from the test port, γ is the propagation coefficient of the grounding grid 10, l is the total length of the grounding grid 10, X is the length of the far end of the grounding grid 10, i.e. the two ports farthest from the test port, R (ω) is the real part of the frequency domain complex impedance of the grounding grid 10, and X (ω) is the imaginary part of the frequency domain complex impedance of the grounding grid 10.
By inputting the frequency-sweep voltage signal through the broadband excitation source, the frequency-sweep current signal flowing out of the grounding grid 10 can be measured through the output port 120, and the distributed impedance characteristic of the grounding grid 10, i.e., the frequency-sweep impedance spectrum, can be calculated according to the frequency-sweep current signal and the frequency-sweep voltage. By recording the soil resistivity of the position of the grounding grid 10, the grounding grid 10 can be subjected to impedance spectrum simulation to obtain a standard impedance spectrum. Comparing and analyzing the sweep frequency impedance spectrum under the broadband excitation source with the standard impedance spectrum obtained by simulation, a frequency band with obvious difference can be found out according to the distributed impedance characteristics of different breakpoints, and whether the current conductor position and the conductor state in the grounding grid 10 reach the corrosion or fracture standard can be judged by comparing with a preset threshold value.
In one embodiment, for a characteristic frequency domain curve in the swept frequency impedance spectrum, which is obviously different from a standard impedance spectrum obtained by simulation, the position of a corroded conductor can be obtained according to an inverse fourier algorithm from the measured swept frequency impedance spectrum to a spatial position, and the corrosion point or the breakpoint position of the conductor of the grounding grid 10 can be further obtained based on distributed impedance information. By measuring the corrosion or break point F of the earth grid 10 a number of times over a long period of time, typically in yearsMINAnd (4) changing the value, and obtaining the frequency band impedance evolution rule under the operation age through comparison and analysis to obtain the corrosion rate. In one embodiment, the corrosion rate may be F annuallyMINThe amount of change in the value is expressed.
The grounding grid corrosion rate detection method provided by the application can avoid digging the grounding grid 10, so that the corrosion rate of the grounding grid 10 can be detected while the grounding grid 10 is prevented from being damaged, the working time of field maintenance personnel can be greatly reduced, the detection efficiency is improved, and therefore latent faults and even substation accidents can be avoided in time. The grounding grid corrosion rate detection system 100 does not need large current injection, avoids ground potential lifting, and has high measurement accuracy.
In one embodiment, the method for detecting the corrosion rate of the grounding grid further comprises the following steps: before providing a sweep frequency voltage signal for the grounding grid, selecting the grid with the minimum unit length from the grids of the grounding grid, and respectively taking two ends of the grid with the minimum unit length as an input port of the grounding grid and an output port of the grounding grid. It is understood that in the method for detecting the corrosion rate of the grounding grid, two ends of the grid with the minimum unit length in the grounding grid 10 can be selected as the input port 110 and the output port 120 respectively. By selecting the two ends of the grid with the minimum unit length in the grounding grid 10 as the input port 110 and the output port 120 respectively, other grids in the grounding grid 10 can be regarded as transmission lines with distributed parameters, and meanwhile, the testing wiring of the grounding grid 10 can be conveniently carried out on site. If the distance between the two measurement ports is long, the wiring is too long, and the frequency response of the test line cannot be ensured.
In one embodiment, calculating the corrosion degree and the corrosion position of the conductor in the grounding grid according to the swept impedance spectrum and the standard impedance spectrum comprises the following steps: and performing Fourier inverse transformation processing on the frequency sweep impedance spectrum to obtain an actual time domain impedance signal, and performing Fourier inverse transformation processing on the standard impedance spectrum to obtain a standard time domain impedance signal. And calculating the corrosion degree and the corrosion position of the conductor in the grounding grid according to the actual time domain impedance signal and the standard time domain impedance signal. In one embodiment, the actual time-domain impedance signal is a real part of a complex value obtained by performing inverse fourier transform processing on the swept-frequency impedance spectrum. In one embodiment, the standard time-domain impedance signal is a real part of a complex value obtained by performing inverse fourier transform processing on a standard impedance spectrum.
It is understood that the master control device 40 in the system 100 for detecting the corrosion rate of the ground grid may perform inverse fourier transform (IFFT) on the measured swept impedance spectrum. The IFFT principle is: first, the conjugate complex number of the frequency domain signal (complex number) is taken, i.e. the imaginary part is inverted. And then FFT transformation is carried out, so that the frequency domain signal can be converted into the time domain. Since the result of the FFT is a complex number, the result of the IFFT on the frequency domain is also a complex number, and at this time, the original time domain signal can be obtained by taking only the real part of the complex number. In one embodiment, the standard time domain impedance signal is:
wherein rho is the resistivity of the soil, S is the total area of the grid of the grounding grid, epsilon∞Is the high frequency dielectric constant, D is the electric flux in the grid of the grounding grid, r is the conductor resistivity of the grounding grid, l is the total of the grounding gridLength.
At the same time, the resistivity measuring device 50 may be used to record the resistivity ρ of the soil at the location of the earth grid 10. In one embodiment, the main control device 40 may also simulate the existence position of the corrosion point or the breakpoint in the grounding grid 10 according to the actual structure of the grounding grid 10 and the measured soil resistivity ρ, so as to obtain a standard impedance spectrum. In the simulation process, each section of conductor in the grounding grid 10 can be numbered, and a certain section of conductor supposed to be corroded is changed circularly during simulation, so that a series of standard impedance spectrums are obtained and then are respectively compared with the actually measured swept frequency impedance spectrums. First, the corrosion degree of the grounding grid 10 is defined as:
wherein Z isM(m，n)For the simulated time-domain impedance signal of the standard impedance spectrum with coordinates of (m, n) break point, ZMThe time domain impedance signal of the frequency sweep impedance spectrum of the grounding grid 10 is obtained for measurement.
In one embodiment, calculating the corrosion degree and the corrosion position of the conductor in the grounding grid according to the actual time-domain impedance signal and the standard time-domain impedance signal comprises: and calculating the positions of all conductors in the grounding grid according to the actual time domain impedance signals. And respectively calculating the ratio of the actual time domain impedance signal to the standard time domain impedance signal according to the conductor position. And judging whether the ratio is larger than a preset threshold value or not. And if the ratio is larger than or equal to the preset threshold value, the conductor corresponding to the standard impedance spectrum is not corroded. And if the ratio is smaller than the preset threshold value, the corrosion position of the conductor corresponding to the standard impedance spectrum is the corrosion position.
In one embodiment, calculating the ratio of the actual time-domain impedance signal to the standard time-domain impedance signal corresponding to each conductor segment according to the conductor position includes: and respectively calculating a standard time domain impedance signal when each section of conductor in the grounding grid is corroded according to the position of the conductor. And respectively calculating the ratio of the actual time domain impedance signal to the standard time domain impedance signal when each section of conductor is corroded.
It can be understood that ZMNamely, the frequency sweep impedance spectrum is subjected to Fourier inversion processing to obtain an actual time domain impedance signal. ZM(m，n)Namely, the standard impedance spectrum is subjected to Fourier inverse transformation processing to obtain a standard time domain impedance signal. In one embodiment, the predetermined threshold may be 0.1 when FMINIf the current simulation position is less than 0.1, the current simulation position (m, n) can be judged to be an erosion point or a breakpoint, and if F is less than 0.1MINIf the current simulation position is greater than 0.1, it can be judged that no obvious corrosion or fracture exists at the current simulation position (m, n). Referring to fig. 3, further, the frequency sweep impedance spectrum of the grounding grid 10 is measured on-line for multiple times, and F is recordedMINThe corrosion rate of the grounding grid 10 can be calculated according to the trend of time.
In one embodiment, the etch rate is FMIN/h,FMINIs the degree of corrosion, and h is the degree of corrosion FMINThe time of (a), wherein,
ZMis a real time domain impedance signal, ZM(m，n)Is a standard time domain impedance signal when the corrosion conductor position is (m, n).
Referring to fig. 4, in one embodiment, the master control device 40 includes a data obtaining unit 410, an impedance spectrum calculating unit 420, a ground grid simulating unit 430, and a corrosion rate calculating unit 440. The data acquisition unit 410 is electrically connected to the sweep power source 20 and the current sensor 30, respectively, for receiving the sweep voltage signal and the sweep current signal. The impedance spectrum calculation unit 420 is electrically connected to the data acquisition unit 410, and is configured to calculate a swept impedance spectrum of the ground grid 10 according to the swept voltage signal and the swept current signal. The grounding grid simulation unit 430 is electrically connected to the resistivity measuring device 50, and is configured to perform impedance spectrum simulation on the grounding grid according to the structure of the grounding grid 10 and the resistivity of the soil, so as to obtain a standard impedance spectrum of the grounding grid 10. The corrosion rate calculation unit 440 is electrically connected to the impedance spectrum calculation unit 420 and the grounding grid simulation unit 430, respectively, and is configured to calculate the corrosion degree and the corrosion rate of the grounding grid 10 according to the swept impedance spectrum and the standard impedance spectrum.
Referring also to fig. 5, in one embodiment, the swept frequency power supply 20 includes a signal generation circuit 210, a power amplification circuit 220, and an impedance transformer 230. The signal generation circuit 210 is used to generate a frequency sweep signal. The input terminal of the power amplifier circuit 220 is electrically connected to the output terminal of the signal generator circuit 210, and is configured to amplify the frequency sweep signal. The impedance transformer 230 is electrically connected to the output terminal of the power amplifier circuit 220 and the input port 110, respectively, and is used for adjusting impedance, current and/or voltage between the output terminal of the power amplifier circuit 220 and the input port 110. In one embodiment, the swept frequency power supply 20 further comprises a power supply 240. The power supply 240 is electrically connected to the signal generating circuit 210, the power amplifying circuit 220 and the impedance converter 230, and is used for supplying power to the signal generating circuit 210, the power amplifying circuit 220 and the impedance converter 230.
In one embodiment, the sweep range of the swept power source 20 is 20Hz to 30 MHz. It is understood that the swept frequency power supply 20 is the excitation source for the grid erosion rate detection system 100. The signal generating circuit 210 may include a signal generator, which may be used to generate a waveform signal and perform frequency adjustment. The power amplification circuit 220 may be used for amplifying the power of the frequency sweep signal. The impedance transformer 230 may be used to transform the impedance, current or voltage between the power amplifier circuit 220 and the grounded grid 10 load. The power supply 240 may provide operating voltages for the various circuits and devices described above. In addition, the swept frequency power supply 20 may further include output monitoring and display circuits for frequency and current, which may facilitate recording and adjusting data during the corrosion rate measurement of the counterpoise 10.
In one embodiment, signal generation circuit 210 includes a signal generation branch 211, a control branch 212, and a signal filtering branch 213. The signal generating branch 211 is used for generating a frequency sweep signal. The output terminal of the control branch 212 is electrically connected to the input terminal of the signal generation branch 211, and is configured to generate a control signal, and send the control signal to the signal generation branch 211, so as to control the signal generation branch 211 to generate the frequency sweep signal. The input end of the signal filtering branch 213 is electrically connected to the output end of the signal generating branch 211, and is configured to perform filtering processing on the frequency sweep signal generated by the signal generating branch 211. It can be understood that the signal filtering branch 213 may include a power frequency notch circuit, which may effectively filter the influence of external power frequency interference on the system operation, thereby improving the accuracy of the ground grid corrosion rate detection system in detecting the corrosion rate.
In one embodiment, the power amplifier circuit 220 includes an input stage branch 221, a boost stage branch 222, and an output stage branch 223. The input end of the input stage branch 221 is electrically connected to the output end of the signal filtering branch 213, and is configured to obtain the frequency sweep signal. The input terminal of the boost stage branch 222 is electrically connected to the output terminal of the input stage branch 221, and is configured to amplify the voltage of the frequency sweep signal. The input terminal of the output stage branch 223 is electrically connected to the output terminal of the driving stage branch 222 for amplifying the current of the frequency sweep signal. In one embodiment, the power amplifier circuit 220 further comprises a protection stage branch 224. The input of the protection stage branch 224 is electrically connected to the output of the output stage branch 223, and the output of the protection stage branch 224 is electrically connected to the impedance transformer 230 for providing protection for the input stage branch 221, the push stage branch 222 and the output stage branch 223. In one embodiment, the output stage branch 223 is a complementary push-pull parallel output structure with six pairs of transistors.
It is understood that the signal generated by the signal generator in the signal generating circuit 210 is usually weak, and cannot drive the grounding grid 10 as a load. Therefore, the power amplifier circuit 220 is required to amplify the generated frequency sweep signal to increase the output power of the frequency sweep signal. It is to be understood that the present application does not limit the operating frequency of the power amplifier circuit 220 as long as it can meet the design requirements of the excitation source. In one embodiment, the operating frequency of the power amplification circuit 220 may be in the frequency band of 30Hz-30 MHz. In addition, the power amplifier circuit 220 can continuously adjust the frequency and current of the frequency sweep signal, and can continuously work under the condition of ensuring enough output current (0-0.05A). It can be understood that the power amplifier circuit 220 is configured to ensure the output frequency of the frequency sweep signal, thereby ensuring the accuracy of the system 100 for detecting the corrosion rate of the ground grid 10.
In one embodiment, the power amplifier circuit 220 may include a power amplifier. The linear power amplifier has the advantages of good electromagnetic compatibility, simple circuit, low cost, small voltage and current ripples and the like, so that the linear power amplifier can be adopted. The input stage, the boost stage and the output stage in the linear power amplifier can adopt the prior art. For the final output of the linear power amplifier, a complementary push-pull output may be employed to reduce conduction losses. In one embodiment, referring to fig. 6, a 15W dc power supply of ± 5V may be used. The six pairs of transistors can form a complementary push-pull parallel output form, the maximum output power POM is designed to be 11W, and the maximum tube consumption of each output tube is as follows:
the maximum collector current per output tube was:
in this embodiment, the resistance unit is Ω. It can be understood that the complementary push-pull parallel output form can be formed by adopting six pairs of transistors, so that the conduction loss can be reduced, and the accuracy of the corrosion rate detection system of the grounding grid corrosion rate can be improved.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (11)
1. A method for detecting corrosion rate of a grounding grid is characterized by comprising the following steps:
providing a frequency sweep voltage signal for a grounding grid, and detecting a frequency sweep current signal flowing out of the grounding grid;
calculating to obtain a frequency sweep impedance spectrum according to the frequency sweep voltage signal and the frequency sweep current signal;
recording the soil resistivity of the position of the grounding grid, and performing impedance spectrum simulation on the grounding grid according to the structure of the grounding grid and the soil resistivity to obtain a standard impedance spectrum;
calculating the corrosion degree and the corrosion position of the conductor in the grounding grid according to the sweep frequency impedance spectrum and the standard impedance spectrum;
and calculating the corrosion rate of the grounding grid according to the corrosion degree and the detection time corresponding to the corrosion degree.
2. The method of detecting the corrosion rate of the grounding grid of claim 1, further comprising:
before providing the sweep frequency voltage signal for the grounding grid, selecting the grid with the minimum unit length from the grids of the grounding grid, and taking two ends of the grid with the minimum unit length as an input port of the grounding grid and an output port of the grounding grid respectively.
3. The method for detecting the corrosion rate of the grounding grid of claim 1, wherein the calculating the corrosion degree and the corrosion position of the conductor in the grounding grid according to the swept impedance spectrum and the standard impedance spectrum comprises:
carrying out Fourier inversion processing on the sweep frequency impedance spectrum to obtain an actual time domain impedance signal, and carrying out Fourier inversion processing on the standard impedance spectrum to obtain a standard time domain impedance signal;
and calculating the corrosion degree and the corrosion position of the conductor in the grounding grid according to the actual time domain impedance signal and the standard time domain impedance signal.
4. The method for detecting the corrosion rate of the grounding grid of claim 3, wherein the calculating the corrosion degree and the corrosion position of the conductor in the grounding grid according to the actual time-domain impedance signal and the standard time-domain impedance signal comprises:
calculating the positions of all conductors in the grounding grid according to the actual time domain impedance signals;
respectively calculating the ratio of the actual time domain impedance signal to the standard time domain impedance signal according to the conductor position;
judging whether the ratio is larger than a preset threshold value or not;
if the ratio is larger than or equal to the preset threshold value, the conductor corresponding to the standard impedance spectrum is not corroded;
and if the ratio is smaller than the preset threshold value, the corrosion position of the conductor corresponding to the standard impedance spectrum is the corrosion position.
5. The method of claim 4, wherein the calculating the ratio of the actual time-domain impedance signal to the standard time-domain impedance signal corresponding to each segment of conductor according to the conductor position comprises:
respectively calculating the standard time domain impedance signal when each section of conductor in the grounding grid is corroded according to the conductor position;
and respectively calculating the ratio of the actual time domain impedance signal to the standard time domain impedance signal when each section of conductor is corroded.
6. The method for detecting the corrosion rate of the grounding grid as claimed in claim 3, wherein the actual time-domain impedance signal is a real part of a complex value obtained by performing inverse Fourier transform on the swept-frequency impedance spectrum.
7. The method for detecting the corrosion rate of the grounding grid as claimed in claim 3, wherein the standard time-domain impedance signal is a real part of a complex value obtained by performing inverse Fourier transform on the standard impedance spectrum.
8. The method for detecting the corrosion rate of the grounding grid according to claim 3, wherein the standard time domain impedance signal is:
wherein rho is the resistivity of the soil, S is the total area of the grid of the grounding grid, epsilon∞And the high-frequency dielectric constant is D, the electric flux in the grid of the grounding grid is D, r is the conductor resistivity of the grounding grid, and l is the total length of the grounding grid.
9. The method of claim 3, wherein the corrosion rate is FMIN/h,FMINIs the degree of corrosion, and h is the degree of corrosion FMINThe time of (a), wherein,
ZMis the actual time domain impedance signal, ZM(m，n)The standard time domain impedance signal when the corrosion conductor position is (m, n).
10. The method for detecting the corrosion rate of the grounding grid of claim 1, wherein the frequency range of the sweep voltage signal is 20 Hz-30 MHz.
11. The method of claim 1, wherein the swept impedance spectrum comprises impedance magnitude-frequency characteristics and impedance phase-frequency characteristics.
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