A fan box transformer fault analysis method based on fault recording data

Abstract

This invention relates to the field of transformer fault analysis technology, and provides a method for fault analysis of wind turbine box-type transformers based on fault recording data. The method includes: acquiring wind energy and converting it into electrical energy, generating electricity through a wind turbine generator; transmitting the electrical energy generated by the wind turbine generator to the box-type transformer for voltage regulation; transmitting the stepped-up electrical energy from the box-type transformer to a substation; collecting and analyzing the operating data of the box-type transformers in real time through the substation's SCADA platform, and summarizing the electrical energy data of multiple box-type transformers; performing real-time analysis on the operating data of each box-type transformer, including but not limited to the following fault types: high-voltage side inter-turn short circuit, low-voltage side single-phase ground fault, low-voltage side two-phase ground fault, low-voltage side two-phase short circuit, and low-voltage side inter-turn short circuit; extracting current characteristics from the fault recording data based on the analysis results; and analyzing five types of faults: high-voltage side inter-turn short circuit, low-voltage side single / two-phase ground fault, phase-to-phase short circuit, and inter-turn short circuit.

Description

Technical Field

[0001] This invention relates to the field of transformer fault analysis technology, and specifically to a method for analyzing the faults of wind turbine transformer boxes based on fault recording data. Background Technology

[0002] Wind turbine (wind power generator) box-type transformers are one of the core pieces of equipment in wind farms, serving as the energy conversion hub for power generation, transmission, and transformation. Their stable and reliable operation is a crucial prerequisite for the reliable operation of wind power generation systems. However, in recent years, the frequency of unplanned shutdowns caused by internal insulation faults in box-type transformers has increased, with some even leading to fires. This is particularly true for integrated generator-transformer wind turbine units, where a fire in the box-type transformer can directly trigger a chain reaction of combustion in the nacelle, ultimately rendering the entire unit unusable and causing significant economic losses. Therefore, implementing effective preventative measures to achieve early fault diagnosis of box-type transformers has become an important research topic for ensuring the safe operation and maintenance of wind farms.

[0003] In traditional operation and maintenance (O&M) models, regular visual inspections by O&M personnel are a common way to assess equipment condition. Routine checks include observing for obvious problems such as oil leaks, abnormal noises, and casing deformation in box-type transformers. However, this method has significant limitations. Visual inspections can only detect some surface-level, obvious signs of faults, and are difficult to detect potential internal faults in box-type transformers. For example, aging of internal insulation materials and loose electrical connections are difficult to diagnose directly from the outside. Moreover, some faults may not show obvious external characteristics in their early stages, and by the time they can be detected through visual inspection, the fault has often progressed to a relatively serious stage, which undoubtedly increases the risk of equipment damage and repair costs. Preventive testing is an important means of testing parameters such as insulation performance in traditional O&M.

[0004] To address the aforementioned problems, we propose a fault analysis method for wind turbine transformer boxes based on fault recording data. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a fault analysis method for wind turbine transformer boxes based on fault recording data. This method overcomes the deficiencies of existing technologies and is rationally designed. By establishing an electromagnetic transient model of a three-winding transformer, it analyzes the electrical characteristic parameters under five types of fault conditions: high-voltage side inter-turn short circuit, low-voltage side single-phase ground fault, two-phase ground fault, phase-to-phase short circuit, and inter-turn short circuit.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for fault analysis of wind turbine transformer boxes based on fault recording data includes: acquiring wind energy and converting it into electrical energy, and generating electricity through a wind turbine generator;

[0008] The electrical energy generated by the wind turbine is transmitted to the box-type transformer for voltage regulation;

[0009] The electrical energy boosted by the box-type transformer is transmitted to the substation.

[0010] The SCADA platform of the substation collects and analyzes the operating data of the box-type transformers in real time, and summarizes the power data of multiple box-type transformers.

[0011] Real-time analysis of the operating data of each box-type transformer is performed, including but not limited to the following fault types: high-voltage side inter-turn short circuit, low-voltage side single-phase ground fault, low-voltage side two-phase ground fault, low-voltage side two-phase short circuit, and low-voltage side inter-turn short circuit.

[0012] Based on the analysis results, current characteristics were extracted from the fault recording data.

[0013] Preferably, the low-voltage side of the box-type transformer uses a star connection, and the high-voltage side uses a delta connection; thus forming a YnD transformer, with a turns ratio of n1 / n2, the voltage formula on the Yn side is:

[0014]

[0015] In the formula, , These represent the voltages of phases A, B, and C on the high-voltage side, respectively, and are the three-phase outputs of the transformer on the high-voltage side.

[0016] The line voltage, representing the low-voltage side, is the voltage between the two lines on the low-voltage side of the transformer.

[0017] Angular frequency represents the rate at which voltage changes with time and is directly proportional to the frequency of the power source.

[0018] Time represents the change of voltage waveform over time;

[0019] The n1 / n2 transformer turns ratio is the ratio of the number of turns on the high-voltage side to the number of turns on the low-voltage side.

[0020] and These represent the phase differences between phase B and phase C voltages relative to phase A voltage, respectively; the current formula on the Yn side is:

[0021]

[0022] In the formula, This represents the instantaneous value of phase A in the first group of three-phase currents; Indicates the magnitude of the current; This represents the instantaneous value of phase B in the first group of three-phase currents; This represents the instantaneous value of phase C in the first group of three-phase currents;

[0023] The voltage formula on side D is:

[0024]

[0025] In the formula, , , These represent the original voltages of phases A, B, and C, respectively. Indicates the magnitude of the voltage; , , These represent the voltages of phases A, B, and C on the low-voltage side, respectively.

[0026] The current formula on side D is:

[0027]

[0028] In the formula, This represents the instantaneous value of phase A in the first group of three-phase currents;

[0029] This represents the instantaneous value of phase B in the first group of three-phase currents;

[0030] This represents the instantaneous value of phase C in the first group of three-phase currents.

[0031] Preferably, the high-voltage side inter-turn short-circuit analysis of the box-type transformer is as follows:

[0032] The high-voltage side of a box-type transformer is divided into A1, B1, and C1. If an inter-turn short circuit occurs in phase A1, the current expression on the high-voltage side is as follows:

[0033]

[0034] Due to the transformer turns ratio Therefore, the effective values ​​of the currents in phases A1 and C1 are equal and greater than those in phase B1. Therefore, the effective values ​​of the currents in phases A, B, and C output from line III to the booster station are obtained: .

[0035] Preferably, the analysis of single-phase ground fault on the low-voltage side of the box-type transformer is as follows: The low-voltage side of the box-type transformer is divided into a1, b1, and c1. If a ground fault occurs on phase a1, then: Combining equation (4), we can deduce the following equation:

[0036]

[0037] In the formula, This represents the current amplitude on the high-voltage side. Since the equivalent wind turbine S0 is not faulty, where S0 and T0 are equivalent models of multiple wind turbines and their corresponding box-type transformers, respectively, the current of the equivalent box-type transformer T0 is given by the following formula:

[0038] In the formula, This indicates the magnitude of the current in phase A of the equivalent box-type transformer T0;

[0039] This indicates the magnitude of the current in phase B of the equivalent box-type transformer T0;

[0040] This indicates the magnitude of the current in phase C of the equivalent box-type transformer T0;

[0041] Reference current;

[0042] The current flowing into the booster station at this time is given by the following formula:

[0043]

[0044] The effective values ​​of the current in each phase are obtained by equation (8):

[0045]

[0046] As shown in equation (9), when a phase a1 of the low-voltage side of the box-type transformer is short-circuited to ground, the effective values ​​of the currents in phases A and C are equal and greater than those in phase B. At the same time, the current of phase A leads phase B by more than 120 degrees, the current of phase C leads phase A by less than 120 degrees, and the current of phase B leads phase C by more than 120 degrees.

[0047] Preferably, the analysis of the two-phase ground fault on the low-voltage side of the box-type transformer is as follows:

[0048] When a phase-to-phase short circuit occurs between phases b1 and c1: , Combining equation (4), we can derive the following equation:

[0049]

[0050] Combining equations (7) and (10), the current flowing into the booster station at this time can be calculated as follows:

[0051]

[0052] The effective values ​​of the current in each phase are calculated as follows:

[0053]

[0054] From equation (12), it can be seen that when phases b1 and c1 on the low-voltage side are short-circuited to ground, the effective values ​​of the currents in phases A and C are equal and greater than those in phase B: At the same time, the current of phase A leads phase B by less than 120 degrees, the current of phase C leads phase A by more than 120 degrees, and the current of phase B leads phase C by less than 120 degrees.

[0055] Preferably, the low-voltage side two-phase short-circuit analysis of the box-type transformer is as follows: when a phase-to-phase short circuit occurs between phases b1 and c1:

[0056]

[0057] Combining equations (4) and (13), we can derive the following equation:

[0058]

[0059] Combining equations (7) and (14), the current flowing into the booster station at this time is calculated as follows:

[0060]

[0061] The effective values ​​of the current in each phase are calculated as follows:

[0062]

[0063] From equation (16), it can be seen that when phases b1 and c1 on the low-voltage side are short-circuited, the effective values ​​of the currents in phases A and C are equal and greater than those in phase B. At the same time, the current of phase A leads phase B by less than 120 degrees, the current of phase C leads phase A by more than 120 degrees, and the current of phase B leads phase C by less than 120 degrees.

[0064] Preferably, the low-voltage side inter-turn short-circuit analysis of the box-type transformer is as follows: If an inter-turn short circuit occurs on phase a1 of the low-voltage side of the box-type transformer:

[0065]

[0066] Due to the transformer turns ratio Therefore: ,and , , respectively with , , Same direction;

[0067] Combining equations (7) and (17), the current flowing into the booster station at this time is calculated as follows:

[0068]

[0069] It can be seen that when an inter-turn short circuit occurs on phase a1 of the low-voltage side of the box-type transformer, the effective values ​​of the currents in phases A and C are equal and greater than those in phase B: .

[0070] This invention provides a fault analysis method for wind turbine transformer boxes based on fault recording data. It offers the following advantages: Based on an electromagnetic transient model of a three-winding transformer, the current amplitude, phase, and temperature characteristics of five types of faults—inter-turn short circuits on the high-voltage side, single-phase / two-phase ground faults on the low-voltage side, phase-to-phase short circuits, and inter-turn short circuits—are analyzed. A multi-dimensional fault discrimination system is constructed. Simulation results show that different faults exhibit unique current amplitude rankings and phase shifts on the primary side of the substation (e.g., when there is an inter-turn short circuit in phase A on the high-voltage side, the current amplitudes of phases A and C increase significantly). Accurate fault location can be achieved by combining the three-phase effective values ​​and phase differences. Through a real-world case study of a wind farm, combining recording data and temperature monitoring, an inter-turn short circuit in phase C on the low-voltage side was identified, revealing the mechanism of abnormal temperature rise caused by insulation defects under high power conditions, thus confirming the effectiveness of the method. Attached Figure Description

[0071] Figure 1.1 A-line fan schematic diagram;

[0072] Figure 1.2 Equivalent schematic diagram of the A-line fan unit;

[0073] Figure 1.3 Schematic diagram of transformer T1;

[0074] Figure 1.4 Transformer fault types;

[0075] Figure 2.1 Direction of short-circuit current to ground fault on phase a1 of the low-voltage side of the transformer

[0076] Figure 2.2 Current vector diagram flowing into the step-up substation when a single-phase ground fault occurs on phase a1 of the low-voltage side of the transformer substation;

[0077] Figure 2.3 Vector diagram of ground fault current flow for phases b1 and c1 on the low-voltage side of the transformer substation;

[0078] Figure 2.4 Current vector diagram flowing into the substation when phases b1 and c1 of the low-voltage side of the transformer are grounded and short-circuited;

[0079] Figure 2.5 Current flow vector diagram of phase-to-phase short circuit between phases b1 and c1 on the low-voltage side of the transformer;

[0080] Figure 2.6 Current vector diagram flowing into the substation when phase B1 and phase C1 of the low-voltage side of the transformer substation experience a phase-to-phase short circuit;

[0081] Figure 2.7Current vector diagram flowing into the step-up substation when an inter-turn short circuit occurs on phase a1 of the low-voltage side of the transformer;

[0082] Figure 3.1 The waveform of the current flowing into the main transformer from the collector line when the line is running stably;

[0083] Figure 3.2(a) Waveform diagram of inter-turn short circuit in phase A on the high-voltage side;

[0084] Figure 3.2(b) Waveform diagram of single-phase ground fault on the low-voltage side (phase a);

[0085] Figure 3.2(c) Waveform diagram of two-phase ground fault on the low-voltage side (b and c);

[0086] Figure 3.2(d) Short-circuit waveform diagram of phases b and c on the low-voltage side;

[0087] Figure 3.2(e) Inter-turn short circuit on phase a of the low-voltage side;

[0088] Figure 4.1 Waveform recording of a fault at a wind farm;

[0089] Figure 4.2 Waveforms of temperature changes in each winding of the Z-type transformer during the detection time;

[0090] Figure 4.3 The effective value of the three-phase current transmitted to the main transformer of the substation within the detection time of the collector line where the Z box transformer is located;

[0091] Figure 4.4 Waveform data diagram when power generation is low;

[0092] Figure 4.5 Waveform data diagram when power generation is high; Detailed Implementation

[0093] 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 embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0094] A fault analysis method for wind turbine transformer boxes based on fault recording data includes:

[0095] Harvesting wind energy and converting it into electrical energy, generating electricity through wind turbines;

[0096] The electrical energy generated by the wind turbine is transmitted to the box-type transformer for voltage regulation;

[0097] The electrical energy boosted by the box-type transformer is transmitted to the substation.

[0098] The SCADA (Supervisory and Data Acquisition) platform of the substation collects and analyzes the operating data (such as voltage, current, power, etc.) of the box-type transformers in real time, and summarizes the power data of multiple box-type transformers.

[0099] Real-time analysis of the operating data of each box-type transformer is performed, including but not limited to the following fault types: high-voltage side inter-turn short circuit, low-voltage side single-phase ground fault, low-voltage side two-phase ground fault, low-voltage side two-phase short circuit, and low-voltage side inter-turn short circuit.

[0100] Based on the analysis results, current characteristics (such as fault current amplitude, phase change, harmonic components, etc.) are extracted from the fault recording data to achieve accurate identification and location of fault types; ultimately, accurate diagnosis and prevention optimization of transformer substation faults are achieved.

[0101] like Figure 1.3 As shown, the low-voltage side of the box-type transformer uses a star connection, and the high-voltage side uses a delta connection; thus forming a YnD transformer. Assuming its turns ratio is n1 / n2, the voltage formula for the Yn (high-voltage) side is:

[0102]

[0103] In the formula, , These represent the voltages of phases A, B, and C on the high-voltage side, respectively, and are the three-phase outputs of the transformer on the high-voltage side.

[0104] The line voltage, representing the low-voltage side, is the voltage between the two lines on the low-voltage side of the transformer.

[0105] Angular frequency represents the rate at which voltage changes with time and is directly proportional to the frequency of the power source.

[0106] Time represents the change of voltage waveform over time;

[0107] The n1 / n2 transformer turns ratio, which is the ratio of the number of turns on the high-voltage side to the number of turns on the low-voltage side, determines the voltage transformation ratio.

[0108] and These represent the phase differences between phase B and phase C voltages relative to phase A voltage, respectively, reflecting the balance and phase relationship of the three-phase electricity.

[0109] The current formula on the Yn side is:

[0110]

[0111] In the formula, This represents the instantaneous value of phase A in the first group of three-phase currents; Indicates the magnitude of the current; This represents the instantaneous value of phase B in the first group of three-phase currents; This represents the instantaneous value of phase C in the first group of three-phase currents;

[0112] The voltage formula on the D (low voltage) side is:

[0113]

[0114] In the formula, , , These represent the original voltages of phases A, B, and C, respectively. Indicates the magnitude of the voltage; , , These represent the voltages of phases A, B, and C on the low-voltage side, respectively.

[0115] The current formula on side D is:

[0116]

[0117] In the formula, This represents the instantaneous value of phase A in the first group of three-phase currents;

[0118] This represents the instantaneous value of phase B in the first group of three-phase currents;

[0119] This represents the instantaneous value of phase C in the first group of three-phase currents.

[0120] Inter-turn short-circuit analysis of the high-voltage side of the box-type transformer:

[0121] The high-voltage side of a box-type transformer is divided into A1, B1, and C1. If an inter-turn short circuit occurs in phase A1, the current expression on the high-voltage side is as follows:

[0122]

[0123] Due to the transformer turns ratio Therefore, the effective values ​​of the currents in phases A1 and C1 are equal and greater than those in phase B1. Therefore, the effective values ​​of the currents in phases A, B, and C output from line III to the booster station are obtained: Similarly, the relationship between the currents of each phase on the primary side of the substation when there is an inter-turn short circuit in phases B1 and C1 on the high-voltage side is calculated, and the relationship is shown in the table below:

[0124] Inter-turn short circuit phase on the high-voltage side of the transformer Current relationship of each phase on the primary side of the booster station <![CDATA[A1]]> <![CDATA[B1]]> <![CDATA[C1]]>

[0125] like Figure 2.1As shown, the analysis of a single-phase ground fault on the low-voltage side of the box-type transformer is as follows:

[0126] The low-voltage side of a box-type transformer is divided into a1, b1, and c1. If a ground fault occurs in phase a1, then: Combining equation (4), we can deduce the following equation:

[0127]

[0128] Since the equivalent wind turbine S0 did not fail, where S0 and T0 are equivalent models of multiple wind turbines and their corresponding box-type transformers, respectively, the current of the equivalent box-type transformer T0 is given by the following formula:

[0129] In the formula, This indicates the magnitude of the current in phase A of the equivalent box-type transformer T0;

[0130] This indicates the magnitude of the current in phase B of the equivalent box-type transformer T0;

[0131] This indicates the magnitude of the current in phase C of the equivalent box-type transformer T0;

[0132] Reference current;

[0133] like Figure 2.2 As shown, the current flowing into the booster station at this time is given by the following formula:

[0134] The effective values ​​of the current in each phase are obtained by equation (8):

[0135]

[0136] As shown in equation (9), when a phase a1 of the low-voltage side of the box-type transformer is short-circuited to ground, the effective values ​​of the currents in phases A and C are equal and greater than those in phase B. At the same time, the current of phase A leads phase B by more than 120 degrees, the current of phase C leads phase A by less than 120 degrees, and the current of phase B leads phase C by more than 120 degrees.

[0137] Similarly, the relationship between the currents of each phase on the primary side of the substation when a single-phase ground fault occurs on phases b1 and c1 of the low-voltage side of the box-type transformer can be calculated; this relationship is shown in the table below:

[0138] Single-phase ground fault on the low-voltage side of the transformer Current relationship of each phase on the primary side of the booster station <![CDATA[a1]]> <![CDATA[b1]]> <![CDATA[c1]]>

[0139] like Figure 2.3 As shown, the analysis of the two-phase ground fault on the low-voltage side of the box-type transformer is as follows:

[0140] When a phase-to-phase short circuit occurs between phases b1 and c1: , Combining equation (4), we can derive the following equation:

[0141]

[0142] like Figure 2.4 As shown, combining equations (7) and (10), the current flowing into the booster station at this time can be calculated as follows:

[0143]

[0144] The effective values ​​of the current in each phase are calculated as follows:

[0145]

[0146] From equation (12), it can be seen that when phases b1 and c1 on the low-voltage side are short-circuited to ground, the effective values ​​of the currents in phases A and C are equal and greater than those in phase B: At the same time, the current of phase A leads phase B by less than 120 degrees, the current of phase C leads phase A by more than 120 degrees, and the current of phase B leads phase C by less than 120 degrees.

[0147] Similarly, the relationships between the phase currents on the primary side of the substation during the other two types of ground faults on the low-voltage side of the box-type transformer can be calculated, as shown in the table below:

[0148] Two-phase ground fault phase on the low-voltage side of the transformer Current relationship of each phase on the primary side of the booster station <![CDATA[a1、b1]]> <![CDATA[b1、c1]]> <![CDATA[c1、a1]]>

[0149] like Figure 2.5 As shown, the low-voltage side two-phase short circuit analysis of the box-type transformer is as follows: When a phase-to-phase short circuit occurs between phases b1 and c1:

[0150]

[0151] Combining equations (4) and (13), we can derive the following equation:

[0152]

[0153] like Figure 2.6 As shown, combining equations (7) and (14), the current flowing into the booster station at this time is calculated as follows:

[0154]

[0155] The effective values ​​of the current in each phase are calculated as follows:

[0156]

[0157] From equation (16), it can be seen that when phases b1 and c1 on the low-voltage side are short-circuited, the effective values ​​of the currents in phases A and C are equal and greater than those in phase B: At the same time, the current of phase A leads phase B by less than 120 degrees, the current of phase C leads phase A by more than 120 degrees, and the current of phase B leads phase C by less than 120 degrees.

[0158] Similarly, for a short circuit between the other two phases on the low-voltage side of the wind turbine-side transformer, the relationship between the phase currents on the primary side of the substation transformer is shown in the table below:

[0159] Low-voltage side phase-to-phase short circuit phase of transformer Current relationship of each phase on the primary side of the booster station <![CDATA[a1、b1]]> <![CDATA[b1、c1]]> <![CDATA[c1、a1]]>

[0160] Analysis of inter-turn short circuit on the low-voltage side of the box-type transformer: If an inter-turn short circuit occurs on phase a1 of the low-voltage side of the box-type transformer:

[0161]

[0162] Due to the transformer turns ratio Therefore: ,and , , respectively with , , Same direction;

[0163] like Figure 2.7 As shown, combining equations (7) and (17), the current flowing into the booster station at this time is calculated as follows:

[0164]

[0165] It can be seen that when an inter-turn short circuit occurs on phase a1 of the low-voltage side of the box-type transformer, the effective values ​​of the currents in phases A and C are equal and greater than those in phase B: Similarly, for a short circuit between the turns of phases b1 and c1 on the low-voltage side of a box-type transformer, the relationship between the currents of each phase on the primary side of the substation is shown in the table below:

[0166] Inter-turn short circuit phase on the low-voltage side of the transformer Current relationship of each phase on the primary side of the booster station <![CDATA[a1]]> <![CDATA[b1]]> <![CDATA[c1]]>

[0167] Example 1: Based on Matlab / Simulink, a system is built as follows Figure 1.1 The diagram shows the schematic of a wind turbine system on a line (referred to as line A) in a wind farm. The wind turbines are connected to a 35kV collector line, where S1-S8 represent the eight wind turbines on this line, T1-T8 are their corresponding box-type transformers, and Z represents the equivalent load. In the wind farm, each wind turbine is equipped with its own box-type transformer. The electricity generated by the turbines is fed into the main transformer of the substation via multiple lines. Each line consists of multiple wind turbines connected in parallel. To study the system state when a box-type transformer fails, we will focus on T1. In this case, the wind turbines on line A can be considered equivalent to... Figure 1.2Where S0 and T0 are the equivalent models of wind turbines S2-S8 and their corresponding transformers, respectively; therefore, when studying the fault characteristics of wind turbine transformers, only one line needs to be analyzed. The specific simulation parameters are shown in the table below:

[0168] Components parameter Fan rated capacity 2MW Low-voltage test of rated voltage for box-type transformers 690V High voltage measurement of box-type transformer rated voltage 35KV box-type transformer turns ratio 1：50 Box-type transformer capacity 1550KVA

[0169] The current waveform diagram of the collector line flowing into the main transformer of the step-up substation when the line is running stably is as follows: Figure 3.1 As shown in Figure 3.2(e), it can be seen from the figure that...

[0170] When multiple box-type transformers are operating normally, the three-phase current flowing into the main transformer of the step-up substation from the collector line is 120 degrees out of phase and has an amplitude of 373A.

[0171] Set the fault to occur at t=40ms, such as Figure 1.4 The figure shows the simulation results of the current waveform flowing into the main transformer of the step-up substation from the collector line when a fault occurs.

[0172] When a short circuit occurs between turns of phase A on the high-voltage side, the current amplitudes of phases A and C in the collector wire will increase, while the current amplitude of phase B will remain unchanged, and the phases of the three-phase currents A, B, and C will remain unchanged.

[0173] When a single-phase ground fault occurs on the low-voltage side, the current amplitudes of phases A and C in the collector wire will decrease, while the current amplitude of phase B will remain unchanged. Furthermore, the current of phase A will lead phase B by more than 120 degrees, the current of phase C will lead phase A by less than 120 degrees, and the current of phase B will lead phase C by more than 120 degrees.

[0174] When a two-phase ground fault occurs on the low-voltage side (phases b and c), the current amplitudes of all three phases (A, B, and C) in the collector wire decrease, with phase B experiencing the largest decrease, while phases A and C experience equal decreases.

[0175] The current in phase A leads phase B by less than 120 degrees, the current in phase C leads phase A by more than 120 degrees, and the current in phase B leads phase C by less than 120 degrees.

[0176] When a short circuit occurs between phases b and c on the low-voltage side, the trend of the changes in the three-phase currents A, B, and C of the collector wires is similar to that when a short circuit occurs between phases b and c to ground.

[0177] When a short circuit occurs between turns of phase a on the low-voltage side, the current amplitudes of phases A and C in the collector wire will decrease, while the current amplitude of phase B will remain unchanged. At the same time, the phases of the three-phase currents A, B, and C will remain unchanged.

[0178] Therefore, the type of fault in the box-type transformer can be determined by the amplitude and phase relationship of the three-phase currents A, B, and C in the collector wire.

[0179] Example 2: In a wind farm, the negative sequence current of one collector line exceeds the upper limit, triggering fault recording. The recorded waveform is as follows: Figure 4.1 As shown, the waveform recording indicates that the voltage of the collector busbar was normal, but the current fluctuation lasted for 112ms, with negative sequence current and a small zero sequence current. 100ms before the fault waveform recording started, the line currents were 2.549A for phase A, 2.578A for phase B, and 2.526A for phase C. 100ms after the fault waveform recording started, the line currents were 2.593A for phase A, 1.606A for phase B, and 1.616A for phase C. When maintenance personnel went to the site for inspection, they found that the nacelle of a wind turbine on the collector line had been burned.

[0180] At the time of the accident, the 35kV voltage of the fault collector line remained in a balanced state, and the zero-sequence voltage was very small. Therefore, it can be determined that the 35kV line was fault-free, and the fault current met the requirements. Furthermore, the phases of the three-phase currents A, B, and C remain unchanged. Simultaneously, historical temperature data of each wind turbine transformer substation along this collector line were reviewed, revealing abnormal temperatures in the three-phase windings of one substation (hereinafter referred to as Z substation). The temperature of the c-phase winding frequently exceeded 100 degrees Celsius, while the temperatures of the other two phases were normal, consistent with the characteristics of an inter-turn short circuit in the c-phase. Based on simulation experiments, it can be preliminarily determined that an inter-turn short circuit occurred in the c-phase on the low-voltage side of Z substation. To ensure the accuracy of the analysis, more detailed waveform data is analyzed. Data extracted from the wind farm server is as follows: Figure 4.2 , Figure 4.3 As shown, where Figure 4.2 This represents the temperature changes of each winding of the Z-type transformer during the detection period. Figure 4.3 The sampling time interval is 10 minutes, and the effective value of the three-phase current transmitted to the main transformer of the substation is given by the collector line where the Z transformer is located within the same time period. Figure 4.4 , Figure 4.5 for Figure 4.2 and Figure 4.3 A magnified view of a portion of the image.

[0181] according to Figure 4.4 Analysis of the observation results shows that under low power output conditions, the three-phase current exhibits significant asymmetry. However, the temperature rise difference between the windings of each phase of the Z-type box transformer is not significant, according to Figure 4.5Waveform analysis shows that when the system is operating at high power, the amplitude of the three-phase current tends to be balanced. However, the temperature of the C-phase winding of the Z-type transformer exhibits an abnormal temperature rise. The formation mechanism of this phenomenon can be explained as follows: Under low power conditions, although the C-phase current is relatively the largest, its absolute value is small, resulting in the winding's heat generation rate being lower than its heat dissipation capacity. The thermal equilibrium state causes the temperature rise of each phase to be similar. Under high power conditions, the magnetic saturation effect of the iron core makes the three-phase current equalized. At this time, due to the large absolute value of the three-phase current, coupled with the inter-turn insulation defects in the C-phase winding leading to an increase in the conductor's equivalent resistance, the temperature rise is abnormal. This temperature distribution characteristic is highly consistent with the typical fault characteristics of the inter-turn short circuit in the C-phase winding of the low-voltage side of the Z-type transformer. Based on this, it can be determined that an inter-turn short circuit fault has occurred in the C-phase winding of the low-voltage side of the transformer.

[0182] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0183] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fault analysis of wind turbine transformer housings based on fault recording data, characterized in that, include: Harvesting wind energy and converting it into electrical energy, generating electricity through wind turbines; The electrical energy generated by the wind turbine is transmitted to the box-type transformer for voltage regulation; The electrical energy boosted by the box-type transformer is transmitted to the substation. The SCADA platform of the substation collects and analyzes the operating data of the box-type transformers in real time, and summarizes the power data of multiple box-type transformers. Real-time analysis of the operating data of each box-type transformer is performed, including but not limited to the following fault types: high-voltage side inter-turn short circuit, low-voltage side single-phase ground fault, low-voltage side two-phase ground fault, low-voltage side two-phase short circuit, and low-voltage side inter-turn short circuit. Based on the analysis results, current characteristics were extracted from the fault recording data.

2. The method for fault analysis of wind turbine transformer based on fault recording data according to claim 1, characterized in that, The low-voltage side of the box-type transformer uses a star connection, and the high-voltage side uses a delta connection; thus forming a YnD transformer. Assuming its turns ratio is n1 / n2, the voltage formula on the Yn side is: In the formula, , These represent the voltages of phases A, B, and C on the high-voltage side, respectively, and are the three-phase outputs of the transformer on the high-voltage side. The line voltage, representing the low-voltage side, is the voltage between the two lines on the low-voltage side of the transformer. Angular frequency represents the rate at which voltage changes with time and is directly proportional to the frequency of the power source. Time represents the change of voltage waveform over time; The n1 / n2 transformer turns ratio is the ratio of the number of turns on the high-voltage side to the number of turns on the low-voltage side. and These represent the phase differences between phase B and phase C voltages relative to phase A voltage, respectively; the current formula on the Yn side is: In the formula, This represents the instantaneous value of phase A in the first group of three-phase currents; Indicates the magnitude of the current; This represents the instantaneous value of phase B in the first group of three-phase currents; This represents the instantaneous value of phase C in the first group of three-phase currents; The voltage formula on side D is: In the formula, , , These represent the original voltages of phases A, B, and C, respectively. Indicates the magnitude of the voltage; , , These represent the voltages of phases A, B, and C on the low-voltage side, respectively. The current formula on side D is: In the formula, This represents the instantaneous value of phase A in the first group of three-phase currents; This represents the instantaneous value of phase B in the first group of three-phase currents; This represents the instantaneous value of phase C in the first group of three-phase currents.

3. The method for wind turbine transformer box-type fault analysis based on fault recording data according to claim 1, characterized in that, Inter-turn short-circuit analysis of the high-voltage side of the box-type transformer: The high-voltage side of a box-type transformer is divided into A1, B1, and C1. If an inter-turn short circuit occurs in phase A1, the current expression on the high-voltage side is as follows: Due to the transformer turns ratio Therefore, the effective values ​​of the currents in phases A1 and C1 are equal and greater than those in phase B1. Therefore, the effective values ​​of the currents in phases A, B, and C output from line III to the booster station are obtained: .

4. The method for wind turbine transformer box-type fault analysis based on fault recording data according to claim 1, characterized in that, Analysis of single-phase ground fault on the low-voltage side of the box-type transformer: The low-voltage side of the box-type transformer is divided into a1, b1, and c1. If a ground fault occurs on phase a1, then: Combining equation (4), we can deduce the following equation: In the formula, This represents the current amplitude on the high-voltage side. Since the equivalent wind turbine S0 is not faulty, where S0 and T0 are equivalent models of multiple wind turbines and their corresponding box-type transformers, respectively, the current of the equivalent box-type transformer T0 is given by the following formula: In the formula, This indicates the magnitude of the current in phase A of the equivalent box-type transformer T0; This indicates the magnitude of the current in phase B of the equivalent box-type transformer T0; This indicates the magnitude of the current in phase C of the equivalent box-type transformer T0; Reference current; The current flowing into the booster station at this time is given by the following formula: The effective values ​​of the current in each phase are obtained by equation (8): As shown in equation (9), when a phase a1 of the low-voltage side of the box-type transformer is short-circuited to ground, the effective values ​​of the currents in phases A and C are equal and greater than those in phase B. At the same time, the current of phase A leads phase B by more than 120 degrees, the current of phase C leads phase A by less than 120 degrees, and the current of phase B leads phase C by more than 120 degrees.

5. The method for wind turbine transformer box-type fault analysis based on fault recording data according to claim 1, characterized in that, Analysis of the two-phase-to-ground short circuit on the low-voltage side of the box-type transformer: When a phase-to-phase short circuit occurs between phases b1 and c1: , Combining equation (4), we can derive the following equation: Combining equations (7) and (10), the current flowing into the booster station at this time can be calculated as follows: The effective values ​​of the current in each phase are calculated as follows: From equation (12), it can be seen that when phases b1 and c1 on the low-voltage side are short-circuited to ground, the effective values ​​of the currents in phases A and C are equal and greater than those in phase B: At the same time, the current of phase A leads phase B by less than 120 degrees, the current of phase C leads phase A by more than 120 degrees, and the current of phase B leads phase C by less than 120 degrees.

6. The method for fault analysis of wind turbine transformer based on fault recording data according to claim 1, characterized in that, Analysis of two-phase short circuit on the low-voltage side of the box-type transformer: When a phase-to-phase short circuit occurs between phases b1 and c1: Combining equations (4) and (13), we can derive the following equation: Combining equations (7) and (14), the current flowing into the booster station at this time is calculated as follows: The effective values ​​of the current in each phase are calculated as follows: From equation (16), it can be seen that when phases b1 and c1 on the low-voltage side are short-circuited, the effective values ​​of the currents in phases A and C are equal and greater than those in phase B. At the same time, the current of phase A leads phase B by less than 120 degrees, the current of phase C leads phase A by more than 120 degrees, and the current of phase B leads phase C by less than 120 degrees.

7. The method for fault analysis of wind turbine transformer based on fault recording data according to claim 1, characterized in that, Analysis of inter-turn short circuit on the low-voltage side of the box-type transformer: If an inter-turn short circuit occurs on phase a1 of the low-voltage side of the box-type transformer: Due to the transformer turns ratio Therefore: ,and , , respectively with , , Same direction; Combining equations (7) and (17), the current flowing into the booster station at this time is calculated as follows: It can be seen that when an inter-turn short circuit occurs on phase a1 of the low-voltage side of the box-type transformer, the effective values ​​of the currents in phases A and C are equal and greater than those in phase B: .

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