Frequency response based transformer winding fault detection method, system, and medium

Abstract

The embodiment of the present application relates to the technical field of transformer fault detection, and discloses a transformer winding fault detection method and system based on frequency response, and a medium, the method comprising: determining the equivalent inductance and equivalent capacitance of the transformer winding. The first-order ground coefficient of the driving point admittance is calculated by using the peak frequency and the trough frequency when the neutral point is grounded, and the first-order open circuit coefficient is calculated by using the peak frequency and the trough frequency when the neutral point is open. The first difference function is constructed by the equivalent inductance, the scaling rate and the first-order ground coefficient, and the second difference function is constructed by the equivalent capacitance and the first-order open circuit coefficient. The fault detection of the transformer winding is carried out according to the comparison between the fluctuation of the first difference function and the second difference function and the preset threshold, and early sensitive detection is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transformer fault detection, and in particular to a transformer winding fault detection method and system based on frequency response and a medium. BACKGROUND

[0002] The transformer winding is a key component of the power system, and its reliability directly affects the stable operation of the power system. However, due to long-term operation, environmental factors, design defects and other reasons, the transformer winding is prone to early faults, which poses a potential threat to the safe operation of the power grid.

[0003] Traditional detection methods mainly rely on periodic power-off maintenance and offline testing, which not only increases maintenance costs, but also affects the continuous power supply of the power system. Moreover, the traditional detection method has poor accuracy for early fault judgment, and cannot respond more sensitively to transformer winding faults, nor can it diagnose the severity of the fault. With the increasing requirements of modern power systems for safety and reliability, it is particularly important to develop an efficient, non-invasive and early warning method for transformer winding faults. SUMMARY

[0004] Therefore, it is necessary to propose a transformer winding fault detection method and system based on frequency response and a medium to solve the above problems.

[0005] A transformer winding fault detection method based on frequency response, the method comprising:

[0006] determining the equivalent inductance and equivalent capacitance of the transformer winding.

[0007] determining a first ground coefficient of the driving point admittance according to the peak frequency and the trough frequency when the neutral point of the transformer winding is grounded.

[0008] determining a first open circuit coefficient of the driving point admittance according to the peak frequency and the trough frequency when the neutral point of the transformer winding is open.

[0009] determining a first difference function according to the equivalent inductance and the first ground coefficient, and determining a second difference function according to the equivalent capacitance and the first open circuit coefficient.

[0010] performing fault detection of the transformer winding according to the comparison between the fluctuations of the first difference function and the second difference function and the preset threshold.

[0011] wherein the determination of the first ground coefficient of the driving point admittance according to the peak frequency and the trough frequency when the neutral point of the transformer winding is grounded comprises:

[0012] Collect the peak frequency and the trough frequency when the neutral point of the transformer winding is grounded.

[0013] According to Determine the first-order ground coefficient of the driving point admittance, wherein, is the first-order ground coefficient of the driving point admittance, is the peak frequency when the neutral point is grounded, is the trough frequency when the neutral point is grounded.

[0014] According to the peak frequency and the trough frequency when the neutral point of the transformer winding is open, the first-order open coefficient of the driving point admittance is determined, and specifically includes:

[0015] Collect the peak frequency and the trough frequency when the neutral point of the transformer winding is open.

[0016] According to Determine the first-order open coefficient of the driving point admittance, wherein, is the first-order open coefficient of the driving point admittance, is the peak frequency when the neutral point is open, is the trough frequency when the neutral point is open.

[0017] According to the equivalent inductance and the first-order ground coefficient, a first difference function is determined, and according to the equivalent capacitance and the first-order open coefficient, a second difference function is determined, and specifically includes:

[0018] According to Determine the first difference function, wherein, is the first difference function, is the equivalent inductance, is a preset scaling rate, is the first-order ground coefficient of the driving point admittance.

[0019] According to Determine the second difference function, wherein, is the second difference function, is the equivalent capacitance, is the first-order open coefficient of the driving point admittance.

[0020] According to the comparison between the fluctuation of the first difference function and the second difference function and a preset threshold, the fault detection of the transformer winding is performed, and specifically includes:

[0021] Determine whether the fluctuation amplitude or the fluctuation frequency of the first difference function and the second difference function is greater than a preset threshold, and the preset threshold is a first amplitude threshold or a first frequency threshold.

[0022] If the fluctuation amplitude or the fluctuation frequency of the first difference function and the second difference function is greater than a preset threshold, the transformer winding fails.

[0023] If the fluctuation amplitude of the first difference function and the second difference function is less than or equal to a preset threshold, the transformer winding does not occur.

[0024] The determining of the equivalent inductance and equivalent capacitance of the transformer winding specifically includes:

[0025] A current excitation is applied to the transformer winding, wherein the current excitation is determined by geometrically scaling the normal operating current of the transformer winding at a preset scaling rate.

[0026] The self-inductance of the transformer winding is determined according to the current excitation and the self-inductance coefficient of the transformer winding, and the mutual inductance of the transformer winding is determined according to the current excitation and the mutual inductance coefficient of the transformer winding.

[0027] An equivalent inductance is determined according to the self-inductance and the mutual inductance.

[0028] The series capacitance and ground capacitance of the transformer winding are obtained, and an equivalent capacitance is determined according to the series capacitance and the ground capacitance.

[0029] The step of determining the self-inductance of the transformer winding according to the current excitation and the self-inductance coefficient of the transformer winding, and determining the mutual inductance of the transformer winding according to the current excitation and the mutual inductance coefficient of the transformer winding, specifically includes:

[0030] according to Get the self-inductance of the transformer winding, where is the magnetic permeability, is the number of coil turns, is the cross-sectional area of ​​the coil, is the length of the coil.

[0031] according to Determine the self-inductance of the transformer winding, where For transformer The self-inductance of a winding, For the The self-inductance of the winding, For current excitation.

[0032] according to Determine the mutual inductance of the transformer windings, where For the The first winding and the The mutual inductance of the windings, For the The self-inductance of the winding, is the self-inductance coefficient of the j-th winding, and k is the coupling coefficient.

[0033] according to Determine the mutual inductance of the transformer windings, where For transformer The first winding and the The mutual inductance between the windings, For the The first winding and the The mutual inductance of the windings, For current excitation.

[0034] The determining of the equivalent inductance according to the self-inductance and the mutual inductance specifically includes:

[0035] according to Determine the equivalent inductance, where is the equivalent inductance, The connection between the i-th winding and the i-th winding of the transformer The mutual inductance between the windings, is the self-inductance of the transformer's first winding.

[0036] The determining of the equivalent capacitance according to the series capacitance and the ground capacitance specifically includes:

[0037] according to Determine the equivalent capacitance, where is the equivalent capacitance, is the series capacitor, is the grounding capacitor.

[0038] The method further comprises:

[0039] The fault level of the transformer winding is determined based on a comparison between the fluctuation of the first difference function and / or the second difference function and a preset fault level judgment condition.

[0040] The step of determining the fault level of the transformer winding according to the comparison between the fluctuation of the first difference function and / or the second difference function and the preset fault level judgment condition specifically includes:

[0041] Determining that the fault level of the transformer winding is a primary fault when the fluctuation amplitude of the first difference function and / or the second difference function reaches a second amplitude threshold, or when the fluctuation frequency of the first difference function and / or the second difference function reaches a second frequency threshold;

[0042] It is determined that the fluctuation amplitude of the first difference function and / or the second difference function reaches a third amplitude threshold, or when the fluctuation frequency of the first difference function and / or the second difference function reaches a third frequency threshold, the fault level of the transformer winding is a secondary fault.

[0043] A frequency response based transformer winding fault detection system, the system comprising:

[0044] An equivalent inductance and equivalent capacitance obtaining module for determining an equivalent inductance and an equivalent capacitance of the transformer winding.

[0045] A first order ground coefficient of driving point admittance determining module for determining a first order ground coefficient of driving point admittance according to a peak frequency and a valley frequency when a neutral point of the transformer winding is grounded.

[0046] A first order open circuit coefficient of driving point admittance determining module for determining a first order open circuit coefficient of driving point admittance according to a peak frequency and a valley frequency when a neutral point of the transformer winding is open.

[0047] A first difference function and a second difference function determining module for determining a first difference function according to the equivalent inductance and the first order ground coefficient, and determining a second difference function according to the equivalent capacitance and the first order open circuit coefficient.

[0048] A fault detection module for detecting a fault of the transformer winding according to a comparison between fluctuations of the first difference function and the second difference function and a preset threshold.

[0049] A computer readable storage medium storing a computer program, the computer program being executed by a processor to make the processor execute steps of the method.

[0050] The embodiment of the present application has the following beneficial effects:

[0051] The present application first obtains an equivalent inductance and an equivalent capacitance of a transformer winding. Further, a first order ground coefficient of driving point admittance is determined according to a peak frequency and a valley frequency when a neutral point of the transformer winding is grounded, and a first order open circuit coefficient of driving point admittance is determined according to a peak frequency and a valley frequency when a neutral point of the transformer winding is open, the first order ground coefficient being an approximate inductance actually measured, and the first order open circuit coefficient being an approximate capacitance actually measured. Finally, a first difference function is determined according to the equivalent inductance and the first order ground coefficient, and a second difference function is determined according to the equivalent capacitance and the first order open circuit coefficient, the first difference function being used to represent a variation characteristic of an ideal equivalent inductance and an approximate inductance actually measured, and the second difference function being used to represent a variation characteristic of an ideal equivalent capacitance and an approximate capacitance actually measured. Therefore, a fault of the transformer winding is detected according to a comparison between fluctuations of the first difference function and the second difference function and a preset threshold.

[0052] The application can early discover possible fault precursors by analyzing the key electrical parameters of the equivalent inductance and equivalent capacitance of the transformer winding, combining the frequency response characteristics of the transformer winding under different operating states (the frequency response is more sensitive than the current), avoiding that the not too serious winding deformation may not cause the change of the current or only produce subtle changes, and performing difference function analysis on the first-order ground coefficient and the first-order open circuit coefficient (approximately the equivalent inductance and the equivalent capacitance, respectively) of the driving point admittance and the ideal equivalent inductance and capacitance measured under the non-working state, and providing a reliable basis for taking preventive maintenance measures. Moreover, not only the electrical characteristics of the transformer winding are considered, but also the indirect characteristics of its mechanical and thermal states are combined, so that its health condition can be more comprehensively evaluated. BRIEF DESCRIPTION OF DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0054] Among them:

[0055] Figure 1 A flowchart of an embodiment of a transformer winding fault detection method based on frequency response provided by the present application;

[0056] Figure 2 A flowchart of another embodiment of a transformer winding fault detection method based on frequency response provided by the present application;

[0057] Figure 3 A flowchart of still another embodiment of a transformer winding fault detection method based on frequency response provided by the present application;

[0058] Figure 4 A structural schematic diagram of an embodiment of a transformer winding fault detection system based on frequency response provided by the present application;

[0059] Figure 5 A structural schematic diagram of an embodiment of a medium provided by the present application. DETAILED DESCRIPTION

[0060] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0061] like Figure 1 As shown, Figure 1 A method for detecting a transformer winding fault based on frequency response is provided by the present invention. The method comprises:

[0062] S101: Determine the equivalent inductance and equivalent capacitance of the transformer winding.

[0063] In one implementation scenario, in order to detect the transformer, it is necessary to apply current excitation to the transformer winding. The current excitation is determined by geometrically scaling the normal operating current of the transformer winding at a preset scaling rate.

[0064] Furthermore, the self-inductance of the transformer winding is determined based on the current excitation and the self-inductance coefficient of the transformer winding, and the mutual inductance of the transformer winding is determined based on the current excitation and the mutual inductance coefficient of the transformer winding.

[0065] Specifically, the self-inductance of the transformer winding is determined according to the following formula:

[0066] ;

[0067] in, For transformer The self-inductance of a winding, For the The self-inductance of the winding, is current excitation;

[0068] Furthermore, the mutual inductance of the transformer windings is determined according to the self-inductance of different transformer windings and the degree of magnetic coupling between the windings.

[0069] Determine the mutual inductance of the transformer windings using the following formula:

[0070] ;

[0071] in, For transformer The first winding and the The mutual inductance between the windings, For the The first winding and the The mutual inductance of the windings, For current excitation.

[0072] Furthermore, the equivalent inductance is determined based on the self-inductance and the mutual inductance.

[0073] Specifically, the equivalent inductance is determined according to the following formula:

[0074] ;

[0075] wherein, is the equivalent inductance, is the mutual inductance between the i-th winding and the j-th winding of the transformer, is the self-inductance of the i-th winding of the transformer.

[0076] Further, the series capacitance and the ground capacitance of the transformer winding are obtained, and the equivalent capacitance is determined according to the series capacitance and the ground capacitance. Specifically, the equivalent capacitance is determined according to the formula as shown below:

[0077] ;

[0078] wherein, is the equivalent capacitance, is the series capacitance, is the ground capacitance.

[0079] S102: determining the first-order ground coefficient of the driving point admittance according to the peak frequency and the valley frequency when the neutral point of the transformer winding is grounded.

[0080] S103: determining the first-order open circuit coefficient of the driving point admittance according to the peak frequency and the valley frequency when the neutral point of the transformer winding is open.

[0081] In one implementation scenario, the driving point admittance of the transformer refers to the equivalent admittance viewed from one side of the transformer, reflecting the response characteristics of the side port to the current. The driving point admittance characterizes the coefficient relationship between the input and output of the transformer winding, and the first-order ground coefficient may be approximately equal to the equivalent inductance , and the first-order open circuit coefficient may be approximately equal to the equivalent capacitance . Therefore, the first-order ground coefficient may be taken as the approximate inductance actually measured, and the first-order open circuit coefficient may be taken as the approximate capacitance actually measured. By combining the frequency response into the calculation, the sensitivity of fault detection can be improved.

[0082] In determining the first-order ground coefficient and the first-order open circuit coefficient of the driving point admittance, first, the peak frequency and the valley frequency when the neutral point of the transformer winding is grounded, and the peak frequency and the valley frequency when the neutral point of the transformer winding is open are collected by a frequency meter or an impedance meter. The neutral point of the transformer refers to the point connected at the end of the winding, which is usually used for grounding or connecting protection devices. The selection of the neutral point is closely related to the connection mode of the winding.

[0083] Further, the first-order ground coefficient of the driving point admittance is determined according to the formula as shown below: ​

[0084] ;

[0085] wherein, is a first-order ground coefficient of the driving-point admittance, is a peak frequency when the neutral point is grounded, is a valley bottom frequency when the neutral point is grounded.

[0086] The first-order open circuit coefficient of the driving-point admittance is determined according to the formula as shown below:

[0087] ;

[0088] wherein, is a first-order open circuit coefficient of the driving-point admittance, is a peak frequency when the neutral point is open, is a valley bottom frequency when the neutral point is open.

[0089] S104: determining a first difference function according to the equivalent inductance and the first-order ground coefficient, and determining a second difference function according to the equivalent capacitance and the first-order open circuit coefficient.

[0090] In one implementation scenario, the first difference function is used to represent the variation characteristics of the ideal equivalent inductance and the actually measured approximate inductance, and the second difference function is used to represent the variation characteristics of the ideal equivalent capacitance and the actually measured approximate capacitance. The first difference function is determined according to the formula as shown below:

[0091] ;

[0092] wherein, is the first difference function, is the equivalent inductance, is a preset scaling rate, is a first-order ground coefficient of the driving-point admittance.

[0093] The second difference function is determined according to the formula as shown below:

[0094] ;

[0095] wherein, is the second difference function, is the equivalent capacitance, is a first-order open circuit coefficient of the driving-point admittance.

[0096] S105: performing fault detection on the transformer winding according to a comparison between the fluctuations of the first difference function and the second difference function and a preset threshold.

[0097] In one implementation scenario, the fault detection of the transformer winding is performed according to comparison of fluctuations of the first difference function and the second difference function with a preset threshold. The first difference function is used to represent the change characteristics of the ideal equivalent inductance and the actually measured approximate inductance, and the second difference function is used to represent the change characteristics of the ideal equivalent capacitance and the actually measured approximate capacitance. When the winding has a fault such as axial deformation or turn-to-turn short circuit, the equivalent inductance of the winding will be obviously changed. When the winding has a fault such as radial deformation, the equivalent capacitance of the winding will be obviously changed. Therefore, the change characteristics of the ideal equivalent inductance and the ideal equivalent capacitance and the actually measured approximate inductance and the actually measured approximate capacitance can be calculated to determine whether the winding has a fault.

[0098] Specifically, the values of the first difference function and the second difference function should be in a stable state under the normal operation of the transformer, and when the first difference function and the second difference function have obvious fluctuations, it can be considered that the winding of the transformer has a fault.

[0099] As can be seen from the above description, the equivalent inductance and the equivalent capacitance of the transformer winding are first acquired. Further, the first-order ground coefficient of the driving point admittance is determined according to the peak frequency and the valley bottom frequency when the neutral point of the transformer winding is grounded, and the first-order open circuit coefficient of the driving point admittance is determined according to the peak frequency and the valley bottom frequency when the neutral point of the transformer winding is open. The first-order ground coefficient is taken as the actually measured approximate inductance, and the first-order open circuit coefficient is taken as the actually measured approximate capacitance. Finally, the first difference function is determined according to the equivalent inductance and the first-order ground coefficient, and the second difference function is determined according to the equivalent capacitance and the first-order open circuit coefficient. The first difference function can be used to represent the change characteristics of the ideal equivalent inductance and the actually measured approximate inductance, and the second difference function can be used to represent the change characteristics of the ideal equivalent capacitance and the actually measured approximate capacitance. Therefore, the fault detection of the transformer winding is performed according to comparison of fluctuations of the first difference function and the second difference function with a preset threshold.

[0100] The present application analyzes the equivalent inductance and the equivalent capacitance and other key electrical parameters of the transformer winding, and combines the frequency response characteristics of the transformer winding under different operating states (the frequency response is more sensitive than the current), avoids that the not too serious winding deformation may not cause the change of the current or only produces slight change, and performs difference function analysis on the first-order ground coefficient and the first-order open circuit coefficient (which are approximately equal to the equivalent inductance and the equivalent capacitance, respectively) of the driving point admittance and the ideal equivalent inductance and the capacitance measured in the non-working state, so that the possible precursors of the fault can be found early, and a reliable basis is provided for taking preventive maintenance measures. Moreover, not only the electrical characteristics of the transformer winding are considered, but also the indirect characteristics of the mechanical and thermal states are combined, so that the health condition of the transformer winding can be more comprehensively evaluated.

[0101] As shown in Figure 2 , the first difference function and the second difference function are calculated according to the equivalent inductance and the equivalent capacitance of the transformer winding, and the first-order ground coefficient and the first-order open circuit coefficient of the driving point admittance are calculated according to the peak frequency and the valley bottom frequency when the neutral point of the transformer winding is grounded and open, respectively. The first-order ground coefficient is taken as the actually measured approximate inductance, and the first-order open circuit coefficient is taken as the actually measured approximate capacitance. The first difference function is determined according to the equivalent inductance and the first-order ground coefficient, and the second difference function is determined according to the equivalent capacitance and the first-order open circuit coefficient. The first difference function can be used to represent the change characteristics of the ideal equivalent inductance and the actually measured approximate inductance, and the second difference function can be used to represent the change characteristics of the ideal equivalent capacitance and the actually measured approximate capacitance. Therefore, the fault detection of the transformer winding is performed according to comparison of fluctuations of the first difference function and the second difference function with a preset threshold. Figure 2A method for detecting a transformer winding fault based on frequency response is provided by the present invention. The method comprises:

[0102] S201: applying current excitation to the transformer winding, where the current excitation is determined by geometrically scaling the normal operating current of the transformer winding at a preset scaling rate.

[0103] In one implementation scenario, to test a transformer, it is necessary to apply current excitation to its windings so that the self-inductance and mutual inductance of the transformer windings can be calculated under this current excitation. The self-inductance and mutual inductance of the transformer windings can be calculated simultaneously with a single application of the current excitation, or the self-inductance and mutual inductance of the transformer windings can be calculated separately by applying the same current excitation twice.

[0104] Among them, the current excitation can be determined by scaling the normal working current of the transformer winding at a preset scaling rate; specifically, since the voltage and current during actual operation are too large to be controlled, the current can be appropriately scaled during data acquisition and detection to prevent the distortion of the measurement data caused by the current being too large. For example, the scaling rate can be Since the current excitation is scaled here, the scaling factor needs to be substituted into the subsequent calculation process to prevent inaccurate data.

[0105] S202: Determine the self-inductance of the transformer winding according to the current excitation and the self-inductance coefficient of the transformer winding, and determine the mutual inductance of the transformer winding according to the current excitation and the mutual inductance coefficient of the transformer winding.

[0106] In one implementation scenario, when determining the self-inductance When the current excitation condition is given, the calculation is performed. The current excitation is determined by scaling the normal operating current of the transformer winding with a preset scaling ratio (assuming the preset scaling ratio is ), calculate the self-inductance according to the following formula:

[0107] ;

[0108] in, For transformer The self-inductance of a winding, For the The self-inductance of the winding, , Indicates the total number of windings, The current excitation is determined by scaling the normal operating current of the transformer winding at a preset scaling rate. Indicates the rate of change of current. The mutual inductance M can be calculated by the magnetic permeability μ, the number of turns N, the cross-sectional area A of the coil, and the length L of the coil as follows:

[0109] ;

[0110] wherein μ is the magnetic permeability, N is the number of turns of the coil, A is the cross-sectional area of the coil, and L is the length of the coil.

[0111] In determining the mutual inductance M, the mutual inductance is calculated according to the following formula under the condition that the same current excitation is given to different windings as in determining the self-inductance:

[0112] ;

[0113] wherein Mij is the mutual inductance between the i-th winding and the j-th winding of the transformer, I is the current excitation, Mij represents the mutual inductance coefficient of the i-th winding and the j-th winding, and Mji represents the mutual inductance coefficient of the j-th winding and the i-th winding. The mutual inductance coefficient Mij and Mji can be determined according to the self-inductance coefficients of different windings of the transformer and the degree of magnetic coupling between the windings as follows:

[0114] ;

[0115] wherein k is the coupling coefficient, which is 1, L is the length of the coil, and μ is the magnetic permeability.

[0116] ​​​​​​​​​​​​​​​​​​​​​​It should be noted that self-induction refers to the electromotive force generated on the transformer winding due to the change of current, that is, when the current through a winding changes, the winding itself will induce an opposite electromotive force due to the change of the magnetic field, which is called self-induction. Mutual induction refers to the mutual induction between two adjacent windings, that is, when the current in one winding changes, it will generate a changing magnetic field, which in turn induces an electromotive force in the adjacent winding, which is called mutual induction. The equivalent inductance in the ideal state can be calculated according to the self-induction and mutual induction, and the equivalent capacitance in the ideal state can be calculated according to the series capacitance and the ground capacitance.

[0117] S203: Determine the equivalent inductance according to the self-induction and mutual induction.

[0118] In one implementation scenario, only the mutual inductance coefficient between the adjacent two windings is considered when calculating the equivalent inductance. The equivalent inductance in the ideal state can be calculated by the following formula:

[0119] ;

[0120] wherein, L is the equivalent inductance, M is the mutual inductance between the i-th winding and the j-th winding, Ls is the self-induction of the i-th winding of the transformer.

[0121] In addition, since the main purpose of the present embodiment is to detect early faults of the transformer, the goal is to be qualitative rather than quantitative, and the failure of any one winding will cause the inductance data characteristics to change significantly, therefore, in another optional implementation, in order to simplify the difficulty of data analysis, only the one-way mutual inductance effect is considered when calculating the equivalent inductance, to facilitate subsequent data processing, and will not affect the implementation effect of fault detection. For example, when calculating the equivalent inductance, it is set that the first inductance is only affected by the mutual inductance between the first winding and the second winding, the second inductance is only affected by the mutual inductance between the second winding and the third winding, and so on. Therefore, the equivalent inductance can be calculated by the following simplified formula:

[0122] ;

[0123] wherein, L is the equivalent inductance, M is the mutual inductance between the i-th winding and the j-th winding, Ls is the self-induction of the i-th winding of the transformer.

[0124] It should be noted that in actual application, it can be determined according to actual needs which calculation method of equivalent inductance to select.

[0125] ​​S204: Obtain the series capacitance and the ground capacitance of the transformer winding, and determine the equivalent capacitance according to the series capacitance and the ground capacitance.

[0126] In one implementation scenario, the series capacitance and the ground capacitance of the transformer winding are first obtained, and specifically, the series capacitance is calculated using a parallel plate capacitance model The calculation is as shown in the following formula:

[0127] ;

[0128] wherein, is the series capacitance of the transformer winding, is the vacuum permittivity, is the relative permittivity of the medium, is the effective overlapping area between the i-th winding and the j-th winding, is the thickness of the inter-turn insulation layer. In the calculation mode of the formula, only the series capacitance between the adjacent two windings is considered. It should be noted that the series capacitance uses the interlayer capacitance, which refers to the capacitance between the layers of the transformer winding. Specifically, since the inter-turn capacitance is small, the present application does not calculate the inter-turn capacitance, but only calculates the interlayer capacitance, which refers to the capacitance between different windings of the transformer.

[0129] When calculating the ground capacitance , the winding can be approximated as a coaxial cylindrical model, and the ground capacitance

[0130] can be calculated by the following formula:

[0131] ;

[0132] wherein, is the ground capacitance of the transformer winding, is the length of the i-th winding, is the outer diameter of the winding, is the inner diameter of the winding. Further, the equivalent capacitance is determined according to the series capacitance and the ground capacitance, and the equivalent capacitance in an ideal case is calculated according to the following formula:

[0133]

[0134] ;

[0135] wherein, is the equivalent capacitance, is the series capacitance, is the ground capacitance.

[0136] ​​​S205: Determine a first ground coefficient of the driving point admittance according to the peak frequency and the valley frequency when the neutral point of the transformer winding is grounded.

[0137] S206: Determine a first open circuit coefficient of the driving point admittance according to the peak frequency and the valley frequency when the neutral point of the transformer winding is open.

[0138] In one implementation scenario, the peak frequency and the valley frequency when the neutral point of the transformer winding is grounded, and the peak frequency and the valley frequency when the neutral point of the transformer winding is open are collected.

[0139] Further, the first ground coefficient of the driving point admittance is determined according to the formula as shown below:

[0140] ;

[0141] wherein, is the first ground coefficient of the driving point admittance, is the peak frequency when the neutral point is grounded, is the valley frequency when the neutral point is grounded.

[0142] The first open circuit coefficient of the driving point admittance is determined according to the formula as shown below:

[0143] ;

[0144] wherein, is the first open circuit coefficient of the driving point admittance, is the peak frequency when the neutral point is open, is the valley frequency when the neutral point is open.

[0145] S207: Determine a first difference function according to the equivalent inductance, a preset scaling rate and the first ground coefficient, and determine a second difference function according to the equivalent capacitance and the first open circuit coefficient.

[0146] In one implementation scenario, the first difference function is determined according to the formula as shown below:

[0147] ;

[0148] wherein, is the first difference function, is the equivalent inductance, is the preset scaling rate, is the first ground coefficient of the driving point admittance.

[0149] The second difference function is determined according to the formula as shown below:

[0150] ;

[0151] wherein, is a second difference function, is an equivalent capacitance, is a first open circuit coefficient of a driving point admittance.

[0152] S208: Determine whether the fluctuation amplitude or fluctuation frequency of the first difference function and the second difference function is greater than a preset threshold value, and the preset threshold value is a first amplitude threshold value or a first frequency threshold value.

[0153] S2081: If the fluctuation amplitude or fluctuation frequency of the first difference function and the second difference function is greater than the preset threshold value, the transformer winding has a fault.

[0154] S2082: If the fluctuation amplitude of the first difference function and the second difference function is less than or equal to the preset threshold value, the transformer winding has no fault.

[0155] In one implementation scenario, it is determined whether the fluctuation amplitude of the first difference function and the second difference function exceeds the first amplitude threshold value, and if it exceeds the first amplitude threshold value, it is determined that the transformer winding has a fault. Specifically, the first amplitude threshold value is set in advance, and the amplitude threshold value can reflect the tolerance of the transformer to the fluctuation amplitude. Once the fluctuation amplitude exceeds the first amplitude threshold value, it can be determined that the transformer winding has a fault. The amplitude threshold value can be obtained by calculation, or can be obtained by summarizing multiple repeated actual operation tests.

[0156] In another implementation scenario, it is determined whether the fluctuation frequency of the first difference function and the second difference function exceeds the first frequency threshold value, and if it exceeds the first frequency threshold value, it is determined that the transformer winding has a fault. Specifically, the first frequency threshold value is set in advance, and the frequency threshold value can reflect the tolerance of the transformer to the fluctuation frequency. Once the fluctuation frequency exceeds the first frequency threshold value, it can be determined that the transformer winding has a fault. The frequency threshold value can be obtained by calculation, or can be obtained by summarizing multiple repeated actual operation tests.

[0157] In yet another implementation scenario, it is determined whether the fluctuation of the first difference function and the second difference function satisfies a preset rule, and if it does not satisfy the preset rule, it is determined that the transformer winding has a fault. Specifically, the normal fluctuation change rule is obtained in advance by calculation or repeated tests, and when the fluctuation deviates from the change rule, it can be determined that the transformer winding has a fault.

[0158] The fluctuation preset rule can refer to the function curve change. Some function curve changes may not be able to be summarized by the change of frequency or amplitude alone, so the fluctuation preset rule can be preset for determination. For example, the curve change of the first difference function and the second difference function when a fault occurs in the past can be set as the preset rule, and when the change deviates from the preset rule, it is determined that the transformer winding has a fault.

[0159] By using the fluctuation amplitude, frequency, regularity and other characteristics of the first difference function and the second difference function, it is possible to sensitively and accurately evaluate and analyze whether a transformer fault occurs.

[0160] From the above description, it can be seen that the present invention applies current excitation to the transformer winding, determines the self-inductance of the transformer winding based on the current excitation and the self-inductance coefficient of the transformer winding, and determines the mutual inductance of the transformer winding based on the current excitation and the mutual inductance coefficient of the transformer winding. The equivalent inductance under ideal conditions is calculated based on the self-inductance and mutual inductance, and the series capacitance and grounding capacitance of the transformer winding are obtained, and the equivalent capacitance under ideal conditions is calculated based on the series capacitance and grounding capacitance. Furthermore, the first-order grounding coefficient of the driving point admittance is determined based on the peak frequency and valley frequency when the neutral point of the transformer winding is grounded, and the first-order open-circuit coefficient of the driving point admittance is determined based on the peak frequency and valley frequency when the neutral point of the transformer winding is open, and the first-order grounding coefficient is converted to the peak frequency and valley frequency when the neutral point of the transformer winding is open. As the approximate inductance actually measured, the first-order open-circuit coefficient As the actual measured approximate capacitance. Finally, a first difference function is determined based on the equivalent inductance, a preset scaling factor, and the first-order grounding coefficient, and a second difference function is determined based on the equivalent capacitance and the first-order open-circuit coefficient. The first difference function can be used to represent the variation characteristics between the ideal equivalent inductance and the actual measured approximate inductance, while the second difference function can be used to represent the variation characteristics between the ideal equivalent capacitance and the actual measured approximate capacitance. Therefore, transformer winding fault detection is performed based on the comparison of the fluctuations of the first and second difference functions with a preset threshold. The present invention detects current changes and combines them with the frequency response (frequency response is more sensitive than current response) to avoid minor or minimal current changes due to less severe winding deformation. The first-order grounding coefficient and the first-order open-circuit coefficient of the driving point admittance (approximately equivalent inductance and equivalent capacitance, respectively) are analyzed using a difference function with the ideal equivalent inductance and capacitance measured in the non-operating state to determine the presence of early faults, promptly detect winding faults, reduce downtime and repair costs, extend equipment life, and improve the overall operational efficiency of the power grid.

[0161] like Figure 3 As shown, Figure 3 A method for detecting a transformer winding fault based on frequency response is provided in accordance with another embodiment of the present invention. The method comprises:

[0162] S301: Determine the fault level of the transformer winding according to a comparison between the fluctuation of the first difference function and / or the second difference function and a preset fault level judgment condition.

[0163] S3011: Determine that the fluctuation amplitude of the first difference function and / or the second difference function reaches a second amplitude threshold, or when the fluctuation frequency of the first difference function and / or the second difference function reaches a second frequency threshold, the fault level of the transformer winding is a level one fault.

[0164] S3012: Determine that the fluctuation amplitude of the first difference function and / or the second difference function reaches a third amplitude threshold, or when the fluctuation frequency of the first difference function and / or the second difference function reaches a third frequency threshold, the fault level of the transformer winding is a secondary fault.

[0165] In one implementation scenario, in order to implement fault classification judgment, the fault level judgment condition can set multiple classification thresholds for the amplitude, frequency and other characteristics of the fluctuation of the first difference function and the second difference function. Specifically, when the amplitude of the fluctuation of the first difference function and / or the second difference function reaches the second amplitude threshold, or when the frequency of the fluctuation of the first difference function and / or the second difference function reaches the second frequency threshold, it can be identified as a first-level fault; when the amplitude of the fluctuation of the first difference function and / or the second difference function reaches the third amplitude threshold, or when the frequency of the fluctuation of the first difference function and / or the second difference function reaches the third frequency threshold, it can be identified as a second-level fault. Among them, the specific threshold value can be determined according to the actual situation of the power grid or transformer, and no specific limitation is made here.

[0166] like Figure 4 As shown, Figure 4 A schematic diagram of a transformer winding fault detection system based on frequency response according to an embodiment of the present invention is provided. A transformer winding fault detection system 10 based on frequency response includes:

[0167] The equivalent inductance and equivalent capacitance determination module 11 is used to determine the equivalent inductance and equivalent capacitance of the transformer winding.

[0168] The first-order grounding coefficient determining module 12 of the driving point admittance is used to determine the first-order grounding coefficient of the driving point admittance according to the peak frequency and the valley frequency when the neutral point of the transformer winding is grounded.

[0169] The first-order open-circuit coefficient determination module 13 of the driving-point admittance is used to determine the first-order open-circuit coefficient of the driving-point admittance according to the peak frequency and the valley frequency when the neutral point of the transformer winding is open-circuited.

[0170] The first difference function and second difference function determining module 14 is configured to determine the first difference function according to the equivalent inductance and the first-order grounding coefficient, and to determine the second difference function according to the equivalent capacitance and the first-order open-circuit coefficient.

[0171] The fault detection module 15 is configured to detect the fault of the transformer winding according to comparison between fluctuation of the first difference function and the second difference function and the preset threshold.

[0172] In one implementation scenario, in the equivalent inductance and equivalent capacitance determination module 11, a current excitation is applied to the transformer winding, the current excitation is determined according to preset scaling of normal working current of the transformer winding; the self-inductance of the transformer winding is determined according to the current excitation and the self-inductance coefficient of the transformer winding, and the mutual inductance of the transformer winding is determined according to the current excitation and the mutual inductance coefficient of the transformer winding; the equivalent inductance is determined according to the self-inductance and the mutual inductance; the series capacitance and the ground capacitance of the transformer winding are obtained, and the equivalent capacitance is determined according to the series capacitance and the ground capacitance.

[0173] In the first-order ground coefficient determination module 12 of the driving point admittance, the peak frequency and the valley frequency when the neutral point of the transformer winding is grounded are collected; the first-order ground coefficient of the driving point admittance is determined according to , wherein, is the first-order ground coefficient of the driving point admittance, is the peak frequency when the neutral point is grounded, is the valley frequency when the neutral point is grounded.

[0174] In the first-order open circuit coefficient determination module 13 of the driving point admittance, the peak frequency and the valley frequency when the neutral point of the transformer winding is open are collected; the first-order open circuit coefficient of the driving point admittance is determined according to , wherein, is the first-order open circuit coefficient of the driving point admittance, is the peak frequency when the neutral point is open, is the valley frequency when the neutral point is open.

[0175] In the first difference function and the second difference function determination module 14, the first difference function is determined according to , wherein, is the first difference function, is the equivalent inductance, is the preset scaling, is the first-order ground coefficient of the driving point admittance; the second difference function is determined according to , wherein, is the second difference function, is the equivalent capacitance, is the first-order open circuit coefficient of the driving point admittance. Wherein, the first difference function is used to represent the change characteristics of the ideal equivalent inductance and the actual measured approximate inductance, and the second difference function is used to represent the change characteristics of the ideal equivalent capacitance and the actual measured approximate capacitance.

[0176] In the fault detection module 15, it is determined whether the fluctuation amplitude or the fluctuation frequency of the first difference function and the second difference function is greater than a preset threshold value, which is a first amplitude threshold value or a first frequency threshold value; if the fluctuation amplitude or the fluctuation frequency of the first difference function and the second difference function is greater than the preset threshold value, the transformer winding has a fault; if the fluctuation amplitude of the first difference function and the second difference function is less than or equal to the preset threshold value, the transformer winding has no fault. Therefore, the fault detection module 17 can determine whether the winding has a fault by calculating the change characteristics of the ideal equivalent inductance and the ideal equivalent capacitance and the actually measured approximate inductance and the actually measured approximate capacitance.

[0177] As Figure 5 shown, Figure 5 is a structural schematic diagram of an embodiment of the medium provided by the present application. The medium 20 stores at least a computer program 21, and the computer program 21 is executed by a processor to implement the method as shown in Figure 1 、 Figure 2 and Figure 3 , and the detailed method can be referred to the above, which will not be repeated here. In an embodiment, the medium 20 can be a storage chip, a hard disk or a mobile hard disk or an optical disc, and other readable and writable storage tools, and can also be a server and the like.

[0178] In addition, the processes depicted in the drawings do not necessarily have to be implemented in the specific order shown or in a continuous order to achieve the desired results. In some embodiments, multi-task processing and parallel processing are also possible or can be advantageous.

[0179] Each of the embodiments in the specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment mainly explains the difference from other embodiments. Especially, for the device, equipment, non-volatile computer readable storage medium embodiments, since they are basically similar to the method embodiments, they are described more simply, and the related parts can be referred to the part of the method embodiment.

[0180] The device, equipment, non-volatile computer readable storage medium and method provided by the embodiments of the present application are corresponding, therefore, the device, equipment, non-volatile computer storage medium also has similar beneficial technical effects as the corresponding method, since the beneficial technical effects of the method have been described in detail above, therefore, the beneficial technical effects of the corresponding device, equipment, non-volatile computer storage medium will not be repeated here.

[0181] The systems, apparatuses, modules, or units disclosed in the above embodiments can be implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer. Specifically, the computer can be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0182] For the sake of description, the above apparatuses are described in various units respectively according to functions. Of course, the functions of the units can be implemented in one or more software and / or hardware in the implementation of the present specification. Those skilled in the art should understand that the embodiments of the present specification can be provided as a method, a system, or a computer program product. Therefore, the embodiments of the present specification can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the embodiments of the present specification can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, a magnetic disk storage, a CD-ROM, an optical storage, and the like) containing computer-usable program code.

[0183] The present specification is described with reference to flowcharts and / or block diagrams of methods, devices (systems) and computer program products according to embodiments of the present specification. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to produce a machine, so that the instructions executed by the computer or other programmable data processing devices produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one or more flows and / or blocks Figure 1 The functions specified in one or more flows and / or blocks

[0184] These computer program instructions can also be stored in a computer-readable memory that can guide the computer or other programmable data processing devices to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including instruction devices that implement the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one or more flows and / or blocks Figure 1 The functions specified in one or more flows and / or blocks

[0185] These computer program instructions can also be loaded into a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 Figure 1 The flowchart blocks or blocks in the multiple flows and / or blocks

[0186] In one typical configuration, the computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0187] The memory can include non-persistent memory and / or volatile memory, such as random access memory (RAM) about which the computer stores information about an operating system, application software, and / or the like. Memory is an example of computer readable media.

[0188] Computer readable media includes permanent and non-permanent, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read only memory (ROM), electrically erasable programmable read only memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), digital versatile disc (DVD), or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information accessible to a computing device. According to the definition herein, computer readable media does not include transitory media such as modulated data signals and carrier waves.

[0189] It should also be noted that the terms "comprising", "containing" or any other variant thereof are intended to cover a non-exclusive inclusion, such that a process, method, article or apparatus that comprises a list of elements does not only include those elements, but can also include other elements not expressly listed or inherent to such process, method, article or apparatus. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article or apparatus that includes the element.

[0190] ​The specification can be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, and the like, that perform particular tasks or implement particular abstract data types. Computer-executable instructions, associated data structures, and program modules represent examples of the program code means for executing steps of the methods disclosed herein. The particular sequence of steps and methods described in this specification is not the only manner in which the methods can be practiced. Likewise, the general description of the sequence of operations above applies to the methods in one or more aspects.

[0191] Each of the embodiments in the specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the difference from other embodiments. In particular, the system embodiments are described simply because they are basically similar to the method embodiments, and the relevant parts can be referred to the description of the method embodiments.

[0192] The above disclosure is merely preferred embodiments of the present application and cannot limit the scope of the present application. Any equivalent changes made according to the claims of the present application are still within the scope of the present application.

Claims

1. A frequency response based transformer winding fault detection method, characterized by, The method comprises: determining the equivalent inductance and equivalent capacitance of the transformer winding; determining a first ground coefficient of the driving point admittance according to the peak frequency and the trough frequency when the neutral point of the transformer winding is grounded; determining a first open circuit coefficient of the driving point admittance according to the peak frequency and the trough frequency when the neutral point of the transformer winding is open; determining a first difference function according to the equivalent inductance and the first ground coefficient, and determining a second difference function according to the equivalent capacitance and the first open circuit coefficient, wherein the determining the first difference function according to the equivalent inductance and the first ground coefficient, and the determining the second difference function according to the equivalent capacitance and the first open circuit coefficient, specifically comprises: determining a first difference function according to the equivalent inductance and the first ground coefficient, and determining a second difference function according to the equivalent capacitance and the first open circuit coefficient, wherein the determining the first difference function according to the equivalent inductance and the first ground coefficient, and the determining the second difference function according to the equivalent capacitance and the first open circuit coefficient, specifically comprises: the first difference function is the equivalent inductance is the preset scaling rate is the first ground coefficient of the driving point admittance; the determining the second difference function according to the equivalent capacitance and the first open circuit coefficient, specifically comprises: determining a first difference function according to the equivalent inductance and the first ground coefficient, and determining a second difference function according to the equivalent capacitance and the first open circuit coefficient, wherein the determining the first difference function according to the equivalent inductance and the first ground coefficient, and the determining the second difference function according to the equivalent capacitance and the first open circuit coefficient, specifically comprises: the second difference function is the equivalent capacitance is the first open circuit coefficient of the driving point admittance; detecting the fault of the transformer winding according to the comparison between the fluctuation of the first difference function and the second difference function and the preset threshold.

2. A frequency response based transformer winding fault detection method as claimed in claim 1, wherein, The determination of the first ground coefficient of the driving point admittance according to the peak frequency and the trough frequency when the neutral point of the transformer winding is grounded specifically comprises: collecting the peak frequency and the trough frequency when the neutral point of the transformer winding is grounded; According to determining a first order ground coefficient of the driving point admittance, wherein, is a first order ground coefficient of the driving point admittance, is a peak frequency when the neutral point is grounded, is a valley bottom frequency when the neutral point is grounded, I is a total number of windings.

3. A frequency response based transformer winding fault detection method as claimed in claim 1, wherein, The determination of the first open circuit coefficient of the driving point admittance according to the peak frequency and the trough frequency when the neutral point of the transformer winding is open specifically comprises: collecting the peak frequency and the trough frequency when the neutral point of the transformer winding is open; According to determining a first open circuit coefficient of the driving point admittance, wherein, is a first open circuit coefficient of the driving point admittance, is a peak frequency when the neutral point is open circuited, is a trough frequency when the neutral point is open circuited, I is a total number of windings.

4. The frequency response based transformer winding fault detection method of claim 1, wherein, The detection of the fault of the transformer winding according to the comparison between the fluctuation of the first difference function and the second difference function and the preset threshold specifically comprises: determining whether the fluctuation amplitude or the fluctuation frequency of the first difference function and the second difference function is greater than the preset threshold, the preset threshold being a first amplitude threshold or a first frequency threshold; if the fluctuation amplitude or the fluctuation frequency of the first difference function and the second difference function is greater than the preset threshold, the transformer winding is faulty; if the fluctuation amplitude of the first difference function and the second difference function is less than or equal to the preset threshold, the transformer winding is not faulty.

5. A frequency response based transformer winding fault detection method as claimed in claim 1, wherein, The method further specifically comprises: determining that the fluctuation amplitude of the first difference function and / or the second difference function reaches a second amplitude threshold, or that the fluctuation frequency of the first difference function and / or the second difference function reaches a second frequency threshold, at which time the fault level of the transformer winding is a first-level fault; determining that the fluctuation amplitude of the first difference function and / or the second difference function reaches a third amplitude threshold, or that the fluctuation frequency of the first difference function and / or the second difference function reaches a third frequency threshold, at which time the fault level of the transformer winding is a second-level fault.

6. A frequency response based transformer winding fault detection system, characterized by, The system comprises: an equivalent inductance and equivalent capacitance acquisition module configured to determine the equivalent inductance and equivalent capacitance of the transformer winding; a first ground coefficient of the driving point admittance determination module configured to determine a first ground coefficient of the driving point admittance according to the peak frequency and the trough frequency when the neutral point of the transformer winding is grounded; a first open circuit coefficient of the driving point admittance determination module configured to determine a first open circuit coefficient of the driving point admittance according to the peak frequency and the trough frequency when the neutral point of the transformer winding is open; The first difference function and the second difference function are determined according to the equivalent inductance and the first ground coefficient, and the second difference function is determined according to the equivalent capacitance and the first open circuit coefficient. determining a first difference function, wherein, is the first difference function, is the equivalent inductance, is a preset scaling rate, is a first ground coefficient of the driving point admittance; and determining a second difference function, wherein, is the second difference function, is the equivalent capacitance, is a first open circuit coefficient of the driving point admittance. a fault detection module configured to detect the fault of the transformer winding according to the comparison between the fluctuation of the first difference function and the second difference function and the preset threshold.

7. A computer-readable storage medium, characterized in that, The computer program is stored in the storage medium and is executed by the processor to make the processor execute the steps of the method according to any one of claims 1 to 5.

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