Large generator main protection dead-zone-free transformation method and system

Abstract

The invention discloses a large-scale generator main protection dead-zone-free transformation method and system, and relates to the technical field of generator protection, and the method comprises the following steps: analyzing a stator winding connection diagram of a large-scale generator, and predicting the fault number and distribution characteristics of same-phase and same-branch turn-to-turn short circuits, same-phase and different-branch turn-to-turn short circuits and interphase short circuits of the generator; analyzing and calculating the predicted internal faults of the generator by using a multi-loop analysis method, solving the magnitude and phase of each branch current under each fault, further calculating the sensitivity coefficient of each main protection scheme to the internal faults, and determining the fault number and the fault type which can be reflected by each main protection scheme; a generator main protection configuration scheme is generated for minimizing a protection action dead zone and minimizing electromagnetic TA. A corresponding main protection scheme is added through flexible winding of the optical current transformer, and a protection dead zone for turn-to-turn short circuit with small number of turns is eliminated, so that the technical improvement of a generator main protection configuration scheme without a dead zone is completed.

Description

Technical Field

[0001] The present invention relates to the technical field of generator protection, and particularly to a method and system for retrofitting the main protection of a large generator without dead zones. Background Art

[0002] Internal faults in the stator windings of AC motors are common and highly destructive faults in motors. During an internal fault, a large short-circuit current will generate a highly destructive electromagnetic force, and may also cause overheating, burning out the windings and the iron core. The non-synchronous magnetic field generated by the fault may greatly exceed the design allowable value, causing serious damage to the rotor. For large generators, the damage caused by internal faults is particularly severe, especially the phase-to-phase short-circuit faults with a high occurrence probability; internal faults in large generators may also pose a great threat to the safe operation of the power system. Therefore, configuring a reliable main protection for internal short circuits in generators is an important task for power workers.

[0003] However, for a long time, only the sensitivity of two-phase short circuits at the machine terminals has been discussed for the main protection against internal short circuits in generators, and the sensitivity of transverse differential protection cannot be discussed either. When designing the main protection configuration scheme for generators (traditional scheme - complete longitudinal differential protection + zero-sequence current type transverse differential protection), only qualitative analysis is made based on experience and concepts. As for the sensitivity of the above main protection configuration scheme during internal short circuits in the stator windings of generators, the designers have no idea, not knowing the amount of protection dead zones and the fault types that cannot operate. The fundamental reason is that the analysis and calculation methods for internal short circuits in generators are not mastered.

[0004] Based on the internal fault analysis ("multi-loop analysis method"), the quantitative design method for the main protection of generators (Patent No.: ZL200410009219.4) applies the results of multi-loop analysis to the design of the main protection against internal faults in the stator windings of large and medium-sized generators. Based on the comprehensive simulation calculation of internal faults in generators using the "multi-loop analysis method" and according to the different winding structures of generators, different quantitative and optimized design processes are proposed, opening up a new way for scientifically formulating the main protection configuration scheme for generators, reasonably selecting the branch lead-out method on the neutral point side of generators, and the configuration scheme of electromagnetic TAs.

[0005] Due to being restricted by the fault characteristics of multi-branch overlapping windings generators (the number of short circuits between turns in the same phase with small number of turns in the same branch is large and the corresponding short-circuited turn ratio is small) and the layout of copper rings on the neutral point side and the installation conditions of electromagnetic TAs, the main protection configuration scheme determined according to the above quantitative design process for multi-branch overlapping windings generators (a = 7 / 9 / 11) has a large protection dead zone, resulting in potential safety hazards in the operation of multi-branch overlapping windings large generators. Summary of the Invention

[0006] In view of the problems existing in the existing retrofit and system for the main protection of large generators without dead zones, the present invention is proposed.

[0007] Therefore, the problems to be solved by the present invention are as follows: The designer does not know how much the protection dead zone is and the types of faults that cannot operate in mind.

[0008] To solve the above technical problems, the present invention provides the following technical solutions:

[0009] In a first aspect, an embodiment of the present invention provides a method for retrofitting the main protection of a large generator without a dead zone, which includes the following steps:

[0010] Analyze the connection diagram of the stator winding of the large generator, and predict the number of faults and their distribution characteristics of the same-phase same-branch turn-to-turn short circuit, same-phase different-branch turn-to-turn short circuit, and phase-to-phase short circuit that may occur in the generator;

[0011] Use the multi-loop analysis method to analyze and calculate the predicted internal faults of the generator, obtain the magnitude and phase of the branch currents under each fault, and then calculate the sensitivity coefficients of various main protection schemes for internal faults, and determine the number of faults and fault types that various main protection schemes can respond to;

[0012] Generate a main protection configuration scheme for the generator, which is used to minimize the protection action dead zone and minimize the number of electromagnetic TAs;

[0013] Retain the established copper ring lead-out method and branch group electromagnetic TA on the neutral point side of the multi-branch overlapping winding generator. Through the main protection configuration scheme of the generator, select to wind a flexible optical TA on the middle branch corresponding to the electromagnetic branch group TA of the multi-branch overlapping winding retrofitted generator, and add the corresponding main protection scheme through the flexible winding of the optical current transformer to eliminate the protection dead zone for small-turn turn-to-turn short circuits.

[0014] As a preferred scheme of the method for retrofitting the main protection of the large generator without a dead zone according to the present invention, wherein: the added flexible optical TA and the main protection scheme include:

[0015] Wind a flexible optical TA on the middle branch corresponding to the branch group electromagnetic TA;

[0016] Set a new protection criterion for comparing currents based on the electromagnetic branch group TA and the corresponding optical TA.

[0017] As a preferred scheme of the method for retrofitting the main protection of the large generator without a dead zone according to the present invention, wherein: the multi-loop analysis method includes:

[0018] Establish a mathematical model of the internal fault of the generator to simulate the current distribution during the internal fault of the generator;

[0019] Use simulation software to calculate the mathematical model to obtain the magnitude and phase of the branch currents.

[0020] As a preferred solution of the method for retrofitting the main protection of large generators without dead zones according to the present invention, wherein: the main protection configuration of the generator includes

[0021] a combination of complete longitudinal differential protection and zero-sequence current type transverse differential protection;

[0022] According to the different winding structures of the generator, different quantitative and optimized design processes are proposed;

[0023] Among them, the combination of longitudinal differential protection and zero-sequence current type transverse differential protection includes:

[0024] Install longitudinal differential protection to form a preliminary pattern of one longitudinal differential for one class, and determine the number and location of branch TAs;

[0025] Select incomplete longitudinal differential protection and cooperate with the remaining zero-sequence current type transverse differential protection to determine the number and location of branch IAs;

[0026] When complete longitudinal differential protection is selected, the neutral-side current can be obtained when the number and location of branch TAs are selected.

[0027] As a preferred solution of the method for retrofitting the main protection of large generators without dead zones according to the present invention, wherein: when the combination of complete longitudinal differential protection and zero-sequence current type transverse differential protection is not satisfied, the selection and composition methods of other transverse differential and longitudinal differential protections are introduced until the design indexes are met, wherein the design indexes are expressed as:

[0028]

[0029] In the formula, ε1 represents a variable, represents a union, the union of all sets of F from i = 1 to N, and N represents the number of sets. Ai

[0030] As a preferred solution of the method for retrofitting the main protection of large generators without dead zones according to the present invention, wherein: the method for judging the protection dead zone includes

[0031] judging whether the protection dead zone of the retrofitted generator main protection configuration exceeds 5%, and more than half of the fault types that cannot act are small-turn number inter-turn short circuits;

[0032] When it is not, wind a flexible optical TA on the intermediate branch corresponding to the electromagnetic type branch group TA, and add a corresponding main protection scheme to eliminate the protection dead zone for small-turn number inter-turn short circuits.

[0033] As a preferred embodiment of the method for modifying the main protection of a large generator without dead zones according to the present invention, when analyzing and calculating internal faults, the calculated inductance coefficients include the inductance coefficients of each stator coil generated by the air-gap magnetic field, the inductance coefficients of each stator coil generated by the end leakage magnetic field, the total inductance coefficient of each stator branch, the inductance coefficients of the excitation circuit and each stator branch, the inductance coefficients of the excitation circuit and each damping circuit, the inductance coefficients of each damping circuit, and the inductance coefficients of each damping circuit and each stator branch.

[0034] When calculating the set inductance coefficients, it is also necessary to calculate the resistance of each stator branch and the self-inductance of the excitation circuit.

[0035] In a second aspect, an embodiment of the present invention provides a system for modifying the main protection of a large generator without dead zones, which includes a fault prediction module, a multi-loop analysis module, a flexible optical TA configuration module, and a simulation and verification module.

[0036] The fault prediction module is used to analyze the connection diagram of the generator stator winding and predict possible fault types, such as inter-turn short circuits in the same branch, inter-turn short circuits in different branches of the same phase, and phase-to-phase short circuits.

[0037] The multi-loop analysis module uses the multi-loop analysis method to perform detailed calculations on the predicted internal faults to determine the magnitudes and phases of the currents in each branch.

[0038] The flexible optical TA configuration module selects an appropriate intermediate branch to wind the flexible optical TA on the basis of retaining the copper ring lead-out method on the neutral point side and the branch group electromagnetic TA.

[0039] The simulation and verification module performs simulation tests on the generated protection scheme to verify its response and effect under various fault conditions.

[0040] In a third aspect, an embodiment of the present invention provides a computer device, including a memory and a processor, where the memory stores a computer program, and: when the processor executes the computer program, any step of the above method for modifying the main protection of a large generator without dead zones is implemented.

[0041] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, on which a computer program is stored, and: when the computer program is executed by a processor, any step of the above method for modifying the main protection of a large generator without dead zones is implemented.

[0042] The beneficial effects of the present invention are as follows: Based on the comprehensive simulation calculation of the internal faults of the generator using the "multi-loop analysis method", and based on the existing branch grouping method of the multi-branch overlapping winding generator, the layout of the electromagnetic branch group TA, and the fault types that cannot operate, a flexible optical TA is wound "targetedly" on the intermediate branch corresponding to the electromagnetic branch group TA, and a new protection criterion of current comparison type based on the electromagnetic branch group TA and the corresponding optical TA is added. On the premise of ensuring that the branch grouping on the neutral point side of the retrofitted generator, the copper ring lead-out method, and the layout of the electromagnetic branch group TA remain unchanged, the protection dead zone for small-turn number inter-turn short circuits is eliminated by the flexible winding of the flexible optical TA and the addition of the corresponding main protection scheme. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings. Among them:

[0044] Figure 1 It is a flowchart of the method for retrofitting the main protection of a large generator without dead zones.

[0045] Figure 2 It is a block diagram of the internal fault simulation calculation of the generator for the method of retrofitting the main protection of a large generator without dead zones.

[0046] Figure 3 It is a schematic diagram of the technical renovation plan for the internal fault main protection and TA configuration of the method for retrofitting the main protection of a large generator without dead zones.

[0047] Figure 4 It is a flowchart of the method for retrofitting the main protection of a multi-branch overlapping winding generator without dead zones for the method of retrofitting the main protection of a large generator without dead zones.

[0048] Figure 5 It is a schematic diagram of the main protection configuration plan for the method of retrofitting the main protection of a large generator without dead zones.

[0049] Figure 6 It is a schematic diagram of three small-turn number same-phase same-branch inter-turn short circuits for the method of retrofitting the main protection of a large generator without dead zones.

[0050] Figure 7 It is a schematic diagram of the new protection criterion of current comparison type for the method of retrofitting the main protection of a large generator without dead zones.

[0051] Figure 8 It is a schematic diagram of the optimized main protection configuration plan for the generator for the method of retrofitting the main protection of a large generator without dead zones. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following provides a detailed description of the specific embodiments of the present invention in conjunction with the accompanying 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 of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0053] In the following description, many specific details are set forth to facilitate a thorough 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 generalizations without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0054] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that mutually excludes other embodiments.

[0055] The present invention is described in detail in conjunction with schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views showing the device structure are enlarged locally not in accordance with the general scale, and the schematic diagrams are only examples and should not limit the scope of protection of the present invention herein. In addition, in actual production, three-dimensional spatial dimensions including length, width, and depth should be included.

[0056] Meanwhile, in the description of the present invention, it should be noted that the orientation or positional relationships indicated by terms such as "upper, lower, inner, and outer" are based on the orientation or positional relationships shown in the accompanying drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first, second, or third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0057] Unless otherwise clearly defined and limited in the present invention, the terms "installed, connected, and coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can also be a mechanical connection, an electrical connection, or a direct connection, and can also be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0058] Embodiment 1

[0059] Refer to Figures 1 to 8, which is the first embodiment of the present invention. This embodiment provides a method for retrofitting the main protection of a large generator without dead zones, including the following steps:

[0060] S1. Analyze the connection diagram of the stator winding of the large generator, and predict the number of faults and their distribution characteristics of the same-phase same-branch turn-to-turn short circuit, same-phase different-branch turn-to-turn short circuit, and phase-to-phase short circuit that may occur in the generator.

[0061] S2. Use the multi-loop analysis method to analyze and calculate the predicted internal faults of the generator, obtain the magnitude and phase of the branch currents under each fault, and then calculate the sensitivity coefficients of various main protection schemes for internal faults, and determine the number of faults and fault types that various main protection schemes can respond to.

[0062] The multi-loop analysis method includes:

[0063] Establish a mathematical model of the internal faults of the generator to simulate the current distribution during internal faults of the generator;

[0064] Use simulation software to calculate the mathematical model to obtain the magnitude and phase of the branch currents.

[0065] S3. Generate a main protection configuration scheme for the generator to minimize the protection action dead zone and minimize the number of electromagnetic TAs.

[0066] The main protection configuration scheme for the generator includes:

[0067] The combination of complete differential protection and zero-sequence current type transverse differential protection;

[0068] According to the different winding structures of the generator, different quantitative and optimization design processes are proposed;

[0069] Among them, the combination of differential protection and zero-sequence current type transverse differential protection includes:

[0070] Install differential protection to form a preliminary pattern of one differential for one class, and determine the number and location of branch TAs;

[0071] Select incomplete differential protection and cooperate with the remaining zero-sequence current type transverse differential protection to determine the number and location of branch IAs;

[0072] When complete differential protection is selected, when determining the number and location of branch TAs, the neutral-point side current can be obtained.

[0073] When the combination of complete differential protection and zero-sequence current type transverse differential protection is not satisfied, introduce the selection and composition methods of other transverse differential and differential protections until the design indexes are met. Among them, the design indexes are expressed as:

[0074]

[0075] where ε1 is represented as a variable, is represented as a union, the union of all F from i = 1 to N Ai of the set, and N represents the number of sets.

[0076] S4. Retain the established copper ring lead-out method on the neutral point side of the multi-branch overlapping winding generator and the electromagnetic type TA of the branch group. Through the generator main protection configuration scheme, select to wind a flexible optical TA on the intermediate branch corresponding to the electromagnetic type branch group TA of the multi-branch overlapping winding retrofitted generator. By the flexible winding of the optical current transformer, add the corresponding main protection scheme to eliminate the protection dead zone for small-turn inter-turn short circuits.

[0077] The judgment method of the protection dead zone includes

[0078] judging whether the protection dead zone of the main protection configuration scheme of the retrofitted generator exceeds 5%, and more than half of the fault types that cannot operate are small-turn inter-turn short circuits;

[0079] When it is not, wind a flexible optical TA on the intermediate branch corresponding to the electromagnetic type branch group TA, add the corresponding main protection scheme to eliminate the protection dead zone for small-turn inter-turn short circuits.

[0080] The added flexible optical TA and main protection scheme include

[0081] wind a flexible optical TA on the intermediate branch corresponding to the electromagnetic type branch group TA;

[0082] Set a new protection criterion for current comparison based on the electromagnetic type branch group TA and the corresponding optical TA.

[0083] When analyzing and calculating internal faults, the calculated inductance coefficients include: the inductance coefficients of each stator coil generated by the air-gap magnetic field, the inductance coefficients of each stator coil generated by the end leakage magnetic field, the total inductance coefficients of each stator branch, the inductance coefficients of the excitation circuit and each stator branch, the inductance coefficients of the excitation circuit and each damping circuit, the inductance coefficients of each damping circuit, the inductance coefficients of each damping circuit and each stator branch;

[0084] When calculating the set inductance coefficients, it is also necessary to calculate the resistance of each stator branch and the self-inductance of the excitation circuit.

[0085] In this embodiment, take the main protection retrofit scheme of the Baihetan DEC generator (8×1000MW) as an example;

[0086] The Baihetan DEC generator adopts an integer slot (q = 5) overlapping winding (the stator winding pitch is y1 = 13), 54 poles, the number of stator slots is 810, 9 branches per phase, and 30 coils per branch. The rated parameters of the generator are: P N = 1000MW, U N= 24 kV, I N = 26728.9 A, cosφ N = 0.9, I f0 = 2528.4 A, I fN = 4371.3 A.

[0087] Through the analysis of the developed diagram of the generator stator winding provided by Dongfang Electric Machinery Co., Ltd. of Dongfang Electric Corporation, the actual internal short circuits are shown in Table 1 and Table 2:

[0088] Table 1 810 same-slot faults of Baihetan DEC generator:

[0089]

[0090] Table 2 9072 end-crossing faults of Baihetan DEC generator:

[0091]

[0092] The quantitative and optimized design method of the main protection of the generator based on the "multi-loop analysis method" has been popularized and applied in the hydropower field. The internal faults of the stator windings of the generator sets of more than 170 large and medium-sized hydropower stations and pumped-storage power stations at home and abroad have been analyzed, and the quantitative design of the main protection scheme has been carried out; Summarize the existing design experience, and consider the fault characteristics of the multi-branch overlapping winding hydro-generator - there are many small-turn same-phase same-branch turn-to-turn short circuit faults and the corresponding short-circuit turn ratio is small. The composition of the corresponding main protection configuration scheme is as Figure 5 shown.

[0093] Table 3 Action conditions of the existing scheme for the same-slot and end faults of Baihetan DEC generator:

[0094]

[0095] The performance of the corresponding main protection configuration scheme of the Baihetan DEC generator is shown in Table 3, and the fault types that the existing scheme cannot act on are further analyzed (shown in Table 4 and Table 5) - there are 819 small-turn same-phase same-branch turn-to-turn short circuits, and the short-circuit turns are 1, 2, 3, 4, 5, and 6 turns respectively. The corresponding short-circuit turn ratios are 3.33% - 20%, and the corresponding number of faults are 486, 201, 107, 18, 6, and 1 respectively;

[0096] Table 4 Number and nature of faults that the existing scheme cannot act reliably on the same-slot faults of Baihetan DEC generator when it is connected to the grid and no-load:

[0097] Table 5 Number and nature of faults that the existing scheme cannot act reliably on the end faults of Baihetan DEC generator when it is connected to the grid and no-load:

[0098]

[0099] As can be seen from Tables 4 - 5, for the same - branch turn - to - turn short - circuit with a small number of short - circuited turns (the ratio of the number of short - circuited turns to the number of turns in each branch coil) less than 5%, it is indeed the common protection dead - zone for the above - mentioned various main protection schemes (which has also been proven by operation practice). And for the same - branch turn - to - turn short - circuit with a small number of turns, the sensitivity of the incomplete split - phase transverse differential protection is not much different from that of the complete split - phase transverse differential protection, and is even better than the complete split - phase transverse differential protection. Here, three cases of the same - branch turn - to - turn short - circuit in the Baihetan DEC generator internal fault (the corresponding number of short - circuited turns are 1 turn and 3 turns respectively) are taken as examples for illustration.

[0100] Figure 6 The fault indicated by the bold solid arrow is that in the Baihetan DEC generator under the grid - connected no - load operation mode, a turn - to - turn short - circuit of the same phase and the same branch occurs between the lower side of the 10th coil in the first branch of phase a and the upper side of the 13th coil in the first branch of phase a, with the number of short - circuited turns being 3 turns (the winding directions of the two short - circuited coils are opposite). The magnitudes (effective values, unit: A, the same below) and phases of the fundamental - wave currents of each branch (including the short - circuit additional branch) of the fault phase are as follows:

[0101] Next, let's look at the sensitivity coefficient of the complete split - phase transverse differential protection (K10_1234 - 56789) for the fault phase: As Figure 6 shown, the current flowing through TA1 is The current flowing through TA2 is

[0102] I d =|I1 - I2| = |3192.14∠223.58° - 1484.52∠41.65°| = 5740.09, I res =0.5|I1 + I2| = 0.5|3192.14∠223.58°+1484.52∠41.65°| = 1386.48 < I N ,

[0103] The corresponding sensitivity coefficient of the complete split - phase transverse differential protection is And Figure 6 the sensitivity coefficient of the incomplete split - phase transverse differential protection (K11_123 - 789) shown is 1.912.

[0104] Also under the grid - connected no - load operation mode, an end - part same - branch turn - to - turn short - circuit occurs between the upper side of the 1st coil in the fifth branch of phase a and the lower side of the 3rd coil in the fifth branch of phase a (as Figure 6The magnitude and phase of the fundamental current of each branch of the fault phase (including the short-circuited additional branch) are as follows:

[0105]

[0106] Similarly, the sensitivity coefficient of the fault phase incomplete phase split differential protection (K11_123-789) is analyzed: Figure 6 As shown, the current flowing through TA3 at this time is The current flowing through TA5 is

[0107]

[0108] The corresponding sensitivity coefficient of incomplete phase-splitting differential protection is

[0109] Figure 6 The sensitivity coefficient of the complete split-phase differential protection (K10_1234-56789) is 0.412, and the incomplete longitudinal differential protection (K21_5 / Figure 6 As shown in the figure, it can move flexibly, and its corresponding sensitivity coefficient is 2.255. Considering that the volume of the small-ratio electromagnetic TA (4000 / 1A) is large, it is difficult to install it under the existing branch grouping method ("123-456-789").

[0110] In the past ten years, flexible optical TA based on Faraday magneto-optical effect has been gradually applied in the field of hydropower and has accumulated certain engineering experience. It has not only solved the saturation and poor low-frequency transmission characteristics of traditional electromagnetic TA, but also made use of its advantages of flexible winding and high measurement accuracy. Through the winding of flexible optical TA, virtual branch lead-out mode (see Shenzhen generator motor main protection optimization design) or the installation of specific branch current transformers (see Xiangjiaba right bank generator main protection optimization design) is realized, which solves the protection dead zone problem caused by the layout of current transformers in the generator main protection design.

[0111] Further consideration can be given to Figure 6 Flexible optical TAs are wound around the 2nd and 8th branches of each phase to improve the sensitivity to the short circuit between the 1 turn and the same branch that actually exists in the above branches. Similarly, in the grid-connected no-load operation mode, the upper side of the 1st coil of the 2nd branch of phase a and the lower side of the 3rd coil of the 2nd branch of phase a have a short circuit between the ends and the same branch (such as Figure 6 The magnitude and phase of the fundamental current of each branch of the fault phase (including the short-circuited additional branch) are as follows:

[0112]

[0113] Similarly, analyze the sensitivity coefficient of the incomplete split-phase transverse differential protection (K11_2 - 8) for the faulty phase: As Figure 6 shown,

[0114] the sensitivity coefficient of the corresponding incomplete split-phase transverse differential protection is

[0115] As mentioned above, by adding flexible optical CTs to the 2nd, 5th, and 8th branches of each phase, the inter-turn short circuits of the same phase and the same branch with 1 - 6 turns occurring in the corresponding branches can be eliminated. However, for the inter-turn short circuits with small number of turns occurring in the branches without flexible optical CTs, it is "powerless". Therefore, based on the understanding of the fault characteristics of inter-turn short circuits with small number of turns, on the basis of the existing branch grouping method and the installation of current transformers, corresponding solutions need to be sought to achieve the transformation of the main protection of the Baihetan DEC generator without dead zones.

[0116] Considering that the fault characteristics of each branch of the Baihetan DEC generator with lap winding are the same, and the variation laws of the corresponding faults are also the same, the composition and performance of the new protection criterion are explained by taking one phase as an example. As Figure 7 shown, taking phase A as an example, based on the current signals collected by the existing electromagnetic type branch group current transformers (123 - 456 - 789) and the added flexible optical CTs (2 - 5 - 8 / corresponding to the middle branches of the electromagnetic type branch group TAs respectively), a new current comparison type protection criterion is constructed:

[0117]

[0118] The calculation results show that for the 18 types of 1-turn inter-turn short circuits of the same phase and the same branch that may actually occur in the a1 branch, the above new protection criterion can basically act sensitively. The 1 type of 1-turn inter-turn short circuit that cannot act is located on the neutral point side of the a1 branch - an end 1-turn inter-turn short circuit occurs between the lower side of the 28th coil of the first branch of phase A and the upper side of the 30th coil of the first branch of phase A. At this time:

[0119]

[0120] Aiming at the protection dead zone of inter-turn short circuits in the existing main protection configuration scheme of the Baihetan DEC generator, based on the analysis of the fault types that the Baihetan DEC generator cannot act on, the flexible optical TAs can be used for their flexible winding advantages. Add optical TAs to the 2nd / 5th / 8th branches of each phase and a set of incomplete split-phase transverse differential protection (the currents on both sides are taken from the flexible optical CTs of the 2nd and 8th branches of each phase) + a set of incomplete longitudinal differential protection (the current on the neutral point side is taken from the flexible optical CT of the 5th branch of each phase), as Figure 8As shown in the figure, the optimized main protection configuration scheme for the Baihetan DEC generator, combined with the new protection criterion of current comparison type (based on the current signals collected by the existing electromagnetic branch group current transformers and the added flexible optical CTs), basically realizes the dead-zone-free protection for the Baihetan DEC generator.

[0121] In summary, the implementation of the technical renovation plan for the main protection configuration of the Baihetan DEC generator based on flexible optical TAs provides a new idea for the technical renovation of the dead-zone-free main protection of multi-branch overlapping-winding generators. That is, on the premise of ensuring that the branch grouping, copper ring lead-out method, and electromagnetic branch TA layout of the generator remain unchanged, select to wind flexible optical TAs "targetedly" on the intermediate branch corresponding to the electromagnetic branch group TAs of the multi-branch overlapping-winding renovated generator, and add corresponding main protection schemes through the flexible winding of optical current transformers to eliminate the protection dead zone for short circuits between turns with small number of turns, so as to complete the dead-zone-free main protection configuration scheme for the renovated generator, achieving a "win-win" situation for the primary electrical specialty (generator) and the secondary specialty (relay protection).

[0122] Embodiment 2

[0123] Based on the first embodiment, this embodiment further provides a dead-zone-free renovation system for the main protection of large generators, including a fault prediction module, a multi-loop analysis module, a flexible optical TA configuration module, and a simulation and verification module;

[0124] The fault prediction module is used to analyze the connection diagram of the generator stator winding and predict possible fault types, such as short circuits between turns in the same branch, short circuits between turns in different branches of the same phase, and phase-to-phase short circuits;

[0125] The multi-loop analysis module uses the multi-loop analysis method to perform detailed calculations on the predicted internal faults to determine the magnitudes and phases of the branch currents;

[0126] The flexible optical TA configuration module winds flexible optical TAs on appropriate intermediate branches on the basis of retaining the copper ring lead-out method on the neutral point side and the branch group electromagnetic TAs;

[0127] The simulation and verification module conducts simulation tests on the generated protection scheme to verify its response and effect under various fault conditions.

[0128] This embodiment also provides a computer device, applicable to the situation of the dead-zone-free renovation method for the main protection of large generators, including a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the dead-zone-free renovation method for the main protection of large generators proposed in the above embodiment.

[0129] The computer device may be a terminal, which includes a processor, a memory, a communication interface, a display screen, and an input device connected via a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The communication interface of the computer device is used to communicate with external terminals in a wired or wireless manner. The wireless manner can be achieved through WIFI, carrier network, NFC (Near Field Communication), or other technologies. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device can be a touch layer covering the display screen, or a button, trackball, or touchpad provided on the housing of the computer device, or an external keyboard, touchpad, or mouse, etc.

[0130] This embodiment also provides a storage medium, on which a computer program is stored. When the program is executed by a processor, it implements the method for realizing the dead-zone-free transformation of the main protection of a large generator as proposed in the above embodiment.

[0131] The storage medium proposed in this embodiment and the data storage method proposed in the above embodiment belong to the same inventive concept. Technical details not described in detail in this embodiment can be referred to in the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0132] 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 within the scope of the claims of the present invention.

Claims

1. A method for modifying a large generator main protection without dead zones, characterized in that: including the following steps, Analyze the connection diagram of the stator winding of a large generator to predict the number of faults and their distribution characteristics of the same-phase same-branch turn-to-turn short circuit, same-phase different-branch turn-to-turn short circuit, and phase-to-phase short circuit that occur in the generator; Use the multi-loop analysis method to analyze and calculate the predicted internal faults of the generator, obtain the magnitude and phase of the branch currents under each fault, and then calculate the sensitivity coefficients of various main protection schemes for internal faults to determine the number of faults and fault types that various main protection schemes can respond to; Generate a main protection configuration scheme for the generator, which is used to minimize the protection dead zone and minimize the number of electromagnetic TAs; Retain the established copper ring lead-out method and branch group electromagnetic TAs on the neutral point side of the multi-branch overlapping winding generator. Through the main protection configuration scheme of the generator, select to wind a flexible optical TA on the middle branch corresponding to the electromagnetic branch group TA of the multi-branch overlapping winding technical transformation generator. By flexibly winding the optical current transformer, add the corresponding main protection scheme to eliminate the protection dead zone for small-turn turn-to-turn short circuits.

2. The method for retrofitting the main protection of a large generator without dead zones according to claim 1, characterized in that: The added flexible optical TA and main protection scheme include, Wind a flexible optical TA on the middle branch corresponding to the branch group electromagnetic TA; Set a new protection criterion based on the current comparison of the electromagnetic branch group TA and the corresponding optical TA.

3. The method for retrofitting the main protection of a large generator without dead zones as described in claim 2, characterized in that: The multi-loop analysis method includes, Establish a mathematical model of the internal faults of the generator to simulate the current distribution during internal faults of the generator; Use simulation software to calculate the mathematical model to obtain the magnitude and phase of the branch currents.

4. The method for retrofitting the main protection of a large generator without dead zones according to claim 3, characterized in that: The main protection configuration scheme of the generator includes, The combination of complete differential protection and zero-sequence current type transverse differential protection; According to the different winding structures of the generator, propose different quantitative and optimized design processes; Among them, the combination of differential protection and zero-sequence current type transverse differential protection includes: Install differential protection to form a preliminary pattern of one longitudinal protection in one category, and determine the number and location of branch TAs; Select incomplete differential protection and cooperate with the remaining zero-sequence current type transverse differential protection to determine the number and location of branch IAs; When complete differential protection is selected, when choosing the number and location of branch TAs, the current from the neutral point side can be obtained.

5. The method for retrofitting the main protection of a large generator without dead zones according to claim 4, characterized in that: When the combination of complete differential protection and zero-sequence current type transverse differential protection is not satisfied, introduce the selection and composition methods of other transverse differential and differential protections until the design indicators are met, where the design indicators are expressed as: where ε1 is represented as a variable, is represented as a union, the union of all F from i = 1 to N Ai of the sets, and N represents the number of sets.

6. The method for retrofitting the main protection of a large generator without dead zones according to claim 5, characterized in that: The judgment method of the protection dead zone includes, Judge whether the protection dead zone of the main protection configuration scheme of the technical transformation generator exceeds 5%, and the fault types that cannot act are more than half of the small-turn turn-to-turn short circuits; When it is not, wind a flexible optical TA on the middle branch corresponding to the electromagnetic branch group TA, add the corresponding main protection scheme, and eliminate the protection dead zone for small-turn turn-to-turn short circuits.

7. The method for retrofitting the main protection of a large generator without dead zones according to claim 6, characterized in that: When analyzing and calculating internal faults, the calculated inductance coefficients include the inductance coefficients generated by the air-gap magnetic field of each stator coil, the inductance coefficients generated by the end leakage magnetic field of each stator coil, the total inductance coefficients of each stator branch, the inductance coefficients of the excitation circuit and each stator branch, the inductance coefficients of the excitation circuit and each damping circuit, the inductance coefficients of each damping circuit, and the inductance coefficients of each damping circuit and each stator branch; When calculating the set inductance coefficient, it is also necessary to calculate the resistance of each stator branch and the self-inductance of the excitation circuit.

8. A main protection dead-zone-free transformation system for a large generator, based on the main protection dead-zone-free transformation method for a large generator according to any one of claims 1 to 7, characterized in that: It includes a fault prediction module, a multi-loop analysis module, a flexible optical TA configuration module, and a simulation and verification module; The fault prediction module is used to analyze the connection diagram of the generator stator winding and predict the possible fault types, such as inter-turn short circuit in the same branch, inter-turn short circuit in different branches of the same phase, and phase-to-phase short circuit; The multi-loop analysis module uses the multi-loop analysis method to perform detailed calculations on the predicted internal faults to determine the magnitude and phase of the current in each branch; The flexible optical TA configuration module selects an appropriate intermediate branch to wind the flexible optical TA on the basis of retaining the neutral point side copper ring lead-out method and the branch group electromagnetic type TA; The simulation and verification module performs simulation tests on the generated protection scheme to verify its response and effect under various fault conditions.

9. A computer device, comprising a memory and a processor, the memory storing a computer program, characterized in that: When the processor executes the computer program, it implements the steps of the method for transforming the main protection of a large generator without dead zones 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 transforming the main protection of a large generator without dead zones according to any one of claims 1 to 7.

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