Current injection device for detecting corrosion of grounding grid of transformer substation

Abstract

A current injection device for detecting corrosion of a transformer substation grounding grid comprises a main power supply and protection module, an excitation current source, a magnetic field signal receiving and processing device and an upper computer. The main power supply is used for supplying power to the excitation current source; the excitation current source is used for injecting alternating current with a specific frequency into a grounding grid of a detected area, and the alternating current generates a magnetic field in the grounding grid to form a magnetic field signal; the magnetic field signal receiving and processing device is used for collecting magnetic field signals, performing noise reduction processing on the magnetic field signals and transmitting the processed magnetic field signals back to the upper computer; and the upper computer is used for comparing the measured magnetic field signal distribution diagram with a normal non-corroded grounding grid image and judging the corrosion condition of the grounding grid in the detected area. The current injection device for detecting the corrosion of the grounding grid of the transformer substation, which is provided by the invention, is accurate in detection and high in automation degree.

Description

Technical Field

[0001] This patent relates to the technical field of substation grounding grid corrosion detection, specifically a current injection device for detecting substation grounding grid corrosion. Background Technology

[0002] Substations are a crucial component of power systems, and the grounding grid within a substation is an equally vital part. The grounding grid protects various electrical equipment and ensures the safety of personnel within the substation, making it of paramount importance. However, buried grounding grids are highly susceptible to corrosion due to environmental factors such as soil temperature and humidity, leading to increased resistance and loss of protective function. Therefore, regular inspection of the grounding grid's corrosion level is essential. Currently, various methods exist for diagnosing grounding grid corrosion in practical engineering applications. For example, based on the experience of the personnel, the degree of conductor corrosion can be estimated, and potentially severely corroded areas can be excavated for inspection. This method is not very efficient in different scenarios. For example, a corrosion detection sensor can be inserted into the soil to measure the electrochemical characteristics of the metal conductors in the soil around the sensor during the corrosion process, thereby judging the corrosion situation. However, this method can only reflect the corrosion situation at the probe location. Another example is measuring the grounding resistance of the substation grounding grid, such as using the two-wire, three-wire, or four-wire method. However, this method is time-consuming and labor-intensive, and the interference current in the ground is not static and may change at any time, which may cause errors in the total current value. This is not conducive to measuring the grounding resistance, and thus leads to errors in the detection of grounding grid corrosion. Summary of the Invention

[0003] The purpose of this invention is to provide a current injection device for detecting corrosion of the grounding grid in substations, thereby solving the technical problems of large detection errors, high manual labor intensity, and low work efficiency in the prior art.

[0004] To solve the above-mentioned technical problems, the technical content of the present invention is as follows: a current injection device for detecting corrosion of substation grounding grid, which includes a main power supply and protection module, an excitation current source, a magnetic field signal receiving and processing device, and a host computer.

[0005] The main power supply is used to power the excitation current source.

[0006] The main power supply and protection module includes a main AC power supply, a current sensor, a comparator, a relay, a temperature sensor, and a microcontroller; the current sensor, comparator, and relay are connected to form an overcurrent protection section; the temperature sensor and microcontroller are connected to form an overtemperature protection section.

[0007] When a short circuit or other issue in the substation grounding grid causes the current output element to exceed a preset threshold, the comparator will trigger a relay to disconnect the excitation source from the grounding grid, thus achieving overcurrent protection. The triggering condition is as follows: ,in .

[0008] The over-temperature protection section uses a temperature sensor to measure the temperature of the power transistor array in real time. When the temperature exceeds a preset safety threshold, the microcontroller immediately activates, cutting off the output to power down the constant current control module. The trigger condition is as follows: ,in .

[0009] An excitation current source is used to inject a specific frequency alternating current into the grounding grid of the area being probed. This alternating current generates a magnetic field in the grounding grid, forming a magnetic field signal.

[0010] The excitation current source includes a power supply module, a waveform generation module, a power amplification module, and a constant current control module.

[0011] The power supply module includes an AC power distribution unit and a DC regulated power supply;

[0012] The waveform generation module includes a function signal generator and a filter. The waveform generation module is used to generate a precise 10Hz sine reference signal, and the higher harmonics are filtered out through the RC circuit in the filter.

[0013] The power amplifier module includes a high-power operational amplifier, a power transistor array, a filter, a current output element, and a cooling fan. The power amplifier module is used to amplify a 10Hz small signal to a 20A large signal and inject it into the grounding grid. The filter removes high-order harmonics generated during the power amplification process and outputs a 10Hz current and a 20A pure sine wave.

[0014] The constant current control module includes a current sensor and a microcontroller, which are used to detect and control the magnitude of the output current in real time, and the output current is stabilized at 20A.

[0015] The AC power distribution unit introduces 220V AC power into the power supply module of the excitation current source. It has a built-in fuse to prevent overcurrent damage to subsequent equipment on the main power supply side. The AC power distribution unit is the power input of the excitation current source and transmits the pre-protected 220V AC power to the DC regulated power supply. The DC regulated power supply internally converts the AC power into stable DC power through rectification and voltage regulation steps to power the subsequent waveform generation module.

[0016] Direct current is transmitted from the DC regulated power supply to the function signal generator, which generates a 10Hz, pure sine wave signal. This signal serves as the template for subsequent power amplification, and its frequency and waveform directly determine the current characteristics injected into the grounding grid. The instantaneous value expression of this sine wave signal is as follows:

[0017]

[0018] Where i(t) is the instantaneous value of the signal (A), and I0 is the peak value (corresponding to the peak value of the 20A effective value after subsequent amplification). A), f = 10 Hz, t is time (s);

[0019] The 10Hz sine wave signal generated by the function signal generator needs to be filtered to remove high-frequency noise.

[0020] The small signal from the filter is transmitted to a high-power operational amplifier. The high-power operational amplifier, as a pre-driver stage, receives the conditioned 10Hz signal and amplifies its power to 1 to 5A, providing sufficient drive current for the subsequent power transistor array.

[0021] The drive current passes through a high-power operational amplifier to the power transistor array, which is the core amplification element. Under the control of the pre-drive signal, the electrical energy is further amplified and converted into a 20A, 10Hz sinusoidal current. Before being output to the grounding grid, the current passes through a filter to remove high-frequency interference waves. Finally, the pure 10Hz, 20A sinusoidal current is input to the grounding grid under test through the copper terminals of the current output element. A cooling fan is installed near the power transistor array to prevent overheating.

[0022] In the constant current control module, the current sensor monitors the output current in real time, and the current deviation is calculated using the following formula:

[0023]

[0024] in, For reference current, This is the measured current. When When (allowable error) is reached, the microcontroller is activated, and the microcontroller controls the high-power operational amplifier and power transistor array to make the following adjustments: When < - When the measured current is <19.5A, the microcontroller increases the driving voltage amplitude of the high-power operational amplifier and simultaneously increases the duty cycle of the power transistor array (12) to raise the output current to [value missing]. Within the range; when > - That is, when the measured current is greater than 19.5A, the microcontroller reduces the driving voltage amplitude of the high-power operational amplifier and simultaneously reduces the duty cycle of the power transistor array, thereby reducing the output current to [a lower value]. Within the range.

[0025] The aforementioned excitation current source injects a stable 10Hz, 20A AC current into the grounding grid, thereby generating a magnetic field on the ground surface. A magnetic field signal receiving and processing device collects the magnetic field signal, performs noise reduction processing, and transmits the processed signal back to the host computer. The host computer compares the measured magnetic field signal distribution map with an image of a normal, uncorroded grounding grid to determine the corrosion status of the grounding grid in the probed area. When the grounding grid conductor undergoes varying degrees of corrosion, two distinct characteristics appear on the three-dimensional magnetic field image: First, because corrosion reduces the resistance of the grounding grid conductor, the surface magnetic field of corroded grounding grid conductors exhibits a weakening trend, with a decreased magnetic field strength amplitude. The more severe the corrosion, the more pronounced the decrease in surface magnetic field strength. Second, concave points appear in the image of the corroded area in the three-dimensional magnetic field map.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention overcomes the limitations of previous methods for detecting grounding grid corrosion and measuring grounding resistance through the above-mentioned device. It uses a non-contact method based on magnetic field method to obtain the degree of grounding grid corrosion, which has better reliability and economy, and is of great significance for ensuring the stable operation of power equipment. Attached Figure Description

[0027] Figure 1 This is an overall structural diagram of the device of the present invention;

[0028] Figure 2 To excite the current source to output a 10Hz 20A sinusoidal current to the grounding grid;

[0029] Figure 3 This is a schematic diagram of the device module architecture of the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] like Figure 1 The diagram shows the overall structure of an electromagnetic detection device for detecting corrosion in a substation grounding grid. The power supply and protection components power the excitation current source and provide over-temperature and over-current protection. Under the power supply, the excitation current source outputs a stable 10Hz, 20A sinusoidal AC current. Figure 2 The magnetic field is injected into the grounding grid, generating a magnetic field on the grounding grid surface. A magnetic field signal receiving device collects the relevant magnetic field data, which, after noise reduction and other processing, is transmitted to a host computer. The host computer compares the measured magnetic field distribution map with the magnetic field image of a normal, uncorroded grounding grid to obtain the grounding grid corrosion rate.

[0032] When grounding grid conductors undergo varying degrees of corrosion, two distinct characteristics emerge in the three-dimensional magnetic field image. First, because corrosion reduces the resistance of the grounding grid conductors, the surface magnetic field of corroded conductors exhibits a weakening trend, with a decrease in magnetic field strength amplitude. The more severe the corrosion, the more pronounced the decrease in surface magnetic field strength. Second, concave points appear in the image of the corroded area within the three-dimensional magnetic field.

[0033] This patent is mainly aimed at Figure 1 The device, comprising the excitation current source, power supply, and protection components, is a current injection device for detecting corrosion of the substation grounding grid. Its modular architecture diagram is shown below. Figure 3 As shown. The power supply and protection module mainly consists of six parts: a main AC power supply 1, a current sensor 2, a comparator 3, a relay 4, a temperature sensor 5, and a microcontroller 6. The current sensor 2, comparator 3, and relay 4 form an overcurrent protection module; the temperature sensor 5 and microcontroller 6 form an overtemperature protection module. The excitation current source mainly includes a power supply module, a waveform generation module, a power amplification module, and a constant current control module. The power supply module includes two parts: an AC power distribution unit 7 and a DC regulated power supply 8; the waveform generation module includes two parts: a function signal generator 9 and a filter 10; the power amplification module includes five parts: a high-power operational amplifier 11, a power transistor array 12, a filter 13, a current output element 14, and a cooling fan 15; the constant current control module includes two parts: a current sensor 16 and a microcontroller 17.

[0034] The main AC power module 1 is the system's energy source, responsible for providing 220V AC power to subsequent connected modules. Overcurrent protection includes a current sensor 2, a comparator 3, and a relay 4. When a short circuit or other issue in the substation grounding grid causes the current output element to exceed a preset threshold, comparator 3 will trigger relay 4, disconnecting the excitation source from the grounding grid, thus achieving overcurrent protection. The triggering condition is as follows: ,in (Overcurrent threshold). Over-temperature protection includes a temperature sensor 5 and a microcontroller 6. The temperature sensor 5 measures the temperature of the power transistor array 12 in real time. When the temperature exceeds a preset safety threshold, the microcontroller 6 will immediately cut off the output to prevent overheating damage to the devices. The trigger condition is... ,in (Over-temperature threshold).

[0035] AC power distribution unit 7 introduces 220V AC power into the power supply module of the excitation current source. It has a built-in fuse to prevent overcurrent damage to downstream equipment on the main power supply side. AC power distribution unit 7 is the power input for the excitation current source and transmits the pre-protected 220V AC power to DC regulated power supply 8. DC regulated power supply 8 internally converts the AC power into stable DC power through rectification and voltage regulation steps to power the subsequent waveform generation module. The DC power is then transmitted from DC regulated power supply 8 to function signal generator 9. Function signal generator 9 generates a 10Hz (error 10±0.01%), pure sine wave signal (distortion <0.1%). This small signal serves as the template for subsequent power amplification; its frequency and waveform directly determine the current characteristics injected into the grounding grid. The instantaneous value expression of this sine wave signal is:

[0036]

[0037] Where i(t) is the instantaneous value of the signal (A), and I0 is the peak value (corresponding to the peak value of the 20A effective value after subsequent amplification). A), f=10Hz, t is time (s). The reason this patent chooses a final grounding grid current frequency of 10Hz is that 10Hz is far from the substation power frequency (50Hz) and high-order harmonics, reducing interference signals during subsequent magnetic field measurements. Furthermore, a 10Hz current injected into the grounding grid generates a stronger magnetic field on the ground surface, resulting in the best three-dimensional magnetic field image drawn by the host computer. The 10Hz sine wave small signal generated by the function signal generator 9 needs to pass through filter 10 to filter out high-frequency noise, ensuring the normal and stable operation of the subsequent power amplification module. Then, the small signal after passing through filter 10 is transmitted to the high-power operational amplifier 11. The high-power operational amplifier 11, as a pre-drive stage, receives the conditioned 10Hz signal and amplifies its power to 1 to 5A, providing sufficient drive current for the subsequent power transistor array 12. This drive current reaches the power transistor array 12 through the high-power operational amplifier 11. The power transistor array 12, as the core amplification element, under the control of the pre-drive signal, further amplifies the electrical energy, converting it into a 20A, 10Hz sine wave current. To suppress high-frequency switching noise generated during power amplification and prevent this noise from flowing into the grounding grid and interfering with the ground magnetic field measurement, high-frequency interference waves are filtered out by filter 13 before the current is output to the grounding grid. Finally, a pure 10Hz, 20A sine wave current is input to the grounding grid under test through the copper terminals of the current output element 14. Since the power transistor array 12 generates heat due to its on-resistance during operation, a cooling fan 15 is required to prevent overheating that could degrade equipment performance or even cause burnout. Furthermore, because the output current may fluctuate due to grounding grid corrosion or changes in soil moisture, a constant current control module is added to ensure a stable 20A output current. The current sensor 16 within this module monitors the output current in real time, and the current deviation is calculated using the following formula:

[0038]

[0039] in, For reference current, This is the measured current. When When (allowable error) is reached, the microcontroller 17 is activated, and the microcontroller 17 controls the high-power operational amplifier 11 and the power transistor array 12 to make the following adjustments: When < - When the measured current is <19.5A, the microcontroller (17) increases the driving voltage amplitude of the high-power operational amplifier (11) and simultaneously increases the duty cycle of the power transistor array (12), thereby increasing the output current to [value missing]. Within the range; when > - When the measured current is greater than 19.5A, the microcontroller (17) reduces the driving voltage amplitude of the high-power operational amplifier (11) and simultaneously reduces the duty cycle of the power transistor array (12), thereby reducing the output current to [value missing]. Within the range.

Claims

1. A current injection device for detecting corrosion of substation grounding grid, characterized in that: Includes a main power supply and protection module, an excitation current source, a magnetic field signal receiving and processing device, and a host computer; The main power supply is used to power the excitation current source; An excitation current source is used to inject a specific frequency alternating current into the grounding grid of the area being probed. This alternating current generates a magnetic field in the grounding grid, forming a magnetic field signal. The magnetic field signal receiving and processing device is used to collect magnetic field signals, perform noise reduction processing on the magnetic field signals, and transmit the processed magnetic field signals back to the host computer. The host computer is used to compare the measured magnetic field signal distribution map with the image of a normal, uncorroded grounding grid to determine the corrosion status of the grounding grid in the detected area.

2. The current injection device for detecting corrosion of substation grounding grid according to claim 1, characterized in that: The main power supply and protection module includes a main AC power supply (1), a current sensor (2), a comparator (3), a relay (4), a temperature sensor (5), and a microcontroller (6); the current sensor (2), the comparator (3), and the relay (4) are connected to form an overcurrent protection section; the temperature sensor (5) and the microcontroller (6) are connected to form an overtemperature protection section.

3. The current injection device for detecting corrosion of substation grounding grid according to claim 2, characterized in that: When the current output element of the current protection section exceeds the preset threshold due to a short circuit or other issues in the substation grounding grid, the comparator (3) will trigger the relay (4) to disconnect the connection between the excitation source and the grounding grid, thereby achieving overcurrent protection. The triggering condition is as follows: ,in .

4. The current injection device for detecting corrosion of substation grounding grid according to claim 2, characterized in that: The over-temperature protection section uses a temperature sensor (5) to measure the temperature of the power transistor array (12) in real time. When the temperature exceeds a preset safety threshold, the microcontroller (6) immediately activates, cutting off the output to power off the constant current control module. The trigger condition is as follows: ,in .

5. A current injection device for detecting corrosion of a substation grounding grid according to claim 1, characterized in that: The excitation current source includes a power supply module, a waveform generation module, a power amplification module, and a constant current control module; The power supply module includes an AC power distribution unit (7) and a DC regulated power supply (8). The waveform generation module includes a function signal generator (9) and a filter (10). The waveform generation module is used to generate a precise 10Hz sine reference signal and filter out high-order harmonics through the RC circuit in the filter (10). The power amplifier module includes a high-power operational amplifier (11), a power transistor array (12), a filter (13), a current output element (14), and a cooling fan (15). The power amplifier module is used to amplify a small 10Hz signal to a large 20A signal and inject it into the grounding grid. The filter (13) filters out the high-order harmonics generated during the power amplification process and outputs a 10Hz current and a pure 20A sine wave. The constant current control module includes a current sensor (17) and a microcontroller (17) for real-time detection and control of the output current, and the output current is stabilized at 20A.

6. A current injection device for detecting corrosion of a substation grounding grid according to claim 5, characterized in that: The AC power distribution unit (7) introduces 220V AC power into the power supply module of the excitation current source. It has a built-in fuse to prevent overcurrent damage to subsequent equipment on the main power supply side. The AC power distribution unit (7) is the power input of the excitation current source and transmits the 220V AC power after preliminary protection to the DC regulated power supply (8). The DC regulated power supply (8) converts the AC power into stable DC power through rectification and voltage regulation steps to power the subsequent waveform generation module.

7. A current injection device for detecting corrosion of a substation grounding grid according to claim 5, characterized in that: DC power is transmitted from the DC regulated power supply (8) to the function signal generator (9). The function signal generator (9) generates a 10Hz, pure sine wave small signal. This small signal is the template for subsequent power amplification. Its frequency and waveform directly determine the current characteristics injected into the grounding grid. The instantaneous value expression of this sine wave small signal is: Where i(t) is the instantaneous value of the signal (A), and I0 is the peak value (corresponding to the peak value of the 20A effective value after subsequent amplification). A), f = 10 Hz, t is time (s); The 10Hz sine wave signal generated by the function signal generator (9) needs to be filtered by the filter (10) to remove high-frequency noise.

8. A current injection device for detecting corrosion of a substation grounding grid according to claim 5, characterized in that: The small signal of the filter (10) is transmitted to the high-power operational amplifier (11). The high-power operational amplifier (11) serves as a pre-drive stage, receiving the conditioned 10Hz signal and amplifying its power to 1 to 5A to provide sufficient drive current for the subsequent power transistor array (12). The driving current passes through the high-power operational amplifier (11) to the power transistor array (12). The power transistor array (12) is the core amplification element. Under the control of the pre-drive signal, the power is further amplified and converted into a 20A, 10Hz sine wave current. Before the current is output to the grounding grid, the high-frequency interference wave is filtered out by the filter (13). Finally, the 10Hz, 20A pure sine wave current is input to the grounding grid to be tested through the copper terminal of the current output element (14).

9. A current injection device for detecting corrosion of a substation grounding grid according to claim 8, characterized in that: A cooling fan (15) is provided near the power transistor array (12) to prevent overheating.

10. A current injection device for detecting corrosion of a substation grounding grid according to claim 5, characterized in that: In the constant current control module, the current sensor (16) monitors the magnitude of the output current in real time, and the current deviation is calculated using the following formula: in, For reference current, This is the measured current. When When (allowable error) is reached, the microcontroller (17) is activated, and the microcontroller (17) controls the high-power operational amplifier (11) and the power transistor array (12) to make the following adjustments: When < - When the measured current is <19.5A, the microcontroller (17) increases the driving voltage amplitude of the high-power operational amplifier (11) and simultaneously increases the duty cycle of the power transistor array (12) to raise the output current to Within the range; when > - When the measured current is greater than 19.5A, the microcontroller (17) reduces the driving voltage amplitude of the high-power operational amplifier (11) and simultaneously reduces the duty cycle of the power transistor array (12) to reduce the output current to [value missing]. Within the range.

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