An insulation resistance leakage current measurement system and method

Abstract

The application belongs to the field of insulator measurement, and relates to an insulating resistance leakage current measurement system and method, which comprises a constant-temperature and constant-humidity isolation box, a high-voltage direct-current power supply, an insulating resistance clamp, an electrometer and a computer. The insulating resistance clamp comprises a copper plate upper electrode, a copper plate lower electrode, a protection electrode, a spring pull rod and a support. The top surface of the copper plate upper electrode is fixedly connected with the bottom of the spring pull rod. The spring pull rod is provided with a rotating bolt, by which the spring tensile modulus can be scaled. The copper plate lower electrode is located below the copper plate upper electrode. The protection electrode is located on both sides of the copper plate lower electrode. The top of the spring pull rod is connected with the high-voltage direct-current power supply. The electrometer is connected with the copper plate lower electrode. The electrometer is connected with the computer through a data transmission line. The application can conveniently correct data fluctuation occurring in the measurement process in time, and improve the efficiency and accuracy of measurement.

Description

Technical Field

[0001] This invention belongs to the field of insulator measurement, and in particular to an insulation resistance leakage current measurement system and method. Background Technology

[0002] Insulation resistance is the most basic insulation indicator for electrical equipment applications and electrical transmission lines. In application, insulation resistance is divided into good insulation resistance and defective insulation resistance. This is based on the fact that during engineering use, environmental factors such as air, dust, and moisture can affect the insulation resistance, causing air gaps and insulation cracks to form inside the insulation device. This can lead to a sudden drop in insulation resistance. The value of the insulation resistance is inherently related to the leakage current flowing through the device. By measuring the leakage current of the insulation resistance, its resistance value and insulation performance can be calculated.

[0003] Leakage current has always been considered an important parameter for evaluating the performance of insulating materials. Therefore, directly or indirectly measuring leakage current has certain reference value for testing the performance of insulating materials. Leakage current refers to the current flowing through the medium or surface surrounding the insulation resistance when a voltage is applied under fault-free conditions. Generally, leakage current includes two parts: conduction current and displacement current. In the actual measurement of the conduction current of a dielectric, the resistive current formed by ion movement is represented as the leakage current. That is, when a DC voltage is applied to the dielectric, the leakage current will decrease over time to reach a stable value. Determining the stable range of the leakage current value after applying pressure is a prerequisite for the accuracy of the leakage current value.

[0004] The leakage current values ​​of samples with different insulating materials often vary between microamps and milliamps, with the resistive component accounting for only 5%-20%, resulting in relatively weak leakage current signals. Traditional methods for measuring leakage current in insulation resistance often employ high-voltage DC devices or withstand voltage devices to supply power, with the microammeter directly reading the leakage current. However, the stable value of the leakage current often cannot be determined through short-term data recording, and ambient temperature and electromagnetic interference during the measurement process indirectly affect the measurement results. Furthermore, data recording and storage are cumbersome. Therefore, there is an urgent need for a system for measuring leakage current in insulation resistance that addresses the design challenges of measuring and processing leakage current under conditions of ambient temperature and external signal interference.

[0005] Current methods for detecting leakage current mainly focus on upgrading algorithms and noise reduction components. The full-current method, fast Fourier transform (FFT) detection method, and lock-in amplification (LLA) algorithm are the main data processing tools. The full-current method processes the signal by directly reading the values ​​from the leakage current detection device. However, it is significantly affected by temperature, humidity, and electromagnetic interference during the detection process, and its measurement accuracy is often not guaranteed. FFT and LLA algorithms have good harmonic detection and bias analysis capabilities, but currently they are mostly concentrated at the data acquisition end, resulting in poor synchronization and timeliness during data acquisition. Therefore, improvements should be made to address potential environmental variables and the stability of the fixture during data acquisition. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an insulation resistance leakage current measurement system and method to solve the technical problem that the prior art is unable to measure the insulation resistance leakage current under temperature and humidity gradients.

[0007] The technical solution adopted by this invention to solve the technical problem is:

[0008] The first aspect of this invention provides an insulation resistance leakage current measurement system, comprising: a constant temperature and humidity isolation chamber, a high-voltage DC power supply, an insulation resistance clamp, an electrometer, and a computer. The high-voltage DC power supply is installed outside the constant temperature and humidity isolation chamber; the insulation resistance clamp is installed inside the constant temperature and humidity isolation chamber, and the insulation resistance clamp includes: an upper copper plate electrode, a lower copper plate electrode, a protective electrode, a spring rod, and a bracket. The top surface of the upper copper plate electrode is fixedly connected to the bottom of the spring rod. The spring rod has a rotating bolt, which allows for scaling of the spring's tensile modulus. The lower copper plate electrode is located below the upper copper plate electrode, and the protective electrodes are located on both sides of the lower copper plate electrode and supported by electrode fixing blocks. The top of the spring rod is connected to the high-voltage DC power supply; the electrometer is connected to the lower copper plate electrode; the electrometer is connected to the computer via a data transmission line, and both the electrometer and the computer are installed outside the constant temperature and humidity isolation chamber.

[0009] Furthermore, the protective electrode, high-voltage DC power supply, electrometer, and constant temperature and humidity isolation chamber are all grounded.

[0010] Furthermore, the electrometer model is Keithley 6517b.

[0011] The second aspect of the present invention provides a measurement method for the above-mentioned measurement system. First, the radial distance of the sample is determined, and electrodes on a copper plate covering the radial distance of the sample are selected. After wiring, the sample is placed inside a constant temperature and humidity isolation chamber. Data is uploaded to a computer via a data transmission line through an electrometer. The computer controls, collects, and stores leakage current measurement data, and sets the measurement temperature and humidity parameters. Based on the uploaded data, the waveform is read on the host computer, and the stable component range of the leakage current is determined based on the waveform trend. The measured value is then determined. The collected leakage current is compared with the normal leakage current of the insulation sample under the same temperature and humidity and the leakage current of the insulation sample failure in the database on the host computer to obtain the insulation status of the current insulation sample.

[0012] Furthermore, the sample to be measured is preheated to the measurement temperature before measurement.

[0013] Furthermore, the preset humidity is set to 30–98% RH.

[0014] The advantages and positive effects of this invention are:

[0015] 1. This invention achieves stable measurement of leakage current in insulating samples using an insulation resistance clamp in conjunction with a constant temperature and humidity isolation chamber. An electrometer collects measurement data in real time, and a computer collects sample data in real time via an RS-232 data transmission line. The computer controls the entire measurement process of the electrometer through a host computer interface and plots waveforms in real time based on the collected data, providing a visual interface for testers. This facilitates timely correction of data fluctuations during the measurement process, improving measurement efficiency and accuracy.

[0016] 2. To avoid the influence of ambient temperature, humidity, and electromagnetic interference on the measurement results, the measuring device needs to be subjected to constant temperature, constant humidity, and isolation operations before measurement. Therefore, a constant temperature and humidity isolation chamber was used as the main measuring chamber for the sample during the testing phase. The temperature and humidity of the isolation chamber were set via a programmable controller based on the datasheet and the ambient temperature of the sample's engineering application. To better isolate electromagnetic signals, the inner wall of the experimental chamber was made of iron plate with observation windows. These windows could be sealed with insulating materials such as tin foil as needed to achieve better test results.

[0017] 3. Considering the fixed nature of traditional fixtures and the limited sample specifications, insulation resistance fixtures can be effectively selected based on the type of leakage current to be measured. The insulation resistance fixture uses acrylic material as a fixing component, a spring-loaded lever to control the distance between the two copper plate electrodes, and external metal bolts for easy wiring. The bottom has the wiring terminals for the test electrodes, allowing for the connection of different external measuring devices as needed based on the test data. During leakage current measurement, the measurement can be adjusted between the body leakage current and the surface leakage current depending on whether the protective electrode is short-circuited.

[0018] 4. In the data acquisition section, a leakage current database for faults or insulation performance degradation is established. By comparing the sampled data, it is possible to determine whether the current sample is in the late stage or early stage of operation. Multiple tests are conducted on the same sample, and cluster analysis is performed on the sampled data to obtain more accurate data results, providing reliable leakage current measurement results for insulation resistance and suggestions for sample fabrication. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a measurement system according to an embodiment of the present invention.

[0020] The above figures include the following reference numerals:

[0021] 1 is a high-voltage DC power supply, 2 is a constant temperature and humidity isolation chamber, 3 is an insulation resistance clamp, 4 is an electrometer, 5 is a computer, 6 is a rotating bolt, 7 is a spring rod, 8 is an upper electrode on the copper plate, 9 is a lower electrode on the copper plate, 10 is a protective electrode, 11 is a measurement sample, and 12 is a data transmission line. Detailed Implementation

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0024] The present invention provides an insulation resistance leakage current measurement system, comprising: a high-voltage DC power supply 1, a constant temperature and humidity isolation chamber 2, an insulation resistance clamp 3, an electrometer 4, and a computer 5. The insulation resistance clamp 3 is installed inside the constant temperature and humidity isolation chamber 2, and the high-voltage DC power supply 1, the electrometer 4, and the computer 5 are all installed outside the constant temperature and humidity isolation chamber 2.

[0025] The insulation resistance fixture 3 includes an upper copper plate electrode 8, a lower copper plate electrode 9, a protective electrode 10, a spring rod 7, and a support. The top surface of the upper copper plate electrode 8 is fixedly connected to the bottom of the spring rod 7, allowing the upper copper plate electrode 8 to move vertically via the spring rod 7. The spring rod 7 has a rotating bolt 6, which allows the spring tensile modulus to be adjusted. The lower copper plate electrode 9 is located below the upper copper plate electrode 8. The measurement sample 11 is placed between the upper copper plate electrode 8 and the lower copper plate electrode 9. The protective electrode 10 is located on both sides of the lower copper plate electrode 9 and is supported by electrode fixing blocks.

[0026] The top of the spring rod 7 is connected to the high-voltage DC power supply 1, the lower electrode 9 of the copper plate is connected to the electrometer 4, and the electrometer 4 is connected to the computer 5 through the data transmission line 12.

[0027] The bracket is used to support the spring rod 7, the upper electrode 8 on the copper plate, the lower electrode 9 on the copper plate, and the protective electrode 10.

[0028] Rotate the rotating bolt 6 counterclockwise. The electrode 8 on the copper plate will shorten as the spring modulus changes. Continue until the distance between the two copper plate electrodes is suitable for the current sample thickness. Place the sample between the upper copper plate electrode 8 and the lower copper plate electrode 9, and adjust the sample position to the center of the copper plate electrodes. At this time, rotate the rotating bolt 6 clockwise until the upper copper plate electrode 8 and the sample are fully adsorbed. Then stop rotating.

[0029] The sample 11 is fixed by the insulation resistance clamp 3, the upper end is connected to the high voltage DC power supply 1 by the spring rod 7, and the lower end is connected to the electrometer 4. After the wiring is completed, it is placed inside the constant temperature and humidity isolation chamber 2, and the data is uploaded to the computer 5 by the electrometer 4 via the data transmission line 12.

[0030] Ensure the protective electrode 10 of the insulation resistance clamp 3, the grounding terminal of the high voltage DC power supply 1, the grounding terminal of the electrometer 4, and the external metal shell of the constant temperature and humidity isolation chamber 2 are reliably grounded. Close the quick-closing valve and adjust the measured temperature and humidity through the program controller.

[0031] The output side of electrometer 4 is connected to computer 5 via RS-232 data transmission line. Computer 5 controls, collects and stores leakage current measurement data, sets measurement temperature and humidity parameters, reads waveform graphs from the host computer based on the uploaded data, determines the stable component range of leakage current under the current working conditions based on the waveform trend, and then determines the measurement value.

[0032] The electrode 8 on the copper plate is connected to the spring rod 7. The rotating bolt 6, the spring rod 7, and the electrode 8 on the copper plate constitute a high-voltage end, which is connected to the high-voltage DC power supply 1 through the power clamp and the signal shielding wire. The power clamp is fixed to the terminal of the rotating bolt 6.

[0033] The lower electrode 9 of the copper plate is the measuring electrode. It is connected to the input terminal of the electrometer 4 via a power clamp.

[0034] After the protective electrode 10 is reliably grounded, it is placed in the constant temperature and humidity isolation chamber 2. The connecting wire is led out through the sealing strip of the constant temperature and humidity isolation chamber 2, and the constant temperature and humidity isolation chamber 2 is closed by the hand-locking valve.

[0035] The electrometer 4 is a Keithley 6517b model, which can be connected to the computer 5 via data transmission cable 12. The setting mode is REM remote control, and the fixture is an external custom fixture.

[0036] In the computer software, configure the serial port, select the port in the serial port interface, determine the data type, and set the temperature and humidity parameters of the experimental chamber.

[0037] After computer 5 is configured, open the valve of the constant temperature and humidity isolation chamber 2, set the required ambient temperature and humidity, and after the constant temperature and humidity isolation chamber 2 reaches the set value and maintains it for 25 minutes, click "Start Data Acquisition" at the port of computer 5.

[0038] After data acquisition, the stable range of the current leakage current component is determined based on the data waveform. The data is saved and then processed to obtain the final measurement result.

[0039] During the data acquisition phase, considering the sensitivity of leakage current to temperature changes, the sample was preheated to the required experimental temperature using a constant temperature and humidity isolation chamber 2. Furthermore, during actual measurements, the preset humidity was maintained within the range of 30–98% RH. It was ensured that the power supply, the outer casing of the constant temperature and humidity isolation chamber 2, and the grounding terminal of the electrometer 4 were reliably grounded to guarantee the safety and compliance of the experimental operation. While awaiting test results, if spikes, prolonged fluctuations, or harmonic components appeared in the waveform plotted from the acquired data, the reliability of the wiring between the two copper plate terminals of the sample clamping system should be considered. After powering off, the sample surface should be cleaned again before starting a new round of measurements.

[0040] This invention has undergone laboratory testing and fully complies with the requirements of the "State Grid Corporation of China Power Safety Work Regulations (Substation Section)" and can be applied in the field.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A measurement method of an insulation resistance leakage current measurement system, characterized by, The measuring sample (11) is placed in the constant temperature and humidity isolation box (2), fixed by the insulation resistance clamp (3), after wiring is completed, data is uploaded to the computer (5) by the electrometer (4) through the data transmission line (12), the leakage current measurement data is controlled, collected and stored by the computer (5), and the measurement temperature and humidity parameters are set, the waveform graph is read according to the uploaded data on the host computer, the leakage current stable component interval is determined according to the waveform trend, and then the measurement value is determined, the collected leakage current is compared with the normal leakage current of the insulation sample under the same temperature and humidity in the database of the host computer and the leakage current of the failed insulation sample, and the insulation condition of the current insulation sample is obtained; The insulation resistance clamp (3) comprises a copper plate upper electrode (8), a copper plate lower electrode (9), a protection electrode (10), a spring pull rod (7) and a support, the top surface of the copper plate upper electrode (8) is fixedly connected with the bottom of the spring pull rod (7), the spring pull rod (7) has a rotating bolt (6), the spring tensile modulus can be scaled through the rotating bolt (6), the copper plate lower electrode (9) is located below the copper plate upper electrode (8), the copper plate lower electrode (9) is connected with the electrometer (4), the electrometer (4) is connected with the computer (5) through the data transmission line (12), the electrometer (4) and the computer (5) are both installed outside the constant temperature and humidity isolation box (2), the protection electrode (10) is located on both sides of the copper plate lower electrode (9) and is supported by the electrode fixing block, the top of the spring pull rod (7) is connected with the high-voltage direct-current power supply (1), and the protection electrode (10), the high-voltage direct-current power supply (1), the electrometer (4) and the constant temperature and humidity isolation box (2) are all grounded.

2. The method of claim 1, wherein, The measuring sample (11) is preheated to the measurement temperature before measurement.

3. The method of claim 1, wherein, In the measurement process, the preset humidity is set to 30-98%RH.

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