Triangular three-dimensional amorphous alloy transformer copper foil winding fault detection method

Abstract

The invention provides a triangular three-dimensional amorphous alloy transformer copper foil winding fault detection method, and relates to the technical field of copper foil winding fault detection, and the method comprises the steps: obtaining the real-time magnetic induction intensity of a first winding of a transformer at a plurality of radially preset positions; and determining and positioning the turn-to-turn short circuit fault based on the magnetic induction intensity of each position and the corresponding magnetic induction intensity threshold. According to the method, based on the electromagnetic physical characteristics of the turn-to-turn short circuit of the copper foil winding, the turn-to-turn short circuit fault of the copper foil winding is judged and positioned through the magnetic induction intensity measured by a plurality of sensitive detection parts of the transformer winding; the method can effectively counteract influences brought by changes of magnetic induction intensity caused by turn-to-turn short circuits of different degrees, can adapt to fault positioning of various turn-to-turn short circuit degrees, effectively solves the problem that turn-to-turn short circuit faults of a copper foil winding type transformer are difficult to recognize and inaccurate in positioning at present, and is higher in accuracy.

Description

Technical Field

[0001] This invention relates to the field of copper foil winding fault detection technology, and more specifically, to a method for detecting copper foil winding faults in a triangular three-dimensional amorphous alloy transformer. Background Technology

[0002] Triangular amorphous alloy transformers, with their core advantages of low loss and high permeability from amorphous alloy cores, and the strong short-circuit resistance, compact size, and small footprint resulting from their triangular structure, have become key power equipment in power distribution network upgrades and energy-saving renovations of industrial power supply systems. They are widely used in urban power grids, new energy grid integration, and high-end manufacturing. As the core conductive and energy transmission component of this type of transformer, the copper foil winding's structural integrity and insulation performance directly determine the transformer's safe operation. Compared to traditional conductor windings, copper foil windings employ a multi-layered, tightly wound process, and must simultaneously adapt to the uneven electric field distribution and concentrated electromagnetic force characteristics of the triangular structure. Therefore, its health status has a more significant impact on the overall operational reliability of the transformer.

[0003] However, during long-term operation, the copper foil windings of delta-shaped amorphous alloy transformers are susceptible to failures due to multiple complex factors. The delta structure requires extremely high winding symmetry; if there are interlayer tension deviations or insufficient end forming precision during copper foil winding, local electric field distortion can easily occur, accelerating insulation aging. Short-circuit impacts during operation can subject the copper foil windings to instantaneous electromagnetic shocks, causing inter-turn relative displacement and even insulation wear. The excitation losses of the amorphous alloy core generate additional temperature rises, which, combined with localized overheating caused by long-term overload operation and the erosion of the copper foil surface insulation layer by aging insulating oil, can all lead to typical faults such as inter-turn short circuits, localized breakdowns, and insulation damage in the copper foil windings. According to industry statistics, inter-turn short circuit faults account for as much as 55%-65% of overall transformer faults, making it the primary cause of unplanned transformer outages.

[0004] In the early stages of copper foil winding faults, due to the small fault range and the slight changes in electrical parameters such as main circuit current and voltage, traditional current differential protection and overcurrent protection devices cannot capture effective fault signals, making it difficult to achieve early warning. As the fault develops covertly, the inter-turn short-circuit current will increase exponentially, and the resulting electrothermal effect will further damage the surrounding insulation structure, rapidly evolving into serious faults such as multi-turn short circuits and winding burnout. This not only causes the transformer to be taken out of service directly, but may also cause problems such as sudden drops in grid voltage and load interruptions, seriously threatening the power supply reliability of the distribution network.

[0005] Therefore, a fault detection method for copper foil windings adapted to the special structure of triangular three-dimensional amorphous alloy transformers is needed. This method should be able to effectively analyze the characteristics of inter-turn short-circuit faults in copper foil windings, accurately extract early fault characteristic parameters of the windings, and seek methods to detect inter-turn short-circuit faults in copper foil windings, thereby achieving accurate fault identification and location. This has significant engineering value and practical significance for improving the fault diagnosis system of triangular three-dimensional amorphous alloy transformers, extending equipment service life, and ensuring the safe and stable operation of the power distribution network. Summary of the Invention

[0006] The purpose of this invention is to provide a method for detecting faults in the copper foil windings of a triangular three-dimensional amorphous alloy transformer, thereby improving the aforementioned problems. To achieve the above objective, the technical solution adopted by this invention is as follows: This application provides a method for detecting faults in the copper foil windings of a triangular three-dimensional amorphous alloy transformer, including: Obtain first information, which includes the real-time first magnetic induction intensity of the first winding of the transformer at multiple radially preset positions; Obtain second information, which includes multiple preset first thresholds, with each first threshold corresponding to one of the positions; Based on the first information and the second information, determine the inter-turn short circuit fault of the first winding; If it is determined that an inter-turn short circuit fault has occurred in the first winding, then multiple first difference change rates are calculated based on multiple first differences and multiple second differences. Based on the multiple first difference change rates, a first region where an inter-turn short circuit fault has occurred is determined. The first region is the region between two adjacent positions. The first difference is the difference between the first magnetic induction intensities corresponding to the two positions, and the second difference is the difference between the first thresholds corresponding to the two positions.

[0007] Furthermore, the first threshold corresponding to a given position is set based on the magnetic induction intensity at that position when the first winding is operating normally.

[0008] Furthermore, obtaining the first information includes: The first magnetic induction intensity is obtained at the first position, second position, third position and fourth position of the first winding, wherein the first position and the third position are respectively located at the upper axial position of the two turns of copper foil closest to and farthest from the iron core in the first sub-winding of the first winding, the second position is located at the middle axial position of the turn of copper foil in the first sub-winding close to the third position, and the fourth position is at the middle oil passage gap between the first sub-winding and the second sub-winding of the first winding, wherein the first sub-winding is a copper foil winding and the second sub-winding is a high voltage winding.

[0009] Furthermore, the first position, the second position, and the third position are respectively located at the copper foil of the first turn, the seventeenth turn, and the twenty-fifth turn of the first sub-winding.

[0010] Furthermore, after obtaining the second information, the process also includes: When the first magnetic induction intensity at the fourth position is greater than the first threshold corresponding to the fourth position, the first current of the multiphase first winding is obtained to obtain multiple first currents; If the first current is greater than the preset first current threshold, then a ground fault of the multi-phase first winding or a short circuit fault between the multi-phase first windings is determined. If there is no first winding with a first current greater than the first current threshold, then an inter-turn short-circuit fault is determined for the first winding.

[0011] Furthermore, the determination of ground faults in the multi-phase first winding or the determination of short-circuit faults between the multi-phase first windings includes: If the first current of only one phase of the first winding is greater than the first current threshold, it is determined that there is a ground short circuit fault in the first winding of that phase. If the first current of the first winding of both phases is greater than the first current threshold, then it is determined that there is a short circuit fault between the first windings of the two phases.

[0012] Furthermore, the determination of the inter-turn short-circuit fault of the first winding based on the first information and the second information includes: If the second magnetic flux density and the third magnetic flux density of the first winding are greater than the second threshold and the third threshold, respectively, it is determined that there is an inter-turn short circuit fault in the first winding. The second magnetic flux density and the third magnetic flux density are the first magnetic flux densities corresponding to the first position and the third position of the first winding, respectively. The second threshold and the third threshold are the first thresholds corresponding to the first position and the third position of the first winding, respectively.

[0013] Furthermore, the determination of the first region where an inter-turn short-circuit fault occurs based on multiple first difference change rates includes: Calculate the third difference and the fourth difference, and calculate the first difference change rate based on the third difference and the fourth difference to obtain the first difference change rate. The third difference is the difference between the first position of the first winding and the first magnetic induction intensity corresponding to the third position. The fourth difference is the difference between the first position of the first winding and the first threshold corresponding to the third position. If the first difference change rate is less than the preset first change rate threshold, it is determined that an inter-turn short circuit fault has occurred in the second region of the first sub-winding of the first winding. The second region is the region between the first turn and the eighth turn of the copper foil of the first sub-winding. If the first difference change rate is greater than the preset first change rate threshold, then the fifth difference and the sixth difference are calculated, and the second difference change rate is calculated based on the fifth difference and the sixth difference to obtain the second difference change rate. The fifth difference is the difference between the first magnetic induction intensity corresponding to the second position and the fourth position of the first winding, and the fourth difference is the difference between the second position and the first threshold corresponding to the fourth position of the first winding. If the second difference change rate is less than the preset second change rate threshold, it is determined that an inter-turn short circuit fault has occurred in the third region of the first winding. The third region is the region between the ninth and seventeenth turns of the first sub-winding. If the second difference change rate is greater than the preset third change rate threshold, then it is determined that an inter-turn short circuit fault has occurred in the fourth region of the first winding. The fourth region is the region between the seventeenth and twenty-fifth turns of the first sub-winding.

[0014] The beneficial effects of this invention are as follows: This invention is based on the electromagnetic physical characteristics of inter-turn short circuits in copper foil windings. It uses the magnetic induction intensity measured at multiple sensitive detection points of the transformer winding to determine and locate inter-turn short circuit faults in copper foil windings. The rate of change of the difference in magnetic induction intensity used can effectively offset the influence of the magnitude change in magnetic induction intensity caused by different degrees of inter-turn short circuits. It can adapt to the fault location of various degrees of inter-turn short circuits and effectively solves the problems of difficult identification and inaccurate location of inter-turn short circuit faults in current copper foil winding transformers, resulting in higher accuracy.

[0015] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing embodiments of the invention. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic flowchart of a method for detecting copper foil winding faults in a triangular three-dimensional amorphous alloy transformer, as described in an embodiment of the present invention. Figure 2 This is another flowchart illustrating a method for detecting copper foil winding faults in a triangular three-dimensional amorphous alloy transformer as described in an embodiment of the present invention. Figure 3 This is a schematic diagram of the winding structure of a triangular three-dimensional amorphous alloy transformer copper foil winding fault detection method described in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the changes in magnetic induction intensity at the axial upper end of the winding at different radial positions when an inter-turn short circuit occurs at different locations in the winding, as described in this embodiment of the invention. Figure 5 This is a schematic diagram illustrating the changes in magnetic induction intensity at the axial midpoint of the winding radially when an inter-turn short circuit occurs at different radial positions in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0019] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0020] Example 1: This embodiment provides a method for detecting copper foil winding faults in a triangular three-dimensional amorphous alloy transformer.

[0021] See Figure 1 The figure shows that the method includes steps S1, S2, S3 and S4.

[0022] S1. Obtain first information, the first information including the real-time first magnetic induction intensity of the first winding of the transformer at multiple radially preset positions; S2. Obtain second information, the second information including multiple preset first thresholds, one first threshold corresponding to one of the positions; S3. Based on the first information and the second information, determine the inter-turn short circuit fault of the first winding; S4. If it is determined that an inter-turn short circuit fault has occurred in the first winding, then a plurality of first difference change rates are calculated based on a plurality of first differences and a plurality of second differences. Based on the plurality of first difference change rates, a first region in which an inter-turn short circuit fault has occurred is determined. The first region is the region between two adjacent positions. The first difference is the difference between the first magnetic induction intensities corresponding to the two positions, and the second difference is the difference between the first thresholds corresponding to the two positions.

[0023] For details, see Figure 2 and Figure 3 For triangular three-dimensional amorphous alloy transformers, the low-voltage winding has fewer turns, typically a copper foil winding, while the high-voltage winding is a copper wire winding. In this embodiment, fiber optic magnetic field sensor devices are first placed at the upper innermost end of the copper foil winding, the upper outermost end of the copper foil winding, the midpoint of the outer copper foil winding in the radial direction and the midpoint of the axial direction, and the midpoint of the oil passage gap between the high-voltage and low-voltage windings, respectively, to detect the magnetic induction intensity at the installation location; such as Figure 3 As shown, taking phase A winding as an example, the innermost, outermost, and radially midpoints of the copper foil winding are the A1, A25, and A17 turns respectively, radially outward from the iron core. This embodiment divides the copper foil winding into three regions radially: A1-A8 turns as region I, A9-A16 turns as region II, and A17-A25 turns as region III. When an inter-turn short-circuit fault occurs in the copper foil winding, the detection method provided in this embodiment can be used to locate the faulty turn specifically in region I, region II, or region III.

[0024] It should be noted that in this embodiment, since the A17 turn is the copper foil position, the sensor must be added between the turns. Therefore, the sensor at the A17 turn position is actually placed between the A16 turn and the A17 turn. For ease of description, the A17 turn will be used to represent the position between the A16 turn and the A17 turn in the following description.

[0025] Furthermore, the magnetic induction intensity values ​​collected by the fiber optic magnetic field sensor device at various locations during normal transformer operation are obtained. The minimum and maximum range of leakage magnetic field intensity during a period of normal transformer operation is used as the range of magnetic induction intensity variation during normal operation. Thus, the corresponding magnetic induction intensity threshold range for each location is set as the basis for subsequent judgment on whether an inter-turn short circuit fault has occurred. Once the real-time magnetic induction intensity value collected at a certain location exceeds its corresponding magnetic induction intensity threshold range, it is judged that an inter-turn short circuit fault may exist.

[0026] Understandably, according to the Biot-Savart law, the magnitude of the magnetic field strength at a point in space is related to the magnitude of the current in the current element, the length of the conductor, and the distance from the current element to that point, as shown in the following equation: ; In the formula, It is a magnetic field element. It is a current element vector. Let be the displacement vector from the current element to the observation point. Let the distance from the current element to the observation point be a point in space. We can obtain: ; In the formula, For the first The radius of the short-circuit loop, These are the angular coordinates on the short-circuit ring. , , These are the unit vectors for the x, y, and z axes, respectively.

[0027] The copper foil winding is spirally wound along the iron core axis, forming a multi-layered concentric cylindrical structure. This results in mutual inductance between the turns due to eddy currents. The radial mutual inductance between the windings generates a leakage magnetic field under the huge short-circuit current, which reduces the surrounding effective magnetic field. Based on Maxwell's induced electric field calculations and the Biot-Savart law approximating the thin conductor, the effective magnetic field model around the copper foil winding is shown in the following equation: ; in, and These are the effective magnetic flux density and the original magnetic flux density, respectively. The permeability of free space, Angular frequency, The electrical conductivity of copper, The thickness is the copper foil thickness.

[0028] Based on the characteristics of inter-turn short circuits in copper foil windings, the leakage magnetic field model at the midpoint P in space can be obtained as shown in the following equation.

[0029] ; In the formula, denoted as the axial magnetic flux coefficient of the copper foil winding. The effective magnetic field coefficient around the copper foil winding. Points of direction, direction and Magnetic flux density in the direction, This is the short-circuit current. The distance from the observation point to the center of the iron core is denoted as ... denoted as denoted as denoted denoted as denoted as denoted denoted as denoted as denoted denoted as denoted as denoted denoted as denoted denoted as denoted denoted as denoted denoted as denoted denoted as denoted denoted as denoted denoted as denoted denoted denoted as denoted denoted denoted as denoted denoted denoted as denoted denoted denoted as denoted denoted denoted denoted as denoted denoted denoted denoted denoted denoted as denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted denoted deno

[0030] Furthermore, it is understandable that changes in magnetic flux density are easier to monitor at the radial ends of the copper foil winding. When a short-circuited turn approaches either end, the magnetic flux density at that end increases, while the change in magnetic flux density at the other end relative to that end is smaller. This allows us to determine which end the short-circuited turn is closer to. If we arbitrarily select two points to monitor changes in magnetic flux density, it is difficult to determine whether the short-circuited turn is located to the left or right of the selected point, because a short circuit affects the surrounding local leakage magnetic field, making it impossible to determine its location. Therefore, this embodiment first selects to measure the magnetic flux density at both radial ends of the copper foil winding to achieve faster and more accurate fault diagnosis and location.

[0031] In this embodiment, the magnetic induction intensity at the gap between the middle oil passages of the high-voltage winding and the low-voltage winding is first detected. If it is greater than the magnetic induction intensity at that position during normal operation, a short-circuit fault in the winding is identified.

[0032] Understandably, during normal operation, the leakage magnetic field amplitude of the winding appears at the gap between the high-pressure and low-pressure oil passages, mainly due to the influence of the axial leakage magnetic field. At the gap, the axial leakage magnetic fields superimpose, maximizing the leakage magnetic field induction intensity. During normal operation of the copper foil winding, the axial leakage magnetic field exhibits a distribution pattern of equal magnitude but opposite direction around the center point. Since the copper foil winding is a sheet-like winding, a short circuit between turns in the copper foil winding exhibits the same axial leakage magnetic field distribution pattern as during normal operation. The balance of the axial leakage magnetic field is not disrupted; it only affects the magnitude of the magnetic field strength and the radial leakage magnetic field distribution. A short circuit between turns in the copper foil winding does not affect the axial leakage magnetic field distribution pattern, only the magnitude of the magnetic field strength and the radial leakage magnetic field distribution. Therefore, this embodiment primarily selects the radial direction as the detection location. Furthermore, when the winding magnetic field is short-circuited between turns, the leakage magnetic field amplitude still appears at the oil passage gap between the high-pressure and low-pressure windings, where the amplitude change is most significant. Therefore, this embodiment uses the magnetic induction intensity threshold range at the gap between the high-pressure and low-pressure oil passages as a sensitive change quantity for fault initiation discrimination. The reason why the maximum magnetic field strength appears at the gap between the high and low pressure oil channels is mainly due to the influence of the axial leakage magnetic field. Therefore, during inter-turn short circuit, the maximum leakage magnetic field strength also appears at the gap between the high and low pressure oil channels. Thus, this location is selected as the sensitive monitoring point for inter-turn short circuit.

[0033] Furthermore, the current of each phase copper foil winding of the transformer, i.e. the change of secondary winding current, is detected. When the current of a certain phase is more than 10 times the normal operating value, the fault is judged to be a short circuit between winding phases or a short circuit to ground of a certain winding; when the three-phase current fluctuates less than the current during normal operation, the fault is judged to be a short circuit between turns.

[0034] It is understandable that changes in magnetic flux are mainly caused by changes in current. During an inter-turn short circuit, the huge short-circuit current in the short-circuit ring causes changes in the surrounding magnetic flux. Similarly, in a ground fault, the faulty phase will also generate a huge short-circuit current, causing changes in the surrounding magnetic flux. Therefore, it is impossible to determine whether it is an inter-turn short circuit or a ground fault based solely on changes in magnetic flux. Thus, this embodiment further introduces a current variable for judgment. The specific principle and steps are as follows: During normal operation, a transformer follows a magnetomotive force balance. The sum of the magnetomotive force of the primary winding and the secondary winding constitutes the excitation magnetomotive force. When an inter-turn short circuit occurs in the secondary copper foil winding, the magnetomotive force balance equation is as follows: ; In the formula, This represents the total number of turns in the primary winding. This is the current flowing through the primary winding after the fault. This represents the total number of turns in the secondary winding when it is in good condition. This refers to the number of turns in the secondary winding section where an inter-turn short circuit occurs. The non-short-circuited portion of the secondary winding after a fault ( The current of ) To short-circuit turn Faulty circulating current in the middle of the flow, This is the excitation current, which generates the main magnetic flux of the transformer. The required current.

[0035] When an inter-turn short circuit occurs, the fault turn current increases dramatically, disrupting the magnetomotive force balance. The main magnetic flux remains unchanged, therefore adjustments are needed to the currents of the primary and secondary windings. The secondary winding is affected by the loop voltage equation, as shown in the following formula: ; In the formula, The voltage across the load. The electromotive force induced by the main magnetic flux in the non-short-circuit winding is... The current flowing through the non-short-circuit part and the load, This is the resistance of the non-short-circuited portion of the secondary winding. This is the leakage reactance of the non-short-circuit portion of the secondary winding.

[0036] Since the main magnetic flux remains constant and the load is fixed, the secondary winding current remains essentially constant during an inter-turn short circuit in the copper foil winding, while the primary winding current changes little. The surge in short-circuit current during an inter-turn short circuit falls between that of a single-phase-to-ground short circuit and a two-phase-to-ground short circuit. An inter-turn short circuit manifests as minimal changes in current between individual phases, while a phase-to-phase short circuit results in a dramatic increase in winding current. Therefore, if the secondary winding current fluctuation is small after the magnetic field sensor at the oil passage gap in the middle of the high and low voltage windings reaches the activation threshold, the short circuit fault can be determined to be an inter-turn short circuit fault in the copper foil winding.

[0037] Therefore, it can be understood that during an inter-turn short circuit, only the short-circuit turn current increases, with almost no effect on the phase current. Thus, during an inter-turn short circuit, the phase current remains constant or fluctuates slightly. A ground fault, however, causes the entire phase to ground, resulting in a dramatic increase in the phase current. Therefore, by detecting the phase current, it is possible to distinguish whether the increase in magnetic flux density is due to a sudden increase in phase current or an inter-turn short circuit, thereby determining whether an inter-turn short circuit fault has occurred.

[0038] Furthermore, in this embodiment, if the current of only one phase winding is more than 10 times that of normal operation, then a ground fault is determined to have occurred in that phase winding. For example, based on the magnitude of the current of each phase of the winding, if the current of phase A is more than 10 times that of normal operation, then a ground fault is determined to have occurred in phase A, and the same applies to phases B and C. If the current of two phase windings is more than 10 times that of normal operation, then a phase-to-phase short circuit is determined to have occurred between these two phase windings. For example, if the currents of phases A and B are both more than 10 times that of normal operation, then a two-phase phase-to-phase short circuit is determined to have occurred, and the same applies to phases A and C, and phases B and C. If the currents of phases A, B, and C are all more than 10 times that of normal operation, then a three-phase short circuit is determined to have occurred.

[0039] It is understandable that this embodiment determines the fault phase information based on the magnitude of the current in each phase during the short circuit. For example, the calculation formula for the three-phase short circuit current is shown below: ; In the formula, This represents the effective value of the three-phase short-circuit current on the secondary side of the transformer. The rated capacity of the transformer. Rated line voltage (kV) on the secondary side of the transformer. This is the per-unit value of the transformer's short-circuit impedance.

[0040] The two-phase short-circuit current is approximately 0.866 times that of the three-phase short-circuit current. Therefore, in this embodiment, the current for grounding and phase-to-phase short-circuit faults is selected to be 10 times or more of the normal operating current.

[0041] Furthermore, if the current of any phase winding does not exceed 10 times the normal operating value, then the inter-turn short circuit fault is judged for each phase copper foil winding. Taking the A phase copper foil winding as an example, if the magnetic induction intensity detected at the innermost (A1 turn) and outermost (A25 turn) of the upper end of the copper foil winding is greater than the normal operating value, then the winding is judged to have an inter-turn short circuit fault.

[0042] It is understandable that if the magnetic induction intensity at the oil passage gap in the middle of the high-voltage winding and the low-voltage winding is greater than the magnetic induction intensity when the winding is operating normally, and if the current fluctuation of each phase is small, and the magnetic induction intensity at the radial observation point of a certain phase winding is higher than the normal operating intensity, then it is determined that the copper foil winding of that phase has an inter-turn short circuit fault.

[0043] Furthermore, if an inter-turn short-circuit fault is determined to have occurred in a certain phase winding, the location of the short-circuit fault is then determined. Taking phase A winding as an example, the specific steps are as follows: First, the initial rate of change of the first difference in magnetic induction intensity at two detection positions at the upper end of the copper foil winding (the upper end of turn A1 and the upper end of turn A25) is used to make a preliminary judgment on the location of the inter-turn short circuit. The corresponding discriminant expression is: ; In the formula, The magnetic induction intensity at the upper end of the inner side (turn A1) of the winding during a fault is measured. The magnetic induction intensity at the upper end of the outer side of the winding (turn A25) during a fault is measured. This represents the magnetic flux density at the upper end of the inner side (turn A1) of the winding during normal operation. The magnetic induction intensity at the upper end of the outer side (A25 turns) of the winding during normal operation.

[0044] Understandably, due to the special lamellar winding structure of copper foil windings, a huge short-circuit current region is generated when a short circuit occurs, which affects the leakage magnetic field strength of the surrounding windings. Specifically, the leakage magnetic field strength increases because the leakage magnetic field at the upper end of the winding is affected not only by the axial leakage magnetic field but also by the radial leakage magnetic field. When an inter-turn short-circuit fault occurs, the leakage magnetic field at the upper end of the short-circuited turn is the strongest. Figure 4 As shown, Figure 4 The diagram illustrates the variation of magnetic flux density at the upper end of the winding with position and short-circuit location, showing a rapid increase in the leakage magnetic field at the short-circuit turn and a gradual decrease towards both ends. Therefore, it is impossible to determine the location of the inter-turn short circuit simply by comparing the magnitude of the magnetic flux density. This implementation introduces the concept of the rate of change of magnetic flux density to achieve fault location. Details are as follows: Taking phase A winding as an example, when an inter-turn short circuit fault occurs, the magnetic flux density at the upper end of the winding will suddenly increase at the short-circuited turn and gradually decrease towards both sides. This means that when the faulted turn is close to turn A1, the magnetic flux density at the upper end of turn A1 will increase, and the closer the faulted turn is to turn A1, the greater the increase in magnetic flux density at the upper end of turn A1. Turn A25 is farther away, and the change in magnetic flux density at the upper end of turn A25 is slight, with little change before and after the inter-turn short circuit. Therefore, when the faulted turn is close to turn A1, the magnetic flux density at the upper end of turn A1 is greater than that at the upper end of turn A25, with the difference being... The value is positive, and the closer the faulty turn is to turn A1, the greater the difference. The larger the difference, the greater the magnetic flux density. Similarly, when the faulty turn is close to turn A25, the greater the increase in magnetic flux density at the top of turn A25. Turn A1, being farther away, experiences only a slight change in magnetic flux density at its top, with minimal variation before and after the inter-turn short circuit. Therefore, when the faulty turn is close to turn A25, the magnetic flux density at the top of turn A25 is greater than that at the top of turn A1, with the difference being [missing value]. The difference is negative, and the closer the faulty turn is to turn A25, the greater the difference. The larger the absolute value, the greater the value.

[0045] Meanwhile, during normal operation, the magnetic flux density at the upper end of turn A25 is greater than that at the upper end of turn A1, therefore the difference... It is negative. Therefore, when When it is positive, the rate of change of the first difference Then it is a negative value; when It is a negative value, and its absolute value is greater than 1. At that time, the rate of change of the first difference The value is positive. In this embodiment, by setting the faulty turn at different radial positions and testing the rate of change of the first difference, it was found that when the faulty turn was set at turns A1-A8, the rate of change of the first difference was negative; when the faulty turn was set at turns A9-A25, the rate of change of the first difference was positive.

[0046] It is understandable that when the rate of change of the first difference is negative, that is... This indicates that the faulty turn is located near the core, specifically in region I of the copper foil winding (between turns A1 and A8), and the first difference rate of change... The larger the absolute value, the greater the difference. The larger the positive value, the greater the increase in magnetic induction intensity at the upper end of turn A1, and the closer the faulty turn is to turn A1; when the first rate of change is positive, i.e. If the fault occurs, it indicates that the inter-turn short circuit fault is located in region II or region III of the copper foil winding, i.e., between turns A9 and A25, and further determines the location of the faulty turn.

[0047] Furthermore, when To further determine the location of the inter-turn short circuit, the second rate of change of magnetic induction intensity at the radial midpoint (turn A17) on the outer side of the copper foil winding and at the midpoint of the high- and low-pressure oil passage gap is used to further determine the more specific location of the faulty turn in region II or region III of the copper foil winding. The corresponding discrimination expression is: ; In the formula, This refers to the magnetic flux density at the midpoint of the A17 winding during an inter-turn short-circuit fault. To transmit the magnetic induction intensity at the midpoint between the high and low pressure oil passages during an inter-turn short-circuit fault. This refers to the magnetic flux density at the midpoint of the A17-turn winding during normal operation. The magnetic induction intensity is located at the midpoint of the gap between the high and low pressure oil passages during normal operation.

[0048] It is understandable that, such as Figure 5As shown, when an inter-turn short-circuit fault occurs, the leakage magnetic field strength in the middle of the winding is mainly determined by the axial leakage magnetic field. Therefore, the distribution pattern of the leakage magnetic field in the middle of the winding shows a gradual increasing trend from the short-circuited turn towards the gap between the high and low pressure oil passages. Furthermore, regardless of whether an inter-turn short circuit occurs, the magnetic induction intensity at the middle position of the high and low pressure oil passages is always greater than the magnetic induction intensity at the detection position in the middle of the A17 turn winding. Therefore, the difference... Sum and difference ( - The magnetic flux density is always negative. Furthermore, once an inter-turn short circuit occurs, regardless of the location of the faulty turn, the difference in magnetic flux density at the midpoint between the high and low pressure oil passages is not significant. Therefore, after an inter-turn short circuit fault, the magnetic flux density at the midpoint between the high and low pressure oil passages remains relatively constant. This can be considered a constant value. However, when an inter-turn short-circuit fault occurs, the magnetic induction intensity at the axial midpoint of the faulty turn will suddenly increase, and the magnetic induction intensity at the axial midpoint of the winding will increase radially towards the gap between the high and low pressure oil passages. Therefore, when the faulty turn is located near the core of turn A17, i.e., in region II (between turns A9 and A16), the magnetic induction intensity at the detection position in the middle of the A17 turn winding will increase, while the magnetic induction intensity at the middle position of the high and low pressure oil passages after an inter-turn short-circuit fault will increase. It can be considered as a constant value; in this case, the difference is... The absolute value is less than the difference. The absolute value, If positive, the second difference rate of change It is negative. And if the rate of change of the second difference... The larger the absolute value, the stronger the... The smaller the absolute value, the greater the increase in magnetic induction intensity of turn A17, and the closer the faulty turn is to turn A9.

[0049] Similarly, when the faulty turn is located near a portion of turn A25 on turn A17, i.e., in region III (between turns A17 and A25), the magnetic induction intensity at the detection position in the middle of the A17 winding will not change, while the magnetic induction intensity at the gap between the high and low pressure oil passages will increase. Therefore, the difference will be... The absolute value is greater than the difference. The absolute value, The second difference rate of change is negative. It is positive.

[0050] Therefore, the second difference rate of change At that time, the faulty turn was determined to be located in region II (between turns A9 and A16). Second difference rate of change. At that time, it was determined that the faulty turn was located in region III (between turns A17 and A25).

[0051] Furthermore, it is understandable that the outer winding of the copper foil has a large number of turns, and when a short circuit fault occurs between turns of the copper foil winding, the magnetic induction intensity in the middle of each turn gradually increases from the faulted turn to the gap between the high and low pressure oil channels. Therefore, the rate of change of the difference in magnetic induction intensity between the center of the A17 turn winding and the center of the gap between the high and low pressure oil channels is selected to further identify the location information of the short circuit between turns of the outer winding of the copper foil.

[0052] Based on the test results obtained from each testing step, information on the normal operation of the copper foil winding, the fault type, and the location of the inter-turn short circuit fault is obtained, which is used to monitor the operating status of the copper foil winding and locate the fault. If an inter-turn short circuit fault occurs, the faulty turn can be specifically located in Region I, Region II, or Region III.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0054] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for detecting faults in the copper foil windings of a triangular three-dimensional amorphous alloy transformer, characterized in that, include: Obtain first information, which includes the real-time first magnetic induction intensity of the first winding of the transformer at multiple radially preset positions; Obtain second information, which includes multiple preset first thresholds, with each first threshold corresponding to one of the positions; Based on the first information and the second information, determine the inter-turn short circuit fault of the first winding; If it is determined that an inter-turn short circuit fault has occurred in the first winding, then multiple first difference change rates are calculated based on multiple first differences and multiple second differences. Based on the multiple first difference change rates, a first region where an inter-turn short circuit fault has occurred is determined. The first region is the region between two adjacent positions. The first difference is the difference between the first magnetic induction intensities corresponding to the two positions, and the second difference is the difference between the first thresholds corresponding to the two positions.

2. The method for detecting copper foil winding faults in a triangular three-dimensional amorphous alloy transformer according to claim 1, characterized in that... The first threshold corresponding to a given position is set based on the magnetic induction intensity at that position when the first winding is operating normally.

3. The method for detecting copper foil winding faults in a triangular three-dimensional amorphous alloy transformer according to claim 1, characterized in that... The acquisition of the first information includes: The first magnetic induction intensity is obtained at the first position, second position, third position and fourth position of the first winding, wherein the first position and the third position are respectively located at the upper axial position of the two turns of copper foil closest to and farthest from the iron core in the first sub-winding of the first winding, the second position is located at the middle axial position of the turn of copper foil in the first sub-winding close to the third position, and the fourth position is at the middle oil passage gap between the first sub-winding and the second sub-winding of the first winding, wherein the first sub-winding is a copper foil winding and the second sub-winding is a high voltage winding.

4. The method for detecting copper foil winding faults in a triangular three-dimensional amorphous alloy transformer according to claim 3, characterized in that... The first position, the second position, and the third position are respectively located at the copper foil of the first turn, the seventeenth turn, and the twenty-fifth turn of the first sub-winding.

5. The method for detecting copper foil winding faults in a triangular three-dimensional amorphous alloy transformer according to claim 3, characterized in that... After obtaining the second information, the process further includes: When the first magnetic induction intensity at the fourth position is greater than the first threshold corresponding to the fourth position, the first current of the multiphase first winding is obtained to obtain multiple first currents; If the first current is greater than the preset first current threshold, then a ground fault of the multi-phase first winding or a short circuit fault between the multi-phase first windings is determined. If there is no first winding with a first current greater than the first current threshold, then an inter-turn short-circuit fault is determined for the first winding.

6. The method for detecting copper foil winding faults in a triangular three-dimensional amorphous alloy transformer according to claim 5, characterized in that... The determination of ground faults in the first winding of multiple phases or the determination of short-circuit faults between the first windings of multiple phases includes: If the first current of only one phase of the first winding is greater than the first current threshold, it is determined that there is a ground short circuit fault in the first winding of that phase. If the first current of the first winding of both phases is greater than the first current threshold, then it is determined that there is a short circuit fault between the first windings of the two phases.

7. The method for detecting copper foil winding faults in a triangular three-dimensional amorphous alloy transformer according to claim 3, characterized in that... The determination of inter-turn short-circuit faults in the first winding based on the first information and the second information includes: If the second magnetic flux density and the third magnetic flux density of the first winding are greater than the second threshold and the third threshold, respectively, it is determined that there is an inter-turn short circuit fault in the first winding. The second magnetic flux density and the third magnetic flux density are the first magnetic flux densities corresponding to the first position and the third position of the first winding, respectively. The second threshold and the third threshold are the first thresholds corresponding to the first position and the third position of the first winding, respectively.

8. The method for detecting copper foil winding faults in a triangular three-dimensional amorphous alloy transformer according to claim 4, characterized in that... The first region where an inter-turn short-circuit fault occurs, determined based on multiple first difference change rates, includes: Calculate the third difference and the fourth difference, and calculate the first difference change rate based on the third difference and the fourth difference to obtain the first difference change rate. The third difference is the difference between the first position of the first winding and the first magnetic induction intensity corresponding to the third position. The fourth difference is the difference between the first position of the first winding and the first threshold corresponding to the third position. If the first difference change rate is less than the preset first change rate threshold, it is determined that an inter-turn short circuit fault has occurred in the second region of the first sub-winding of the first winding. The second region is the region between the first turn and the eighth turn of the copper foil of the first sub-winding. If the first difference change rate is greater than the preset first change rate threshold, then the fifth difference and the sixth difference are calculated, and the second difference change rate is calculated based on the fifth difference and the sixth difference to obtain the second difference change rate. The fifth difference is the difference between the first magnetic induction intensity corresponding to the second position and the fourth position of the first winding, and the fourth difference is the difference between the second position and the first threshold corresponding to the fourth position of the first winding. If the second difference change rate is less than the preset second change rate threshold, it is determined that an inter-turn short circuit fault has occurred in the third region of the first winding. The third region is the region between the ninth and seventeenth turns of the first sub-winding. If the second difference change rate is greater than the preset third change rate threshold, then it is determined that an inter-turn short circuit fault has occurred in the fourth region of the first winding. The fourth region is the region between the seventeenth and twenty-fifth turns of the first sub-winding.

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