CN111610363A - Broadband frequency response detection system and method for transformer characteristic analysis - Google Patents
Broadband frequency response detection system and method for transformer characteristic analysis Download PDFInfo
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- CN111610363A CN111610363A CN202010178456.2A CN202010178456A CN111610363A CN 111610363 A CN111610363 A CN 111610363A CN 202010178456 A CN202010178456 A CN 202010178456A CN 111610363 A CN111610363 A CN 111610363A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
- G01R23/04—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage adapted for measuring in circuits having distributed constants
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
Abstract
The invention discloses a broadband frequency response detection system and a broadband frequency response detection method for transformer characteristic analysis, and relates to the fields of power electronic technology and power systems. The high-frequency alternating current signal generating module adopts direct digital frequency synthesis (DDS) technology and is used for generating broadband high-frequency alternating current signals, and the frequency response analyzing module mainly completes the analysis of the high-frequency alternating current signals f1～f2The processing of real-time acquisition, filtering, amplification, detection, demodulation, result display and the like effectively detects and analyzes the material of the transformer winding.
Description
Technical Field
The present invention relates to the field of power electronics and power systems, and more particularly, to a wideband frequency response detection system and method for transformer characteristic analysis.
Background
The mode that the winding replaces the copper material with materials such as aluminium, aluminum alloy or copper clad aluminium can be adopted by some distribution transformer manufacturing companies in China to reduce production cost, the phenomenon of replacing copper with aluminium is relatively hidden, and after production is completed, finished product appearance and wiring terminals are difficult to identify.
The existing winding material analysis means is difficult to detect whether the winding material contains aluminum, aluminum alloy or aluminum-clad copper, such as an X-ray method, the method provides a blackness contrast analysis result of an X-ray transmission photo of the copper material and an aluminum winding transformer by researching the X-ray transmission rule of a copper and aluminum test product and simulating an X-ray transmission test when the distribution transformer coil uses the copper and aluminum wires, and the method has complex operation and poor engineering practicability; the resistance temperature coefficient method is a traditional method for nondestructive testing of metal materials, and the method can not be used in engineering all the time because the direct current resistance value of a winding is too low, the low-voltage side is usually in the milliohm level, and the measurement precision and error control cannot meet the judgment requirements easily.
The multi-parameter comprehensive identification method comprehensively judges and identifies the distribution transformer by utilizing the characteristics that different winding materials of the distribution transformer have different performance parameters such as size, weight, direct current resistance and the like, but the method can only judge the winding material of the dry type transformer and has certain limitation, and the judgment standard is difficult to determine.
And the electric eddy current technology is used for identification, so that nondestructive detection is difficult to realize.
For a loop formed by connecting two different conductors in series, when the temperature of two joints is constant, the thermoelectric force in the loop is only related to the metal material forming the thermocouple, so that the thermoelectric force value can be used for identifying the metal material.
Disclosure of Invention
The embodiment of the invention aims to provide a broadband frequency response detection system and a broadband frequency response detection method for transformer characteristic analysis, which overcome the defects and shortcomings at least by a gate, can effectively solve the problems of difficult operation, difficult realization, long period and difficult popularization of various transformer winding material analysis schemes, and can effectively detect and analyze the transformer winding material.
In order to achieve the above object, an embodiment of the present invention provides a wideband frequency response detection system for transformer characteristic analysis, including a high-frequency alternating current signal generation module and a frequency response analysis module; the high-frequency alternating current signal generating module adopts a direct digital frequency synthesis (DDS) technology and is used for generating a broadband high-frequency alternating current signal, and the frequency is continuously changed within a broadband range; the frequency response analysis module mainly completes the analysis of the high-frequency alternating current signal f1～f2Real-time acquisition, filtering, amplification, demodulation, result display and the like;
in order to achieve the above object, an embodiment of the present invention provides a wideband frequency response detection system for transformer characteristic analysis, where the detection system includes a signal synthesis circuit, a signal conditioning circuit, a power management circuit, a detection/demodulation module, and a main control module, where the signal synthesis circuit takes a programmable gate array (FPGA) and a high-speed digital-to-analog converter (DAC) as a core to implement modulation, coding, and frequency synthesis of a high-frequency alternating signal; the signal conditioning circuit mainly comprises a filter, an amplifying circuit and a protection circuit, and is used for conditioning a signal after digital-to-analog conversion to obtain stronger signal driving capability; the detection/demodulation module comprises a low-pass filter, a broadband operational amplifier and a power detector and is used for collecting, filtering, amplifying and demodulating a high-frequency alternating current signal; the main control module is mainly used for recording/analyzing the detection/demodulation data, displaying the result and the like.
In order to achieve the above object, an embodiment of the present invention provides a wideband frequency response detection method for transformer characteristic analysis, where the method includes: signal synthesis circuit of high-frequency alternating current signal generation module generates broadband high-frequency alternating current signal f1～f2The frequency is continuously changed in a broadband range, and the signal after the digital-to-analog conversion is conditioned through a signal conditioning circuit to obtain stronger signal driving capability; high frequency alternating current signal f1～f2Injecting the excitation signal into a winding of the tested transformer in a direct connection mode as an excitation signal; the frequency response analysis module collects the excitation signal f flowing through the detected transformer winding in real time1～f2The system enters a detection/demodulation module in a direct connection mode, amplification processing is finished through a broadband operational amplifier after out-of-band signals are filtered through low-pass filtering, the amplified signals are sent to a main control module in real time after detection, algorithm analysis is carried out on data according to a skin effect and winding parasitic parameter model, collected and analyzed data are displayed, and a material analysis result is given;
to achieve the above object, an embodiment of the present invention provides a broadband frequency response detection method for transformer characteristic analysis, where the method includes analyzing data by using a theoretical basis of skin effect: the effect of an alternating current in a conductor is an increase in current density towards the surface of the conductor as the conductor conducts a high frequency alternating current signal. The constant current is uniformly distributed over the cross section of the straight long conductor. For alternating currents, self-induced electromotive forces occur in the conductors against the passage of the current. The magnitude of this electromotive force is proportional to the magnetic flux cut by the conductor per unit time. Taking a conductor with a circular cross section as an example, the closer to the center of the conductor, the greater the self-induced electromotive force generated by external magnetic lines of force; the closer to the surface, the less the self-induced electromotive force is, the less the influence of the magnetic lines of force in the magnetic field lines. This results in a greater current density towards the surface of the conductor. Since the self-induced electromotive force increases with increasing frequency, the skin effect is more pronounced with increasing frequency. The skin effect reduces the effective cross-sectional area of the conductor when current passes through it, thus increasing its effective impedance:
calculating the formula:
where, penetration depth, f is the frequency of the alternating current signal, p is the resistivity, and μ is the absolute permeability
The difference of the penetration depth is visually and physically represented as that the impedance of the conductor is different, namely, the impedance presented by the conductor is also different in different frequency bands, and further, the frequency response of the conductor is different. Factors that affect the depth of penetration include frequency, resistivity, and absolute permeability, and at the same frequency, the depth of penetration is related only to the material of the conductor. It can be further concluded that the effect on the frequency response of a single conductor at high frequency ac signals depends only on the conductor material.
In order to achieve the above object, an embodiment of the present invention provides a wideband frequency response detection method for transformer characteristic analysis, where the method includes analyzing data based on a theoretical basis of a winding parasitic parameter model, and analyzing a frequency response of a section of conductor only depending on a material of the conductor, but for a winding, a length of the winding, a winding manner, a magnetic core, a parasitic parameter, and the like all affect a frequency response characteristic of the winding. Under different bandwidths, leakage inductance, distributed capacitance and the like all bring influence on frequency response analysis.
Inter-turn capacitance
The definition of the capacitance is as follows:
and C, winding turn-to-turn capacitance: dielectric constant, determined by the medium between the two plates, S: the area k of the positive electrode plate is: electrostatic force constants d: distance between the pole plates
Interlayer capacitance refers to the capacitance between layers of each individual winding.
It is known that, when calculating a transformer, it generally occurs that a single winding needs to be wound by 2 layers or more than 2 layers, and then an electric field is formed between every 2 layers, that is, an equivalent capacitance effect is generated
So that a capacitance equivalent model of the winding can be obtained;
under the condition that the magnetic core is determined, the distributed capacitance is mainly influenced by the winding process, so that if single-frequency alternating current is adopted to carry out frequency response characteristic analysis, the fluctuation of an analysis result is large, and the scheme of broadband multi-frequency point and multi-data analysis is adopted, the influence of the distributed capacitance on the frequency response characteristic can be gradually approximated and eliminated.
Compared with the prior art, the invention has the following advantages:
1. because a high-frequency alternating current generating module is designed, a broadband high-frequency alternating current signal f is generated1～f2The frequency is in a broadband range and continuously changes, and the operation of identifying the material of the transformer winding is simple and convenient and is easy to popularize;
2. frequency response analysis module for high frequency alternating current signal f1～f2The real-time acquisition, filtering, amplification, demodulation and display of results have short detection period and simple and convenient test flow.
Drawings
FIG. 1 is a block diagram of a wideband frequency response detection system that may be used for transformer characterization according to the present invention;
FIG. 2 is a block diagram of a high frequency alternating current signal generating module of a broadband frequency response detection system for transformer characterization according to an embodiment of the present invention;
FIG. 3 shows a high-frequency alternating current signal f of a broadband frequency response detection system of the present invention for transformer characterization1～f2A schematic diagram;
FIG. 4 is a block diagram of a frequency response analysis module of a wideband frequency response detection system that may be used for transformer characterization according to the present invention;
FIG. 5 is a schematic diagram of a frequency response analysis module of the broadband frequency response detection system for transformer characteristic analysis according to the present invention;
FIG. 6 is a capacitance equivalent model of a transformer winding of the present invention;
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
FIG. 1 is a block diagram of a wideband frequency response detection system that may be used for transformer characterization. As shown in FIG. 1, the broadband frequency response detection system for transformer winding material analysis comprises a high-frequency alternating current signal generation module for generating a high-frequency alternating current signal f1～f2As shown in fig. 3, the frequency is continuously changed in a broadband range, and is injected into the winding of the tested transformer as an excitation signal in a direct connection manner; and the frequency response analysis module is mainly used for completing the processing of real-time acquisition, filtering, amplification, detection, demodulation, result display and the like of the excitation signal flowing through the tested transformer winding, displaying acquired analysis data in real time and giving an analysis result of the material.
Fig. 2 is a structural diagram of a high-frequency alternating current signal generating module of a broadband frequency response detecting system which can be used for transformer characteristic analysis according to the present invention. The high-frequency alternating current signal generation module adopts a direct digital frequency synthesis (DDS) technology and adopts a design framework of a high-speed programmable logic chip (FPGA) and a high-speed digital-to-analog converter (DAC). The device consists of a signal synthesis circuit, a signal conditioning circuit and a power circuit. The signal synthesis circuit takes a high-speed programmable chip (FPGA) and a high-speed digital-to-analog converter (DAC) as cores, and realizes modulation, coding and frequency synthesis of high-frequency alternating current signals. The signal conditioning circuit mainly comprises a filter circuit, an amplifying circuit and a protection circuit, and is used for conditioning a signal after digital-to-analog conversion to obtain strong signal driving capability.
Fig. 4 is a structural diagram of a frequency response analysis module of a broadband frequency response detection system that can be used for transformer characteristic analysis according to the present invention. The frequency response analysis module mainly completes the analysis of the high-frequency alternating current signal f1～f2The real-time acquisition, filtering, amplification, detection, demodulation, result display and other processing. High frequency alternating current signal f1～f2After flowing through the winding of the tested transformer, the direct connection mode enters a detection/demodulation module, the out-of-band signal is filtered by low-pass filtering, the amplification processing is finished by a broadband operational amplifier, and the amplified out-of-band signal is subjected toAnd after detection, the data are sent to the main control module in real time. The main control module mainly completes the functions of recording/analyzing the detection/demodulation data, displaying the result and the like. The test result is shown in fig. 5, by comparing the frequency response curves, the analysis result of the transformer winding material can be clearly and intuitively given, and the measurement period is less than 1 s.
One of the theoretical bases on which the present invention relies is the skin effect, which is the effect of the increase in the current density of the alternating current in the conductor near the surface of the conductor when the conductor conducts a high-frequency alternating current signal. The constant current is uniformly distributed over the cross section of the straight long conductor. For alternating currents, self-induced electromotive forces occur in the conductors against the passage of the current. The magnitude of this electromotive force is proportional to the magnetic flux cut by the conductor per unit time. Taking a conductor with a circular cross section as an example, the closer to the center of the conductor, the greater the self-induced electromotive force generated by external magnetic lines of force; the closer to the surface, the less the self-induced electromotive force is, the less the influence of the magnetic lines of force in the magnetic field lines. This results in a greater current density towards the surface of the conductor. Since the self-induced electromotive force increases with increasing frequency, the skin effect is more pronounced with increasing frequency. The skin effect reduces the effective cross-sectional area of the conductor when current passes through it, thus increasing its effective impedance:
calculating the formula:
where, penetration depth, f is the frequency of the alternating current signal, p is the resistivity, and μ is the absolute permeability
The difference of the penetration depth is visually and physically represented as that the impedance of the conductor is different, namely, the impedance presented by the conductor is also different in different frequency bands, and further, the frequency response of the conductor is different. Factors that affect the depth of penetration include frequency, resistivity, and absolute permeability, and at the same frequency, the depth of penetration is related only to the material of the conductor. It can be further concluded that the effect on the frequency response of a single conductor at high frequency ac signals depends only on the conductor material.
The invention also can analyze the data by depending on the theoretical basis of a winding parasitic parameter model, and the frequency response analysis of a section of conductor only depends on the material of the conductor, but for the winding, the length, the winding mode, the magnetic core, the parasitic parameters and the like of the winding all affect the frequency response characteristics of the winding. Under different bandwidths, leakage inductance, distributed capacitance and the like all bring influence on frequency response analysis.
Inter-turn capacitance
The definition of the capacitance is as follows:
and C, winding turn-to-turn capacitance: dielectric constant, determined by the medium between the two plates, S: the area k of the positive electrode plate is: electrostatic force constants d: distance between the pole plates
Interlayer capacitance refers to the capacitance between layers of each individual winding.
It is known that when calculating a transformer, it generally occurs that a single winding needs to be wound by 2 layers or more than 2 layers, and then an electric field is formed between every 2 layers, i.e. an equivalent capacitance effect is generated.
A capacitive equivalent model of the winding can be obtained as shown in fig. 6.
Under the condition that the magnetic core is determined, the distributed capacitance is mainly influenced by the winding process, so that if single-frequency alternating current is adopted to carry out frequency response characteristic analysis, the fluctuation of an analysis result is large, and the scheme of broadband multi-frequency point and multi-data analysis is adopted, the influence of the distributed capacitance on the frequency response characteristic can be gradually approximated and eliminated.
Claims (6)
1. A broadband frequency response detection system for transformer characteristic analysis comprises a high-frequency alternating current signal generation module and a frequency response analysis module, and is characterized in that:
the high-frequency alternating current signal generation module adopts direct digital frequency synthesis (DDS) technology, comprises a signal synthesis circuit, a signal conditioning circuit and a power supply management circuit, and mainly has the function of generating a broadband high-frequency alternating current signal f1～f2The frequency is continuously changed within a broadband range;
the frequency response analysis module comprises a detection/demodulation module and a main control module and is mainly used for completing the detection of the high-frequency alternating current signal f1～f2The real-time acquisition, filtering, amplification, detection, demodulation, result display and other processing.
2. The system of claim 1, wherein the system comprises:
the signal synthesis circuit contained in the high-frequency alternating current signal generation module takes a high-speed programmable chip (FPGA) and a high-speed digital-to-analog converter (DAC) as cores, and can realize modulation, coding and frequency synthesis of high-frequency alternating current signals;
the signal conditioning circuit mainly comprises a filter, an amplifying circuit and a protection circuit, and can condition signals after digital-to-analog conversion to obtain strong signal driving capability.
3. The system of claim 1, wherein the system comprises:
the detection/modulation module contained in the frequency response analysis module comprises a low-pass filter, a broadband operational amplifier and a power detector and is used for collecting, filtering, amplifying and demodulating a high-frequency alternating current signal;
the main control module mainly completes the recording/analysis of the detection/demodulation data, the display of the result and the like.
4. A method for detecting a broadband frequency response usable for transformer characterization, the method comprising:
signal synthesis circuit of high-frequency alternating current signal generation module generates broadband high-frequency alternating current signal f1～f2The frequency is continuously changed in a broadband range, and the signal after the digital-to-analog conversion is conditioned through the signal conditioning circuit, so that the signal obtains stronger signal driving energyForce;
high frequency alternating current signal f1～f2Injecting the excitation signal into a winding of the tested transformer in a direct connection mode as an excitation signal;
the frequency response analysis module collects the excitation signal f flowing through the detected transformer winding in real time1～f2The data enters a detection/demodulation module in a direct connection mode, amplification processing is completed through a broadband operational amplifier after out-of-band signals are filtered through low-pass filtering, the amplified signals are sent to a main control module in real time after detection, algorithm analysis is carried out on the data according to a skin effect and winding parasitic parameter model, collected and analyzed data are displayed, and a material analysis result is given.
5. The method of claim 4, wherein the skin effect is an effect of an increase in current density in the conductor near the surface of the conductor when the conductor conducts a high frequency alternating current signal;
calculating the formula:
where is the penetration depth, f is the alternating current signal frequency, ρ is the resistivity, and μ is the absolute permeability.
6. The method of claim 4, wherein the winding parasitic parametric model is:
the frequency response analysis of a section of conductor only depends on the material of the conductor, but for the winding, the length, winding mode, magnetic core, parasitic parameters and the like of the winding all affect the frequency response characteristics. Under different bandwidths, leakage inductance, distributed capacitance and the like can all affect frequency response analysis;
the definition of the turn-to-turn capacitance is as follows:
wherein C is winding turn-to-turn capacitance; : the dielectric constant is determined by the medium between the two polar plates; s: the area of the positive plate; k: an electrostatic force constant; d: the distance between the plates;
interlayer capacitance refers to the capacitance between layers of each individual winding.
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| CN202915884U (en) * | 2012-11-23 | 2013-05-01 | 北京博电新力电气股份有限公司 | Winding deformation tester |
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| CN110231373A (en) * | 2019-06-27 | 2019-09-13 | 北华大学 | A kind of detection method and detection device of transformer winding material |
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2020
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| CN202916357U (en) * | 2012-10-18 | 2013-05-01 | 厦门红相电力设备股份有限公司 | Comprehensive test instrument for power transformer winding deformation |
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