CN111624404A - Online transformer impedance spectrum measurement system and measurement method - Google Patents
Online transformer impedance spectrum measurement system and measurement method Download PDFInfo
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- CN111624404A CN111624404A CN202010385050.1A CN202010385050A CN111624404A CN 111624404 A CN111624404 A CN 111624404A CN 202010385050 A CN202010385050 A CN 202010385050A CN 111624404 A CN111624404 A CN 111624404A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
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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
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
Abstract
The present disclosure discloses an online transformer impedance spectrum measurement system, including: the signal measurement module is used for outputting first voltage excitation signals with different frequencies to excite the transformer and measuring the amplitude and the phase of current response signals with different frequencies output by the transformer; the linear voltage doubling module is used for boosting the first voltage excitation signal into a second voltage excitation signal and inputting the second voltage excitation signal into a transformer; and the upper computer is used for recording the amplitude and the phase of the current response signals with different frequencies and generating a transformer impedance spectrum. The disclosure also discloses an online transformer impedance spectrum measurement method. The method can accurately evaluate the insulation defect in the transformer insulation by measuring the impedance under the broadband.
Description
Technical Field
The disclosure belongs to the technical field of online transformer impedance spectrum measurement, and particularly relates to an online transformer impedance spectrum measurement system and a measurement method.
Background
The transformer is an indispensable part of power equipment, plays roles of power transportation and voltage conversion, is easy to break down due to long-time operation and complicated internal stress field, and needs to evaluate the state of the power transformer in real time. The stability problem of transformer insulation is receiving wide attention, and therefore, it is important to evaluate and reasonably prevent the overall insulation of the transformer.
At present, the traditional detection method is offline, a part of insulating paper or insulating oil in the transformer is taken out for aging and moisture detection when the transformer is offline, and equipment cannot be detected in real time, so that potential risks are caused.
The above information disclosed in this background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is well known to those of ordinary skill in the art.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide an online transformer impedance spectrum measuring system, which can accurately evaluate the insulation defects in the transformer insulation by measuring the impedance under a wide frequency band.
In order to achieve the purpose, the following technical scheme is provided in the disclosure:
an on-line transformer impedance spectroscopy measurement system comprising:
the signal measurement module is used for outputting first voltage excitation signals with different frequencies to excite the transformer and measuring the amplitude and the phase of current response signals with different frequencies output by the transformer;
the linear voltage doubling module is used for boosting the first voltage excitation signal into a second voltage excitation signal and inputting the second voltage excitation signal into a transformer;
and the upper computer is used for recording the amplitude and the phase of the current response signals with different frequencies and generating a transformer impedance spectrum.
Preferably, the signal measuring module is connected to a high-voltage grounding terminal of the transformer, and the linear voltage doubling module is connected to a low-voltage grounding terminal of the transformer.
Preferably, the signal measurement module adopts a lock-in amplifier.
Preferably, the frequency of the first voltage excitation signal is 1mHz-10kHz, and the voltage is 0-5V.
Preferably, the linear voltage doubling module includes a voltage operational amplifier, a first adjusting resistor and a second adjusting resistor, the first adjusting resistor is connected to the non-inverting input terminal of the voltage operational amplifier, and the second adjusting resistor is connected to the inverting input terminal of the voltage operational amplifier.
Preferably, the second voltage excitation signal has the same frequency as the first voltage excitation signal.
Preferably, the voltage amplitude of the second voltage excitation signal is 0-50V.
The present disclosure also provides an online impedance spectrum measurement method for a transformer, including the following steps:
s100: the signal measurement module outputs first voltage excitation signals with different frequencies;
s200: the first voltage excitation signal is boosted by the linear voltage-multiplying module to obtain a second voltage excitation signal and is input to a low-voltage grounding end of the transformer;
s300: the second voltage excitation signal generates current response signals with different frequencies for the excitation of the transformer and is output to the signal measurement module from a high-voltage grounding end of the transformer;
s400: the signal measurement module measures the current response signals with different frequencies and obtains the amplitude and the phase corresponding to the frequencies;
s500: and the upper computer generates a transformer impedance spectrum according to the amplitude and the phase of the measured current response signals with different frequencies.
Preferably, the frequency of the first voltage excitation signal is 1mHz-10 kHz.
Preferably, the frequency of the second voltage excitation signal is the same as the frequency of the first voltage excitation signal.
Compared with the prior art, the beneficial effect that this disclosure brought does:
1. the method realizes the accurate measurement of the amplitude and the phase of the ultralow frequency signal as low as 1mHz by fully utilizing the performance of the phase-locked amplifier, thereby realizing the accurate measurement of the impedance of the online transformer within a wide frequency range (1 mHz-10 kHz);
2. the voltage amplitude of the transformer low-voltage side ground terminal is adjusted by adjusting the frequency of a voltage excitation signal output by the phase-locked amplifier, so that a larger impedance measurement range can be realized;
3. the method has the advantages of low cost, portability, simplicity and convenience in operation and the like, and is suitable for measuring and analyzing the impedance spectrum of the online transformer.
Drawings
Fig. 1 is a schematic structural diagram of an online transformer impedance spectrum measurement system according to an embodiment of the present disclosure;
fig. 2 is a schematic diagram of a transformer connected to a signal measurement module and a linear voltage doubling module according to an embodiment of the present disclosure;
fig. 3 is a schematic structural diagram of a linear voltage doubling module according to an embodiment of the present disclosure;
fig. 4(a) is a schematic diagram of the real part of the impedance spectrum of a transformer provided by an embodiment of the present disclosure;
fig. 4(b) is a schematic diagram of the imaginary part of the impedance spectrum of the transformer.
Detailed Description
Specific embodiments of the present disclosure will be described in detail below with reference to fig. 1 to 4 (b). While specific embodiments of the disclosure are shown in the drawings, it should be understood that the disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
It should be noted that certain terms are used throughout the description and claims to refer to particular components. As one skilled in the art will appreciate, various names may be used to refer to a component. This specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. The description which follows is a preferred embodiment of the invention, but is made for the purpose of illustrating the general principles of the invention and not for the purpose of limiting the scope of the invention. The scope of the present disclosure is to be determined by the terms of the appended claims.
To facilitate an understanding of the embodiments of the present disclosure, the following detailed description is to be considered in conjunction with the accompanying drawings, and the drawings are not to be construed as limiting the embodiments of the present disclosure.
In one embodiment, as shown in fig. 1, the present disclosure provides an online transformer impedance spectroscopy measurement system, comprising:
the signal measurement module is used for outputting first voltage excitation signals with different frequencies to excite the transformer and measuring the amplitude and the phase of current response signals with different frequencies output by the transformer;
the linear voltage doubling module is used for boosting the first voltage excitation signal into a second voltage excitation signal and inputting the second voltage excitation signal into a transformer;
and the upper computer is used for recording the amplitude and the phase of the current response signals with different frequencies and generating a transformer impedance spectrum.
In the embodiment, the excitation voltage signals with different frequencies are applied to the transformer, and the impedance spectrum of the transformer is generated in real time by measuring the impedance values of the current response signals with different frequencies.
In another embodiment, the signal measuring module is connected to a high-voltage ground terminal of the transformer, and the linear voltage doubling module is connected to a low-voltage ground terminal of the transformer.
In the embodiment, because the current of the high-voltage grounding end of the transformer is lower in the operation process, the noise of the current response signal output by the transformer is low, and the measurement error of the current response signal can be reduced by connecting the signal measurement module to the high-voltage grounding end of the transformer; similarly, because the current of the low-voltage grounding end of the transformer is larger in the operation process, the linear voltage doubling module is connected to the low-voltage end of the transformer, and the influence of the noise generated by the operation of the transformer on the voltage excitation signal output by the linear voltage doubling module can be reduced to the minimum.
In another embodiment, the signal measurement module employs a lock-in amplifier.
In this embodiment, the lock-in amplifier has a frequency filtering function, and meanwhile, the lock-in amplifier has the characteristics of high measurement accuracy and wide measurement frequency band, and can well meet the requirement of transformer impedance spectrum measurement.
It should be noted that the lock-in amplifier includes two coupling modes, i.e., dc and ac. When the current response signal of the transformer is measured by adopting the alternating current coupling, the measurement result is relatively accurate when the signal frequency is above 10Hz, and the measurement result has serious amplitude and phase errors when the signal frequency is lower than 10Hz, because the alternating current coupling is equivalent to a high-pass filter, and when the signal frequency is too low, the phase-locked amplifier cannot distinguish a direct current signal and a low-frequency signal. Therefore, when the transformer is measured, the working mode of the phase-locked amplifier needs to be switched at 10 Hz.
In another embodiment, the first voltage excitation signal has a frequency of 1mHz-10kHz and a voltage of 0-5V.
In the embodiment, the phase-locked amplifier can output the voltage excitation signal with the input frequency of 1mHz-10kHz and the amplitude of 0-5V, so that the accurate measurement of the amplitude and the phase of the ultralow frequency signal as low as 1mHz and the accurate measurement of the impedance of the transformer in a wide frequency range (1 mHz-10 kHz) can be realized, and meanwhile, the amplitude of the excitation voltage applied to the grounding end of the low-voltage side of the transformer is adjusted by adjusting the frequency of the voltage excitation signal output by the phase-locked amplifier, so that the impedance measurement of the transformer in a larger range can be realized.
In another embodiment, the linear voltage doubling module includes a voltage operational amplifier, a first adjusting resistor Rd and a second adjusting resistor Rk, the first adjusting resistor Rd is connected to the non-inverting input terminal of the voltage operational amplifier, and the second adjusting resistor Rk is connected to the inverting input terminal of the voltage operational amplifier.
In this embodiment, the voltage operational amplifier preferably uses an OPA512, which is a type of OPA capable of satisfying high voltage output and basically does not change gain when the frequency of the input voltage reaches 10 kHz.
In another embodiment, the second voltage excitation signal has the same frequency as the first voltage excitation signal.
In this embodiment, since the linear voltage doubling module is linear amplification, the phase and frequency of the voltage excitation signal are not changed, and only the amplitude thereof is changed.
In another embodiment, the voltage amplitude of the second voltage excitation signal is 0-50V.
In this embodiment, the applied voltage is generally 50-200V in the current study of the impedance spectrum of the transformer, but if the amplitude of the voltage applied to the low-voltage ground terminal of the transformer is too high, the current will be too large and exceed the range of the lock-in amplifier, and the accuracy will be reduced due to too high linear voltage-multiplying factor, so the voltage excitation signal applied to the low-voltage ground terminal of the transformer is limited to be less than 50V in this embodiment.
In another embodiment, the present disclosure further provides an online impedance spectrum measurement method for a transformer, including the following steps:
s100: the signal measurement module outputs first voltage excitation signals with different frequencies;
s200: the first voltage excitation signal is boosted by the linear voltage-multiplying module to obtain a second voltage excitation signal and is input to a low-voltage grounding end of the transformer;
s300: the second voltage excitation signal generates current response signals with different frequencies for the excitation of the transformer and is output to the signal measurement module from a high-voltage grounding end of the transformer;
s400: the signal measurement module measures the current response signals with different frequencies and obtains the amplitude and the phase corresponding to the frequencies;
s500: and the upper computer generates a transformer impedance spectrum according to the amplitude and the phase of the measured current response signals with different frequencies.
In this embodiment, first, several frequency points need to be selected arbitrarily, the impedance amplitude of the transformer at the frequency points is measured, and the range of the impedance amplitude is preliminarily estimated. And according to the estimated impedance amplitude, setting the amplitude of the excitation voltage output by the phase-locked amplifier and adjusting the amplification factor of the linear voltage doubling module, so that the excitation voltage applied to the grounding end of the low-voltage side of the transformer can generate a current response with the amplitude slightly lower than 10 muA. Because the response current amplitude is lower than 10 mua, the maximum value of the range of the phase-locked amplifier, and can be directly input into the input end of the phase-locked amplifier. But the magnitude of the response current must not be less than 2fA (i.e. the lowest value of the lock-in amplifier range), otherwise the measurement accuracy will be reduced under the influence of ambient noise.
In order to facilitate understanding of the technical solution of the present embodiment, the following description is made by way of example.
Specifically, some frequency points are selected, for example, 10mHz, 1Hz, and 100Hz are selected, under an arbitrary frequency point, the voltage of the lock-in amplifier is increased from 0 to a proper voltage, the response current value is observed, the amplification factor is adjusted to prevent the response current value from exceeding the range of the lock-in amplifier, the impedance of each frequency point can be calculated through the voltage current and the amplification factor, two frequency points with the minimum impedance value and the maximum impedance value are found out from the impedance, if the highest impedance is 300M Ω, and the lowest impedance is 10M Ω, the amplification factor can be determined to be 7 times, the frequency point is the maximum impedance of the transformer, the over-range is not caused when the maximum impedance is the frequency point, and the current is not too small when the minimum impedance is the frequency point. After the amplification factor is determined, the whole impedance spectrum of the transformer can be swept, the impedance spectrum of the transformer to be detected is finally obtained, the impedance spectrum is compared with a standard impedance spectrum, the standard impedance spectrum can be the impedance spectrum measured during the primary operation of the transformer, as shown in fig. 4(a) to 4(b), fig. 4(a) is the real part of the impedance spectrum of the transformer with different moisture degrees, and fig. 4(b) is the imaginary part of the impedance spectrum, and the defects possibly appearing in the transformer can be determined by comparing the curve amplitudes, the peak values and the positions of the peak values of the normal transformer and the moisture transformer in fig. 4(a) and 4(b), whether a new platform is arranged, the positions of the platform and other information. As can be seen from observing the impedance spectrums shown in fig. 4(a) to 4(b), the amplitude of the impedance spectrum will rise, the amplitude of the peak will also rise, the peak will move to the right of the impedance spectrum, a new platform will appear near some frequency points, and the platform will also move to the right along with the increase of the water content of the transformer, and if a similar phenomenon appears in the impedance spectrum, the transformer should be overhauled in time to avoid the insulation failure of the transformer. Some of the groups in the schematic contain significant amounts of water, typically greater than 3% water, and can cause severe insulation failure.
The foregoing describes the general principles of the present application in conjunction with specific embodiments, however, it is noted that the advantages, effects, etc. mentioned in the present application are merely examples and are not limiting, and they should not be considered essential to the various embodiments of the present application. Furthermore, the foregoing disclosure of specific details is for the purpose of illustration and description and is not intended to be limiting, since the foregoing disclosure is not intended to be exhaustive or to limit the disclosure to the precise details disclosed.
The foregoing description has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit embodiments of the application to the form disclosed herein. While a number of example aspects and embodiments have been discussed above, those of skill in the art will recognize certain variations, modifications, alterations, additions and sub-combinations thereof.
Claims (10)
1. An on-line transformer impedance spectroscopy measurement system comprising:
the signal measurement module is used for outputting first voltage excitation signals with different frequencies to excite the transformer and measuring the amplitude and the phase of current response signals with different frequencies output by the transformer;
the linear voltage doubling module is used for boosting the first voltage excitation signal into a second voltage excitation signal and inputting the second voltage excitation signal into a transformer;
and the upper computer is used for recording the amplitude and the phase of the current response signals with different frequencies and generating a transformer impedance spectrum.
2. The system of claim 1, wherein preferably, the signal measurement module is connected to a high voltage ground terminal of the transformer, and the linear voltage doubling module is connected to a low voltage ground terminal of the transformer.
3. The system of claim 1, wherein the signal measurement module employs a lock-in amplifier.
4. The system of claim 1, wherein the first voltage excitation signal has a frequency of 1mHz-10kHz and a voltage of 0-5V.
5. The system of claim 1, wherein the linear voltage doubling module comprises a voltage operational amplifier, a first regulating resistor connected to a non-inverting input of the voltage operational amplifier, and a second regulating resistor connected to an inverting input of the voltage operational amplifier.
6. The system of claim 1, wherein the second voltage excitation signal is at the same frequency as the first voltage excitation signal.
7. The system of claim 6, wherein the second voltage excitation signal has a voltage amplitude of 0-50V.
8. A method for online measurement of transformer impedance spectrum according to the system of any one of claims 1-7, comprising the steps of:
s100: the signal measurement module outputs first voltage excitation signals with different frequencies;
s200: the first voltage excitation signal is boosted by the linear voltage-multiplying module to obtain a second voltage excitation signal and is input to a low-voltage grounding end of the transformer;
s300: the second voltage excitation signal generates current response signals with different frequencies for the excitation of the transformer and is output to the signal measurement module from a high-voltage grounding end of the transformer;
s400: the signal measurement module measures the current response signals with different frequencies and obtains the amplitude and the phase corresponding to the frequencies;
s500: and the upper computer generates a transformer impedance spectrum according to the amplitude and the phase of the measured current response signals with different frequencies.
9. The method of claim 8, wherein the first voltage excitation signal has a frequency of 1mHz-10 kHz.
10. The method of claim 8, wherein the frequency of the second voltage excitation signal is the same as the frequency of the first voltage excitation signal.
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