Porcelain insulator impulse voltage defect detection method and device based on voltage change rate

Abstract

The invention discloses a porcelain insulator impulse voltage defect detection method and device based on a voltage change rate, and the method comprises the steps: applying high-voltage pulses to the two ends of a porcelain insulator to be detected, measuring the voltage waveform data of the two ends of the porcelain insulator, extracting a voltage amplitude from the data, and calculating the voltage change rate within a set time interval, comprehensive judgment is carried out according to double criteria of whether the voltage amplitude is lower than a preset amplitude threshold value and whether the voltage change rate exceeds a preset change rate threshold value, and as long as any criterion exceeds the threshold value, it can be judged that the porcelain insulator has the internal breakdown defect. According to the invention, the defect that the traditional single amplitude criterion is easy to miss judgment is overcome, small defects in the porcelain insulator can be accurately identified, the zero-value insulator which is broken down in the impact withstand voltage process can be effectively detected, the accuracy of insulator detection is improved, and powerful support is provided for ensuring the safe and stable operation of a power grid.

Description

Technical Field

[0001] The present invention relates to a transmission line defect detection and evaluation technology, and in particular to a method and device for detecting porcelain insulator impulse voltage defects based on voltage change rate. Background Art

[0002] Line insulators are key components in overhead transmission lines, their primary function being to provide mechanical connection and electrical isolation between conductors and towers. Disc-type suspension insulators are the most widely used type. During operation, insulators are subject to a variety of complex natural environmental factors. In terms of electrical performance, insulators must possess sufficient voltage resistance to withstand transient overvoltages and lightning strikes during operation. Mechanically, insulators must withstand not only the tensile stress generated by the weight of components such as conductors but also thermal and electrical stresses caused by temperature changes and electric field effects. Porcelain insulators are widely used in transmission lines of all voltage levels because their ceramic material possesses excellent chemical stability, high-temperature resistance, and aging resistance, allowing them to adapt to a variety of complex operating environments.

[0003] Traditional methods for testing porcelain insulators include power frequency spark testing, power frequency withstand voltage testing, megohmmeters, distributed voltage measurement (live working), and spark fork testing (live working). These methods have been widely used in engineering practice, but each has its limitations. In contrast, testing using a portable impulse voltage generator is a more efficient and accurate technique. This technique generally involves applying a high-voltage pulse exceeding 60 kV across the insulator, with a rising edge rate of 1 kV / μs. The characteristics of the falling edge are determined by the insulator's equivalent first-order RC discharge circuit. Normal insulators will not breakdown under the application of a high-voltage pulse; instead, they will discharge in a first-order RC curve after the voltage reaches its peak. However, due to the presence of significant internal penetrating defects, zero-value insulators will experience internal breakdown during the rising edge of the pulse voltage, resulting in significant discharge. Using the charging voltage amplitude as a criterion has been a widely used method.

[0004] It should be noted that the information disclosed in the above background technology section is only used to understand the background of this application, and therefore may include information that does not constitute prior art known to ordinary technicians in this field. Summary of the Invention

[0005] The main purpose of the present invention is to overcome the defects existing in the above-mentioned background technology and provide a method and device for detecting impulse voltage defects of porcelain insulators based on voltage change rate.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for detecting impulse voltage defects in porcelain insulators based on voltage change rate comprises the following steps:

[0008] Apply high voltage pulses to both ends of the porcelain insulator to be tested;

[0009] measuring voltage waveform data at both ends of the porcelain insulator;

[0010] Extract the voltage amplitude based on the voltage waveform data and calculate the voltage change rate of the voltage waveform within a set time interval;

[0011] A comprehensive judgment is made based on the dual criteria of whether the voltage amplitude is lower than a preset amplitude threshold and whether the voltage change rate exceeds a preset change rate threshold. If either criterion exceeds the threshold, it is determined that the porcelain insulator has an internal penetration defect.

[0012] Furthermore, the generation of the high voltage pulse includes:

[0013] Charge the discharge capacitor to the set voltage value;

[0014] The switch device is triggered to conduct, so that the discharge capacitor generates a high-voltage pulse after being boosted by the transformer and applied to the porcelain insulator.

[0015] Furthermore, the calculation of the voltage change rate includes:

[0016] Extract voltage data at fixed time intervals during the voltage decay process;

[0017] The absolute value of the voltage difference between adjacent time intervals is calculated as a basis for determining the voltage change rate.

[0018] Furthermore, the dual-criteria determination includes:

[0019] If the voltage amplitude is lower than the preset amplitude threshold, or the voltage change rate exceeds the preset change rate threshold, it is determined that an internal breakdown defect exists;

[0020] The preset change rate threshold is dynamically adjusted according to the voltage attenuation characteristics of normal insulators.

[0021] Furthermore, the method further comprises:

[0022] The voltage waveform data is collected through the measurement circuit and transmitted to the data processing module after analog-to-digital conversion;

[0023] The data processing module synchronously performs calculation and determination of the voltage amplitude and the voltage change rate.

[0024] Furthermore, the operation process of the method includes:

[0025] (1) After charging to the set voltage, a high voltage pulse is triggered and applied to the insulator;

[0026] (2) Collect and process voltage waveform data;

[0027] (3) Output the detection results based on the dual criteria and feedback the judgment information through the interactive device.

[0028] A device for detecting impulse voltage defects of porcelain insulators based on voltage change rate, comprising:

[0029] High-voltage pulse generating circuit, used to generate and apply high-voltage pulses to both ends of the porcelain insulator to be tested;

[0030] A measurement circuit is used to collect voltage waveform data at both ends of the insulator;

[0031] The data processing module is used to calculate the voltage amplitude and the voltage change rate within a set time interval, and make a comprehensive judgment based on the dual criteria of whether the voltage amplitude is lower than a preset amplitude threshold and whether the voltage change rate exceeds a preset change rate threshold. If either criterion exceeds the threshold, it is determined that the porcelain insulator has an internal breakdown defect.

[0032] Furthermore, the high-voltage pulse generating circuit includes a discharge capacitor, a switching device and a transformer. The discharge capacitor is controlled to be charged and discharged by the switching device, and outputs a high-voltage pulse to the insulator after being boosted by the transformer.

[0033] Furthermore, the measurement circuit includes:

[0034] High-voltage isolation circuit, used to safely extract high-voltage signals from both ends of the insulator;

[0035] The analog-to-digital conversion unit converts the analog voltage signal into a digital signal and transmits it to the data processing module.

[0036] Furthermore, the data processing module includes:

[0037] A voltage amplitude extraction unit is used to extract the voltage amplitude from the voltage waveform data collected by the measurement circuit;

[0038] a voltage change rate calculation unit, configured to extract voltage data at set time intervals and calculate the absolute value of the voltage difference between adjacent intervals;

[0039] a determination unit, configured to compare the voltage amplitude and the voltage change rate to see whether they exceed a preset threshold value, and if any one of the determination criteria exceeds the threshold value, determine that the porcelain insulator has an internal breakdown defect;

[0040] The output unit feeds back the test results through sound and light prompts or display screen.

[0041] The present invention has the following beneficial effects:

[0042] The present invention proposes a method and device for detecting impulse voltage defects in porcelain insulators based on the voltage change rate. By combining the dual criteria of voltage amplitude and voltage change rate for comprehensive judgment, it effectively solves the problem of missed judgment caused by relying solely on voltage amplitude in traditional porcelain insulator detection. Traditional methods are difficult to accurately identify small defects because some zero-value insulators have a high breakdown voltage amplitude under high-voltage pulses or breakdown occurs during the withstand voltage process. The present invention significantly improves the detection sensitivity of internal through-hole defects by extracting voltage waveform data in real time and calculating the voltage change rate within a set time interval. It is particularly suitable for scenarios with small defects and local breakdowns. By combining the dual criteria of voltage amplitude and voltage change rate, it ensures that even if the breakdown moment is missed, the defect can still be reliably determined by comparing the voltage difference. Ultimately, the present invention provides a new judgment scheme for porcelain insulator zero detection, enhancing the ability to ensure the safety of power grid operation.

[0043] Other beneficial effects of the embodiments of the present invention will be further described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The figure is an overall flow chart of the porcelain insulator impulse voltage defect detection based on voltage change rate of the present invention.

[0045] Figure 2 Schematic diagram of the structure of a porcelain insulator impulse voltage defect detection device according to an embodiment of the present invention.

[0046] Figure 3 Schematic diagram of a measurement circuit and data processing module according to an embodiment of the present invention.

[0047] Figure 4 4 is a flowchart of an embodiment of the present invention.

[0048] Figure 5 This is the voltage curve at the breakdown moment of the 420KN zero-value insulator according to an embodiment of the present invention.

[0049] Figure 6 This is the voltage curve at the breakdown moment of a 300KN zero-value insulator according to an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope of the present invention and its application.

[0051] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for both fixing and coupling or communication.

[0052] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0053] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0054] At present, the pulse detection method for porcelain insulators generally takes the amplitude of the insulator charging voltage as the zero judgment standard. However, the inventors have found that due to the small internal defects of some insulators, relying solely on the amplitude as a judgment criterion will result in missed judgments. Some zero-value insulators that can only be eliminated through high-voltage steep wave experiments often have small defects. After the impulse voltage is applied at both ends, the amplitude of their breakdown voltage is often very high. In addition, some insulators will not break down until they are in the process of withstand voltage. Therefore, it is easy to miss judgments if only the amplitude criterion is used. The present invention proposes a porcelain insulator defect detection method and device that can collect voltage waveforms and calculate the rate of change, so as to achieve accurate detection of internal defects of porcelain insulators. When the internal defects are small, the present invention can identify the breakdown process for the breakdown that occurs during the withstand voltage process, and then judge the zero value, effectively preventing power grid accidents caused by the zero value of porcelain insulators, and providing support for the safe operation of the power grid.

[0055] See Figure 1 The embodiment of the present invention provides a method for detecting impulse voltage defects of porcelain insulators based on voltage change rate, comprising the following steps:

[0056] Apply high voltage pulses to both ends of the porcelain insulator to be tested;

[0057] measuring voltage waveform data at both ends of the porcelain insulator;

[0058] Extract the voltage amplitude based on the voltage waveform data and calculate the voltage change rate of the voltage waveform within a set time interval;

[0059] A comprehensive judgment is made based on the dual criteria of whether the voltage amplitude is lower than a preset amplitude threshold and whether the voltage change rate exceeds a preset change rate threshold. If either criterion exceeds the threshold, it is determined that the porcelain insulator has an internal breakdown defect.

[0060] The method of the present invention provides a new basis for zero detection of porcelain insulators (detecting zero-value insulators by detecting internal breakdown defects), detects the penetration defects inside them, makes up for the shortcomings of the traditional single amplitude judgment method, can accurately identify small defects inside porcelain insulators, and improve the reliability of insulator operation.

[0061] In some embodiments, the generation of the high-voltage pulse includes: charging the discharge capacitor to a set voltage value; triggering the switch device to turn on, so that the discharge capacitor generates a high-voltage pulse after being boosted by the transformer, and applying it to the porcelain insulator.

[0062] In some embodiments, the calculation of the voltage change rate includes: extracting voltage data at fixed time intervals during the voltage decay process; and calculating the absolute value of the voltage difference between adjacent time intervals as a basis for determining the voltage change rate.

[0063] In some embodiments, the dual-criteria judgment includes: if the voltage amplitude is lower than a preset amplitude threshold, or the voltage change rate exceeds a preset change rate threshold, it is determined that an internal breakdown defect exists; the preset change rate threshold is dynamically adjusted according to the voltage attenuation characteristics of a normal insulator.

[0064] In some embodiments, the method further includes: collecting voltage waveform data through a measurement circuit, and transmitting it to a data processing module after analog-to-digital conversion; the data processing module synchronously performs calculation and determination of voltage amplitude and voltage change rate.

[0065] In some embodiments, the operation process of the method includes: (1) triggering a high-voltage pulse to be applied to the insulator after charging to a set voltage; (2) collecting and processing voltage waveform data; (3) outputting the detection results based on the dual judgment criteria, and feeding back the judgment information through an interactive device.

[0066] An embodiment of the present invention also provides a porcelain insulator impulse voltage defect detection device based on voltage change rate, comprising: a high-voltage pulse generating circuit, used to generate and apply high-voltage pulses to both ends of the porcelain insulator to be tested; a measuring circuit, used to collect voltage waveform data at both ends of the insulator; a data processing module, used to calculate the voltage amplitude and the voltage change rate within a set time interval, and perform a comprehensive judgment based on the dual criteria of whether the voltage amplitude is lower than a preset amplitude threshold and whether the voltage change rate exceeds a preset change rate threshold. If any one of the criteria exceeds the threshold, it is determined that the porcelain insulator has an internal breakdown defect.

[0067] In some embodiments, the high-voltage pulse generating circuit includes a discharge capacitor, a switching device and a transformer. The discharge capacitor is controlled to be charged and discharged by the switching device, and the high-voltage pulse is output to the insulator after being boosted by the transformer.

[0068] See Figure 2 In one embodiment, the high-voltage pulse generating circuit includes a charging and discharging capacitor C1, a first switching device IGBT1, a second switching device IGBT2, a boost and control circuit, and a transformer T; by controlling the conduction timing of the first switching device IGBT1 and the second switching device IGBT2 located at the front end and the back end of the boost and control circuit, the boost and control circuit boosts the power supply voltage to a set value and charges the capacitor C1; the transformer T transmits the high-voltage pulse from the primary side to the secondary side and provides a high-voltage pulse for the insulator to be tested; the primary and secondary sides of the transformer T are respectively connected to diodes, including a primary-side diode D1 and a secondary-side diode D2; the discharge energy of the discharge capacitor C1 is boosted by the secondary side of the transformer T to form a high-voltage pulse, which is applied to both ends of the insulator to be tested.

[0069] See Figure 3 In some embodiments, the measurement circuit includes: a high-voltage isolation circuit for safely extracting high-voltage signals at both ends of the insulator; an ADC, or analog-to-digital conversion unit, for converting analog voltage signals into digital signals and transmitting them to a data processing module.

[0070] See Figure 3 In some embodiments, the data processing module includes: a voltage amplitude extraction unit, used to extract the voltage amplitude from the voltage waveform data collected by the measurement circuit; a voltage change rate calculation unit, used to extract voltage data at set time intervals and calculate the absolute value of the voltage difference between adjacent intervals; a judgment unit, used to compare whether the voltage amplitude and the voltage change rate exceed a preset threshold value. If any criterion exceeds the threshold value, it is determined that the porcelain insulator has an internal breakdown defect; and an output unit, which feeds back the detection results through sound and light prompts or a display screen.

[0071] The following further describes specific embodiments of the present invention and experimental verification.

[0072] A porcelain insulator pulse voltage detection device includes two parts: a high-voltage pulse generating circuit and a measuring circuit. Its specific structure is as follows: Figure 2 shown.

[0073] During actual testing, a porcelain insulator is placed on the high-voltage side. Capacitor C1 discharges when the second switching device, IGBT2, turns on. This energy is transferred to the secondary side via the transformer, charging the insulator under test. Voltage data is extracted from the measurement circuit, and internal breakdown is determined based on the voltage amplitude and rate of change.

[0074] The principle of this measurement circuit can be explained by a simple breakdown mechanism. Since the internal breakdown of the zero-value insulator may occur during the withstand voltage process, their voltage amplitude is also very high, or the average voltage value calculated over a period of time will also be very high. Figure 5 and Figure 6 Therefore, calculating the voltage change at a specific time interval can accurately reflect the breakdown process. Generally, the voltage jump during the breakdown process is higher than 40kV.

[0075] The voltage U2 across the insulator collected by the measurement circuit is sampled by the analog-to-digital conversion unit ADC. In addition to extracting the voltage amplitude, the rate of change of the voltage within a given time interval, such as 1ms, is also calculated, and the judgment is completed using a dual criterion.

[0076] Insulators with very small defects may experience breakdown during the withstand voltage test. Since the amplitude is the same as for normal insulators, it cannot be identified using the amplitude method. Therefore, the rate of change of voltage is calculated. If the voltage changes suddenly within 1ms, breakdown is considered to have occurred, and the value is then determined to be zero. The formula is as follows:

[0077] |ΔU|=|U t -U t-1 |>m

[0078] When using voltage change to determine breakdown, the threshold m can be varied. When m is smaller, the criterion becomes more sensitive to breakdown due to local defects. However, m should not be too small, as normal insulators are already in a voltage decay process.

[0079] For the range of m, the internal insulation resistance of a normal insulator is >1000GΩ. Assuming the external insulation resistance of the insulator is 1GΩ (which is much lower than the external insulation resistance of a clean insulator), measurements show that the equivalent capacitances of typical 70kN, 210kN, and 550kN insulators are 56pF, 94pF, and 123pF, respectively. Assuming 100pF, τ = R × C = 100ms. The insulator voltage decays fastest in the first 1ms after reaching its peak. Assuming the initial voltage is 60kV,

[0080]

[0081] It can be seen that it is small enough. When the external insulation resistance is even smaller due to contamination, take 100MΩ. At this time, τ=R×C=10ms,

[0082]

[0083] It can be seen that this is still far less than the voltage change caused by breakdown. In actual testing, as long as the external insulation state of the insulator is guaranteed to be >100MΩ, the judgment value can be any m>6.3kV.

[0084] Another advantage of this detection solution is that the voltage sampling frequency can be very low, such as 1ms. This is because, under impulse voltage, after the zero-value insulator breaks down, the voltage cannot effectively recover due to the limited energy of the primary-side capacitor C1. Therefore, even if the breakdown moment is missed, when comparing the post-breakdown voltage value with the pre-breakdown voltage value, the |ΔU| value is still large enough to exceed the threshold m. This advantage increases the internal microcontroller's voltage change rate calculation speed, thereby improving zero detection speed.

[0085] The operation logic of the porcelain insulator fast pulse detection device is:

[0086] Step S1: Capacitor C1 is charged. The MCU controls the first switching device IGBT1 to boost the voltage of C1 to a set value.

[0087] Step S2: Capacitor C1 is discharged, and the energy forms a high-voltage pulse on the secondary side after passing through transformer T.

[0088] Step S3: Measurement judgment. The voltage information is extracted from the measurement circuit. In addition to the amplitude, the |ΔU| is calculated at 1ms intervals within the first 100ms of the voltage decay. If either of the two does not meet the requirements, the voltage is judged to be zero.

[0089] The process of high voltage pulse detection of porcelain insulators is as follows Figure 4 When the device is in use, connect an insulator to the high-voltage terminal and press the test button. The microcontroller automatically charges capacitor C1 to the set value and then discharges it. The detection circuit collects voltage information during the insulator's charge and discharge process and makes a comprehensive judgment using the dual criteria of voltage amplitude and rate of change.

[0090] Figure 5 It is an atypical zero-value insulator with an impulse voltage peak of 64.8 kV, and it breaks down during the withstand voltage process. If a single voltage amplitude is used as the judgment criterion, it may be mistakenly judged as a normal insulator.

[0091] Figure 6It is an atypical zero-value insulator with an impulse voltage peak of 63.6kV. It breaks down after 2ms of withstand voltage. If a single voltage amplitude is used as the criterion, or the average voltage over a period of time after the impulse is applied is high enough, it may be mistakenly judged as a normal insulator. After adding the voltage change rate,

[0092] |ΔU3|=|U t＝3000μs -U t＝2000μs |>35kV

[0093] With such a large rate of voltage change, it can be determined that breakdown occurred between t = 2000 μs and t = 3000 μs, and the chip can be determined to be zero value.

[0094] In summary, the present invention proposes a method and apparatus for detecting defects in porcelain insulators under impulse voltage based on the voltage change rate. This method includes a high-voltage pulse detection circuit for porcelain insulators and a novel voltage zero determination method and apparatus. By using the voltage change rate as another criterion alongside the voltage amplitude criterion to determine whether a porcelain insulator has an internal breakdown defect, this method overcomes the problem of missing detection of zero-value insulators that undergo breakdown during the withstand voltage test. Compared to traditional methods that rely solely on impulse voltage amplitude, this method is more adaptable to detecting insulators with minor defects and localized breakdowns.

[0095] The above description further details the present invention in conjunction with specific / preferred embodiments, and the specific implementation of the present invention should not be construed as being limited to these descriptions. Persons skilled in the art will appreciate that, without departing from the spirit of the present invention, they may make various substitutions or modifications to the described embodiments, and these substitutions or modifications should be considered to fall within the scope of protection of the present invention. Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "preferred embodiments," "examples," "specific examples," or "some examples" indicates that the specific features, structures, materials, or characteristics described in conjunction with such embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Persons skilled in the art may combine and assemble the different embodiments or examples described in this specification, as well as features of different embodiments or examples, without conflicting opinions. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications may be made herein without departing from the scope of protection of the patent application.

Claims

1. A method for detecting impulse voltage defects in porcelain insulators based on voltage change rate, characterized in that: The following steps are involved: Apply high voltage pulses to both ends of the porcelain insulator to be tested; measuring voltage waveform data at both ends of the porcelain insulator; Extract the voltage amplitude based on the voltage waveform data and calculate the voltage change rate of the voltage waveform within a set time interval; A comprehensive judgment is made based on the dual criteria of whether the voltage amplitude is lower than a preset amplitude threshold and whether the voltage change rate exceeds a preset change rate threshold. If either criterion exceeds the threshold, it is determined that the porcelain insulator has an internal breakdown defect.

2. The method according to claim 1, characterized in that The generation of the high voltage pulse comprises: Charge the discharge capacitor to the set voltage value; The trigger switch device is turned on, so that the discharge capacitor generates a high-voltage pulse after being stepped up by the transformer and applied to the porcelain insulator.

3. The method according to claim 1, characterized in that The calculation of the voltage change rate includes: Extract voltage data at fixed time intervals during the voltage decay process; The absolute value of the voltage difference between adjacent time intervals is calculated as a basis for determining the voltage change rate.

4. The method according to claim 1, wherein The dual criteria determination includes: If the voltage amplitude is lower than the preset amplitude threshold, or the voltage change rate exceeds the preset change rate threshold, it is determined that an internal breakdown defect exists; The preset change rate threshold is dynamically adjusted according to the voltage attenuation characteristics of normal insulators.

5. The method according to any one of claims 1 to 4, characterized in that The method further comprises: The voltage waveform data is collected through the measurement circuit and transmitted to the data processing module after analog-to-digital conversion; The data processing module synchronously performs calculation and determination of the voltage amplitude and the voltage change rate.

6. The method according to any one of claims 1 to 5, characterized in that The operation process of the method includes: (1) After charging to the set voltage, a high voltage pulse is triggered and applied to the insulator; (2) Collect and process voltage waveform data; (3) Output the detection results based on the dual criteria and feedback the judgment information through the interactive device.

7. A porcelain insulator impulse voltage defect detection device based on voltage change rate, characterized in that: include: High-voltage pulse generating circuit, used to generate and apply high-voltage pulses to both ends of the porcelain insulator to be tested; A measurement circuit is used to collect voltage waveform data at both ends of the insulator; The data processing module is used to calculate the voltage amplitude and the voltage change rate within a set time interval, and make a comprehensive judgment based on the dual criteria of whether the voltage amplitude is lower than a preset amplitude threshold and whether the voltage change rate exceeds a preset change rate threshold. If either criterion exceeds the threshold, it is determined that the porcelain insulator has an internal breakdown defect.

8. The device according to claim 7, characterized in that The high-voltage pulse generating circuit includes a discharge capacitor, a switching device and a transformer. The discharge capacitor is controlled to be charged and discharged by the switching device, and is boosted by the transformer to output a high-voltage pulse to the insulator.

9. The device according to claim 7, characterized in that The measurement circuit comprises: High-voltage isolation circuit, used to safely extract high-voltage signals from both ends of the insulator; The analog-to-digital conversion unit converts the analog voltage signal into a digital signal and transmits it to the data processing module.

10. The device according to any one of claims 7 to 9, characterized in that The data processing module includes: A voltage amplitude extraction unit is used to extract the voltage amplitude from the voltage waveform data collected by the measurement circuit; a voltage change rate calculation unit, configured to extract voltage data at set time intervals and calculate the absolute value of the voltage difference between adjacent intervals; a determination unit, configured to compare the voltage amplitude and the voltage change rate to see whether they exceed a preset threshold value, and if any one of the determination criteria exceeds the threshold value, determine that the porcelain insulator has an internal breakdown defect; The output unit feeds back the test results through sound and light prompts or display screen.

Images