CN111025022A - Transformer short-circuit fault positioning detection method and system - Google Patents

Transformer short-circuit fault positioning detection method and system Download PDF

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CN111025022A
CN111025022A CN201911382589.5A CN201911382589A CN111025022A CN 111025022 A CN111025022 A CN 111025022A CN 201911382589 A CN201911382589 A CN 201911382589A CN 111025022 A CN111025022 A CN 111025022A
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transformer
short
circuit fault
winding
frequency
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CN111025022B (en
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马志钦
杨贤
蔡玲珑
何国强
孙文星
江丹宇
赵东生
周永言
刘剑锋
向谆
潘君镇
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Electric Power Research Institute of Guangdong Power Grid Co Ltd
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Electric Power Research Institute of Guangdong Power Grid Co Ltd
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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
    • G01R27/08—Measuring resistance by measuring both voltage and current
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge
    • G01B7/18—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge using change in resistance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
    • G01R1/28—Provision in measuring instruments for reference values, e.g. standard voltage, standard waveform
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
    • G01R1/30—Structural combination of electric measuring instruments with basic electronic circuits, e.g. with amplifier
    • 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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  • General Physics & Mathematics (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)

Abstract

The invention discloses a positioning detection method and a positioning detection system for a short-circuit fault of a transformer, which are used for solving the technical problem that the short-circuit fault position cannot be positioned in the detection of the transformer fault. The invention comprises the following steps: detecting a normal transformer and a transformer to be detected by using a transformer winding deformation fault positioning detection system, measuring frequency sweep impedance curves of the normal transformer and the transformer to be detected, comparing the frequency sweep impedance curves of the normal transformer and the transformer to be detected, judging whether the transformer to be detected has a short-circuit fault according to a comparison result, and calculating and analyzing a position area of the winding where the short-circuit fault occurs. The short-circuit fault location detection system is connected with the transformer through establishment, the short-circuit fault location detection system is used for locating the position of the short-circuit fault of the transformer through obtaining the sweep frequency impedance curve of the transformer, the defect that the short-circuit fault of the transformer cannot be located in the prior art is overcome, and the short-circuit fault location detection system has important significance for preventing power grid accidents.

Description

Transformer short-circuit fault positioning detection method and system
Technical Field
The invention relates to the technical field of transformer winding deformation detection, in particular to a method and a system for positioning and detecting a short-circuit fault of a transformer.
Background
The transformer is one of the main devices of the power system, and plays a role of the junction of grid interconnection and power exchange. The short-circuit resistance of the transformer is insufficient, and the main reason for short-circuit damage of the transformer is that the short-circuit resistance of the transformer is insufficient. Besides, improper operation management is also a considerable factor. The short-circuit resistance of the transformer is insufficient, which is mainly characterized in that a part of the transformer still generates winding deformation and even insulation breakdown under the conditions of short-circuit current impact below the specified intensity and protection quick action.
However, when a short-circuit fault occurs to a winding inside a transformer at present, a worker who performs field maintenance cannot position the position of the short-circuit fault of the winding immediately, so that the maintenance time of the transformer is increased, the power failure time is prolonged, a large amount of economic loss is caused, and the winding of the transformer is greatly damaged when the transformer is in a short-circuit state for a long time, and the whole transformer is scrapped when the transformer is serious.
In summary, in the prior art, when a short-circuit fault occurs in a transformer, a technical problem that the short-circuit fault cannot be located exists.
Disclosure of Invention
The invention provides a positioning and detecting method and a positioning and detecting system for a short-circuit fault of a transformer, which solve the technical problem that the short-circuit fault cannot be positioned when the short-circuit fault occurs in the transformer.
The invention provides a positioning and detecting method for a short-circuit fault of a transformer, which is suitable for a positioning and detecting system for the short-circuit fault of the transformer, and comprises the following steps:
step S1: short-circuiting one side of a winding of a normal transformer, connecting the other side of the winding with a transformer short-circuit fault positioning and detecting system, detecting the normal transformer by the transformer short-circuit fault positioning and detecting system, and measuring a sweep frequency impedance curve of the normal transformer;
step S2: detecting the transformer to be detected by using a transformer short-circuit fault positioning detection system to obtain a frequency sweeping impedance curve of the transformer to be detected, comparing the frequency sweeping impedance curve of the transformer to be detected with a frequency sweeping impedance curve of a normal transformer, and judging whether the transformer to be detected has a fault according to a comparison result;
step S3: if the judgment result is that the transformer to be tested has a fault, judging whether the fault type is a short-circuit fault or not according to the sweep frequency impedance curve;
step S4: and if the fault type is judged to be a short-circuit fault, calculating and analyzing the position area of the short-circuit fault of the transformer winding to be tested.
Preferably, in step S1, the transformer short-circuit fault location detection system sends a sinusoidal signal of 10Hz to 1MHz, amplifies the power of the signal and applies the amplified signal to the normal transformer winding, and the transformer short-circuit fault location detection system collects the voltage and current of the normal transformer winding, calculates the impedance value of the transformer to be measured, and draws a sweep frequency impedance curve.
Preferably, in step S2, one side of the winding of the transformer to be tested is short-circuited, and the other side of the winding is connected to the transformer short-circuit fault location detection system, if the frequency-sweep impedance curve of the transformer to be tested completely coincides with the frequency-sweep impedance curve of the normal transformer, the transformer to be tested has no fault, and if the frequency-sweep impedance curve of the transformer to be tested does not coincide with the frequency-sweep impedance curve of the normal transformer, the transformer.
Preferably, in step S3, the impedance value change rate of the sweep impedance curve at 50Hz is calculated, and if the impedance value change rate exceeds 2%, the fault type is a short-circuit fault.
Preferably, in step S4, a correlation coefficient between the frequency sweep impedance curve of the transformer to be tested and the frequency sweep impedance curve of the normal transformer is calculated.
Preferably, a sinusoidal signal is injected from the high-voltage side of the transformer to be tested, and the position of the short-circuit fault of the low-voltage side is judged;
if the correlation coefficient is 0 at 1-100kHz, the correlation coefficient is 0.2-0.5 at 100-600kHz, and the correlation coefficient is 1.3-1.8 at 600kHz-1000kHz, the short-circuit fault of the middle end of the winding at the low-voltage side is judged;
at 1-100kHz, the correlation coefficient is between 0.1-0.3, at 100-600kHz, the correlation coefficient is between 1.1-1.5, at 600kHz-1000kHz, the correlation coefficient is between 1-1.3, and then the upper end or the lower end of the winding at the low-voltage side is judged to have short-circuit fault.
Preferably, a sinusoidal signal is injected from the high-voltage side of the transformer to be tested, and the position of the short-circuit fault of the high-voltage side is judged;
if the frequency is between 1 and 1000kHz and the correlation coefficient is between 1 and 1.5, judging that the upper end of the high-voltage side winding has a short-circuit fault;
if the correlation coefficient is between 1 and 100kHz, between 1.7 and 1.8, between 100 and 600kHz, between 2 and 2.1, between 600kHz and 1000kHz, and between 2 and 2.1, judging that the middle end of the high-voltage side winding has short-circuit fault;
if the correlation coefficient is between 1.9 and 2 at 1-100kHz, between 1.6 and 1.8 at 100-600kHz and between 1.8 and 1.9 at 600kHz-1000kHz, the lower end of the high-voltage side winding is judged to have short-circuit fault.
Preferably, when short-circuit faults occur at the middle end and the lower end of the high-voltage side winding, in a low frequency range of 1kHz-100kHz, the larger the sweep frequency impedance value of the winding is, the smaller the fault degree is; in the middle and high frequency range of 100kHz-600kHz, the larger the frequency sweep impedance value of the winding is, the larger the fault degree is.
Preferably, when a short-circuit fault occurs at the upper end of the high-voltage side winding, the larger the high-frequency band of the resonance point of the frequency-sweep impedance curve moves between 200kHz and 300kHz, the larger the fault degree is.
A transformer short-circuit fault positioning detection system comprises a signal generator, a power amplifier, a data acquisition card and a microprocessor, wherein the microprocessor is respectively connected with the input end of the signal generator and the output end of the data acquisition card, and the output end of the signal generator is connected with the input end of the power amplifier.
According to the technical scheme, the invention has the following advantages:
according to the invention, the transformer short-circuit fault positioning detection system is connected with the transformer, and the position of the transformer short-circuit fault is positioned by acquiring the sweep frequency impedance curve and the correlation coefficient of the transformer to be detected and the normal transformer, so that the defect that the position of the transformer short-circuit fault cannot be positioned in the prior art is solved, operation and maintenance personnel can be guided to carry out maintenance work, and the transformer short-circuit fault positioning detection system has important significance for preventing power grid accidents.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.
Fig. 1 is a method flowchart of a transformer short-circuit fault location detection method and system according to an embodiment of the present invention.
Fig. 2 is a transformer simulation graph of a transformer short-circuit fault location detection method and system according to an embodiment of the present invention.
Fig. 3(a) is a low-frequency sweep impedance curve diagram of the transformer short-circuit fault location detection method and system according to the embodiment of the present invention when injecting a signal at the high-voltage side.
Fig. 3(b) is a low-frequency sweep impedance curve diagram of the transformer short-circuit fault location detection method and system according to the embodiment of the present invention when injecting a signal at the high-voltage side.
Fig. 4(a) is a graph of short-circuit at each position of a short-circuit fault (low frequency band 0-500Hz) at the upper end of a high-voltage side winding according to the short-circuit fault location detection method and system for a transformer provided by the embodiment of the present invention.
Fig. 4(b) is a graph of short circuit at each position of a short circuit fault (low frequency band 0-500Hz) in a middle-end short circuit fault of a high-voltage side winding according to the method and system for positioning and detecting a short circuit fault of a transformer provided by the embodiment of the invention.
Fig. 4(c) is a graph of short-circuit at each position of short-circuit fault (low frequency band 0-500Hz) at the lower end of the high-voltage side winding according to the short-circuit fault location detection method and system for the transformer provided by the embodiment of the invention.
Fig. 5(a) is a 1kHz-100kHz frequency sweep impedance curve diagram when the short circuit fault occurs at the upper end of the high-voltage side winding short circuit fault winding according to the positioning and detecting method and system for the short circuit fault of the transformer provided by the embodiment of the invention.
Fig. 5(b) is a 100kHz-600kHz frequency sweep impedance curve diagram when the short circuit fault occurs at the upper end of the high-voltage side winding short circuit fault winding according to the positioning and detecting method and system for the short circuit fault of the transformer provided by the embodiment of the invention.
Fig. 6(a) is a 1kHz-100kHz sweep impedance curve diagram during a short-circuit fault at the middle end of a high-voltage side winding short-circuit fault winding of the transformer short-circuit fault positioning detection method and system provided by the embodiment of the invention.
Fig. 6(b) is a 100kHz-600kHz frequency sweep impedance curve diagram when a short-circuit occurs at the middle end of a high-voltage side winding short-circuit fault winding according to the transformer short-circuit fault location detection method and system provided by the embodiment of the invention.
Fig. 7(a) is a 1kHz-100kHz sweep impedance curve diagram when the short-circuit fault occurs at the lower end of the high-voltage side winding short-circuit fault winding in the transformer short-circuit fault positioning detection method and system provided by the embodiment of the invention.
Fig. 7(b) is a 100kHz-600kHz sweep impedance curve diagram when the lower end of the high-voltage side winding short-circuit fault occurs in the positioning detection method and system for the short-circuit fault of the transformer according to the embodiment of the present invention.
Fig. 8(a) is a sweep impedance curve when a short-circuit fault at the upper end of a winding of a transformer is located at the low-voltage side according to the method and system for locating and detecting a short-circuit fault of a transformer provided by the embodiment of the present invention.
Fig. 8(b) is a sweep impedance curve when a short-circuit fault at the upper end of a winding of the transformer short-circuit fault location detection method and system provided by the embodiment of the present invention is located at the low-voltage side.
Fig. 8(c) is a sweep impedance curve when the short-circuit fault at the upper end of the winding of the transformer positioning and detecting method and system provided by the embodiment of the invention is located at the low-voltage side.
Fig. 9(a) is a 1kHz-100kHz sweep impedance curve diagram when the upper end of the high-voltage side winding of the low-voltage side injection signal is in short-circuit fault, according to the positioning and detecting method and system for short-circuit fault of the transformer provided by the embodiment of the invention.
Fig. 9(b) is a 100kHz-600kHz frequency sweep impedance curve diagram when the upper end of the high-voltage side winding of the low-voltage side injection signal provided by the embodiment of the invention has a short-circuit fault.
Fig. 10(a) is a 1kHz-100kHz frequency sweep impedance curve diagram when a short-circuit fault occurs in the middle-end of the low-voltage side injection signal high-voltage side winding of the transformer short-circuit fault location detection method and system according to the embodiments of the present invention.
Fig. 10(b) is a 100kHz-600kHz frequency sweep impedance curve diagram when a short-circuit fault occurs in the middle-end of the high-voltage side winding of the low-voltage side injection signal according to the method and system for positioning and detecting a short-circuit fault of a transformer provided by the embodiment of the invention.
Fig. 11(a) is a 1kHz-100kHz sweep impedance curve diagram when the lower end of the high-voltage side winding of the low-voltage side injection signal is in short-circuit fault according to the positioning and detecting method and system for short-circuit fault of the transformer provided by the embodiment of the invention.
Fig. 11(b) is a 100kHz-600kHz sweep impedance curve diagram when the lower end of the high-voltage side winding of the low-voltage side injection signal has a short-circuit fault according to the positioning and detecting method and system for a short-circuit fault of a transformer provided by the embodiment of the invention.
Fig. 12 is a frequency-sweep impedance curve diagram of the low-voltage side injection signal low-voltage side winding short-circuit fault location detection method and system according to the embodiment of the present invention.
Detailed Description
The embodiment of the invention provides a positioning and detecting method and a positioning and detecting system for a short-circuit fault of a transformer, which are used for solving the defect that the position of the short-circuit fault of the transformer cannot be positioned in the prior art.
In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the embodiments described below 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.
Example 1
Referring to fig. 1, fig. 1 is a flowchart of a method and a system for positioning and detecting a short-circuit fault of a transformer according to an embodiment of the present invention.
The invention provides a positioning and detecting method for a short-circuit fault of a transformer, which is suitable for a positioning and detecting system for the short-circuit fault of the transformer, and comprises the following steps:
step S1: the method comprises the steps that a winding on one side of a normal transformer is in short circuit, a winding on the other side of the normal transformer is connected with a transformer short-circuit fault positioning and detecting system, the normal transformer is detected by using the transformer short-circuit fault positioning and detecting system, short-circuit impedance under a specific frequency band (10hz-1Mhz) is measured, and a sweep frequency impedance curve of the normal transformer is drawn according to frequency change and an impedance value;
step S2: detecting the transformer to be detected by using a transformer short-circuit fault positioning detection system to obtain a frequency sweeping impedance curve of the transformer to be detected, comparing the frequency sweeping impedance curve of the transformer to be detected with a frequency sweeping impedance curve of a normal transformer, and judging whether the transformer to be detected has a fault according to a comparison result;
step S3: if the judgment result is that the transformer to be tested has a fault, judging whether the fault type is a short-circuit fault or not according to the sweep frequency impedance curve;
step S4: and if the fault type is judged to be a short-circuit fault, calculating and analyzing the position area of the short-circuit fault of the transformer winding to be tested. Therefore, whether the area of the winding with the deformation fault is a low-voltage side winding or a high-voltage side winding is judged, and the fault area is located at the middle end, the upper end or the lower end of the winding.
As a preferred embodiment, in step S1, the transformer short-circuit fault location detection system sends a sinusoidal signal of 10Hz to 1MHz, amplifies the power of the signal, and applies the amplified signal to the normal transformer winding, and the transformer short-circuit fault location detection system collects the voltage and current of the normal transformer winding, calculates the impedance value of the transformer to be measured, and draws a sweep frequency impedance curve.
As a preferred embodiment, in step S2, a winding on one side of the transformer to be tested is short-circuited, and the other side of the transformer to be tested is connected to the transformer short-circuit fault location detection system, and if the frequency-sweep impedance curve of the transformer to be tested completely coincides with the frequency-sweep impedance curve of the normal transformer, the transformer to be tested has no fault, and if the frequency-sweep impedance curve of the transformer to be tested does not coincide with the frequency-sweep impedance curve of the normal transformer.
As a preferred embodiment, in step S3, the impedance value change rate of the sweep impedance curve at 50Hz is calculated, and if the impedance value change rate exceeds 2%, the fault type is a short-circuit fault.
As a preferred embodiment, in step S4, a correlation coefficient between the frequency sweep impedance curve of the transformer to be tested and the frequency sweep impedance curve of the normal transformer is calculated.
As a preferred embodiment, a sinusoidal signal is injected from the high-voltage side of the transformer to be tested, and the position of the short-circuit fault of the low-voltage side is judged;
if the correlation coefficient is 0 at 1-1-50kHz, the correlation coefficient is 0.2-0.5 at 100-300kHz, the correlation coefficient is 0.2-0.5 at 600kHz-800kHz, and the correlation coefficient is 1.3-1.8, judging that the middle end of the winding at the low-voltage side has short-circuit fault;
at 1-1-50kHz, the correlation coefficient is between 0.1-0.3, at 100-300kHz, the correlation coefficient is between 1.1-1.5, at 600kHz-800kHz, the correlation coefficient is between 1-1.3, and then the upper end or the lower end of the winding at the low-voltage side is judged to have short-circuit fault.
As a preferred embodiment, a sinusoidal signal is injected from the high-voltage side of the transformer to be tested, and the position of the short-circuit fault of the high-voltage side is judged;
if the frequency is between 1 and 1kHz to 500kHz and the correlation coefficient is between 1 and 1.5, judging that the upper end of the high-voltage side winding has a short-circuit fault;
if the correlation coefficient is between 1-1 kHz and 50kHz, the correlation coefficient is between 1.7 and 1.8, the correlation coefficient is between 100kHz and 300kHz, the correlation coefficient is between 2 and 2.1, and the correlation coefficient is between 600kHz and 800kHz, the middle end of the high-voltage side winding is judged to have short-circuit fault;
if the correlation coefficient is between 1.9 and 2 at 1-100kHz, between 1.6 and 1.8 at 100-300kHz and between 600kHz and 800kHz, and the correlation coefficient is between 1.8 and 1.9, the lower end of the high-voltage side winding is judged to have short-circuit fault.
As a preferred embodiment, when short-circuit faults occur at the middle end and the lower end of the high-voltage side winding, in a low-frequency band of 1kHz-100kHz, the larger the sweep frequency impedance value of the winding is, the smaller the fault degree is; in the middle and high frequency range of 100kHz-600kHz, the larger the frequency sweep impedance value of the winding is, the larger the fault degree is.
As a preferred embodiment, when the upper end of the high-voltage side winding is in short circuit fault, the larger the resonance point of the frequency sweep impedance curve moves in a high-frequency band between 200kHz and 300kHz, the larger the fault degree is. Two small peaks are generated on two sides of the first resonance peak between 200kHz and 300kHz, the change rule of the two small peaks is opposite, the peak value of the left small peak is increased along with the increase of the fault degree, and the peak value of the right small peak is decreased along with the increase of the fault degree.
Example 2
The embodiment provides a transformer short-circuit fault positioning detection system, which comprises a signal generator, a power amplifier, a data acquisition card and a microprocessor, wherein the microprocessor is respectively connected with the input end of the signal generator and the output end of the data acquisition card, and the output end of the signal generator is connected with the input end of the power amplifier.
Further, the working process of the transformer short-circuit fault positioning and detecting system is explained, a signal generator of the transformer short-circuit fault positioning and detecting system sends a sinusoidal signal of 10Hz-1MHz, the sinusoidal signal is transmitted to a power amplifier, the power amplifier receives the signal and then amplifies the sinusoidal signal, the amplified signal is applied to a transformer winding, a data acquisition card acquires voltage and current in the transformer winding and transmits the data of the voltage and the current to a microprocessor, the microprocessor calculates a transformer impedance value according to the data of the voltage and the current, draws a frequency sweep impedance curve, and judges the area of the transformer winding with the short-circuit fault according to the frequency sweep impedance curve of the transformer to be detected and the frequency sweep impedance curve of the normal transformer.
Example 3
In this embodiment, how to solve the swept frequency impedance by the transformer winding deformation fault location detection system is specifically described;
short-circuiting the high-voltage side or low-voltage side of the transformer, and loading the sweep frequency signal at the head end of the winding at the non-short-circuit side
Figure BDA0002342656610000081
After the signal passes through the winding, the output signal of the tail end of the winding is obtained by utilizing the grounding resistor R
Figure BDA0002342656610000082
According to the data, the frequency sweep impedance value of the transformer can be obtained as follows:
Figure BDA0002342656610000083
wherein
Figure BDA0002342656610000084
To detect current, ω is the angular frequency of the injected signal; r is the resistance of the transformer; x is the reactance of the transformer.
The obtained swept impedance value is:
Figure BDA0002342656610000091
because the value of the nameplate of the transformer is generally represented by impedance voltage, the tested sweep frequency impedance | ZkThe value of (j ω) | at a frequency of 50Hz needs to be normalized before being compared with the nameplate value, specifically:
Figure BDA0002342656610000092
wherein Ie is the rated current of the transformer, and Ue is the rated voltage of the transformer.
The correlation coefficient Rxy is calculated according to the following formula:
(3-1) there are 2 transfer function amplitude sequences x (k), y (k) with length N, k being 0, 1, 2, and N-1, and x (k), y (k) being real numbers, the standard deviation of the two sequences is:
Figure BDA0002342656610000093
(3-2) calculating the covariance of the two sequences:
Figure BDA0002342656610000094
(3-3) calculating normalized covariance coefficients of the two sequences:
Figure BDA0002342656610000095
(3-3) calculating the correlation coefficient R according to the following formulaXY：
Figure BDA0002342656610000096
Further, a short-circuit experiment is performed on the transformer winding, the short circuit of the 1-2 cake at the upper end of the winding is an upper end short circuit, the short circuit of the 1-2 cake at the middle end of the winding is a middle end short circuit, and the short circuit of the 1-2 cake at the lower end of the winding is a lower end short circuit, so that a sweep frequency impedance curve (normal and high-voltage winding short circuit conditions) is obtained as shown in fig. 2.
From the simulation results shown in fig. 2, it can be seen that the full-band frequency-sweep impedance curve of the high-voltage side injected signal cannot effectively identify the waveform change, so the frequency-sweep impedance curve is transformed as follows:
Z′k＝20log10(Zk)
the frequency sweep impedance curve changed by the above formula is divided into a low frequency band (10Hz to 500Hz) and a full frequency band (10Hz to 1MHz) for research, and fig. 3(a) is a low frequency band frequency sweep impedance curve and fig. 3(b) is a full frequency band frequency sweep impedance curve.
As can be seen from fig. 3(a), the amplitude of the fault frequency sweep impedance curve is significantly lower than that in the normal case at the low frequency band, but the curves of the upper, middle and lower short circuit faults at the low frequency band are not different, and the impedance values at 50Hz of the 4 curves are extracted for comparison, as shown in table 1.
TABLE 1 comparison of impedance at 50Hz for a swept frequency impedance curve
State of winding Is normal Short circuit at the upper end Short circuit at middle terminal Short circuit at lower end
Impedance (L) 24.22 19.84 19.84 19.84
Deviation/%) 0 18.08 18.08 18.08
As can be seen from table 1, the deviation of the impedance values of the 3 fault curves is the same as that of the normal condition, and 18.08% of the impedance values exceed the range of 2%, so that the winding fault can be determined, but the specific position of the winding fault cannot be determined.
Fig. 3(b) is a full-band frequency-sweep impedance curve, the results of the upper-end short circuit and the lower-end short circuit are basically the same due to symmetry, but the amplitude of the lower-end short circuit fault is higher than that of the upper-end short circuit at 800-1000 kHz. The difference between the middle-end short circuit and the former two is larger, the amplitude of the high-frequency band is higher than that of the upper end and the lower end, the amplitude is basically the same as that of the normal condition, and the correlation coefficient between the fault curve and the normal curve is calculated, as shown in table 2.
TABLE 2 correlation coefficient of Normal versus Fault curves
Figure BDA0002342656610000101
As can be seen from table 2, the winding fault can be determined by using the correlation coefficient, and the difference between the middle-end short circuit and the upper-end short circuit and the lower-end short circuit is larger as in the above analysis.
When a sinusoidal signal is injected into the high-voltage side of the transformer and the high-voltage side winding has a short-circuit fault (low frequency band is 0-500Hz), as shown in FIG. 4(a), 4(a) is the winding upper end short circuit, FIG. 4(b) is the winding middle end short circuit, and FIG. 4(c) is the winding lower end short circuit.
In different parts of the winding, as the degree of the short-circuit fault is increased (from short circuit 1-2 cakes to short circuit 1-6 cakes), the slope of the frequency-sweeping impedance curve of the low-frequency side of the winding is gradually reduced, because the impedance value of the winding is reduced due to the increase of the short-circuit fault (the number of short-circuit cakes is increased), and the amplitude is reflected on the curve chart to be lower. Data for 50Hz impedance values taken from the upper end of the winding are given in the following table
TABLE 3 50Hz impedance variation table under different winding faults
Figure BDA0002342656610000111
As can be seen from table 3, the impedance value at 50Hz is already out of the normal range of 2%, so that it is possible to quickly judge that the winding is faulty.
For example, fig. 5(a) is a frequency-sweep impedance curve during short-circuit fault at the upper end of the winding from 1kHz to 100kHz, and fig. 5(b) is a frequency-sweep impedance curve during short-circuit fault at the upper end of the winding from 100kHz to 600 kHz.
The resonance point of the frequency sweep impedance curve is shifted to a high frequency band between 200kHz and 300kHz as the fault degree is increased when the fault is positioned at the upper end of the high voltage side.
This phenomenon can be explained by the following formula,
Figure BDA0002342656610000112
wherein, L is the transformer inductance, C is the transformer capacitance, and f is the frequency.
As the short-circuit fault of the winding is increased (the number of short-circuit cakes is increased), the inductance of the winding is reduced, and the resonance frequency of the winding is shifted to a high frequency band according to the formula. It can be seen from table 4 that the correlation coefficient between the frequency bands is not obviously regular.
TABLE 4 correlation coefficient of sweep frequency impedance curve under different short circuit faults
Figure BDA0002342656610000113
FIG. 6(a) is a frequency-sweep impedance curve during a short-circuit fault at the middle end of the winding from 1kHz to 100kHz, and FIG. 6(b) is a frequency-sweep impedance curve during a short-circuit fault at the middle end of the winding from 100kHz to 600 kHz. FIG. 7(a) is a plot of swept-frequency impedance at short-circuit fault at the lower end of the winding from 1kHz to 100kHz, and FIG. 7(b) is a plot of swept-frequency impedance at short-circuit fault at the lower end of the winding from 100kHz to 600 kHz.
For short-circuit faults at the middle end and the lower end of the A-phase high-voltage winding, the sweep frequency impedance value of the winding is gradually reduced along with the increase of the fault degree in a low frequency range of 1kHz-100 kHz; while in the medium and high frequency range of 100kHz to 600kHz the swept impedance value of the winding increases gradually (in both cases presenting a diametrically opposite trend) with increasing fault level. Therefore, the fault of the winding can be judged by using the impedance value and the correlation coefficient at 50Hz, and the judgment accuracy is improved.
Fig. 8(a), 8(b), and 8c are respectively sweep impedance curves when the upper end of the winding, the middle end of the winding, and the lower end of the winding are located at the low voltage side, and it can be seen that the sweep curves at different positions and degrees only show differences in amplitude at this time, and the displacement of the resonance point is not obvious.
As can be seen from the above discussion, when the frequency sweep signal is injected from the high-voltage side (the low-voltage side is short-circuited and the fault is located at the high-voltage side), 150kHz-250kHz can be selected as a characteristic frequency band to diagnose the fault degree and position of the winding short circuit. The correlation coefficients are shown in Table 5 below.
TABLE 5 TABLE for the phase relation ratio of the upper, middle and lower ends of the winding respectively short-circuited by 1-2 cakes
Figure BDA0002342656610000121
Meanwhile, the sensitivity of the frequency sweep impedance method is proved to be far greater than that of the short-circuit impedance method, and the fault of the low-voltage winding can be judged in the middle and high frequency range.
Injecting signals at the low-voltage side of the transformer winding, and measuring a sweep frequency impedance curve graph of the short-circuit fault of the high-voltage side winding, wherein a sweep frequency impedance curve in the case of the short-circuit fault of the upper end of the winding with 1kHz-100kHz is shown in fig. 9(a), and a sweep frequency impedance curve in the case of the short-circuit fault of the upper end of the winding with 100kHz-600kHz is shown in fig. 9 (b). When the upper end of the winding has short circuit fault, two small peaks are generated on two sides of the first resonance peak between 200kHz and 300kHz, and the change rule of the two small peaks is opposite (the peak value of the left small peak is increased along with the fault degree, and the right small peak is reduced).
FIG. 10(a) is a plot of swept-frequency impedance during a short-circuit fault at the middle of the winding from 1kHz to 100kHz, and FIG. 10(b) is a plot of swept-frequency impedance during a short-circuit fault at the middle of the winding from 100kHz to 600 kHz. When short circuit fault occurs at the middle end of the winding, the original first resonance peak is split into two sub-peaks, and the two sub-peaks have opposite trend along with the aggravation of fault degree.
FIG. 11(a) is a plot of swept-frequency impedance at short-circuit fault at the lower end of the winding from 1kHz to 100kHz, and FIG. 11(b) is a plot of swept-frequency impedance at short-circuit fault at the lower end of the winding from 100kHz to 600 kHz. It can be known that the curve of the two frequency bands does not change obviously along with the aggravation of the short-circuit fault.
FIG. 12 is a graph of the swept impedance at the time of short circuit fault on the low-voltage side of the winding, and it can be known from the above discussion that when a swept signal is injected from the low-voltage side, the full-band swept impedance curve (between 500Hz and 1MHz) has two relatively obvious resonance peaks, where the first resonance peak is between 200kHz and 400kHz, and the peak value is relatively large (about 4000-6000 Ω); the second resonance peak is 800kHz later, with a peak around 1000 Ω. At the moment, the fault is placed on the high-voltage side winding, and the first resonance peak (200kHz-300kHz) has different change characteristics according to different fault positions; when the fault is placed on the low voltage side, the first resonance peak will decrease by 1k Ω with the downward movement of the fault location (from top to middle or from middle to bottom).
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (10)

1. A transformer short-circuit fault positioning detection method is characterized by being suitable for a pre-established transformer short-circuit fault positioning detection system, and comprises the following steps:
step S1: short-circuiting one side of a winding of a normal transformer, connecting the other side of the winding with a transformer short-circuit fault positioning and detecting system, detecting the normal transformer by the transformer short-circuit fault positioning and detecting system, and measuring a sweep frequency impedance curve of the normal transformer;
step S2: detecting the transformer to be detected by using a transformer short-circuit fault positioning detection system to obtain a frequency sweeping impedance curve of the transformer to be detected, comparing the frequency sweeping impedance curve of the transformer to be detected with a frequency sweeping impedance curve of a normal transformer, and judging whether the transformer to be detected has a fault according to a comparison result;
step S3: if the judgment result is that the transformer to be tested has a fault, judging whether the fault type is a short-circuit fault or not according to the sweep frequency impedance curve;
step S4: and if the fault type is judged to be a short-circuit fault, calculating and analyzing the position area of the short-circuit fault of the transformer winding to be tested.
2. The transformer short-circuit fault location detection method according to claim 1, wherein in step S1, the transformer short-circuit fault location detection system sends out a sinusoidal signal of 10Hz to 1MHz, power amplification is performed on the signal, and then the signal is applied to a normal transformer winding, the transformer short-circuit fault location detection system collects voltage and current of the normal transformer winding, calculates an impedance value of the transformer to be detected, and draws a sweep frequency impedance curve.
3. The transformer short-circuit fault location detection method according to claim 1, characterized in that in step S2, one side of the to-be-detected transformer is short-circuited, and the other side is connected to a transformer short-circuit fault location detection system, if the sweep-frequency impedance curve of the to-be-detected transformer completely coincides with the sweep-frequency impedance curve of the normal transformer, the to-be-detected transformer has no fault, and if the sweep-frequency impedance curve of the to-be-detected transformer does not coincide with the sweep-frequency impedance curve of the normal transformer, the.
4. The transformer short-circuit fault location detection method according to claim 3, wherein in step S3, the impedance value change rate of the sweep impedance curve at 50Hz is calculated, and if the impedance value change rate exceeds 2%, the fault type is a short-circuit fault.
5. The transformer short-circuit fault location detection method according to claim 4, wherein in step S4, a correlation coefficient between a frequency sweep impedance curve of the transformer to be detected and a frequency sweep impedance curve of a normal transformer is calculated.
6. The transformer short-circuit fault location detection method according to claim 5, characterized in that a sinusoidal signal is injected from the high-voltage side of the transformer to be detected, and the position of the low-voltage side short-circuit fault is judged;
if the correlation coefficient is 0 at 1-100kHz, the correlation coefficient is 0.2-0.5 at 100-600kHz, and the correlation coefficient is 1.3-1.8 at 600kHz-1000kHz, the short-circuit fault of the middle end of the winding at the low-voltage side is judged;
at 1-100kHz, the correlation coefficient is between 0.1-0.3, at 100-600kHz, the correlation coefficient is between 1.1-1.5, at 600kHz-1000kHz, the correlation coefficient is between 1-1.3, and then the upper end or the lower end of the winding at the low-voltage side is judged to have short-circuit fault.
7. The transformer short-circuit fault location detection method according to claim 5, characterized in that a sinusoidal signal is injected from the high-voltage side of the transformer to be detected, and the position of the high-voltage side short-circuit fault is judged;
if the frequency is between 1 and 1000kHz and the correlation coefficient is between 1 and 1.5, judging that the upper end of the high-voltage side winding has a short-circuit fault;
if the correlation coefficient is between 1 and 100kHz, between 1.7 and 1.8, between 100 and 600kHz, between 2 and 2.1, between 600kHz and 1000kHz, and between 2 and 2.1, judging that the middle end of the high-voltage side winding has short-circuit fault;
if the correlation coefficient is between 1.9 and 2 at 1-100kHz, between 1.6 and 1.8 at 100-600kHz and between 1.8 and 1.9 at 600kHz-1000kHz, the lower end of the high-voltage side winding is judged to have short-circuit fault.
8. The transformer short-circuit fault location detection method according to claim 7, characterized in that when a short-circuit fault occurs at the middle end and the lower end of the high-voltage side winding, the larger the swept frequency impedance value of the winding is, the smaller the fault degree is at a low frequency range of 1kHz-100 kHz; in the middle and high frequency range of 100kHz-600kHz, the larger the frequency sweep impedance value of the winding is, the larger the fault degree is.
9. The transformer short-circuit fault location detection method according to claim 7, characterized in that when a short-circuit fault occurs at the upper end of the high-voltage side winding, the larger the high-frequency band movement of the resonance point of the frequency-sweep impedance curve between 200kHz and 300kHz is, the larger the fault degree is.
10. The transformer short-circuit fault positioning detection system is characterized by comprising a signal generator, a power amplifier, a data acquisition card and a microprocessor, wherein the microprocessor is respectively connected with the input end of the signal generator and the output end of the data acquisition card, and the output end of the signal generator is connected with the input end of the power amplifier.
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