Method for identifying and analyzing overall defects and local defects of oil-immersed insulating bushings

Abstract

The present invention relates to a method for identifying and analyzing the overall defects and local defects of oil-immersed insulating bushings, which belongs to the field of detection and analysis of insulation defects of power equipment. The overall defect identification and analysis module is based on the frequency domain dielectric response characteristics under different measurement voltages, and the types of overall defects of oil-immersed insulating bushings (core moisture defects, insulating oil moisture defects) are identified and analyzed by comparing the changing laws of the frequency domain curves of dielectric characteristic quantities under different measurement voltages; the local defect identification and analysis module is based on the analysis of the changing laws of local discharge characteristic quantities under different measurement voltages, and the types of local defects (capacitor screen short circuit defects, corona discharge defects, suspended discharge defects) are identified and analyzed by the changing laws of the maximum discharge amount of negative pulses and the repetition rate of positive pulse discharges and the measurement voltage. The present invention can guarantee the safe and stable operation of bushings and power transformers to the greatest extent.

Description

Technical Field

[0001] The invention belongs to the field of insulation defect detection and analysis of power equipment, and relates to a method for identifying and analyzing overall defects and local defects of an oil-immersed insulating bushing. Background Art

[0002] Bushing is a key component of power transformers. Its failure rate has remained high in recent years. With the increase of voltage level, the harm caused by insulation failure caused by bushing has become more serious. The overall performance degradation of bushing insulation materials and local defects of insulation structure are the main causes of bushing failure. The overall performance degradation of insulation materials is usually caused by moisture, while local defects are usually caused by process defects or local insulation performance degradation, and only appear in local locations of bushing. Therefore, there is an urgent need for a method that can effectively identify the type of insulation defects of bushings, provide a theoretical reference for judging the insulation health status of bushings, and provide reliable technical support for preventing further development of bushing defects and safe and reliable operation of bushings.

[0003] At present, oil-immersed insulating bushings are used the most in power grids. According to statistics, in my country's 110kV and above power transmission and transformation systems, the use rate of oil-immersed insulating bushings accounts for more than 90% of all bushings. The existing methods for testing the insulation performance of oil-immersed insulating bushings mainly include insulation resistance, capacitance, power frequency dielectric loss, and analysis of dissolved gas in oil. These parameters can only be used to preliminarily judge the insulation reliability and overall insulation state of the bushing, and cannot accurately reflect the hidden dangers that cause local defects. Frequency domain dielectric spectroscopy has the characteristics of non-destructiveness and wide test bandwidth, and is widely used in insulation detection of oil-immersed insulating bushings. This method is sensitive to the performance degradation of the bushing insulation material, but it can only reflect the overall insulation performance of the bushing, and cannot diagnose local defects in its internal insulating medium. As a commonly used withstand voltage test method in the insulation performance detection of power equipment, partial discharge test can directly reflect the insulation withstand voltage level of power equipment and is an effective means to discover local defects in insulation. In terms of the existing achievements in diagnosing bushing insulation defects, Qu Wentao et al. conducted training analysis on the local discharge test results of bushings based on the chaotic quantum particle optimization support vector machine, and proposed a method for identifying typical local defect types of bushings; Zhang Wenfu et al. conducted training and classification on the local discharge test data based on the improved gray wolf algorithm to optimize the support vector machine, and proposed a method for identifying bushing local discharge patterns; Zhang Yubo et al. conducted testing and training analysis on the oil chromatogram of bushing insulating oil based on the BP neural network, and proposed a method for identifying bushing moisture defects. The above methods can identify some local discharge defects of bushings (such as bushing top discharge defects, grading ring discharge defects, and end screen poor contact discharge defects), but the identification and analysis of overall defects caused by the deterioration of insulating materials has not been reported. In addition, the existing bushing local discharge analysis methods are relatively simple, and there is a limitation of only considering a single characteristic parameter. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method for identifying and analyzing the overall defects and local defects of oil-immersed insulating bushings, including an overall defect identification and analysis module and a local defect identification and analysis module. The overall defect identification and analysis module is based on the frequency domain dielectric response characteristics under different measurement voltages, and identifies and analyzes the types of overall defects of oil-immersed insulating bushings (core moisture defects, insulating oil moisture defects) by comparing the changing laws of the frequency domain curves of dielectric characteristic quantities under different measurement voltages; the local defect identification and analysis module is based on the analysis of the changing laws of local discharge characteristic quantities under different measurement voltages, and identifies and analyzes the types of local defects (capacitor screen short circuit defects, corona discharge defects, suspended discharge defects) by analyzing the changing laws of the maximum local discharge amount of negative pulses and the repetition rate of positive pulse discharges with the measurement voltage.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for identifying and analyzing overall defects and local defects of an oil-immersed insulating bushing, comprising:

[0007] Using the integrity defect identification and analysis module, based on the frequency domain dielectric response characteristics under different measurement voltages, the types of integrity defects of the oil-immersed insulating bushing are identified and analyzed by comparing the change rules of the frequency domain curves of the dielectric characteristic quantities under different measurement voltages. The types of integrity defects of the oil-immersed insulating bushing include core moisture defects and insulating oil moisture defects.

[0008] Using the local defect identification and analysis module, based on the analysis of the changing law of local discharge characteristic quantities under different measuring voltages, the types of local defects are identified and analyzed through the changing law of the maximum negative pulse discharge amount and the positive pulse discharge repetition rate with the measuring voltage. The types of local defects include capacitor screen short circuit defects, corona discharge defects and suspended discharge defects.

[0009] Furthermore, the method specifically comprises the following steps:

[0010] S1: Determine whether the power frequency dielectric loss of the bushing exceeds the standard: if it does not exceed the standard value, proceed to step S2; if it exceeds the standard value, proceed to step S3;

[0011] S2: Determine whether the rate of change of the power frequency capacitance of the bushing exceeds the standard: if the rate of change of the capacitance does not exceed the standard value, proceed to step S4; if the rate of change of the power frequency capacitance exceeds the standard, proceed to step S5;

[0012] S3: Analyze the variation law of the frequency domain curve of the dielectric characteristic quantity of the bushing under different measurement voltages: if the low-frequency dielectric loss curve of the bushing moves upward with the increase of the measurement voltage, proceed to step S6; if the low-frequency dielectric loss curve does not move upward with the increase of the measurement voltage, proceed to step S8;

[0013] S4: Determine whether the maximum discharge capacity of the bushing under the standard voltage exceeds the standard: if it does not exceed 10pC, go to step S7; if it exceeds 10pC, go to step S8;

[0014] S5: Determine whether the maximum discharge capacity of the bushing under the standard voltage exceeds the standard: if it does not exceed 10pC, it is determined that the bushing has a capacitor screen short circuit defect and the process ends; if it exceeds 10pC, go to step S8;

[0015] S6: Identify and analyze the integrity defects of the casing, and end the process after obtaining the results;

[0016] S7: Determine whether the change in power frequency dielectric loss of the bushing exceeds the standard, and end the process after the determination result;

[0017] S8: Identify and analyze local defects of the casing and end the process after obtaining the results.

[0018] Furthermore, the step S2 specifically includes: measuring the power frequency capacitance of the bushing and comparing it with the bushing nameplate value, thereby determining the capacitance change rate.

[0019] Further, the step S4 specifically includes: judging whether the bushing has local defects by the maximum discharge amount, wherein for new bushings just out of the factory, applying The power frequency measurement voltage is The power frequency measurement voltage, where U m is the highest voltage marked on the bushing nameplate; if the maximum discharge amount does not exceed the preset threshold, go to step S7; if the maximum discharge amount exceeds the preset threshold, go to step S8.

[0020] Further, the step S5 specifically includes: judging whether the bushing has local defects by the maximum discharge amount, wherein for new bushings just out of the factory, applying The power frequency measurement voltage is The power frequency measurement voltage, where U m It is the highest voltage marked on the bushing nameplate; if it does not exceed the preset threshold, it is determined that the bushing has a capacitor screen short circuit defect and the process ends; if it exceeds the preset threshold, go to step S8.

[0021] Further, the step S6 specifically includes: performing a frequency domain dielectric response test on the bushing at different voltages, and as the measured voltage increases, if the real part curve of the low-frequency capacitance of the bushing moves downward, it is judged that the bushing has a core moisture defect, and the process ends; if as the measured voltage increases, the real part curve of the low-frequency capacitance of the bushing does not move downward, it is judged that the bushing has an insulating oil moisture defect, and the process ends.

[0022] Further, the step S7 specifically includes: if the power frequency dielectric loss change does not exceed the standard value, it is judged that the bushing has no insulation defects and is a normal bushing, and the process ends; if the power frequency dielectric loss change exceeds the standard value, it is judged that the bushing needs to be monitored more closely, and the process ends.

[0023] Further, in step S8, a partial discharge test is carried out on the bushing under different measuring voltages, and a warning value of the negative pulse maximum discharge amount growth rate and a warning value of the positive pulse discharge repetition rate growth rate are specified. If both exceed the standard at the same time, it is judged that the bushing has a corona discharge defect and the process is terminated; if both do not exceed the standard at the same time, it is judged that the bushing has a suspended discharge defect and the process is terminated.

[0024] The beneficial effects of the present invention are as follows: in recent years, oil-immersed insulating bushings have experienced a high incidence of failures; before insulation failures occur in the bushings, the present invention can be used to effectively detect and identify the defects of the bushings; the present invention can guarantee the safe and stable operation of the bushings and power transformers to the greatest extent, and can bring higher economic and social benefits; the present invention can provide reliable technical support for the quality control of oil-immersed insulating bushings and guarantee their safe operation, and has significant engineering value; in addition, the present invention can also be used by colleges and universities and scientific research institutions to provide technical support for analyzing the laws of bushing failures.

[0025] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0027] Figure 1 A framework diagram for identifying and analyzing overall defects and local defects of oil-immersed insulating bushings according to the present invention;

[0028] Figure 2 The present invention is a flow chart of the method for identifying and analyzing overall defects and local defects of oil-immersed insulating bushings. DETAILED DESCRIPTION

[0029] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0030] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0031] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0032] See also Figure 1The present invention provides a method for identifying and analyzing the overall defects and local defects of oil-immersed insulating bushings, including an overall defect identification and analysis module and a local defect identification and analysis module. The overall defect identification and analysis module is based on the frequency domain dielectric response characteristics under different measurement voltages, and identifies and analyzes the types of overall defects of oil-immersed insulating bushings (core moisture defects, insulating oil moisture defects) by comparing the changing laws of the frequency domain curves of dielectric characteristic quantities under different measurement voltages; the local defect identification and analysis module is based on the analysis of the changing laws of local discharge characteristic quantities under different measurement voltages, and identifies and analyzes the types of local defects (capacitor screen short circuit defects, corona discharge defects, suspended discharge defects) by analyzing the changing laws of the maximum discharge amount of negative pulses and the repetition rate of positive pulse discharges and the measurement voltage. Compared with the traditional bushing insulation defect detection method based on a single characteristic parameter, the present invention is conducive to the discovery of defects in bushings during factory tests, handover tests, and diagnostic tests, effectively distinguishing overall defects and local defects of bushings, and can identify and analyze the causes of local defects, providing technical support for the scientific formulation of bushing quality control and maintenance decisions.

[0033] like Figure 2 As shown in the figure, the method flow for identifying and analyzing the overall defects and local defects of oil-immersed insulating bushings is as follows:

[0034] Step 1: Determine whether the power frequency dielectric loss of the bushing exceeds the standard. According to the national standard "GB / T 4109-2008 Insulating bushings with AC voltage higher than 1000V" and the State Grid Corporation's enterprise standard "Q / GDW 1168-2013 Power Transmission and Transformation Equipment Condition Inspection Test Procedure", the power frequency dielectric loss can be used as a basis for determining whether the bushing has insulation degradation. If it does not exceed the standard value (0.7% for oil-immersed insulating bushings), proceed to step S2; if it exceeds the standard value, proceed to step S3.

[0035] Step 2: Determine whether the rate of change of the power frequency capacitance of the bushing exceeds the standard. According to the national standard "GB / T 4109-2008 Insulating bushings with AC voltage higher than 1000V", the rate of change of the power frequency capacitance can be used as a basis for determining whether the bushing has insulation degradation. By measuring the power frequency capacitance of the bushing and comparing it with the bushing nameplate value, if the rate of change of the capacitance does not exceed the standard value (the standard stipulates ±5%), proceed to step S4; if the rate of change of the capacitance exceeds the standard value, proceed to step S5.

[0036] Step 3: Analyze the variation of the frequency domain curve of the dielectric characteristic quantity of the bushing under different measurement voltages. If the low-frequency dielectric loss curve (1mHz-1Hz) of the bushing moves up as the measurement voltage increases, proceed to step S6; if the low-frequency dielectric loss curve (1mHz-1Hz) of the bushing does not move up as the measurement voltage increases, proceed to step S8.

[0037] Step 4: Determine whether the maximum discharge of the bushing under standard voltage exceeds the standard. According to the State Grid Corporation of China's enterprise standard "Q / GDW 1168-2013 Power Transmission and Transformation Equipment Condition Inspection and Test Procedure", the maximum discharge can determine whether there are local defects in the bushing. The power frequency measurement voltage is The power frequency measurement voltage (where U m is the highest voltage marked on the bushing nameplate). If the maximum discharge capacity does not exceed 10pC, go to step S7; if the maximum discharge capacity exceeds 10pC, go to step S8.

[0038] Step 5: Determine whether the maximum discharge of the bushing under standard voltage exceeds the standard. According to the State Grid Corporation of China's enterprise standard "Q / GDW 1168-2013 Power Transmission and Transformation Equipment Condition Inspection and Test Procedure", the maximum discharge can determine whether there are local defects in the bushing. The power frequency measurement voltage is The power frequency measurement voltage (where U m is the highest voltage marked on the bushing nameplate). If it does not exceed 10pC, it is determined that the bushing has a capacitor screen short circuit defect and the process ends; if the maximum discharge amount exceeds 10pC, go to step S8.

[0039] Step 6: Identify and analyze the overall defects of the bushing. Conduct frequency domain dielectric response tests on the bushing at different voltages. If the real part curve of the low-frequency capacitance of the bushing (1mHz-1Hz) moves downward as the measured voltage increases, it is judged that the bushing has a core moisture defect, and the process ends; if the real part curve of the low-frequency capacitance of the bushing (1mHz-1Hz) does not move downward as the measured voltage increases, it is judged that the bushing has an insulating oil moisture defect, and the process ends.

[0040] Step 7: Determine whether the change in the power frequency dielectric loss of the bushing exceeds the standard. According to the State Grid Corporation's corporate standard "Q / GDW1168-2013 Power Transmission and Transformation Equipment Condition Inspection and Test Procedure", the change in the power frequency dielectric loss can be used as a basis for judging whether the bushing has insulation degradation. If the change in the power frequency dielectric loss does not exceed the standard value (the standard stipulates 0.3%), it is judged that the bushing has no insulation defects and is a normal bushing, and the process ends; if the change in the power frequency dielectric loss exceeds the standard value, it is judged that the bushing needs to be further monitored and the process ends.

[0041] Step 8: Identify and analyze local defects of the bushing. Carry out partial discharge tests on the bushing at different measurement voltages and specify the maximum discharge growth rate k of the negative pulse. Q-UThe warning value is 25pC / kV, and the positive pulse discharge repetition rate growth rate k N-U The warning value is 15 (N / s) / kV. If both exceed the standard at the same time, it is judged that the bushing has a corona discharge defect and the process ends; if both do not exceed the standard at the same time, it is judged that the bushing has a suspended discharge defect and the process ends.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for identifying and analyzing overall defects and local defects of oil-immersed insulating bushings, characterized in that: include: Using the integrity defect identification and analysis module, based on the frequency domain dielectric response characteristics under different measurement voltages, the types of integrity defects of the oil-immersed insulating bushing are identified and analyzed by comparing the change rules of the frequency domain curves of the dielectric characteristic quantities under different measurement voltages. The types of integrity defects of the oil-immersed insulating bushing include core moisture defects and insulating oil moisture defects. Using the local defect identification and analysis module, based on the analysis of the change law of local discharge characteristic quantities under different measurement voltages, the types of local defects are identified and analyzed through the change law of the maximum discharge amount of negative pulses and the repetition rate of positive pulse discharge and the measurement voltage. The types of local defects include capacitor screen short circuit defects, corona discharge defects and suspended discharge defects. This method specifically comprises the following steps: S1: Determine whether the power frequency dielectric loss of the bushing exceeds the standard: if it does not exceed the standard value, proceed to step S2; if it exceeds the standard value, proceed to step S3; S2: Determine whether the rate of change of the power frequency capacitance of the bushing exceeds the standard: if the rate of change of the capacitance does not exceed the standard value, proceed to step S4; if the rate of change of the power frequency capacitance exceeds the standard, proceed to step S5; S3: Analyze the variation law of the frequency domain curve of the dielectric characteristic quantity of the bushing under different measurement voltages: if the low-frequency dielectric loss curve of the bushing moves upward with the increase of the measurement voltage, proceed to step S6; if the low-frequency dielectric loss curve does not move upward with the increase of the measurement voltage, proceed to step S8; S4: Determine whether the maximum discharge capacity of the bushing under the standard voltage exceeds the standard: if it does not exceed 10 pC, go to step S7; if it exceeds 10 pC, go to step S8; S5: Determine whether the maximum discharge amount of the bushing under the standard voltage exceeds the standard: if it does not exceed 10 pC, it is determined that the bushing has a capacitor screen short circuit defect and the process ends; if it exceeds 10 pC, go to step S8; S6: Identify and analyze the overall defects of the bushing, and conduct frequency domain dielectric response tests on the bushing at different voltages. If the real part curve of the low-frequency capacitance of the bushing moves downward as the measured voltage increases, it is judged that the bushing has a core moisture defect, and the process ends; if the real part curve of the low-frequency capacitance of the bushing does not move downward as the measured voltage increases, it is judged that the bushing has an insulating oil moisture defect, and the process ends; S7: Determine whether the power frequency dielectric loss variation of the bushing exceeds the standard. If the power frequency dielectric loss variation does not exceed the standard value, it is determined that the bushing has no insulation defects and is a normal bushing, and the process ends. If the power frequency dielectric loss variation exceeds the standard value, it is determined that the bushing needs to be monitored more closely, and the process ends. S8: Identify and analyze local defects of the bushing, conduct local discharge tests on the bushing under different measuring voltages, and specify the warning value of the negative pulse maximum discharge growth rate and the warning value of the positive pulse discharge repetition rate growth rate. If both exceed the standard at the same time, it is judged that the bushing has a corona discharge defect and the process is terminated; if both do not exceed the standard at the same time, it is judged that the bushing has a suspended discharge defect and the process is terminated.

2. The method for identifying and analyzing overall defects and local defects of oil-immersed insulating bushings according to claim 1 is characterized in that: The step S2 specifically includes: measuring the power frequency capacitance of the bushing and comparing it with the bushing nameplate value, thereby determining the capacitance change rate.

3. The method for identifying and analyzing overall defects and local defects of oil-immersed insulating bushing according to claim 1 is characterized in that: The step S4 specifically includes: judging whether the bushing has a local defect by the maximum discharge amount, wherein for a new bushing just produced by the factory, applying The power frequency measurement voltage is The power frequency measurement voltage is U m is the highest voltage marked on the bushing nameplate; if the maximum discharge amount does not exceed the preset threshold, go to step S7; if the maximum discharge amount exceeds the preset threshold, go to step S8.

4. The method for identifying and analyzing overall defects and local defects of oil-immersed insulating bushings according to claim 1, characterized in that: The step S5 specifically includes: judging whether the bushing has a local defect by the maximum discharge amount, wherein for a new bushing just produced by the factory, applying The power frequency measurement voltage is The power frequency measurement voltage is U m It is the highest voltage marked on the bushing nameplate; if it does not exceed the preset threshold, it is determined that the bushing has a capacitor screen short circuit defect and the process ends; if it exceeds the preset threshold, go to step S8.

Images