Current transformer oil level monitoring system based on ultrasonic echo detection

Abstract

The invention discloses a current transformer oil level monitoring system based on ultrasonic echo detection, which relates to the technical field of electric power monitoring and comprises the following steps: acquiring original echo time sequence data; calculating the distance between the transmitting end and the top of the metal expander by combining the propagation velocity of the ultrasonic waves in the air; and when the oil level height value is lower than a set threshold value, an alarm signal is triggered. According to the invention, the problems of easy clamping stagnation, complex installation, large temperature drift and environmental interference and the like of the traditional float-type, pressure-type and window observation methods are effectively overcome, remote uploading and local acousto-optic prompt are supported, and intelligent inspection and fault pre-warning identification under unattended operation are realized; and the operation safety, the monitoring reliability and the operation and maintenance intelligent level of the oil-immersed current transformer are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of power monitoring technology, and in particular to a current transformer oil level monitoring system based on ultrasonic echo detection. Background Technology

[0002] With the continuous advancement of smart grid and digital transformation of power systems, the demand for intelligent and online monitoring of substation equipment is increasing. The safety and stability of power equipment operation are directly related to the reliable operation of the entire power grid. Especially in high-voltage transmission and distribution, current transformers are one of the key devices, and their health status directly affects the measurement accuracy and the accuracy of relay protection actions. Oil-immersed current transformers are widely used due to their excellent insulation performance, and the change of their internal oil level is an important indicator reflecting whether there are faults such as oil leakage, overheating, discharge, or insulation deterioration. Therefore, achieving real-time, accurate, and non-contact monitoring of oil level changes has become a key link in ensuring the safe operation of the power system. The traditional method of relying on manual inspection is no longer able to meet the development trend of efficient, intelligent, and unmanned operation and maintenance of modern power grids.

[0003] Currently, monitoring of oil levels in current transformers primarily employs float-type level gauges, pressure sensors, or window observation methods. These methods have significant drawbacks. Float-type gauges are susceptible to oil contamination, leading to jamming. Pressure sensors require invasive installation, which is not only complex to modify and carries high sealing risks, but is also easily affected by temperature drift, impacting measurement accuracy. Window observation relies on manual observation, which is severely affected by ambient light, glass contamination, and other factors, making it impossible to achieve data-driven, remote monitoring. More importantly, existing technologies generally lack a high-precision, continuous, dynamic measurement method for the positional changes of metal expansion joints without contacting the insulating oil or damaging the original sealing structure. This results in an inability to reliably reflect the true oil level status in real time, leading to problems such as large monitoring blind spots, poor reliability, and high maintenance costs. Summary of the Invention

[0004] In view of the problems existing in the current transformer oil level monitoring system based on ultrasonic echo detection, this invention is proposed.

[0005] Therefore, the problem to be solved by the present invention is: how to provide a non-contact, high-precision, and remotely early warning method for monitoring the oil level of current transformers, so as to overcome the defects of existing technologies that rely on manual inspection, have high risks of invasive measurement, are susceptible to environmental interference, and cannot monitor oil level anomalies in real time.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] In a first aspect, embodiments of the present invention provide a current transformer oil level monitoring system based on ultrasonic echo detection, comprising: an ultrasonic transmitting and receiving module for directionally transmitting ultrasonic pulse signals to the surface of a metal expander, receiving echo signals reflected from the surface of the metal expander, and acquiring raw echo time series data; a signal processing distance calculation module for preprocessing the received echo signals, extracting the time delay information of the effective echo, and calculating the distance between the transmitting end and the top of the metal expander in combination with the propagation speed of ultrasonic waves in air; and an oil level status analysis and early warning module for converting the distance between the transmitting end and the top of the metal expander into a corresponding oil level height value, and triggering an alarm signal when the oil level height value is lower than a set threshold.

[0008] As a preferred embodiment of the current transformer oil level monitoring system based on ultrasonic echo detection described in this invention, the ultrasonic transmitting and receiving module includes a high-frequency excitation driving submodule, an anti-interference sensing probe submodule, and a dynamic gain adjustment submodule.

[0009] The signal processing distance calculation module includes a composite filtering noise reduction submodule, an envelope peak accurate positioning submodule, and a temperature-varying sound speed compensation calculation submodule.

[0010] The oil level status analysis and early warning module includes an oil level mapping calibration submodule, a trend prediction and diagnosis submodule, and a multi-level linkage alarm submodule.

[0011] As a preferred embodiment of the current transformer oil level monitoring system based on ultrasonic echo detection described in this invention, the high-frequency excitation drive submodule is used to generate a high-voltage pulse signal with a nanosecond-level rising edge, to excite the piezoelectric crystal and emit a narrow-beam ultrasonic wave adapted to complex outdoor electromagnetic environments.

[0012] The anti-interference sensor probe submodule is used to sense echo signals in real time and convert them into electrical signals to suppress reflection interference caused by rainwater adhesion and dust deposition on the acoustic interface.

[0013] The dynamic gain adjustment submodule is used to automatically adjust the amplification factor of the receiving channel according to the intensity of the echo signal;

[0014] The composite filtering and noise reduction submodule is used to combine infinite impulse response bandpass filtering to filter out power frequency interference, switching operation pulses and environmental stray noise, while retaining the characteristic waveform of the noiseless echo signal.

[0015] The envelope peak precise positioning submodule is used to perform Hilbert transform on the characteristic waveform of the noiseless echo signal, construct the analytical signal envelope, and fit the arrival time of the echo between discrete sampling points by interpolation.

[0016] The temperature-varying sound speed compensation calculation submodule is used to fuse ambient temperature sensor data, dynamically correct the sound speed parameters in the air, and calculate the distance between the transmitter and the top of the metal expander by combining the flight time.

[0017] The oil level mapping calibration submodule is used to establish a nonlinear mapping model of distance-oil level based on the distance between the acquired transmitter and the top of the metal expander, and to convert the actual oil level height value. The nonlinear mapping model is obtained by training based on equipment structural parameters and multi-condition measured data.

[0018] The trend prediction and diagnosis submodule is used to perform first-order difference operation on the oil level height value, identify the changing trend of the oil level height value, issue an early deterioration warning before the alarm threshold is reached, and improve the fault prediction capability.

[0019] The multi-level linkage alarm submodule is used to set graded alarm strategies according to the degree of abnormality of oil level values, and upload alarm information to the operation and maintenance platform through wireless communication interface, supporting remote monitoring and emergency response linkage.

[0020] As a preferred embodiment of the current transformer oil level monitoring system based on ultrasonic echo detection described in this invention, the high-frequency excitation drive submodule includes a pulse waveform shaping unit, a voltage amplitude control unit, and a transmission timing synchronization unit.

[0021] The anti-interference sensing probe submodule includes a hydrophobic and anti-fouling coating unit, a dual-frequency composite transducer unit, and a vibration isolation support unit.

[0022] The dynamic gain adjustment submodule includes a signal strength detection unit, a gain curve preset unit, and a limiting protection circuit unit.

[0023] The composite filtering and noise reduction submodule includes an adaptive bandpass filtering unit, a wavelet basis denoising unit, and a residual noise identification and removal unit.

[0024] The envelope peak precise positioning submodule includes a Hilbert envelope generation unit, a multi-point interpolation fitting unit, and an echo validity verification unit.

[0025] The temperature-varying sound speed compensation solution submodule includes a real-time temperature acquisition unit, a sound speed lookup table correction unit, and a flight time compensation calculation unit.

[0026] The oil level mapping calibration submodule includes a structural parameter modeling unit, a multi-point measurement calibration unit, and a model online update unit.

[0027] The trend prediction and diagnosis submodule includes a differential rate of change calculation unit, an abnormal fluctuation identification unit, and an early warning generation unit.

[0028] The multi-level linkage alarm submodule includes a three-level alarm setting unit, a communication protocol adaptation unit, and a local audio-visual prompt unit.

[0029] As a preferred embodiment of the current transformer oil level monitoring system based on ultrasonic echo detection described in this invention, the pulse waveform shaping unit is used to generate a steep high-voltage pulse with a rise time of less than 10ns through a high-speed switching circuit and an impedance matching network, thereby improving the time resolution and directionality of the emitted ultrasonic pulse signal.

[0030] The voltage amplitude control unit is used to dynamically adjust the excitation voltage amplitude according to the ambient temperature feedback, so as to enhance the emission energy in low temperature environment to compensate for sound wave attenuation.

[0031] The transmission timing synchronization unit is used to establish a hardware-triggered synchronization mechanism with the main control unit to precisely control the phase relationship between the transmission time and the sampling start time;

[0032] The hydrophobic and antifouling coating unit is used to coat the ultrasonic probe radiation surface with nanoscale hydrophobic material, so that rainwater slides off and dust is reduced, thereby reducing the interference of external media on the sound wave propagation path.

[0033] The dual-frequency composite transducer unit is used to integrate the high-frequency main detection channel and the low-frequency auxiliary detection channel. By comparing the consistency of the dual-channel echoes, abnormal reflections are identified, and misjudgments caused by local contamination are eliminated.

[0034] The vibration isolation support unit is used to fix the body of the ultrasonic probe with an elastic vibration damping structure, effectively isolating the mechanical vibration generated by the current transformer during operation from being transmitted to the sensor and preventing the generation of false signals.

[0035] The signal strength detection unit is used to monitor the first wave amplitude in real time during the process of automatically adjusting the receiving channel of the echo signal strength, and to form the input basis for gain adjustment.

[0036] The gain curve preset unit is used to preset a multi-segment automatic gain adjustment control curve to achieve dynamic and smooth adjustment of gain over time.

[0037] The amplitude limiting protection circuit unit is used to receive the echo signal and automatically connect to the amplitude limiting circuit.

[0038] As a preferred embodiment of the current transformer oil level monitoring system based on ultrasonic echo detection described in this invention, the adaptive bandpass filter unit is used to dynamically adjust the filter frequency band according to the on-site electromagnetic environment to initially suppress power frequency interference and switching transient pulses; the output is connected to a wavelet basis denoising unit, which is used to perform multi-scale decomposition using a db4 wavelet basis based on signal-to-noise ratio, and to attenuate the high-frequency noise coefficient using a soft threshold function; the denoised echo signal is then transmitted to a residual noise identification and elimination unit, which is used to identify interference segments through sliding variance detection.

[0039] The Hilbert envelope generation unit is used to perform orthogonal transformation on the received signal to construct a smooth and continuous analytical envelope curve, and the multi-point interpolation fitting unit selects key sampling points at the rising edge of the envelope.

[0040] The real-time temperature acquisition unit is used to acquire the ambient temperature during installation, and the acquired data is input into the sound velocity lookup table correction unit.

[0041] The structural parameter modeling unit is used to establish an initial distance-oil level mapping function based on the internal geometry of the current transformer. Due to individual differences and assembly errors, the multi-point measurement and calibration unit collects corresponding distance data by injecting standard oil before the equipment is put into operation.

[0042] The differential rate of change calculation unit is used to perform a first-order differential operation on the oil level height value within a sliding window to extract the rate of change per unit time.

[0043] When the rate of change exceeds the normal range At that time, the abnormal fluctuation identification unit activates the dynamic threshold to determine whether there is oil leakage or internal discharge gas generation.

[0044] When the trend prediction and diagnosis submodule identifies an abnormal change in the oil level height, the three-level alarm setting unit automatically classifies the levels as early warning, severe, and emergency based on the degree of oil level drop.

[0045] The communication protocol adapter unit uploads alarm information to the monitoring system wirelessly to achieve remote real-time alarm. The local audible and visual prompt unit triggers audible and visual signals simultaneously to assist on-site personnel in quickly locating the problem and monitoring the oil level of the current transformer.

[0046] As a preferred embodiment of the current transformer oil level monitoring system based on ultrasonic echo detection described in this invention, the monitoring of the current transformer oil level includes: transmitting ultrasonic pulse signals through an ultrasonic transmitter-receiver module and receiving echo signals from the surface of a metal expander; performing composite filtering and noise reduction, precise positioning of the envelope peak, and temperature-varying sound velocity compensation calculation through a signal processing distance calculation module; calculating the distance between the transmitter and the top of the metal expander; inputting this distance data into an oil level status analysis and early warning module; converting it into an oil level height value through an oil level mapping calibration submodule; and then having the trend prediction and diagnosis submodule perform first-order differential operations to identify the changing trend.

[0047] When an anomaly occurs, the three-level alarm setting unit of the multi-level linkage alarm submodule activates the hierarchical alarm, the communication protocol adaptation unit realizes remote uploading, and the local sound and light prompt unit synchronizes the on-site alarm.

[0048] The formula for performing the first-order difference operation on the oil level height value is as follows:

[0049]

[0050] in, This indicates the change in oil level between the current moment and the previous moment. This indicates the oil level height measured at the current moment. This indicates the oil level height value at the previous sampling time;

[0051] The formula for calculating the distance between the transmitter and the top of the metal expander is as follows:

[0052]

[0053] in, This indicates the distance between the transmitter and the top of the metal expander. This indicates the speed at which ultrasound travels through the air, after correction by the real-time temperature acquisition unit. This represents the time difference between the ultrasonic wave emission and the echo arrival, as determined by the envelope peak precise positioning submodule.

[0054] Secondly, embodiments of the present invention provide a current transformer oil level monitoring method based on ultrasonic echo detection, comprising: directionally transmitting ultrasonic pulse signals to the surface of a metal expander, receiving echo signals reflected from the surface of the metal expander, and acquiring raw echo time series data; preprocessing the received echo signals, extracting time delay information of effective echoes, and calculating the distance between the transmitting end and the top of the metal expander in combination with the propagation speed of ultrasonic waves in air; converting the distance between the transmitting end and the top of the metal expander into a corresponding oil level height value, and triggering an alarm signal when the oil level height value is lower than a set threshold.

[0055] Thirdly, embodiments of the present invention provide a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement any step of the above-described current transformer oil level monitoring system based on ultrasonic echo detection.

[0056] Fourthly, embodiments of the present invention provide a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program is executed by a processor, it implements any step of the above-described current transformer oil level monitoring system based on ultrasonic echo detection.

[0057] The beneficial effects of this invention are as follows: By employing a non-contact measurement technology based on ultrasonic echo detection, this invention achieves high-precision, continuous, and dynamic monitoring of the displacement of the metal expander of a current transformer, thereby accurately reflecting internal oil level changes. Through the collaborative work of the ultrasonic transmitting and receiving module, the signal processing distance calculation module, and the oil level status analysis and early warning module, combined with temperature compensation, multi-level filtering, envelope precise positioning, and a distance-oil level mapping model, it effectively overcomes the problems of easy jamming, complex installation, and large susceptibility to temperature drift and environmental interference inherent in traditional float-type, pressure-type, and window observation methods. At the same time, through trend prediction diagnosis and a multi-level linkage alarm mechanism, early warnings can be issued at the initial stage of oil level anomalies, and remote uploading and local audio-visual prompts are supported. This enables intelligent inspection and fault precursor identification under unattended operation, significantly improving the safety of oil-immersed current transformer operation, the reliability of monitoring, and the level of intelligent operation and maintenance. Attached Figure Description

[0058] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0059] Figure 1 This is a flowchart of a current transformer oil level monitoring system based on ultrasonic echo detection, provided as an embodiment of the present invention.

[0060] Figure 2 This is a schematic diagram of a current transformer oil level monitoring system based on ultrasonic echo detection, provided as an embodiment of the present invention.

[0061] Figure 3 This is a schematic diagram of the structure of a medium in a current transformer oil level monitoring system based on ultrasonic echo detection, provided as an embodiment of the present invention.

[0062] Figure 4This is a schematic diagram of the structure of a computing device for a current transformer oil level monitoring system based on ultrasonic echo detection, provided as an embodiment of the present invention. Detailed Implementation

[0063] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0064] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0065] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0066] This invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0067] Furthermore, in the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0068] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0069] Example

[0070] Reference Figure 1 and Figure 4 This is the first embodiment of the present invention, which provides a current transformer oil level monitoring system based on ultrasonic echo detection, comprising:

[0071] S1: Ultrasonic transmitting and receiving module, used to directionally transmit ultrasonic pulse signals to the surface of the metal expander, receive the echo signals formed by the reflection from the surface of the metal expander, and obtain the original echo time series data.

[0072] S2: Signal processing distance calculation module, used to preprocess the received echo signal, extract the time delay information of the effective echo, and calculate the distance between the transmitter and the top of the metal expander by combining the propagation speed of ultrasound in the air.

[0073] S3: Oil level status analysis and early warning module, which is used to convert the distance between the transmitter and the top of the metal expander into the corresponding oil level height value, and trigger an alarm signal when the oil level height value is lower than the set threshold.

[0074] The ultrasonic transmitting and receiving module includes a high-frequency excitation drive submodule, an anti-interference sensor probe submodule, and a dynamic gain adjustment submodule.

[0075] The signal processing distance calculation module includes a composite filtering noise reduction submodule, an envelope peak accurate positioning submodule, and a temperature-varying sound speed compensation calculation submodule;

[0076] The oil level status analysis and early warning module includes an oil level mapping and calibration submodule, a trend prediction and diagnosis submodule, and a multi-level linkage alarm submodule.

[0077] Among them, the high-frequency excitation drive submodule is used to generate a high-voltage pulse signal with a nanosecond-level rising edge, which excites the piezoelectric crystal and emits a narrow beam of ultrasonic waves that are adapted to complex outdoor electromagnetic environments.

[0078] The anti-interference sensor probe submodule is used to sense echo signals in real time and convert them into electrical signals to suppress reflection interference caused by rainwater adhesion and dust deposition on the acoustic interface.

[0079] The dynamic gain adjustment submodule is used to automatically adjust the amplification factor of the receiving channel according to the strength of the echo signal;

[0080] The composite filtering and noise reduction submodule is used to combine infinite impulse response bandpass filtering to filter out power frequency interference, switching operation pulses and environmental stray noise, while retaining the characteristic waveform of the noiseless echo signal.

[0081] The envelope peak precise positioning submodule is used to perform Hilbert transform on the characteristic waveform of the noiseless echo signal, construct the analytical signal envelope, and fit the arrival time of the echo between discrete sampling points by interpolation.

[0082] The temperature-varying sound speed compensation submodule is used to fuse ambient temperature sensor data, dynamically correct the sound speed parameters in the air, and calculate the distance between the transmitter and the top of the metal expander by combining the flight time.

[0083] The oil level mapping calibration submodule is used to establish a nonlinear mapping model between the distance between the acquired transmitter and the top of the metal expander and the oil level, and to convert the actual oil level height value. The nonlinear mapping model is obtained by training based on the equipment structural parameters and multi-condition measured data.

[0084] The trend prediction and diagnosis submodule is used to perform first-order difference calculation on the oil level height value, identify the changing trend of the oil level height value, issue early deterioration warning before the alarm threshold is reached, and improve the fault prediction capability.

[0085] The multi-level linkage alarm submodule is used to set graded alarm strategies based on the degree of abnormality of the oil level value, and upload alarm information to the operation and maintenance platform through the wireless communication interface, supporting remote monitoring and emergency response linkage.

[0086] The high-frequency excitation drive submodule includes a pulse waveform shaping unit, a voltage amplitude control unit, and a transmission timing synchronization unit.

[0087] The anti-interference sensor probe submodule includes a hydrophobic and anti-fouling coating unit, a dual-frequency composite transducer unit, and a vibration isolation support unit;

[0088] The dynamic gain adjustment submodule includes a signal strength detection unit, a gain curve preset unit, and a limiting protection circuit unit;

[0089] The composite filtering and noise reduction submodule includes an adaptive bandpass filter unit, a wavelet basis denoising unit, and a residual noise identification and removal unit;

[0090] The envelope peak precise localization submodule includes a Hilbert envelope generation unit, a multi-point interpolation fitting unit, and an echo validity verification unit;

[0091] The temperature-varying sound speed compensation solution module includes a real-time temperature acquisition unit, a sound speed lookup table correction unit, and a flight time compensation calculation unit.

[0092] The oil level mapping calibration submodule includes a structural parameter modeling unit, a multi-point measurement calibration unit, and a model online update unit;

[0093] The trend prediction and diagnosis submodule includes a differential rate of change calculation unit, an abnormal fluctuation identification unit, and an early warning generation unit;

[0094] The multi-level linkage alarm submodule includes a three-level alarm setting unit, a communication protocol adaptation unit, and a local audio-visual prompt unit.

[0095] Among them, the pulse waveform shaping unit is used to generate steep high-voltage pulses with a rise time of less than 10ns through a high-speed switching circuit and an impedance matching network, thereby improving the time resolution and directionality of the emitted ultrasonic pulse signal.

[0096] The voltage amplitude control unit is used to dynamically adjust the excitation voltage amplitude according to the ambient temperature feedback, so as to enhance the emission energy in low temperature environment to compensate for sound wave attenuation.

[0097] The transmission timing synchronization unit is used to establish a hardware-triggered synchronization mechanism with the main control unit to precisely control the phase relationship between the transmission time and the sampling start time;

[0098] The hydrophobic and antifouling coating unit is used to coat the radiating surface of the ultrasonic probe with nanoscale hydrophobic materials, allowing rainwater to slide off and reducing the adhesion of dust, thereby reducing the interference of external media on the sound wave propagation path.

[0099] The dual-frequency composite transducer unit is used to integrate the high-frequency main detection channel and the low-frequency auxiliary detection channel. By comparing the consistency of the echoes of the two channels, abnormal reflections are identified, and misjudgments caused by local contamination are eliminated.

[0100] The vibration isolation support unit is used to fix the body of the ultrasonic probe with an elastic vibration damping structure, effectively isolating the mechanical vibration generated by the current transformer during operation from being transmitted to the sensor and preventing the generation of false signals.

[0101] The signal strength detection unit is used to monitor the first wave amplitude in real time during the automatic adjustment of the receiving channel of the echo signal strength, and to form the input basis for gain adjustment.

[0102] The gain curve preset unit is used to preset multi-segment automatic gain adjustment control curves to achieve dynamic and smooth adjustment of gain over time.

[0103] The amplitude limiting protection circuit unit is used to receive echo signals and automatically connect to the amplitude limiting circuit.

[0104] The adaptive bandpass filter unit is used to dynamically adjust the filter frequency band according to the electromagnetic environment on site, and initially suppress power frequency interference and switching transient pulses. The output is connected to the wavelet basis denoising unit, which is used to perform multi-scale decomposition using the db4 wavelet basis based on the signal-to-noise ratio, and to attenuate the high-frequency noise coefficient by combining a soft threshold function. The denoised echo signal is then fed into the residual noise identification and elimination unit, which is used to identify interference segments by sliding variance detection.

[0105] Furthermore, db4 is a specific type of wavelet basis, where the 4 indicates that the wavelet basis has 4 vanishing moments. The order of the vanishing moments determines the wavelet's ability to suppress polynomial trends in the signal. The higher the order, the stronger the ability to represent smooth signals.

[0106] The Hilbert envelope generation unit is used to perform orthogonal transformation on the received signal to construct a smooth and continuous analytical envelope curve. The multi-point interpolation fitting unit selects key sampling points at the rising edge of the envelope.

[0107] The real-time temperature acquisition unit is used to acquire the ambient temperature during the initial installation, and the acquired data is input into the sound velocity lookup table correction unit.

[0108] The structural parameter modeling unit is used to establish the initial distance-oil level mapping function based on the internal geometry of the current transformer. Due to individual differences and assembly errors, the multi-point measurement and calibration unit collects the corresponding distance data by injecting standard oil before the equipment is put into operation.

[0109] The differential rate of change calculation unit is used to perform first-order differential operation on the oil level height value within a sliding window to extract the rate of change per unit time.

[0110] When the rate of change exceeds the normal range At that time, the abnormal fluctuation identification unit activates the dynamic threshold to determine whether there is oil leakage or internal discharge gas generation.

[0111] When the trend prediction and diagnosis submodule identifies an abnormal change in the oil level height, the three-level alarm setting unit automatically classifies the levels as early warning, severe, and emergency based on the degree of oil level drop.

[0112] The communication protocol adapter unit uploads alarm information to the monitoring system wirelessly to achieve remote real-time alarm. The local audible and visual prompt unit triggers audible and visual signals simultaneously to assist on-site personnel in quickly locating the problem and monitoring the oil level of the current transformer.

[0113] Furthermore, the normal range refers to the range of slow fluctuations in oil level caused by normal temperature changes under stable operating conditions. The rate of change is usually no more than 0.5 mm / h. This range is determined based on a large amount of measured data: under typical operating conditions where the daily average temperature difference does not exceed 15℃, the rate of change of oil level with temperature expansion and contraction is concentrated between 0.1 and 0.3 mm / h. Based on this, the system sets a dynamic threshold of ±0.6 mm / h (i.e., historical average ± 3 times standard deviation). When the differential change rate calculation unit detects that the rate of change of oil level continues to exceed 0.6 mm / h, it is judged as an abnormal fluctuation, which may be caused by oil leakage or internal discharge gas generation, thereby triggering the abnormal fluctuation identification unit to further identify and warn.

[0114] The monitoring of the current transformer oil level includes transmitting ultrasonic pulse signals through an ultrasonic transmitter and receiver module and receiving echo signals from the surface of the metal expander. The signal processing distance calculation module performs composite filtering and noise reduction, precise positioning of the envelope peak, and temperature-varying sound velocity compensation calculation to calculate the distance between the transmitter and the top of the metal expander. This distance data is input into the oil level status analysis and early warning module, converted into an oil level height value through the oil level mapping calibration submodule, and then identified by the trend prediction and diagnosis submodule using first-order differential operation.

[0115] When an anomaly occurs, the three-level alarm setting unit of the multi-level linkage alarm submodule activates the hierarchical alarm, the communication protocol adaptation unit realizes remote uploading, and the local sound and light prompt unit synchronizes the on-site alarm.

[0116] The formula for performing a first-order difference operation on the oil level height value is:

[0117]

[0118] in, This indicates the change in oil level between the current moment and the previous moment. This indicates the oil level height measured at the current moment. This indicates the oil level height value at the previous sampling time;

[0119] The formula for calculating the distance between the transmitter and the top of the metal expander is:

[0120]

[0121] in, This indicates the distance between the transmitter and the top of the metal expander. This indicates the speed at which ultrasound travels through the air, after correction by the real-time temperature acquisition unit. This represents the time difference between the ultrasonic wave emission and the echo arrival, as determined by the envelope peak precise positioning submodule.

[0122] In a preferred embodiment, a current transformer oil level monitoring method based on ultrasonic echo detection includes: directionally transmitting ultrasonic pulse signals to the surface of a metal expander; receiving echo signals reflected from the surface of the metal expander to obtain raw echo time series data; preprocessing the received echo signals to extract the time delay information of the effective echoes and calculating the distance between the transmitting end and the top of the metal expander in combination with the propagation speed of ultrasonic waves in air; converting the distance between the transmitting end and the top of the metal expander into a corresponding oil level height value; and triggering an alarm signal when the oil level height value is lower than a set threshold.

[0123] The above-mentioned unit modules can be embedded in the processor of the computer device in hardware form or independent of it, or they can be stored in the memory of the computer device in software form, so that the processor can call and execute the corresponding operations of the above modules.

[0124] In one embodiment, a computer device is provided, which may be a terminal. The computer device includes a processor, memory, a communication interface, a display screen, and an input device connected via a system bus. The processor of the computer device provides computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage medium. The communication interface of the computer device is used for wired or wireless communication with external terminals. Wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. The display screen of the computer device may be an LCD screen or an e-ink display screen. The input device of the computer device may be a touch layer covering the display screen, or buttons, a trackball, or a touchpad located on the casing of the computer device, or an external keyboard, touchpad, or mouse, etc.

[0125] In summary, this invention achieves high-precision, continuous, and dynamic monitoring of the displacement of the metal expander of a current transformer by employing a non-contact measurement technology based on ultrasonic echo detection, thereby accurately reflecting internal oil level changes. Through the collaborative work of the ultrasonic transmitting and receiving module, the signal processing distance calculation module, and the oil level status analysis and early warning module, combined with temperature compensation, multi-level filtering, envelope precise positioning, and a distance-oil level mapping model, it effectively overcomes the problems of easy jamming, complex installation, and significant susceptibility to temperature drift and environmental interference inherent in traditional float-type, pressure-type, and window observation methods. Furthermore, through trend prediction diagnosis and a multi-level linkage alarm mechanism, early warnings can be issued at the initial stage of oil level anomalies, and remote uploading and local audible and visual prompts are supported. This enables intelligent inspection and fault precursor identification under unattended operation, significantly improving the safety of oil-immersed current transformer operation, the reliability of monitoring, and the level of intelligent operation and maintenance.

[0126] After introducing the method and system of exemplary embodiments of the present invention, the following references are made. Figure 3 A computer-readable storage medium according to exemplary embodiments of the present invention will be described, please refer to... Figure 3The computer-readable storage medium shown is an optical disc 30, on which a computer program (i.e., a program product) is stored. When the computer program is run by a processor, it implements the steps described in the above method implementation, such as: directionally emitting ultrasonic pulse signals to the surface of the metal expander, receiving echo signals reflected from the surface of the metal expander, and acquiring raw echo time series data; preprocessing the received echo signals, extracting the time delay information of the effective echoes, and calculating the distance between the transmitting end and the top of the metal expander by combining the propagation speed of ultrasonic waves in the air; converting the distance between the transmitting end and the top of the metal expander into a corresponding oil level height value, and triggering an alarm signal when the oil level height value is lower than a set threshold. The specific implementation methods of each step will not be repeated here.

[0127] It should be noted that examples of computer-readable storage media may also include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other optical and magnetic storage media, which will not be elaborated here.

[0128] After introducing the methods and media of exemplary embodiments of the present invention, the following references are made. Figure 4 A computational device for adaptive recovery of low-voltage power grid self-healing control according to an exemplary embodiment of the present invention.

[0129] Figure 4 A block diagram is shown of an exemplary computing device 40 suitable for implementing embodiments of the present invention. The computing device 40 may be a computer system or a server. Figure 4 The computing device 40 shown is merely an example and should not impose any limitation on the functionality and scope of use of the embodiments of the present invention.

[0130] like Figure 4 As shown, the components of computing device 40 may include, but are not limited to: one or more processors or processing units 401, system memory 402, and bus 403 connecting different system components (including system memory 402 and processing unit 401).

[0131] The computing device 40 typically includes a variety of computer system readable media. These media can be any available media that can be accessed by the computing device 40, including volatile and non-volatile media, and removable and non-removable media.

[0132] System memory 402 may include computer system readable media in the form of volatile memory, such as random access memory (RAM) 4021 and / or cache memory 4022. Computing device 40 may further include other removable / non-removable, volatile / non-volatile computer system storage media. By way of example only, ROM 4023 may be used to read and write non-removable, non-volatile magnetic media (…). Figure 4 (Not shown in the image, usually referred to as "hard drive"). Although not shown in... Figure 4 The diagram illustrates that disk drives for reading and writing to removable non-volatile disks (e.g., "floppy disks") and optical disc drives for reading and writing to removable non-volatile optical discs (e.g., CD-ROMs, DVD-ROMs, or other optical media) can be provided. In these cases, each drive can be connected to bus 403 via one or more data media interfaces. System memory 402 may include at least one program product having a set (e.g., at least one) of program modules configured to perform the functions of the embodiments of the present invention.

[0133] A program / utility 4025 having a set (at least one) of program modules 4024 may be stored, for example, in system memory 402, and such program modules 4024 include, but are not limited to, an operating system, one or more application programs, other program modules, and program data, each or some combination of these examples may include an implementation of a network environment. Program modules 4024 typically perform the functions and / or methods described in the embodiments of the present invention.

[0134] The computing device 40 can also communicate with one or more external devices 404 (such as a keyboard, pointing device, display, etc.). This communication can be performed via the input / output (I / O) interface 405. Furthermore, the computing device 40 can also communicate with one or more networks (e.g., local area networks (LANs), wide area networks (WANs), and / or public networks, such as the Internet) via a network adapter 406. Figure 4 As shown, network adapter 406 communicates with other modules of computing device 40 (such as processing unit 401) via bus 403. It should be understood that, although... Figure 4 As not shown, it can be used in conjunction with computing device 40 with other hardware and / or software modules.

[0135] The processing unit 401 executes various functional applications and data processing by running programs stored in the system memory 402. For example, it directionally emits ultrasonic pulse signals to the surface of the metal expander, receives echo signals reflected from the surface of the metal expander, and obtains raw echo time series data; it preprocesses the received echo signals, extracts the time delay information of the effective echoes, and calculates the distance between the transmitting end and the top of the metal expander by combining the propagation speed of ultrasonic waves in the air; it converts the distance between the transmitting end and the top of the metal expander into the corresponding oil level height value, and triggers an alarm signal when the oil level height value is lower than a set threshold.

[0136] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0137] In the several embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the coupling or direct coupling or communication connection shown or discussed may be through some communication interface; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0138] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0139] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0140] If the functionality is implemented as a software functional unit and sold or used as an independent product, it can be stored in a processor-executable, non-volatile, computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0141] Finally, it should be noted that the above embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0142] Furthermore, although the operations of the method of the present invention are described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0143] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A current transformer oil level monitoring system based on ultrasonic echo detection, characterized in that: include, The ultrasonic transmitting and receiving module is used to directionally transmit ultrasonic pulse signals to the surface of the metal expander, receive the echo signals formed by the reflection of the metal expander surface, and obtain the original echo time series data. The signal processing distance calculation module is used to preprocess the received echo signal, extract the time delay information of the effective echo, and calculate the distance between the transmitter and the top of the metal expander by combining the propagation speed of ultrasound in the air. The oil level status analysis and early warning module is used to convert the distance between the transmitter and the top of the metal expander into a corresponding oil level height value, and trigger an alarm signal when the oil level height value is lower than a set threshold.

2. The current transformer oil level monitoring system based on ultrasonic echo detection as described in claim 1, characterized in that: The ultrasonic transmitting and receiving module includes a high-frequency excitation driving submodule, an anti-interference sensing probe submodule, and a dynamic gain adjustment submodule. The signal processing distance calculation module includes a composite filtering noise reduction submodule, an envelope peak accurate positioning submodule, and a temperature-varying sound speed compensation calculation submodule. The oil level status analysis and early warning module includes an oil level mapping calibration submodule, a trend prediction and diagnosis submodule, and a multi-level linkage alarm submodule.

3. The current transformer oil level monitoring system based on ultrasonic echo detection as described in claim 2, characterized in that: The high-frequency excitation drive submodule is used to generate a high-voltage pulse signal with a nanosecond-level rising edge, which excites the piezoelectric crystal and emits a narrow beam of ultrasonic waves that are adapted to complex outdoor electromagnetic environments. The anti-interference sensor probe submodule is used to sense echo signals in real time and convert them into electrical signals to suppress reflection interference caused by rainwater adhesion and dust deposition on the acoustic interface. The dynamic gain adjustment submodule is used to automatically adjust the amplification factor of the receiving channel according to the intensity of the echo signal; The composite filtering and noise reduction submodule is used to combine infinite impulse response bandpass filtering to filter out power frequency interference, switching operation pulses and environmental stray noise, while retaining the characteristic waveform of the noiseless echo signal. The envelope peak precise positioning submodule is used to perform Hilbert transform on the characteristic waveform of the noiseless echo signal, construct the analytical signal envelope, and fit the arrival time of the echo between discrete sampling points by interpolation. The temperature-varying sound speed compensation calculation submodule is used to fuse ambient temperature sensor data, dynamically correct the sound speed parameters in the air, and calculate the distance between the transmitter and the top of the metal expander by combining the flight time. The oil level mapping calibration submodule is used to establish a nonlinear mapping model of distance-oil level based on the distance between the acquired transmitter and the top of the metal expander, and to convert the actual oil level height value. The nonlinear mapping model is obtained by training based on equipment structural parameters and multi-condition measured data. The trend prediction and diagnosis submodule is used to perform first-order difference operation on the oil level height value, identify the changing trend of the oil level height value, issue an early deterioration warning before the alarm threshold is reached, and improve the fault prediction capability. The multi-level linkage alarm submodule is used to set graded alarm strategies according to the degree of abnormality of oil level values, and upload alarm information to the operation and maintenance platform through wireless communication interface, supporting remote monitoring and emergency response linkage.

4. The current transformer oil level monitoring system based on ultrasonic echo detection as described in claim 3, characterized in that: The high-frequency excitation drive submodule includes a pulse waveform shaping unit, a voltage amplitude regulation unit, and a transmission timing synchronization unit. The anti-interference sensing probe submodule includes a hydrophobic and anti-fouling coating unit, a dual-frequency composite transducer unit, and a vibration isolation support unit. The dynamic gain adjustment submodule includes a signal strength detection unit, a gain curve preset unit, and a limiting protection circuit unit. The composite filtering and noise reduction submodule includes an adaptive bandpass filtering unit, a wavelet basis denoising unit, and a residual noise identification and removal unit. The envelope peak precise positioning submodule includes a Hilbert envelope generation unit, a multi-point interpolation fitting unit, and an echo validity verification unit. The temperature-varying sound speed compensation solution submodule includes a real-time temperature acquisition unit, a sound speed lookup table correction unit, and a flight time compensation calculation unit. The oil level mapping calibration submodule includes a structural parameter modeling unit, a multi-point measurement calibration unit, and a model online update unit. The trend prediction and diagnosis submodule includes a differential rate of change calculation unit, an abnormal fluctuation identification unit, and an early warning generation unit. The multi-level linkage alarm submodule includes a three-level alarm setting unit, a communication protocol adaptation unit, and a local audio-visual prompt unit.

5. The current transformer oil level monitoring system based on ultrasonic echo detection as described in claim 4, characterized in that: The pulse waveform shaping unit is used to generate steep high-voltage pulses with a rise time of less than 10ns through a high-speed switching circuit and an impedance matching network, thereby improving the time resolution and directionality of the emitted ultrasonic pulse signal. The voltage amplitude control unit is used to dynamically adjust the excitation voltage amplitude according to the ambient temperature feedback, so as to enhance the emission energy in low temperature environment to compensate for sound wave attenuation. The transmission timing synchronization unit is used to establish a hardware-triggered synchronization mechanism with the main control unit to precisely control the phase relationship between the transmission time and the sampling start time; The hydrophobic and antifouling coating unit is used to coat the ultrasonic probe radiation surface with nanoscale hydrophobic material, so that rainwater slides off and dust is reduced, thereby reducing the interference of external media on the sound wave propagation path. The dual-frequency composite transducer unit is used to integrate the high-frequency main detection channel and the low-frequency auxiliary detection channel. By comparing the consistency of the dual-channel echoes, abnormal reflections are identified, and misjudgments caused by local contamination are eliminated. The vibration isolation support unit is used to fix the body of the ultrasonic probe with an elastic vibration damping structure, effectively isolating the mechanical vibration generated by the current transformer during operation from being transmitted to the sensor and preventing the generation of false signals. The signal strength detection unit is used to monitor the first wave amplitude in real time during the process of automatically adjusting the receiving channel of the echo signal strength, and to form the input basis for gain adjustment. The gain curve preset unit is used to preset a multi-segment automatic gain adjustment control curve to achieve dynamic and smooth adjustment of gain over time. The amplitude limiting protection circuit unit is used to receive the echo signal and automatically connect to the amplitude limiting circuit.

6. The current transformer oil level monitoring system based on ultrasonic echo detection as described in claim 5, characterized in that: The adaptive bandpass filter unit is used to dynamically adjust the filter frequency band according to the on-site electromagnetic environment, and initially suppress power frequency interference and switching transient pulses; the output is connected to the wavelet basis denoising unit, which is used to perform multi-scale decomposition using the db4 wavelet basis based on the signal-to-noise ratio, and to attenuate the high-frequency noise coefficient by combining a soft threshold function. The denoised echo signal is then fed into the residual noise identification and elimination unit, which is used to identify interference segments by sliding variance detection. The Hilbert envelope generation unit is used to perform orthogonal transformation on the received signal to construct a smooth and continuous analytical envelope curve, and the multi-point interpolation fitting unit selects key sampling points at the rising edge of the envelope. The real-time temperature acquisition unit is used to acquire the ambient temperature during installation, and the acquired data is input into the sound velocity lookup table correction unit. The structural parameter modeling unit is used to establish an initial distance-oil level mapping function based on the internal geometry of the current transformer. Due to individual differences and assembly errors, the multi-point measurement and calibration unit collects corresponding distance data by injecting standard oil before the equipment is put into operation. The differential rate of change calculation unit is used to perform a first-order differential operation on the oil level height value within a sliding window to extract the rate of change per unit time. When the rate of change exceeds the normal range At that time, the abnormal fluctuation identification unit activates the dynamic threshold to determine whether there is oil leakage or internal discharge gas generation. When the trend prediction and diagnosis submodule identifies an abnormal change in the oil level height, the three-level alarm setting unit automatically classifies the levels as early warning, severe, and emergency based on the degree of oil level drop. The communication protocol adapter unit uploads alarm information to the monitoring system wirelessly to achieve remote real-time alarm. The local audible and visual prompt unit triggers audible and visual signals simultaneously to assist on-site personnel in quickly locating the problem and monitoring the oil level of the current transformer.

7. The current transformer oil level monitoring system based on ultrasonic echo detection as described in claim 6, characterized in that: The monitoring of the current transformer oil level includes transmitting ultrasonic pulse signals through an ultrasonic transmitter and receiver module and receiving echo signals from the surface of the metal expander. The signal processing distance calculation module performs composite filtering and noise reduction, precise positioning of the envelope peak, and temperature-varying sound velocity compensation calculation to calculate the distance between the transmitter and the top of the metal expander. This distance data is input into the oil level status analysis and early warning module, converted into an oil level height value through the oil level mapping calibration submodule, and then identified by the trend prediction and diagnosis submodule using first-order differential operation to identify the changing trend. When an anomaly occurs, the three-level alarm setting unit of the multi-level linkage alarm submodule activates the hierarchical alarm, the communication protocol adaptation unit realizes remote uploading, and the local sound and light prompt unit synchronizes the on-site alarm. The formula for performing the first-order difference operation on the oil level height value is as follows: ; in, This indicates the change in oil level between the current moment and the previous moment. This indicates the oil level height value measured at the current moment. This indicates the oil level height value at the previous sampling time; The formula for calculating the distance between the transmitter and the top of the metal expander is as follows: ; in, This indicates the distance between the transmitter and the top of the metal expander. This indicates the speed at which ultrasound travels through the air, after correction by the real-time temperature acquisition unit. This represents the time difference between the ultrasonic wave emission and the echo arrival, as determined by the envelope peak precise positioning submodule.

8. A method for monitoring the oil level of a current transformer based on ultrasonic echo detection, based on the current transformer oil level monitoring system based on ultrasonic echo detection as described in any one of claims 1 to 7, characterized in that: include, An ultrasonic pulse signal is directionally emitted toward the surface of a metal expander, and the echo signal reflected from the surface of the metal expander is received to obtain the original echo time series data. The received echo signal is preprocessed to extract the time delay information of the effective echo, and the distance between the transmitter and the top of the metal expander is calculated by combining the propagation speed of ultrasound in the air. The distance between the transmitter and the top of the metal expander is converted into a corresponding oil level value, and an alarm signal is triggered when the oil level value is lower than a set threshold.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, it implements the steps of the current transformer oil level monitoring system based on ultrasonic echo detection as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the processor, it implements the steps of the current transformer oil level monitoring system based on ultrasonic echo detection as described in any one of claims 1 to 7.

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