CN112577852B - Transformer insulating oil viscosity monitoring method based on multi-frequency ultrasonic waves - Google Patents
Transformer insulating oil viscosity monitoring method based on multi-frequency ultrasonic waves Download PDFInfo
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Abstract
The invention discloses a method for monitoring viscosity of transformer insulating oil based on multi-frequency ultrasonic waves. Through the multifrequency ultrasonic wave insulating oil viscosity on-line monitoring system who builds, ultrasonic signal under the 9 different frequencies of periodic emission obtains the multifrequency ultrasonic signal data behind the insulating oil and the real-time oil temperature when measuring, calculates characteristic parameter through the ultrasonic signal data that obtain, and characteristic parameter includes: and finally, calculating the viscosity of the transformer insulating oil in operation according to the frequency value, the attenuation coefficient and the ultrasonic wave speed after normalization processing by combining the real-time oil temperature during measurement and the viscosity of new oil at 40 ℃. The method effectively improves the accuracy of the detection of the viscosity of the insulating oil and realizes the online monitoring of the viscosity of the insulating oil.
Description
Technical Field
The invention belongs to the field of online monitoring of the state of transformer insulating oil, and particularly relates to a method for monitoring the viscosity of transformer insulating oil based on multi-frequency ultrasonic waves.
Background
The transformer is a core device of a power system and plays an important role in the processes of electric energy conversion and transmission. The transformer oil is used as an essential part of an oil-immersed transformer, and plays roles of insulation and heat dissipation. The quality of the insulating oil directly affects the operation safety of the transformer, the thermal diffusivity of the insulating oil is reduced due to the overhigh viscosity of the insulating oil, the transformer overheating risk is generated, the insulating performance of the insulating oil is reduced due to the overlow viscosity of the insulating oil, and the viscosity of the insulating oil is taken as an important parameter for measuring the state of the oil and needs to be paid attention.
Ultrasonic waves are more and more widely paid attention and applied as a nondestructive testing method, various physical processes such as scattering, refraction and absorption can occur when the ultrasonic waves propagate in a medium, and the ultrasonic waves can be attenuated to different degrees when the ultrasonic waves propagate in oil products with different viscosities, so that the viscosity measurement of the insulating oil can be realized by utilizing an ultrasonic measurement method.
At present, the acquisition of the viscosity parameters of the insulating oil still remains in the regular detection of oil products, and GB/T265-1988 'petroleum product kinematic viscosity measurement method and dynamic viscosity calculation method' is mainly adopted for the off-line measurement mode of regularly taking oil samples from a transformer in operation and the like, so that the method is complex and tedious, wastes manpower and material resources, has long oil taking period, cannot realize the real-time monitoring of the viscosity of the insulating oil of the transformer, and possibly introduces various impurities and moisture in the oil taking process, thereby not only reducing the insulating property of the transformer, but also influencing the accuracy of the viscosity measurement result of the insulating oil. Therefore, a method for monitoring the viscosity of the transformer insulating oil based on multi-frequency ultrasonic waves is urgently needed.
Disclosure of Invention
In order to overcome the defects mentioned in the background art, the invention provides a method for monitoring the viscosity of transformer insulating oil based on multi-frequency ultrasonic waves, which comprises the following steps:
the first step is as follows: on-line monitoring system for viscosity of insulating oil
The method comprises the following steps of building a multi-frequency ultrasonic insulating oil viscosity online monitoring system, wherein the multi-frequency ultrasonic insulating oil viscosity online monitoring system comprises an ultrasonic emission control module (1), a first ultrasonic emission sensor (2), a second ultrasonic receiving sensor (3), a temperature sensor (4), a preamplifier (5), a data collector (6), a signal transmission line (11), a terminal (12) and a timer (13); the first ultrasonic transmitting sensor (2), the second ultrasonic receiving sensor (3) and the temperature sensor (4) are installed on an oil way (8) between an oil conservator (9) and a transformer oil tank (7), the ultrasonic transmitting control module (1) is connected to the first ultrasonic transmitting sensor (2) to regularly control the first ultrasonic transmitting sensor (2) to sequentially send out multi-frequency ultrasonic signals, and the frequency f of the multi-frequency ultrasonic signalsi(i is 1, 2, …, 9) is f1＝800kHz、f2＝850kHz、f3＝900kHz、f4＝950kHz、f5＝1000kHz、f6＝1050kHz、f7＝1100kHz、f8＝1150kHz、f91200kHz, the peak-peak value of the multi-frequency ultrasonic signal is constant to U, the second ultrasonic receiving sensor (3) collects the multi-frequency ultrasonic signal which sequentially passes through the insulating oil (10), the collected multi-frequency ultrasonic signal sequentially passes through the preamplifier (5) and then is stored in the data collector (6), the temperature sensor (4) transmits the measured real-time oil temperature T to the data collector (6) for storage, and the timer (13) sequentially sends out the ultrasonic emission control module (1) at the starting time T of the multi-frequency ultrasonic signall，fiThe moment t when the multi-frequency ultrasonic signals sequentially reach the second ultrasonic receiving sensor (3)a，fiSent to a data acquisition unit (6) for storage, tl，fi、ta，fi(i 1, 2, 9.) when 9 ultrasonic signals are sequentially sent out from the first ultrasonic sensor (2) and sequentially arrive at the second ultrasonic sensor (3), the terminal (12) acquires data from the data collector (6), processes the data and updates the viscosity database of the insulating oil (10) every day;
secondly, amplifying and denoising the multi-frequency ultrasonic signals, and drawing a curve:
drawing frequency f according to the multi-frequency ultrasonic signal data acquired from the data acquisition unit (6) and amplified by the preamplifier (5)iUltrasonic waveform curves respectively 800kHz, 850kHz, 900kHz, 950kHz, 1000kHz, 1050kHz, 1100kHz, 1150kHz and 1200kHz, and denoising the multi-frequency ultrasonic signals by using a wavelet denoising method;
thirdly, calculating the attenuation coefficient and the ultrasonic wave speed of the multi-frequency ultrasonic signal:
obtaining different frequencies fiPeak-peak value U of denoised ultrasonic wave waveform curve signalfi；
The attenuation coefficient calculation formula is as follows:
in the formula, alphafiIs a frequency of fiThe unit of the attenuation coefficient of the ultrasonic signal is decibel/centimeter, U is the peak-peak value of the initial multi-frequency ultrasonic signal set by the ultrasonic emission control module (1), the unit is volt, L is the distance between the first ultrasonic emission sensor (2) and the second ultrasonic receiving sensor (3), and the unit is centimeter;
said frequency is fiThe formula for calculating the ultrasonic wave velocity of (2) is as follows:
wherein the unit of the ultrasonic wave speed is centimeter per second;
fourthly, normalization processing of characteristic parameters:
for attenuation coefficient alphafiAnd ultrasonic frequency fiVelocity v of ultrasonic wavefiThe normalization treatment is carried out, and the normalization treatment is carried out,
the normalization process calculation formula is as follows:
in the formula, X*Normalizing the processed characteristic parameter, specifically the attenuation coefficient normalization parameter alphafi *Ultrasonic frequency normalization parameter fi *Ultrasonic wave velocity normalization parameter vfi *X is a characteristic parameter to be normalized, in particular an attenuation coefficient alphafiAnd ultrasonic frequency fiVelocity v of ultrasonic wavefiMax () is the function of finding the maximum value, min () is the function of finding the minimum value;
and fifthly, calculating the viscosity of the insulating oil:
the insulating oil (10) has a viscosity calculated as,
wherein mu is the viscosity of the insulating oil (10) at 40 ℃, the unit is square millimeter/second, beta is a temperature correction factor, K1、K2、K3Are all constants and are obtained by fitting a large amount of experimental data in a laboratory0The viscosity of the brand new insulating oil at 40 ℃ is measured in square millimeter/second;
sixthly, updating the insulating oil viscosity database:
and storing the measured characteristic parameters and the calculated viscosity of the insulating oil (10) into a database, and if the viscosity of the insulating oil (10) at 40 ℃ exceeds 10% of the viscosity of the brand-new insulating oil at 40 ℃, immediately giving early warning information by a terminal (12).
The invention has the advantages that:
the multi-frequency ultrasonic online monitoring system for the viscosity of the insulating oil, which is designed by the invention, considers the measurement influence of temperature on the viscosity of the insulating oil, can measure the viscosity of the insulating oil of the transformer in real time during operation, solves the problems that the conventional insulating oil viscosity is long in periodic oil taking and measuring period, and the measurement is easily influenced by factors such as sampling and storage, improves the real-time property and the accuracy of the detection of the viscosity of the insulating oil, and ensures the safety and the stability of the operation of the transformer.
Drawings
FIG. 1 is a flow chart of a method for monitoring viscosity of transformer insulating oil based on multi-frequency ultrasonic waves
FIG. 2 is an on-line monitoring system of a transformer insulating oil viscosity monitoring method based on multi-frequency ultrasonic waves
Detailed Description
The invention is further described below with reference to the accompanying drawings:
fig. 1 is a flowchart of a method for monitoring viscosity of transformer insulating oil based on multi-frequency ultrasonic waves, fig. 2 is an on-line monitoring system of the method for monitoring viscosity of transformer insulating oil based on multi-frequency ultrasonic waves, and it can be seen from fig. 1 and fig. 2 that the method for monitoring viscosity of transformer insulating oil based on multi-frequency ultrasonic waves comprises the following steps:
the first step is as follows: on-line monitoring system for viscosity of insulating oil
The method comprises the following steps of building a multi-frequency ultrasonic insulating oil viscosity online monitoring system, wherein the multi-frequency ultrasonic insulating oil viscosity online monitoring system comprises an ultrasonic emission control module (1), a first ultrasonic emission sensor (2), a second ultrasonic receiving sensor (3), a temperature sensor (4), a preamplifier (5), a data collector (6), a signal transmission line (11), a terminal (12) and a timer (13); a first ultrasonic transmitting sensor (2), a second ultrasonic receiving sensor (3) and a temperature sensor (4) are arranged on an oil way (8) between an oil conservator (9) and a transformer oil tank (7), and an ultrasonic transmitting control module (1)) Is connected to the first ultrasonic transmitting sensor (2) to periodically control the first ultrasonic transmitting sensor (2) to sequentially transmit multi-frequency ultrasonic signals, and the frequency f of the multi-frequency ultrasonic signalsi(i is 1, 2, …, 9) is f1＝800kHz、f2＝850kHz、f3＝900kHz、f4＝950kHz、f5＝1000kHz、f6＝1050kHz、f7＝1100kHz、f8＝1150kHz、f91200kHz, the peak-peak value of the multi-frequency ultrasonic signal is constant to U, the second ultrasonic receiving sensor (3) collects the multi-frequency ultrasonic signal which sequentially passes through the insulating oil (10), the collected multi-frequency ultrasonic signal sequentially passes through the preamplifier (5) and then is stored in the data collector (6), the temperature sensor (4) transmits the measured real-time oil temperature T to the data collector (6) for storage, and the timer (13) sequentially sends out the ultrasonic emission control module (1) at the starting time T of the multi-frequency ultrasonic signall，fiThe moment t when the multi-frequency ultrasonic signals sequentially reach the second ultrasonic receiving sensor (3)a，fiSent to a data acquisition unit (6) for storage, tl，fi、ta，fi(i 1, 2, 9.) when 9 ultrasonic signals are sequentially sent out from the first ultrasonic sensor (2) and sequentially arrive at the second ultrasonic sensor (3), the terminal (12) acquires data from the data collector (6), processes the data and updates the viscosity database of the insulating oil (10) every day;
secondly, amplifying and denoising the multi-frequency ultrasonic signals, and drawing a curve:
drawing frequency f according to the multi-frequency ultrasonic signal data acquired from the data acquisition unit (6) and amplified by the preamplifier (5)iUltrasonic waveform curves respectively 800kHz, 850kHz, 900kHz, 950kHz, 1000kHz, 1050kHz, 1100kHz, 1150kHz and 1200kHz, and denoising the multi-frequency ultrasonic signals by using a wavelet denoising method;
thirdly, calculating the attenuation coefficient and the ultrasonic wave speed of the multi-frequency ultrasonic signal:
obtaining different frequencies fiPeak-peak value U of denoised ultrasonic wave waveform curve signalfi；
The attenuation coefficient calculation formula is as follows:
in the formula, alphafiIs a frequency of fiThe unit of the attenuation coefficient of the ultrasonic signal is decibel/centimeter, U is the peak-peak value of the initial multi-frequency ultrasonic signal set by the ultrasonic emission control module (1), the unit is volt, L is the distance between the first ultrasonic emission sensor (2) and the second ultrasonic receiving sensor (3), and the unit is centimeter;
said frequency is fiThe formula for calculating the ultrasonic wave velocity of (2) is as follows:
wherein the unit of the ultrasonic wave speed is centimeter per second;
fourthly, normalization processing of characteristic parameters:
for attenuation coefficient alphafiAnd ultrasonic frequency fiVelocity v of ultrasonic wavefiThe normalization treatment is carried out, and the normalization treatment is carried out,
the normalization process calculation formula is as follows:
in the formula, X*Normalizing the processed characteristic parameter, specifically the attenuation coefficient normalization parameter alphafi *Ultrasonic frequency normalization parameter fi *Ultrasonic wave velocity normalization parameter vfi *X is a characteristic parameter to be normalized, in particular an attenuation coefficient alphafiAnd ultrasonic frequency fiVelocity v of ultrasonic wavefiMax () is the function of finding the maximum value, min () is the function of finding the minimum value;
and fifthly, calculating the viscosity of the insulating oil:
the insulating oil (10) has a viscosity calculated as,
wherein mu is the viscosity of the insulating oil (10) at 40 ℃, the unit is square millimeter/second, beta is a temperature correction factor, K1、K2、K3Are all constants and are obtained by fitting a large amount of experimental data in a laboratory0The viscosity of the brand new insulating oil at 40 ℃ is measured in square millimeter/second;
sixthly, updating the insulating oil viscosity database:
and storing the measured characteristic parameters and the calculated viscosity of the insulating oil (10) into a database, and if the viscosity of the insulating oil (10) at 40 ℃ exceeds 10% of the viscosity of the brand-new insulating oil at 40 ℃, immediately giving early warning information by a terminal (12).
Claims (1)
1. A transformer insulating oil viscosity monitoring method based on multi-frequency ultrasonic waves is characterized by comprising the following steps:
the first step is as follows: on-line monitoring system for viscosity of insulating oil
The method comprises the following steps of building a multi-frequency ultrasonic insulating oil viscosity online monitoring system, wherein the multi-frequency ultrasonic insulating oil viscosity online monitoring system comprises an ultrasonic emission control module (1), a first ultrasonic emission sensor (2), a second ultrasonic receiving sensor (3), a temperature sensor (4), a preamplifier (5), a data collector (6), a signal transmission line (11), a terminal (12) and a timer (13); the first ultrasonic transmitting sensor (2), the second ultrasonic receiving sensor (3) and the temperature sensor (4) are arranged on an oil way (8) between an oil conservator (9) and a transformer oil tank (7), and the ultrasonic transmitting control module (1) is connected to the first ultrasonic transmitting sensor (2) to periodically control the first ultrasonic transmitting sensor (2) to followSending out multiple frequency ultrasonic signal with frequency fi(i is 1, 2, …, 9) is f1＝800kHz、f2＝850kHz、f3＝900kHz、f4＝950kHz、f5＝1000kHz、f6＝1050kHz、f7＝1100kHz、f8＝1150kHz、f91200kHz, the peak-peak value of the multi-frequency ultrasonic signal is constant to U, the second ultrasonic receiving sensor (3) collects the multi-frequency ultrasonic signal which sequentially passes through the insulating oil (10), the collected multi-frequency ultrasonic signal sequentially passes through the preamplifier (5) and then is stored in the data collector (6), the temperature sensor (4) transmits the measured real-time oil temperature T to the data collector (6) for storage, and the timer (13) sequentially sends out the ultrasonic emission control module (1) at the starting time T of the multi-frequency ultrasonic signall，fiThe moment t when the multi-frequency ultrasonic signals sequentially reach the second ultrasonic receiving sensor (3)a，fiSent to a data acquisition unit (6) for storage, tl，fi、ta，fi(i is 1, 2, 9. the time when the 9 ultrasonic signals are sequentially sent from the first ultrasonic transmitting sensor (2) and sequentially arrive at the second ultrasonic receiving sensor (3), the terminal (12) acquires data from the data collector (6) every day, processes the data and updates the viscosity database of the insulating oil (10);
secondly, amplifying and denoising the multi-frequency ultrasonic signals, and drawing a curve:
drawing frequency f according to the multi-frequency ultrasonic signal data acquired from the data acquisition unit (6) and amplified by the preamplifier (5)iUltrasonic waveform curves respectively 800kHz, 850kHz, 900kHz, 950kHz, 1000kHz, 1050kHz, 1100kHz, 1150kHz and 1200kHz, and denoising the multi-frequency ultrasonic signals by using a wavelet denoising method;
thirdly, calculating the attenuation coefficient and the ultrasonic wave speed of the multi-frequency ultrasonic signal:
obtaining different frequencies fiPeak-peak value U of denoised ultrasonic wave waveform curve signalfi；
The attenuation coefficient calculation formula is as follows:
in the formula, alphafiIs a frequency of fiThe unit of the attenuation coefficient of the ultrasonic signal is decibel/centimeter, U is the peak-peak value of the initial multi-frequency ultrasonic signal set by the ultrasonic emission control module (1), the unit is volt, L is the distance between the first ultrasonic emission sensor (2) and the second ultrasonic receiving sensor (3), and the unit is centimeter;
said frequency is fiThe formula for calculating the ultrasonic wave velocity of (2) is as follows:
wherein the unit of the ultrasonic wave speed is centimeter per second;
fourthly, normalization processing of characteristic parameters:
for attenuation coefficient alphafiAnd ultrasonic frequency fiVelocity v of ultrasonic wavefiThe normalization treatment is carried out, and the normalization treatment is carried out,
the normalization process calculation formula is as follows:
in the formula, X*Normalizing the processed characteristic parameter, specifically the attenuation coefficient normalization parameter alphafi *Ultrasonic frequency normalization parameter fi *Ultrasonic wave velocity normalization parameter vfi *X is a characteristic parameter to be normalized, in particular an attenuation coefficient alphafiAnd ultrasonic frequency fiVelocity v of ultrasonic wavefiMax () is the function of finding the maximum value, min () is the function of finding the minimum value;
and fifthly, calculating the viscosity of the insulating oil:
the insulating oil (10) has a viscosity calculated as,
wherein mu is the viscosity of the insulating oil (10) at 40 ℃, the unit is square millimeter/second, beta is a temperature correction factor, K1、K2、K3Are all constants and are obtained by fitting a large amount of experimental data in a laboratory0The viscosity of the brand new insulating oil at 40 ℃ is measured in square millimeter/second;
sixthly, updating the insulating oil viscosity database:
and storing the measured characteristic parameters and the calculated viscosity of the insulating oil (10) into a database, and if the viscosity of the insulating oil (10) at 40 ℃ exceeds 10% of the viscosity of the brand-new insulating oil at 40 ℃, immediately giving early warning information by a terminal (12).
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| CN100410646C (en) * | 2005-05-20 | 2008-08-13 | 苏州科技学院 | Ultrasonic method and equipment for measuring solid viscosity |
| CN103499514A (en) * | 2013-09-25 | 2014-01-08 | 北京化工大学 | Method and device for testing fluid viscosity on line |
| US9448150B2 (en) * | 2014-02-03 | 2016-09-20 | Cameron International Corporation | Method and apparatus for determining kinematic viscosity through the transmission and reception of ultrasonic energy |
| CN109917255B (en) * | 2019-04-27 | 2020-04-24 | 西南交通大学 | Partial discharge positioning method under temperature rise of transformer insulating oil |
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