CN108801892B - Transformer substation grounding grid corrosion diagnosis method and system - Google Patents
Transformer substation grounding grid corrosion diagnosis method and system Download PDFInfo
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- CN108801892B CN108801892B CN201810630092.XA CN201810630092A CN108801892B CN 108801892 B CN108801892 B CN 108801892B CN 201810630092 A CN201810630092 A CN 201810630092A CN 108801892 B CN108801892 B CN 108801892B
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- 238000005260 corrosion Methods 0.000 title claims abstract description 38
- 238000003745 diagnosis Methods 0.000 title claims abstract description 31
- 230000005284 excitation Effects 0.000 claims abstract description 96
- 230000001939 inductive effects Effects 0.000 claims abstract description 29
- 230000003750 conditioning Effects 0.000 claims abstract description 24
- 230000001276 controlling effects Effects 0.000 claims abstract description 18
- 230000000875 corresponding Effects 0.000 claims abstract description 13
- 230000005540 biological transmission Effects 0.000 claims abstract description 9
- 230000003321 amplification Effects 0.000 claims description 13
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 13
- 238000000034 methods Methods 0.000 claims description 5
- 238000001228 spectrum Methods 0.000 claims description 5
- 238000006243 chemical reactions Methods 0.000 claims description 3
- 239000004020 conductors Substances 0.000 description 5
- 238000010586 diagrams Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000001514 detection method Methods 0.000 description 2
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
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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
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
Abstract
Description
Technical Field
The invention relates to the technical field of power grid signal processing, in particular to a method and a system for diagnosing corrosion of a transformer substation grounding grid.
Background
The transformer substation measurement environment comprises various strong current equipment and weak current equipment, and the electromagnetic environment is very complex. A strong power frequency electromagnetic field exists in the space near the transformer substation grounding grid. When a switching operation or a system failure occurs, a strong transient electromagnetic field is generated in the space. The strong power frequency and the strong transient electromagnetic field generate interference to equipment in the transformer substation. The grounding grid corrosion diagnosis device applied to the transformer substation is very weak in acquired signals, and if interference is not inhibited, the signals cannot be acquired or the interference signals are taken as useful signals, so that a measurement result is wrong, the position of a grounding grid corrosion point cannot be detected or the position of the corrosion point is misjudged, and the diagnosis of grounding grid corrosion is seriously influenced.
At present, the grounding grid corrosion diagnosis device adopts the principle of pilot frequency excitation and electromagnetic induction, utilizes an induction coil to detect an electromagnetic field induced on the ground surface by the grounding grid under the action of excitation current, and positions a grounding grid topological structure and a corrosion point position through the distribution of electromagnetic field intensity. However, in the environment of strong interference of a transformer substation, the sensing coil is induced by other electromagnetic waves, a useful signal is submerged by background interference, and even if a wave trap and a filter are added in a signal acquisition channel, the effect is still not obvious. And with the increase of the area of the grounding grid, the current in the conductor of the grounding grid is greatly reduced, and the induction signal of the ground surface is weaker. For the above two reasons, when actual measurement is performed, the distribution of the detected electromagnetic field intensity is often disordered, so that the detection is invalid.
Therefore, the accuracy and reliability of the grounding grid corrosion diagnosis under the complex background of the strong interference of the transformer substation need to be considered, and an effective method for improving the signal-to-noise ratio of the device needs to be found.
Disclosure of Invention
The invention aims to solve the technical problem that the method and the system for diagnosing the corrosion of the grounding grid of the transformer substation can effectively reduce the diagnosis error and improve the diagnosis precision aiming at the defects of the prior art.
On one hand, the method for diagnosing corrosion of the grounding grid of the transformer substation, provided by the invention, comprises the following steps:
the excitation source injects excitation current with programmable transmission power to the tested grounding grid;
the induction coil induces an electromagnetic field generated by the grounding grid due to the exciting current and transmits an induced electromagnetic field signal to the receiver;
the receiver controls the excitation source according to the amplitude of the electromagnetic field signal, so that the electromagnetic field signal output by the receiver is in a preset range; the predetermined range is established according to whether a signal conditioning channel of the receiver is saturated or not;
the receiver calculates to obtain the optimal working frequency according to the frequency characteristic of the background noise; controlling an excitation source to inject excitation current corresponding to the optimal working frequency into the grounding grid to be tested according to the optimal working frequency;
and diagnosing the corrosion condition of the grounding grid to be tested according to the imaginary part of the electromagnetic field signal output by the receiver.
On the other hand, the corrosion diagnosis system for the grounding grid of the transformer substation provided by the invention is characterized by comprising the following components: the device comprises an excitation source, a receiver, an induction coil and a diagnosis unit;
the induction coil is connected with the receiver, and the excitation source is wirelessly connected with the receiver; the excitation source is connected with the grounding grid to be tested; the diagnosis unit is connected with a receiver;
the excitation source is used for injecting excitation current with programmable transmission power into the tested grounding grid;
the induction coil is used for inducing an electromagnetic field generated by the grounding grid due to the exciting current and transmitting an electromagnetic field signal obtained by induction to the receiver;
the receiver is used for controlling the excitation source according to the amplitude of the electromagnetic field signal so that the electromagnetic field signal output by the receiver is in a preset range; the predetermined range is established according to whether a signal conditioning channel of the receiver is saturated or not; calculating to obtain the optimal working frequency according to the frequency characteristic of the background noise; controlling an excitation source to inject excitation current corresponding to the optimal working frequency into the grounding grid to be tested according to the optimal working frequency;
and the diagnosis unit is used for diagnosing the corrosion condition of the grounding grid to be detected according to the imaginary part of the electromagnetic field signal output by the receiver.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention adopts 'gain double closed loop automatic control', the transmitting power of the current excitation source and the amplification factor and the attenuation factor of the data acquisition channel are programmable by programs, thus improving the amplitude of the signal to the greatest extent on the premise of ensuring that the measurement channel does not generate saturation distortion.
2. The invention adopts frequency closed-loop control, the frequency of the excitation waveform and the frequency selection frequency of the receiver can be programmed, and the interference frequency band is avoided in the complex transformer substation electromagnetic environment, so that the noise is suppressed to the maximum extent.
3. The invention adopts an imaginary component detection method, designs a phase-locked amplifier to extract the imaginary component of the sensor induction signal, and separates the imaginary component from a background signal by utilizing the characteristic that the corrosion conductor induction signal is mainly concentrated on the imaginary component, thereby improving the accuracy of the corrosion fault detection of the grounding grid.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a flow chart of a method in an embodiment of the invention;
FIG. 2 is a schematic diagram of a system architecture in an embodiment of the invention;
FIG. 3 is a schematic diagram of a dual closed-loop control loop according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a frequency control loop according to an embodiment of the present invention.
Detailed Description
For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
As shown in fig. 1, the method for diagnosing corrosion of a grounding grid of a transformer substation according to the present invention includes the following steps:
101. the excitation source injects excitation current with programmable transmission power to the tested grounding grid;
102. the induction coil induces an electromagnetic field generated by the grounding grid due to the exciting current and transmits an induced electromagnetic field signal to the receiver;
103. the receiver controls the excitation source according to the amplitude of the electromagnetic field signal, so that the electromagnetic field signal output by the receiver is in a preset range; the predetermined range is established according to whether a signal conditioning channel of the receiver is saturated or not;
104. the receiver calculates to obtain the optimal working frequency according to the frequency characteristic of the background noise; controlling an excitation source to inject excitation current corresponding to the optimal working frequency into the grounding grid to be tested according to the optimal working frequency;
105. and diagnosing the corrosion condition of the grounding grid to be tested according to the imaginary part of the electromagnetic field signal output by the receiver.
Step 103, specifically comprising:
the program control amplifier amplifies the electromagnetic field signal amplified by the frequency selection amplifier again and then sends the amplified electromagnetic field signal to the program control filter;
the first AD converter converts the output signal of the programmable filter and feeds the converted output signal back to the first-stage gain controller;
the first-stage gain controller calculates whether the output signal of the programmable filter saturates a signal conditioning channel through a control algorithm: if yes, controlling the programmable control amplifier to reduce the amplification factor; if not, the programmable control amplifier is controlled to increase the amplification factor.
As shown in fig. 2 and 3, in the receiver, the first programmable amplifier, the programmable filter, the first AD converter, and the one-stage gain controller constitute a first closed-loop control loop.
Step 103, further comprising:
the phase-locked amplifier receives and processes the output signal of the program-controlled filter to obtain an electromagnetic field signal output by the receiver;
the second AD converter converts the electromagnetic field signal output by the receiver and feeds the electromagnetic field signal back to the second-level gain controller;
the two-stage gain controller calculates whether the electromagnetic field signal output by the receiver satisfies a linear conversion range of the second AD converter: if so, controlling the excitation source to reduce the amplitude of the excitation current injected into the tested grounding grid; and if not, controlling the excitation source to increase the amplitude of the excitation current injected into the tested grounding grid.
As shown in fig. 2 and 3, in the receiver and the driver, the signal conditioning channel, the second AD converter, the two-stage gain controller, the driver controller, the second programmable amplifier, and the power amplifier form a second closed-loop control loop.
Step 104, specifically comprising:
the frequency controller acquires the frequency spectrum characteristic of background noise;
the frequency controller calculates to obtain the optimal working frequency according to the background noise spectrum characteristic;
and the frequency controller sends an instruction to the excitation source according to the optimal working frequency, so that the excitation source injects excitation current corresponding to the optimal working frequency into the tested grounding grid.
Step 104, further comprising:
the frequency controller respectively controls the frequency-selecting amplifier and the program-controlled filter according to the optimal working frequency, so that the corresponding pass band frequency and cut-off frequency correspond to the optimal working frequency.
As shown in fig. 2 and 4, in the receiver and the driver, the signal conditioning channel, the frequency controller, the driver controller, the programmable waveform generator, and the power amplifier form a frequency control loop.
As shown in fig. 2, the corrosion diagnosis system for the grounding grid of the transformer substation comprises: the device comprises an excitation source, a receiver, an induction coil and a diagnosis unit;
the induction coil is connected with the receiver, and the excitation source is wirelessly connected with the receiver; the excitation source is connected with the grounding grid to be tested; the diagnosis unit is connected with a receiver;
the excitation source is used for injecting excitation current with programmable transmission power into the tested grounding grid;
the induction coil is used for inducing an electromagnetic field generated by the grounding grid due to the exciting current and transmitting an electromagnetic field signal obtained by induction to the receiver;
the receiver is used for controlling the excitation source according to the amplitude of the electromagnetic field signal so that the electromagnetic field signal output by the receiver is in a preset range; the predetermined range is established according to whether a signal conditioning channel of the receiver is saturated or not; calculating to obtain the optimal working frequency according to the frequency characteristic of the background noise; controlling an excitation source to inject excitation current corresponding to the optimal working frequency into the grounding grid to be tested according to the optimal working frequency;
and the diagnosis unit is used for diagnosing the corrosion condition of the grounding grid to be detected according to the imaginary part of the electromagnetic field signal output by the receiver.
Further, the receiver includes: the system comprises a signal conditioning channel, a receiver controller, a converter and a first wireless communication module;
the signal conditioning channel includes: the frequency-selecting amplifier, the first program-controlled amplifier, the program-controlled filter and the phase-locked amplifier;
the converter includes: a first AD converter and a second AD converter;
the receiver controller includes: a frequency controller, and a gain controller and a two-stage gain controller;
the input end of the frequency-selective amplifier is connected with the induction coil, and the output end of the frequency-selective amplifier is sequentially connected with the first program-controlled amplifier, the program-controlled filter and the phase-locked amplifier;
the output end of the phase-locked amplifier is connected with the diagnosis unit;
the input end of the first AD converter is connected with the output end of the program-controlled filter, and the output end of the first AD converter is connected with the input end of the first-stage gain controller; the output end of the first-stage gain controller is connected with the first program control amplifier.
Still further, the excitation source includes: the power amplifier, the second program control amplifier, the programmable waveform generator, the excitation source controller and the second wireless communication module;
the output end of the power amplifier is connected with a tested grounding grid; the second wireless communication module is wirelessly connected with the first wireless communication module;
the second wireless communication module is also connected with the excitation source controller;
the output end of the excitation source controller is sequentially connected with the programmable waveform generator, the second programmable amplifier and the power amplifier;
the output end of the phase-locked amplifier is also connected with the input end of the second AD converter;
the output end of the second AD converter is connected with the input end of the second-stage gain controller;
the second-level gain controller is connected with the first wireless communication module.
Still further, the output end of the frequency controller is sequentially connected with the excitation source controller, the programmable waveform generator and the power amplifier.
Still further, the output end of the frequency controller is respectively connected with a frequency-selecting amplifier and a program-controlled filter.
In the invention, a 'double closed-loop control loop' is designed, so that the transmitting power of a current excitation source and the amplification factor and the attenuation factor of a data acquisition channel are both programmable by programs, and the amplitude of a signal is improved to the greatest extent on the premise of ensuring that a measurement channel does not generate saturation distortion.
A frequency closed loop is designed, so that the frequency of an excitation waveform and the frequency selection frequency of a receiver can be programmed, the interference frequency band is avoided in the complex transformer substation electromagnetic environment, and the noise is suppressed to the maximum extent.
The method adopts an imaginary component detection method, designs a phase-locked amplifier to extract the imaginary component of the sensor induction signal, and separates the imaginary component from a background signal by utilizing the characteristic that the corrosion conductor induction signal is mainly concentrated on the imaginary component, thereby improving the accuracy of the corrosion fault detection of the grounding grid.
The technical solution of the present invention is described in detail below with reference to examples:
as shown in fig. 2 to 3, first, an excitation current with programmable transmission power is injected between two ground down conductors of a selected ground grid by an excitation source;
the receiver controller sends an instruction to the program-controlled amplifier, and can control the gain of the data acquisition channel to form a first closed-loop control loop;
if the signal conditioning channel is saturated, the receiver sends an instruction to the excitation source controller through the wireless communication module (the first wireless communication module and the second wireless communication module) so as to reduce the sending power;
the excitation source controller sends an instruction to the programmable amplifier, and can control the transmission output power to form a second closed-loop control loop, so that the double closed-loop control of the gain of the whole diagnostic device is realized.
The signal conditioning channel of the system consists of four stages of a frequency selection amplifier, a first program control amplifier, a program control filter and a phase-locked amplifier, wherein the first loop in the double closed-loop control loop consists of the program control amplifier, the first AD converter and a first-stage gain controller in the receiver controller.
The working process can be as follows: (1) the gain control unit sends an instruction to the program control amplifier to enable the amplification factor of the program control amplifier to be maximum; (2) the first AD converter collects signals in the signal conditioning channel, and the collected values are transmitted to a first-stage gain control unit in the receiver controller; (3) and (3) calculating by the first-stage gain control unit through a control algorithm according to the acquired signal amplitude to determine whether the amplification factor needs to be reduced or not under the amplification factor, compiling a control command according to the result, and sending the control command to the program-controlled amplifier, and repeating the steps (1), (2) and (3) until the acquired signal amplitude meets the requirement of the input range of the phase-locked amplifier.
In this way, the signal conditioning channel will obtain maximum signal amplification. The second loop of the double closed loop control loop is composed of a signal conditioning channel, an AD converter II, a secondary gain control unit in the receiver, an excitation source controller, a program control amplifier and a power amplifier, and the working process is as follows: (1) the receiver controller sends an instruction to the excitation source controller to control the amplification factor of the program-controlled amplifier to be maximum, and at the moment, the excitation source sends excitation current with the maximum power; (2) after the signal conditioning channel determines the amplification factor, the phase-locked amplified signal is input to a receiver controller through a second AD converter; (3) the secondary gain controller calculates whether the amplitude of the excitation current needs to be reduced or not under the amplitude of the excitation current according to the acquired signal amplitude through an algorithm; (4) and repeating the three steps until the amplitude of the acquired signal meets the linear conversion range of the second AD converter.
Secondly, the frequency selection frequency in the receiver can send an instruction to the frequency selection amplifying module and the programmable filter module through the controller to switch the passing frequency of the channel;
in addition, the receiver sends an instruction to the excitation source controller through the wireless communication module, so that the receiver controls the programmable filter wave generator in the excitation source to obtain a waveform with required frequency, and a frequency control loop is formed, so that the working frequency is switched in a complex and changeable transformer substation electromagnetic environment, and an interference frequency band is avoided.
The frequency loop is composed of a frequency-selecting amplifier, a first program-controlled filter, a frequency controller, an excitation source controller, a programmable waveform generator and a power amplifier in the signal conditioning channel.
The working process can be as follows: (1) the receiver controller acquires the frequency spectrum characteristic of background noise and obtains the optimal working frequency through an algorithm; (2) the frequency controller is programmed into a control instruction by the optimal working frequency obtained by calculation, and controls a frequency-selecting amplifier and a program-controlled filter in a signal conditioning channel to respectively enable the passband frequency and the cut-off frequency to be the required optimal working frequency; (3) the receiver controller sends an instruction to the excitation source controller to control the programmable waveform generator to generate a sine wave at an optimal working frequency, and the sine wave is power-amplified to generate an excitation current.
And thirdly, after the signals in the signal conditioning channel of the receiver are processed by amplification, filtering, notch and the like, the signals and the reference signals of 0 degree and 90 degree are processed by a phase-locked amplifier AD630 to obtain a real part and an imaginary part of the induction signal. Where the reference signal is provided by the receiver controller IO port and the imaginary signal reflects the response of the corroded conductor to the excitation signal.
And finally, diagnosing the corrosion condition of the transformer substation grounding network according to the obtained imaginary part signal three-dimensional distribution pattern sensed by different grounding network positions.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
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