A method for overvoltage inversion based on tail-end current monitoring of a lightning arrester

Abstract

The application relates to a method for overvoltage inversion based on a tail end current of a lightning arrester, which comprises the following steps: step 1, a three-phase operation lightning arrester scale test model and a head end voltage and a corresponding tail end current waveform sample library are established; step 2, a lightning arrester scale test electromagnetic transient simulation model and a lightning arrester head end voltage frequency-head end voltage amplitude-tail end current waveform corresponding relationship library are established; step 3, a fast Fourier transform method is used to obtain an impulse current I i (t) of different frequencies; a voltage waveform U(k) under a set frequency current I(k) is obtained through the lightning arrester head end voltage frequency-head end voltage amplitude-tail end current waveform corresponding relationship library, and different frequency currents and the corresponding voltage waveforms U(k) are synthesized to obtain a head end voltage U(t) corresponding to the collected lightning arrester tail end current. The application can effectively reflect the lightning arrester action overvoltage condition, accurately analyze the electromagnetic transient process of a power system, and provide strong technical support for overvoltage process analysis and intelligent identification.

Description

Technical Field

[0001] This invention relates to the field of online overvoltage monitoring technology for surge arresters, and in particular to an overvoltage inversion method based on surge arrester tail current monitoring. Background Technology

[0002] Surge arresters are the primary equipment for overvoltage prevention in power systems. In high-voltage projects, surge arresters are distributed at different locations in substations. With increasing practical experience, their deployment methods have become increasingly sophisticated, effectively protecting the main equipment affected by overvoltage. Existing surge arrester monitoring devices can monitor leakage current under normal operation and record the moment of overvoltage. However, researchers have not yet conducted studies on the recording of surge arrester impulse current amplitude and waveform, missing the opportunity to explore data mining using this information-rich state variable. Summary of the Invention

[0003] The purpose of this invention is to provide an overvoltage inversion method based on the monitoring of the tail current of a surge arrester. By monitoring the tail current of the surge arrester, the amplitude and waveform of the voltage at the head of the surge arrester can be inferred, providing technical support for the intelligent identification of overvoltage amplitude and type.

[0004] This invention provides an overvoltage inversion method based on surge arrester tail current monitoring, comprising the following steps:

[0005] Step 1: Establish a scaled-down test model of a three-phase operation surge arrester. By implementing a scaled-down test, a typical lightning waveform is applied to the front end of the surge arrester. At the same time, the corresponding surge arrester front end voltage and surge arrester tail end current waveform are measured to establish a sample library of front end voltage and its corresponding tail end current waveform.

[0006] Step 2: Establish an electromagnetic transient simulation model for the scaled-down test of the surge arrester. Use the initial impulse voltage used in the scaled-down test as an excitation and input it into the electromagnetic transient simulation model for the scaled-down test of the surge arrester to obtain the corresponding tail current data of the surge arrester. Calculate the corresponding initial voltage of the tail current of the surge arrester under different conditions and establish a database of the correspondence between the frequency of the initial voltage of the surge arrester, the amplitude of the initial voltage of the initial voltage, and the waveform of the tail current.

[0007] Step 3: Using the Fast Fourier Transform (FFT) method, the acquired surge arrester tail current I(t) waveform is transformed from the time domain to the frequency domain to obtain its impulse current I at different frequencies. i (t); The voltage waveform U(k) under the set frequency current I(k) is obtained by using the correspondence library of the voltage frequency-voltage amplitude-current waveform at the start of the surge arrester. The voltage waveforms U(k) of different frequency currents are synthesized to obtain the start voltage U(t) corresponding to the collected surge arrester tail current.

[0008] Furthermore, the method for establishing the electromagnetic transient simulation model of the surge arrester scaled-down test in step 2 includes:

[0009] Based on the finite element field analysis method, the potential distribution parameters, related metal components and capacitance distribution calculation results in the scaled-down test of the surge arrester are obtained, and the calculation results are used as parameters to establish an electromagnetic transient simulation model of the scaled-down test of the surge arrester.

[0010] Furthermore, step 3 also includes:

[0011] The voltage waveform U(t) at the first end is obtained, and its wavefront time, wavetail time, and amplitude are obtained. Based on the sample library of the first end voltage and its corresponding tail end current obtained from the scaled-down test model, an intelligent identification algorithm is used to intelligently identify the voltage type at the first end of the surge arrester.

[0012] By employing the above scheme and the overvoltage inversion method based on the current monitoring at the tail end of the surge arrester, the overvoltage situation of the surge arrester can be effectively reflected, thereby enabling accurate analysis of the electromagnetic transient process of the power system and providing strong technical support for overvoltage process analysis and intelligent identification.

[0013] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall process of the present invention.

[0015] Figure 2 This is a schematic diagram of the installation method of the surge arrester of the present invention.

[0016] Figure 3 This is a simulation model diagram of the electromagnetic transient circuit for monitoring the tail current of the surge arrester according to the present invention.

[0017] Figure 4 This is a comparison chart of the experimental and simulation results of this invention.

[0018] Among them: (a) the waveform of the tail current measured in the experiment; (b) the waveform of the impulse generator measured in the experiment using an oscilloscope; (c) the voltage and current waveform obtained from the simulation. Detailed Implementation

[0019] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0020] This embodiment provides a method for accurate analysis of the overvoltage process of a surge arrester. This method utilizes finite element analysis and the construction of an ATP-EMTP simulation model, fully leveraging the current monitoring data at the tail end of the surge arrester to analyze the amplitude and waveform of the overvoltage at the head end. This allows for the inversion of the overvoltage process, uncovering the information-rich state variable of the surge arrester's impulse current. The overall process is as follows: Figure 1 As shown, it includes:

[0021] 1. Establish a scaled-down test model of a three-phase operation surge arrester.

[0022] A scaled-down test model of a three-phase surge arrester was established using a 35kV surge arrester. The surge arrester installation method during the scaled-down test was as follows: Figure 2 Connect an impulse voltage generator to the conductor, adjust the parameters of the impulse voltage generator, apply a typical lightning waveform to the front end (high voltage end) of the surge arrester, and simultaneously measure the corresponding surge arrester front end voltage and surge arrester tail end (grounding end) current waveforms, thereby establishing a sample library of front end voltage and its corresponding tail end current waveforms.

[0023] 2. Establish a simulation model for electromagnetic transient distributed parameters in a scaled-down test.

[0024] Based on the site layout, a model of the electric and magnetic fields of the surge arrester was established in the finite element analysis software. The properties of the relevant materials of the surge arrester are shown in Table 1.

[0025] Table 1. Material Properties Related to Surge Arresters

[0026] Air 1 <![CDATA[10 10 ]]> Composite jacket 5.1 <![CDATA[10 10 ]]> Epoxy resin 4.2 <![CDATA[10 10 ]]> Zinc oxide resistors 800 <![CDATA[10 6 ]]> aluminum gasket 5500 <![CDATA[2.83×10 -8 ]]> Metal flanges and bolts 5000 <![CDATA[9.78×10 -8 ]]>

[0027] The potential distribution parameters, related metal components, and capacitance distribution in the scaled-down arrester test were obtained using the finite element method (FEM). Since the inductance between metal components decreases with increasing distance, for simplicity, the inductance between distant metal components was disregarded; the inductance of a single arrester was calculated to be 93 μH through field analysis. Using the FEM field calculation results as parameters, an electromagnetic transient simulation model of the scaled-down arrester test was established in the electromagnetic transient simulation software ATP-EMTP, as follows: Figure 3 .

[0028] By using the initial impulse voltage of the scaled-down test as an excitation and inputting it into the electromagnetic transient simulation model of the scaled-down test, the corresponding surge arrester tail current data can be obtained.

[0029] Comparing the simulation results with the experimental results revealed good consistency. Figure 4This indicates that by establishing a scaled-down electromagnetic transient simulation model consistent with actual operating conditions, the corresponding head-end voltage of the arrester tail-end current under different conditions can be calculated, thereby establishing a database of the correspondence between the arrester head-end voltage frequency, head-end voltage amplitude, and tail-end current waveform, providing data support for the inversion of head-end overvoltage in arrester tail-end current monitoring.

[0030] 3. Overvoltage inversion from surge arrester tail current

[0031] The fast Fourier transform method is used to transform the acquired surge arrester tail current I(t) waveform from the time domain to the frequency domain, thereby obtaining the impulse current I at different frequencies. i (t).

[0032] By obtaining the voltage waveform U(k) under a specific frequency current I(k) through the correspondence library of the voltage frequency, voltage amplitude and current waveform at the surge arrester, the voltage waveform U(k) at the surge arrester ...

[0033] By obtaining the final first-terminal voltage waveform U(t), key parameters such as the waveform head time, waveform tail time, and amplitude can be obtained. Based on the first-terminal voltage and its corresponding tail current waveform sample library obtained from the scaled-down test model, an intelligent identification algorithm is used to intelligently identify the first-terminal voltage type of the surge arrester, providing theoretical support for the overvoltage analysis and intelligent identification of the surge arrester.

[0034] This invention establishes a sample library of typical front-end voltages and their corresponding rear-end currents by conducting scaled-down surge arrester tests. Using finite element field analysis, it obtains various distributed parameters from the scaled-down surge arrester tests. Based on these parameters, an electromagnetic transient simulation model of the scaled-down surge arrester test is established using electromagnetic transient analysis software. The simulation establishes a database of the correspondence between front-end voltage frequency, front-end voltage amplitude, and rear-end current waveform. Based on the fast Fourier transform method, it effectively realizes intelligent inversion of the front-end voltage based on surge arrester rear-end current monitoring. This effectively reflects the overvoltage conditions of the surge arrester operation, thereby enabling precise analysis of the electromagnetic transient processes of the power system and providing strong technical support for overvoltage process analysis and intelligent identification.

[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An overvoltage inversion method based on surge arrester tail current monitoring, characterized in that, Includes the following steps: Step 1: Establish a scaled-down test model of a three-phase operation surge arrester. By implementing a scaled-down test, a typical lightning waveform is applied to the front end of the surge arrester. At the same time, the corresponding surge arrester front end voltage and surge arrester tail end current waveform are measured to establish a sample library of front end voltage and its corresponding tail end current waveform. Step 2: Establish an electromagnetic transient simulation model for the scaled-down test of the surge arrester. Use the initial impulse voltage used in the scaled-down test as an excitation and input it into the electromagnetic transient simulation model for the scaled-down test of the surge arrester to obtain the corresponding tail current data of the surge arrester. Calculate the corresponding initial voltage of the tail current of the surge arrester under different conditions and establish a database of the correspondence between the frequency of the initial voltage of the surge arrester, the amplitude of the initial voltage of the initial voltage, and the waveform of the tail current. Step 3: Using the Fast Fourier Transform (FFT) method, the acquired surge arrester tail current I(t) waveform is transformed from the time domain to the frequency domain to obtain its impulse current I at different frequencies. i (t); The voltage waveform U(k) under the set frequency current I(k) is obtained by using the correspondence library of the voltage frequency-voltage amplitude-current waveform at the start of the surge arrester. The voltage waveform U(k) of different frequency currents and their corresponding voltage waveforms U(k) are synthesized to obtain the start voltage U(t) corresponding to the collected surge arrester tail current. The voltage waveform U(t) at the first end is obtained, and its wavefront time, wavetail time, and amplitude are obtained. Based on the sample library of the first end voltage and its corresponding tail end current obtained from the scaled-down test model, an intelligent identification algorithm is used to intelligently identify the voltage type at the first end of the surge arrester.

2. The overvoltage inversion method based on surge arrester tail current monitoring according to claim 1, characterized in that, The method for establishing the electromagnetic transient simulation model of the surge arrester scaled-down test in step 2 includes: Based on the finite element field analysis method, the potential distribution parameters, related metal components and capacitance distribution calculation results in the scaled-down test of the surge arrester are obtained, and the calculation results are used as parameters to establish an electromagnetic transient simulation model of the scaled-down test of the surge arrester.

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