Deterioration State Monitoring Method of Silicone Rubber Composite Insulator Based on Lissajous Figure Features

Abstract

The present invention discloses a method for monitoring the degradation state of silicone rubber composite insulators based on Lissajous figure features. This method is mainly applicable to online real-time monitoring of the degradation state of silicone rubber insulators. The specific steps of this method are as follows: (1) Measure the input voltage and leakage current of healthy insulators; (2) Construct a Lissajous figure from the input voltage and leakage current signals; (3) Extract the characteristic parameters of the Lissajous figure of healthy insulators; (4) Normalize the voltage and current data of the insulators to be measured; (5) Calculate the comprehensive degradation monitoring coefficient CMI and evaluate the degradation state of the insulators. This method can monitor the degradation state of insulators online in real time. Compared with the existing technology, it has a lower implementation cost and higher efficiency, and is of great significance for accurately evaluating the severity of degradation of silicone rubber composite insulators.

Description

Technical Field

[0001] The present invention belongs to the field of insulator deterioration state monitoring and diagnosis, and particularly relates to a method for monitoring the deterioration state of silicone rubber composite insulators based on Lissajous figure features. Background Art

[0002] Silicone rubber composite insulators are widely used in transmission lines and EMU trains in China due to their excellent pollution resistance characteristics, and their insulation state directly affects the reliability of power supply. Under the combined action of contaminants and atmospheric environments such as high temperature, rain, and air pressure, the insulation characteristics of silicone rubber composite insulators will continuously deteriorate, resulting in a reduction in their insulation performance. In severe cases, flashover accidents may even occur, causing the insulators to be punctured, seriously affecting the power supply reliability and the safety of residents' lives and property. Since the voltage levels of most insulators are very high and they are installed in narrow spaces or at high altitudes, this makes inspections inconvenient. And the priority of replacing insulators varies according to the degree of deterioration state. Therefore, it is of great significance to grasp the deterioration state of silicone rubber composite insulators in real time to ensure sustainable, safe, and reliable power supply.

[0003] Currently, the detection of insulator deterioration state still mainly relies on traditional electrical detection methods, including insulation resistance testing, withstand voltage testing, dielectric loss angle measurement, etc. Unfortunately, these parameters will only change after serious deterioration phenomena occur in the insulator material, and it is difficult to detect the slight deterioration state of the insulator, with low detection sensitivity. In recent years, scholars have developed several new detection technologies applicable to the deterioration state of insulators, including microwave detection, scanning electron microscopy analysis, infrared spectroscopy analysis, etc. Unfortunately, these methods need to be carried out under power-off conditions and cannot achieve the purpose of real-time monitoring of insulator state. In addition, equipment such as microwave detection sources and scanning electron microscopy sources is relatively expensive, which becomes an important factor restricting their further promotion.

[0004] Therefore, researching new detection methods for the deterioration state of silicone rubber composite insulators, realizing the real-time grasp of the deterioration state, reducing and improving the detection sensitivity to the initial deterioration state is of great significance for staff to formulate maintenance strategies in a timely manner and reduce the accident rate caused by insulator deterioration. Summary of the Invention

[0005] In order to solve the problems of low sensitivity, high cost, and inability to detect in real time existing in the current detection methods of silicone rubber composite insulators, the present invention provides a method for monitoring the deterioration state of silicone rubber composite insulators based on Lissajous figure features.

[0006] The technical solution adopted by the present invention is as follows:

[0007] 1. A method for monitoring the degradation state of silicone rubber composite insulators based on the characteristics of Lissajous figures, characterized in that: by online measuring the instantaneous values of the input voltage and leakage current of the insulators, the degradation state of the silicone rubber composite insulators is monitored through the following steps:

[0008] The first step: Measure the input voltage and leakage current of healthy insulators

[0009] In the initial stage of the operation of the insulators, use a voltage transformer and a current transformer to measure the input voltage and leakage current of the insulators. Assume that their instantaneous values are respectively expressed as u(t)=U0 cos(ωt) and i(t)=I0 cos(ωt + θ), where t is the measurement time and θ is the phase difference between the leakage current and the input voltage;

[0010] The second step: Construct a Lissajous figure from the input voltage and leakage current signals

[0011] According to Euler's formula, eliminate the intermediate variable t to obtain the correlation between the input voltage u(t) and the leakage current i(t), and draw a Lissajous figure representing the insulation characteristics of the insulators themselves. This process can be expressed as:

[0012]

[0013] Among them, U0 and I0 are respectively the amplitudes of the input voltage and leakage current of healthy insulators;

[0014] The third step: Extract the characteristic parameters of the Lissajous figure of healthy insulators

[0015] Convert the Lissajous figure into a binary figure, and use digital image processing technology to extract the morphological characteristics of the Lissajous figure, including the major axis, minor axis, perimeter, area, and eccentricity, a total of 5 graphic characteristics, which are respectively denoted as H i , i = 1 to 5;

[0016] The fourth step: Normalize the voltage and current data of the insulator to be measured

[0017] After the insulators have been in operation for a period of time or a failure occurs, under the same measurement conditions, measure the input voltage and leakage current of the insulator to be measured, which are respectively denoted as u1(t)=U1cos(ωt) and i1(t)=I1cos(ωt + θ1), where θ1 is the phase difference between the leakage current and the input voltage of the insulator to be measured, and perform normalization processing according to the following formulas (2) and (3) to eliminate the influence of voltage fluctuations:

[0018]

[0019] Among them, u1'(t) and i1'(t) are respectively the instantaneous values of the input voltage and leakage current of the insulator to be measured after normalization; U1 and I1 are respectively the amplitudes of the measured input voltage and leakage current;

[0020] Step 5: Calculate the comprehensive deterioration monitoring coefficient CMI and evaluate the deterioration state of the insulator

[0021] Construct the Lissajous figure of the insulator to be measured using the normalized insulator voltage and current data, and extract its five morphological features, denoted as F i , where i = 1 to 5, and calculate the comprehensive deterioration monitoring coefficient CMI:

[0022]

[0023] Evaluate the deterioration state of the insulator according to the magnitude of CMI. If CMI = 0, it means that the insulation state of the silicone rubber insulator is normal; the smaller CMI is, the milder the deterioration state of the silicone rubber insulator; the larger CMI is, the more severe the deterioration state of the silicone rubber insulator.

[0024] The beneficial effects of the present invention are as follows. By combining the input voltage and leakage current of the insulator to convert into a Lissajous figure, and using the morphological features of the Lissajous figure to monitor the deterioration state of the silicone rubber composite insulator, compared with the existing detection methods, it has the following advantages:

[0025] 1) The Lissajous figure of the proposed insulator contains both the input voltage information and the leakage current information of the insulator. Any slight change in its insulation state will cause a change in the characteristics of the Lissajous figure. Therefore, it has higher sensitivity than the traditional electrical parameter detection method;

[0026] 2) The proposed technology is based on real-time measurement of the insulator voltage and leakage current data, and can realize on-line real-time monitoring of the insulator deterioration state, overcoming the disadvantage that the traditional electrical detection method needs to be carried out under power-off conditions;

[0027] 3) The proposed technology only needs to use the existing voltage transformer on the primary side of the insulator to measure the input voltage, and additionally install a current transformer to measure the leakage current of the insulator to achieve it. Compared with some existing expensive new detection technologies, the proposed technology has lower implementation cost, higher efficiency, and can realize real-time monitoring of the insulator deterioration state. Description of the Drawings

[0028] Figure 1 is a flowchart of the present invention. Detailed Embodiments

[0029] The present invention will be further described below in conjunction with the drawings:

[0030] 1. A method for monitoring the degradation state of silicone rubber composite insulators based on the characteristics of Lissajous figures, characterized in that: by online measuring the instantaneous values of the input voltage and leakage current of the insulator, the degradation state of the silicone rubber composite insulator is monitored through the following steps:

[0031] The first step: Measure the input voltage and leakage current of a healthy insulator

[0032] In the initial stage of the insulator operation, use a voltage transformer and a current transformer to measure the input voltage and leakage current of the insulator. Assume that their instantaneous values are expressed as u(t)=U0 cos(ωt) and i(t)=I0 cos(ωt + θ), where t is the measurement time and θ is the phase difference between the leakage current and the input voltage;

[0033] The second step: Construct a Lissajous figure from the input voltage and leakage current signals

[0034] According to Euler's formula, eliminate the intermediate variable t to obtain the correlation between the input voltage u(t) and the leakage current i(t), and draw the Lissajous figure representing the insulation characteristics of the insulator itself. This process can be expressed as:

[0035]

[0036] Among them, U0 and I0 are the amplitudes of the input voltage and leakage current of the healthy insulator respectively;

[0037] The third step: Extract the characteristic parameters of the Lissajous figure of the healthy insulator

[0038] Convert the Lissajous figure into a binary image, and use digital image processing technology to extract the morphological characteristics of the Lissajous figure, including the major axis, minor axis, perimeter, area, and eccentricity, a total of 5 graphic characteristics, which are respectively denoted as H i , i = 1 to 5;

[0039] The fourth step: Normalize the voltage and current data of the insulator to be measured

[0040] After the insulator has been in operation for a period of time or a failure occurs, under the same measurement conditions, measure the input voltage and leakage current of the insulator to be measured, which are respectively denoted as u1(t)=U1cos(ωt) and i1(t)=I1cos(ωt + θ1), where θ1 is the phase difference between the leakage current and the input voltage of the insulator to be measured, and perform normalization processing according to the following formulas (2) and (3) to eliminate the influence of voltage fluctuations:

[0041]

[0042] Among them, u1'(t) and i1'(t) are the instantaneous values of the input voltage and leakage current of the insulator under test after normalization, respectively; U1 and I1 are the amplitudes of the measured input voltage and leakage current, respectively.

[0043] Step 5: Calculate the comprehensive deterioration monitoring coefficient CMI and evaluate the deterioration state of the insulator

[0044] Construct the Lissajous figure of the insulator under test using the normalized insulator voltage and current data, and extract its five morphological features, denoted as F i , where i = 1 to 5, and calculate the comprehensive deterioration monitoring coefficient CMI:

[0045]

[0046] Evaluate the deterioration state of the insulator according to the magnitude of CMI. If CMI = 0, it means that the insulation state of the silicone rubber insulator is normal; the smaller CMI is, the milder the deterioration state of the silicone rubber insulator is; the larger CMI is, the more severe the deterioration state of the silicone rubber insulator is.

Claims

1. A method for monitoring the deterioration state of silicone rubber composite insulators based on the characteristics of Lissajous figures, characterized in that: By online measuring the instantaneous values of the input voltage and leakage current of the insulator, the deterioration state of the silicone rubber composite insulator is monitored through the following steps: The first step: Measure the input voltage and leakage current of the healthy insulator In the initial stage of the insulator operation, the input voltage and leakage current of the insulator are measured by a voltage transformer and a current transformer. Assume that their instantaneous values are respectively expressed as u(t) = U0 cos(ωt) and i(t) = I0 cos(ωt + θ), where t is the measurement time and θ is the phase difference between the leakage current and the input voltage; The second step: Construct a Lissajous figure from the input voltage and leakage current signals According to Euler's formula, eliminate the intermediate variable t to obtain the correlation between the input voltage u(t) and the leakage current i(t), and draw a Lissajous figure representing the insulation characteristics of the insulator itself. This process can be expressed as: where U0 and I0 are respectively the amplitudes of the input voltage and leakage current of the healthy insulator; The third step: Extract the characteristic parameters of the Lissajous figure of the healthy insulator Convert the Lissajous figure into a binary image, and use digital image processing technology to extract the morphological features of the Lissajous figure, including the major axis, minor axis, perimeter, area, and eccentricity, a total of 5 figure features, which are respectively denoted as H i , where i = 1 to 5; The fourth step: Normalize the voltage and current data of the insulator to be measured After the insulator has been in operation for a period of time or a failure occurs, under the same measurement conditions, measure the input voltage and leakage current of the insulator to be measured, which are respectively denoted as u1(t) = U1cos(ωt) and i1(t) = I1cos(ωt + θ1), where θ1 is the phase difference between the leakage current and the input voltage of the insulator to be measured, and perform normalization processing according to the following formulas (2) and (3) to eliminate the influence of voltage fluctuations: where u1'(t) and i1'(t) are respectively the instantaneous values of the input voltage and leakage current of the insulator to be measured after normalization; U1 and I1 are respectively the amplitudes of the measured input voltage and leakage current; The fifth step: Calculate the comprehensive deterioration monitoring coefficient CMI and evaluate the deterioration state of the insulator Construct the Lissajous figure of the insulator to be measured using the normalized insulator voltage and current data, and extract its five morphological features, denoted as F i , where i = 1 to 5, and calculate the comprehensive degradation monitoring coefficient CMI: Evaluate the deterioration state of the insulator according to the magnitude of CMI. If CMI = 0, it means that the insulation state of the silicone rubber insulator is normal; the smaller CMI is, the milder the deterioration state of the silicone rubber insulator is; the larger CMI is, the more severe the deterioration state of the silicone rubber insulator is.

Images