CN101339234A - Portable CVT error measurement method and device - Google Patents

Abstract

The invention relates to an error testing method for a portable CVT (a capacitor voltage transformer) and a device thereof. The technical proposal of the invention comprises a portable on-site testing method of a CVT error, the analysis of the component elements of the CVT error, a principle that the CVT error is measured by a low-pressure process and the conversion principle of high-and-low voltage side excitation resistance in pilot frequency. The portable on-site measuring device of the CVT error measures the error under 2 percent of rated voltage, the transformation ratio of the CVT and a medium-voltage transformer. A 5Hz pilot frequency signal is input; an accurate hardware circuit is designed to be used for measuring a secondary excitation resistance on a secondary side; and a software algorithm module is built up to reckon the excitation resistance of a CVT primary side when the CVT is in a high voltage. The hardware designed by the invention has little circuits and is easy to be modulated. A micro-computer processing system can be used for realizing the automatic measurement of the parameter of a transformer. When measuring the CVT error, the error testing method and the device thereof provided by the invention can implement the rapid on-site measurement of the difference and the angular difference of the CVT without requiring a large-sized voltage booster, a high-grade standard of the voltage transformer and a loading box.

Description

Portable CVT error measurement method and device

Technical field

The invention belongs to the fields of measurement of high-voltage mutual inductor measuring parameter, relate to Portable CVT (capacitance type potential transformer) error testing method and device specifically.

Background technology

Along with the continuous expansion of electric system transmission line capability, the line voltage grade progressively raises, and novel capacitance type potential transformer is used more and more widely in middle and high piezoelectricity net.The CVT of domestic production even also export to ground such as Southeast Asia, Europe and the U.S..Along with generating plant and electrical network (power transmission and transformation system) are progressively kept separate accounts, the accuracy of critical point electric energy metrical is increasingly important, CVT is as one of important composition of electric power meter, the accuracy of its translation data and rationality are directly connected to the calculating of total errors of electric energy countings, the economic interests that are related to generating plant, electrical network and user are so must carry out accuracy test to CVT.

Just begun CVT site error verification work the nineties in last century, most measuring method that adopts series connection or parallel resonance to boost, need configuration increasing apparatus (step-up transformer, tuning coil, tuning capacity), error of measurement loop equipment such as (standard potential transformer, testers), test wiring complexity, required device category are various, heavy, difficult, the on-the-spot installation not only wasted time and energy, and has potential safety hazard.Because CVT capacitive load big (maximum can reach several ten thousand pF), required testing transformer and the capacity of power supply is big, electric pressure is high so site test is very difficult, can't carry out field-checking even sometimes.Therefore the on-line monitoring project of CVT has been studied by some mechanisms, by or monitoring three-phase voltage, electric current and harmonic content etc. negative to leakage capacity current, dielectric loss angle, secondary voltage and the secondary of CVT, judge whether operate as normal of CVT indirectly, but can not provide the exact value of CVT error.At present, also do not have relevant documents and materials to propose the on-the-spot portable type measuring method of CVT error, more do not have whole measuring system.

Goal of the invention

The objective of the invention is at the deficiencies in the prior art, propose to adopt the alien frequencies design proposal, the method and the measurement mechanism of in-site measurement CVT error, and a kind of Portable CVT error measurement method and device that adopts converter technique, digitized processing proposed, solve and on-the-spotly be difficult to measure or the problem of energy measurement CVT error not.

To achieve these goals, the method applied in the present invention is:

First step: the no-load voltage ratio of measuring error, CVT and middle pressure transformer under 2% rated voltage

At first, on the primary side of CVT, apply 0.5% and 2% rated voltage.For the CVT of 500kV, its rated voltage of 2% is 10kV, so the stepup transformer that check system is joined 10kV in needing.Measure the no-load error of CVT under 0.5% and 2% rated voltage according to classic method

An admittance Y ₅And Y ₂₀Global error under (comprising excitation admittance and drain capacitance admittance) and 2% rated voltage

, release Z ₁Simultaneously, according to the once survey voltage U 1 of CVT, measure the voltage U 2 at secondary side, calculate the no-load voltage ratio value, this no-load voltage ratio is the no-load voltage ratio of whole C VT, adopts and measures this no-load voltage ratio value with the method for standard transformation mutual inductor error of measurement, and precision can guarantee 0.02%; After the carrier communication δ terminal of CVT untied, C1 and C2 parallel connection, the parallel connected end of C1 and C2 applies the voltage of 10kV;

Second step: measure and proofread and correct the variable frequency excitation admittance

Apply voltage and the voltage of 5Hz, 10V and the voltage of 5Hz, 12V of 5Hz, 8V, excitation admittance value Y80`, Y100` and the Y120` of the secondary side when measuring frequency conversion at secondary side; Consider the CVT for different materials, the excitation admittance under the different voltages with 50Hz of 5Hz may not be equal fully, needs the measurement update coefficient; Apply 5Hz at secondary side, the voltage of 2V, measure Y20``, apply the voltage of 50Hz, 20V then at secondary side, measure Y20`, calculate the correction coefficient Km of excitation admittance: then according in the no-load voltage ratio k2 of pressure transformer, Y80`, Y100` and Y120` are converted primary side admittance value Y80, Y100, Y120, calculate difference DELTA Y with the Y20 admittance ₈₀, Δ Y ₁₀₀, Δ Y ₁₂₀, release error difference by admittance value

With

Third step: composition error is calculated

By the error difference under sum of errors under the 2% rated voltage point 80%, 100% and 120% rated voltage, calculate no-load error and the load error of CVT under 80%, 100% and 120% rated voltage, by frequency on hardware design circuit and temperature measuring circuit, calculate the additive error under on-the-spot mains frequency and the temperature respectively, with no-load error and load error addition, just calculate the composition error of CVT automatically then.

The present invention is according to said method, and the present invention also provides a kind of device:

A kind of CVT error testing device, constitute by digital signal processor (DSP), signal input unit and host computer, wherein DSP interconnects with signal input unit and host computer respectively, be characterized in: DSP also measures the loop with a frequency measurement loop and a no-load voltage ratio and is connected, and is connected with a power amplification circuit by D/A (D/A) converter.

Above-mentioned signal input unit is a two-way, and wherein one the tunnel is the differential pressure signal of CVT, and another road is a voltage source signal, and two paths of signals is connected with DSP by sample circuit, amplifying circuit, filtering circuit and A/D (mould/number) converter respectively successively.

The filtering circuit that above-mentioned voltage source signal is passed through also is connected with DSP by 90 degree phase-shift circuits and phase discriminator.

The excitation impedance conversion relation of the present invention during for different-frequency measure adopted the ANSYS simulation software to carry out emulation, and carried out site test, and conclusion is: frequency is high more, and excitation impedance is more little, and same frequency is parallel, and be linear.Adopt the error of this measuring method in-site measurement CVT, the test simple and fast; Owing to have the measure of software and hardware anti-interference process, the in-site measurement data accurately and reliably; Built-in large database and memory function have the many and big characteristics of memory capacity of process information amount, are convenient to the long preservation data.The test macro volume is little, be easy to carry; on-the-spot test is very convenient; can improve the quality and the efficient of maintenance; strengthen the specific aim of maintenance; save lot of manpower and material resources, prolong the time between overhauls(TBO), improve the equipment availability coefficient; but reduce stop time and startup-shutdown number of times, prolong the serviceable life of equipment.Adopt low frequency method in-site measurement CVT error, start a new direction in mutual inductor parameter measurement field.

The hardware circuit of the present invention design is few, be convenient to debugging, can realize the automatic measurement of mutual inductor parameter with microprocessor system.When using this method to measure the CVT error, do not need bulky increasing apparatus, do not need high-grade voltage transformer (VT) standard, do not need Burden box, can realize ratio, the angular difference of the on-the-spot CVT of test fast.

Description of drawings

Fig. 1 is the capacitance type potential transformer equivalent circuit diagram.

Fig. 2 is the T type equivalent circuit diagram of PT (voltage transformer (VT)).

Fig. 3 is the theory diagram of apparatus of the present invention.

Fig. 4 is a software flow pattern of the present invention.

Among Fig. 1, X _C-equivalent capacitance (C ₁+ C ₂) reactance; X _T1, X _T2The leakage reactance (converting primary side) of '-middle pressure transformer one Secondary Winding; R ₁Winding of-middle pressure transformer and compensation reactor winding D.C. resistance and capacitive divider loss substitutional resistance sum (R ₁=R _C+ R _K+ R _T1); R ₂The direct current resistance (converting primary side) of '-middle pressure transformer Secondary Winding; Z _mThe excitation impedance of-middle pressure transformer; X _kThe reactance of-compensation reactor.

Among Fig. 2, Ym is primary circuit excitation admittance, and Y is the admittance of voltage transformer (VT) actual load, Z ₁` is an impedance of voltage transformer (VT) and secondary impedance, Z ₁Vector value for primary circuit resistance, reactance value and electric capacity; Z ₂' be the resistance and the reactance value of secondary circuit.

Embodiment

The present invention will be further described in detail below in conjunction with accompanying drawing.

Before method of testing of the present invention is described again, the CVT error by principle is carried out following description.

1) CVT error analysis

Capacitance type potential transformer mainly partly is made up of capacitive divider, intermediate transformer, compensation reactor and damper etc., and back three parts are generically and collectively referred to as electromagnetic unit.Formation characteristics according to CVT, error division following (supply frequency variation, temperature variation, electric capacitance change etc. all can impact the error of CVT, are referred to as additive error) for the sum of errors temperature variation of voltage divider error, electromagnetic unit error and the supply frequency of CVT.

A, voltage divider error

When high-voltage capacitance C1 and middle piezoelectricity hold the actual value of C2 and ratings when unequal, will produce error.

$f_c=\frac{C_{1n}}{C_{1n}+C_{2n}}-\frac{C_1}{C_1+C_2}$

${\mathrm{\δ}}_c=\frac{C_1}{C_1+C_2}({\mathrm{tg\δ}}_2-{\mathrm{tg\δ}}_1)\×{3440}^{\′}$

B, electromagnetic unit error

The electromagnetic unit winding of CVT has internal impedance, exists no-load error; When the CVT secondary connects load, also exist load error.The error of CVT mainly causes that by no-load error and the load branch circuit that excitatory branch road causes the load error of (comprise damper load) forms.No-load error is because no-load current I _mIn an impedance, produce voltage drop Δ U ₀Cause.

${\mathrm{\ΔU}}_0=I_0\{R_1+j[{\mathrm{\ω}}_n(L_{T1}+L_K)-\frac{1}{{\mathrm{\ω}}_n(C_1+C_2)}\left]\right\}$

Load error is by load current I ₂The voltage drop Δ U that on impedance loop, produces _LCause.

$\mathrm{\Δ}{U}_L=I_2\{(R_1+{R_2}^{\′})+j[{\mathrm{\ω}}_n(L_k+L_{T1}+{L^{\′}}_{T2})-\frac{1}{{\mathrm{\ω}}_n(C_1+C_2)}\left]\right\}$

C, additive error

When mains frequency changed, the capacitive reactance of CVT will change from opposite direction with induction reactance, produced the frequency additive error.

ω _nThe specified angular frequency of-electrical network; ω-electrical network actual angular frequency; P-active power, kW; The Q-reactive power, kW; U '-specified middle piezoelectricity is pressed kV; The C-equivalent capacitance.

When environment temperature changed, the electric capacity of capacitor also can be along with changing, and this is the basic reason that temperature causes additive error.

In this measuring method, ceiling voltage is 10kV only, so ignore the influence of high-voltage connection to error.

As can be seen from the above analysis, the total error of CVT is as follows:

f＝f _k+f _f+f _ω+f _τ

δ＝δ _k+δ _f+δ _ω+δ _τ

f _k, δ _kBe no-load error, f _f, δ _fBe load error, f _ω, δ _ωBe frequency error, f _τ, δ _τBe temperature error.Measure no-load error and load error respectively so the composition error of CVT can adopt, measure frequency and variation of temperature simultaneously and calculate frequency error and temperature error, last addition draws the composition error of CVT.

2) low-pressure process is measured CVT error principle

X with primary side in the equivalent circuit of capacitance type potential transformer _c, X _k, X _T1And R ₁Carry out addition Z ₁Replace.

Z ₁＝X _C+X _K+X _T1+R ₁

X with secondary side in the equivalent circuit diagram of capacitance type potential transformer _T2' and R ₂' carry out addition, use Z then ₂' replace:

Z ₂′＝X _T′+R ₂′

The equivalent circuit of the capacitance type potential transformer common PT equivalent circuit that will become so, promptly common electromagnetic potential transformer T type equivalent electrical circuit, its error is made up of no-load error and load error two parts

$\widetilde{\mathrm{\ϵ}}=\widetilde{{\mathrm{\ϵ}}_c}+\widetilde{{\mathrm{\ϵ}}_f}=-Y_m{Z}_1-Y(Z_1+{Z_2}^{\′})$

Ym is primary circuit excitation admittance, Y _m=1/Z _m, be the primary circuit admittance, be a nonlinear element, relevant with impressed voltage, Y is the admittance of voltage transformer (VT) actual load, Z ₁` is an impedance of voltage transformer (VT) and secondary impedance.Z ₁Be the vector value of primary circuit resistance, reactance value and electric capacity, can regard constant as, Z ₂' be the resistance and the reactance value of secondary circuit, also can constant.So, and under correspondent voltage, measure Ym and Z as long as under low pressure measure error ₁, Z ₂' etc. parameter, just can calculate the error of voltage transformer (VT).But for high voltage potential transformer, its no-load error also comprises the error that is caused by equivalent drain capacitance admittance, promptly

${\widetilde{\mathrm{\ϵ}}}_k=-Y_m{Z}_1-Y_c{Z}_1$

So can choose 2 points arbitrarily (generally get 5% and 20% rated voltage), record the Voltage Transformer error

With an admittance Y ₅And Y ₂₀(comprising excitation admittance and drain capacitance admittance), and get the difference of twice measurement result

$\mathrm{\Δ}{\widetilde{\mathrm{\ϵ}}}_k={\widetilde{\mathrm{\ϵ}}}_{k20}-{\widetilde{\mathrm{\ϵ}}}_{k5}$

ΔY＝Y ₂₀-Y ₅

Connection and following formula can be released

$\mathrm{\Δ}{\widetilde{\mathrm{\ϵ}}}_k={\widetilde{\mathrm{\ϵ}}}_{k20}-{\widetilde{\mathrm{\ϵ}}}_{k5}=-(Y_{20}-Y_5)Z_1,$ Promptly

$Z_1=-\frac{\mathrm{\Δ}{\widetilde{\mathrm{\ϵ}}}_k}{\mathrm{\ΔY}}$

Then, measuring admittance Y80, a Y100, Y120 for 80%, 100% and 120% time, calculate difference DELTA Y with the Y20 admittance ₈₀, Δ Y ₁₀₀, Δ Y ₁₂₀, release error difference by admittance value:

$\mathrm{\Δ}{\widetilde{\mathrm{\ϵ}}}_{k80}={\mathrm{\ΔY}}_{80}\×Z_1$

$\mathrm{\Δ}{\widetilde{\mathrm{\ϵ}}}_{k100}={\mathrm{\ΔY}}_{100}\×Z_1$

$\mathrm{\Δ}{\widetilde{\mathrm{\ϵ}}}_{k120}=\mathrm{\Δ}{Y}_{120}\×Z_1$

Simultaneously, be chosen under 20% the rated voltage and measure global error (comprising no-load error and load error), calculate the error of voltage transformer (VT) under 80%, 100%, 120% by error difference again, promptly apply low-voltage at secondary side, measure Y80, Y100, the Y120 of primary side voltage:

${\widetilde{\mathrm{\ϵ}}}_{80}=\mathrm{\Δ}{\widetilde{\mathrm{\ϵ}}}_{k80}+{\widetilde{\mathrm{\ϵ}}}_{20}$

${\widetilde{\mathrm{\ϵ}}}_{100}=\mathrm{\Δ}{\widetilde{\mathrm{\ϵ}}}_{k100}+{\widetilde{\mathrm{\ϵ}}}_{20}$

${\widetilde{\mathrm{\ϵ}}}_{120}=\mathrm{\Δ}{\widetilde{\mathrm{\ϵ}}}_{k120}+{\widetilde{\mathrm{\ϵ}}}_{20}$

When taking off limited load, measuring error is the lower limit load error; When capping was loaded, measuring error was a upper limit load error; When getting rated load, measuring error is the rated load error.Low-pressure process that Here it is is measured the high-voltage mutual inductor error by principle.

3) high and low pressure side excitation impedance conversion principle during alien frequencies

Constituted the primary circuit between the low-voltage capacitance of CVT and compensation reactor etc. and the middle pressure transformer, when the secondary side at CVT applies the alternating voltage of 50Hz, might form resonant tank at primary side, the high pressure winding of pressure transformer in causing burning out, and when the carrier communication δ terminal of CVT is untied, its maximum withstand voltage 3KV that is generally.So, consider to apply 5Hz, be lower than the alternating voltage of 20V at secondary side, adopt method that alien frequencies boosts at the admittance value of measuring admittance Y80, a Y100, Y120 for 80%, 100% and 120% time.

According to the relation between magnetic flux and the potential:

E＝4.44fNΦ

Φ is the magnetic flux of magnetic circuit, and f is a frequency, and N is the number of turn of coil, and E is an electromotive force.During for zero load, electromotive force approximates voltage.So, can think roughly that the voltage of secondary side is the excitation admittance equivalence that 50Hz, 120V and 5Hz, 12V equivalence produce.So apply the voltage of 5Hz, 8V at secondary side, measure Y80; Apply the voltage of 5Hz, 10V, measure Y100; Apply the voltage of 5Hz, 12V, measure Y120.

According to foregoing description, concrete grammar of the present invention is:

1) no-load voltage ratio of error, CVT and the middle pressure transformer under measurement 2% rated voltage

At first, on the primary side of CVT, apply 0.5% and 2% rated voltage.For the CVT of 500kY, its rated voltage of 2% is 10kY, so the stepup transformer that check system is joined 10kY in needing.Measure the no-load error of CVT under 0.5% and 2% rated voltage according to classic method

An admittance Y ₅And Y ₂₀Global error under (comprising excitation admittance and drain capacitance admittance) and 2% rated voltage

Release Z ₁

Simultaneously, according to the once survey voltage U 1 of CVT, measure the voltage U 2 at secondary side, calculate the no-load voltage ratio value, this no-load voltage ratio is the no-load voltage ratio of whole C VT, adopts and measures this no-load voltage ratio value with the method for standard transformation mutual inductor error of measurement, and precision can guarantee 0.02%.

U1/U2＝K1

After the carrier communication δ terminal of CVT untied, C1 and C2 parallel connection (promptly becoming the equivalent circuit of CVT), the parallel connected end of C1 and C2 applies the voltage of 10kV.

K2＝U1`/U2

2) measure and proofread and correct the variable frequency excitation admittance

Apply voltage and the voltage of 5Hz, 10V and the voltage of 5Hz, 12V of 5Hz, 8V, excitation admittance value Y80`, Y100` and the Y120` of the secondary side when measuring frequency conversion at secondary side.

Consider the CVT for different materials, the excitation admittance under the different voltages with 50Hz of 5Hz may not be equal fully, needs the measurement update coefficient.

Apply 5Hz at secondary side, the voltage of 2V is measured Y20``.Apply the voltage of 50Hz, 20V then at secondary side, measure Y20`.Calculate the correction coefficient Km of excitation admittance:

Km＝Y20`/Y20``

The no-load voltage ratio k2 of pressure transformer in the basis converts primary side admittance value Y80, Y100, Y120 with Y80`, Y100` and Y120` then.Calculate difference DELTA Y with the Y20 admittance ₈₀, Δ Y ₁₀₀, Δ Y ₁₂₀, release error difference by admittance value

With

3) composition error is calculated

By the error difference under sum of errors under the 2% rated voltage point 80%, 100% and 120% rated voltage, can calculate no-load error and the load error of CVT under 80%, 100% and 120% rated voltage.By frequency on hardware design circuit and temperature measuring circuit, calculate the additive error under on-the-spot mains frequency and the temperature respectively, then with no-load error and load error addition, just can calculate the composition error of CVT automatically.

Whole device of the present invention is controlled by 32 bit DSPs (digital signal processor).

The DSP output signal by D/A converter power controlling amplifying circuit, produces the voltage source of frequency variation signal and 10kV.

The no-load voltage ratio metering circuit adopts 24 A/D, guarantees 0.02% measuring accuracy.

The differential pressure signal of CVT (with the difference of inductive voltage divider) and voltage source signal enter A/D converter by sampling, amplification and filter circuit and measure, and signal input part also adopts magnetic bead etc. to carry out Anti-interference Design.

Middle fracture by DSP carries out frequency measurement, by the temperature sensor measurement temperature.

Carry out communication by DSP control RTL8019 chip and host computer.

Slave computer software of the present invention is write by the C language, the data rough handling after the output of control transfer relay, voltage source and the A/D sampling, and adopt ICP/IP protocol to write signal procedure.

Host computer adopts C++ to write functions such as data filtering, Error Calculation, waveform demonstration, data storage and data printing based on win2000 operating system.

The course of work of the present invention is:

The first step, with the A of measuring system, the two ends that the X terminal is connected to CVT, a, x are connected to secondary side, and X and x short circuit are selected to begin to measure.Instrument begins to boost automatically and while auditory tone cues user notes handling safety.Reality shows the no-load error value of current magnitude of voltage and mutual inductor during instrument, records no-load error, load error and the no-load voltage ratio of tested mutual inductor, and system is depressurized to zero-bit automatically then, finishes first step test.

In second step, with high-pressure side A, X and x short circuit, a, x are connected to secondary side.The magnitude of voltage when in real time measuring alien frequencies during instrument and the excitatory admittance of mutual inductor, instrument be from boosting to the excitatory admittance that each rules point records mutual inductor, calculates the sum of errors underloading error under the rated load of each rules point.

The 3rd step, survey frequency and temperature.

In the 4th step, data transmission is calculated composition error to host computer, shows all data and waveform, storage or print data.

The content that is not described in detail in this instructions belongs to this area professional and technical personnel's known prior art.

Claims (4)

1, a kind of Portable CVT error method of testing, its method is:

First step: the no-load voltage ratio of measuring error, CVT and middle pressure transformer under 2% rated voltage

At first, on the primary side of CVT, apply 0.5% and 2% rated voltage.For the CVT of 500kV, its rated voltage of 2% is 10kV, so the stepup transformer that check system is joined 10kV in needing.Measure the no-load error of CVT under 0.5% and 2% rated voltage according to classic method

An admittance Y ₅And Y ₂₀Global error under (comprising excitation admittance and drain capacitance admittance) and 2% rated voltage

Release Z ₁Simultaneously, according to the once survey voltage U 1 of CVT, measure the voltage U 2 at secondary side, calculate the no-load voltage ratio value, this no-load voltage ratio is the no-load voltage ratio of whole C VT, adopts and measures this no-load voltage ratio value with the method for standard transformation mutual inductor error of measurement, and precision can guarantee 0.02%; After the carrier communication δ terminal of CVT untied, C1 and C2 parallel connection, the parallel connected end of C1 and C2 applies the voltage of 10kV;

Second step: measure and proofread and correct the variable frequency excitation admittance

Apply voltage and the voltage of 5Hz, 10V and the voltage of 5Hz, 12V of 5Hz, 8V, excitation admittance value Y80`, Y100` and the Y120` of the secondary side when measuring frequency conversion at secondary side; Consider the CVT for different materials, the excitation admittance under the different voltages with 50Hz of 5Hz may not be equal fully, needs the measurement update coefficient; Apply 5Hz at secondary side, the voltage of 2V, measure Y20``, apply the voltage of 50Hz, 20V then at secondary side, measure Y20`, calculate the correction coefficient Km of excitation admittance: then according in the no-load voltage ratio k2 of pressure transformer, Y80`, Y100` and Y120` are converted primary side admittance value Y80, Y100, Y120, calculate difference DELTA Y with the Y20 admittance ₈₀, Δ Y ₁₀₀, Δ Y ₁₂₀, release error difference by admittance value With

Third step: composition error is calculated

By the error difference under sum of errors under the 2% rated voltage point 80%, 100% and 120% rated voltage, calculate no-load error and the load error of CVT under 80%, 100% and 120% rated voltage, by frequency on hardware design circuit and temperature measuring circuit, calculate the additive error under on-the-spot mains frequency and the temperature respectively, with no-load error and load error addition, just calculate the composition error of CVT automatically then.

2, a kind of CVT error testing device, constitute by digital signal processor (DSP), signal input unit and host computer, wherein DSP interconnects with signal input unit and host computer respectively, it is characterized in that: DSP also measures the loop with a frequency measurement loop and a no-load voltage ratio and is connected, and is connected with a power amplification circuit by D/A converter.

3, CVT error testing device as claimed in claim 2, it is characterized in that: signal input unit is a two-way, wherein one the tunnel is the differential pressure signal of CVT, another road is a voltage source signal, and two paths of signals is connected with DSP by sample circuit, amplifying circuit, filtering circuit and A/D converter respectively successively.

4, CVT error testing device as claimed in claim 3 is characterized in that: the filtering circuit that voltage source signal is passed through also is connected with DSP by 90 degree phase-shift circuits and phase discriminator.

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