CN104502626A - High-dynamic-response oil flow rate measuring device and measuring method - Google Patents

Abstract

The invention discloses a high-dynamic-response oil flow rate measuring device and an oil flow rate measuring method. The high-dynamic-response oil flow rate measuring device comprises two sets of identical ultrasonic energy conversion devices which are installed at the two sides of a pipeline via a Z method. The drive signal input ends of the ultrasonic energy conversion devices are connected with the same drive signal generation device. The signal output ends of the ultrasonic energy conversion devices are respectively connected with the signal input end of a processing device. The processing device comprises a first filtering module and a second filtering module. The first filtering module is connected with the first input end of an analog-to-digital conversion module via a first operational amplifier. The second filtering module is connected with the second input end of the analog-to-digital conversion module via a second operational amplifier. The signal output end of the analog-to-digital conversion module is connected with the signal input end of the processing module. The signal output end of the processing module is connected with a display module. The high-dynamic-response oil flow rate measuring device has advantages of being high in dynamic response, short in sampling time and high in sampling rate so that solving of gas misoperation of an immersion type power transformer and arrangement of heavy gas setting values are facilitated.

Description

A kind of oily Flow Velocity measurement mechanism of high dynamic response and measuring method

Technical field

The present invention relates to a kind of oily Flow Velocity measurement mechanism and measuring method, particularly relate to measurement mechanism and measuring method that a kind of insulating oil to sudden change of flow speed in pipeline carries out high dynamic response measurement.

Background technology

Oil-immersed power transformer and reactor are the widely used high-tension apparatuses of current electric system, and gas relay protection is also weighed protection most important a kind of safeguard measure when being then oil-immersed power transformer generation internal fault.Often there is the fault that causes transformer to trip due to the protection malfunction of oil-immersed power transformer body in each electric power enterprise in recent years, and electric system and transformer reliability operation level and power consumer power supply reliability are all affected.In view of gaseous shield is to the fault high sensitivity and the vital role that reflect Transformer Winding turn-to-turn short circuit or built-in electrical insulation electric arc; once malfunction thoroughly must investigate thoroughly reason of false action; can put into operation after oil-immersed power transformer body non-fault; thus add a large amount of work on the spot, therefore must take measures to stop protection malfunction.

In oil-immersed power transformer, the grave gas protection of Buchholz relay relies on the insulating oil of transformer body inside to spring up realization to conservator; when pressure in transformer-cabinet raises; the baffle plate of Buchholz relay inside will be impacted when insulating oil springs up to conservator; when reaching certain speed; baffle plate bearing pressure exceedes setting valve when arranging pressure, the closing of contact.As can be seen here, insulating oil flow condition in pipeline directly reacted Buchholz relay baffle plate bear the size of oil flow pressure, the flow velocity size of insulating oil stream and baffle plate proportional pressure relation, therefore, the size of research pipeline oil Flow Velocity is had very important significance, it is to some gas malfunction in solution at the scene application, and arranging of grave gas setting valve is very helpful.

Ultrasonic flow-velocity meter utilizes ultrasonic transducer to produce ultrasound wave to propagate in measuring media, detects measured medium fluid to the impact of multi-beam transmission time to reach a kind of checkout equipment of testing goal.The flowmeter kind with ultrasound wave being principle is at present a lot, technology is comparative maturity also, they have fluid-velocity survey function, by being converted into flow with measurement caliber, these flowmeters mostly adopt time difference method principle, but not identical according to the measuring method of mistiming, is subdivided into again multi-pulse transit-time, frequency-difference method, phase difference method etc., special time measurement chip is used to survey the time in addition.The difference of these measuring methods is finally all summed up as the difference of the measurement to the mistiming, because if velocimeter will reach enough measuring accuracy, just need being separated with enough resolution between event time, in other words the time that the standard will be able to surveyed is less, in conventional application scenario, the transmission distance of ultrasonic measurement is mostly within 200mm, and the velocity of sound is at about 1400m/s.If reach the precision of 5/1000ths, just need measuring system will reach about 10ps to the resolution of time.

Summary of the invention

The object of this invention is to provide a kind of oily Flow Velocity measurement mechanism and measuring method of high dynamic response, the oily fluid-velocity survey of high dynamic response can be carried out to oil-immersed power transformer body ducted insulating oil stream, there is the advantage that dynamic response is high, the sampling time is short and sampling rate is high, for the setting of the gas malfunction and grave gas setting valve that solve immersion power transformer is offered help.

The present invention adopts following technical proposals:

A kind of oily Flow Velocity measurement mechanism of high dynamic response, comprise the identical ultrasound transducer apparatus of two covers being arranged on pipeline both sides by Z method, the driving signal input of two cover ultrasound transducer apparatus connects same drive singal generation device, the signal input part of the signal output part difference connection handling device of two cover ultrasound transducer apparatus, described treating apparatus comprises the first filtration module and the second filtration module that connect two cover ultrasound transducer apparatus signal output parts respectively, first filtration module connects the first input end of analog-to-digital conversion module by the first operational amplifier, second filtration module connects the second input end of analog-to-digital conversion module by the second operational amplifier, the signal input part of the signal output part connection handling module of analog-to-digital conversion module, the signal output part of processing module connects display module.

Described first filtration module and the second filtration module adopt low-pass filter.

Described analog-to-digital conversion module adopts synchronized sampling analog to digital converter.

The signal input part of described processing module connects keyboard input module.

Utilize the oily Flow Velocity measuring method of the oily Flow Velocity measurement mechanism of high dynamic response described in claim 1, comprise the following steps:

A: install the identical ultrasound transducer apparatus of two covers in pipeline both sides Z method, use same drive singal generation device to drive two cover ultrasound transducer apparatus simultaneously;

B: use synchronous sampling technique to sample to the electric signal that two cover ultrasound transducer apparatus export respectively, and two groups of electric signal are carried out filtering, amplification and analog-to-digital conversion process respectively, then the signal after process is delivered to processing module;

C: processing module calculates the phase differential of two groups of signals by DFT algorithm, and utilize phase difference calculating to draw the mistiming, then try to achieve oily flow transmission instantaneous velocity according to the mounting means of two cover ultrasound transducer apparatus.

In described step B, low-pass filter is utilized to carry out filtering.

In described step B when carrying out synchronized sampling, sample frequency is 32 times of the driving signal frequency that ultrasound transducer apparatus sends.

In described step C, the computing method of oily flow transmission instantaneous velocity are as follows:

C1: processing module calculates the phase differential of two groups of signals by DFT algorithm, wherein discrete Fourier transformation DFT formula is:

$X\left(k\right)=\mathrm{DFT}\left[x\left(n\right)\right]=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)W_N^{\mathrm{kn}},k=\mathrm{0,1},...,N-1;$ Wherein

be twiddle factor, N is that DFT converts burst length, equals sampled data length; When frequency input signal is f, sample frequency f _swith the pass of overtone order k be wherein f _sfor sample frequency, N is 32 points, f _sfor 32Mhz, k are 1;

C2: according to the discrete sample signals of input, the real part imaginary part of X (k) corresponding under calculating fundamental frequency, phase information can obtain from the real part of this point and imaginary part:

C3: the phase information according to trying to achieve in step C2 obtains phase differential wherein for the first via signal phase of being tried to achieve by step C2, for the second road signal phase of being tried to achieve by step C2, in following formula, radian is transformed into angle.

C4: according to formula obtain mistiming t;

C5: utilize mistiming t, according to the angle theta of sound-wave path and pipeline, the length L of transmission path, the velocity of sound S of insulating oil, obtain oily flow transmission instantaneous velocity V, $V=\frac{S^2}{2*L*\cos \mathrm{\θ}}\×t.$

The present invention adopts ultrasonic wave principle, the identical ultrasound transducer apparatus of two covers utilizing Z method to be arranged on pipeline both sides realizes two-channel synchro measure, the drive singal of two cover ultrasound transducer apparatus is sent by same drive singal generation device, can ensure that ultrasonic signal is sending but not completely the same by phase place when connecting tube and fluid, make measured data have minimum inherent error, avoid needing the frequent defect switching sending and receiving sensor during the monaural velocimeter of existing employing.The present invention utilizes high-frequency synchronous sampled measurements technology and DFT algorithm to calculate phase differential, phase differential is due to when ultrasound wave is through transmission medium, the ultrasound wave propagated along transmission medium flow direction accelerates to arrive receiving end, otherwise slow down and arrive, this causes two that inject ultrasonic transducer and creates a phase differential with frequency in-phase signal, phase place extent and mistiming are directly proportional, accurately record this difference and just can obtain high-precision signal propagation time, this method overcomes the drawback existing for tiny time difference of asynchronous measurement forward and reverse direction flow velocity signal.In the present invention, single measurement computation period is in 10ms, sampled data output speed is greater than p.s. 100 times, improve a lot in real-time and slewing rate compared with common ultrasonic flow-velocity meter, realize catching dynamically flutterring of change procedure of oil stream in age at failure by high sample rate, there is the advantage that dynamic response is high, the sampling time is short and sampling rate is high, for the setting of the gas malfunction and grave gas setting valve that solve immersion power transformer is offered help.

Accompanying drawing explanation

Fig. 1 is mounting structure schematic diagram of the present invention;

Fig. 2 is theory diagram of the present invention.

Embodiment

As depicted in figs. 1 and 2, the oily Flow Velocity measurement mechanism of high dynamic response of the present invention, comprise the identical ultrasound transducer apparatus 2 of two covers being arranged on pipeline 1 both sides by Z method, the driving signal input of two cover ultrasound transducer apparatus 2 connects same drive singal generation device 3, the signal input part of the signal output part difference connection handling device of two cover ultrasound transducer apparatus 2, described treating apparatus comprises the first filtration module 4 and the second filtration module 5 connecting two cover ultrasound transducer apparatus 2 signal output parts respectively, first filtration module 4 connects the first input end of analog-to-digital conversion module 8 by the first operational amplifier 6, second filtration module 5 connects the second input end of analog-to-digital conversion module 8 by the second operational amplifier 7, the signal input part of the signal output part connection handling module 9 of analog-to-digital conversion module 8, the signal output part of processing module 9 connects display module 10, the signal input part of processing module 9 connects keyboard input module.In the present embodiment, drive singal generation device 3 can adopt ultrasonic drive circuit; Drive singal adopts 1MHz standard sine signal, about about the 10V of amplitude.Sinusoidal signal production process is: first produce 1MHz square wave by crystal oscillation fractional frequency, then by 1MHz Square wave injection low-pass filter, is finally driven by LT1026 and produces about 10V sinusoidal signal.First filtration module 4 and the second filtration module 5 can adopt low-pass filter; Described analog-to-digital conversion module 8 adopts synchronized sampling analog to digital converter, as the AD6659 of ADI company.Processing module 9 can adopt TI company DSP device, as DSP28335.。

The oily Flow Velocity measuring method of high dynamic response of the present invention, comprises the following steps:

A: install the identical ultrasound transducer apparatus 2 of two covers in pipeline 1 both sides Z method, uses same drive singal generation device 3 to drive two cover ultrasound transducer apparatus 2 simultaneously;

B: use synchronous sampling technique to sample to the electric signal that two cover ultrasound transducer apparatus 2 export respectively, and two groups of electric signal are carried out filtering, amplification and analog-to-digital conversion process respectively, then the signal after process is delivered to processing module 9; When carrying out filtering process, low-pass filter can be adopted to carry out filtering; When carrying out synchronized sampling, sample frequency is 32 times of the driving signal frequency that ultrasound transducer apparatus 2 sends;

C: processing module 9 calculates the phase differential of two groups of signals by DFT algorithm, and utilize phase difference calculating to draw the mistiming, then try to achieve oily flow transmission instantaneous velocity according to the mounting means of two groups of ultrasound transducer apparatus 2.

The computing method of oil flow transmission instantaneous velocity are as follows:

C1: processing module 9 calculates the phase differential of two groups of signals by DFT algorithm, wherein discrete Fourier transformation DFT formula is:

$X\left(k\right)=\mathrm{DFT}\left[x\left(n\right)\right]=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)W_N^{\mathrm{kn}},k=\mathrm{0,1},...,N-1;$ Wherein

be twiddle factor, N is that DFT converts burst length, equals sampled data length; When frequency input signal is f, input signal f is here the 1MHz signal injected by ultrasonic drive circuit, then sample frequency f _swith the pass of overtone order k be wherein f _sfor sample frequency, N is 32 points, f _sfor 32Mhz, only demand 1 subharmonic here, k is 1.

C2: according to the discrete sample signals of input, the real part imaginary part of X (k) corresponding under calculating fundamental frequency, phase information can obtain from the real part of this point and imaginary part:

C3: the phase information according to trying to achieve in step C2 obtains phase differential wherein for the first via signal phase of being tried to achieve by step C2, for the second road signal phase of being tried to achieve by step C2, in following formula, radian is transformed into angle,

C4: according to formula obtain mistiming t;

C5: utilize mistiming t, according to the angle theta of sound-wave path and pipeline 1, the velocity of sound S of the length L of transmission path, 25# insulating oil, obtains oily flow transmission instantaneous velocity,

$V=\frac{S^2}{2*L*\cos \mathrm{\θ}}\×t.$

In the present embodiment, in computation process, first, by discrete Fourier transformation DFT formula be:

$X\left(k\right)=\mathrm{DFT}\left[x\left(n\right)\right]=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)W_N^{\mathrm{kn}},k=\mathrm{0,1},...,N-1$ Be converted to the form of real part imaginary part:

$X\left(k\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}\left\{\mathrm{Re}\right[x\left(n\right)\left]\mathrm{Re}\right[W_N^{\mathrm{nk}}]-\mathrm{Im}[x\left(n\right)\left]\mathrm{Im}\right[W_N^{\mathrm{nk}}]+j\left(\mathrm{Re}\right[x\left(n\right)\left]\mathrm{Im}\right[W_N^{\mathrm{nk}}]+\mathrm{Im}[x\left(n\right)\left]\mathrm{Re}\right[W_N^{\mathrm{nk}}\left]\right)\}$ , wherein, $W_N^{\mathrm{nk}}=e^{-j\frac{2\mathrm{pi}}{N}\mathrm{kn}}=\cos (2\mathrm{pi}/\mathrm{Nkn})+j\sin (2\mathrm{pi}/\mathrm{Nkn}).$ real part imaginary part part be constant, can be calculated in initialize routine during concrete program calculation and be left in an array variable;

Secondly, trigger sampling by timer and read sampled value in interruption, two groups of sampled value sequences that the two paths of signals of acquisition is corresponding leave in two arrays respectively;

Again, calculate the DFT of a wherein road signal, obtain the real part imaginary part of this road signal, concrete grammar is be multiplied by corresponding twiddle factor by sampled value to add up, sequence number is consistent, result leaves in variable X areal and Xaimag respectively, then calculates the DFT of an other road signal, and the result obtaining real part and imaginary part calculating equally leaves in Xbreal and Xbimag respectively;

Then, atan2 (Xaimag, Xareal)-atan2 (Xbimag is calculated, Xbreal) variable angle is left in, then t is the two paths of signals mistiming: t=(angle*T)/2 π, T are the standard signal cycle of injecting, and are 1us during 1Mhz;

Finally, according to the passing time of viscosity determination ultrasound wave in oil stream of transformer oil stream, actual measurement 25# transformer insulation oil, acoustic velocity value is 1410 meter per seconds per second, finally according to factor calibration measurements accuracy such as mounting means caliber wall thickness materials.

In the present invention, two identical ultrasound transducer apparatus 2 inside of cover are all integrated with ultrasound wave and accept and launch two parts, because the connecting tube 1 between transformer body and conservator is generally DN80 caliber, so select Z method to install when installing ultrasound transducer apparatus 2, Z method is installed and is belonged to the ordinary skill in the art.As shown in Figure 1, the ultrasound transducer apparatus 2 that Z method is arranged on connecting tube 1 both sides sends the ultrasonic signal with homophase frequently simultaneously, ultrasonic signal transmits and carries the ultrasound transducer apparatus 2 that flow rate information arrives opposite setting in connecting tube 1, and the ultrasound transducer apparatus 2 arranged by opposite reception is reduced to electric signal.The ultrasound transducer apparatus 2 being separately positioned on connecting tube 1 both sides can send ultrasound wave and can accept ultrasound wave again, can ensure that the ultrasound wave sent has almost consistent transmission path when co-current flow and counter-current flow like this.When measuring, two overlap ultrasound transducer apparatus 2 and are driven by same drive singal generation device 3, and ultrasonic signal and adverse current are transmitted simultaneously, and when can ensure that ultrasound wave transmission is transmitted from starting point, two-way ultrasound wave is synchronous.Like this, then carry out synchronized sampling by the electric signal received two cover ultrasound transducer apparatus 2, the phase difference that two electric signal only have flow velocity to cause can be guaranteed.In the present invention, two cover ultrasound transducer apparatus 2 restore the electric signal of received two-way with flow rate information respectively, due to the reason of time and tide transmission, will cause the phase difference of two path signal, two path signal other information except phase place is variant are all identical.Although also there is the intrinsic difference caused by transmission path, can be revised by algorithm, adopting during monaural velocimeter without the need to picture needs the frequent sending and receiving sensor that switches to obtain time and tide data.

The two path signal that two cover ultrasound transducer apparatus 2 restore, a road is following current ultrasonic electric signal, and an other road is adverse current ultrasonic electric signal.As shown in Figure 1, for attenuating noise signal affects measured signal, the two path signal of reduction enters the first filtration module 4 and the second filtration module 5 respectively, filtration module adopts the low-pass filter of sallen-key topological structure, can filtering high fdrequency component, ensure that follow-up treatment circuit not by the impact of aliasing effect, accurate phase information can be calculated by DFT algorithm.The present invention is provided with analog filter, according to the frequency characteristic of drive singal, the electric signal that first filtration module 4 and the second filtration module 5 export enters analog-to-digital conversion module 8 respectively by the first operational amplifier 6 and the second operational amplifier 7, analog-to-digital conversion module 8 adopts synchronized sampling analog to digital converter, as the AD6659 of ADI company, there is resolution and the two-way independently ALT-CH alternate channel of 12, maximum slew rate can reach 80MSPS, sampling rate is adjustable, analog input bandwidth can arrive 700MHZ, input voltage range can reach the differential signal of 2Vp-p, system requirements can be met well.

Two path signal uses the method for synchronized sampling to complete sampling, controlling of sampling is realized by processing module 9, ensure two path signal frequency division at equal intervals, reduce the error of calculation caused by spectral leakage, the time that sends of sampling time and drive singal is undertaken synchronously by gps time, to ensure system time and the electric system time consistency of oily Flow Velocity measurement mechanism of the present invention, exporting data like this can carry out synchronous comparison with the electric current and voltage gathered or other non electrical quantity data.

Claims (8)

1. the oily Flow Velocity measurement mechanism of a high dynamic response, it is characterized in that: comprise the identical ultrasound transducer apparatus of two covers being arranged on pipeline both sides by Z method, the driving signal input of two cover ultrasound transducer apparatus connects same drive singal generation device, the signal input part of the signal output part difference connection handling device of two cover ultrasound transducer apparatus, described treating apparatus comprises the first filtration module and the second filtration module that connect two cover ultrasound transducer apparatus signal output parts respectively, first filtration module connects the first input end of analog-to-digital conversion module by the first operational amplifier, second filtration module connects the second input end of analog-to-digital conversion module by the second operational amplifier, the signal input part of the signal output part connection handling module of analog-to-digital conversion module, the signal output part of processing module connects display module.

2. the oily Flow Velocity measurement mechanism of high dynamic response according to claim 1, is characterized in that: described first filtration module and the second filtration module adopt low-pass filter.

3. the oily Flow Velocity measurement mechanism of high dynamic response according to claim 2, is characterized in that: described analog-to-digital conversion module adopts synchronized sampling analog to digital converter.

4. the oily Flow Velocity measurement mechanism of high dynamic response according to claim 3, is characterized in that: the signal input part of described processing module connects keyboard input module.

5. utilize the oily Flow Velocity measuring method of the oily Flow Velocity measurement mechanism of high dynamic response described in claim 1, it is characterized in that, comprise the following steps:

A: install the identical ultrasound transducer apparatus of two covers in pipeline both sides Z method, use same drive singal generation device to drive two cover ultrasound transducer apparatus simultaneously;

B: use synchronous sampling technique to sample to the electric signal that two cover ultrasound transducer apparatus export respectively, and two groups of electric signal are carried out filtering, amplification and analog-to-digital conversion process respectively, then the signal after process is delivered to processing module;

C: processing module calculates the phase differential of two groups of signals by DFT algorithm, and utilize phase difference calculating to draw the mistiming, then try to achieve oily flow transmission instantaneous velocity according to the mounting means of two cover ultrasound transducer apparatus.

6. the oily Flow Velocity measuring method of high dynamic response according to claim 5, is characterized in that: in described step B, utilizes low-pass filter to carry out filtering.

7. the oily Flow Velocity measuring method of high dynamic response according to claim 6, is characterized in that: in described step B when carrying out synchronized sampling, and sample frequency is 32 times of the driving signal frequency that ultrasound transducer apparatus sends.

8. the oily Flow Velocity measuring method of high dynamic response according to claim 7, is characterized in that, in described step C, the computing method of oily flow transmission instantaneous velocity are as follows:

C1: processing module calculates the phase differential of two groups of signals by DFT algorithm, wherein discrete Fourier transformation DFT formula is:

$X\left(k\right)=\mathrm{DFT}\left[x\left(n\right)\right]=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)W_N^{\mathrm{kn}},k=\mathrm{0,1},..,N-1;$ Wherein

be twiddle factor, N is that DFT converts burst length, equals sampled data length; When frequency input signal is f, sample frequency f _swith the pass of overtone order k be wherein f _sfor sample frequency, N is 32 points, f _sfor 32Mhz, k are 1;

C2: according to the discrete sample signals of input, the real part imaginary part of X (k) corresponding under calculating fundamental frequency, phase information can obtain from the real part of this point and imaginary part:

C3: the phase information according to trying to achieve in step C2 obtains phase difference φ; Wherein φ ₁for the first via signal phase of being tried to achieve by step C2, φ ₂for the second road signal phase of being tried to achieve by step C2, in following formula, radian is transformed into angle.

C4: according to formula t=[(φ ₁-φ ₂) * T]/2 π obtain mistiming t;

C5: utilize mistiming t, according to the angle theta of sound-wave path and pipeline, the velocity of sound S of the length L of transmission path, 25# insulating oil, obtains oily flow transmission instantaneous velocity V, $V=\frac{S^2}{2*L*\cos }\×t.$