A method and apparatus for calibrating a capacitance current tester

Abstract

The application belongs to the technical field of power system testing, and specifically discloses a method and device for calibrating a capacitance current tester, which comprises the following steps: determining an equivalent capacitance theoretical value based on the capacitance and equivalent coefficient of an equivalent circuit, wherein the equivalent circuit is constructed by connecting a capacitor, an inductor and a resistor in series, and the equivalent circuit is an equivalent circuit for simulating a neutral point ungrounded system to ground; measuring the equivalent circuit by using the capacitance current tester to obtain a capacitance measured value; and calibrating the capacitance current tester by comparing the difference between the theoretical value and the measured value based on the equivalent capacitance theoretical value and the capacitance measured value. According to the application, an electromagnetic voltage transformer is not needed to be configured, the error and uncertainty introduced by the electromagnetic voltage transformer can be avoided, and the complicated operation caused by the need to equip corresponding electromagnetic voltage transformers for different voltage grades can also be avoided, so that the capacitance current tester can be efficiently and accurately calibrated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of power system testing, and more particularly to a method and device for calibrating a capacitance current tester. BACKGROUND

[0002] In power system testing, the capacitance and capacitance current of a neutral non-grounded system are generally measured by a capacitance current tester. In order to ensure the accuracy of the measurement of the capacitance current tester, the capacitance current tester needs to be calibrated.

[0003] The calibration method in the prior art is to connect a standard capacitor to the primary side of an electromagnetic voltage transformer and connect the capacitance current tester to the secondary side of the electromagnetic voltage transformer, and to calibrate the capacitance current tester by analyzing the difference between the capacitance value measured by the capacitance current tester and the nominal value of the standard capacitor. The above-mentioned existing calibration method has the following defects: it is difficult to calibrate in the case of high capacitance and high transformation ratio of the electromagnetic voltage transformer; the calibration accuracy is limited by the voltage ratio difference and phase difference parameter error of the electromagnetic voltage transformer; different voltage levels need to be equipped with corresponding electromagnetic voltage transformers, resulting in a complicated calibration process. How to efficiently and accurately calibrate the capacitance current tester is a technical problem to be solved in the field. SUMMARY

[0004] In view of the defects of the prior art, the purpose of the present application is to efficiently and accurately calibrate the capacitance current tester.

[0005] To achieve the above-mentioned purpose, in a first aspect, the present application provides a method for calibrating a capacitance current tester, comprising:

[0006] determining an equivalent capacitance theoretical value based on the capacitance and equivalent coefficient of the equivalent circuit, the equivalent circuit being constructed by connecting a capacitor, an inductor and a resistor in series (the values of the inductor and the resistor in the equivalent circuit are determined based on the impedance at the open delta of the electromagnetic voltage transformer), the equivalent circuit being an equivalent circuit for simulating the neutral non-grounded system to ground, and the equivalent coefficient representing the mapping relationship between the capacitance of the equivalent circuit and the equivalent capacitance theoretical value;

[0007] measuring the equivalent circuit by the capacitance current tester to obtain a capacitance measured value;

[0008] calibrating the capacitance current tester by comparing the difference between the theoretical value and the measured value based on the equivalent capacitance theoretical value and the capacitance measured value.

[0009] In a possible implementation, determining the equivalent capacitance theoretical value based on the capacitance and equivalent coefficient of the equivalent circuit comprises determining the equivalent capacitance theoretical value by the following formula:

[0010] ;

[0011] wherein, represents an equivalent capacitance theoretical value, represents an equivalent coefficient, represents a standard capacitance value of the equivalent circuit.

[0012] In a possible implementation, the equivalent coefficient is determined based on a system wiring mode and a winding ratio at an open delta of the electromagnetic voltage transformer;

[0013] The system wiring mode is a 3VT wiring mode or a 1VT wiring mode.

[0014] In a possible implementation, in a case where the system wiring mode is the 3VT wiring mode, ;

[0015] wherein, represents a winding ratio at an open delta of the electromagnetic voltage transformer.

[0016] In a possible implementation, in a case where the system wiring mode is the 1VT wiring mode, ;

[0017] wherein, represents a winding ratio at an open delta of the electromagnetic voltage transformer.

[0018] In a possible implementation, the equivalent circuit is measured by a capacitance current tester to obtain a capacitance measured value, including:

[0019] When the equivalent circuit is measured by the capacitance current tester, an image of a display screen of the capacitance current tester is collected, and the display screen of the capacitance current tester is used to display the capacitance measured value;

[0020] The collected image is subjected to image recognition to extract the capacitance measured value.

[0021] In a possible implementation, the method further includes:

[0022] The capacitance discharge module is controlled to perform a discharge operation on the capacitance in the equivalent circuit.

[0023] In a second aspect, the application provides a device for calibrating a capacitance current tester, including: an equivalent circuit and a processor;

[0024] The equivalent circuit is constructed by connecting a capacitance, an inductance and a resistance in series, and the equivalent circuit is used to simulate an equivalent circuit of a neutral point ungrounded system to ground;

[0025] The processor is configured to:

[0026] The equivalent capacitance theoretical value is determined based on an equivalent circuit capacitance and an equivalent coefficient, and the equivalent coefficient represents a mapping relationship between the equivalent circuit capacitance and the equivalent capacitance theoretical value;

[0027] The equivalent circuit is measured by the capacitance current tester to obtain a capacitance measured value;

[0028] Based on the equivalent capacitance theoretical value and the capacitance measured value, the capacitance current tester is calibrated by comparing the difference between the theoretical value and the measured value.

[0029] In a possible implementation, the method further includes:

[0030] The data acquisition module is configured to acquire an image of a display screen of the capacitance current tester when the capacitance current tester measures the equivalent circuit, and the display screen of the capacitance current tester is configured to display the capacitance measured value.

[0031] The processor is configured to perform image recognition on the acquired image and extract the capacitance measured value.

[0032] In a possible implementation, the method further includes a capacitance discharge module.

[0033] The processor is further configured to control the capacitance discharge module to perform a discharge operation on the capacitance in the equivalent circuit.

[0034] Overall, compared with the prior art, the above technical solutions conceived by the present application have the following beneficial effects:

[0035] (1) In the calibration scheme of the present application, no electromagnetic voltage transformer needs to be configured, which can avoid the error and uncertainty introduced by the electromagnetic voltage transformer, and also avoid the complicated operation caused by the need to equip corresponding electromagnetic voltage transformers for different voltage levels, thereby realizing efficient and accurate calibration of the capacitance current tester.

[0036] (2) By accurately calibrating the capacitance current tester, the performance indicators of the instrument, such as measurement accuracy and stability, can be monitored in real time. When these indicators are abnormal, the system can issue an early warning to prompt the operator to check and maintain, thereby realizing a pre-diagnosis function. Secondly, the calibration scheme can record the usage history and calibration data of the instrument, and by analyzing these data, the health status of the instrument can be evaluated, and potential fault risks can be found in time. Therefore, the calibration scheme of the present application can be applied to the pre-diagnosis and health management of the capacitance current tester.

[0037] (3) In the case of high capacitance, high transformation ratio of the electromagnetic voltage transformer, the equivalent circuit can also simulate the equivalent capacitance of the neutral point ungrounded system to the ground, so that the present application can realize calibration of the capacitance current tester with multiple transformation ratios and in a wide range. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a flowchart of a method for calibrating a capacitance current tester provided by an embodiment of the present application;

[0039] Figure 2 is a schematic diagram of a simulation model provided by an embodiment of the present application;

[0040] Figure 3 is a structural schematic diagram of a device for calibrating a capacitance current tester provided by an embodiment of the present application. DETAILED DESCRIPTION

[0041] In order to make the objects, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0042] In the embodiments of the present application, the words such as "exemplary" or "for example" are used to mean serving as an example, illustration or description. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or having more advantages than other embodiments or design solutions. Rather, the words such as "exemplary" or "for example" are used in the specific manner to present the relevant concept.

[0043] In the description of the embodiments of the present application, unless otherwise specified, "a plurality of" means two or more, for example, a plurality of processing units means two or more processing units, and the like; a plurality of elements means two or more elements, and the like.

[0044] The embodiments of the present application are described below with reference to the accompanying drawings in the embodiments of the present application.

[0045] Figure 1 is a flowchart of a method for calibrating a capacitance current tester provided by an embodiment of the present application, as shown in Figure 1 the method comprises the following steps S101 to S103.

[0046] In step S101, based on the capacitance of an equivalent circuit and an equivalent coefficient, a theoretical value of an equivalent capacitance is determined, the equivalent circuit is constructed by connecting a capacitance, an inductance and a resistance in series (the values of the inductance and the resistance in the equivalent circuit are determined based on the impedance at the open delta of the electromagnetic voltage transformer), the equivalent circuit is an equivalent circuit for simulating the neutral point ungrounded system to ground, and the equivalent coefficient represents the mapping relationship between the capacitance of the equivalent circuit and the theoretical value of the equivalent capacitance.

[0047] In step S102, the equivalent circuit is measured by the capacitance current tester to obtain a measured value of the capacitance.

[0048] Step S103, based on the equivalent capacitance theoretical value and the capacitance measured value, the capacitance current tester is calibrated by comparing the difference between the theoretical value and the measured value.

[0049] Specifically, in the calibration scheme of the present application, an equivalent circuit is constructed by connecting a capacitor, an inductor and a resistor in series, the equivalent circuit is an equivalent circuit for simulating the neutral point ungrounded system to ground, the present application adopts the mode of "measuring the equivalent circuit by the capacitance current tester" to replace the existing mode of "connecting a standard capacitor on the primary side of the electromagnetic voltage transformer, and connecting the capacitance current tester on the secondary side of the electromagnetic voltage transformer", and the present application does not need to configure the electromagnetic voltage transformer.

[0050] Meanwhile, the equivalent coefficient is used to represent the mapping relationship between the capacitance of the equivalent circuit and the equivalent capacitance theoretical value, and then the equivalent capacitance theoretical value can be determined based on the capacitance of the equivalent circuit and the equivalent coefficient, and then the capacitance current tester can be calibrated by comparing the difference between the theoretical value and the measured value based on the equivalent capacitance theoretical value and the capacitance measured value.

[0051] Therefore, in the calibration scheme of the present application, the electromagnetic voltage transformer does not need to be configured, the error and uncertainty introduced by the electromagnetic voltage transformer can be avoided, the operation of equipping corresponding electromagnetic voltage transformers for different voltage levels can be avoided, and the capacitance current tester can be calibrated efficiently and accurately.

[0052] By accurately calibrating the capacitance current tester, the performance indicators of the instrument, such as measurement accuracy and stability, can be monitored in real time. When these indicators are abnormal, the system can give an early warning to prompt the operator to check and maintain, thereby realizing the pre-diagnosis function. Secondly, the calibration scheme can record the use history and calibration data of the instrument, and through the analysis of these data, the health status of the instrument can be evaluated, and potential fault hazards can be found in time. Therefore, the calibration scheme of the present application can be applied to the pre-diagnosis and health management of the capacitance current tester.

[0053] In addition, in the case of high capacitance and high transformation ratio of the electromagnetic voltage transformer, the equivalent circuit can also simulate the equivalent capacitance of the neutral point ungrounded system to ground, so that the present application can realize the calibration of the capacitance current tester with multiple transformation ratios and in a wide range.

[0054] In one possible implementation, the above-mentioned determination of the equivalent capacitance theoretical value based on the capacitance of the equivalent circuit and the equivalent coefficient includes determining the equivalent capacitance theoretical value by the following formula:

[0055] ;

[0056] wherein, C represents the equivalent capacitance theoretical value, C represents the equivalent coefficient, a standard capacitance value representing the equivalent circuit.

[0057] In a possible implementation, the equivalent coefficient is determined based on a system wiring mode and a winding ratio at an open delta of the electromagnetic voltage transformer, the system wiring mode being the 3VT wiring mode or the 1VT wiring mode.

[0058] In a possible implementation, in a case where the system wiring mode is the 3VT wiring mode, ;

[0059] wherein, a winding ratio at an open delta of the electromagnetic voltage transformer.

[0060] In a possible implementation, in a case where the system wiring mode is the 1VT wiring mode, ;

[0061] wherein, a winding ratio at an open delta of the electromagnetic voltage transformer.

[0062] In a possible implementation, the measurement of the equivalent circuit by the capacitance current tester to obtain the capacitance measured value comprises the following steps.

[0063] When the capacitance current tester measures the equivalent circuit, an image of a display screen of the capacitance current tester is collected, the display screen of the capacitance current tester being used to display the capacitance measured value.

[0064] The collected image is subjected to image recognition to extract the capacitance measured value.

[0065] In a possible implementation, the method further comprises the following steps.

[0066] The capacitance discharging module is controlled to perform a discharging operation on the capacitance in the equivalent circuit.

[0067] Specifically, the capacitance discharging module mainly consists of a switching element, a discharging resistor, a control circuit, and necessary protection elements. The switching element is responsible for turning on or off the discharging path of the capacitance, the discharging resistor is connected in series with the capacitance to limit the discharging current, the control circuit operates the switching element according to external signals or internal timing logic, and the protection elements ensure the safety of the circuit in abnormal conditions. The discharging process: first, a trigger signal needs to be sent to the control circuit, which will make the switching element conductive, thereby connecting the capacitance and the discharging resistor to form a discharging loop; as the capacitance discharges through the discharging resistor, its voltage gradually decreases, and when it reaches the preset discharging end point, the control circuit will turn off the switching element to cut off the discharging path, completing the discharging operation of the capacitance.

[0068] It can be understood that the prior art does not consider the capacitor discharge problem, and there is a safety hazard. The application improves safety by controlling the capacitor discharge module to perform a discharge operation on the capacitor in the equivalent circuit.

[0069] Figure 2 is a schematic diagram of the simulation model provided by the embodiments of the application, as Figure 2 shown, the effectiveness of the method for calibrating the capacitor current tester provided by the application is verified based on Matlab / Simscape simulation.

[0070] Specifically, as Figure 2 shown, the graphical interface provided by Matlab / Simscape can be used to construct the electromagnetic voltage transformer simulation circuit and the equivalent simulation circuit. The former is used to simulate the measurement of the capacitor current tester on the neutral point ungrounded system, and the latter is used to simulate the measurement of the capacitor current tester on the equivalent circuit.

[0071] Simulation test: the simulation can be run in the Matlab / Simscape environment to simulate the measurement of the capacitor current tester on the neutral point ungrounded system, and to display , and to simulate the measurement of the capacitor current tester on the equivalent circuit, and to display to check whether the behavior of the model meets the expectations, that is, to check whether displayed by the former simulation is the same as displayed by the latter simulation. If they are the same, it indicates that the equivalent circuit can effectively simulate the equivalent capacitance of the neutral point ungrounded system to ground.

[0072] Through simulation verification, it can be determined that in the open-delta injection method, the equivalent circuit can effectively simulate the equivalent capacitance of the neutral point ungrounded system to ground, and , represents the equivalent capacitance theoretical value, represents the equivalent coefficient, represents the standard capacitance value of the equivalent circuit, the value is determined by the VT transformation ratio and the system wiring mode in the actual working condition of the power distribution network.

[0073] Through simulation verification, it can also be determined that when 1VT and the neutral point is connected, ; when 3VT, . In the formula, : the winding transformation ratio of the open-delta of the electromagnetic voltage transformer. The capacitor current theoretical value , represents the angular frequency, This indicates the phase voltage. Among them, 1VT and 3VT are two different types of electromagnetic voltage transformers with different wiring methods. 1VT usually represents a single-phase electromagnetic voltage transformer, while 3VT usually represents a three-phase electromagnetic voltage transformer.

[0074] Virtual simulation reduces the number of physical prototype tests and shortens the R&D cycle; it reveals the error mechanism of the tester under complex working conditions (such as sensor temperature drift and electromagnetic interference), guiding the coordinated optimization of hardware and algorithms; and it generates high-confidence simulation data to provide a theoretical basis for the formulation of calibration specifications.

[0075] Figure 3 This is a schematic diagram of the structure of the device for calibrating the capacitance current tester provided in the embodiments of this application, as shown below. Figure 3 As shown, this application also provides a device for calibrating a capacitance current tester, the device comprising: an equivalent circuit and a processor;

[0076] The equivalent circuit is constructed by connecting capacitors, inductors, and resistors in series. The equivalent circuit is used to simulate the equivalent circuit of a neutral point ungrounded system to ground.

[0077] The processor is used for:

[0078] Based on the capacitance and equivalent coefficient of the equivalent circuit, the theoretical value of the equivalent capacitance is determined. The equivalent coefficient characterizes the mapping relationship between the capacitance of the equivalent circuit and the theoretical value of the equivalent capacitance.

[0079] The equivalent circuit is measured using a capacitance current tester to obtain the measured capacitance value.

[0080] Based on the theoretical value of equivalent capacitance and the measured value of capacitance, the capacitance current tester is calibrated by comparing the difference between the theoretical value and the measured value.

[0081] In one possible implementation, such as Figure 3 As shown, it also includes: a data acquisition module;

[0082] The data acquisition module is used to acquire images from the display screen of the capacitance current tester when the capacitance current tester measures the equivalent circuit. The display screen of the capacitance current tester is used to display the measured capacitance value.

[0083] The processor is used to perform image recognition on the acquired images and extract the measured capacitance values.

[0084] In one possible implementation, such as Figure 3 As shown, it also includes: a capacitor discharge module;

[0085] The processor is also used to control the capacitor discharge module to perform discharge operations on the capacitors in the equivalent circuit.

[0086] It is understood that the various numerical designations used in the embodiments of this application are merely for the convenience of description and are not intended to limit the scope of the embodiments of this application.

[0087] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method of calibrating a capacitance current tester, comprising: The method comprises the following steps: determining an equivalent capacitance theoretical value based on an equivalent circuit capacitance and an equivalent coefficient, the equivalent circuit being constructed by connecting a capacitance, an inductance and a resistance in series, the equivalent circuit being an equivalent circuit for simulating a neutral ungrounded system to ground, and the equivalent coefficient representing a mapping relationship between the equivalent circuit capacitance and the equivalent capacitance theoretical value; measuring the equivalent circuit by using a capacitance current tester to obtain a capacitance measured value; calibrating the capacitance current tester by comparing the difference between the equivalent capacitance theoretical value and the capacitance measured value.

2. The method of calibrating a capacitance current tester of claim 1, wherein, The equivalent circuit capacitance and the equivalent coefficient are used to determine the equivalent capacitance theoretical value, and the equivalent circuit capacitance and the equivalent coefficient are determined by the following formula: ； wherein, represents an equivalent capacitance theoretical value, represents an equivalent coefficient, represents a standard capacitance value of the equivalent circuit.

3. The method of calibrating a capacitance current tester of claim 1, wherein, The equivalent coefficient is determined based on a system wiring mode and a winding ratio of an open delta of an electromagnetic voltage transformer; The system wiring mode is a 3VT wiring mode or a 1VT wiring mode.

4. The method of calibrating a capacitance current tester of claim 3, wherein, In the case of a system connection mode of 3VT connection mode, ; wherein, Kop represents the open delta winding ratio of the electromagnetic voltage transformer.

5. The method of calibrating a capacitance current tester of claim 3, wherein, In the case of a system connection mode of 1VT connection mode, ; wherein, Kop represents the open delta winding ratio of the electromagnetic voltage transformer.

6. The method of calibrating a capacitance current tester of claim 1, wherein, The capacitance measured value is obtained by measuring the equivalent circuit by using the capacitance current tester, and the method comprises the following steps: When the equivalent circuit is measured by using the capacitance current tester, an image of a display screen of the capacitance current tester is collected, the display screen of the capacitance current tester being used to display the capacitance measured value; The collected image is subjected to image recognition to extract the capacitance measured value.

7. The method of calibrating a capacitance current tester according to any of claims 1-6, wherein, The method further comprises the following steps: The capacitance discharge module is controlled to perform a discharge operation on the capacitance in the equivalent circuit.

8. A device for calibrating a capacitance current tester, characterized by, The method comprises the following steps: an equivalent circuit and a processor; the equivalent circuit being constructed by connecting a capacitance, an inductance and a resistance in series, the equivalent circuit being an equivalent circuit for simulating a neutral ungrounded system to ground; the processor being configured to: determine an equivalent capacitance theoretical value based on an equivalent circuit capacitance and an equivalent coefficient, the equivalent coefficient representing a mapping relationship between the equivalent circuit capacitance and the equivalent capacitance theoretical value; measure the equivalent circuit by using a capacitance current tester to obtain a capacitance measured value; calibrate the capacitance current tester by comparing the difference between the equivalent capacitance theoretical value and the capacitance measured value.

9. The apparatus of claim 8, wherein, The method further comprises the following steps: a data collection module; the data collection module being configured to collect an image of a display screen of the capacitance current tester when the equivalent circuit is measured by using the capacitance current tester, the display screen of the capacitance current tester being used to display the capacitance measured value; the processor being configured to perform image recognition on the collected image to extract the capacitance measured value.

10. The apparatus of claim 8, wherein: The method further comprises the following steps: a capacitance discharge module; the processor being further configured to control the capacitance discharge module to perform a discharge operation on the capacitance in the equivalent circuit.

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