An Automatic Verification Method for the Limiting Function of Generator Grid Connection Protection and Excitation System
By automatically verifying the generator grid connection protection and excitation system limiting functions, the problem of incoordination between generator protection and limiting functions during grid operation is solved, thus achieving safe and stable system operation and reducing the fault range.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- STATE GRID LIAONING ELECTRIC POWER CO LTD
- Filing Date
- 2022-12-23
- Publication Date
- 2026-06-30
AI Technical Summary
Improper setting of the control parameters of the generator grid protection and excitation system can lead to a lack of protection and limiting functions or incoordination of the generator during grid operation, resulting in system safety and stability problems.
An automatic verification method for generator grid connection protection and excitation system limiting functions is provided. By automatically verifying the corresponding limiting functions of generator rotor overload protection, loss of excitation protection, overexcitation protection, stator overvoltage protection and stator overload protection and excitation system, the method ensures that their operating characteristics are matched and coordinated, including automatic verification of functions such as overexcitation limitation, underexcitation limitation, volt-hertz limitation and stator overvoltage limitation.
It realizes automatic verification of generator grid connection protection and excitation system limiting functions, prevents protection failure and false operation, enhances system safety and stability, reduces the scope of fault damage, and improves the accuracy and efficiency of power plant management.
Smart Images
Figure CN115951216B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of power system technology, and in particular relates to an automatic verification method for generator grid connection protection and excitation system limiting functions. Background Technology
[0002] In recent years, with the construction of ultra-high voltage and high-voltage direct current transmission lines across the national power grid, and the development of new energy sources such as pumped storage, wind power, and photovoltaics, the power industry has increasingly emphasized the requirements related to grid-machine coordination. The latest national and industry standards have all put forward corresponding specific requirements.
[0003] The state has put forward requirements for grid-machine coordination to "prevent grid-machine coordination and large-scale wind power grid disconnection accidents." These requirements include: generator excitation systems, speed control systems, generator and transformer relay protection, low-frequency load shedding, generator primary frequency regulation, generator leading-phase operation, out-of-synchronization oscillation, and generator de-excitation asynchronous operation.
[0004] The excitation system is equipped with comprehensive limiting and protection units, including overexcitation limiting, underexcitation limiting, V / Hz limiting, and overvoltage protection. The generator-transformer unit protection system also includes excitation winding overload protection, loss of excitation protection, overexcitation protection, and generator overvoltage protection, all related to the excitation system. Therefore, the excitation system settings should be coordinated with the generator-transformer unit protection settings based on abnormal system operating conditions to fully utilize the limiting functions of the excitation system and ensure the safe and stable operation of the unit.
[0005] Currently, the settings for generator grid connection protection and excitation system control parameters are usually entrusted to commissioning units and equipment manufacturers for adjustment or setting, and some even use the commissioning settings from the infrastructure department. After the generator is put into normal operation, problems such as the lack of generator grid connection protection and limitation and coordination with the actual power grid are very likely to occur. Summary of the Invention
[0006] To address the shortcomings of the existing technologies, this invention provides an automatic verification method for the grid connection protection and excitation system limiting functions of generators. Its purpose is to automatically verify the coordination relationship between the grid connection protection and excitation system limiting functions of generators, prevent grid connection protection and limiting functions from failing to operate or malfunctioning, ensure the safe and stable operation of the system, reduce the scope of fault damage, and enhance the verification and management of grid connection protection and limiting settings in power plants.
[0007] The technical solution adopted by the present invention to achieve the above objectives is as follows:
[0008] An automatic verification method for the limiting function of generator grid connection protection and excitation system includes:
[0009] Automatic verification of generator rotor overload protection and excitation system overexcitation limitation function;
[0010] Automatic verification of generator loss-of-excitation protection and excitation system low-excitation limiting function;
[0011] Automatic verification of generator overexcitation protection and excitation system volt-hertz limiting function;
[0012] Automatic verification of generator stator overvoltage protection and excitation system stator overvoltage limiting function;
[0013] Automatic verification of generator stator overload protection and excitation system stator overcurrent limiting function.
[0014] Furthermore, the automatic verification of the generator rotor overload protection and excitation system overexcitation limiting function is as follows: the excitation system overexcitation limiting function needs to cooperate with the generator rotor overload protection in an inverse time-delay characteristic, which is a prerequisite for limiting the excitation current when obtaining the strong excitation time. The generator rotor overload protection setting is greater than the overexcitation limiter action setting, and at the same time, the generator rotor overload capacity corresponding value is greater than the rotor overload protection setting. The generator rotor overload capacity corresponding value, rotor overload protection setting and overexcitation limiter action setting decrease step by step, leaving a level difference among the three.
[0015] Furthermore, the automatic verification of the generator loss-of-excitation protection and excitation system low-excitation limiting function is as follows: the excitation system low-excitation limiting should act before the generator loss-of-excitation protection. The low-excitation limiting curve should match the static stability limit boundary and have a certain margin. From the beginning of generator loss of excitation until the final instability, the measured power and impedance at the generator terminal should first enter the low-excitation limiting region, and then enter the low-excitation protection region, finally obtaining the protection circle of loss of excitation.
[0016] Furthermore, the automatic verification of the generator overexcitation protection and excitation system volt-hertz limiting function is as follows: the excitation system volt-hertz limiting should match the generator's overexcitation characteristics, have definite-time and inverse-time characteristics, and the excitation regulation of the generator's dynamic process should not be affected by the operation of the voltage-frequency ratio limiting unit; the inverse-time characteristic adopts a non-functional multi-point expression method, which is coordinated with the definite-time and inverse-time characteristics of the overexcitation protection.
[0017] Furthermore, the automatic verification of the generator stator overvoltage protection and excitation system stator overvoltage limiting function: If the excitation system has a stator overvoltage limiting function, it should cooperate with the generator stator overvoltage protection. The limiting element should act before the unit protection. The stator overvoltage limiting of the excitation system is generally a time limit, with the same characteristics as the generator stator overvoltage protection.
[0018] Furthermore, the automatic verification of the generator stator overload protection and excitation system stator overcurrent limiting function is as follows: the excitation system stator overcurrent limiting should coordinate with the generator stator overload protection, following the principle that stator current limiting should act before stator overload protection. The stator overcurrent limiting action area should be smaller than the stator overload protection action area, and the stator overload protection action area should also be smaller than the generator's allowable overload capacity, with an appropriate margin.
[0019] Furthermore, the automatic verification of the generator rotor overload protection and excitation system overexcitation limiting function includes the following: the overexcitation inverse time characteristic function type is consistent with the generator magnetic field overcurrent characteristic function type; there is a level difference between the overexcitation inverse time and the generator rotor winding overload protection characteristic; the overexcitation inverse time delay under the peak current is reduced by 2 seconds compared to the generator rotor overload protection delay.
[0020] The overexcitation inverse-time starting value is less than the starting value of the generator rotor overload protection, which is 105%-110% of the generator's rated field current. The starting value does not affect the inverse-time characteristics. The forced excitation inverse-time limiting value is 5%-10% less than the starting value than the generator's rated field current to release accumulated heat. It can also be limited to the starting value. Then, based on the forced excitation limiting action signal, the field current is reduced.
[0021] The excitation system overexcitation limitation and generator rotor overload protection, along with the generator rotor forced excitation capability curve, follow the inverse-time overheating characteristic.
[0022]
[0023] In the formula: I * is the per-unit value of rotor current; A is the heat capacity constant; T is time.
[0024] Furthermore, the automatic verification of the generator loss-of-excitation protection and excitation system under-excitation limiting function includes determining the under-excitation limiting action curve based on the generator's static stability limits for different active power and the generator's end heating conditions; when determining the leading phase curve based on the system's static stability conditions, the under-excitation action curve of the system is determined according to the system's equivalent impedance under the minimum operating mode; based on the active power P = P N The allowable reactive power is Q = -0.05Q. N When P = 0, Q = -0.3Q N Two points determine the motion curve of the underexcitation limit, where P N Q N These are the rated active power and rated reactive power, respectively; when there is a large advance, the setting should be based on the static stability limit value with a 10% reserve factor, and should not exceed the PQ operating curve provided by the manufacturer;
[0025] The general principles for setting the underexcitation limit are: to define it reasonably across the entire range of active power output, to meet the stator end thermal stability limit requirements, to meet the static stability limit requirements, to adjust it according to changes in generator terminal voltage, and to coordinate with the loss of excitation protection. The underexcitation limit action curve is set on the generator's PQ plane based on the system reactive power reserve determined by the phase advance test, while the impedance-type loss of excitation protection is calculated on the RX measurement impedance plane at the generator terminals. Both are reduced to the same coordinate plane for discussion. When checking the underexcitation limit of the excitation system, the generator loss of excitation protection, the phase advance test, and the PQ limit, the power point is selected corresponding to the active power point set in the underexcitation limit setting.
[0026] Furthermore, the automatic verification of the generator overexcitation protection and the excitation system volt-hertz limiting function includes the following: the generator set overexcitation protection is equipped with either definite-time overexcitation protection or inverse-time overexcitation protection, consisting of a low set value and a high set value, with inverse-time overexcitation protection being preferred; when the generator set overexcitation protection is configured with definite-time protection, its low set value part operates to signal, and its high set value part operates to disconnect; when the generator set overexcitation protection is configured with inverse-time protection, the inverse-time protection operates to disconnect; the inverse-time overexcitation protection starting value is higher than 1.07 times the rated value.
[0027] Furthermore, the automatic verification of the generator stator overvoltage protection and excitation system stator overvoltage limiting function includes the following: The stator overvoltage protection setting value is set at a high value, provided it does not exceed the generator's overvoltage capacity. For hydro-generator sets, the overvoltage protection setting value is determined based on the stator winding insulation condition, and according to DL / T 684, it is 1.5 times higher than the rated voltage with a 0.5s operating time. For thyristor excitation, it is 1.3 times higher than the rated voltage with a 0.3s operating time; the protection trips the generator. For steam turbine generator sets, the overvoltage protection setting value is determined based on the stator winding insulation condition, and according to DL / T 684, it is 1.3 times higher than the rated voltage with a 0.5s operating time; the protection trips the generator.
[0028] The automatic verification of the generator stator overload protection and excitation system stator overcurrent limiting function involves the excitation system stator overcurrent limiting having an inverse time characteristic. The excitation regulator's operating time corresponding to each stator current multiple is determined based on the stator overcurrent limit of the excitation regulator and the set value or parameter setting of the stator overcurrent limit in the excitation regulator. The overload protection time setting value corresponding to each stator current multiple is determined based on the generator protection setting value. The generator stator overload capacity characterizes the generator equipment's ability to pass stator current, and the allowable time corresponding to each stator current multiple is determined by looking up its capacity curve.
[0029] The present invention has the following beneficial effects and advantages:
[0030] This invention's automatic verification method enhances generator resilience, prevents grid-connected protection and limiting malfunctions and failures, ensures safe and stable system operation, reduces the scope of fault damage, and strengthens the verification and management of grid-connected protection and limiting settings in power plants. It verifies whether the operating characteristics of generator grid-connected protection and excitation system limiting are correctly matched. It achieves automatic verification of the coordination relationship between generator grid-connected protection and excitation system limiting functions, providing support for generator safety operation analysis and decision-making. Attached Figure Description
[0031] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:
[0032] Figure 1 This is a characteristic curve of the excitation system overexcitation limitation and generator rotor overload protection of the present invention;
[0033] Figure 2 This is a volt-hertz limiting characteristic curve of the generator overexcitation protection and excitation system of the present invention. Detailed Implementation
[0034] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.
[0035] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.
[0036] The following reference Figure 1 and Figure 2 The technical solutions of some embodiments of the present invention are described below.
[0037] Example 1
[0038] This invention provides an embodiment of an automatic verification method for the grid connection protection and excitation system limiting function of a generator, comprising:
[0039] Automatic verification of generator rotor overload protection and excitation system overexcitation limitation function;
[0040] Automatic verification of generator loss-of-excitation protection and excitation system low-excitation limiting function;
[0041] Automatic verification of generator overexcitation protection and excitation system volt-hertz limiting function;
[0042] Automatic verification of generator stator overvoltage protection and excitation system stator overvoltage limiting function;
[0043] Automatic verification of generator stator overload protection and excitation system stator overcurrent limiting function.
[0044] The automatic verification of the generator rotor overload protection and excitation system overexcitation limiting function described in this invention requires the excitation system overexcitation limiting function to have an inverse time characteristic in coordination with the generator rotor overload protection. This is a prerequisite for limiting the excitation current when obtaining the strong excitation time. The generator rotor overload protection setting must be greater than the overexcitation limiter action setting. At the same time, the generator rotor overload capacity corresponding value must be greater than the rotor overload protection setting. The generator rotor overload capacity corresponding value, rotor overload protection setting value and overexcitation limiter action setting value decrease step by step, and a certain level difference should be left for the three.
[0045] The automatic verification of the generator loss-of-excitation protection and excitation system low-excitation limitation function described in this invention follows the principle that the excitation system low-excitation limitation should precede the generator loss-of-excitation protection action. The low-excitation limitation curve should match the static stability limit boundary and have a certain margin. From the beginning of generator loss of excitation until the final instability, the power and impedance measured at the generator terminals should first enter the low-excitation limitation zone, and then enter the low-excitation protection zone, finally obtaining the protection circle of loss of excitation.
[0046] The automatic verification of the generator overexcitation protection and excitation system volt-hertz limiting function described in this invention includes: the excitation system volt-hertz limiting should match the generator's overexcitation characteristics and should have definite-time and inverse-time characteristics; the excitation regulation during the generator's dynamic process should not be affected by the operation of the voltage-frequency ratio limiting unit. The inverse-time characteristic should preferably adopt a non-functional multi-point expression method and should be coordinated with the definite-time and inverse-time characteristics of the overexcitation protection.
[0047] The automatic verification of the generator stator overvoltage protection and excitation system stator overvoltage limiting function described in this invention is as follows: If the excitation system has a stator overvoltage limiting function, it should cooperate with the generator stator overvoltage protection. The limiting element should act before the unit protection. The stator overvoltage limiting of the excitation system is generally a time limit, which has the same characteristics as the generator stator overvoltage protection.
[0048] The automatic verification of the generator stator overload protection and excitation system stator overcurrent limiting function described in this invention is as follows: the excitation system stator overcurrent limiting should coordinate with the generator stator overload protection, following the principle that stator current limiting should act before stator overload protection. The stator overcurrent limiting action area should be smaller than the stator overload protection action area, and the stator overload protection action area should also be smaller than the generator's allowable overload capacity, with an appropriate margin.
[0049] Example 2
[0050] This invention provides another embodiment, which is an automatic verification method for the grid connection protection and excitation system limiting function of a generator, specifically including:
[0051] 1. Automatic verification of generator rotor overload protection and excitation system overexcitation limitation function.
[0052] The automatic verification of the generator rotor overload protection and excitation system overexcitation limitation function ensures that the overexcitation inverse time characteristic function type is consistent with the generator magnetic field overcurrent characteristic function type. There is a step difference between the overexcitation inverse time and the generator rotor winding overload protection characteristics. The overexcitation inverse time delay under the peak current should be appropriately reduced compared to the generator rotor overload protection delay, but it should not be too large, and it can generally be taken as 2s.
[0053] The overexcitation inverse-time starting value is less than the starting value of the generator rotor overload protection, which is generally 105%-110% of the generator's rated field current. The starting value does not affect the inverse-time characteristics. The forced excitation inverse-time limit value is generally reduced by 5%-10% of the generator's rated field current to release accumulated heat. It can also be limited to the starting value, and then the operator reduces the field current according to the forced excitation limit action signal.
[0054] Overexcitation system overexcitation limitation and generator rotor overload protection generally follow the inverse-time overheating characteristic of the generator rotor forced excitation capability curve:
[0055]
[0056] In the formula:
[0057] I * —Per-unit value of rotor current;
[0058] A—Heat capacity constant;
[0059] T – Time.
[0060] The overexcitation limit of the excitation system and the characteristic curves of the generator rotor overload protection are as follows: Figure 1 As shown, for steam turbine generators, A is generally required to be no less than 33.75, and the excitation limit of the excitation system is usually set to 30.
[0061] 2. Automatic verification of generator loss of excitation protection and excitation system low excitation limit function.
[0062] The automatic verification of the generator loss-of-excitation protection and under-excitation system under-excitation limiting function, and the under-excitation limiting action curve, are determined according to the generator's static stability limits for different active power and the generator's end heating conditions. When determining the leading phase curve based on the system's static stability conditions, the under-excitation action curve of the system should be determined based on the system's equivalent impedance under the system's minimum operating mode. If there are no special requirements for the leading phase, it can generally be determined according to the active power P = P N The allowable reactive power is Q = -0.05Q. N When P = 0, Q = -0.3Q N Two points determine the motion curve of the underexcitation limit, where P N Q N These are the rated active power and rated reactive power, respectively. When a large leading power is required, a reserve factor of about 10% can generally be reserved based on the static stability limit value, but it cannot exceed the PQ operating curve provided by the manufacturer.
[0063] The general principles for setting the underexcitation limit can be summarized as follows: reasonably defining it across the entire active power output range, meeting the stator end thermal stability limit requirements, meeting the static stability limit requirements, adjusting it according to changes in generator terminal voltage, and coordinating it with the loss-of-excitation protection. The underexcitation limit action curve is set on the generator's PQ plane based on the system reactive power reserve determined by the phase-advancing test, while the impedance-type loss-of-excitation protection is calculated on the generator terminal RX measured impedance plane. In order to correctly verify the coordination relationship between them, both must be reduced to the same coordinate plane for discussion. When checking the underexcitation limit of the excitation system, the generator loss-of-excitation protection, the phase-advancing test, and the PQ limit, the power point can be selected corresponding to the active power point set in the underexcitation limit setting.
[0064] 3. Automatic verification of generator overexcitation protection and excitation system volt-hertz limiting function.
[0065] The automatic verification of the generator overexcitation protection and the excitation system's volt-hertz limiting function requires that the generator set overexcitation protection be equipped with either definite-time overexcitation protection or inverse-time overexcitation protection, consisting of both low-set and high-set parts, with inverse-time overexcitation protection being preferred. When the generator set overexcitation protection is configured with definite-time protection, its low-set part should operate to signal, and its high-set part should operate to disconnect the generator. When the generator set overexcitation protection is configured with inverse-time protection, the inverse-time protection should operate to disconnect the generator. The inverse-time overexcitation protection's starting value must be higher than 1.07 times the rated value.
[0066] Generator overexcitation protection and excitation system volt-hertz limiting characteristic curves are as follows: Figure 2 As shown.
[0067] 4. Automatic verification of generator stator overvoltage protection and excitation system stator overvoltage limiting function.
[0068] The automatic verification of the generator stator overvoltage protection and excitation system stator overvoltage limiting function requires that the stator overvoltage protection setting value be higher than the generator's overvoltage capacity, provided it does not exceed the generator's overvoltage capability. For hydro-generator sets, the overvoltage protection setting value is determined based on the stator winding insulation condition, and according to DL / T684, it should be 1.5 times higher than the rated voltage, with an operating time of 0.5s; for those using thyristor excitation, it should be 1.3 times higher than the rated voltage, with an operating time of 0.3s. The protection will trip the generator. For steam turbine generator sets, the overvoltage protection setting value is determined based on the stator winding insulation condition, and according to DL / T684, it should be 1.3 times higher than the rated voltage, with an operating time of 0.5s. The protection will trip the generator.
[0069] 5. Automatic verification of generator stator overload protection and excitation system stator overcurrent limiting function.
[0070] The automatic verification of the generator stator overload protection and excitation system stator overcurrent limiting function is described. The stator overcurrent limiting of the excitation system is generally inverse time-delay characteristic. The excitation regulator action time corresponding to each stator current multiple can be determined according to the stator overcurrent limiting of the excitation regulator and the set value or parameter setting of the stator overcurrent limiting in the excitation regulator. The overload protection time setting value corresponding to each stator current multiple is determined according to the generator protection setting value. The generator stator overload capacity characterizes the generator equipment's ability to pass stator current. The allowable time corresponding to each stator current multiple should be determined by referring to its capacity curve.
[0071] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.
[0072] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.
[0073] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.
[0074] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.
[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.
Claims
1. An automatic verification method for the limiting function of generator grid connection protection and excitation system, characterized in that: include: Automatic verification of generator rotor overload protection and excitation system overexcitation limiting function; wherein, the overexcitation inverse-time characteristic function type is consistent with the generator magnetic field overcurrent characteristic function type, and there is a step difference between the overexcitation inverse-time and generator rotor winding overload protection characteristics. The overexcitation inverse-time delay under the peak current is reduced by 2 seconds compared to the generator rotor overload protection delay; the overexcitation inverse-time starting value is less than the generator rotor overload protection starting value, which is 105%-110% of the generator rated magnetic field current. The starting value does not affect the inverse-time characteristic. The forced excitation inverse-time limiting value is reduced by 5%-10% of the generator rated magnetic field current compared to the starting value to release accumulated heat, or it can be limited to the starting value. Then, according to the forced excitation limiting action signal, the magnetic field current is reduced; the excitation system overexcitation limiting and generator rotor overload protection and generator rotor forced excitation capability curve follow the inverse-time overheating characteristics: In the formula: Where A is the rotor current per unit value; A is the heat capacity constant; T is time; Automatic verification of generator loss-of-excitation protection and under-excitation limit function of excitation system; wherein, the under-excitation limit action curve is determined according to the static stability limit of generator with different active power and generator end heating conditions; when determining the leading phase curve from the system static stability condition, the under-excitation action curve of the system is determined according to the equivalent impedance of the system under the minimum operating mode; according to active power P=P N The allowable reactive power is Q = -0.05Q. N When P=0, Q=-0.3Q N Two points determine the motion curve of the underexcitation limit, where P N Q N These are the rated active power and rated reactive power, respectively. When there is a large advance, the setting should be based on a 10% reserve coefficient according to the static stability limit value, and should not exceed the PQ operating curve provided by the manufacturer. The principle for setting the underexcitation limit is: to define it reasonably within the full range of active power output, to meet the thermal stability limit requirements at the stator end, to meet the static stability limit requirements, to adjust it according to the changes in the generator terminal voltage, and to coordinate with the loss of excitation protection. The underexcitation limit action curve is set on the generator PQ plane based on the system reactive power reserve determined by the advance test, while the impedance-type loss of excitation protection is calculated on the RX measurement impedance plane at the generator terminal. The two are referred to the same coordinate plane for discussion. When checking the underexcitation limit of the excitation system, the generator loss of excitation protection, the advance test and the PQ limit, the power point is selected according to the active power point set in the corresponding underexcitation limit setting. Automatic verification of generator overexcitation protection and excitation system volt-hertz limiting function; wherein, the generator set overexcitation protection is equipped with definite-time overexcitation protection or inverse-time overexcitation protection consisting of two parts: low setting value and high setting value, with inverse-time overexcitation protection being preferred; when the generator set overexcitation protection is configured with definite-time protection, its low setting value part operates to signal, and its high setting value part operates to disconnect the grid; when the generator set overexcitation protection is configured with inverse-time protection, the inverse-time protection operates to disconnect the grid; the inverse-time overexcitation protection starting value is higher than 1.07 times the rated value; Automatic verification of generator stator overvoltage protection and excitation system stator overvoltage limiting function; wherein, the stator overvoltage protection setting value adopts a high setting value under the premise of not exceeding the generator's overvoltage capacity; for hydro-generator sets, the overvoltage protection setting value is determined according to the stator winding insulation condition, and according to DL / T 684, it is 1.5 times higher than the rated voltage, with an operating time of 0.5s; for those using thyristor excitation, it is 1.3 times higher than the rated voltage, with an operating time of 0.3s; the protection operates to disconnect the generator; for steam turbine generator sets, the overvoltage protection setting value is determined according to the stator winding insulation condition, and according to DL / T 684, it is 1.3 times higher than the rated voltage, with an operating time of 0.5s; the protection operates to disconnect the generator. Automatic verification of generator stator overload protection and excitation system stator overcurrent limiting function; wherein, the excitation system stator overcurrent limiting has an inverse time characteristic. The excitation regulator action time corresponding to each stator current multiple is determined according to the stator overcurrent limiting of the excitation regulator and the set value or parameter setting of the stator overcurrent limiting in the excitation regulator. The overload protection time setting value corresponding to each stator current multiple is determined according to the generator protection setting value. The generator stator overload capacity characterizes the generator equipment's ability to pass stator current. The allowable time corresponding to each stator current multiple is determined by looking up its capacity curve.
2. The automatic verification method for generator grid connection protection and excitation system limiting function according to claim 1, characterized in that: The automatic verification of the generator rotor overload protection and excitation system overexcitation limiting function: The excitation system overexcitation limiting function needs to cooperate with the generator rotor overload protection in an inverse time-delay characteristic, which is a prerequisite for limiting the excitation current when obtaining the strong excitation time. The generator rotor overload protection setting is greater than the overexcitation limiter action setting, and at the same time, the generator rotor overload capacity corresponding value is greater than the rotor overload protection setting. The generator rotor overload capacity corresponding value, rotor overload protection setting and overexcitation limiter action setting decrease step by step to leave a level difference among the three.
3. The automatic verification method for generator grid connection protection and excitation system limiting function according to claim 1, characterized in that: The automatic verification of the generator loss-of-excitation protection and excitation system low-excitation limitation function is as follows: the excitation system low-excitation limitation should act before the generator loss-of-excitation protection. The low-excitation limitation curve should match the static stability limit boundary and have a certain margin. From the beginning of generator loss of excitation until the final instability, the power and impedance at the generator terminal should first enter the low-excitation limitation zone, and then enter the low-excitation protection zone, finally obtaining the protection circle of loss of excitation.
4. The automatic verification method for generator grid connection protection and excitation system limiting function according to claim 1, characterized in that: The automatic verification of the generator overexcitation protection and excitation system volt-hertz limiting function is as follows: the excitation system volt-hertz limiting should match the generator's overexcitation characteristics, have definite time and inverse time characteristics, and the excitation regulation of the generator's dynamic process should not be affected by the operation of the voltage and frequency ratio limiting unit; the inverse time characteristic adopts a non-functional multi-point expression method, which is coordinated with the definite time and inverse time characteristics of the overexcitation protection.
5. The automatic verification method for generator grid connection protection and excitation system limiting function according to claim 1, characterized in that: Automatic verification of the generator stator overvoltage protection and excitation system stator overvoltage limiting function: If the excitation system has a stator overvoltage limiting function, it should be coordinated with the generator stator overvoltage protection. The limiting element should act before the unit protection. The stator overvoltage limiting of the excitation system is a time limit function, with the same characteristics as the generator stator overvoltage protection.
6. The automatic verification method for generator grid connection protection and excitation system limiting function according to claim 1, characterized in that: The automatic verification of the generator stator overload protection and excitation system stator overcurrent limiting function is as follows: the excitation system stator overcurrent limiting should coordinate with the generator stator overload protection, following the principle that stator current limiting should act before stator overload protection. The stator overcurrent limiting action area should be smaller than the stator overload protection action area, and the stator overload protection action area should also be smaller than the generator's allowable overload capacity, with an appropriate margin.
7. The automatic verification method for generator grid connection protection and excitation system limiting function according to claim 1, characterized in that: The heat capacity constant A is greater than 33.75 for steam turbine generators.
8. The automatic verification method for the limiting function of generator grid connection protection and excitation system according to claim 1, characterized in that: The heat capacity constant A is limited to 30 for forced excitation of the excitation system.