Turn-to-turn short circuit fault monitoring method based on magnetic flux leakage power frequency component amplitude change
Through a monitoring method based on the amplitude change of the leakage magnetic power frequency component, the magnetic field sensor is used to collect the internal leakage magnetic strength of the power transformer, which solves the problem of insufficient monitoring sensitivity between turns short circuit faults in the prior art, and realizes the inter-turn short circuit faults of the power transformer between turns short circuits Fast and accurate monitoring reduces the risk of damage and fire accidents.
Patent Information
- Application Number
- CN202411511591.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-28
- Publication Date
- 2025-01-07
AI Technical Summary
In the case of power transformer short circuit failure, the sensitivity and speed of differential protection and gas protection are insufficient, making it difficult to effectively monitor and prevent faults, resulting in transformer damage and fire accidents.
The monitoring method based on the amplitude change of the leakage magnetic power frequency component is adopted, and the radial leakage magnetic intensity inside the power transformer is collected through the magnetic field sensor. After Fourier transformation, the monitoring of the short circuit fault between turns is realized based on the amplitude distribution of the radial magnetic field. .
This method can quickly and accurately diagnose short-circuit faults between turns of the power transformer, improve the accuracy and sensitivity of fault diagnosis, and reduce the risk of power transformer damage and fire accidents.
Smart Images
Figure CN119270136A_ABST
Abstract
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 monitoring method based on the amplitude change of leakage magnetic power frequency component. Background Art
[0002] Power transformers are important equipment in the power system. The most important equipment for the power system to achieve voltage rise and fall is the power transformer, so the power transformer is the core main equipment for voltage conversion and power transmission in the power system. Therefore, transformer failure will seriously affect the reliability of power supply and the normal operation of the system. According to previous data statistics, about 70%-80% of transformer failures are inter-turn failures of the windings. One of the more important problems is the inter-turn short circuit of the windings. Inter-turn short circuit is the direct contact of two or more turns of coils that are close to each other due to the destruction of the insulation layer. When the transformer is pressurized and shaped during the production process, excessive force will cause damage to the coil insulation. Long-term operation is prone to insulation aging. The transformer will have an inter-turn short circuit failure when there is overcurrent or overvoltage. The probability of damage to the transformer after a short circuit increases significantly, and transformer damage accidents caused by transformer short circuits account for 50% of the total accidents. In addition, after an internal fault occurs in the power transformer, there is a high probability that an explosion and fire accident will occur, causing serious accidents and property losses.
[0003] At present, current differential protection and gas protection are mainly used as the main protection of transformers in engineering, but these protection methods have various shortcomings when facing inter-turn short circuit. Differential protection is the main protection of transformers, and the main faults it responds to are inter-phase short circuit of transformer internal windings, single-phase serious inter-turn short circuit and other conditions. When a slight inter-turn short circuit occurs in the transformer, the current in the short-circuited turn is large and destructive, but the characteristic quantity reflected on the differential current between phases has only a slight change, so it is difficult for differential protection to effectively protect the inter-turn short circuit fault of power transformers. In addition, although gas protection is for internal faults of transformers. However, the judgment basis of heavy gas protection is the oil speed in the oil pillow connecting pipe, and the inter-turn fault requires a large electric power to drive the oil flow rate to the set value, and it takes a certain amount of time for the oil flow to accelerate to the set value, and its action time will be affected by factors such as the location of the fault point, gas production and production rate, and the viscosity of the insulating oil. Therefore, although heavy gas protection can protect the inter-turn short circuit fault of power transformers, its sensitivity and rapidity are insufficient. Therefore, it is of great significance to develop a method that can quickly monitor turn-to-turn short-circuit faults. Summary of the invention
[0004] The technical problem to be solved by the present invention is to provide a turn-to-turn short-circuit fault monitoring method based on the change in the amplitude 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 quickly and accurately diagnose the turn-to-turn short-circuit fault of the power transformer.
[0005] The present invention adopts the following technical solutions: A method for monitoring turn-to-turn short-circuit faults based on the change in amplitude of a leakage magnetic power frequency component comprises the following steps: Collect the radial leakage magnetic intensity inside the power transformer and obtain the radial magnetic field amplitude after Fourier transformation; The inter-turn short-circuit fault monitoring of power transformer is realized based on the radial magnetic field amplitude distribution.
[0006] Preferably, a magnetic field sensor is used to collect the radial magnetic leakage intensity inside the power transformer.
[0007] Preferably, the magnetic field sensor and the box wall of the power transformer are arranged at the same potential.
[0008] Preferably, the magnetic field sensor comprises a plurality of magnetic field sensors, which are sequentially arranged at intervals in the power transformer.
[0009] Preferably, the magnetic field sensor is arranged between the high voltage winding and the inner wall of the power transformer housing.
[0010] Preferably, a plurality of magnetic field sensors are horizontally arranged along the axial direction inside the power transformer.
[0011] Preferably, when the power transformer operates normally, its leakage magnetic intensity is symmetrically distributed in height, and when a turn-to-turn short circuit fault occurs in the power transformer winding, a reverse short circuit current appears in the short circuit loop formed by the short circuit turn.
[0012] Preferably, the magnetic field sensor adopts an improved optical fiber magnetic field sensor.
[0013] Preferably, the improved optical fiber magnetic field sensor has a cylindrical metal housing with a diameter of 4-16 mm and a length of 40-80 mm.
[0014] Preferably, the improved optical fiber magnetic field sensor is 300-340 mm away from the outermost side of the high-voltage winding and 12-52 mm away from the inner wall of the transformer housing.
[0015] Compared with the prior art, the present invention has at least the following beneficial effects: A turn-to-turn short-circuit fault monitoring method based on the change of the amplitude of the leakage magnetic power frequency component is proposed. When a turn-to-turn short-circuit fault occurs in a power transformer, there is an obvious change in the leakage magnetic amplitude distribution inside the transformer, and the leakage magnetic distribution change is very sensitive, which provides the possibility for sensitive monitoring of turn-to-turn short-circuit faults.
[0016] Furthermore, when a turn-to-turn short circuit fault occurs in a power transformer, the change characteristics of the radial magnetic field inside the power transformer are most obvious. By collecting the radial leakage magnetic intensity, the accuracy of fault diagnosis can be improved.
[0017] 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.
[0018] Furthermore, the magnetic field sensor is arranged between the high-voltage winding and the inner wall of the power transformer housing, which can reduce the influence of the magnetic field sensor on the insulation safety of the power transformer.
[0019] Furthermore, a plurality of magnetic field sensors are horizontally arranged along the axial direction inside the power transformer, so that the leakage magnetic distribution inside the power transformer can be more accurately collected, thereby improving the accuracy of the method for monitoring turn-to-turn short-circuit faults.
[0020] Furthermore, the improved optical fiber magnetic field sensor used in the present invention can resist strong electromagnetic interference, is suitable for large current and strong magnetic field environments, and has good electrical insulation.
[0021] In summary, the present invention uses an improved optical fiber sensor to collect the leakage magnetic distribution inside the power transformer, and then obtains the power frequency component amplitude characteristics of the leakage magnetic through Fourier transform and interpolation method, and then realizes rapid monitoring of the inter-turn short-circuit fault of the power transformer by monitoring the amplitude characteristics of the power frequency component of the leakage magnetic inside the power transformer.
[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 It is the sensor layout diagram; Figure 2 It is the radial magnetic field amplitude distribution diagram under normal working conditions; Figure 3 This is the radial magnetic field amplitude distribution diagram after the 52nd turn is short-circuited; Figure 4 The short-path magnetic field amplitude distribution diagram between turns at different positions. DETAILED DESCRIPTION
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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, the singular forms "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] The present invention provides a method for monitoring turn-to-turn short-circuit faults based on the change in the amplitude of the leakage magnetic power frequency component. Based on a 500kV real transformer model, a simulation is first performed to determine whether the turn-to-turn short-circuit fault of the power transformer can be located by using the transformer leakage magnetic power frequency phase. Then, the feasibility of the method of the present invention is verified through experimental examples, thereby providing an effective way to protect the power transformer.
[0033] There is a close connection between the electric field and the magnetic field, and they are an integral relationship. Therefore, when a 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.
[0034] The present invention provides a method for monitoring turn-to-turn short-circuit faults based on the change in amplitude of a leakage magnetic power frequency component, comprising the following steps: S1. Collect the radial leakage magnetic intensity inside the transformer through a magnetic field sensor, and obtain the radial magnetic field amplitude after Fourier transformation; Firstly, because the monitoring judgment basis of the present invention is the change of the amplitude of the power frequency component of the leakage magnetic field, a magnetic field sensor should be placed inside the power transformer to obtain the change of the leakage magnetic field intensity.
[0035] According to the experiment, the sensor is placed near the inner wall of the transformer, and then the radial leakage magnetic intensity is measured to obtain better results. The specific arrangement is Figure 1 As shown, the three-layer windings of the power transformer are low voltage, medium voltage and high voltage windings from the inside to the outside.
[0036] Among them, the highest high-voltage winding is the 104th one, with a height of 3010mm, and the lowest high-voltage winding is the 1st one, with a height of 890mm.
[0037] In this embodiment, an improved optical fiber magnetic field sensor is used to capture the leakage magnetic component. The improved optical fiber magnetic field sensor has a cylindrical metal housing of φ10 mm×60 mm.
[0038] The improved 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 along the radial direction.
[0039] In the radial direction, it is 322mm away from the outermost side of the high-voltage winding and 30mm away from the inner wall of the transformer casing.
[0040] When the power transformer works under normal conditions, the radial magnetic leakage waveform at different points is measured by magnetic field sensor, and then the Fourier transform and interpolation method are used to obtain the following: Figure 2 The radial magnetic field amplitude distribution waveform under normal operating conditions is shown.
[0041] from Figure 2 It can be seen that when the power transformer works normally, its leakage flux amplitude is symmetrical in value and remains symmetrical on the axis parallel to the center of the winding.
[0042] Then, when the 52nd turn of the power transformer has a turn-to-turn short circuit, the radial magnetic leakage waveform at different points is measured by a magnetic field sensor, and then Fourier transform and interpolation method are used, such as Figure 3 The radial magnetic field amplitude distribution waveform after the 52nd turn is short-circuited is shown. From the figure, it can be seen that when a turn-to-turn short-circuit fault occurs in the power transformer, its radial magnetic field amplitude distribution undergoes a significant change.
[0043] In order to verify the universality of this result, the inter-turn short-circuit fault points are set at different locations, and the radial magnetic leakage waveforms at different points are measured by magnetic field sensors. Then, the Fourier transform and interpolation method are used as follows: Figure 4 The short-path magnetic field amplitude distribution diagram between turns at different positions is shown.
[0044] from Figure 4 It can be seen that no matter where the inter-turn short circuit occurs, from the highest coil to the lowest coil, and any coil in the middle, even if only one turn of the coil is short-circuited, the radial magnetic field amplitude distribution will change significantly.
[0045] S2. Realize the inter-turn short-circuit fault monitoring of power transformer based on the radial magnetic field amplitude distribution.
[0046] When the power transformer is working normally, its leakage magnetic intensity has the characteristic of symmetrical distribution in height. However, when a turn-to-turn short circuit fault occurs in the transformer winding, a reverse short-circuit current will appear in the short-circuit loop formed by the short-circuit turn, thereby destroying the symmetry of the leakage magnetic distribution inside the power transformer.
[0047] So suppose the magnetic field strengths measured by the seven magnetic field sensors are B1, B2, B3, B4, B5, B6, and B7 from bottom to top; Then make B1=abs(B7-B1), B2=abs(B6-B2), B3=abs(B5-B3); Therefore, when the power transformer is working normally B1 B2 B3 is approximately 0, so when one of the three differences is not zero (greater than 0.002), it is determined that a turn-to-turn short circuit fault has occurred in the power transformer; in this determination method, it is only necessary to measure the radial magnetic field waveform at both ends of the winding.
[0048] 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.
[0049] In order to verify the feasibility of the present invention, the following examples are carried out: First, the 91st winding is short-circuited, and several corresponding radial magnetic field waveforms are measured. Then, the corresponding radial magnetic field amplitude is obtained by Fourier transform and interpolation method as shown in Table 1: Table 1 Example 1
[0050] Finally get B1=0.001, B2=0.0055>0.002, B3=0.0002, which means that a turn-to-turn short circuit occurred in the transformer winding, which is consistent with the actual situation.
[0051] Then the 65th winding is short-circuited, and several corresponding radial magnetic field waveforms are measured. Then, the corresponding radial magnetic field amplitude is obtained by Fourier transform and interpolation method as shown in Table 2: Table 2 Example 2
[0052] Finally get B1=0.0105>0.002, B2=0.0027>0.002, B3=0.0141>0.002, which shows that a turn-to-turn short circuit occurs in the transformer winding, which is consistent with the actual situation.
[0053] In summary, the present invention is a turn-to-turn short-circuit fault monitoring method based on the change in the amplitude of the leakage magnetic power frequency component. By monitoring the amplitude characteristics of the leakage magnetic power frequency component inside the power transformer, it realizes rapid monitoring of the turn-to-turn short-circuit fault of the power transformer, and provides a usable method for insulation protection of the power 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 monitoring turn-to-turn short-circuit faults based on the change in the amplitude of the power frequency component of leakage flux, characterized in that: The following steps are involved: Collect the radial leakage magnetic intensity inside the power transformer and obtain the radial magnetic field amplitude after Fourier transformation; The inter-turn short-circuit fault monitoring of power transformer is realized based on the radial magnetic field amplitude distribution.
2. The method for monitoring turn-to-turn short-circuit faults based on the amplitude change of leakage magnetic power frequency component according to claim 1 is characterized in that: A magnetic field sensor is used to collect the radial leakage magnetic intensity inside the power transformer.
3. The method for monitoring turn-to-turn short-circuit faults based on the amplitude change of leakage magnetic power frequency component according to claim 2 is characterized in that: The magnetic field sensor is arranged at the same potential as the box wall of the power transformer.
4. The method for monitoring turn-to-turn short-circuit faults based on the change in amplitude of leakage magnetic power frequency component according to claim 2, characterized in that: The magnetic field sensors include a plurality of sensors which are sequentially arranged at intervals in the power transformer.
5. The method for monitoring turn-to-turn short-circuit faults based on the amplitude change of leakage magnetic power frequency component according to claim 4 is characterized in that: The magnetic field sensor is arranged between the high voltage winding and the inner wall of the power transformer housing.
6. The method for monitoring turn-to-turn short-circuit faults based on the amplitude change of leakage magnetic power frequency component according to claim 4, characterized in that: A plurality of magnetic field sensors are horizontally arranged along the axial direction inside the power transformer.
7. The method for monitoring turn-to-turn short-circuit faults based on the amplitude change of leakage magnetic power frequency component according to claim 1, characterized in that: When the power transformer operates normally, its leakage magnetic intensity is symmetrically distributed in height. When a turn-to-turn short circuit fault occurs in the power transformer winding, a reverse short circuit current appears in the short circuit loop formed by the short circuit turn.
8. The method for monitoring turn-to-turn short-circuit faults based on the amplitude change of leakage magnetic power frequency component according to claim 1, characterized in that: The magnetic field sensor adopts an improved optical fiber magnetic field sensor.
9. The method for monitoring turn-to-turn short-circuit faults based on the amplitude change of leakage magnetic power frequency component according to claim 8, characterized in that: The improved optical fiber magnetic field sensor has a cylindrical metal housing with a diameter of 4-16 mm and a length of 40-80 mm.
10. The method for monitoring turn-to-turn short-circuit faults based on the change in amplitude of leakage magnetic power frequency component according to claim 8, characterized in that: The improved optical fiber magnetic field sensor is 300~340mm away from the outermost side of the high-voltage winding and 12~52mm away from the inner wall of the transformer shell.