Transformer fault detection method and device and computer equipment

Abstract

The invention relates to a transformer fault detection method and device and computer equipment. The method comprises the steps of obtaining fault phases of the transformer according to fault recording data of the transformer, obtaining a first fault type of the transformer according to a phase difference under the condition that the number of the fault phases meets a number requirement condition, obtaining zero-sequence current of a current sampling point in the process of sampling the fault recording data according to a preset period, and obtaining a second fault type of the transformer according to the zero-sequence current. Obtaining a second fault type of the transformer according to the zero-sequence current and the current break variable between the current sampling point and the sampling point of the previous period, obtaining a target fault type of the transformer according to the first fault type and the second fault type, and obtaining the target fault type of the transformer according to the rated voltage, the actual voltage and the fault type of the transformer. And obtaining fault location of the transformer. By adopting the method, the transformer fault can be accurately identified.

Description

Technical Field

[0001] The present application relates to the technical field of power systems, and particularly to a transformer fault detection method, device, and computer equipment. Background Art

[0002] As the core hub equipment for power transmission and distribution in a power system, the operating stability of a power transformer directly determines the power supply quality and continuity of the power grid. With the superimposition of the growth of the power system load and complex operating conditions, transformer faults occur frequently, and the fault types tend to be diversified.

[0003] Currently, the short-circuit fault identification technology based on oscillogram data mainly relies on two types of methods: one is the transient feature analysis method, which detects faults by extracting the mutation characteristics or harmonic components of current and voltage signals; the other is the steady-state feature analysis method, which calculates the zero-sequence and negative-sequence current amplitudes using the symmetrical component method, or determines the fault type by the steady-state phase angle shift. However, when the transient or steady-state features of the oscillogram data are not significant due to noise interference or minor faults, the misjudgment rate of a single data source or single algorithm model increases significantly. Summary of the Invention

[0004] Based on this, it is necessary to provide a transformer fault detection method, device, and computer equipment that can accurately identify transformer faults for the above technical problems.

[0005] In a first aspect, the present application provides a transformer fault detection method, including:

[0006] Obtaining the fault phase of the transformer according to the fault oscillogram data of the transformer;

[0007] When the number of fault phases meets the quantity requirement condition, obtaining the first fault type of the transformer according to the phase difference;

[0008] During the process of sampling the fault oscillogram data at a preset period, obtaining the zero-sequence current of the current sampling point and the current mutation of the current between the current sampling point and the previous cycle sampling point, and obtaining the second fault type of the transformer according to the zero-sequence current and the current mutation; each sampling point corresponds to a data point in the fault oscillogram data;

[0009] Obtaining the target fault type of the transformer according to the first fault type and the second fault type;

[0010] Obtaining the fault location of the transformer according to the rated voltage, actual voltage, and fault type of the transformer.

[0011] In one of the embodiments, the step of obtaining the fault phase of the transformer according to the fault oscillogram data of the transformer includes:

[0012] Obtain the fault point in the fault recording data of the transformer, and obtain the fault data of the fault point; the fault data includes the pre-fault data of the week before the fault point and the post-fault data of two weeks after the fault point.

[0013] For each phase of the transformer, obtain the voltage amplitude ratio and the current amplitude ratio according to the fault data.

[0014] When the voltage amplitude ratio does not exceed the first threshold and the current amplitude ratio is not less than the second threshold, determine that the current phase is the fault phase.

[0015] In one embodiment, the step of obtaining the first fault type of the transformer according to the phase difference includes:

[0016] Obtain the zero-sequence voltage and zero-sequence current according to the phase current and phase voltage of each phase.

[0017] When the zero-sequence voltage and zero-sequence current meet the parameter requirements and the number of fault phases is 2, obtain the first phase difference between the inter-phase voltage and inter-phase current between the fault phases; the zero-sequence voltage and zero-sequence current meeting the parameter requirements include that the zero-sequence voltage is not less than the third threshold or the zero-sequence current is not less than the fourth threshold.

[0018] When the first phase difference is within the first range, determine that the first fault type of the transformer is a two-phase short-circuit grounding fault.

[0019] When the zero-sequence voltage and zero-sequence current meet the parameter requirements and the number of fault phases is not 2, or the first phase difference is not within the first range, obtain the first fault type of the transformer according to the second phase difference between the phase voltage and phase current of the fault phase.

[0020] When the zero-sequence voltage and zero-sequence current do not meet the parameter requirements and the number of fault phases is 3, determine that the first fault type of the transformer is a three-phase short-circuit fault; the zero-sequence voltage and zero-sequence current not meeting the parameter requirements include that the zero-sequence voltage is less than the third threshold and the zero-sequence current is less than the fourth threshold.

[0021] When the zero-sequence voltage and zero-sequence current do not meet the parameter requirements and the number of fault phases is not 3, obtain the third phase difference between the phase currents of the fault phases.

[0022] When the third phase difference is within the second range, determine that the first fault type of the transformer is a three-phase short-circuit fault.

[0023] When the third phase difference is not within the second range, determine that the first fault type of the transformer is a two-phase inter-phase short-circuit fault.

[0024] In one embodiment, the step of obtaining the first fault type of the transformer according to the second phase difference between the phase voltage and the phase current of the faulty phase includes:

[0025] When there is only one faulty phase and the second phase difference is within the first range, it is determined that the first fault type of the transformer is a single-phase short-circuit to ground fault;

[0026] When there are at least two faulty phases and the second phase difference is within the first range, or when there is only one faulty phase and the second phase difference is not within the first range, the fourth phase difference between the zero-sequence current and the phase current of the faulty phase and the fifth phase difference between the zero-sequence voltage and the phase voltage of the faulty phase are obtained;

[0027] When there is only one faulty phase and the fourth phase difference does not exceed the phase threshold, or when there is only one faulty phase and the fifth phase difference is within the third range, it is determined that the first fault type of the transformer is a single-phase short-circuit to ground fault;

[0028] When the phase difference condition is satisfied, that is, there are at least two faulty phases and the fifth phase difference is within the third range, it is determined that the first fault type of the transformer is a two-phase short-circuit to ground fault; the phase difference condition is that when there is only one faulty phase, the fourth phase difference exceeds the phase threshold and the fifth phase difference of the faulty phase is not within the third range.

[0029] In one embodiment, the step of obtaining the second fault type of the transformer according to the zero-sequence current and the current mutation includes:

[0030] The minimum value among the current mutations of all phases is used as the target mutation;

[0031] When the sampling cumulative quantity is less than the target quantity, the corresponding phase cumulative quantity is obtained according to the target mutation and the zero-sequence current; the phase cumulative quantity includes single-phase cumulative quantity, two-phase cumulative quantity and three-phase cumulative quantity;

[0032] When the ratio between the phase cumulative quantity and the target quantity is not less than the fault threshold, the fault state corresponding to the phase cumulative quantity is used as the second fault type of the transformer; the second fault type includes single-phase short-circuit to ground fault, two-phase short-circuit to ground fault, two-phase inter-phase short-circuit fault and three-phase short-circuit fault.

[0033] In one embodiment, the absolute value of the zero-sequence current is greater than the current threshold; the step of obtaining the corresponding phase cumulative quantity according to the target mutation and the zero-sequence current includes:

[0034] When the target mutation and the zero-sequence current satisfy the first relationship, and the other mutations of the other phases except the target phase corresponding to the target mutation satisfy the second relationship, the phase cumulative quantity corresponding to the target phase is incremented by 1;

[0035] When the target mutation amount and the zero-sequence current do not satisfy the first relationship and other mutation amounts satisfy the third relationship, increase the corresponding phase cumulative quantity of the other phases by 1.

[0036] In one embodiment, the absolute value of the zero-sequence current does not exceed the current threshold; the step of obtaining the corresponding phase cumulative quantity according to the target mutation amount and the zero-sequence current includes:

[0037] When the current mutation amount of each phase satisfies the fourth relationship with the currents of each phase at the previous cycle sampling point, increase the three-phase cumulative quantity by 1;

[0038] When the target mutation amount, other mutation amounts and the currents of each phase at the previous cycle sampling point satisfy the fifth relationship, increase the corresponding cumulative quantities of the other two phases by 1.

[0039] In one embodiment, the rated voltage includes the high-voltage side rated voltage, the medium-voltage side rated voltage and the low-voltage side rated voltage before the transformer fault; the actual voltage includes the high-voltage side actual voltage, the medium-voltage side actual voltage and the low-voltage side actual voltage of each phase of the transformer before the fault; the step of obtaining the fault location of the transformer according to the rated voltage, the actual voltage and the fault type of the transformer includes:

[0040] Obtain the target mean voltage corresponding to the actual voltages of all phases; the target mean voltage includes the high-voltage side voltage mean, the medium-voltage side voltage mean and the low-voltage side voltage mean;

[0041] Obtain the maximum mean voltage and the minimum mean voltage among the high-voltage side voltage mean, the medium-voltage side voltage mean and the low-voltage side voltage mean;

[0042] When the fault type is a single-phase ground short-circuit fault, or a two-phase ground short-circuit fault, or a two-phase interphase short-circuit fault, obtain the first fault location of the transformer according to the target voltage mean, the maximum mean voltage and the minimum mean voltage; the first fault location includes a high-voltage side fault, a medium-voltage side fault and a low-voltage side fault;

[0043] When the fault type is a three-phase short-circuit fault, obtain the second fault location of the transformer according to the rated voltage, the maximum mean voltage and the minimum mean voltage; the second fault location includes the access states of each winding of the transformer and the faulty winding.

[0044] In a second aspect, the present application also provides a transformer fault detection device, including:

[0045] A phase acquisition module, configured to obtain the fault phase of the transformer according to the fault recording data of the transformer;

[0046] The first detection module is used to obtain the first fault type of the transformer according to the phase difference when the number of fault phases meets the quantity requirement condition;

[0047] The second detection module is used to obtain the zero-sequence current of the current sampling point and the current mutation of the current sampling point and the sampling point of the previous cycle during the process of sampling the fault recording data according to a preset period, and obtain the second fault type of the transformer according to the zero-sequence current and the current mutation; each sampling point corresponds to a data point in the fault recording data;

[0048] The target detection module is used to obtain the target fault type of the transformer according to the first fault type and the second fault type;

[0049] The fault location module obtains the fault location of the transformer according to the rated voltage, actual voltage and fault type of the transformer.

[0050] In a third aspect, the present application further provides a computer device, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the method steps of any item in the first aspect are implemented.

[0051] In a fourth aspect, the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the method steps of any item in the first aspect are implemented.

[0052] In a fifth aspect, the present application further provides a computer program product, including a computer program. When the computer program is executed by a processor, the method steps of any item in the first aspect are implemented.

[0053] For the above transformer fault detection method, device and computer device, by obtaining the fault phases of the transformer according to the fault recording data of the transformer, when the number of fault phases meets the quantity requirement condition, obtaining the first fault type of the transformer according to the phase difference, during the process of sampling the fault recording data according to a preset period, obtaining the zero-sequence current of the current sampling point and the current mutation of the current sampling point and the sampling point of the previous cycle, obtaining the second fault type of the transformer according to the zero-sequence current and the current mutation, obtaining the target fault type of the transformer according to the first fault type and the second fault type, and obtaining the fault location of the transformer according to the rated voltage, actual voltage and fault type of the transformer, it is possible to comprehensively diagnose the faults of the transformer from two dimensions of steady state and transient state, and improve the accuracy and reliability of fault detection. Description of the Drawings

[0054] To more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following will briefly introduce the drawings required for the description of the embodiments of the present application or related technologies. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0055] Figure 1 It is an application environment diagram of the transformer fault detection method in an embodiment;

[0056] Figure 2 It is a schematic flowchart of the transformer fault detection method in an embodiment;

[0057] Figure 3 It is a schematic flowchart of the fault location step in an embodiment;

[0058] Figure 4 It is a schematic flowchart of the transformer fault detection method in another embodiment;

[0059] Figure 5 It is a structural block diagram of the transformer fault detection device in an embodiment;

[0060] Figure 6 It is an internal structure diagram of a computer device in an embodiment. Detailed implementation manners

[0061] In order to make the objectives, technical solutions and advantages of the present application clearer, the following further details the present application in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0062] The transformer fault detection method provided by the embodiments of the present application can be applied to, for example Figure 1In the application environment shown. Among them, the terminal 102 communicates with the server 104 through the network. The data storage system can store the data that the server 104 needs to process. The data storage system can be integrated on the server 104, or can be placed on the cloud or other network servers. Among them, the terminal 102 is used to obtain the fault phase of the transformer according to the fault recording data of the transformer. When the number of fault phases meets the quantity requirement condition, according to the phase difference, obtain the first fault type of the transformer. During the process of sampling the fault recording data according to a preset period, obtain the zero-sequence current of the current sampling point, and the current mutation of the current sampling point and the sampling point of the previous period. According to the zero-sequence current and the current mutation, obtain the second fault type of the transformer. According to the first fault type and the second fault type, obtain the target fault type of the transformer. According to the rated voltage, actual voltage and fault type of the transformer, obtain the fault location of the transformer. Among them, the terminal 102 can be but is not limited to various personal computers, laptop computers, smart phones, tablet computers, Internet of Things devices and portable wearable devices. The Internet of Things devices can be smart speakers, smart TVs, smart air conditioners, smart in-vehicle devices, projection devices, etc. The portable wearable devices can be smart watches, smart bracelets, head-mounted devices, etc. The head-mounted devices can be virtual reality (VR) devices, augmented reality (AR) devices, smart glasses, etc. The server 104 can be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server providing cloud computing services.

[0063] In an exemplary embodiment, as Figure 2 shown, a transformer fault detection method is provided. Taking the application of this method to the Figure 1 terminal 102 in it as an example for illustration, it includes the following steps S202 to step S210. Among them:

[0064] S202: Obtain the fault phase of the transformer according to the fault recording data of the transformer.

[0065] Optionally, the fault recording data refers to the electrical quantity waveforms and related status information that are collected and recorded in real time by a fault recorder when a transformer in a power system fails (such as short circuit, grounding, winding overheating, etc.) or operates abnormally. The fault phase refers to the electrical phase involved in the fault point and the fault types between each phase when the transformer fails, such as single-phase short circuit to ground, two-phase short circuit to ground, etc. Among them, the power system usually uses three-phase alternating current (phases A, B, and C), and the phase difference between each phase is 120°.

[0066] Exemplarily, by comparing the three-phase current / voltage waveforms, if the current of a certain phase suddenly increases and the waveform is distorted while the other phases have no obvious changes, it may be a single-phase fault.

[0067] S204: When the number of faulty phases meets the quantity requirement, obtain the first fault type of the transformer according to the phase difference.

[0068] Optionally, in the analysis of transformer faults, after determining the number of phases involved in the fault (such as single-phase, two-phase or three-phase), further judge the specific first fault type (such as single-phase grounding, two-phase short circuit, etc.) through the phase difference (that is, the phase relationship between the faulty phase current / voltage). For example, obtain the first fault type of the transformer through the steady-state short-circuit fault identification algorithm. Among them, the phase difference refers to the phase angle difference between the currents of each faulty phase or between the current and voltage during the fault. Under different fault types, the phase relationship of the electrical quantities of the faulty phases has unique laws. After the fault continuously enters the stable state, the amplitude and phase of the current and voltage tend to be stable, and the electrical quantity characteristics at this time can be used to reliably identify the fault type. Among them, the steady-state short-circuit fault identification algorithm mainly matches different fault types through the electrical quantity characteristic of the phase difference.

[0069] S206: During the process of sampling the fault recording data according to a preset period, obtain the zero-sequence current of the current sampling point and the current mutation between the current sampling point and the sampling point of the previous period, and obtain the second fault type of the transformer according to the zero-sequence current and the current mutation; each sampling point corresponds to a data point in the fault recording data.

[0070] Optionally, the zero-sequence current reflects the component with equal magnitude and the same phase in the three-phase current during asymmetrical faults (such as single-phase grounding, two-phase grounding) in a three-phase power system. During normal operation, the three-phase current is symmetrical and the zero-sequence current is 0 (or close to 0). When an asymmetrical fault occurs, the zero-sequence current will increase significantly. Generally, if there is a zero-sequence current, it indicates that a grounding fault (single-phase or two-phase grounding) has occurred, and the current flows through the grounding circuit; if the zero-sequence current is 0, it indicates that the fault is an interphase short circuit (such as two-phase short circuit, three-phase short circuit), and the three-phase current is still symmetrical (no grounding path). The current mutation refers to the absolute value of the difference between the currents of two adjacent sampling points, which reflects the change rate of the current in a very short time. When a sudden fault occurs, the current will change rapidly, so as to judge whether it is a sudden transient fault (such as a grounding short-circuit fault).

[0071] S208: Obtain the target fault type of the transformer according to the first fault type and the second fault type.

[0072] Optionally, the first fault type is identified by steady-state power characteristics and has high detection accuracy for continuous faults (such as stable grounding and long-term phase-to-phase short circuits). The second fault type is identified by transient power characteristics and responds quickly to instantaneous and highly sudden faults (such as instantaneous grounding and transient phase-to-phase short circuits). When the first fault type and the second fault type are the same, it indicates that both dimensions support this conclusion and the reliability is high. Then, directly use this fault type as the target fault type of the transformer. When the first fault type and the second fault type are inconsistent, in the power system, sudden short-circuit faults (such as internal winding short circuits in transformers) are extremely harmful and need to be quickly cleared. The identification based on transient characteristics can trigger protection in time at the initial stage of the fault (even before entering the steady state) due to its fast response speed, avoiding the expansion of the fault. Therefore, the second fault type can be preferentially selected as the target fault type of the transformer.

[0073] Optionally, due to the magnetizing inrush current (the transient current is very large but not a fault), system oscillations, load mutations, etc. when the transformer is switched on, it may also cause transient current fluctuations. The steady-state algorithm can filter out transient interference and avoid misjudgment by analyzing the long-term trend of electrical quantities. Therefore, the first fault type can also be selected as the target fault type of the transformer. In practical applications, the target fault type of the transformer can be determined from the first fault type and the second fault type according to the actual requirements of fault detection.

[0074] S210: Obtain the fault location of the transformer according to the rated voltage, actual voltage and fault type of the transformer.

[0075] Optionally, the rated voltage includes the rated voltages of the high, medium and low sides of the transformer. Among them, the rated voltages of the high, medium and low sides refer to the designed nominal voltages of the three windings in a three-winding transformer, which are used to characterize the voltage levels and power transmission capabilities of each winding. A three-winding transformer has three independent windings, which are respectively connected to the power grids of the high, medium and low voltage levels to achieve the conversion of electrical energy between the three voltages. According to the rated voltage, actual voltage and fault type of the transformer, the location where the fault occurs can be determined. For example, if the fault type is single-phase grounding, if the fault location is grounding on the high-voltage side, the neutral point needs to be grounded, and there may be a large zero-sequence current and an increase in the open-delta voltage of the voltage transformer during the fault; if it is grounding on the low-voltage side, it may be due to line grounding or winding insulation damage, and the fault current is relatively small. By comparing the magnitudes of the rated voltages of the three sides, the voltage side with a higher insulation risk can be preferentially checked.

[0076] In the above transformer fault detection method, by obtaining the fault phase of the transformer according to the fault recording data of the transformer, when the number of fault phases meets the quantity requirement condition, obtaining the first fault type of the transformer according to the phase difference. During the process of sampling the fault recording data at a preset period, obtaining the zero-sequence current of the current sampling point and the current mutation of the current sampling point and the sampling point of the previous period. According to the zero-sequence current and the current mutation, obtaining the second fault type of the transformer, obtaining the target fault type of the transformer according to the first fault type and the second fault type, and obtaining the fault location of the transformer according to the rated voltage, actual voltage and fault type of the transformer, it is possible to comprehensively diagnose the faults of the transformer from two dimensions of steady state and transient state, improving the accuracy and reliability of fault detection.

[0077] In an exemplary embodiment, the step of obtaining the fault phase of the transformer according to the fault recording data of the transformer includes: obtaining the fault point in the fault recording data of the transformer, and obtaining the fault data of the fault point; the fault data includes the pre-fault data of the previous cycle of the fault point and the post-fault data of the two cycles after the fault point; for each phase of the transformer, obtaining the voltage amplitude ratio and the current amplitude ratio according to the fault data; when the voltage amplitude ratio does not exceed the first threshold and the current amplitude ratio is not less than the second threshold, determining the current phase as the fault phase.

[0078] Optionally, the fault recording data is the voltage and current waveform data of each side of the transformer recorded by the fault recorder, including the complete electrical quantity changes before, during and after the fault. The fault point is the specific moment (i.e., the sampling point) when the fault occurs determined by waveform analysis. For the current fault point, obtaining the steady-state data of the previous cycle before the current fault point and the fault data of the two cycles after the current fault point. The comparison of the front and back fault data reflects the change characteristics of the electrical quantity after the fault.

[0079] Further, according to the fault data, obtaining the voltage amplitude ratio and the current amplitude ratio, where the voltage amplitude ratio is the voltage amplitude of a certain phase after the fault / the voltage amplitude of the same phase before the fault, and the current amplitude ratio is the current amplitude of a certain phase after the fault / the current amplitude of the same phase before the fault. Usually, when the power system is operating normally, the voltage / current amplitude ratio is close to 1; when a short-circuit fault occurs in a certain phase, the voltage of that phase drops significantly due to the sudden drop of the short-circuit impedance (amplitude ratio << 1), and the current increases significantly due to the conduction of the short-circuit loop (amplitude ratio >> 1). Therefore, by setting the first threshold and the second threshold, it is possible to detect whether a fault occurs in each phase. Among them, the first threshold can be set to 0.8 - 0.9 (adjusted according to transformer parameters and protection settings) to judge whether the voltage drops significantly, and the second threshold can be set to 1.2 - 2.0 (determined according to the short-circuit current multiple) to judge whether the current increases significantly.

[0080] Exemplarily, take the previous cycle before the fault point (i.e., the reciprocal of the frequency of the current sine wave) and the two cycles after the fault point as the pre-fault data and post-fault data respectively, denoted as U ibef 、U iaft 、I ibef and I iaft (where i represents the three phases A, B, and C respectively), calculate the amplitude ratios ratu i 、ratioi i of the three-phase voltage and current before and after the fault. The mathematical expressions are as follows:

[0081]

[0082]

[0083] If ratu i <ratu TH and rati i >rati TH , then determine that this phase is the fault phase, and record the number M of fault phases (where 0 ≤ M ≤ 3). If M ≥ 1, further perform fault detection. If M < 1, end the fault judgment (indicating that the signal change is small or there is no fault).

[0084] In this embodiment, by obtaining the pre-fault and post-fault data at the fault point, obtaining the voltage amplitude and current amplitude before and after the fault, and comparing the amplitude changes before and after the fault, the interference of normal operation fluctuations can be excluded, and the accuracy of fault detection can be improved.

[0085] In an exemplary embodiment, the steps of obtaining the first fault type of a transformer according to the phase difference include: obtaining the zero-sequence voltage and zero-sequence current according to the phase current and phase voltage of each phase; when the zero-sequence voltage and zero-sequence current meet the parameter requirements and the number of fault phases is 2, obtaining the first phase difference between the phase voltage and phase current between the fault phases; the zero-sequence voltage and zero-sequence current meeting the parameter requirements includes that the zero-sequence voltage is not less than the third threshold or the zero-sequence current is not less than the fourth threshold; when the first phase difference is within the first range, determining that the first fault type of the transformer is a two-phase short-circuit grounding fault; when the zero-sequence voltage and zero-sequence current meet the parameter requirements and the number of fault phases is not 2, or the first phase difference is not within the first range, obtaining the first fault type of the transformer according to the second phase difference between the phase voltage and phase current of the fault phase; when the zero-sequence voltage and zero-sequence current do not meet the parameter requirements and the number of fault phases is 3, determining that the first fault type of the transformer is a three-phase short-circuit fault; the zero-sequence voltage and zero-sequence current not meeting the parameter requirements includes that the zero-sequence voltage is less than the third threshold and the zero-sequence current is less than the fourth threshold; when the zero-sequence voltage and zero-sequence current do not meet the parameter requirements and the number of fault phases is not 3, obtaining the third phase difference between the phase currents of the fault phases; when the third phase difference is within the second range, determining that the first fault type of the transformer is a three-phase short-circuit fault; when the third phase difference is not within the second range, determining that the first fault type of the transformer is a two-phase interphase short-circuit fault.

[0086] Optionally, the zero-sequence voltage refers to the effective value of the zero-sequence component of the three-phase voltage, which reflects the degree of asymmetry of the three-phase voltage, and the zero-sequence current refers to the effective value of the zero-sequence component of the three-phase current, which reflects the degree of asymmetry of the three-phase current. The first fault type of the transformer is judged according to the phase voltage, phase current, zero-sequence voltage and zero-sequence current of each phase.

[0087] Specifically, if the zero-sequence voltage and zero-sequence current meet (zero-sequence voltage ≥ third threshold or zero-sequence current ≥ fourth threshold), and the number of fault phases is 2, then calculate the first phase difference between the phase voltage and phase current between the fault phases. Since the zero-sequence component in the grounding fault will change the phase relationship of the interphase electrical quantities, if the first phase difference is within the first range, it is determined as a two-phase short-circuit grounding fault. If the zero-sequence voltage and zero-sequence current meet the above conditions, but the number of fault phases is not 2, or the first phase difference is not within the first range, then calculate the second phase difference between the phase voltage and phase current of the fault phase, and determine the fault type accordingly.

[0088] Another branch of judgment: If the zero-sequence voltage and zero-sequence current do not satisfy (zero-sequence voltage < the third threshold and zero-sequence current < the fourth threshold), and the number of fault phases is 3, it indicates that there is no zero-sequence component and three-phase faults occur simultaneously, then it is determined as a three-phase short-circuit fault. If the zero-sequence voltage and zero-sequence current do not satisfy the above conditions, and the number of fault phases is not 3, at this time, the three-phase currents are asymmetric but there is no zero-sequence component, then calculate the third phase difference between the phase currents of the fault phases. If the third phase difference is within the second range, it is determined as a three-phase short-circuit fault; if the third phase difference is not within the second range, it is determined as a two-phase interphase short-circuit fault.

[0089] In other embodiments, the step of obtaining the first fault type of the transformer according to the second phase difference between the phase voltage and phase current of the fault phase includes: when the second phase difference of only one fault phase is within the first range, determining that the first fault type of the transformer is a single-phase short-circuit grounding fault; when the second phase differences of at least two fault phases are within the first range, or the second phase difference of only one fault phase is not within the first range, obtaining the fourth phase difference between the zero-sequence current and phase current of the fault phase, and the fifth phase difference between the zero-sequence voltage and phase voltage of the fault phase; when the fourth phase difference of only one fault phase does not exceed the phase threshold, or the fifth phase difference of only one fault phase is within the third range, determining that the first fault type of the transformer is a single-phase short-circuit grounding fault; when the fifth phase differences of at least two fault phases satisfy the phase difference condition and are within the third range, determining that the first fault type of the transformer is a two-phase short-circuit grounding fault; the phase difference condition is that the fourth phase difference of only one fault phase exceeds the phase threshold and the fifth phase difference of the fault phase is not within the third range.

[0090] Optionally, if the second phase difference of only one fault phase is within the first range, it indicates that only one phase satisfies the grounding fault characteristics, then it is determined as a single-phase short-circuit grounding fault; if the second phase differences of at least two fault phases are within the first range, it indicates that at least two phases satisfy the grounding fault characteristics, then further calculate the fourth phase difference between the zero-sequence current and phase current of the fault phase, and the fifth phase difference between the zero-sequence voltage and phase voltage of the fault phase.

[0091] Further, if the fourth phase difference of only one faulty phase does not exceed the phase threshold, since the phase difference between the zero-sequence current and the current of this phase is small, it conforms to the characteristics of single-phase grounding; or if the fifth phase difference of only one faulty phase is within the third range, since the zero-sequence voltage is close to the voltage of this phase, it conforms to the characteristics of single-phase grounding, and it is also determined as a single-phase short-circuit grounding fault. If there are two phases that satisfy the phase difference range, it means that there is a direct short-circuit path between these two phases and a grounding fault is formed to the ground, then the first fault is determined as a two-phase short-circuit grounding fault; if only one phase has a fourth phase difference that does not exceed the phase threshold and the fifth phase difference of this phase does not satisfy the phase difference range, it means that although there is a zero-sequence component in this phase, the phase relationship between its zero-sequence voltage and phase voltage does not conform to the characteristics of single-phase grounding, then it is also determined as a two-phase short-circuit grounding fault.

[0092] Exemplarily, calculate the zero-sequence voltage U0, current I0 and their effective values U 0rms and U 0TH according to the three-phase voltage and current, and their mathematical expressions are:

[0093] U0 = (U A + U B + U C ) / 3

[0094] I0 = (I A + I B + I C ) / 3

[0095] U 0rms = rms(U0)

[0096] I 0rms = rms(I0)

[0097] If U 0rms > U 0TH or I 0rms > I 0TH , judge whether the number M of faulty phases is equal to 2. If it is 2, calculate the inter-phase voltage and inter-phase current of the corresponding two phases, and calculate the phase difference Δφu2i between the inter-phase voltage and the inter-phase current; if 70° ≤ Δφu2i ≤ 90°, then judge that the fault is a two-phase short-circuit grounding fault; if M is not equal to 2 or Δφu2i > 90° or Δφu2i < 70°, then calculate the phase difference Δφui between the corresponding phase voltage and phase current.

[0098] If only one phase satisfies 70° ≤ Δφui ≤ 90°, then judge that the fault is a single-phase short-circuit grounding fault; otherwise, calculate the phase difference Δφii0 between the zero-sequence current and the corresponding phase current and the phase difference Δφuu0 between the zero-sequence current and the corresponding phase voltage.

[0099] If only one phase satisfies Δφii0 ≤ 10° or 165° ≤ Δφuu0 ≤ 195°, it is determined as a single-phase short-circuit grounding fault; otherwise, it is determined as a two-phase short-circuit grounding fault.

[0100] If U 0rms <U 0TH and I 0rms <I 0TH , determine whether M is equal to 3. If it is 3, it is determined as a three-phase short-circuit grounding fault; if M is not equal to 3, calculate the phase difference Δφii between the phase currents corresponding to M. If the phase difference is close to 105° < Δφii < 135°, it is determined as a three-phase short-circuit fault; otherwise, it is determined as a two-phase short-circuit fault.

[0101] In the above embodiments, by determining whether it is a grounding fault and a non-grounding fault based on the zero-sequence voltage and zero-sequence current, and comprehensively identifying the fault type of the transformer through various phase differences, the accuracy of steady-state short-circuit fault identification can be improved.

[0102] In an exemplary embodiment, the steps of obtaining the second fault type of the transformer according to the zero-sequence current and the current mutation amount include: taking the minimum value among the current mutation amounts of all phases as the target mutation amount; in the case where the sampling cumulative quantity is less than the target quantity, obtaining the corresponding phase cumulative quantity according to the target mutation amount and the zero-sequence current; the phase cumulative quantity includes single-phase cumulative quantity, two-phase cumulative quantity, and three-phase cumulative quantity; in the case where the ratio between the phase cumulative quantity and the target quantity is not less than the fault threshold, taking the fault state corresponding to the phase cumulative quantity as the second fault type of the transformer; the second fault type includes single-phase short-circuit grounding fault, two-phase short-circuit grounding fault, two-phase interphase short-circuit fault, and three-phase short-circuit fault.

[0103] Optionally, at a certain sampling point, if only the current mutation amount and zero-sequence current of one phase satisfy the conditions, it indicates that there may be a single-phase fault trend, and the cumulative quantity of this phase is increased. If the current mutation amounts and zero-sequence currents of two phases satisfy the conditions, it indicates that there may be a two-phase fault, and the corresponding two-phase cumulative quantity is increased according to the specific fault situation. If the current mutation amounts and zero-sequence currents of three phases satisfy the conditions, it indicates that there may be a three-phase fault, and the three-phase cumulative quantity is increased.

[0104] Further, when the ratio between the cumulative quantity of a certain phase and the target quantity is not less than the fault threshold, it indicates that the occurrence of this fault type in the period is relatively frequent and reaches the level where the fault type can be determined. Therefore, the fault state corresponding to the cumulative quantity of this phase is taken as the second fault type of the transformer.

[0105] In other embodiments, the absolute value of the zero-sequence current is greater than the current threshold; the step of obtaining the corresponding phase cumulative quantity according to the target mutation quantity and the zero-sequence current includes: when the target mutation quantity and the zero-sequence current satisfy the first relationship and the other mutation quantities of the other phases except the target phase corresponding to the target mutation quantity satisfy the second relationship, increasing the phase cumulative quantity corresponding to the target phase by 1; when the target mutation quantity and the zero-sequence current do not satisfy the first relationship and the other mutation quantities satisfy the third relationship, increasing the phase cumulative quantity corresponding to the other phases by 1.

[0106] Optionally, the first relationship is used to determine whether the association between the target mutation quantity and the zero-sequence current conforms to a certain fault characteristic, and the second relationship is for the conditions of the current mutation quantities of the other phases except the target phase corresponding to the target mutation quantity. When the target mutation quantity and the zero-sequence current satisfy the first relationship and the other mutation quantities satisfy the second relationship, it indicates that the current change situation of the target phase and its association with the zero-sequence current conform to a specific fault mode at the current sampling moment. At this time, the phase cumulative quantity corresponding to the target phase is increased by 1. For example, if the target phase is phase A and the above conditions are met, the single-phase cumulative quantity of phase A is incremented by 1, indicating that at the current sampling point, from the perspective of current change and zero-sequence current characteristics, it is more likely that a fault-related situation has occurred in the target phase (phase A).

[0107] Optionally, the third relationship is similar to the second relationship, but it is the constraint condition for the other mutation quantities when the target mutation quantity and the zero-sequence current do not satisfy the first relationship. When the target mutation quantity and the zero-sequence current do not satisfy the first relationship and the other mutation quantities satisfy the third relationship, it indicates that the fault characteristic is more inclined to the other phases. At this time, the phase cumulative quantity corresponding to the other phases is increased by 1. For example, if the target phase is phase A and does not satisfy the first relationship, but the mutation quantities of phase B and phase C satisfy the third relationship, the two-phase cumulative quantity corresponding to phase B and phase C (the other phases) is incremented by 1, indicating that from the electrical quantity characteristics of the current sampling point, it is more likely that a fault has occurred in the other phases.

[0108] In other embodiments, the absolute value of the zero-sequence current does not exceed the current threshold; the step of obtaining the corresponding phase cumulative quantity according to the target mutation quantity and the zero-sequence current includes: when the current mutation quantity of each phase satisfies the fourth relationship with the currents of each phase at the previous cycle sampling point, increasing the three-phase cumulative quantity by 1; when the target mutation quantity, the other mutation quantities and the currents of each phase at the previous cycle sampling point satisfy the fifth relationship, increasing the two-phase cumulative quantity corresponding to the other phases by 1.

[0109] Optionally, the fourth relationship is used to determine whether the association between the sudden change in current of each phase at the current sampling point and the current of each phase at the sampling point of the previous cycle conforms to a certain fault characteristic. When the sudden change in current of each phase satisfies the fourth relationship with the current of each phase at the sampling point of the previous cycle, it indicates that the change in the three-phase current at the current sampling moment conforms to a specific fault mode, and this mode tends to have faults occur simultaneously in the three phases. At this time, the cumulative quantity of the three phases is increased by 1, indicating that from the perspective of the current change characteristics, the current sampling point is more inclined to the three-phase short-circuit fault situation, so the cumulative quantity related to the three-phase fault is increased.

[0110] Optionally, the fifth relationship is used to determine whether the comprehensive association among the target sudden change quantity, other sudden change quantities, and the current of each phase at the sampling point of the previous cycle conforms to another fault characteristic. When the target sudden change quantity, other sudden change quantities, and the current of each phase at the sampling point of the previous cycle satisfy the fifth relationship, it indicates that the fault characteristic is more inclined to faults occurring in two phases and is not a ground fault. At this time, the cumulative quantity of the corresponding two phases of the other phases is increased by 1. For example, if the target sudden change quantity corresponds to phase A, when the sudden change quantities of phases B and C and the current of each phase at the sampling point of the previous cycle satisfy the fifth relationship, the cumulative quantity of the corresponding two phases of phases B and C will be increased by 1, indicating that from the perspective of the electrical quantity characteristics of the current sampling point, it is more likely to be a two-phase short-circuit fault between phases.

[0111] Exemplarily, define the number of sampling points in a cycle as N. Initially, for single-phase ground short-circuit fault: the cumulative quantity of phase A is A_count = 0, the cumulative quantity of phase B is B_count = 0, and the cumulative quantity of phase C is C_count = 0; for two-phase ground short-circuit fault: the cumulative quantity of phases AB is AB_count = 0, the cumulative quantity of phases BC is BC_count = 0, and the cumulative quantity of phases CA is CA_count = 0; for two-phase short-circuit fault between phases: the cumulative quantity between phases AB is A - B_count = 0, the cumulative quantity between phases BC is B - C_count = 0, and the cumulative quantity between phases AC is A - C_count = 0; for three-phase ground short-circuit fault: the cumulative quantity of phases ACB is ABC_count = 0; the sampling counter k = 0; the counter of zero-sequence current I0_count = 0.

[0112] For the currents of phases A, B, and C, data is taken point by point forward and backward from the fault starting point. The current data points are respectively denoted as 、 、 , and the corresponding data points of the previous cycle are respectively denoted as 、 、 , and the sampling counter k is cumulatively incremented by 1 each time. Then the zero-sequence current and the sudden change in three-phase current Δi kThe mathematical expression is:

[0113]

[0114] Take the minimum value I among the sudden changes of three-phase current 、 、 as the target sudden change. min

[0115] First, judge whether the absolute value of the zero-sequence current is greater than the threshold I 0TH :

[0116] (1) If | | > I 0TH , then the count I0_count is incremented by one, and compare the magnitudes of the two results of |I min - 0| and |Imin - |.

[0117] If |I min - 0| < |I min - | ||, and the sudden change of phase A is the minimum value I min , then judge:

[0118] , if satisfied, then A_count is incremented by 1;

[0119] If |I min - 0| ≥ |I min - | ||, and the sudden change of phase A is the minimum value I min , then judge:

[0120] , if satisfied, then BC_count is incremented by 1.

[0121] (2) If | | ≤ I 0TH , judge:

[0122] , if satisfied, then ABC_count is incremented by 1;

[0123] If not satisfied, and the sudden change of phase A is the minimum value I min , then judge:

[0124] , if satisfied, then B - C_count is incremented by 1.

[0125] ​It can be understood that in this embodiment, only the case where the mutant variable of phase A is the minimum value is described. Similarly, when the mutant variable of phase B or phase C is the minimum value, the corresponding phase cumulative quantity is obtained in the same manner as that of phase A, which will not be elaborated here.

[0126] Exemplarily, if k≥N, calculate the ratio of each count quantity to N, and determine whether these ratios are greater than 70%: if A_count / N≥70%, it is a single-phase ground short-circuit fault of phase A; if B_count / N≥70%, it is a single-phase ground short-circuit fault of phase B; if C_count / N≥70%, it is a single-phase ground short-circuit fault of phase C; if AB_count / N≥70%, it is a two-phase ground short-circuit fault of phases AB; if BC_count / N≥70%, it is a two-phase ground short-circuit fault of phases BC; if CA_count / N≥70%, it is a two-phase ground short-circuit fault of phases CA; if A-B_count / N≥70%, it is an inter-phase fault of phases AB; if B-C_count / N≥70%, it is an inter-phase fault of phases BC; if C-A_count / N≥70%, it is an inter-phase fault of phases CA; if ABC_count / N≥70%, it is a three-phase short-circuit fault of phases ABC.

[0127] In the above embodiment, by determining whether the zero-sequence current exceeds the threshold, it is divided into a ground fault type and a non-ground fault type. In the ground fault branch, it is determined as a single-phase ground or two-phase ground fault according to whether the mutant variable is close to the zero-sequence current and is the minimum value. In the non-ground fault branch, it is determined as a two-phase inter-phase short circuit or a three-phase short circuit according to the three-phase mutant variables, and then the second fault type of the transformer is obtained, which can improve the accuracy of transient short-circuit fault identification.

[0128] In other embodiments, such as Figure 3As shown, the rated voltage includes the rated voltage of the high-voltage side, the rated voltage of the medium-voltage side, and the rated voltage of the low-voltage side before the transformer fault; the actual voltage includes the actual voltage of the high-voltage side, the actual voltage of the medium-voltage side, and the actual voltage of the low-voltage side of each phase of the transformer before the fault; the steps for obtaining the fault location of the transformer according to the rated voltage, actual voltage, and fault type of the transformer include: obtaining the target mean voltage corresponding to the actual voltage of all phases; the target mean voltage includes the mean voltage of the high-voltage side, the mean voltage of the medium-voltage side, and the mean voltage of the low-voltage side; obtaining the maximum mean voltage and the minimum mean voltage among the mean voltage of the high-voltage side, the mean voltage of the medium-voltage side, and the mean voltage of the low-voltage side; in the case where the fault type is a single-phase ground short-circuit fault, or a two-phase ground short-circuit fault, or a two-phase interphase short-circuit fault, obtaining the first fault location of the transformer according to the target voltage mean, the maximum mean voltage, and the minimum mean voltage; the first fault location includes a high-voltage side fault, a medium-voltage side fault, and a low-voltage side fault; in the case where the fault type is a three-phase short-circuit fault, obtaining the second fault location of the transformer according to the rated voltage, the maximum mean voltage, and the minimum mean voltage; the second fault location includes the access state of each winding of the transformer and the faulty winding.

[0129] Optionally, for non-three-phase faults such as single-phase ground short-circuit, two-phase ground short-circuit, and two-phase interphase short-circuit, since non-three-phase faults usually occur in a winding of a certain voltage level, the fault location can be determined according to the difference between the rated voltage mean and the extreme values.

[0130] Exemplarily, obtain the rated voltages of the high, medium, and low sides before the fault, which are UHn, UMn, and ULn respectively. Calculate the three-phase effective value means rms_bef_avgh, rms_bef_avgm, and rms_bef_avgl of the actual voltages of the high, medium, and low sides before the fault, and calculate the maximum maxrms_bef_avg and the minimum minrms_bef_avg among the three means.

[0131] When the fault type is a single-phase ground short-circuit fault, judge whether rms_bef_avgh is equal to maxrms_bef_avg. If it is equal, determine that the final fault type is A / B / C-H-Earth; if it is not equal, judge whether rms_bef_avgh is equal to minrms_bef_avg. If it is equal, determine that the final fault type is A / B / C-L-Earth; otherwise, determine that the final fault type is A / B / C-M-Earth. Among them, A / B / C represents the single-phase ground fault phase, H / M / L represents the high, medium, and low sides of the transformer, and Earth represents the ground short-circuit fault.

[0132] When the fault type is a two-phase-to-earth short-circuit fault, similar to the single-phase-to-earth short-circuit fault, determine whether rms_bef_avgh is equal to maxrms_bef_avg. If it is equal, determine that the final fault type is AB / BC / CA-H-Earth; if not, determine whether rms_bef_avgh is equal to minrms_bef_avg. If it is equal, determine that the final fault type is AB / BC / CA-L-Earth; otherwise, determine that the final fault type is AB / BC / CA-M-Earth. Here, AB / BC / CA represents the two-phase-to-earth fault phases, H / M / L represent the high, medium, and low sides of the transformer, and Earth represents the earth short-circuit fault.

[0133] When the fault type is a two-phase short-circuit fault between phases, similar to the single-phase-to-earth short-circuit fault and the two-phase-to-earth short-circuit fault, determine that the final fault types are A+B / B+C / C+A-H-Earth, A+B / B+C / C+A-M-Earth, and A+B / B+C / C+A-L-Earth. Here, A+B / B+C / C+A represents the two-phase short-circuit fault phases between phases.

[0134] When the fault type is a three-phase short-circuit fault, if maxrms_bef_avg < 1.1UMn, determine that the final fault type is ABC-M-L; if maxrms_bef_avg ≥ 1.1UMn, determine whether the average effective values of the voltages before the fault on the other two sides are both less than UMn. If they are less, determine that the final fault type is ABC-H-L; if not, determine whether minrms_bef_avg < 0.01ULn. If it is satisfied, determine that the final fault type is ABC-H-M; if minrms_bef_avg ≥ 0.01ULn, determine whether the three-phase voltage effective values before the fault are the maximum values. If so, determine ABC-M+L-H; if the three-phase voltage effective values before the fault are the minimum values, determine ABC-H+M-L; if the three-phase voltage effective values before the fault are the maximum values, determine ABC-M+L-H; otherwise, determine that the final fault type is ABC-H+L-M. Here, H-L means the high-voltage winding is connected to the excitation, the medium-voltage winding is not connected, and the low-voltage winding is short-circuited in three phases. The same applies to H-M and M-L; H+M-L means the high-voltage winding and the medium-voltage winding are normally connected to the excitation, and the low-voltage winding is short-circuited in three phases. The same applies to H+L-M and M+L-H.

[0135] In this embodiment, by obtaining the fault location of the transformer according to the rated voltage, actual voltage, and fault type of the transformer, the accuracy of short-circuit fault location can be improved.

[0136] In other embodiments, as Figure 4 shown, a transformer fault detection method is provided, and this method includes the following steps:

[0137] (1)Obtain fault recording data: Obtain the fault point in the fault recording data of the transformer, and obtain the fault data of the fault point; the fault data includes the pre-fault data of the previous cycle before the fault point and the post-fault data of the two cycles after the fault point; for each phase of the transformer, according to the fault data, obtain the voltage amplitude ratio and the current amplitude ratio; when the voltage amplitude ratio does not exceed the first threshold and the current amplitude ratio is not less than the second threshold, determine that the current phase is the fault phase.

[0138] (2)Steady-state short-circuit fault identification: When the number of fault phases meets the quantity requirement condition, obtain the zero-sequence voltage and zero-sequence current according to the phase current and phase voltage of each phase; when the zero-sequence voltage and zero-sequence current meet the parameter requirement condition and the number of fault phases is 2, obtain the first phase difference between the phase voltage and phase current between the fault phases; the zero-sequence voltage and zero-sequence current meeting the parameter requirement condition includes that the zero-sequence voltage is not less than the third threshold or the zero-sequence current is not less than the fourth threshold; when the first phase difference is within the first range, determine that the first fault type of the transformer is two-phase short-circuit grounding fault; when the zero-sequence voltage and zero-sequence current meet the parameter requirement condition and the number of fault phases is not 2, or the first phase difference is not within the first range, when the second phase difference of only one fault phase is within the first range, determine that the first fault type of the transformer is single-phase short-circuit grounding fault; when the second phase difference of at least two fault phases is within the first range or the second phase difference of only one fault phase is not within the first range, obtain the fourth phase difference between the zero-sequence current and the phase current of the fault phase, and the fifth phase difference between the zero-sequence voltage and the phase voltage of the fault phase; when the fourth phase difference of only one fault phase does not exceed the phase threshold or the fifth phase difference of only one fault phase is within the third range, determine that the first fault type of the transformer is single-phase short-circuit grounding fault; when the fifth phase difference of at least two fault phases meets the phase difference condition and is within the third range, determine that the first fault type of the transformer is two-phase short-circuit grounding fault; the phase difference condition is that the fourth phase difference of only one fault phase exceeds the phase threshold and the fifth phase difference of the fault phase is not within the third range. When the zero-sequence voltage and zero-sequence current do not meet the parameter requirement condition and the number of fault phases is 3, determine that the first fault type of the transformer is three-phase short-circuit fault; the zero-sequence voltage and zero-sequence current not meeting the parameter requirement condition includes that the zero-sequence voltage is less than the third threshold and the zero-sequence current is less than the fourth threshold; when the zero-sequence voltage and zero-sequence current do not meet the parameter requirement condition and the number of fault phases is not 3, obtain the third phase difference between the phase currents of the fault phases; when the third phase difference is within the second range, determine that the first fault type of the transformer is three-phase short-circuit fault; when the third phase difference is not within the second range, determine that the first fault type of the transformer is two-phase interphase short-circuit fault.

[0139] (3)Transient short - circuit fault identification: Take the minimum value among the sudden changes in current of all phases as the target sudden change; each sampling point corresponds to a data point in the fault recording data. When the cumulative number of samples is less than the target number, when the absolute value of the zero - sequence current is greater than the current threshold, when the target sudden change and the zero - sequence current satisfy the first relationship, and the other sudden changes of the other phases except the target phase corresponding to the target sudden change satisfy the second relationship, increase the phase cumulative number corresponding to the target phase by 1; when the target sudden change and the zero - sequence current do not satisfy the first relationship, and the other sudden changes satisfy the third relationship, increase the phase cumulative number corresponding to the other phases by 1. When the absolute value of the zero - sequence current does not exceed the current threshold, when the sudden change in current of each phase satisfies the fourth relationship with the currents of each phase at the previous - cycle sampling point, increase the three - phase cumulative number by 1; when the target sudden change, the other sudden changes and the currents of each phase at the previous - cycle sampling point satisfy the fifth relationship, increase the phase cumulative numbers corresponding to the other two phases by 1. When the ratio between the phase cumulative number and the target number is not less than the fault threshold, take the fault state corresponding to the phase cumulative number as the second fault type of the transformer; the second fault type includes single - phase short - circuit grounding fault, two - phase short - circuit grounding fault, two - phase inter - phase short - circuit fault, and three - phase short - circuit fault.

[0140] (4)Target fault identification: Obtain the target fault type of the transformer according to the first fault type and the second fault type.

[0141] (5)Fault location: Obtain the target mean voltage corresponding to the actual voltages of all phases; the target mean voltage includes the mean voltage of the high - voltage side, the mean voltage of the medium - voltage side, and the mean voltage of the low - voltage side; obtain the maximum mean voltage and the minimum mean voltage among the mean voltage of the high - voltage side, the mean voltage of the medium - voltage side, and the mean voltage of the low - voltage side. When the fault type is single - phase grounding short - circuit fault, or two - phase grounding short - circuit fault, or two - phase inter - phase short - circuit fault, obtain the first fault location of the transformer according to the target voltage mean, the maximum mean voltage, and the minimum mean voltage; the first fault location includes high - voltage - side fault, medium - voltage - side fault, and low - voltage - side fault. When the fault type is three - phase short - circuit fault, obtain the second fault location of the transformer according to the rated voltage, the maximum mean voltage, and the minimum mean voltage; the second fault location includes the connection status of each winding of the transformer and the faulty winding.

[0142] In other embodiments, taking a 500 kV transformer with a sampling frequency of 10,000 Hz, a high-voltage side PT transformation ratio of 500 kV / 100 V, and a current transformation ratio of 1250 A / 1 A as an example of a fault occurrence, the transformer fault detection method in the embodiments of the present application is used for fault identification: One cycle of data before the fault and two cycles of data after the fault are taken for steady-state short-circuit fault identification and transient short-circuit fault identification respectively. When using steady-state short-circuit fault identification, the number of faulty phases M = 1 is calculated, that is, phase A is the faulty phase, and the zero-sequence voltage U 0rms = 3.57 V and the zero-sequence current I 0rms = 0.236 A are greater than the threshold value. Furthermore, the phase difference Δφui between the voltage and current of phase A is calculated as 85.73°, which meets the conditions. Therefore, it is determined as a single-phase ground short-circuit fault of phase A. When using transient short-circuit fault identification, the number of sampling points in one cycle is 200. Taking the data of one cycle for calculation, the results are A_count: 163, B_count: 0, C_count: 1, AB_count: 16, BC_count: 0, AC_count: 2, A_B_count: 4, B_C_count: 21, A_C_count: 6, ABC_count: 61, I0_count = 192. The proportion of A_count in 200 sampling points is 81.5%, exceeding 70%. Therefore, it is determined as a single-phase ground short-circuit fault of phase A. According to the steady-state and transient short-circuit fault identification algorithms, the fault identification results are consistent, both being a single-phase ground short-circuit fault of phase A. In fault location, the average effective value of the voltages of phases A, B, and C on the corresponding side of the faulty phase A before the fault is 57.5576 V, which is the maximum value among the effective values of the voltages before the fault on the high, medium, and low sides. Therefore, the final output short-circuit fault type is A-H-Earth.

[0143] In this embodiment, by obtaining the faulty phase of the transformer according to the fault recording data of the transformer, and when the number of faulty phases meets the quantity requirement conditions, obtaining the first fault type of the transformer according to the phase difference. During the process of sampling the fault recording data according to a preset period, obtaining the zero-sequence current at the current sampling point and the current mutation between the current sampling point and the sampling point of the previous period, obtaining the second fault type of the transformer according to the zero-sequence current and the current mutation, obtaining the target fault type of the transformer according to the first fault type and the second fault type, and obtaining the fault location of the transformer according to the rated voltage, actual voltage, and fault type of the transformer, it is possible to comprehensively diagnose the transformer from both the steady-state and transient dimensions, improving the accuracy and reliability of fault detection.

[0144] It should be understood that although the steps in the flowcharts involved in the above embodiments are sequentially shown according to the indications of the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily executed at the same moment, but can be executed at different moments. The execution order of these steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or steps or stages in other steps.

[0145] Based on the same inventive concept, an embodiment of the present application further provides a transformer fault detection device for implementing the above-mentioned transformer fault detection method. The solution provided by this device to solve the problem is similar to the solution described in the above method. Therefore, the specific limitations in one or more embodiments of the following transformer fault detection devices can refer to the limitations on the transformer fault detection method in the above text, and will not be repeated here.

[0146] In an exemplary embodiment, as Figure 5 shown, a transformer fault detection device is provided, including: a phase acquisition module 10, a first detection module 20, a second detection module 30, a target detection module 40, and a fault location module 50, where:

[0147] The phase acquisition module 10 is configured to obtain the fault phase of the transformer according to the fault recording data of the transformer.

[0148] The first detection module 20 is configured to obtain the first fault type of the transformer according to the phase difference when the number of fault phases meets the quantity requirement condition.

[0149] The second detection module 30 is configured to obtain the zero-sequence current of the current sampling point and the current mutation of the current sampling point and the previous cycle sampling point during the process of sampling the fault recording data according to a preset period, and obtain the second fault type of the transformer according to the zero-sequence current and the current mutation; each sampling point corresponds to a data point in the fault recording data.

[0150] The target detection module 40 is configured to obtain the target fault type of the transformer according to the first fault type and the second fault type.

[0151] The fault location module 50 obtains the fault location of the transformer according to the rated voltage, actual voltage, and fault type of the transformer.

[0152] In an exemplary embodiment, the phase acquisition module 10 is further configured to obtain a fault point in the fault recording data of the transformer, and obtain the fault data of the fault point; the fault data includes the pre-fault data of the previous cycle before the fault point and the post-fault data of the two cycles after the fault point; for each phase of the transformer, according to the fault data, obtain the voltage amplitude ratio and the current amplitude ratio; when the voltage amplitude ratio does not exceed the first threshold and the current amplitude ratio is not less than the second threshold, determine that the current phase is the fault phase.

[0153] In an exemplary embodiment, the first detection module 20 is further configured to obtain zero-sequence voltage and zero-sequence current according to the phase current and phase voltage of each phase; when the zero-sequence voltage and zero-sequence current meet the parameter requirement conditions and the number of fault phases is 2, obtain the first phase difference between the phase voltage and phase current between the fault phases; the zero-sequence voltage and zero-sequence current meeting the parameter requirement conditions include that the zero-sequence voltage is not less than the third threshold or the zero-sequence current is not less than the fourth threshold; when the first phase difference is within the first range, determine that the first fault type of the transformer is a two-phase short-circuit grounding fault; when the zero-sequence voltage and zero-sequence current meet the parameter requirement conditions and the number of fault phases is not 2, or the first phase difference is not within the first range, obtain the first fault type of the transformer according to the second phase difference between the phase voltage and phase current of the fault phase; when the zero-sequence voltage and zero-sequence current do not meet the parameter requirement conditions and the number of fault phases is 3, determine that the first fault type of the transformer is a three-phase short-circuit fault; the zero-sequence voltage and zero-sequence current not meeting the parameter requirement conditions include that the zero-sequence voltage is less than the third threshold and the zero-sequence current is less than the fourth threshold; when the zero-sequence voltage and zero-sequence current do not meet the parameter requirement conditions and the number of fault phases is not 3, obtain the third phase difference between the phase currents of the fault phases; when the third phase difference is within the second range, determine that the first fault type of the transformer is a three-phase short-circuit fault; when the third phase difference is not within the second range, determine that the first fault type of the transformer is a two-phase interphase short-circuit fault.

[0154] In an exemplary embodiment, the first detection module 20 is further configured to determine that the first fault type of the transformer is a single-phase short-circuit to ground fault when the second phase difference of only one fault phase is within the first range; when the second phase difference of at least two fault phases is within the first range, or the second phase difference of only one fault phase is not within the first range, obtain the fourth phase difference between the zero-sequence current and the phase current of the fault phase, and the fifth phase difference between the zero-sequence voltage and the phase voltage of the fault phase; determine that the first fault type of the transformer is a single-phase short-circuit to ground fault when the fourth phase difference of only one fault phase does not exceed the phase threshold, or the fifth phase difference of only one fault phase is within the third range; determine that the first fault type of the transformer is a two-phase short-circuit to ground fault when the fifth phase difference of at least two fault phases that meet the phase difference condition is within the third range; the phase difference condition is that the fourth phase difference of only one fault phase exceeds the phase threshold and the fifth phase difference of the fault phase is not within the third range.

[0155] In an exemplary embodiment, the second detection module 30 is further configured to use the minimum value of the current mutation amounts of all phases as the target mutation amount; when the sampling cumulative quantity is less than the target quantity, obtain the corresponding phase cumulative quantity according to the target mutation amount and the zero-sequence current; the phase cumulative quantity includes single-phase cumulative quantity, two-phase cumulative quantity, and three-phase cumulative quantity; when the ratio between the phase cumulative quantity and the target quantity is not less than the fault threshold, use the fault state corresponding to the phase cumulative quantity as the second fault type of the transformer; the second fault type includes single-phase short-circuit to ground fault, two-phase short-circuit to ground fault, two-phase inter-phase short-circuit fault, and three-phase short-circuit fault.

[0156] In an exemplary embodiment, the absolute value of the zero-sequence current is greater than the current threshold; the second detection module 30 is further configured to increase the phase cumulative quantity corresponding to the target phase by 1 when the target mutation amount and the zero-sequence current satisfy the first relationship, and the other mutation amounts of the other phases except the target phase corresponding to the target mutation amount satisfy the second relationship; increase the phase cumulative quantity corresponding to the other phases by 1 when the target mutation amount and the zero-sequence current do not satisfy the first relationship, and the other mutation amounts satisfy the third relationship.

[0157] In an exemplary embodiment, the absolute value of the zero-sequence current does not exceed the current threshold; the second detection module 30 is further configured to increase the three-phase cumulative quantity by 1 when the current mutation amount of each phase satisfies the fourth relationship with the phase currents of the previous cycle sampling points; increase the two-phase cumulative quantity corresponding to the other phases by 1 when the target mutation amount, the other mutation amounts, and the phase currents of the previous cycle sampling points satisfy the fifth relationship.

[0158] In an exemplary embodiment, the rated voltage includes the rated voltage of the high-voltage side, the rated voltage of the medium-voltage side, and the rated voltage of the low-voltage side before the transformer fault; the actual voltage includes the actual voltage of the high-voltage side, the actual voltage of the medium-voltage side, and the actual voltage of the low-voltage side of each phase of the transformer before the fault; the fault location module 50 also acquires the target mean voltage corresponding to the actual voltages of all phases; the target mean voltage includes the mean voltage of the high-voltage side, the mean voltage of the medium-voltage side, and the mean voltage of the low-voltage side; acquires the maximum mean voltage and the minimum mean voltage among the mean voltage of the high-voltage side, the mean voltage of the medium-voltage side, and the mean voltage of the low-voltage side; in the case where the fault type is a single-phase ground short-circuit fault, or a two-phase ground short-circuit fault, or a two-phase inter-phase short-circuit fault, acquires the first fault location of the transformer according to the target voltage mean, the maximum mean voltage, and the minimum mean voltage; the first fault location includes a high-voltage side fault, a medium-voltage side fault, and a low-voltage side fault; in the case where the fault type is a three-phase short-circuit fault, acquires the second fault location of the transformer according to the rated voltage, the maximum mean voltage, and the minimum mean voltage; the second fault location includes the connection state of each winding of the transformer and the faulty winding.

[0159] Each module in the above transformer fault detection device can be implemented in whole or in part by software, hardware, and their combination. Each of the above modules can be embedded in the processor in the computer device in the form of hardware or be independent of it, or can be stored in the memory in the computer device in the form of software, so as to facilitate the processor to call and execute the operations corresponding to each of the above modules.

[0160] In an exemplary embodiment, a computer device is provided. The computer device can be a terminal, and its internal structure diagram can be as Figure 6As shown in the figure. The computer device includes a processor, a memory, an input / output interface, a communication interface, a display unit, and an input device. Among them, the processor, the memory, and the input / output interface are connected through a system bus, and the communication interface, the display unit, and the input device are connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The input / output interface of the computer device is used to exchange information between the processor and external devices. The communication interface of the computer device is used to communicate with external terminals in a wired or wireless manner, and the wireless manner can be achieved through WIFI, a mobile cellular network, near field communication (NFC), or other technologies. When the computer program is executed by the processor, it implements a transformer fault detection method. The display unit of the computer device is used to form a visually visible picture, which can be a display screen, a projection device, or a virtual reality imaging device. The display screen can be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device can be a touch layer covering the display screen, or a button, a trackball, or a touchpad provided on the outer shell of the computer device, or an external keyboard, touchpad, or mouse, etc.

[0161] Those skilled in the art can understand that Figure 6 the structure shown in the figure is only a block diagram of some structures related to the solution of this application, and does not constitute a limitation on the computer device to which the solution of this application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements.

[0162] In an exemplary embodiment, a computer device is provided, including a memory and a processor. A computer program is stored in the memory, and when the processor executes the computer program, the steps in the above method embodiments are implemented.

[0163] In an embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by the processor, the steps in the above method embodiments are implemented.

[0164] In an embodiment, a computer program product is provided, including a computer program. When the computer program is executed by the processor, the steps in the above method embodiments are implemented.

[0165] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, database, or other medium used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include Read-Only Memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, Resistive Random Access Memory (ReRAM), Magnetoresistive Random Access Memory (MRAM), Ferroelectric Random Access Memory (FRAM), Phase Change Memory (PCM), graphene memory, etc. Volatile memory can include Random Access Memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM), etc. The databases involved in the embodiments provided in this application can include at least one of relational databases and non-relational databases. Non-relational databases can include distributed databases based on blockchain, etc., without limitation. The processors involved in the embodiments provided in this application can be general-purpose processors, central processors, graphics processors, digital signal processors, programmable logic devices, data processing logics based on quantum computing, Artificial Intelligence (AI) processors, etc., without limitation.

[0166] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this application.

[0167] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims.

Claims

1. A transformer fault detection method, characterized in that, The method includes: Obtaining the fault phase of the transformer according to the fault recording data of the transformer; When the number of the fault phases meets the quantity requirement condition, obtaining the first fault type of the transformer according to the phase difference; During the process of sampling the fault recording data at a preset period, obtaining the zero-sequence current of the current sampling point and the current mutation of the current sampling point and the previous cycle sampling point, and obtaining the second fault type of the transformer according to the zero-sequence current and the current mutation; each sampling point corresponds to a data point in the fault recording data; Obtaining the target fault type of the transformer according to the first fault type and the second fault type; Obtaining the fault location of the transformer according to the rated voltage, the actual voltage of the transformer and the fault type; 2. The method according to claim 1, wherein The obtaining the fault phase of the transformer according to the fault recording data of the transformer includes: Obtaining the fault point in the fault recording data of the transformer and obtaining the fault data of the fault point; the fault data includes the pre-fault data of the previous cycle of the fault point and the post-fault data of the two cycles after the fault point; For each phase of the transformer, obtaining the voltage amplitude ratio and the current amplitude ratio according to the fault data; When the voltage amplitude ratio does not exceed the first threshold and the current amplitude ratio is not less than the second threshold, determining the current phase as the fault phase.

3. The method according to claim 1, wherein The obtaining the first fault type of the transformer according to the phase difference includes: Obtaining the zero-sequence voltage and the zero-sequence current according to the phase current and the phase voltage of each phase; When the zero-sequence voltage and the zero-sequence current meet the parameter requirement condition and the number of the fault phases is 2, obtaining the first phase difference between the inter-phase voltage and the inter-phase current between the fault phases; the zero-sequence voltage and the zero-sequence current meeting the parameter requirement condition includes that the zero-sequence voltage is not less than the third threshold or the zero-sequence current is not less than the fourth threshold; When the first phase difference is within the first range, determining the first fault type of the transformer as a two-phase short circuit to ground fault; When the zero-sequence voltage and the zero-sequence current meet the parameter requirement condition and the number of the fault phases is not 2, or the first phase difference is not within the first range, obtaining the first fault type of the transformer according to the second phase difference between the phase voltage and the phase current of the fault phase; When the zero-sequence voltage and the zero-sequence current do not meet the parameter requirement condition and the number of the fault phases is 3, determining the first fault type of the transformer as a three-phase short circuit fault; the zero-sequence voltage and the zero-sequence current not meeting the parameter requirement condition includes that the zero-sequence voltage is less than the third threshold and the zero-sequence current is less than the fourth threshold; When the zero-sequence voltage and the zero-sequence current do not meet the parameter requirement condition and the number of the fault phases is not 3, obtaining the third phase difference between the phase currents of the fault phases; When the third phase difference is within the second range, determine that the first fault type of the transformer is a three-phase short-circuit fault; when the third phase difference is not within the second range, determine that the first fault type of the transformer is a two-phase interphase short-circuit fault.

4. The method according to claim 3, wherein The obtaining of the first fault type of the transformer according to the second phase difference between the phase voltage and the phase current of the fault phase includes: When there is only one fault phase and the second phase difference is within the first range, determine that the first fault type of the transformer is a single-phase short-circuit grounding fault; When there are at least two fault phases and the second phase difference is within the first range, or when there is only one fault phase and the second phase difference is not within the first range, obtain the fourth phase difference between the zero-sequence current and the phase current of the fault phase, and the fifth phase difference between the zero-sequence voltage and the phase voltage of the fault phase; When there is only one fault phase and the fourth phase difference does not exceed the phase threshold, or when there is only one fault phase and the fifth phase difference is within the third range, determine that the first fault type of the transformer is a single-phase short-circuit grounding fault; When the phase difference condition is met or when there are two fault phases and the fifth phase difference is within the third range, determine that the first fault type of the transformer is a two-phase short-circuit grounding fault; the phase difference condition is that there is only one fault phase and the fourth phase difference exceeds the phase threshold and the fifth phase difference of the fault phase is not within the third range.

5. The method according to claim 1, characterized in that, The obtaining of the second fault type of the transformer according to the zero-sequence current and the current mutation amount includes: Take the minimum value among the current mutation amounts of all phases as the target mutation amount; When the sampling cumulative quantity is less than the target quantity, obtain the corresponding phase cumulative quantity according to the target mutation amount and the zero-sequence current; the phase cumulative quantity includes single-phase cumulative quantity, two-phase cumulative quantity and three-phase cumulative quantity; When the ratio between the phase cumulative quantity and the target quantity is not less than the fault threshold, take the fault state corresponding to the phase cumulative quantity as the second fault type of the transformer; the second fault type includes single-phase short-circuit grounding fault, two-phase short-circuit grounding fault, two-phase interphase short-circuit fault and three-phase short-circuit fault.

6. The method according to claim 5, wherein The absolute value of the zero-sequence current is greater than the current threshold; The obtaining of the corresponding phase cumulative quantity according to the target mutation amount and the zero-sequence current includes: When the target mutation amount and the zero-sequence current satisfy the first relationship, and the other mutation amounts of the other phases except the target phase corresponding to the target mutation amount satisfy the second relationship, increase the phase cumulative quantity corresponding to the target phase by 1; When the target mutation amount and the zero-sequence current do not satisfy the first relationship, and the other mutation amounts satisfy the third relationship, increase the phase cumulative quantity corresponding to the other phase by 1.

7. The method according to claim 6, characterized in that, The absolute value of the zero-sequence current does not exceed the current threshold; The obtaining of the corresponding phase cumulative quantity according to the target mutation amount and the zero-sequence current includes: When the sudden change in current of each phase satisfies the fourth relationship with the currents of each phase at the sampling points in the previous cycle, increase the three-phase cumulative quantity by 1; When the target sudden change quantity, the other sudden change quantities, and the currents of each phase at the sampling points in the previous cycle satisfy the fifth relationship, increase the cumulative quantities of the corresponding two phases of the other phase by 1.

8. The method according to claim 1, characterized in that The rated voltage includes the rated voltage of the high-voltage side, the rated voltage of the medium-voltage side, and the rated voltage of the low-voltage side before the transformer fault; the actual voltage includes the actual voltage of the high-voltage side, the actual voltage of the medium-voltage side, and the actual voltage of the low-voltage side of each phase of the transformer before the fault; The obtaining the fault location of the transformer according to the rated voltage, the actual voltage, and the fault type of the transformer includes: Obtain the target mean voltage corresponding to the actual voltages of all phases; the target mean voltage includes the mean voltage of the high-voltage side, the mean voltage of the medium-voltage side, and the mean voltage of the low-voltage side; Obtain the maximum mean voltage and the minimum mean voltage among the mean voltage of the high-voltage side, the mean voltage of the medium-voltage side, and the mean voltage of the low-voltage side; When the fault type is a single-phase ground short-circuit fault, or a two-phase ground short-circuit fault, or a two-phase interphase short-circuit fault, obtain the first fault location of the transformer according to the target voltage mean, the maximum mean voltage, and the minimum mean voltage; the first fault location includes a high-voltage side fault, a medium-voltage side fault, and a low-voltage side fault; When the fault type is a three-phase short-circuit fault, obtain the second fault location of the transformer according to the rated voltage, the maximum mean voltage, and the minimum mean voltage; the second fault location includes the access states of the windings of the transformer and the faulty winding.

9. A transformer fault detection device, characterized in that, The device includes: A phase acquisition module, configured to obtain the fault phase of the transformer according to the fault recording data of the transformer; A first detection module, configured to obtain the first fault type of the transformer according to the phase difference when the number of fault phases meets the quantity requirement condition; A second detection module, configured to obtain the zero-sequence current at the current sampling point and the sudden change in current between the current sampling point and the sampling points in the previous cycle during the process of sampling the fault recording data at a preset cycle, and obtain the second fault type of the transformer according to the zero-sequence current and the sudden change in current; A target detection module, configured to obtain the target fault type of the transformer according to the first fault type and the second fault type; A fault location module, configured to obtain the fault location of the transformer according to the rated voltage, the actual voltage, and the fault type of the transformer.

10. A computer device, comprising a memory and a processor, the memory storing a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 8.

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