CN108801892A - Grounding net of transformer substation corrosion diagnosis method and system - Google Patents

Abstract

A method for diagnosing corrosion of a substation grounding grid, comprising: an excitation source injects an excitation current with programmable transmission power into the grounding grid under test; an induction coil senses the electromagnetic field generated by the excitation current in the grounding grid, and transmits the induced electromagnetic field signal to a 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 within a predetermined range; the predetermined range is formulated according to whether the signal conditioning channel of the receiver is saturated; Optimum working frequency; and according to the optimal operating frequency, control the excitation source to inject the excitation current corresponding to the optimal operating frequency into the grounding grid under test; diagnose the corrosion of the grounding grid under test according to the imaginary part of the electromagnetic field signal output by the receiver. It can effectively reduce the diagnosis error and improve the diagnosis accuracy.

Description

Substation Grounding Grid Corrosion Diagnosis Method and System

technical field

The invention relates to the technical field of power grid signal processing, and more specifically, to a method and system for diagnosing corrosion of a substation grounding grid.

Background technique

The measurement environment of the substation contains various strong current equipment and weak current equipment, and the electromagnetic environment is very complex. There is a strong power frequency electromagnetic field in the space near the substation grounding grid. When switching operations or system failures occur, strong transient electromagnetic fields are generated in the space. Strong power frequency and strong transient electromagnetic field will interfere with the equipment in the substation. The grounding grid corrosion diagnosis device used in substations collects very weak signals. If the interference is not suppressed, the measurement results will be wrong because the weak signal is not collected or the interference signal is taken as a useful signal, and the grounding cannot be detected. The location of the corrosion point of the grid or the misjudgment of the location of the corrosion point will have a serious impact on the diagnosis of the corrosion of the grounding grid.

At present, the grounding grid corrosion diagnosis device adopts the principle of different frequency excitation and electromagnetic induction, and uses the induction coil to detect the electromagnetic field induced by the grounding grid on the ground surface under the action of the excitation current, and locates the topological structure of the grounding grid and the location of the corrosion point through the distribution of the electromagnetic field intensity. However, in the environment of strong interference in the substation, the sensing coil is induced by other electromagnetic waves, and the useful signal is submerged by the background interference. Even if notch filters and filters are added to the signal acquisition channel, the effect is still not significant. Moreover, with the increase of the area of the ground grid, the current in the ground grid conductor is greatly reduced, and the induction signal on the ground surface is weaker. Based on the above two reasons, in the actual measurement, the distribution of the detected electromagnetic field strength is often chaotic, which makes the detection invalid.

Therefore, it is necessary to consider the accuracy and reliability of grounding grid corrosion diagnosis under the complex background of strong interference in substations, and find an effective method to improve the signal-to-noise ratio of the device.

Contents of the invention

The technical problem to be solved by the present invention is to provide a substation grounding grid corrosion diagnosis method and system for the deficiencies of the prior art, which can effectively reduce the diagnosis error and improve the diagnosis accuracy.

On the one hand, the substation grounding grid corrosion diagnosis method provided by the present invention comprises the following steps:

The excitation source injects an excitation current with programmable transmission power into the ground grid under test;

The induction coil induces the electromagnetic field generated by the excitation current of the grounding grid, and transmits the 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 within a predetermined range; the predetermined range is determined according to whether the signal conditioning channel of the receiver is saturated;

The receiver calculates the optimal operating frequency according to the frequency characteristics of the background noise; and controls the excitation source to inject the excitation current corresponding to the optimal operating frequency into the ground grid under test according to the optimal operating frequency;

According to the imaginary part of the electromagnetic field signal output by the receiver, the corrosion condition of the grounding grid under test is diagnosed.

On the other hand, the substation grounding grid corrosion diagnosis system provided by the present invention is characterized in that it includes: an excitation source, a receiver, an induction coil and a diagnosis unit;

The induction coil is connected to the receiver, the excitation source is wirelessly connected to the receiver; the excitation source is connected to the ground grid under test; the diagnostic unit is connected to the receiver;

The excitation source is used to inject an excitation current with programmable transmission power into the ground grid under test;

The induction coil is used to induce the electromagnetic field generated by the grounding grid due to the excitation current, and transmit the induced electromagnetic field signal to the receiver;

The receiver is used to control the excitation source according to the amplitude of the electromagnetic field signal, so that the electromagnetic field signal output by the receiver is within a predetermined range; the predetermined range is determined according to whether the signal conditioning channel of the receiver is saturated; and, according to the background noise frequency The optimal operating frequency is obtained through characteristic calculation; and according to the optimal operating frequency, the excitation source is controlled to inject the excitation current corresponding to the optimal operating frequency into the ground grid under test;

The diagnosis unit is used for diagnosing the corrosion condition of the grounding grid under test according to the imaginary part of the electromagnetic field signal output by the receiver.

Compared with the prior art, the present invention has the following beneficial effects:

1. The present invention adopts "gain double-closed-loop automatic control". The transmission power of the current excitation source and the amplification factor and attenuation factor of the data acquisition channel are programmable, so that the maximum possible to increase the amplitude of the signal.

2. The present invention adopts "frequency closed-loop control", and the frequency of the excitation waveform and the frequency selection frequency of the receiver can be programmed to avoid interference frequency bands and suppress noise to the greatest extent in the complex electromagnetic environment of the substation.

3. The present invention adopts the imaginary component detection method, designs the lock-in amplifier to extract the imaginary component of the sensor induction signal, utilizes the characteristics that the corrosion conductor induction signal is mainly concentrated in the imaginary component, and separates it from the background signal, thereby improving the detection efficiency of the ground grid corrosion fault accuracy.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and embodiment, in the accompanying drawing:

Fig. 1 is the method flowchart in the embodiment of the present invention;

Fig. 2 is a schematic diagram of a system structure in an embodiment of the present invention;

Fig. 3 is a schematic structural diagram of a double closed-loop control loop in an embodiment of the present invention;

Fig. 4 is a schematic structural diagram of a frequency control loop in an embodiment of the present invention.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation manners of the present invention will now be described in detail with reference to the accompanying drawings.

As shown in Figure 1, the method for diagnosing corrosion of substation grounding grid of the present invention comprises the following steps:

101. The excitation source injects an excitation current with programmable transmission power into the ground grid under test;

102. The induction coil senses the electromagnetic field generated by the grounding grid due to the excitation current, and transmits the 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 within a predetermined range; the predetermined range is determined according to whether the signal conditioning channel of the receiver is saturated;

104. The receiver calculates the optimal operating frequency according to the frequency characteristics of the background noise; and controls the excitation source to inject the excitation current corresponding to the optimal operating frequency into the ground grid under test according to the optimal operating frequency;

105. Diagnose the corrosion condition of the ground grid under test according to the imaginary part of the electromagnetic field signal output by the receiver.

Step 103 specifically includes:

The program-controlled amplifier re-amplifies the electromagnetic field signal amplified by the frequency-selective amplifier and sends it to the program-controlled filter;

The first AD converter converts the output signal of the program-controlled filter and feeds it back to the first-stage gain controller;

The first-stage gain controller calculates whether the output signal of the program-controlled filter saturates the signal conditioning channel through the control algorithm: if yes, control the program-controlled amplifier to reduce the amplification factor; if not, control the program-controlled amplifier to increase the amplification factor.

As shown in FIGS. 2 and 3 , in the receiver, the first program-controlled amplifier, the program-controlled filter, the first AD converter and the primary gain controller constitute a first closed-loop control loop.

Step 103, also includes:

The lock-in amplifier receives the output signal of the program-controlled filter for processing, and obtains the electromagnetic field signal output by the receiver;

The second AD converter converts the electromagnetic field signal output by the receiver and feeds it back to the secondary gain controller;

The two-stage gain controller calculates whether the electromagnetic field signal output by the receiver satisfies the linear conversion range of the second AD converter: if so, then control the excitation source to reduce the amplitude of the excitation current injected into the ground grid under test; if not, then control the excitation source Increase the magnitude of the excitation current injected into the ground grid under test.

As shown in Figures 2 and 3, in the receiver and the excitation source, the signal conditioning channel, the second AD converter, the secondary gain controller, the excitation source controller, the second program-controlled amplifier and the power amplifier constitute the second closed-loop control circuit.

Step 104 specifically includes:

The frequency controller acquires the spectrum characteristics of the background noise;

The frequency controller calculates the optimal operating frequency according to the background noise spectrum characteristics;

The frequency controller sends instructions to the excitation source according to the optimum operating frequency, so that the excitation source injects an excitation current corresponding to the optimum operating frequency into the ground grid under test.

Step 104, also includes:

The frequency controller controls the frequency-selective amplifier and the program-controlled filter respectively according to the optimal operating frequency, so that the corresponding passband frequency and cut-off frequency correspond to the optimal operating frequency.

As shown in Figures 2 and 4, in the receiver and excitation source, the signal conditioning channel, frequency controller, excitation source controller, programmable waveform generator and power amplifier constitute a frequency control loop.

As shown in Figure 2, the substation grounding grid corrosion diagnosis system includes: excitation source, receiver, induction coil and diagnosis unit;

The induction coil is connected to the receiver, the excitation source is wirelessly connected to the receiver; the excitation source is connected to the ground grid under test; the diagnostic unit is connected to the receiver;

The excitation source is used to inject an excitation current with programmable transmission power into the ground grid under test;

The induction coil is used to induce the electromagnetic field generated by the grounding grid due to the excitation current, and transmit the induced electromagnetic field signal to the receiver;

The receiver is used to control the excitation source according to the amplitude of the electromagnetic field signal, so that the electromagnetic field signal output by the receiver is within a predetermined range; the predetermined range is determined according to whether the signal conditioning channel of the receiver is saturated; and, according to the background noise frequency The optimal operating frequency is obtained through characteristic calculation; and according to the optimal operating frequency, the excitation source is controlled to inject the excitation current corresponding to the optimal operating frequency into the ground grid under test;

The diagnosis unit is used for diagnosing the corrosion condition of the grounding grid under test according to the imaginary part of the electromagnetic field signal output by the receiver.

Further, the receiver includes: a signal conditioning channel, a receiver controller, a converter and a first wireless communication module;

The signal conditioning channel includes: a frequency-selective amplifier, a first program-controlled amplifier, a program-controlled filter and a lock-in amplifier;

The converter includes: a first AD converter and a second AD converter;

The receiver controller includes: a frequency controller, a gain controller and a secondary gain controller;

The input terminal of the frequency selective amplifier is connected to the induction coil, and the output terminal is connected to the first program-controlled amplifier, program-controlled filter and lock-in amplifier in sequence;

The output end of the lock-in amplifier is connected to the diagnostic unit;

The input end of the first AD converter is connected to the output end of the program-controlled filter, and the output end is connected to the input end of the first-stage gain controller; the output end of the first-stage gain controller is connected to the first program-controlled amplifier.

Furthermore, the excitation source includes: a power amplifier, a second programmable amplifier, a programmable waveform generator, an excitation source controller and a second wireless communication module;

The output end of the power amplifier is connected to the ground grid under test; the second wireless communication module is wirelessly connected to the first wireless communication module;

The second wireless communication module is also connected to the excitation source controller;

The output end of the excitation source controller is sequentially connected to the programmable waveform generator, the second programmable amplifier and the power amplifier;

The output terminal of the lock-in amplifier is also connected with the input terminal of the second AD converter;

The output end of the second AD converter is connected to the input end of the secondary gain controller;

The secondary gain controller is connected to the first wireless communication module.

Still further, the output terminal of the frequency controller is sequentially connected to an excitation source controller, a programmable waveform generator and a power amplifier.

Still further, the output terminals of the frequency controller are respectively connected to a frequency-selective amplifier and a program-controlled filter.

In the present invention, a "double closed-loop control loop" is designed, so that the transmission power of the current excitation source and the amplification factor and attenuation factor of the data acquisition channel are programmable, so that under the premise that no saturation distortion occurs in the measurement channel, Increase the amplitude of the signal as much as possible.

A "frequency closed loop" is designed, so that the frequency of the excitation waveform and the frequency selection frequency of the receiver can be programmed, so as to avoid the interference frequency band in the complex electromagnetic environment of the substation and suppress the noise to the greatest extent.

Using the imaginary component detection method, a lock-in amplifier is designed to extract the imaginary component of the sensor induction signal, and the characteristics of the corroded conductor induction signal mainly concentrated in the imaginary component are used to separate it from the background signal, thereby improving the accuracy of grounding grid corrosion fault detection.

Describe technical scheme of the present invention in detail below in conjunction with example:

As shown in Figures 2 to 3, first, an excitation current with programmable transmission power is injected between the two grounding downconductors of the selected grounding grid through the excitation source;

The receiver controller sends instructions to the program-controlled amplifier, which can control the gain of the data acquisition channel, forming the first closed-loop control loop;

If the signal conditioning channel is saturated, the receiver sends instructions to the excitation source controller through the wireless communication module (the first wireless communication module and the second wireless communication module) to reduce the transmission power;

The excitation source controller sends instructions to the programmable amplifier, which can control the transmission output power to form a second closed-loop control loop, thus realizing the double closed-loop control of the gain of the entire diagnostic device.

The signal conditioning channel of the system is composed of four stages: frequency selective amplifier, first program-controlled amplifier, program-controlled filter and lock-in amplifier. The first loop in the double closed-loop control loop is composed of program-controlled amplifier, first AD converter and receiver controller Composed of a first-stage gain controller.

The working process can be: (1) the gain control unit sends instructions to the program-controlled amplifier to maximize its magnification; (2) the first AD converter collects the signal in the signal conditioning channel, and the collected value is transmitted to the receiver controller (3) The first-level gain control unit calculates from the collected signal amplitude through the control algorithm whether the amplification factor needs to be reduced under the amplification factor, and sends the result compilation control command to the program-controlled amplifier, Repeat steps (1), (2) and (3) until the collected signal amplitude meets the input range requirements of the lock-in amplifier.

In this way, the signal conditioning channel will obtain the maximum signal amplification factor. The second loop in the double closed-loop control loop is composed of signal conditioning channel, AD converter II, secondary gain control unit in the receiver, excitation source controller, program-controlled amplifier and power amplifier. Its working process is: (1) receiving The machine controller sends an instruction to the excitation source controller to make it control the amplification factor of the program-controlled amplifier to the maximum, and the excitation source sends the excitation current with the maximum power at this time; (2) After the signal conditioning channel determines the amplification factor, the lock-in amplified The signal is input to the receiver controller through the second AD converter; (3) the secondary gain controller calculates whether the amplitude of the excitation current needs to be reduced under the excitation current amplitude through an algorithm by the collected signal amplitude; ( 4) Repeat the above three steps until the collected signal amplitude satisfies the linear conversion range of the second AD converter.

Secondly, the frequency selection frequency in the receiver can send instructions to the frequency selection amplification module and programmable filter module through the controller to switch the passing frequency of the channel;

In addition, the receiver sends instructions to the excitation source controller through the wireless communication module, so that it can control the programmable filter generator in the excitation source to obtain the waveform of the required frequency, so as to form a frequency control loop. In complex and changeable substation electromagnetic In the environment, switch the working frequency and avoid the interference frequency band.

The frequency loop is composed of a frequency selective amplifier in the signal conditioning channel, a first program-controlled filter, a frequency controller, an excitation source controller, a programmable waveform generator and a power amplifier.

The working process can be: (1) the receiver controller obtains the spectrum characteristics of the background noise, and obtains the optimal operating frequency through an algorithm; (2) the frequency controller compiles the control command from the calculated optimal operating frequency, and the control signal Adjust the frequency-selective amplifier and program-controlled filter in the channel to make the pass-band frequency and cut-off frequency the optimum operating frequency; (3) The receiver controller sends instructions to the excitation source controller to make it control programmable The waveform generator generates a sine wave at the optimum operating frequency, and the sine wave is amplified by power to generate an excitation current.

Again, the signal in the signal conditioning channel of the receiver is amplified, filtered, notched, etc., and the reference signals of 0° and 90° are processed by the lock-in amplifier AD630 to obtain the real part and imaginary part of the induction signal. The reference signal is provided by the IO port of the receiver controller, and the imaginary part signal reflects the response of the corroded conductor to the excitation signal.

Finally, according to the three-dimensional distribution graph of the imaginary part signal induced by different grounding grid positions, the corrosion condition of the substation grounding grid is diagnosed.

Embodiments of the present invention have been described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementations, and the above-mentioned specific implementations are only illustrative, rather than restrictive, and those of ordinary skill in the art will Under the enlightenment of the present invention, many forms can also be made without departing from the gist of the present invention and the protection scope of the claims, and these all belong to the protection of the present invention.

Claims (10)

1. a kind of grounding net of transformer substation corrosion diagnosis method, which is characterized in that include the following steps：

Driving source injects the programmable exciting current of transmission power to tested grounded screen；

The electromagnetic field that induction coil inductive grounding net is generated by exciting current, and the electromagnetic field signal that induction obtains is sent to and is connect Receipts machine；

Receiver controls driving source according to the amplitude of electromagnetic field signal, makes the electromagnetic field signal that receiver exports in preset range It is interior；Whether the preset range is saturated according to the signal condition channel of receiver and is formulated；

Frequency optimum traffic is calculated according to ambient noise frequency characteristic in receiver；And it is controlled and is encouraged according to frequency optimum traffic The corresponding exciting current of frequency optimum traffic is injected in source to tested grounded screen；

The corrosion condition for being tested grounded screen is diagnosed according to the imaginary part of the electromagnetic field signal of receiver output.

2. grounding net of transformer substation corrosion diagnosis method according to claim 1, which is characterized in that the receiver is according to electricity The amplitude of magnetic field signal controls driving source, makes the electromagnetic field signal that receiver exports within a predetermined range, specifically includes：

Programmable amplifier is sent to programmable filter after amplifying the amplified electromagnetic field signal of frequency-selective amplifier again；

First AD converter feeds back to one step gain controller after converting the output signal of programmable filter；

Whether the output signal that one step gain controller calculates programmable filter by control algolithm makes signal condition channel be saturated： If so, control programmable amplifier reduces amplification factor；If it is not, then controlling programmable amplifier increases amplification factor.

3. grounding net of transformer substation corrosion diagnosis method according to claim 2, which is characterized in that the receiver is according to electricity The amplitude of magnetic field signal controls driving source, makes the electromagnetic field signal that receiver exports within a predetermined range, further includes：

The output signal that lock-in amplifier receives programmable filter is handled, and the electromagnetic field signal of receiver output is obtained；

Second AD converter feeds back to two level gain controller after converting the electromagnetic field signal that receiver exports；

Two level gain controller calculates the linear transformation the model whether electromagnetic field signal that receiver exports meets the second AD converter It encloses：If so, control driving source reduces the amplitude that injection is tested the exciting current of grounded screen；If it is not, then controlling driving source increase Injection is tested the amplitude of the exciting current of grounded screen.

4. grounding net of transformer substation corrosion diagnosis method according to claim 1, which is characterized in that the receiver is according to the back of the body Frequency optimum traffic is calculated in scape noise frequency characteristic；And driving source is controlled according to frequency optimum traffic and is noted to tested grounded screen Enter the corresponding exciting current of frequency optimum traffic, specifically includes：

Frequency controller obtains background noise spectrum characteristic；

Frequency optimum traffic is calculated according to background noise spectrum characteristic in frequency controller；

Frequency controller sends to driving source according to frequency optimum traffic and instructs, and driving source is made to inject best work to tested grounded screen The corresponding exciting current of working frequency.

5. grounding net of transformer substation corrosion diagnosis method according to claim 4, which is characterized in that the receiver is according to the back of the body Frequency optimum traffic is calculated in scape noise frequency characteristic；And driving source is controlled according to frequency optimum traffic and is noted to tested grounded screen Enter the corresponding exciting current of frequency optimum traffic, further includes：

Frequency controller controls frequency-selective amplifier and programmable filter respectively according to frequency optimum traffic, makes corresponding band connection frequency It is corresponding with frequency optimum traffic with cutoff frequency.

6. a kind of grounding net of transformer substation corrosion diagnosis system, which is characterized in that including：It driving source, receiver, induction coil and examines Disconnected unit；

The induction coil is connected with receiver, and driving source is wirelessly connected with receiver；Driving source is connected with tested grounded screen；Institute State diagnosis unit connection receiver；

The driving source, for injecting the programmable exciting current of transmission power to tested grounded screen；

The induction coil, for the electromagnetic field that inductive grounding net is generated by exciting current, and the electromagnetic field that induction is obtained is believed Number it is sent to receiver；

The receiver makes the electromagnetic field signal that receiver exports exist for controlling driving source according to the amplitude of electromagnetic field signal In preset range；Whether the preset range is saturated according to the signal condition channel of receiver and is formulated；And it is made an uproar according to background Frequency optimum traffic is calculated in acoustic frequency characteristic；And driving source is controlled according to frequency optimum traffic and is injected most to tested grounded screen The corresponding exciting current of good working frequency；

The diagnosis unit, the imaginary part of the electromagnetic field signal for export according to receiver to the corrosion condition of tested grounded screen into Row diagnosis.

7. grounding net of transformer substation corrosion diagnosis system according to claim 6, which is characterized in that the receiver includes： Signal condition channel, receiver controller, converter and the first wireless communication module；

The signal condition channel includes：Frequency-selective amplifier, the first programmable amplifier, programmable filter and lock-in amplifier；

The converter includes：First AD converter and the second AD converter；

The receiver controller includes：Frequency controller and gain controller and two level gain controller；

The input terminal of the frequency-selective amplifier is connected with induction coil, and output end is sequentially connected the first programmable amplifier, program-controlled filter Wave device and lock-in amplifier；

The output end of the lock-in amplifier connects diagnosis unit；

The input terminal of first AD converter is connected with the output end of programmable filter, output end and one step gain controller Input terminal is connected；The output end of the one step gain controller connects the first programmable amplifier.

8. grounding net of transformer substation corrosion diagnosis system according to claim 7, which is characterized in that the driving source includes： Power amplifier, the second programmable amplifier, programmable waveform generator, driving source controller and the second wireless communication module；

The output end of the power amplifier is connected with tested grounded screen；Second wireless communication module and the first wireless communication Module is wirelessly connected；

Second wireless communication module is also connected with driving source controller；

The output end of the driving source controller is sequentially connected programmable waveform generator, the second programmable amplifier is put into power Big device；

The output end of the lock-in amplifier is also connected with the input terminal of the second AD converter；

The output end of second AD converter is connected with the input terminal of two level gain controller；

The two level gain controller is connected with the first wireless communication module.

9. grounding net of transformer substation corrosion diagnosis system according to claim 8, which is characterized in that

The output end of the frequency controller is sequentially connected driving source controller, programmable waveform generator and power amplifier.

10. grounding net of transformer substation corrosion diagnosis system according to claim 9, which is characterized in that

The output end of the frequency controller is also respectively connected with frequency-selective amplifier and programmable filter.