CN101871975A - System and method for testing cable transfer impedance time domain - Google Patents

Abstract

The invention provides a system for testing a cable transfer impedance time domain. The system comprises a high voltage pulse signal generator for generating an excitation signal; an oscilloscope for receiving an injection signal and a response signal; an attenuator for attenuating the excitation signal; a coaxial structure current probe for observing the injection signal and the response signal at the same time; a coaxial clamp for fixing the tested cable; and an impedance match network. The invention has the following technical effects: (1) the invention is suitable for the time domain testing method, and the frequency domain transfer impedance curve can be acquired through the data process; (2) the injection pulse and the response pulse waveforms can be observed at the same time, and the pulse wave shield effect can be directly acquired; and (3) the acquired model can be applied to the analysis of the cable on the electromagnetic pulse coupling condition.

Description

Cable transfer impedance time domain test macro and method of testing

Technical field

The present invention relates to a kind of test macro and method of testing of cable transfer impedance, specifically, relate to a kind of cable transfer impedance time domain test macro and method of testing.

Background technology

The shielding quality of cable is to weigh the key factor of cable performance, and the surperficial transfer impedance of cable is an important parameter that can reflect the shielding quality of cable relatively objectively, therefore, surperficial transfer impedance to multiple cable is carried out testing research, just can determine the performance quality of these cable shield quality, thereby bring convenience for selecting for use of cable.

Substantially all measuring under frequency domain of present existing cable transfer impedance, the employing point-frequency measurement method that wherein has, the S parameter of directly utilizing network analyzer to carry out that has are analyzed transfer impedance.It has following weak point: when the electromagnetic pulse hardening of assessment shielded cable, test result is directly perceived inadequately on the one hand, and test data also is not easy to the time-domain analysis application on the other hand.

The time domain measurement method that transfer impedance also occurred at present.People such as Zhou Qiming had once designed a kind of time domain measurement device.Can access the transport function of cable transfer impedance by this method, but the used equipment complexity of this method, and used fibre-optic transmission system (FOTS).In addition, test result is still waiting to investigate with the consistance of the frequency domain test method of maturation.In addition along with the widespread use of various composite cables in the engineering, the screen layer of cable and heart yearn are all complicated all the more, the measurement range that existing surperficial transfer impedance measurement mechanism and method of testing can reach has been subjected to challenge, designs a kind ofly to have widely that test specification, more practical method of testing become inevitable development trend.

Summary of the invention

The objective of the invention is to overcome the deficiencies in the prior art part, a kind of new cable transfer impedance time domain test macro and method of testing are provided.

Cable transfer impedance time domain test macro of the present invention comprises following ingredient:

Be used to produce the high-voltage pulse signal generator of pumping signal;

Be used to receive the oscillograph that injects signal and response signal, have and be used to receive passage that injects signal and the passage that receives response signal;

The attenuator of pumping signal is used to decay;

Be used for observing the coaxial configuration current probe that injects signal and response signal simultaneously, have the input port that links to each other with the high-voltage pulse signal generator, monitoring port that links to each other with oscillograph and the output port that links to each other with impedance circuit;

The coaxial anchor clamps that are used for fixing tested cable;

Impedance matching network.

Preferably,

Said high-voltage pulse signal generator is selected from and can produces the forward position less than the two exponential pulse signals of 3ns and the high-voltage pulse signal generator of square-wave signal;

Said coaxial configuration current probe is selected from Luo-coil;

Be with the shielding pipe box on the said coaxial anchor clamps, two ends have BNC connector.

The time domain method of testing of cable transfer impedance of the present invention comprises the following steps:

1) high-voltage pulse takes place: the high-voltage pulse pumping signal that produces amplitude and controlling cycle by the high-voltage pulse signal generator;

2) read pumping signal: export the high-voltage pulse pumping signal that produces in the step 1) monitoring port by the coaxial configuration current probe to oscillograph, receive and injected pulse that the read test system obtains;

3) encourage tested cable: with the high-voltage pulse pumping signal that produces in the step 1), the output port by the coaxial configuration current probe exports the interior circuit of being made up of the screen layer and the heart yearn of tested cable to, and internally circuit applies square-wave signal and encourages;

4) determine impedance matching network: the characteristic impedance and the oscillographic impedance computation of the device that constitutes according to tested cable and coaxial anchor clamps also determined the resistance of resistance in the impedance matching network;

5) receive response signal: will be connected to oscillograph by the external circuit that the screen layer and the coaxial anchor clamps of tested cable are formed, and receive the also response impulse of read test system acquisition;

6) obtain the transfer impedance of tested cable: according to step 2) and the injected pulse and the response impulse of step 5) gained, obtain the transfer impedance of tested cable by computing;

Compute mode is as follows:

Voltage U according to the injected system that measures ₁(t) and in the characteristic impedance R of circuit ₁, the electric current in obtaining in the circuit is:

$I_1\left(t\right)=\frac{U_1\left(t\right)}{R_1}---\left(3\right)$

Respectively with the U that collects ₂(t) and I ₁(t) do Fast Fourier Transform (FFT), obtain the frequency domain value of electric current and voltage

With

Try to achieve the frequency spectrum of the transfer impedance of cable by formula (4);

$Z_t\left(\mathrm{j\ω}\right)=\frac{{\hat{U}}_2\left(\mathrm{j\ω}\right)}{L{\hat{I}}_1\left(\mathrm{j\ω}\right)}---\left(4\right)$

7) set up the transfer impedance computation model: according to step 2) and the injected pulse I of step 5) gained ₁(t) and response impulse U ₂(t), adopt parameter estimation method to obtain the ssystem transfer function model of transfer impedance.

$H\left(z\right)=\frac{b_0+b_1{z}^{-1}+\·\·\·+b_n{z}^{-M}}{1+a_1{z}^{-1}+\·\·\·+a_N{z}^{-N}}$

The principle of work of cable transfer impedance time domain test macro of the present invention is: screen layer and heart yearn by cable are formed interior circuit, the screen layer of tested cable and coaxial anchor clamps are formed external circuit, and then by the electric current of external circuit in measuring and the transfer impedance that voltage method obtains tested cable.

Data processing method of the present invention is: according to the pulse signal that injects test macro and the response impulse of system, the utilization method for parameter estimation is set up the ssystem transfer function model of transfer impedance, be the system of transport function with the injected pulse process with the cable surface transfer impedance again, obtain a new output signal, whether the pulse of contrast original response is consistent with the new output signal that the system that injected pulse passes through to be set up obtains, thereby checking is to the correctness of transfer impedance system that item is built.

Test macro of the present invention and method of testing have following technique effect:

1) the present invention is not only applicable to the time domain method of testing and can obtains frequency domain transfer impedance curve by data processing yet;

2) transfer impedance time domain test macro of the present invention can be observed injected pulse and response impulse waveform simultaneously, can directly obtain the pulsating wave shield effectiveness of cable;

3) model that obtains by time domain tests test method of the present invention and data processing method can be applicable in the analysis of cable to electromagnetic pulse coupling situation.

Description of drawings

Come the present invention is described in further detail below in conjunction with the drawings and specific embodiments.

Fig. 1 is a cable transfer impedance time domain test macro connection diagram;

Fig. 2 is the coaxial configuration current probe inner structure synoptic diagram in the time domain test macro;

Fig. 3 (a) is characteristic impedance Z less than the impedance matching network connection diagram in the time domain test macro of 50 Ω:

Fig. 3 (b) is characteristic impedance Z greater than the impedance matching network connection diagram in the time domain test macro of 50 Ω:

Fig. 4 (a) is the injected pulse of time domain test macro;

Fig. 4 (b) is the response impulse of time domain test macro;

Fig. 5 is the transfer impedance that records of time domain, frequency domain and modeling gained result's contrast.

Embodiment

Embodiment 1

As shown in Figure 1 and Figure 2, cable transfer impedance time domain test macro of the present invention, comprise following ingredient: 1) be used to produce the high-voltage pulse signal generator of pumping signal, used high-voltage pulse signal generator can produce two exponential pulse signals and the square-wave signal of forward position less than 3ns; 2) be used to receive the oscillograph that injects signal and response signal, have and be used to receive passage 1 that injects signal and the passage 2 that receives response signal; 3) be used to the to decay attenuator of pumping signal; 4) be used for observing the coaxial configuration current probe that injects signal and response signal simultaneously, have the input port that links to each other with the high-voltage pulse signal generator, monitoring port that links to each other with oscillograph and the output port that links to each other with impedance circuit; 5) be used for fixing the coaxial anchor clamps of tested cable; Coaxial anchor clamps are cylindrical copper shielded-plate tube covers.These anchor clamps are coaxial with the tested cable that is mounted in it, and two ends all adopt BNC connector to be connected with external device.6) impedance matching network.

The coaxial configuration current probe is a kind of Luo-coil (Rogowski coil, sieve Koffsky coil) of special construction, and the employed Luo-coil skeleton of this current probe is a manganese-zinc ferrite, the skeleton overall dimensions are: external diameter 10mm, internal diameter 6mm, height 5mm, coiling line footpath 0.5mm is altogether around 10 circles; Pull-up resistor is 50 Ω.

Used impedance matching network is used to suppress signal reflex in the cable transfer impedance time domain test macro of the present invention.The instrument port resistance that is adopted in the test all is 50 Ω, if the characteristic impedance and the instrument port of circuit do not match in the test macro, and reflection coefficient is greater than then needing to add this match circuit at 0.2 o'clock.

Embodiment 2

The cable that with the model is SYV 50-3 is an example, adopts test macro of the present invention to measure its transfer impedance, carries out according to the following steps:

1) high-voltage pulse takes place: the high-voltage pulse signal that produces amplitude and controlling cycle by the high-voltage pulse signal generator;

2) read pumping signal: export the high-voltage pulse pumping signal that produces in the step 1) monitoring port by the coaxial configuration current probe to oscillograph, receive and injected pulse that the read test system obtains; Waveform needs amplitude and the oscillographic withstand voltage suitable attenuator decay pumping signal of choosing according to high-voltage pulse signal herein shown in Fig. 4 (a);

3) encourage tested cable: with the high-voltage pulse pumping signal that produces in the step 1), the output port by the coaxial configuration current probe exports the interior circuit of being made up of the screen layer and the heart yearn of tested cable to, and internally circuit applies square-wave signal and encourages;

4) determine impedance matching network: the characteristic impedance of the device that constitutes according to tested cable and coaxial anchor clamps and used oscillographic impedance (being generally 50 Ω) is calculated and definite impedance matching network in the resistance of resistance.

Concrete computing method are: when adding match circuit, if characteristic impedance Z is less than 50 Ω, then the connected mode of match circuit shown in Fig. 3 (a), R wherein _s, R _pBe respectively:

$R_s=50\sqrt{1-\frac{Z}{50}},$ $R_p=\frac{Z}{\sqrt{1-\frac{Z}{50}}}---\left(1\right)$

If characteristic impedance Z is greater than 50 Ω, then the connected mode of match circuit shown in Fig. 3 (b), R wherein _s, R _pBe respectively:

$R_s=Z\sqrt{1-\frac{50}{Z}},$ $R_p=\frac{50}{\sqrt{1-\frac{50}{Z}}}---\left(2\right)$

5) receive response signal: will be connected to oscillograph by the external circuit that the screen layer and the coaxial anchor clamps of tested cable are formed, and receive the also response impulse of read test system acquisition, shown in Fig. 4 (b);

6) obtain the transfer impedance of tested cable: according to the step 2 shown in Fig. 4 (a) and (b)) and the injected pulse and the response impulse of step 5) gained, obtain the transfer impedance of tested cable by computing;

Compute mode is as follows:

Voltage U according to the injected system that measures ₁(t) and in the characteristic impedance R of circuit ₁, the electric current in obtaining in the circuit is:

$I_1\left(t\right)=\frac{U_1\left(t\right)}{R_1}---\left(3\right)$

Because the definition of transfer impedance provides,, need carry out Fourier analysis to measurement data in order to convert from result in time domain in frequency domain.Respectively with the U that collects ₂(t) and I ₁(t) do Fast Fourier Transform (FFT), obtain the frequency domain value of electric current and voltage

With And then can try to achieve the frequency spectrum of the transfer impedance of cable by formula (4).

$Z_t\left(\mathrm{j\ω}\right)=\frac{{\hat{U}}_2\left(\mathrm{j\ω}\right)}{L{\hat{I}}_1\left(\mathrm{j\ω}\right)}---\left(4\right)$

The foundation of transfer impedance computation model: according to step 2) and the injected pulse I of step 5) gained 7) ₁(t) and response impulse U ₂(t), adopt parameter estimation method to obtain the ssystem transfer function model of transfer impedance:

$H\left(z\right)=\frac{{\mathrm{<figure-callout\; id="0"\; label="b"\; filenames="HSA00000164314200022.png"\; state="\{\{state\}\}">b</figure-callout>}}_0+b_1{z}^{-1}+\&CenterDot;\&CenterDot;\&CenterDot;+b_n{z}^{-M}}{1+a_1{z}^{-1}+\&CenterDot;\&CenterDot;\&CenterDot;+a_N{z}^{-N}}$

8) compliance test result

With step 2) input signal that produces is through being the system H (z) of transport function with the cable surface transfer impedance, obtains a new output signal

Contrast original response pulse U ₂(t) the new output signal that obtains of the system that passes through to be set up with injected pulse

Whether consistent, thus checking is to the correctness of transfer impedance system that item is built.

Cable transfer impedance that Fig. 5 records for the cable transfer impedance that adopts cable transfer impedance time domain test macro of the present invention and method of testing and record and traditional frequency domain method and modeling gained result's contrast.Among this figure, solid line a represents the result of time domain approach test, i.e. the result who is measured by method provided by the present invention; Solid line b represents the result of frequency domain test, i.e. the result who is recorded by Excavation Cluster Based on Network Analysis instrument method; Dotted line is represented modeling gained result.Wherein, horizontal ordinate is represented frequency, and ordinate is represented transfer impedance.

By on the figure as can be seen: the amplitude versus frequency characte of the transfer impedance that two kinds of measuring methods and modeling obtain has reached similar effect, the transfer impedance amplitude versus frequency characte that obtains is coincide better, be the alternative existing frequency domain test method of native system and method, and have certain superiority.In addition, modeling result not only can be with utilizing less parameter (M+N+1 parameter) to reflect the Changing Pattern of transfer impedance well, and removed the noise of bringing in the test, can express the amplitude versus frequency characte of cable transfer impedance more accurate, more intuitively.

Claims (5)

1. the cable transfer impedance time domain test macro is characterized in that, comprises following ingredient:

Be used to produce the high-voltage pulse signal generator of pumping signal;

Be used to receive the oscillograph that injects signal and response signal, have and be used to receive passage that injects signal and the passage that receives response signal;

The attenuator of pumping signal is used to decay;

Be used for observing the coaxial configuration current probe that injects signal and response signal simultaneously, have the input port that links to each other with the high-voltage pulse signal generator, monitoring port that links to each other with oscillograph and the output port that links to each other with impedance circuit;

The coaxial anchor clamps that are used for fixing tested cable;

Impedance matching network.

2. cable transfer impedance time domain test macro according to claim 1 is characterized in that, said high-voltage pulse signal generator is selected from and can produces the forward position less than the two exponential pulse signals of 3ns and the high-voltage pulse signal generator of square-wave signal.

3. cable transfer impedance time domain test macro according to claim 1 is characterized in that, said coaxial configuration current probe is selected from Luo-coil.

4. cable transfer impedance time domain test macro according to claim 1 is characterized in that, is with the shielding pipe box on the said coaxial anchor clamps, and two ends have BNC connector.

5. the time domain method of testing of cable transfer impedance is characterized in that, comprises the following steps:

1) high-voltage pulse takes place: the high-voltage pulse pumping signal that produces amplitude and controlling cycle by the high-voltage pulse signal generator;

2) read pumping signal: export the high-voltage pulse pumping signal that produces in the step 1) monitoring port by the coaxial configuration current probe to oscillograph, receive and injected pulse that the read test system obtains;

3) encourage tested cable: with the high-voltage pulse pumping signal that produces in the step 1), the output port by the coaxial configuration current probe exports the interior circuit of being made up of the screen layer and the heart yearn of tested cable to, and internally circuit applies square-wave signal and encourages;

4) determine impedance matching network: the characteristic impedance and the oscillographic impedance computation of the device that constitutes according to tested cable and coaxial anchor clamps also determined the resistance of resistance in the impedance matching network;

5) receive response signal: will be connected to oscillograph by the external circuit that the screen layer and the coaxial anchor clamps of tested cable are formed, and receive the also response impulse of read test system acquisition;

6) obtain the transfer impedance of tested cable: according to step 2) and the injected pulse and the response impulse of step 5) gained, obtain the transfer impedance of tested cable by computing;

Compute mode is as follows:

Voltage U according to the injected system that measures ₁(t) and in the characteristic impedance R of circuit ₁, the electric current in obtaining in the circuit is:

$I_1\left(t\right)=\frac{{\stackrel{\&CenterDot;}{U}}_1\left(t\right)}{R_1}---\left(3\right)$

Respectively with the U that collects ₂(t) and I ₁(t) do Fast Fourier Transform (FFT), obtain the frequency domain value of electric current and voltage With

Try to achieve the frequency spectrum of the transfer impedance of cable by formula (4);

$Z_t\left(\mathrm{j\&omega;}\right)=\frac{{\hat{U}}_2\left(\mathrm{j\&omega;}\right)}{L{\hat{I}}_1\left(\mathrm{j\&omega;}\right)}---\left(4\right)$

7) set up the transfer impedance computation model: according to step 2) and the injected pulse I of step 5) gained ₁(t) and response impulse U ₂(t), adopt parameter estimation method to obtain the ssystem transfer function model of transfer impedance.

$H\left(z\right)=\frac{b_0+b_1{z}^{-1}+\&CenterDot;\&CenterDot;\&CenterDot;+b_n{z}^{-M}}{1+a_1{z}^{-1}+\&CenterDot;\&CenterDot;\&CenterDot;+a_N{z}^{-N}}$

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