Method and device for detecting resistive current of surge arrester and surge arrester detection system

Abstract

The application discloses a lightning arrester resistance current detection method, device and lightning arrester detection system. The method comprises the following steps: determining three-phase third harmonic current capacitive components and three-phase third harmonic current resistance components; determining three-phase third harmonic resistance currents of a three-phase lightning arrester according to the three-phase third harmonic current resistance components; determining three-phase fundamental wave resistance currents of the three-phase lightning arrester according to three-phase interphase capacitances, three-phase fundamental wave current resistance components and three-phase fundamental wave voltage effective values; and determining that the three-phase lightning arrester is in an abnormal state if any one of the three-phase third harmonic resistance currents is greater than or equal to a first preset threshold value or any one of the three-phase fundamental wave resistance currents is greater than or equal to a second preset threshold value. The method can effectively eliminate power grid harmonics and interphase capacitance interference in the case that the power grid contains harmonics, and can realize reliable and accurate extraction of lightning arrester resistance currents in normal and abnormal states of the lightning arrester.

Description

Technical Field

[0001] This application relates to the field of electrical measurement technology, and in particular to a method, device and system for detecting resistive current in surge arresters. Background Technology

[0002] Currently, surge arrester resistive current detection technologies and instruments mainly employ the fundamental wave method, harmonic method, and compensation method. The fundamental wave method uses the secondary voltage of the input voltage transformer as a reference signal, along with the current signal from the zinc oxide surge arrester. After Fourier transform, the fundamental voltage, the fundamental current peak value, and the current-voltage angle are obtained. Then, the fundamental resistive current is calculated through orthogonal decomposition. The compensation method is similar in principle to the fundamental wave method, except that it obtains the resistive current by compensating for the capacitive component. The harmonic method only requires a single current signal as input.

[0003] In the process of developing this application, the applicant discovered that the aforementioned related technologies have at least the following problems:

[0004] On the one hand, eliminating phase-to-phase interference simply relies on obtaining the phase angle of phase C by subtracting half of the phase angle of phase A by subtracting half of the phase angle of phase A, without considering the difference in capacitance between phases A and B and between phases B and C. This makes the resistive current test of the surge arrester affected by the interference of phase-to-phase capacitance. On the other hand, for surge arresters of 110kV and below, they are inevitably affected by the third harmonic voltage during operation, resulting in inaccurate test results and affecting the accurate evaluation of the surge arrester's condition. Summary of the Invention

[0005] In view of this, this application provides a method, device, system and storage medium for detecting the resistive current of a surge arrester. The main purpose is to solve the problem that the resistive current test of zinc oxide surge arresters under operating voltage is affected by power grid harmonics and phase-to-phase interference, resulting in inaccurate detection results of the resistive current of the surge arrester.

[0006] According to a first aspect of this application, a method for detecting the resistive current of a surge arrester is provided, the method comprising:

[0007] In response to the arrester resistive current detection command, the three-phase voltage and leakage current of the three-phase arrester included in the arrester resistive current detection command are obtained;

[0008] Based on the three-phase voltage and leakage current, determine the effective values ​​of the three-phase fundamental voltage, the three-phase third harmonic voltage, the three-phase fundamental current, the three-phase third harmonic current, the first phase difference, and the second phase difference of the three-phase surge arrester. The first phase difference is the phase difference between the three-phase fundamental voltage and the three-phase fundamental current, and the second phase difference is the phase difference between the three-phase third harmonic voltage and the three-phase third harmonic current.

[0009] Based on the first phase difference, the effective values ​​of the three-phase fundamental voltage and the effective values ​​of the three-phase fundamental current, determine the capacitive component and the resistive component of the three-phase fundamental current.

[0010] Based on the second phase difference, the effective value of the three-phase third harmonic voltage, and the effective value of the three-phase third harmonic current, determine the capacitive component and the resistive component of the three-phase third harmonic current.

[0011] Based on the resistive components of the three-phase third harmonic current, determine the three-phase third harmonic resistive current of the three-phase surge arrester;

[0012] The three-phase phase-to-phase capacitance of the three-phase surge arrester is determined based on the effective value of the three-phase fundamental voltage, the capacitive component of the three-phase fundamental current, the effective value of the three-phase third harmonic voltage, and the capacitive component of the three-phase third harmonic current.

[0013] The three-phase fundamental resistive current of the three-phase surge arrester is determined based on the three-phase interphase capacitance, the resistive component of the three-phase fundamental current, and the effective value of the three-phase fundamental voltage.

[0014] The three-phase third harmonic resistive current is compared with the first preset threshold, and the three-phase fundamental resistive current is compared with the second preset threshold.

[0015] If any one of the three-phase third harmonic resistive currents is greater than or equal to the first preset threshold, or if any one of the three-phase fundamental resistive currents is greater than or equal to the second preset threshold, the three-phase surge arrester is determined to be in an abnormal state.

[0016] Optionally, the steps of determining the effective values ​​of the three-phase fundamental voltage, the three-phase third harmonic voltage, the three-phase fundamental current, the three-phase third harmonic current, the first phase difference, and the second phase difference of the three-phase surge arrester based on the three-phase voltage and leakage current specifically include:

[0017] The three-phase voltage and leakage current are converted from digital signals using an A / D converter to obtain digital signals.

[0018] Using a preset algorithm, the digital signal is calculated to obtain the effective values ​​of the three-phase fundamental voltage, the effective values ​​of the three-phase third harmonic voltage, the first initial phase angle, the second initial phase angle, the effective values ​​of the three-phase fundamental current, the effective values ​​of the three-phase third harmonic current, the third initial phase angle, and the fourth initial phase angle. Among them, the first initial phase angle is the initial phase angle of the three-phase fundamental voltage, the second initial phase angle is the initial phase angle of the three-phase third harmonic voltage, the third initial phase angle is the initial phase angle of the three-phase fundamental current, and the fourth initial phase angle is the initial phase angle of the three-phase third harmonic current.

[0019] The first phase difference and the second phase difference are determined based on the effective values ​​of the three-phase fundamental voltage, the effective values ​​of the three-phase third harmonic voltage, the first initial phase angle, the second initial phase angle, the effective values ​​of the three-phase fundamental current, the effective values ​​of the three-phase third harmonic current, the third initial phase angle, and the fourth initial phase angle.

[0020] Optionally, the step of determining the capacitive component and resistive component of the three-phase fundamental current based on the first phase difference, the effective value of the three-phase fundamental voltage, and the effective value of the three-phase fundamental current specifically includes:

[0021] Based on the first phase difference and the effective value of the three-phase fundamental voltage, the effective value of the three-phase fundamental current is orthogonally decomposed to obtain the capacitive component of the three-phase fundamental current with a voltage lead of 90 degrees.

[0022] Based on the effective value of the three-phase fundamental voltage, the three-phase fundamental current is orthogonally decomposed to obtain the resistive component of the three-phase fundamental current in the same direction as the voltage.

[0023] Optionally, the step of determining the capacitive component and resistive component of the three-phase third harmonic current based on the second phase difference, the effective value of the three-phase third harmonic voltage, and the effective value of the three-phase third harmonic current specifically includes:

[0024] Based on the second phase difference and the effective value of the third harmonic voltage, the effective value of the three-phase third harmonic current is orthogonally decomposed to obtain the capacitive component of the three-phase third harmonic current with a voltage lead of 90 degrees.

[0025] Based on the effective value of the three-phase third harmonic voltage, the effective value of the three-phase third harmonic current is orthogonally decomposed to obtain the resistive components of the three-phase third harmonic in the same direction as the voltage.

[0026] Optionally, the step of determining the three-phase inter-phase capacitance of a three-phase surge arrester based on the effective value of the three-phase fundamental voltage, the capacitive component of the three-phase fundamental current, the effective value of the three-phase third harmonic voltage, and the capacitive component of the three-phase third harmonic current specifically includes:

[0027] Assume the three phases of the three-phase surge arrester are phase A, phase B, and phase C;

[0028] Based on the three-phase fundamental current capacitive component, the three-phase third harmonic current capacitive component, the three-phase fundamental voltage effective value and the three-phase third harmonic voltage effective value, the phase-to-phase capacitance between phase A and phase B, the phase-to-phase capacitance between phase A and phase C and the phase-to-phase capacitance between phase B and phase C of the three-phase surge arrester are calculated using the first and second preset equation sets respectively.

[0029] The first set of pre-defined equations is:

[0030] I a1C =ωC A U a1 -ωC AB U b1 sin(30°)-ωC AC U c1 sin(30°)

[0031] I b1C =ωC B U b1 -ωC BC U c1 sin(30°)-ωC AB U a1 sin(30°)

[0032] I c1C =ωC C U c1 -ωC AC U a1 sin(30°)-ωC BC U b1 sin(30°)

[0033] Among them, the above I a1C I is the capacitive component of the fundamental current in phase A; b1C This refers to the capacitive component of the fundamental current in phase B; the aforementioned I c1C The fundamental current of phase C is the capacitive component; ω is a constant; C is a constant. A The equivalent capacitance of phase A; the above C B The equivalent capacitance of phase B; the above C C The equivalent capacitance of phase C; the above U a1 The effective value of the fundamental voltage of phase A; the above U b1 This is the effective value of the fundamental voltage of phase B; the above U c1 This is the effective value of the fundamental voltage of phase C; the above C AB C is the interphase capacitance between phase A and phase B; AC This refers to the interphase capacitance between phase A and phase C; the aforementioned C BC This refers to the interphase capacitance between phase B and phase C.

[0034] The second set of pre-defined equations is:

[0035] I a3C =3ωU a3 (C A +C AB +C AC )

[0036] I b3C =3ωU b3 (C B +C AB +C BC )

[0037] I c3C =3ωU c3 (C C +C AC +C BC )

[0038] Among them, the above Ia3C The third harmonic capacitive component of phase A; the above I b3C The third harmonic capacitive component of phase B; the above I c3C The third harmonic capacitive component of phase C; the above U a3 The effective value of the third harmonic voltage of phase A; the above U b3 The effective value of the third harmonic voltage of phase B; the above U c3 This is the effective value of the third harmonic voltage of phase C.

[0039] Optionally, the step of determining the three-phase fundamental resistive current of the three-phase surge arrester based on the three-phase interphase capacitance, the resistive component of the three-phase fundamental current, and the effective value of the three-phase fundamental voltage specifically includes:

[0040] Based on the three-phase interphase capacitance, the resistive component of the three-phase fundamental current, and the effective value of the three-phase fundamental voltage, the fundamental resistive current of the A-phase valve plate, the fundamental resistive current of the B-phase valve plate, and the fundamental resistive current of the C-phase valve plate of the three-phase surge arrester are calculated using the third preset equation set.

[0041] The third set of pre-defined equations includes:

[0042] I a1-R =I aa1-R +ωC AB U b1 cos(30°)-ωC AC U c1 cos(30°)

[0043] I b1-R =I bb1-R +ωC BC U c1 cos(30°)-ωC AB U a1 cos(30°)

[0044] I c1-R =I cc1-R +ωC AC U a1 cos(30°)-ωC BC U b1 cos(30°)

[0045] Among them, the above I a1-R The fundamental current resistive component of phase A; the above I b1-R This refers to the resistive component of the fundamental current in phase B; the aforementioned I c1-R The fundamental current resistive component of phase C; the above I aa1-R This refers to the fundamental resistive current of the A-phase valve plate itself; the aforementioned I bb1-R This refers to the fundamental resistive current of the B-phase valve plate itself; the aforementioned I cc1-R This is the fundamental resistive current of the C-phase valve plate itself.

[0046] According to a second aspect of this application, a device for detecting the resistive current of a surge arrester is provided, the device comprising:

[0047] The acquisition module is used to acquire the three-phase voltage and leakage current of the three-phase arrester included in the surge arrester resistive current detection command in response to the surge arrester resistive current detection command.

[0048] The first determining module is used to determine the effective values ​​of the three-phase fundamental voltage, the effective values ​​of the three-phase third harmonic voltage, the effective values ​​of the three-phase fundamental current, the effective values ​​of the three-phase third harmonic current, the first phase difference, and the second phase difference of the three-phase surge arrester based on the three-phase voltage and the leakage current. The first phase difference is the phase difference between the three-phase fundamental voltage and the three-phase fundamental current, and the second phase difference is the phase difference between the three-phase third harmonic voltage and the three-phase third harmonic current.

[0049] The second determining module is used to determine the capacitive component and resistive component of the three-phase fundamental current based on the first phase difference, the effective value of the three-phase fundamental voltage, and the effective value of the three-phase fundamental current.

[0050] The third determining module is used to determine the capacitive component and resistive component of the three-phase third harmonic current based on the second phase difference, the effective value of the three-phase third harmonic voltage, and the effective value of the three-phase third harmonic current.

[0051] The fourth determining module is used to determine the three-phase third harmonic resistive current of the three-phase surge arrester based on the resistive component of the three-phase third harmonic current.

[0052] The fifth determining module is used to determine the three-phase phase-to-phase capacitance of the three-phase surge arrester based on the effective value of the three-phase fundamental voltage, the capacitive component of the three-phase fundamental current, the effective value of the three-phase third harmonic voltage, and the capacitive component of the three-phase third harmonic current.

[0053] The sixth determining module is used to determine the three-phase fundamental resistive current of the three-phase surge arrester based on the three-phase interphase capacitance, the resistive component of the three-phase fundamental current, and the effective value of the three-phase fundamental voltage.

[0054] The comparison module is used to compare the three-phase third harmonic resistive current with a first preset threshold and the three-phase fundamental resistive current with a second preset threshold.

[0055] The seventh determination module is used to determine that the three-phase surge arrester is in an abnormal state if any one of the three-phase third harmonic resistive currents is greater than or equal to the first preset threshold, or any one of the three-phase fundamental resistive currents is greater than or equal to the second preset threshold.

[0056] Optionally, the first determining module is specifically used for:

[0057] The three-phase voltage and leakage current are converted from digital signals using an A / D converter to obtain digital signals.

[0058] Using a preset algorithm, the digital signal is calculated to obtain the effective values ​​of the three-phase fundamental voltage, the effective values ​​of the three-phase third harmonic voltage, the first initial phase angle, the second initial phase angle, the effective values ​​of the three-phase fundamental current, the effective values ​​of the three-phase third harmonic current, the third initial phase angle, and the fourth initial phase angle. Among them, the first initial phase angle is the initial phase angle of the three-phase fundamental voltage, the second initial phase angle is the initial phase angle of the three-phase third harmonic voltage, the third initial phase angle is the initial phase angle of the three-phase fundamental current, and the fourth initial phase angle is the initial phase angle of the three-phase third harmonic current.

[0059] The first phase difference and the second phase difference are determined based on the effective values ​​of the three-phase fundamental voltage, the effective values ​​of the three-phase third harmonic voltage, the first initial phase angle, the second initial phase angle, the effective values ​​of the three-phase fundamental current, the effective values ​​of the three-phase third harmonic current, the third initial phase angle, and the fourth initial phase angle.

[0060] Optionally, the second determining module is specifically used for:

[0061] Based on the first phase difference and the effective value of the three-phase fundamental voltage, the effective value of the three-phase fundamental current is orthogonally decomposed to obtain the capacitive component of the three-phase fundamental current with a voltage lead of 90 degrees.

[0062] Based on the effective value of the three-phase fundamental voltage, the three-phase fundamental current is orthogonally decomposed to obtain the resistive component of the three-phase fundamental current in the same direction as the voltage.

[0063] Optionally, the third determining module is specifically used for:

[0064] Based on the second phase difference and the effective value of the third harmonic voltage, the effective value of the three-phase third harmonic current is orthogonally decomposed to obtain the capacitive component of the three-phase third harmonic current with a voltage lead of 90 degrees.

[0065] Based on the effective value of the three-phase third harmonic voltage, the effective value of the three-phase third harmonic current is orthogonally decomposed to obtain the resistive components of the three-phase third harmonic in the same direction as the voltage.

[0066] Optionally, the fifth determining module is specifically used for:

[0067] Assume the three phases of the three-phase surge arrester are phase A, phase B, and phase C;

[0068] Based on the three-phase fundamental current capacitive component, the three-phase third harmonic current capacitive component, the three-phase fundamental voltage effective value and the three-phase third harmonic voltage effective value, the phase-to-phase capacitance between phase A and phase B, the phase-to-phase capacitance between phase A and phase C and the phase-to-phase capacitance between phase B and phase C of the three-phase surge arrester are calculated using the first and second preset equation sets respectively.

[0069] The first set of pre-defined equations is:

[0070] I a1C =ωC A U a1 -ωC AB U b1 sin(30°)-ωC AC U c1 sin(30°)

[0071] I b1C =ωC B U b1 -ωC BC U c1 sin(30°)-ωC AB U a1 sin(30°)

[0072] I c1C =ωC C U c1 -ωC AC U a1 sin(30°)-ωC BC U b1 sin(30°)

[0073] Among them, the above I a1C I is the capacitive component of the fundamental current in phase A; b1C This refers to the capacitive component of the fundamental current in phase B; the aforementioned I c1C The fundamental current of phase C is the capacitive component; ω is a constant; C is a constant. A The equivalent capacitance of phase A; the above C B The equivalent capacitance of phase B; the above C C The equivalent capacitance of phase C; the above U a1 The effective value of the fundamental voltage of phase A; the above U b1 This is the effective value of the fundamental voltage of phase B; the above U c1 This is the effective value of the fundamental voltage of phase C; the above C AB C is the interphase capacitance between phase A and phase B; AC This refers to the interphase capacitance between phase A and phase C; the aforementioned C BC This refers to the interphase capacitance between phase B and phase C.

[0074] The second set of pre-defined equations is:

[0075] I a3C =3ωU a3 (C A +C AB +C AC )

[0076] I b3C =3ωU b3 (CB +C AB +C BC )

[0077] I c3C =3ωU c3 (C C +C AC +C BC )

[0078] Among them, the above I a3C The third harmonic capacitive component of phase A; the above I b3C The third harmonic capacitive component of phase B; the above I c3C The third harmonic capacitive component of phase C; the above U a3 The effective value of the third harmonic voltage of phase A; the above U b3 The effective value of the third harmonic voltage of phase B; the above U c3 This is the effective value of the third harmonic voltage of phase C.

[0079] Optionally, the sixth determining module is specifically used for:

[0080] Based on the three-phase interphase capacitance, the resistive component of the three-phase fundamental current, and the effective value of the three-phase fundamental voltage, the fundamental resistive current of the A-phase valve plate, the fundamental resistive current of the B-phase valve plate, and the fundamental resistive current of the C-phase valve plate of the three-phase surge arrester are calculated using the third preset equation set.

[0081] The third set of pre-defined equations includes:

[0082] I a1-R =I aa1-R +ωC AB U b1 cos(30°)-ωC AC U c1 cos(30°)

[0083] I b1-R =I bb1-R +ωC BC U c1 cos(30°)-ωC AB U a1 cos(30°)

[0084] I c1-R =I cc1-R +ωC AC U a1 cos(30°)-ωC BC U b1 cos(30°)

[0085] Among them, the above I a1-R The fundamental current resistive component of phase A; the above I b1-RThis refers to the resistive component of the fundamental current in phase B; the aforementioned I c1-R The fundamental current resistive component of phase C; the above I aa1-R This refers to the fundamental resistive current of the A-phase valve plate itself; the aforementioned I bb1-R This refers to the fundamental resistive current of the B-phase valve plate itself; the aforementioned I cc1-R This is the fundamental resistive current of the C-phase valve plate itself.

[0086] According to a third aspect of this application, a surge arrester detection system is proposed, including a surge arrester resistive current detection device according to the second aspect.

[0087] Optionally, the system also includes:

[0088] Three-phase surge arrester;

[0089] Voltage transformer, connected in parallel with three-phase surge arrester;

[0090] The first sensor is located on the secondary side of the voltage transformer connected in parallel with the three-phase surge arrester. The first sensor is used to collect the three-phase voltage.

[0091] The second sensor is installed between the three-phase surge arrester and the grounding lead. The second sensor is used to collect leakage current.

[0092] A / D conversion module, used to convert three-phase voltage and leakage current into digital signals;

[0093] The first calculation module is used to calculate the effective values ​​of the three-phase fundamental voltage, the three-phase third harmonic voltage, the three-phase fundamental current, the three-phase third harmonic current, the first initial phase angle, and the second initial phase angle of the three-phase surge arrester.

[0094] The second calculation module is used to calculate the three-phase third harmonic resistive current and the three-phase fundamental resistive current of the three-phase surge arrester.

[0095] The display module is used to display the three-phase third harmonic resistive current and the three-phase fundamental resistive current.

[0096] According to a fourth aspect of this application, a readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described in any one of the first aspects.

[0097] By employing the above technical solution, this application provides a method, device, and system for detecting the resistive current of a surge arrester. It uses the capacitive component of the leakage current as a parameter to calculate the interphase coupling capacitance. Utilizing the numerical relationships between the capacitive component of the fundamental total leakage current of the three-phase surge arrester, the fundamental voltage, and the equivalent capacitance of the arrester's varistor and the interphase coupling capacitance, as well as the numerical relationships between the capacitive component of the third harmonic total leakage current of the three-phase surge arrester, the fundamental voltage, and the equivalent capacitance of the arrester's varistor and the interphase coupling capacitance, the equivalent capacitance of the three-phase arrester's varistor and the interphase coupling capacitance between each pair of phases are calculated. Then, using the relationship between the fundamental resistive current and the interphase coupling capacitance current, the fundamental resistive current that removes interphase interference current is obtained through compensation. Subsequently, based on a first preset threshold and a second preset threshold, the three-phase fundamental resistive current and the three-phase third harmonic resistive current of the three-phase surge arrester are accurately detected. By observing the changes in resistive current, the state of the three-phase surge arrester is accurately determined. By using the above method, the resistive current component can be extracted from the effective values ​​of the fundamental and third harmonic voltages in the voltage signal. When the power grid contains harmonics, it can effectively eliminate grid harmonics and phase-to-phase capacitance interference. It can reliably and accurately extract the resistive current of the surge arrester under both normal and abnormal conditions.

[0098] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0099] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0100] Figure 1 A schematic flowchart of a surge arrester resistive current detection method provided in an embodiment of this application is shown;

[0101] Figure 2 A schematic flowchart of another surge arrester resistive current detection method provided in an embodiment of this application is shown;

[0102] Figure 3 This shows a vector diagram illustrating the fundamental resistive current calculation of the A-phase surge arrester of the three-phase surge arrester provided in this application embodiment;

[0103] Figure 4 A schematic flowchart of a surge arrester resistive current detection method according to a specific embodiment of this application is shown;

[0104] Figure 5 A schematic diagram of the structure of a surge arrester resistive current detection device provided in an embodiment of this application is shown. Detailed Implementation

[0105] Exemplary embodiments of the present application will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0106] This application provides a method for detecting the resistive current of a surge arrester, such as... Figure 1 As shown, the method includes:

[0107] 101. In response to the surge arrester resistive current detection command, obtain the three-phase voltage, leakage current and three-phase capacitance of the three-phase surge arrester included in the surge arrester resistive current detection command.

[0108] This application provides a method for detecting the resistive current of a surge arrester. In practical applications, the zinc oxide resistance element is encapsulated inside a porcelain bushing or silicone rubber. Under long-term AC operating voltage, initially only a small leakage current flows, which is the sum of capacitive and resistive currents. Under long-term AC operating voltage, the sign of zinc oxide resistance element degradation is the continuous increase in resistive current, leading to accelerated temperature rise. Over time, it eventually fails due to thermal imbalance, endangering the normal operation of the power system. Therefore, for AC zinc oxide surge arresters, periodically detecting the resistive current of their resistance elements is very meaningful. However, after the surge arrester deteriorates due to moisture, due to its nonlinear characteristics, a third harmonic component resistive current will be generated under the fundamental voltage. For surge arresters of 110kV and below, the third harmonic voltage is inevitably involved in operation. The phase-to-phase interference and the influence of harmonic voltage cause inaccurate resistive current detection results, thus affecting the accurate evaluation of the surge arrester's condition. Based on the above problems, this application proposes a method for detecting the resistive current of a surge arrester, which achieves an effective evaluation of the arrester's condition by testing the resistive current of the fundamental and third harmonic waves.

[0109] Specifically, in response to the surge arrester resistive current detection command, the three-phase voltage, leakage current, and three-phase capacitance of the three-phase surge arrester contained in the detection command are acquired. It should be noted that the three-phase voltage is the grid voltage signal obtained by the voltage transformer connected in parallel with the three-phase surge arrester, and the leakage current is the total leakage current signal of the three-phase surge arrester under the action of grid harmonics.

[0110] It is understandable that the three phases of a three-phase surge arrester are phase A, phase B, and phase C, the three-phase voltages of the three-phase surge arrester are phase A voltage, phase B voltage, and phase C voltage, the leakage currents are phase A leakage current, phase B leakage current, and phase C leakage current, and the three-phase capacitances are phase A capacitance, phase B capacitance, and phase C capacitance.

[0111] Optionally, after receiving the secondary voltage signal of the parallel voltage transformer of the three-phase surge arrester via a signal line, the three-phase voltage of the three-phase surge arrester is obtained through preset transformation ratio parameters. The preset transformation ratio parameters refer to the voltage transformer transformation ratio.

[0112] 102. Based on the three-phase voltage and leakage current, determine the effective values ​​of the three-phase fundamental voltage, the three-phase third harmonic voltage, the three-phase fundamental current, the three-phase third harmonic current, the first phase difference, and the second phase difference of the three-phase surge arrester.

[0113] In this step, after acquiring the three-phase voltage and leakage current of the three-phase surge arrester, the acquired three-phase voltage and leakage current signals are converted from analog to digital signals to improve the anti-interference capability during transmission. Further, the acquired digital signals are subjected to FFT (Fast Fourier Transform) analysis. Through FFT analysis of the digital signals, the effective values ​​of the three-phase fundamental voltage, the effective values ​​of the three-phase third harmonic voltage, the initial phase angle of the voltage, the effective values ​​of the three-phase fundamental current, the effective values ​​of the three-phase third harmonic current, and the initial phase angle of the current are obtained. Then, the first phase difference between the three-phase fundamental voltage and current, and the second phase difference between the three-phase third harmonic voltage and current are calculated.

[0114] It is understandable that the effective values ​​of the three-phase fundamental voltages of the three-phase surge arrester are the effective values ​​of the fundamental voltages of phase A, phase B, and phase C, respectively; the effective values ​​of the three-phase third harmonic voltages are the effective values ​​of the harmonic voltages of phase A, phase B, and phase C, respectively; the effective values ​​of the three-phase fundamental currents are the effective values ​​of the fundamental currents of phase A, phase B, and phase C, respectively; and the effective values ​​of the three-phase third harmonic currents are the effective values ​​of the harmonic currents of phase A, phase B, and phase C, respectively.

[0115] 103. Based on the first phase difference, the effective value of the three-phase fundamental voltage, and the effective value of the three-phase fundamental current, determine the capacitive component and the resistive component of the three-phase fundamental current.

[0116] In this step, the effective value of the three-phase fundamental current is orthogonally decomposed based on the first phase difference between the three-phase fundamental voltage and current. Specifically, the effective value of the three-phase fundamental current is orthogonally decomposed based on the effective value of the three-phase fundamental voltage to obtain the capacitive component of the three-phase fundamental current that leads the voltage by 90 degrees. Further, the effective value of the three-phase fundamental current is orthogonally decomposed based on the effective value of the three-phase fundamental voltage to obtain the resistive component of the three-phase fundamental current that is in the same direction as the voltage.

[0117] It is understandable that the capacitive components of the three-phase fundamental current are the capacitive components of the fundamental current of phase A, phase B, and phase C, respectively; and the resistive components of the three-phase fundamental current are the resistive components of the fundamental current of phase A, phase B, and phase C, respectively.

[0118] 104. Based on the second phase difference, the effective value of the three-phase third harmonic voltage, and the effective value of the three-phase third harmonic current, determine the capacitive component and the resistive component of the three-phase third harmonic current.

[0119] In this step, the effective value of the three-phase third harmonic current is calculated by orthogonal decomposition using the second phase difference between the three-phase third voltage and current. Specifically, the effective value of the three-phase third harmonic current is orthogonally decomposed based on the effective value of the three-phase third harmonic voltage to obtain the capacitive component of the three-phase third harmonic current that leads the voltage by 90 degrees. Further, the effective value of the three-phase third harmonic current is orthogonally decomposed based on the effective value of the three-phase third harmonic voltage to obtain the resistive component of the three-phase third harmonic current that is in the same direction as the voltage.

[0120] It is understandable that the capacitive components of the three-phase third harmonic current are the capacitive components of the third harmonic current of phase A, phase B, and phase C, respectively; and the resistive components of the three-phase third harmonic current are the resistive components of the third harmonic current of phase A, phase B, and phase C, respectively.

[0121] Using the above method, the fundamental and third harmonic components of the surge arrester leakage current under the influence of power grid harmonics are extracted. Orthogonal decomposition calculations are then performed using the vector relationship between the three-phase voltage and current to obtain the capacitive and resistive components of the fundamental and third harmonic leakage currents of the three-phase surge arresters. This facilitates the subsequent calculation of the phase-to-phase interference coupling capacitance between the three-phase surge arresters using the capacitive components of the fundamental and third harmonic leakage currents.

[0122] 105. Determine the three-phase third harmonic resistive current of the three-phase surge arrester based on the resistive component of the three-phase third harmonic current.

[0123] In this step, since the three-phase voltages of the third harmonic are in the same direction, it means that the third harmonic resistive current of the surge arrester is not affected by the phase-to-phase capacitance. Therefore, the resistive component of the three-phase third harmonic current is the third harmonic resistive current of the three-phase surge arrester itself.

[0124] It is understandable that the three-phase third harmonic resistive currents of a three-phase surge arrester are the third harmonic resistive currents of phase A, phase B, and phase C, respectively.

[0125] The above method enables the orthogonal decomposition calculation of the vector relationship between the three-phase voltage and current of the third harmonic to obtain the third harmonic resistive current of the three-phase surge arrester itself.

[0126] 106. Determine the three-phase phase-to-phase capacitance of the three-phase surge arrester based on the effective value of the three-phase fundamental voltage, the capacitive component of the three-phase fundamental current, the effective value of the three-phase third harmonic voltage, and the capacitive component of the three-phase third harmonic current.

[0127] In this step, because the fundamental resistive component of the three-phase surge arrester is affected by the interphase coupling capacitance, the resistive component of the fundamental leakage current obtained at this time includes the interference current generated by the interphase coupling capacitance. It is necessary to compensate for the interference current generated by the interphase coupling capacitance before the fundamental resistive current of the surge arrester itself can be obtained. Therefore, the capacitive component of the leakage current is used as a parameter to obtain the interphase coupling capacitance. Using the numerical relationships between the capacitive component of the fundamental leakage current of the three-phase surge arrester, the fundamental voltage, the equivalent capacitance of the surge arrester's varistor, and the interphase coupling capacitance, as well as the numerical relationships between the capacitive component of the third harmonic leakage current of the three-phase surge arrester, the fundamental voltage, the equivalent capacitance of the surge arrester's varistor, and the interphase coupling capacitance, the varistor capacitance, the equivalent capacitance of the varistor, and the interphase coupling capacitance between the three-phase surge arresters are obtained.

[0128] It is understandable that the three-phase interphase capacitances of a three-phase surge arrester are the interphase capacitances between phases A and B, phases A and C, and phases B and C.

[0129] 107. Determine the three fundamental resistive currents of the three-phase surge arrester based on the three-phase interphase capacitance, the resistive component of the three-phase fundamental current, and the effective value of the three-phase fundamental voltage.

[0130] In this step, the interphase capacitance interference is compensated by the reverse compensation current formed by the capacitive current of the phase-to-phase capacitance of the three-phase surge arrester, and the resistive current of the three-phase surge arrester itself is obtained, that is, the three-phase fundamental resistive current of the three-phase surge arrester.

[0131] The above methods can effectively eliminate voltage harmonics and interphase coupling capacitance interference, thereby improving the accuracy of the fundamental current obtained from the three-phase surge arrester.

[0132] It is understandable that the three-phase fundamental resistive currents of a three-phase surge arrester are the fundamental resistive currents of phase A, phase B, and phase C, respectively.

[0133] 108. Compare the three-phase third harmonic resistive current with the first preset threshold, and compare the three-phase fundamental resistive current with the second preset threshold.

[0134] 109. If any one of the three-phase third harmonic resistive currents is greater than or equal to the first preset threshold, or any one of the three-phase fundamental resistive currents is greater than or equal to the second preset threshold, the three-phase surge arrester is determined to be in an abnormal state.

[0135] In steps 108 and 109, after obtaining the three-phase fundamental resistive current and the three-phase third harmonic resistive current of the three-phase surge arrester, the three-phase third harmonic resistive current is compared with a first preset threshold, and simultaneously, the three-phase fundamental resistive current is compared with a second preset threshold. When any third harmonic resistive current is greater than or equal to the first preset threshold, or any fundamental resistive current is greater than or equal to the second preset threshold, it indicates that the third harmonic resistive current or the single-phase surge arrester corresponding to the fundamental resistive current is in an abnormal state, and at this time, it can be determined that the surge arrester has failed.

[0136] By using the above method, the fundamental resistive current and the third harmonic resistive current of the three-phase surge arrester are extracted, and then the state of the surge arrester can be accurately determined by detecting the change in resistive current.

[0137] Optionally, a test can be performed when the three-phase surge arrester is first put into operation and before any fault occurs, to obtain the initial values ​​of the three-phase fundamental resistive current and the three-phase third harmonic resistive current. A first preset threshold is set as one times the initial value of the three-phase third harmonic resistive current, for subsequent comparison and detection of the three-phase third harmonic resistive current during the operation of the three-phase surge arrester. Simultaneously, a second preset threshold is set as one times the initial value of the three-phase fundamental resistive current, for subsequent comparison and detection of the three-phase fundamental resistive current during the operation of the three-phase surge arrester. Furthermore, when any resistive current in the three-phase surge arrester exceeds 50% of its initial value, a warning can be issued to alert the testing personnel to pay attention to the three-phase surge arrester. This method effectively improves the accuracy of three-phase surge arrester testing and reduces the possibility of three-phase surge arrester failure.

[0138] The surge arrester resistive current detection method provided in this application uses the capacitive component of the leakage current as a parameter to obtain the interphase coupling capacitance. It calculates the equivalent capacitance of the three-phase surge arrester's valve and the interphase coupling capacitance by utilizing the numerical relationships between the capacitive component of the three-phase surge arrester's fundamental total leakage current, the fundamental voltage, the equivalent capacitance of the surge arrester's valve, and the interphase coupling capacitance. Furthermore, it uses the relationship between the fundamental resistive current and the interphase coupling capacitance current to compensate for and obtain the fundamental resistive current that removes interphase interference current. Subsequently, based on a first preset threshold and a second preset threshold, it accurately detects the three-phase fundamental resistive current and the three-phase third harmonic resistive current of the three-phase surge arrester. By observing changes in the resistive current, it accurately determines the state of the three-phase surge arrester. By using the above method, the resistive current component can be extracted from the effective values ​​of the fundamental and third harmonic voltages in the voltage signal. When the power grid contains harmonics, it can effectively eliminate grid harmonics and phase-to-phase capacitance interference. It can reliably and accurately extract the resistive current of the surge arrester under both normal and abnormal conditions.

[0139] Furthermore, as a refinement and extension of the specific implementation methods of the above embodiments, and to fully illustrate the specific implementation process of this embodiment, this application provides another method for detecting the resistive current of a surge arrester, such as... Figure 2 As shown, the method includes:

[0140] 201. In response to the surge arrester detection command, obtain the three-phase voltage and leakage current of the three-phase surge arrester included in the surge arrester detection command.

[0141] In this step, in response to the surge arrester resistive current detection command, the three-phase voltage, leakage current, and three-phase capacitance of the three-phase surge arrester contained in the detection command are acquired. It should be noted that the three-phase voltage is the grid voltage signal obtained by the voltage transformer connected in parallel with the three-phase surge arrester, and the leakage current is the total leakage current signal of the three-phase surge arrester under the action of grid harmonics.

[0142] 202. Perform A / D conversion on the three-phase voltage and leakage current to obtain digital signals.

[0143] In this step, the acquired three-phase voltage and leakage current of the surge arrester are converted from analog to digital signals to improve the anti-interference capability of the transmission process.

[0144] 203. Using a preset algorithm, calculate the digital signal to obtain the effective value of the three-phase fundamental voltage, the effective value of the three-phase third harmonic voltage, the first initial phase angle, the second initial phase angle, the effective value of the three-phase fundamental current, the effective value of the three-phase third harmonic current, the third initial phase angle, and the fourth initial phase angle, where the first initial phase angle is the initial phase angle of the three-phase fundamental voltage, the second initial phase angle is the initial phase angle of the three-phase third harmonic voltage, the third initial phase angle is the initial phase angle of the three-phase fundamental current, and the fourth initial phase angle is the initial phase angle of the three-phase third harmonic current.

[0145] 204. Determine the first phase difference and the second phase difference based on the effective values ​​of the three-phase fundamental voltage, the effective values ​​of the three-phase third harmonic voltage, the first initial phase angle, the second initial phase angle, the effective values ​​of the three-phase fundamental current, the effective values ​​of the three-phase third harmonic current, the third initial phase angle, and the fourth initial phase angle.

[0146] In steps 203 and 204, a preset algorithm is used to analyze and calculate the digital signal to obtain the effective values ​​of the three-phase fundamental voltage, the effective values ​​of the three-phase third harmonic voltage, the initial phase angles of the three-phase fundamental voltage and third harmonic voltage, the effective values ​​of the three-phase fundamental current and third harmonic current, and the initial phase angles of the three-phase fundamental current and third harmonic current. Then, the first phase difference between the three-phase fundamental voltage and current, and the second phase difference between the three-phase third harmonic voltage and current are calculated.

[0147] It should be noted that the default algorithm is the FFT algorithm.

[0148] 205. Based on the first phase difference and the effective value of the three-phase fundamental voltage, the effective value of the three-phase fundamental current is orthogonally decomposed to obtain the capacitive component of the three-phase fundamental current that leads the voltage by 90 degrees.

[0149] 206. Based on the effective value of the three-phase fundamental voltage, the three-phase fundamental current is orthogonally decomposed to obtain the resistive component of the three-phase fundamental current in the same direction as the voltage.

[0150] In steps 205 and 206, the effective value of the three-phase fundamental current is orthogonally decomposed and calculated using the first phase difference between the three-phase fundamental voltage and current. Specifically, the effective value of the three-phase fundamental current is orthogonally decomposed based on the effective value of the three-phase fundamental voltage to obtain the capacitive component of the three-phase fundamental current that leads the voltage by 90 degrees.

[0151] Furthermore, the effective values ​​of the three-phase fundamental currents are orthogonally decomposed based on the effective values ​​of the three-phase fundamental voltages to obtain the resistive components of the three-phase fundamental currents in the same direction as the voltages.

[0152] 207. Based on the second phase difference and the effective value of the third harmonic voltage, the effective value of the three-phase third harmonic current is orthogonally decomposed to obtain the capacitive component of the three-phase third harmonic current with a voltage lead of 90 degrees.

[0153] 208. Based on the effective value of the three-phase third harmonic voltage, the effective value of the three-phase third harmonic current is orthogonally decomposed to obtain the resistive components of the three-phase third harmonic in the same direction as the voltage.

[0154] In steps 207 and 208, the effective value of the three-phase third harmonic current is calculated by orthogonal decomposition using the second phase difference between the three-phase third voltage and current. Specifically, the effective value of the three-phase third harmonic current is orthogonally decomposed based on the effective value of the three-phase third harmonic voltage to obtain the capacitive component of the three-phase third harmonic current that leads the voltage by 90 degrees.

[0155] Furthermore, the effective values ​​of the three-phase third harmonic currents are orthogonally decomposed based on the effective values ​​of the three-phase third harmonic voltages to obtain the resistive components of the three-phase third harmonic currents in the same direction as the voltages.

[0156] Using the above method, the fundamental and third harmonic components of the surge arrester leakage current under the influence of power grid harmonics are extracted. Orthogonal decomposition calculations are then performed using the vector relationship between the three-phase voltage and current to obtain the capacitive and resistive components of the fundamental and third harmonic leakage currents of the three-phase surge arresters. This facilitates the subsequent calculation of the phase-to-phase interference coupling capacitance between the three-phase surge arresters using the capacitive components of the fundamental and third harmonic leakage currents.

[0157] 209. Determine the three-phase third harmonic resistive current of the three-phase surge arrester based on the resistive component of the three-phase third harmonic current.

[0158] In this step, since the three-phase voltages of the third harmonic are in the same direction, it means that the third harmonic resistive current of the surge arrester is not affected by the phase-to-phase capacitance. Therefore, the resistive component of the three-phase third harmonic current is the third harmonic resistive current of the three-phase surge arrester itself.

[0159] 210. Assume that the three phases of a three-phase surge arrester are phase A, phase B, and phase C.

[0160] 211. Based on the three-phase capacitance, the three-phase fundamental current capacitive component, the three-phase third harmonic current capacitive component, the three-phase fundamental voltage effective value, and the three-phase third harmonic voltage effective value, use the first preset equation set and the second preset equation set to calculate the phase-to-phase capacitance between phase A and phase B, the phase-to-phase capacitance between phase A and phase C, and the phase-to-phase capacitance between phase B and phase C of the three-phase surge arrester.

[0161] In steps 209 and 210, the three phases of the three-phase surge arrester are assumed to be phases A, B, and C. Since the fundamental resistive component of the three-phase surge arrester is affected by the interphase coupling capacitance, the resistive component of the fundamental leakage current obtained at this time includes the interference current generated by the interphase coupling capacitance. The interference current generated by the interphase coupling capacitance needs to be compensated before the fundamental resistive current of the surge arrester itself can be obtained. Therefore, the capacitive component of the leakage current is used as a parameter to obtain the interphase coupling capacitance. Using the numerical relationships between the capacitive component of the fundamental leakage current of the three-phase surge arrester, the fundamental voltage, the equivalent capacitance of the surge arrester's varistor, and the interphase coupling capacitance, as well as the numerical relationships between the capacitive component of the third harmonic leakage current of the three-phase surge arrester, the fundamental voltage, the equivalent capacitance of the surge arrester's varistor, and the interphase coupling capacitance, the varistor capacitance, the equivalent capacitance of the varistor, and the interphase coupling capacitance between the three-phase surge arresters are obtained.

[0162] Specifically, the first set of pre-defined equations is as follows:

[0163] I a1C =ωC A U a1 -ωC AB U b1 sin(30°)-ωC AC U c1 sin(30°)

[0164] I b1C =ωC B U b1 -ωC BC U c1 sin(30°)-ωC AB U a1 sin(30°)

[0165] I c1C =ωC C U c1 -ωC AC U a1 sin(30°)-ωC BC U b1 sin(30°)

[0166] Among them, the above I a1C I is the capacitive component of the fundamental current in phase A; b1C This refers to the capacitive component of the fundamental current in phase B; the aforementioned I c1C The fundamental current of phase C is the capacitive component; ω is a constant; C is a constant. A The equivalent capacitance of phase A; the above C B The equivalent capacitance of phase B; the above C C The equivalent capacitance of phase C; the above U a1 The effective value of the fundamental voltage of phase A; the above U b1This is the effective value of the fundamental voltage of phase B; the above U c1 This is the effective value of the fundamental voltage of phase C; the above C AB C is the interphase capacitance between phase A and phase B; AC This refers to the interphase capacitance between phase A and phase C; the aforementioned C BC This is the interphase capacitance between phase B and phase C.

[0167] Furthermore, the second set of pre-defined equations is as follows:

[0168] I a3C =3ωU a3 (C A +C AB +C AC )

[0169] I b3C =3ωU b3 (C B +C AB +C BC )

[0170] I c3C =3ωU c3 (C C +C AC +C BC )

[0171] Among them, the above I a3C The third harmonic capacitive component of phase A; the above I b3C The third harmonic capacitive component of phase B; the above I c3C The third harmonic capacitive component of phase C; the above U a3 The effective value of the third harmonic voltage of phase A; the above U b3 The effective value of the third harmonic voltage of phase B; the above U c3 This is the effective value of the third harmonic voltage of phase C.

[0172] In a specific embodiment, such as Figure 3 The diagram shown is a vector diagram illustrating the fundamental resistive current calculation of phase A of a three-phase surge arrester. Specifically, in the diagram, U... a1 U b1 U c1 These are the effective values ​​of the three-phase fundamental voltages of the three-phase surge arrester; I a1 I b1 I c1 These are the three-phase fundamental leakage currents of the three-phase surge arrester; Φ a1 Φ b1 Φ c1 These are the phase differences between the three-phase fundamental voltage and the total current of the three-phase surge arrester; I a1-c I b1-c I c1-cThese are the capacitive components of the three-phase fundamental leakage current of the three-phase surge arrester; I a1-R I is the resistive component of the fundamental leakage current of phase A of the three-phase surge arrester; aa1-c I is the fundamental capacitive current of the valve plate of phase A surge arrester; aa1-R I is the fundamental resistive current of the valve plate of phase A surge arrester; ab1 For the fundamental voltage of phase B of the surge arrester to pass through the interphase capacitor C AB The resulting capacitive current; I ac1 For the fundamental voltage of phase C of the surge arrester to pass through the interphase capacitor C AC The resulting capacitive current; I ab1 I ac1 The angle between the current and the Y-axis is 60°. The three-phase fundamental current I... a1 I b1 I c1 Based on the three-phase fundamental voltage U a1 U b1 U c1 Orthogonal decomposition was performed to obtain the capacitive component I of the three-phase fundamental current with a voltage lead of 90 degrees. a1-c I b1-c I c1-c The three-phase third harmonic currents are orthogonally decomposed based on the three-phase third harmonic voltages to obtain the capacitive components of the three-phase third harmonic currents that lead the voltage by 90 degrees. Furthermore, the three-phase fundamental current I... a1 I b1 I c1 Based on the three-phase fundamental voltage U a1 U b1 U c1 Perform orthogonal decomposition to obtain the resistive component I of the three-phase fundamental current in the same direction as the voltage. a1-R It should be noted that only the resistive component of phase A is shown in the figure; the three-phase third harmonic currents are orthogonally decomposed based on the three-phase third harmonic voltages to obtain the resistive components of the three-phase third harmonic currents in the same direction as the voltages. Taking phase A as an example, the fundamental current capacitive component I of phase A... a1-c The fundamental capacitive current I of the surge arrester itself aa1-c The fundamental voltage of phase B of the surge arrester passes through the interphase capacitor C. AB The resulting capacitive current I ab1 The fundamental voltage of phase C of the surge arrester passes through the interphase capacitor C. AC The resulting capacitive current I ac1 The three are obtained through vector calculation. Similarly, the capacitive components of phases B and C are calculated in the same way as those of phase A, thus yielding the first set of pre-defined equations. Likewise, the capacitive components of the three-phase third harmonic are also derived from the capacitive current of the arrester's own varistor, the fundamental voltage of phase B of the arrester, and the interphase capacitance C. AB The resulting capacitive current and the fundamental voltage of phase C of the surge arrester pass through the interphase capacitor C.AC The resulting capacitive currents are calculated using vector calculations of the three phases. However, unlike the fundamental voltage, the current formed by the interphase capacitance is in the same direction as the capacitive current of its own valve plate, thus yielding the second set of preset equations. Furthermore, considering that the arrester valve plate will also exhibit a third harmonic component in the resistive current under the fundamental voltage after aging, this application selects the capacitive current component as a parameter for calculating the interphase coupling capacitance. By simultaneously solving the first and second sets of preset equations, the interphase capacitance C of the three-phase arrester can be obtained. AB C BC and C AC .

[0173] 212. Based on the three-phase interphase capacitance, the resistive component of the three-phase fundamental current, and the effective value of the three-phase fundamental voltage, use the third preset equation set to calculate the fundamental resistive current of the A-phase valve plate, the fundamental resistive current of the B-phase valve plate, and the fundamental resistive current of the C-phase valve plate of the three-phase surge arrester.

[0174] In this step, the interphase capacitance interference is compensated by the reverse compensation current formed by the capacitive current of the phase-to-phase capacitance of the three-phase surge arrester, and the resistive current of the three-phase surge arrester itself is obtained, that is, the fundamental resistive current of the three-phase valve plate of the three-phase surge arrester. It can be understood that the fundamental resistive current of the valve plate itself is the fundamental resistive current that removes the interphase interference current.

[0175] Specifically, the third set of pre-defined equations includes:

[0176] I a1-R =I aa1-R +ωC AB U b1 cos(30°)-ωC AC U c1 cos(30°)

[0177] I b1-R =I bb1-R +ωC BC U c1 cos(30°)-ωC AB U a1 cos(30°)

[0178] I c1-R =I cc1-R +ωC AC U a1 cos(30°)-ωC BC U b1 cos(30°)

[0179] Among them, the above I a1-R The fundamental current resistive component of phase A; the above I b1-R This refers to the resistive component of the fundamental current in phase B; the aforementioned Ic1-R The fundamental current resistive component of phase C; the above I aa1-R This refers to the fundamental resistive current of the A-phase valve plate itself; the aforementioned I bb1-R This refers to the fundamental resistive current of the B-phase valve plate itself; the aforementioned I cc1-R This is the fundamental resistive current of the C-phase valve plate itself.

[0180] In a specific embodiment, the fundamental resistive current of the surge arrester is calculated based on vector analysis of the influence of inter-phase capacitance on the fundamental resistive component of the three-phase surge arrester. For example... Figure 3 As shown, taking phase A as an example, the fundamental current resistive component I of phase A... a1-R The fundamental resistive current I of the surge arrester's own valve plate aa1-R The fundamental voltage of phase B of the surge arrester passes through the interphase capacitor C. AB The resulting capacitive current I ab1 The fundamental voltage of phase C of the surge arrester passes through the interphase capacitor C. AC The resulting capacitive current I ac1 The three vectors are then used to calculate the three-phase fundamental resistive current of the three-phase surge arrester. A compensation current in the direction of the capacitive current formed by the acquired interphase capacitance is then applied to compensate for interphase capacitance interference.

[0181] By using the above method, the resistive current component is extracted from the effective values ​​of the fundamental and third harmonic voltages in the voltage signal. This enables the effective elimination of grid harmonics and phase-to-phase capacitance interference when the grid contains harmonics, and provides a stable and accurate reflection of the arrester's resistive current changes. The arrester's resistive current can be reliably and accurately extracted under both normal and abnormal conditions.

[0182] 213. Compare the three-phase third harmonic resistive current with the first preset threshold, and compare the three-phase fundamental resistive current with the second preset threshold.

[0183] 214. If any one of the three-phase third harmonic resistive currents is greater than or equal to the first preset threshold, or any one of the three-phase fundamental resistive currents is greater than or equal to the second preset threshold, the three-phase surge arrester is determined to be in an abnormal state.

[0184] In steps 213 and 214, after obtaining the three-phase fundamental resistive current and the three-phase third harmonic resistive current of the three-phase surge arrester, the three-phase third harmonic resistive current is compared with a first preset threshold, and simultaneously, the three-phase fundamental resistive current is compared with a second preset threshold. When any third harmonic resistive current is greater than or equal to the first preset threshold, or any fundamental resistive current is greater than or equal to the second preset threshold, it indicates that the third harmonic resistive current or the single-phase surge arrester corresponding to the fundamental resistive current is in an abnormal state, and at this time, it can be determined that the surge arrester has failed.

[0185] By using the above method, the fundamental resistive current and the third harmonic resistive current of the three-phase surge arrester are extracted, and then the state of the surge arrester can be accurately determined by detecting the change in resistive current.

[0186] In a specific embodiment, such as Figure 4 As shown, this application provides a method for detecting the resistive current of a surge arrester, applicable to single-section surge arresters. A single-section surge arrester refers to a single-encapsulated surge arrester without an intermediate flange; generally, surge arresters with voltage levels of 110kV and below adopt this structure. Specifically, the method for detecting the resistive current of the surge arrester is as follows:

[0187] S1: Connect the secondary voltage signal of the parallel voltage transformer to the three-phase surge arrester via the signal line, and obtain the three-phase operating voltage of the surge arrester after setting the transformation ratio parameters. At the same time, use a current sensor connected to the grounding lead of the surge arrester to obtain the total leakage current of the three-phase surge arrester.

[0188] S2: Perform A / D conversion on the acquired three-phase voltage and three-phase current of the surge arrester to convert the acquired analog signals into digital signals.

[0189] S3: Perform FFT analysis and calculation on the digital signal obtained in step S2.

[0190] S4: Through FFT analysis of digital signals, obtain the effective values ​​of the three-phase fundamental voltage and the third harmonic voltage, and the first initial phase angle; obtain the effective values ​​of the three-phase fundamental current and the third harmonic current, and the second initial phase angle, and then calculate the first phase difference between the three-phase fundamental voltage and current, and the second phase difference between the third harmonic voltage and current.

[0191] S5: Orthogonal decomposition calculation of three-phase current. The three-phase fundamental current and the third harmonic current are orthogonally decomposed and calculated by using the first phase difference between the three-phase fundamental voltage and current and the second phase difference between the third harmonic voltage and current.

[0192] S6-1: As Figure 3 As shown, the three-phase fundamental current I a1 I b1 I c1 Based on the three-phase fundamental voltage U a1 U b1 U c1 Orthogonal decomposition was performed to obtain the capacitive component I of the three-phase fundamental current with a voltage lead of 90 degrees. a1-c I b1-c I c1-c The three-phase third harmonic currents are orthogonally decomposed based on the three-phase third harmonic voltages to obtain the capacitive components of the three-phase third harmonic currents that lead the voltage by 90 degrees.

[0193] S6-2: As Figure 3 As shown, the three-phase fundamental current Ia1 I b1 I c1 Based on the three-phase fundamental voltage U a1 U b1 U c1 Perform orthogonal decomposition to obtain the resistive component I of the three-phase fundamental current in the same direction as the voltage. a1-R The three-phase third harmonic currents are orthogonally decomposed based on the three-phase third harmonic voltages to obtain the resistive components of the three-phase third harmonic currents in the same direction as the voltages.

[0194] S7: At this point, the three-phase fundamental resistive and capacitive components not only include the resistive and capacitive currents of the surge arrester itself, but also the interference currents formed by the interphase coupling capacitances of the other two phases. Taking phase A as an example, as follows... Figure 3 As shown, the capacitive component I of the fundamental current in phase A a1-c The fundamental capacitive current I of the surge arrester itself aa1-c The fundamental voltage of phase B of the surge arrester passes through the interphase capacitor C. AB The resulting capacitive current I ab1 The fundamental voltage of phase C of the surge arrester passes through the interphase capacitor C. AC The resulting capacitive current I ac1 The vector calculations of the three phases are obtained. The compatibility components of phases B and C are calculated in the same way as those of phase A, therefore the first set of pre-defined equations can be obtained. That is:

[0195] I a1C =ωC A U a1 -ωC AB U b1 sin(30°)-ωC AC U c1 sin(30°)

[0196] I b1C =ωC B U b1 -ωC BC U c1 sin(30°)-ωC AB U a1 sin(30°)

[0197] I c1C =ωC C U c1 -ωC AC U a1 sin(30°)-ωC BC U b1 sin(30°)

[0198] Among them, the above I a1C I is the capacitive component of the fundamental current in phase A; b1CThis refers to the capacitive component of the fundamental current in phase B; the aforementioned I c1C The fundamental current of phase C is the capacitive component; ω is a constant; C is a constant. A The equivalent capacitance of phase A; the above C B The equivalent capacitance of phase B; the above C C The equivalent capacitance of phase C; the above U a1 The effective value of the fundamental voltage of phase A; the above U b1 This is the effective value of the fundamental voltage of phase B; the above U c1 This is the effective value of the fundamental voltage of phase C; the above C AB C is the interphase capacitance between phase A and phase B; AC This refers to the interphase capacitance between phase A and phase C; the aforementioned C BC This is the interphase capacitance between phase B and phase C.

[0199] Similarly, the capacitive component of the three-phase third harmonic is also generated by the capacitive current of the arrester's own varistor, the fundamental voltage of phase B of the arrester, and the phase-to-phase capacitance C. AB The resulting capacitive current and the fundamental voltage of phase C of the surge arrester pass through the interphase capacitor C. AC The resulting capacitive currents are calculated using vector calculations. Unlike the fundamental wave, the current formed by the interphase capacitance is in the same direction as the capacitive current of its own valence plate. Therefore, the second set of pre-defined equations can be obtained. That is:

[0200] I a3C =3ωU a3 (C A +C AB +C AC )

[0201] I b3C =3ωU b3 (C B +C AB +C BC )

[0202] I c3C =3ωU c3 (C C +C AC +C Bc )

[0203] Among them, the above I a3C The third harmonic capacitive component of phase A; the above I b3C The third harmonic capacitive component of phase B; the above I c3C The third harmonic capacitive component of phase C; the above U a3 The effective value of the third harmonic voltage of phase A; the above U b3 The effective value of the third harmonic voltage of phase B; the above U c3 This is the effective value of the third harmonic voltage of phase C.

[0204] S8: Considering that the resistive current of the surge arrester will also exhibit a third harmonic component under the fundamental voltage after the surge arrester varistor ages, this invention selects the capacitive current component as a parameter for calculating the interphase coupling capacitance. By simultaneously solving the two sets of preset equations obtained in S7, the interphase capacitance C of the three-phase surge arrester can be obtained. AB C BC C AC .

[0205] S9: Calculate the fundamental resistive current of the surge arrester itself based on vector analysis of the influence of phase-to-phase capacitance on the fundamental resistive component of the three-phase surge arrester. For example... Figure 3 As shown, taking phase A as an example, the fundamental current resistive component I of phase A... a1-R The fundamental resistive current I of the surge arrester's own valve plate aa1-R The fundamental voltage of phase B of the surge arrester passes through the interphase capacitor C. AB The resulting capacitive current I ab1 The fundamental voltage of phase C of the surge arrester passes through the interphase capacitor C. AC The resulting capacitive current I ac1 The vector calculations of these three elements yield the third pre-defined system of equations. That is:

[0206] I a1-R =I aa1-R +ωC AB U b1 cos(30°)-ωC AC U c1 cos(30°)

[0207] I b1-R =I bb1-R +ωC BC U c1 cos(30°)-ωC AB U a1 cos(30°)

[0208] I c1-R =I cc1-R +ωC AC U a1 cos(30°)-ωC BC U b1 cos(30°)

[0209] Among them, the above I a1-R The fundamental current resistive component of phase A; the above I b1-R This refers to the resistive component of the fundamental current in phase B; the aforementioned I c1-R The fundamental current resistive component of phase C; the above I aa1-R This refers to the fundamental resistive current of the A-phase valve plate itself; the aforementioned I bb1-R This refers to the fundamental resistive current of the B-phase valve plate itself; the aforementioned I cc1-RThis is the fundamental resistive current of the C-phase valve plate itself.

[0210] S10: By applying a compensation current that is reversed to the capacitive current formed by the phase-to-phase capacitance obtained from S9, the phase-to-phase capacitance interference is compensated, and the three-phase fundamental resistive current of the three-phase surge arrester itself is obtained.

[0211] S11: The three-phase voltages of the third harmonic are in the same direction, so the three-phase resistive current of the third harmonic is not affected by phase-to-phase interference. The obtained three-phase third harmonic resistive current is the three-phase third harmonic resistive current of the surge arrester itself.

[0212] The surge arrester resistive current detection method provided in this application extracts the fundamental and third harmonic components of the surge arrester leakage current under the influence of power grid harmonics. It then uses the vector relationship between the three-phase voltage and current to perform orthogonal decomposition calculations to obtain the capacitive and resistive components of the fundamental and third harmonic leakage current. Further, the capacitive components of the fundamental and third harmonic leakage current are used to solve for the interphase interference coupling capacitance between the three-phase surge arresters. The fundamental resistive current, which eliminates interphase interference current, is obtained by compensating for the relationship between the fundamental resistive current and the interphase coupling capacitance current. Simultaneously, the third harmonic resistive current of the surge arrester is unaffected by the interphase capacitance; it can be obtained by orthogonal decomposition calculations using the vector relationship between the three-phase voltage and current of the third harmonic. By extracting the resistive current component from the effective values ​​of the fundamental and third harmonic voltages in the voltage signal, the method effectively eliminates power grid harmonics and interphase capacitance interference when the power grid contains harmonics, achieving reliable and accurate extraction of the surge arrester resistive current under both normal and abnormal conditions. For single-section surge arresters with voltage levels of 110kV and below, under the influence of power grid harmonics, regardless of whether the surge arrester is functioning normally or not, this patented method can accurately extract the fundamental and third harmonic components of the resistive current of the surge arrester. By observing the changes in resistive current, the state of the surge arrester can be correctly determined.

[0213] Furthermore, as Figure 1 In a specific implementation of the method, this application provides a surge arrester resistive current detection device 500, such as... Figure 5 As shown, the device includes:

[0214] The acquisition module 501 is used to acquire the three-phase voltage and leakage current of the three-phase arrester included in the arrester resistive current detection command in response to the arrester resistive current detection command.

[0215] The first determining module 502 is used to determine the effective values ​​of the three-phase fundamental voltage, the three-phase third harmonic voltage, the three-phase fundamental current, the three-phase third harmonic current, the first phase difference, and the second phase difference of the three-phase surge arrester based on the three-phase voltage and the leakage current. The first phase difference is the phase difference between the three-phase fundamental voltage and the three-phase fundamental current, and the second phase difference is the phase difference between the three-phase third harmonic voltage and the three-phase third harmonic current.

[0216] The second determining module 503 is used to determine the capacitive component and resistive component of the three-phase fundamental current based on the first phase difference, the effective value of the three-phase fundamental voltage, and the effective value of the three-phase fundamental current.

[0217] The third determining module 504 is used to determine the capacitive component and resistive component of the three-phase third harmonic current based on the second phase difference, the effective value of the three-phase third harmonic voltage, and the effective value of the three-phase third harmonic current.

[0218] The fourth determining module 505 is used to determine the three-phase third harmonic resistive current of the three-phase surge arrester based on the resistive component of the three-phase third harmonic current.

[0219] The fifth determining module 506 is used to determine the three-phase interphase capacitance of the three-phase surge arrester based on the effective value of the three-phase fundamental voltage, the capacitive component of the three-phase fundamental current, the effective value of the three-phase third harmonic voltage, and the capacitive component of the three-phase third harmonic current.

[0220] The sixth determining module 507 is used to determine the three-phase fundamental resistive current of the three-phase surge arrester based on the three-phase interphase capacitance, the resistive component of the three-phase fundamental current, and the effective value of the three-phase fundamental voltage.

[0221] The comparison module 508 is used to compare the three-phase third harmonic resistive current with a first preset threshold and the three-phase fundamental resistive current with a second preset threshold.

[0222] The seventh determination module 509 is used to determine that the three-phase surge arrester is in an abnormal state if any one of the three-phase third harmonic resistive currents is greater than or equal to a first preset threshold, or any one of the three-phase fundamental resistive currents is greater than or equal to a second preset threshold.

[0223] Optionally, the first determining module 502 is specifically used for:

[0224] The three-phase voltage and leakage current are converted from digital signals using an A / D converter to obtain digital signals.

[0225] Using a preset algorithm, the digital signal is calculated to obtain the effective values ​​of the three-phase fundamental voltage, the effective values ​​of the three-phase third harmonic voltage, the first initial phase angle, the second initial phase angle, the effective values ​​of the three-phase fundamental current, the effective values ​​of the three-phase third harmonic current, the third initial phase angle, and the fourth initial phase angle. Among them, the first initial phase angle is the initial phase angle of the three-phase fundamental voltage, the second initial phase angle is the initial phase angle of the three-phase third harmonic voltage, the third initial phase angle is the initial phase angle of the three-phase fundamental current, and the fourth initial phase angle is the initial phase angle of the three-phase third harmonic current.

[0226] The first phase difference and the second phase difference are determined based on the effective values ​​of the three-phase fundamental voltage, the effective values ​​of the three-phase third harmonic voltage, the first initial phase angle, the second initial phase angle, the effective values ​​of the three-phase fundamental current, the effective values ​​of the three-phase third harmonic current, the third initial phase angle, and the fourth initial phase angle.

[0227] Optionally, the second determining module 503 is specifically used for:

[0228] Based on the first phase difference and the effective value of the three-phase fundamental voltage, the effective value of the three-phase fundamental current is orthogonally decomposed to obtain the capacitive component of the three-phase fundamental current with a voltage lead of 90 degrees.

[0229] Based on the effective value of the three-phase fundamental voltage, the three-phase fundamental current is orthogonally decomposed to obtain the resistive component of the three-phase fundamental current in the same direction as the voltage.

[0230] Optionally, the third determining module 504 is specifically used for:

[0231] Based on the second phase difference and the effective value of the third harmonic voltage, the effective value of the three-phase third harmonic current is orthogonally decomposed to obtain the capacitive component of the three-phase third harmonic current with a voltage lead of 90 degrees.

[0232] Based on the effective value of the three-phase third harmonic voltage, the effective value of the three-phase third harmonic current is orthogonally decomposed to obtain the resistive components of the three-phase third harmonic in the same direction as the voltage.

[0233] Optionally, the fifth determining module 506 is specifically used for:

[0234] Assume the three phases of the three-phase surge arrester are phase A, phase B, and phase C;

[0235] Based on the three-phase fundamental current capacitive component, the three-phase third harmonic current capacitive component, the three-phase fundamental voltage effective value and the three-phase third harmonic voltage effective value, the phase-to-phase capacitance between phase A and phase B, the phase-to-phase capacitance between phase A and phase C and the phase-to-phase capacitance between phase B and phase C of the three-phase surge arrester are calculated using the first and second preset equation sets respectively.

[0236] The first set of pre-defined equations is:

[0237] I a1C =ωC AU a1 -ωC AB U b1 sin(30°)-ωC AC U c1 sin(30°)

[0238] I b1C =ωC B U b1 -ωC BC U c1 sin(30°)-ωC AB U a1 sin(30°)

[0239] I c1C =ωC C U c1 -ωC AC U a1 sin(30°)-ωC BC U b1 sin(30°)

[0240] Among them, the above I a1C I is the capacitive component of the fundamental current in phase A; b1C This refers to the capacitive component of the fundamental current in phase B; the aforementioned I c1C The fundamental current of phase C is the capacitive component; ω is a constant; C is a constant. A The equivalent capacitance of phase A; the above C B The equivalent capacitance of phase B; the above C C The equivalent capacitance of phase C; the above U a1 The effective value of the fundamental voltage of phase A; the above U b1 This is the effective value of the fundamental voltage of phase B; the above U c1 This is the effective value of the fundamental voltage of phase C; the above C AB C is the interphase capacitance between phase A and phase B; AC This refers to the interphase capacitance between phase A and phase C; the aforementioned C BC This refers to the interphase capacitance between phase B and phase C.

[0241] The second set of pre-defined equations is:

[0242] I a3C =3ωU a3 (C A +C AB +C AC )

[0243] I b3C =3ωU b3 (C B +C AB +C BC )

[0244] I c3C =3ωU c3 (C C +C AC +C Bc )

[0245] Among them, the above I a3C The third harmonic capacitive component of phase A; the above I b3C The third harmonic capacitive component of phase B; the above I c3C The third harmonic capacitive component of phase C; the above U a3 The effective value of the third harmonic voltage of phase A; the above U b3 The effective value of the third harmonic voltage of phase B; the above U c3 This is the effective value of the third harmonic voltage of phase C.

[0246] Optionally, the sixth determining module 507 is specifically used for:

[0247] Based on the three-phase interphase capacitance, the resistive component of the three-phase fundamental current, and the effective value of the three-phase fundamental voltage, the fundamental resistive current of the A-phase valve plate, the fundamental resistive current of the B-phase valve plate, and the fundamental resistive current of the C-phase valve plate of the three-phase surge arrester are calculated using the third preset equation set.

[0248] The third set of pre-defined equations includes:

[0249] I a1-R =I aa1-R +ωC AB U b1 cos(30°)-ωC AC U c1 cos(30°)

[0250] I b1-R =I bb1-R +ωC BC U c1 cos(30°)-ωC AB U a1 cos(30°)

[0251] I c1-R =I cc1-R +ωC AC U a1 cos(30°)-ωC BC U b1 cos(30°)

[0252] Among them, the above I a1-R The fundamental current resistive component of phase A; the above I b1-R This refers to the resistive component of the fundamental current in phase B; the aforementioned I c1-R The fundamental current resistive component of phase C; the above Iaa1-R This refers to the fundamental resistive current of the A-phase valve plate itself; the aforementioned I bb1-R This refers to the fundamental resistive current of the B-phase valve plate itself; the aforementioned I cc1-R This is the fundamental resistive current of the C-phase valve plate itself.

[0253] The surge arrester resistive current detection device provided in this application uses the capacitive component of the leakage current as a parameter to obtain the interphase coupling capacitance. It calculates the equivalent capacitance of the three-phase surge arrester's valve and the interphase coupling capacitance by utilizing the numerical relationships between the capacitive component of the three-phase surge arrester's fundamental total leakage current, the fundamental voltage, the equivalent capacitance of the surge arrester's valve, and the interphase coupling capacitance, as well as the numerical relationships between the capacitive component of the three-phase surge arrester's third harmonic total leakage current, the fundamental voltage, the equivalent capacitance of the surge arrester's valve, and the interphase coupling capacitance. Then, using the relationship between the fundamental resistive current and the interphase coupling capacitance current, it compensates for and obtains the fundamental resistive current to remove interphase interference current. Subsequently, based on a first preset threshold and a second preset threshold, it accurately detects the three-phase fundamental resistive current and the three-phase third harmonic resistive current of the three-phase surge arrester, and accurately determines the state of the three-phase surge arrester by observing changes in resistive current. By using the above method, the resistive current component can be extracted from the effective values ​​of the fundamental and third harmonic voltages in the voltage signal. When the power grid contains harmonics, it can effectively eliminate grid harmonics and phase-to-phase capacitance interference. It can reliably and accurately extract the resistive current of the surge arrester under both normal and abnormal conditions.

[0254] Furthermore, this application provides a surge arrester detection system, including the surge arrester resistive current detection device described in the above embodiments.

[0255] Furthermore, the surge arrester detection system also includes:

[0256] Three-phase surge arrester; voltage transformer connected in parallel with the three-phase surge arrester; first sensor, located on the secondary side of the voltage transformer connected in parallel with the three-phase surge arrester, used to collect three-phase voltage; second sensor, located between the three-phase surge arrester and the grounding lead, used to collect leakage current; A / D conversion module, used to convert three-phase voltage and leakage current into digital signals; first calculation module, used to calculate the effective values ​​of the three-phase fundamental voltage, the three-phase third harmonic voltage, the three-phase fundamental current, the three-phase third harmonic current, the first initial phase angle, and the second initial phase angle of the three-phase surge arrester; second calculation module, used to calculate multiple harmonic resistive currents and multiple fundamental resistive currents of the three-phase surge arrester; display module, used to display multiple harmonic resistive currents and multiple fundamental resistive currents.

[0257] In this embodiment, the first sensor receives a voltage signal from the secondary side of a voltage transformer connected in parallel with the three-phase surge arrester, and the second sensor receives a current signal from the grounding lead of the three-phase surge arrester. The acquired voltage and current signals are simultaneously sent to the device's A / D conversion module to convert the acquired analog signals into digital signals. Further, the converted digital signals are input to the FFT calculation module, i.e., the first calculation module. The first calculation module acquires the effective values ​​of the three-phase fundamental voltage and third harmonic voltage, and the first initial phase angle. Simultaneously, it acquires the effective values ​​of the three-phase fundamental current and third harmonic current, and the second initial phase angle. Subsequently, the acquired parameters are used by the resistive current calculation module, i.e., the second calculation module, to calculate the fundamental resistive current and third harmonic resistive current of the three-phase surge arrester itself. The resistive current value is then displayed through the display module to achieve accurate evaluation of the surge arrester's condition.

[0258] In an exemplary embodiment, this application also provides a readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the surge arrester resistive current detection method.

[0259] Through the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented in hardware or by using software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (such as a CD-ROM, USB flash drive, external hard drive, etc.) and includes several instructions to cause an electronic device (such as a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0260] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing this application.

[0261] Those skilled in the art will understand that the modules in the apparatus of the implementation scenario can be distributed within the apparatus of the implementation scenario as described, or they can be located in one or more apparatuses different from this implementation scenario, with corresponding changes. The modules of the above-described implementation scenario can be combined into one module, or they can be further divided into multiple sub-modules.

[0262] The serial numbers in this application are for descriptive purposes only and do not represent the superiority or inferiority of the implementation scenario.

[0263] The above disclosures are only a few specific implementation scenarios of this application. However, this application is not limited to these. Any variations that can be conceived by those skilled in the art should fall within the protection scope of this application.

Claims

1. A method for detecting the resistive current of a surge arrester, characterized in that, include: In response to the arrester resistive current detection command, the three-phase voltage and leakage current of the three-phase arrester included in the arrester resistive current detection command are obtained; Based on the three-phase voltage and the leakage current, determine the effective values ​​of the three-phase fundamental voltage, the three-phase third harmonic voltage, the three-phase fundamental current, the three-phase third harmonic current, the first phase difference, and the second phase difference of the three-phase surge arrester, wherein the first phase difference is the phase difference between the three-phase fundamental voltage and the three-phase fundamental current, and the second phase difference is the phase difference between the three-phase third harmonic voltage and the three-phase third harmonic current; Based on the first phase difference, the effective value of the three-phase fundamental voltage, and the effective value of the three-phase fundamental current, determine the capacitive component and the resistive component of the three-phase fundamental current; Based on the second phase difference, the effective value of the three-phase third harmonic voltage, and the effective value of the three-phase third harmonic current, the capacitive component and the resistive component of the three-phase third harmonic current are determined. Based on the resistive components of the three-phase third harmonic current, determine the three-phase third harmonic resistive current of the three-phase surge arrester; The three-phase phase-to-phase capacitance of the three-phase surge arrester is determined based on the effective value of the three-phase fundamental voltage, the capacitive component of the three-phase fundamental current, the effective value of the three-phase third harmonic voltage, and the capacitive component of the three-phase third harmonic current. The three-phase fundamental resistive current of the three-phase surge arrester is determined based on the three-phase interphase capacitance, the resistive component of the three-phase fundamental current, and the effective value of the three-phase fundamental voltage. The three-phase third harmonic resistive current is compared with a first preset threshold, and the three-phase fundamental resistive current is compared with a second preset threshold. If any one of the three-phase third harmonic resistive currents is greater than or equal to the first preset threshold, or if any one of the three-phase fundamental resistive currents is greater than or equal to the second preset threshold, the three-phase surge arrester is determined to be in an abnormal state.

2. The method according to claim 1, characterized in that, The step of determining the effective values ​​of the three-phase fundamental voltage, the three-phase third harmonic voltage, the three-phase fundamental current, the three-phase third harmonic current, the first phase difference, and the second phase difference of the three-phase surge arrester based on the three-phase voltage and the leakage current specifically includes: The three-phase voltage and the leakage current are converted from digital signals using an A / D converter. Using a preset algorithm, the digital signal is calculated to obtain the effective value of the three-phase fundamental voltage, the effective value of the three-phase third harmonic voltage, the first initial phase angle, the second initial phase angle, the effective value of the three-phase fundamental current, the effective value of the three-phase third harmonic current, the third initial phase angle, and the fourth initial phase angle, wherein the first initial phase angle is the initial phase angle of the three-phase fundamental voltage, the second initial phase angle is the initial phase angle of the three-phase third harmonic voltage, the third initial phase angle is the initial phase angle of the three-phase fundamental current, and the fourth initial phase angle is the initial phase angle of the three-phase third harmonic current. The first phase difference and the second phase difference are determined based on the effective values ​​of the three-phase fundamental voltage, the effective values ​​of the three-phase third harmonic voltage, the first initial phase angle, the second initial phase angle, the effective values ​​of the three-phase fundamental current, the effective values ​​of the three-phase third harmonic current, the third initial phase angle, and the fourth initial phase angle.

3. The method according to claim 1, characterized in that, The step of determining the capacitive component and resistive component of the three-phase fundamental current based on the first phase difference, the effective value of the three-phase fundamental voltage, and the effective value of the three-phase fundamental current specifically includes: Based on the first phase difference and the effective value of the three-phase fundamental voltage, the effective value of the three-phase fundamental current is orthogonally decomposed to obtain the capacitive component of the three-phase fundamental current that leads the voltage by 90 degrees. Based on the effective value of the three-phase fundamental voltage, the three-phase fundamental current is orthogonally decomposed to obtain the resistive component of the three-phase fundamental current in the same direction as the voltage.

4. The method according to claim 1, characterized in that, The step of determining the capacitive component and resistive component of the three-phase third harmonic current based on the second phase difference, the effective value of the three-phase third harmonic voltage, and the effective value of the three-phase third harmonic current specifically includes: Based on the second phase difference and the effective value of the third harmonic voltage, the effective value of the three-phase third harmonic current is orthogonally decomposed to obtain the capacitive component of the three-phase third harmonic current with a voltage lead of 90 degrees. Based on the effective value of the three-phase third harmonic voltage, the effective value of the three-phase third harmonic current is orthogonally decomposed to obtain the resistive component of the three-phase third harmonic in the same direction as the voltage.

5. The method according to claim 1, characterized in that, The step of determining the three-phase inter-phase capacitance of the three-phase surge arrester based on the effective value of the three-phase fundamental voltage, the capacitive component of the three-phase fundamental current, the effective value of the three-phase third harmonic voltage, and the capacitive component of the three-phase third harmonic current specifically includes: Let the three phases of the three-phase surge arrester be phase A, phase B, and phase C; Based on the three-phase fundamental current capacitance component, the three-phase third harmonic current capacitance component, the three-phase fundamental voltage effective value and the three-phase third harmonic voltage effective value, the phase-to-phase capacitance between phase A and phase B, the phase-to-phase capacitance between phase A and phase C and the phase-to-phase capacitance between phase B and phase C of the three-phase surge arrester are calculated using the first preset equation set and the second preset equation set, respectively. The first set of preset equations is: I a1C =ωC A U a1 -ωC AB U b1 sin(30°)-ωC AC U c1 sin(30°) I b1C =ωC B U b1 -ωC BC U c1 sin(30°)-ωC AB U a1 sin(30°) I c1C =ωC C U c1 -ωC AC U a1 sin(30°)-ωC BC U b1 sin(30°) Among them, the above I a1C I is the capacitive component of the fundamental current in phase A; b1C This refers to the capacitive component of the fundamental current in phase B; the aforementioned I c1C The fundamental current of phase C is the capacitive component; ω is a constant; C is a constant. A The equivalent capacitance of phase A; the aforementioned C B The equivalent capacitance of phase B; the above C C The equivalent capacitance of phase C; the above U a1 The effective value of the fundamental voltage of phase A; the above U b1 This is the effective value of the fundamental voltage of phase B; the above U c1 This is the effective value of the fundamental voltage of phase C; the above C AB C is the interphase capacitance between phase A and phase B; AC This refers to the interphase capacitance between phase A and phase C; the aforementioned C BC This refers to the interphase capacitance between phase B and phase C. The second set of preset equations is: I a3C =3ωU a3 (C A +C AB +C AC ) I b3C =3ωU b3 (C B +C AB +C BC ) I c3C =3ωU c3 (C C +C AC +C BC ) Among them, the above I a3C The third harmonic capacitive component of phase A; the above I b3C The third harmonic capacitive component of phase B; the above I c3C The third harmonic capacitive component of phase C; the above U a3 The effective value of the third harmonic voltage of phase A; the above U b3 The effective value of the third harmonic voltage of phase B; the above U c3 This represents the effective value of the third harmonic voltage of phase C.

6. The method according to claim 5, characterized in that, The step of determining the three-phase fundamental resistive current of the three-phase surge arrester based on the three-phase interphase capacitance, the resistive component of the three-phase fundamental current, and the effective value of the three-phase fundamental voltage specifically includes: Based on the three-phase interphase capacitance, the three-phase fundamental current resistive component, and the three-phase fundamental voltage effective value, the fundamental resistive current of the A-phase valve plate, the fundamental resistive current of the B-phase valve plate, and the fundamental resistive current of the C-phase valve plate of the three-phase surge arrester are calculated using the third preset equation set. The third set of preset equations includes: I a1-R = I aa1-R +ωC AB U b1 cos(30°)-ωC AC U c1 cos(30°) I b1-R = I bb1-R +ωC BC U c1 cos(30°)-ωC AB U a1 cos(30°) I c1-R = I cc1-R +ωC AC U a1 cos(30°)-ωC BC U b1 cos(30°) Among them, the above I a1-R The fundamental current resistive component of phase A; the above I b1-R This refers to the resistive component of the fundamental current in phase B; the aforementioned I c1-R The fundamental current resistive component of phase C; the above I aa1-R This refers to the fundamental resistive current of the A-phase valve plate itself; the aforementioned I bb1-R This refers to the fundamental resistive current of the B-phase valve plate itself; the aforementioned I cc1-R This is the fundamental resistive current of the C-phase valve plate itself.

7. A device for detecting the resistive current of a surge arrester, characterized in that, include: The acquisition module is used to acquire the three-phase voltage and leakage current of the three-phase arrester included in the surge arrester resistive current detection command in response to the surge arrester resistive current detection command. The first determining module is used to determine the effective values ​​of the three-phase fundamental voltage, the effective value of the three-phase third harmonic voltage, the effective value of the three-phase fundamental current, the effective value of the three-phase third harmonic current, the first phase difference, and the second phase difference of the three-phase surge arrester based on the three-phase voltage and the leakage current. The first phase difference is the phase difference between the three-phase fundamental voltage and the three-phase fundamental current, and the second phase difference is the phase difference between the three-phase third harmonic voltage and the three-phase third harmonic current. The second determining module is used to determine the capacitive component and the resistive component of the three-phase fundamental current based on the first phase difference, the effective value of the three-phase fundamental voltage, and the effective value of the three-phase fundamental current. The third determining module is used to determine the capacitive component and the resistive component of the three-phase third harmonic current based on the second phase difference, the effective value of the three-phase third harmonic voltage, and the effective value of the three-phase third harmonic current. The fourth determining module is used to determine the three-phase third harmonic resistive current of the three-phase surge arrester based on the resistive component of the three-phase third harmonic current. The fifth determining module is used to determine the three-phase interphase capacitance of the three-phase surge arrester based on the effective value of the three-phase fundamental voltage, the capacitive component of the three-phase fundamental current, the effective value of the three-phase third harmonic voltage, and the capacitive component of the three-phase third harmonic current. The sixth determining module is used to determine the three-phase fundamental resistive current of the three-phase surge arrester based on the three-phase interphase capacitance, the resistive component of the three-phase fundamental current, and the effective value of the three-phase fundamental voltage. The comparison module is used to compare the three-phase third harmonic resistive current with a first preset threshold and to compare the three-phase fundamental resistive current with a second preset threshold. The seventh determining module is used to determine that the three-phase surge arrester is in an abnormal state if any one of the three-phase third harmonic resistive currents is greater than or equal to the first preset threshold, or any one of the three-phase fundamental resistive currents is greater than or equal to the second preset threshold.

8. A surge arrester detection system, characterized in that, include: The surge arrester resistive current detection device as described in claim 7.

9. The surge arrester detection system according to claim 8, characterized in that, Also includes: Three-phase surge arrester; A voltage transformer is connected in parallel with the three-phase surge arrester; The first sensor is located on the secondary side of the voltage transformer connected in parallel with the three-phase surge arrester. The first sensor is used to collect the three-phase voltage. The second sensor is installed between the three-phase surge arrester and the grounding lead, and the second sensor is used to collect leakage current; An A / D conversion module is used to convert the three-phase voltage and the leakage current into digital signals; The first calculation module is used to calculate the effective values ​​of the three-phase fundamental voltage, the three-phase third harmonic voltage, the three-phase fundamental current, the three-phase third harmonic current, the first initial phase angle, and the second initial phase angle of the three-phase surge arrester. The second calculation module is used to calculate the three-phase third harmonic resistive current and the three-phase fundamental resistive current of the three-phase surge arrester. The display module is used to display the three-phase third harmonic resistive current and the three-phase fundamental resistive current.

10. A readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

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