Synchronous motor excitation transformer low-voltage side single-phase earth fault identification and positioning method and device

Abstract

The invention discloses a synchronous motor excitation transformer low-voltage side single-phase earth fault identification and positioning method. The method comprises the following steps: obtaining an excitation DC side voltage and an excitation AC side voltage of a synchronous motor; calculating an excitation direct current side voltage fundamental component effective value and an excitation alternating current side voltage fundamental component effective value; and judging whether a single-phase earth fault occurs on the low-voltage side of the exciting transformer based on the effective value of the excitation direct-current side voltage fundamental component and the effective value of the excitation alternating-current side voltage fundamental component, respectively calculating the phase angle difference between the excitation direct-current side voltage fundamental component and the phase fundamental component of each phase of the excitation alternating-current side, and identifying a fault phase according to the phase angle difference. According to the method, the single-phase earth fault of the low-voltage side of the exciting transformer is accurately identified and the fault phase is positioned by quantifying the fault judgment condition, the sensitivity is high, and the applicability is high.

Description

Technical Field

[0001] The invention belongs to the field of power system fault diagnosis, and in particular relates to a method and a device for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer. Background Art

[0002] The ground fault of the excitation circuit is one of the most common faults of synchronous motors, mainly including the ground fault caused by insulation breakdown between the excitation winding and the rotor shaft and the ground fault occurring at the lead and joint on the low-voltage side of the excitation transformer. In actual operation, the rotor grounding protection installed on the synchronous motor can accurately reflect the ground fault of the excitation winding, but it cannot correctly identify and locate the ground fault on the low-voltage side of the excitation transformer, but it is mistakenly reported as an excitation winding ground fault, thereby misleading the direction of fault investigation. Since the phase voltage transformer for ground monitoring is usually not installed on the low-voltage side of the excitation transformer, the ground protection based on zero-sequence voltage cannot be realized. And since the single-phase ground fault does not affect the line voltage on the low-voltage side of the excitation transformer, the excitation voltage and excitation current will not change, so the fault cannot be reflected by the excitation overcurrent protection. Therefore, how to accurately identify the ground fault on the low-voltage side of the excitation transformer and locate the grounding position is an actual on-site problem that needs to be solved urgently.

[0003] At present, there are some methods for identifying single-phase grounding faults on the low-voltage side of the excitation transformer. One of the methods is described in the document "Analysis and Treatment of a Rare Single-Point Grounding Fault of Generator Rotor", written by Xiang Fangwei, "Hongshuihe" Vol. 38, No. 5, 2019. This method identifies single-phase grounding faults on the low-voltage side of the excitation transformer by checking whether there is a large fluctuation in the positive and negative voltages of the rotor to the ground, and checks the voltages of each phase to the ground on the low-voltage side of the excitation transformer when it is idling, and considers the phase with lower voltage to be the grounded phase. The advantage of this method is that it is simple and intuitive; the disadvantage is that since the low-voltage side of the excitation transformer is usually not equipped with a phase voltage transformer to the ground in the actual field, it is difficult to determine the grounded phase by directly observing the phase voltage on the low-voltage side of the excitation transformer.

[0004] Another document, "Online Identification Method for Single-Phase Grounding Fault on Low-Voltage Side of Excitation Transformer", authored by Chen Jun, Wang Yunfan, Yan Wei, etc., "Electric Power Automation Equipment", Vol. 34, No. 11, 2014, discloses a technical solution that uses the ratio of the fundamental component of the rotor positive and negative voltages to the ground to the DC excitation voltage as the fault identification criterion. The advantage of this method is that it conducts real-time quantitative analysis of the problem and realizes online fault identification; the disadvantage is that when the control angle of the rectifier thyristor changes due to the influence of the working conditions, the DC excitation voltage also changes accordingly, and the reduction of the DC excitation voltage will lead to a decrease in the accuracy of fault judgment. Therefore, this technical solution has the problem that the accuracy of fault identification is affected by changes in working conditions, and its applicability is insufficient. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer, which improves the recognition accuracy of a single-phase grounding fault on the low-voltage side of the excitation transformer and locates the grounding fault phase.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] According to a first aspect of the present invention, a method for identifying and locating a single-phase ground fault on the low-voltage side of a synchronous motor excitation transformer is proposed, comprising the following steps:

[0008] Step 1, obtaining the excitation DC side voltage and the excitation AC side voltage of the synchronous motor;

[0009] Step 2, calculating the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage;

[0010] Step 3: determine whether a single-phase grounding fault occurs on the low-voltage side of the excitation transformer based on the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage. If yes, proceed to step 4; otherwise, end the fault identification process.

[0011] Step 4, respectively calculating the phase angle difference between the fundamental wave component of the excitation DC side voltage and the fundamental wave component of each phase voltage of the excitation AC side, and identifying the fault phase according to the phase angle difference.

[0012] According to some embodiments, the excitation DC side voltage in step 1 is the positive voltage of the rotor to ground or the negative voltage of the rotor to ground, and the excitation AC side voltage is the high voltage side phase voltage of the excitation transformer or the low voltage side phase voltage of the excitation transformer.

[0013] According to some embodiments, the step 1, obtaining the excitation DC side voltage and the excitation AC side voltage data, is specifically: reading the excitation DC side voltage and the excitation AC side voltage data from an acquisition device, or directly acquiring the excitation DC side voltage and the excitation AC side voltage data.

[0014] According to some embodiments, the acquisition device is a synchronous motor protection device or a fault recording device.

[0015] According to some embodiments, judging whether a single-phase grounding fault occurs on the low-voltage side of the excitation transformer based on the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage in step 3 specifically includes:

[0016] If the effective value of the fundamental component of the excitation DC side voltage is greater than the DC side set value threshold U dc.set , the effective value of the fundamental component of the excitation AC side voltage is greater than the AC side set value threshold U ac.set , and the ground fault coefficient k is greater than the ground fault coefficient constant K set, it is determined that a single-phase grounding fault occurs on the low-voltage side of the excitation transformer, otherwise it is determined that no single-phase grounding fault occurs on the low-voltage side of the excitation transformer;

[0017] The calculation formula of the ground fault coefficient is:

[0018]

[0019] Where, k represents the ground fault coefficient, U dc Indicates the effective value of the fundamental component of the excitation DC side voltage, U ac It represents the effective value of the fundamental component of the excitation AC side voltage, and k0 represents the voltage conversion coefficient.

[0020] According to some embodiments, the effective value of the fundamental component of the excitation AC side voltage U ac It is the maximum or average effective value of the fundamental component of the three-phase voltage on the high-voltage side of the excitation transformer, or the maximum or average effective value of the fundamental component of the three-phase voltage on the low-voltage side of the excitation transformer.

[0021] According to some embodiments, the DC side set value threshold U dc.set The value range is 5~10V; the AC side set value threshold U ac.set The value range is 0.8U n ~0.9U n , if the excitation AC side voltage is the phase voltage on the high voltage side of the excitation transformer, then U n Indicates the rated phase voltage on the high voltage side of the excitation transformer; if the excitation AC side voltage is the phase voltage on the low voltage side of the excitation transformer, then U n Indicates the rated phase voltage on the low-voltage side of the excitation transformer.

[0022] According to some embodiments, in step 3: if the excitation AC side voltage is the high voltage side phase voltage of the excitation transformer, the voltage conversion coefficient k0 is the transformation ratio k of the excitation transformer. T ; If the excitation AC side voltage is the low-voltage side phase voltage of the excitation transformer, the voltage conversion coefficient k0 is 1.

[0023] According to some embodiments, in step 3, the ground fault coefficient constant K set The value range is 0.01 to 0.4.

[0024] According to some embodiments, the phase angle difference between the fundamental component of the excitation DC side voltage and the fundamental component of each phase voltage of the excitation AC side is calculated as follows:

[0025]

[0026] In the formula, It represents the phase angle difference between the fundamental component of the excitation DC side voltage and the fundamental component of the excitation AC side phase voltage. A, B, and C are taken to represent phase A, phase B, and phase C respectively; θ dc It represents the phase angle of the fundamental component of the excitation DC side voltage, Indicates the excitation AC side Phase angle of the fundamental component of the phase voltage;

[0027] The step of identifying the fault phase according to the phase angle difference specifically includes:

[0028] According to the phase difference calculate Phase correction phase angle difference The calculation formula is:

[0029]

[0030] In the formula, express The corrected phase angle difference of the phase; Δθ0 represents the conversion angle; θ represents the phase angle deviation caused by the grounding resistor and capacitor. The calculation formula of θ is:

[0031] θ=180°-arctan(ωR g C g ) Formula (4)

[0032] In the formula, arctan represents the inverse tangent function, R g Indicates the grounding resistance of the fault point, C g Indicates the capacitance of the excitation winding to ground;

[0033] if Phase correction phase angle difference Less than the angle determination value Δθ set , then judge Phase is the fault phase;

[0034] Among them, Δθ set Indicates the angle determination value, ranging from 5 to 10°.

[0035] According to some embodiments, if the excitation AC side voltage is the phase voltage on the high-voltage side of the excitation transformer, the conversion angle Δθ0 is the angle at which the phase voltage on the high-voltage side of the excitation transformer leads the phase voltage on the low-voltage side of the excitation transformer; if the excitation AC side voltage is the phase voltage on the low-voltage side of the excitation transformer, the conversion angle Δθ0 is 0°.

[0036] According to a second aspect of the present invention, a device for identifying and locating a single-phase ground fault on the low-voltage side of a synchronous motor excitation transformer is provided, comprising:

[0037] A data acquisition unit, used for reading or collecting the excitation DC side voltage and the excitation AC side voltage data of the synchronous motor;

[0038] The calculation unit is used to calculate the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage, the ground fault coefficient k, and the phase angle difference between the fundamental wave component of the excitation DC side voltage and the fundamental wave component of each phase voltage of the excitation AC side in real time. and corrected phase angle difference

[0039] The logic judgment unit judges whether a single-phase grounding fault occurs on the low-voltage side of the excitation transformer based on the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage. If so, the fault phase is identified based on the phase angle difference between the fundamental wave component of the excitation DC side voltage and the fundamental wave component of each phase voltage on the excitation AC side; otherwise, the fault identification process is terminated.

[0040] According to a third aspect of the present invention, an electronic device is proposed, comprising: a processor; and a memory storing computer instructions, wherein when the computer instructions are executed by the processor, the processor executes the method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer as described above.

[0041] According to a fourth aspect of the present invention, a non-transitory computer storage medium is proposed, storing a computer program. When the computer program is executed by multiple processors, the processors execute the method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer as described above.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) The present invention performs fault judgment based on the fundamental component of the excitation DC side voltage and the phase voltage of the excitation AC side. When a single-phase grounding fault occurs on the low-voltage side of the excitation transformer, the fundamental component of the excitation DC side voltage is only related to the grounding resistance and the capacitance of the excitation winding to the ground, while the phase voltage of the excitation AC side is not affected by changes in the rectifier control angle. Therefore, the present invention has higher reliability.

[0044] (2) The present invention fully considers the phase angle relationship between the fundamental component of the excitation DC side voltage and the phase voltage on the excitation AC side, and realizes the automatic identification function of the ground fault phase by calculating the phase angle relationship, instead of relying solely on the phase voltage on the low-voltage side of the excitation transformer which is difficult to observe. Therefore, the present invention is more feasible. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a schematic diagram of an application scenario of an exemplary embodiment of the present invention;

[0046] Figure 2 is a schematic diagram of a method flow provided by an exemplary embodiment of the present invention;

[0047] Figure 3 is a schematic diagram of a fault circuit provided by an exemplary embodiment of the present invention;

[0048] Figure 4 It is a timing diagram of the rotor positive voltage to ground, the rotor negative voltage to ground and the three-phase voltage data on the high-voltage side of the excitation transformer collected during a fault process in an exemplary embodiment of the present invention;

[0049] Figure 5 is a timing diagram of the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage during a fault process in an exemplary embodiment of the present invention;

[0050] Figure 6 is a timing diagram of a ground fault coefficient during a fault process in an exemplary embodiment of the present invention;

[0051] Figure 7 It is a timing diagram of the phase angle difference and the corrected phase angle difference of the fundamental wave component of the excitation DC side voltage and the fundamental wave component of the excitation AC side voltage during a fault process in an exemplary embodiment of the present invention;

[0052] Figure 8 It is a structural schematic diagram of a device for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer provided in an exemplary embodiment of the present invention.

[0053] Fig. 9 is a structural diagram of an electronic device provided by an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0054] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] The present invention provides a method, device and electronic equipment for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer, which is applied to a self-parallel-excited synchronous motor. Figure 1 The figure is a schematic diagram of an application scenario of an exemplary embodiment of the present invention.

[0056] Figure 2 A schematic flow chart of a method provided by an exemplary embodiment of the present invention is shown, and the method comprises the following steps:

[0057] Step 1, obtaining the excitation DC side voltage and the excitation AC side voltage of the synchronous motor;

[0058] Step 2, calculating the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage;

[0059] Step 3: determine whether a single-phase grounding fault occurs on the low-voltage side of the excitation transformer based on the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage. If yes, proceed to step 4; otherwise, end the fault identification process.

[0060] Step 4, respectively calculating the phase angle difference between the fundamental wave component of the excitation DC side voltage and the fundamental wave component of each phase voltage of the excitation AC side, and identifying the fault phase according to the phase angle difference.

[0061] According to some preferred embodiments, the excitation DC side voltage in step 1 is the positive voltage of the rotor to ground or the negative voltage of the rotor to ground, and the excitation AC side voltage is the high voltage side phase voltage of the excitation transformer or the low voltage side phase voltage of the excitation transformer.

[0062] According to some preferred embodiments, the step 1, obtaining the excitation DC side voltage and the excitation AC side voltage data, is specifically: reading the excitation DC side voltage and the excitation AC side voltage data from an acquisition device, or directly acquiring the excitation DC side voltage and the excitation AC side voltage data.

[0063] According to some preferred embodiments, the acquisition device is a synchronous motor protection device or a fault recording device.

[0064] According to some preferred embodiments, judging whether a single-phase grounding fault occurs on the low-voltage side of the excitation transformer based on the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage in step 3 specifically includes:

[0065] If the effective value of the fundamental component of the excitation DC side voltage is greater than the DC side set value threshold U dc.set , the effective value of the fundamental component of the excitation AC side voltage is greater than the AC side set value threshold U ac.set , and the ground fault coefficient k is greater than the ground fault coefficient constant K set , it is determined that a single-phase grounding fault occurs on the low-voltage side of the excitation transformer, otherwise it is determined that no single-phase grounding fault occurs on the low-voltage side of the excitation transformer;

[0066] The calculation formula of the ground fault coefficient is:

[0067]

[0068] Where, k represents the ground fault coefficient, U dc Indicates the effective value of the fundamental component of the excitation DC side voltage, U ac It represents the effective value of the fundamental component of the excitation AC side voltage, and k0 represents the voltage conversion coefficient.

[0069] According to some preferred embodiments, the effective value of the fundamental wave component of the excitation AC side voltage U acIt is the maximum or average effective value of the fundamental component of the three-phase voltage on the high-voltage side of the excitation transformer, or the maximum or average effective value of the fundamental component of the three-phase voltage on the low-voltage side of the excitation transformer.

[0070] According to some preferred embodiments, the DC side set value threshold U dc.set The value range is 5~10V; the AC side set value threshold U ac.set The value range is 0.8U n ~0.9U n , if the excitation AC side voltage is the phase voltage on the high voltage side of the excitation transformer, then U n Indicates the rated phase voltage on the high voltage side of the excitation transformer; if the excitation AC side voltage is the phase voltage on the low voltage side of the excitation transformer, then U n Indicates the rated phase voltage on the low-voltage side of the excitation transformer.

[0071] According to some preferred embodiments, in step 3: if the excitation AC side voltage is the high voltage side phase voltage of the excitation transformer, the voltage conversion coefficient k0 is the transformation ratio k of the excitation transformer. T ; If the excitation AC side voltage is the low-voltage side phase voltage of the excitation transformer, the voltage conversion coefficient k0 is 1.

[0072] According to some preferred embodiments, in step 3, the ground fault coefficient constant K set The value range is 0.01 to 0.4.

[0073] According to some preferred embodiments, the phase angle difference calculation formula between the fundamental wave component of the excitation DC side voltage and the fundamental wave component of each phase voltage of the excitation AC side is:

[0074]

[0075] In the formula, It represents the phase angle difference between the fundamental component of the excitation DC side voltage and the fundamental component of the excitation AC side phase voltage. A, B, and C are taken to represent phase A, phase B, and phase C respectively; θ dc It represents the phase angle of the fundamental component of the excitation DC side voltage, Indicates the excitation AC side Phase angle of the fundamental component of the phase voltage;

[0076] The step of identifying the fault phase according to the phase angle difference specifically includes:

[0077] According to the phase difference calculate Phase correction phase angle difference The calculation formula is:

[0078]

[0079] In the formula, express The corrected phase angle difference of the phase; Δθ0 represents the conversion angle; θ represents the phase angle deviation caused by the grounding resistor and capacitor. The calculation formula of θ is:

[0080] θ=180°-arctan(ωR g C g ) Formula (4)

[0081] In the formula, arctan represents the inverse tangent function, R g Indicates the grounding resistance of the fault point, C g Indicates the capacitance of the excitation winding to ground;

[0082] if Phase correction phase angle difference Less than the angle determination value Δθ set , then judge Phase is the fault phase;

[0083] Among them, Δθ set Indicates the angle determination value, ranging from 5 to 10°.

[0084] According to some preferred embodiments, if the excitation AC side voltage is the phase voltage on the high-voltage side of the excitation transformer, the conversion angle Δθ0 is the angle at which the phase voltage on the high-voltage side of the excitation transformer leads the corresponding phase voltage on the low-voltage side of the excitation transformer; if the excitation AC side voltage is the phase voltage on the low-voltage side of the excitation transformer, the conversion angle Δθ0 is 0°.

[0085] Taking the parameters of a domestic 660MW steam turbine synchronous generator set and a single-phase grounding fault on the low-voltage side of an excitation transformer as an example, the technical solution of the present invention is specifically described.

[0086] Figure 3 is a schematic diagram of a fault circuit provided by an exemplary embodiment of the present invention, wherein: U h Represents the three-phase voltage on the high-voltage side of the excitation transformer, and the rated phase voltage is T represents the excitation transformer, the wiring method is Yd-11, the transformation ratio is k T is 22kV / 0.9kV; F represents the ground fault point, the fault point is on phase C, and the ground resistance R g 1kΩ; thyristor V T1 —V T6 The three-phase rectifier bridge is formed, and its rectifier control angle is 60°; the excitation winding resistance R r is 0.175Ω, the excitation winding inductance L ris 1.368H; the distributed capacitances C1 and C2 of the excitation winding to the ground are both 2μF. The fault time is 50ms, and the calculation and fault identification and positioning are performed according to the steps of the method of the present invention, the steps are as follows:

[0087] Select the rotor positive voltage U r+ As the excitation DC side voltage, the high-voltage side voltage of the excitation transformer is selected as the excitation AC side voltage. The timing diagram of the rotor positive voltage to ground, the rotor negative voltage to ground and the three-phase voltage data on the high-voltage side of the excitation transformer collected during the fault process is shown in the figure below: Figure 4 shown.

[0088] In this embodiment, the full-cycle Fourier algorithm is preferably used, and the effective value of the fundamental component of the excitation AC side voltage U ac Take the effective value of the three-phase voltage on the high-voltage side of the excitation transformer U h.A , U h.B , U h.C The average value of the excitation DC side voltage fundamental component U during the fault process is calculated. dc And the effective value of the fundamental component of the excitation AC side voltage U ac The timing diagram of the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage during the fault process is shown in Figure 5 shown.

[0089] In this embodiment, the DC side constant threshold U dc.set Set to 10V; AC side set value threshold U ac.set Set to 0.8U n , which is 10.16kV. Figure 5 It can be seen that after the fault occurs, the effective value of the fundamental component of the excitation DC side voltage U dc Greater than the DC side set value threshold U dc.set And the effective value of the fundamental component of the excitation AC side voltage U ac Greater than the AC side set value threshold U ac.set In this embodiment, the voltage on the excitation AC side is the voltage on the high voltage side of the excitation transformer, so the voltage conversion coefficient k0 is the transformation ratio k of the excitation transformer. T , thus calculating the ground fault coefficient k during the fault process. The ground fault coefficient time sequence diagram during the fault process is as follows Figure 6 In this embodiment, the ground fault coefficient constant K set Take 0.05, then Figure 6 It can be seen that after the fault occurs, the ground fault coefficient k is greater than the ground fault coefficient constant K set Therefore, it is determined that a single-phase grounding fault has occurred on the low-voltage side of the excitation transformer, and the step of locating the fault phase is entered.

[0090] The value of θ is 128.5° calculated from the grounding resistance of the fault point and the capacitance of the excitation winding to the ground. The value of Δθ0 is -30° according to the excitation transformer connection mode Yd-11. The phase angle difference Δθ between the fundamental component of the excitation DC side voltage and each phase voltage of the excitation AC side is calculated respectively. A , Δθ B With Δθ C , and then calculate the correction phase angle difference β of phases A, B, and C respectively A , β B With β C ,like Figure 7 In this embodiment, the angle determination value Δθ set Take 5°, then Figure 7 It can be seen that only β C Less than the angle determination value Δθ set , so it is determined that the fault phase is phase C.

[0091] The above identification and positioning results are consistent with the fault situation, verifying the technical solution provided by the present invention.

[0092] In another embodiment, for the above-mentioned domestic 660MW steam turbine synchronous generator set, when the rectification control angle of the three-phase rectifier bridge is 45°, 60° and 75°, and through a variety of single-phase grounding faults on the low-voltage side of the excitation transformer with different grounding resistances (0-10kΩ), the process steps of the method of the present invention are used to calculate the calculation results of some intermediate steps of the method after the fault as shown in Table 1, as well as the grounding fault coefficient k, the correction phase angle difference Ground fault coefficient constant K set Still take 0.05, angle determination value Δθ set Still take 5°.

[0093] Table 1 Calculation results of different grounding resistance faults at different rectifier control angles (a) Rectifier control angle is 45°

[0094]

[0095] (b) The rectifier control angle is 60°

[0096]

[0097] (c) The rectifier control angle is 75°

[0098]

[0099] The calculation results in Table 1 show that under various fault conditions with different rectifier control angles and different grounding resistances, the grounding fault coefficient k calculated in step 3 is greater than the grounding fault coefficient constant K. set , the corrected phase angle difference calculated in step 4 Only β C Less than the angle determination value Δθ set , thus indicating that the present invention can correctly identify the single-phase grounding fault on the low-voltage side of the excitation transformer and accurately locate the faulty phase under different fault conditions.

[0100] If the data of the above different fault conditions are used to calculate the ground fault coefficient k according to the method described in the prior art document "Online Identification Method of Single-Phase Ground Fault on Low Voltage Side of Excitation Transformer" (Chen Jun, Wang Yunfan, Yan Wei, etc., "Electric Power Automation Equipment", Vol. 34, No. 11, 2014), the calculation results shown in Table 2 can be obtained. According to the ground fault coefficient constant K described in the document set The range is 0.2 to 0.4, and the most sensitive threshold value is 0.2.

[0101] Table 2 Calculation results of the method in the literature "Online identification method for single-phase ground fault on the low-voltage side of the excitation transformer"

[0102]

[0103]

[0104] Comparing the calculation results in Table 1 and Table 2, we can see that:

[0105] The sensitivity of the method in the document "Online Identification Method for Single-Phase Grounding Fault on Low Voltage Side of Excitation Transformer" is greatly affected by the rectifier control angle. When the rectifier control angle decreases, the sensitivity of the criterion decreases significantly, and the fault cannot be identified when the grounding resistance is large; and it does not have the function of locating the fault phase. However, when the method of the present invention is used, when the grounding resistance is the same, the calculated grounding fault coefficient k is almost the same and does not change with the rectifier control angle. Therefore, this method has stronger applicability.

[0106] Figure 8 A schematic diagram showing the structure of a device for identifying and locating a single-phase ground fault on the low-voltage side of a synchronous motor excitation transformer provided by an exemplary embodiment of the present invention includes:

[0107] A data acquisition unit, used for reading or collecting the excitation DC side voltage and the excitation AC side voltage data of the synchronous motor;

[0108] The calculation unit is used to calculate the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage, the ground fault coefficient k, and the phase angle difference between the fundamental wave component of the excitation DC side voltage and the fundamental wave component of each phase voltage of the excitation AC side in real time. and corrected phase angle difference

[0109] The logic judgment unit judges whether a single-phase grounding fault occurs on the low-voltage side of the excitation transformer based on the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage. If so, the fault phase is identified based on the phase angle difference between the fundamental wave component of the excitation DC side voltage and the fundamental wave component of each phase voltage on the excitation AC side; otherwise, the fault identification process is terminated.

[0110] Figure 8 The device shown can execute the aforementioned method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer according to an embodiment of the present invention.

[0111] The device performs functions similar to the method provided above. For other functions, please refer to the previous description and will not be repeated here.

[0112] Fig. 9 The structure diagram of an electronic device provided by the present invention is shown, which includes a processor and a memory. The memory stores computer instructions, and when the computer instructions are executed by the processor, the processor executes the computer instructions to implement the method and detailed solution described above.

[0113] It should be understood that the above device embodiments are only illustrative, and the device disclosed in the present invention can also be implemented in other ways. For example, the division of units / modules described in the above embodiments is only a logical function division, and there may be other division methods in actual implementation. For example, multiple units, modules or components can be combined, or can be integrated into another system, or some features can be ignored or not executed.

[0114] In addition, unless otherwise specified, each functional unit / module in each embodiment of the present invention may be integrated into one unit / module, each unit / module may exist physically separately, or two or more units / modules may be integrated together. The above-mentioned integrated unit / module may be implemented in the form of hardware or in the form of a software program module.

[0115] If the integrated unit / module is implemented in the form of hardware, the hardware may be a digital circuit, an analog circuit, etc. The physical implementation of the hardware structure includes but is not limited to transistors, memristors, etc. If not otherwise specified, the processor or chip may be any appropriate hardware processor, such as a CPU, a GPU, an FPGA, a DSP, an ASIC, etc. If not otherwise specified, the on-chip cache, the off-chip memory, and the memory may be any appropriate magnetic storage medium or magneto-optical storage medium, such as a resistive random access memory RRAM (Resistive Random Access Memory), a dynamic random access memory DRAM (Dynamic Random Access Memory), a static random access memory SRAM (Static Random-Access Memory), an enhanced dynamic random access memory EDRAM (Enhanced Dynamic Random Access Memory), a high-bandwidth memory HBM (High-Bandwidth Memory), a hybrid memory cube HMC (Hybrid Memory Cube), etc.

[0116] If the integrated unit / module is implemented in the form of a software program module and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, which is stored in a memory and includes several instructions for a computer device (which can be a personal computer, a server or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present disclosure. The aforementioned memory includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk and other media that can store program codes.

[0117] An embodiment of the present invention further provides a non-transitory computer storage medium storing a computer program. When the computer program is executed by multiple processors, the processors execute the method and the refined scheme described above.

[0118] It should be clearly understood that the present invention describes how to form and use specific examples, but the present invention is not limited to any details of these examples. On the contrary, based on the teachings of the content disclosed in the present invention, these principles can be applied to many other embodiments.

[0119] In addition, it should be noted that the above-mentioned figures are only schematic illustrations of the processes included in the method according to an exemplary embodiment of the present invention, and are not intended to be limiting. It is easy to understand that the processes shown in the above-mentioned figures do not indicate or limit the time sequence of these processes. In addition, it is also easy to understand that these processes can be performed synchronously or asynchronously, for example, in multiple modules.

[0120] The above embodiments are only for illustrating the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any equivalent replacement or modification made on the basis of the technical solution in accordance with the technical idea proposed by the present invention does not exceed the protection scope of the present invention.

Claims

1. A method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer, characterized in that: The following steps are involved: Step 1, obtaining the excitation DC side voltage and the excitation AC side voltage of the synchronous motor; Step 2, calculating the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage; Step 3: determine whether a single-phase grounding fault occurs on the low-voltage side of the excitation transformer based on the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage. If yes, proceed to step 4; otherwise, end the fault identification process. Step 4, respectively calculating the phase angle difference between the fundamental wave component of the excitation DC side voltage and the fundamental wave component of each phase voltage of the excitation AC side, and identifying the fault phase according to the phase angle difference.

2. The method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer according to claim 1 is characterized in that: The excitation DC side voltage in step 1 is the positive voltage of the rotor to the ground or the negative voltage of the rotor to the ground, and the excitation AC side voltage is the high voltage side phase voltage of the excitation transformer or the low voltage side phase voltage of the excitation transformer.

3. The method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer according to claim 1 is characterized in that: The step 1, obtaining the excitation DC side voltage and the excitation AC side voltage data, specifically comprises: reading the excitation DC side voltage and the excitation AC side voltage data from a collection device, or directly collecting the excitation DC side voltage and the excitation AC side voltage data.

4. The method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer according to claim 3 is characterized in that: The acquisition device is a synchronous motor protection device or a fault recording device.

5. The method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer according to claim 1 is characterized in that: The step 3 of judging whether a single-phase grounding fault occurs on the low-voltage side of the excitation transformer based on the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage specifically includes: If the effective value of the fundamental component of the excitation DC side voltage is greater than the DC side set value threshold U dc.set , the effective value of the fundamental component of the excitation AC side voltage is greater than the AC side set value threshold U ac.set , and the ground fault coefficient k is greater than the ground fault coefficient constant K set , it is determined that a single-phase grounding fault occurs on the low-voltage side of the excitation transformer, otherwise it is determined that no single-phase grounding fault occurs on the low-voltage side of the excitation transformer; The calculation formula of the ground fault coefficient is: Where, k represents the ground fault coefficient, U dc Indicates the effective value of the fundamental component of the excitation DC side voltage, U ac It represents the effective value of the fundamental component of the excitation AC side voltage, and k0 represents the voltage conversion coefficient.

6. The method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer according to claim 5 is characterized in that: The effective value of the fundamental component of the excitation AC side voltage U ac It is the maximum or average effective value of the fundamental component of the three-phase voltage on the high-voltage side of the excitation transformer, or the maximum or average effective value of the fundamental component of the three-phase voltage on the low-voltage side of the excitation transformer.

7. The method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer according to claim 5, characterized in that: The DC side set value threshold U dc.set The value range is 5~10V; the AC side set value threshold U ac.set The value range is 0.8U n ~0.9U n , if the excitation AC side voltage is the phase voltage on the high voltage side of the excitation transformer, then U n Indicates the rated phase voltage on the high voltage side of the excitation transformer; if the excitation AC side voltage is the phase voltage on the low voltage side of the excitation transformer, then U n Indicates the rated phase voltage on the low-voltage side of the excitation transformer.

8. The method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer according to claim 5, characterized in that: In step 3: if the excitation AC side voltage is the phase voltage on the high voltage side of the excitation transformer, the voltage conversion coefficient k0 is the transformation ratio k of the excitation transformer. T ; If the excitation AC side voltage is the low-voltage side phase voltage of the excitation transformer, the voltage conversion coefficient k0 is 1.

9. The method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer according to claim 5, characterized in that: In step 3, the ground fault coefficient constant K set The value range is 0.01 to 0.

4.

10. The method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer according to claim 1, characterized in that: The calculation formula of the phase angle difference between the fundamental wave component of the excitation DC side voltage and the fundamental wave component of each phase voltage of the excitation AC side is: In the formula, It represents the phase angle difference between the fundamental component of the excitation DC side voltage and the fundamental component of the excitation AC side phase voltage. A, B, and C are taken to represent phase A, phase B, and phase C respectively; θ dc It represents the phase angle of the fundamental component of the excitation DC side voltage, Indicates the excitation AC side Phase angle of the fundamental component of the phase voltage; The step of identifying the fault phase according to the phase angle difference specifically includes: According to the phase difference calculate Phase correction phase angle difference The calculation formula is: In the formula, express The corrected phase angle difference of the phase; Δθ0 represents the conversion angle; θ represents the phase angle deviation caused by the grounding resistor and capacitor. The calculation formula of θ is: θ = 180° - arctan(ωR g C g ) Equation (4) In the formula, arctan represents the inverse tangent function, R g Indicates the grounding resistance of the fault point, C g Indicates the capacitance of the excitation winding to ground; if Phase correction phase angle difference Less than the angle determination value Δθ set , then judge Phase is the fault phase; Among them, Δθ set Indicates the angle determination value, ranging from 5 to 10°.

11. The method for identifying and locating a single-phase grounding fault on the low-voltage side of a synchronous motor excitation transformer according to claim 10, characterized in that: If the excitation AC side voltage is the phase voltage on the high voltage side of the excitation transformer, the conversion angle Δθ0 is the angle at which the phase voltage on the high voltage side of the excitation transformer leads the corresponding phase voltage on the low voltage side of the excitation transformer; If the excitation AC side voltage is the low-voltage side phase voltage of the excitation transformer, the conversion angle Δθ0 is 0°.

12. A device for identifying and locating single-phase grounding faults on the low-voltage side of a synchronous motor excitation transformer, characterized in that: include: A data acquisition unit, used for reading or collecting the excitation DC side voltage and the excitation AC side voltage data of the synchronous motor; The calculation unit is used to calculate the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage, the ground fault coefficient k, and the phase angle difference between the fundamental wave component of the excitation DC side voltage and the fundamental wave component of each phase voltage of the excitation AC side in real time. and corrected phase angle difference The logic judgment unit judges whether a single-phase grounding fault occurs on the low-voltage side of the excitation transformer based on the effective value of the fundamental wave component of the excitation DC side voltage and the effective value of the fundamental wave component of the excitation AC side voltage. If so, the fault phase is identified based on the phase angle difference between the fundamental wave component of the excitation DC side voltage and the fundamental wave component of each phase voltage on the excitation AC side; otherwise, the fault identification process is terminated.

13. An electronic device, characterized in that: include: processor; as well as A memory storing computer instructions, which, when executed by the processor, causes the processor to execute the method according to any one of claims 1 to 11.

14. A non-transitory computer storage medium storing a computer program, which, when executed by a plurality of processors, causes the processors to execute the method according to any one of claims 1 to 11.

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