CN115902356B - Non-invasive measurement method for high-frequency component of power-on voltage of electric locomotive - Google Patents
Non-invasive measurement method for high-frequency component of power-on voltage of electric locomotive Download PDFInfo
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Abstract
The invention relates to a non-invasive measurement method of a high-frequency component of a power-receiving voltage of an electric locomotive, which comprises the following steps: estimating a parasitic capacitance value of the electric locomotive according to the structure and corresponding parameters of the downlink cable of the electric locomotive obtained in the field; constructing a measuring system, and disposing a current sensor meeting the sensitivity requirement on the ground wire of the shielding sheath; the sensitivity of the current sensor is determined according to the rated power and parasitic capacitance value of the electric locomotive; calibrating the measurement system, and calibrating a transfer function representing the relation between the power-on voltage and the output voltage of the measurement system; determining a high-frequency component of the power receiving voltage of the tested electric locomotive based on the transfer function and the measured value of the measuring system; by means of the core-skin coaxial structure which is stably existing in the pantograph downlink cable, a current sensor is deployed on the ground wire of the shielding sheath, so that the power frequency component with high amplitude and the component with relatively low amplitude but high frequency are separated, and the interference of the traction network background voltage on measurement is greatly reduced.
Description
Technical Field
The invention relates to the field of electric signal characteristic measurement, in particular to a non-invasive measurement method for a high-frequency component of a power receiving voltage of an electric locomotive.
Background
The electric locomotive is influenced by ground subsidence, misoperation and other factors in the running process, the arc net arc discharge phenomenon is easy to occur, and the characteristics of the electric locomotive need to be detected in time and compensation operation is given. The existing arc detection of the electric locomotive bow net shoots the bow net through optical equipment, and whether arc discharge occurs between the bow net and the existing electric locomotive bow net is judged through blue light. The method has the defects that the purchase cost and the subsequent maintenance cost of blue light equipment are high, and the blue light equipment is difficult to comprehensively spread on non-important passenger electric locomotives such as existing line trucks and the like.
In electrical power systems, however, the measurement of electrical quantities is already well established and the price of the equipment is synthesized. If the pantograph voltage of the electric locomotive can be obtained through electric measurement, the electric locomotive pantograph voltage is further used as a basis for analyzing the arc discharge of the pantograph net, and the gap in the aspect of arc detection of the existing wire can be greatly filled. The measurement difficulty of the scheme is two:
firstly, the voltage of the pantograph side of the electric locomotive is up to 25KV, but the voltage is limited by extremely high safety operation standards of the electric locomotive, and the conventional contact type partial pressure measurement scheme is high in scheme risk and difficult to compliance because of contact with the high-voltage side. Therefore, a non-conventional scheme is used to make "non-invasive" measurements of the power-on voltage.
Secondly, the measurement system is difficult to calibrate. Unlike conventional experiments, where various source signals can be manually configured for calibration, the component experimental process in the traction network is uncontrolled. And the high-amplitude power frequency component (background voltage) and the low-amplitude but high-frequency component of the voltage are mixed together, so that the measuring system is difficult to perform targeted efficiency.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a non-invasive measurement method for the high-frequency component of the power-receiving voltage of the electric locomotive, which solves the problem of larger interference caused by the background voltage of a traction network when the high-frequency component of the power-receiving voltage of the electric locomotive is measured.
According to a first aspect of the present invention, there is provided a non-invasive measurement method of a high frequency component of a power supply voltage of an electric locomotive, comprising:
step 2, constructing a measuring system for measuring high-frequency components of the voltage to be received, which comprises the following steps: a current sensor meeting the sensitivity requirement is deployed on the ground wire of the shielding sheath; sensitivity of the current sensor
Determining according to rated power P and parasitic capacitance value C of the electric locomotive;
step 3, calibrating the measurement system, namely calibrating a transfer function representing the relation between the power-on voltage and the output voltage of the measurement system
The method comprises the steps of carrying out a first treatment on the surface of the Based on the transfer function->
And the measured value of the measuring system determines the high-frequency component of the power receiving voltage of the tested electric locomotive.
On the basis of the technical scheme, the invention can also make the following improvements.
Optionally, the sensitivity of the current sensor
The determining method of (1) comprises the following steps: />
wherein ,
and representing the maximum frequency corresponding to the high-frequency component of the power receiving transient voltage of the electric locomotive.
Optionally, the step 3 determines a transfer function of the measurement system
The process of (1) comprises:
step 301, installing a voltage standard device meeting the frequency range requirement and the sensitivity requirement, wherein the voltage standard device is connected between the pantograph end of the electric locomotive and the ground in a bridging way;
step 302, synchronously sampling to obtain a set of waveform data of the voltages output by the voltage standard device and the measurement system, comparing at least two sets of waveform data, and calculating to obtain the transfer function
。
Optionally, the lower cut-off frequency of the voltage standard is not higher than
The upper limit cut-off frequency is not lower than +.>
Sensitivity is +.>
。
Optionally, the step 302 includes:
step 30201, performing windowed Fourier transform on the two sets of waveform data to obtain an output amplitude data sequence of the voltage etalon
Output amplitude data sequence of the measuring system +.>
And a frequency data sequence f constituted based on the sampling rate and the sampling number of the waveform data;
step 30302, from the data sequence
The extracted data form a data array->
In the data sequence
Corresponding data are extracted, and the corresponding data are divided by corresponding values in the frequency data sequence f to obtain a data sequence +.>
；
Step 30303, setting a column representing the data number
And data sequence->
And after obtaining the coefficient of the fitting target model by fitting and solving, determining the transfer function of the measurement system as the fitting target model corresponding to the coefficient.
Optionally, the frequency data sequence
；
wherein ,
，/>
and N is the sampling rate and the sampling times of the waveform data respectively.
Optionally, the extracting data in step 30301 forms a data array
The process of (1) comprises:
selecting a frequency band range, dividing the frequency band range into
A ten-fold sub-band;
within each sub-band, from the data sequence
Corresponding elements are extracted and the larger +.>
Respectively, constitute a data sequence containing m×n elements +.>
。
Optionally, the fitting target model is
Y represents a data sequence +.>
X represents the data sequence +.>
Data of->
and />
For the coefficients to be determined.
According to the non-invasive measurement method for the high-frequency component of the power-on voltage of the electric locomotive, the bow-side voltage is inverted by measuring the current in the incoming wire shielding layer by means of the special core-skin structure of the incoming wire of the electric locomotive. Thanks to the characteristic that the penetration capacity of the high-frequency component in the parasitic capacitance is far higher than that of the power frequency component, the high-frequency component can be highlighted even under the background interference of the power frequency with high amplitude. Aiming at the dilemma that the operation requirement of the electric locomotive is extremely high and the real-time calibration is difficult, the invention provides a calibration method of the measurement system by means of the characteristic that the medium-and high-frequency band transfer functions of the rogowski coil are consistent, and finally realizes the calibration of the measurement system by means of the medium-frequency components specific to the experiment and the traction network in the library.
Drawings
FIG. 1 is a flow chart of a non-invasive measurement method of the high frequency component of the power voltage of an electric locomotive provided by the invention;
fig. 2 is a cross-sectional view of an incoming coaxial cable of an electric locomotive according to an embodiment of the present invention;
FIG. 3 is an equivalent circuit diagram of an openable and closable self-integrating Rogowski coil according to an embodiment of the invention;
FIG. 4 is a schematic diagram of calibration of a measurement system according to an embodiment of the present invention;
fig. 5 is a schematic diagram of an electric locomotive traction network according to an embodiment of the present invention
To->
Schematic diagram of time-frequency domain display of the specific components in (a);
fig. 6 is a flowchart of a screening method for spectral lines in a characteristic frequency domain according to an embodiment of the present invention.
Detailed Description
The principles and features of the present invention are described below with reference to the drawings, the examples are illustrated for the purpose of illustrating the invention and are not to be construed as limiting the scope of the invention.
Fig. 1 is a flow chart of a non-invasive measurement method of a high frequency component of a power receiving voltage of an electric locomotive according to the present invention, as shown in fig. 1, the non-invasive measurement method includes:
and step 1, estimating a parasitic capacitance value C of the electric locomotive according to the structure of the downlink cable of the electric locomotive obtained in the field and the corresponding parameters.
In specific implementation, the parasitic capacitance value C can be estimated by the structure and corresponding parameters of the downlink cable of the electric locomotive obtained in the field and the environment.
Step 2, constructing a measuring system for measuring high-frequency components of the voltage to be received, which comprises the following steps: a current sensor meeting the sensitivity requirement is deployed on the ground wire of the shielding sheath; sensitivity of current sensor
Is determined according to the rated power P and the parasitic capacitance value C of the electric locomotive.
In specific implementation, the current sensor can measure through a non-invasive current probe, and the measuring system can further comprise an analog-digital conversion group, an upper computer and the like which are cascaded with the current sensor, so that the measuring data of the current sensor can be obtained in real time.
Step 3, calibrating the measuring system, namely calibrating a transfer function representing the relation between the power receiving voltage and the output voltage of the measuring system
The method comprises the steps of carrying out a first treatment on the surface of the Based on a transfer function->
And the measured value of the measuring system determines the high-frequency component of the power receiving voltage of the tested electric locomotive.
According to the non-invasive measurement method for the high-frequency component of the power voltage of the electric locomotive, provided by the invention, by means of the core-skin coaxial structure stably existing in the downlink cable of the pantograph, the current sensor is deployed on the ground wire of the shielding skin, so that the power frequency component with high amplitude and the component with relatively low amplitude but high frequency are separated, the measurement of the high-frequency voltage component is converted into the measurement of the current, the interference of the background voltage of the traction network on the measurement is greatly reduced, and the measurement object is highlighted.
Example 1
In the embodiment, the U-I conversion is realized through the inherent structure of the electric locomotive, and further the measurement and detection of the high-frequency voltage component are realized through non-invasive current measurement. In addition, the method reasonably designs the calibration method in the station, and effectively avoids the problems of larger background voltage, difficult calibration and the like in the measurement process. As can be seen in conjunction with fig. 1, an embodiment of the non-invasive measurement method includes:
and step 1, estimating a parasitic capacitance value C of the electric locomotive according to the structure of the downlink cable of the electric locomotive obtained in the field and the corresponding parameters.
Step 2, constructing a measuring system for measuring high-frequency components of the voltage to be received, which comprises the following steps: a current sensor meeting the sensitivity requirement is deployed on the ground wire of the shielding sheath; sensitivity of current sensor
Is determined according to the rated power P and the parasitic capacitance value C of the electric locomotive.
In one possible embodiment, the sensitivity of the current sensor
The determining method of (1) comprises the following steps:
wherein ,
the maximum frequency corresponding to the high-frequency component of the power receiving transient voltage of the electric locomotive is represented. Specifically, the->
The cut-off frequency can be deviated by +/-1% of the maximum frequency, and the frequency response range can cover all high-frequency components in transient voltage in the arc-wire arc process.
Step 3, calibrating the measuring system, namely calibrating a transfer function representing the relation between the power receiving voltage and the output voltage of the measuring system
The method comprises the steps of carrying out a first treatment on the surface of the Based on a transfer function->
And the measured value of the measuring system determines the high-frequency component of the power receiving voltage of the tested electric locomotive.
In one possible exemplary embodiment, the step 3 involves determining a transfer function of the measuring system
The process of (1) comprises:
step 301, installing a voltage standard meeting the frequency range requirement and the sensitivity requirement, wherein the voltage standard is connected between the pantograph end of the electric locomotive and the ground in a bridging way.
In one possible embodiment, the voltage etalon is required to meet the frequency range requirement and the sensitivity requirement, and the lower cut-off frequency (±0.2% deviation) of the voltage etalon is not higher than
The upper cutoff frequency (+ -0.2% deviation) is not lower than
Sensitivity is +.>
。
wherein ,
representing the maximum frequency corresponding to the high frequency component of the power-on transient voltage of the electric locomotive, < >>
Representing the minimum frequency corresponding to the high-frequency component of the power-receiving transient voltage of the electric locomotive.
Step 302, synchronously sampling to obtain a set of waveform data of the voltage output by the voltage standard device and the measurement system, comparing based on at least two sets of waveform data, and calculating to obtain a transfer function
。
In the specific implementation, the voltage standard device executes the ascending access (or descending cutting) operation of the pantograph, and synchronously records the waveform data of the output voltages of the voltage standard device and the measuring system in the sampling process by means of the acquisition card and the upper computer, and the sampling rate
The sampling depth is not less than 16 bit and the data volume of the two groups of waveforms is +.>
And is not less than 20000.
In one possible embodiment, step 302 includes:
step 30201, performing windowed Fourier transform on the two sets of waveform data to obtain an output amplitude data sequence of the voltage etalon
Output amplitude data sequence of measuring system +.>
And a frequency data sequence f constituted based on the sampling rate and the sampling number of the waveform data.
Step 30302, from the data sequence
The extracted data form a data array->
In the data sequence->
Extracting corresponding data from the sequence, dividing the corresponding data by corresponding values in the frequency data sequence f, and constructing a data array
。
In one possible embodiment, the process of extracting data in step 30301 includes:
selecting a frequency band range, and setting the frequency band range
Divided into->
And tens of frequency sub-bands.
Within each sub-band, a slave data sequence
Corresponding elements are extracted and the larger +.>
Respectively, constitute a data sequence containing m×n elements +.>
。
The data array
And data sequence->
For sensitivity estimation, in particular, the numbers may be +.>
、
、/>
… …, specifically:
step 30303, setting a column representing the data number
And data sequence->
And after obtaining the coefficient of the fitting target model by fitting and solving the fitting target model, determining the transfer function of the measurement system as the fitting target model corresponding to the coefficient.
In one possible embodiment, the fitting of the target model is
Y represents a data array
X represents the data sequence +.>
Data of->
and />
For the coefficients to be determined.
In particular, the data sequence
And data sequence->
For parameter->
、/>
Can be fit to solve for two unknown coefficients +.>
and />
The values of (2) are +.>
and />
And further acquiring a transfer function of the measurement system.
At a frequency of
The corresponding components are, for example, the power supply voltage +.>
Output of measuring system->
The relationship between may be:
example 2
Embodiment 2 provided by the present invention is a specific application embodiment of a method for non-invasive measurement of a high frequency component of a power receiving voltage of an electric locomotive provided by the present invention, and as can be seen from fig. 1, the specific application embodiment of the non-invasive measurement method includes:
and step 1, estimating a parasitic capacitance value C of the electric locomotive according to the structure and corresponding parameters of the downlink cable of the electric locomotive obtained in the field.
In this embodiment, taking an electric locomotive of a certain HXDXX model in a middle China as an example, through boarding preliminary measurement, it can be known that the incoming cable part of the model can be divided into 3 sections (including radian bending), and as shown in table 1, the values of various parameters of the incoming cable parts obtained through measurement are shown in the table:
TABLE 1 values of various parameters for various portions of incoming cable
Wherein q=1, 2 or 3 represents the respective section of which,
weight coefficient representing the q-th section cable, < ->
The equivalent length of the q-th section cable is shown, and the 2 nd section is the cable bending part.
By looking up the type of the matched cable of the electric locomotive, the internal structure of the cable is shown in fig. 2. Specific parameters are as follows: radius of copper conductor
6.45mm shielding layer radius from the axis +.>
=16.75 mm. Relative dielectric constant of insulating material
. By combining the above data, stray capacitance estimates can be calculated.
Step 2, constructing and measuring the power receiving voltageA measurement system for high frequency components, comprising: a current sensor meeting the sensitivity requirement is deployed on the ground wire of the shielding sheath; sensitivity of the current sensor
And determining according to the rated power P and the parasitic capacitance value C of the electric locomotive.
Referring to the information about the electric locomotive and literature, the rated power of the electric locomotive of the model is known
. The frequency corresponding to the transient voltage component can be up to +.>
=200 MHz. Thus, the gains required to complete the measurement are: />
In view of the fact that the current sensor is "non-invasive" in the embodiments of the present invention, the probe should be designed as an openable rogowski coil. Since the ground current of the shielding layer is characterized by high frequency and small amplitude, the gain of the probe and the frequency band covered by the probe are important design targets. Based on this consideration, the core is designed as a "nanocrystalline" material with high magnetic permeability, its relative permeability
. The equivalent circuit model is shown in figure 2. According to the design principle of the rogowski coil, the current sensor conforming to the gain can be designed according to the following parameters:
(1) the number of turns of the coil is 16.
(2) Two layers of nano crystals are stacked to be as high as
Is a structure of (a).
(3) The ends are connected in parallel
Load resistorAnd (3) resistance.
(4) Inner radius of rogowski coil winding
=56 mm, outer radius ∈>
=74mm。
The actual value of the gain calculated based on the above parameters is about
=3.1631 V/A。
In practice, the difference between the actual gain value and the design value can be corrected by the digital processing part.
Fig. 4 is a schematic diagram of calibration of a measurement system according to an embodiment of the present invention, and as can be seen from fig. 4, a current sensor is disposed on an in-ground line of a shielding sheath, and a stray capacitance of a shielding layer is equivalent between the in-ground line and a pantograph end of an electric locomotive. The voltage standard device is directly connected between the pantograph end of the electric locomotive and the ground in a bridging way.
After the equipment is installed, the signal output of the probe and the etalon is extended to a synchronous acquisition system controlled by NI 8841. In the measuring system based on the NI platform, the signal waveform of the measuring system and the waveform of the voltage standard device obtained by the acquisition card are respectively recorded as
、/>
The lengths are ∈>
。
Step 3, calibrating the measurement system, namely calibrating a transfer function representing the relation between the power-on voltage and the output voltage of the measurement system
The method comprises the steps of carrying out a first treatment on the surface of the Based on the transfer function->
And the measured value of the measuring system determines the high-frequency component of the power receiving voltage of the tested electric locomotive.
First, the waveforms of the measurement system and the etalon are subjected to windowed fourier transform to obtain frequency domain information of both:
wherein ,
、/>
the length of the signal is N, which is the signal of the measuring system and the standard device respectively. k is the frequency index of the signal,
。/>
the window functions used for the windowing process, here exemplified by Hann windows, are:
after windowing and Fourier transformation are completed, frequency domain information is properly processed to obtain a frequency spectrum with physical significance:
as can be seen from practical investigation, when the pantograph of the electric locomotive is contacted with the traction network, the electric locomotive is in a circuit
To the point of
Abnormal components exist in the frequency band, as shown in fig. 5. Therefore, in the calibration process, the component is taken as an observation object to passThe "sensitivity estimation data series" is collated by the flowchart shown in fig. 6, and the result is shown in the sensitivity estimation data series in table 2.
TABLE 2 sensitivity estimation data array
In Table 2, it will
Is integrated with all the values of (2) to obtain +.>
A plurality of columns; will->
And->
One-to-one correspondence of the quotient is that the result is integrated>
And (5) a plurality of columns. Based on this, a fitting objective function can be constructed>
. To->
As a function +.>
The method comprises the steps of carrying out a first treatment on the surface of the To->
As a function +.>
The data are carried into the function to be fitted, and the method can be solved:
finally, the calibration of the whole measurement system can be completed based on the real load:
wherein ,
for the system to measure the amplitude of the signal at fHz, f is the observed frequency, +.>
Is the inversion result at fHz. Packaging the coefficients of the intermediate process to obtain a transfer function at the frequency fHz>
。
The arc-drawing phenomenon of the pantograph and the traction net of the electric locomotive can be caused by a plurality of factors such as misoperation, ageing of the pantograph body and the like, and the arc-drawing phenomenon is easy to become a hidden trouble of net burning if the arc-drawing phenomenon is not identified. The high-frequency signal characteristics caused by the electric arc are measured in real time, so that hazard exacerbation can be effectively prevented. Aiming at the high-frequency component of the voltage, the non-invasive measurement method of the high-frequency component of the power receiving voltage of the electric locomotive provided by the embodiment of the invention inverts the bow-side voltage by measuring the current in the incoming wire shielding layer by means of the special core-skin structure of the incoming wire of the electric locomotive. Thanks to the characteristic that the penetration capacity of the high-frequency component in the parasitic capacitance is far higher than that of the power frequency component, the high-frequency component can be highlighted even under the background interference of the power frequency with high amplitude. Aiming at the dilemma that the operation requirement of the electric locomotive is extremely high and the real-time calibration is difficult, the invention provides a calibration method of the measurement system by means of the characteristic that the medium-and high-frequency band transfer functions of the rogowski coil are consistent, and finally realizes the calibration of the measurement system by means of the medium-frequency components specific to the experiment and the traction network in the library.
The measurement system to be calibrated is made to observe the same component as the etalon, i.e. the medium frequency component specific to 1kHz to 10kHz in the traction network, by in-library experiments. Under the frequency band, the standard device can calibrate the probe of the measuring system, and further the calibration result of the intermediate frequency part is extended to the high frequency band where the electric arc is located by means of the characteristic that the transfer function of the Rogowski coil probe has consistency at the intermediate frequency and the high frequency.
In particular, the method is different from the non-invasive technical patent in the existing electric locomotive field, is a real-time and quantitative measurement for the high-frequency component of the electric signal, and has application fields not limited to fault judgment. And is a real-time measurement on-board, and is not limited to a space between certain two split-phase sections.
In summary, the coaxial structure of the incoming cable of the electric locomotive is skillfully utilized, the arc characteristic component is extracted from the large background voltage, and the measuring system is calibrated through reasonable in-house experiments, so that the operation specification of the electric locomotive is met, and the whole set of scheme is practically feasible.
In the foregoing embodiments, the descriptions of the embodiments are focused on, and for those portions of one embodiment that are not described in detail, reference may be made to the related descriptions of other embodiments.
It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (6)
1. A method for non-intrusive measurement of a high frequency component of a received voltage of an electric locomotive, the method comprising:
step 1, estimating a parasitic capacitance value C of an electric locomotive according to a structure and corresponding parameters of a downlink cable of the electric locomotive obtained in the field;
step 2, constructing a measuring system for measuring high-frequency components of the voltage to be received, which comprises the following steps: a current sensor meeting the sensitivity requirement is deployed on the ground wire of the shielding sheath; sensitivity of the current sensor
Determining according to rated power P and parasitic capacitance value C of the electric locomotive;
step 3, calibrating the measurement system, namely calibrating a transfer function representing the relation between the power-on voltage and the output voltage of the measurement system
The method comprises the steps of carrying out a first treatment on the surface of the Based on the transfer function->
And the measured value of the measuring system determines the high-frequency component of the power receiving voltage of the tested electric locomotive;
sensitivity of the current sensor
The determining method of (1) comprises the following steps:
wherein ,
representing the maximum frequency corresponding to the high-frequency component of the power-receiving transient voltage of the electric locomotive;
determining a transfer function of the measurement system in the step 3
The process of (1) comprises:
step 301, installing a voltage standard device meeting the frequency range requirement and the sensitivity requirement, wherein the voltage standard device is connected between the pantograph end of the electric locomotive and the ground in a bridging way;
step 302, synchronously sampling to obtain a set of waveform data of the voltages output by the voltage standard device and the measurement system, comparing at least two sets of waveform data, and calculating to obtain the transfer function
。
2. The non-invasive measurement method according to claim 1, wherein the lower cut-off frequency of the voltage etalon is not higher than
The upper limit cut-off frequency is not lower than +.>
Sensitivity is +.>
。
3. The non-invasive measurement method according to claim 1, wherein said step 302 comprises:
step 30201, performing windowed Fourier transform on the two sets of waveform data to obtain an output amplitude data sequence of the voltage etalon
Output amplitude data sequence of the measuring system +.>
And a frequency data sequence f constituted based on the sampling rate and the sampling number of the waveform data;
step 30302, from the data sequence
The extracted data form a data array->
In the data sequence->
Corresponding data are extracted, and the corresponding data are divided by corresponding values in the frequency data sequence f to obtain a data sequence +.>
；
Step 30303, setting a column representing the data number
And data sequence->
And after obtaining the coefficient of the fitting target model by fitting and solving, determining the transfer function of the measurement system as the fitting target model corresponding to the coefficient.
4. A non-invasive measurement method according to claim 3, characterized in that the frequency data sequence
；
wherein ,
，/>
and N is the sampling rate and the sampling times of the waveform data respectively.
5. A non-invasive measurement method according to claim 3, wherein the extracted data in step 30301 constitutes a data array
The process of (1) comprises:
selecting a frequency band range, dividing the frequency band range into
A ten-fold sub-band;
within each sub-band, from the data sequence
Corresponding elements are extracted and the larger +.>
Respectively, constitute a data sequence containing m×n elements +.>
。
6. A non-invasive measurement method according to claim 3, wherein the fitted target model is
Y represents a data sequence +.>
X represents the data sequence +.>
Data of->
And
for the coefficients to be determined. />
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