CN104215203B - A kind of deformation of transformer winding online test method and system based on ultrasonic wave - Google Patents

Abstract

The invention discloses an ultrasonic-based online transformer winding deformation detection method and system, comprising the following steps: S1: select a point to be measured, and an ultrasonic transmitting probe emits an ultrasonic signal; S2: propagate the ultrasonic signal into the interior of the transformer; S3 : the ultrasonic receiving probe receives the echo signal and converts it into an echo electric signal; S4: optimizes the echo electric signal; S5: calculates the propagation time of the ultrasonic signal inside the transformer according to the optimized echo electric signal; S6: Perform receiving compensation for the path of ultrasonic waves propagating inside the transformer, and then obtain the distance between the measured point and the transformer shell; S7: Move the ultrasonic probe to the next measured point on the transformer shell, repeat S1-S6; S8: Test all the measured points After the point, the data is processed, and the transformer winding deformation diagnosis report is given. The invention realizes the on-line monitoring of transformer winding deformation, and is easy to be applied in practice.

Description

An ultrasonic-based online detection method and system for transformer winding deformation

technical field

The invention belongs to the technical field of electric power information detection, and relates to an ultrasonic-based online detection method for transformer winding deformation.

Background technique

Power transformers are important and expensive, and may be damaged immediately due to accidental collisions or powerful electromotive forces caused by system short-circuit faults during transportation, but generally only a certain degree of winding deformation occurs. If the deformation is not found and repaired in time, It may cause power system failure. After the transformer winding is deformed, some damage accidents occur immediately, while others can still run for a long time. Transformers whose windings have been deformed will continue to operate for quite a long time. If they cannot be repaired in a timely manner, the cumulative effect will develop further. Correct and timely deformation detection can ensure that the faulty components of the transformer are replaced in time, and the non-faulty components are used to the maximum extent, thereby prolonging the actual service life of the transformer.

In recent years, more and more researches have been done on the shape detection of transformer windings, and a large number of detection methods have been proposed. As the number of power transformers put into the power grid in my country is increasing, the traditional off-line detection method has been difficult to meet the requirements. The traditional short-circuit impedance method, low-voltage pulse method, and frequency response analysis method have achieved some results in the detection of winding deformation, but these traditional methods have problems such as inability to detect online, poor sensitivity, low anti-interference ability, and difficulty in data acquisition. shortcoming.

Contents of the invention

The object of the present invention is to provide an ultrasonic-based online detection method for transformer winding deformation, so as to solve the problem that the existing transformer winding deformation cannot be detected online.

The second object of the present invention is to provide an ultrasonic-based online detection method for transformer winding deformation, so as to solve the problem that the existing transformer winding deformation cannot be detected in time, so that it cannot be repaired in time.

The third purpose of the present invention is to provide an ultrasonic-based online transformer winding deformation detection method to solve the problems of poor sensitivity, low anti-interference ability, and difficult data acquisition in existing transformer winding deformation detection methods.

In order to achieve the above object, the present invention provides an ultrasonic-based online detection method for transformer winding deformation, comprising the following steps:

S1: Select a point to be measured on the transformer shell, emit ultrasonic signals, and start timing;

S2: receiving the echo signal of the ultrasonic signal and converting it into an echo electrical signal;

S3: Optimizing the echo electrical signal and stopping timing;

S4: Perform receiving compensation on the ultrasonic propagation path, and calculate the distance between the measured point and the transformer shell;

S5: Find the next measured point, repeat S1-S4;

S6: After testing all the measured points, process the distance data and give a diagnosis report of transformer winding deformation.

Preferably, the step S1 further includes: generating a high-frequency square-wave pulse through a high-frequency oscillator circuit, and the high-frequency square-wave pulse excites the ultrasonic transmitting probe through an excitation circuit to emit ultrasonic signals.

Preferably, the step S1 further includes: using a self-excited oscillation circuit to generate a high-frequency oscillation signal to excite the piezoelectric chip to generate the high-frequency square wave pulse, so that the ultrasonic transmitting probe emits ultrasonic waves of a corresponding frequency.

Preferably, the step S1 further includes: referring to the modulation method of the ultrasonic communication, obtaining a special oscillation signal by changing the duty ratio of the oscillation waveform, so that the echo signal received by the ultrasonic receiving probe is different from the interference The waveform of the signal is significantly different.

Preferably, the step S1 further includes: using a low-frequency soft probe and an ultrasonic coupling agent to remove the air thin layer, so that the ultrasonic signal can smoothly propagate into the transformer.

Preferably, the step S2 further includes: receiving the echo signal by the ultrasonic receiving probe and converting it into an echo electrical signal.

Preferably, the step S3 specifically includes: firstly, performing amplification and filtering processing on the echo electric signal, and outputting an amplification and filtering signal; secondly, performing optimization processing of time gain compensation or comparative shaping on the amplification and filtering signal, and Output the signal for optimization processing; finally, stop timing after optimization processing.

Preferably, the step S3 further includes: when performing time gain compensation, calculating the number of decibels by which the sound intensity gain is reduced due to absorption; The relationship is to perform gain compensation on the attenuated echo signal, restore the waveform of the received echo signal, and perform secondary amplification on the waveform restored signal.

Preferably, the step S4 further includes: after stopping the timing, obtaining the propagation time of the ultrasonic wave; measuring the temperature, calculating the current sound velocity according to the temperature value, and performing temperature compensation according to the current sound velocity and propagation time.

Preferably, the step S4 specifically includes: calculating the distance between the position where the echo signal is received and the center position of the transformer shell according to the distance from the position where the ultrasonic signal is transmitted to the center position of the transformer shell, adjusting the position where the echo signal is received, and according to the timing Time to calculate the distance between the measured point and the transformer shell.

The present invention also provides an ultrasonic-based transformer winding deformation online detection system, including a single-chip microcomputer, a transmitting probe, a receiving probe, a signal optimization module, a temperature compensation circuit and a timer;

The ultrasonic transmitting probe sends an ultrasonic signal, and the single-chip microcomputer controls the timer to start timing; the ultrasonic receiving probe receives the echo signal of the ultrasonic signal, and converts the echo signal into an echo electric signal output; The signal optimization module optimizes the echo electric signal and outputs an optimized echo signal to the single-chip microcomputer, and the single-chip microcomputer controls the timer to stop timing, and the timer outputs a timing signal; the temperature compensation circuit measures the temperature , and input the temperature signal into the single chip microcomputer;

The single-chip microcomputer receives the temperature signal, the timing signal and the optimized echo signal, performs temperature compensation on the propagation path of the optimized echo signal according to the temperature signal and the timing signal, and calculates the distance between the measured point and the transformer shell.

Preferably, it also includes a power drive circuit, the power drive circuit includes a high frequency oscillating circuit, an excitation circuit and a single-chip microcomputer drive circuit; Under the action of high-frequency square wave pulses, the transmitting probe is excited to emit ultrasonic signals; the single-chip microcomputer drive circuit is used to drive the single-chip microcomputer.

Preferably, the signal optimization module includes a time gain compensation circuit, a secondary amplification circuit and a comparison shaping circuit;

The time gain compensation circuit is provided with a first threshold, and the comparison shaping circuit is provided with a second threshold, the first threshold is used to select echo signals whose transmission distance is greater than a certain distance, and the second threshold is used to select transmission Echo signals whose distance is less than the certain distance;

When the echo signal does not meet the second threshold, the amplified and filtered signal is input to the time gain compensation circuit for processing and then output a time gain compensation signal, and the time gain compensation signal is input to a secondary amplifier circuit for processing and output for secondary amplification signal to the microcontroller;

When the echo signal does not meet the first threshold, the amplified and filtered signal is input to the comparison and shaping circuit for processing, and then the comparison and shaping signal is output to the single-chip microcomputer.

The invention discloses an ultrasonic-based on-line detection method and system for transformer winding deformation, which has a series of advantages such as the detection process is free from electromagnetic interference, intuitively reflects the deformation position and degree of the winding, and can be detected in real time under the running state of the transformer.

Compared with the prior art, the beneficial effects of the present invention are as follows:

First, the present invention realizes non-stop on-line monitoring of transformer windings. By adopting ultrasonic distance measurement, the ultrasonic signal will not interfere with the electrical signal, and the electrical signal will not affect the ultrasonic distance measurement, so that the transformer does not need to be turned off during measurement, thereby not affecting its normal voltage transformation work, and the anti-interference ability is high.

Second, the present invention can intuitively judge the specific position of transformer winding deformation. By scanning and measuring the distance between each point on the surface of the transformer shell and the transformer winding, a set of data reports on the distance from the transformer shell to the transformer winding are formed, which can be directly compared with the corresponding data without the transformer, and the deformation of the current transformer winding can be analyzed Situation, data acquisition is easy, and the data report is intuitive and easy to understand.

Third, the present invention is easy to be applied in actual engineering. The transformer winding deformation online detection system based on ultrasonic is adopted. The ultrasonic probe sends and receives signals, and the distance measurement can be completed by the single-chip microcomputer and other corresponding signal processing circuits. It has high sensitivity, is easy to operate and use, and is suitable for large-scale promotion to practice. In the work of transformer winding deformation detection.

Description of drawings

Fig. 1 is a kind of flow chart of the online detection method of transformer winding deformation based on ultrasonic in the present invention;

Fig. 2 is a composition block diagram of the transformer winding deformation online detection system of the present invention;

Figure 3 Schematic diagram of the basic measurement of transformer windings.

detailed description

The present invention will be further described below in conjunction with accompanying drawing and specific embodiment, but implementation and protection scope of the present invention are not limited to this:

This embodiment provides an ultrasonic-based transformer winding deformation online detection system, as shown in Figure 2, including a single-chip microcomputer, a transmitting probe, a receiving probe, a signal optimization module, a temperature compensation circuit and a timer;

When working, the ultrasonic transmitting probe is first driven by the power drive circuit to send ultrasonic signals. The power drive circuit includes a high-frequency oscillation circuit, an excitation circuit and a single-chip microcomputer drive circuit; the high-frequency oscillation circuit generates a high-frequency square wave pulse, and the excitation circuit generates a high-frequency square wave Under the action of the pulse, the transmitting probe is excited to emit ultrasonic signals; at the same time, the single-chip microcomputer driving circuit drives the single-chip microcomputer to start working, and the single-chip microcomputer controls the timer to start timing.

Secondly, the ultrasonic receiving probe receives the echo signal of the ultrasonic signal sent, and converts the echo signal into an echo electrical signal output; the signal optimization module optimizes the echo electrical signal: the signal optimization module includes a time gain compensation circuit, Secondary amplifier circuit and comparison shaping circuit;

The time gain compensation circuit is provided with a first threshold, and the comparison shaping circuit is provided with a second threshold. In this embodiment, the first threshold of the time gain compensation circuit is used to select echo signals whose transmission distance is greater than 50 cm, that is, signals less than 50 cm will be At this time, the amplified and filtered signal smaller than 50cm enters the microcontroller through the comparison shaping circuit; the second threshold of the comparison shaping circuit is used to select the echo signal with a transmission distance of less than 50cm, that is, the signal larger than 50cm will be rejected due to more attenuation. The automatic rejection cannot be received. At this time, the signal larger than 50cm will enter the single-chip microcomputer through the time gain compensation circuit and the secondary amplifier circuit.

Among them, the amplified and filtered signal is input to the time gain compensation circuit to process and output the time gain compensation signal, and the time gain compensation signal is input to the secondary amplifying circuit for processing, and then the secondary amplified signal is output as the optimized echo signal to the microcontroller; the amplified and filtered signal is input to the comparison shaping circuit After processing, the comparative shaping signal is output as the optimized echo signal to the single-chip microcomputer.

After the single-chip microcomputer receives the optimized echo signal, it controls the timer to stop timing, and the timer outputs a timing signal to the single-chip microcomputer; at the same time, the temperature compensation circuit measures the temperature and inputs the temperature signal into the single-chip microcomputer.

The single-chip microcomputer receives the temperature signal, the timing signal and the optimized echo signal, performs temperature compensation on the propagation path of the optimized echo signal according to the temperature signal and the timing signal, and calculates the distance between the measured point and the transformer shell.

This embodiment also provides an ultrasonic-based online detection method for transformer winding deformation, referring to Figure 1, the method includes the following steps:

S1: Select a point to be measured, and the ultrasonic emitting probe emits ultrasonic signals.

The power drive circuit generates a high frequency square wave pulse through a high frequency oscillating circuit, and the high frequency square wave pulse excites the ultrasonic transmitting probe through the excitation circuit to emit ultrasonic signals. Wherein, the high-frequency oscillation circuit includes a self-excited oscillation circuit and a piezoelectric wafer, and the self-excited oscillation circuit generates a high-frequency oscillation signal to excite the piezoelectric wafer to generate the above-mentioned high-frequency square wave pulse, and the high-frequency square wave pulse Load it on the ultrasonic emitting probe to make it emit ultrasonic waves of corresponding frequency. At the same time, the power drive circuit drives the single chip microcomputer to start the timer to start counting.

Referring to the modulation method of ultrasonic communication, a special oscillating signal is obtained by changing the duty cycle of the oscillating waveform, so that the waveform of the echo signal received by the ultrasonic receiving probe is obviously different from that of the interference signal, which is convenient for reception.

In this embodiment, the modulation method of ultrasonic communication is a basic binary digital signal modulation method, such as 2ASK, 2FSK or 2PSK, and the method of changing the duty ratio of the signal waveform accordingly refers to the change of the duty ratio of the general 2ASK, 2FSK or 2PSK signal waveform mode, and send ultrasonic pulse signal after modulation.

S2: propagating the ultrasonic signal into the inside of the transformer.

Use low-frequency soft probes and ultrasonic coupling agents to remove thin air layers, so that ultrasonic signals can smoothly propagate into the interior of the transformer.

The protective film of the low-frequency soft probe adopts a soft rubber film, which can be in closer contact with the surface of the measured object, so that the ultrasonic probe will not be affected by pressure when it contacts the transformer shell, so that its impedance, static capacitance and other parameters will not be affected. In addition, ultrasonic couplants are used to remove air thin layers. During measurement, the ultrasonic coupling agent is filled in the contact layer between the probe and the workpiece to be tested, and the air layer in the contact surface between the ultrasonic probe and the workpiece to be tested is squeezed out, so that the ultrasonic probe can transmit and receive smoothly through the tested workpiece. Ultrasonic of the workpiece.

In this embodiment, the ultrasonic coupling agent is transformer oil.

S3: The ultrasonic receiving probe receives the echo signal and converts it into an echo electrical signal.

The ultrasonic receiving probe receives the echo pulse signal reflected by the transformer winding, and the ultrasonic receiving probe converts the ultrasonic echo signal into an echo electrical signal, and the echo electrical signal is a signal in the form of a pulse.

S4: Optimizing the echo electrical signal.

First, the echo electric signal is optimized by using a filter amplifier circuit: a first-stage amplifier filter circuit is used for filter amplification, and the amplified filter signal is output. Since the echo signal will decrease and be mixed with clutter as the distance increases during the propagation of the ultrasonic wave, amplification and filtering are required. In this embodiment, the primary amplification and filtering circuit uses NE5532 to amplify the signal. NE5532 is a dual op-amp, high-performance, low-noise operational amplifier. Compared with most standard op-amps, it shows better noise performance, and has relatively high small-signal bandwidth and power supply bandwidth.

Secondly, the ultrasonic echo signal with a transmission distance greater than 50cm enters the time gain compensation circuit for gain compensation:

A time gain compensation circuit is used to amplify the seriously attenuated echo signal reflected by the transformer winding.

Since the ultrasonic wave will attenuate when it propagates in the air, that is, the sound intensity will decrease with the increase of the propagation distance, so the attenuated signal needs to be compensated. Assuming that the initial sound intensity is I ₀ , after x distance, the sound intensity becomes I due to absorption attenuation, then the absorption of ultrasonic waves can be expressed by formula (1):

I＝I ₀ e ^-αx (1)

where α is the air attenuation coefficient.

It can be seen from the above formula that when the ultrasonic wave propagates in the air, as the propagation distance increases, its total energy gradually weakens, and its law is exponentially attenuated. Therefore, the echo pulse amplitudes at different distances have different absorption degrees due to their different sound paths, so that the echo pulse amplitudes vary greatly. Since a comparator circuit is usually used in the echo pulse signal processing, the The echo pulse (shaped as a bell) is compared with a fixed reference voltage, and the echo pulse is shaped into a square wave; due to the large difference in the echo pulse amplitude at different distances, the arrival time of the echo is uncertain, resulting in measurement error occurs.

If the ultrasonic wave emitted by the probe reaches a reflective surface through the distance x and returns through the original path, the incident sound intensity and reflected sound intensity are I _i and I _r respectively, which can be obtained from formula (1):

I _r ＝I _i e ^-αax (2)

It can be seen that the number of decibels (dB) by which the sound intensity gain L is reduced due to absorption is:

L=4.3×2αx=4.3αct (4)

In the formula, c is the propagation speed of the sound wave in the air, and t is the time elapsed in the propagation process. Due to the air attenuation coefficient α, the propagation speed c can be determined, so it can be proved that the decibels of the amplitude reduction of the ultrasonic wave at the propagation distance x is proportional to the time t for the ultrasonic wave to pass through this distance. Thus, gain compensation must be performed for echoes on attenuation. According to formula (4), the received gain G can be directly proportional to the echo time t, or the gain G and the echo time t can be exponentially increased to compensate for the attenuation. Finally, the signal received by the receiver remains unchanged.

The specific implementation process of this time gain compensation method is as follows:

1) Convert the amplification gain corresponding to a certain distance obtained through experiments into the tap position of the digital potentiometer;

2) Solidify these position parameters into Flash;

3) During the measurement process, the single-chip microcomputer obtains the corresponding gain by looking up the table, and then sets the corresponding gain through serial.

After determining the receiving gain, load it on the received signal to restore the signal waveform, output the time gain compensation signal to the secondary amplifier circuit, and the secondary amplifier circuit performs secondary amplification on the time gain compensation signal and outputs the secondary amplified signal signal to the microcontroller.

The ultrasonic echo signal whose transmission distance is less than 50cm enters the comparison and shaping circuit for comparison and shaping, and outputs the comparison shaping signal to the single-chip microcomputer.

S5: Calculate the propagation time of the ultrasonic signal inside the transformer according to the optimized processed echo electric signal.

The second-level amplified signal or the comparison shaping signal is input to the single-chip microcomputer to drive the single-chip microcomputer to control the timer to stop timing, and the timing signal is obtained and transmitted to the single-chip microcomputer, thereby obtaining the ultrasonic propagation time.

The temperature of the ultrasonic coupling agent is measured, the current sound velocity is calculated according to the temperature value, and the propagation time is temperature compensated according to the current sound velocity.

Temperature compensation is the process of calculating the sound velocity at the current temperature, specifically according to the following formula:

V _t =V ₀ +α(TT ₀ ) (5)

Among them, V _t is the speed of sound when the temperature is T, T ₀ is the standard temperature, V ₀ is the speed of sound when the temperature is T ₀ , and α is the temperature coefficient. Correspondingly, in the transformer oil in this embodiment, t ₀ =20°C, V ₀ =1923m/s, α=-1.8m/s·°C. Then bring the corresponding parameters into the formula (5) to convert the sound velocity, and then perform temperature compensation for the ultrasonic propagation time.

S6: Perform receiving compensation for the path of ultrasonic waves propagating inside the transformer, and then obtain the distance between the measured point and the transformer shell;

Calculate the distance between the receiving probe and the center of the transformer shell according to the distance between the receiving probe and the center of the transformer shell, and place the receiving probe to receive the echo signal.

Figure 3 reflects the basic measurement of the high-voltage side winding. It can be seen from the figure that there is a certain angle between the incident ultrasonic wave and the normal line of the transformer winding, and the return route of the echo is not along the original route. It is necessary to use another separately installed receiving probe to receive the echo reflected by the transformer winding.

The calculation shows that the change of the ultrasonic propagation path caused by the refraction of the ultrasonic signal in the transformer shell is negligible. Then suppose the distance from the receiving probe to the center is z, let O ₃ A ₂ =x, that is, the distance from the transmitting probe to the center is x, then we have

A ₁ P＝d ₁ +R-Rcosθ ₁ (7)

The location of the receiving probe is

A ₂ B ₂ ＝(A ₁ P+d ₂ )arctan(θ ₂ +θ ₃ ) (8)

z ₁ =O ₃ B ₂ =O ₂ A ₁ +A ₂ B ₂ (9)

The comprehensive formula (6), (7), (8), (9) has

According to the trigonometric function, it can be known that the value range of the arctangent function is , so, compared with parameters such as x, its value is small enough or even negligible.

If the thickness of the steel plate is neglected, then there is

After determining the winding measurement point, the placement position of the ultrasonic receiving probe can be known through (11) formula.

The single-chip microcomputer can obtain the distance between the measured point and the transformer casing according to the propagation time and propagation speed of the ultrasonic signal obtained in step S5 and the calculated placement position of the receiving probe.

S7: Move the ultrasonic probe to the next measured point on the transformer shell, repeat S1-S6, and measure the next set of data.

S8: After testing all the measured points, process the data of all the measured points, and give the transformer winding deformation diagnosis report.

In this embodiment, a segment of the actual transformer winding is cut and placed in a steel plate box filled with transformer oil to form a transformer model. The layout of the transformer model is basically the same as that of the actual transformer. The transformer model is tested with the prototype of the transformer winding deformation ultrasonic detection system provided by the invention. During the test, take the upper end of the winding as the starting position and slowly move downwards along the longitudinal direction at equal intervals, and measure once at each interval until a line is measured in the longitudinal direction, then move the ultrasonic probe along the horizontal direction for an interval, and then move along the Slowly move down from the upper end of the winding in the longitudinal direction and measure each point in the longitudinal direction point by point, and so on. After the ultrasonic probe scans the entire surface of the winding, the data of the distance between each point on the winding surface and the surface of the fuel tank can be obtained. These data are processed by a computer. , and finally give the detection report of the transformer winding state.

Table 1 Transformer winding deformation measurement data

It can be seen from Table 1 that the ultrasonic method to measure the transformer not only has high resolution, but also has high precision, and can accurately detect the winding deformation.

Of course, in the implementation process of the method of the present invention, the above-mentioned embodiments are not limited. For example, the coupling agent of the transformer can be other media that does not affect the performance of the transformer and is conducive to the propagation of sound waves, and the amplification filter circuit can also be an amplifier with other performances that can match the method. filter circuits, etc.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any deformation or replacement made by those skilled in the art within the technical scope disclosed in the present invention shall be Should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (11)

1. a transformer winding deformation online detection method based on ultrasonic wave, is characterized in that, comprises the following steps: S1: Select a point to be measured on the transformer shell, emit ultrasonic signals, and start timing; S2: receiving the echo signal of the ultrasonic signal and converting it into an echo electrical signal; S3: Optimizing the echo electrical signal and stopping timing; S4: Perform receiving compensation on the ultrasonic propagation path, and calculate the distance between the measured point and the transformer shell; S5: Find the next measured point, repeat S1-S4; S6: After testing all the measured points, process the distance data and give the transformer winding deformation diagnosis report; The step S3 specifically includes: firstly, performing amplification and filtering processing on the echo electric signal, and outputting the amplification and filtering signal; secondly, performing optimization processing on the amplification and filtering signal for time gain compensation or comparative shaping, and outputting the optimized processing signal; finally, stop timing after optimization; Among them, the time gain compensation is specifically: 1) Convert the amplification gain corresponding to the preset distance obtained through experiments into the tap position of the digital potentiometer; 2) Solidify the position parameters into Flash; 3) During the measurement process, the corresponding gain is obtained by looking up the table, and then the corresponding gain is set in series to perform time gain compensation. 2. A kind of ultrasonic-based transformer winding deformation online detection method according to claim 1, characterized in that, said step S1 further comprises: A high-frequency oscillation circuit generates a high-frequency square-wave pulse, and the high-frequency square-wave pulse excites the ultrasonic transmitting probe through an excitation circuit to emit ultrasonic signals. 3. A kind of ultrasonic-based transformer winding deformation online detection method according to claim 2, characterized in that, said step S1 further comprises: The high-frequency oscillation signal is generated by the self-excited oscillation circuit to excite the piezoelectric chip to generate the high-frequency square wave pulse, so that the ultrasonic transmitting probe emits ultrasonic waves of a corresponding frequency. 4. A method for online detection of transformer winding deformation based on ultrasonic waves according to claim 3, wherein said step S1 further comprises: referring to the modulation method of ultrasonic communication, obtaining a The special oscillating signal makes the waveform of the echo signal received by the ultrasonic receiving probe obviously different from that of the interference signal. 5. A kind of ultrasonic-based transformer winding deformation online detection method according to claim 1, characterized in that, said step S1 further comprises: A low-frequency soft probe and an ultrasonic coupling agent are used to remove the air thin layer, so that the ultrasonic signal can smoothly propagate into the transformer. 6 . An ultrasonic-based online transformer winding deformation detection method according to claim 1 , wherein the step S2 further comprises: receiving the echo signal by the ultrasonic receiving probe and converting it into an echo electric signal. 7 . 7. An ultrasonic-based online transformer winding deformation detection method according to claim 1, wherein said step S3 further comprises: when performing time gain compensation, calculating the number of decibels by which the sound intensity gain is reduced due to absorption ; According to the relationship between the decibels of the amplitude reduction of the ultrasonic wave in the propagation distance and the time when the ultrasonic wave passes through the distance, the attenuated echo signal is compensated for gain, so that the waveform of the received echo signal is recovered, and the signal recovered by the waveform is performed in the second stage. enlarge. 8. An ultrasonic-based online transformer winding deformation detection method according to claim 1, characterized in that said step S4 further comprises: after stopping the timing, obtaining the propagation time of the ultrasonic wave; measuring the temperature, and calculating the current temperature according to the temperature value Sound velocity, temperature compensation is performed according to the current sound velocity and propagation time. 9. A kind of ultrasonic-based transformer winding deformation online detection method according to claim 1, characterized in that, said step S4 specifically comprises: Calculate the distance between the position of receiving the echo signal and the center of the transformer shell according to the distance between the transmitting ultrasonic signal position and the center of the transformer shell, adjust the position of receiving the echo signal, and calculate the distance between the measured point and the transformer shell according to the timing. 10. An ultrasonic-based transformer winding deformation online detection system, characterized in that it includes a single-chip microcomputer, a transmitting probe, a receiving probe, a signal optimization module, a temperature compensation circuit and a timer; The ultrasonic transmitting probe sends an ultrasonic signal, and the single-chip microcomputer controls the timer to start timing; the ultrasonic receiving probe receives the echo signal of the ultrasonic signal, and converts the echo signal into an echo electric signal output; The signal optimization module optimizes the echo electric signal and outputs an optimized echo signal to the single-chip microcomputer, and the single-chip microcomputer controls the timer to stop timing, and the timer outputs a timing signal; the temperature compensation circuit measures the temperature , and input the temperature signal into the single chip microcomputer; The single-chip microcomputer receives the temperature signal, the timing signal and the optimized echo signal, performs temperature compensation on the propagation path of the optimized echo signal according to the temperature signal and the timing signal, and calculates the distance between the measured point and the transformer shell; The signal optimization module includes a time gain compensation circuit, a secondary amplifier circuit and a comparison shaping circuit; The time gain compensation circuit is provided with a first threshold, and the comparison shaping circuit is provided with a second threshold, the first threshold is used to select echo signals whose transmission distance is greater than a certain distance, and the second threshold is used to select transmission Echo signals whose distance is less than the certain distance; When the echo signal does not meet the second threshold, the amplified and filtered signal is input to the time gain compensation circuit for processing and then output a time gain compensation signal, and the time gain compensation signal is input to a secondary amplifier circuit for processing and output for secondary amplification signal to the microcontroller; When the echo signal does not meet the first threshold, the amplified and filtered signal is input to the comparison shaping circuit for processing, and then the comparison shaping signal is output to the single-chip microcomputer; Among them, the time gain compensation is specifically: 1) Convert the amplification gain corresponding to the preset distance obtained through experiments into the tap position of the digital potentiometer; 2) Solidify the position parameters into Flash; 3) During the measurement process, the corresponding gain is obtained by looking up the table, and then the corresponding gain is set in series to perform time gain compensation. 11. The transformer winding deformation online detection system based on ultrasonic waves according to claim 10, characterized in that, it also includes a power drive circuit, and the power drive circuit includes a high-frequency oscillation circuit, an excitation circuit and a single-chip microcomputer drive circuit; The high-frequency oscillation circuit is used to generate high-frequency square wave pulses, and the excitation circuit is used to excite the transmitting probe to emit ultrasonic signals under the action of high-frequency square wave pulses; the single-chip microcomputer drive circuit is used to drive the single-chip microcomputer.