Generator rotor winding turn-to-turn short circuit fault judgment method and system

Abstract

The invention discloses a generator rotor winding turn-to-turn short circuit fault judgment method and system, and relates to the technical field of generator fault detection. Calculating a real-time excitation current theoretical value by considering the saturation characteristic of the generator based on the operation parameters; the excitation current deviation ratio is calculated through the real-time excitation current theoretical value and the current excitation current actual value; and judging the running state of the generator rotor according to the excitation current deviation ratio. According to the generator rotor winding turn-to-turn short-circuit fault judgment method provided by the invention, on the basis of not damaging the original structure of the generator, the generator rotor winding turn-to-turn short-circuit fault judgment is carried out after the generator saturation state correction by collecting the operation parameters of the generator in the existing system; the method can be carried out in a non-stop state of the generator, normal operation of the generator is not affected, and the calculation precision of online measurement when the generator operates in a saturation state is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of generator fault detection, and particularly to a method and system for judging the inter-turn short circuit fault of a generator rotor winding. Background Art

[0002] The rotor is an important part of a generator, which mainly includes a rotating shaft, a pole winding, a damper winding, etc. The generator rotor has a large moment of inertia and operates at a high speed normally, causing the rotor coil to bear a large centrifugal force for a long time. Under the action of the centrifugal force, the turns of the rotor winding will be deformed or loosened. When exceeding the bearing limit of the rotor, the insulation between turns of the rotor winding is damaged, which will cause a short circuit fault of the rotor winding.

[0003] Statistical data shows that the inter-turn short circuit of the rotor winding is a relatively easy-to-occur fault of the generator. A slight inter-turn short circuit has a great impact on the operation of the generator, so it is easy to be ignored and allowed to continue to develop. When the inter-turn short circuit of the rotor winding develops to a certain extent, the rotor current will increase significantly, the winding temperature will rise significantly, the waveform of the terminal voltage of the machine will be distorted, the vibration amplitude of the unit will increase, and other mechanical faults will occur. Therefore, it is very necessary and significant to monitor the inter-turn short circuit fault of the rotor winding.

[0004] At present, the methods for judging the inter-turn short circuit fault of the rotor include the AC impedance and power loss method, the inter-pole voltage method, the coil voltage method, the recurrent surge oscillograph (RSO for short), the method of changing the excitation current and reactive power, the method of detecting the coil waveform, etc. Some of these methods can only be tested offline, some are tested online but require the installation of special sensors to damage the original structure of the generator, and some are tested online but there are problems of inaccurate measurement due to the influence of the generator saturation effect. Summary of the Invention

[0005] In view of the above problems, the present invention is proposed.

[0006] Therefore, the technical problems solved by the present invention are: monitoring and judging the insulation state between turns of the generator rotor winding without damaging the original structure of the generator; the problem that online measurement is inaccurate due to the saturation effect under the saturated state of the generator.

[0007] To solve the above technical problems, the present invention provides the following technical solution: A method for judging the inter-turn short circuit fault of a generator rotor winding, including:

[0008] Obtaining the operation parameters of the generator;

[0009] Calculating the theoretical value of the real-time excitation current based on the operation parameters and considering the saturation characteristics of the generator;

[0010] Calculate the excitation current deviation ratio based on the theoretical value of the real-time excitation current and the actual value of the current excitation current;

[0011] Judge the operating state of the generator rotor according to the excitation current deviation ratio.

[0012] As a preferred scheme of the method for judging the inter-turn short-circuit fault of the generator rotor winding described in the present invention, wherein: the acquisition of the generator operating parameters includes acquiring the generator operating voltage and current, active power, and reactive power by communicating with the excitation regulator;

[0013] Measure and obtain the mechanical angle by installing an absolute photoelectric encoder sensor;

[0014] Obtain the no-load characteristic curve of the generator through the test data of the generator.

[0015] As a preferred scheme of the method for judging the inter-turn short-circuit fault of the generator rotor winding described in the present invention, wherein: the calculation of the theoretical value of the real-time excitation current includes fitting the generator saturation characteristic using an exponential function according to the generator no-load characteristic data;

[0016] Estimate the initial slope, saturation potential, and time constant, optimize according to the nonlinear least squares method, and establish an objective function;

[0017] Use an optimization algorithm to iteratively solve to determine the optimal slope, saturation potential, and time constant parameters;

[0018] Calculate the potential of the generator in the unsaturated state according to the determined slope;

[0019] Determine the saturation coefficient of the generator;

[0020] Calculate the power angle of the generator using the mechanical angle measured by the photoelectric encoder sensor and the voltage signal collected in real time;

[0021] Calculate the theoretical value of the excitation current using the saturation coefficient and the power angle of the generator.

[0022] As a preferred scheme of the method for judging the inter-turn short-circuit fault of the generator rotor winding described in the present invention, wherein: the exponential function is expressed as,

[0023]

[0024] In the formula, E sat.m is the iron core saturation limit potential, τ is the saturation time constant, k is the initial slope in the unsaturated region, I f is the excitation current;

[0025] The objective function is expressed as,

[0026]

[0027] The potential is expressed as,

[0028] E usat = k·I f ;

[0029] The saturation coefficient is expressed as,

[0030]

[0031] where E usat represents the unsaturated potential, and E sat represents the saturated potential.

[0032] As a preferred embodiment of the method for judging the inter-turn short circuit fault of the generator rotor winding according to the present invention, wherein: the theoretical value of the real-time excitation current is expressed as,

[0033]

[0034] e q = Ucosδ

[0035]

[0036] X ad = K sat X adu

[0037] where X adu is the unsaturated direct-axis reactance value of the generator, and its value is equal to the k value in per-unit value, is the power factor angle, i d , i q are the direct-axis and quadrature-axis currents respectively, e q is the quadrature-axis potential, R a is the stator resistance of the generator, X d is the direct-axis reactance of the generator, I f_ideal is the theoretical value of the excitation current, and X ad is the direct-axis reactance value of the generator after saturation correction.

[0038] As a preferred embodiment of the method for judging the inter-turn short circuit fault of the generator rotor winding according to the present invention, wherein: the excitation current deviation ratio is expressed as,

[0039]

[0040] where I f_real is the actual value of the current.

[0041] As a preferred solution of the method for judging the inter-turn short-circuit fault of the generator rotor winding described in the present invention, wherein: judging the operating state of the generator rotor includes judging it as a normal state when p% ≤ 5%;

[0042] When 5% < p% < 10%, it is judged as a slight short circuit, an alarm signal is sent, and its operating state is continuously monitored;

[0043] When 10% ≤ p%, it is judged as a serious short circuit.

[0044] Another object of the present invention is to provide a system for judging the inter-turn short-circuit fault of the generator rotor winding, which can more accurately judge the operating state of the generator rotor by constructing a system for judging the inter-turn short-circuit fault of the generator rotor winding, and improve the online fault diagnosis accuracy.

[0045] To solve the above technical problems, the present invention provides the following technical solution: A system for judging the inter-turn short-circuit fault of the generator rotor winding, including: an acquisition module for acquiring the system operating parameters and the rotor mechanical angle in the generator excitation regulator; a calculation module for calculating the real-time theoretical value and the deviation ratio between the theoretical value and the measured value; a monitoring module for judging the operating state of the generator rotor.

[0046] A computer device includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the method for judging the inter-turn short-circuit fault of the generator rotor winding as described above are implemented.

[0047] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method for judging the inter-turn short-circuit fault of the generator rotor winding as described above are implemented.

[0048] The beneficial effects of the present invention: The method for judging the inter-turn short-circuit fault of the generator rotor winding provided by the present invention, without damaging the original structure of the generator, judges the inter-turn short-circuit fault of the generator rotor winding by collecting the operating parameters of the generator in the existing system and correcting through the generator saturation state. This method can be carried out without shutting down the generator, does not affect the normal operation of the generator, and improves the calculation accuracy of online measurement when the generator is operating in the saturation state. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0050] Figure 1The overall flowchart of a method for judging the inter-turn short-circuit fault of a generator rotor winding provided by an embodiment of the present invention.

[0051] Figure 2 The overall structure diagram of a system for judging the inter-turn short-circuit fault of a generator rotor winding provided by an embodiment of the present invention.

[0052] Figure 3 The schematic diagram of the fitting of the no-load characteristic of a generator for a method for judging the inter-turn short-circuit fault of a generator rotor winding provided by an embodiment of the present invention.

[0053] Figure 4 The flowchart of the fitting of the no-load characteristic of a generator for a method for judging the inter-turn short-circuit fault of a generator rotor winding provided by an embodiment of the present invention.

[0054] Figure 5 The flowchart for calculating the power angle of a generator for a method for judging the inter-turn short-circuit fault of a generator rotor winding provided by an embodiment of the present invention.

[0055] Figure 6 The schematic diagram of the system for judging the inter-turn short-circuit fault of a generator rotor winding of a system for judging the inter-turn short-circuit fault of a generator rotor winding provided by an embodiment of the present invention. Detailed implementation manners

[0056] To make the above objects, features and advantages of the present invention more obvious and understandable, the following will describe the detailed implementation manners of the present invention in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0057] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0058] Example 1, referring to Figure 1 、 Figure 3 、 Figure 4 and Figure 5 , an embodiment of the present invention provides a method for judging the inter-turn short-circuit fault of a generator rotor winding, including:

[0059] Step S1, obtaining the operating voltage and current, active power, reactive power, mechanical angle, no-load characteristic curve and basic parameters of the generator.

[0060] The basic parameters include, but are not limited to, generator capacity, transient reactance, subtransient reactance, etc.

[0061] In step S1, the operating voltage and current, active power, and reactive power of the generator can be obtained by communicating with the excitation regulator. The mechanical angle can be measured by installing an absolute photoelectric encoder sensor. The no-load characteristic curve of the generator can be obtained from the test data of the generator.

[0062] In step S1, the obtained generator operating parameters can be sent to the generator rotor winding inter-turn short circuit monitoring system for subsequent processing and storage of steps.

[0063] Step S2, calculate the theoretical value of the real-time excitation current considering the saturation characteristics of the generator based on the obtained data and parameters. First, fit the saturation characteristics of the generator according to the no-load characteristic data of the generator. In order to achieve higher accuracy and reflect the physical essence of saturation, an exponential function is used for fitting, as shown in Equation (1):

[0064]

[0065] In the formula, E sat.m is the iron core saturation limit electromotive force, τ is the saturation time constant, k is the initial slope in the unsaturated region, and I f is the excitation current.

[0066] As Figure 3 shown, estimate the initial slope k 0 according to the data in Region I, generally the selection range is (0 - 0.7)I fn ; estimate the saturation electromotive force E sat.m0 and the time constant τ 0 according to the data in Region II. Region I is the linear region, Region II is the saturated region, and I fn represents the rated excitation current of the generator.

[0067] Then optimize the selected parameters according to the nonlinear least squares method, and set up the objective function as shown in Equation (2):

[0068]

[0069] Among them, N represents the total number, and Ei is the i-th measured electromotive force.

[0070] Use the Levenberg - Marquardt algorithm to iterate and solve to determine the optimal parameters k, E sat.m , τ, as Figure 4 shown in the process. The Levenberg - Marquardt algorithm combines the advantages of the Gauss - Newton method and the gradient descent method, can converge quickly when dealing with nonlinear least squares problems, and can also avoid some unstable problems.

[0071] According to the determined slope k, the electromotive force of the generator in the unsaturated state is calculated using formula (3):

[0072] E usat = k·I f (3)

[0073] The saturation coefficient of the generator is defined as:

[0074]

[0075] where E usat represents the unsaturated electromotive force, and E sat represents the saturated electromotive force.

[0076] That is, the ratio of the unsaturated electromotive force E usat to the saturated electromotive force E sat .

[0077] The mechanical angle and the voltage signal collected in real time are measured by the optoelectronic coding sensor, and the generator power angle δ is calculated according to the method shown in the following process. Figure 5

[0078] The saturation coefficient obtained by using formula (4) and the generator power angle δ are used to calculate the theoretical value of the excitation current according to the following steps.

[0079]

[0080] e q = Ucosδ (6)

[0081]

[0082]

[0083] X ad = K sat X adu (10)

[0084] where X adu is the unsaturated direct-axis reactance value of the generator, and its value in per-unit value is equal to the k value, is the power factor angle, i d , i q are the direct-axis and quadrature-axis currents respectively, e q is the quadrature-axis electromotive force, R a is the stator resistance of the generator, X d is the direct-axis reactance of the generator, I f_ideal is the theoretical value of the excitation current, and X ad is the direct-axis reactance value of the generator after saturation correction.

[0085] ​Step S3: Calculate the excitation current deviation ratio using the obtained real-time theoretical value of the excitation current and the actual value of the current excitation current, that is

[0086]

[0087] In the formula, I f_real is the actual value of the current.

[0088] In step S3, perform a fault judgment based on the calculated deviation ratio p%. According to the deviation ratio p%, the fault level is divided into three levels: normal state, slight short circuit, and serious fault;

[0089] When p% ≤ 5%, it is judged as the normal state;

[0090] When 5% < p% < 10%, it is judged as a slight short circuit;

[0091] When 10% ≤ p%, it is judged as a serious short circuit.

[0092] Step S4: Judge the operating state of the generator rotor according to the calculated excitation current deviation ratio.

[0093] In step S4, based on the deviation ratio calculated in step 3, judge the inter-turn short circuit state of the generator rotor winding. Specifically, if the deviation ratio is less than or equal to 5%, it is determined that the generator rotor is in a normal state; if the deviation ratio is greater than 5% and less than 10%, it is determined that there is a slight short circuit fault in the generator rotor winding, and an alarm signal can be issued to continue monitoring its operating state; if the deviation ratio is greater than or equal to 10%, it is determined that there is a serious fault in the generator rotor winding.

[0094] Example 2, referring to Figure 2 、 Figure 5 and Figure 6 , is an embodiment of the present invention, and provides a system for judging the inter-turn short circuit fault of a generator rotor winding, including:

[0095] Figure 2 Shows the block diagram of the system for judging the inter-turn short circuit fault of the generator rotor winding provided by the embodiment of the present disclosure. Figure 6 Shows the schematic diagram of the acquisition module provided by the embodiment of the present disclosure. This system for judging the inter-turn short circuit fault of the generator rotor winding can be realized by combining software and hardware.

[0096] This system 10 for judging the inter-turn short circuit fault of the generator rotor winding includes an acquisition module 11, a calculation module 12, and a judgment module 13.

[0097] Among them, the acquisition module 11 includes an absolute photoelectric encoder sensor acquisition unit and a communication acquisition unit with the excitation regulator. The absolute photoelectric encoder sensor is installed at the end of the generator rotor shaft to obtain the mechanical angle of the generator rotor, and then according toFigure 5 The process shown calculates the power angle of the generator; the operating parameters of the generator are obtained by communicating with the excitation system regulator.

[0098] The calculation module 12 is used for fitting the no-load characteristic of the generator, calculating the power angle of the generator, calculating the saturation coefficient of the generator, and calculating the excitation current deviation ratio;

[0099] The monitoring module 13 is used to judge the operating state of the inter-turn winding of the generator rotor. If the deviation ratio is less than or equal to 5%, it is determined that the generator rotor is in a normal state; if the deviation ratio is greater than 5% and less than 10%, it is determined that there is a slight short-circuit fault in the inter-turn of the generator rotor winding, and an alarm signal can be issued to continue monitoring its operating state; if the deviation ratio is greater than or equal to 10%, it is determined that there is a serious fault in the inter-turn of the generator rotor winding;

[0100] Optionally, the absolute photoelectric encoder sensor has a digital output function.

[0101] An absolute photoelectric encoder sensor is installed at the end of the generator rotor to obtain the mechanical angle of the generator operation; the operating parameters of the generator are obtained by communicating with the excitation system regulator; the basic parameters and no-load characteristic operation curve of the generator are obtained; the saturation characteristic of the generator is fitted according to the no-load characteristic operation curve; the theoretical value of the generator excitation current in the real-time operation state is calculated based on the obtained generator parameters considering the saturation characteristic of the generator; the excitation current deviation ratio is calculated according to the theoretical value and the real-time value of the excitation current; the operating state of the generator rotor is determined by judging the size of the calculated deviation ratio.

[0102] Embodiment 3, an embodiment of the present invention, which is different from the previous two embodiments in that:

[0103] If the said function is realized in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or a part of the technical solution can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. And the aforementioned storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs that can store program codes.

[0104] The logic and / or steps represented in the flowchart or otherwise described herein can, for example, be considered as a definitional sequence of executable instructions for implementing logical functions, which can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device. As used in this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.

[0105] More specific examples (non-exhaustive list) of computer-readable media include the following: an electrical connection part (electronic device) having one or more wirings, a portable computer diskette (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium can even be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpretation, or other appropriate processing as necessary, and then stored in a computer memory.

[0106] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application-specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), and the like.

[0107] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for judging a short-circuit fault in a generator rotor winding, characterized in that: Including: Obtain the operating parameters of the generator; Based on the operating parameters, considering the saturation characteristics of the generator, calculate the theoretical value of the real-time excitation current; Calculate the excitation current deviation ratio through the theoretical value of the real-time excitation current and the actual value of the current excitation current; Judge the operating state of the generator rotor according to the excitation current deviation ratio.

2. The generator rotor winding turn-to-turn short-circuit fault judgment method according to claim 1, characterized in that: The obtaining of the operating parameters of the generator includes obtaining the operating voltage and current, active power, and reactive power of the generator by communicating with the excitation regulator; Obtain the mechanical angle by measuring with an absolute photoelectric encoder sensor; Obtain the no-load characteristic curve of the generator through the test data of the generator.

3. The generator rotor winding turn-to-turn short-circuit fault judgment method according to claim 2, characterized in that: The calculating of the theoretical value of the real-time excitation current includes fitting the saturation characteristics of the generator using an exponential function according to the no-load characteristic data of the generator; Estimate the initial slope, saturation potential, and time constant, optimize according to the nonlinear least squares method, and set up an objective function; Use an optimization algorithm to iteratively solve to determine the optimal slope, saturation potential, and time constant parameters; Calculate the potential of the generator in the unsaturated state according to the determined slope; Determine the saturation coefficient of the generator; Calculate the power angle of the generator using the mechanical angle measured by the photoelectric encoder sensor and the voltage signal collected in real time; Calculate the theoretical value of the excitation current using the saturation coefficient and the power angle of the generator.

4. The generator rotor winding turn-to-turn short-circuit fault judgment method according to claim 3, characterized in that: The exponential function is expressed as In the formula, E sat.m is the core saturation limiting potential, τ is the saturation time constant, k is the initial slope of the unsaturated region, I f is the excitation current; The objective function is expressed as where N represents the total number, and Ei is the i-th measured potential. The potential is expressed as E usat =k·I f The saturation coefficient is expressed as Among them, E usat represents the unsaturated potential, E sat represents the saturation potential.

5. The generator rotor winding turn-to-turn short-circuit fault judgment method according to claim 4, characterized in that: The theoretical value of the real-time excitation current is expressed as And q =Ucosδ X ad =K sat X adu Among them, X adu is the unsaturated direct-axis reactance of the generator, which is equal to the k value at the per-unit value. is the power factor angle, i d 、i q are the direct-axis and quadrature-axis currents, e q is the cross-axis potential, R a is the stator resistance of the generator, X d is the direct axis reactance of the generator, I f_ideal is the theoretical value of the excitation current, X ad is the direct-axis reactance value of the generator after saturation correction.

6. The generator rotor winding turn-to-turn short-circuit fault judgment method according to claim 5, characterized in that: The excitation current deviation ratio is expressed as Among them, I f_real is the actual value of current.

7. The generator rotor winding turn-to-turn short circuit fault judgment method according to claim 6, characterized in that: The judging of the operating state of the generator rotor includes when p% ≤ 5%, judging it as a normal state; When 5% < p% < 10%, judge it as a minor short circuit, send an alarm signal, and continue to monitor its operating state; When 10% ≤ p%, judge it as a serious short circuit.

8. A system using the generator rotor winding turn-to-turn short-circuit fault judgment method as claimed in any one of claims 1 to 7, characterized in that: Including: An acquisition module for obtaining the system operating parameters and rotor mechanical angle in the generator excitation regulator; A calculation module for calculating the real-time theoretical value and the deviation ratio between the theoretical value and the measured value; A monitoring module for judging the operating state of the generator rotor.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, it implements the steps of the method for judging the inter-turn short circuit fault of the generator rotor winding according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the processor, it implements the steps of the method for judging the inter-turn short circuit fault of the generator rotor winding according to any one of claims 1 to 7.

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