CN105319447B - A kind of dielectric loss angle tangent method of testing and tester - Google Patents

Abstract

The invention discloses a kind of dielectric loss angle tangent method of testing and tester, this method of testing includes step: one, electric current and voltage signal acquisition: operating current and operating voltage to tested electrical equipment detect the most in real time, and are acquired by signal acquisition circuit；Two, signal transacting: the current value and the magnitude of voltage that gather each sampling instant by sampling sequencing are respectively processed；When the current value gathering any one sampling instant and magnitude of voltage process, including step: 201, signal receives and synchronizes storage；202, current time dielectric loss angle tangent calculates: data group builds and next sampling instant signal analysis and processing；This tester includes current detecting unit, voltage detection unit, signal acquisition circuit and data processor.The present invention is reasonable in design, realization is convenient and using effect is good, can test by the dielectric loss angle tangent to tested electrical equipment easy, quick, and real-time is good, and measuring accuracy is high.

Description

A kind of dielectric loss angle tangent method of testing and tester

Technical field

The invention belongs to power equipment on-line testing technique field, especially relate to a kind of dielectric loss angle tangent online Method of testing and tester.

Background technology

Dielectric loss angle, leakage current and dielectric electric capacity Cx are three features weighing insulation of electrical installation degree Amount.Owing to dielectric loss angle tangent (i.e. tan δ) is only dependent upon properties of materials and unrelated with the size and dimension of material, therefore It is very effective using tan δ as the parameter of equipment integral insulation situation.

In recent years, along with the development of state inspection, dielectric loss (hereinafter referred to as dielectric loss) online measuring technique also day Benefit comes into one's own, and gradually develops multiple detection method, primarily forms following Liang great branch: the first is real mainly by " hardware " Existing detection method, with bridge method, zero crossing phase-comparison method as representative, the method relies on hardware unit to realize, by hardware The impact of itself is relatively big, and the degree of accuracy is difficult to ensure that；It two is the method realized mainly by " software ", mainly have correlation function algorithm, Higher modes influence, discrete fourier transform algorithm etc., generally measure working voltage and stream respectively by devices such as sensors Through the electric current of test product, then the analog signal measured is converted into data signal, then uses correlation analysis method to extract electricity Pressure and the fundamental phase difference information of electric current, thus estimate Dielectric loss angle.Software Method, with its preferable anti-interference and stability, becomes For the most ideal detection method.

When using traditional Fourier transformation converter technique to carry out dielectric loss test, two fundamental phase subtract each other the most available Dielectric loss angle, and then dielectric loss angle tangent can be calculated.But there is real-time relatively in traditional Fourier transformation converter technique The problems such as difference, measuring accuracy are relatively low.

Summary of the invention

The technical problem to be solved is for above-mentioned deficiency of the prior art, it is provided that a kind of dielectric loss Angle tangent value method of testing, its method step is simple, reasonable in design and realization is convenient, using effect is good, can be easy, quickly to quilt The dielectric loss angle tangent of detecting electric equipment is tested, and real-time is good, and measuring accuracy is high.

For solving above-mentioned technical problem, the technical solution used in the present invention is: a kind of dielectric loss angle tangent test side Method, it is characterised in that: the method comprises the following steps:

Step one, electric current and voltage signal acquisition: use current detecting unit and voltage detection unit to tested electrically Operating current and the operating voltage of equipment detect the most in real time, and by signal acquisition circuit and adopt according to set in advance Sample frequency f_sThe voltage signal that the current signal being detected current detecting unit and voltage detection unit are detected is carried out respectively Gather, and the current value that each sampling instant collected and the equal synchronous driving of magnitude of voltage are to data processor；

Step 2, signal transacting: signal described in each sampling instant, according to sampling sequencing, is adopted by described data processor Current value and the magnitude of voltage of collector collection are respectively processed；The current value of each sampling instant collection and the process side of magnitude of voltage Method is the most identical, when the current value gathering any one sampling instant and magnitude of voltage process, comprises the following steps:

Step 201, signal receive and synchronize storage: described data processor receives signals collecting electricity described in current time After the current value of road collection and magnitude of voltage, carry out the current value received and magnitude of voltage synchronizing storage, and to current time institute The total sampling number stating signal acquisition circuit judges: as total sampling number ＞ N of signal acquisition circuit described in current time Time, enter step 202；Otherwise, step 203 is entered；Wherein, N is positive integer and N=f_s/ f (1-22), in formula (1-22), f is The frequency of supply of tested electrical equipment, f_sFor the sample frequency being pre-designed；

Step 202, current time dielectric loss angle tangent calculate: described data processor calls dielectric loss angle tangent The dielectric loss angle tangent of value computing module electrical equipment tested to current time calculates, and process is as follows:

Step 2021, data group build: the current value of signal acquisition circuit collection described in current time and front N' are adopted Current value one current data group of composition that signal acquisition circuit described in the sample moment gathers, and according to sampling sequencing to described Current value described in N'+1 in current data group is ranked up from front to back；Meanwhile, by signal acquisition circuit described in current time Magnitude of voltage one voltage data group of composition that signal acquisition circuit described in the magnitude of voltage gathered and front N' sampling instant gathers, and According to sampling sequencing, magnitude of voltage described in the N'+1 in described voltage data group is ranked up from front to back；

Wherein, N' is positive integer and N'=N or N-1；

As N'=N, current value described in the N'+1 in described current data group is denoted as i (0), i (1), i the most respectively (2) ..., magnitude of voltage described in i (N), the N'+1 in described voltage data group be denoted as u (0), u (1), u the most respectively (2)、…、u(N)；

As N'=N-1, current value described in the N'+1 in described current data group is denoted as i (1), i the most respectively (2) ..., magnitude of voltage described in i (N), the N'+1 in described voltage data group be denoted as the most respectively, u (1), u (2) ..., u (N)；

Wherein, i (N) and u (N) is respectively current value and the magnitude of voltage that signal acquisition circuit described in current time gathers；

Step 2022, dielectric loss angle tangent calculate: according to formula And tie Close current data group and described voltage data group described in step 2021, calculate Jie of the tested electrical equipment of current time Matter loss tangent tan δ；

Wherein, as N'=N, a in formula (1-21)_i1And b_i1According to formulaCalculate；Further, a_u1And b_u1According to formulaCalculate；

As N'=N-1, a_i1And b_i1According to formulaCount Calculate；Further, a_u1And b_u1According to formulaCalculate；

Step 203, next sampling instant signal analysis and processing: according to the method described in step 201 to step 202, institute State data processor current value and the magnitude of voltage of signal acquisition circuit collection described in next sampling instant are processed.

Said method, is characterized in that: the N=16 described in step 201～100.

Meanwhile, the invention discloses a kind of simple in construction, reasonable in design and use medium easy and simple to handle, that using effect is good Loss angle tangent value tester, it is characterised in that: include the electricity that the operating current of tested electrical equipment is detected in real time Voltage detection unit that stream detector unit, operating voltage to tested electrical equipment detect in real time, to current detecting list Signal acquisition circuit that the voltage signal that the current signal that detected of unit and voltage detection unit are detected is acquired respectively and The dielectric loss angle tangent that process and synchronize draw current tested electrical equipment signal collected to signal acquisition circuit The data processor of value, described current detecting unit and voltage detection unit all connect with signal acquisition circuit；Described tested The operating current of electrical equipment is three-phase current, and described current detecting unit is three-phase current detection unit；Described tested electricity The operating voltage of gas equipment is three-phase voltage, and described voltage detection unit is detecting voltage by three phase unit.

Above-mentioned tester, is characterized in that: also include the host computer connected with data processor.

Above-mentioned tester, is characterized in that: described signal acquisition circuit is A/D converter, and described data processor is DSP core Sheet.

Above-mentioned tester, is characterized in that: described current detecting unit includes three respectively to described tested electrical equipment The current transformer that detects the most in real time of three-phase operating current, described voltage detection unit includes three respectively to described The voltage transformer that the three-phase operating voltage of tested electrical equipment detects the most in real time.

Above-mentioned tester, is characterized in that: described current detecting unit also include three respectively with three described Current Mutual Inductances The first signal conditioning circuit that device connects and three the first low pass filtered that first signal conditioning circuit described with three connects respectively Wave circuit, three described first low-pass filter circuits all connect with signal acquisition circuit；Described voltage detection unit also includes three The individual secondary signal modulate circuit connected with three described voltage transformers respectively and three respectively with three described secondary signals The second low-pass filter circuit that modulate circuit connects, three described second low-pass filter circuits all connect with signal acquisition circuit； Three described first low-pass filter circuits and three described second low-pass filter circuits are second-order low-pass filter circuit, and described two Rank low-pass filter circuit connects with signal acquisition circuit.

Above-mentioned tester, is characterized in that: described second-order low-pass filter circuit includes chip U3 and chip U4, described chip U3 It is operational amplifier with chip U4；

The normal phase input end of described chip U3 divides two-way, and a road is ground connection after electric capacity C2, and another road is through resistance R8, electric capacity C1 Connecting with its inverting input with after resistance R10, the wiring point between resistance R8 and electric capacity C1 is described second-order low-pass filter electricity The input on road；The inverting input of described chip U3 ground connection after resistance R9；

The normal phase input end of described chip U4 divides two-way, and a road is ground connection after electric capacity C4, and another road is through resistance R12, electric capacity Connect with its inverting input after C3 and resistance R14, the wiring point between resistance R12 and electric capacity C3 after resistance R11 with described The output of chip U3 connects；The inverting input of described chip U4 ground connection after resistance R13, the output of described chip U4 is The output of described second-order low-pass filter circuit and its connect with signal acquisition circuit.

Above-mentioned tester, is characterized in that: three described first signal conditioning circuits and three described secondary signal conditioning electricity Road is analog signal conditioner circuit, and described analog signal conditioner circuit includes biasing circuit and connects with described biasing circuit Scaling circuit, described scaling circuit connects with described second-order low-pass filter circuit；

Described biasing circuit includes that chip U1, described chip U1 are that operational amplifier and its normal phase input end are after resistance R4 Ground connection；The inverting input of described chip U1 divides three tunnels, a road to connect with its output after resistance R3, and another road is through resistance R2 Being followed by bias voltage Vin, the 3rd tunnel output with current transformer or voltage transformer after resistance R1 connects；

Described scaling circuit includes that chip U2, described chip U2 are operational amplifier and its positive input end grounding； The inverting input of described chip U2 divides two-way, and a road connects with its output after resistance R6, another road after resistance R5 with The output of chip U1 connects；The output of described chip U2 after resistance R7 with the input of described second-order low-pass filter circuit Connect.

Above-mentioned tester, is characterized in that: described chip U1, chip U2, chip U3 and chip U4 are chip OP07.

The present invention compared with prior art has the advantage that

1, the dielectric loss angle tangent method of testing step used is simple, reasonable in design and realizes conveniently, putting into into This is low.

2, the dielectric loss angle tangent method of testing data handling procedure used is simple and data processing amount is little, according to Fourier coefficient just can convert and draw the dielectric loss angle tangent of current time electrical equipment to be tested, and without to being examined Surveying voltage and carry out Fourier expansion with current signal, Fourier coefficient just can convert according to detected curtage value and push away Draw；Meanwhile, and based on queuing theory and utilize the signal collected value of current time and front multiple sampling instants to gather Signal value just can complete dielectric loss angle tangent and calculate process.

3, the dielectric loss angle tangent method of testing used is in a kind of real time fourier processing algorithm, with tradition Fu Leaf transformation algorithm is compared, and real-time is good, can realize dielectric loss angle on-line monitoring truly.

4, the dielectric loss angle tangent method of testing used is a kind of medium based on instantaneous active Yu reactive current Loss tangent on-line monitoring method, it is to avoid measure power-factor angle, and then reduce the measurement that hardware null offset is brought Error.

5, the dielectric loss angle tangent method of testing using effect used is good, the dielectric loss angle tangent calculated Accurately, measuring accuracy is high, it is achieved that real real-time in-line testing dielectric loss angle tangent for value.Use the inspection of dynamic reactive electric current Survey theory, determine the pass between dielectric loss angle tangent tan δ and instantaneous voltage, electric current by trigonometric function mathematical relationship System, and application queue is theoretical that Fourier Transform Algorithm improves the real-time Fourier algorithm of formation, it is to avoid conventional Fourier Calculate primitive period renewal defect once, it is ensured that the real-time of data.Thus, use the present invention to efficiently solve medium There is the problem of specified poor real, poor accuracy in loss angle on-line monitoring, real-time is good and highly sensitive.

6, the dielectric loss angle tangent tester simple in construction used, reasonable in design and easy-to-connect, use operation Simplicity, using effect are good, can complete test real-time, accurate and the simultaneous display process of dielectric loss angle tangent.Further, adopted Second-order low-pass filter circuit simple, reasonable in design and input cost is low, using effect is good, can be to detected electric current and voltage Signal carries out effective filtering process, it is achieved effectively detect faint electric current with voltage signal, thus can effectively solve existing With the presence of electric current and voltage detecting circuit signal interference problem, thus ensure the accuracy of institute's calculation medium loss tangent.

In sum, the present invention is reasonable in design, realization is convenient and using effect is good, can easy, quickly to tested electrically The dielectric loss angle tangent of equipment is tested, and real-time is good, and measuring accuracy is high.

Below by drawings and Examples, technical scheme is described in further detail.

Accompanying drawing explanation

The method flow frame that Fig. 1 is the present invention when processing the current value of a sampling instant collection and magnitude of voltage Figure.

Fig. 1-1 is tested electrical equipment operating current and the phasor diagram of operating voltage.

Fig. 2 is the schematic block circuit diagram of present media loss angle tangent value tester.

Fig. 3 is the circuit theory diagrams of analog signal conditioner circuit of the present invention.

Fig. 4 is the result of calculation comparison diagram of " real-time FFT " and " traditional FFT " that the present invention uses.Description of reference numerals:

1 current detecting unit；1-1 current transformer；1-2 the first signal conditioning circuit；

1-3 the first low-pass filter circuit；2 voltage detection units；

2-1 voltage transformer；2-2 secondary signal modulate circuit；

2-3 the second low-pass filter circuit；3 signal acquisition circuits.

4 data processors；5 host computers.

Detailed description of the invention

A kind of dielectric loss angle tangent method of testing as shown in Figure 1, comprises the following steps:

Step one, electric current and voltage signal acquisition: use current detecting unit 1 and voltage detection unit 2 to tested electricity Operating current and the operating voltage of gas equipment detect the most in real time, and by signal acquisition circuit 3 and according to presetting Sample frequency f_sThe voltage signal that the current signal being detected current detecting unit 1 is detected with voltage detection unit 2 divides It is not acquired, and the current value that each sampling instant collected and the equal synchronous driving of magnitude of voltage are to data processor 4；

Step 2, signal transacting: described data processor 4 is according to sampling sequencing, to signal described in each sampling instant Current value and magnitude of voltage that Acquisition Circuit 3 gathers are respectively processed；The current value of each sampling instant collection and the place of magnitude of voltage Reason method is the most identical, when the current value gathering any one sampling instant and magnitude of voltage process, comprises the following steps:

Step 201, signal receive and synchronize storage: described data processor 4 receives signals collecting described in current time After the current value of circuit 3 collection and magnitude of voltage, carry out the current value received and magnitude of voltage synchronizing storage, and to current time Total sampling number of described signal acquisition circuit 3 judges: when total sampling number of signal acquisition circuit 3 described in current time During ＞ N, enter step 202；Otherwise, step 203 is entered；Wherein, N is positive integer and N=f_s/ f (1-22), in formula (1-22) F is the frequency of supply of tested electrical equipment, f_sFor the sample frequency being pre-designed；

Step 202, current time dielectric loss angle tangent calculate: described data processor 4 is just calling dielectric loss angle The dielectric loss angle tangent cutting value computing module electrical equipment tested to current time calculates, and process is as follows:

Step 2021, data group build: adopt for the current value gathered by signal acquisition circuit described in current time 3 and front N' Current value one current data group of composition that signal acquisition circuit 3 described in the sample moment gathers, and according to sampling sequencing to institute State current value described in the N'+1 in current data group to be ranked up from front to back；Meanwhile, by signals collecting electricity described in current time Magnitude of voltage one voltage data of composition that signal acquisition circuit 3 described in the magnitude of voltage of road 3 collection and front N' sampling instant gathers Group, and according to sampling sequencing, magnitude of voltage described in the N'+1 in described voltage data group is ranked up from front to back；

Wherein, N' is positive integer and N'=N or N-1；

As N'=N, current value described in the N'+1 in described current data group is denoted as i (0), i (1), i the most respectively (2) ..., magnitude of voltage described in i (N), the N'+1 in described voltage data group be denoted as u (0), u (1), u the most respectively (2)、…、u(N)；

As N'=N-1, current value described in the N'+1 in described current data group is denoted as i (1), i the most respectively (2) ..., magnitude of voltage described in i (N), the N'+1 in described voltage data group be denoted as the most respectively, u (1), u (2) ..., u (N)；

Wherein, i (N) and u (N) is respectively current value and the magnitude of voltage that signal acquisition circuit 3 described in current time gathers；

Step 2022, dielectric loss angle tangent calculate: according to formula And tie Close current data group and described voltage data group described in step 2021, calculate Jie of the tested electrical equipment of current time Matter loss tangent tan δ；

Wherein, as N'=N, a in formula (1-21)_i1And b_i1According to formulaCalculate；Further, a_u1And b_u1According to formulaCalculate；

As N'=N-1, a_i1And b_i1According to formulaCount Calculate；Further, a_u1And b_u1According to formulaCalculate；

Step 203, next sampling instant signal analysis and processing: according to the method described in step 201 to step 202, institute State data processor 4 current value and the magnitude of voltage of signal acquisition circuit 3 collection described in next sampling instant are processed.

In the present embodiment, the N=16 described in step 201～100.

Further, N=20.During actually used, can according to specific needs the value size of N be adjusted accordingly.

In the present embodiment, f=50Hz.

Wherein, frequency of supply is the frequency to the alternating current that tested electrical equipment is powered.

When using traditional Fourier transformation converter technique that electrical equipment carries out dielectric loss test, first become according to Fourier Change fundamental current and the fundamental voltage extracting tested electrical equipment, further according to fundamental voltage and the angle relationship of fundamental current Calculate the dielectric loss angle tangent (i.e. tan δ) of tested electrical equipment.

According to Fourier Transform Algorithm, a periodic signal can be decomposed into DC component c0 (i.e. 0 frequency by Fourier transformation Rate) and the linear superposition of sinusoidal signal of different frequency, refers to formula:C in formula (1-1)_mFor the m subharmonic obtained after Fourier transformation Amplitude, the angular frequency of m subharmonic is m ω, and the initial phase of m subharmonic isAnd its virtual value isM is the most whole Number and m=1,2,3 ...；

Meanwhile, formula (1-1) can also be expressed as: Wherein, a_mAnd b_mBe Fourier coefficient andω=2 π f, f are fundamental frequency；

As m=1, the expression formula of fundametal compoment isIn formula (1-3)For Fourier Obtaining the initial phase of fundamental signal after conversion, the angular frequency of fundamental signal is ω and first-harmonic virtual value is

When using traditional Fourier Transform Algorithm that the dielectric loss angle tangent of tested electrical equipment is calculated, First the operating current of tested electrical equipment is carried out periodic sampling, it is thus achieved that current sampling signal (i.e. current sample sequence)；Again The current sampling signal obtained is carried out discrete Fourier transform, it is thus achieved that the frequency spectrum of this signal, and try to achieve fundamental current signal (also referred to as current first harmonics component), is denoted as:θ in formula (1-4)₂For to sampling The initial phase of the fundamental signal obtained after carrying out Fourier transformation to the operating current of tested electrical equipment, fundamental signal Angular frequency is ω_iAnd I is first-harmonic virtual value；Herein, the operating current of tested electrical equipment is that tested electrical equipment band is born Electric current during carrying row；

In like manner, the operating voltage of tested electrical equipment is carried out periodic sampling, it is thus achieved that voltage sampling signal (i.e. adopt by voltage Sample sequence)；Again the voltage sampling signal obtained is carried out discrete Fourier transform, it is thus achieved that the frequency spectrum of this signal, and try to achieve base Wave voltage signal (also referred to as voltage fundamental component), is denoted as:Formula (1-5) Middle θ₁The initial phase of the fundamental signal for obtaining after the operating current sampling tested electrical equipment is carried out Fourier transformation Position, the angular frequency of fundamental signal is ω_uAnd U is first-harmonic virtual value；Herein, the operating voltage of tested electrical equipment is tested Voltage when electrical equipment bringing onto load runs.Wherein, ω_u=ω_i=ω.

Traditional Fourier Transform Algorithm is used to carry out dielectric loss angle tangent when calculating, two fundamental signals The phase place of (i.e. fundamental current signal and fundamental voltage signal) is subtracted each other and is i.e. obtained dielectric loss angle δ, i.e.

After the operating current of tested electrical equipment and operating voltage are carried out Fourier transformation respectively, it is thus achieved that such as Fig. 1-1 Shown phasor diagram.

In step 2022, the derivation of formula (1-27) and (1-28) is as follows: can be found out by Fig. 1-1: the nothing of operating current Merit component I_q=Isin Φ (1-7), real component I of operating current_p=Icos Φ (1-8)；Wherein, Φ=θ₁-θ₂=(ω t+ θ₁)-(ωt+θ₂) (1-9)；

By trigonometric function relation sin (alpha-beta)=sin α cos β-cos α sin β, can obtain:

$\begin{array}{c}{I}_q=I\sin \mathrm{\Φ}=I\sin \[(\mathrm{\ω}t+{\mathrm{\θ}}_1)-(\mathrm{\ω}t+{\mathrm{\θ}}_2)\]=I({\mathrm{sin\θ}}_1{\mathrm{cos\θ}}_2-{\mathrm{cos\θ}}_1{\mathrm{sin\θ}}_2)\\ =\frac{1}{U}(U{\mathrm{sin\θ}}_{1}I{\mathrm{cos\θ}}_2-U{\mathrm{cos\θ}}_{1}I{\mathrm{sin\θ}}_2)\end{array}---(1-10);$

$\begin{array}{c}{I}_p=I\cos \mathrm{\Φ}+I\cos \[(\mathrm{\ω}t+{\mathrm{\θ}}_1)-(\mathrm{\ω}t+{\mathrm{\θ}}_2)\]=I({\mathrm{cos\θ}}_1{\mathrm{cos\θ}}_2+{\mathrm{sin\θ}}_1{\mathrm{sin\θ}}_2)\\ =\frac{1}{U}(U{\mathrm{cos\θ}}_{1}I{\mathrm{cos\θ}}_2+U{\mathrm{sin\θ}}_{1}I{\mathrm{sin\θ}}_2)\end{array}---(1-11);$

Thus can draw: the dielectric loss angle tangent of tested electrical equipment:

$\tan \mathrm{\δ}=\frac{I_p}{I_q}=\frac{U{\mathrm{cos\θ}}_{1}I{\mathrm{cos\θ}}_2+U{\mathrm{sin\θ}}_{1}I{\mathrm{sin\θ}}_2}{U{\mathrm{sin\θ}}_{1}I{\mathrm{cos\θ}}_2-U{\mathrm{cos\θ}}_{1}I{\mathrm{sin\θ}}_2}---(1-12);$

In formula (1-12), Ucos θ₁、Usinθ₁、Icosθ₂With Isin θ₂, Fourier algorithm all can be utilized collecting The operating current of tested electrical equipment and operating voltage carry out decomposition and draw.

Wherein, according to formula (1-2), the operating current of the tested electrical equipment collected is discrete signal and enters it Obtain after row real time fourier processing: In formula (1-13), N be positive integer and n=1,2,3 ...；b_inAnd a_inIt is Fourier coefficient, i₀For DC component；

In like manner, the operating voltage of the tested electrical equipment collected is discrete signal and it is carried out real-time Fourier's change Obtain after changing:In formula (1-14), b_unWith a_unIt is Fourier coefficient, u₀For DC component；

Wherein, operating current and operating voltage to the tested electrical equipment collected carry out real-time Fourier's change respectively After changing, obtaining fundamental current signal is i₁(t)=b_i1cos(ωt)+a_i1Sin (ω t) (1-15), and fundamental voltage signal is u₁ (t)=b_u1cos(ωt)+a_u1sin(ωt) (1-16)；

Meanwhile, according to formulaWith And ω_u=ω_i=ω, draws

$u_1\left(t\right)=b_{u1}cos\left(\mathrm{\ω}t\right)+a_{u1}sin\left(\mathrm{\ω}t\right)=\sqrt{2}Usin(\mathrm{\ω}t+{\mathrm{\θ}}_1)---(1-18);$

According to formula (1-17) and (1-18), can drawWith

Thus, formula (1-12) can be transformed into:

A in formula (1-21)_i1And b_i1It is collecting Tested electrical equipment operating current carry out the Fourier coefficient of the fundamental current signal obtained after Fourier transformation, a_u1With b_u1It is Fu of the fundamental voltage signal obtained after the tested electrical equipment operating voltage collected is carried out Fourier transformation In leaf system number.

Assume that, when the operating current to tested electrical equipment and operating voltage are sampled, sample frequency is f_s, the most often The sampling number N=f of individual primitive period_s/ f (1-22), wherein f is fundamental frequency,

FormulaIn, a_mAnd b_mIt is Fourier Coefficient；

Wherein,

$b_m=\frac{2}{N}\underset{k=1}{\overset{N}{\Σ}}f\left(k\right)cos\left(m\mathrm{\ω}k\right)=\frac{2}{N}\underset{k=1}{\overset{N}{\Σ}}f\left(k\right)cos\frac{m\·2k\mathrm{\π}\·f_s}{N}---(1-24);$

In formula (1-23) and (1-24), k be positive integer and its represent the sequence number of sampled point, k=in a primitive period 1、2、3、…、N；F (k) is the signal value that kth sampled point collects in a primitive period, in u (k) is a primitive period The magnitude of voltage that kth sampled point collects；

According to formula (1-23) and (1-24), draw:

$\begin{array}{cc}{a}_1=\frac{2}{N}\underset{k=1}{\overset{N}{\Σ}}f\left(k\right)sin\frac{2k\mathrm{\π}\·f_s}{N}---(1-25),& b_1=\frac{2}{N}\underset{k=1}{\overset{N}{\Σ}}f\left(k\right)cos\frac{2k\mathrm{\π}\·f_s}{N}---(1-26)\end{array}.$

According to formula (1-25) and (1-26), draw:

$\begin{array}{cc}\left\{\begin{array}{c}{a}_{i1}=\frac{2}{N}\underset{k=1}{\overset{N}{\Σ}}i\left(k\right)\sin \frac{2k\mathrm{\π}\·f_s}{N}\\ b_{i1}=\frac{2}{N}\underset{k=1}{\overset{N}{\Σ}}i\left(k\right)\cos \frac{2k\mathrm{\π}\·f_s}{N}\end{array}\right.---(1-27),& \left\{\begin{array}{c}{a}_{u1}=\frac{2}{N}\underset{k=1}{\overset{N}{\Σ}}u\left(k\right)\sin \frac{2k\mathrm{\π}\·f_s}{N}\\ b_{u1}=\frac{2}{N}\underset{k=1}{\overset{N}{\Σ}}u\left(k\right)\cos \frac{2k\mathrm{\π}\·f_s}{N}\end{array}\right.---(1-28);\end{array}$

In formula (1-27), i (k) is the current value that kth sampled point collects in a primitive period；Formula (1-28) In, u (k) is the magnitude of voltage that kth sampled point collects in a primitive period.

It addition, a_i1And b_i1Also can be according to formula Enter Row calculates；In formula (1-29), k' be positive integer and its represent the sequence number of sampled point in a primitive period, k'=1,2, 3、…、N-1；I (k') be kth in a primitive period ' the current value that collects of individual sampled point, in i (N) is a primitive period The current value that last sampled point (i.e. n-th sampled point) collects, i (0) is first sampled point in the primitive period The current value that one sampled point in front side collects；

In like manner, a_u1And b_u1Also can be according to formula Calculate；In formula (1-30), k' be positive integer and its represent the sequence number of sampled point in a primitive period, k'=1,2, 3、…、N-1；U (k') be kth in a primitive period ' the magnitude of voltage that collects of individual sampled point, in u (N) is a primitive period The magnitude of voltage that last sampled point (i.e. n-th sampled point) collects, u (0) is first sampled point in the primitive period The magnitude of voltage that one sampled point in front side collects.

Thus, the dielectric loss angle tangent computational methods used in step 202 of the present invention, for based on instantaneous active and nothing The dielectric loss angle tangent on-line monitoring method of merit electric current, is avoided that measurement power-factor angle, and then reduces the drift of hardware zero point The measure error that shipper pole comes.

During it addition, use traditional Fourier algorithm to carry out dielectric loss angle tangent calculating, can only be a first-harmonic week Phase, (i.e. 20ms, corresponding fundamental frequency is 50Hz) calculated once.And use the present invention to carry out dielectric loss angle tangent calculating Time, just can calculate once in each sampling instant.Thus the calculating frequency of dielectric loss angle tangent is increased to tradition Fu In leaf algorithm calculate N times of frequency, i.e. calculate a dielectric loss angle tangent in a sampling period (i.e. 20ms/N), so Can effectively solve the problem that traditional Fourier algorithm carries out the poor real existed when dielectric loss angle tangent calculates.Cause And, dielectric loss angle tangent method of testing disclosed by the invention, it is possible to be referred to as real-time Fourier algorithm, it is to avoid in traditional Fu The data basis of leaf transformation must assure that the problem that sampled data is a complete primitive period, and real-time is good.

Further, when using the present invention to carry out dielectric loss angle tangent calculating, current data group and voltage number need to first be built According to group.During actual implementation, build based on queuing theory, and according to the sequencing in sampling time, to current data group Magnitude of voltage described in current value described in N'+1 and the N'+1 in voltage data group is ranked up, and forms current value queue and magnitude of voltage Queue.So, there is one group of periodic quantity all the time in the current value queue of arbitrary sampling instant and magnitude of voltage queue, and the most more Newly, so can realize measure real-time, it is achieved that instantaneity truly.Thus, the dielectric loss that the present invention uses Angle tangent value computational methods are the real time fourier processing method being integrally formed queuing theory and Fourier transform principle. The data renewal time of the present invention only has conventional Fourier transform algorithm to update the timeAnd consider each based on queuing theory The current value of sampling instant and the renewal of magnitude of voltage, thus instantaneous result of calculation is more accurate, sensitivity is higher.

A kind of dielectric loss angle tangent tester as shown in Figure 2, including the operating current to tested electrical equipment The voltage detecting that the current detecting unit 1 that detects in real time, operating voltage to tested electrical equipment detect in real time The voltage signal that unit 2, the current signal being detected current detecting unit 1 are detected with voltage detection unit 2 is carried out respectively The signal acquisition circuit 3 that gathers and process signal acquisition circuit 3 is signal collected and synchronizes to draw current tested electricity The data processor 4 of the dielectric loss angle tangent of gas equipment, described current detecting unit 1 and voltage detection unit 2 all with letter Number Acquisition Circuit 3 connects；The operating current of described tested electrical equipment is three-phase current, and described current detecting unit 1 is three Phase current sensing unit；The operating voltage of described tested electrical equipment is three-phase voltage, and described voltage detection unit 2 is three-phase Voltage detection unit.

In the present embodiment, dielectric loss angle tangent tester of the present invention, also include connecting with data processor 4 Host computer 5.

In the present embodiment, described signal acquisition circuit 3 is A/D converter.

Further, described data processor 4 is dsp chip.

Time actually used, described data processor 4 can also use other type of data processing chip, for ARM chip Deng.

In the present embodiment, described current detecting unit 1 includes three three-phase works to described tested electrical equipment respectively Making the current transformer 1-1 that electric current detects the most in real time, described voltage detection unit 2 includes three respectively to described tested The voltage transformer 2-1 that the three-phase operating voltage of examination electrical equipment detects the most in real time.

Meanwhile, described current detecting unit 1 also includes three first connected respectively with three described current transformer 1-1 Signal conditioning circuit 1-2 and three the first low-pass filter circuits that first signal conditioning circuit 1-2 described with three connects respectively 1-3, three described first low-pass filter circuit 1-3 all connect with signal acquisition circuit 3；Described voltage detection unit 2 also includes Three secondary signal modulate circuit 2-2 connected with three described voltage transformer 2-1 respectively and three respectively with described in three The second low-pass filter circuit 2-3 that secondary signal modulate circuit 2-2 connects, three described second low-pass filter circuit 2-3 all with Signal acquisition circuit 3 connects；Three described first low-pass filter circuit 1-3 and three described second low-pass filter circuit 2-3 are equal For second-order low-pass filter circuit, described second-order low-pass filter circuit connects with signal acquisition circuit 3.

As it is shown on figure 3, in the present embodiment, described second-order low-pass filter circuit includes chip U3 and chip U4, described chip U3 and chip U4 is operational amplifier.

The normal phase input end of described chip U3 divides two-way, and a road is ground connection after electric capacity C2, and another road is through resistance R8, electric capacity C1 Connecting with its inverting input with after resistance R10, the wiring point between resistance R8 and electric capacity C1 is described second-order low-pass filter electricity The input on road；The inverting input of described chip U3 ground connection after resistance R9.

The normal phase input end of described chip U4 divides two-way, and a road is ground connection after electric capacity C4, and another road is through resistance R12, electric capacity Connect with its inverting input after C3 and resistance R14, the wiring point between resistance R12 and electric capacity C3 after resistance R11 with described The output of chip U3 connects；The inverting input of described chip U4 ground connection after resistance R13, the output of described chip U4 is The output of described second-order low-pass filter circuit and its connect with signal acquisition circuit 3.

In the present embodiment, three described first signal conditioning circuit 1-2 and three described secondary signal modulate circuit 2-2 are equal For analog signal conditioner circuit, described analog signal conditioner circuit includes biasing circuit and the ratio connected with described biasing circuit Computing circuit, described scaling circuit connects with described second-order low-pass filter circuit.

Described biasing circuit includes that chip U1, described chip U1 are that operational amplifier and its normal phase input end are after resistance R4 Ground connection；The inverting input of described chip U1 divides three tunnels, a road to connect with its output after resistance R3, and another road is through resistance R2 Being followed by bias voltage Vin, the 3rd tunnel output with current transformer 1-1 or voltage transformer 2-1 after resistance R1 connects.

Described scaling circuit includes that chip U2, described chip U2 are operational amplifier and its positive input end grounding； The inverting input of described chip U2 divides two-way, and a road connects with its output after resistance R6, another road after resistance R5 with The output of chip U1 connects；The output of described chip U2 after resistance R7 with the input of described second-order low-pass filter circuit Connect.

During physical cabling, the output of described voltage transformer 2-1 is denoted as Uin, the output of described current transformer 1-1 It is denoted as Iin.

In the present embodiment, described chip U1, chip U2, chip U3 and chip U4 are chip OP07.

In the present embodiment, the resistance of resistance R9, R10, R13 and R14 is r, and the resistance of resistance R8 and R12 is r₂, electricity The resistance of resistance R7 and R11 is r₁, the capacitance (i.e. reactance) of electric capacity C1 and C3 is C₁, capacitance (the i.e. electricity of electric capacity C2 and C4 Anti-) it is C₂。

In the present embodiment, owing to described data processor 4 is dsp chip, thereby through described analog signal conditioner circuit The voltage signal that the current signal detected or voltage signal are all adjusted to 0V～3V (specially 0.5V～2.5V) inputs extremely Data processor 4, carries out processing and calculating the dielectric loss of the tested electrical equipment of current time by data processor 4 Angle tangent value, and be that the dielectric loss angle tangent calculated carries out simultaneous display by host computer 5.

When calculating dielectric loss angle tangent, signal interference problem always affects on-line insulation inspection system peace The key factor of full reliability service, especially in the electromagnetic interference environment of some complexity, the detection difficulty of small-signal is bigger, logical Normal way is design simulation filter circuit or uses filtering algorithm to carry out digital filtering.

As it is shown on figure 3, in the present embodiment, the low-pass filter circuit used is second-order low-pass filter circuit, and this filter Wave circuit is that two-stage voltage controlled voltage source filter circuit is in series, and every one-level filter circuit had both introduced negative-feedback, introduced again positive and negative Feedback；When the frequency of detected signal tends to 0, the reactance of electric capacity C1 and C3 tends to infinite；When the frequency of detected signal tends to Time infinite, the reactance of electric capacity C2 and C4 tends to 0.

The transmission function of described second-order low-pass filter circuit is:

$A_u\left(s\right)=\frac{2}{1+\[c_2{r}_1+c_2{r}_2-c_1{r}_1\]s+c_1{c}_2{r}_1{r}_2{s}^2}\×\frac{2}{1+\[c_2{r}_1+c_2{r}_2-c_1{r}_1\]s+c_1{c}_2{r}_1{\mathrm{rs}}^2}---(1-31).$

In the present embodiment, (also referred to as peak-to-peak value refers to one to the voltage peak-to-peak value produced by signal generator SDG1020 Difference between signal peak and minimum in cycle) it is 4V and the frequency alternating current that is respectively 50Hz, 150Hz and 250Hz Pressure signal, tests the circuit performance of described second-order low-pass filter circuit.Draw after tested, be the friendship of 50Hz for frequency Stream voltage signal, the output voltage of described second-order low-pass filter circuit is the most undamped；It is the alternating voltage of 150Hz for frequency Signal, the output voltage peak-to-peak value of described second-order low-pass filter circuit is 54mV, attenuation ratio 54/4000=1.35%；For Frequency is the ac voltage signal of 250Hz, and the output voltage peak-to-peak value of described second-order low-pass filter circuit, within 20mV, declines Subtract ratio less than 20/4000=0.5%.Therefore, described second-order low-pass filter circuit is to three times and more than three times harmonic waves of electrical network Inhibition is clearly.

The method of testing used conventional Fourier transform algorithm (hereinafter referred to as " traditional FFT ") and the present invention below is (i.e. Real time fourier processing algorithm, hereinafter referred to as " real-time FFT ") contrast.The present invention is within each primitive period (i.e. 20ms) Gathering current value and the magnitude of voltage of 20 sampled points, starting input signal is the voltage letter that peak-to-peak value is 4V and frequency is 50Hz Number, peak-to-peak value is become 2V suddenly by running.The medium that " traditional FFT " and " real-time FFT " both approaches calculates Loss tangent, refers to table 1；Further, the dielectric loss angle tangent comparing result that the two calculates refers to Fig. 4.

The dielectric loss angle tangent contrast table that table 1 " traditional FFT " and " real-time FFT " calculate

As shown in Figure 4, during the 52nd sampled point, the voltage signal of input changes (peak-to-peak value becomes 2V from 4V), this Shi Caiyong " real-time FFT " just can follow the trend of voltage signal and present downward trend, and " traditional FFT " still keeps a cycle The calculated value of (i.e. primitive period).Therefore, compared with " real-time FFT ", " traditional FFT ", due to intrinsic defect, occurs at signal During sudden change can the time delay of an at least cycle (primitive period), and period data are the biggest with signal actual difference.Fig. 4 Middle abscissa is sampling number, and the ordinate of the Voltage Peak peak value of input signal is voltage and its unit is V, " traditional FFT " and The ordinate of " real-time FFT " is the dielectric loss angle tangent calculated.

The present invention is used the dielectric loss angle tangent result of calculation of " real-time FFT " method be analyzed below, and The phase angle difference of given institute's input current and voltage be respectively 90 °-85 °, 90 °-80 °, 90 °-75 °, 90 °-70 °, 90 °-65 ° and 90 °-60 °, i.e., when δ is respectively 5 °, 10 °, 15 °, 20 °, 25 ° and 30 °, use " real-time FFT " method to dielectric loss angle tangent Value calculates, and result of calculation refers to table 2:

Table 2 " real-time FFT " dielectric loss angle tangent result of calculation table

As shown in Figure 2, " real-time FFT " disclosed by the invention method is used to calculate the maximum of dielectric loss angle tangent Error is the least, specific as follows: when-85 °, δ=90 °=5 °, worst error e1=(0.097702-0.0874)/0.0874= 11.4%；When δ=10 °, worst error e2=(0.182562-0.1763)/0.1763=3.5%；When δ=15 °, maximum Error e 3=(0.273428-0.2679)/0.2679=2.0%；When δ=20 °, worst error e4=(0.367488- 0.3639)/0.3639=0.0098%；When δ=25 °, worst error e5=(0.445992-0.4663)/0.4663=- 4.2%；When δ=30 °, worst error e3=(0.550209-0.5773)/0.5773=-4.6%；Thus can find out: use The full accuracy of " real-time FFT " disclosed by the invention method can ensure thousand effectiveness of classifications, within normality precision can reach 5%.

The above, be only presently preferred embodiments of the present invention, not impose any restrictions the present invention, every according to the present invention Any simple modification, change and the equivalent structure change that above example is made by technical spirit, all still falls within skill of the present invention In the protection domain of art scheme.

Claims (10)

1. a dielectric loss angle tangent method of testing, it is characterised in that: the method comprises the following steps:

Step one, electric current and voltage signal acquisition: use current detecting unit (1) and voltage detection unit (2) to tested electricity Operating current and the operating voltage of gas equipment detect the most in real time, and by signal acquisition circuit (3) and according to setting in advance Fixed sample frequency f_sThe voltage that the current signal being detected current detecting unit (1) and voltage detection unit (2) are detected Signal is acquired respectively, and the current value that each sampling instant collected and the equal synchronous driving of magnitude of voltage are to data processor (4)；

Step 2, signal transacting: signal described in each sampling instant, according to sampling sequencing, is adopted by described data processor (4) Current value and magnitude of voltage that collector (3) gathers are respectively processed；The current value of each sampling instant collection and the place of magnitude of voltage Reason method is the most identical, when the current value gathering any one sampling instant and magnitude of voltage process, comprises the following steps:

Step 201, signal receive and synchronize storage: described data processor (4) receives signals collecting electricity described in current time After current value that road (3) gathers and magnitude of voltage, carry out the current value received and magnitude of voltage synchronizing storage, and to current time Total sampling number of described signal acquisition circuit (3) judges: when total sampling of signal acquisition circuit described in current time (3) During number of times ＞ N, enter step 202；Otherwise, step 203 is entered；Wherein, N is positive integer and N=f_s/ f (1-22), formula (1- 22) in, f is the frequency of supply of tested electrical equipment, f_sFor the sample frequency being pre-designed；

Step 202, current time dielectric loss angle tangent calculate: described data processor (4) calls dielectric loss angle tangent The dielectric loss angle tangent of value computing module electrical equipment tested to current time calculates, and process is as follows:

Step 2021, data group build: the current value gathered by signal acquisition circuit described in current time (3) and front N' sampling Current value one current data group of composition that signal acquisition circuit described in moment (3) gathers, and according to sampling sequencing to institute State current value described in the N'+1 in current data group to be ranked up from front to back；Meanwhile, by signals collecting electricity described in current time Magnitude of voltage one voltage of composition that signal acquisition circuit (3) described in magnitude of voltage that road (3) gathers and front N' sampling instant gathers Data group, and according to sampling sequencing, magnitude of voltage described in the N'+1 in described voltage data group is ranked up from front to back；

Wherein, N' is positive integer and N'=N or N-1；

As N'=N, current value described in the N'+1 in described current data group is denoted as i (0), i (1), i the most respectively (2) ..., magnitude of voltage described in i (N), the N'+1 in described voltage data group be denoted as u (0), u (1), u the most respectively (2)、…、u(N)；

As N'=N-1, current value described in the N'+1 in described current data group be denoted as the most respectively i (1), i (2) ..., Magnitude of voltage described in i (N), the N'+1 in described voltage data group is denoted as the most respectively, u (1), u (2) ..., u (N)；

Wherein, i (N) and u (N) is respectively current value and the magnitude of voltage that signal acquisition circuit (3) described in current time gathers；

Step 2022, dielectric loss angle tangent calculate: according to formula, and combine step (1-21) Current data group described in rapid 2021 and described voltage data group, the medium calculating the tested electrical equipment of current time damages Consumption angle tangent value tan δ；

Wherein, as N'=N, a in formula (1-21)_i1And b_i1According to formulaCalculate；Further, a_u1And b_u1According to formulaCalculate；

As N'=N-1, a_i1And b_i1According to formulaCalculate；And And, a_u1And b_u1According to formulaCalculate；

Step 203, next sampling instant signal analysis and processing: according to the method described in step 201 to step 202, described number The current value and the magnitude of voltage that gather signal acquisition circuit (3) described in next sampling instant according to processor (4) process.

2. according to a kind of dielectric loss angle tangent method of testing described in claim 1, it is characterised in that: institute in step 201 The N=16～100 stated.

3. the tester realizing dielectric loss angle tangent method of testing as claimed in claim 1, it is characterised in that: include The current detecting unit (1) that the operating current of tested electrical equipment is detected in real time, the work to tested electrical equipment The voltage detection unit (2), the current signal being detected current detecting unit (1) and the voltage that detect in real time as voltage are examined Survey signal acquisition circuit (3) that unit (2) voltage signal that detected is acquired respectively and signal acquisition circuit (3) is adopted Collection signal carries out processing and synchronize to draw the data processor (4) of the dielectric loss angle tangent of current tested electrical equipment, Described current detecting unit (1) and voltage detection unit (2) all connect with signal acquisition circuit (3)；Described tested electrically set Standby operating current is three-phase current, and described current detecting unit (1) is three-phase current detection unit；Described tested electrically set Standby operating voltage is three-phase voltage, and described voltage detection unit (2) is detecting voltage by three phase unit.

4. according to the tester described in claim 3, it is characterised in that: also include the host computer connected with data processor (4) (5)。

5. according to the tester described in claim 3 or 4, it is characterised in that: described signal acquisition circuit (3) is A/D converter, Described data processor (4) is dsp chip.

6. according to the tester described in claim 3 or 4, it is characterised in that: described current detecting unit (1) includes three difference The current transformer (1-1) that the three-phase operating current of described tested electrical equipment is detected the most in real time, described voltage Detector unit (2) include three respectively three-phase operating voltage to described tested electrical equipment detect the most in real time Voltage transformer (2-1).

7. according to the tester described in claim 6, it is characterised in that: described current detecting unit (1) also includes three difference The first signal conditioning circuit (1-2) connected with three described current transformers (1-1) and three respectively described with three first The first low-pass filter circuit (1-3) that signal conditioning circuit (1-2) connects, three described first low-pass filter circuits (1-3) are equal Connect with signal acquisition circuit (3)；Described voltage detection unit (2) also include three respectively with three described voltage transformers (2-1) the secondary signal modulate circuit (2-2) connected and three connect with three described secondary signal modulate circuits (2-2) respectively The second low-pass filter circuit (2-3), three described second low-pass filter circuits (2-3) all connect with signal acquisition circuit (3)； Three described first low-pass filter circuits (1-3) and three described second low-pass filter circuits (2-3) are second-order low-pass filter Circuit, described second-order low-pass filter circuit connects with signal acquisition circuit (3).

8. according to the tester described in claim 7, it is characterised in that: described second-order low-pass filter circuit includes chip U3 and core Sheet U4, described chip U3 and chip U4 are operational amplifier；

The normal phase input end of described chip U3 divides two-way, and a road is ground connection after electric capacity C2, and another road is through resistance R8, electric capacity C1 and electricity Connecting with its inverting input after resistance R10, the wiring point between resistance R8 and electric capacity C1 is described second-order low-pass filter circuit Input；The inverting input of described chip U3 ground connection after resistance R9；

The normal phase input end of described chip U4 divides two-way, and a road is ground connection after electric capacity C4, another road through resistance R12, electric capacity C3 and Connect with its inverting input after resistance R14, the wiring point between resistance R12 and electric capacity C3 after resistance R11 with described chip The output of U3 connects；The inverting input of described chip U4 ground connection after resistance R13, the output of described chip U4 is described The output of second-order low-pass filter circuit and its connect with signal acquisition circuit (3).

9. according to the tester described in claim 8, it is characterised in that: three described first signal conditioning circuits (1-2) and three Individual described secondary signal modulate circuit (2-2) is analog signal conditioner circuit, and described analog signal conditioner circuit includes biasing Circuit and the scaling circuit connected with described biasing circuit, described scaling circuit and described second-order low-pass filter circuit Connect；

Described biasing circuit includes that chip U1, described chip U1 are operational amplifier and its normal phase input end is followed by through resistance R4 Ground；The inverting input of described chip U1 divides three tunnels, a road to connect with its output after resistance R3, and another road is after resistance R2 Meeting bias voltage Vin, the 3rd tunnel output with current transformer (1-1) or voltage transformer (2-1) after resistance R1 connects；

Described scaling circuit includes that chip U2, described chip U2 are operational amplifier and its positive input end grounding；Described The inverting input of chip U2 divides two-way, and a road connects with its output after resistance R6, another road after resistance R5 with chip The output of U1 connects；The output of described chip U2 after resistance R7 with the input phase of described second-order low-pass filter circuit Connect.

10. according to the tester described in claim 9, it is characterised in that: described chip U1, chip U2, chip U3 and chip U4 It is chip OP07.