Turn-to-turn short circuit fault positioning method based on magnetic leakage power frequency component phase change

Abstract

The invention discloses a turn-to-turn short circuit fault positioning method based on magnetic flux leakage power frequency component phase change, and belongs to the technical field of power transformer detection, and the method comprises the steps: respectively obtaining the data of a magnetic field sensor and a voltage sensor, and obtaining a power frequency magnetic flux leakage phase and an input voltage power frequency phase after Fourier transform; determining a power frequency magnetic flux leakage phase difference based on the obtained power frequency magnetic flux leakage phase and the input voltage power frequency phase; and carrying out fault positioning by taking a 180-degree anti-phase point of a leakage flux phase under a normal working condition as a reference.

Description

Technical Field

[0001] The invention belongs to the technical field of power transformer detection, and in particular relates to a turn-to-turn short-circuit fault locating method based on phase change of leakage magnetic power frequency component. Background Art

[0002] The UHV AC / DC transmission system is the main channel for energy transmission, ensuring the efficient development and clean utilization of my country's energy. Power transformers are important equipment in UHV AC / DC transmission systems, so transformer failures will seriously affect the normal operation of UHV AC / DC transmission systems. According to statistics, about 70%-80% of transformer failures are inter-turn failures of the windings, one of which is the inter-turn short circuit of the windings. Inter-turn short circuit is a direct contact between two or more turns of coils that are close to each other due to insulation damage. When a single-turn inter-turn short circuit fault occurs in the power transformer winding due to insulation damage between turns or between cakes, it will cause the adjacent damaged turns to form a short-circuit ring. At the same time, the inter-turn short circuit will change the normal excitation of the power transformer, causing the core excitation characteristics to enter the saturation zone, accompanied by severe vibration, resulting in irreversible deformation of the winding such as twisting and bulging. Under the action of the alternating magnetic field of the power transformer, the short-circuit ring induces a short-circuit current, causing the local temperature to rise sharply. Under the impact of the electromotive force, the deformation of the winding will be further aggravated due to the cumulative effect, causing a larger range of winding insulation damage, and then causing multiple turns of serious turn-to-turn short-circuit faults, or even more serious inter-turn breakdown, phase-to-phase short circuit, main insulation discharge or complete breakdown, triggering safety accidents such as explosions and fires, causing serious accidents and property losses.

[0003] At present, many methods for detecting turn-to-turn short-circuit faults have been widely used in practice and have achieved good results. However, it is difficult to locate the position of turn-to-turn short-circuit faults with existing monitoring technologies. Only manual methods can be used for detection, but due to the complex internal structure of power transformers, this method is not only inefficient, but also prone to secondary faults of transformers due to human error.

[0004] Therefore, it is of great significance to develop an effective method for locating inter-turn short-circuit faults in power transformers. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a turn-to-turn short-circuit fault locating method based on the phase change of the leakage magnetic power frequency component in view of the deficiencies in the above-mentioned prior art, so as to solve the technical problem of how to perform interval locating of the turn-to-turn short-circuit fault of the power transformer.

[0006] The present invention adopts the following technical solutions: A method for locating turn-to-turn short-circuit faults based on phase changes of leakage magnetic power frequency components comprises the following steps: S1, respectively obtain the data of the magnetic field sensor and the voltage sensor, and obtain the power frequency leakage magnetic phase and the input voltage power frequency phase after Fourier transformation; S2, determining the power frequency leakage magnetic phase difference based on the obtained power frequency leakage magnetic phase and the input voltage power frequency phase; S3. Fault location is performed based on the 180° reverse phase point of the leakage flux under normal operating conditions.

[0007] Preferably, in step S1, a magnetic field sensor is arranged on the inner wall of the transformer to measure radial magnetic leakage intensity.

[0008] Preferably, the magnetic field sensor is arranged at the same potential as the inner wall of the transformer.

[0009] Preferably, the magnetic field sensor is an optical fiber magnetic field sensor.

[0010] Preferably, in step S2, the power frequency leakage magnetic phase difference is specifically:

[0011] in, and They refer to the phase of the magnetic field and the phase of the input voltage at a certain position. is the average value of the product of the corresponding discrete points of the magnetic field waveform and the input voltage waveform, and They refer to the effective value of the magnetic field and the peak value of the input voltage at a certain position respectively.

[0012] Preferably, for:

[0013] in, is the number of discrete points taken on the waveform, They refer to the magnetic field intensity waveform and input voltage waveform at a certain position respectively.

[0014] Preferably, in step S2, the power frequency fundamental phase of the leakage magnetic intensity is calculated using FFT and the phase of the input voltage , then let Find the phase difference.

[0015] Preferably, in step S3, when the inter-turn short circuit occurs above the winding, the 180° reverse phase point is below the 180° reverse phase point under normal operating conditions, and the position of the inter-turn short circuit fault is located by comparing the positions.

[0016] Preferably, in step S3, when the inter-turn short circuit occurs at the bottom of the winding, the 180° reverse phase point is above the 180° reverse phase point under normal operating conditions, and the position of the inter-turn short circuit fault is located by comparing the positions.

[0017] Preferably, in step S3, when the inter-turn short circuit occurs in the middle of the winding, the position of the 180° reverse phase point is the same as the 180° reverse phase point in normal working condition, and the position of the inter-turn short circuit fault is located by comparing the positions.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: A turn-to-turn short-circuit fault locating method based on the phase change of leakage flux power frequency component. When a turn-to-turn short-circuit fault occurs inside a power transformer, the leakage flux power frequency phase inside the transformer will change significantly, and the change in leakage flux reacts quickly. At the same time, the change in the leakage flux power frequency phase is also related to the position of the turn-to-turn short-circuit fault, which provides the possibility for rapid interval positioning of the turn-to-turn short-circuit fault.

[0019] Furthermore, the magnetic field sensor is arranged on the inner wall of the power transformer housing to reduce the influence of the magnetic field sensor on the insulation safety of the power transformer.

[0020] Furthermore, the equipotential arrangement of the magnetic field sensor and the box wall of the power transformer can reduce the influence of the internal electric field of the transformer on the leakage magnetic sensor.

[0021] Furthermore, when the inter-turn short circuit occurs above the winding, the height of the 180° reverse phase point of the leakage magnetic power frequency phase is located at the lower part of the winding, thereby determining the location of the inter-turn short circuit fault.

[0022] Furthermore, when the inter-turn short circuit occurs at the bottom of the winding, the height of the 180° reverse phase point of the leakage magnetic power frequency phase is located at the top of the winding, thereby determining the location of the inter-turn short circuit fault.

[0023] Furthermore, when the inter-turn short circuit occurs in the middle of the winding, the height of the 180° reverse phase point of the leakage magnetic power frequency phase is located in the middle of the winding, thereby determining the location of the inter-turn short circuit fault.

[0024] In summary, the present invention utilizes the law of leakage flux change when a turn-to-turn short-circuit fault occurs inside the transformer to achieve a relatively accurate positioning of the transformer turn-to-turn short-circuit fault point. The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a sensor layout diagram of the present invention; Figure 2 Schematic diagram of radial magnetic field phase distribution when short circuit faults occur at different positions of the present invention; Figure 3This is a fault location flow chart of the present invention; Figure 4 It is a schematic diagram of the parameters of the power transformer of the present invention; Figure 5 This is a schematic diagram of the waveform measured by the sensor 1 of the present invention; Figure 6 This is a schematic diagram of the waveform measured by the sensor 9 of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "one side", "one end", "one side" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0028] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0030] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0031] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0032] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0033] The present invention provides a method for locating turn-to-turn short-circuit faults based on the phase change of the leakage magnetic power frequency component. Based on a 500kV real transformer model, through experiments and simulations, relevant laws are summarized and a method for quickly locating the turn-to-turn short-circuit faults of a power transformer by utilizing the transformer leakage magnetic power frequency phase is proposed. Then, the feasibility of the locating method is verified through experimental examples, thereby providing an effective way for detecting power transformers.

[0034] There is a close connection between the electric field and the magnetic field, and they are an integrated relationship; therefore, when a turn-to-turn short circuit fault occurs in the power transformer, the spatial distribution of leakage magnetic flux around the power transformer winding is affected by the winding current and the fault location, and shows a certain regularity. When the proportion of short-circuit turns is small, the leakage magnetic flux change is still significant and the sensitivity is very high.

[0035] See also Figure 3 The present invention provides a method for locating turn-to-turn short-circuit faults based on phase changes of leakage magnetic power frequency components, comprising the following steps: S1, respectively obtain the data of the magnetic field sensor and the voltage sensor, and obtain the power frequency leakage magnetic phase and the input voltage power frequency phase after Fourier transformation; See also Figure 1 Because the positioning of the present invention is based on the change in the phase of the leakage magnetic power frequency component, a magnetic field sensor must be placed inside the power transformer to obtain the change in the leakage magnetic intensity. Based on experimental experience, the sensor is placed on the inner wall of the transformer; then, the radial leakage magnetic intensity is measured to achieve better results.

[0036] The three layers of windings of the power transformer are low voltage, medium voltage and high voltage windings from the inside to the outside. The highest winding of the high voltage winding is the 104th winding, and the lowest winding of the high voltage winding is the 1st winding.

[0037] An optical fiber magnetic field sensor is used to capture the leakage magnetic component. The modified optical fiber magnetic field sensor has a cylindrical metal shell of φ10mm×60mm; The optical fiber magnetic field sensor is arranged at the same potential as the wall of the power transformer box, so it is necessary to establish a metal connection with the inner wall of the transformer. At the same time, the radial magnetic field component is measured, so the optical fiber magnetic field sensor is arranged horizontally.

[0038] S2, determining the power frequency leakage magnetic phase difference based on the obtained power frequency leakage magnetic phase and the input voltage power frequency phase; The phase in the present invention refers to the difference between the power frequency fundamental phase of the leakage magnetic intensity at a certain position and the input voltage phase. There are two common calculation methods: 1. Use the relevant function formula to calculate as follows: (1) (2) in, and They refer to the magnetic field phase and input voltage phase at a certain position, A and B refer to the effective value of the magnetic field and input voltage at a certain position, respectively. Then They refer to the magnetic field intensity waveform and input voltage waveform at a certain position respectively.

[0039] 2. First, use FFT to calculate the power frequency fundamental phase of the leakage magnetic intensity and the phase of the input voltage, which are , then let Find the phase difference.

[0040] S3. Fault location is performed based on the 180° reverse phase point of the leakage flux under normal operating conditions.

[0041] The position of the 180° reverse phase point of the leakage magnetic phase changes with the position of the short-circuit turn. The corresponding relationship between the reverse phase point position and the short-circuit turn position is opposite.

[0042] See also Figure 2 When a turn-to-turn short circuit fault occurs in the power transformer, the radial magnetic leakage waveform at different points is measured by a magnetic field sensor, and then the corresponding phase difference is calculated by Fourier transform.

[0043] from Figure 2 It can be seen that when a turn-to-turn short circuit occurs at different positions of the power transformer, the leakage flux phase has a certain numerical regularity, as follows: First of all, it can be seen from the figure that the power transformer has a 180° anti-phase point at a certain position regardless of whether the turn-to-turn short circuit occurs. However, the position of the 180° anti-phase point will also change with the different positions of the turn-to-turn short circuit.

[0044] Taking the 180° reverse phase point of the leakage flux phase under normal working conditions as the reference, it can be seen from the figure that when the inter-turn short circuit occurs in the upper part of the winding, its 180° reverse phase point is below the 180° reverse phase point under normal working conditions; When the inter-turn short circuit occurs in the lower part of the winding, its 180° reverse phase point is above the 180° reverse phase point under normal working conditions; When the inter-turn short circuit occurs in the middle of the winding, the position of its 180° reverse phase point is the same as the 180° reverse phase point under normal operating conditions, and the only difference is the phase.

[0045] When the ratio of turn-to-turn short-circuit faults is less than or equal to 20%, the measured phase relationship conforms to the law obtained in the above figure. Therefore, for the location of turn-to-turn short-circuit faults in general power transformers, it is only necessary to measure the 180° reverse phase point under normal working conditions of the power transformer, and then monitor the 180° reverse phase point after the turn-to-turn short-circuit fault occurs, and finally locate the position of the turn-to-turn short-circuit fault by comparing the positions of the two.

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0047] Example 1 See also Figure 4 , the three-layer winding of the power transformer is low voltage, medium voltage and high voltage winding from the inside to the outside; the highest winding of the high voltage winding is the 104th winding, with a height of 3050mm; the lowest winding of the high voltage winding is the 1st winding, with a height of 850mm; firstly, a turn-to-turn short circuit fault occurs in the upper part of the transformer winding, and after the magnetic field sensor is installed at the height shown in Table 1, the corresponding radial magnetic field waveform is measured, and then the corresponding radial magnetic field phase distribution is obtained by Fourier transform, and compared with the normal situation, as shown in Table 1: Table 1

[0048] It can be seen from the phase diagram that the 180° reverse phase point of the fault condition is below the 180° reverse phase point of the normal condition, so according to the positioning method of the present invention, it can be obtained that the turn-to-turn short-circuit fault is located at the upper part of the winding, which is consistent with the actual situation.

[0049] See also Figure 5 and Figure 6 , which is the leakage magnetic waveform measured by sensor 1 and sensor 9. It can be seen from the figure that when a turn-to-turn short circuit fault occurs in the power transformer, the power frequency phase of the internal leakage magnetic field of the power transformer will change suddenly, and the phase mutation values ​​at different positions are different. And the phase of the input voltage is stable, so when a turn-to-turn short circuit fault occurs, the phase difference will change accordingly.

[0050] Example 2 In Example 2, the parameters of the power transformer used are the same as above. Figure 4 As shown, the three-layer winding of the power transformer is low voltage, medium voltage and high voltage winding from the inside to the outside. The highest high-voltage winding is the 104th winding, with a height of 3050mm; the lowest high-voltage winding is the 1st winding, with a height of 850mm. Then we make the transformer have an inter-turn short circuit fault at the lower part of the winding. After installing the magnetic field sensor at the height shown in Table 2, we measure several corresponding radial magnetic field waveforms, and then use Fourier transform to find the corresponding radial magnetic field phase distribution, and compare it under normal conditions, as shown in Table 2. Table 2

[0051] It can be seen from the phase diagram that the 180° reverse phase point of the fault condition is above the 180° reverse phase point of the normal condition, so according to the positioning method of the present invention, it can be obtained that the turn-to-turn short-circuit fault is located at the lower part of the winding, which is consistent with the actual situation.

[0052] At this time, the leakage magnetic field waveforms measured by each sensor are basically the same as the waveforms in Example 1.

[0053] In summary, the present invention provides a method for locating turn-to-turn short-circuit faults based on phase changes of leakage magnetic power frequency components, which achieves relatively accurate positioning of the turn-to-turn short-circuit fault point of the transformer.

[0054] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for locating turn-to-turn short-circuit faults based on phase change of leakage magnetic power frequency component, characterized in that: The following steps are involved: S1, respectively obtain the data of the magnetic field sensor and the voltage sensor, and obtain the power frequency leakage magnetic phase and the input voltage power frequency phase after Fourier transformation; S2, determining the power frequency leakage magnetic phase difference based on the obtained power frequency leakage magnetic phase and the input voltage power frequency phase; S3. Fault location is performed based on the 180° reverse phase point of the leakage flux under normal operating conditions.

2. The method for locating turn-to-turn short-circuit faults based on phase change of leakage magnetic power frequency component according to claim 1, characterized in that: In step S1, a magnetic field sensor is arranged on the inner wall of the transformer to measure radial leakage magnetic intensity.

3. The method for locating turn-to-turn short-circuit faults based on phase change of leakage magnetic power frequency component according to claim 2, characterized in that: The magnetic field sensor is arranged at the same potential as the inner wall of the transformer.

4. The method for locating turn-to-turn short-circuit faults based on phase change of leakage magnetic power frequency component according to claim 2, characterized in that: The magnetic field sensor is an optical fiber magnetic field sensor.

5. The method for locating turn-to-turn short-circuit faults based on phase change of leakage magnetic power frequency component according to claim 1, characterized in that: In step S2, the power frequency leakage magnetic phase difference is specifically: in, and They refer to the phase of the magnetic field and the phase of the input voltage at a certain position. is the average value of the product of the corresponding discrete points of the magnetic field waveform and the input voltage waveform, and They refer to the effective value of the magnetic field and the peak value of the input voltage at a certain position respectively.

6. The method for locating turn-to-turn short-circuit faults based on phase change of leakage magnetic power frequency component according to claim 5, characterized in that: for: in, is the number of discrete points taken on the waveform, They refer to the magnetic field intensity waveform and input voltage waveform at a certain position respectively.

7. The method for locating turn-to-turn short-circuit faults based on phase change of leakage magnetic power frequency component according to claim 1, characterized in that: In step S2, the power frequency fundamental phase of the leakage magnetic intensity is calculated using FFT and the phase of the input voltage , then let Find the phase difference.

8. The method for locating turn-to-turn short-circuit faults based on phase change of leakage magnetic power frequency component according to claim 1, characterized in that: In step S3, when the inter-turn short circuit occurs above the winding, the 180° reverse phase point is below the 180° reverse phase point under normal operating conditions, and the position of the inter-turn short circuit fault is located by comparing the positions.

9. The method for locating turn-to-turn short-circuit faults based on phase change of leakage magnetic power frequency component according to claim 1, characterized in that: In step S3, when the inter-turn short circuit occurs at the bottom of the winding, the 180° reverse phase point is above the 180° reverse phase point under normal working conditions, and the position of the inter-turn short circuit fault is located by comparing the positions.

10. The method for locating turn-to-turn short-circuit faults based on phase change of leakage magnetic power frequency component according to claim 1, characterized in that: In step S3, when the turn-to-turn short circuit occurs in the middle of the winding, the position of the 180° reverse phase point is the same as the 180° reverse phase point in the normal working condition, and the position of the turn-to-turn short circuit fault is located by comparing the positions.

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