Construction method of low-frequency phase-selection circuit breaker opening reignition arc transient model

Abstract

The invention relates to the technical field of low-frequency phase-selection circuit breakers, in particular to a low-frequency phase-selection circuit breaker opening reignition arc transient model construction method, which comprises the following steps: S1, simulation model construction: constructing a self-defined low-frequency phase-selection circuit breaker simulation model; s2, fault type analysis and opening action determination: analyzing a plurality of fault types; s3, analyzing a reignition arc transient process: analyzing the reignition arc transient process when the low-frequency phase selection circuit breaker is actually opened; s4, setting voltage and current constraint conditions: realizing simulation of arc reignition; s5, designing an opening and closing logic control module: designing the opening and closing logic control module; s6, writing an FORTRAN script and realizing functions: realizing a function of customizing opening and closing of the low-frequency phase-selection circuit breaker; and S7, constructing and verifying a simulation circuit: constructing the simulation circuit. According to the invention, through accurately simulating the arcing characteristic of the circuit breaker in the low-frequency environment, the harm caused by the reignition of the arc can be effectively avoided, so that the reliability and the safety of the low-frequency phase selection circuit breaker are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of low-frequency phase-selective circuit breakers, and in particular to a method for constructing a transient model of a low-frequency phase-selective circuit breaker when the circuit breaker is opened and restrike occurs. Background Art

[0002] In the power system, low-frequency phase-selective circuit breakers are widely used in power grid fault handling to ensure system stability and safety. The main function of low-frequency phase-selective circuit breakers is to quickly open the circuit breaker and effectively isolate the fault section when a short circuit or ground fault occurs to prevent the fault from further expanding. With the increasing complexity of the power system, the performance requirements of low-frequency phase-selective circuit breakers under high voltage and complex environmental conditions are increasing. Especially in low-frequency transmission and high voltage environments, the performance and arcing characteristics of circuit breakers directly affect the reliability and safety of the power system.

[0003] Existing low-frequency phase-selective circuit breakers usually rely on standard electrical models to control current and voltage, but these technologies have many shortcomings in practical applications. For example, the circuit breaker control system in the existing technology cannot effectively simulate the arcing characteristics in a low-frequency environment, which makes it easy for the circuit breaker to reignite during the opening process, increasing the risk of system failure. In addition, most existing methods lack the ability to dynamically respond to different fault types, and cannot automatically adjust the opening strategy according to the fault type. There is also a lack of accurate modeling of the arc extinguishing ability during the opening process, which affects the response speed and stability of the circuit breaker.

[0004] The purpose of the present invention is to provide a method for constructing a transient model of low-frequency phase-selective circuit breaker opening and restrike, which can dynamically adjust the opening strategy according to different fault types, has good adaptability and versatility, is suitable for different voltage levels and arc extinguishing medium conditions, and significantly improves the stability and operation efficiency of the power system. Summary of the invention

[0005] The present invention provides a method for constructing a transient model of a low-frequency phase-selective circuit breaker opening and restrike arcing.

[0006] A method for constructing a transient model of a low-frequency phase-selective circuit breaker restrike arcing comprises the following steps:

[0007] S1, simulation model building: building a custom low-frequency phase-selective circuit breaker simulation model in the PSCAD / EMTDC simulation environment, the custom low-frequency phase-selective circuit breaker simulation model including the first branch and the second branch;

[0008] S2, fault type analysis and tripping action determination: Analyze various fault types of the flexible low-frequency power transmission system, including three-phase short circuit fault, two-phase short circuit fault, two-phase ground short circuit fault, single-phase ground short circuit fault, determine the tripping action of the low-frequency phase-selective circuit breaker according to the fault type, including A-phase action, B-phase action, and C-phase action, and set the corresponding control signal;

[0009] S3, restrike transient process analysis: Analyze the restrike transient process when the low-frequency phase-selective circuit breaker is actually opened, including the start of opening, low-frequency arcing, low-frequency current interruption, transient recovery voltage generation, high-frequency arc breakdown, high-frequency current interruption, and complete arc extinction. According to the current and voltage characteristics of the restrike transient process, it is divided into multiple stages, including the start of opening to low-frequency current interruption, transient recovery voltage generation, high-frequency current breakdown and arc extinction;

[0010] S4, voltage and current constraint setting: setting different voltage and current constraint conditions for each stage of circuit breaker opening, and controlling the opening and closing of the ideal circuit breaker in the second branch of the low-frequency phase-selective circuit breaker according to the voltage and current constraint conditions at each stage, so as to simulate the arc reignition;

[0011] S5, opening and closing logic control module design: Design the opening and closing logic control module of the self-defined low-frequency phase-selective circuit breaker restrike model in the PSCAD / EMTDC simulation environment. The opening and closing logic control module includes external input parameters, internal output parameters and corresponding circuit breaker internal parameters, and parameter setting interface;

[0012] S6, FORTRAN script writing and function realization: In the script of the opening and closing logic control module, the code is written in FORTRAN language to realize the function of customizing the opening and closing of the low-frequency phase-selective circuit breaker;

[0013] S7, simulation circuit construction and verification: Build a simulation circuit to test and verify whether the low-frequency phase-selective circuit breaker model can reproduce the arc reignition phenomenon in the actual opening process, realize the phase-selective breaking function, and be effectively applied in the flexible low-frequency system.

[0014] Optionally, the first branch is composed of a resistor R, an inductor L, and a capacitor C connected in series, and the second branch is composed of a single ideal circuit breaker.

[0015] Optionally, the fault type in S2 is determined by analyzing the terminal-to-ground voltage U of the low-frequency phase-selective circuit breaker on both sides during the transient process after the fault. n and the current I of the line where the low-frequency phase-selective circuit breaker is located line To judge, by controlling the fault type control signal and the action phase signal, the circuit breaker phase selection function is realized.

[0016] Optionally, the input quantity of the opening and closing logic control module of the restrike model of the low-frequency phase-selective circuit breaker in S5 is the voltage U across the low-frequency phase-selective circuit breaker. brk and the current I flowing through the low-frequency phase-selective circuit breaker brk The output is the opening and closing signal of the ideal circuit breaker in the second branch of the low-frequency phase-selective circuit breaker.

[0017] Optionally, the corresponding circuit breaker internal parameters in S5 include opening time, low-frequency current cutting and high-frequency current cutting, dielectric insulation recovery capacity curve, high-frequency arc extinguishing capacity curve, and low-frequency phase selection circuit breaker initial state.

[0018] Optionally, the corresponding internal parameters of the circuit breaker are obtained by analyzing and processing the cutoff current, dielectric insulation recovery capability, and high-frequency arc extinguishing capability.

[0019] Optionally, the cut-off current includes a power frequency cut-off current I lc , high frequency cut-off current I hc By calculating the average cut-off current, the power frequency cut-off current and the high frequency cut-off current are combined to indicate the average level of the current cut off by the circuit breaker during the opening process. The average cut-off current is expressed as:

[0020]

[0021] Among them, f is the current angular frequency, i is the current amplitude, and α and β are parameters determined by the contact material.

[0022] Optionally, the dielectric insulation recovery capacity is expressed as:

[0023] U=A(t-t0)+B;

[0024] Among them, U represents the dielectric strength, t is time, t0 is the moment when the contacts begin to separate, A is the rising rate of the dielectric recovery strength, and B is the transient recovery voltage of the SF6 low-frequency circuit breaker before the current passes through zero.

[0025] Optionally, the high frequency arc extinguishing capability is expressed as:

[0026] d / dt=C(t-t0)+D;

[0027] Among them, di / dt is the high-frequency arc extinguishing capability, C is the rising rate of the high-frequency arc extinguishing capability, and D is the rising rate of the high-frequency arc extinguishing capability before contact separation.

[0028] Beneficial effects of the present invention:

[0029] The present invention can effectively avoid the harm caused by the reignition of the arc by accurately simulating the arcing characteristics of the circuit breaker in a low-frequency environment, thereby improving the reliability and safety of the low-frequency phase-selective circuit breaker.

[0030] The present invention, by realizing the phase-selective breaking operation function of the low-frequency phase-selective circuit breaker, can respond to different fault types and accurately control the opening action, has good adaptability and versatility, is suitable for different voltage levels and arc extinguishing medium conditions, and improves the stability and operation efficiency of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 A schematic diagram of a simulation model of a low-frequency phase-selective circuit breaker according to an embodiment of the present invention;

[0033] Figure 2 A logical flow chart of a post-fault phase selection judgment process according to an embodiment of the present invention;

[0034] Figure 3 It is a schematic diagram of the opening and closing logic control flow of the restrike transient process of the low-frequency phase-selective circuit breaker according to an embodiment of the present invention;

[0035] Figure 4 A schematic diagram of an internal parameter setting interface of a circuit breaker according to an embodiment of the present invention;

[0036] Figure 5 A schematic diagram of three-phase current flowing through a low-frequency phase-selective circuit breaker according to an embodiment of the present invention;

[0037] Figure 6 A schematic diagram of voltages at both ends of a low-frequency phase-selective circuit breaker according to an embodiment of the present invention;

[0038] Figure 7 A schematic diagram of the opening and closing signals of a low-frequency phase-selective circuit breaker according to an embodiment of the present invention;

[0039] Figure 8 Schematic diagram of high-frequency arcing current of phase A of a low-frequency phase-selective circuit breaker according to an embodiment of the present invention;

[0040] Fig. 9 A schematic diagram of transient recovery voltage of phase A of a low-frequency phase-selective circuit breaker according to an embodiment of the present invention;

[0041] Fig.10 Schematic diagram of the start signal when phase A of the low-frequency phase-selective circuit breaker reignites arcs according to an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. At the same time, it is explained here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and those skilled in the art may also adopt other alternatives to implement some known technologies; and the accompanying drawings are only for more specific description of the embodiments, and are not intended to specifically limit the present invention.

[0043] It should be noted that the references to "one embodiment", "an embodiment", "an exemplary embodiment", "some embodiments" and the like in the specification indicate that the embodiments described may include specific features, structures or characteristics, but not every embodiment may include the specific features, structures or characteristics. In addition, when a specific feature, structure or characteristic is described in conjunction with an embodiment, it should be within the knowledge of a person skilled in the art to implement such feature, structure or characteristic in conjunction with other embodiments (whether or not explicitly described).

[0044] In general, a term can be understood, at least in part, from its use in context. For example, depending, at least in part, on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in the singular sense, or can be used to describe a combination of features, structures, or characteristics in the plural sense. Additionally, the term "based on" can be understood as not necessarily intended to convey an exclusive set of factors, but can instead, depending, at least in part, on the context, allow for the presence of other factors that are not necessarily explicitly described.

[0045] like Figure 1-Figure 10 As shown, a method for constructing a transient model of a low-frequency phase-selective circuit breaker opening and restrike arcing comprises the following steps:

[0046] Step 1. Build a custom low-frequency phase-selective circuit breaker simulation model in the PSCAD / EMTDC simulation environment. The model consists of two branches: Branch 1 is composed of a resistor R, an inductor L, and a capacitor C in series. Its function is to avoid the sudden change of voltage and current of the energy storage components in the circuits on both sides caused by the opening and closing operations of the low-frequency phase-selective circuit breaker, which will cause meaningless numerical oscillations and simulate the stray parameters of the circuit breaker. Branch 2 consists of a single ideal circuit breaker, which controls the on and off of the line. Its control signal is given by the circuit breaker opening and closing logic control module, such as Figure 1 .

[0047] Step 2: Analyze four typical fault types of flexible low-frequency power transmission system: three-phase short circuit fault, two-phase short circuit fault, two-phase ground short circuit fault, and single-phase ground short circuit fault. According to the fault type, determine the opening action of three low-frequency phase-selective circuit breakers: A phase action, B phase action, and C phase action. Set the corresponding control signal as the fault type control signal and the action phase signal. The judgment process is as follows: Figure 2 ;

[0048] Step 3: Analyze the restrike transient process when the low-frequency phase-selective circuit breaker is actually opened. The process consists of 7 sub-processes: start of opening, low-frequency arcing, low-frequency current interruption, transient recovery voltage generation, high-frequency arc breakdown, high-frequency current interruption, and complete arc extinction. According to the current and voltage characteristics of each sub-process, it is divided into 4 stages: start of opening to low-frequency current interruption, transient recovery voltage generation, high-frequency current breakdown, and arc extinction.

[0049] Step 4: Set different voltage and current constraints for the four stages of circuit breaker opening, and control the opening and closing of the ideal circuit breaker in the low-frequency phase-selective circuit breaker branch 2 according to the constraints of each stage to simulate the arc reignition. The brief flow chart is as follows: Figure 3 .

[0050] Step 5: Customize the opening and closing logic control module of the restrike model of the low-frequency phase-selective circuit breaker in the PSCAD / EMTDC simulation environment, including 4 external input parameters and 1 internal output parameter, as well as the corresponding internal parameters of the circuit breaker, and set the parameter setting interface, such as Figure 4 .

[0051] Step 6: In the script Script of the opening and closing logic control module, code is written in FORTRAN language to realize the above-mentioned custom low-frequency phase-selective circuit breaker opening and closing functions.

[0052] Step 7. After completing steps 1 to 6, build a complete simulation circuit for testing to verify whether the low-frequency phase-selective circuit breaker model can reproduce the arc reignition phenomenon in the actual opening process, realize the phase-selective breaking function, and be effectively applied in the flexible low-frequency system, thereby verifying the rationality and effectiveness of the constructed model.

[0053] In step 2, the type of fault occurring on the low-frequency line where the low-frequency phase-selective circuit breaker is located is determined based on the terminal-to-ground voltage U n and the current I of the line where the low-frequency phase-selective circuit breaker is located line To judge, by controlling the fault type control signal and the action phase signal, the circuit breaker phase selection function is realized.

[0054] In step 5, the input quantity of the opening and closing logic control module of the low-frequency phase-selective circuit breaker restrike transient model is the voltage U across the low-frequency phase-selective circuit breaker. brk and the current I flowing through the low-frequency phase-selective circuit breaker brk The output is the opening and closing signal of the ideal circuit breaker in low-frequency phase-selective circuit breaker branch 2.

[0055] In step 5, the internal parameters mainly include the opening time, low-frequency current cutoff and high-frequency current cutoff, dielectric insulation recovery capacity curve, high-frequency arc extinguishing capacity curve, and the initial state of the low-frequency phase-selective circuit breaker. The above parameters can be obtained by analyzing and processing the field test data and circuit breaker equipment parameters. The main parameter sources are as follows:

[0056] a. Cut-off current: Power frequency cut-off current I lc , high frequency cut-off current I hc , the average cut-off current calculation formula is:

[0057]

[0058] Among them, f is the current angular frequency, i is the current amplitude, and α and β are parameters determined by the contact material;

[0059] b. Dielectric insulation recovery capacity calculation formula:

[0060] U=A(t-t0)+B;

[0061] Among them, U represents the dielectric strength, t is time, t0 is the moment when the contacts begin to separate, A is the rising rate of dielectric insulation recovery strength, and B is the transient recovery voltage of the SF6 low-frequency circuit breaker before the current passes through zero;

[0062] c. Calculation formula for high frequency arc extinguishing capability:

[0063] d / dt=C(t-t0)+D;

[0064] Among them, / dt is the high-frequency arc extinguishing capability, C is the rising rate of the high-frequency arc extinguishing capability, and D is the rising rate of the high-frequency arc extinguishing capability before contact separation.

[0065] Model Validation:

[0066] Taking the low-frequency phase-selective circuit breaker at 220kV voltage level as an example, a test circuit was built to analyze the voltage and current at both ends of the low-frequency phase-selective circuit breaker when opening, and to verify the rationality and effectiveness of the proposed model.

[0067] The voltage across the low-frequency phase-selective circuit breaker, the current flowing through the low-frequency phase-selective circuit breaker, and the restrike condition of the low-frequency phase-selective circuit breaker in the test circuit are shown in Figure 1. Figures 5 to 9As shown. The opening time set for the low-frequency phase-selective circuit breaker model is 0.04s. When the low-frequency phase-selective circuit breaker receives the opening signal, the circuit breaker fault judgment module starts to run and determines the phase selection operation. The low-frequency current of phase A crosses zero first, and the contact of phase A begins to separate, followed by phases B and C. When the current flowing through the low-frequency phase-selective circuit breaker is lower than the low-frequency cut-off current for the first time, the transient recovery voltage at both ends of the low-frequency phase-selective circuit breaker begins to gradually increase. When it is greater than the dielectric strength at this moment, the insulation gap will be broken down by the arc, resulting in the occurrence of the reignition phenomenon. The first reignition time is 0.0412s. After that, with the change of the transient recovery voltage at both ends of the low-frequency phase-selective circuit breaker and the dielectric strength between the contact gap, multiple breakdowns occurred inside the low-frequency phase-selective circuit breaker, and there was a mutual influence between the phase reignitions. Until 0.11762s, the contact gap of the low-frequency phase-selective circuit breaker was large enough and could not be broken down again. The arcs of each phase were extinguished one after another, and the opening was successful.

[0068] The above analysis of the simulation results of the test circuit can be concluded that the transient simulation model of the low-frequency phase-selective circuit breaker opening and restrike arc can well simulate the restrike phenomenon occurring during the transient process of the low-frequency circuit breaker opening operation, and can accurately reflect the coupling phenomenon during the phase-selective action of the three-phase circuit breaker.

[0069] The present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention. In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without the description of these details. In addition, in order to avoid unnecessary confusion about the essence of the present invention, well-known methods, processes, procedures, components and circuits are not described in detail.

[0070] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for constructing a transient model of a low-frequency phase-selective circuit breaker restrike arc, characterized in that: The following steps are involved: S1, simulation model building: building a custom low-frequency phase-selective circuit breaker simulation model in the PSCAD / EMTDC simulation environment, the custom low-frequency phase-selective circuit breaker simulation model including the first branch and the second branch; S2, fault type analysis and tripping action determination: Analyze various fault types of the flexible low-frequency power transmission system, including three-phase short circuit fault, two-phase short circuit fault, two-phase ground short circuit fault, single-phase ground short circuit fault, determine the tripping action of the low-frequency phase-selective circuit breaker according to the fault type, including A-phase action, B-phase action, and C-phase action, and set the corresponding control signal; S3, restrike transient process analysis: Analyze the restrike transient process when the low-frequency phase-selective circuit breaker is actually opened, including the start of opening, low-frequency arcing, low-frequency current interruption, transient recovery voltage generation, high-frequency arc breakdown, high-frequency current interruption, and complete arc extinction. According to the current and voltage characteristics of the restrike transient process, it is divided into multiple stages, including the start of opening to low-frequency current interruption, transient recovery voltage generation, high-frequency current breakdown and arc extinction; S4, voltage and current constraint setting: setting different voltage and current constraint conditions for each stage of circuit breaker opening, and controlling the opening and closing of the ideal circuit breaker in the second branch of the low-frequency phase-selective circuit breaker according to the voltage and current constraint conditions at each stage, so as to simulate the arc reignition; S5, opening and closing logic control module design: Design the opening and closing logic control module of the self-defined low-frequency phase-selective circuit breaker restrike model in the PSCAD / EMTDC simulation environment. The opening and closing logic control module includes external input parameters, internal output parameters and corresponding circuit breaker internal parameters, and parameter setting interface; S6, FORTRAN script writing and function realization: In the script of the opening and closing logic control module, the code is written in FORTRAN language to realize the function of opening and closing the custom low-frequency phase-selective circuit breaker; S7, simulation circuit construction and verification: Build a simulation circuit to test and verify whether the low-frequency phase-selective circuit breaker model can reproduce the arc reignition phenomenon in the actual opening process, realize the phase-selective breaking function, and be applied in the flexible low-frequency system.

2. The method for constructing a transient model of a low-frequency phase-selective circuit breaker opening and restrike according to claim 1, characterized in that: The first branch is composed of a resistor R, an inductor L, and a capacitor C connected in series, and the second branch is composed of a single ideal circuit breaker.

3. The method for constructing a transient model of a low-frequency phase-selective circuit breaker opening and restrike according to claim 2, characterized in that: The fault type in S2 is determined by analyzing the terminal-to-ground voltage U of the low-frequency phase-selective circuit breaker on both sides during the transient process after the fault. n and the current I of the line where the low-frequency phase-selective circuit breaker is located line To judge, by controlling the fault type control signal and the action phase signal, the circuit breaker phase selection function is realized.

4. The method for constructing a transient model of a low-frequency phase-selective circuit breaker restrike arcing according to claim 3, characterized in that: The input quantity of the opening and closing logic control module of the restrike model of the low-frequency phase-selective circuit breaker in S5 is the voltage U across the low-frequency phase-selective circuit breaker. brk and the current I flowing through the low-frequency phase-selective circuit breaker brk The output is the opening and closing signal of the ideal circuit breaker in the second branch of the low-frequency phase-selective circuit breaker.

5. The method for constructing a transient model of a low-frequency phase-selective circuit breaker opening and restrike according to claim 4, characterized in that: The corresponding circuit breaker internal parameters in S5 include opening time, low-frequency current cutoff and high-frequency current cutoff, dielectric insulation recovery capacity curve, high-frequency arc extinguishing capacity curve, and low-frequency phase-selective circuit breaker initial state.

6. The method for constructing a transient model of a low-frequency phase-selective circuit breaker restrike arcing according to claim 5, characterized in that: The corresponding internal parameters of the circuit breaker are obtained by analyzing and processing the cutoff current, the dielectric insulation recovery capability, and the high-frequency arc extinguishing capability.

7. The method for constructing a transient model of a low-frequency phase-selective circuit breaker restrike arcing according to claim 6, characterized in that: The cut-off current includes the power frequency cut-off current I lc , high frequency cut-off current I hc By calculating the average cut-off current, the power frequency cut-off current and the high frequency cut-off current are combined to indicate the average level of the current cut off by the circuit breaker during the opening process. The average cut-off current is expressed as: Among them, f is the current angular frequency, i is the current amplitude, and α and β are parameters determined by the contact material.

8. The method for constructing a transient model of a low-frequency phase-selective circuit breaker restrike when opening according to claim 7, characterized in that: The dielectric insulation recovery capacity is expressed as: U=A(t-t0)+B; Among them, U represents the dielectric strength, t is time, t0 is the moment when the contacts begin to separate, A is the rising rate of the dielectric recovery strength, and B is the transient recovery voltage of the SF6 low-frequency circuit breaker before the current passes through zero.

9. The method for constructing a transient model of a low-frequency phase-selective circuit breaker restrike when opening according to claim 8, characterized in that: The high frequency arc extinguishing capability is expressed as: di / dt=C(t-t0)+D; Among them, di / dt is the high-frequency arc extinguishing capability, C is the rising rate of the high-frequency arc extinguishing capability, and D is the rising rate of the high-frequency arc extinguishing capability before contact separation.

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