CN113985338A - Primary loop optimization and modeling method for field broadband test of direct current transformer - Google Patents
Primary loop optimization and modeling method for field broadband test of direct current transformer Download PDFInfo
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Abstract
The application provides a primary loop optimization and modeling method for a field broadband test of a direct current transformer, which comprises the steps of hanging a lead on a tubular bus through a hoop; finishing one-time test wire hanging in a direct current field, connecting the direct current field with a high-frequency and step current source, receiving a standard signal by a direct current electronic transformer calibrator, and receiving an FT3 digital message output by a control room merging unit through an optical fiber to finish calculation and analysis of related indexes of the direct current transformer; the impedance of the test primary loop is reduced; the load required by the test is reduced, the test current is unchanged, and the loop area is reduced. The method and the device can effectively reduce the capacity of the test broadband current source, remarkably improve the working efficiency of the field broadband test of the direct current transformer, protect the safety of primary equipment, reduce the length of a primary loop of the test and reduce the test operation risk of other equipment.
Description
Technical Field
The application relates to the technical field of direct current transformers, in particular to a primary loop optimization and modeling method for a field broadband test of a direct current transformer.
Background
After a circuit for the grounding electrode fails, the safe operation of a direct current transmission system is influenced, meanwhile, hidden dangers exist for human and animal safety along the circuit for the grounding electrode, but the broadband measurement performance of the direct current transformer used for quickly sensing and accurately transmitting and transforming fault information in the converter station is particularly important for the operation of the grounding electrode. In practical engineering, the direct current transformer needs to have a strong broadband measurement capability while meeting the direct current component transmission accuracy, and particularly, in a flexible direct current transmission system, the requirements on step response and harmonic transmission characteristic indexes of the direct current transformer are high. In the related standards promulgated by the country, the requirements of corresponding indexes are also made on the error precision, the frequency response and the step response of the direct current transformer.
In terms of engineering, generally, a direct current transformer is over ten meters away from the ground, a plurality of strands of primary test large current wires are heavy, and if a plurality of strands of primary test large current wires are connected in series from connecting wires such as a tube bus, damage to primary equipment due to overweight of the test wires or improper operation in the test process is possible. In view of the above reasons, in the field broadband test of the direct current transformer, the anchor ear is used for hanging the conducting wire on the tubular bus, so that the primary equipment is safe, and the length of the primary loop of the test can be reduced according to the requirement. Meanwhile, in order to prevent the signal of the test loop from being connected into the non-test loop in series, the direct current transformer and other primary equipment are separated and disconnected as much as possible, so that the risks of test operation and the like of other equipment are reduced.
Disclosure of Invention
The application provides a primary loop optimization and modeling method for a field broadband test of a direct current transformer, which aims to solve the problems that a common direct current transformer is over ten meters away from the ground, a multi-strand large-current primary test wire is heavy, and if the multi-strand large-current primary test wire is connected in series from a connecting wire such as a tube bus, the damage of primary equipment caused by the overweight of the test wire or misoperation in the test process is possible.
On the one hand, the application provides a primary loop optimization method for a field broadband test of a direct current transformer, which comprises the following steps:
a lead is hung on the pipe bus through a hoop;
finishing one-time test wire hanging in a direct current field, connecting the direct current field with a high-frequency and step current source, receiving a standard signal by a direct current electronic transformer calibrator, and receiving an FT3 digital message output by a control room merging unit through an optical fiber to finish calculation and analysis of related indexes of the direct current transformer;
the impedance of the test primary loop is reduced;
the load required by the test is reduced, the test current is unchanged, and the loop area is reduced.
Optionally, the step of completing the calculation analysis of the related indexes of the direct current transformer includes that a test wire is hooked in the direct current field and connected to the high-frequency and step current source, the direct current electronic transformer calibrator receives the standard signal and receives the FT3 digital message output by the control room merging unit through the optical fiber:
the complex frequency domain expression of the primary loop impedance of the direct current transformer broadband characteristic test is as follows:
Z(s)＝R+sL(s) (1)
in the formula, s is j omega, the inductive reactance is increased along with the increase of the frequency, the resistance is not changed greatly along with the frequency, and the impedance in the primary test loop is increased along with the increase of the frequency.
Optionally, the step of reducing the impedance of the test primary loop includes:
under the condition that the power supply power cannot be increased, the impedance of a primary loop of the test is reduced, the field broadband test current rising process of the direct current transformer can be equivalent to a single-turn coil passing through a time-varying electromagnetic field, and the integral expression of the relation between induced electromotive force and magnetic flux change in the loop is as follows:
the above formula shows that the variable magnetic field generates a variable electric field, the larger the right loop area of the equation is, the larger the suppression effect of the inductance is, and the above formula is changed into a differential form by the stokes theorem:
the property of the induction electric field is different from that of the electrostatic field or the stable electric field; in the case of a static field, due to
Namely, it is
The value is also 0, namely when the accuracy test of the direct current transformer is carried out, the primary loop is easy to carry out large current rising, and the rising is difficult during the broadband test;
for a simple single turn round loop, if the radius r of the wire is tested at one time0Much smaller than the loop radius r, the circular loop inductance is then approximately:
the magnetic permeability mu value in the above formula is obtained through magnetic field intensity and magnetic density or vacuum magnetic permeability and relative magnetic permeability, the circular loop inductance and the loop area are in a direct proportion relation, the influence of the wire radius on the inductance is small, and then the simple square loop inductance is as follows:
the simple rectangular loop single turn coil loop inductance is:
optionally, the step of reducing the load required by the test, the test current being unchanged, and the loop area includes:
the method comprises the following steps that firstly, broadband test equipment is moved to the position near a detected direct current transformer through an overhead working truck, and the loop area is reduced; and secondly, the primary lead is twisted and wound to reduce the loop area, so that a tester does not need to operate on an overhead working truck.
Optionally, the step of reducing the load required by the test, the test current being unchanged, and the loop area further includes:
obtaining the equivalent resistance and the resistance R of the tested direct current transformerctAnd LctObtaining equivalent resistance and inductance R of standard shunt in high frequency and step current sourcebAnd Lb；
Acquiring relevant parameters under the shapes of the primary loops of different tests,
if the test primary loop is circular, the radius of the circle is r, wherein the radius r of the primary test lead is0Calculating the equivalent inductance L according to the formula (4)dObtaining R of a primary test loop through a resistance testerdCalculating the equivalent impedance Z of the primary loop when the frequency required by the test loading is large or small through the primary loop impedance complex frequency domain expression (1)YX；
If the primary loop is square, the side length is w, wherein the radius r of the primary test wire0Calculating the equivalent inductance L according to the formula (5)dObtaining R of a primary test loopdCalculating the equivalent impedance Z of the primary loop when the frequency required by the test loading is obtained through the primary loop impedance complex frequency domain expressionZFX；
If the test is rectangular, the width a and the length b are obtained, wherein the radius r of the wire is tested at one time0Calculating the equivalent inductance L according to a formuladObtaining R of a primary test loopdCalculating the equivalent impedance Z of the primary loop when the frequency required by the test loading is obtained through the primary loop impedance complex frequency domain expressionJX；
Obtaining the impedance of different test primary circuits under the same test current frequency, drawing the impedance schematic diagram of the test primary circuits under the frequency change, and comparing ZZFX、ZJX、ZYXAnd selecting the smallest primary wiring loop which is the final test, and performing the field broadband test of the direct current transformer.
On the other hand, the method for modeling the primary loop in the field broadband test of the direct current transformer comprises the steps of combining the two engineering solutions provided in the above, selecting a primary loop wiring method with a smaller test loop, and establishing a primary loop equivalent model.
According to the technical scheme, the method for optimizing and modeling the primary loop of the field broadband test of the direct current transformer comprises the steps of hanging a lead on a pipe bus through a hoop; finishing one-time test wire hanging in a direct current field, connecting the direct current field with a high-frequency and step current source, receiving a standard signal by a direct current electronic transformer calibrator, and receiving an FT3 digital message output by a control room merging unit through an optical fiber to finish calculation and analysis of related indexes of the direct current transformer; the impedance of the test primary loop is reduced; the load required by the test is reduced, the test current is unchanged, and the loop area is reduced.
The method and the device can effectively reduce the capacity of the test broadband current source, remarkably improve the working efficiency of the field broadband test of the direct current transformer, protect the safety of primary equipment, reduce the length of a primary loop of the test and reduce the test operation risk of other equipment.
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In order to more clearly explain the technical solution of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious to those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of a field synchronous testing scheme provided herein;
fig. 2 is a schematic diagram of a wideband testing system for a dc transformer provided in the present application;
fig. 3 is an equivalent schematic diagram of impedance of a primary loop in a broadband test of the dc current transformer provided by the present application;
FIG. 4 is a schematic diagram of a primary loop impedance test with frequency variation provided herein;
FIG. 5 is a schematic diagram of the dimensions of a one-time test rectangular loop provided herein;
FIG. 6 is a schematic diagram of the load power required for the test at different current values and loop areas provided by the present application;
FIG. 7 is a schematic diagram of two possible field solutions for reducing the loop area provided by the present application;
FIG. 8 is a schematic diagram of a field test connection of frequency response of a DC current transformer provided herein;
fig. 9 is a schematic diagram of a calibrator platform recording a dc current transformer frequency response test waveform provided herein;
fig. 10 is a schematic diagram of an error curve of the dc current transformer provided in the present application.
Detailed Description
Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following examples do not represent all embodiments consistent with the present application. But merely as exemplifications of systems and methods consistent with certain aspects of the application, as recited in the claims.
Referring to fig. 1, a schematic diagram of a field synchronous testing scheme provided by the present application includes: controlling a direct current broadband current signal source device through an upper computer to generate a direct current source and a harmonic current source; the method comprises the following steps that a front-end unit acquires standard signals, digital signals of a direct current transformer to be tested are led out through optical fibers and sent to a broadband test system, and error data calculation and analysis of the direct current transformer are carried out; a direct current transformer broadband characteristic field synchronous test system for a grounding electrode is designed, and a test of steady-state accuracy, frequency response and direct current component superposition alternating current component transmission and transformation characteristics of a direct current transformer is carried out. The output of the direct current transformer adopted by the current engineering is mostly a digital interface, and the transmitted current value is a primary current value, so that the principle of a direct comparison method is needed during field test. In combination with field engineering, the method for testing the broadband characteristic of the direct current transformer under the large span range is provided in the text as shown in fig. 1.
Referring to fig. 2, for the schematic diagram of the wideband test system for the dc transformer provided by the present application, the front-end unit acquires and obtains a standard signal, a digital signal of the dc transformer to be tested is led out by an optical fiber, and the digital signal is sent to the wideband test system, and the steps of calculating and analyzing error data of the dc transformer include:
the direct current transformer to be tested is connected with a high-stability direct current source, the high-stability direct current source generates direct current and passes through the direct current comparator, the electronic direct current transformer calibrator receives standard secondary signals of the direct current comparator through the multi-type signal acquisition receiving unit, digital signals of the merging unit of the protection control room are transmitted to the tested digital interface of the calibrator, and the upper computer completes error calculation of the direct current transformer.
When the frequency response of the direct current transformer is carried out, the upper computer controls the signal generator to convert the simulated test signal into a primary small voltage signal, the power amplifier amplifies a primary large current according to the small voltage signal, and a high-frequency current standard signal is obtained through standard voltage sampling. The calibrator is driven by the synchronous signal to obtain the standard signal and the digital signal to be tested, and the calculation of parameters such as frequency response amplitude error, phase error and the like is completed.
The high-stability direct-current source comprises an upper computer, a signal generator, a power amplifier and a back-extraction part, wherein the upper computer simulation module sets current sampling points at different test points by setting signals required by different tests and outputs real-time simulation sampling instantaneous value data with a high sampling rate; the high-precision shunt is a high-power high-precision resistor.
The upper computer simulation module sets current sampling points at different test points by setting signals required by different tests, simulates step length of 2 mu s, and can output real-time simulation sampling instantaneous value data with high sampling rate. During field test, the output of a high-frequency signal source can be configured by adopting dynamic current test software, the high-frequency signal source can output a small analog quantity voltage signal of harmonic waves and direct current superposed harmonic waves, and a corresponding primary current quantity is generated by a power amplifier. The primary current is output to the tested object, and the secondary small voltage is output through the internal converter. The secondary small voltage is connected to the front unit and is verified by the optical fiber communication and direct current electronic transformer verification system so as to verify the tested object. In addition, the high-precision shunt is a high-power high-precision resistor, the bearing power can reach 5kW, the resistance value is 10m omega, and the resistor precision is superior to 0.2%. Because the accuracy of the power amplifier and the shunt can not ensure the absolute accuracy of the output current, in order to ensure the accuracy during verification, the calibrator ensures the accuracy of the test system by performing real-time high-accuracy 'back mining' on the output signal, and the whole AD acquisition accuracy reaches 0.05 level.
In the converter station, the installation position of the earth electrode direct current transformer is farthest from a protection control room compared with other transformers, so that a synchronous verification method based on dual-channel optical fiber transmission of absolute delay is adopted. In addition, in a field test of the converter station, factors such as electromagnetic interference, self noise of test equipment, weak secondary analog quantity of a standard source and the like increase the difficulty of accurately extracting direct-current components and harmonic signals. In order to facilitate the smooth development of the broadband characteristic test of the direct current transformer on the site, the requirement for acquisition of direct current components and acquisition of broadband signals are considered when the front unit of the calibrator is designed. Therefore, the front unit which gives consideration to the acquisition of different analog quantity signals is designed, and the accuracy, frequency response and step response integrated calibration system of the direct current transformer is constructed.
The leading unit gathers and obtains standard signal, draws the digital signal of being surveyed direct current transformer by the optic fibre, sends to wide band test system, and the step of carrying out direct current transformer error data calculation and analysis still includes:
the calibration instrument acquires synchronous acquisition of a standard signal and a digital signal of a tested mutual inductor, calculates and analyzes a message to acquire a primary value of the standard signal and the digital signal of the tested mutual inductor, accurately extracts the amplitude and the phase of the signal when calculating the frequency response precision for two indexes of an amplitude error and a phase error which reflect the frequency characteristics, and calculates a ratio error and a phase error according to the amplitude and phase information of the standard harmonic signal and the tested harmonic signal; defining the current error fn of the direct current transformer for measuring the fundamental current or the nth harmonic component as follows:
k is the rated transformation ratio of the direct current transformer; i is1nIs the root mean square value of the nth harmonic component of the primary current, and represents the fundamental component when n is equal to 1; i is2nIs the root mean square value of the nth harmonic component of the secondary current of the direct current transformer, and represents a base when n is equal to 1A wave component; phase error delta of harmonic current transformernIs defined as the primary current phasor I1nPhasor with secondary current I2nThe phasor direction is determined by taking the phase difference of an ideal current transformer as zero when the secondary current phasor I2nLeading primary current phasor I1nThe phase difference is positive when the phase difference is positive, and negative when the phase difference is negative.
Generally, a direct current transformer is over ten meters away from the ground, a plurality of strands of test large-current primary leads are heavy, and if a plurality of strands of test large-current primary leads are connected in series from connecting leads such as a tube bus, primary equipment damage caused by overweight of the test leads or misoperation in the test process is possible. In view of the practical consideration of the engineering, in the field broadband test of the direct current transformer, the anchor ear is used for hanging the conducting wire on the tubular bus, so that the primary equipment is safe, and the length of the primary loop of the test can be reduced according to the requirement. In addition, in order to prevent the signal of the test loop from being connected into the non-test loop in series, the direct current transformer and other primary equipment are separated and disconnected as much as possible, and therefore risks of test operation and the like of other equipment are reduced.
On the one hand, the application provides a primary loop optimization method for a field broadband test of a direct current transformer, which comprises the following steps:
a lead is hung on the pipe bus through a hoop;
finishing one-time test wire hanging in a direct current field, connecting the direct current field with a high-frequency and step current source, receiving a standard signal by a direct current electronic transformer calibrator, and receiving an FT3 digital message output by a control room merging unit through an optical fiber to finish calculation and analysis of related indexes of the direct current transformer;
the impedance of the test primary loop is reduced;
the load required by the test is reduced, the test current is unchanged, and the loop area is reduced.
Further, the step of completing the calculation analysis of the related indexes of the direct current transformer comprises the following steps of completing the hooking of a test wire in a direct current field, connecting the test wire with a high-frequency and step current source, receiving a standard signal by a direct current electronic transformer calibrator, and receiving an FT3 digital message output by a merging unit of a control room through an optical fiber:
the complex frequency domain expression of the primary loop impedance of the direct current transformer broadband characteristic test is as follows:
Z(s)＝R+sL(s) (1)
in the formula, s is j omega, the inductive reactance is increased along with the increase of the frequency, the resistance is not changed greatly along with the frequency, and the impedance in the primary test loop is increased along with the increase of the frequency.
Further, the step of reducing the impedance of the test primary loop comprises:
under the condition that the power supply power cannot be increased, the impedance of a primary loop of the test is reduced, the field broadband test current rising process of the direct current transformer can be equivalent to a single-turn coil passing through a time-varying electromagnetic field, and the integral expression of the relation between induced electromotive force and magnetic flux change in the loop is as follows:
the above formula shows that the variable magnetic field generates a variable electric field, the larger the right loop area of the equation is, the larger the suppression effect of the inductance is, and the above formula is changed into a differential form by the stokes theorem:
the property of the induction electric field is different from that of the electrostatic field or the stable electric field; in the case of a static field, due to
Namely, it is
The value is also 0, namely when the accuracy test of the direct current transformer is carried out, the primary loop is easy to carry out large current rising, and the rising is difficult during the broadband test;
for a simple single turn circular loop, if one triesRadius r of wire inspection0Much smaller than the loop radius r, the circular loop inductance is then approximately:
the magnetic permeability mu value in the above formula is obtained through magnetic field intensity and magnetic density or vacuum magnetic permeability and relative magnetic permeability, the circular loop inductance and the loop area are in a direct proportion relation, the influence of the wire radius on the inductance is small, and then the simple square loop inductance is as follows:
the simple rectangular loop single turn coil loop inductance is:
further, the step of reducing the load required by the test, the test current being constant, and the loop area comprising:
the method comprises the following steps that firstly, broadband test equipment is moved to the position near a detected direct current transformer through an overhead working truck, and the loop area is reduced; and secondly, the primary lead is twisted and wound to reduce the loop area, so that a tester does not need to operate on an overhead working truck.
Further, the step of reducing the load required by the test, the test current being unchanged, and the loop area further includes:
obtaining the equivalent resistance and the resistance R of the tested direct current transformerctAnd LctObtaining equivalent resistance and inductance R of standard shunt in high frequency and step current sourcebAnd Lb；
Acquiring relevant parameters under the shapes of the primary loops of different tests,
if the test primary loop is circular, the radius of the circle is r, wherein the radius r of the primary test lead is0Root of Chinese characterCalculating the equivalent inductance L according to the formula (4)dObtaining R of a primary test loop through a resistance testerdCalculating the equivalent impedance Z of the primary loop when the frequency required by the test loading is large or small through the primary loop impedance complex frequency domain expression (1)YX；
If the primary loop is square, the side length is w, wherein the radius r of the primary test wire0Calculating the equivalent inductance L according to the formula (5)dObtaining R of a primary test loopdCalculating the equivalent impedance Z of the primary loop when the frequency required by the test loading is obtained through the primary loop impedance complex frequency domain expressionZFX；
If the test is rectangular, the width a and the length b are obtained, wherein the radius r of the wire is tested at one time0Calculating the equivalent inductance L according to a formuladObtaining R of a primary test loopdCalculating the equivalent impedance Z of the primary loop when the frequency required by the test loading is obtained through the primary loop impedance complex frequency domain expressionJX；
Obtaining the impedance of different test primary circuits under the same test current frequency, drawing the impedance schematic diagram of the test primary circuits under the frequency change, and comparing ZZFX、ZJX、ZYXAnd selecting the smallest primary wiring loop which is the final test, and performing the field broadband test of the direct current transformer.
On the other hand, the method for modeling the primary loop in the field broadband test of the direct current transformer comprises the steps of combining the two engineering solutions provided in the above, selecting a primary loop wiring method with a smaller test loop, and establishing a primary loop equivalent model.
Referring to fig. 3, an equivalent schematic diagram of impedance of a primary loop for a wideband test of a dc current transformer provided by the present application, and referring to fig. 4, a schematic diagram of impedance of a primary loop for a test under frequency change provided by the present application, where R is a dashed box in the diagramctAnd LctFor the detected DC current transformer equivalent resistance, inductance, RdAnd LdFor testing equivalent inductance and resistance, R, of high-current multi-strand braided wire and other elements of loopbAnd LbIn high-frequency and step current sourcesEquivalent resistance and inductance of a standard shunt. P1And P2The current flows from the polar end and the non-polar end of the direct current transformer1To P2. If the direct current transformer is subjected to a steady-state calibration test, namely, only aiming at a direct current component transmission characteristic test and the traffic-isolated direct action of an inductor, the fact that the impedance of a primary test loop only has a resistance component is not difficult to find, so that the power required by the port is not large during the test, even if the primary test loop is long, the current rise is relatively easy during field detection, and particularly the error test current rise of the current transformer in a GIS pipeline under the power frequency is easy to be large.
Referring to fig. 5, a is a width of a rectangle, b is a length of the rectangle, r is a radius of a conducting wire, and generally r is much smaller than the length and the width of the rectangle, and a dimension diagram of a rectangular loop for one test provided by the present application can be expressed as:
taking the change of the loop area under the frequency of 50Hz and the change of the required test power supply load as an example, the selected test lead is calculated to be a copper lead with the sectional area of 400mm2, the line distance is the size b in the test line size schematic diagram, the size a in the line size schematic diagram is considered according to 2 meters, and the approximate load power loss is shown in fig. 6.
Referring to fig. 6, a schematic diagram of load power required for the test under different current values and loop areas is provided for the present application, and as the loop area and the test current increase, the required current source power also increases continuously. In order to reduce the load required by the test in the field and reduce the loop area as much as possible under the condition that the test current is unchanged, two engineering solutions are generally provided, see fig. 7, which is a schematic diagram of two field feasible schemes for reducing the loop area provided by the application. In another method, the primary lead is twisted and wound, so that the loop area is reduced as much as possible, and a tester does not need to operate on an overhead working truck. As can be seen from fig. 7, the two schemes can actually achieve reduction of the loop area, and only for field tests, a suitable scheme is selected in consideration of factors such as installation positions of transformers, field test operation techniques, safety risk management and control of testers and the like. According to the experience of carrying out the direct current transformer test on site, the broadband test equipment is carried or hoisted into the overhead working car hopper with narrow space, so that the operation difficulty is high, if the test needs a small current and the broadband test load meets the requirement, the second scheme is suggested to be adopted, and the test requirement can be generally met.
Example (b):
referring to fig. 8, for the schematic diagram of the wiring of the dc current transformer frequency response field test provided by the present application, the area of the primary loop should be as small as possible when the frequency response of the dc current transformer on the ground is carried out on the field, referring to fig. 9, a schematic diagram of the calibration instrument platform recording the waveform of the dc current transformer frequency response test provided by the present application is shown, wherein the experimental data is shown in table 1:
TABLE 1 high frequency test results
In order to be more suitable for actual field engineering, a test of superposing the direct current component and the alternating current component of the direct current transformer at the internal connection point of the converter station is carried out on the field, and the result is shown in table 2.
TABLE 2 test results
Referring to fig. 10, a schematic diagram of an error curve of the dc current transformer provided by the present application can be seen from table 2, that both the transmitted and transformed ac component and the dc component thereof meet the requirements of the regulations. In addition, the error accuracy of different channels output by the merging unit of the direct current transformer is tested, and it can be seen that the accuracy of the direct current transformer of the grounding electrode meets the requirement of 0.2 level when the rated current is 1 to 100 percent. Although the current divider is the same, the error results of the two channels are different because the remote modules are independent respectively, but the whole error trends are consistent, in view of the above situation, field verification can be carried out on rated current percentages one by one when a direct current system is powered off, and the error coefficient of the merging unit is adjusted according to the test result so as to achieve the purpose that the errors of the channels are consistent as much as possible.
The method for optimizing and modeling the primary loop of the field broadband test of the direct current transformer comprises the steps of hanging a lead on a pipe bus through a hoop; finishing one-time test wire hanging in a direct current field, connecting the direct current field with a high-frequency and step current source, receiving a standard signal by a direct current electronic transformer calibrator, and receiving an FT3 digital message output by a control room merging unit through an optical fiber to finish calculation and analysis of related indexes of the direct current transformer; the impedance of the test primary loop is reduced; the load required by the test is reduced, the test current is unchanged, and the loop area is reduced. The method and the device can effectively reduce the capacity of the test broadband current source, remarkably improve the working efficiency of the field broadband test of the direct current transformer, protect the safety of primary equipment, reduce the length of a primary loop of the test and reduce the test operation risk of other equipment.
While there have been shown and described what are at present considered the fundamental principles and essential features of the application, and advantages thereof, it will be apparent to those skilled in the art that the application is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
The embodiments provided in the present application are only a few examples of the general concept of the present application, and do not limit the scope of the present application. Any other embodiments extended according to the scheme of the present application without inventive efforts will be within the scope of protection of the present application for a person skilled in the art.
Claims (6)
1. A primary loop optimization method for a field broadband test of a direct current transformer is characterized by comprising the following steps:
a lead is hung on the pipe bus through a hoop;
finishing one-time test wire hanging in a direct current field, connecting the direct current field with a high-frequency and step current source, receiving a standard signal by a direct current electronic transformer calibrator, and receiving an FT3 digital message output by a control room merging unit through an optical fiber to finish calculation and analysis of related indexes of the direct current transformer;
the impedance of the test primary loop is reduced;
the load required by the test is reduced, the test current is unchanged, and the loop area is reduced.
2. The method for optimizing the primary loop of the on-site broadband test of the direct current transformer according to claim 1, wherein the step of completing the hooking of a test wire in the direct current field, connecting the test wire to a high-frequency current source and a step current source, receiving a standard signal by a direct current electronic transformer calibrator, and completing the calculation and analysis of the related indexes of the direct current transformer by receiving an FT3 digital message output by a merging unit of a control room through an optical fiber comprises the following steps:
the complex frequency domain expression of the primary loop impedance of the direct current transformer broadband characteristic test is as follows:
Z(s)＝R+sL(s) (1)
in the formula, s is j omega, the inductive reactance is increased along with the increase of the frequency, the resistance is not changed greatly along with the frequency, and the impedance in the primary test loop is increased along with the increase of the frequency.
3. The method for optimizing the field broadband test primary loop of the direct current transformer according to claim 1, wherein the step of reducing the impedance of the test primary loop comprises the following steps:
under the condition that the power supply power cannot be increased, the impedance of a primary loop of the test is reduced, the field broadband test current rising process of the direct current transformer can be equivalent to a single-turn coil passing through a time-varying electromagnetic field, and the integral expression of the relation between induced electromotive force and magnetic flux change in the loop is as follows:
the above formula shows that the variable magnetic field generates a variable electric field, the larger the right loop area of the equation is, the larger the suppression effect of the inductance is, and the above formula is changed into a differential form by the stokes theorem:
the property of the induction electric field is different from that of the electrostatic field or the stable electric field; in the case of a static field, due to
Namely, it is
The value is also 0, namely when the accuracy test of the direct current transformer is carried out, the primary loop is easy to carry out large current rising, and the rising is difficult during the broadband test;
for a simple single turn round loop, if the radius r of the wire is tested at one time0Much smaller than the loop radius r, the circular loop inductance is then approximately:
the magnetic permeability mu value in the above formula is obtained through magnetic field intensity and magnetic density or vacuum magnetic permeability and relative magnetic permeability, the circular loop inductance and the loop area are in a direct proportion relation, the influence of the wire radius on the inductance is small, and then the simple square loop inductance is as follows:
the simple rectangular loop single turn coil loop inductance is:
4. the method for optimizing the primary loop of the field broadband test of the direct current transformer according to claim 1, wherein the step of reducing the load required by the test, keeping the test current constant, and reducing the loop area comprises the steps of:
the method comprises the following steps that firstly, broadband test equipment is moved to the position near a detected direct current transformer through an overhead working truck, and the loop area is reduced; and secondly, the primary lead is twisted and wound to reduce the loop area, so that a tester does not need to operate on an overhead working truck.
5. The method for optimizing the primary loop of the field broadband test of the direct current transformer according to claim 4, wherein the step of reducing the load required by the test, keeping the test current constant, and reducing the loop area further comprises:
obtaining the equivalent resistance and the resistance R of the tested direct current transformerctAnd LctObtaining equivalent resistance and inductance R of standard shunt in high frequency and step current sourcebAnd Lb；
Acquiring relevant parameters under the shapes of the primary loops of different tests,
if the test primary loop is circular, the radius of the circle is r, wherein the radius r of the primary test lead is0Calculating the equivalent inductance L according to the formula (4)dObtaining R of a primary test loop through a resistance testerdCalculating the equivalent impedance Z of the primary loop when the frequency required by the test loading is large or small through the primary loop impedance complex frequency domain expression (1)YX；
If the primary loop is square, the side length is w, wherein the radius r of the primary test wire0Calculating the equivalent inductance L according to the formula (5)dObtaining R of a primary test loopdCalculating the equivalent impedance Z of the primary loop when the frequency required by the test loading is obtained through the primary loop impedance complex frequency domain expressionZFX；
If the test is rectangular, the width a and the length b are obtained, wherein the radius r of the wire is tested at one time0Calculating the equivalent inductance L according to a formuladObtaining R of a primary test loopdCalculating the equivalent impedance Z of the primary loop when the frequency required by the test loading is obtained through the primary loop impedance complex frequency domain expressionJX；
Obtaining the impedance of different test primary circuits under the same test current frequency, drawing the impedance schematic diagram of the test primary circuits under the frequency change, and comparing ZZFX、ZJX、ZYXAnd selecting the smallest primary wiring loop which is the final test, and performing the field broadband test of the direct current transformer.
6. A primary loop modeling method for a field broadband test of a direct current transformer is characterized in that a primary loop wiring method with a smaller test loop is selected to establish a primary loop equivalent model by combining two engineering solutions provided in claim 4.
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